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Sample records for superconducting rf cavity

  1. TESLA superconducting RF cavity development

    International Nuclear Information System (INIS)

    Koepke, K.

    1995-01-01

    The TESLA collaboration has made steady progress since its first official meeting at Cornell in 1990. The infrastructure necessary to assemble and test superconducting rf cavities has been installed at the TESLA Test Facility (TTF) at DESY. 5-cell, 1.3 GHz cavities have been fabricated and have reached accelerating fields of 25 MV/m. Full sized 9-cell copper cavities of TESLA geometry have been measured to verify the higher order modes present and to evaluate HOM coupling designs. The design of the TESLA 9-cell cavity has been finalized and industry has started delivery. Two prototype 9-cell niobium cavities in their first tests have reached accelerating fields of 10 MV/m and 15 MV/m in a vertical dewar after high peak power (HPP) conditioning. The first 12 m TESLA cryomodule that will house 8 9-cell cavities is scheduled to be delivered in Spring 1995. A design report for the TTF is in progress. The TTF test linac is scheduled to be commissioned in 1996/1997. (orig.)

  2. Cryogenic system for TRISTAN superconducting RF cavity

    International Nuclear Information System (INIS)

    Hosoyama, K.; Hara, K.; Kabe, A.; Kojima, Yuuji; Ogitsu, T.; Sakamoto, Y.; Kawamura, S.; Ishimaru, Y.

    1990-01-01

    A cryogenic system consisting of a helium refrigerator (4 kW at 4.4 K) and a liquid helium distribution transfer system for TRISTAN 508 MHz 32 x 5-cell superconducting RF cavities was designed and constructed. After the performance test of the cryogenic system, 16 x 5-cell superconducting RF cavities in 8 cryostats were installed in underground TRISTAN electron-positron collider and connected to the helium refrigerator on the ground level through the transfer line (total length about 330 m) and cooled by liquid helium pool boiling in parallel. The cryogenic system and its operation experience are described. (author)

  3. Tuner Design for PEFP Superconducting RF Cavities

    International Nuclear Information System (INIS)

    Tang, Yazhe; An, Sun; Zhang, Liping; Cho, Yong Sub

    2009-01-01

    A superconducting radio frequency (SRF) cavity will be used to accelerate a proton beam after 100 MeV at 700 MHz in a linac of the Proton Engineering Frontier Project (PEFP) and its extended project. In order to control the SRF cavity's operating frequency at a low temperature, a new tuner has been developed for the PEFP SRF cavities. Each PEFP superconducting RF cavity has one tuner to match the cavity resonance frequency with the desired accelerator operating frequency; or to detune a cavity frequency a few bandwidths away from a resonance, so that the beam will not excite the fundamental mode, when the cavity is not being used for an acceleration. The PEFP cavity tuning is achieved by varying the total length of the cavity. The length of the cavity is controlled differentially by tuner acting with respect to the cavity body. The PEFP tuner is attached to the helium vessel and drives the cavity Field Probe (FP) side to change the frequency of the cavity

  4. Eccentric superconducting rf cavity separator structure

    International Nuclear Information System (INIS)

    Aggus, J.R.; Giordano, S.T.; Halama, H.J.

    1976-01-01

    An accelerator apparatus is described having an eccentric-shaped, iris-loaded deflecting cavity for an rf separator for a high energy high momentum, charged particle accelerator beam. In one embodiment, the deflector is superconducting, and the apparatus of this invention provides simplified machining and electron beam welding techniques. Model tests have shown that the electrical characteristics provide the desired mode splitting without adverse effects

  5. Fast thermometry for superconducting rf cavity testing

    International Nuclear Information System (INIS)

    Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N.; Kotelnikov, Sergey; Makulski, Andrzej; Nehring, Roger; Pischalnikov, Yuriy; Fermilab

    2007-01-01

    Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity

  6. Fast thermometry for superconducting rf cavity testing

    Energy Technology Data Exchange (ETDEWEB)

    Orris, Darryl; Bellantoni, Leo; Carcagno, Ruben H.; Edwards, Helen; Harms, Elvin Robert; Khabiboulline, Timergali N.; Kotelnikov, Sergey; Makulski, Andrzej; Nehring, Roger; Pischalnikov, Yuriy; /Fermilab

    2007-06-01

    Fast readout of strategically placed low heat capacity thermometry can provide valuable information of Superconducting RF (SRF) cavity performance. Such a system has proven very effective for the development and testing of new cavity designs. Recently, several resistance temperature detectors (RTDs) were installed in key regions of interest on a new 9 cell 3.9 GHz SRF cavity with integrated HOM design at FNAL. A data acquisition system was developed to read out these sensors with enough time and temperature resolution to measure temperature changes on the cavity due to heat generated from multipacting or quenching within power pulses. The design and performance of the fast thermometry system will be discussed along with results from tests of the 9 cell 3.9GHz SRF cavity.

  7. Automated Hydroforming of Seamless Superconducting RF Cavity

    International Nuclear Information System (INIS)

    Nagata, Tomohiko; Shinozawa, Seiichi; Abe, Noriyuki; Nagakubo, Junki; Murakami, Hirohiko; Tajima, Tsuyoshi; Inoue, Hitoshi; Yamanaka, Masashi; Ueno, Kenji

    2012-01-01

    We are studying the possibility of automated hydroforming process for seamless superconducting RF cavities. Preliminary hydroforming tests of three-cell cavities from seamless tubes made of C1020 copper have been performed. The key point of an automated forming is to monitor and strictly control some parameters such as operation time, internal pressure and material displacements. Especially, it is necessary for our studies to be able to control axial and radial deformation independently. We plan to perform the forming in two stages to increase the reliability of successful forming. In the first stage hydroforming by using intermediate constraint dies, three-cell cavities were successfully formed in less than 1 minute. In parallel, we did elongation tests on cavity-quality niobium and confirmed that it is possible to achieve an elongation of >64% in 2 stages that is required for our forming of 1.3 GHz cavities.

  8. Magnetic shielding for superconducting RF cavities

    Science.gov (United States)

    Masuzawa, M.; Terashima, A.; Tsuchiya, K.; Ueki, R.

    2017-03-01

    Magnetic shielding is a key technology for superconducting radio frequency (RF) cavities. There are basically two approaches for shielding: (1) surround the cavity of interest with high permeability material and divert magnetic flux around it (passive shielding); and (2) create a magnetic field using coils that cancels the ambient magnetic field in the area of interest (active shielding). The choice of approach depends on the magnitude of the ambient magnetic field, residual magnetic field tolerance, shape of the magnetic shield, usage, cost, etc. However, passive shielding is more commonly used for superconducting RF cavities. The issue with passive shielding is that as the volume to be shielded increases, the size of the shielding material increases, thereby leading to cost increase. A recent trend is to place a magnetic shield in a cryogenic environment inside a cryostat, very close to the cavities, reducing the size and volume of the magnetic shield. In this case, the shielding effectiveness at cryogenic temperatures becomes important. We measured the permeabilities of various shielding materials at both room temperature and cryogenic temperature (4 K) and studied shielding degradation at that cryogenic temperature.

  9. Superconducting rf and beam-cavity interactions

    International Nuclear Information System (INIS)

    Bisognano, J.J.

    1987-01-01

    Beam-cavity interactions can limit the beam quality and current handling capability of linear and circular accelerators. These collective effects include cumulative and regenerative transverse beam breakup (BBU) in linacs, transverse multipass beam breakup in recirculating linacs and microtrons, longitudinal and transverse coupled-bunch instabilities in storage rings, and a variety of transverse and longitudinal single-bunch phenomena (instabilities, beam breakup, and energy deposition). The superconducting radio frequency (SRF) environment has a number of features which distinguish it from room temperature configuration with regard to these beam-cavity interactions. Typically the unloaded Qs of the lower higher order modes (HOM) are at the 10 9 level and require significant damping through couplers. High gradient CW operation, which is a principal advantage of SRF, allows for better control of beam quality, which for its preservation requires added care which respect to collective phenomena. Gradients are significantly higher than those attainable with copper in CW operation but remain significantly lower than those obtainable with pulsed copper cavities. Finally, energy deposition by the beam into the cavity can occur in a cryogenic environment. In this note those characteristics of beam-cavity interactions which are of particular importance for superconducting RF cavities are highlighted. 6 refs., 4 figs

  10. Theory of RF superconductivity for resonant cavities

    Science.gov (United States)

    Gurevich, Alex

    2017-03-01

    An overview of a theory of electromagnetic response of superconductors in strong radio-frequency (RF) electromagnetic fields is given with the emphasis on applications to superconducting resonant cavities for particle accelerators. The paper addresses fundamentals of the BCS surface resistance, the effect of subgap states and trapped vortices on the residual surface resistance at low RF fields, and a nonlinear surface resistance at strong fields, particularly the effect of the RF field suppression of the surface resistance. These issues are essential for the understanding of the field dependence of high quality factors Q({B}a)˜ {10}10{--}{10}11 achieved on the Nb cavities at 1.3-2 K in strong RF fields B a close to the depairing limit, and the extended Q({B}a) rise which has been observed on Ti and N-treated Nb cavities. Possible ways of further increase of Q({B}a) and the breakdown field by optimizing impurity concentration at the surface and by multilayer nanostructuring with materials other than Nb are discussed.

  11. Cryogenic system for TRISTAN superconducting RF cavities

    International Nuclear Information System (INIS)

    Hosoyama, K.; Hara, K.; Kabe, A.; Kojima, Y.; Ogitsu, T.; Sakamoto, Y.; Kawamura, S.; Matsumoto, K.

    1993-01-01

    A large cryogenic system has been designed, constructed and operated in the TRISTAN electron-positron collider at KEK for 508 MHz, 32x5-cell superconducting RF cavities. A 6.5 kW, 4.4 K helium refrigerator with 5 turbo-expanders on the ground level supplies liquid helium in parallel to the 16 cryostats in the TRISTAN tunnel through about 250 m long multichannel transfer line. Two 5-cell cavities are coupled together, enclosed in a cryostat and cooled by about 830 L pool boiling liquid helium. A liquid nitrogen circulation system with a turbo-expander has been adopted for 80 K radiation shields in the multichannel transfer line and the cryostats to reduce liquid nitrogen consumption and to increase the operation stability of the system. The cryogenic system has a total of about 18 000 hours of operating time from the first cool down test in August 1988 to November 1991. The design principle and outline of the cryogenic system and the operational experience are presented. (orig.)

  12. Adaptive compensation of Lorentz force detuning in superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Pischalnikov, Yuriy [Fermilab; Schappert, Warren [Fermilab

    2011-11-01

    The Lorentz force can dynamically detune pulsed Superconducting RF cavities and considerable additional RF power can be required to maintain the accelerating gradient if no effort is made to compensate. Fermilab has developed an adaptive compensation system for cavities in the Horizontal Test Stand, in the SRF Accelerator Test Facility, and for the proposed Project X.

  13. Superconducting rf cavities for accelerator application

    International Nuclear Information System (INIS)

    Proch, D.

    1988-01-01

    The subject of this paper is a review of superconducting cavities for accelerator application (β = 1). The layout of a typical accelerating unit is described and important parameters are discussed. Recent cavity measurements and storage ring beam tests are reported and the present state of the art is summarized

  14. Preparation and handling of superconducting RF cavities

    International Nuclear Information System (INIS)

    Furuya, Takaaki

    1990-01-01

    The present paper outlines the recent preparation methods for superconducting cavities used in various laboratories and universities, and reports the problems of the cavity fabrication at KEK as an example of mass production. Preparation and handling are first addressed, focusing on material, fabrication, surface treatment, rinsing, clean environment, and heat treatment. Cavity production at KEK is then described, centering on defects on the surface and clean environments. Field gradients of more than 20 MV/m have been obtained by 1.5-3 GHz single cavities, for multi-cell cavities Eacc of 10 MV/m are available at any frequency range. The successful construction of thirty-two cavities for TRISTAN at KEK is due to the careful checking of the surface and quality control of all processes against the surface defects and contaminations. Eacc of 5 MV/m has been achieved by 94 % of the TRISTAN cavities at the first cold test, but 6 % of them had to be reworked because of the surface defects. These defects could not be detected by an X-ray photograph or visual inspections during the fabrication processes. (N.K.)

  15. Status of superconducting RF cavity development

    International Nuclear Information System (INIS)

    Shepard, K.W.

    1989-01-01

    For several reasons, a brief historical review seems appropriate at this time. The twenty-fifth anniversary of the first acceleration of beam with a superconducting cavity will occur shortly [1,2,3]. Also, the scope of accelerator applications of superconducting radio-frequency (SRF) devices has, within the last few months, begun to increase rapidly [4] - to the point that it seems likely that early expectations for this technology will largely be fulfilled. Since the object is to accelerate beam, a simple one parameter measure of the technology is the total of how much beam has been accelerated. Figure 1 shows the total accumulated voltage in tests and/or operation of superconducting accelerating cavities with beam, up to the time indicated, as reported in the open literature [4-35]. This parameter has been divided into two terms: first, the subtotal for electron accelerating velocity-of-light structures, and second the subtotal for low-velocity, ion accelerating structures. To restate: each of these terms represents as a function of time an integrated, accumulative total voltage produced by SRF hardware and demonstrated with beam. 56 refs., 4 figs

  16. Superconducting RF Cavities Past, Present and Future

    CERN Document Server

    Chiaveri, Enrico

    2003-01-01

    In the last two decades many laboratories around the world, notably Argonne (ANL), TJNAF (formerly CEBAF), CERN, DESY and KEK, decided to develop the technology of superconducting (SC) accelerating cavities. The aim was either to increase the accelerator energy or to save electrical consumption or both. This technology has been used extensively in the operating machines showing good performances and strong reliability. At present, the technology using bulk niobium (Nb) or Nb coated on copper (Cu) is mature enough to be applied for many different applications, such as synchrotron light sources and spallation neutron drivers. Results, R&D work and future projects will be presented with emphasis on application to linear accelerators.

  17. RF Processing of the Couplers for the SNS Superconducting Cavities

    International Nuclear Information System (INIS)

    Y.Kang; I.E. Campisi; D. Stout; A. Vassioutchenko; M. Stirbet; M. Drury; T. Powers

    2005-01-01

    All eighty-one fundamental power couplers for the 805 MHz superconducting cavities of the SNS linac have been RF conditioned and installed in the cryomodules successfully. The couplers were RF processed at JLAB or at the SNS in ORNL: more than forty couplers have been RF conditioned in the SNS RF Test Facility (RFTF) after the first forty couplers were conditioned at JLAB. The couplers were conditioned up to 650 kW forward power at 8% duty cycle in traveling and standing waves. They were installed on the cavities in the cryomodules and then assembled with the airside waveguide transitions. The couplers have been high power RF tested with satisfactory accelerating field gradients in the cooled cavities

  18. First prototype Copper-Niobium RF Superconducting Cavity

    CERN Multimedia

    1983-01-01

    This is the first RF superconducting cavity made of copper with a very thin layer of pure niobium deposited on the inner wall by sputtering. This new developpment lead to a considerable increase of performance and stability of superconducting cavities and to non-negligible economy. The work was carried out in the ISR workshop. This technique was adopted for the LEP II accelerating cavities. At the centre is Cristoforo Benvenuti, inventor of this important technology, with his assistants, Nadia Circelli and Max Hauer, carrying the sputtering electrode. See also 8209255, 8312339.

  19. 1.3 GHz superconducting RF cavity program at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    Ginsburg, C.M.; Arkan, T.; Barbanotti, S.; Carter, H.; Champion, M.; Cooley, L.; Cooper, C.; Foley, M.; Ge, M.; Grimm, C.; Harms, E.; /Fermilab

    2011-03-01

    At Fermilab, 9-cell 1.3 GHz superconducting RF (SRF) cavities are prepared, qualified, and assembled into cryomodules (CMs) for Project X, an International Linear Collider (ILC), or other future projects. The 1.3 GHz SRF cavity program includes targeted R&D on 1-cell 1.3 GHz cavities for cavity performance improvement. Production cavity qualification includes cavity inspection, surface processing, clean assembly, and one or more cryogenic low-power CW qualification tests which typically include performance diagnostics. Qualified cavities are welded into helium vessels and are cryogenically tested with pulsed high-power. Well performing cavities are assembled into cryomodules for pulsed high-power testing in a cryomodule test facility, and possible installation into a beamline. The overall goals of the 1.3 GHz SRF cavity program, supporting facilities, and accomplishments are described.

  20. Basic principles of RF superconductivity and superconducting cavities

    OpenAIRE

    Schmüser, P

    2006-01-01

    The basics of superconductivity are outlined with special emphasis on the features which are relevant for the application of superconductors in radio frequency cavities for particle acceleration. For a cylindrical resonator (“pill box cavity”) the electromagnetic field in the cavity and important parameters such as resonance frequency, quality factor and shunt impedance are calculated analytically. The design and performance of practical cavities is shortly addressed.

  1. Early prototype of a superconducting RF cavity for LEP

    CERN Multimedia

    CERN PhotoLab

    1979-01-01

    As early as 1979, before LEP became an approved project, studies were located in the ISR Division. Although Cu-cavities were foreseen, certainly for the 1st energy-stage, superconducting cavities were explored as a possible alternative for the 2nd energy-stage. This began with very basic studies of manufacture and properties of Nb-cavities. This one, held by Mr.Girel, was made from bulk Nb-sheet, 2.5 mm thick. It was dimensioned for tests at 500 MHz (LEP accelerating RF was 352.2 MHz). See also 8004204, 8007354, 8209255, 8210054, 8312339.

  2. Operating experience with high beta superconducting RF cavities

    International Nuclear Information System (INIS)

    Dylla, H.F.; Doolittle, L.R.; Benesch, J.F.

    1993-01-01

    The number of installed and operational β=1 superconducting rf cavities has grown significantly over the last two years in accelerator laboratories in Europe, Japan and the U.S. The total installed acceleration capability as of mid-1993 is approximately 1 GeV at nominal gradients. Major installations at CERN, DESY, KEK and CEBAF have provided large increments to the installed base and valuable operational experience. A selection of test data and operational experience gathered to date is reviewed

  3. Operating experience with high beta superconducting rf cavities

    International Nuclear Information System (INIS)

    Dylla, H.F.; Doolittle, L.R.; Benesch, J.F.

    1993-06-01

    The number of installed and operational β = 1 superconducting rf cavities has grown significantly over the last two years in accelerator laboratories in Europe, Japan and the US. The total installed acceleration capability as of mid-1993 is approximately 1 GeV at nominal gradients. Major installations at CERN, DESY, KEK and CEBAF have provided large increments to the installed base and valuable operational experience. A selection of test data and operational experience gathered to date is reviewed

  4. HOM Coupler Optimisation for the Superconducting RF Cavities in ESS

    CERN Document Server

    Ainsworth, R; Calaga, R

    2012-01-01

    The European Spallation Source (ESS) will be the world’s most powerful next generation neutron source. It consists of a linear accelerator, target, and instruments for neutron experiments. The linac is designed to accelerate protons to a final energy of 2.5 GeV, with an average design beam power of 5 MW, for collision with a target used to produce a high neutron flux. A section of the linac will contain Superconducting RF (SCRF) cavities designed at 704 MHz. Beam induced HOMs in these cavities may drive the beam unstable and increase the cryogenic load, therefore HOM couplers are installed to provide sufficient damping. Previous studies have shown that these couplers are susceptible to multipacting, a resonant process which can absorb RF power and lead to heating effects. This paper will show how a coupler suffering from multipacting has been redesigned to limit this effect. Optimisation of the RF damping is also discussed.

  5. RF Characterization of Niobium Films for Superconducting Cavities

    CERN Document Server

    Aull† , S; Doebert, S; Junginger, T; Ehiasarian, AP; Knobloch, J; Terenziani, G

    2013-01-01

    The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The Quadrupole Resonator modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HIPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HIPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

  6. Niobium superconducting rf cavity fabrication by electrohydraulic forming

    CERN Document Server

    Cantergiani, E.; Léaux, F.; Perez Fontenla, A.T.; Prunet, S.; Dufay-Chanat, L.; Koettig, T.; Bertinelli, F.; Capatina, O.; Favre, G.; Gerigk, F.; Jeanson, A. C.; Fuzeau, J.; Avrillaud, G.; Alleman, D.; Bonafe, J.; Marty, P.

    2016-01-01

    Superconducting rf (SRF) cavities are traditionally fabricated from superconducting material sheets or made of copper coated with superconducting material, followed by trim machining and electron-beam welding. An alternative technique to traditional shaping methods, such as deep-drawing and spinning, is electrohydraulicforming (EHF). InEHF, half-cells areobtainedthrough ultrahigh-speed deformation ofblank sheets, using shockwaves induced in water by a pulsed electrical discharge. With respect to traditional methods, such a highly dynamic process can yield interesting results in terms of effectiveness, repeatability, final shape precision, higher formability, and reduced springback. In this paper, the first results of EHFon high purity niobium are presented and discussed. The simulations performed in order to master the multiphysics phenomena of EHF and to adjust its process parameters are presented. The microstructures of niobium half- cells produced by EHFand by spinning have been compared in terms of damage...

  7. Design Topics for Superconducting RF Cavities and Ancillaries

    International Nuclear Information System (INIS)

    Padamsee, H

    2014-01-01

    RF superconductivity has become a major subfield of accelerator science. There has been an explosion in the number of accelerator applications and in the number of laboratories engaged. The first lecture at this meeting of the CAS presented a review of fundamental design principles to develop cavity geometries to accelerate velocity-of-light particles (β = v/c ~ 1), moving on to the corresponding design principles for medium-velocity (medium-β) and low-velocity (low-β) structures. The lecture included mechanical design topics. The second lecture dealt with input couplers, higher-order mode extraction couplers with absorbers, and tuners of both the slow and fast varieties

  8. Design Topics for Superconducting RF Cavities and Ancillaries

    Energy Technology Data Exchange (ETDEWEB)

    Padamsee, H [Cornell University, CLASSE (United States)

    2014-07-01

    RF superconductivity has become a major subfield of accelerator science. There has been an explosion in the number of accelerator applications and in the number of laboratories engaged. The first lecture at this meeting of the CAS presented a review of fundamental design principles to develop cavity geometries to accelerate velocity-of-light particles (β = v/c ~ 1), moving on to the corresponding design principles for medium-velocity (medium-β) and low-velocity (low-β) structures. The lecture included mechanical design topics. The second lecture dealt with input couplers, higher-order mode extraction couplers with absorbers, and tuners of both the slow and fast varieties.

  9. Characterization of a superconducting Pb photocathode in a superconducting rf photoinjector cavity

    CERN Document Server

    Barday, R; Jankowiak, A; Kamps, T; Knobloch, J; Kugeler, O; Matveenko, A; Neumann, A; Schmeißer, M; Volker, J; Kneisel, P; Nietubyc, R; Schubert S; Smedley J; Sekutowicz, J; Will, I

    2014-01-01

    Photocathodes are a limiting factor for the next generation of ultrahigh brightness photoinjectors. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity to measure the quantum efficiency, its spatial distribution, and the work function. We will also discuss how the cathode surface contaminants modify the performance of the photocathode as well as the gun cavity and we discuss the possibilities to remove these contaminants.

  10. Niobium superconducting rf cavity fabrication by electrohydraulic forming

    Science.gov (United States)

    Cantergiani, E.; Atieh, S.; Léaux, F.; Perez Fontenla, A. T.; Prunet, S.; Dufay-Chanat, L.; Koettig, T.; Bertinelli, F.; Capatina, O.; Favre, G.; Gerigk, F.; Jeanson, A. C.; Fuzeau, J.; Avrillaud, G.; Alleman, D.; Bonafe, J.; Marty, P.

    2016-11-01

    Superconducting rf (SRF) cavities are traditionally fabricated from superconducting material sheets or made of copper coated with superconducting material, followed by trim machining and electron-beam welding. An alternative technique to traditional shaping methods, such as deep-drawing and spinning, is electrohydraulic forming (EHF). In EHF, half-cells are obtained through ultrahigh-speed deformation of blank sheets, using shockwaves induced in water by a pulsed electrical discharge. With respect to traditional methods, such a highly dynamic process can yield interesting results in terms of effectiveness, repeatability, final shape precision, higher formability, and reduced springback. In this paper, the first results of EHF on high purity niobium are presented and discussed. The simulations performed in order to master the multiphysics phenomena of EHF and to adjust its process parameters are presented. The microstructures of niobium half-cells produced by EHF and by spinning have been compared in terms of damage created in the material during the forming operation. The damage was assessed through hardness measurements, residual resistivity ratio (RRR) measurements, and electron backscattered diffraction analyses. It was found that EHF does not worsen the damage of the material during forming and instead, some areas of the half-cell have shown lower damage compared to spinning. Moreover, EHF is particularly advantageous to reduce the forming time, preserve roughness, and to meet the final required shape accuracy.

  11. Adaptive Feedforward Cancellation of Sinusoidal Disturbances in Superconducting RF Cavities

    CERN Document Server

    Kandil, T H; Hartung, W; Khalil, H; Popielarski, J; Vincent, J; York, R C

    2004-01-01

    A control method, known as adaptive feedforward cancellation (AFC) is applied to damp sinusoidal disturbances due to microphonics in superconducting RF (SRF) cavities. AFC provides a method for damping internal, and external sinusoidal disturbances with known frequencies. It is preferred over other schemes because it uses rudimentary information about the frequency response at the disturbance frequencies, without the necessity of knowing an analytic model (transfer function) of the system. It estimates the magnitude and phase of the sinusoidal disturbance inputs and generates a control signal to cancel their effect. AFC, along with a frequency estimation process, is shown to be very successful in the cancellation of sinusoidal signals from different sources. The results of this research may significantly reduce the power requirements and increase the stability for lightly loaded continuous-wave SRF systems.

  12. Technical training: RF superconductivity and accelerator cavity applications

    CERN Multimedia

    Technical Training

    2016-01-01

    We are happy to announce a new training course organised by the TE-VSC group in the field of the physics and applications of superconductors. The course provides an overview and update of the theory of radiofrequency and superconductors:   RF Superconductivity and Accelerator Cavity Applications https://cern.ch/course/?164VAC19 One timetable only:  Tuesday, 8 March 2016: from 2 p.m. to 4 p.m. Wednesday, 9 March 2016: from 9.30 a.m to 11.30 a.m. Thursday, 10 March 2016: from 9.30 a.m to 11.30 a.m. Monday, 14 March 2016: from 9.30 a.m to 11.30 a.m. Tuesday, 15 March 2016: from 9.30 a.m to 11.30 a.m. Wednesday, 16 March 2016: from 9.30 a.m to 11.30 a.m. Thursday, 17 March 2016: from 9.30 a.m to 11.30 a.m. Target audience: Experts in radiofrequency or solid state physics (PhD level). Pre-requisites: Basic knowledge of quantum physics and superc...

  13. Researches on bake effect on RF superconducting cavities

    International Nuclear Information System (INIS)

    Hao Jiankui; Zhao Kui; Zhu Feng

    2005-01-01

    The Q-slope at high gradient affects the performance of superconducting cavity greatly. Recent researches show that low temperature (100-150) degree C heat treatment (bake) has positive effects on the performance of superconducting cavities. A lot of cavity tests are analyzed based on bake treatment. The average gradient E acc,max and E acc at Q=1 x 10 10 are increased by more than 3.5 MV/m. Q at E acc,max is increased and the Q-slope is improved. Analysis on bake temperature shows that higher bake temperature leads to higher Q value. Comparison of BCP and EP cavities shows that at least 60-80 μm EP is needed for BCP surface. More than 10-15 μm removal of the surface by BCP will degrade the performance of an EP cavity. Oxygen diffusion model is used to illustrate bake effect. (authors)

  14. Mechanical Design and Fabrication Studies for SPL Superconducting RF Cavities

    CERN Document Server

    Atieh, S; Aviles Santillana, I; Capatina, O; Renaglia, T; Tardy, T; Valverde Alonso, N; Weingarten, W

    2011-01-01

    CERN’s R&D programme on the Superconducting Proton Linac’s (SPL) superconducting radio frequency (SRF) elliptical cavities made from niobium sheets explores new mechanical design and consequently new fabrication methods, where several opportunities for improved optimization were identified. A stainless steel helium vessel is under design rather than a titanium helium vessel using an integrated brazed transition between Nb and the SS helium vessel. Different design and fabrication aspects were proposed and the results are discussed hereafter.

  15. Study of thermal effects in superconducting RF cavities

    International Nuclear Information System (INIS)

    Bousson, S.; Caruette, A.; Fouaidy, M.; Hammoudi, N.; Junquera, T.; Lesrel, J.; Yaniche, J.F.

    1999-01-01

    A high speed thermometric system equipped with 64 fixed surface thermometers is used to investigate thermal effects in several 3 GHz cavities. An evaluation of the time response of our thermometers is presented. A method based on RF signal analysis is proposed to evaluate the normal zone propagation rate during thermal breakdown. (authors)

  16. Elliptical superconducting RF cavities for FRIB energy upgrade

    Science.gov (United States)

    Ostroumov, P. N.; Contreras, C.; Plastun, A. S.; Rathke, J.; Schultheiss, T.; Taylor, A.; Wei, J.; Xu, M.; Xu, T.; Zhao, Q.; Gonin, I. V.; Khabiboulline, T.; Pischalnikov, Y.; Yakovlev, V. P.

    2018-04-01

    The multi-physics design of a five cell, βG = 0 . 61, 644 MHz superconducting elliptical cavity being developed for an energy upgrade in the Facility for Rare Isotope Beams (FRIB) is presented. The FRIB energy upgrade from 200 MeV/u to 400 MeV/u for heaviest uranium ions will increase the intensities of rare isotope beams by nearly an order of magnitude. After studying three different frequencies, 1288 MHz, 805 MHz, and 644 MHz, the 644 MHz cavity was shown to provide the highest energy gain per cavity for both uranium and protons. The FRIB upgrade will include 11 cryomodules containing 5 cavities each and installed in 80-meter available space in the tunnel. The cavity development included extensive multi-physics optimization, mechanical and engineering analysis. The development of a niobium cavity is complete and two cavities are being fabricated in industry. The detailed design of the cavity sub-systems such as fundamental power coupler and dynamic tuner are currently being pursued. In the overall design of the cavity and its sub-systems we extensively applied experience gained during the development of 650 MHz low-beta cavities at Fermi National Accelerator Laboratory (FNAL) for the Proton Improvement Plan (PIP) II.

  17. Microphonics detuning compensation in 3.9 GHZ superconducting RF cavities

    International Nuclear Information System (INIS)

    Ruben Carcagno

    2003-01-01

    Mechanical vibrations can detune superconducting radio frequency (SCRF) cavities unless a tuning mechanism counteracting the vibrations is present. Due to their narrow operating bandwidth and demanding mechanical structure, the 13-cell 3.9GHz SCRF cavities for the Charged Kaons at Main Injector (CKM) experiment at Fermilab are especially susceptible to this microphonic phenomena. We present early results correlating RF frequency detuning with cavity vibration measurements for CKM cavities; initial detuning compensation results with piezoelectric actuators are also presented

  18. Microphonics detuning compensation in 3.9 GHZ superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ruben Carcagno et al.

    2003-10-20

    Mechanical vibrations can detune superconducting radio frequency (SCRF) cavities unless a tuning mechanism counteracting the vibrations is present. Due to their narrow operating bandwidth and demanding mechanical structure, the 13-cell 3.9GHz SCRF cavities for the Charged Kaons at Main Injector (CKM) experiment at Fermilab are especially susceptible to this microphonic phenomena. We present early results correlating RF frequency detuning with cavity vibration measurements for CKM cavities; initial detuning compensation results with piezoelectric actuators are also presented.

  19. Microscopic Investigation of Materials Limitations of Superconducting RF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Anlage, Steven [Univ. of Maryland, College Park, MD (United States)

    2017-08-04

    Our overall goal is to contribute to the understanding of defects that limit the high accelerating gradient performance of Nb SRF cavities. Our approach is to develop a microscopic connection between materials defects and SRF performance. We developed a near-field microwave microscope to establish this connection. The microscope is based on magnetic hard drive write heads, which are designed to create very strong rf magnetic fields in very small volumes on a surface.

  20. Low-Level RF Control of Microphonics in Superconducting Spoke-Loaded Cavities

    International Nuclear Information System (INIS)

    Conway, Z.A.; Kelly, M.P.; Sharamentov, S.I.; Shepard, K.W.; Davis, G.; Delayen, Jean; Doolittle, Lawrence

    2007-01-01

    This paper presents the results of cw RF frequency control and RF phase-stabilization experiments performed with a piezoelectric fast tuner mechanically coupled to a superconducting, 345 MHz, < = 0.5 triple-spoke-loaded cavity operating at 4.2K. The piezoelectric fast tuner damped low-frequency microphonic-noise by an order of magnitude. Two methods of RF phase-stabilization were characterized: overcoupling with negative phase feedback, and also fast mechanical tuner feedback. The = 0.5 triple-spoke-loaded cavity RF field amplitude and phase errors were controlled to ±0.5% and ±30 respectively.

  1. Pre-tuning of TRISTAN superconducting RF cavities

    International Nuclear Information System (INIS)

    Tajima, Tsuyoshi; Furuya, Takaaki; Suzuki, Toshiji; Iino, Yohsuke.

    1990-01-01

    Pre-tuning of thirty-two TRISTAN superconducting cavities has been done. In this paper are described the pre-tuning system and the results of all the cavities. The average field flatness was 1.4 % after pre-tuning. From our experience, the followings are important, 1) to evacuate the cavity during the process of the pre-tuning to avoid the uncertainty in evacuation, 2) pre-tuning is needed after annealing because it causes changes of the cell length and the field profile and 3) field flatness sometimes changes when expanded and 4) cells should not be expanded more than 1.5 mm after pre-tuning since inelastic deformation occurs. (author)

  2. SNS Superconducting RF cavity modeling-iterative learning control

    International Nuclear Information System (INIS)

    Kwon, S.-I.; Regan, Amy; Wang, Y.-M.

    2002-01-01

    The Spallation Neutron Source (SNS) Superconducting RF (SRF) linear accelerator is operated with a pulsed beam. For the SRF control system to track the repetitive electromagnetic field reference trajectory, both feedback and feedforward controllers have been proposed. The feedback controller is utilized to guarantee the closed loop system stability and the feedforward controller is used to improve the tracking performance for the repetitive reference trajectory and to suppress repetitive disturbances. As the iteration number increases, the feedforward controller decreases the tracking error. Numerical simulations demonstrate that inclusion of the feedforward controller significantly improves the control system performance over its performance with just the feedback controller

  3. SNS Superconducting RF cavity modeling-iterative learning control

    CERN Document Server

    Kwon, S I; Wang, Y M

    2002-01-01

    The Spallation Neutron Source (SNS) Superconducting RF (SRF) linear accelerator is operated with a pulsed beam. For the SRF control system to track the repetitive electromagnetic field reference trajectory, both feedback and feedforward controllers have been proposed. The feedback controller is utilized to guarantee the closed loop system stability and the feedforward controller is used to improve the tracking performance for the repetitive reference trajectory and to suppress repetitive disturbances. As the iteration number increases, the feedforward controller decreases the tracking error. Numerical simulations demonstrate that inclusion of the feedforward controller significantly improves the control system performance over its performance with just the feedback controller.

  4. First cold test of TESLA superconducting RF cavity in horizontal cryostat (CHECHIA)

    International Nuclear Information System (INIS)

    Kuzminski, J.

    1996-01-01

    In the framework of the TESLA project, the horizontal cryostat (CHECHIA) was built to test a superconducting RF cavity equipped with its helium vessel, magnetic shielding, cold tuner, main coupler and higher order modes couplers under realistic conditions before final assembly of eight cavities into TESLA Test Facility cryo-module. The results of the first cold tests in CHECHIA, performed at DESY with a 9-cell cavity (C19) to be used in the TTF injector are presented. (author)

  5. Progress on the high-current 704 MHz superconducting RF cavity at BNL

    International Nuclear Information System (INIS)

    Xu, W.; Astefanous, C.; Belomestnykh, S.; Ben-Zvi, I.

    2012-01-01

    The 704 MHz high current superconducting cavity has been designed with consideration of both performance of fundamental mode and damping of higher order modes. A copper prototype cavity was fabricated by AES and delivered to BNL. RF measurements were carried out on this prototype cavity, including fundamental pass-band and HOM spectrum measurements, HOM studies using bead-pull setup, prototyping of antenna-type HOM couplers. The measurements show that the cavity has very good damping for the higher-order modes, which was one of the main goals for the high current cavity design. 3D cavity models were simulated with Omega3P code developed by SLAC to compare with the measurements. The paper describes the cavity design, RF measurement setups and results for the copper prototype. The progress with the niobium cavity fabrication will also be described.

  6. First cold test of TESLA superconducting RF cavity in horizontal cryostat (CHECHIA)

    International Nuclear Information System (INIS)

    Kuzminski, J.

    1996-01-01

    In the framework of the TESLA project, the horizontal cryostat (CHECHIA) was built to test a superconducting RF cavity equipped with its helium vessel, magnetic shielding, cold tuner, main coupler and higher order modes couplers under realistic conditions before final assembly of eight cavities into TESLA Test Facility cryo-module. The results of the first cold tests in CHECHIA, performed at DESY with a 9-cell cavity (C19) to be used in the TTF injector are presented. Additional measurements of mechanical stability under RF operation (frequency variation with He pressure, Lorentz detuning) and cryogenic and electric measurements of power dissipation are presented. (author)

  7. Multiplacting analysis on 650 MHz, BETA 0.61 superconducting RF LINAC cavity

    International Nuclear Information System (INIS)

    Seth, Sudeshna; Som, Sumit; Mandal, Aditya; Ghosh, Surajit; Saha, S.

    2013-01-01

    Design, analysis and development of high-β multi-cell elliptical shape Superconducting RF linac cavity has been taken up by VECC, Kolkata as a part of IIFC collaboration. The project aims to provide the-art technology achieving very high electric field gradient in superconducting linac cavity, which can be used in high energy high current proton linear accelerator to be built for ADSS/SNS programme in India and in Project-X at Fermilab, USA. The performance of this type of superconducting RF structure can be greatly affected due to multipacting when we feed power to the cavity. Multipacting is a phenomenon of resonant electron multiplication in which a large number of electrons build up an electron Avalanche which absorbs RF Energy leading to remarkable power losses and heating of the walls, making it impossible to raise the electric field by increasing the RF Power. Multipacting analysis has been carried out for 650 MHz, β=0.61, superconducting elliptical cavity using 2D code MultiPac 2.1 and 3 D code CST particle studio and the result is presented in this paper. (author)

  8. Physics and chemistry of niobium materials in the context of superconducting RF cavity applications

    International Nuclear Information System (INIS)

    Roy, S.B.

    2016-01-01

    Superconducting radio frequency (SCRF) cavities excel over the normal conducting RF cavities in the long pulse or continuous wave high energy particle accelerations, and niobium (Nb) is currently the material of choice for fabrication of such SCRF cavities. However the accelerating gradients attained in the Nb SCRF cavities deployed in various high energy particle accelerators are significantly below the theoretical limit predicted by the superconducting properties of Nb. Thus it is very important to understand the physics and chemistry of Nb materials in some details so as to maximize the SCRF cavity performance. This abstract will discuss some issues which help in the development of high gradient and energy efficient Nb SCRF cavities in a cost effective manner. (author)

  9. Preparation of niobium coated copper superconducting rf cavities for the large electron positron collider

    International Nuclear Information System (INIS)

    Benvenuti, C.; Bloess, D.; Chiaveri, E.; Hilleret, N.; Minestrini, M.; Weingarten, W.

    1988-01-01

    Since 1980 development work has been carried out at CERN aiming at producing niobium coated superconducting RF cavities in the framework of the foreseen LEP energy upgrading above the initial 55 GeV. During 1987 a 4-cell LEP cavity without coupling ports has been successfully coated for the first time. Meanwhile, cathodes for coating the coupling ports were built and tested. The effort has been subsequently directed to preparing at least one (possibly 2) coated cavity(ies) to be installed in LEP during 1989. In this paper the various production steps of these cavities are reconsidered in view of industrial production

  10. Design and development of RF system for vertical test stand for characterization of superconducting RF cavities

    International Nuclear Information System (INIS)

    Mohania, Praveen; Rajput, Vikas; Baxy, Deodatta; Agrawal, Ankur; Mahawar, Ashish; Adarsh, Kunver; Singh, Pratap; Shrivastava, Purushottam

    2011-01-01

    RRCAT is developing a Vertical Test Stand (VTS) to test and qualify 1.3 GHz/650 MHz, SCRF Cavities in collaboration with Fermi National Accelerator Laboratory (FNAL) under Indian Institutions' Fermilab Collaboration. The technical details for VTS is being provided by FNAL, USA. The RF System of VTS needs to provide stable RF power to SCRF cavity with control of amplitude, relative phase and frequency. The incident, reflected, transmitted power and field decay time constant of the cavity are measured to evaluate cavity performance parameters (E, Qo). RF Power is supplied via 500 W Solid State amplifier, 1270-1310 MHz being developed by PHPMS, RRCAT. VTS system is controlled by PXI Platform and National Instruments LabVIEW software. Low Level RF (LLRF) system is used to track the cavity frequency using Phase Locked Loop (PLL). The system is comprised of several integrated functional modules which would be assembled, optimized, and tested separately. Required components and instruments have been identified and procurement for the same is underway. Inhouse development for the Solid State RF amplifier and instrument interfacing is in progress. This paper describes the progress on the development of the RF system for VTS. (author)

  11. Development of L-band niobium superconducting RF cavities with high accelerating field

    International Nuclear Information System (INIS)

    Saito, Kenji; Noguchi, Shuichi; Ono, Masaaki; Kako, Eiji; Shishido, Toshio; Matsuoka, Masanori; Suzuki, Takafusa; Higuchi, Tamawo.

    1994-01-01

    Superconducting RF cavity is a candidate for the TeV energy e + /e - linear collider of next generation if the accelerating field is improved to 25-30 MV/m and much cost down is achieved in cavity fabrication. Since 1990, KEK has continued R and D of L-band niobium superconducting cavities focusing on the high field issue. A serious problem like Q-degradation due to vacuum discharge came out on the way, however, it has been overcome and presently all of cavities which were annealed at 1400degC achieved the accelerating field of >25 MV/m with enough Qo value. Recent results on single cell cavities are described in this paper. (author)

  12. Cryomodule tests of four Tesla-like cavities in the Superconducting RF Test Facility at KEK

    Directory of Open Access Journals (Sweden)

    Eiji Kako

    2010-04-01

    Full Text Available A 6-m cryomodule including four Tesla-like cavities was developed, and was tested in the Superconducting RF Test Facility phase-I at KEK. The performance as a total superconducting cavity system was checked in the cryomodule tests at 2 K with high rf power. One of the four cavities achieved a stable pulsed operation at 32  MV/m, which is higher than the operating accelerating gradient in the ILC. The maximum accelerating gradient (E_{acc,max⁡} obtained in the vertical cw tests was maintained or slightly improved in the cryomodule tests operating in a pulse mode. Compensation of the Lorentz force detuning at 31  MV/m was successfully demonstrated by a piezo tuner and predetuning.

  13. Conceptual design of the RF accelerating cavities for a superconducting cyclotron

    International Nuclear Information System (INIS)

    Maggiore, M.; Calabretta, L.; Di Giacomo, M.; Rifuggiato, D.; Battaglia, D.; Piazza, L.

    2006-01-01

    A superconducting cyclotron accelerating ions up to 250 A MeV, for medical applications and radioactive ions production is being studied at Laboratori Nazionali del Sud in Catania. The radio frequency (RF) system, working in the fourth harmonic, is based on four normal conducting radio frequency cavities operating at 93 MHz. This paper describes an unusual multi-stem cavity design, performed with 3D electromagnetic codes. Our aim is to obtain a cavity, completely housed inside the cyclotron, with a voltage distribution ranging from 65 kV in the injection region to a peak value of 120 kV in the extraction region, and having a low power consumption

  14. On active disturbance rejection based control design for superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, John; Morris, Dan; Usher, Nathan [National Superconducting Cyclotron Laboratory (NSCL), Michigan State University, East Lansing, MI 48824-1321 (United States); Gao, Zhiqiang, E-mail: z.gao@csuohio.edu [Center for Advanced Control Technologies, Fenn College of Engineering, Cleveland State University, Cleveland, OH 44115-2214 (United States); Zhao Shen; Nicoletti, Achille; Zheng Qinling [Center for Advanced Control Technologies, Fenn College of Engineering, Cleveland State University, Cleveland, OH 44115-2214 (United States)

    2011-07-01

    Superconducting RF (SRF) cavities are key components of modern linear particle accelerators. The National Superconducting Cyclotron Laboratory (NSCL) is building a 3 MeV/u re-accelerator (ReA3) using SRF cavities. Lightly loaded SRF cavities have very small bandwidths (high Q) making them very sensitive to mechanical perturbations whether external or self-induced. Additionally, some cavity types exhibit mechanical responses to perturbations that lead to high-order non-stationary transfer functions resulting in very complex control problems. A control system that can adapt to the changing perturbing conditions and transfer functions of these systems would be ideal. This paper describes the application of a control technique known as 'Active Disturbance Rejection Control' (ARDC) to this problem.

  15. Development of Infrastructure Facilities for Superconducting RF Cavity Fabrication, Processing and 2 K Characterization at RRCAT

    Science.gov (United States)

    Joshi, S. C.; Raghavendra, S.; Jain, V. K.; Puntambekar, A.; Khare, P.; Dwivedi, J.; Mundra, G.; Kush, P. K.; Shrivastava, P.; Lad, M.; Gupta, P. D.

    2017-02-01

    An extensive infrastructure facility is being established at Raja Ramanna Centre for Advanced Technology (RRCAT) for a proposed 1 GeV, high intensity superconducting proton linac for Indian Spallation Neutron Source. The proton linac will comprise of a large number of superconducting Radio Frequency (SCRF) cavities ranging from low beta spoke resonators to medium and high beta multi-cell elliptical cavities at different RF frequencies. Infrastructure facilities for SCRF cavity fabrication, processing and performance characterization at 2 K are setup to take-up manufacturing of large number of cavities required for future projects of Department of Atomic Energy (DAE). RRCAT is also participating in a DAE’s approved mega project on “Physics and Advanced technology for High intensity Proton Accelerators” under Indian Institutions-Fermilab Collaboration (IIFC). In the R&D phase of IIFC program, a number of high beta, fully dressed multi-cell elliptical SCRF cavities will be developed in collaboration with Fermilab. A dedicated facility for SCRF cavity fabrication, tuning and processing is set up. SCRF cavities developed will be characterized at 2K using a vertical test stand facility, which is already commissioned. A Horizontal Test Stand facility has also been designed and under development for testing a dressed multi-cell SCRF cavity at 2K. The paper presents the infrastructure facilities setup at RRCAT for SCRF cavity fabrication, processing and testing at 2K.

  16. Plasma processing of large curved surfaces for superconducting rf cavity modification

    Directory of Open Access Journals (Sweden)

    J. Upadhyay

    2014-12-01

    Full Text Available Plasma-based surface modification of niobium is a promising alternative to wet etching of superconducting radio frequency (SRF cavities. We have demonstrated surface layer removal in an asymmetric nonplanar geometry, using a simple cylindrical cavity. The etching rate is highly correlated with the shape of the inner electrode, radio-frequency (rf circuit elements, gas pressure, rf power, chlorine concentration in the Cl_{2}/Ar gas mixtures, residence time of reactive species, and temperature of the cavity. Using variable radius cylindrical electrodes, large-surface ring-shaped samples, and dc bias in the external circuit, we have measured substantial average etching rates and outlined the possibility of optimizing plasma properties with respect to maximum surface processing effect.

  17. Fiber Optic Based Thermometry System for Superconducting RF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kochergin, Vladimir [Microxact Inc.

    2013-05-06

    Thermometry is recognized as the best technique to identify and characterize losses in SRF cavities. The most widely used and reliable apparatus for temperature mapping at cryogenic temperatures is based on carbon resistors (RTDs). The use of this technology on multi-cell cavities is inconvenient due to the very large number of sensors required to obtain sufficient spatial resolution. Recent developments make feasible the use of multiplexible fiber optic sensors for highly distributed temperature measurements. However, sensitivity of multiplexible cryogenic temperature sensors was found extending only to 12K at best and thus was not sufficient for SRF cavity thermometry. During the course of the project the team of MicroXact, JLab and Virginia Tech developed and demonstrated the multiplexible fiber optic sensor with adequate response below 20K. The demonstrated temperature resolution is by at least a factor of 60 better than that of the best multiplexible fiber optic temperature sensors reported to date. The clear path toward at least 10times better temperature resolution is shown. The first to date temperature distribution measurements with ~2.5mm spatial resolution was done with fiber optic sensors at 2K to4K temperatures. The repeatability and accuracy of the sensors were verified only at 183K, but at this temperature both parameters significantly exceeded the state of the art. The results of this work are expected to find a wide range of applications, since the results are enabling the whole new testing capabilities, not accessible before.

  18. High-Q operation of superconducting rf cavities: Potential impact of thermocurrents on the rf surface resistance

    Directory of Open Access Journals (Sweden)

    J.-M. Vogt

    2015-04-01

    Full Text Available For many new accelerator applications, superconducting radio frequency systems are the enabling technology. In particular for CW applications, much effort is being expended to minimize the power dissipation (surface resistance of niobium cavities. Starting in 2009, we suggested a means of reducing the residual resistance by performing a thermal cycle [O. Kugeler et al., in Proceedings of the 14th International Conference on RF Superconductivity (2009, p. 352], a procedure of warming up a cavity after initial cooldown to about 20 K and cooling it down again. In subsequent studies [J. M. Vogt, O. Kugeler, and J. Knobloch, Phys. Rev. ST Accel. Beams 16, 102002 (2013], this technique was used to manipulate the residual resistance by more than a factor of 2. It was postulated that thermocurrents during cooldown generate additional trapped magnetic flux that impacts the cavity quality factor. Here, we present a more extensive study that includes measurements of two additional passband modes and that confirms the effect. In this paper, we also discuss simulations that support the claim. While the layout of the cavity LHe tank system is cylindrically symmetric, we show that the temperature dependence of the material parameters results in a nonsymmetric current distribution. Hence a significant amount of magnetic flux can be generated at the rf surface.

  19. Effect of low temperature baking on the RF properties of niobium superconducting cavities for particle accelerators

    International Nuclear Information System (INIS)

    Gianluigi Ciovati

    2004-01-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some ''anomalous'' losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low temperature (100 C-150 C) ''in situ'' bake under ultra-high vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from ''anomalous'' losses (so-called ''Q-drop'') without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37 K-280 K and resonant frequency shift between 6 K-9.3 K provide information about the surface resistance, energy gap, penetration depth and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with Nuclear Reaction Analysis (NRA). The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models

  20. A technique for monitoring fast tuner piezoactuator preload forces for superconducting rf cavities

    International Nuclear Information System (INIS)

    Pischalnikov, Y.; Branlard, J.; Carcagno, R.; Chase, B.; Edwards, H.; Orris, D.; Makulski, A.; McGee, M.; Nehring, R.; Poloubotko, V.; Sylvester, C.; Fermilab

    2007-01-01

    The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities [1]. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant static force (preload) on the piezo actuator in the range of 10 to 50% of its specified blocking force. Determining the preload force during cool-down, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. The design and testing of piezo actuator preload sensor technology is discussed. Results from measurements of preload sensors installed on the tuner of the Capture Cavity II (CCII)[2] tested at FNAL are presented. These results include measurements during cool-down, warmup, and cavity tuning along with dynamic Lorentz force compensation

  1. A technique for monitoring fast tuner piezoactuator preload forces for superconducting rf cavities

    Energy Technology Data Exchange (ETDEWEB)

    Pischalnikov, Y.; Branlard, J.; Carcagno, R.; Chase, B.; Edwards, H.; Orris, D.; Makulski, A.; McGee, M.; Nehring, R.; Poloubotko, V.; Sylvester, C.; /Fermilab

    2007-06-01

    The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities [1]. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant static force (preload) on the piezo actuator in the range of 10 to 50% of its specified blocking force. Determining the preload force during cool-down, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. The design and testing of piezo actuator preload sensor technology is discussed. Results from measurements of preload sensors installed on the tuner of the Capture Cavity II (CCII)[2] tested at FNAL are presented. These results include measurements during cool-down, warmup, and cavity tuning along with dynamic Lorentz force compensation.

  2. Study of a power coupler for superconducting RF cavities used in high intensity proton accelerator

    International Nuclear Information System (INIS)

    Souli, M.

    2007-07-01

    The coaxial power coupler needed for superconducting RF cavities used in the high energy section of the EUROTRANS driver should transmit 150 kW (CW operation) RF power to the protons beam. The calculated RF and dielectric losses in the power coupler (inner and outer conductor, RF window) are relatively high. Consequently, it is necessary to design very carefully the cooling circuits in order to remove the generated heat and to ensure stable and reliable operating conditions for the coupler cavity system. After calculating all type of losses in the power coupler, we have designed and validated the inner conductor cooling circuit using numerical simulations results. We have also designed and optimized the outer conductor cooling circuit by establishing its hydraulic and thermal characteristics. Next, an experiment dedicated to study the thermal interaction between the power coupler and the cavity was successfully performed at CRYOHLAB test facility. The critical heat load Qc for which a strong degradation of the cavity RF performance was measured leading to Q c in the range 3 W-5 W. The measured heat load will be considered as an upper limit of the residual heat flux at the outer conductor cold extremity. A dedicated test facility was developed and successfully operated for measuring the performance of the outer conductor heat exchanger using supercritical helium as coolant. The test cell used reproduces the realistic thermal boundary conditions of the power coupler mounted on the cavity in the cryo-module. The first experimental results have confirmed the excellent performance of the tested heat exchanger. The maximum residual heat flux measured was 60 mW for a 127 W thermal load. As the RF losses in the coupler are proportional to the incident RF power, we can deduce that the outer conductor heat exchanger performance is continued up to 800 kW RF power. Heat exchanger thermal conductance has been identified using a 2D axisymmetric thermal model by comparing

  3. Reduction of field emission in superconducting cavities with high power pulsed RF

    International Nuclear Information System (INIS)

    Graber, J.; Crawford, C.; Kirchgessner, J.; Padamsee, H.; Rubin, D.; Schmueser, P.

    1994-01-01

    A systematic study is presented of the effects of pulsed high power RF processing (HPP) as a method of reducing field emission (FE) in superconducting radio frequency (SRF) cavities to reach higher accelerating gradients for future particle accelerators. The processing apparatus was built to provide up to 150 kW peak RF power to 3 GHz cavities, for pulse lengths from 200 μs to 1 ms. Single-cell and nine-cell cavities were tested extensively. The thermal conductivity of the niobium for these cavities was made as high as possible to ensure stability against thermal breakdown of superconductivity. HPP proves to be a highly successful method of reducing FE loading in nine-cell SRF cavities. Attainable continuous wave (CW) fields increase by as much as 80% from their pre-HPP limits. The CW accelerating field achieved with nine-cell cavities improved from 8-15 MV/m with HPP to 14-20 MV/m. The benefits are stable with subsequent exposure to dust-free air. More importantly, HPP also proves effective against new field emission subsequently introduced by cold and warm vacuum ''accidents'' which admitted ''dirty'' air into the cavities. Clear correlations are obtained linking FE reduction with the maximum surface electric field attained during processing. In single cells the maximums reached were E peak =72 MV/m and H peak =1660 Oe. Thermal breakdown, initiated by accompanying high surface magnetic fields is the dominant limitation on the attainable fields for pulsed processing, as well as for final CW and long pulse operation. To prove that the surface magnetic field rather than the surface electric fields is the limitation to HPP effectiveness, a special two-cell cavity with a reduced magnetic to electric field ratio is successfully tested. During HPP, pulsed fields reach E peak =113 MV/m (H peak =1600 Oe) and subsequent CW low power measurement reached E peak =100 MV/m, the highest CW field ever measured in a superconducting accelerator cavity. ((orig.))

  4. Development of a Solid State RF Amplifier in the kW Regime for Application with Low Beta Superconducting RF Cavities

    CERN Document Server

    Piel, Christian; Borisov, A; Kolesov, Sergej; Piel, Helmut

    2005-01-01

    Projects based on the use of low beta superconducting cavities for ions are under operation or development at several labs worldwide. Often these cavities are individually driven by RF power sources in the kW regime. For an ongoing project a modular 2 kW, 176 MHz unconditionally stable RF amplifier for CW and pulsed operation was designed, built, and tested. Extended thermal analysis was used to develop a water cooling system in order to optimize the performance of the power transistors and other thermally loaded components. The paper will outline the design concept of the amplifier and present first results on the test of the amplifier with a superconducting cavity.

  5. Structural and superconducting properties of sputter-deposited niobium films for applications in RF accelerating cavities

    CERN Document Server

    Peck, M A

    2000-01-01

    The present work presents the results of a systematic study of superconducting and structural properties of niobium films sputter deposited onto the inner walls of radiofrequency copper resonators. The measured superconducting quantities include the surface resistance, the critical temperature, the penetration depth and the upper and lower critical fields. In addition to films grown with different discharge gases (Xe, Kr, Ar, Ne and Ar-Ne mixtures) and to films grown on substrates prepared under different conditions, the study also includes massive niobium cavities. The surface resistance is analysed in terms of its dependence on the temperature and on the rf field amplitude and, when possible, compared to theoretical predictions. In general, good agreement with BCS theory is observed. All experimental results are presented in the form of a simple, but adequate parameterisation. The residual resistance is observed to be essentially uncorrelated with the other variables, but strongly dependent on the macroscop...

  6. Mechanical design of 56 MHz superconducting RF cavity for RHIC collider

    Energy Technology Data Exchange (ETDEWEB)

    Pai, C.; Ben-Zvi, I.; Burrill, A.; Chang, X.; McIntyre, G.; Than, Y.; Tuozzolo, J.; Wu, Q.

    2011-03-28

    A 56 MHz Superconducting RF Cavity operating at 4.4K is being constructed for the RHIC collider. This cavity is a quarter wave resonator with beam transmission along the centerline. This cavity will increase collision luminosity by providing a large longitudinal bucket for stored bunches of RHIC ion beam. The major components of this assembly are the niobium cavity with the mechanical tuner, its titanium helium vessel and vacuum cryostat, the support system, and the ports for HOM and fundamental dampers. The cavity and its helium vessel must meet equivalent safety with the ASME pressure vessel code and it must not be sensitive to frequency shift due to pressure fluctuations from the helium supply system. Frequency tuning achieved by a two stage mechanical tuner is required to meet performance parameters. This tuner mechanism pushes and pulls the tuning plate in the gap of niobium cavity. The tuner mechanism has two separate drive systems to provide both coarse and fine tuning capabilities. This paper discusses the design detail and how the design requirements are met.

  7. Development of high pressure rinsing set up for 650 MHz, 5- cell superconducting RF cavity cleaning

    International Nuclear Information System (INIS)

    Suhane, S.K.; Chauhan, S.K.; Bose, A.; Kokil, S.V.; Rajput, D.S.; Oraon, B.; Md Hussain; Sahu, A.; Raghavendra, S.; Joshi, S.C.

    2015-01-01

    High pressure rinsing (HPR) is an ultra-cleanliness process for the surface preparation of high field superconducting RF cavities. Any dust particle or chemical residue on the interior of cavity causes field emission. Jets of high pressure (80-100 bar) ultra pure water dislodge surface contaminants that normally resist removal with conventional rinsing procedures, leading to substantial reduction in field emission and better cavity performance. For cleaning of 650 MHz, 5-cell SRF cavities, a high pressure rinsing set up has been developed at RRCAT. The HPR tool has a rotating wand coaxial with the vertically mounted SRF cavity that is moving up and down. Fan style spray nozzles are attached to the end of the rotating wand and the water jets emerging from spray nozzles scan the entire internal surface of the cavity. The set-up was installed in a specially built clean area meeting cleanliness class 100 standards. The ultrapure water with resistivity 2 ≥ 18 MΩ-cm required for rinsing is obtained from a dedicated water purification system installed for this purpose. The paper describes the salient design and constructional details of the high pressure rinsing set up. Characterization of water jet parameters based on the momentum transfer between the water jet and a load cell is also presented. (author)

  8. Biased HiPIMS technology for superconducting rf accelerating cavities coating

    CERN Document Server

    G. Rosaz, G.; Sonato, D.; Calatroni, S.; Ehiasarian, A.; Junginger, T.; Taborelli, M.

    2016-01-01

    In the last few years the interest of the thin film science and technology community on High Impulse Power Magnetron Sputtering (HIPIMS) coatings has steadily increased. HIPIMS literature shows that better thin film morphology, denser and smoother films can be achieved when compared with standard dc Magnetron Sputtering (dcMS) coating technology. Furthermore the capability of HIPIMS to produce a high quantity of ionized species can allow conformal coatings also for complex geometries. CERN already studied the possibility to use such a coating method for SRF accelerating cavities. Results are promising but not better from a RF point of view than dcMS coatings. Thanks to these results the next step is to go towards a biased HiPIMS approach. However the geometry of the cavities leads to complex changes in the coating setup in order to apply a bias voltage. Coating system tweaking and first superconducting properties of biased samples are presented.

  9. Dynamic compensation of an rf cavity failure in a superconducting linac

    Directory of Open Access Journals (Sweden)

    Jean-Luc Biarrotte

    2008-07-01

    Full Text Available An accelerator driven system (ADS for transmutation of nuclear waste typically requires a 600 MeV–1 GeV accelerator delivering a proton flux of a few mA for demonstrators, and of a few tens of mA for large industrial systems. Such a machine belongs to the category of the high-power proton accelerators, with an additional requirement for exceptional “reliability”: because of the induced thermal stress to the subcritical core, the number of unwanted “beam trips” should not exceed a few per year, a specification that is several orders of magnitude above usual performance. In order to meet this extremely high reliability, the accelerator needs to implement, to the maximum possible extent, a fault-tolerance strategy that would allow beam operation in the presence of most of the envisaged faults that could occur in its beam line components, and in particular rf systems’ failures. This document describes the results of the simulations performed for the analysis of the fault-tolerance capability of the XT-ADS superconducting linac in the case of an rf cavity failure. A new simulation tool, mixing transient rf behavior of the accelerating cavities with full 6D description of the beam dynamics, has been developed for this purpose. Fast fault-recovery scenarios are proposed, and required research and development is identified.

  10. Linear beam dynamics and ampere class superconducting RF cavities at RHIC

    Science.gov (United States)

    Calaga, Rama R.

    The Relativistic Heavy Ion Collider (RHIC) is a hadron collider designed to collide a range of ions from protons to gold. RHIC operations began in 2000 and has successfully completed five physics runs with several species including gold, deuteron, copper, and polarized protons. Linear optics and coupling are fundamental issues affecting the collider performance. Measurement and correction of optics and coupling are important to maximize the luminosity and sustain stable operation. A numerical approach, first developed at SLAC, was implemented to measure linear optics from coherent betatron oscillations generated by ac dipoles and recorded at multiple beam position monitors (BPMs) distributed around the collider. The approach is extended to a fully coupled 2D case and equivalence relationships between Hamiltonian and matrix formalisms are derived. Detailed measurements of the transverse coupling terms are carried out at RHIC and correction strategies are applied to compensate coupling both locally and globally. A statistical approach to determine BPM reliability and performance over the past three runs and future improvements also discussed. Aiming at a ten-fold increase in the average heavy-ion luminosity, electron cooling is the enabling technology for the next luminosity upgrade (RHIC II). Cooling gold ion beams at 100 GeV/nucleon requires an electron beam of approximately 54 MeV and a high average current in the range of 50-200 mA. All existing e-Coolers are based on low energy DC accelerators. The only viable option to generate high current, high energy, low emittance CW electron beam is through a superconducting energy-recovery linac (SC-ERL). In this option, an electron beam from a superconducting injector gun is accelerated using a high gradient (˜ 20 MV/m) superconducting RF (SRF) cavity. The electrons are returned back to the cavity with a 180° phase shift to recover the energy back into the cavity before being dumped. A design and development of a half

  11. Suppression of multipacting in high power RF couplers operating with superconducting cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ostroumov, P.N., E-mail: ostroumov@frib.msu.edu [Facility for Rare Isotope Beams (FRIB), Michigan State University, East Lansing, MI 48824 (United States); Kazakov, S. [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Morris, D.; Larter, T.; Plastun, A.S.; Popielarski, J.; Wei, J.; Xu, T. [Facility for Rare Isotope Beams (FRIB), Michigan State University, East Lansing, MI 48824 (United States)

    2017-06-01

    Capacitive input couplers based on a 50 Ω coaxial transmission line are frequently used to transmit RF power to superconducting (SC) resonators operating in CW mode. It is well known that coaxial transmission lines are prone to multipacting phenomenon in a wide range of RF power level and operating frequency. The Facility for Rare Isotope Beams (FRIB) being constructed at Michigan State University includes two types of quarter wave SC resonators (QWR) operating at 80.5 MHz and two types of half wave SC resonators (HWR) operating at 322 MHz. As was reported in ref. [1] a capacitive input coupler used with HWRs was experiencing strong multipacting that resulted in a long conditioning time prior the cavity testing at design levels of accelerating fields. We have developed an insert into 50 Ω coaxial transmission line that provides opportunity to bias the RF coupler antenna and protect the amplifier from the bias potential in the case of breakdown in DC isolation. Two of such devices have been built and are currently used for the off-line testing of 8 HWRs installed in the cryomodule.

  12. Niobium superconducting cavity

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    This 5-cell superconducting cavity, made from bulk-Nb, stems from the period of general studies, not all directed towards direct use at LEP. This one is dimensioned for 1.5 GHz, the frequency used at CEBAF and also studied at Saclay (LEP RF was 352.2 MHz). See also 7908227, 8007354, 8209255, 8210054, 8312339.

  13. The LHC superconducting cavities

    CERN Document Server

    Boussard, Daniel; Häbel, E; Kindermann, H P; Losito, R; Marque, S; Rödel, V; Stirbet, M

    1999-01-01

    The LHC RF system, which must handle high intensity (0.5 A d.c.) beams, makes use of superconducting single-cell cavities, best suited to minimizing the effects of periodic transient beam loading. There will be eight cavities per beam, each capable of delivering 2 MV (5 MV/m accelerating field) at 400 MHz. The cavities themselves are now being manufactured by industry, using niobium-on-copper technology which gives full satisfaction at LEP. A cavity unit includes a helium tank (4.5 K operating temperature) built around a cavity cell, RF and HOM couplers and a mechanical tuner, all housed in a modular cryostat. Four-unit modules are ultimately foreseen for the LHC (two per beam), while at present a prototype version with two complete units is being extensively tested. In addition to a detailed description of the cavity and its ancillary equipment, the first test results of the prototype will be reported.

  14. Upgrade of the cryogenic infrastructure of SM18, CERN main test facility for superconducting magnets and RF cavities

    Science.gov (United States)

    Perin, A.; Dhalla, F.; Gayet, P.; Serio, L.

    2017-12-01

    SM18 is CERN main facility for testing superconducting accelerator magnets and superconducting RF cavities. Its cryogenic infrastructure will have to be significantly upgraded in the coming years, starting in 2019, to meet the testing requirements for the LHC High Luminosity project and for the R&D program for superconducting magnets and RF equipment until 2023 and beyond. This article presents the assessment of the cryogenic needs based on the foreseen test program and on past testing experience. The current configuration of the cryogenic infrastructure is presented and several possible upgrade scenarios are discussed. The chosen upgrade configuration is then described and the characteristics of the main newly required cryogenic equipment, in particular a new 35 g/s helium liquefier, are presented. The upgrade implementation strategy and plan to meet the required schedule are then described.

  15. Modern technologies in rf superconductivity

    International Nuclear Information System (INIS)

    Lengeler, H.

    1994-01-01

    The development and application of superconducting rf cavities in particle accelerators is a fine example of advanced technology and of close cooperation with industry. This contribution examines the theoretical and present-day practical limitations of sc cavities and describes some advanced technologies needed for their large scale applications. (orig.)

  16. On a possibility of using a superconducting cavity in the RF system of the storage ring LESR-N100

    CERN Document Server

    Androsov, V P; Telegin, Yu P

    2002-01-01

    In the Kharkov Institute of Physics and Technology the design project of the 200 MeV electron storage ring LESR-N100 is under development. The essential feature of this facility is the large beam energy spread (of about 1%). To ensure a reasonable beam lifetime the RF-system should provide the accelerating voltage of about 0.5 MV, while the total energy losses do not exceed approx 700 eV/turn. The power dissipated in two 700 MHz normal-conducting (NC) cavities much exceeds the power transmitted to the beam. We considered a possibility to use in LESR-N100 a high-Q superconducting RF-cavity (SRF-cavity) in which the dissipated power is the same order of magnitude as the beam-transmitted power. The studies show that the system with SRF-cavity cannot operate in the standard mode when the cavity is matched to the power transmission line at some nominal beam current. The optimal operation mode with high overcoupling is proposed that requires the RF-power one order of magnitude less than in the case of Nc-cavities.

  17. Development of superconducting RF cavity at 1050 MHz frequency for an electron LINAC

    International Nuclear Information System (INIS)

    Sarkar, S.G.; Mondal, J.; Mittal, K.C.

    2011-01-01

    This paper reports the design of a prototype superconducting cavity at 1050 MHz and design of associated die punch and machining fixtures for the cavity fabrication. The cavity is of β= 1 and elliptical in shape. The circle-straight line-ellipse-type structure design has been optimized by 'SUPERFISH' - a 2 dimensional code for cavity tuning. The 3 Dimensional EM field analysis of the cavity structure has been done using 'CST' software. The ratio of the maximum surface electric field to the accelerating gradient, E pk /E acc , is optimised to 1.984 and H pk /E acc is optimised to 4.141 mT/(MV/m). Bore radius of the cavity has been chosen such a way so that the cell-to-cell coupling remains as high as 1.85%. The cavity is designed to achieve 25 MV/m accelerating gradient. (author)

  18. Reducing field emission in the superconducting rf cavities for the next generation of particle accelerators

    International Nuclear Information System (INIS)

    Shu, Q.S.; Hartung, W.; Leibovich, A.; Kirchgessner, J.; Moffat, D.; Padamsee, H.; Rubin, D.; Sears, J.

    1991-01-01

    This paper reports on field emission, which is an obstacle to reaching the higher fields called for in future applications of superconducting radio frequency cavities to particle accelerators. The authors used heat treatment up to 1500 degrees C in an ultra-high vacuum furnace, along with processing of cavities and temperature mapping, to suppress field emission and analyze emitter properties. In 27 tests of 1-cell 1500 MHz fired accelerating cavities, on the average the accelerating field E acc increased to 24 MV/m (H pk = 1250 Oe) from 13 MV/m with chemical treatment alone; the highest E acc reached was 30.5 MV/m

  19. Study of thermal effects in superconducting RF cavities; Etude des effets thermiques dans le cavites supraconductrices

    Energy Technology Data Exchange (ETDEWEB)

    Bousson, S.; Caruette, A.; Fouaidy, M.; Hammoudi, N.; Junquera, T.; Lesrel, J.; Yaniche, J.F. [Services Techniques, Inst. de Physique Nucleaire, Paris-11 Univ., 91 - Orsay (France)

    1999-11-01

    A high speed thermometric system equipped with 64 fixed surface thermometers is used to investigate thermal effects in several 3 GHz cavities. An evaluation of the time response of our thermometers is presented. A method based on RF signal analysis is proposed to evaluate the normal zone propagation rate during thermal breakdown. (authors) 2 refs., 3 figs.

  20. Field emission in RF cavities

    International Nuclear Information System (INIS)

    Bonin, B.

    1996-01-01

    Electron field emission limits the accelerating gradient in superconducting cavities. It is shown how and why it is an important problem. The phenomenology of field emission is then described, both in DC and RF regimes. Merits of a few plausible 'remedies' to field emission are discussed. (author)

  1. Superconducting cavities for HERA

    International Nuclear Information System (INIS)

    Dwersteg, B.; Ebeling, W.; Moeller, W.D.; Renken, D.; Proch, D.; Sekutowicz, J.; Susta, J.; Tong, D.

    1988-01-01

    Superconducting 500 MHz cavities are developed to demonstrate the feasibility of upgrading the e-beam energy of the HERA storage ring. A prototype module with 2 x 4 cell resonators and appropriate fundamental and higher mode couplers has been designed at DESY and is being built by industrial firms. The design and results of RF and cryogenic measurements are reported in detail. 17 references, 10 figures, 2 tables

  2. Mirror-smooth surfaces and repair of defects in superconducting RF cavities by mechanical polishing

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, C. A. [Fermilab; Cooley, L. D. [Fermilab

    2012-11-22

    Mechanical techniques for polishing the inside surface of niobium superconducting radio-frequency (SRF) cavities have been systematically explored. By extending known techniques to fine polishing, mirror-like finishes were produced, with <15 nm RMS (root mean square) roughness over 1 mm2 scan area. This is an order of magnitude less than the typical roughness produced by the electropolishing of niobium cavities. The extended mechanical polishing (XMP) process was applied to several SRF cavities which exhibited equator defects that caused quench at <20 MV m-1 and were not improved by further electropolishing. Cavity optical inspection equipment verified the complete removal of these defects, and minor acid processing, which dulled the mirror finish, restored performance of the defective cells to the high gradients and quality factors measured for adjacent cells when tested with other harmonics. This innate repair feature of XMP could be used to increase manufacturing yield. Excellent superconducting properties resulted after initial process optimization, with quality factor Q of 3 × 1010 and accelerating gradient of 43 MV m-1 being attained for a single-cell TESLA cavity, which are both close to practical limits. Several repaired nine-cell cavities also attained Q > 8 × 109 at 35 MV m-1, which is the specification for the International Linear Collider. Future optimization of the process and pathways for eliminating requirements for acid processing are also discussed.

  3. Study of quality and field limitation of superconducting 1.3 GHz 9-Cell RF-cavities at DESY

    International Nuclear Information System (INIS)

    Schlander, Felix

    2013-01-01

    The European XFEL and the International Linear Collider are based on superconducting rf cavities made of niobium. Their advantages are low ohmic losses which allow high duty cycles and the possibility to use a large beam aperture which is substantial to prevent wake fields at high current accelerators. To reach the theoretical limits of superconducting cavities, it is required to understand the present performance limitations. These are field emission, thermal breakdown (quench) and the ohmic losses dependent on the accelerating field, which are expressed in the quality factor. As the limiting mechanisms themselves are understood in general, the origin of the quench is often unclear. To determine the quench locations, a localisation tool for thermal breakdown using the second sound in superfluid helium has been installed at the cavity test facility at DESY and the results for a sample of about 30 cavities have been examined. The features of the distribution of the quench locations have been analysed and it has been found that the quench locations are in the area of the highest surface magnetic field and not necessarily at the equator of the cells. The data sample has been extended in an attempt to characterise the average behaviour of the quality factor related to the accelerating field. An analysis of the surface resistance of individual cavities shows that a recently developed model for the surface resistance of niobium is not able to describe the measurement in all detail, but the application of an additional mechanism showed promising results.

  4. Study of quality and field limitation of superconducting 1.3 GHz 9-Cell RF-cavities at DESY

    Energy Technology Data Exchange (ETDEWEB)

    Schlander, Felix

    2013-01-15

    The European XFEL and the International Linear Collider are based on superconducting rf cavities made of niobium. Their advantages are low ohmic losses which allow high duty cycles and the possibility to use a large beam aperture which is substantial to prevent wake fields at high current accelerators. To reach the theoretical limits of superconducting cavities, it is required to understand the present performance limitations. These are field emission, thermal breakdown (quench) and the ohmic losses dependent on the accelerating field, which are expressed in the quality factor. As the limiting mechanisms themselves are understood in general, the origin of the quench is often unclear. To determine the quench locations, a localisation tool for thermal breakdown using the second sound in superfluid helium has been installed at the cavity test facility at DESY and the results for a sample of about 30 cavities have been examined. The features of the distribution of the quench locations have been analysed and it has been found that the quench locations are in the area of the highest surface magnetic field and not necessarily at the equator of the cells. The data sample has been extended in an attempt to characterise the average behaviour of the quality factor related to the accelerating field. An analysis of the surface resistance of individual cavities shows that a recently developed model for the surface resistance of niobium is not able to describe the measurement in all detail, but the application of an additional mechanism showed promising results.

  5. Thermal behaviour analysis of SRF cavities and superconducting HOM couplers

    International Nuclear Information System (INIS)

    Fouaidy, M.; Junquera, T.

    1993-01-01

    Two individual papers appear in this report, titled Thermal model calculations in superconducting RF cavities, and Thermal study of HOM couplers for superconducting RF cavities. Both were indexed separately for the INIS database. (R.P.)

  6. Superconducting versus normal conducting cavities

    CERN Document Server

    Podlech, Holger

    2013-01-01

    One of the most important issues of high-power hadron linacs is the choice of technology with respect to superconducting or room-temperature operation. The favour for a specific technology depends on several parameters such as the beam energy, beam current, beam power and duty factor. This contribution gives an overview of the comparison between superconducting and normal conducting cavities. This includes basic radiofrequency (RF) parameters, design criteria, limitations, required RF and plug power as well as case studies.

  7. Comparative Simulation Studies of Multipacting in Higher-Order-Mode Couplers of Superconducting RF Cavities

    International Nuclear Information System (INIS)

    Li, Y. M.; Liu, Kexin; Geng, Rongli

    2014-01-01

    Multipacting (MP) in higher-order-mode (HOM) couplers of the International Linear Collider (ILC) baseline cavity and the Continuous Electron Beam Accelerator Facility (CEBAF) 12 GeV upgrade cavity is studied by using the ACE3P suites, developed by the Advanced Computations Department at SLAC. For the ILC cavity HOM coupler, the simulation results show that resonant trajectories exist in three zones, corresponding to an accelerating gradient range of 0.6A-1.6 MV/m, 21A-34 MV/m, 32A-35 MV/m, and > 40MV/m, respectively. For the CEBAF 12 GeV upgrade cavity HOM coupler, resonant trajectories exist in one zone, corresponding to an accelerating gradient range of 6A-13 MV/m. Potential implications of these MP barriers are discussed in the context of future high energy pulsed as well as medium energy continuous wave (CW) accelerators based on superconducting radio frequency cavities. Frequency scaling of MPA's predicted in HOM couplers of the ILC, CBEAF upgrade, SNS and FLASH third harmonic cavity is given and found to be in good agreement with the analytical result based on the parallel plate model

  8. Comparative simulation studies of multipacting in higher-order-mode couplers of superconducting rf cavities

    Directory of Open Access Journals (Sweden)

    Y. M. Li

    2014-02-01

    Full Text Available Multipacting (MP in higher-order-mode (HOM couplers of the International Linear Collider (ILC baseline cavity and the Continuous Electron Beam Accelerator Facility (CEBAF 12 GeV upgrade cavity is studied by using the ACE3P suites, developed by the Advanced Computations Department at SLAC. For the ILC cavity HOM coupler, the simulation results show that resonant trajectories exist in three zones, corresponding to an accelerating gradient range of 0.6–1.6  MV/m, 21–34   MV/m, 32–35  MV/m and >40  MV/m, respectively. For the CEBAF 12 GeV upgrade cavity HOM coupler, resonant trajectories exist in one zone, corresponding to an accelerating gradient range of 6–13  MV/m. Potential implications of these MP barriers are discussed in the context of future high-energy pulsed as well as medium-energy continuous wave accelerators based on superconducting radio frequency cavities. Frequency scaling of MP’s predicted in HOM couplers of the ILC, CEBAF upgrade, Spallation Neutron Source (SNS, and Free-Electron Laser in Hamburg (FLASH third harmonic cavity is given and found to be in good agreement with the analytical result based on the parallel plate model.

  9. Comparative Simulation Studies of Multipacting in Higher-Order-Mode Couplers of Superconducting RF Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y. M. [Peking University, Beijing (China); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Liu, Kexin [Peking University, Beijing (China); Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2014-02-01

    Multipacting (MP) in higher-order-mode (HOM) couplers of the International Linear Collider (ILC) baseline cavity and the Continuous Electron Beam Accelerator Facility (CEBAF) 12 GeV upgrade cavity is studied by using the ACE3P suites, developed by the Advanced Computations Department at SLAC. For the ILC cavity HOM coupler, the simulation results show that resonant trajectories exist in three zones, corresponding to an accelerating gradient range of 0.6-1.6 MV/m, 21-34 MV/m, 32-35 MV/m, and > 40MV/m, respectively. For the CEBAF 12 GeV upgrade cavity HOM coupler, resonant trajectories exist in one zone, corresponding to an accelerating gradient range of 6-13 MV/m. Potential implications of these MP barriers are discussed in the context of future high energy pulsed as well as medium energy continuous wave (CW) accelerators based on superconducting radio frequency cavities. Frequency scaling of MP's predicted in HOM couplers of the ILC, CBEAF upgrade, SNS and FLASH third harmonic cavity is given and found to be in good agreement with the analytical result based on the parallel plate model.

  10. New results of development on high efficiency high gradient superconducting rf cavities

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Li, Z. K. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Hao, Z. K. [Peking Univ., Beijing (China); Liu, K. X. [Peking Univ., Beijing (China); Zhao, H. Y. [OTIC, Ningxia (China); Adolphsen, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-09-01

    We report on the latest results of development on high-efficiency high-gradient superconducting radio frequency (SRF) cavities. Several 1-cell cavities made of large-grain niobium (Nb) were built, processed and tested. Two of these cavities are of the Low Surface Field (LSF) shape. Series of tests were carried out following controlled thermal cycling. Experiments toward zero-field cooling were carried out. The best experimentally achieved results are Eacc = 41 MV/m at Q0 = 6.5×1010 at 1.4 K by a 1-cell 1.3 GHz large-grain Nb TTF shape cavity and Eacc = 49 MV/m at Q0 = 1.5×1010 at 1.8 K by a 1-cell 1.5 GHz large-grain Nb CEBAF upgrade low-loss shape cavity.

  11. Electron bunch train excited higher-order modes in a superconducting RF cavity

    Science.gov (United States)

    Gao, Yong-Feng; Huang, Sen-Lin; Wang, Fang; Feng, Li-Wen; Zhuang, De-Hao; Lin, Lin; Zhu, Feng; Hao, Jian-Kui; Quan, Sheng-Wen; Liu, Ke-Xin

    2017-04-01

    Higher-order mode (HOM) based intra-cavity beam diagnostics has been proved effective and convenient in superconducting radio-frequency (SRF) accelerators. Our recent research shows that the beam harmonics in the bunch train excited HOM spectrum, which have much higher signal-to-noise ratio than the intrinsic HOM peaks, may also be useful for beam diagnostics. In this paper, we will present our study on bunch train excited HOMs, including a theoretical model and recent experiments carried out based on the DC-SRF photoinjector and SRF linac at Peking University. Supported by National Natural Science Foundation of China (11275014)

  12. Surface characterization of Nb samples electropolished with real superconducting rf accelerator cavities

    Directory of Open Access Journals (Sweden)

    Xin Zhao

    2010-12-01

    Full Text Available We report the results of surface characterizations of niobium (Nb samples electropolished together with a single cell superconducting radio-frequency accelerator cavity. These witness samples were located in three regions of the cavity, namely at the equator, the iris, and the beam pipe. Auger electron spectroscopy was utilized to probe the chemical composition of the topmost four atomic layers. Scanning electron microscopy with energy dispersive x ray for elemental analysis was used to observe the surface topography and chemical composition at the micrometer scale. A few atomic layers of sulfur (S were found covering the samples nonuniformly. Niobium oxide granules with a sharp geometry were observed on every sample. Some Nb-O granules appeared to also contain sulfur.

  13. Submacropulse electron-beam dynamics correlated with higher-order modes in Tesla-type superconducting rf cavities

    Directory of Open Access Journals (Sweden)

    A. H. Lumpkin

    2018-06-01

    Full Text Available We report the direct observations of submacropulse beam centroid oscillations correlated with higher order modes (HOMs which were generated by off-axis electron beam steering in TESLA-type superconducting rf cavities. The experiments were performed at the Fermilab Accelerator Science and Technology (FAST facility using its unique configuration of a photocathode rf gun injecting beam into two separated nine-cell cavities in series with corrector magnets and beam position monitors (BPMs located before, between, and after them. Oscillations of ∼100  kHz in the vertical plane and ∼380  kHz in the horizontal plane with up to 600-μm amplitudes were observed in a 3-MHz micropulse repetition rate beam with charges of 100, 300, 500, and 1000  pC/b. However, the effects were much reduced at 100  pC/b. The measurements were based on HOM detector circuitry targeting the first and second dipole passbands, rf BPM bunch-by-bunch array data, imaging cameras, and a framing camera. Calculations reproduced the oscillation frequencies of the phenomena in the vertical case. In principle, these fundamental results may be scaled to cryomodule configurations of major accelerator facilities.

  14. Effect of the Tuner on the Field Flatness of SNS Superconducting RF Cavities

    CERN Document Server

    Sun, A

    2004-01-01

    Field flatness in a multi-cell superconducting cavity affects not only the net accelerating voltage, but also the peak surface field and the Lorenz Force detuning coefficient. Our measurement indicates that the field flatness changes both external Q of the Fundamental Power Coupler (FPC) and external Q of the Field Probe (FP). The field amplitude tilts linearly to the distance between the cell center and the cavity’s geometry center (pivot point). The tilt rate has been measured in a cryomodule cold (2 K) test, being about 2%/100 kHz, relative the field flatness at the cavity’s center frequency of 805 MHz. Bead-pull measurements confirmed that the field flatness change is 2.0%/100 kHz for a medium β cavity with helium vessel, and 1.72%/100 kHz without helium vessel. These results matched the predictions of simulations using ANSYS and SUPERFISH. A detailed analysis reveals that longitudinal capacitive gap deformation is the main cause of the frequency change. Field flatness change ...

  15. Thermal design studies in superconducting rf cavities: Phonon peak and Kapitza conductance

    Directory of Open Access Journals (Sweden)

    A. Aizaz

    2010-09-01

    Full Text Available Thermal design studies of superconducting radio frequency (SRF cavities involve two thermal parameters, namely the temperature dependent thermal conductivity of Nb at low temperatures and the heat transfer coefficient at the Nb-He II interface, commonly known as the Kapitza conductance. During the fabrication process of the SRF cavities, Nb sheet is plastically deformed through a deep drawing process to obtain the desired shape. The effect of plastic deformation on low temperature thermal conductivity as well as Kapitza conductance has been studied experimentally. Strain induced during the plastic deformation process reduces the thermal conductivity in its phonon transmission regime (disappearance of phonon peak by 80%, which may explain the performance limitations of the defect-free SRF cavities during their high field operations. Low temperature annealing of the deformed Nb sample could not recover the phonon peak. However, moderate temperature annealing during the titanification process recovered the phonon peak in the thermal conductivity curve. Kapitza conductance measurements for the Nb-He II interface for various surface topologies have also been carried out before and after the annealing. These measurements reveal consistently increased Kapitza conductance after the annealing process was carried out in the two temperature regimes.

  16. Nonlinear Near-Field Microwave Microscopy for RF Defect Localization in Nb-Based Superconducting Radio Frequency Cavities

    Science.gov (United States)

    Tai, Tamin

    2011-03-01

    Niobium Superconducting Radio Frequency (SRF) cavities are very sensitive to localized defects that give rise to quenches at high accelerating gradients. In order to identify these defects via scanning microscopy, and to further understand the origins of the quench under high radio frequency excitation (1-3 GHz), a scanning probe with localized and up to ~ 200 mT RF magnetic field is required for low temperature microscopy to achieve sub-micron resolution. For this purpose, we developed a micro loop probe on silicon substrate with outer diameter 20 μ m and inner diameter 17 μ m and successfully fabricated it by lithography. The probe has been used to identify a signal arising from the nonlinear Meissner effect in a Nb thin film. In addition, a magnetic write head is another promising candidate to achieve this goal of understanding localized defect behavior under high RF magnetic field at low temperatures. We will discuss and compare both types of probe for nonlinear scanning microscopy and RF defect localization in superconductors. We acknowledge the support of DOE/HEP.

  17. Surface Characterization of Impurities in Superconducting Niobium for Radio Frequency (RF) Cavities used in Particle Accelerators

    Science.gov (United States)

    Maheshwari, Prateek

    Niobium (Nb) is the material of choice for Superconducting Radio Frequency (SRF) Cavities used in particle accelerators owing to its high critical temperature (Tc = 9.2 K) and critical magnetic field (≈ 200mT). However, niobium tends to harbor interstitial impurities such as H, C, O and N, which are detrimental to cavity performance. Since the magnetic field penetration depth (lambda) of niobium is 40nm, it is important to characterize these impurities using surface characterization techniques. Also, it is known that certain heat treatments improve cavity efficiency via interstitial impurity removal from the surface of niobium. Thus, a systematic study on the effect of these heat treatments on the surface impurity levels is needed. In this work, surface analysis of both heat treated and non heat treated (120°C-1400°C) large grain (single crystal) bulk niobium samples was performed using secondary ion mass spectrometry (SIMS) and Transmission Electron Microscopy (TEM). Impurity levels were compared on the surface using SIMS after various types of heat treatments expected to improve cavity performance, and the effect of these heat treatments on the surface impurities were examined. SIMS characterization of ion implanted standards of C, N, O, D showed that quantification of C, N and O impurities in Nb is achievable and indicated that H is very mobile in Nb. It was hence determined that quantification of H in Nb is not possible using SIMS due to its high diffusivity in Nb. However, a comparative study of the high temperature heat treated (600°C-1400°C) and non heat treated (control) samples revealed that hydrogen levels decreased by upto a factor of 100. This is attributed to the dissociation of the niobium surface oxide layer, which acts as a passivating film on the surface, and subsequent desorption of hydrogen. Reformation of this oxide layer on cool down disallows any re-absorption of hydrogen, indicating that the oxide acts as a surface barrier for

  18. Plasma treatment of bulk niobium surface for superconducting rf cavities: Optimization of the experimental conditions on flat samples

    Directory of Open Access Journals (Sweden)

    M. Rašković

    2010-11-01

    Full Text Available Accelerator performance, in particular the average accelerating field and the cavity quality factor, depends on the physical and chemical characteristics of the superconducting radio-frequency (SRF cavity surface. Plasma based surface modification provides an excellent opportunity to eliminate nonsuperconductive pollutants in the penetration depth region and to remove the mechanically damaged surface layer, which improves the surface roughness. Here we show that the plasma treatment of bulk niobium (Nb presents an alternative surface preparation method to the commonly used buffered chemical polishing and electropolishing methods. We have optimized the experimental conditions in the microwave glow discharge system and their influence on the Nb removal rate on flat samples. We have achieved an etching rate of 1.7  μm/min⁡ using only 3% chlorine in the reactive mixture. Combining a fast etching step with a moderate one, we have improved the surface roughness without exposing the sample surface to the environment. We intend to apply the optimized experimental conditions to the preparation of single cell cavities, pursuing the improvement of their rf performance.

  19. Flux trapping in superconducting cavities

    International Nuclear Information System (INIS)

    Vallet, C.; Bolore, M.; Bonin, B.; Charrier, J.P.; Daillant, B.; Gratadour, J.; Koechlin, F.; Safa, H.

    1992-01-01

    The flux trapped in various field cooled Nb and Pb samples has been measured. For ambient fields smaller than 3 Gauss, 100% of the flux is trapped. The consequences of this result on the behavior of superconducting RF cavities are discussed. (author) 12 refs.; 2 figs

  20. Development of a multi-scale simulation model of tube hydroforming for superconducting RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H.S. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States); Sumption, M.D., E-mail: sumption.3@osu.edu [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States); Bong, H.J. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States); Lim, H. [Sandia National Laboratories, Albuquerque, NM (United States); Collings, E.W. [Department of Materials Science and Engineering, The Ohio State University, Columbus, OH (United States)

    2017-01-02

    This work focuses on finite element modeling of the hydroforming process for niobium tubes intended for use in superconducting radio frequency (SRF) cavities. The hydroforming of tubular samples into SRF-relevant shapes involves the complex geometries and loading conditions which develop during the deformation, as well as anisotropic materials properties. Numerical description of the process entails relatively complex numerical simulations. A crystal plasticity (CP) model was constructed that included the evolution of crystallographic orientation during deformation as well as the anisotropy of tubes in all directions and loading conditions. In this work we demonstrate a multi-scale simulation approach which uses both microscopic CP and macroscopic continuum models. In this approach a CP model (developed and implemented into ABAQUS using UMAT) was used for determining the flow stress curve only under bi-axial loading in order to reduce the computing time. The texture of the materials obtained using orientation imaging microscopy (OIM) and tensile test data were inputs for this model. Continuum FE analysis of tube hydroforming using the obtained constitutive equation from the CP modeling was then performed and compared to the results of hydraulic bulge testing. The results show that high quality predictions of the deformation under hydroforming of Nb tubes can be obtained using CP-FEM based on their known texture and the results of tensile tests. The importance of the CP-FEM based approach is that it reduces the need for hydraulic bulge testing, using a relatively simple computational approach.

  1. Development of a multi-scale simulation model of tube hydroforming for superconducting RF cavities

    International Nuclear Information System (INIS)

    Kim, H.S.; Sumption, M.D.; Bong, H.J.; Lim, H.; Collings, E.W.

    2017-01-01

    This work focuses on finite element modeling of the hydroforming process for niobium tubes intended for use in superconducting radio frequency (SRF) cavities. The hydroforming of tubular samples into SRF-relevant shapes involves the complex geometries and loading conditions which develop during the deformation, as well as anisotropic materials properties. Numerical description of the process entails relatively complex numerical simulations. A crystal plasticity (CP) model was constructed that included the evolution of crystallographic orientation during deformation as well as the anisotropy of tubes in all directions and loading conditions. In this work we demonstrate a multi-scale simulation approach which uses both microscopic CP and macroscopic continuum models. In this approach a CP model (developed and implemented into ABAQUS using UMAT) was used for determining the flow stress curve only under bi-axial loading in order to reduce the computing time. The texture of the materials obtained using orientation imaging microscopy (OIM) and tensile test data were inputs for this model. Continuum FE analysis of tube hydroforming using the obtained constitutive equation from the CP modeling was then performed and compared to the results of hydraulic bulge testing. The results show that high quality predictions of the deformation under hydroforming of Nb tubes can be obtained using CP-FEM based on their known texture and the results of tensile tests. The importance of the CP-FEM based approach is that it reduces the need for hydraulic bulge testing, using a relatively simple computational approach.

  2. RF superconductivity at CEBAF

    International Nuclear Information System (INIS)

    1990-01-01

    The Continuous Electron Beam Accelerator Facility (CEBAF) is a 4 GeV continuous beam electron accelerator being constructed to perform nuclear physics research. Construction began in February 1987 and initial operation is scheduled for February 1994. The present report describes its prototyping, problems/solutions, further development, facilities, design status, production and upgrade potential. The accelerator is 1.4 km in circumference, and has a race-track shape. It is of the recirculated linear accelerator type, and employs a total of five passes. Two linacs on opposite sides of the race-track each provide 400 MeV per pass. Beams of various energies are transported by separated arcs at each end of the straight sections to provide the recirculation. There are 4 recirculation arcs at the injector end, and 5 arcs at the other end. The full energy beam is routed by an RF separator to between one and three end stations, as desired, on a bucket-by-bucket basis. The average output beam current is 200 microamperes. Acceleration is provided by 338 superconducting cavities, which are arranged in pairs, each of which is enclosed in a helium vessel and suspended inside a vacuum jacket without ends. (N.K.)

  3. SPS RF Accelerating Cavity

    CERN Multimedia

    1979-01-01

    This picture shows one of the 2 new cavities installed in 1978-1979. The main RF-system of the SPS comprises four cavities: two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3). These cavities are of the travelling-wave type operating at a centre frequency of 200.2 MHz. They are wideband, filling time about 700 ns and untuned. The power amplifiers, using tetrodes are installed in a surface building 200 m from the cavities. Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979. The number of power amplifiers was also increased: to the first 2 MW plant a second 2 MW plant was added and by end 1979 there were 8 500 kW units combined in pairs to feed each of the 4 cavities with up to about 1 MW RF power, resulting in a total accelerating voltage of about 8 MV. See also 7412016X, 7412017X, 7411048X

  4. AC/RF Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, G [Jefferson Lab (United States)

    2014-07-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  5. AC/RF Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi [JLAB

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  6. Technical tasks in superconducting cavities

    Energy Technology Data Exchange (ETDEWEB)

    Saito, Kenji [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan)

    1997-11-01

    The feature of superconducting rf cavities is an extremely small surface resistance on the wall. It brings a large energy saving in the operation, even those are cooled with liquid helium. That also makes possible to operate themselves in a higher field gradient comparing to normal conducting cavities, and brings to make accelerators compact. These merits are very important for the future accelerator engineering which is planed at JAERI for the neutron material science and nuclear waste transmutation. This machine is a high intensity proton linac and uses sc cavities in the medium and high {beta} sections. In this paper, starting R and D of proton superconducting cavities, several important technical points which come from the small surface resistance of sc cavities, are present to succeed it and also differences between the medium and high - {beta} structures are discussed. (author)

  7. ISR RF cavities

    CERN Multimedia

    1983-01-01

    In each ISR ring the radiofrequency cavities were installed in one 9 m long straight section. The RF system of the ISR had the main purpose to stack buckets of particles (most of the time protons)coming from the CPS and also to accelerate the stacked beam. The installed RF power per ring was 18 kW giving a peak accelerating voltage of 20 kV. The system had a very fine regulation feature allowing to lower the voltage down to 75 V in a smooth and well controlled fashion.

  8. Baking effect on Niobium superconducting RF cavities and its physical interpretation

    Energy Technology Data Exchange (ETDEWEB)

    Saito, K. [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan); Kneisel, P. [Thomas Jefferson Accelerator Facility, VA, (United States)

    2000-07-01

    Recently a very surprising phenomenon has been discovered at JLab and Saclay with chemically polished niobium cavities, which the baking during vacuum evacuation has benefits to improve the cavity performance: high Q and high gradient. We have confirmed the same effect on the electropolished niobium cavities. We have analyzed the temperature dependence of the surface resistance in order to understand this effect in the frame or BCS theory. In this paper these results will be presented. (author)

  9. Proposal to negotiate a collaboration agreement related to the application of novel cavity fabrication techniques and Nb/Cu sputter coating technology in the field of superconducting RF for the Future Circular Collider (FCC) study

    CERN Document Server

    2015-01-01

    Proposal to negotiate a collaboration agreement related to the application of novel cavity fabrication techniques and Nb/Cu sputter coating technology in the field of superconducting RF for the Future Circular Collider (FCC) study

  10. Investigation of Plasma Etching for Superconducting RF Cavities Surface Preparation. Final Report

    International Nuclear Information System (INIS)

    Vuskovic, Leposava

    2009-01-01

    Our results show that plasma-treated samples are comparable or superior to a BCP sample, both in the size of features and sharpness of the boundaries between individual features at the surface. Plasma treatment of bulk Nb cavities is a promising technique for microwave cavities preparation used in particle acceleration application. Etching rates are sufficiently high to enable efficient removal of mechanically damaged surface layer with high reproducibility. No impurities are deposited on the bulk Nb surface during plasma treatment. Surface topology characteristic are promising for complex cavity geometry, since discharge conforms the profile of the reaction chamber. In view of these experimental results, we propose plasma treatment for producing microwave cavities with high Q factor instead of using bulk Nb treated with wet etching process.

  11. Superconducting RF activities at Cornell University

    International Nuclear Information System (INIS)

    Kirchgessner, J.; Moffat, D.; Padamsee, H.; Rubin, D.; Sears, J.; Shu, Q.S.

    1990-01-01

    This paper outlines the RF superconductivity research and development work that has taken place at Cornell Laboratory of Nuclear Studies over the past years. The work that has been performed since the last RF superconductivity workshop is emphasized together with a discussion of the direction of future efforts. Past work is summarized first, focusing on research and development activities in the area of RF superconductivity. Superconducting TeV linear collider is then discussed focusing on the application of superconducting RF to a future TeV linear collider. Linear collider structure development is then described centering on the development of a simpler (thereby cheaper) structure for a TeV linear collider. B-factory with superconducting RF is outlined focusing on the formulation of a conceptual design for a B-factory. B-factory structure development is discussed in relation to the advancement in the capability of SC cavities to carry beam currents of several amperes necessary for a high luminosity storage ring. High gradients are discussed as the key to the realization of a high energy superconducting linac or a superconducting RF B-factory. (N.K.)

  12. Status of RF superconductivity at Argonne

    International Nuclear Information System (INIS)

    Shepard, K.W.

    1990-01-01

    Development of a superconducting slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first superconducting heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerator System). The Physics Division at ANL has continued to develop superconducting RF technology for accelerating heavy-ions, with the result that the linac has been in an almost continuous process of upgrade and expansion. In 1987, the Engineering Physics Division at ANL began developing of superconducting RF components for the acceleration of high-brightness proton and deuterium beams. The two divisions collaborate in work on several applications of RF superconductivity, and also in work to develop the technology generally. The present report briefly describes major features of the superconducting heavy-ion linac (very-low-velocity superconducting linac, positive ion injector), proton accelerating structures (superconducting resonant cavities for acceleration of high-current proton and deuteron beams, RF properties of oxide superconductors), and future work. Both divisions expect to continue a variety of studies, frequently in collaboration, to advance the basic technology of RF superconductivity. (N.K.)

  13. Superconducting RF for energy-recovery linacs

    International Nuclear Information System (INIS)

    Liepe, M.; Knobloch, J.

    2006-01-01

    Since superconducting RF for particle accelerators made its first appearance in the 1970s, it has found highly successful application in a variety of machines. Recent progress in this technology has made so-called Energy-Recovery Linacs (ERLs)-originally proposed in 1965-feasible, and interest in this type of machine has increased enormously. A superconducting linac is the driving heart of ERLs, and emittance preservation and cost efficiency is of utmost importance. The resulting challenges for the superconducting cavity technology and RF field control are manifold. In March 2005 the first international workshop on ERLs was held at Newport News, VA, to explore the potential of ERLs and to discuss machine-physics and technology challenges and their solutions. This paper reviews the state-of-the-art in superconducting RF and RF control for ERLs, and summarizes the discussions of the SRF working group on this technology during the ERL2005 workshop

  14. R&D for the Post-EP Processes of Superconducting RF Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Saeki, Takayuki [KEK; Funahashi, Y. [KEK; Hayano, H. [KEK; Kato, Seigo [KEK; Nishiwaki, Michiru [KEK; Sawabe, Motoaki [KEK; Ueno, Kenji [KEK; Watanabe, K. [KEK; Antoine, Claire [CEA, Gif-sur-Yvette; Berry, Stefurn [CEA, Gif-sur-Yvette; Eozenou, F. [CEA, Gif-sur-Yvette; Gasser, Y. [CEA, Gif-sur-Yvette; Visentin, B. [CEA, Gif-sur-Yvette; Clemens, William A. [JLAB; Geng, Rongli [JLAB; Manus, Robert [JLAB; Tyagi, Puneet [GUAS/AS, Ibaraki

    2009-11-01

    The Electro-Polishing (EP) process is the best candidate of final surface treatment for the production of ILC cavities. Nevertheless, the broad distribution of the gradient caused by field emitters in cavities is sitll a serious problem for the EP process. A candidate source of field emitter is the sulfur component which is produced in the EP process and remains the inner-surface of cavities. We studied the effect of Ethanole- and degreaser-rinse processes after the EP process by a unique method. Moreover, we tried to test the sponge cleaning as the post-EP process to remove the field emitter inside the cavcity. This article describe the results of series tests of the post-EP process at KEK.

  15. Designing focusing solenoids for superconducting RF accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Davis, G.; Kashikhin, V.V.; Page, T.; Terechkine, I.; Tompkins, J.; Wokas, T.; /Fermilab

    2006-08-01

    The design of a focusing solenoid for use in a superconducting RF linac requires resolving a range of problems with conflicting requirements. Providing the required focusing strength contradicts the goal of minimizing the stray field on the surfaces of adjacent superconducting RF cavities. The requirement of a compact solenoid, able to fit into a gap between cavities, contradicts the need of mechanical support necessary to restrain electromagnetic forces that can result in coil motion and subsequent quenching. In this report we will attempt to address these and other issues arising during the development of focusing solenoids. Some relevant test data will also be presented.

  16. Superconducting rf activities at Cornell University

    International Nuclear Information System (INIS)

    Padamsee, H.; Hakimi, M.; Kirchgessner, J.

    1988-01-01

    Development of rf superconductivity for high energy accelerators has been a robust activity at the Cornell Laboratory of Nuclear Studies (LNS) for many years. In order to realize the potential of rf superconductivity, a two-pronged approach has been followed. On the one hand accelerator applications were selected where the existing state-of-the art of superconducting rf is competitive with alternate technologies, then LNS engaged in a program to design, construct and test suitable superconducting cavities, culminating in a full system test in an operating accelerator. On the second front the discovery and invention of ideas, techniques and materials required to make superconducting rf devices approach the ideal in performance has been aggressively pursued. Starting with the development of superconducting cavities for high energy electron synchrotrons, the technology was extended to high energy e + e - storage rings. The LE5 cavity design has now been adopted for use in the Continuous Electron Beam Accelerator Facility (CEBAF). When completed, this project will be one of the largest applications of SRF technology, using 440 LE5 modules[4]. In the last two years, the cavity design and the technology have been transferred to industry and CEBAF. Cornell has tested the early industrial prototypes and cavity pairs. LNS has developed, in collaboration with CEBAF, designs and procedures for cavity pair and cryomodule assembly and testing. Advanced research for future electron accelerators is badly needed if particle physicists hope to expand the energy frontier. Superconducting cavity technology continues to offer attractive opportunities for further advances in achievable voltage at reasonable cost for future accelerators. For Nb, the full potential implies an order of magnitude increase over current capabilities. 20 references, 11 figures

  17. Study of field-limiting defects in superconducting RF cavities for electron-accelerators

    International Nuclear Information System (INIS)

    Aderhold, Sebastian

    2015-02-01

    Superconducting radio-frequency resonators made from niobium are an integral part of many accelerator projects. Their main advantage are the low ohmic losses resulting in the possibility for a long pulse structure and high duty cycles up to continous wave (cw) operation. The European X-Ray Free-Electron Laser (XFEL) and the International Linear Collider (ILC) are based on this technology. In some cases the resonators reach accelerating electric fields close to the theoretical limit of bulk niobium. Yet most resonators are limited at lower fields and mass production for large scale accelerator projects suffers from the spread in the achievable gradient per resonator. The main limitations are field emission and the breakdown of superconductivity (quench). While field emission is mostly attributed to the overall surface cleanliness of the resonator, quench is usually associated with local defects. Optical inspection of the inner surface of the resonators with unprecedented resolution, accuracy and a special illumination has been established at DESY and used to study such local surface defects. More than 30 resonators have been inspected. Distinctive features from these inspections have been catalogued and assessed for their potential risk for the performance of the resonator. Several confirmed quenching defects could be extracted for further analysis and could be traced back to likely origins in the production process. A new, automated set-up for optical inspection of large series of resonators, named OBACHT, has been developed and successfully commissioned. Its design includes the minimal need for operator interference, reproducibility, robustness and versatility, in order to fit the requirements for application both in a laboratory and in a production environment. To facilitate the comparison of the results obtained during the global R and D effort on resonators for the ILC, the ILC global yield database has been established. The yield and selection rules for the

  18. Superconducting elliptical cavities

    CERN Document Server

    Sekutowicz, J K

    2011-01-01

    We give a brief overview of the history, state of the art, and future for elliptical superconducting cavities. Principles of the cell shape optimization, criteria for multi-cell structures design, HOM damping schemes and other features are discussed along with examples of superconducting structures for various applications.

  19. Higher order mode damping in a five-cell superconducting rf cavity with a photonic band gap coupler cell

    Science.gov (United States)

    Arsenyev, Sergey A.; Temkin, Richard J.; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Boulware, Chase H.; Grimm, Terry L.; Rogacki, Adam R.

    2016-08-01

    We present a study of higher order mode (HOM) damping in the first multicell superconducting radio-frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving higher average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery linacs (ERLs). Beam current in ERLs is limited by the beam breakup instability, caused by parasitic HOMs interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The five-cell cavity with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. The measurements agreed well with the simulations.

  20. Higher order mode damping in a five-cell superconducting rf cavity with a photonic band gap coupler cell

    Directory of Open Access Journals (Sweden)

    Sergey A. Arsenyev

    2016-08-01

    Full Text Available We present a study of higher order mode (HOM damping in the first multicell superconducting radio-frequency (SRF cavity with a photonic band gap (PBG coupler cell. Achieving higher average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery linacs (ERLs. Beam current in ERLs is limited by the beam breakup instability, caused by parasitic HOMs interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The five-cell cavity with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. The measurements agreed well with the simulations.

  1. New achievements in RF cavity manufacturing

    International Nuclear Information System (INIS)

    Lippmann, G.; Pimiskern, K.; Kaiser, H.

    1993-01-01

    Dornier has been engaged in development, manufacturing and testing of Cu-, Cu/Nb- and Nb-cavities for many years. Recently, several different types of RF cavities were manufactured. A prototype superconducting (s.c.) B-Factory accelerating cavity (1-cell, 500 MHz) was delivered to Cornell University, Laboratory of Nuclear Studies. A second lot of 6 s.c. cavities (20-cell, 3000 MHz) was fabricated on contract from Technical University of Darmstadt for the S-DALINAC facility. Finally, the first copper RF structures (9-cell, 1300 MHz) for TESLA were finished and delivered to DESY, two s.c. niobium structures of the same design are in production. Highlights from the manufacturing processes of these cavities are described and first performance results will be reported

  2. Superconducting cavity development at RRCAT

    International Nuclear Information System (INIS)

    Joshi, S.C.

    2015-01-01

    Raja Ramanna Centre for Advanced Technology (RRCAT), Indore pursuing a program on 'R and D Activities for High Energy Proton Linac based Spallation Neutron Source'. Spallation neutron source (SNS) facility will provide high flux pulse neutrons for research in the areas of condensed matter physics, materials science, chemistry, biology and engineering. This will complement the existing synchrotron light source facility, INDUS-2 at RRCAT and reactor based neutron facilities at BARC. RRCAT is also participating in approved mega project on 'Physics and Advanced Technology for High Intensity Proton Accelerator' to support activities of Indian Institutions - Fermilab Collaboration (IIFC). The SNS facility will have a 1 GeV superconducting proton injector linac and 1 GeV accumulator ring. The linac will comprise of large number of superconducting radio-frequency (SCRF) cavities operating at different RF frequencies housed in suitable cryomodules. Thus, an extensive SCRF cavity infrastructure setup is being established. In addition, a scientific and technical expertise are also being developed for fabrication, processing and testing of the SCRF cavities for series production. The paper presents the status of superconducting cavity development at RRCAT

  3. Materials for superconducting cavities

    International Nuclear Information System (INIS)

    Bonin, B.

    1996-01-01

    The ideal material for superconducting cavities should exhibit a high critical temperature, a high critical field, and, above all, a low surface resistance. Unfortunately, these requirements can be conflicting and a compromise has to be found. To date, most superconducting cavities for accelerators are made of niobium. The reasons for this choice are discussed. Thin films of other materials such as NbN, Nb 3 Sn, or even YBCO compounds can also be envisaged and are presently investigated in various laboratories. It is shown that their success will depend critically on the crystalline perfection of these films. (author)

  4. Pulsed rf superconductivity program at SLAC

    International Nuclear Information System (INIS)

    Campisi, I.E.; Farkas, Z.D.

    1984-08-01

    Recent tests performed at SLAC on superconducting TM 010 caavities using short rf pulses (less than or equal to 2.5 μs) have established that at the cavity surface magnetic fields can be reached in the vicinity of the theoretical critical fields without an appreciable increase in average losses. Tests on niobium and lead cavities are reported. The pulse method seems to be best suited to study peak field properties of superconductors in the microwave band, without the limitations imposed by defects. The short pulses also seem to be more effective in decreasing the causes of field emission by rf processing. Applications of the pulsed rf superconductivity to high-gradient linear accelerators are also possible

  5. Microscopic investigation of RF surfaces of 3 GHz niobium accelerator cavities following RF processing

    International Nuclear Information System (INIS)

    Graber, J.; Barnes, P.; Flynn, T.; Kirchgessner, J.; Knobloch, J.; Moffat, D.; Muller, H.; Padamsee, H.; Sears, J.

    1993-01-01

    RF processing of Superconducting accelerating cavities is achieved through a change in the electron field emission (FE) characteristics of the RF surface. The authors have examined the RF surfaces of several single-cell 3 GHz cavities, following RF processing, in a Scanning Electron Microscope (SEM). The RF processing sessions included both High Peak Power (P ≤ 50 kW) pulsed processing, and low power (≤ 20 W) continuous wave processing. The experimental apparatus also included a thermometer array on the cavity outer wall, allowing temperature maps to characterize the emission before and after RF processing gains. Multiple sites have been located in cavities which showed improvements in cavity behavior due to RF processing. Several SEM-located sites can be correlated with changes in thermometer signals, indicating a direct relationship between the surface site and emission reduction due to RF processing. Information gained from the SEM investigations and thermometry are used to enhance the theoretical model of RF processing

  6. Status report on CERN activities aiming at the production of sputter-coated copper superconducting RF cavities for LEP

    International Nuclear Information System (INIS)

    Benvenuti, C.; Bloess, D.; Chiaveri, E.; Hilleret, N.; Minestrini, M.; Weingarten, W.

    1990-01-01

    To upgrade LEP energy above 55 GeV, the first step will consist in installing 32 SC cavities of 352 MHz frequency at Point 2 of the machine. This operation will be carried out in steps and should be completed by the end of 1991. It has been decided that 8 of the 32 cavities will be Nb coated copper cavities, the crucial part of which (i.e. the cavity proper) will be manufactured and coated at CERN. For the time being, 4 of these 8 cavities have been prepared. They present Q 0 values at low field of about 10 10 , while at the specified operating field of 5 MV/m their Q 0 range between 5 and 7 x 10 9 . In order to carry out assembly, coating and rinsing of cavities in better (i.e. cleaner) conditions, an experimental hall is being prepared, which will become operational after summer 1989, such as to be used for the manufacturing of the second batch of 4 coated cavities. In parallel with this main activity, some work is also being devoted to the study of coatings of higher T c materials, namely NbTiN. Due to the higher T c , these new coatings should present a lower BCS RF resistivity, a necessary condition to obtain higher Q 0 values. The first cavity coated so far with NbTiN (a single cell cavity of 500 MHz frequency) gave encouraging results, which however are not better than what was obtained with a Nb film. (author)

  7. Impact of cool-down conditions at T_{c} on the superconducting rf cavity quality factor

    Directory of Open Access Journals (Sweden)

    J.-M. Vogt

    2013-10-01

    Full Text Available Many next-generation, high-gradient accelerator applications, from energy-recovery linacs to accelerator-driven systems (ADS rely on continuous wave (CW operation for which superconducting radio-frequency (SRF systems are the enabling technology. However, while SRF cavities dissipate little power, they must be cooled by liquid helium and for many CW accelerators the complexity as well as the investment and operating costs of the cryoplant can prove to be prohibitive. We investigated ways to reduce the dynamic losses by improving the residual resistance (R_{res} of niobium cavities. Both the material treatment and the magnetic shielding are known to have an impact. In addition, we found that R_{res} can be reduced significantly when the cool-down conditions during the superconducting phase transition of the niobium are optimized. We believe that not only do the cool-down conditions impact the level to which external magnetic flux is trapped in the cavity but also that thermoelectric currents are generated which in turn create additional flux that can be trapped. Therefore, we investigated the generation of flux and the dynamics of flux trapping and release in a simple model niobium-titanium system that mimics an SRF cavity in its helium tank. We indeed found that thermal gradients along the system during the superconducting transition can generate a thermoelectric current and magnetic flux, which subsequently can be trapped. These effects may explain the observed variation of the cavity’s R_{res} with cool-down conditions.

  8. LEP superconducting cavity

    CERN Multimedia

    1995-01-01

    Engineers work in a clean room on one of the superconducting cavities for the upgrade to the LEP accelerator, known as LEP-2. The use of superconductors allow higher electric fields to be produced so that higher beam energies can be reached.

  9. A new measurement tool for characterization of superconducting rf accelerator cavities using high-performance LTS SQUIDs

    Energy Technology Data Exchange (ETDEWEB)

    Vodel, W [Friedrich-Schiller-University Jena, Helmholtzweg 5, 07743 Jena (Germany); Neubert, R [Friedrich-Schiller-University Jena, Helmholtzweg 5, 07743 Jena (Germany); Nietzsche, S [Friedrich-Schiller-University Jena, Helmholtzweg 5, 07743 Jena (Germany); Seidel, P [Friedrich-Schiller-University Jena, Helmholtzweg 5, 07743 Jena (Germany); Knaack, K [DESY Hamburg (Germany); Wittenburg, K [DESY Hamburg (Germany); Peters, A [Heidelberger Ionenstrahl-Therapiezentrum, Heidelberg (Germany)

    2007-11-15

    This paper presents a new system to measure very low currents in an accelerator environment, using a cryogenic current comparator (CCC). In principle a CCC is a conventional current transformer using the high-performance SQUID technology to sense the magnetic fields caused by the beam current. Since the system is sensitive on a pA level, it is an optimum device to detect dark currents of superconducting cavities. The system presented here is designed for the test facilities of the superconducting accelerator modules for the European XFEL at the Deutsches Elektronen-Synchrotron (DESY) in Hamburg. Measurements in a quiet environment showed that an intrinsic noise level of the CCC of 40 pA Hz{sup -1/2} could be achieved.

  10. Beam tests and operation of superconducting cavities

    International Nuclear Information System (INIS)

    Akai, Kazunori

    1990-01-01

    Beam tests and operation of superconducting cavities conducted since the third workshop on RF superconductivity (Argonne, Sep. 1987) are reported in this paper. The paper is concerned particularly with electron machines. Storage and acceleration of the beam are discussed, focusing on the CERN test in SPS, the DESY test in PETRA, the superconducting injector at Darmstadt, and the KEK beam tests in T-AR. Then, long-term performance of the cavity in the ring is discussed focusing on Eacc (max) and O-value, environmental conditions, and operational experience in T-MR. RF controllability is addressed, centering on the Robinson stability, cavity tuning loop, quench detection and interlocks, recovery procedure, field calibration, and phase adjustment. Higher order modes are also discussed. Superconducting cavities have been operated successfully in accelerators. It has been confirmed that the superconducting cavities can be used stably for experimental use. For more than 5000 hours the cavities have indicated no essential degradation of the cavity performance. The study of long-term performance should be continued in longer range of period. (N.K.)

  11. Superconducting niobium in high rf magnetic fields

    International Nuclear Information System (INIS)

    Mueller, G.

    1988-01-01

    The benefit of superconducting cavities for accelerator applications depends on the field and Q/sub 0/ levels which can be achieved reliably in mass producible multicell accelerating structures. The presently observed field and Q/sub 0/ limitations are caused by anomalous loss mechanisms which are not correlated with the intrinsic properties of the pure superconductor but rather due to defects or contaminants on the superconducting surface. The ultimate performance levels of clean superconducting cavities built from pure Nb will be given by the rf critical field and the surface resistance of the superconductor. In the first part of this paper a short survey is given of the maximum surface magnetic fields achieved in single-cell cavities. The results of model calculations for the thermal breakdown induced by very small defects and for the transition to the defect free case is discussed in part 2. In the last chapter, a discussion is given for the rf critical field of Nb on the basis of the Ginzburg-Landau Theory. It is shown that not only purity but also the homogeneity of the material should become important for the performance of superconducting Nb cavities at field levels beyond 100mT. Measurement results of the upper critical field for different grades of commercially available Nb sheet materials are given. 58 references, 20 figures, 1 table

  12. Investigation of superconducting niobium 1170 MHz cavities

    International Nuclear Information System (INIS)

    Anashin, V.V.; Bibko, S.I.; Fadeyev, E.I.

    1988-01-01

    The design, fabrication and experiments with superconducting L-band single cell cavities are described. These cavities model a cell of an accelerating RF structure. The cavities have been fabricated from technical grade and higher purity grade sheet niobium using deep-drawing, electron beam welding and chemical polishing. They have spherical geometry and are excited in the TM 010 mode. A computerized set-up was used for cavity tests. Qo=1.5 x 10 9 and E acc = 4.3 MV/m were obtained in the cavity made of higher purity grade niobium. 6 references, 8 figures, 3 tables

  13. Demonstration of superconducting micromachined cavities

    Energy Technology Data Exchange (ETDEWEB)

    Brecht, T., E-mail: teresa.brecht@yale.edu; Reagor, M.; Chu, Y.; Pfaff, W.; Wang, C.; Frunzio, L.; Devoret, M. H.; Schoelkopf, R. J. [Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States)

    2015-11-09

    Superconducting enclosures will be key components of scalable quantum computing devices based on circuit quantum electrodynamics. Within a densely integrated device, they can protect qubits from noise and serve as quantum memory units. Whether constructed by machining bulk pieces of metal or microfabricating wafers, 3D enclosures are typically assembled from two or more parts. The resulting seams potentially dissipate crossing currents and limit performance. In this letter, we present measured quality factors of superconducting cavity resonators of several materials, dimensions, and seam locations. We observe that superconducting indium can be a low-loss RF conductor and form low-loss seams. Leveraging this, we create a superconducting micromachined resonator with indium that has a quality factor of two million, despite a greatly reduced mode volume. Inter-layer coupling to this type of resonator is achieved by an aperture located under a planar transmission line. The described techniques demonstrate a proof-of-principle for multilayer microwave integrated quantum circuits for scalable quantum computing.

  14. Additive Manufactured Superconducting Cavities

    Science.gov (United States)

    Holland, Eric; Rosen, Yaniv; Woolleet, Nathan; Materise, Nicholas; Voisin, Thomas; Wang, Morris; Mireles, Jorge; Carosi, Gianpaolo; Dubois, Jonathan

    Superconducting radio frequency cavities provide an ultra-low dissipative environment, which has enabled fundamental investigations in quantum mechanics, materials properties, and the search for new particles in and beyond the standard model. However, resonator designs are constrained by limitations in conventional machining techniques. For example, current through a seam is a limiting factor in performance for many waveguide cavities. Development of highly reproducible methods for metallic parts through additive manufacturing, referred to colloquially as 3D printing\\x9D, opens the possibility for novel cavity designs which cannot be implemented through conventional methods. We present preliminary investigations of superconducting cavities made through a selective laser melting process, which compacts a granular powder via a high-power laser according to a digitally defined geometry. Initial work suggests that assuming a loss model and numerically optimizing a geometry to minimize dissipation results in modest improvements in device performance. Furthermore, a subset of titanium alloys, particularly, a titanium, aluminum, vanadium alloy (Ti - 6Al - 4V) exhibits properties indicative of a high kinetic inductance material. This work is supported by LDRD 16-SI-004.

  15. Superconducting TESLA cavities

    Directory of Open Access Journals (Sweden)

    B. Aune

    2000-09-01

    Full Text Available The conceptional design of the proposed linear electron-positron collider TESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with an accelerating gradient of E_{acc}≥25 MV/m at a quality factor Q_{0}≥5×10^{9}. The design goal for the cavities of the TESLA Test Facility (TTF linac was set to the more moderate value of E_{acc}≥15 MV/m. In a first series of 27 industrially produced TTF cavities the average gradient at Q_{0}=5×10^{9} was measured to be 20.1±6.2 MV/m, excluding a few cavities suffering from serious fabrication or material defects. In the second production of 24 TTF cavities, additional quality control measures were introduced, in particular, an eddy-current scan to eliminate niobium sheets with foreign material inclusions and stringent prescriptions for carrying out the electron-beam welds. The average gradient of these cavities at Q_{0}=5×10^{9} amounts to 25.0±3.2 MV/m with the exception of one cavity suffering from a weld defect. Hence only a moderate improvement in production and preparation techniques will be needed to meet the ambitious TESLA goal with an adequate safety margin. In this paper we present a detailed description of the design, fabrication, and preparation of the TESLA Test Facility cavities and their associated components and report on cavity performance in test cryostats and with electron beam in the TTF linac. The ongoing research and development towards higher gradients is briefly addressed.

  16. The Superconducting TESLA Cavities

    CERN Document Server

    Aune, B.; Bloess, D.; Bonin, B.; Bosotti, A.; Champion, M.; Crawford, C.; Deppe, G.; Dwersteg, B.; Edwards, D.A.; Edwards, H.T.; Ferrario, M.; Fouaidy, M.; Gall, P-D.; Gamp, A.; Gössel, A.; Graber, J.; Hubert, D.; Hüning, M.; Juillard, M.; Junquera, T.; Kaiser, H.; Kreps, G.; Kuchnir, M.; Lange, R.; Leenen, M.; Liepe, M.; Lilje, L.; Matheisen, A.; Möller, W-D.; Mosnier, A.; Padamsee, H.; Pagani, C.; Pekeler, M.; Peters, H-B.; Peters, O.; Proch, D.; Rehlich, K.; Reschke, D.; Safa, H.; Schilcher, T.; Schmüser, P.; Sekutowicz, J.; Simrock, S.; Singer, W.; Tigner, M.; Trines, D.; Twarowski, K.; Weichert, G.; Weisend, J.; Wojtkiewicz, J.; Wolff, S.; Zapfe, K.

    2000-01-01

    The conceptional design of the proposed linear electron-positron colliderTESLA is based on 9-cell 1.3 GHz superconducting niobium cavities with anaccelerating gradient of Eacc >= 25 MV/m at a quality factor Q0 > 5E+9. Thedesign goal for the cavities of the TESLA Test Facility (TTF) linac was set tothe more moderate value of Eacc >= 15 MV/m. In a first series of 27industrially produced TTF cavities the average gradient at Q0 = 5E+9 wasmeasured to be 20.1 +- 6.2 MV/m, excluding a few cavities suffering fromserious fabrication or material defects. In the second production of 24 TTFcavities additional quality control measures were introduced, in particular aneddy-current scan to eliminate niobium sheets with foreign material inclusionsand stringent prescriptions for carrying out the electron-beam welds. Theaverage gradient of these cavities at Q0 = 5E+9 amounts to 25.0 +- 3.2 MV/mwith the exception of one cavity suffering from a weld defect. Hence only amoderate improvement in production and preparation technique...

  17. High Accelerating Field Superconducting Radio Frequency Cavities

    Science.gov (United States)

    Orr, R. S.; Saito, K.; Furuta, F.; Saeki, T.; Inoue, H.; Morozumi, Y.; Higo, T.; Higashi, Y.; Matsumoto, H.; Kazakov, S.; Yamaoka, H.; Ueno, K.; Sato, M.

    2008-06-01

    We have conducted a study of a series of single cell superconducting RF cavities at KEK. These tests were designed to investigate the effect of surface treatment on the maximum accelerating field attainable. All of these cavities are of the ICHIRO shape, based on the Low Loss shape. Our results indicate that accelerating fields as high as the theoretical maximum of 50MV/m are attainable.

  18. The LEP2 superconducting RF system

    CERN Document Server

    Butterworth, A; Brunner, O; Ciapala, Edmond; Frischholz, Hans; Geschonke, Günther; Peschardt, E; Sladen, J

    2008-01-01

    The upgrade of LEP2 energy to beyond the W boson production threshold required the progressive installation of a completely new radio-frequency (RF) accelerating system. The new system used superconducting (SC) cavities, which complemented and partially replaced the original LEP1 RF system based on conventional copper cavity technology. The final system consisted of 56 copper and 288 SC cavities and provided a peak acceleration of more than 3600 MV/turn. This paper describes the main elements of the SC system and reviews the 5 years of LEP2 operation at gradients well beyond the design specification. Also presented are some of the main performance limitations and problems encountered together with the various solutions and procedures found to eliminate them or reduce their effects.

  19. Investigation of a 2K superfluid liquid helium refrigerator system and research of superconducting RF cavities. Report from the short visiting and research program aboard supported by the Japanese education ministry

    International Nuclear Information System (INIS)

    Saito, Kenji

    2001-01-01

    The author visited at Jefferson Lab for two months from July 5 '99 to September 2 by the short visit and research program financed by the Japanese Education Ministry for the investigation the CEBAF 2K refrigerator system and research superconducting RF cavities. Here, the result will be presented. (author)

  20. A New Vacuum Brazing Route for Niobium-316L Stainless Steel Transition Joints for Superconducting RF Cavities

    Science.gov (United States)

    Kumar, Abhay; Ganesh, P.; Kaul, R.; Bhatnagar, V. K.; Yedle, K.; Ram Sankar, P.; Sindal, B. K.; Kumar, K. V. A. N. P. S.; Singh, M. K.; Rai, S. K.; Bose, A.; Veerbhadraiah, T.; Ramteke, S.; Sridhar, R.; Mundra, G.; Joshi, S. C.; Kukreja, L. M.

    2015-02-01

    The paper describes a new approach for vacuum brazing of niobium-316L stainless steel transition joints for application in superconducting radiofrequency cavities. The study exploited good wettability of titanium-activated silver-base brazing alloy (CuSil-ABA®), along with nickel as a diffusion barrier, to suppress brittle Fe-Nb intermetallic formation, which is well reported during the established vacuum brazing practice using pure copper filler. The brazed specimens displayed no brittle intermetallic layers on any of its interfaces, but instead carried well-distributed intermetallic particles in the ductile matrix. The transition joints displayed room temperature tensile and shear strengths of 122-143 MPa and 80-113 MPa, respectively. The joints not only exhibited required hermeticity (helium leak rate high vacuum but also withstood twelve hour degassing heat treatment at 873 K (suppresses Q-disease in niobium cavities), without any noticeable degradation in the microstructure and the hermeticity. The joints retained their leak tightness even after undergoing ten thermal cycles between the room temperature and the liquid nitrogen temperature, thereby establishing their ability to withstand service-induced low cycle fatigue conditions. The study proposes a new lower temperature brazing route to form niobium-316L stainless steel transition joints, with improved microstructural characteristics and acceptable hermeticity and mechanical properties.

  1. Laboratory report on RF superconductivity at Peking University

    International Nuclear Information System (INIS)

    Kui, Zhao; Baocheng, Zhang; Lifang, Wang; Jin, Yu; Rongli, Geng; Genfa, Wu; Tong, Wang; Jinhu, Song; Chia-erh, Chen

    1996-01-01

    The activities on RF superconductivity at Peking University in the past two years are reported. Two 1.5 GHz Nb cavities were successfully fabricated using Chinese Nb sheets in 1994. One of the cavities has been measured, and the results are given. A laser driven DC electron gun has been designed and constructed which is the pre-testing device of photo-electron gun using superconducting cavity. A series of experiments on the cathode and cavity will be performed in the near future. Two superconducting accelerating devices are being considered for two projects in China. (R.P.)

  2. Superconducting cavities developments efforts at RRCAT

    International Nuclear Information System (INIS)

    Puntambekar, A.; Bagre, M.; Dwivedi, J.; Shrivastava, P.; Mundra, G.; Joshi, S.C.; Potukuchi, P.N.

    2011-01-01

    Superconducting RE cavities are the work-horse for many existing and proposed linear accelerators. Raja Ramanna Centre for Advanced Technology (RRCAT) has initiated a comprehensive R and D program for development of Superconducting RF cavities suitable for high energy accelerator application like SNS and ADS. For the initial phase of technology demonstration several prototype 1.3 GHz single cell-cavities have been developed. The work began with development of prototype single cell cavities in aluminum and copper. This helped in development of cavity manufacturing process, proving various tooling and learning on various mechanical and RF qualification processes. The parts manufacturing was done at RRCAT and Electron beam welding was carried out at Indian industry. These cavities further served during commissioning trials for various cavity processing infrastructure being developed at RRCAT and are also a potential candidate for Niobium thin film deposition R and D. Based on the above experience, few single cell cavities were developed in fine grain niobium. The critical technology of forming and machining of niobium and the intermediate RF qualification were developed at RRCAT. The EB welding of bulk niobium cavities was carried out in collaboration with IUAC, New Delhi at their facility. As a next logical step efforts are now on for development of multicell cavities. The prototype dumbbells and end group made of aluminium, comprising of RF and HOM couplers ports have also been developed, with their LB welding done at Indian industry. In this paper we shall present the development efforts towards manufacturing of 1.3 GHz single cell cavities and their initial processing and qualification. (author)

  3. Instrumentation for localized superconducting cavity diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Conway, Z. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Physics Division; Ge, M. [Cornell Lab. for Accelerator-Based Sciences and Education, Ithaca, NY (United States); Iwashita, Y. [Kyoto Univ. (Japan)

    2017-01-12

    Superconducting accelerator cavities are now routinely operated at levels approaching the theoretical limit of niobium. To achieve these operating levels more information than is available from the RF excitation signal is required to characterize and determine fixes for the sources of performance limitations. This information is obtained using diagnostic techniques which complement the analysis of the RF signal. In this paper we describe the operation and select results from three of these diagnostic techniques: the use of large scale thermometer arrays, second sound wave defect location and high precision cavity imaging with the Kyoto camera.

  4. Design of an L-band normally conducting RF gun cavity for high peak and average RF power

    Energy Technology Data Exchange (ETDEWEB)

    Paramonov, V., E-mail: paramono@inr.ru [Institute for Nuclear Research of Russian Academy of Sciences, 60-th October Anniversary prospect 7a, 117312 Moscow (Russian Federation); Philipp, S. [Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen (Germany); Rybakov, I.; Skassyrskaya, A. [Institute for Nuclear Research of Russian Academy of Sciences, 60-th October Anniversary prospect 7a, 117312 Moscow (Russian Federation); Stephan, F. [Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen (Germany)

    2017-05-11

    To provide high quality electron bunches for linear accelerators used in free electron lasers and particle colliders, RF gun cavities operate with extreme electric fields, resulting in a high pulsed RF power. The main L-band superconducting linacs of such facilities also require a long RF pulse length, resulting in a high average dissipated RF power in the gun cavity. The newly developed cavity based on the proven advantages of the existing DESY RF gun cavities, underwent significant changes. The shape of the cells is optimized to reduce the maximal surface electric field and RF loss power. Furthermore, the cavity is equipped with an RF probe to measure the field amplitude and phase. The elaborated cooling circuit design results in a lower temperature rise on the cavity RF surface and permits higher dissipated RF power. The paper presents the main solutions and results of the cavity design.

  5. Rf superconducting devices

    International Nuclear Information System (INIS)

    Hartwig, W.H.; Passow, C.

    1975-01-01

    Topics discussed include (1) the theory of superconductors in high-frequency fields (London surface impedance, anomalous normal surface resistance, pippard nonlocal theory, quantum mechanical model, superconductor parameters, quantum mechanical calculation techniques for the surface, impedance, and experimental verification of surface impedance theories); (2) residual resistance (separation of losses, magnetic field effects, surface resistance of imperfect and impure conductors, residual loss due to acoustic coupling, losses from nonideal surfaces, high magnetic field losses, field emission, and nonlinear effects); (3) design and performance of superconducting devices (design considerations, materials and fabrication techniques, measurement of performance, and frequency stability); (4) devices for particle acceleration and deflection (advantages and problems of using superconductors, accelerators for fast particles, accelerators for particles with slow velocities, beam optical devices separators, and applications and projects under way); (5) applications of low-power superconducting resonators (superconducting filters and tuners, oscillators and detectors, mixers and amplifiers, antennas and output tanks, superconducting resonators for materials research, and radiation detection with loaded superconducting resonators); and (6) transmission and delay lines

  6. Industrial production of SC RF accelerating cavities at CERCA. Latest results

    International Nuclear Information System (INIS)

    Boutes, J.L.; Maccioni, P.

    1996-01-01

    CERCA is one of the most experienced companies throughout the world for the manufacture of superconducting RF accelerating devices. The latest results obtained during the past 2 years on CERCA's superconducting cavities are presented. (K.A.)

  7. Technology of RF superconductivity

    International Nuclear Information System (INIS)

    Anon.

    1995-01-01

    This work has several parts, two of which are collaborative development projects with the majority of the work being performed at Argonne. The first is the development of a superconducting RFQ structure in collaboration with AccSys Technology Inc. of Pleasanton, California, funded as a Phase II SBIR grant. Another is a collaborative project with the Nuclear Science Centre, New Delhi, India (who are funding the work) to develop new superconducting ion accelerating structures. Other initiatives are developing various aspects of the technology required to utilize ATLAS as a secondary beam linac for radioactive beams

  8. Cryostat for TRISTAN superconducting cavity

    International Nuclear Information System (INIS)

    Mitsunobu, S.; Furuya, T.; Hara, K.

    1990-01-01

    Superconducting cavities generate rather high heat load of hundreds watts in one cryostat and have high sensitivity for pressure. We adopted usual pool-boiling type cooling for its stable pressure operation. Two 5-cell Nb cavities were installed in one flange type cryostat. Tuning mechanics actuated by a pulse-motor and a Piezo-electric element are set at outside of vacuum end flange. The design and performance of the cryostat for TRISTAN superconducting cavities are described. (author)

  9. Superconducting Radio-Frequency Cavities

    Science.gov (United States)

    Padamsee, Hasan S.

    2014-10-01

    Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

  10. Design of rf conditioner cavities

    International Nuclear Information System (INIS)

    Govil, R.; Rimmer, R.A.; Sessler, A.; Kirk, H.G.

    1992-06-01

    Theoretical studies are made of radio frequency structures which can be used to condition electron beams so as to greatly reduce the stringent emittance requirements for successful lasing in a free-electron laser. The basic strategy of conditioning calls for modulating an electron beam in the transverse dimension, by a periodic focusing channel, while it traverses a series of rf cavities, each operating in a TM 210 mode. In this paper, we analyze the cavities both analytically and numerically (using MAFIA simulations). We find that when cylindrical symmetry is broken the coupling impedance can be greatly enhanced. We present results showing various performance characteristics as a function of cavity parameters, as well as possible designs for conditioning cavities

  11. Beam induced rf cavity transient voltage

    International Nuclear Information System (INIS)

    Kramer, S.L.; Wang, J.M.

    1998-10-01

    The authors calculate the transient voltage induced in a radio frequency cavity by the injection of a relativistic bunched beam into a circular accelerator. A simplified model of the beam induced voltage, using a single tone current signal, is generated and compared with the voltage induced by a more realistic model of a point-like bunched beam. The high Q limit of the bunched beam model is shown to be related simply to the simplified model. Both models are shown to induce voltages at the resonant frequency ω r of the cavity and at an integer multiple of the bunch revolution frequency (i.e. the accelerating frequency for powered cavity operation) hω ο . The presence of two nearby frequencies in the cavity leads to a modulation of the carrier wave exp(hω ο t). A special emphasis is placed in this paper on studying the modulation function. These models prove useful for computing the transient voltage induced in superconducting rf cavities, which was the motivation behind this research. The modulation of the transient cavity voltage discussed in this paper is the physical basis of the recently observed and explained new kinds of longitudinal rigid dipole mode which differs from the conventional Robinson mode

  12. RF Power Requirements for PEFP SRF Cavity Test

    International Nuclear Information System (INIS)

    Kim, Han Sung; Seol, Kyung Tae; Kwon, Hyeok Jung; Cho, Yong Sub

    2011-01-01

    For the future extension of the PEFP (Proton Engineering Frontier Project) Proton linac, preliminary study on the SRF (superconducting radio-frequency) cavity is going on including a five-cell prototype cavity development to confirm the design and fabrication procedures and to check the RF and mechanical properties of a low-beta elliptical cavity. The main parameters of the cavity are like followings. - Frequency: 700 MHz - Operating mode: TM010 pi mode - Cavity type: Elliptical - Geometrical beta: 0.42 - Number of cells: 5 - Accelerating gradient: 8 MV/m - Epeak/Eacc: 3.71 - Bpeak/Eacc: 7.47 mT/(MV/m) - R/Q: 102.3 ohm - Epeak: 29.68 MV/m (1.21 Kilp.) - Geometrical factor: 121.68 ohm - Cavity wall thickness: 4.3 mm - Stiffening structure: Double ring - Effective length: 0.45 m For the test of the cavity at low temperature of 4.2 K, many subsystems are required such as a cryogenic system, RF system, vacuum system and radiation shielding. RF power required to generate accelerating field inside cavity depends on the RF coupling parameters of the power coupler and quality factor of the SRF cavity and the quality factor itself is affected by several factors such as operating temperature, external magnetic field level and surface condition. Therefore, these factors should be considered to estimate the required RF power for the SRF cavity test

  13. Application of RF Superconductivity to High-Current Linac

    International Nuclear Information System (INIS)

    Chan, K.C.D.

    1998-01-01

    In 1997, the authors initiated a development program in Los Alamos for high-current superconducting proton-linac technology to build prototypes components of this linac to demonstrate the feasibility. The authors are building 700-MHz niobium cavities with elliptical shapes, as well as power couplers to transfer high RF power to these cavities. The cavities and power couplers will be integrated in cryostats as linac cryomodules. In this paper, they describe the linac design and the status of the development program

  14. Analysis of performance limitations for superconducting cavities

    International Nuclear Information System (INIS)

    J. R. Delayen; L. R. Doolittle; C. E. Reece

    1998-01-01

    The performance of superconducting cavities in accelerators can be limited by several factors, such as: field emission, quenches, arcing, rf power; and the maximum gradient at which a cavity can operate will be determined by the lowest of these limitations for that particular cavity. The CEBAF accelerator operates with over 300 cavities and, for each of them, the authors have determined the maximum operating gradient and its limiting factor. They have developed a model that allows them to determine the distribution of gradients that could be achieved for each of these limitations independently of the others. The result of this analysis can guide an R and D program to achieve the best overall performance improvement. The same model can be used to relate the performance of single-cell and multi-cell cavities

  15. The LHC Superconducting RF System

    CERN Document Server

    Boussard, Daniel

    1999-01-01

    The European Laboratory for Particle Physics (CERN), the largest high energy physics laboratory worldwide, is constructing the Large Hadron Collider (LHC) in the existing 27 km circumference LEP (Large Electron Positron) collider tunnel. For the LHC, superconducting cavities, operating at 4.5 K, will provide the required acceleration field for ramping the beam energy up to 7 TeV and for keeping the colliding proton beams tightly bunched. Superconducting cavities were chosen, not only because of their high acceleration field leading to a small contribution to the machine impedance, but also because of their high stored energy which minimises the effects of periodic transient beam loading associated with the high beam intensity (0.5 A). There will be eight single-cell cavities per beam, each delivering 2 MV (5.3 MV/m) at 400 MHz. The cavities themselves are now being manufactured by industrial firms, using niobium on copper technology which gives full satisfaction at LEP. A complete cavity prototype assembly in...

  16. Superconducting cavities for beauty factories

    International Nuclear Information System (INIS)

    Lengeler, H.

    1992-01-01

    The possibilities and merits of superconducting accelerating cavities for Beauty-factories are considered. There exist already large sc systems of size and frequency comparable to the ones needed for Beauty-factories. Their status and operation experience is discussed. A comparison of normal conducting and superconducting systems is done for two typical Beauty-factory rings

  17. Normal Conducting RF Cavity for MICE

    International Nuclear Information System (INIS)

    Li, D.; DeMello, A.; Virostek, S.; Zisman, M.; Summers, D.

    2010-01-01

    Normal conducting RF cavities must be used for the cooling section of the international Muon Ionization Cooling Experiment (MICE), currently under construction at Rutherford Appleton Laboratory (RAL) in the UK. Eight 201-MHz cavities are needed for the MICE cooling section; fabrication of the first five cavities is complete. We report the cavity fabrication status including cavity design, fabrication techniques and preliminary low power RF measurements.

  18. Status of Tristan superconducting RF program

    International Nuclear Information System (INIS)

    Noguchi, S.; Akai, K.; Arinaga, M.

    1988-01-01

    The TRISTAN accelerator complex consists of an injector linac system, an accumulation ring (AR) and a main colliding beam ring (MR). The injector linac system is composed of a 2.5 GeV main linac, a 200 MeV high current (10 A) linac for positron generation and a 250 MeV positron preaccelerator. These linacs are now operated with a pulse width of 2 nsec and a repetition rate of 20 pps, which is raised to 50 pps in the near future. The TRISTAN AR is used as a beam accumulator and energy booster for the TRISTAN MR, and additionally it can be operated as an electron-positron collider and as a storage ring for the synchrotron radiation research. The electron (positron) beam of 50 mA (10 mA) peak current is injected from the main linac. The accumulation rate of positrons is now typically 5 mA/min. There are 8 RF cavity sections in two long straight sections, of which 6 sections are occupied by 11 cell APS cavities and 2 sections are used for the beam test of the superconducting cavities. The TRISTAN MR was designed so that it could achieve as high energy as possible for its size, therefore it has very long straight sections for RF cavities. The normal conducting cavities, which are 9-cell APS type and have a shunt impedance of 22.5 M Omega/m, are distributed to 3 straight sections. The remaining straight section named NIKKO division, is allotted to the superconducting cavities. MR accelerated the first electron beam to 25.5 GeV on 24th of October 1986. The energy upgrading program was approved in 1986 and the construction of 32 5-cell superconducting cavities and a 4.5 KW helium refrigerator system started. It is expected that the accelerating field and the Q value are better than 5 MV/m and 1 x 10 9 , respectively. 8 references, 13 figures, 4 tables

  19. Design of RF structures for a superconducting proton linac

    International Nuclear Information System (INIS)

    Pande, Rajni; Roy, Shweta; Rao, S.V.L.S.; Krishnagopal, S.; Singh, P.

    2013-01-01

    One of the main components of the Accelerator Driven System (ADS) programme in India is a 1 GeV, high intensity CW proton accelerator that will be superconducting after the radio-frequency quadrupole (RFQ), i.e. after 3 MeV. The superconducting linac will consist of various superconducting structures like Half Wave Resonators, Spoke Resonators and elliptical cavities, operating at RF frequencies of 162.5 MHz, 325 MHz and 650 MHz. The paper will discuss the optimization of the electromagnetic design of the various superconducting structures. (author)

  20. Nano-fabricated superconducting radio-frequency composites, method for producing nano-fabricated superconducting rf composites

    Science.gov (United States)

    Norem, James H.; Pellin, Michael J.

    2013-06-11

    Superconducting rf is limited by a wide range of failure mechanisms inherent in the typical manufacture methods. This invention provides a method for fabricating superconducting rf structures comprising coating the structures with single atomic-layer thick films of alternating chemical composition. Also provided is a cavity defining the invented laminate structure.

  1. Design of RF system for CYCIAE-230 superconducting cyclotron

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Zhiguo, E-mail: bitbearAT@hotmail.com; Ji, Bin; Fu, Xiaoliang; Cao, Xuelong; Zhao, Zhenlu; Zhang, Tinajue

    2017-05-11

    The CYCIAE230 is a low-current, compact superconducting cyclotron designed for proton therapy. The Radio Frequency system consists of four RF cavities and applies second harmonic to accelerate beams. The driving power for the cavity system is estimated to be approximately 150 kW. The LLRF controller is a self-made device developed and tested at low power using a small-scale cavity model. In this paper, the resonator systems of an S.C. cyclotron in history are reviewed. Contrary to those RF systems, the cavities of the CYCIAE230 cyclotron connect two opposite dees. Two high-power RF windows are included in the system. Each window carries approximately 75 kW RF power from the driver to the cavities. Thus, the RF system for the CY-CIAE230 cyclotron is operated in driven push–pull mode. The two-way amplifier-coupler-cavity systems are operated with approximately the same amount of RF power but 180° out of phase compared with each other. The design, as well as the technical advantage and limitations of this operating mode, of the CYCIAE230 cyclotron RF system is analyzed.

  2. Design of RF system for CYCIAE-230 superconducting cyclotron

    Science.gov (United States)

    Yin, Zhiguo; Ji, Bin; Fu, Xiaoliang; Cao, Xuelong; Zhao, Zhenlu; Zhang, Tinajue

    2017-05-01

    The CYCIAE230 is a low-current, compact superconducting cyclotron designed for proton therapy. The Radio Frequency system consists of four RF cavities and applies second harmonic to accelerate beams. The driving power for the cavity system is estimated to be approximately 150 kW. The LLRF controller is a self-made device developed and tested at low power using a small-scale cavity model. In this paper, the resonator systems of an S.C. cyclotron in history are reviewed. Contrary to those RF systems, the cavities of the CYCIAE230 cyclotron connect two opposite dees. Two high-power RF windows are included in the system. Each window carries approximately 75 kW RF power from the driver to the cavities. Thus, the RF system for the CY-CIAE230 cyclotron is operated in driven push-pull mode. The two-way amplifier-coupler-cavity systems are operated with approximately the same amount of RF power but 180° out of phase compared with each other. The design, as well as the technical advantage and limitations of this operating mode, of the CYCIAE230 cyclotron RF system is analyzed.

  3. 17th International Conference on RF Superconductivity

    CERN Document Server

    Laxdal, Robert E.; Schaa, Volker R.W.

    2015-01-01

    RF superconductivity is the key technology of accelerators for particle physics, nuclear physics and light sources. SRF 2015 covered the latest advances in the science, technology, and applications of superconducting RF. There was also an industrial exhibit during the conference with the key vendors in the community available to discuss their capabilities and products.

  4. COMPARISON OF RF CAVITY TRANSPORT MODELS FOR BBU SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Ilkyoung Shin,Byung Yunn,Todd Satogata,Shahid Ahmed

    2011-03-01

    The transverse focusing effect in RF cavities plays a considerable role in beam dynamics for low-energy beamline sections and can contribute to beam breakup (BBU) instability. The purpose of this analysis is to examine RF cavity models in simulation codes which will be used for BBU experiments at Jefferson Lab and improve BBU simulation results. We review two RF cavity models in the simulation codes elegant and TDBBU (a BBU simulation code developed at Jefferson Lab). elegant can include the Rosenzweig-Serafini (R-S) model for the RF focusing effect. Whereas TDBBU uses a model from the code TRANSPORT which considers the adiabatic damping effect, but not the RF focusing effect. Quantitative comparisons are discussed for the CEBAF beamline. We also compare the R-S model with the results from numerical simulations for a CEBAF-type 5-cell superconducting cavity to validate the use of the R-S model as an improved low-energy RF cavity transport model in TDBBU. We have implemented the R-S model in TDBBU. It will improve BBU simulation results to be more matched with analytic calculations and experimental results.

  5. Comparison Of RF Cavity Transport Models For BBU Simulations

    International Nuclear Information System (INIS)

    Shin, Ilkyoung; Yunn, Byung; Satogata, Todd; Ahmed, Shahid

    2011-01-01

    The transverse focusing effect in RF cavities plays a considerable role in beam dynamics for low-energy beamline sections and can contribute to beam breakup (BBU) instability. The purpose of this analysis is to examine RF cavity models in simulation codes which will be used for BBU experiments at Jefferson Lab and improve BBU simulation results. We review two RF cavity models in the simulation codes elegant and TDBBU (a BBU simulation code developed at Jefferson Lab). elegant can include the Rosenzweig-Serafini (R-S) model for the RF focusing effect. Whereas TDBBU uses a model from the code TRANSPORT which considers the adiabatic damping effect, but not the RF focusing effect. Quantitative comparisons are discussed for the CEBAF beamline. We also compare the R-S model with the results from numerical simulations for a CEBAF-type 5-cell superconducting cavity to validate the use of the R-S model as an improved low-energy RF cavity transport model in TDBBU. We have implemented the R-S model in TDBBU. It will improve BBU simulation results to be more matched with analytic calculations and experimental results.

  6. Superconducting rf development at ATLAS

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, K.W.; Kedzie, M.; Clifft, B.E. [Argonne National Lab., IL (United States); Roy, A.; Potukuchi, P. [Nuclear Science Centre, New Delhi (India); Givens, J.; Potter, J.; Crandall, K. [AccSys Technology, Inc., Pleasanton, CA (United States); Added, N. [Sao Paulo Univ., SP (Brazil)

    1993-12-31

    The ATLAS superconducting heavy-ion linac began operation in 1978 and has operated nearly continuously since that time, while undergoing a series of upgrades and expansions, the most recent being the ``uranium upgrade`` completed earlier this year and described below. In its present configuration the ATLAS linac consists of an array of 64 resonant cavities operating from 48 to 145 MHz, which match a range of particle velocities .007 < {beta} = v/c < .2. The linac provides approximately 50 MV of effective accelerating potential for ions of q/m > 1/10 over the entire periodic table. Delivered beams include 5 {minus} 7 pnA of {sup 238}U{sup 39+} at 1535 MeV. At present more than 10{sup 6} cavity-hours of operation at surface electric fields of 15 MV/m have been accumulated. Superconducting structure development at ATLAS is aimed at improving the cost/performance of existing low velocity structures both for possible future ATLAS upgrades, and also for heavy-ion linacs at other institutions. An application of particular current interest is to develop structures suitable for accelerating radioactive ion beams. Such structures must accelerate very low charge to mass ratio beams and must also have very large transverse acceptance.

  7. Industrialization of Superconducting RF Accelerator Technology

    Science.gov (United States)

    Peiniger, Michael; Pekeler, Michael; Vogel, Hanspeter

    2012-01-01

    Superconducting RF (SRF) accelerator technology has basically existed for 50 years. It took about 20 years to conduct basic R&D and prototyping at universities and international institutes before the first superconducting accelerators were built, with industry supplying complete accelerator cavities. In parallel, the design of large scale accelerators using SRF was done worldwide. In order to build those accelerators, industry has been involved for 30 years in building the required cavities and/or accelerator modules in time and budget. To enable industry to supply these high tech components, technology transfer was made from the laboratories in the following three regions: the Americas, Asia and Europe. As will be shown, the manufacture of the SRF cavities is normally accomplished in industry whereas the cavity testing and module assembly are not performed in industry in most cases, yet. The story of industrialization is so far a story of customized projects. Therefore a real SRF accelerator product is not yet available in this market. License agreements and technology transfer between leading SRF laboratories and industry is a powerful tool for enabling industry to manufacture SRF components or turnkey superconducting accelerator modules for other laboratories and users with few or no capabilities in SRF technology. Despite all this, the SRF accelerator market today is still a small market. The manufacture and preparation of the components require a range of specialized knowledge, as well as complex and expensive manufacturing installations like for high precision machining, electron beam welding, chemical surface preparation and class ISO4 clean room assembly. Today, the involved industry in the US and Europe comprises medium-sized companies. In Japan, some big enterprises are involved. So far, roughly 2500 SRF cavities have been built by or ordered from industry worldwide. Another substantial step might come from the International Linear Collider (ILC) project

  8. Present status of superconducting cavity developments

    Energy Technology Data Exchange (ETDEWEB)

    Ouchi, Nobuo; Kusano, Joichi; Hasegawa, Kazuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment] [and others

    1997-11-01

    An R and D work of a superconducting (SC) cavity for the high intensity proton linac has begun at JAERI in collaboration with KEK. The RF field calculation and the structural analysis have been made to determine the cavity shape in the proton energy range between 100 and 1500 MeV. The results indicate the feasibility of a SC proton linac. A vertical test stand with clean room, water rinsing system, cavity evacuation pumping system, cryostat and data acquisition system has been installed to demonstrate the cavity performance. A single cell cavity of {beta}=0.5 has been fabricated and tested at the test stand to obtain the Q-value and the maximum surface electric field strength. The measured Q-values have been found to be high enough for our requirement while the field strength was limited to about 75% of the specification by the multipacting. We describe the preliminary design of the SC cavity, the overview of the vertical test stand and experimental results of the single cell cavity. (author)

  9. Computer codes for RF cavity design

    International Nuclear Information System (INIS)

    Ko, K.

    1992-08-01

    In RF cavity design, numerical modeling is assuming an increasingly important role with the help of sophisticated computer codes and powerful yet affordable computers. A description of the cavity codes in use in the accelerator community has been given previously. The present paper will address the latest developments and discuss their applications to cavity toning and matching problems

  10. Computer codes for RF cavity design

    International Nuclear Information System (INIS)

    Ko, K.

    1992-01-01

    In RF cavity design, numerical modeling is assuming an increasingly important role with the help of sophisticated computer codes and powerful yet affordable computers. A description of the cavity codes in use in the accelerator community has been given previously. The present paper will address the latest developments and discuss their applications to cavity tuning and matching problems. (Author) 8 refs., 10 figs

  11. Superconducting cavities for the APT accelerator

    International Nuclear Information System (INIS)

    Krawczyk, F.L.; Gentzlinger, R.C.; Haynes, B.; Montoya, D.I.; Rusnak, B.; Shapiro, A.H.

    1997-01-01

    The design of an Accelerator Production of Tritium (APT) facility being investigated at Los Alamos includes a linear accelerator using superconducting rf-cavities for the acceleration of a high-current cw proton beam. For electron accelerators with particles moving at the speed of light (β ∼ 1.0), resonators with a rounded shape, consisting of ellipsoidal and cylindrical sections, are well established. They are referred to as elliptical cavities. For the APT-design, this shape has been adapted for much slower proton beams with β ranging from 0.60 to 0.94. This is a new energy range, in which resonators of an elliptical type have never been used before. Simulations with the well-proven electromagnetic modeling tools MAFIA and SUPERFISH were performed. The structures have been optimized for their rf and mechanical properties as well as for beam dynamics requirements. The TRAK-RF simulation code is used to investigate potential multipacting in these structures. All the simulations will be put to a final test in experiments performed on single cell cavities that have started in the structures laboratory

  12. Cryogenic testing of the 2.1 GHz five-cell superconducting RF cavity with a photonic band gap coupler cell

    Science.gov (United States)

    Arsenyev, Sergey A.; Temkin, Richard J.; Haynes, W. Brian; Shchegolkov, Dmitry Yu.; Simakov, Evgenya I.; Tajima, Tsuyoshi; Boulware, Chase H.; Grimm, Terrence L.; Rogacki, Adam R.

    2016-05-01

    We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2 K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55 × 108, in agreement with prediction.

  13. HOM Dampers or not in Superconducting RF Proton Linacs

    CERN Document Server

    Tückmantel, Joachim

    2009-01-01

    Circular machines are plagued by Coupled Bunch Instabilities, driven by impedance peaks, irrespectively of their frequency relation to machine lines; hence all cavity Higher Order Modes are possible drivers. This is the fundamental reason that all superconducting RF cavities in circular machines are equipped with HOM dampers. This raises the question if HOM damping would not be imperative also in high current proton linacs where a mechanism akin to CBI might exist. To clarify this question we have simulated the longitudinal bunched beam dynamics in linacs, allowing bunch-to-bunch variations in time-of-arrival. Simulations were executed for a generic proton linac with properties close to SNS or the planned SPL at CERN. It was found that for monopole HOMs with high Qext large beam scatter or even beam loss cannot be excluded. Therefore omitting HOM dampers on superconducting RF cavities in high current proton linacs, even pulsed ones, is a very risky decision.

  14. HOM Dampers or not in SUPERCONDUCTING RF Proton Linacs

    CERN Document Server

    Tückmantel, Joachim

    2009-01-01

    Circular machines are plagued by Coupled Bunch Instabilities, driven by impedance peaks, irrespectively of their frequency relation to machine lines; hence all cavity Higher Order Modes are possible drivers. This is the fundamental reason that all superconducting RF cavities in circular machines are equipped with HOM dampers. This raises the question if HOM damping would not be imperative also in high current proton linacs where a mechanism akin to CBI might exist. To clarify this question we have simulated the longitudinal bunched beam dynamics in linacs, allowing bunch-to-bunch variations in time-of-arrival. Simulations were executed for a generic proton linac with properties close to SNS or the planned SPL at CERN. It was found that for monopole HOMs with high Qext large beam scatter or even beam loss cannot be excluded. Therefore omitting HOM dampers on superconducting RF cavities in high current proton linacs, even pulsed ones, is a very risky decision.

  15. Study of a power coupler for superconducting RF cavities used in high intensity proton accelerator; Etude et developpement d'un coupleur de puissance pour les cavites supraconductrices destinees aux accelerateurs de protons de haute intensite

    Energy Technology Data Exchange (ETDEWEB)

    Souli, M

    2007-07-15

    The coaxial power coupler needed for superconducting RF cavities used in the high energy section of the EUROTRANS driver should transmit 150 kW (CW operation) RF power to the protons beam. The calculated RF and dielectric losses in the power coupler (inner and outer conductor, RF window) are relatively high. Consequently, it is necessary to design very carefully the cooling circuits in order to remove the generated heat and to ensure stable and reliable operating conditions for the coupler cavity system. After calculating all type of losses in the power coupler, we have designed and validated the inner conductor cooling circuit using numerical simulations results. We have also designed and optimized the outer conductor cooling circuit by establishing its hydraulic and thermal characteristics. Next, an experiment dedicated to study the thermal interaction between the power coupler and the cavity was successfully performed at CRYOHLAB test facility. The critical heat load Qc for which a strong degradation of the cavity RF performance was measured leading to Q{sub c} in the range 3 W-5 W. The measured heat load will be considered as an upper limit of the residual heat flux at the outer conductor cold extremity. A dedicated test facility was developed and successfully operated for measuring the performance of the outer conductor heat exchanger using supercritical helium as coolant. The test cell used reproduces the realistic thermal boundary conditions of the power coupler mounted on the cavity in the cryo-module. The first experimental results have confirmed the excellent performance of the tested heat exchanger. The maximum residual heat flux measured was 60 mW for a 127 W thermal load. As the RF losses in the coupler are proportional to the incident RF power, we can deduce that the outer conductor heat exchanger performance is continued up to 800 kW RF power. Heat exchanger thermal conductance has been identified using a 2D axisymmetric thermal model by comparing

  16. RF tuning system for superconducting cyclotron at VECC

    International Nuclear Information System (INIS)

    Mandal, Aditya; Som, S.; Pal, Saikat; Seth, S.; Mukherjee, A.K.; Gangopadhyay, P.; Prasad, J.S.; Raj, P.R.; Manna, S.K.; Banerjee, M.; Krishnaiah, K.V.; Maskawade, S.; Saha, M.S.; Biswas, S.; Panda, Umashakar

    2009-01-01

    The RF system of Superconducting cyclotron at VECC has operational frequency 9-27 MHz. It has three numbers of tunable rf amplifier cavities as well as six numbers of tunable Main resonant cavities. RF tuning system takes care of movement of nine stepper motor based sliding short movement and hydraulic driven three coupling capacitors and three trimmer capacitors. The PC-based stepper motor controlled sliding short movement system has positional accuracy of around 20 micron and PC-based hydraulically driven couplers and trimmers system has 10 micron positional accuracy. The RF power is capacitively coupled to the dee (accelerating electrode) of the main resonant cavity through Coupler (Coupling capacitor). The coupling capacitor is used to match the impedance of the main resonant cavity to the 50 Ohm output impedance of final RF power amplifier. Trimmer capacitor operates in closed loop for the adjustment of cavity phase variation arising due to temperature variation and beam loading of the cavity. Coupler can travel 100 mm. and trimmer has 20 mm. travels. A PLC based PID control system has been developed for positional control of the coupler and trimmer. One position control mode of trimmer is same as coupling capacitor and another is velocity control mode. Velocity control mode operates in close-loop. The positional data of different frequencies of nine stepper motors and three coupling capacitors are stored in a database. (author)

  17. A prototype superconducting cavity for TRISTAN

    International Nuclear Information System (INIS)

    Furuya, T.; Hara, K.; Hosoyama, K.

    1987-01-01

    Following the feasibility study on the 3-cell superconducting cavity in the TRISTAN Accumulation Ring (TAR), a 5-cell 508 MHz Nb cavity was constructed and tested in the TAR. The cavity was equipped with a RF input coupler on a beam pipe, two HOM couplers on the other beam pipe and two additional HOM couplers on the equator of an end cell. The maximum accelerating field (Eaxx) was 4.5 MV/m with a Q value of about 1x10 9 at 4.2 deg K. The field was limited by the electron field emission and neither electron multipacting nor breakdown caused by couplers was observed. Damping of the HOM was sufficient and the input coupler was tested up to 82 KW in total reflection. A frequency tuning system consisted of two piezo electric and mechanical tuners. The piezo tuner was fast enough and the mechanical tuner covered wide range. In the beam test, the single bunch electron current of 29 mA was captured by the superconducting cavity alone and 13 mA was accelerated to 4.8 GeV. The maximum power transferred to the beam was 26 KW. The refrigeration system worked very stably

  18. Fundamental Power Couplers for Superconducting Cavities

    International Nuclear Information System (INIS)

    Isidoro E. Campisi

    2001-01-01

    Fundamental power couplers (FPC's) for superconducting cavities must meet very strict requirements to perform at high power levels (hundreds of kilowatts) and in a variety of conditions (CS, pulsed, travelling wave, standing wave) without adversely affecting the performance of the cavities they are powering. Producing good coupler designs and achieving operational performances in accelerator environments are challenging tasks that have traditionally involved large resources from many laboratories. The designs involve state-of-the-art activities in RF, cryogenic and mechanical engineering, materials science, vacuum technology, and electromagnetic field modeling. Handling, assembly and conditioning procedures have been developed to achieve ever-increasing power levels and more reliable operation. In this paper, the technical issues associated with the design, construction, assembly, processing, and operation of FPC's will be reviewed, together with the progress in FPC activities in several laboratories during the past few years

  19. A New RF System for the CEBAF Normal Conducting Cavities

    International Nuclear Information System (INIS)

    Curt Hovater; Hai Dong; Alicia Hofler; George Lahti; John Musson; Tomasz Plawski

    2004-01-01

    The CEBAF Accelerator at Jefferson Lab is a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. CEBAF also has numerous normal conducting cavities for beam conditioning in the injector and for RF extraction to the experimental halls. The RF systems that presently control these cavities are becoming expensive to maintain, therefore a replacement RF control system is now being developed. For the new RF system, cavity field control is maintained digitally using an FPGA which contains the feedback algorithm. The system incorporates digital down conversion, using quadrature under-sampling at an IF frequency of 70 MHz. The VXI bus-crate was chosen as the operating platform because of its excellent RFI/EMI properties and its compatibility with the EPICS control system. The normal conducting cavities operate at both the 1497 MHz accelerating frequency and the sub-harmonic frequency of 499 MHz. To accommodate this, the ne w design will use different receiver-transmitter daughter cards for each frequency. This paper discusses the development of the new RF system and reports on initial results

  20. The quest for high-gradient superconducting cavities

    International Nuclear Information System (INIS)

    Padamsee, H.

    1999-01-01

    Superconducting RF cavities excel in applications requiring continuous waves or long pulse voltages. Since power losses in the walls of the cavity increase as the square of the accelerating voltage, copper cavities become uneconomical as demand for high continuous wave voltage grows with particle energy. For these reasons, RF superconductivity has become an important technology for high energy and high luminosity accelerators. The state of art in performance of sheet metal niobium cavities is best represented by the statistics of more than 300 5-cell, 1.5-GHz cavities built for CEBAF. Key aspects responsible for the outstanding performance of the CEBAF cavities set are the anti-multipactor, elliptical cell shape, good fabrication and welding techniques, high thermal conductivity niobium, and clean surface preparation. On average, field emission starts at the electric field of 8.7 MV/m, but there is a large spread, even though the cavities received nominally the same surface treatment and assembly procedures. In some cavities, field emission was detected as low as 3 MV/m. In others, it was found to be as high as 19 MV/m. As we will discuss, the reason for the large spread in the gradients is the large spread in emitter characteristics and the random occurrence of emitters on the surface. One important phenomenon that limits the achievable RF magnetic field is thermal breakdown of superconductivity, originating at sub-millimeter-size regions of high RF loss, called defects. Simulation reveal that if the defect is a normal conducting region of 200 mm radius, it will break down at 5 MV/m. Producing high gradients and high Q in superconducting cavities demands excellent control of material properties and surface cleanliness. The spread in gradients that arises from the random occurrence of defects and emitters must be reduced. It will be important to improve installation procedures to preserve the excellent gradients now obtained in laboratory test in vertical cryostats

  1. Plasma processing of superconducting radio frequency cavities

    Science.gov (United States)

    Upadhyay, Janardan

    The development of plasma processing technology of superconducting radio frequency (SRF) cavities not only provides a chemical free and less expensive processing method, but also opens up the possibility for controlled modification of the inner surfaces of the cavity for better superconducting properties. The research was focused on the transition of plasma etching from two dimensional flat surfaces to inner surfaces of three dimensional (3D) structures. The results could be applicable to a variety of inner surfaces of 3D structures other than SRF cavities. Understanding the Ar/Cl2 plasma etching mechanism is crucial for achieving the desired modification of Nb SRF cavities. In the process of developing plasma etching technology, an apparatus was built and a method was developed to plasma etch a single cell Pill Box cavity. The plasma characterization was done with the help of optical emission spectroscopy. The Nb etch rate at various points of this cavity was measured before processing the SRF cavity. Cylindrical ring-type samples of Nb placed on the inner surface of the outer wall were used to measure the dependence of the process parameters on plasma etching. The measured etch rate dependence on the pressure, rf power, dc bias, temperature, Cl2 concentration and diameter of the inner electrode was determined. The etch rate mechanism was studied by varying the temperature of the outer wall, the dc bias on the inner electrode and gas conditions. In a coaxial plasma reactor, uniform plasma etching along the cylindrical structure is a challenging task due to depletion of the active radicals along the gas flow direction. The dependence of etch rate uniformity along the cylindrical axis was determined as a function of process parameters. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the

  2. Hydroforming of superconducting TESLA cavities

    International Nuclear Information System (INIS)

    Singer, W.; Kaiser, H.; Singer, X.

    2003-01-01

    Seamless fabrication of single-cell and multi-cell TESLA shape cavities by hydroforming has been developed at DESY. The forming takes place by expanding the seamless tube with internal water pressure while simultaneously swaging it axially. Tube radius and axial displacement are being computer controlled in accordance with results of FEM simulations and the experimentally obtained strain-stress curve of tube material. Several Nb single cell cavities have been produced. A first bulk Nb double cell cavity has been fabricated. The Nb seamless tubes have been produced by spinning and deep drawing. Surface treatment such as buffered chemical polishing, (BCP), electropolishing (EP), high pressure ultra pure water rinsing (HPR), annealing at 800degC and baking at ca. 150degC have been applied. The best single cell bulk Nb cavity has reached an accelerating gradient of Eacc > 42 MV/m after ca. 250 μm BCP and 100 μm EP. Several bimetallic NbCu single cell cavities of TESLA shape have been fabricated. The seamless tubes have been produced by explosive bonding and subsequent flow forming. The thicknesses of Nb and Cu layers in the tube wall are about 1 mm and 3 mm respectively. The RF performance of NbCu clad cavities is similar to that of bulk Nb cavities. The highest accelerating gradient achieved was 40 MV/m after ca. 180 μm BCP, annealing at 800degC and baking at 140degC for 30 hours. The degradation of the quality factor Qo after repeated quenching is moderate, after ca. 150 quenches it reaches the saturation point of Qo=1.4x10 10 at low field. This indicates that on the basis of RF performance and material costs the combination of hydroforming with tube cladding is a very promising option. (author)

  3. A design and performance analysis tool for superconducting RF systems

    International Nuclear Information System (INIS)

    Schilcher, T.; Simrock, S.N.; Merminga, L.; Wang, D.X.

    1997-01-01

    Superconducting rf systems are usually operated with continuous rf power or with rf pulse lengths exceeding 1 ms to maximize the overall wall plug power efficiency. Typical examples are CEBAF at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) and the TESLA Test Facility at DESY. The long pulses allow for effective application of feedback to stabilize the accelerating field in presence of microphonics, Lorentz force detuning, and fluctuations of the beam current. In this paper the authors describe a set of tools to be used with MATLAB and SIMULINK, which allow to analyze the quality of field regulation for a given design. The tools include models for the cavities, the rf power source, the beam, sources of field perturbations, and the rf feedback system. The rf control relevant electrical and mechanical characteristics of the cavity are described in form of time-varying state space models. The power source is modeled as a current generator and includes saturation characteristics and noise.An arbitrary time structure can be imposed on the beam current to reflect a macro-pulse structure and bunch charge fluctuations. For rf feedback several schemes can be selected: Traditional amplitude and phase control as well as I/Q control. The choices for the feedback controller include analog or digital approaches and various choices of frequency response. Feed forward can be added to further suppress repetitive errors. The results of a performance analysis of the CEBAF and the TESLA Linac rf system using these tools are presented

  4. Introduction to Superconducting RF Structures and the Effect of High Pressure Rinsing

    Energy Technology Data Exchange (ETDEWEB)

    Tajima, Tsuyoshi [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-30

    This presentation begins by describing RF superconductivity and SRF accelerating structures. Then the use of superconducting RF structures in a number of accelerators around the world is reviewed; for example, the International Linear Collider (ILC) will use ~16,000 SRF cavities with ~2,000 cryomodules to get 500 GeV e⁺/e⁻ colliding energy. Field emission control was (and still is) a very important practical issue for SRF cavity development. It has been found that high-pressure ultrapure water rinsing as a final cleaning step after chemical surface treatment resulted in consistent performance of single- and multicell superconducting cavities.

  5. Introduction to Superconducting RF Structures and the Effect of High Pressure Rinsing

    International Nuclear Information System (INIS)

    Tajima, Tsuyoshi

    2016-01-01

    This presentation begins by describing RF superconductivity and SRF accelerating structures. Then the use of superconducting RF structures in a number of accelerators around the world is reviewed; for example, the International Linear Collider (ILC) will use ~16,000 SRF cavities with ~2,000 cryomodules to get 500 GeV e@@@/e@@@ colliding energy. Field emission control was (and still is) a very important practical issue for SRF cavity development. It has been found that high-pressure ultrapure water rinsing as a final cleaning step after chemical surface treatment resulted in consistent performance of single- and multicell superconducting cavities.

  6. Diagram of a LEP superconducting cavity

    CERN Multimedia

    1991-01-01

    This diagram gives a schematic representation of the superconducting radio-frequency cavities at LEP. Liquid helium is used to cool the cavity to 4.5 degrees above absolute zero so that very high electric fields can be produced, increasing the operating energy of the accelerator. Superconducting cavities were used only in the LEP-2 phase of the accelerator, from 1996 to 2000.

  7. A database for superconducting cavities for the TESLA Test Facility

    International Nuclear Information System (INIS)

    Gall, P.D.; Goessel, A.; Gubarev, V.; Iversen, J.

    2006-01-01

    We look back on 10 years experience using a database for superconducting cavities for the TESLA Test Facility (TTF). The database was developed to collect data of every preparation step and measurement in order to optimize cavity production and preparation techniques to meet the ambitious goal of high accelerating gradients at high quality factors. Data from 110 superconducting 9-cell cavities, 50 single cell cavities, several 2- to 7-cell cavities and about 60 RF couplers were collected in the database. In addition, company measurements on sub-assemblies and parts forming the next 30 9-cell cavities were stored, thus establishing the database as part of a quality management system. This database is dynamically accessible via an extensive graphical web-interface based on ORACLE products, which enables the users to select and analyse the collected data easily from anywhere

  8. Tunable Q-Factor RF Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Balcazar, Mario D. [Fermilab; Yonehara, Katsuya [Fermilab; Moretti, Alfred [Fermilab; Kazakevitch, Gregory [Fermilab

    2018-01-01

    Intense neutrino beam is a unique probe for researching beyond the standard model. Fermilab is the main institution to produce the most powerful and widespectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gasfilled RF cavity is proposed. The goal of this measurement is to study a tunable Qfactor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.

  9. Working on an LHC superconducting cavity

    CERN Multimedia

    Laurent Guiraud

    2000-01-01

    The delicate superconducting equipment for CERN’s LHC collider has to be assembled in ultra-clean conditions to safeguard performance. Here we see the power supply being installed on one of the superconducting cavities.

  10. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  11. Fundamental of cryogenics (for superconducting RF technology)

    CERN Document Server

    Pierini, Paolo

    2013-01-01

    This review briefly illustrates a few fundamental concepts of cryogenic engineering, the technological practice that allows reaching and maintaining the low-temperature operating conditions of the superconducting devices needed in particle accelerators. To limit the scope of the task, and not to duplicate coverage of cryogenic engineering concepts particularly relevant to superconducting magnets that can be found in previous CAS editions, the overview presented in this course focuses on superconducting radio-frequency cavities.

  12. Prototype rf cavity for the HISTRAP accelerator

    International Nuclear Information System (INIS)

    Mosko, S.W.; Dowling, D.T.; Olsen, D.K.

    1989-01-01

    HISTRAP, a proposed synchrotron-cooling-storage ring designed to both accelerate and decelerate very highly charged very heavy ions for atomic physics research, requires an rf accelerating system to provide /+-/2.5 kV of peak accelerating voltage per turn while tuning through a 13.5:1 frequency range in a fraction of a second. A prototype half-wave, single gap rf cavity with biased ferrite tuning was built and tested over a continuous tuning range of 200 kHz through 2.7 MHz. Initial test results establish the feasibility of using ferrite tuning at the required rf power levels. The resonant system is located entirely outside of the accelerator's 15cm ID beam line vacuum enclosure except for a single rf window which serves as an accelerating gap. Physical separation of the cavity and the beam line permits in situ vacuum baking of the beam line at 300/degree/C

  13. Linear collider applications of superconducting RF

    International Nuclear Information System (INIS)

    Rubin, D.L.

    1990-01-01

    The most promising technology for producing interactions of electrons and positrons in TeV energy range is the linear collider. In the linear collider each and every collision of charged particles depends on the production of the charges at rest and then the acceleration of those charges to full energy. The particles that exit the interaction region are discharded. A consequence of this mode of operation is that the luminosity of the machine is ultimately determined by the efficiency with which AC power can be converted into beam power. The consideration of superconducting cavities is motivated by the need for high efficiency. Thus, the high emittance around a beam collider and low emittance around beams are discussed first in the present report. Flat beams are then addressed focusing on the characteristics of the source, final focus, and beam stability. The beam stability, in particular, is discussed in detail in relation to the multiple bunch transverse stability, wake field induced energy spread, trapped modes, pulse width, duty cycle, RF power, and refrigerator power. (N.K.)

  14. High power tests of dressed supconducting 1.3 GHz RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Hocker, A.; Harms, E.R.; Lunin, A.; Sukhanov, A.; /Fermilab

    2011-03-01

    A single-cavity test cryostat is used to conduct pulsed high power RF tests of superconducting 1.3 GHz RF cavities at 2 K. The cavities under test are welded inside individual helium vessels and are outfitted ('dressed') with a fundamental power coupler, higher-order mode couplers, magnetic shielding, a blade tuner, and piezoelectric tuners. The cavity performance is evaluated in terms of accelerating gradient, unloaded quality factor, and field emission, and the functionality of the auxiliary components is verified. Test results from the first set of dressed cavities are presented here.

  15. Electron Source based on Superconducting RF

    Science.gov (United States)

    Xin, Tianmu

    High-bunch-charge photoemission electron-sources operating in a Continuous Wave (CW) mode can provide high peak current as well as the high average current which are required for many advanced applications of accelerators facilities, for example, electron coolers for hadron beams, electron-ion colliders, and Free-Electron Lasers (FELs). Superconducting Radio Frequency (SRF) has many advantages over other electron-injector technologies, especially when it is working in CW mode as it offers higher repetition rate. An 112 MHz SRF electron photo-injector (gun) was developed at Brookhaven National Laboratory (BNL) to produce high-brightness and high-bunch-charge bunches for electron cooling experiments. The gun utilizes a Quarter-Wave Resonator (QWR) geometry for a compact structure and improved electron beam dynamics. The detailed RF design of the cavity, fundamental coupler and cathode stalk are presented in this work. A GPU accelerated code was written to improve the speed of simulation of multipacting, an important hurdle the SRF structure has to overcome in various locations. The injector utilizes high Quantum Efficiency (QE) multi-alkali photocathodes (K2CsSb) for generating electrons. The cathode fabrication system and procedure are also included in the thesis. Beam dynamic simulation of the injector was done with the code ASTRA. To find the optimized parameters of the cavities and beam optics, the author wrote a genetic algorithm Python script to search for the best solution in this high-dimensional parameter space. The gun was successfully commissioned and produced world record bunch charge and average current in an SRF photo-injector.

  16. RF cavity evaluation with the code SUPERFISH

    International Nuclear Information System (INIS)

    Hori, T.; Nakanishi, T.; Ueda, N.

    1982-01-01

    The computer code SUPERFISH calculates axisymmetric rf fields and is most applicable to re-entrant cavities of an Alvarez linac. Some sample results are shown for the first Alvarez's in NUMATRON project. On the other hand the code can also be effectivily applied to TE modes excited in an RFQ linac when the cavity is approximately considered as positioning at an infinite distance from the symmetry axis. The evaluation was made for several RFQ cavities, models I, II and a test linac named LITL, and useful results for the resonator design were obtained. (author)

  17. A superconducting test cavity for DORIS

    International Nuclear Information System (INIS)

    Bauer, W.; Brandelik, A.; Lekmann, W.; Szecsi, L.

    1978-03-01

    A summary of experimental goals, technical requirements and possible solutions for the construction of a superconducting accelerating cavity to be tested at DORIS is given. The aim of the experiment is to prove the applicability of superconducting cavities in storage rings and to study the problems typical for this application. The paper collects design considerations about cavity geometry and fabrication, input coupling, output coupling for higher modes, tuner, cryostat and controls. (orig.) [de

  18. PEP-II RF cavity revisited

    International Nuclear Information System (INIS)

    Rimmer, R.A.; Koehler, G.; Li, D.; Hartman, N.; Folwell, N.; Hodgson, J.; Ko, K.; McCandless, B.

    1999-01-01

    This report describes the results of numerical simulations of the PEP-II RF cavity performed after the completion of the construction phase of the project and comparisons are made to previous calculations and measured results. These analyses were performed to evaluate new calculation techniques for the HOM distribution and RF surface heating that were not available at the time of the original design. These include the use of a high frequency electromagnetic element in ANSYS and the new Omega 3P code to study wall losses, and the development of broadband time domain simulation methods in MAFIA for the HOM loading. The computed HOM spectrum is compared with cavity measurements and observed beam-induced signals. The cavity fabrication method is reviewed, with the benefit of hindsight, and simplifications are discussed

  19. Performance of Superconducting Cavities as Required for the SPL

    CERN Document Server

    Weingarten, Wolfgang

    2008-01-01

    This document outlines an optimisation analysis for the RF cavities of the planned Superconducting Proton Linac (SPL) at CERN with regard to the operating frequency and temperature. The analysis is based on a phenomenological assessment of the field dependent Q-value, as taken from published test results from RF cavities of various proveniences. It turns out that the design Q-value at an accelerating gradient of 25 MV/m ($\\Beta$ = 1 cavity) of $1^{.}10^{10}$ at 704 (1408) MHz is attainable at 1.9 (1.6) K, respectively, however, with the present state-of-the-art manufacturing, at the expense of some reprocessing. The optimum of the total electrical grid power consumption (composed of RF and cryogenics) is estimated as a function of frequency and operating temperature for both the low and high power SPL. This document outlines an optimisation analysis for the RF cavities of the planned Superconducting Proton Linac (SPL) at CERN with regard to the operating frequency and temperature. The analysis is based on a p...

  20. Digital base-band rf control system for the superconducting Darmstadt electron linear accelerator

    Directory of Open Access Journals (Sweden)

    M. Konrad

    2012-05-01

    Full Text Available The accelerating field in superconducting cavities has to be stabilized in amplitude and phase by a radio-frequency (rf control system. Because of their high loaded quality factor superconducting cavities are very susceptible for microphonics. To meet the increased requirements with respect to accuracy, availability, and diagnostics, the previous analog rf control system of the superconducting Darmstadt electron linear accelerator S-DALINAC has been replaced by a digital rf control system. The new hardware consists of two components: An rf module that converts the signal from the cavity down to the base-band and a field-programmable gate array board including a soft CPU that carries out the signal processing steps of the control algorithm. Different algorithms are used for normal-conducting and superconducting cavities. To improve the availability of the control system, techniques for automatic firmware and software deployment have been implemented. Extensive diagnostic features provide the operator with additional information. The architecture of the rf control system as well as the functionality of its components will be presented along with measurements that characterize the performance of the system, yielding, e.g., an amplitude stabilization down to (ΔA/A_{rms}=7×10^{-5} and a phase stabilization of (Δϕ_{rms}=0.8° for superconducting cavities.

  1. Muon spin rotation studies of niobium for superconducting rf applications

    Directory of Open Access Journals (Sweden)

    A. Grassellino

    2013-06-01

    Full Text Available In this work we investigate superconducting properties of niobium samples via application of the muon spin rotation/relaxation (μSR technique. We employ for the first time the μSR technique to study samples that are cut out from large and small grain 1.5 GHz radio frequency (rf single cell niobium cavities. The rf test of these cavities was accompanied by full temperature mapping to characterize the rf losses in each of the samples. Results of the μSR measurements show that standard cavity surface treatments like mild baking and buffered chemical polishing performed on the studied samples affect their surface pinning strength. We find an interesting correlation between high field rf losses and field dependence of the sample magnetic volume fraction measured via μSR. The μSR line width observed in zero-field-μSR measurements matches the behavior of Nb samples doped with minute amounts of Ta or N impurities. A lower and an upper bound for the upper critical field H_{c2} of these cutouts is found.

  2. Fast Ferroelectric L-Band Tuner for Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2012-07-03

    Design, analysis, and low-power tests are described on a ferroelectric tuner concept that could be used for controlling external coupling to RF cavities for the superconducting Energy Recovery Linac (ERL) in the electron cooler of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). The tuner configuration utilizes several small donut-shaped ferroelectric assemblies, which allow the design to be simpler and more flexible, as compared to previous designs. Design parameters for 704 and 1300 MHz versions of the tuner are given. Simulation results point to efficient performance that could reduce by a factor-of-ten the RF power levels required for driving superconducting cavities in the BNL ERL.

  3. Fast Ferroelectric L-Band Tuner for Superconducting Cavities

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2012-01-01

    Design, analysis, and low-power tests are described on a ferroelectric tuner concept that could be used for controlling external coupling to RF cavities for the superconducting Energy Recovery Linac (ERL) in the electron cooler of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). The tuner configuration utilizes several small donut-shaped ferroelectric assemblies, which allow the design to be simpler and more flexible, as compared to previous designs. Design parameters for 704 and 1300 MHz versions of the tuner are given. Simulation results point to efficient performance that could reduce by a factor-of-ten the RF power levels required for driving superconducting cavities in the BNL ERL.

  4. Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities

    International Nuclear Information System (INIS)

    Alicia Hofler; Jean Delayen

    2005-01-01

    Electronic damping of microphonic vibrations in superconducting rf cavities involves an active modulation of the cavity field amplitude in order to induce ponderomotive forces that counteract the effect of ambient vibrations on the cavity frequency. In lightly beam loaded cavities, a reduction of the microphonics-induced frequency excursions leads directly to a reduction of the rf power required for phase and amplitude stabilization. Jefferson Lab is investigating such an electronic damping scheme that could be applied to the JLab 12 GeV upgrade, the RIA driver, and possibly to energy-recovering superconducting linacs. This paper discusses a model and presents simulation results for electronic damping of microphonic vibrations

  5. Superconducting multi-cell trapped mode deflecting cavity

    Science.gov (United States)

    Lunin, Andrei; Khabiboulline, Timergali; Gonin, Ivan; Yakovlev, Vyacheslav; Zholents, Alexander

    2017-10-10

    A method and system for beam deflection. The method and system for beam deflection comprises a compact superconducting RF cavity further comprising a waveguide comprising an open ended resonator volume configured to operate as a trapped dipole mode; a plurality of cells configured to provide a high operating gradient; at least two pairs of protrusions configured for lowering surface electric and magnetic fields; and a main power coupler positioned to optimize necessary coupling for an operating mode and damping lower dipole modes simultaneously.

  6. Development of superconducting acceleration cavity technology for free electron lasers

    International Nuclear Information System (INIS)

    Lee, Jong Min; Lee, Byung Cheol; Kim, Sun Kook; Jeong, Young Uk; Cho, Sung Oh

    2000-10-01

    As a result of the cooperative research between the KAERI and Peking University, the key technologies of superconducting acceleration cavity and photoelectron gun have been developed for the application to high power free electron lasers. A 1.5-GHz, 1-cell superconducting RF cavity has been designed and fabricated by using pure Nb sheets. The unloaded Q values of the fabricated superconducting cavity has been measured to be 2x10 9 at 2.5K, and 8x10 9 at 1.8K. The maximum acceleration gradient achieved was 12 MeV/m at 2.5K, and 20MV/m at 1.8 K. A cryostat for the 1-cell superconducting cavity has been designed. As a source of electron beam, a DC photocathode electron gun has been designed and fabricated, which is composed of a photocathode evaporation chamber and a 100-keV acceleration chamber. The efficiency of the Cs2Te photocathode is 3% nominally at room temperature, 10% at 290 deg C. The superconducting photoelectron gun system developed has been estimated to be a good source of high-brightness electron beam for high-power free electron lasers

  7. Development of superconducting acceleration cavity technology for free electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jong Min; Lee, Byung Cheol; Kim, Sun Kook; Jeong, Young Uk; Cho, Sung Oh

    2000-10-01

    As a result of the cooperative research between the KAERI and Peking University, the key technologies of superconducting acceleration cavity and photoelectron gun have been developed for the application to high power free electron lasers. A 1.5-GHz, 1-cell superconducting RF cavity has been designed and fabricated by using pure Nb sheets. The unloaded Q values of the fabricated superconducting cavity has been measured to be 2x10{sup 9} at 2.5K, and 8x10{sup 9} at 1.8K. The maximum acceleration gradient achieved was 12 MeV/m at 2.5K, and 20MV/m at 1.8 K. A cryostat for the 1-cell superconducting cavity has been designed. As a source of electron beam, a DC photocathode electron gun has been designed and fabricated, which is composed of a photocathode evaporation chamber and a 100-keV acceleration chamber. The efficiency of the Cs2Te photocathode is 3% nominally at room temperature, 10% at 290 deg C. The superconducting photoelectron gun system developed has been estimated to be a good source of high-brightness electron beam for high-power free electron lasers.

  8. Status of superconducting RF test facility (STF)

    International Nuclear Information System (INIS)

    Hayano, Hitoshi

    2005-01-01

    A superconducting technology was recommended for the main linac design of the International Linear Collider (ILC) by the International Technology Recommendation Panel (ITRP). The basis for this design has been developed and tested at DESY, and R and D is progressing at many laboratories around the world including DESY, Orsay, KEK, FNAL, SLAC, Cornell, and JLAB. In order to promote Asian SC-technology for ILC, construction of a test facility in KEK was discussed and decided. The role and status of the superconducting RF test facility (STF) is reported in this paper. (author)

  9. Piezoelectric Tuner Compensation of Lorentz Detuning in Superconducting Cavities

    International Nuclear Information System (INIS)

    Jean Delayen; Davis, G.

    2003-01-01

    Pulsed operation of superconducting cavities can induce large variations of the resonant frequency through excitation of the mechanical modes by the radiation pressure. The phase and amplitude control system must be able to accommodate this frequency variation; this can be accomplished by increasing the capability of the rf power source. Alternatively, a piezo electric tuner can be activated at the same repetition rate as the rf to counteract the effect of the radiation pressure. We have demonstrated such a system on the prototype medium beta SNS cryomodule with a reduction of the dynamic Lorentz detuning during the rf pulse by a factor of 3. Piezo electric tuners can also be used to reduce the level of microphonics in low-current cw accelerators. We have measured the amplitude and phase of the transfer function of the piezo control system (from input voltage to cavity frequency) up to several kHz

  10. Progress in diagnostic techniques for SC [superconducting] cavities

    International Nuclear Information System (INIS)

    Reece, C.E.

    1988-01-01

    Despite the very real progress that has been made, the routine performance of superconducting cavities still falls far short of both the theoretical expectations and the performance of afew exceptional examples. It is the task of systematically applied diagnostic techniques to reveal additional information concerning the response of superconducting surfaces to applied RF fields. In this paper we will direct our attention to discussions of recent developments in diagnostic techniqeus, such as thermometry in superfluid helium, and scanning laser acoustic microscopy. 18 refs., 12 figs

  11. Study of superconducting cavities for high power proton accelerators

    International Nuclear Information System (INIS)

    Biarrotte, J.L.

    2000-01-01

    The research program on hybrid reactors has started in France in order to study the technologies allowing the transmutation of radioactive wastes thanks to a spallation neutron source supplied by a linear high intensity proton accelerator. The study of the high energy part of this accelerator (superconducting accelerator for hybrid) has started, and its aim is the design of superconducting radiofrequency cavities which make the two different sections of the accelerator (0.47 and 0.65). This thesis presents the advance of the work carried out on this topic since 1997, in particular the design and optimization of the 5-cell cavities which work at the 704.4 MHz frequency. The experimental part of the study has been carried out in parallel with the industrial fabrication (Cerca) of several prototypes of mono-cell cavities. These cavities have shown very good RF performances during the tests in vertical cryostat; the A 102 A cavity, in particular develops a Q0 of 7.10 10 (indicating very low RF losses) and reaches an accelerator field of 25 MV/m, i.e. more than two times the specified value (about 10 MV/V). Finally, a new risk analysis method for the excitation of the upper modes is proposed. This method shows in particular the uselessness of the implementation of HOM couplers on the cavities for a continuous beam use. (J.S.)

  12. LEP superconducting cavities go into storage

    CERN Multimedia

    Patrice Loïez

    2001-01-01

    Superconducting radio-frequency cavities from the LEP-2 phase (1996-2000) are put into storage in the tunnel that once housed the Intersecting Storage Rings (ISR), the world’s first proton collider, located at CERN.

  13. The influence of chemical treatments on the superconducting properties of technical niobium materials and their effect on the performance of superconducting radio frequency cavities

    International Nuclear Information System (INIS)

    Roy, S B; Sahni, V C; Myneni, G R

    2009-01-01

    We present the results of a study of superconducting response in the niobium materials used in the fabrication of high accelerating gradient (>25 MV m -1 ) superconducting radio frequency (SC-RF) cavities. These results clearly show that the typical surface chemical treatment deployed during the fabrication of SC-RF cavities affects the superconducting properties of pure niobium materials. Such SC-RF cavities operating at 2 K are often found to show anomalous RF losses, causing either a strong degradation of the quality factor or a thermal breakdown for cavity magnetic fields between 1 and 1.5 kOe. The results of our study suggest a correlation between the field for the first flux-line penetration in these chemically treated technical niobium materials and the reported onset field of anomalous losses in the SC-RF cavities.

  14. The influence of chemical treatments on the superconducting properties of technical niobium materials and their effect on the performance of superconducting radio frequency cavities

    Science.gov (United States)

    Roy, S. B.; Myneni, G. R.; Sahni, V. C.

    2009-10-01

    We present the results of a study of superconducting response in the niobium materials used in the fabrication of high accelerating gradient (>25 MV m-1) superconducting radio frequency (SC-RF) cavities. These results clearly show that the typical surface chemical treatment deployed during the fabrication of SC-RF cavities affects the superconducting properties of pure niobium materials. Such SC-RF cavities operating at 2 K are often found to show anomalous RF losses, causing either a strong degradation of the quality factor or a thermal breakdown for cavity magnetic fields between 1 and 1.5 kOe. The results of our study suggest a correlation between the field for the first flux-line penetration in these chemically treated technical niobium materials and the reported onset field of anomalous losses in the SC-RF cavities.

  15. Superconducting RF separator for Omega Spectrometer

    CERN Multimedia

    1977-01-01

    The photo shows an Nb-deflector for the superconducting RF separator ready for installation in its cryostat (visible at the back). Each deflector was about 3 m long. L. Husson and P. Skacel (Karlsruhe) stand on the left, A. Scharding (CERN) stands on the right. This particle separator, the result of a collaboration between the Gesellshaft für Kernforschung, Karlsruhe, and CERN was installed in the S1 beam line to Omega spectrometer. (See Annual Report 1977.)

  16. Pressurized rf cavities in ionizing beams

    Directory of Open Access Journals (Sweden)

    B. Freemire

    2016-06-01

    Full Text Available A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF_{6} and O_{2} were measured.

  17. Prototype superconducting radio-frequency cavity for LEP

    CERN Multimedia

    1985-01-01

    This niobium superconducting cavity was part of the prototype stages for an upgrade to LEP, known as LEP-2. Superconducting cavities would eventually replace the traditional copper cavities and allow beam energies of 100 GeV.

  18. Superconducting RF Development at Nuclear Science Centre

    CERN Document Server

    Roy, Amit

    2005-01-01

    A Superconducting Linac is being installed as a booster for the 15 UD Pelletron accelerator at Nuclear Science Centre (NSC). The accelerating structure for this linac is a Nb QWR cavity, designed and fabricated as a joint collaboration between NSC and ANL, USA. Initial cavities required for the first linac module were fabricated at ANL. For fabrication of cavities required for future modules a Superconducting Resonator Fabrication Facility has been set up at NSC. Three quarter wave resonator (QWR) cavities have been fabricated using the in-house facility. This facility has been used for repairs on the resonators which sprung leaks. Fabrication of fifteen resonators for the second and third linac modules is under progress. Eight resonators along with a superconducting solenoid has been installed in the first linac cryostat and tested for energy gain with a pulsed beam of 90 MeV Si from the Pelletron. Acceleration of the ions to 96 MeV was measured downstream and beam transmission through the linac was measured...

  19. Radiation measurements during cavities conditioning on APS RF test stand

    International Nuclear Information System (INIS)

    Grudzien, D.M.; Kustom, R.L.; Moe, H.J.; Song, J.J.

    1993-01-01

    In order to determine the shielding structure around the Advanced Photon Source (APS) synchrotron and storage ring RF stations, the X-ray radiation has been measured in the near field and far field regions of the RF cavities during the normal conditioning process. Two cavity types, a prototype 352-MHz single-cell cavity and a 352-MHz five-cell cavity, are used on the APS and are conditioned in the RF test stand. Vacuum measurements are also taken on a prototype 352-MHz single-cell cavity and a 352-MHz five-cell cavity. The data will be compared with data on the five-cell cavities from CERN

  20. Contamination issues in superconducting cavity technology

    International Nuclear Information System (INIS)

    Kneisel, Peter

    1997-01-01

    The application of radio-frequency superconductivity technology in particle accelerator projects has become increasingly evident in recent years. Several large scale projects around the world are either completed or close to completion, such as CEBAF, HERA, TRISTAN and LEP. And superconducting cavity technology is seriously being considered for future applications in linear colliders (TESLA), high current proton accelerators (APT, spallation neutron sources), muon colliders and free electron lasers for industrial application. The reason for this multitude of activities are matured technology based on a better understanding of the phenomena encountered in superconducting cavities and the influence of improved material properties and contamination and quality control measures

  1. Physics design of APT linac with normal conducting rf cavities

    International Nuclear Information System (INIS)

    Nath, S.; Billen, J.H.; Stovall, J.E.; Takeda, Harunori; Young, L.M.

    1996-01-01

    The accelerator based production of tritium calls for a high-power, cw proton linac. Previous designs for such a linac use a radiofrequency quadrupole (RFQ), followed by a drift-tube linac (DTL) to an intermediate energy and a coupled-cavity linc (CCL) to the final energy. The Los Alamos design uses a high-energy (6.7 MeV) RFQ followed by the newly developed coupled-cavity drift-tube linac (CCDTL) and a CCL. This design accommodates external electromagnetic quadrupole lenses which provide a strong uniform focusing lattice from the end of the RFQ to the end of the CCL. The cell lengths in linacs of traditional design are typically graded as a function of particle velocity. By making groups of cells symmetric in both the CCDTL and CCL, the cavity design as well as mechanical design and fabrication is simplified without compromising the performance. At higher energies, there are some advantages of using superconducting rf cavities. Currently, such schemes are under vigorous study. This paper describes the linac design based on normal conducting cavities and presents simulation results

  2. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by TEM and EELS

    OpenAIRE

    Trenikhina, Y.; Romanenko, A.; Kwon, J.; Zuo, J. -M.; Zasadzinski, J. F.

    2015-01-01

    Nanoscale defect structure within the magnetic penetration depth of ~100nm is key to the performance limitations of niobium superconducting radio frequency (SRF) cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride for...

  3. Tuning of External Q And Phase for The Cavities of A Superconducting Linear Accelerator

    CERN Document Server

    Katalev, V V

    2004-01-01

    The RF power required for a certain gradient of a superconducting cavity depends on the beam current and coupling between the cavity and waveguide. The coupling with the cavity may be changed by variation of Qext. Different devices can be used to adjust Qext or phase. In this paper three stub and E-H tuners are compared and their usability for the RF power distribution system for the superconducting accelerator of the European Xray laser and the TESLA linear collider is considered. The tuners were analyzed by using the scattering matrix. Advantages and limitations of the devices are presented.

  4. Surface processing for bulk niobium superconducting radio frequency cavities

    Science.gov (United States)

    Kelly, M. P.; Reid, T.

    2017-04-01

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4 mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single- or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies on real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and ‘nitrogen doping’ of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.

  5. Operating experience with superconducting cavities at Jefferson Lab

    International Nuclear Information System (INIS)

    Reece, C.E.

    1998-01-01

    The CEBAF recirculating superconducting electron linac at Jefferson Lab is now in full operation supporting nuclear physics experiments in three target halls at up to 4.4 GeV. The 330 SRF cavities, operating at 2.0 K, continue to perform well above design specifications, and have accumulated over 8,000,000 operating cavity hours. The authors have to date no evidence of degradation of cavity performance. The SRF cavities have demonstrated excellent reliability. The one klystron per cavity design provides CEBAF with flexibility and redundancy for normal operations. Several techniques have been developed for establishing optimum operating conditions for the 330 independent systems. Operation of the cavities and control systems at the full design current of 1 mA has recently been achieved. The principal constraints on usable gradient for low current operations are (1) discharge at the cold ceramic rf window induced by electron field emission in cavities, (2) tuner controls, and (3) stability of the waveguide vacuum in the region between the warm and cold windows. Several cryomodules have been improved by application of rf helium processing while installed on the beamline

  6. Material studies for CLIC RF cavities

    CERN Document Server

    Taborelli, M

    2004-01-01

    Following the EST/SM suggestion of replacing copper by molybdenum or tungsten for the construction of the RF cavity irises, different CLIC main beam accelerating structures were produced, extensively operated and disassembled for iris surface inspection. The observed surface modifications were found to be very similar to those obtained by sparking in a dedicated laboratory set-up, showing the superior behaviour of both Mo and W with respect to Cu, in terms of surface erosion and conditioning. The iris thermomechanical fatigue due to RF heating was simulated by high power pulsed laser irradiation. A CuZr alloy was found to be much more resistant than pure Cu. Measurements at higher pulse number will be performed on CuZr in order to extrapolate its fatigue behaviour up to the nominal CLIC duration. Finally a possible future development of a hybrid probe beam acceleration structure will be presented.

  7. High field conditioning of cryogenic RF cavities

    International Nuclear Information System (INIS)

    Cole, M.; Debiak, T.; Lom, C.; Shephard, W.; Sredniawski, J.

    1993-01-01

    Space-based and other related accelerators have conditioning and operation requirements that are not found in most machines. The use of cryogenic copper, relatively poor vacuum, and limited power storage and operating time put unusual demands on the high-field conditioning process and present some concerns. Two CW cryogenic engineering model open-quotes sparkerclose quotes cavities have been fabricated and tested to fairly high field levels. Tests included initial and repeated conditioning as well as sustained RF operations. The two cavities were an engineering model TDL and an engineering model RFQ. Both cavities operated at 425 MHz. The DTL was conditioned to 46 MV/m at 100% duty factor (CW) at cryogenic temperature. This corresponds to a gap voltage of 433 kV and a real estate accelerating gradient (energy gain/total cavity length) of 6.97 MV/m. The authors believe this to be record performance for cryo CW operation. During cryo pulsed operation, the same cavity reached 48 MV/m with 200 μsec pulses at 0.5% DF. The RFQ was conditioned to 30 MV/m CW at cryo, 85 kV gap voltage. During a brief period of cryo pulsed operation, the RFQ operated at 46 MV/m, or 125 kV gap voltage. Reconditioning experiments were performed on both cavities and no problems were encountered. It should be noted that the vacuum levels were not very stringent during these tests and no special cleanliness or handling procedures were followed. The results of these tests indicate that cavities can run CW without difficulty at cryogenic temperatures at normal conservative field levels. Higher field operation may well be possible, and if better vacuums are used and more attention is paid to cleanliness, much higher fields may be attainable

  8. Cs2Te normal conducting photocathodes in the superconducting rf gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

    2010-01-01

    The superconducting radio frequency photoinjector (SRF gun) is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs2Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs2Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

  9. Criteria for vacuum breakdown in rf cavities

    International Nuclear Information System (INIS)

    Peter, W.; Faehl, R.J.; Kadish, A.; Thode, L.E.

    1983-01-01

    A new high-voltage scaling based on Kilpatrick's criterion is presented that suggests that voltages more than twice the Kilpatrick limit can be obtained with identical initial conditions of vacuum and surface cleanliness. The calculations are based on the experimentally observed decrease in secondary electron emission with increasing ion-impact energy above 100 keV. A generalized secondary-emission package has been developed to simulate actual cavity dynamics in conjunction with our 2 1/2-dimensional fully electromagnetic particle-in-cell code CEMIT. The results are discussed with application to the suppression of vacuum breakdown in rf accelerator devices

  10. Calculation of rf fields in axisymmetric cavities

    International Nuclear Information System (INIS)

    Iwashita, Y.

    1985-01-01

    A new code, PISCES, has been developed for calculating a complete set of rf electromagnetic modes in an axisymmetric cavity. The finite-element method is used with up to third-order shape functions. Although two components are enough to express these modes, three components are used as unknown variables to take advantage of the symmetry of the element matrix. The unknowns are taken to be either the electric field components or the magnetic field components. The zero-divergence condition will be satisfied by the shape function within each element

  11. Characterization of Superconducting Cavities for HIE-ISOLDE

    CERN Document Server

    Martinello, Martina

    2013-01-01

    In this report the radiofrequency measurements done for the superconducting cavities developed at CERN for the HIE-ISOLDE project are analyzed. The purpose of this project is improve the energy of the REX-ISOLDE facility by means of a superconducting LINAC. In this way it will be possible to reach higher accelerating gradients, and so higher particle energies (up to 10MeV/u). At this purpose the Niobium thin film technology was preferred to the Niobium bulk technology because of the technical advantages like the higher thermal conductivity of Copper and the higher stiffness of the cavities which are less sentitive to mechanical vibrations. The Niobium coating is being optimized on test prototypes which are qualified by RF measurements at cold.

  12. Fast Ferroelectric L-Band Tuner for Superconducting Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2011-03-01

    Analysis and modeling is presented for a fast microwave tuner to operate at 700 MHz which incorporates ferroelectric elements whose dielectric permittivity can be rapidly altered by application of an external voltage. This tuner could be used to correct unavoidable fluctuations in the resonant frequency of superconducting cavities in accelerator structures, thereby greatly reducing the RF power needed to drive the cavities. A planar test version of the tuner has been tested at low levels of RF power, but at 1300 MHz to minimize the physical size of the test structure. This test version comprises one-third of the final version. The tests show performance in good agreement with simulations, but with losses in the ferroelectric elements that are too large for practical use, and with issues in bonding of ferroelectric elements to the metal walls of the tuner structure.

  13. Fast Ferroelectric L-Band Tuner for Superconducting Cavities

    International Nuclear Information System (INIS)

    Hirshfield, Jay L.

    2011-01-01

    Analysis and modeling is presented for a fast microwave tuner to operate at 700 MHz which incorporates ferroelectric elements whose dielectric permittivity can be rapidly altered by application of an external voltage. This tuner could be used to correct unavoidable fluctuations in the resonant frequency of superconducting cavities in accelerator structures, thereby greatly reducing the RF power needed to drive the cavities. A planar test version of the tuner has been tested at low levels of RF power, but at 1300 MHz to minimize the physical size of the test structure. This test version comprises one-third of the final version. The tests show performance in good agreement with simulations, but with losses in the ferroelectric elements that are too large for practical use, and with issues in bonding of ferroelectric elements to the metal walls of the tuner structure.

  14. Status of RF superconductivity at Argonne

    International Nuclear Information System (INIS)

    Shepard, K.W.

    1989-01-01

    Development of a superconducting (SC) slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first SC heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerating System), which began regularly scheduled operation in 1978. To date, more than 40,000 hours of bean-on target operating time has been accumulated with ATLAS. The Physics Division at ANL has continued to develop SC RF technology for accelerating heavy-ions, with the result that the SC linac has, up to the present, has been in an almost continuous process of upgrade and expansion. It should be noted that this has been accomplished while at the same time maintaining a vigorous operating schedule in support of the nuclear and atomic physics research programs of the division. In 1987, the Engineering Physics Division at ANL began development of SC RF components for the acceleration of high-brightness proton and deuterium beams. This work has included the evaluation of RF properties of high-T c oxide superconductors, both for the above and for other applications. The two divisions collaborated while they worked on several applications of RF SC, and also worked to develop the technology generally. 11 refs., 6 figs

  15. Status of RF superconductivity at Argonne

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, K.W.

    1989-01-01

    Development of a superconducting (SC) slow-wave structures began at Argonne National Laboratory (ANL) in 1971, and led to the first SC heavy-ion linac (ATLAS - the Argonne Tandem-Linac Accelerating System), which began regularly scheduled operation in 1978. To date, more than 40,000 hours of bean-on target operating time has been accumulated with ATLAS. The Physics Division at ANL has continued to develop SC RF technology for accelerating heavy-ions, with the result that the SC linac has, up to the present, has been in an almost continuous process of upgrade and expansion. It should be noted that this has been accomplished while at the same time maintaining a vigorous operating schedule in support of the nuclear and atomic physics research programs of the division. In 1987, the Engineering Physics Division at ANL began development of SC RF components for the acceleration of high-brightness proton and deuterium beams. This work has included the evaluation of RF properties of high-{Tc} oxide superconductors, both for the above and for other applications. The two divisions collaborated while they worked on several applications of RF SC, and also worked to develop the technology generally. 11 refs., 6 figs.

  16. Fabrication and tests and RF control of the superconducting resonators of the Saclay heavy ion LINAC

    International Nuclear Information System (INIS)

    Cauvin, B.; Coret, M.; Fouan, J.P.; Girard, J.; Girma, J.L.; Leconte, P.; Lussignol, Y.; Moreau, R.; Passerieux, J.P.; Ramstein, G.; Wartski, L.

    1987-01-01

    Two types of niobium superconducting resonators used in the Saclay linac are discussed. The outer cylinder and RF ports are identical for the two designs, but internal structures are different: full wave helix with three gaps behavior; or half wave with two gaps behavior. All cavities (34 full wave, 16 half) were tested for field and mounted in the machine cryostats. Cavity fabrication and performance are summarized. Vibration tests and Rf control are described. It is argued that helix resonators can overcome problems due to vibration. The very low lock out time percentage measured in an acceleration test with 21 cavities supports this confidence

  17. Coupled superconducting resonant cavities for a heavy ion linac

    Energy Technology Data Exchange (ETDEWEB)

    Shepard, K W [Argonne National Lab., IL (United States); Roy, A [Nuclear Science Center, New Delhi (India)

    1992-11-01

    A design for a superconducting niobium slow-wave accelerating structure has been explored that may have performance and cost advantages over existing technology. The option considered is an array of pairs of quarter-wave coaxial-line resonant cavities, the two elements of each pair strongly coupled through a short superconducting transmission line. In the linac formed by such an array, each paired structure is independently phased. A disadvantage of two-gap slow wave structures is that each cavity is relatively short, so that a large number of independently-phased elements is required for a linac. Increasing the number of drift tubes per cavity reduces the number of independently-phased elements but at the cost of reducing the range of useful velocity acceptance for each element. Coupling two cavities splits the accelerating rf eigenmode into two resonant modes each of which covers a portion of the full velocity acceptance range of the original, single cavity mode. Using both of these resonant modes makes feasible the use of coupled cavity pairs for a linac with little loss in velocity acceptance. (Author) 2 figs., 8 refs.

  18. Coupled superconducting resonant cavities for a heavy ion linac

    International Nuclear Information System (INIS)

    Shepard, K.W.; Roy, A.

    1992-01-01

    A design for a superconducting niobium slow-wave accelerating structure has been explored that may have performance and cost advantages over existing technology. The option considered is an array of pairs of quarter-wave coaxial-line resonant cavities, the two elements of each pair strongly coupled through a short superconducting transmission line. In the linac formed by such an array, each paired structure is independently phased. A disadvantage of two-gap slow wave structures is that each cavity is relatively short, so that a large number of independently-phased elements is required for a linac. Increasing the number of drift tubes per cavity reduces the number of independently-phased elements but at the cost of reducing the range of useful velocity acceptance for each element. Coupling two cavities splits the accelerating rf eigenmode into two resonant modes each of which covers a portion of the full velocity acceptance range of the original, single cavity mode. Using both of these resonant modes makes feasible the use of coupled cavity pairs for a linac with little loss in velocity acceptance. (Author) 2 figs., 8 refs

  19. Multi-Physics Analysis of the Fermilab Booster RF Cavity

    International Nuclear Information System (INIS)

    Awida, M.; Reid, J.; Yakovlev, V.; Lebedev, V.; Khabiboulline, T.; Champion, M.

    2012-01-01

    After about 40 years of operation the RF accelerating cavities in Fermilab Booster need an upgrade to improve their reliability and to increase the repetition rate in order to support a future experimental program. An increase in the repetition rate from 7 to 15 Hz entails increasing the power dissipation in the RF cavities, their ferrite loaded tuners, and HOM dampers. The increased duty factor requires careful modelling for the RF heating effects in the cavity. A multi-physic analysis investigating both the RF and thermal properties of Booster cavity under various operating conditions is presented in this paper.

  20. Superconducting Super Collider Laboratory coupled-cavity linac mechanical design

    International Nuclear Information System (INIS)

    Starling, W.J.; Cain, T.

    1992-01-01

    A collaboration between the Superconducting Super Collider Laboratory (SSCL) and the Los Alamos National Laboratory (LANL) for the engineering and mechanical design of the SSCL Coupled-Cavity Linac (CCL) has yielded an innovative example of the well known side coupled-cavity type of linear accelerator. The SSCL CCL accelerates an H - beam from 70 MeV to 600 MeV with an rf cavity structure consisting of eight tanks in each of nine modules for a total length of about 112 meters. Magnetically-coupled bridge couplers transfer power from tank to tank within a module. A single rf power input is located at the center bridge coupler of each module. The bridge couplers permit placement along the beam line of combined function focusing/steering electromagnets and diagnostic pods for beam instrumentation. Each tank and bridge coupler is rf frequency stabilized, nominally to 1,283 MHz, by water pumped through integral water passages. Air isolation grooves surround the water passages at each braze joint so that water-to-vacuum interfaces are avoided. Each tank is supported by adjustable spherical bearing rod end struts to permit alignment and accommodate thermal expansion and contraction of the rf structure. Tank struts, electromagnet/diagnostic pod support frames, vacuum manifolds and utilities are all mounted to a girder-and-leg support stand running the full length of the CCL. (Author) tab., fig

  1. STRUCTURAL ANALYSIS OF SUPERCONDUCTING ACCELERATOR CAVITIES

    International Nuclear Information System (INIS)

    Schrage, D.

    2000-01-01

    The static and dynamic structural behavior of superconducting cavities for various projects was determined by finite element structural analysis. The β = 0.61 cavity shape for the Neutron Science Project was studied in detail and found to meet all design requirements if fabricated from five millimeter thick material with a single annular stiffener. This 600 MHz cavity will have a Lorentz coefficient of minus1.8 Hz/(Mv/meter) 2 and a lowest structural resonance of more than 100 Hz. Cavities at β = 0.48, 0.61, and 0.77 were analyzed for a Neutron Science Project concept which would incorporate 7-cell cavities. The medium and high beta cavities were found to meet all criteria but it was not possible to generate a β = 0.48 cavity with a Lorentz coefficient of less than minus3 Hz/(Mv/meter) 2

  2. Superconducting cavity driving with FPGA controller

    International Nuclear Information System (INIS)

    Czarski, Tomasz; Koprek, Waldemar; Pozniak, Krzysztof T.; Romaniuk, Ryszard S.; Simrock, Stefan; Brandt, Alexander; Chase, Brian; Carcagno, Ruben; Cancelo, Gustavo; Koeth, Timothy W.

    2006-01-01

    A digital control of superconducting cavities for a linear accelerator is presented. FPGA-based controller, supported by Matlab system, was applied. Electrical model of a resonator was used for design of a control system. Calibration of the signal path is considered. Identification of cavity parameters has been carried out for adaptive control algorithm. Feed-forward and feedback modes were applied in operating the cavities. Required performance has been achieved; i.e. driving on resonance during filling and field stabilization during flattop time, while keeping reasonable level of the power consumption. Representative results of the experiments are presented for different levels of the cavity field gradient

  3. Superconducting Radio-Frequency Cavities for Low-Beta Particle Accelerators

    Science.gov (United States)

    Kelly, Michael

    2012-01-01

    High-power proton and ion linac projects based on superconducting accelerating cavities are driving a worldwide effort to develop and build superconducting cavities for beta < 1. Laboratories and institutions building quarter-wave, halfwave and single- or multi-spoke cavities continue to advance the state of the art for this class of cavities, and the common notion that low-beta SRF cavities fill a need in niche applications and have low performance is clearly no longer valid. This article reviews recent developments and results for SC cavity performance for cavities with beta up to approximately 0.5. The considerable ongoing effort on reduced beta elliptical cell cavities is not discussed. An overview of associated subsystems required to operate low-beta cavities, including rf power couplers and fast and slow tuners, is presented.

  4. Novel automatic phase lock determination for superconducting cavity tests at vertical test stand at RRCAT

    International Nuclear Information System (INIS)

    Singh, Kunver Adarsh Pratap; Mohania, Praveen; Rajput, Vikas; Baxy, Deodatta; Shrivastava, Purushottam

    2015-01-01

    RRCAT has developed a Vertical Test Stand (VTS) which is used to test the Nb superconducting cavities under cryogenic conditions. In the VTS, RF cavity is characterized for its quality factor variation vs the accelerating gradient. The RF system is an essential part of the VTS which is required to provide stable RF power to the cavity in terms of amplitude, frequency and phase. RF system of VTS consists of several modules including the LLRF system. The LLRF system consists of the 'Frequency Control Module' which controls the input frequency to the SCRF cavity. Due to high quality factor, bandwidth of the cavity is less than 1 Hz. Even slight mechanical vibrations (microphonics) causes change in cavity resonance frequency resulting in total reflection of incident power. A PLL based frequency tracking module has been used to track the resonant frequency of RF cavity. This module changes RF source frequency according to change in Cavity resonance frequency. A novel method using a LabView based computer program has been developed which changes the phase of input RF signal using IQ modulator and monitors the transmitted power, incident and reflected power. The program plots the graph between phase and ratio of transmitted power to incident/reflected power and gives optimum locking phase for operation which has resulted in significant saving in the overall process time for the tests of the cavities in VTS. (author)

  5. Digital Measurement System for the HIE-Isolde Superconducting Accelerating Cavities

    CERN Document Server

    Elias, Michal

    Extensive R&D efforts are being invested at CERN into the fundamental science of the RF superconductivity, cavity design, niobium sputtering, coating and RF properties of superconducting cavities. Fast and precise characterization and measurements of RF parameters of the newly produced cavities is essential for advances with the cavity production. The currently deployed analogue measurement system based on an analogue phase discriminators and tracking RF generators is not optimal for efficient work at the SM18 superconducting cavity test stand. If exact properties of the cavity under test are not known a traditional feedback loop will not be able to find resonant frequency in a reasonable time or even at all. This is mainly due to a very high Q factor. The resonance peak is very narrow (fraction of a Hz at 100 MHz). If the resonant frequency is off by several bandwidths, small changes of the cavity field during the tuning will not be measureable. Also cavity field will react only very slowly to any change...

  6. Superconducting RF activities at Cornell University

    International Nuclear Information System (INIS)

    Kirchgessner, J.; Barnes, P.; Belomestnykh, S.; Chojnacki, E.; Ehrlich, R.; Flynn, G.; Graber, J.; Hartung, W.; Hays, T.; Kaplan, R.; and others.

    1996-01-01

    The decision was made to try to increase the luminosity of CESR as high as possible with a single magnet ring. This, the Phase-III plan, can yield a luminosity of 1 x 10 33 with 45 bunches in each beam for a total current in each beam of 0.5 amperes. This plan utilizes four superconducting, single cell cavities. The use of only four SC accelerating cells as compared to the present twenty normal conducting cells decreases both the broad band and narrow band impedances sufficiently to allow stable operation at these half ampere current levels. (R.P.)

  7. Development of superconducting cavities at JAERI

    International Nuclear Information System (INIS)

    Ouchi, N.

    2001-01-01

    Development of superconducting (SC) cavities is continued for the high intensity proton accelerator in JAERI. In FY-1999, we carried out R and D work; (1) 2nd vertical test of β=0.886 single-cell cavity, (2) vertical test for observation of Q-disease without heat treatment after electropolishing, (3) vertical test of β=0.5 5-cell cavity, (4) pretuning, surface treatment and vertical test of β=0.886 5-cell cavity, (5) pulsed operation of β=0.886 single-cell cavity in the vertical test to confirm the validity of a new model calculation. This paper describes the present status of the R and D work for the SC cavities in JAERI. (author)

  8. Mechanical design of SXLS [Superconducting X-ray Lithography Source] radio-frequency cavity

    International Nuclear Information System (INIS)

    Mortazavi, P.; Sharma, S.; Keane, J.; Thomas, M.

    1989-01-01

    This paper presents the mechanical design of a Radio-Frequency (RF) cavity to be used on a compact storage ring for Superconducting X-ray Lithography Source (SXLS). Various design features of this cavity are discussed, including basic geometrical configuration, structural design, initial and operational tuning, vacuum multipactoring, power window, and damping of higher order modes. A second application of this cavity design for beam life extension in an existing storage ring is also described. 2 refs., 6 figs

  9. Mechanical design of SXLS (Superconducting X-ray Lithography Source) radio-frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Mortazavi, P.; Sharma, S.; Keane, J.; Thomas, M.

    1989-01-01

    This paper presents the mechanical design of a Radio-Frequency (RF) cavity to be used on a compact storage ring for Superconducting X-ray Lithography Source (SXLS). Various design features of this cavity are discussed, including basic geometrical configuration, structural design, initial and operational tuning, vacuum multipactoring, power window, and damping of higher order modes. A second application of this cavity design for beam life extension in an existing storage ring is also described. 2 refs., 6 figs.

  10. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Wolak, M. A.; Tan, T.; Krick, A.; Johnson, E.; Hambe, M.; Chen, Ke; Xi, X. X.

    2014-01-01

    We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB2 films on these substrates showed uniformly good superconducting properties including Tc of 37-40 K, residual resistivity ratio of up to 14, and root-mean-square roughness Rq of 20-30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB2 by the HPCVD technique, an important step towards superconducting rf cavities with MgB2 coating.

  11. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    M. A. Wolak

    2014-01-01

    Full Text Available We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD. To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB_{2} films on these substrates showed uniformly good superconducting properties including T_{c} of 37–40 K, residual resistivity ratio of up to 14, and root-mean-square roughness R_{q} of 20–30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB_{2} by the HPCVD technique, an important step towards superconducting rf cavities with MgB_{2} coating.

  12. RF cavity using liquid dielectric for tuning and cooling

    Science.gov (United States)

    Popovic, Milorad [Warrenville, IL; Johnson, Rolland P [Newport News, VA

    2012-04-17

    A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

  13. Digital control of the superconducting cavities for the LEP energy upgrade

    International Nuclear Information System (INIS)

    Gavallari, G.; Ciapala, E.

    1992-01-01

    The superconducting (SC) cavities for the LEP200 energy upgrade will be installed in units of 16 as for the present copper cavity system. Similar equipment will be used for RF power generation and distribution, for the low-level RF system and for digital control. The SC cavities and their associated equipment however require different interface hardware and new control software. To simplify routine operation control of the SC cavity units is made to resemble as closely as possible that of the existing units. Specific controls for the SC cavities at the equipment level, the facilities available and the integration of the SC cavity units into the LEP RF control system are described. (author)

  14. Superconducting cavity driving with FPGA controller

    Energy Technology Data Exchange (ETDEWEB)

    Czarski, T.; Koprek, W.; Pozniak, K.T.; Romaniuk, R.S. [Warsaw Univ. of Technology (Poland); Simrock, S.; Brand, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Chase, B.; Carcagno, R.; Cancelo, G. [Fermi National Accelerator Lab., Batavia, IL (United States); Koeth, T.W. [Rutgers - the State Univ. of New Jersey, NJ (United States)

    2006-07-01

    The digital control of several superconducting cavities for a linear accelerator is presented. The laboratory setup of the CHECHIA cavity and ACC1 module of the VU-FEL TTF in DESY-Hamburg have both been driven by a Field Programmable Gate Array (FPGA) based system. Additionally, a single 9-cell TESLA Superconducting cavity of the FNPL Photo Injector at FERMILAB has been remotely controlled from WUT-ISE laboratory with the support of the DESY team using the same FPGA control system. These experiments focused attention on the general recognition of the cavity features and projected control methods. An electrical model of the resonator was taken as a starting point. Calibration of the signal path is considered key in preparation for the efficient driving of a cavity. Identification of the resonator parameters has been proven to be a successful approach in achieving required performance; i.e. driving on resonance during filling and field stabilization during flattop time while requiring reasonable levels of power consumption. Feed-forward and feedback modes were successfully applied in operating the cavities. Representative results of the experiments are presented for different levels of the cavity field gradient. (orig.)

  15. Superconducting cavity driving with FPGA controller

    International Nuclear Information System (INIS)

    Czarski, T.; Koprek, W.; Pozniak, K.T.; Romaniuk, R.S.; Simrock, S.; Brand, A.; Chase, B.; Carcagno, R.; Cancelo, G.; Koeth, T.W.

    2006-01-01

    The digital control of several superconducting cavities for a linear accelerator is presented. The laboratory setup of the CHECHIA cavity and ACC1 module of the VU-FEL TTF in DESY-Hamburg have both been driven by a Field Programmable Gate Array (FPGA) based system. Additionally, a single 9-cell TESLA Superconducting cavity of the FNPL Photo Injector at FERMILAB has been remotely controlled from WUT-ISE laboratory with the support of the DESY team using the same FPGA control system. These experiments focused attention on the general recognition of the cavity features and projected control methods. An electrical model of the resonator was taken as a starting point. Calibration of the signal path is considered key in preparation for the efficient driving of a cavity. Identification of the resonator parameters has been proven to be a successful approach in achieving required performance; i.e. driving on resonance during filling and field stabilization during flattop time while requiring reasonable levels of power consumption. Feed-forward and feedback modes were successfully applied in operating the cavities. Representative results of the experiments are presented for different levels of the cavity field gradient. (orig.)

  16. Superconducting Cavity Development for the CEBAF Upgrade

    International Nuclear Information System (INIS)

    I.E. Campisi; J.R. Delayen; L.R. Doolittle; P.Kneisel; J. Mammosser; L. Phillips

    1999-01-01

    Long-term plans for CEBAF at Jefferson Lab call for achieving 12 GeV in the middle of the next decade and 24 GeV after 2010. In support of these plans, an Upgrade Cryomodule, capable of providing more than twice the operating voltage of the existing CEBAF modules within the same length, is being developed. In particular, this requires the development of superconducting cavities capable of consistently operating at gradients above 12 MV/m and Q approximately 10 10 . We have engaged in a complete review of all the processes and procedures involved in the fabrication and assembly of cavities, and are modifying our chemical processing, cleaning, and assembly facilities. While we have retained the cell shape of existing CEBAF cavities, the new superconducting structure will be substantially different in several respects, such as the higher-order-modes damping and the fundamental power coupling systems. Design features and experimental results will be presented

  17. Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

    Science.gov (United States)

    Upadhyay, J.; Palczewski, A.; Popović, S.; Valente-Feliciano, A.-M.; Im, Do; Phillips, H. L.; Vušković, L.

    2017-12-01

    An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity's inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

  18. Experimental Studies of Light Emission Phenomena in Superconducting RF Cavitites

    Energy Technology Data Exchange (ETDEWEB)

    Anthony, P.L.; /SLAC; Delayen, J.R.; /Jefferson Lab; Fryberger, D.; /SLAC; Goree, W.S.; Mammosser, J.; /Jefferson Lab /SNS Project, Oak Ridge; Szalata, Z.M.; II, J.G.Weisend /SLAC

    2009-08-04

    Experimental studies of light emission phenomena in superconducting RF cavities, which we categorize under the general heading of cavity lights, are described. The cavity lights data, which were obtained using a small CCD video camera, were collected in a series of nine experimental runs ranging from {approx} 1/2 to {approx} 2 h in duration. The video data were recorded on a standard VHS tape. As the runs progressed, additional instrumentation was added. For the last three runs a LabVIEW controlled data acquisition system was included. These runs furnish evidence for several, possibly related, light emission phenomena. The most intriguing of these is what appear to be small luminous objects {le} 1.5 mm in size, freely moving about in the vacuum space, generally without wall contact, as verified by reflections of the tracks in the cavity walls. In addition, on a number of occasions, these objects were observed to bounce off of the cavity walls. The wall-bounce aspect of most of these events was clearly confirmed by pre-bounce and post-bounce reflections concurrent with the tracks. In one of the later runs, a mode of behavior was observed that was qualitatively different from anything observed in the earlier runs. Perhaps the most perplexing aspect of this new mode was the observation of as many as seven luminous objects arrayed in what might be described as a macromolecular formation, coherently moving about in the interior of the cavity for extended periods of time, evidently without any wall contact. It is suggested that these mobile luminous objects are without explanation within the realm of established physics. Some remarks about more exotic theoretical possibilities are made, and future plans are discussed.

  19. Room temperature RF characterization of Nb make super conducting radio frequency cavities at RRCAT

    International Nuclear Information System (INIS)

    Mahawar, Ashish; Mohania, Praveen; Shrivastava, Purushottam; Yadav, Anand; Puntambekar, Avinash

    2015-01-01

    In order to ensure that the final welded Nb superconducting RF cavities are at the correct frequency the cavity structures are measured at various development stages for their resonant frequency. These measurements are performed at room temperature using a cavity measurement setup developed in house and a VNA. These measurements are critical to identify the length a cavity structure needs to be trimmed before welding. Measurement of resonant frequencies of Nb made cavity structures were performed for half cell, dumb bell, single cell, long end cell and short end cell structures. These structures were then joined to develop single cell and multi-cell 650 MHz/1300 MHz cavities. The present paper describes room temperature cavity characterization being carried out at RRCAT. (author)

  20. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  1. Development of Low Level RF Control Systems for Superconducting Heavy Ion Linear Accelerators, Electron Synchrotrons and Storage Rings

    CERN Document Server

    Aminov, Bachtior; Kolesov, Sergej; Pekeler, Michael; Piel, Christian; Piel, Helmut

    2005-01-01

    Since 2001 ACCEL Instruments is supplying low level RF control systems together with turn key cavity systems. The early LLRF systems used the well established technology based on discrete analogue amplitude and phase detectors and modulators. Today analogue LLRF systems can make use of advanced vector demodulators and modulators combined with a fast computer controlled analogue feed back loop. Feed forward control is implemented to operate the RF cavity in an open loop mode or to compensate for predictable perturbations. The paper will introduce the general design philosophy and show how it can be adapted to different tasks as controlling a synchrotron booster nc RF system at 500 MHz, or superconducting storage ring RF cavities, as well as a linear accelerator at 176 MHz formed by a chain of individually driven and controlled superconducting λ/2 cavities.

  2. Prediction of multipactor in the iris region of rf deflecting mode cavities

    Directory of Open Access Journals (Sweden)

    G. Burt

    2011-12-01

    Full Text Available Multipactor is a major cause of field limitation in many superconducting rf cavities. Multipacting is a particular issue for deflecting mode cavities as the typical behavior is not well studied, understood, or parametrized. In this paper an approximate analytical model for the prediction of multipactor in the iris region of deflecting mode cavities is developed. This new but simple model yields a clear explanation on the broad range of rf field levels over which the multipactor can occur. The principle multipactors under investigation here are two-point multipactors associated with cyclotron motion in the cavity’s rf magnetic field. The predictions from the model are compared to numerical simulations and good agreement is obtained. The results are also compared to experimental results previously reported by KEK and are also found in good agreement.

  3. Building of radio frequency cavity for Superconducting Cyclotron

    International Nuclear Information System (INIS)

    Ahammed, M.; DuttaGupta, A.; Mandal, B.Ch.; Saha, S.; Bhattacharya, P.; Manna, B.; Hembrom, B.; Murmu, S.; Sur, S.; Murali, S.; Chaudhuri, J.; Bhandari, R.K.

    2009-01-01

    Full text: RF cavity for Superconducting Cyclotron is a room temperature cavity having 10 m tall coaxial structure placed symmetrically above and below the median plane. The structure is made of copper and operates within the frequency range of 9 to 27 MHz. The frequency is varied with the help of sliding shorts, which moves up and down. Part of the cavity is in air and rest is in vacuum. After fabrication of individual components, assembly of sub-system has been started by carrying out numeral critical (around 500 joints approx.) soldering and brazing joints of which some of them are located within centimeter of distance. All these joints were tested for vacuum and water sealing including many temporary joints sealed by O rings and C seals. Main criticalities involve in fabricating these sub-assemblies are maintaining dimensional accuracies, concentricity and parallelism. Moreover challenges faced during transportation and handling of this subassembly while carrying out soldering and actual site assembly, were overcome by employing several specially designed fixtures. Fixtures were used to control distortion that would take place during soldering and brazing and to avoid any damage which is likely to occur because of less mechanical strength of soldering and brazing joint. This paper highlights the above difficulties and challenges faced during the actual site assembly of the whole RF system because of its limited accessibility, compactness, requirements of upper and lower resonator cavity to be symmetric and ultra cleanliness. (author)

  4. RF cavity R and D at LBNL for the NLC Damping Rings, FY2000/2001

    International Nuclear Information System (INIS)

    Rimmer, R.A.; Atkinson, D.; Corlett, J.N.; Koehler, G.; Li, D.; Hartman, N.; Rasson, J.; Saleh, T.; Weidenbach, W.

    2001-01-01

    This report contains a summary of the R and D activities at LBNL on RF cavities for the NLC damping rings during fiscal years 2000/2001. This work is a continuation of the NLC RF system R and D of the previous year [1]. These activities include the further optimization and fine tuning of the RF cavity design for both efficiency and damping of higher-order modes (HOMs). The cavity wall surface heating and stresses were reduced at the same time as the HOM damping was improved over previous designs. Final frequency tuning was performed using the high frequency electromagnetic analysis capability in ANSYS. The mechanical design and fabrication methods have been developed with the goals of lower stresses, fewer parts and simpler assembly compared to previous designs. This should result in substantial cost savings. The cavity ancillary components including the RF window, coupling box, HOM loads, and tuners have been studied in more detail. Other cavity options are discussed which might be desirable to either further lower the HOM impedance or increase the stored energy for reduced transient response. Superconducting designs and the use of external ''energy storage'' cavities are discussed. A section is included in which the calculation method is summarized and its accuracy assessed by comparisons with the laboratory measurements of the PEP-II cavity, including errors, and with the beam-sampled spectrum

  5. Electromagnetic characterization of superconducting radio-frequency cavities for gw detection

    Science.gov (United States)

    Ballantini, R.; Bernard, Ph; Chincarini, A.; Gemme, G.; Parodi, R.; Picasso, E.

    2004-03-01

    The electromagnetic properties of a prototype gravitational wave detector, based on two coupled superconducting microwave cavities, were tested. The radio-frequency (rf) detection system was carefully analysed. With the use of piezoelectric crystals small harmonic displacements of the cavity walls were induced and the parametric conversion of the electromagnetic field inside the cavities explored. Experimental results of bandwidth and sensitivity of the parametric converter versus stored energy and voltage applied to the piezoelectric crystal are reported. A rf control loop, developed to stabilize phase changes on signal paths, gave a 125 dBc rejection of the drive mode on a time scale of 1 h.

  6. Electromagnetic characterization of superconducting radio-frequency cavities for gw detection

    International Nuclear Information System (INIS)

    Ballantini, R; Bernard, Ph; Chincarini, A; Gemme, G; Parodi, R; Picasso, E

    2004-01-01

    The electromagnetic properties of a prototype gravitational wave detector, based on two coupled superconducting microwave cavities, were tested. The radio-frequency (rf) detection system was carefully analysed. With the use of piezoelectric crystals small harmonic displacements of the cavity walls were induced and the parametric conversion of the electromagnetic field inside the cavities explored. Experimental results of bandwidth and sensitivity of the parametric converter versus stored energy and voltage applied to the piezoelectric crystal are reported. A rf control loop, developed to stabilize phase changes on signal paths, gave a 125 dBc rejection of the drive mode on a time scale of 1 h

  7. Comparison of Measured and Calculated Coupling between a Waveguide and an RF Cavity Using CST Microwave Studio

    Energy Technology Data Exchange (ETDEWEB)

    J. Shi; H. Chen; S. Zheng; D. Li; R.A. Rimmer; H. Wang

    2006-06-26

    Accurate predications of RF coupling between an RF cavity and ports attached to it have been an important study subject for years for RF coupler and higher order modes (HOM) damping design. We report recent progress and a method on the RF coupling simulations between waveguide ports and RF cavities using CST Microwave Studio in time domain (Transit Solver). Comparisons of the measured and calculated couplings are presented. The simulated couplings and frequencies agree within {approx} 10% and {approx} 0.1% with the measurements, respectively. We have simulated couplings with external Qs ranging from {approx} 100 to {approx} 100,000, and confirmed with measurements. The method should also work well for higher Qs, and can be easily applied in RF power coupler designs and HOM damping for normal-conducting and superconducting cavities.

  8. Comparison of Measured and Calculated Coupling between a Waveguide and an RF Cavity Using CST Microwave Studio

    International Nuclear Information System (INIS)

    J. Shi; H. Chen; S. Zheng; D. Li; R.A. Rimmer; H. Wang

    2006-01-01

    Accurate predications of RF coupling between an RF cavity and ports attached to it have been an important study subject for years for RF coupler and higher order modes (HOM) damping design. We report recent progress and a method on the RF coupling simulations between waveguide ports and RF cavities using CST Microwave Studio in time domain (Transit Solver). Comparisons of the measured and calculated couplings are presented. The simulated couplings and frequencies agree within ∼ 10% and ∼ 0.1% with the measurements, respectively. We have simulated couplings with external Qs ranging from ∼ 100 to ∼ 100,000, and confirmed with measurements. The method should also work well for higher Qs, and can be easily applied in RF power coupler designs and HOM damping for normal-conducting and superconducting cavities

  9. Test results for a heat-treated 4-cell 805 MHz superconducting cavity

    International Nuclear Information System (INIS)

    Rusnak, B.; Shapiro, A.H.

    1995-01-01

    Assessing superconducting technology for potential upgrades to existing proton accelerators as well as applications to future high-current machines necessitates developing expertise in the processing and handling of multicell cavities at useful frequencies. In order to address some of these technological issues, Los Alamos has purchased a 4-cell 805-MHz superconducting cavity from Siemens AG. The individual cavity cells were double-sided titanium heat-treated after equatorial welding, then the irises were welded to complete the cavity assembly. The resulting high RRR (residual resistance ratio) in the cells enables stable operation at higher cavity field levels than are possible with lower RRR material. Additionally, the high thermal conductivity of the material is conducive to rf and high peak power processing. The cavity was also cleaned at Los Alamos with high-pressure water rinsing. Results from the initial cavity tests, utilizing various processing techniques, are presented

  10. Superconducting niobium cavities with high gradients

    International Nuclear Information System (INIS)

    Kneisel, P.; Saito, K.

    1992-01-01

    Present accelerator projects making use of superconducting cavity technology are constructed with design accelerating gradients E acc ranging between 5 MV/m and 8 MV/m and Q-values of several 10 9 . Future plans for upgrades of existing accelerators or for linear colliders call for gradients greater than 15 MV/m corresponding to peak surface electric fields above 30 MV/m. These demands challenge state-of-the-art production technology and require improvements in processing and handling of these cavities to overcome the major performance limitation of field emission loading. This paper reports on efforts to improve the performance of cavities made from niobium from different suppliers by using improved cleaning techniques after processing and ultrahigh vacuum annealing at temperatures of 1400 C. In single cell L-band cavities peak surface electric fields as high as 50 MV/m have been measured without significant field emission loading. (Author) 8 refs., fig

  11. Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma

    Directory of Open Access Journals (Sweden)

    J. Upadhyay

    2017-12-01

    Full Text Available An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity’s inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.

  12. Analytical and numerical study of New field emitter processing for superconducting cavities

    Science.gov (United States)

    Volkov, Vladimir; Petrov, Victor

    2018-02-01

    In this article a scientific prove for a new technology to maximize the accelerating gradient in superconducting cavities by processing on higher order mode frequencies is presented. As dominant energy source the heating of field emitters by an induced rf current (rf-heating) is considered. The field emitter structure is assumed to be a chain of conductive particles, which are formed by attractive forces.

  13. Design of large aperture 500 MHz 5-cell superconducting cavity

    International Nuclear Information System (INIS)

    Wei Yelong; Feng Ziqiang; Lu Changwang; Yu Haibo; Liu Jianfei; Hou Hongtao; Ma Zhenyu; Mao Dongqing

    2012-01-01

    With the potential application of Energy Recovery Linac (ERL), the superconducting (SC) cavities were developed to deliver much higher current than before. Nowadays, the current of the international SC accelerator designed has already exceeded 100 mA. This paper presents the design of a new 500 MHz 5-cell SC cavity (SINAP 5-cell cavity), in which the parameters r/Q= 515.5 Ω of the fundamental mode and the geometry factor G=275.8 are under an acceptable Radio Frequency (RF) field level. (B peak /E acc =4.31 mT/MV/m and E peak /E acc =2.48). This design employs a larger beam pipe to propagate the Higher Order Modes (HOMs) out of the cavity and increases the damping efficiently for the dangerous HOMs. By simulation technique, it has been found that almost all the dangerous HOMs (including TE 111 , TM 110 , and TM 011 ) can be propagated into the beam pipe and are absorbed by ferrite absorbers, when the beam pile is enlarged. Finally, the loss factor for the new 5-cell cavity is also calculated. (authors)

  14. An RF cavity for barrier bucket experiment in the AGS

    Energy Technology Data Exchange (ETDEWEB)

    Fujieda, M.; Iwashita, Y. [Kyoto Univ. (Japan); Mori, Y. [and others

    1998-11-01

    A barrier bucket experiment in the AGS is planed in 1998. An accumulation of the beam, which intensity of 1.0 x 10{sup 14}ppp is, acceleration after the injection with a barrier bucket scheme and other RF gymnastics experiments will be studied. An isolated RF pulse of 40 kV per cavity is necessary for the experiment. The RF frequency is 2 MHz and the isolated pulse is generated at the repetition rate of the revolution frequency of 357 kHz. We have developed the barrier cavity for this experiment. The cavity is loaded with FINEMET core. It has low Q value but high shunt impedance. It makes the necessary power less than that of ferrite-loaded cavity for an isolated RF pulse. (author)

  15. Finite element analyses for RF photoinjector gun cavities

    International Nuclear Information System (INIS)

    Marhauser, F.

    2006-01-01

    This paper details electromagnetical, thermal and structural 3D Finite Element Analyses (FEA) for normal conducting RF photoinjector gun cavities. The simulation methods are described extensively. Achieved results are presented. (orig.)

  16. Finite element analyses for RF photoinjector gun cavities

    Energy Technology Data Exchange (ETDEWEB)

    Marhauser, F. [Berliner Elektronenspeicherring-Gesellschaft fuer Synchrotronstrahlung mbH (BESSY), Berlin (Germany)

    2006-07-01

    This paper details electromagnetical, thermal and structural 3D Finite Element Analyses (FEA) for normal conducting RF photoinjector gun cavities. The simulation methods are described extensively. Achieved results are presented. (orig.)

  17. Analytical and semi-analytical formalism for the voltage and the current sources of a superconducting cavity under dynamic detuning

    CERN Document Server

    Doleans, M

    2003-01-01

    Elliptical superconducting radio frequency (SRF) cavities are sensitive to frequency detuning because they have a high Q value in comparison with normal conducting cavities and weak mechanical properties. Radiation pressure on the cavity walls, microphonics, and tuning system are possible sources of dynamic detuning during SRF cavity-pulsed operation. A general analytic relation between the cavity voltage, the dynamic detuning function, and the RF control function is developed. This expression for the voltage envelope in a cavity under dynamic detuning and dynamic RF controls is analytically expressed through an integral formulation. A semi-analytical scheme is derived to calculate the voltage behavior in any practical case. Examples of voltage envelope behavior for different cases of dynamic detuning and RF control functions are shown. The RF control function for a cavity under dynamic detuning is also investigated and as an application various filling schemes are presented.

  18. RF control studies for moderate beamtime coupling between SRF cavities

    International Nuclear Information System (INIS)

    Doolittle, L.R.; Wang, D.X.

    1998-01-01

    When an SRF accelerator is designed, there is motivation to move the cavities close together on the beamline. Assuming the beamline apertures are not shrunk as well, this compaction (which will increase the overall accelerating gradient and/or lower the dynamic cryogenic heat load) increases the inter-cavity coupling. Within certain limits, the control system can compensate for this coupling by retuning each of the cavities. This paper describes constraints on the RF system, tuners, couplers, and control systems that are required to provide stable operation of cavities in the presence of inter-cavity coupling that exceeds the loaded bandwidth of an individual cavity

  19. RF properties of superconducting Pb electroplated onto Cu

    International Nuclear Information System (INIS)

    Delayen, J.R.

    1988-01-01

    The properties of Pb as a superconducting material for high power rf applications are reviewed. The most common method of producing Pb superconducting resonators, which is by electrodeposition of a thin layer on a Cu substrate, is described, and some suggestions for further development are presented. 56 references, 11 figures, 1 table

  20. LEP superconducting accelerating cavity module

    CERN Multimedia

    1995-01-01

    With its 27-kilometre circumference, the Large Electron-Positron (LEP) collider was the largest electron-positron accelerator ever built. The excavation of the LEP tunnel was Europe’s largest civil-engineering project prior to the Channel Tunnel. Three tunnel-boring machines started excavating the tunnel in February 1985 and the ring was completed three years later. In its first phase of operation, LEP consisted of 5176 magnets and 128 accelerating cavities. CERN’s accelerator complex provided the particles and four enormous detectors, ALEPH, DELPHI, L3 and OPAL, observed the collisions. LEP was commissioned in July 1989 and the first beam circulated in the collider on 14 July. The collider's initial energy was chosen to be around 91 GeV, so that Z bosons could be produced. The Z boson and its charged partner the W boson, both discovered at CERN in 1983, are responsible for the weak force, which drives the Sun, for example. Observing the creation and decay of the short-lived Z boson was a critical test of...

  1. Demountable damped cavity for HOM-damping in ILC superconducting accelerating cavities

    Energy Technology Data Exchange (ETDEWEB)

    Konomi, T., E-mail: konomi@ims.ac.jp [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Yasuda, F. [University of Tokyo, Bunkyo-ku, Tokyo 113-8654 (Japan); Furuta, F. [Laboratory for Elementary-Particle Physics, Cornell University, Ithaca, NY 14853 (United States); Saito, K. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2014-01-11

    We have designed a new higher-order-mode (HOM) damper called a demountable damped cavity (DDC) as part of the R and D efforts for the superconducting cavity of the International Linear Collider (ILC). The DDC has two design concepts. The first is an axially symmetrical layout to obtain high damping efficiency. The DDC has a coaxial structure along the beam axis to realize strong coupling with HOMs. HOMs are damped by an RF absorber at the end of the coaxial waveguide and the accelerating mode is reflected by a choke filter mounted at the entrance of the coaxial waveguide. The second design concept is a demountable structure to facilitate cleaning, in order to suppress the Q-slope problem in a high field. A single-cell cavity with the DDC was fabricated to test four performance parameters. The first was frequency matching between the accelerating cavity and the choke filter. Since the bandwidth of the resonance frequency in a superconducting cavity is very narrow, there is a possibility that the accelerating field will leak to the RF absorber because of thermal shrinkage. The design bandwidth of the choke filter is 25 kHz. It was demonstrated that frequency matching adjusted at room temperature could be successfully maintained at 2 K. The second parameter was the performance of the demountable structure. At the joint, the magnetic field is 1/6 of the maximum field in the accelerating cavity. Ultimately, the accelerating field reached 19 MV/m and Q{sub 0} was 1.5×10{sup 10} with a knife-edge shape. The third parameter was field emission and multipacting. Although the choke structure has numerous parallel surfaces that are susceptible to the multipacting problem, it was found that neither field emission nor multipacting presented problems in both an experiment and simulation. The final parameter was the Q values of the HOM. The RF absorber adopted in the system is a Ni–Zn ferrite type. The RF absorber shape was designed based on the measurement data of permittivity

  2. Demountable damped cavity for HOM-damping in ILC superconducting accelerating cavities

    International Nuclear Information System (INIS)

    Konomi, T.; Yasuda, F.; Furuta, F.; Saito, K.

    2014-01-01

    We have designed a new higher-order-mode (HOM) damper called a demountable damped cavity (DDC) as part of the R and D efforts for the superconducting cavity of the International Linear Collider (ILC). The DDC has two design concepts. The first is an axially symmetrical layout to obtain high damping efficiency. The DDC has a coaxial structure along the beam axis to realize strong coupling with HOMs. HOMs are damped by an RF absorber at the end of the coaxial waveguide and the accelerating mode is reflected by a choke filter mounted at the entrance of the coaxial waveguide. The second design concept is a demountable structure to facilitate cleaning, in order to suppress the Q-slope problem in a high field. A single-cell cavity with the DDC was fabricated to test four performance parameters. The first was frequency matching between the accelerating cavity and the choke filter. Since the bandwidth of the resonance frequency in a superconducting cavity is very narrow, there is a possibility that the accelerating field will leak to the RF absorber because of thermal shrinkage. The design bandwidth of the choke filter is 25 kHz. It was demonstrated that frequency matching adjusted at room temperature could be successfully maintained at 2 K. The second parameter was the performance of the demountable structure. At the joint, the magnetic field is 1/6 of the maximum field in the accelerating cavity. Ultimately, the accelerating field reached 19 MV/m and Q 0 was 1.5×10 10 with a knife-edge shape. The third parameter was field emission and multipacting. Although the choke structure has numerous parallel surfaces that are susceptible to the multipacting problem, it was found that neither field emission nor multipacting presented problems in both an experiment and simulation. The final parameter was the Q values of the HOM. The RF absorber adopted in the system is a Ni–Zn ferrite type. The RF absorber shape was designed based on the measurement data of permittivity and

  3. Research on DC-RF superconducting photocathode injector for high average power FELs

    International Nuclear Information System (INIS)

    Zhao Kui; Hao Jiankui; Hu Yanle; Zhang Baocheng; Quan Shengwen; Chen Jiaer; Zhuang Jiejia

    2001-01-01

    To obtain high average current electron beams for a high average power Free Electron Laser (FEL), a DC-RF superconducting injector is designed. It consists of a DC extraction gap, a 1+((1)/(2)) superconducting cavity and a coaxial input system. The DC gap, which takes the form of a Pierce configuration, is connected to the 1+((1)/(2)) superconducting cavity. The photocathode is attached to the negative electrode of the DC gap. The anode forms the bottom of the ((1)/(2)) cavity. Simulations are made to model the beam dynamics of the electron beams extracted by the DC gap and accelerated by the superconducting cavity. High quality electron beams with emittance lower than 3 π-mm-mrad can be obtained. The optimization of experiments with the DC gap, as well as the design of experiments with the coaxial coupler have all been completed. An optimized 1+((1)/(2)) superconducting cavity is in the process of being studied and manufactured

  4. RF Coupler Design for the TRIUMF ISAC-II Superconducting Quarter Wave Resonator

    CERN Document Server

    Poirier, R L; Harmer, P; Laxdal, R E; Mitra, A K; Sekatchev, I; Waraich, B; Zvyagintsev, V

    2004-01-01

    An RF Coupler for the ISAC-II medium beta (β=0.058 and 0.071) superconducting quarter wave resonators was designed and tested at TRIUMF. The main goal of this development was to achieve stable operation of superconducting cavities at high acceleration gradients and low thermal load to the helium refrigeration system. The cavities will operate at 6 MV/m acceleration gradient in overcoupled mode at a forward power 200 W at 106 MHz. The overcoupling provides ±20 Hz cavity bandwidth, which improves the stability of the RF control system for fast helium pressure fluctuations, microphonics and environmental noise. Choice of materials, cooling with liquid nitrogen, aluminum nitride RF window and thermal shields insure a small thermal load on the helium refrigeration system by the Coupler. An RF finger contact which causedμdust in the coupler housing was eliminated without any degradation of the coupler performance. RF and thermal calculations, design and test results on the coupler are p...

  5. Near-Field Microwave Magnetic Nanoscopy of Superconducting Radio Frequency Cavity Materials

    OpenAIRE

    Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

    2013-01-01

    A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two new measurements are performed to demonstrate these capabilities with a novel near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual- Resistance-Ratio bulk Nb sample showing strong localized nonlinear response for the first time, with surfa...

  6. Electron-beam direct drive for rf accelerator cavities

    International Nuclear Information System (INIS)

    Nahemow, M.D.; Humphries, S. Jr.

    1987-01-01

    This paper describes a Program to Demonstrate Electron-Beam Direct Drive for Radio Frequency (RF) Linear Accelerators at the Westinghouse R and D Center. The experimental program was undertaken using an existing electron beam facility at the Westinghouse R and C Center to demonstrate the potential of the Direct Drive RF Cavities for High Power Beams concept discussed as part of a program to develop a viable alternate concept for driving RF linear accelerators

  7. Development of superconducting crossbar-H-mode cavities for proton and ion accelerators

    Directory of Open Access Journals (Sweden)

    F. Dziuba

    2010-04-01

    Full Text Available The crossbar-H-mode (CH structure is the first superconducting multicell drift tube cavity for the low and medium energy range operated in the H_{21} mode. Because of the large energy gain per cavity, which leads to high real estate gradients, it is an excellent candidate for the efficient acceleration in high power proton and ion accelerators with fixed velocity profile. A prototype cavity has been developed and tested successfully with a gradient of 7  MV/m. A few new superconducting CH cavities with improved geometries for different high power applications are under development at present. One cavity (f=325  MHz, β=0.16, seven cells is currently under construction and studied with respect to a possible upgrade option for the GSI UNILAC. Another cavity (f=217  MHz, β=0.059, 15 cells is designed for a cw operated energy variable heavy ion linac application. Furthermore, the EUROTRANS project (European research program for the transmutation of high level nuclear waste in an accelerator driven system, 600 MeV protons, 352 MHz is one of many possible applications for this kind of superconducting rf cavity. In this context a layout of the 17 MeV EUROTRANS injector containing four superconducting CH cavities was proposed by the Institute for Applied Physics (IAP Frankfurt. The status of the cavity development related to the EUROTRANS injector is presented.

  8. Test of superconducting radio-frequency cavity bombarded by protons

    Science.gov (United States)

    O'Donnell, J. M.; McCloud, B. J.; Morris, C. L.; McClelland, J. B.; Rusnak, B.; Thiessen, H. A.; Langenbrunner, J. L.

    1992-05-01

    A beam of 2 × 10 10 protons/s was focused onto a small area on the high-field iris of a superconducting cavity operating at the resonance frequency. The input, reflected, and stored power were monitored. The cavity remained in steady state during this test. We conclude that such superconducting cavities will remain viable in the high-proton-flux environments proposed in the design of a superconducting accelerator for pions (PILAC).

  9. Test of superconducting radio-frequency cavity bombarded by protons

    Energy Technology Data Exchange (ETDEWEB)

    O' Donnell, J.M.; McCloud, B.J.; Morris, C.L.; McClelland, J.B.; Rusnak, B.; Thiessen, H.A. (Los Alamos National Lab., NM (United States)); Langenbrunner, J.L. (Dept. of Physics and Astronomy, Univ. Minnesota, Minneapolis, MN (United States))

    1992-05-10

    A beam of 2x10{sup 10} protons/s was focused onto a small area on the high-field iris of a superconducting cavity operating at the resonance frequency. The input, reflected, and stored power were monitored. The cavity remained in steady state during this test. We conclude that such superconducting cavities will remain viable in the high-proton-flux environments proposed in the design of a superconducting accelerator for pions (PILAC). (orig.).

  10. Beam simulations with initial bunch noise in superconducting RF proton linacs

    CERN Document Server

    Tückmantel, J

    2010-01-01

    Circular machines are plagued by coupled bunch instabilities (CBI), driven by impedance peaks, where then all cavity higher order modes (HOMs) are possible drivers. Limiting the CBI growth rate is the fundamental reason that all superconducting rf cavities in circular machines are equipped with HOM dampers. The question arises if for similar reasons HOM damping would not be imperative also in high current superconducting rf proton linacs. Therefore we have simulated the longitudinal bunched beam dynamics in such machines, also including charge and position noise on the injected bunches. Simulations were executed for a generic linac with properties close to the planned SPL at CERN, SNS, or Project X at FNAL. It was found that with strong bunch noise and monopole HOMs with high Qext large beam scatter, possibly exceeding the admittance of a receiving machine, cannot be excluded. A transverse simulation shows similar requirements. Therefore including initial bunch noise in any beam dynamic study on superconducti...

  11. The Influence of Grain Boundaries on the Properties of Superconducting Radio Frequency Cavity Niobium

    Science.gov (United States)

    Sung, Zu Hawn

    Grain boundaries (GBs) in niobium are multiply connected defects that may be responsible for significant performance degradation in superconducting radio frequency (RF) cavities. Magneto optical (MO) studies show that early flux penetration often occurs at GBs. One possible mechanism is that a locally reduced superconducting gap (Delta) at the GB reduces the depairing current density (Jb) and thus leads to a local reduction of the critical field. Alternatively vortices may penetrate the GB preferentially because of field enhancement at a GB groove, or for other reasons. In all these cases, the effect of high RF fields is to produce additional power dissipation, which in turn produces a reduction in quality factor (Q 0) and leads to a premature quench of the cavity. To further our understanding of the superconducting properties of SRF-quality Nb, we made extensive superconducting characterizations by magneto-optical imaging, which allowed assessment of the uniformity of properties on scales down to about 5 microm and by direct transport voltage-current methods in single and bi-crystals treated by standard cavity optimization treatments of BCP (buffered chemical treatment) and EP (electropolishing). We correlated these superconducting characterizations to microstructural properties using scanning laser and scanning electron microscopy and then thinned some samples to examine them at the nanometer scale using analytical transmission electron microscopy (TEM). We also developed special metallographic sample preparation techniques that allowed us to apply these experimental approaches to very soft superconducting RF niobium in the polished conditions characteristics of a real inner cavity surface. Using MO imaging, we found that GBs can preferentially admit flux penetration when the plane of a GB is aligned parallel to the vector of the external magnetic field. In DC transport in the superconducting state, we found preferential flux flow at the GB and could detect the

  12. High Pressure, High Gradient RF Cavities for Muon Beam Cooling

    CERN Document Server

    Johnson, R P

    2004-01-01

    High intensity, low emittance muon beams are needed for new applications such as muon colliders and neutrino factories based on muon storage rings. Ionization cooling, where muon energy is lost in a low-Z absorber and only the longitudinal component is regenerated using RF cavities, is presently the only known cooling technique that is fast enough to be effective in the short muon lifetime. RF cavities filled with high-pressure hydrogen gas bring two advantages to the ionization technique: the energy absorption and energy regeneration happen simultaneously rather than sequentially, and higher RF gradients and better cavity breakdown behavior are possible than in vacuum due to the Paschen effect. These advantages and some disadvantages and risks will be discussed along with a description of the present and desired RF R&D efforts needed to make accelerators and colliders based on muon beams less futuristic.

  13. Modeling high-power RF accelerator cavities with SPICE

    International Nuclear Information System (INIS)

    Humphries, S. Jr.

    1992-01-01

    The dynamical interactions between RF accelerator cavities and high-power beams can be treated on personal computers using a lumped circuit element model and the SPICE circuit analysis code. Applications include studies of wake potentials, two-beam accelerators, microwave sources, and transverse mode damping. This report describes the construction of analogs for TM mn0 modes and the creation of SPICE input for cylindrical cavities. The models were used to study continuous generation of kA electron beam pulses from a vacuum cavity driven by a high-power RF source

  14. Progress on a prototype main ring rf cavity

    International Nuclear Information System (INIS)

    Swain, G.; Kandarian, R.; Thiessen, H.A.; Poirier, R.; Smythe, W.R.

    1989-01-01

    A prototype rf cavity and rf drive system for a hadron facility main ring has been designed and will be tested in the Proton Storage Ring (PSR) at Los Alamos as a part of a collaborative effort between LANL and TRIUMF. The cavity uses an orthogonally biased ferrite tuner. The design provides for accelerating gap voltages up to 200 kV for the 49.3 to 50.8 MHz range. Progress on the cavity construction and testing is described. 13 refs., 5 figs

  15. Superconducting cavity material for the European XFEL

    Science.gov (United States)

    Singer, W.; Singer, X.; Brinkmann, A.; Iversen, J.; Matheisen, A.; Navitski, A.; Tamashevich, Y.; Michelato, P.; Monaco, L.

    2015-08-01

    Analysis of the strategy for superconducting cavity material procurement and quality management is done on the basis of the experience with the cavity production for the European x-ray free electron laser (EXFEL) facility. An adjustment of the material specification to EXFEL requirements, procurement of material, quality control (QC), documentation, and shipment to cavity producers have been worked out and carried out by DESY. A multistep process of qualification of the material suppliers included detailed material testing, single- and nine-cell cavity fabrication, and cryogenic radiofrequency tests. Production of about 25 000 semi-finished parts of high purity niobium and niobium-titanium alloy in a period of three years has been divided finally between companies Heraeus, Tokyo Denkai, Ningxia OTIC, and PLANSEE. Consideration of large-grain (LG) material as a possible option for the EXFEL has resulted in the production of one cryogenic module consisting of seven (out of eight) LG cavities. LG materials fulfilled the EXFEL requirements and showed even 25% to 30% higher unloaded quality factor. A possible shortage of the required quantity of LG material on the market led, however, to the choice of conventional fine-grain (FG) material. Eddy-current scanning (ECS) has been applied as an additional QC tool for the niobium sheets and contributed significantly to the material qualification and sorting. Two percent of the sheets have been rejected, which potentially could affect up to one-third of the cavities. The main imperfections and defects in the rejected sheets have been analyzed. Samples containing foreign material inclusions have been extracted from the sheets and electrochemically polished. Some inclusions remained even after 150 μm surface layer removal. Indications of foreign material inclusions have been found in the industrially fabricated and treated cavities and a deeper analysis of the defects has been performed.

  16. An Automated 476 MHz RF Cavity Processing Facility at SLAC

    CERN Document Server

    McIntosh, P; Schwarz, H

    2003-01-01

    The 476 MHz accelerating cavities currently used at SLAC are those installed on the PEP-II B-Factory collider accelerator. They are designed to operate at a maximum accelerating voltage of 1 MV and are routinely utilized on PEP-II at voltages up to 750 kV. During the summer of 2003, SPEAR3 will undergo a substantial upgrade, part of which will be to replace the existing 358.54 MHz RF system with essentially a PEP-II high energy ring (HER) RF station operating at 476.3 MHz and 3.2 MV (or 800 kV/cavity). Prior to installation, cavity RF processing is required to prepare them for use. A dedicated high power test facility is employed at SLAC to provide the capability of conditioning each cavity up to the required accelerating voltage. An automated LabVIEW based interface controls and monitors various cavity and test stand parameters, increasing the RF fields accordingly such that stable operation is finally achieved. This paper describes the high power RF cavity processing facility, highlighting the features of t...

  17. Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

    Science.gov (United States)

    Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

    2014-06-01

    A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two measurements are performed to demonstrate these capabilities with a near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual-Resistance-Ratio bulk Nb sample showing strong localized nonlinear response, with surface RF magnetic field Bsurface˜102 mT. The second is a raster scanned harmonic response image on a MgB2 thin film demonstrating a uniform nonlinear response over large areas.

  18. Cs_{2}Te normal conducting photocathodes in the superconducting rf gun

    Directory of Open Access Journals (Sweden)

    R. Xiang

    2010-04-01

    Full Text Available The superconducting radio frequency photoinjector (SRF gun is one of the latest applications of superconducting rf technology in the accelerator field. Since superconducting photocathodes with high quantum efficiency are yet unavailable, normal conducting cathode material is the main choice for SRF photoinjectors. However, the compatibility between the photocathode and the cavity is one of the challenges for this concept. Recently, a SRF gun with Cs_{2}Te cathode has been successfully operated in Forschungszentrum Dresden-Rossendorf. In this paper, we will present the physical properties of Cs_{2}Te photocathodes in the SC cavity, such as the quantum efficiency, the lifetime, the rejuvenation, the charge saturation, and the dark current.

  19. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Science.gov (United States)

    Dhakal, Pashupati; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2017-03-01

    Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF) cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q0(Bp) curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q0(Bp) .

  20. Role of thermal resistance on the performance of superconducting radio frequency cavities

    Directory of Open Access Journals (Sweden)

    Pashupati Dhakal

    2017-03-01

    Full Text Available Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of Q_{0}(B_{p} curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of Q_{0}(B_{p}.

  1. Frequency control of RF booster cavity in TRIUMF

    International Nuclear Information System (INIS)

    Fong, K.; Laverty, M.

    1993-01-01

    A booster is used in the TRIUMF cyclotron to increase the energy gain per turn for beam orbits corresponding to energies greater than 370 MeV. It operates at 92.24 MHz, the 4 th harmonic of the cyclotron main rf, and at a nominal voltage of 150 kV. Excitation is provided by a 90 kW rf system that is phase locked to the main rf. When the main rf is interrupted due to sparking or other causes, a controller built into the low frequency source of the booster rf system disables the phase-locked loop, and reconfigures the source as a temperature stabilized oscillator operating at the last locked frequency. When the cyclotron rf is restored it usually will be at different frequency. The oscillator tunes automatically to this new frequency. The acquisition time is extended by the controller to match the response time of the mechanical tuner in the cavity

  2. Recent progress in the superconducting RF Program at TRIUMF/ISAC

    Energy Technology Data Exchange (ETDEWEB)

    Laxdal, R.E. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada)]. E-mail: lax@triumf.ca; Fong, K. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada); Laverty, M. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada); Mitra, A. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada); Poirier, R. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada); Sekachev, I. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada); Zvyagintsev, V. [University of British Columbia, TRIUMF, 4004 Westbrook Mall, Vancouver, BC, V6T2A3 (Canada)

    2006-07-15

    A heavy ion superconducting linac is being installed at TRIUMF to increase the final energy of radioactive beams from ISAC. A first stage of 20 MV consisting of five medium beta cryomodules each with four quarter wave bulk niobium cavities and a superconducting solenoid is being installed with commissioning scheduled for December 2005. The cavities have been fully characterized for rf performance. Two cryomodules have been tested at cold temperatures. A high beta cavity ({beta} {sub 0} = 0.104) for the next phase is presently in design. A weak phase lock loop technique is used to monitor the control loop phase noise to characterize system microphonics. A recent highlight is the acceleration of heavy ions by one cryomodule as a proof of system integrity. The report will summarize all aspects of the program.

  3. Digital Low-Level RF Controls for Future Superconducting Linear Colliders

    CERN Document Server

    Simrock, Stefan

    2005-01-01

    The requirements for RF Control Systems of Superconducting Linear Colliders are not only defined in terms of the quality of field control but also with respect to operability, availability, and maintainability of the RF System, and the interfaces to other subsystems. The field control of the vector-sum of many cavities driven by one klystron in pulsed mode at high gradients is a challenging task since severe Lorentz force detuning, microphonics and beam induced field errors must be suppressed by several orders of magnitude. This is accomplished by a combination of local and global feedback and feedforward control. Sensors monitor individual cavity probe signals, and forward and reflected wave as well as the beam properties including beam energy and phase while actuators control the incident wave of the klystron and individual cavity resonance frequencies. The operability of a large llrf system requires a high degree of automation while the high availability requires robust algorithms, redundancy, and extremel...

  4. Measurement of RF characteristics of magnetic alloys for an RF cavity of the accumulator cooler ring

    International Nuclear Information System (INIS)

    Watanabe, M.; Chiba, Y.; Katayama, T.; Koseki, T.; Ohtomo, K.; Tsutsui, H.

    2004-01-01

    The magnetic alloy (MA)-loaded RF cavity has been studied for an RF stacking system of the accumulator cooler ring (ACR). RF characteristics of several high-permeability MA cores were measured in the frequency range between 1 and 50 MHz. The effects of the cut-core configuration, cutting the core and leaving air gaps between two circular halves, were also investigated. The results show that the shunt impedance remains high and the appropriate inductance and Q-value can be obtained by increasing the gap width of the cut core in the frequency region of the ACR cavity

  5. High power RF test of an 805 MHz RF cavity for a muon cooling channel

    International Nuclear Information System (INIS)

    Li, Derun; Corlett, J.; MacGill, R.; Rimmer, R.; Wallig, J.; Zisman, M.; Moretti, A.; Qian, Z.; Wu, V.; Summers, D.; Norem, J.

    2002-01-01

    We present recent high power RF test results on an 805 MHz cavity for a muon cooling experiment at Lab G in Fermilab. In order to achieve high accelerating gradient for large transverse emittance muon beams, the cavity design has adopted a pillbox like shape with 16 cm diameter beam iris covered by thin Be windows, which are demountable to allow for RF tests of different windows. The cavity body is made from copper with stiff stainless steel rings brazed to the cavity body for window attachments. View ports and RF probes are available for visual inspections of the surface of windows and cavity and measurement of the field gradient. Maximum of three thermo-couples can be attached to the windows for monitoring the temperature gradient on the windows caused by RF heating. The cavity was measured to have Q 0 of about 15,000 with copper windows and coupling constant of 1.3 before final assembling. A 12 MW peak power klystron is available at Lab G in Fermilab for the high power test. The cavity and coupler designs were performed using the MAFIA code in the frequency and the time domain. Numerical simulation results and cold test measurements on the cavity and coupler will be presented for comparisons

  6. Fabrication process for the PEP II RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Franks, R.M.; Rimmer, R.A. [Lawrence Berkeley National Lab., CA (United States); Schwarz, H. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1997-06-05

    This paper presents the major steps used in the fabrication of the 26 RF Cavities required for the PEP-II B-factory. Several unique applications of conventional processes have been developed and successfully implemented: electron beam welding (EBW), with minimal porosity, of .75 inch (19 mm) copper cross-sections; extensive 5-axis milling of water channels; electroplating of .37 inch (10 mm) thick OFE copper; tuning of the cavity by profiling beam noses prior to final joining with the cavity body; and machining of the cavity interior, are described here.

  7. Higher order mode damping in Kaon factory RF cavities

    International Nuclear Information System (INIS)

    Enegren, T.; Poirier, R.; Griffin, J.; Walling, L.; Thiessen, H.A.; Smythe, W.R.

    1989-05-01

    Proposed designs for Kaon factory accelerators require that the rf cavities support beam currents on the order of several amperes. The beam current has Fourier components at all multiples of the rf frequency. Empty rf buckets produce additional components at all multiples of the revolution frequency. If a Fourier component of the beam coincides with the resonant frequency of a higher order mode of the cavity, which is inevitable if the cavity has a large frequency swing, significant excitation of this mode can occur. The induced voltage may then excite coupled bunch mode instabilities. Effective means are required to damp higher order modes without significantly affecting the fundamental mode. A mode damping scheme based on coupled transmission lines has been investigated and is report

  8. Ignition and monitoring technique for plasma processing of multicell superconducting radio-frequency cavities

    Science.gov (United States)

    Doleans, Marc

    2016-12-01

    An in-situ plasma processing technique has been developed at the Spallation Neutron Source (SNS) to improve the performance of the superconducting radio-frequency (SRF) cavities in operation. The technique uses a low-density reactive neon-oxygen plasma at room-temperature to improve the surface work function, to help remove adsorbed gases on the RF surface, and to reduce its secondary emission yield. SNS SRF cavities have six accelerating cells and the plasma typically ignites in the cell where the electric field is the highest. This article details the technique to ignite and monitor the plasma in each cell of the SNS cavities.

  9. Development of the L-band superconducting cavity system

    Energy Technology Data Exchange (ETDEWEB)

    Ota, T.; Kakutani, N.; Sukenobu, S. [Toshiba Corp., Yokohama, Kanagawa (JP)] [and others

    2000-02-01

    R and D activities on superconducting cavities in 1998 at TOSHIBA are presented. An L-band single-cell niobium cavity with four ports on the beam pipes was fabricated in our company and tested at KEK. The cryostat and refrigerator system for the cavity were designed and fabricated. The cryostat installed the cavity was tested in low temperature. R and D of hydroforming to fabricate seamless cavities is also presented. (author)

  10. Development of the L-band superconducting cavity system

    International Nuclear Information System (INIS)

    Ota, T.; Kakutani, N.; Sukenobu, S.

    2000-01-01

    R and D activities on superconducting cavities in 1998 at TOSHIBA are presented. An L-band single-cell niobium cavity with four ports on the beam pipes was fabricated in our company and tested at KEK. The cryostat and refrigerator system for the cavity were designed and fabricated. The cryostat installed the cavity was tested in low temperature. R and D of hydroforming to fabricate seamless cavities is also presented. (author)

  11. Plasma Etching of superconducting radio frequency cavity by Ar/Cl2 capacitively coupled Plasma

    Science.gov (United States)

    Upadhyay, Janardan; Popovic, Svetozar; Valente-Feliciano, Anne-Marie; Phillips, Larry; Vuskovic, Lepsha

    2016-09-01

    We are developing plasma processing technology of superconducting radio frequency (SRF) cavities. The formation of dc self-biases due to surface area asymmetry in this type of plasma and its variation on the pressure, rf power and gas composition was measured. Enhancing the surface area of the inner electrode to reduce the asymmetry was studied by changing the contour of the inner electrode. The optimized contour of the electrode based on these measurements was chosen for SRF cavity processing. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity is used, which previously mechanically polished, buffer chemically etched afterwards and rf tested at cryogenic temperatures for a baseline test. Plasma processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise manner to establish segmented plasma processing. The cavity is rf tested afterwards at cryogenic temperatures. The rf test and surface condition results are presented.

  12. Accelerating RF cavity of the Booster

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    Each of the 4 PS Booster rings has a single accelerating cavity. It consists of 2 quarter-wave ferrite-loaded resonators. There are 2 figure-of-eight loops on the ferrite loads for tuning the frequency throughout the acceleration cycle, from 3 to 8 MHz (from 50 MeV at injection to the original Booster energy of 800 MeV, 2 GeV today). The cavities have a flat design, to fit the ring-to-ring distance of 36 cm. The tube for forced-air cooling is visible in the left front. See also 8301084.

  13. Accelerating RF cavity of the Booster

    CERN Multimedia

    CERN PhotoLab

    1983-01-01

    Each of the 4 PS Booster rings has a single accelerating cavity.It consists of 2 quarter-wave ferrite-loaded resonators. 2 figure-of-eight loops tune the frequency throughout the accelerating cycle, from 3 to 8 MHz (from 50 MeV at injection to the original Booster energy of 800 MeV, 2 GeV today). The cavities have a flat design, to fit the ring-to-ring distance of 36 cm, and are forced-air cooled. The 2 round objects in the front-compartments are the final-stage power-tetrodes. See also 8111095.

  14. MEASUREMENT OF RF LOSSES DUE TO TRAPPED FLUX IN A LARGE-GRAIN NIOBIUM CAVITY

    International Nuclear Information System (INIS)

    Gianluigi Ciovati; Alex Gurevich

    2008-01-01

    Trapped magnetic field in superconducting niobium is a well known cause of radio-frequency (RF) residual losses. In this contribution, we present the results of RF tests on a single-cell cavity made of high-purity large grain niobium before and after allowing a fraction of the Earth's magnetic field to be trapped in the cavity during the cooldown below the critical temperature Tc. This experiment has been done on the cavity before and after a low temperature baking. Temperature mapping allowed us to determine the location of hot-spots with high losses and to measure their field dependence. The results show not only an increase of the low-field residual resistance, but also a larger increase of the surface resistance for intermediate RF field (higher ''medium field Qslope''), which depends on the amount of the trapped flux. These additional field-dependent losses can be described as losses of pinned vortices oscillating under the applied RF magnetic field

  15. Synchronization of RF fields of Indus 2 RF cavities for proper injection and acceleration of beam

    International Nuclear Information System (INIS)

    Tiwari, Nitesh; Bagduwal, Pritam S.; Lad, M.; Hannurkar, P.R.

    2009-01-01

    Indus-2 is a synchrotron light source with designed parameters of 2.5 GeV, 300 mA beam current. Four RF cavities fed from four RF power stations have been used for beam acceleration from 550 MeV to 2.5 GeV and synchrotron loss compensation. Particle should reach the RF cavity at the proper phase for proper acceptance of the beam in ring. At injection if the phase is not proper the acceptance efficiency reduces and the maximum stored current in the ring also gets limited. Equal contribution from four cavities at every value of current and energy level is very important. Improper phase will cause the imbalance of the power among different station hence will limit maximum stored current and reduce life time of the stored beam. Phase optimization was done in two-step, first at injection to have better injection rate and the stations were operated at the sufficient power for control loops to operate. Then at 2 GeV and 2.5 GeV energy so that beam extracts equal power from all four RF stations. Phase synchronization of all four cavities from injection to 2.5 GeV has already been done at 50 mA stored beam current. If phases of RF fields inside four RF cavities is not proper then beam will not see the total RF voltage as summation of all four cavity gap voltages, hence it is a very important parameter to be optimized and maintained during operation. (author)

  16. Updating the CSNS injector linac to 250 MeV with superconducting double-spoke cavities

    International Nuclear Information System (INIS)

    Li Zhihui; Fu Shinian

    2015-01-01

    In order to update the beam power from 100 kW to 500 kW in the China Spallation neutron source (CSNS) Phase Ⅱ, one of the important measures is to replace the 80 m long beam transport line between the present 80 MeV linac injector and the rapid cycling synchrotron (RCS) to another kind of acceleration structure. In this paper, we proposed a scheme based on 324 MHz double-spoke superconducting cavities. Unlike the superconducting elliptical cavity and normal conducting coupled cavity linac (CCL) structure, the double-spoke cavity belongs to the TE mode structure and has a smaller transverse dimension compared with that of the TH mode one. It can work at base frequency as the drift tube Linac (DTL) section, so that the cost and complexity of the RF system will be much decreased, and the behaviors of the beam dynamics are also improved significantly because of the low charge density and larger longitudinal acceptance. Furthermore, because of the relatively longer interactive length between the charged particle and the electromagnetic field per cell, it needs relatively less cell numbers and it has larger velocity acceptance compared with the double frequency TH structures. The superconducting section consists of 14 periods, each of which includes 3 superconducting cavities encapsulated in one cryomodule and a doublet in room temperate. The general considerations on cavity and beam dynamics design are discussed and the main results are presented. (authors)

  17. Karlsruhe: En route to a superconducting r.f. separator

    CERN Multimedia

    1973-01-01

    A superconducting r.f. separator is under construction at Karlsruhe for use at the SPS in the beam-line to the Omega spectrometer. Tests on a section of the first 3 m deflector have given results close to the desired parameters.

  18. Improving superconducting RF technology for high energy particle accelerators

    International Nuclear Information System (INIS)

    Leconte, P.

    1991-01-01

    A review of the state of the art is given. It shows recent proofs of success of the technology. An important R and D effort remains to be done in order to collect all the expectable benefits of RF superconductivity. (author)

  19. R.F. cavity design for the NSLS

    International Nuclear Information System (INIS)

    Batchelor, K.; Galayda, J.; Hawrylak, R.

    1981-01-01

    The r.f cavity design for the Booster, vuv ring and x-ray ring of the NSLS is described together with the mechanical design of tuners, coupling and monitoring loops and the temperature control systems. The results of higher order mode measurements as compared with Superfish calculations are also presented

  20. RF-cavity for the X-ray generator NESTOR

    International Nuclear Information System (INIS)

    Androsov, V.P.; Gvozd, A.M.; Karnaukhov, I.M.; Telegin, Yu.N.; Chernov, K.N.; Ostreyko, G.N.; Sedlyarov, I.K.

    2007-01-01

    In the Kharkov Institute of Physics and Technology 225 MeV electron storage ring NESTOR is under development. The paper describes the design and parameters of a 700 MHz cavity that has been fabricated at BINP for the NESTOR RF-system. Now the low-power and vacuum tests of the cavity are under way at BINP. We present here the results of 3D simulations of the cavity with ANSYS code. The problem of multibunch instabilities in NESTOR is also discussed

  1. Cavity design and beam simulations for the APS rf gun

    International Nuclear Information System (INIS)

    Borland, M.

    1991-01-01

    An earlier note discussed the preliminary design of the 1-1/2 cell RF cavity for the APS RF gun. This note describes the final design, including cavity properties and simulation results from the program rf gun. The basic idea for the new design was that the successful SSRL design could be improved upon by reducing fields that had nonlinear dependence on radius. As discussed previously, this would reduce the emittance and produce tighter momentum and time distributions. In addition, it was desirable to increase the fields in the first half-cell relative to the fields in the second half-cell, in order to allow more rapid initial acceleration, which would reduce the effects of space charge. Both of these goals were accomplished in the new design

  2. Early 500 MHz prototype LEP RF Cavity with superposed storage cavity

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    The principle of transferring the RF power back and forth between the accelerating cavity and a side-coupled storage cavity was demonstrated with this 500 MHz prototype. In LEP, the accelerating frequency was 352.2 MHz, and accelerating and storage cavities were consequently larger. See also 8002294, 8006061, 8407619X, and Annual Reports 1980, p.115; 1981, p.95; 1985, vol.I, p.13.

  3. PEP-II RF Cavity Revisited (LCC-0032)

    Energy Technology Data Exchange (ETDEWEB)

    Rimmer, R.

    2004-03-23

    This report describes the results of numerical simulations of the PEP-II RF cavity performed after the completion of the construction phase of the project and comparisons are made to previous calculations and measured results. These analyses were performed to evaluate new calculation techniques for the HOM distribution and RF surface heating that were not available at the time of the original design. These include the use of a high frequency electromagnetic element in ANSYS and the new Omega 3P code to study wall losses, and the development of broadband time domain simulation methods in MAFIA for the HOM loading. The computed HOM spectrum is compared with cavity measurements and observed beam-induced signals. The cavity fabrication method is reviewed, with the benefit of hindsight, and simplifications are discussed.

  4. A digital closed loop control system for automatic phase locking of superconducting cavities of IUAC Linac

    International Nuclear Information System (INIS)

    Dutt, R.N.; Rai, A.; Pandey, A.; Sahu, B.K.; Patra, P.; Karmakar, J.; Chaudhari, G.K.; Mathur, Y.; Ghosh, S.; Kanjilal, D.

    2013-01-01

    A closed loop digital control system has been designed and tested to automate the tuning process of superconducting resonators of LINAC at Inter-University Accelerator Centre, New Delhi. The mechanism controls the proportional valves of the He gas based pneumatic tuner in response to the phase and frequency errors of the cavity RF field. The main RF phase lock loop (PLL) is automatically closed once the resonant frequency is within locking range of the resonator PLL. The digital control scheme was successfully tested on few resonators of LINAC cryostat 1. A high stability of phase lock was observed. The details of the digital automation system are presented in the paper. (author)

  5. 3D multiphysics modeling of superconducting cavities with a massively parallel simulation suite

    Directory of Open Access Journals (Sweden)

    Oleksiy Kononenko

    2017-10-01

    Full Text Available Radiofrequency cavities based on superconducting technology are widely used in particle accelerators for various applications. The cavities usually have high quality factors and hence narrow bandwidths, so the field stability is sensitive to detuning from the Lorentz force and external loads, including vibrations and helium pressure variations. If not properly controlled, the detuning can result in a serious performance degradation of a superconducting accelerator, so an understanding of the underlying detuning mechanisms can be very helpful. Recent advances in the simulation suite ace3p have enabled realistic multiphysics characterization of such complex accelerator systems on supercomputers. In this paper, we present the new capabilities in ace3p for large-scale 3D multiphysics modeling of superconducting cavities, in particular, a parallel eigensolver for determining mechanical resonances, a parallel harmonic response solver to calculate the response of a cavity to external vibrations, and a numerical procedure to decompose mechanical loads, such as from the Lorentz force or piezoactuators, into the corresponding mechanical modes. These capabilities have been used to do an extensive rf-mechanical analysis of dressed TESLA-type superconducting cavities. The simulation results and their implications for the operational stability of the Linac Coherent Light Source-II are discussed.

  6. Superconducting spoke cavities for high-velocity applications

    Energy Technology Data Exchange (ETDEWEB)

    Hopper, Christopher S. [Old Dominion U.; Delayen, Jean R. [Old Dominion U., JLAB

    2013-10-01

    To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.

  7. Quench detection on a superconducting radio-frequency cavity

    OpenAIRE

    Lai, Ru-Yu; Spirn, Daniel

    2017-01-01

    We study quench detection in superconducting accelerator cavities cooled with He-II. A rigorous mathematical formula is derived to localize the quench position from dynamical data over a finite time interval at a second sound detector.

  8. Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

    Energy Technology Data Exchange (ETDEWEB)

    Romanenko, A., E-mail: aroman@fnal.gov; Grassellino, A.; Barkov, F. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Suter, A.; Salman, Z.; Prokscha, T. [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

    2014-02-17

    We investigate “hot” regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-μSR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth λ{sub L}=23±2 nm. In contrast, a cutout sample from the 120 ∘C baked cavity shows a much larger λ>100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.

  9. Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

    International Nuclear Information System (INIS)

    Romanenko, A.; Grassellino, A.; Barkov, F.; Suter, A.; Salman, Z.; Prokscha, T.

    2014-01-01

    We investigate “hot” regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-μSR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth λ L =23±2 nm. In contrast, a cutout sample from the 120 ∘C baked cavity shows a much larger λ>100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions

  10. Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

    Science.gov (United States)

    Romanenko, A.; Grassellino, A.; Barkov, F.; Suter, A.; Salman, Z.; Prokscha, T.

    2014-02-01

    We investigate "hot" regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-μSR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth λL=23±2 nm. In contrast, a cutout sample from the 120 ∘C baked cavity shows a much larger λ >100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.

  11. Numerical simulation of a split cavity oscillator and rf conversion

    International Nuclear Information System (INIS)

    Lemke, R.W.

    1991-07-01

    We have conducted an extensive investigation of the split cavity oscillator (SCO) using particle-in-cell simulation. The goal of this work is to test and optimize an inverse diode rf convertor for use with a cylindrical SCO, while simultaneously determining factors that control rf extraction efficiency. We present results from simulations of several configurations including the SCO with inverse diode extractor, the SCO in conjunction with post-acceleration and inverse diode extraction, and the SCO, using electron beams with a variety of currents, voltages, and radii. 7 refs., 8 figs

  12. Aging of residual surface resistance of superconducting lead cavities

    DEFF Research Database (Denmark)

    Danielsen, M.

    1972-01-01

    Measurements of the residual surface resistance of superconducting lead cavities as a function of time during a period of a month showed an oscillating variation. An explanation of the ageing curves is proposed. ©1972 The American Institute of Physics......Measurements of the residual surface resistance of superconducting lead cavities as a function of time during a period of a month showed an oscillating variation. An explanation of the ageing curves is proposed. ©1972 The American Institute of Physics...

  13. Travelling Wave Structure of an SPS RF Cavity

    CERN Multimedia

    CERN PhotoLab

    1974-01-01

    The RF cavities for acceleration of particles in the SPS have a travelling-wave structure. They operate at a fixed frequency of 200 MHz (h = 4620). With a quality factor of Q = 100, the bandwidth covers the small frequency swing for the acceleration of protons from as low as 10 GeV to the top energy of 450 GeV. Later on, for the acceleration of ions, with a larger frequency swing, turn-to-turn phase jumps did the trick. Two cavities, each consisting of 5 tank sections, were installed in long straight section 3. Each cavity is driven by a power amplifier of 750 kW CW (1 MW pulsed). Another 2 cavities were added later on. See also 7411033 and 7802190.

  14. The elbe accelerator facility starts operation with the superconducting rf gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schneider, C; Schurig, R; Staufenbiel, F; Teichert, J; Kamps, T; Rudolph, J; Schenk, M; Klemz, G; Will, I

    2010-01-01

    As the first superconducting rf photo-injector (SRF gun) in practice, the FZD 3+1/2 cell SRF gun is successfully connected to the superconducting linac ELBE. This setting will improve the beam quality for ELBE users. It is the first example for an accelerator facility fully based on superconducting RF technology. For high average power FEL and ERL sources, the combination of SRF linac and SRF gun provides a new chance to produce beams of high average current and low emittance with relative low power consumption. The main parameters achieved from the present SRF gun are the final electron energy of 3 MeV, 16 μA average current, and rms transverse normalized emittances of 3 mm mrad at 77 pC bunch charge. A modified 3+1/2 cell niobium cavity has been fabricated and tested, which will increase the rf gradient in the gun and thus better the beam parameters further. In this paper the status of the integration of the SRF gun with the ELBE linac will be presented, and the latest results of the beam experiments will ...

  15. Photocathodes inside superconducting cavities. Studies on the feasibility of a superconducting photoelectron source of high brightness. External report

    International Nuclear Information System (INIS)

    Michalke, A.

    1992-01-01

    We have done studies and experiments to explore the feasibility of a photoemission RF gun with a superconducting accelerator cavity. This concept promises to provide an electron beam of high brightness in continuous operation. It is thus of strong interest for a free-electron-laser or a linear collider based on a superconducting accelerator. In a first step we studied possible technical solutions for its components, especially the material of the photocathode and the geometrical shape of the cavity. Based on these considerations, we developed the complete design for a prototype electron source. The cathode material was chosen to be alkali antimonide. In spite of its sensitivity, it seems to be the best choice for a gun with high average current due to its high quantum efficiency. The cavity shape was at first a reentrant-type single cell of 500 MHz. It is now replaced by a more regular two-and-half cell shape, an independent half cell added for emittance correction. Its beam dynamics properties are investigated by numerical simulations; we estimated a beam brightness of about 5x10 11 A/(m.rad) 2 . But the mutual interactions between alkali antimonide photocathode and superconducting cavity must be investigated experimentally, because they are completely unkown. (orig.)

  16. Cooling tests of the cryomodules at superconducting RF test facility (STF)

    International Nuclear Information System (INIS)

    Ohuchi, Norihito; Nakai, Hirotaka; Kojima, Yuuji

    2009-01-01

    KEK has been constructing the Superconducting RF Test Facility (STF) with aiming at a center of the ILC-R and D in Asia from 2005. In this project, KEK targets manufacturing and operational experiences of the RF cavity and cryomodule toward the ILC, and two cryomodules have been developed. These cryomodules are 6 meter long and have 4 nine-cell cavities in each cryostat. The designs of the cryomodules are based on the TESLA Type-3 (TTF-3) at DESY, however, each cryostat has the different type of cavities, TESLA-like type and Low-Loss type. The tests of the cryomodules were performed in two steps. In the first test, measurements of the cryogenic performances of these cryomodules were the main objective. One nine-cell cavity was assembled in each cryomodule and cool-down of the two cryomodules was performed, individually. In the second test, the four TESLA-like cavities were assembled in the cryomodule as complete integration. Cool-down of the cryomodule to 2 K was successfully completed, and thermal performances of the cryomodule and cooling capacity of the cryogenics system were studied in detail. In this paper, we will report the design of the cryomodules and the thermal performances at these cold tests. (author)

  17. MEASUREMENT OF HIGH Q RF CAVITY IMPEDANCE WITH BEAM

    International Nuclear Information System (INIS)

    Limborg, Cecile

    2003-01-01

    An inexpensive method to measure, with beam, the Rs and Q of narrow-band high order resonances in RF cavities was developed on SPEAR. The two main results of this study are: (1) an improved operational stability of SPEAR; and (2) the decision to keep the present cavities for the proposed SPEAR upgrade. SPEAR3 will be run initially at 200 mA, twice the present current. Just beyond the current threshold, and before step loss, there is a regime in which the beam performs large amplitude, low frequency oscillations. Detailed measurements were performed to characterize the frequency, amplitude, growth and damping time of these relaxation oscillations

  18. Fabrication, tests, and RF control of the 50 superconducting resonators of the Saclay heavy ion linac

    International Nuclear Information System (INIS)

    Cauvin, B.; Coret, M.; Fouan, J.P.

    1988-01-01

    Two types of niobium superconducting resonators are currently in use in the linac Outer cylinder and RF ports are identical for both designs but internal structures are different full wave helix (λ) with three gaps behavior or half-wave (λ/2) with two gaps behavior. The λ structure is based on a Karlsruhe design. All cavities (34 λ and 16 λ/2) are now fabricated, tested for field, and mounted in the eight machine cryostats. Resonator characteristics are listed. Frequencies are multiples of the low energy bunching frequency (13.5 MHz). The high magnetic fields arise at the welds joining helix to can (λ/2) or half-helices together (λ)

  19. RF field control for Kaon Factory booster cavities

    International Nuclear Information System (INIS)

    Craig, S.T.; de Jong, M.S.

    1992-08-01

    A conceptual design is developed for control of the Kaon Factory booster rf accelerating fields. This design addresses control of cavity: tuning, voltage amplitude, and voltage phase angle. Time-domain simulations were developed to evaluate the proposed controllers. These simulations indicate that adequate tuning performance can be obtained with the combination of adaptive feed forward and proportional feedback control. Voltage amplitude and voltage phase can be adequately controlled using non-adaptive feed forward and proportional feedback control. (Author) (figs., tabs.)

  20. RF field control for KAON Factory booster cavities

    International Nuclear Information System (INIS)

    Craig, S.T.; de Jong, M.S.

    1990-11-01

    A conceptual design is developed for control of the KAON Factory Booster rf accelerating fields. This design addresses control of cavity: tuning, voltage amplitude, and voltage phase angle. Time-domain simulations were developed to evaluated the proposed controllers. These simulations indicated that adequate tuning performance can be obtained with the combination of adaptive feed-forward and proportional feedback control. Voltage amplitude and voltage phase can be adequately controlled using non-adaptive feedforward and proportional feedback control

  1. Simulation of plasma loading of high-pressure RF cavities

    Science.gov (United States)

    Yu, K.; Samulyak, R.; Yonehara, K.; Freemire, B.

    2018-01-01

    Muon beam-induced plasma loading of radio-frequency (RF) cavities filled with high pressure hydrogen gas with 1% dry air dopant has been studied via numerical simulations. The electromagnetic code SPACE, that resolves relevant atomic physics processes, including ionization by the muon beam, electron attachment to dopant molecules, and electron-ion and ion-ion recombination, has been used. Simulations studies have been performed in the range of parameters typical for practical muon cooling channels.

  2. Simulation of plasma loading of high-pressure RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Yu, K. [Brookhaven National Lab. (BNL), Upton, NY (United States). Computational Science Initiative; Samulyak, R. [Brookhaven National Lab. (BNL), Upton, NY (United States). Computational Science Initiative; Stony Brook Univ., NY (United States). Dept. of Applied Mathematics and Statistics; Yonehara, K. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Freemire, B. [Northern Illinois Univ., DeKalb, IL (United States)

    2018-01-11

    Muon beam-induced plasma loading of radio-frequency (RF) cavities filled with high pressure hydrogen gas with 1% dry air dopant has been studied via numerical simulations. The electromagnetic code SPACE, that resolves relevant atomic physics processes, including ionization by the muon beam, electron attachment to dopant molecules, and electron-ion and ion-ion recombination, has been used. Simulations studies have also been performed in the range of parameters typical for practical muon cooling channels.

  3. Measurement and identification of HOM's in RF cavities

    International Nuclear Information System (INIS)

    Goldberg, D.A.; Rimmer, R.A.

    1997-05-01

    One of the major sources of beam impedance in accelerators is the higher-order modes (HOM's) of the RF cavities. We report here on a number of techniques for the identification of HOM's and measurement of their properties. Central to these techniques is the application of symmetry principles and the effects of symmetry-breaking perturbations (including mode-mixing) to the 'standard' techniques of spectrum measurements and bead pulls

  4. On losses caused in RF cavities by longitudinal electric fields

    International Nuclear Information System (INIS)

    Halbritter, J.

    1976-02-01

    Rf modes with large longitudinal electric fields (div E vector unequal to 0) at the cavity wall systematically show worse rf properties than modes with div E vector identical with 0; e.g. enlarged rf residual losses. While magnetic residual losses R sub(res) proportional f 2 are due to uncharged inhomogeneities in the oxide coating the metal, the electric residual losses R sub(orthogonal) occur via charged states in the oxide: the recharging of those states by tunnel exchange causes excitation across the energy gap of the superconductor yielding residual losses at high rf field strengths. The interaction of E sub(orthogonal) with the charges generate (longitudinal) phonons showing up as contribution to R sub(orthogonal). The resulting R sub(orthogonal) increases with E sub(orthogonal) and is nearly independent of frequency f, indicating the importance of R sub(orthogonal) for low frequency sc cavities, especially at high field strengths. In addition R sub(orthogonal) can account for the observed large residual losses of strip line modes in narrow junctions and joints between superconductors. (orig.) [de

  5. Characterization of Nb coating in HIE-ISOLDE QWR superconducting accelerating cavities by means of SEM-FIB and TEM

    CERN Document Server

    Bartova, Barbora; Taborelli, M; Aebersold, A B; Alexander, D T L; Cantoni, M; Calatroni, Sergio; CERN. Geneva. ATS Department

    2015-01-01

    The Quarter Wave Resonators (QWR) high-β cavities (0.3 m diameter and 0.9 m height) are made from OFE 3D-forged copper and are coated by DC-bias diode sputtering with a thin superconducting layer of niobium. The Nb film thickness, morphology, purity and quality are critical parameters for RF performances of the cavity. They have been investigated in a detailed material study.

  6. Effect of cooldown and residual magnetic field on the performance of niobium–copper clad superconducting radio-frequency cavity

    International Nuclear Information System (INIS)

    Dhakal, Pashupati; Ciovati, Gianluigi

    2017-01-01

    Here, we present the results of rf measurements on a niobium–copper clad superconducting radio-frequency cavity with different cooldown conditions and residual magnetic field in a vertical test Dewar in order to explore the effect of thermal current induced magnetic field and its trapping on the performance of the cavity. The residual resistance, extracted from the Q 0 (T) curves in the temperature range 4.3–1.5 K, showed no dependence on a temperature gradient along the cavity during the cooldown across the critical temperature up to ~50 K m –1 . The rf losses due to the trapping of residual magnetic field during the cavity cooldown were found to be ~4.3 nΩ μT –1 , comparable to the values measured in bulk niobium cavities. An increase of residual resistance following multiple cavity quenches was observed along with evidence of trapping of magnetic flux generated by thermoelectric currents.

  7. RF Tests of an 805 MHz Pillbox Cavity at Lab G of Fermilab

    International Nuclear Information System (INIS)

    D. Li; J. Corlett; R. MacGill; M. Zisman; J. Norem; A. Moretti; Z. Qian; J. Wallig; V. Wu; Y. Torun; R.A. Rimmer

    2003-01-01

    We report recent high power RF tests on an 805 MHz RF pillbox cavity with demountable windows over beam apertures at Lab G of Fermilab, a dedicated facility for testing of MUCOOL (muon cooling) components. The cavity is installed inside a superconducting solenoidal magnet. A 12 MW peak RF power klystron is used for the tests. The cavity has been processed both with and without magnetic field. Without magnetic field, a gradient of 34 MV/m was reached rather quickly with very low sparking rate. In a 2.5 T solenoidal field, a 16 MV/m gradient was achieved, following several weeks of conditioning. Strong multipacting effects associated with high radiation levels were measured during processing with the magnetic field. More recently Be windows with TiN-coated surface have been installed and tested with and without the external magnetic field. 16 MV/m gradient without magnetic field was reached quickly as planned. Less multipacting was observed during the conditioning, indicating that the TiN-coated surface on the windows had indeed helped to reduce the secondary electron emission significantly. A gradient of 16.5 MV/m was finally achieved with magnet on in solenoidal mode and the field up to 4 T. Preliminary inspection of the Be window surface found no visual damage, in comparison with Cu windows where substantial surface damage was found. Preliminary understanding of conditioning the cavity in a strong magnetic field has been developed. More thorough window and cavity surface inspection is under way

  8. RF tests of an 805 MHz pillbox cavity at Lab G of Fermilab

    International Nuclear Information System (INIS)

    Li, Derun; Corlett, J.; MacGill, R.; Wallig, J.; Zisman, M.; Moretti, A.; Qian, Z.; Wu, V.; Rimmer, R.; Norem, J.; Torun, Y.

    2003-01-01

    We report recent high power RF tests on an 805 MHz RF pillbox cavity with demountable windows for beam apertures at Lab G of Fermilab, a dedicated facility for testing of MUCOOL (muon cooling) components. The cavity is installed inside a superconducting solenoidal magnet. A 12 MW peak RF power klystron is used for the tests. The cavity has been processed both with and without magnetic field. Without magnetic field, a gradient of 34 MV/m was reached rather quickly with very low sparking rate. In a 2.5 T solenoidal field, a 16 MV/m gradient was achieved, and it had to take many weeks of conditioning. Strong multipacting effects associated with high radiation levels were measured during the processing with the magnetic field. More recently Be windows with TiN-coated surface have been installed and tested at conditions of with and without the external magnetic field. A conservative 16 MV/m gradient without magnetic field was reached quickly as planned. Less multipacting was observed during the conditioning, it indicated that the TiN-coated surface on the windows had indeed helped to reduce the secondary electron emissions significantly. A modest gradient of 16.5 MV/m was finally achieved with magnet on in solenoidal mode and the field up to 4 T. Preliminary inspection on Be windows surface found no damage at all, in comparison with Cu windows where substantial surface damage was found. Preliminary understanding of conditioning cavity in a strong magnetic field has been developed. More through window and cavity surface inspection is under way

  9. Evidence for preferential flux flow at the grain boundaries of superconducting RF-quality niobium

    Science.gov (United States)

    Sung, Z.-H.; Lee, P. J.; Gurevich, A.; Larbalestier, D. C.

    2018-04-01

    The question of whether grain boundaries (GBs) in niobium can be responsible for lowered operating field (B RF) or quality factor (Q 0) in superconducting radio frequency (SRF) cavities is still controversial. Here, we show by direct DC transport across planar GBs isolated from a slice of very large-grain SRF-quality Nb that vortices can preferentially flow along the grain boundary when the external magnetic field lies in the GB plane. However, increasing the misalignment between the GB plane and the external magnetic field vector markedly reduces preferential flux flow along the GB. Importantly, we find that preferential GB flux flow is more prominent for a buffered chemical polished than for an electropolished bi-crystal. The voltage-current characteristics of GBs are similar to those seen in low angle grain boundaries of high temperature superconductors where there is clear evidence of suppression of the superconducting order parameter at the GB. While local weakening of superconductivity at GBs in cuprates and pnictides is intrinsic, deterioration of current transparency of GBs in Nb appears to be extrinsic, since the polishing method clearly affect the local GB degradation. The dependence of preferential GB flux flow on important cavity preparation and experimental variables, particularly the final chemical treatment and the angle between the magnetic field and the GB plane, suggests two more reasons why real cavity performance can be so variable.

  10. Calculation of mechanical vibration frequencies of stiffened superconducting cavities

    International Nuclear Information System (INIS)

    Black, S.J.; Spalek, G.

    1992-01-01

    We calculated the frequencies of transverse and longitudinal mechanical-vibration modes of the HEPL- modified, CERN/DESY four-cell superconducting cavity, using finite-element techniques. We compared the results of these calculations, including the stiffening of the cavity with rods, with mode frequencies measured at HEPL. The correlation between data was significant. The same techniques were also used to design and optimize the stiffening scheme for the seven-cell 805-MHz superconducting cavity being developed at Los Alamos. In this report, we describe the final stiffening scheme and the results of our calculations

  11. Calculation of mechanical vibration frequencies of stiffened superconducting cavities

    International Nuclear Information System (INIS)

    Black, S.J.; Spalek, G.

    1992-01-01

    We calculated the frequencies of transverse and longitudinal mechanical-vibration modes of the HEPL-modified, CERN/DESY four-cell superconducting cavity, using finite-element techniques. We compared the results of these calculations, including the stiffening of the cavity with rods, with mode frequencies measured at HEPL. The correlation between data was significant. The same techniques were also used to design and optimize the stiffening scheme for the seven-cell 805-MHz superconducting cavity being developed at Los Alamos. In this report, we describe the final stiffening scheme and the results of our calculations. (Author) 6 figs., 5 tabs., 4 refs

  12. RF Design and Operating Performance of the BNL/AES 1.3 GHz Single Cell Superconducting RF Photocathode Electron Gun

    International Nuclear Information System (INIS)

    Cole, Michael; Kneisel, Peter; Ben-Zvi, Ilan; Burrill, Andrew; Hahn, H.; Rao, Triveni; Zhao, Y.

    2005-01-01

    Over the past several years Advanced Energy Systems and BNL have been collaborating on the development and testing of a fully superconducting photocathode electron gun. Over the past year we have begun to realize significant results which have been published elsewhere (1). This paper will review the RF design of the gun under test and present results of its performance under various operating conditions. Results for cavity quality factor will be presented for various operating temperatures and cavity field gradients. We will also discuss future plans for testing using this gun.

  13. Localization of rf breakdowns in a standing wave cavity

    Directory of Open Access Journals (Sweden)

    Faya Wang

    2009-04-01

    Full Text Available At SLAC, a five-cell, normal-conducting, L-band (1.3 GHz, standing-wave (SW cavity was built as a prototype positron capture accelerator for the ILC. The structure met the ILC gradient goal but required extensive rf processing. When rf breakdowns occurred, a large variation was observed in the decay rate of the stored energy in the cavity after the input power was shut off. It appeared that the breakdowns were isolating sections of the cavity, and that the trapped energy in those sections was then partitioned among its natural modes, producing a distinct beating pattern during the decay. To explore this phenomenon further, an equivalent circuit model of cavity was created that reproduces well its normal operating characteristics. The model was then used to compute the spectra of trapped energy for different numbers of isolated cells. The resulting modal patterns agree well with those of the breakdown data, and thus such a comparison appears to provide a means of identifying the irises on which the breakdowns occurred.

  14. Wireless overhead line temperature sensor based on RF cavity resonance

    International Nuclear Information System (INIS)

    Ghafourian, Maryam; Nezhad, Abolghasem Zeidaabadi; Bridges, Greg E; Thomson, Douglas J

    2013-01-01

    The importance of maximizing power transfer through overhead transmission lines necessitates the use of dynamic power control to keep transmission line temperatures within acceptable limits. Excessive conductor operating temperatures lead to an increased sag of the transmission line conductor and may reduce their expected life. In this paper, a passive wireless sensor based on a resonant radio frequency (RF) cavity is presented which can be used to measure overhead transmission line temperature. The temperature sensor does not require a power supply and can be easily clamped to the power line with an antenna attached. Changing temperature causes a change of cavity dimensions and a shift in resonant frequency. The resonant frequency of the cavity can be interrogated wirelessly. This temperature sensor has a resolution of 0.07 °C and can be interrogated from distances greater than 4.5 m. The sensor has a deviation from linearity of less than 2 °C. (paper)

  15. Latest Development in Superconducting RF Structures for beta=1 Particle Acceleration

    International Nuclear Information System (INIS)

    Peter Kneisel

    2006-01-01

    Superconducting RF technology is since nearly a decade routinely applied to different kinds of accelerating devices: linear accelerators, storage rings, synchrotron light sources and FEL's. With the technology recommendation for the International Linear Collider (ILC) a year ago, new emphasis has been placed on improving the performance of accelerating cavities both in Q-value and in accelerating gradients with the goal to achieve performance levels close to the fundamental limits given by the material parameters of the choice material, niobium. This paper will summarize the challenges to SRF technology and will review the latest developments in superconducting structure design. Additionally, it will give an overview of the newest results and will report on the developments in alternative materials and technologies

  16. Status of rf superconductivity at Argonne National Laboratory

    International Nuclear Information System (INIS)

    Markovich, P.M.; Shepard, K.W.; Zinkann, G.P.

    1987-01-01

    This paper reports the status of hardware development for the linac portion of the Argonne tandem-linac accelerator system (ATLAS). The ATLAS superconducting linac consists of an independent-phased array of 45 superconducting niobium resonators of the split-ring type. The linac has been operating in its present form since 1985, on a 24-hours per day, 5 days per week schedule. An upgrade of the ATLAS system is currently under construction the positive-ion injector (PII). The PII system will consist of an ECR positive-ion source mounted on a high-voltage platform injecting a very-low-velocity superconducting linac. The completed system will provide for the acceleration of beams of mass up to uranium, and will replace the tandem electrostatic accelerator as the injector for ATLAS. The status of resonator development for the superconducting linac is reported in this paper. Accelerating gradients in the existing ATLAS linac are currently limited by excessive heating and rf loss in the fast-tuning system associated with each superconducting resonator. Development of an upgraded fast-tuning system is also reported here. 7 refs., 5 figs

  17. Complex envelope control of pulsed accelerating fields in superconducting cavities

    CERN Document Server

    Czarski, T

    2010-01-01

    A digital control system for superconducting cavities of a linear accelerator is presented in this work. FPGA (Field Programmable Gate Arrays) based controller, managed by MATLAB, was developed to investigate a novel firmware implementation. The LLRF - Low Level Radio Frequency system for FLASH project in DESY is introduced. Essential modeling of a cavity resonator with signal and power analysis is considered as a key approach to the control methods. An electrical model is represented by the non-stationary state space equation for the complex envelope of the cavity voltage driven by the current generator and the beam loading. The electromechanical model of the superconducting cavity resonator including the Lorentz force detuning has been developed for a simulation purpose. The digital signal processing is proposed for the field vector detection. The field vector sum control is considered for multiple cavities driven by one klystron. An algebraic, complex domain model is proposed for the system analysis. The c...

  18. Superconducting radio frequency cavities: design, development and results

    International Nuclear Information System (INIS)

    Prakash, P.N.; Mistri, K.K.; Sonti, S.S.K.; Sacharias, J.; Raiand, A.; Kanjilal, D.

    2013-01-01

    In recent years, the development of superconducting niobium cavities has evoked a lot of interest among the accelerator physics community of India. Many laboratories are planning to develop superconducting niobium cavities for new accelerators and applications. Inter-University Accelerator Centre (IUAC) has been engaged in the indigenous development of niobium resonators for over a decade. During this period, several quarter wave resonators have been successfully built, tested and installed in the superconducting linac at IUAC. A new niobium low beta resonator for the High Current Injector (HCI) project has been designed, prototyped and tested. In addition to the in-house projects, IUAC is nearing completion of two niobium single spoke resonators (SSR1) for Fermi Lab, USA. Under the Indian Institutions and Fermi Lab Collaboration (IIFC), Raja Ramanna Centre for Advanced Technology, Indore and Inter-University Accelerator Centre have jointly developed TESLA-type 1.3 GHz single cell cavities which have achieved very high accelerating gradients. Buoyed by the success of this work, a 5-cell 1.3 GHz cavity with simple end tubes has been successfully built. This cavity is presently at Fermi Lab for 2 K tests. Recently, a 650 MHz, β=0.9 single cell cavity has also been successfully completed and is ready for cold tests. There are plans to develop a 650 MHz, β=0.6 single cell cavity in collaboration with VECC, Kolkata. This paper presents the status of the niobium cavities developed at Inter-University Accelerator Centre. (author)

  19. Vacuum characteristics of the rf cavity for TRISTAN main ring

    International Nuclear Information System (INIS)

    Mizuno, H.; Akemoto, M.; Sakai, S.; Yamazaki, Y.; Higo, T.; Morozumi, Y.; Takata, K.

    1987-01-01

    In the TRISTAN main ring 52 accelerating units of alternating periodic structure (APS) are to be installed into the 6 straight sections around the Fuji, Tsukuba and Oho experimental areas. An accelerating unit which is 5365 mm long is composed of two 9 accelerating cell structures. At present (Jan. 1987) 32 units have been installed and under operation at a beam energy of 25 GeV. The remaining 20 units will be set up in this summer. To achieve the necessary beam life longer than 5 hours, the cavity sections should be pumped down to the pressure less than 5 X 10 -9 Torr with an operating RF power of 200 kW per each 9-cell cavity and the e+- beam. For this purpose a sufficient baking which is the most efficient method of reducing the outgassing rates of the parts of vacuum system is required for the APS cavity. A circulating water boiler system with electric heaters and a water pump was developed for the easy operation and maintenance of the RF vacuum system. The cavity unit is made of low-carbon steel S25C, and inner surface is electro-plated with copper of 100 μm thickness in a pyrophosphorous-acid bath. The area of inner surface and the volume of the cavity are about 18 M 2 and 1 m 3 , respectively. The unit is baked at 135 0 C by circulating 145 0 C hot water in the cooling channel. After the bake-out process for 24 hours the outgassing rate is dominated by the hydrogen permeation from the cooling water channel through the iron wall into the vacuum. to suppress this permeation, the anti-corrosion agent is added to the water by 5% in volume. All of the units were baked for 10 days at 135 0 C before they were installed into the straight sections

  20. Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

    International Nuclear Information System (INIS)

    Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R

    2016-01-01

    Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0 -values. In this contribution we present the results from cryogenic RF tests of 1.3–1.5 GHz single-cell cavities made of ingot Nb of medium (RRR = 100–150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0 -value of 2 × 10 10 at 2 K after standard processing treatments. The performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching. (paper)

  1. Superconducting radio-frequency cavities made from medium and low-purity niobium ingots

    Science.gov (United States)

    Ciovati, Gianluigi; Dhakal, Pashupati; Myneni, Ganapati R.

    2016-06-01

    Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q 0-values. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR = 100-150) and low (RRR = 60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with an average Q 0-value of 2 × 1010 at 2 K after standard processing treatments. The performances of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.

  2. Coupler Development and Gap Field Analysis for the 352 MHz Superconducting CH-Cavity

    CERN Document Server

    Liebermann, H; Ratzinger, U; Sauer, A C

    2004-01-01

    The cross-bar H-type (CH) cavity is a multi-gap drift tube structure based on the H-210 mode currently under development at IAP Frankfurt and in collaboration with GSI. Numerical simulations and rf model measurements showed that the CH-type cavity is an excellent candidate to realize s.c. multi-cell structures ranging from the RFQ exit energy up to the injection energy into elliptical multi-cell cavities. The reasonable frequency range is from about 150 MHz up to 800 MHz. A 19-cell, β=0.1, 352 MHz, bulk niobium prototype cavity is under development at the ACCEL-Company, Bergisch-Gladbach. This paper will present detailed MicroWave Studio simulations and measurements for the coupler development of the 352 MHz superconducting CH cavity. It will describe possibilities for coupling into the superconducting CH-Cavity. The development of the coupler is supported by measurement on a room temperature CH-copper model. We will present the first results of the measurements of different couplers, e.g. capacitiv...

  3. Application of superconducting magnesium diboride (MGB2) in superconducting radio frequency cavities

    Science.gov (United States)

    Tan, Teng

    The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates

  4. Design and results of the radio frequency quadrupole RF system at the Superconducting Super Collider Laboratory

    International Nuclear Information System (INIS)

    Grippe, J.; Marsden, E.; Marrufo, O.; Regan, A.; Rees, D.; Ziomek, C.

    1993-05-01

    The Superconducting Super Collider Laboratory (SSCL) and the Los Alamos National Laboratory (LANL) entered into a joint venture to design and develop a 600 kW amplifier and its low-level controls for use in the Radio-Frequency Quadrupole (RFQ) accelerating cavity of the SSC. The design and development work has been completed. After being tested separately, the high power amplifier and low level RF control system were integrated and tested on a test cavity. Results of that tests are given. Tests were then carried out on the actual RFQ with and without the presence of the accelerated beam. Results of these tests are also given, along with the phase and amplitude information

  5. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

    Energy Technology Data Exchange (ETDEWEB)

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan [Variable Energy Cyclotron Centre, Kolkata (India)

    2013-02-15

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and {+-}0.2{sup 0}, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ('Dee' voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  6. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

    International Nuclear Information System (INIS)

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-01-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9–27 MHz with amplitude and phase stability of 100 ppm and ±0.2 0 , respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages (“Dee” voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  7. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

    Science.gov (United States)

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-02-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.20, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  8. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata.

    Science.gov (United States)

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-02-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.2(0), respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  9. Development of a high-power RF cavity for the PEP-II B factory

    International Nuclear Information System (INIS)

    Rimmer, R.A.; Allen, M.A.; Saba, J.; Schwarz, H.

    1995-03-01

    The authors describe the development and fabrication of the first high-power RF cavity for PEP-II. Design choices and fabrication technologies for the first cavity and subsequent production cavities are described. Conditioning and high-power testing of the first and subsequent cavities are discussed, as well as integration of the cavity into modular RF systems for both high-energy and low-energy rings. Plans for installation of the cavity raft assemblies in the RF sections of the PEP tunnel are also considered

  10. Application of International Linear Collider superconducting cavities for acceleration of protons

    Directory of Open Access Journals (Sweden)

    P. N. Ostroumov

    2007-12-01

    Full Text Available Beam acceleration in the International Linear Collider (ILC will be provided by 9-cell 1300 MHz superconducting (SC cavities. The cavities are designed for effective acceleration of charged particles moving with the speed of light and are operated on π-mode to provide a maximum accelerating gradient. A significant research and development effort has been devoted to develop ILC SC technology and its rf system which resulted in excellent performance of ILC cavities. Therefore, the proposed 8-GeV proton driver in Fermilab is based on ILC cavities above ∼1.2  GeV. The efficiency of proton beam acceleration by ILC cavities drops fast for lower velocities and it was proposed to develop squeezed ILC-type (S-ILC cavities operating at 1300 MHz and designed for β_{G}=0.81, geometrical beta, to accelerate protons or H^{-} from ∼420  MeV to 1.2 GeV. This paper discusses the possibility of avoiding the development of new β_{G}=0.81 cavities by operating ILC cavities on 8/9π-mode of standing wave oscillations.

  11. Evaluation of a new method of RF power coupling to acceleration cavity of charged particles accelerators

    Directory of Open Access Journals (Sweden)

    A M Poursaleh

    2017-08-01

    Full Text Available In this paper, the feasibility studty of a new method of RF power coupling to acceleration cavity of charged particles accelerator will be evaluated. In this method a slit is created around the accelerator cavity, and RF power amplifier modules is connected directly to the acceleration cavity. In fact, in this design, the cavity in addition to acting as an acceleration cavity, acts as a RF power combiner. The benefits of this method are avoiding the use of RF vacuum tubes, transmission lines, high power combiner and coupler. In this research, cylindrical and coaxial cavities were studied, and a small sample coaxial cavity is build by this method. The results of the resarch showed that compact, economical and safe RF accelerators can be achieved by the proposed method

  12. The Test of LLRF control system on superconducting cavity

    OpenAIRE

    Zhu, Zhenglong; Wang, Xianwu; Wen, Lianghua; Chang, Wei; Zhang, Ruifeng; Gao, Zheng; Chen, Qi

    2014-01-01

    The first generation Low-Level radio frequency(LLRF) control system independently developed by IMPCAS, the operating frequency is 162.5MHz for China ADS, which consists of superconducting cavity amplitude stability control, phase stability control and the cavity resonance frequency control. The LLRF control system is based on four samples IQ quadrature demodulation technique consisting an all-digital closed-loop feedback control. This paper completed the first generation of ADS LLRF control s...

  13. Understanding Quality Factor Degradation in Superconducting Niobium Cavities at Low Microwave Field Amplitudes

    Science.gov (United States)

    Romanenko, A.; Schuster, D. I.

    2017-12-01

    In niobium superconducting radio frequency (SRF) cavities for particle acceleration, a decrease of the quality factor at lower fields—a so-called low field Q slope or LFQS—has been a long-standing unexplained effect. By extending the high Q measurement techniques to ultralow fields, we discover two previously unknown features of the effect: (i) saturation at rf fields lower than Eacc˜0.1 MV /m ; (ii) strong degradation enhancement by growing thicker niobium pentoxide. Our findings suggest that the LFQS may be caused by the two level systems in the natural niobium oxide on the inner cavity surface, thereby identifying a new source of residual resistance and providing guidance for potential nonaccelerator low-field applications of SRF cavities.

  14. Studies of niobium and development of niobium resonant RF cavities for accelerator driven system

    International Nuclear Information System (INIS)

    Mondal, Jayanta

    2013-01-01

    The present approach for the fabrication of superconducting radio frequency (SRF) cavities is to roll and deep draw sheets of polycrystalline high-purity niobium. Jefferson Laboratory pioneered the use of large-grain/single-crystal Nb directly sliced from an ingot for the fabrication of single-crystal high-purity Nb SRF cavities. The large grain/single crystal niobium has several potential advantages over the polycrystalline niobium and has become a viable alternative to the standard fine grain (ASTM grain size>6 μm), high purity (RRR ≥ 250 ) niobium for the fabrication of high-performance SRF cavities for particle accelerators. The present study includes the prototype single cell low beta cavity design, fabrication, EB welding and low temperature RF test at 2K. In this study also the medium field Q-Slope has been analyzed with the help of an added non linear term in Heabel's analytical model and a linear increase of surface resistance Rs with the magnetic field

  15. Wakefield and RF Kicks Due to Coupler Asymmetry in TESLA-Type Accelerating Cavities

    International Nuclear Information System (INIS)

    Bane, K

    2008-01-01

    In a future linear collider, such as the International Linear Collider (ILC), trains of high current, low emittance bunches will be accelerated in a linac before colliding at the interaction point. Asymmetries in the accelerating cavities of the linac will generate fields that will kick the beam transversely and degrade the beam emittance and thus the collider performance. In the main linac of the ILC, which is filled with TESLA-type superconducting cavities, it is the fundamental (FM) and higher mode (HM) couplers that are asymmetric and thus the source of such kicks. The kicks are of two types: one, due to (the asymmetry in) the fundamental RF fields and the other, due to transverse wakefields that are generated by the beam even when it is on axis. In this report we calculate the strength of these kicks and estimate their effect on the ILC beam. The TESLA cavity comprises nine cells, one HM coupler in the upstream end, and one (identical, though rotated) HM coupler and one FM coupler in the downstream end (for their shapes and location see Figs. 1, 2) [1]. The cavity is 1.1 m long, the iris radius 35 mm, and the coupler beam pipe radius 39 mm. Note that the couplers reach closer to the axis than the irises, down to a distance of 30 mm

  16. Gridded thermionic gun and integral superconducting ballistic bunch compression cavity

    Energy Technology Data Exchange (ETDEWEB)

    Schultheiss, Thomas [Advanced Energy Systems, Inc., Medford, NY (United States)

    2015-11-16

    Electron-Ion colliders such as the Medium energy Electron Ion Collider (MEIC) being developed by JLAB require high current electrons with low energy spread for electron cooling of the collider ring. Accelerator techniques for improving bunch charge, average current, emittance, and energy spread are required for Energy Recovery Linacs (ERLs) and Circulator Rings (CR) for next generation colliders for nuclear physics experiments. Example candidates include thermionic-cathode electron guns with RF accelerating structures. Thermionic cathodes are known to produce high currents and have excellent lifetime. The success of the IR and THz Free-Electron Laser (FEL) designed and installed by Advanced Energy Systems at the Fritz Haber Institute (FHI) of the Max Planck Society in Berlin [1,2] demonstrates that gridded thermionic cathodes and rf systems be considered for next generation collider technology. In Phase 1 Advanced Energy Systems (AES) developed and analyzed a design concept using a superconducting cavity pair and gridded thermionic cathode. Analysis included Beam Dynamics and thermal analysis to show that a design of this type is feasible. The latest design goals for the MEIC electron cooler were for electron bunches of 420 pC at a frequency of 952.6 MHz with a magnetic field on the cathode of 2kG. This field magnetizes the beam imparting angular momentum that provides for helical motion of the electrons in the cooling solenoid. The helical motion increases the interaction time and improves the cooling efficiency. A coil positioned around the cathode providing 2kG field was developed. Beam dynamics simulations were run to develop the particle dynamics near the cathode and grid. Lloyd Young added capability to Tstep to include space charge effects between two plates and include image charge effects from the grid. He also added new pepper-pot geometry capability to account for honeycomb grids. These additions were used to develop the beam dynamics for this gun. The

  17. Cryomodule tests of the TESLA-like superconducting cavity in KEK-STF

    International Nuclear Information System (INIS)

    Kako, Eiji; Sato, Masato; Shishido, Toshio; Noguchi, Shuichi; Hatori, Hirofumi; Hayano, Hitoshi; Yamamoto, Yasuchika; Watanabe, Ken

    2008-01-01

    Construction of STF (Superconducting RF Test Facility) is being carried out at KEK. The STF-Baseline superconducting cavity system, which includes four TESLA-like 9-cell cavities, input couplers and frequency tuners, has been developed for the future ILC project. A 6-m cryomodule including one of four TESLA-like cavities was assembled, and the cryomodule was installed in the tunnel for the initial test, called the STF Phase-0.5. The first cool-down of the cryomodule and high power tests of the cavity had been carried out at 2 K from October to November, 2007. The maximum accelerating gradient (Eacc, max) of 19.3 MV/m was achieved in a specific pulse width of 1.5 msec and a repetition rate of 5 Hz, (23.4 MV/m in a shorter pulse width of 0.6 msec). Compensation of Lorentz force detuning at 18 MV/m was successfully demonstrated by using a piezo tuner. The second cryomodule test for four cavities, called the STF Phase-1.0, is scheduled in July, 2008. (author)

  18. Fabrication and vertical test experience of the European X-ray Free Electron Laser 3.9 GHz superconducting cavities

    Science.gov (United States)

    Pierini, P.; Bertucci, M.; Bosotti, A.; Chen, J. F.; Maiano, C. G.; Michelato, P.; Monaco, L.; Moretti, M.; Pagani, C.; Paparella, R.; Sertore, D.; Vogel, E.

    2017-04-01

    We report the experience of the production, processing and qualification testing of the superconducting radio frequency cavities at 3.9 GHz for the third harmonic system at the European XFEL (EXFEL) injector. The rf structure concept, originally developed for the FLASH FEL facility, was adapted to the new interfaces provided by the EXFEL design and the cavities were procured from a qualified vendor, delivered ready for the testing at the INFN infrastructure. A total of 23 cavities, three prototypes and two batches of 10, have been realized and tested up to specifications.

  19. A 3D printed superconducting aluminium microwave cavity

    Energy Technology Data Exchange (ETDEWEB)

    Creedon, Daniel L. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Goryachev, Maxim; Kostylev, Nikita; Tobar, Michael E., E-mail: michael.tobar@uwa.edu.au [ARC Centre of Excellence for Engineered Quantum Systems, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Sercombe, Timothy B. [School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley 6009 (Australia)

    2016-07-18

    3D printing of plastics, ceramics, and metals has existed for several decades and has revolutionized many areas of manufacturing and science. Printing of metals, in particular, has found a number of applications in fields as diverse as customized medical implants, jet engine bearings, and rapid prototyping in the automotive industry. Although many techniques are used for 3D printing metals, they commonly rely on computer controlled melting or sintering of a metal alloy powder using a laser or electron beam. The mechanical properties of parts produced in such a way have been well studied, but little attention has been paid to their electrical properties. Here we show that a microwave cavity (resonant frequencies 9.9 and 11.2 GHz) 3D printed using an Al-12Si alloy exhibits superconductivity when cooled below the critical temperature of aluminium (1.2 K), with a performance comparable with the common 6061 alloy of aluminium. Superconducting cavities find application in numerous areas of physics, from particle accelerators to cavity quantum electrodynamics experiments. The result is achieved even with a very large concentration of non-superconducting silicon in the alloy of 12.18%, compared with Al-6061, which has between 0.4% and 0.8%. Our results may pave the way for the possibility of 3D printing superconducting cavity configurations that are otherwise impossible to machine.

  20. A 3D printed superconducting aluminium microwave cavity

    International Nuclear Information System (INIS)

    Creedon, Daniel L.; Goryachev, Maxim; Kostylev, Nikita; Tobar, Michael E.; Sercombe, Timothy B.

    2016-01-01

    3D printing of plastics, ceramics, and metals has existed for several decades and has revolutionized many areas of manufacturing and science. Printing of metals, in particular, has found a number of applications in fields as diverse as customized medical implants, jet engine bearings, and rapid prototyping in the automotive industry. Although many techniques are used for 3D printing metals, they commonly rely on computer controlled melting or sintering of a metal alloy powder using a laser or electron beam. The mechanical properties of parts produced in such a way have been well studied, but little attention has been paid to their electrical properties. Here we show that a microwave cavity (resonant frequencies 9.9 and 11.2 GHz) 3D printed using an Al-12Si alloy exhibits superconductivity when cooled below the critical temperature of aluminium (1.2 K), with a performance comparable with the common 6061 alloy of aluminium. Superconducting cavities find application in numerous areas of physics, from particle accelerators to cavity quantum electrodynamics experiments. The result is achieved even with a very large concentration of non-superconducting silicon in the alloy of 12.18%, compared with Al-6061, which has between 0.4% and 0.8%. Our results may pave the way for the possibility of 3D printing superconducting cavity configurations that are otherwise impossible to machine.

  1. A 3D printed superconducting aluminium microwave cavity

    Science.gov (United States)

    Creedon, Daniel L.; Goryachev, Maxim; Kostylev, Nikita; Sercombe, Timothy B.; Tobar, Michael E.

    2016-07-01

    3D printing of plastics, ceramics, and metals has existed for several decades and has revolutionized many areas of manufacturing and science. Printing of metals, in particular, has found a number of applications in fields as diverse as customized medical implants, jet engine bearings, and rapid prototyping in the automotive industry. Although many techniques are used for 3D printing metals, they commonly rely on computer controlled melting or sintering of a metal alloy powder using a laser or electron beam. The mechanical properties of parts produced in such a way have been well studied, but little attention has been paid to their electrical properties. Here we show that a microwave cavity (resonant frequencies 9.9 and 11.2 GHz) 3D printed using an Al-12Si alloy exhibits superconductivity when cooled below the critical temperature of aluminium (1.2 K), with a performance comparable with the common 6061 alloy of aluminium. Superconducting cavities find application in numerous areas of physics, from particle accelerators to cavity quantum electrodynamics experiments. The result is achieved even with a very large concentration of non-superconducting silicon in the alloy of 12.18%, compared with Al-6061, which has between 0.4% and 0.8%. Our results may pave the way for the possibility of 3D printing superconducting cavity configurations that are otherwise impossible to machine.

  2. Entangling a nanomechanical resonator and a superconducting microwave cavity

    International Nuclear Information System (INIS)

    Vitali, D.; Tombesi, P.; Woolley, M. J.; Doherty, A. C.; Milburn, G. J.

    2007-01-01

    We propose a scheme able to entangle at the steady state a nanomechanical resonator with a microwave cavity mode of a driven superconducting coplanar waveguide. The nanomechanical resonator is capacitively coupled with the central conductor of the waveguide and stationary entanglement is achievable up to temperatures of tens of milliKelvin

  3. Investigation of the superconducting properties of niobium radio-frequency cavities

    Science.gov (United States)

    Ciovati, Gianluigi

    Radio-frequency (rf) superconducting cavities are widely used to increase the energy of a charged particle beam in particle accelerators. The maximum gradients of cavities made of bulk niobium have constantly improved over the last ten years and they are approaching the theoretical limit of the material. Nevertheless, rf tests of niobium cavities are still showing some "anomalous" losses (so-called "Q-drop"), characterized by a marked increase of the surface resistance at high rf fields, in absence of field emission. A low temperature "in-situ" baking under ultra-high vacuum has been successfully applied by several laboratories to reduce those losses and improve the cavity's quality factor. Several models have been proposed to explain the cause of the Q-drop and the baking effect. We investigated the effect of baking on niobium material parameters by measuring the temperature dependence of a cavity's surface impedance and comparing it with the Bardeen-Cooper-Schrieffer's theory of superconductivity. It was found that baking allows interstitial oxygen to diffuse from the surface deeper into the bulk. This produces a significant reduction of the normal electrons' mean free path, which causes an increase of the quality factor. The optimum baking parameters are 120°C for 24-48 h. We were also able to identify the origin of the Q-drop as due to a high magnetic field, rather then electric field, by measuring the quality factor of a cavity as function of the rf field in a resonant mode with only magnetic field present on the surface. With the aid of a thermometry system, we were able to localize the losses in the high magnetic field region. We measured the Q-drop in cavities which had undergone different treatments, such as anodization, electropolishing and post-purification, and with different metallurgical properties and we study the effectiveness of baking in each case. As a result, none of the models proposed so far can explain all the experimental observations. We

  4. Design and development progress of a LLRF control system for a 500 MHz superconducting cavity

    Science.gov (United States)

    Lee, Y. S.; Kim, H. W.; Song, H. S.; Lee, J. H.; Park, K. H.; Yu, I. H.; Chai, J. S.

    2012-07-01

    The LLRF (low-level radio-frequency) control system which regulates the amplitude and the phase of the accelerating voltage inside a RF cavity is essential to ensure the stable operation of charged particle accelerators. Recent advances in digital signal processors and data acquisition systems have allowed the LLRF control system to be implemented in digitally and have made it possible to meet the higher demands associated with the performance of LLRF control systems, such as stability, accuracy, etc. For this reason, many accelerator laboratories have completed or are completing the developments of digital LLRF control systems. The digital LLRF control system has advantages related with flexibility and fast reconfiguration. This paper describes the design of the FPGA (field programmable gate array) based LLRF control system and the status of development for this system. The proposed LLRF control system includes an analog front-end, a digital board (ADC (analog to digital converter), DAC (digital to analog converter), FPGA, etc.) and a RF & clock generation system. The control algorithms will be implemented by using the VHDL (VHSIC (very high speed integrated circuits) hardware description language), and the EPICS (experiment physics and industrial control system) will be ported to the host computer for the communication. In addition, the purpose of this system is to control a 500 MHz RF cavity, so the system will be applied to the superconducting cavity to be installed in the PLS storage ring, and its performance will be tested.

  5. Prototype Control System for Compensation of Superconducting Cavities Detuning Using Piezoelectric Actuators

    Science.gov (United States)

    Przygoda, K.; Piotrowski, A.; Jablonski, G.; Makowski, D.; Pozniak, T.; Napieralski, A.

    2009-08-01

    Pulsed operation of high gradient superconducting radio frequency (SCRF) cavities results in dynamic Lorentz force detuning (LFD) approaching or exceeding the bandwidth of the cavity of order of a few hundreds of Hz. The resulting modulation of the resonance frequency of the cavity is leading to a perturbation of the amplitude and phase of the accelerating field, which can be controlled only at the expense of RF power. Presently, at various labs, a piezoelectric fast tuner based on an active compensation scheme for the resonance frequency control of the cavity is under study. The tests already performed in the Free Electron Laser in Hamburg (FLASH), proved the possibility of Lorentz force detuning compensation by the means of the piezo element excited with the single period of sine wave prior to the RF pulse. The X-Ray Free Electron Laser (X-FEL) accelerator, which is now under development in Deutsche Elektronen-Synchrotron (DESY), will consists of around 800 cavities with a fast tuner fixture including the actuator/sensor configuration. Therefore, it is necessary to design a distributed control system which would be able to supervise around 25 RF stations, each one comprised of 32 cavities. The Advanced Telecomunications Computing Architecture (ATCA) was chosen to design, develop, and build a Low Level Radio Frequency (LLRF) controller for X-FEL. The prototype control system for Lorentz force detuning compensation was designed and developed. The control applications applied in the system were fitted to the main framework of interfaces and communication protocols proposed for the ATCA-based LLRF control system. The paper presents the general view of a designed control system and shows the first experimental results from the tests carried out in FLASH facility. Moreover, the possibilities for integration of the piezo control system to the ATCA standards are discussed.

  6. Control Instabilities in a Pulsed Multi-Cavity RF System with Vector Sum Feedback (A Mathematical Analysis)

    CERN Document Server

    Tückmantel, Joachim

    2001-01-01

    Upcoming projects relying on pulsed linear accelerators intend to use superconducting RF systems. Cost reasons suggest driving several cavities by a common transmitter, controlled over a vector sum feedback system, possibly supported by a feed forward system. Numerical simulations hint that such a system may become uncontrollable under certain conditions. In the present paper, for a model very close to reality, we will present a mathematical proof that in fact spontaneous symmetry braking is possible for these configurations, defining also the precise conditions under which it will take place. These can be used as an estimate for the real RF system stability limits. The listing of a small program demonstrating the mechanism numerically for two cavities is attached.

  7. Control Instabilities in a Pulsed Multi-Cavity RF System with Vector Sum Feedback (A Mathematical Analysis) 052

    CERN Document Server

    Tückmantel, Joachim

    2001-01-01

    Upcoming projects relying on pulsed linear accelerators intend to use superconducting RF systems. Cost reasons suggest driving several cavities by a common transmitter, controlled over a vector sum feedback system, possibly supported by a feed forward system. Numerical simulations hint that such a system may become uncontrollable under certain conditions. In the present paper, for a model very close to reality, we will present a mathematical proof that in fact spontaneous symmetry braking is possible for these configurations, defining also the precise conditions under which it will take place. These can be used as an estimate for the real RF system stability limits. The listing of a small program demonstrating the mechanism numerically for two cavities is attached.

  8. NbN thin films for superconducting radio frequency cavities

    Science.gov (United States)

    Roach, W. M.; Skuza, J. R.; Beringer, D. B.; Li, Z.; Clavero, C.; Lukaszew, R. A.

    2012-12-01

    NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed.

  9. NbN thin films for superconducting radio frequency cavities

    International Nuclear Information System (INIS)

    Roach, W M; Clavero, C; Lukaszew, R A; Skuza, J R; Beringer, D B; Li, Z

    2012-01-01

    NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m −1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed. (paper)

  10. EXCESS RF POWER REQUIRED FOR RF CONTROL OF THE SPALLATION NEUTRON SOURCE (SNS) LINAC, A PULSED HIGH-INTENSITY SUPERCONDUCTING PROTON ACCELERATOR

    International Nuclear Information System (INIS)

    Lynch, M.; Kwon, S.

    2001-01-01

    A high-intensity proton linac, such as that being planned for the SNS, requires accurate RF control of cavity fields for the entire pulse in order to avoid beam spill. The current design requirement for the SNS is RF field stability within ±0.5% and ±0.5 o [1]. This RF control capability is achieved by the control electronics using the excess RF power to correct disturbances. To minimize the initial capital costs, the RF system is designed with 'just enough' RF power. All the usual disturbances exist, such as beam noise, klystron/HVPS noise, coupler imperfections, transport losses, turn-on and turn-off transients, etc. As a superconducting linac, there are added disturbances of large magnitude, including Lorentz detuning and microphonics. The effects of these disturbances and the power required to correct them are estimated, and the result shows that the highest power systems in the SNS have just enough margin, with little or no excess margin

  11. Superconducting Accelerating Cavity Pressure Sensitivity Analysis

    International Nuclear Information System (INIS)

    Rodnizki, J.; Horvits, Z.; Ben Aliz, Y.; Grin, A.; Weissman, L.

    2014-01-01

    The measured sensitivity of the cavity was evaluated and it is full consistent with the measured values. It was explored that the tuning system (the fog structure) has a significant contribution to the cavity sensitivity. By using ribs or by modifying the rigidity of the fog we may reduce the HWR sensitivity. During cool down and warming up we have to analyze the stresses on the HWR to avoid plastic deformation to the HWR since the Niobium yield is an order of magnitude lower in room temperature

  12. Niobium Coatings for the HIE-ISOLDE QWR Superconducting Accelerating Cavities

    CERN Document Server

    Jecklin, N; Delaup, B; Ferreira, L; Mondino, I; Sublet, A; Therasse, M; Venturini Desolaro, W

    2013-01-01

    The HIE-ISOLDE (High Intensity and Energy at ISOLDE) project is the upgrade of the existing ISOLDE (Isotope Separator On Line DEvice) facility at CERN, which is dedicated to the production of a large variety of radioactive ion beams for nuclear physics experiments. A new linear accelerator made of 20 ȕ=10.3% and 12 ȕ=6.3% quarter-wave resonators (QWR) superconducting (SC) accelerating cavities at 101 MHz will be built, and in a first phase two cryomodules of 5 high-ȕ cavities each are scheduled to accelerate first beams in 2015. The cavities are made of a copper substrate, with a sputter-coated superconductive niobium (Nb) layer, operated at 4.5 K with an accelerating field of 6 MV/m at 10W Radio-Frequency (RF) losses (Q=4.5· 108). In this paper we will discuss the baseline surface treatment and coating procedure which allows obtaining the required performance, as well as the steps undertaken in order to prepare series production of the required number of cavities guaranteeing their quality and functional...

  13. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Shahid, E-mail: shahid.ahmed@ieee.org [BML Munjal University, Gurgaon, Haryana 123413 (India); Mammosser, John D. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2015-07-15

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O{sub 2} (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM{sub 010}-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  14. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    Science.gov (United States)

    Ahmed, Shahid; Mammosser, John D.

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  15. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity

    International Nuclear Information System (INIS)

    Ahmed, Shahid; Mammosser, John D.

    2015-01-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar–O 2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM 010 -mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper

  16. Microwave induced plasma discharge in multi-cell superconducting radio-frequency cavity.

    Science.gov (United States)

    Ahmed, Shahid; Mammosser, John D

    2015-07-01

    A R&D effort for in situ cleaning of 1.5 GHz Superconducting Radio Frequency (SRF) cavities at room temperature using the plasma processing technique has been initiated at Jefferson Lab. This is a step toward the cleaning of cryomodules installed in the Continuous Electron Beam Accelerator Facility (CEBAF). For this purpose, we have developed an understanding of plasma discharge in a 5-cell CEBAF-type SRF cavity having configurations similar to those in the main accelerator. The focus of this study involves the detailed investigations of developing a plasma discharge inside the cavity volume and avoids the breakdown condition in the vicinity of the ceramic RF window. A plasma discharge of the gas mixture Ar-O2 (90%:10%) can be established inside the cavity volume by the excitation of a resonant 4π/5 TM010-mode driven by a klystron. The absence of any external magnetic field for generating the plasma is suitable for cleaning cavities installed in a complex cryomodule assembly. The procedures developed in these experimental investigations can be applied to any complex cavity structure. Details of these experimental measurements and the observations are discussed in the paper.

  17. Design and performance of a new induction furnace for heat treatment of superconducting radiofrequency niobium cavities.

    Science.gov (United States)

    Dhakal, Pashupati; Ciovati, Gianluigi; Rigby, Wayne; Wallace, John; Myneni, Ganapati Rao

    2012-06-01

    Superconducting radio frequency (SRF) cavities made of high purity niobium (Nb) are the building blocks of many modern particle accelerators. The fabrication process includes several cycles of chemical and heat treatment at low (∼120 °C) and high (∼800 °C) temperatures. In this contribution, we describe the design and performance of an ultra-high-vacuum furnace which uses an induction heating system to heat treat SRF cavities. Cavities are heated by radiation from the Nb susceptor. By using an all-niobium hot zone, contamination of the Nb cavity by foreign elements during heat treatment is minimized and allows avoiding subsequent chemical etching. The furnace was operated up to 1400 °C with a maximum pressure of ∼1 × 10(-5) Torr and the maximum achievable temperature is estimated to be higher than 2000 °C. Initial results on the performance of a single cell 1.5 GHz cavity made of ingot Nb heat treated at 1200 °C using this new induction furnace and without subsequent chemical etching showed a reduction of the RF losses by a factor of ∼2 compared to cavities made of fine-grain Nb which underwent standard chemical and heat treatments.

  18. Cerenkov Radiator Driven by a Superconducting RF Electron Gun

    International Nuclear Information System (INIS)

    Poole, B.R.; Harris, J.R.

    2011-01-01

    The Naval Postgraduate School (NPS), Niowave, Inc., and Boeing have recently demonstrated operation of the first superconducting RF electron gun based on a quarter wave resonator structure. In preliminary tests, this gun has produced 10 ps long bunches with charge in excess of 78 pC, and with beam energy up to 396 keV. Initial testing occurred at Niowave's Lansing, MI facility, but the gun and diagnostic beam line are planned for installation in California in the near future. The design of the diagnostic beam line is conducive to the addition of a Cerenkov radiator without interfering with other beam line operations. Design and simulations of a Cerenkov radiator, consisting of a dielectric lined waveguide will be presented. The dispersion relation for the structure is determined and the beam interaction is studied using numerical simulations. The characteristics of the microwave radiation produced in both the short and long bunch regimes will be presented.

  19. Development of high purity niobium material for superconducting cavities

    International Nuclear Information System (INIS)

    Umezawa, Hiroaki; Takeuchi, Koichi; Sakita, Kohei; Suzuki, Takafusa; Saito, Kenji; Noguchi, Shuichi.

    1993-01-01

    For the superconducting niobium cavities, issues of thermal quench and field emission have to be solved to achieve a high field gradient (>25MV/m) for TESLA (TeV Energy Superconducting Linear Accelerator). In order to overcome the quench, upgrading of thermal conductivity of niobium material at the low temperature is very important. On the reduction of the field emission not only dust particles but also defect, impurity and inhomogeneity should be considered. Therefore development of high purity niobium material is very important to solve these issues. This paper describes the our latest R and D for high purity niobium material. (author)

  20. Perpendicular biased ferrite tuned RF cavity for the TRIUMF KAON Factory booster ring

    International Nuclear Information System (INIS)

    Poirier, R.L.; Enegren, T.; Haddock, C.

    1989-03-01

    The rf cavity for the booster ring requires a frequency swing of 46 MHz to 62 MHz at a repetition rate of 50 Hz. The possibility of using the LANL booster cavity design with a yttrium garnet ferrite tuner biased perpendicular to the rf field, in the longitudinal direction, is being investigated. In order to minimize the stray magnetic biasing field on the beam axis, an alternative scheme similar to the design being proposed for the LANL main ring cavity in which the ferrite is perpendicular biased in the radial direction, is being considered. The behaviour of the rf cavity and the magnetizing circuit for both designs are discussed

  1. ECR plasma cleaning for superconducting cavities

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Suehiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2000-02-01

    A superconducting linac has been operating well as a heavy ion energy booster of the tandem accelerator at JAERI since 1994. Forty superconducting quarter wave resonators are used in the linac. They have high performances in average. Some of them are, however, suffering from 'Q-disease' that has been caused by hydrogen absorption into niobium during electro-polishing and the precipitation of niobium-hydrides on the surface at the vicinity of about 120K during precooling. A method of electron cyclotron resonance (ECR) plasma cleaning was applied to spare resonator in order to investigate if it is useful as a curing method of Q-disease. ECR plasma was excited in the resonator by 2.45 GHz microwave in a magnetic field of about 87.5 mT. In the first preliminary experiments, hydrogen, helium, water and oxigen gases were investigated. Every case was done at a pressure of about 3x10{sup -3} Pa. The results show that apparent recovery from Q-disease was found with helium and oxigen gases. (author)

  2. Material options for the superconducting rf system of the Future Circular Collider

    CERN Document Server

    Aull, Sarah; Butterworth, Andy; Schwerg, Nikolai

    2018-01-01

    The design of the superconducting RF (SRF) systems of the Future Circular Collider (FCC) machine variants requires a thorough comparison of the different options for cavity material, oper- ating temperature and frequency. We collected representative SRF performance data at different frequencies and temperatures of bulk niobium as the standard technology and of niobium thin films as a potential alternative and develop a perspective for future performance for all material- frequency-temperature combinations as function of accelerating gradient. Based on this perspective, we estimate the corresponding cryogenic grid power for the different FCC machines showing the most favourable accelerating gradients for the different materials and operating temperatures. Further- more, we discuss advantages, disadvantages and limitations of the different technology options to be taken into consideration.

  3. A 201-MHz Normal Conducting RF Cavity for the International MICE Experiment

    International Nuclear Information System (INIS)

    Li, D.; DeMello, A.J.; Virostek, Steve; Zisman, Michael S.; Rimmer, Robert

    2008-01-01

    MICE is a demonstration experiment for the ionization cooling of muon beams. Eight RF cavities are proposed to be used in the MICE cooling channel. These cavities will be operated in a strong magnetic field; therefore, they must be normal conducting. The cavity design and construction are based on the successful experience and techniques developed for a 201-MHz prototype cavity for the US MUCOOL program. Taking advantage of a muon beamΛ s penetration property, the cavity employs a pair of curved thin beryllium windows to terminate conventional beam irises and achieve higher cavity shunt impedance. The cavity resembles a round, closed pillbox cavity. Two half-shells spun from copper sheets are joined by e-beam welding to form the cavity body. There are four ports on the cavity equator for RF couplers, vacuum pumping and field probes. The ports are formed by means of an extruding technique.

  4. A low energy muon spin rotation and point contact tunneling study of niobium films prepared for superconducting cavities

    Science.gov (United States)

    Junginger, Tobias; Calatroni, S.; Sublet, A.; Terenziani, G.; Prokscha, T.; Salman, Z.; Suter, A.; Proslier, T.; Zasadzinski, J.

    2017-12-01

    Point contact tunneling and low energy muon spin rotation are used to probe, on the same samples, the surface superconducting properties of micrometer thick niobium films deposited onto copper substrates using different sputtering techniques: diode, dc magnetron and HIPIMS. The combined results are compared to radio-frequency tests performances of RF cavities made with the same processes. Degraded surface superconducting properties are found to correlate to lower quality factors and stronger Q-slope. In addition, both techniques find evidence for surface paramagnetism on all samples and particularly on Nb films prepared by HIPIMS.

  5. Minimization of power consumption during charging of superconducting accelerating cavities

    International Nuclear Information System (INIS)

    Bhattacharyya, Anirban Krishna; Ziemann, Volker; Ruber, Roger; Goryashko, Vitaliy

    2015-01-01

    The radio frequency cavities, used to accelerate charged particle beams, need to be charged to their nominal voltage after which the beam can be injected into them. The standard procedure for such cavity filling is to use a step charging profile. However, during initial stages of such a filling process a substantial amount of the total energy is wasted in reflection for superconducting cavities because of their extremely narrow bandwidth. The paper presents a novel strategy to charge cavities, which reduces total energy reflection. We use variational calculus to obtain analytical expression for the optimal charging profile. Energies, reflected and required, and generator peak power are also compared between the charging schemes and practical aspects (saturation, efficiency and gain characteristics) of power sources (tetrodes, IOTs and solid state power amplifiers) are also considered and analysed. The paper presents a methodology to successfully identify the optimal charging scheme for different power sources to minimize total energy requirement.

  6. Field stabilization in superconducting cavities under pulsed operating

    International Nuclear Information System (INIS)

    Tessier, J.M.

    1996-01-01

    Within the framework of Tesla linear accelerator project, superconducting cavity battery is used to accelerate electrons and positrons. These cavities require pulsed running and must reach very high accelerating gradients. Under the action of the Lorentz force, the resonance frequency shifts and leaves the band-pass width, which hinders the field from taking its maximal value inside the cavity. The setting of an auto-oscillating loop allows to bring the generator frequency under the control of the cavity frequency. A feedback system is needed to reduce the energy dispersion inside the particle packets. The effects of the mechanical vibrations that disturb the accelerating voltage phase between two impulses are also compensated by a feedback loop. This thesis describes all these phenomena and computes their effects on the energy dispersion of the beam in both cases of relativistic and non-relativistic particles. (A.C.)

  7. Minimization of power consumption during charging of superconducting accelerating cavities

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, Anirban Krishna, E-mail: anirban.bhattacharyya@physics.uu.se; Ziemann, Volker; Ruber, Roger; Goryashko, Vitaliy

    2015-11-21

    The radio frequency cavities, used to accelerate charged particle beams, need to be charged to their nominal voltage after which the beam can be injected into them. The standard procedure for such cavity filling is to use a step charging profile. However, during initial stages of such a filling process a substantial amount of the total energy is wasted in reflection for superconducting cavities because of their extremely narrow bandwidth. The paper presents a novel strategy to charge cavities, which reduces total energy reflection. We use variational calculus to obtain analytical expression for the optimal charging profile. Energies, reflected and required, and generator peak power are also compared between the charging schemes and practical aspects (saturation, efficiency and gain characteristics) of power sources (tetrodes, IOTs and solid state power amplifiers) are also considered and analysed. The paper presents a methodology to successfully identify the optimal charging scheme for different power sources to minimize total energy requirement.

  8. Rf structure of superconducting cyclotron for therapy application

    International Nuclear Information System (INIS)

    Takekoshi, Hidekuni; Matsuki, Seishi; Mashiko, Katuo; Shikazono, Naomoto.

    1981-01-01

    Advantages of fast neutrons in therapeutical application are now widely recognized. Fast neutrons are generated by bombarding a thick beryllium target with high energy protons and deuterons. The AVF cyclotrons which deliver 50 MeV protons and 25 MeV deuterons are commonly used and are commercially available now. At the treatment usually rotational irradiation is taken to prevent an injury to normal tissue from the high LET effect of fast neutrons. The construction cost of both cyclotrons and isocentric irradiation installation are relatively high, so that the spread of neutron therapy is obstructed. A superconducting cyclotron for neutron therapy application was proposed by a Chalk River group. This low cost design allows the installation to be a dedicated facility located in a hospital, and small size allows installations of the complete cyclotron in a rotatable gantry. The design studies of the superconducting cyclotron based on this idea are going on at Kyoto University. The full scale model experiments for a rf structure of the cyclotron were carried out. (author)

  9. High temperature superconducting films by rf magnetron sputtering

    International Nuclear Information System (INIS)

    Kadin, A.M.; Ballentine, P.H.

    1989-01-01

    The authors have produced sputtered films of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O by rf magnetron sputtering from an oxide target consisting of loose reacted powder. The use of a large 8-inch stoichiometric target in the magnetron mode permits films located above the central region to be free of negative-ion resputtering effects, and hence yields reproducible, uniform stoichiometric compositions for a wide range of substrate temperatures. Superconducting YBCO films have been obtained either by sputtering at low temperatures followed by an 850 0 C oxygen anneal, or alternatively by depositing onto substrates heated to ∼600 - 650 0 C and cooling in oxygen. Films prepared by the former method on cubic zirconia substrate consist of randomly oriented crystallites with zero resistance above 83 K. Those deposited on zirconia at medium temperatures without the high-temperature anneal contain smooth partially oriented crystallites, with a slightly depressed T/sub c/ ∼75K. Finally, superconducting films have been deposited on MgO using a BiSrCaCu/sub 2/O/sub x/ powder target

  10. X-ray imaging of superconducting radio frequency cavities

    Science.gov (United States)

    Musser, Susan Elizabeth

    The goal of this research was to develop an improved diagnostic technique to identify the location of defects that limit superconducting radio frequency (SRF) cavity performance during cavity testing or in existing accelerators. SRF cavities are primarily constructed of niobium. Electrons within the metal of a cavity under high electric field gradient have a probability of tunneling through the potential barrier. i e. leave the surface or are field emitted in regions where defects are encountered. Field emitted electrons are accelerated in the electric fields within the cavity. The electrons can have complicated trajectories and strike the cavity walls thus producing x-rays via Coulomb interactions and/or bremsstrahlung radiation. The endpoint energy of an x-ray spectrum predicts the electron maximum final kinetic energy within the cavity. Field emission simulations can then predict the source of the field-emitted electrons and the defect(s). In a multicell cavity the cells are coupled together and act as a set of coupled oscillators. There are multiple passbands of excitation for a multicell structure operating in a particular mode. For different passbands of operation the direction and amplitude of the fields within a cavity change from that of the normal accelerating mode. Field emitted electrons have different trajectories depending on the mode and thus produce x-rays in different locations. Using a collimated sodium iodide detector and subjecting a cavity to multiple passband modes at high electric field gradient the source of a cavity's x-rays can be determined. Knowing the location of the x-rays and the maximum electron kinetic energy; field emission simulations for different passband modes can be used to determine and verify the source of the field emitted electrons from mode to mode. Once identified, the defect(s) can be repaired or modifications made to the manufacturing process.

  11. RF cavity for the Novosibirsk race-track microtron-recuperator

    International Nuclear Information System (INIS)

    Gavrilov, N.; Kuptsov, I.; Kurkin, G.; Mironenko, L.; Petrov, V.; Sedlyarov, I.; Veshcherevich, V.

    1994-01-01

    Geometry, engineering design and characteristics of a 181 MHz RF cavity are described. The cavity has copper clad stainless steel walls and has a Q of 42,000 and a shunt impedance of 8.5 MOhm. The cavities of that type are parts of an RF system of a CW race-track microtron-recuperator (RTMR). 10 refs.; 16 figs.; 1 tab

  12. THE Low-level Radio Frequency System for the superconducting cavities of National Synchrotron Light Source II

    International Nuclear Information System (INIS)

    Ma, H.; Rose, J.; Holub, B.; Cupolo, J.; Oliva, J.; Sikora, R.; Yeddulla, M.

    2011-01-01

    A digital low-level radio frequency (LLRF) field controller has been developed for the storage ring of The National Synchrotron Light Source-II (NSLS-II). The primary performance goal for the LLRF is to support the required RF operation of the superconducting cavities with a beam current of 500mA and a 0.14 degree or better RF phase stability. The digital field controller is FPGA-based, in a standard format 19-inch/I-U chassis. It has an option of high-level control support with MATLAB running on a local host computer through a USB2.0 port. The field controller has been field tested with the high-power superconducting RF (SRF) at Canadian light Source, and successfully stored a high beam current of 250 mA. The test results show that required specifications for the cavity RF field stability are met. This digital field controller is also currently being used as a development platform for other functional modules in the NSLS-II RF systems.

  13. Measurement of Microwave Parameters of a Superconducting Niobium Cavity

    Science.gov (United States)

    Azaryan, N. S.; Baturitskii, M. A.; Budagov, Yu. A.; Demin, D. L.; Dem‧yanov, S. E.; Karpovich, V. A.; Kniga, V. V.; Krivosheev, R. M.; Lyubetskii, N. V.; Maksimov, S. I.; Pobol‧, I. L.; Rodionova, V. N.; Shirkov, G. D.; Shumeiko, N. M.; Yurevich, S. V.

    2017-01-01

    This paper describes a method for direct measurement of the amplitude-frequency characteristics and the Q factor of empty superconducting niobium radio frequency Tesla-type cavities. An automated measuring complex that permits recording the superconductivity effect and measuring high Q values has been developed. Measurements have been made of the Q factors of the investigated objects (the first domestic 1.3-GHz niobium cavities) at a level no lower than 0.1·109 (with a maximum value of 1.2·1010) and a level of relative losses lower than 130 dB (with a minimum factor of 139.7 dB) at liquid nitrogen temperature.

  14. Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

    International Nuclear Information System (INIS)

    Upadhyay, Janardan; Phillips, Larry; Valente, Anne-Marie

    2011-01-01

    Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

  15. Etching of Niobium Sample Placed on Superconducting Radio Frequency Cavity Surface in Ar/CL2 Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Janardan Upadhyay, Larry Phillips, Anne-Marie Valente

    2011-09-01

    Plasma based surface modification is a promising alternative to wet etching of superconducting radio frequency (SRF) cavities. It has been proven with flat samples that the bulk Niobium (Nb) removal rate and the surface roughness after the plasma etchings are equal to or better than wet etching processes. To optimize the plasma parameters, we are using a single cell cavity with 20 sample holders symmetrically distributed over the cell. These holders serve the purpose of diagnostic ports for the measurement of the plasma parameters and for the holding of the Nb sample to be etched. The plasma properties at RF (100 MHz) and MW (2.45 GHz) frequencies are being measured with the help of electrical and optical probes at different pressures and RF power levels inside of this cavity. The niobium coupons placed on several holders around the cell are being etched simultaneously. The etching results will be presented at this conference.

  16. Effect of mild baking on superconducting niobium cavities investigated by sequential nanoremoval

    Directory of Open Access Journals (Sweden)

    A. Romanenko

    2013-01-01

    Full Text Available The near-surface nanostructure of niobium determines the performance of superconducting microwave cavities. Subtle variations in surface nanostructure lead to yet unexplained phenomena such as the dependence of the quality factor of these resonating structures on the magnitude of rf fields—an effect known as the “Q slopes”. Understanding and controlling the Q slopes is of great practical importance for particle accelerators. Here we investigate the mild baking effect—120°C vacuum baking for 48 hours—which strongly affects the Q slopes. We used a hydrofluoric acid rinse alternating with oxidation in water as a tool for stepwise material removal of about 2  nanometers/step from the surface of superconducting niobium cavities. Applying removal cycles on mild baked cavities and measuring the quality factor dependence on the rf fields after one or several such cycles allowed us to explore the distribution of lossy layers within the first several tens of nanometers from the surface. We found that a single HF rinse results in the increase of the cavity quality factor. The low field Q slope was shown to be mostly controlled by the material structure within the first six nanometers from the surface. The medium field Q slope evolution was fitted using linear (∝B peak surface magnetic field and quadratic (∝B^{2} terms in the surface resistance and it was found that best fits do not require the quadratic term. We found that about 10 nanometers of material removal are required to bring back the high field Q slope and about 20–50 nanometers to restore the onset field to the prebaking value.

  17. HF power couplers for pulsed superconducting cavity resonators; Coupleurs de puissance HF pour cavites supraconductrices en mode pulse

    Energy Technology Data Exchange (ETDEWEB)

    Jenhani, Hassen [Laboratoire de l' Accelerateur Lineaire, IN2P3-CNRS et Universite de Paris-Sud, BP 34, F-91898 Orsay Cedex (France)

    2006-11-15

    Recent years have seen an impressive improvement in the accelerating gradients obtained in superconducting cavities. Consequently, such cavities have become attractive candidates for large superconducting linear accelerator projects such as the European XFEL and the International Linear Collider (ILC). As a result, there is a strong interest in reducing RF conditioning time and improving the performance of the input power couplers for these cavities. The so-called TTF-III input power coupler, adopted for the XFEL superconducting RF cavities are complex components. In order to better understand the behavior of this component we have performed a series of experiments on a number of such couplers. Initially, we developed a fully automated RF high power test stand for coupler conditioning procedure. Following this, we performed a series of coupler conditioning tests. This has allowed the study of the coupler behavior during processing. A number of experiments were carried out to evaluate the in-situ baking effect on the conditioning time. Some of the conditioned couplers were sent to DESY in order to be tested on 9-cells TESLA cavities under cryogenic conditions. These tests have shown that the couplers in no way limit the cavity performance, even up to gradients of 35 MV/m. The main objective of our coupler studies was the reduction of their conditioning time, which represents one of the most important criteria in the choice of coupler for high energy linacs. Excellent progress in reducing the conditioning time has been demonstrated by making appropriate modifications to the conditioning procedure. Furthermore, special attention was paid to electron generation processes in the couplers, via multipacting. Simulations of this process were made on both the TTF-III coupler and on a new coupler prototype, TTF-V. Experiments aimed at suppressing multipacting were also successfully achieved by using a DC bias on the inner conductor of the co-axial coupler. (author)

  18. Highly Sensitive Measurements of the Dark Current of Superconducting Cavities for TESLA Using a SQUID Based Cryogenic Current Comparator

    CERN Document Server

    Vodel, W; Nietzsche, S

    2004-01-01

    This contribution presents a Cryogenic Current Comparator (CCC) as an excellent tool for detecting dark currents generated, e.g. by superconducting cavities for the upcoming TESLA project (X-FEL) at DESY. To achieve the maximum possible energy the gradient of the superconducting RF cavities should be pushed close to the physical limit of 50 MV/m. The undesired field emission of electrons (so-called dark current) of the superconducting RF cavities at strong fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value to compare and classify the cavities. The main component of the CCC is a highly sensitive LTS-DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the dark current. For this reason the input coil of the SQUID is connected across a special designed toroidal niobium pick-up coil for the passing electron beam. A noise limited current resolution of nearly 2 pA/√(Hz) with a measu...

  19. Magnetization measurement of niobium for superconducting cavity material evaluation

    International Nuclear Information System (INIS)

    Wake, Masayoshi; Saito, Kenji.

    1995-05-01

    A series of magnetization measurements on niobium materials for superconducting cavities was performed, and the method was found to be very useful for material evaluation. The effects of annealing, chemical polishing and machining were clearly observed by this method. The material quality and the processing of the material can be properly evaluated by measuring the magnetization. An observation of the Q-disease effect indicates the possibility of using this method for the studies beyond material evaluation. (J.P.N)

  20. An rf separated kaon beam from the Main Injector: Superconducting aspects

    Energy Technology Data Exchange (ETDEWEB)

    D.A. Edwards

    1998-11-01

    ThE report is intended to focus on the superconducting aspects of a potential separated kaon beam facility for the Main Injector, and most of this document reflects that emphasis. However, the RF features cannot be divorced from the overall beam requirements, and so the next section is devoted to the latter subject. The existing optics design that meets the needs of the two proposed experiments is outliied, and its layout at Fermilab is shown. The frequency and deflection gradient choices present implementation dMiculties, and the section closes with some commentary on these issues. Sec. 3 provides an introduction to cavity design considerations, and, in particular carries forward the discussion of resonator shape and frequency selection. The R&D program is the subject of Sec. 4. Provisional parameter choices will be summarized. Initial steps toward cavity fabrication based `on copper models have been taken. The next stages in cavity fabrication will be reviewed in some detail. The infrastructure needs and availability will be discussed. Sec. 5 discusses what maybe characterized as the in~edlents of a point design. At this writing, some aspects are clear and some are not. The basic systems are reasonably clear and are described. The final section presents a cost and schedule estimate for both the Ft&D and production phase. Some supporting material and elaboration is provided in the Appendices.

  1. Room temperature RF characterization of niobium SCRF cavities and their prototypes

    International Nuclear Information System (INIS)

    Mahawar, Ashish; Mohania, Praveen; Shrivastava, P.; Yadav, Anand; Puntambekar, A.M.

    2013-01-01

    Raja Ramanna Centre for Advanced Technology is working on development of 1.3 GHz and 650 MHz multi-cell SCRF cavities. The multi-cell cavities require RF characterization at various stages of fabrication to ensure that the final welded cavity has the right resonant frequency. The prototype cavities as well as the final cavities were extensively characterized at each stage of half cell, dumb bell and end group development and assembly stages. The paper will provide details of the RF characterizations done and the final results achieved. (author)

  2. 3 GHz digital rf control at the superconducting Darmstadt electron linear accelerator: First results from the baseband approach and extensions for other frequencies

    Directory of Open Access Journals (Sweden)

    A. Araz

    2010-08-01

    Full Text Available The low level rf system for the superconducting Darmstadt electron linear accelerator (S-DALINAC developed 20 years ago and operating since converts the 3 GHz signals from the cavities down to the baseband and not to an intermediate frequency. While designing the new, digital rf control system this concept was kept: the rf module does the I/Q and amplitude modulation/demodulation while the low frequency board, housing an field programmable gate array analyzes and processes the signals. Recently, the flexibility of this concept was realized: By replacing the modulator/demodulators on the rf module, cavities operating at frequencies other than the one of the S-DALINAC can be controlled with only minor modifications: A 6 GHz version, needed for a harmonic bunching system at the S-DALINAC and a 324 MHz solution to be used on a room temperature cavity at GSI, are currently under design. This paper reviews the concept of the digital low level rf control loops in detail and reports on the results gained during first operation with a superconducting cavity.

  3. Effect of low temperature baking in nitrogen on the performance of a niobium superconducting radio frequency cavity

    OpenAIRE

    Pashupati Dhakal; Santosh Chetri; Shreyas Balachandran; Peter J. Lee; Gianluigi Ciovati

    2018-01-01

    We report the rf performance of a single cell superconducting radiofrequency cavity after low temperature baking in a nitrogen environment. A significant increase in quality factor has been observed when the cavity was heat treated in the temperature range of 120–160 °C with a nitrogen partial pressure of ∼25  m Torr. This increase in quality factor as well as the Q-rise phenomenon (anti-Q-slope) is similar to those previously obtained with high temperature nitrogen doping as well as titanium...

  4. Effect of Low Temperature Baking in Nitrogen on the Performance of a Niobium Superconducting Radio Frequency Cavity

    OpenAIRE

    Dhakal, Pashupati; Chetri, Santosh; Balachandran, Shreyas; Lee, Peter J.; Ciovati, Gianluigi

    2017-01-01

    We report the rf performance of a single-cell superconducting radiofrequency cavity after low temperature baking in a nitrogen environment. A significant increase in quality factor has been observed when the cavity was heat treated in the temperature range of 120-160 {\\deg}C with a nitrogen partial pressure of ~25 mTorr. This increase in quality factor as well as the Q-rise phenomenon (anti-Q-slope) is similar to those previously obtained with high temperature nitrogen doping as well as titan...

  5. Modeling the interaction of a heavily beam loaded SRF cavity with its low-level RF feedback loops

    Science.gov (United States)

    Liu, Zong-Kai; Wang, Chaoen; Chang, Lung-Hai; Yeh, Meng-Shu; Chang, Fu-Yu; Chang, Mei-Hsia; Chang, Shian-Wen; Chen, Ling-Jhen; Chung, Fu-Tsai; Lin, Ming-Chyuan; Lo, Chih-Hung; Yu, Tsung-Chi

    2018-06-01

    A superconducting radio frequency (SRF) cavity provides superior stability to power high intensity light sources and can suppress coupled-bunch instabilities due to its smaller impedance for higher order modes. Because of these features, SRF cavities are commonly used for modern light sources, such as the TLS, CLS, DLS, SSRF, PLS-II, TPS, and NSLS-II, with an aggressive approach to operate the light sources at high beam currents. However, operating a SRF cavity at high beam currents may result with unacceptable stability problems of the low level RF (LLRF) system, due to drifts of the cavity resonant frequency caused by unexpected perturbations from the environment. As the feedback loop gets out of control, the cavity voltage may start to oscillate with a current-dependent characteristic frequency. Such situations can cause beam abort due to the activation of the interlock protection system, i.e. false alarm of quench detection. This malfunction of the light source reduces the reliability of SRF operation. Understanding this unstable mechanism to prevent its appearance becomes a primary task in the pursuit of highly reliable SRF operation. In this paper, a Pedersen model, including the response of the LLRF system, was used to simulate the beam-cavity interaction of a SRF cavity under heavy beam loading. Causes for the onset of instability at high beam current will be discussed as well as remedies to assure the design of a stable LLRF system.

  6. SQUID Based Cryogenic Current Comparator for Measurements of the Dark Current of Superconducting Cavities

    CERN Document Server

    Vodel, W; Neubert, R; Nietzsche, S

    2005-01-01

    This contribution presents a LTS-SQUID based Cryogenic Current Comparator (CCC) for detecting dark currents, generated e.g. by superconducting cavities for the upcoming X-FEL project at DESY. To achieve the maximum possible energy the gradients of the superconducting RF cavities should be pushed close to the physical limit of 50 MV/m. The measurement of the undesired field emission of electrons (the so-called dark current) in correlation with the gradient will give a proper value to compare and classify the cavities. The main component of the CCC is a high performance LTS-DC SQUID system which is able to measure extremely low magnetic fields, e.g. caused by the extracted dark current. For this reason the input coil of the SQUID is connected across a special designed toroidal niobium pick-up coil (inner diameter: about 100 mm) for the passing electron beam. A noise limited current resolution of nearly 2 pA/√(Hz) with a measurement bandwidth of up to 70 kHz was achieved without the pick-up coil. Now, ...

  7. Resistivity changes in superconducting-cavity-grade Nb following high-energy proton irradiation

    International Nuclear Information System (INIS)

    Snead, C.L. Jr.; Hanson, A.; Greene, G.A.

    1997-01-01

    Niobium superconducting rf cavities are proposed for use in the proton LINAC accelerators for spallation-neutron applications. Because of accidental beam loss and continual halo losses along the accelerator path, concern for the degradation of the superconducting properties of the cavities with accumulating damage arises. Residual-resistivity-ratio (RRR) specimens of Nb, with a range of initial RRR's were irradiated at room temperature with protons at energies from 200 to 2000 MeV. Four-probe resistance measurements were made at room temperature and at 4.2 K both prior to and after irradiation. Nonlinear increases in resistivity simulate expected behavior in cavity material after extended irradiation, followed by periodic anneals to room temperature: For RRR = 316 material, irradiations to (2 - 3) x 10 15 p/cm 2 produce degradations up to the 10% level, a change that is deemed operationally acceptable. Without. periodic warming to room temperature, the accumulated damage energy would be up to a factor of ten greater, resulting in unacceptable degradations. Likewise, should higher-RRR material be used, for the same damage energy imparted, relatively larger percentage changes in the RRR will result

  8. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    Science.gov (United States)

    Tian, Hui; Ribeill, Guilhem; Xu, Chen; Reece, Charles E.; Kelley, Michael J.

    2011-03-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  9. Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications

    Science.gov (United States)

    Becker, Chaoyue; Posen, Sam; Groll, Nickolas; Cook, Russell; Schlepütz, Christian M.; Hall, Daniel Leslie; Liepe, Matthias; Pellin, Michael; Zasadzinski, John; Proslier, Thomas

    2015-02-01

    We present an analysis of Nb3Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb3Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (Tc) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ˜2 μm thick Nb3Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb3Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low Tc regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb3Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

  10. Analysis of Nb{sub 3}Sn surface layers for superconducting radio frequency cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Chaoyue [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Posen, Sam; Hall, Daniel Leslie [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States); Groll, Nickolas; Proslier, Thomas, E-mail: prolier@anl.gov [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Cook, Russell [Nanoscience and Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Schlepütz, Christian M. [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Liepe, Matthias [Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York 14853 (United States); Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Pellin, Michael [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Zasadzinski, John [Department of Physics, Illinois Institute of Technology, Chicago, Illinois 60616 (United States)

    2015-02-23

    We present an analysis of Nb{sub 3}Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb{sub 3}Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (T{sub c}) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ∼2 μm thick Nb{sub 3}Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb{sub 3}Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low T{sub c} regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb{sub 3}Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

  11. A novel approach to characterizing the surface topography of niobium superconducting radio frequency (SRF) accelerator cavities

    International Nuclear Information System (INIS)

    Tian Hui; Ribeill, Guilhem; Xu Chen; Reece, Charles E.; Kelley, Michael J.

    2011-01-01

    As superconducting niobium radio-frequency (SRF) cavities approach fundamental material limits, there is increased interest in understanding the details of topographical influences on realized performance limitations. Micro- and nano-roughness are implicated in both direct geometrical field enhancements as well as complications of the composition of the 50 nm surface layer in which the super-currents typically flow. Interior surface chemical treatments such as buffered chemical polishing (BCP) and electropolishing (EP) used to remove mechanical damage leave surface topography, including pits and protrusions of varying sharpness. These may promote RF magnetic field entry, locally quenching superconductivity, so as to degrade cavity performance. A more incisive analysis of surface topography than the widely used average roughness is needed. In this study, a power spectral density (PSD) approach based on Fourier analysis of surface topography data acquired by both stylus profilometry and atomic force microscopy (AFM) is introduced to distinguish the scale-dependent smoothing effects, resulting in a novel qualitative and quantitative description of Nb surface topography. The topographical evolution of the Nb surface as a function of different steps of well-controlled EP is discussed. This study will greatly help to identify optimum EP parameter sets for controlled and reproducible surface levelling of Nb for cavity production.

  12. Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications

    International Nuclear Information System (INIS)

    Becker, Chaoyue; Posen, Sam; Hall, Daniel Leslie; Groll, Nickolas; Proslier, Thomas; Cook, Russell; Schlepütz, Christian M.; Liepe, Matthias; Pellin, Michael; Zasadzinski, John

    2015-01-01

    We present an analysis of Nb 3 Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb 3 Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (T c ) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ∼2 μm thick Nb 3 Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb 3 Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low T c regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb 3 Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators

  13. Construction and present status of KEKB superconducting cavities

    International Nuclear Information System (INIS)

    Tajima, T.; Akai, K.; Ezura, E; Furuya, T.; Hosoyama, K.; Mitsunobu, S.

    2000-01-01

    The superconducting cavity (SCC) for KEKB is 508 MHz single-cell cavity that has large beam pipes (22 cm and 30 cm i.d.) so that higher-order modes propagate out of the cavity and be absorbed by a lossy material. The input coupler is the TRISTAN-type coaxial one with some modifications such that dc bias voltage can be applied to avoid multipactoring during beam operation, fins to efficiently cool the outer conductor and a heater to remove condensed gases. The higher-order mode absorber is made of ferrite directly sinter-bonded on the inner surface of the copper pipe using a technique called Hot Isostatic Press (HIP). One prototype cavity was tested up to 0.57 A at TRISTAN Accumulation Ring (AR) in 1996. Then, four cavities were constructed for KEKB. One of the cavities achieved an accelerating field of 19 MV/m at a test in a vertical cryostat; this field is the world record at this frequency to our knowledge. No degradation of the field after assembly into horizontal cryostats was observed up to the available power of 300 kW that corresponds to ∼12 MV/m. These four cavities were installed in KEKB tunnel and are expected to supply 6 MV in total voltage to the 1.1 A electron beam in high energy ring (HER). Since beam commissioning started in Dec. 1998, the system has been supplying 6 MV and working very smoothly without any trouble. The maximum current has been 0.51 A and power delivered to beam per cavity is 370-380 kW/cavity up to the end of Apr., 1999. (author)

  14. A statistical model for field emission in superconducting cavities

    International Nuclear Information System (INIS)

    Padamsee, H.; Green, K.; Jost, W.; Wright, B.

    1993-01-01

    A statistical model is used to account for several features of performance of an ensemble of superconducting cavities. The input parameters are: the number of emitters/area, a distribution function for emitter β values, a distribution function for emissive areas, and a processing threshold. The power deposited by emitters is calculated from the field emission current and electron impact energy. The model can successfully account for the fraction of tests that reach the maximum field Epk in an ensemble of cavities, for eg, 1-cells at sign 3 GHz or 5-cells at sign 1.5 GHz. The model is used to predict the level of power needed to successfully process cavities of various surface areas with high pulsed power processing (HPP)

  15. High-power RF cavity R ampersand D for the PEP-II B Factory

    International Nuclear Information System (INIS)

    Rimmer, R.; Lambertson, G.; Hodgson, J.

    1994-06-01

    We describe the development of a high-power test model of the 476 MHz RF cavity for the PEP-II B Factory. This cavity is designed to demonstrate the feasibility of a high-power design with higher-order mode (HOM) damping waveguides and the fabrication technologies involved, and it can also be used to evaluate aperture or loop couplers and various RF windows. Changes to the RF design to reduce peak surface heating are discussed and results of finite-element analyses of temperature and stress are presented. Fabrication methods for the prototype and subsequent production cavities are discussed

  16. Technical Developments on Reduced $\\beta$ Superconducting Cavities at CERN

    CERN Document Server

    Aberle, O; Calatroni, Sergio; Chiaveri, Enrico; Häbel, E; Hanni, R; Losito, R; Marque, S; Tückmantel, Joachim

    1999-01-01

    Several authors proposed the construction of superconducting proton linacs using the LEP2 cavities once LEP will be decommissioned. However only a fraction (about half) of these cavities can be used as they are for the high-energy part (b~1) of such a linac, the low energy part requiring the development of accelerating structures optimized for lower values of the particle velocity. At CERN an R&D programme on reduced-b single-cell cavities started in 1996 in order to study and explore the limits of the technology successfully used for the production of LEP2 cavities (copper cavities niobium-plated using the magnetron sputtering technique). Four different geometries were extensively investigated, each representing part of a multicell structure optimized for particles having b=0.48, b=0.625, b=0.66 and b=0.8 respectively. The results were encouraging for the last two types and therefore a new phase of R&D aimed at the production of multicell cavities for b=0.66 and b=0.8 was started. The goal is to demo...

  17. Superconducting Prototype Cavities for the Spallation Neutron Source (SNS) Project

    International Nuclear Information System (INIS)

    Ciovati, G.; Kneisel, P.; Brawley, J.; Bundy, R.; Campisi, I.; Davis, K.; Macha, K.; Machie, D.; Mammosser, J.; Morgan, S.; Sundelin, R.; Turlington, L.; Wilson, K.; Doleans, M.; Kim, S.H.; Barni, D.; Pagani, C.; Pierini, P.; Matsumoto, K.; Mitchell, R.; Schrage, D.; Parodi, R.; Sekutowicz, J.; Ylae-Oijala, P.

    2001-01-01

    The Spallation Neutron Source project includes a superconducting linac section in the energy range from 192 MeV to 1000 MeV, operating at a frequency of 805 MHz at 2.1 K. For this energy range two types of cavities are needed with geometrical beta - values of beta= 0.61 and beta= 0.81. An aggressive cavity prototyping program is being pursued at Jlab, which calls for fabricating and testing of four beta= 0.61 cavities and two beta= 0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler on each beam pipe and a port for a high power coaxial input coupler. Three of the four beta= 0.61 cavities will be used for a cryomodule test in early 2002. At this time four medium beta cavities and one high beta cavity have been completed at JLab. The first tests on the beta=0.61 cavity and the beta= 0.81 exceeded the design values for gradient and Q - value: E acc = 1 0.3 MV/m and Q = 5 x 10 9 at 2.1K for beta= 0.61 and E acc = 12.3 MV/m and Q = 5 x 10 9 at 2.1K for beta= 0.81. One of the medium beta cavities has been equipped with an integrated helium vessel and measurements of the static and dynamic Lorentz force detuning will be done and compared to the ''bare'' cavities. In addition two single cell cavities have been fabricated, equipped with welded-on HOM couplers. They are being used to evaluate the HOM couplers with respect to multipacting, fundamental mode rejection and HOM damping as far as possible in a single cell. This paper will describe the cavity design with respect to electrical and mechanical features, the fabrication efforts and the results obtained with the different cavities existing at the time of this workshop

  18. Development of the RF cavity for the SKKUCY-9 compact cyclotron

    International Nuclear Information System (INIS)

    Shin, Seungwook; Lee, Jongchul; LEE, Byeong-No; Ha, Donghyup; Namgoong, Ho; Chai, Jongseo

    2015-01-01

    A 9 MeV compact cyclotron, named SKKUCY-9, for a radiopharmaceutical compound especially fludeoxyglucose (FDG) production for a positron emission tomography (PET) machine was developed at Sungkyunkwan University. H − ions which are produced from a Penning Ionization Gauge(PIG) ion source, travel through a normal conducting radio frequency (RF) cavity which operates at 83.2 MHz for an acceleration and electro-magnet for a beam focusing until the ions acquire energy of about 9 MeV. For installation at a small local hospital, our SKKUCY-9 cyclotron is developed to be compact and light-weight, comparable to conventional medical purpose cyclotrons. For compactness, we adapted a deep valley and large angle hill type for the electro-magnet design. Normally a RF cavity is installed inside of the empty space of the magnet valley region, which is extremely small in our case. We faced problems such as difficulties of installing the RF cavity, low Q-value. Despite of those difficulties, a compact RF cavity and its system including a RF power coupler to feed amplified RF power to the RF cavity and a fine tuner to compensate RF frequency variations was successfully developed and tested

  19. Development of the RF cavity for the SKKUCY-9 compact cyclotron

    Science.gov (United States)

    Shin, Seungwook; Lee, Jongchul; LEE, Byeong-No; Ha, Donghyup; Namgoong, Ho; Chai, Jongseo

    2015-09-01

    A 9 MeV compact cyclotron, named SKKUCY-9, for a radiopharmaceutical compound especially fludeoxyglucose (FDG) production for a positron emission tomography (PET) machine was developed at Sungkyunkwan University. H- ions which are produced from a Penning Ionization Gauge(PIG) ion source, travel through a normal conducting radio frequency (RF) cavity which operates at 83.2 MHz for an acceleration and electro-magnet for a beam focusing until the ions acquire energy of about 9 MeV. For installation at a small local hospital, our SKKUCY-9 cyclotron is developed to be compact and light-weight, comparable to conventional medical purpose cyclotrons. For compactness, we adapted a deep valley and large angle hill type for the electro-magnet design. Normally a RF cavity is installed inside of the empty space of the magnet valley region, which is extremely small in our case. We faced problems such as difficulties of installing the RF cavity, low Q-value. Despite of those difficulties, a compact RF cavity and its system including a RF power coupler to feed amplified RF power to the RF cavity and a fine tuner to compensate RF frequency variations was successfully developed and tested.

  20. Beam self-excited rf cavity driver for a deflector or focusing system

    International Nuclear Information System (INIS)

    Wadlinger, E.A.

    1996-01-01

    A bunched beam from and accelerator can excite and power an rf cavity which then drives either a deflecting or focusing (including nonlinear focusing) rf cavity with and amplitude related to beam current. Rf power, generated when a bunched beam loses energy to an rf field when traversing an electric field that opposes the particle's motion, is used to drive a separate (or the same) cavity to either focus or deflect the beam. The deflected beam can be stopped by an apertures or directed to a different area of a target depending on beam current. The beam-generated rf power can drive a radio-frequency quadrupole (RFQ) that can change the focusing properties of a beam channel as a function of beam current (space- charge force compensation or modifying the beam distribution on a target). An rf deflector can offset a beam to a downstream sextupole, effectively producing a position-dependent quadrupole field. The combination of rf deflector plus sextupole will produce a beam current dependent quadropole-focusing force. A static quadrupole magnet plus another rf deflector can place the beam back on the optic axis. This paper describes the concept, derives the appropriate equations for system analysis, and fives examples. A variation on this theme is to use the wake field generated in an rf cavity to cause growth in the beam emittance. The beam current would then be apertured by emittance defining slits

  1. Beam self-excited rf cavity driver for a deflector or focusing system

    International Nuclear Information System (INIS)

    Wadlinger, E.A.

    1996-01-01

    A bunched beam from an accelerator can excite and power an rf cavity which then drives either a deflecting or focusing (including nonlinear focusing) rf cavity with an amplitude related to beam current. Rf power, generated when a bunched beam loses energy to an rf field when traversing an electric field that opposes the particle's motion, is used to drive a separate (or the same) cavity to either focus or deflect the beam. The deflected beam can be stopped by an aperture or directed to a different area of a target depending on beam current. The beam-generated rf power can drive a radiofrequency quadrupole that can change the focusing properties of a beam channel as a function of beam current (space-charge-force compensation or modifying the beam distribution on a target). An rf deflector can offset a beam to a downstream sextupole, effectively producing a position-dependent quadrupole field. The combination of rf deflector plus sextupole will produce a beam current dependent quadrupole-focusing force. A static quadrupole magnet plus another rf deflector can place the beam back on the optic axis. This paper describes the concept, derives the appropriate equations for system analysis, and gives examples. A variation on this theme is to use the wake field generated in an rf cavity to cause growth in the beam emittance. The beam current would then be apertured by emittance defining slits. (author)

  2. The interaction between a beam and a superconducting cavity module: Measurements in CESR and CESR-Phase 3 goals

    Energy Technology Data Exchange (ETDEWEB)

    Belomestnykh, S; Flynn, G; Hartung, W; Kirchgessner, J; Moffat, D; Muller, H; Padamsee, H; Pisharody, M; Veshcherevich, V [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies

    1996-08-01

    Plans for the next generation of electron-positron colliders (B-factories and B-factory-like machines) call for high beam currents to produce luminosities of the order of 10 (exp 33). To store these high currents in a machine, special attention must be paied to the interaction of the beam with discontinuities in the surrounding vacuum chamber. RF cavities are among the biggest perturbations in accelerator vacuum chambers and are therefore among the biggest sources of beam instabilities. Accelerating structures of new machines are being designed to have smaller impedance to reduce the beam-cavity interaction. Prototypes for the cavity, input coupler, cryostat, and higher-order mode (HOM) loads were subjected and are tested in CESR. A superconducting (SRF) cavity was installed in addition to the four five-cell normal conducting cavities. As a result, the calorimetry and RF power results agree with predictions up to their respective uncertainties. The results of wake potential sampling suggested that the wake fields of the SRF cavity will not limit the performance of CESR in bunch train operation. No beam instabilities or dangerous HOMs were encountered while sweeping the HOM frequencies using the cavity tuner or while exciting multipole HOMs by displacing the beam off axis. (G.K.)

  3. The Path to High Q-Factors in Superconducting Accelerating Cavities: Flux Expulsion and Surface Resistance Optimization

    Energy Technology Data Exchange (ETDEWEB)

    Martinello, Martina [Illinois Inst. of Technology, Chicago, IL (United States)

    2016-12-01

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator

  4. The path to high Q-factors in superconducting accelerating cavities: Flux expulsion and surface resistance optimization

    Science.gov (United States)

    Martinello, Martina

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator

  5. Study of Electron Swarm in High Pressure Hydrogen Gas Filled RF Cavities

    International Nuclear Information System (INIS)

    Yonehara, K.; Chung, M.; Jansson, A.; Moretti, A.; Popovic, M.; Tollestrup, A.; Alsharo'a, M.; Johnson, R.P.; Notani, M.; Oka, T.; Wang, H.

    2010-01-01

    A high pressure hydrogen gas filled RF cavity has been proposed for use in the muon collection system for a muon collider. It allows for high electric field gradients in RF cavities located in strong magnetic fields, a condition frequently encountered in a muon cooling channel. In addition, an intense muon beam will generate an electron swarm via the ionization process in the cavity. A large amount of RF power will be consumed into the swarm. We show the results from our studies of the HV RF breakdown in a cavity without a beam and present some results on the resulting electron swarm dynamics. This is preliminary to actual beam tests which will take place late in 2010.

  6. Traveling wave linear accelerator with RF power flow outside of accelerating cavities

    Science.gov (United States)

    Dolgashev, Valery A.

    2016-06-28

    A high power RF traveling wave accelerator structure includes a symmetric RF feed, an input matching cell coupled to the symmetric RF feed, a sequence of regular accelerating cavities coupled to the input matching cell at an input beam pipe end of the sequence, one or more waveguides parallel to and coupled to the sequence of regular accelerating cavities, an output matching cell coupled to the sequence of regular accelerating cavities at an output beam pipe end of the sequence, and output waveguide circuit or RF loads coupled to the output matching cell. Each of the regular accelerating cavities has a nose cone that cuts off field propagating into the beam pipe and therefore all power flows in a traveling wave along the structure in the waveguide.

  7. Auto-tuning systems for J-PARC LINAC RF cavities

    International Nuclear Information System (INIS)

    Fang, Z.; Kobayashi, T.; Fukui, Y.; Futatsukawa, K.; Michizono, S.; Yamaguchi, S.; Anami, S.; Suzuki, H.; Sato, F.; Shinozaki, S.; Chishiro, E.

    2014-01-01

    The 400-MeV proton linear accelerator (LINAC) at the Japan Proton Accelerator Research Complex (J-PARC) consists of 324-MHz low-β and 972-MHz high-β accelerator sections. From October 2006 to May 2013, only the 324-MHz low-β accelerator section was in operation. From the summer of 2013 the J-PARC LINAC was upgraded by installing the 972-MHz high-β accelerator section, and the proton beam was successfully accelerated to 400 MeV in January 2014. Auto-tuning systems for the J-PARC LINAC RF cavities have been successfully developed. A first generation design, an auto-tuning system using a mechanical tuner controller, was developed and operated for the first 3 years. Then the second-generation auto-tuning system was developed using a new approach to the RF cavity warm-up process, and this was applied to the accelerator operation for the subsequent 4 years. During the RF cavity warm-up process in this system, the mechanical tuner is constantly fixed and the input RF frequency is automatically tuned to the cavity resonance frequency using the FPGA (Field-Programmable Gate Array) of the digital feedback RF control system. After the input power level reaches the required value, input RF frequency tuning is stopped and it is switched to the operation frequency. Then, the mechanical tuner control begins operation. This second-generation auto-tuning system was extremely effective for the 324-MHz cavity operation. However, if we apply this approach to the 972-MHz RF cavities, an interlock due to the RF cavity reflection amplitude occasionally occurs at the end of the warm-up process. In order to solve this problem a third generation novel auto-tuning system was successfully developed in December 2013 and applied to the operation of the J-PARC LINAC, including the 972-MHz ACS RF cavities. During the warm-up process both the mechanical tuner controller and the input RF frequency tuning are in operation, and good matching between the input RF frequency and the RF cavity is

  8. Auto-tuning systems for J-PARC LINAC RF cavities

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Z., E-mail: fang@post.kek.jp [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Kobayashi, T.; Fukui, Y.; Futatsukawa, K.; Michizono, S.; Yamaguchi, S.; Anami, S. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Suzuki, H.; Sato, F.; Shinozaki, S.; Chishiro, E. [Japan Atomic Energy Agency (JAEA), 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

    2014-12-11

    The 400-MeV proton linear accelerator (LINAC) at the Japan Proton Accelerator Research Complex (J-PARC) consists of 324-MHz low-β and 972-MHz high-β accelerator sections. From October 2006 to May 2013, only the 324-MHz low-β accelerator section was in operation. From the summer of 2013 the J-PARC LINAC was upgraded by installing the 972-MHz high-β accelerator section, and the proton beam was successfully accelerated to 400 MeV in January 2014. Auto-tuning systems for the J-PARC LINAC RF cavities have been successfully developed. A first generation design, an auto-tuning system using a mechanical tuner controller, was developed and operated for the first 3 years. Then the second-generation auto-tuning system was developed using a new approach to the RF cavity warm-up process, and this was applied to the accelerator operation for the subsequent 4 years. During the RF cavity warm-up process in this system, the mechanical tuner is constantly fixed and the input RF frequency is automatically tuned to the cavity resonance frequency using the FPGA (Field-Programmable Gate Array) of the digital feedback RF control system. After the input power level reaches the required value, input RF frequency tuning is stopped and it is switched to the operation frequency. Then, the mechanical tuner control begins operation. This second-generation auto-tuning system was extremely effective for the 324-MHz cavity operation. However, if we apply this approach to the 972-MHz RF cavities, an interlock due to the RF cavity reflection amplitude occasionally occurs at the end of the warm-up process. In order to solve this problem a third generation novel auto-tuning system was successfully developed in December 2013 and applied to the operation of the J-PARC LINAC, including the 972-MHz ACS RF cavities. During the warm-up process both the mechanical tuner controller and the input RF frequency tuning are in operation, and good matching between the input RF frequency and the RF cavity is

  9. Detuning related coupler kick variation of a superconducting nine-cell 1.3 GHz cavity

    Science.gov (United States)

    Hellert, Thorsten; Dohlus, Martin

    2018-04-01

    Superconducting TESLA-type cavities are widely used to accelerate electrons in long bunch trains, such as in high repetition rate free electron lasers. The TESLA cavity is equipped with two higher order mode couplers and a fundamental power coupler (FPC), which break the axial symmetry of the cavity. The passing electrons therefore experience axially asymmetrical coupler kicks, which depend on the transverse beam position at the couplers and the rf phase. The resulting emittance dilution has been studied in detail in the literature. However, the kick induced by the FPC depends explicitly on the ratio of the forward to the backward traveling waves at the coupler, which has received little attention. The intention of this paper is to present the concept of discrete coupler kicks with a novel approach of separating the field disturbances related to the standing wave and a reflection dependent part. Particular attention is directed to the role of the penetration depth of the FPC antenna, which determines the loaded quality factor of the cavity. The developed beam transport model is compared to dedicated experiments at FLASH and European XFEL. Both the observed transverse coupling and detuning related coupler kick variations are in good agreement with the model. Finally, the expected trajectory variations due to coupler kick variations at European XFEL are investigated and results of numerical studies are presented.

  10. Operating experience with superconducting cavities at the TESLA test facility

    International Nuclear Information System (INIS)

    Moeller, Wolf-Dietrich

    2003-01-01

    A description of the TESLA Test Facility, which has been set up at DESY by the TeV Energy Superconducting Accelerator (TESLA) collaboration, will be given as it is now after five years of installation and operation. The experience with the first three modules, each containing 8 superconducting 9-cell cavities, installed and operated in the TTF-linac will be described. The measurements in the vertical and horizontal cryostats as well as in the modules will be compared. Recent results of the operation at the TESLA design current, macropulses of 800 μsec with bunches of 3.2 nC at a rate of 2.25 MHz are given. New measurement results of the higher order modes (HOM) will be presented. The operation and optimisation of the TTF Free Electron Laser (TTF-FEL) will also be covered in this paper. (author)

  11. Test results of the Los Alamos ferrite-tuned rf cavity

    International Nuclear Information System (INIS)

    Friedrichs, C.C.; Spalek, G.; Carlini, R.D.; Smythe, W.R.

    1987-03-01

    An rf accelerating cavity appropriate for use in a 20% frequency bandwidth synchrotron has been designed, fabricated, and is now being tested at Los Alamos. The cavity-amplifier system was designed to produce a peak rf gap voltage of 90 kV over the range from 50 to 60 MHz. Special features of the system are the transversely biased ferrite tuner, capacitive coupling of the amplifier to the cavity, and a 15-cm beam pipe. High-power rf testing of the cavity-amplifier system started in August 1986, using an adjustable dc power supply to bias the ferrite. This paper describes the cavity-amplifier circuit and the test results to the present time. Future plans are also discussed

  12. Effect of low temperature baking in nitrogen on the performance of a niobium superconducting radio frequency cavity

    Directory of Open Access Journals (Sweden)

    Pashupati Dhakal

    2018-03-01

    Full Text Available We report the rf performance of a single cell superconducting radiofrequency cavity after low temperature baking in a nitrogen environment. A significant increase in quality factor has been observed when the cavity was heat treated in the temperature range of 120–160 °C with a nitrogen partial pressure of ∼25  m Torr. This increase in quality factor as well as the Q-rise phenomenon (anti-Q-slope is similar to those previously obtained with high temperature nitrogen doping as well as titanium doping. In this study, a cavity N_{2}-treated at 120 °C and at 140 °C showed no degradation in accelerating gradient, however the accelerating gradient was reduced by ∼25% with a 160 °C N_{2} treatment, compared to the baseline tests after electropolishing. Sample coupons treated in the same conditions as the cavity were analyzed by scanning electron microscope, x-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a complex surface composition of Nb_{2}O_{5}, NbO and NbN_{(1−x}O_{x} within the rf penetration depth. Furthermore, magnetization measurements showed no significant change on bulk superconducting properties.

  13. Effect of low temperature baking in nitrogen on the performance of a niobium superconducting radio frequency cavity

    Science.gov (United States)

    Dhakal, Pashupati; Chetri, Santosh; Balachandran, Shreyas; Lee, Peter J.; Ciovati, Gianluigi

    2018-03-01

    We report the rf performance of a single cell superconducting radiofrequency cavity after low temperature baking in a nitrogen environment. A significant increase in quality factor has been observed when the cavity was heat treated in the temperature range of 120 - 160 °C with a nitrogen partial pressure of ˜25 m Torr . This increase in quality factor as well as the Q -rise phenomenon (anti-Q -slope) is similar to those previously obtained with high temperature nitrogen doping as well as titanium doping. In this study, a cavity N2 -treated at 120 °C and at 140 °C showed no degradation in accelerating gradient, however the accelerating gradient was reduced by ˜25 % with a 160 °C N2 treatment, compared to the baseline tests after electropolishing. Sample coupons treated in the same conditions as the cavity were analyzed by scanning electron microscope, x-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a complex surface composition of Nb2O5 , NbO and NbN(1 -x )Ox within the rf penetration depth. Furthermore, magnetization measurements showed no significant change on bulk superconducting properties.

  14. First heavy ion beam tests with a superconducting multigap CH cavity

    Science.gov (United States)

    Barth, W.; Aulenbacher, K.; Basten, M.; Busch, M.; Dziuba, F.; Gettmann, V.; Heilmann, M.; Kürzeder, T.; Miski-Oglu, M.; Podlech, H.; Rubin, A.; Schnase, A.; Schwarz, M.; Yaramyshev, S.

    2018-02-01

    Very compact accelerating-focusing structures, as well as short focusing periods, high accelerating gradients and short drift spaces are strongly required for superconducting (sc) accelerator sections operating at low and medium energies for continuous wave (cw) heavy ion beams. To keep the GSI-super heavy element (SHE) program competitive on a high level and even beyond, a standalone sc cw linac (Helmholtz linear accelerator) in combination with the GSI high charge state injector (HLI), upgraded for cw operation, is envisaged. Recently the first linac section (financed by Helmholtz Institute Mainz (HIM) and GSI) as a demonstration of the capability of 217 MHz multigap crossbar H-mode structures (CH) has been commissioned and extensively tested with heavy ion beam from the HLI. The demonstrator setup reached acceleration of heavy ions up to the design beam energy. The required acceleration gain was achieved with heavy ion beams even above the design mass to charge ratio at high beam intensity and full beam transmission. This paper presents systematic beam measurements with varying rf amplitudes and phases of the CH cavity, as well as phase space measurements for heavy ion beams with different mass to charge ratio. The worldwide first and successful beam test with a superconducting multigap CH cavity is a milestone of the R&D work of HIM and GSI in collaboration with IAP in preparation of the HELIAC project and other cw-ion beam applications.

  15. The fundamental science of nitrogen-doping of niobium superconducting cavities

    Science.gov (United States)

    Gonnella, Daniel Alfred

    Doping of niobium superconducting RF cavities with impurities has been demonstrated to have the ability to significantly improve the cryogenic efficiency of the accelerating structures. Doping SRF cavities with nitrogen is a relatively simple additional step to cavity preparation that can make drastic improvements in a cavity's intrinsic quality factor, Q0. Nitrogen-doping consists of treating SRF cavities at high temperatures in a low nitrogen-atmosphere. This leads to two important effects: an improvement in Q0 at low fields, and the presence of an "anti-Q slope" in which the cryogenic efficiency of doped cavities actually improves at higher fields. After its initial discovery, nitrogen-doping showed real promise but many fundamental scientific questions remained about the process. Nitrogen-doped cavities consistently quenched at lower fields than un-doped cavities, cooling the cavities through their critical temperature slowly led to poor performance, and the mechanism behind the Q0 improvement was not well understood. This dissertation focuses on addressing these issues. Single-cell 1.3 GHz cavities were prepared with different nitrogen-dopings and their effects studied systematically. It was found that nitrogen-doping drastically lowers the mean free path of the RF penetration layer of the niobium, leading to a lowering of the temperature-dependent BCS resistance, RBCS, at low fields. Theoretical work to predict the anti-Q slope was compared with experimental results to more fundamentally understand the nature of the field dependence of RBCS. Nitrogen-doped cavities were found to have a much larger sensitivity of residual resistance from trapped magnetic flux than un-doped cavities. Fast cool downs with large spatial temperature gradients through Tc were found to more efficiently expel magnetic flux. The full dependence of this sensitivity to trapped magnetic flux was studied as a function of changing mean free path and found to be in good agreement with

  16. Beam orbit control in TESLA superconducting cavities from dipole mode measurements

    International Nuclear Information System (INIS)

    Paparella, R.

    2006-09-01

    The knowledge of the electromagnetic interaction between a beam and the surrounding vacuum chamber is necessary in order to optimize the accelerator performance in terms of stored current. Many instability phenomena may occur in the machine because of the fields produced by the beam and acting back on itself. Basically, these fields, wake-fields, produce an extra voltage, affecting the longitudinal dynamics, and a transverse kick which deflects the beam. In this thesis we present the results of theoretical and experimental investigations to demonstrate the possibility of using the dipolar wake fields of the superconducting accelerating to measure the beam transverse position. After an introduction to the ILC project and to the TESLA technology, of superconducting RF cavities, we will approach the problem from an analytical point of view in chapter 2. The expression of the wake fields in a cylindrical cavity will be investigated and the electromagnetic field modes derived from Maxwell equations in an original way. Graphical solutions of a Matlab program simulating the fields due to a particle passing through a pill-box cavity along a generic path will be shown. The interaction of the beam with higher order modes (HOM) in the TESLA cavities has been studied in the past at the TESLA Test Facility (TTF) in order to determine whether the modes with the highest loss factor are sufficiently damped. Starting from the results obtained before 2003, HOM signals has been better observed and examined in order to use dipole modes to find the electric center of each cavity in the first TTF accelerating module. The results presented in chapter 3 will show that by monitoring the HOM signal amplitude for two polarizations of a dipole mode, one can measure electrical center of the modes with a resolution of 50 μm. Moreover, a misalignment of the first TTF module with respect to the gun axis has been predicted using cavity dipole modes. Alternatives to this method are described in

  17. Impact of nitrogen doping of niobium superconducting cavities on the sensitivity of surface resistance to trapped magnetic flux

    Science.gov (United States)

    Gonnella, Dan; Kaufman, John; Liepe, Matthias

    2016-02-01

    Future particle accelerators such as the SLAC "Linac Coherent Light Source-II" (LCLS-II) and the proposed Cornell Energy Recovery Linac require hundreds of superconducting radio-frequency (SRF) niobium cavities operating in continuous wave mode. In order to achieve economic feasibility of projects such as these, the cavities must achieve a very high intrinsic quality factor (Q0) to keep cryogenic losses within feasible limits. To reach these high Q0's in the case of LCLS-II, nitrogen-doping of niobium cavities has been selected as the cavity preparation technique. When dealing with Q0's greater than 1 × 1010, the effects of ambient magnetic field on Q0 become significant. Here, we show that the sensitivity to RF losses from trapped magnetic field in a cavity's walls is strongly dependent on the cavity preparation. Specifically, standard electropolished and 120 °C baked cavities show a sensitivity of residual resistance from trapped magnetic flux of ˜0.6 and ˜0.8 nΩ/mG trapped, respectively, while nitrogen-doped cavities show a higher sensitivity of residual resistance from trapped magnetic flux of ˜1 to 5 nΩ/mG trapped. We show that this difference in sensitivities is directly related to the mean free path of the RF surface layer of the niobium: shorter mean free paths lead to less sensitivity of residual resistance to trapped magnetic flux in the dirty limit (ℓ ≪ ξ0), while longer mean free paths lead to lower sensitivity of residual resistance to trapped magnetic flux in the clean limit (ℓ ≫ ξ0). These experimental results are also shown to have good agreement with recent theoretical predictions for pinned vortex lines oscillating in RF fields.

  18. Effect of the annealing temperature for the hydrogen Q-degradation on superconducting cavities

    International Nuclear Information System (INIS)

    Ota, Tomoko; Sukenobu, Satoru; Tanabe, Yoshio; Onishi, Yoshimichi; Noguchi, Shuichi; Ono, Masaaki; Saito, Kenji; Shishido, Toshio; Yamazaki, Yoshishige

    1997-01-01

    Hydrogen Q-degradation was studied in niobium superconducting cavities prepared by barrel polishing, and electropolishing without annealing, though a fast cooling down of cavities. Cavity performance with various annealing temperature were tested using a 1.3GHz single-cell cavity to compare the effects of annealing temperature for hydrogen Q-degradation. (author)

  19. High-Q superconducting niobium cavities for gravitational wave detectors

    International Nuclear Information System (INIS)

    De Paula, L A N; Furtado, S R; Aguiar, O D; N F Oliveira Jr, N F Oliveira Jr; Castro, P J; Barroso, J J

    2014-01-01

    The main purpose of this work is to optimize the electric Q-factor of superconducting niobium klystron cavities to be used in parametric transducers of the Mario Schenberg gravitational wave detector. Many cavities were manufactured from niobium with relatively high tantalum impurities (1420 ppm) and they were cryogenically tested to determine their resonance frequencies, unloaded electrical quality factors (Q 0 ) and electromagnetic couplings. These cavities were closed with a flat niobium plate with tantalum impurities below 1000 ppm and an unloaded electrical quality factors of the order of 10 5 have been obtained. AC conductivity of the order of 10 12 S/m has been found for niobium cavities when matching experimental results with computational simulations. These values for the Q-factor would allow the detector to reach the quantum limit of sensitivity of ∼ 10 −22 Hz −1/2 in the near future, making it possible to search for gravitational waves around 3.2 kHz. The experimental tests were performed at the laboratories of the National Institute for Space Research (INPE) and at the Institute for Advanced Studies (IEAv - CTA)

  20. Fundamental mode rf power dissipated in a waveguide attached to an accelerating cavity

    International Nuclear Information System (INIS)

    Kang, Y.W.

    1993-01-01

    An accelerating RF cavity usually requires accessory devices such as a tuner, a coupler, and a damper to perform properly. Since a device is attached to the wall of the cavity to have certain electrical coupling of the cavity field through the opening. RF power dissipation is involved. In a high power accelerating cavity, the RF power coupled and dissipated in the opening and in the device must be estimated to design a proper cooling system for the device. The single cell cavities of the APS storage ring will use the same accessories. These cavities are rotationally symmetric and the fields around the equator can be approximated with the fields of the cylindrical pillbox cavity. In the following, the coupled and dissipated fundamental mode RF power in a waveguide attached to a pillbox cavity is discussed. The waveguide configurations are (1) aperture-coupled cylindrical waveguide with matched load termination; (2) short-circuited cylindrical waveguide; and (3) E-probe or H-loop coupled coaxial waveguide. A short-circuited, one-wavelength coaxial structure is considered for the fundamental frequency rejection circuit of an H-loop damper

  1. Calculation of wake field and couple impedance of upgraded and old RF cavity in Hefei electron storage ring

    International Nuclear Information System (INIS)

    Xu Hongliang; Wang Lin; Sun Baogen; Li Weimin; Liu Jinying; He Duohui

    2003-01-01

    The phase II upgrading project of Hefei 800 MeV electron storage ring is being done, and the important component of the project, the RF cavity, will be finished soon. The old RF cavity with many disadvantages will be replaced by the new one. To estimate the effect of RF cavity coupling impedance to storing bunch intensity fully, the wake potential and the broad band couple impedance of RF cavity were calculated with MAFIA program. And the calculation results were compared between new and old cavity, it is found that the impedance of the new is bigger than that of the old

  2. Investigation of local losses as a function of material removal in a large-grain superconducting niobium cavity

    International Nuclear Information System (INIS)

    Gianluigi Ciovati; Peter Kneisel

    2006-01-01

    The performance of a superconducting radio-frequency (RF) cavity made of residual resistivity ratio (RRR) > 200 large-grain niobium has been investigated as a function of material removal, between 70 and 240 ?m, by buffered chemical polishing (BCP). Temperature maps of the cavity surface at 1.7 and 2.0 K were taken for each step of chemical etching and revealed localized losses (''hot-spots''), which contribute to the degradation of the cavity quality factor as a function of the RF surface field. It was found that the number of ''hot-spots'' decreased for larger material removal. Interestingly, the losses at the ''hot-spots'' at different locations evolved differently for successive material removal. The cavity achieved peak surface magnetic fields of about of 130 mT and was limited mostly by thermal quench. By measuring the temperature dependence of the surface resistance (Rs) at low field between 4.2 K and 1.7 K, the variation of material parameters such as the energy gap at 0 K, the residual resistance and the mean free path as a function of material removal could also be investigated. This contribution presents the results of the RF tests along with the temperature maps and the analysis of the losses caused by the ''hot-spots''

  3. Buffer Chemical Polishing and RF Testing of the 56 MHz SRF Cavity

    Energy Technology Data Exchange (ETDEWEB)

    Burrill,A.

    2009-01-01

    The 56 MHz cavity presents a unique challenge in preparing it for RF testing prior to construction of the cryomodule. This challenge arises due to the physical dimensions and subsequent weight of the cavity, and is further complicated by the coaxial geometry, and the need to properly chemically etch and high pressure rinse the entire inner surface prior to RF testing. To the best of my knowledge, this is the largest all niobium SRF cavity to be chemically etched and subsequently tested in a vertical dewar at 4K, and these processes will be the topic of this technical note.

  4. Design of rf-cavities in the funnel of accelerators for transmutation technologies

    International Nuclear Information System (INIS)

    Krawczyk, F.L.; Bultman, N.K.; Chan, K.D.C.; Martineau, R.L.; Nath, S.; Young, L.M.

    1994-01-01

    Funnels are a key component of accelerator structures proposed for transmutation technologies. In addition to conventional accelerator elements, specialized rf-cavities are needed for these structures. Simulations were done to obtain their electromagnetic field distribution and to minimize the rf-induced heat loads. Using these results a structural and thermal analysis of these cavities was performed to insure their reliability at high average power and to determine their cooling requirements. For one cavity the thermal expansion data in return was used to estimate the thermal detuning

  5. Dependence of the microwave surface resistance of superconducting niobium on the magnitude of the rf field

    Energy Technology Data Exchange (ETDEWEB)

    Romanenko, A.; Grassellino, A. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

    2013-06-24

    Utilizing difference in temperature dependencies we decoupled Bardeen-Cooper-Schrieffer (BCS) and residual components of the microwave surface resistance of superconducting niobium at all rf fields up to B{sub rf}{approx}115 mT. We reveal that the residual resistance decreases with field at B{sub rf} Less-Than-Or-Equivalent-To 40 mT and strongly increases in chemically treated niobium at B{sub rf}>80 mT. We find that BCS surface resistance is weakly dependent on field in the clean limit, whereas a strong and peculiar field dependence emerges after 120 Degree-Sign C vacuum baking.

  6. Research and development of an ultra clean surface for RF cavities

    International Nuclear Information System (INIS)

    Miwa, Hajime; Ikeda, Tokumi; Suzuki, Takafusa; Kurosawa, Kiyosi; Kako, Eiji; Noguchi, Shuichi; Saito, Kenji; Kneisel, P.

    1993-01-01

    Suppression of field emission is essentially important in order to attain higher accelerating gradients. Therefore, elimination of residual dust particles on the inner surface of RF cavities is necessary. Surface of a niobium cavity was simulated in silicon wafers, and analysis of dust particles was performed by a particle counter used for semiconductor industries. Experimental results in various surface treatments and applications to niobium cavities are described in this paper. (author)

  7. Design of inductively detuned RF extraction cavities for the Relativistic Klystron Two Beam Accelerator

    International Nuclear Information System (INIS)

    Henestroza, E.; Yu, S.S.; Li, H.

    1995-04-01

    An inductively detuned traveling wave cavity for the Relativistic Klystron Two Beam Accelerator expected to extract high RF power at 11. 424 GHz for the 1 TeV Center of Mass Next Linear Collider has been designed. Longitudinal beam dynamics studies led to the following requirements on cavity design: (a) Extraction of 360 MW of RF power with RF component of the current being 1.15 kAmps at 11.424 GHz, (b) Inductively detuned traveling wave cavity with wave phase velocity equal to 4/3 the speed of light, (c) Output cavity with appropriate Q ext and eigenfrequency for proper matching. Furthermore, transverse beam dynamics require low shunt impedances to avoid the beam break-up instability. We describe the design effort to meet these criteria based on frequency-domain and time-domain computations using 2D- and 3D- electromagnetic codes

  8. Experience with two large-scale Hell-cryostats for a superconducting RF particle separator working in closed cycle with a 300 W refrigerator

    CERN Document Server

    Barth, W

    1976-01-01

    The contribution of the Karlsruhe Institut fur Experimental Kernphysik to the RF particle separator at the SPS/CERN consists of the two superconducting deflectors and their Hell-cryostats with the cryogenic and vacuum accessories. The cryostats have to fulfil specifications concerning tightness, thermal insulation, adjustment of the cavities to the beam and reliability. Corresponding cryogenic and RF tests are performed in Karlsruhe before a 300 W refrigerator simulating normal and emergency conditions. Following a description of cryostats design the results of these measurements are compared with the specifications. Operating experience with the cryostats in closed circuit with the refrigerator are reported. (5 refs).

  9. Effect of low-temperature baking on the radio-frequency properties of niobium superconducting cavities for particle accelerators

    International Nuclear Information System (INIS)

    Ciovati, Gianluigi

    2004-01-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some 'anomalous' losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low-temperature (100-150 deg. C) 'in situ' bake under ultrahigh vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from 'anomalous' losses (so-called 'Q drop') without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37-280 K and resonant frequency shift between 6-9.3 K provide information about the surface resistance, energy gap, penetration depth, and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with nuclear reaction analysis. The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper

  10. Effect of low-temperature baking on the radio-frequency properties of niobium superconducting cavities for particle accelerators

    Science.gov (United States)

    Ciovati, Gianluigi

    2004-08-01

    Radio-frequency superconducting (SRF) cavities are widely used to accelerate a charged particle beam in particle accelerators. The performance of SRF cavities made of bulk niobium has significantly improved over the last ten years and is approaching the theoretical limit for niobium. Nevertheless, RF tests of niobium cavities are still showing some "anomalous" losses that require a better understanding in order to reliably obtain better performance. These losses are characterized by a marked dependence of the surface resistance on the surface electromagnetic field and can be detected by measuring the quality factor of the resonator as a function of the peak surface field. A low-temperature (100-150°C) "in situ" bake under ultrahigh vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor at low field and a recovery from "anomalous" losses (so-called "Q drop") without field emission at higher field. A series of experiments with a CEBAF single-cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37-280K and resonant frequency shift between 6-9.3K provide information about the surface resistance, energy gap, penetration depth, and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity. The hydrogen content of small niobium samples inserted in the cavity during its surface preparation was analyzed with nuclear reaction analysis. The single-cell cavity has been tested at three different temperatures before and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper describes

  11. Conceptual design of a sapphire loaded coupler for superconducting radio-frequency 1.3 GHz cavities

    Science.gov (United States)

    Xu, Chen; Tantawi, Sami

    2016-02-01

    This paper explores a hybrid mode rf structure that served as a superconducting radio-frequency coupler. This application achieves a reflection S(1 ,1 ) varying from 0 to -30 db and delivers cw power at 7 KW. The coupler has good thermal isolation between the 2 and 300 K sections due to vacuum separation. Only one single hybrid mode can propagate through each section, and no higher order mode is coupled. The analytical and numerical analysis for this coupler is given and the design is optimized. The coupling mechanism to the cavity is also discussed.

  12. Conceptual design of a sapphire loaded coupler for superconducting radio-frequency 1.3 GHz cavities

    Directory of Open Access Journals (Sweden)

    Chen Xu

    2016-02-01

    Full Text Available This paper explores a hybrid mode rf structure that served as a superconducting radio-frequency coupler. This application achieves a reflection S_{(1,1} varying from 0 to −30  db and delivers cw power at 7 KW. The coupler has good thermal isolation between the 2 and 300 K sections due to vacuum separation. Only one single hybrid mode can propagate through each section, and no higher order mode is coupled. The analytical and numerical analysis for this coupler is given and the design is optimized. The coupling mechanism to the cavity is also discussed.

  13. Shunt impedance of spiral loaded resonant rf cavities

    International Nuclear Information System (INIS)

    Peebles, P.Z. Jr.; Parvarandeh, M.

    1975-01-01

    Based upon a treatment of the spiral loaded resonant radio frequency cavity as a shorted quarter-wave transmission line, a model for shunt impedance is developed. The model is applicable to loosely wound spirals in large diameter containers. Theoretical shunt impedance is given for spirals wound from tubing of circular or rectangular cross section. The former produces higher shunt impedance. Measurements made at Oak Ridge National Laboratory on 17 copper cavities are described which support the theoretical results. Theoretical results are also compared to data from twenty-three additional cavities measured at Los Alamos Scientific Laboratory. It is shown that the theoretical function forms a useful means of interpreting the quality of constructed cavities. (author)

  14. Effect of transients on the beam in the Superconducting Supercollider Coupled-Cavity Linac

    International Nuclear Information System (INIS)

    Young, L.M.; Nath, S.

    1992-01-01

    Each module of the Superconducting Super Collider (SSC) Coupled-Cavity Linac (CCL) consists of eight tanks (10 accelerating cells each) coupled with bridge couplers. The radio frequency (rf) power drive is in the center of the module at the bridge coupler between the fourth and fifth tanks. In this simulation of the beam dynamics, the rf power is turned on 10 μs before the beam is turned on. This time lapse allows the fields to build up and stabilize before they are required by the beam. When the beam is turned on, the beam loading causes the fields to change. This transient state of the fields together with their effect on the beam is presented. A model has been developed to calculate field distribution throughout the module as a function of time. Beam dynamics simulations were run with the results of this model at several times during the beam pulse. An estimate of the effect of the transients is given by the results of these simulations

  15. Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient

    International Nuclear Information System (INIS)

    Lal, Shankar; Pant, K. K.

    2016-01-01

    Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday’s law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.

  16. Magnetic losses and instabilities in ferrite garnet tuned RF cavities for synchrotrons

    International Nuclear Information System (INIS)

    Shapiro, V.E.

    1994-01-01

    The aim of this paper is to introduce basic notions and elucidate the main features of magnetic losses and nonlinear effects in high power rf cavities with perpendicularly biased ferrite garnet used for varying the frequency in rapid cycling synchrotrons. A method of analysis is developed using a minimum of specific details. Simple formulae and estimates of the trend of magnetic loss, nonlinear frequency shift and possible instabilities in the cavities as a function of rf power level and ferrite garnet parameters are presented. Numerical examples correspond to the TRIUMF KAON Booster synchrotron. (author). 14 refs., 5 figs

  17. Trimming algorithm of frequency modulation for CIAE-230 MeV proton superconducting synchrocyclotron model cavity

    Energy Technology Data Exchange (ETDEWEB)

    Li, Pengzhan, E-mail: lipengzhan@ciae.ac.cn; Zhang, Tianjue; Ji, Bin; Hou, Shigang; Guo, Juanjuan; Yin, Meng; Xing, Jiansheng; Lv, Yinlong; Guan, Fengping; Lin, Jun

    2017-01-21

    A new project, the 230 MeV proton superconducting synchrocyclotron for cancer therapy, was proposed at CIAE in 2013. A model cavity is designed to verify the frequency modulation trimming algorithm featuring a half-wave structure and eight sets of rotating blades for 1 kHz frequency modulation. Based on the electromagnetic (EM) field distribution analysis of the model cavity, the variable capacitor works as a function of time and the frequency can be written in Maclaurin series. Curve fitting is applied for theoretical frequency and original simulation frequency. The second-order fitting excels at the approximation given its minimum variance. Constant equivalent inductance is considered as an important condition in the calculation. The equivalent parameters of theoretical frequency can be achieved through this conversion. Then the trimming formula for rotor blade outer radius is found by discretization in time domain. Simulation verification has been performed and the results show that the calculation radius with minus 0.012 m yields an acceptable result. The trimming amendment in the time range of 0.328–0.4 ms helps to reduce the frequency error to 0.69% in Simulation C with an increment of 0.075 mm/0.001 ms, which is half of the error in Simulation A (constant radius in 0.328–0.4 ms). The verification confirms the feasibility of the trimming algorithm for synchrocyclotron frequency modulation. - Highlights: • A model cavity is designed to verify the trimming algorithm of frequency modulation. • The RF frequency is expressed by fitting approximation and Maclaurin series. • The variable capacitor of the cavity works as a function of time. • The trimming formula for blade radius is found by discretization in time domain. • The amendment solution helps to reduce the frequency error.

  18. Long term performance of the superconducting cavities of the Saclay heavy ion linac

    International Nuclear Information System (INIS)

    Cauvin, B.; Desmons, M.; Girard, J.; Letonturier, P.

    1993-12-01

    The Saclay heavy ion superconducting linac has been in operation at full energy since mid 1989. The 50 independent superconducting helix resonators have now accelerated beams for more than 20000 hours. The long term performances of the linac, and more specifically of the superconducting R.F. technology, are discussed: vibrations of the resonators, cryostat design and operation, beam time, vacuum accidents, multipactor during operation due to small leaks, stability of the electric fields, cryogenics operation. 4 figs., 6 refs

  19. MA-core loaded untuned RF compression cavity for HIRFL-CSR

    International Nuclear Information System (INIS)

    Mei Lirong; Xu Zhe; Yuan Youjin; Jin Peng; Bian Zhibin; Zhao Hongwei; Xia Jiawen

    2012-01-01

    To meet the requirements of high energy density physics and plasma physics research at HIRFL-CSR the goal of achieving a higher accelerating gap voltage was proposed. Therefore, a magnetic alloy (MA)-core loaded radio frequency (RF) cavity that can provide a higher accelerating gap voltage compared to standard ferrite loaded cavities has been studied at IMP. In order to select the proper magnetic alloy material to load the RF compression cavity, measurements of four different kinds of sample MA-cores have been carried out. By testing the small cores, the core composition was selected to obtain the desired performance. According to the theoretical calculation and simulation, which show reasonable consistency for the MA-core loaded cavity, the desired performance can be achieved. Finally about 1000 kW power will be needed to meet the requirements of 50 kV accelerating gap voltage by calculation.

  20. Beam Acceleration by a Multicell RF Cavity Structure Proposed for an Improved Yield in Hydroforming

    International Nuclear Information System (INIS)

    Kang, Yoon W.; Shin, Ki; Fathy, A.E.; Holmes, Jeffrey A.

    2012-01-01

    We study the accelerating properties of a new multicell cavity structure with irises forming a rectangular aperture between the cavity cells. We are interested in this structure because, from a mechanical point of view, it may be possible to manufacture with high quality using a hydroforming process. RF analysis shows that the rectangular iris shape provides some asymmetric transverse focusing per half RF period, particularly for low beam energies. If the horizontal and vertical rectangular irises are interleaved, the net transverse focusing could be increased. Here we present studies of the acceleration and transport properties of these cavities by tracking particles using the ORBIT Code through time-dependent 3D cavity fields taken from CST MWS.

  1. Beam dynamics study and superconducting triple spoke cavity design for the EURISOL driver

    International Nuclear Information System (INIS)

    Ponton, A.

    2009-07-01

    EURISOL will be the next generation source of intense radioactive ion beams. Its accelerator complex consists of a driver linac, a set of targets and sources and a post-accelerator linac which aims at supplying different experimental areas with the exotic ions. The presented study deals with the driver accelerator: a superconducting RF linac capable of accelerating different ion kinds (D + , 3 He 2+ and H - ) up to a maximal power of 4 MW. First beam dynamics studies pointed out a very good acceleration efficiency when triple spoke cavities working at a frequency of 352 MHz are used in the medium energy part (0.2 < beta < 0.4). Thanks to a novel geometry, the electromagnetic design of the proposed cavity leads to 33 MV/m and 72 mT for the peak electric field and magnetic induction respectively at an ambitious accelerating field of 8 MV/m. The beam transport was then simulated and optimized in the original layout and calculations were also performed considering an alternative, periodic solution, for the low energy part. The 'all-periodic' linac keeps the beam qualities better by strongly reducing the emittance growth and the halo formation. (author)

  2. Development of a cryogenic radiation detector for mapping radio frequency superconducting cavity field emissions

    Energy Technology Data Exchange (ETDEWEB)

    Danny Dotson; John Mammosser

    2005-05-01

    Field emissions in a super conducting helium cooled RF cavity and the production of radiation (mostly X-Rays) have been measured externally on cryomodules at Jefferson Lab since 1991. External measurements are limited to radiation energies above 100 keV due to shielding of the stainless steel cryogenic body. To measure the onset of and to map field emissions from a superconducting cavity requires the detecting instrument be inside the shield and within the liquid Helium. Two possible measurement systems are undergoing testing at JLab. A CsI detector array set on photodiodes and an X-Ray film camera with a fixed aperture. Several devices were tested in the cell with liquid Helium without success. The lone survivor, a CsI array, worked but saturated at high power levels due to backscatter. The array was encased in a lead shield with a slit opening set to measure the radiation emitted directly from the cell eliminating a large portion of the backscatter. This is a work in progress and te sting should be complete before the PAC 05. The second system being tested is passive. It is a shielded box with an aperture to expose radiation diagnostic film located inside to direct radiation from the cell. Developing a technique for mapping field emissions in cryogenic cells will assist scientists and engineers in pinpointing any surface imperfections for examination.

  3. RF Behavior of Cylindrical Cavity Based 240 GHz, 1 MW Gyrotron for Future Tokamak System

    Science.gov (United States)

    Kumar, Nitin; Singh, Udaybir; Bera, Anirban; Sinha, A. K.

    2017-11-01

    In this paper, we present the RF behavior of conventional cylindrical interaction cavity for 240 GHz, 1 MW gyrotron for futuristic plasma fusion reactors. Very high-order TE mode is searched for this gyrotron to minimize the Ohmic wall loading at the interaction cavity. The mode selection process is carried out rigorously to analyze the mode competition and design feasibility. The cold cavity analysis and beam-wave interaction computation are carried out to finalize the cavity design. The detail parametric analyses for interaction cavity are performed in terms of mode stability, interaction efficiency and frequency. In addition, the design of triode type magnetron injection gun is also discussed. The electron beam parameters such as velocity ratio and velocity spread are optimized as per the requirement at interaction cavity. The design studies presented here confirm the realization of CW, 1 MW power at 240 GHz frequency at TE46,17 mode.

  4. A high gradient test of a single-cell superconducting radio frequency cavity with a feedback waveguide

    Science.gov (United States)

    Kostin, Roman; Avrakhov, Pavel; Kanareykin, Alexei; Solyak, Nikolay; Yakovlev, Vyacheslav; Kazakov, Sergey; Wu, Genfa; Khabiboulline, Timergali; Rowe, Allan; Rathke, John

    2015-09-01

    The most severe problem of the international linear collider (ILC-type) is its high cost, resulting in part from the enormous length of the collider. This length is determined mainly by the achievable accelerating gradient in the RF system of the collider. In current technology, the maximum acceleration gradient in superconducting (SC) structures is determined mainly by the value of the surface RF magnetic field. In order to increase the gradient, a superconducting traveling wave accelerating (STWA) structure is suggested. Utilization of STWA structure with small phase advance per cell for future high energy linear colliders such as ILCs may provide an accelerating gradient 1.2-1.4 times larger [1] than a standing wave structure. However, STWA structure requires a feedback waveguide for power redirecting from the end of the structure back to the front end of accelerating structure. Recent tests of a 1.3 GHz model of a single-cell cavity with waveguide feedback demonstrated an accelerating gradient comparable to the gradient of a single-cell ILC-type cavity from the same manufacturer [2]. In the present paper, high gradient test results are presented.

  5. RF properties of 700 MHz, β= 0.42 elliptical cavity for high current ...

    Indian Academy of Sciences (India)

    ADSS) that will be mainly utilized for the transmutation of nuclear waste and enrichment of U233. Design and development of superconducting medium velocity cavity has been taken up as a part of the accelerator-driven subcritical system ...

  6. Traveling wave tube oscillator/amplifier with superconducting rf circuit

    International Nuclear Information System (INIS)

    Jasper, L.J. Jr.

    1989-01-01

    This patent describes a device comprising: an electron gun for producing an electron beam; a collector for collecting the electron beam; a vacuum housing surrounding the electron beam and having an integral slow wave circuit, the circuit being made from superconducting ceramic material; means for maintaining the temperature of the superconducting ceramic below its critical temperature; means for extracting an output signal from the slow wave circuit; means for creating a magnetic field within the vacuum housing so that interaction between the electron beam and the slow wave circuit produces the output signal

  7. RF cavities of CESAR (2 MeV electron storage ring).

    CERN Multimedia

    Service Photo; CERN PhotoLab

    1968-01-01

    RF cavity. There were 2 identical ones: one for stacking (accumulation) procedures; the other for scanning with "empty buckets" (measurement of beam density distribution). Both were operated at h=2 (2nd harmonic of the revolution frequency), i.e. at around 24.4 MHz. Voltage, frequency and phase were programmed with analogue circuits.

  8. CESAR, 2 MeV electron storage ring; construction period; RF cavity.

    CERN Multimedia

    Service Photo; CERN PhotoLab

    1962-01-01

    RF cavity. There were 2 identical ones: one for stacking (accumulation) procedures; the other for scanning with "empty buckets" (measurement of beam density distribution). Both were operated at h=2 (2nd harmonic of the revolution frequency), i.e. at around 24.4 MHz. Voltage, frequency and phase were programmed with analogue circuits.

  9. Proton acceleration by RF TE{sub 11} mode in a cylindrical cavity

    Energy Technology Data Exchange (ETDEWEB)

    Sobajima, Masaaki; Yoshikawa, Kiyoshi; Ohnishi, Masami; Yamamoto, Yasushi; Masuda, Kai [Kyoto Univ., Uji (Japan). Inst. of Advanced Energy

    1997-03-01

    We found that protons are accelerated significantly by RF TE{sub 11} mode in a cylindrical cavity. In this method, protons get the perpendicular kinetic energy, so we thought it might be a compact accelerator, and studied the feasibility by numerical simulation. (author)

  10. Sparking limits, cavity loading, and beam breakup instability associated with high-current rf linacs

    International Nuclear Information System (INIS)

    Faehl, R.J.; Lemons, D.S.; Thode, L.E.

    1982-01-01

    The limitations on high-current rf linacs due to gap sparking, cavity loading, and the beam breakup instability are studied. It appears possible to achieve cavity accelerating gradients as high as 35 MV/m without sparking. Furthermore, a linear analysis, as well as self-consistent particle simulations of a multipulsed 10 kA beam, indicated that only a negligible small fraction of energy is radiated into nonfundamental cavity modes. Finally, the beam breakup instability is analyzed and found to be able to magnify initial radial perturbations by a factor of no more than about 20 during the beam transit time through a 1 GeV accelerator

  11. Superconducting accelerometer using niobium-on-sapphire rf resonator

    International Nuclear Information System (INIS)

    Blair, D.G.

    1979-01-01

    An accelerometer is described which uses a rf niobium-on-sapphire resonator as its sensor element. The accelerometer uses a magnetically levitated spool as a test mass and the spool modulates the inductance of the resonator; its position is servo controlled to maintain the resonator at the external rf excitation frequency. The accelerometer has high sensitivity over the full audio frequency range, but is optimized for frequencies between 100 Hz and 1 kHz, where the calculated displacement sensitivity approaches 10 -15 cm for a 1 Hz measurement bandwidth. The system noise sources are analyzed and possible improvements are discussed

  12. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by transmission electron microscopy and electron energy loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Trenikhina, Y., E-mail: yuliatr@fnal.gov [Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616 (United States); Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Romanenko, A., E-mail: aroman@fnal.gov [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States); Kwon, J.; Zuo, J.-M. [Materials Science and Engineering Department, University of Illinois, Urbana, Illinois 61801 (United States); Zasadzinski, J. F. [Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616 (United States)

    2015-04-21

    Nanoscale defect structure within the magnetic penetration depth of ∼100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120 °C baking. Furthermore, we demonstrate that adding 800 °C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120 °C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120 °C bake.

  13. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by transmission electron microscopy and electron energy loss spectroscopy

    Science.gov (United States)

    Trenikhina, Y.; Romanenko, A.; Kwon, J.; Zuo, J.-M.; Zasadzinski, J. F.

    2015-04-01

    Nanoscale defect structure within the magnetic penetration depth of ˜100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120 °C baking. Furthermore, we demonstrate that adding 800 °C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120 °C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120 °C bake.

  14. Nanostructural features degrading the performance of superconducting radio frequency niobium cavities revealed by transmission electron microscopy and electron energy loss spectroscopy

    International Nuclear Information System (INIS)

    Trenikhina, Y.; Romanenko, A.; Kwon, J.; Zuo, J.-M.; Zasadzinski, J. F.

    2015-01-01

    Nanoscale defect structure within the magnetic penetration depth of ~100 nm is key to the performance limitations of niobium superconducting radio frequency cavities. Using a unique combination of advanced thermometry during cavity RF measurements, and TEM structural and compositional characterization of the samples extracted from cavity walls, we discover the existence of nanoscale hydrides in electropolished cavities limited by the high field Q slope, and show the decreased hydride formation in the electropolished cavity after 120°C baking. Furthermore, we demonstrate that adding 800°C hydrogen degassing followed by light buffered chemical polishing restores the hydride formation to the pre-120°C bake level. We also show absence of niobium oxides along the grain boundaries and the modifications of the surface oxide upon 120°C bake

  15. Rf transfer in the Coupled-Cavity Free-Electron Laser Two-Beam Accelerator

    International Nuclear Information System (INIS)

    Makowski, M.A.

    1991-01-01

    A significant technical problem associated with the Coupled-Cavity Free-Electron Laser Two-Beam Accelerator is the transfer of RF energy from the drive accelerator to the high-gradient accelerator. Several concepts have been advanced to solve this problem. This paper examines one possible solution in which the drive and high-gradient cavities are directly coupled to one another by means of holes in the cavity walls or coupled indirectly through a third intermediate transfer cavity. Energy cascades through the cavities on a beat frequency time scale which must be made small compared to the cavity skin time but large compared to the FEL pulse length. The transfer is complicated by the fact that each of the cavities in the system can support many resonant modes near the chosen frequency of operation. A generalized set of coupled-cavity equations has been developed to model the energy transfer between the various modes in each of the cavities. For a two cavity case transfer efficiencies in excess of 95% can be achieved. 3 refs., 2 figs

  16. An improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities

    Energy Technology Data Exchange (ETDEWEB)

    Ciovati, Gianluigi

    2006-07-01

    Radio-frequency (RF) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve RF field values approaching the theoretical limit for niobium is represented by ''anomalous'' losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100 mT, in absence of field emission. These high field losses are often referred to as ''Q-drop''. It has been observed that the Q-drop is drastically reduced by baking the cavities at 120 C for about 48 h under ultrahigh vacuum. An improved oxygen diffusion model for the niobium-oxide system is proposed to explain the benefit of the low-temperature baking on the Q-drop in niobium superconducting rf cavities. The model shows that baking at 120 C for 48 h allows oxygen to diffuse away from the surface, and therefore increasing the lower critical field towards the value for pure niobium.

  17. High current electron beam acceleration in dielectric-filled RF cavities

    International Nuclear Information System (INIS)

    Faehl, R.J.; Keinigs, R.K.

    1996-01-01

    The acceleration of charged particles in radio frequency (RF) cavities is a widely used mode in high energy accelerators. Advantages include very high accelerating gradients and very stable phase control. A traditional limitation for such acceleration has been their use for intense, high current beam generation. This constraint arises from the inability to store a large amount of electromagnetic energy in the cavity and from loading effects of the beam on the cavity. The authors have studied a simple modification to transcend these limitations. Following Humphries and Huang, they have conducted analytic and numerical investigations of RF accelerator cavities in which a high dielectric constant material, such as water, replaces most of the cavity volume. This raises the stored energy in a cavity of given dimensions by a factor var-epsilon/var-epsilon 0 . For a water fill, var-epsilon/var-epsilon 0 ∼ 80, depending on the frequency. This introduction of high dielectric constant material into the cavity reduces the resonant frequencies by a factor of (var-epsilon/var-epsilon 0 ) 1/2 . This reduced operating frequency mans that existing high efficiency power supplies, at lower frequencies, can be used for an accelerator

  18. MEASUREMENT OF THE TRANSVERSE BEAM DYNAMICS IN A TESLA-TYPE SUPERCONDUCTING CAVITY

    Energy Technology Data Exchange (ETDEWEB)

    Halavanau, A. [NICADD, DeKalb; Eddy, N. [Fermilab; Edstrom, D. [Fermilab; Lunin, A. [Fermilab; Piot, P. [NICADD, DeKalb; Ruan, J. [Fermilab; Solyak, N. [Fermilab

    2016-09-26

    Superconducting linacs are capable of producing intense, ultra-stable, high-quality electron beams that have widespread applications in Science and Industry. Many project are based on the 1.3-GHz TESLA-type superconducting cavity. In this paper we provide an update on a recent experiment aimed at measuring the transfer matrix of a TESLA cavity at the Fermilab Accelerator Science and Technology (FAST) facility. The results are discussed and compared with analytical and numerical simulations.

  19. Strong Meissner screening change in superconducting radio frequency cavities due to mild baking

    OpenAIRE

    Romanenko, A.; Grassellino, A.; Barkov, F.; Suter, A.; Salman, Z.; Prokscha, T.

    2013-01-01

    We investigate "hot" regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-$\\mu$SR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth $\\lambda_\\mathrm{L} = 23 \\pm 2$ nm. In contrast, a cutout sample from the 120$^\\...

  20. Effects of Electric and Magnetic Fields on the Performance of a Superconducting Cavity

    International Nuclear Information System (INIS)

    Gianluigi Ciovati; Peter Kneisel; Jacek Sekutowicz; Waldemar Singer

    2005-01-01

    A special two-cell cavity was designed to obtain surface field distributions suitable for investigation of electric and magnetic field effects on cavity performance. The cavity design and preliminary results were presented in a previous contribution. The bulk niobium cavity was heat-treated in a vacuum furnace at 1250 C to improve thermal conductivity. Three seamless hydroformed Nb/Cu cavities of the same design were fabricated to investigate the role of the electron beam welds located in high field areas. This paper will present RF test results at 2 K for the bulk niobium and one of the seamless cavities