Emittance investigation of RF photo-injector

CERN Document Server

Yang Mao Rong; Li Zheng; Li Ming; Xu Zhou

2002-01-01

A high-power laser beam illuminates a photocathode surface placed on an end wall of an RF cavity. The emitted electrons are accelerated immediately to a relativistic energy by the strong RF find in the cavity. But space charge effect induces beam emittance growth especially near the cathode where the electrons are still nonrelativistic. The author analyzes the factors which lead the transverse emittance growth and method how to resolve this problem. After introducing solenoidal focusing near the photocathode, the beam emittance growth is suppressed dramatically. The beam emittance is given also after compensation and simulation results. The measurements show these results are coincident

Amorphous NEA Silicon Photocathodes - A Robust RF Gun Electron Source. Final Report

International Nuclear Information System (INIS)

Mulhollan, Gregory A.

2009-01-01

Amorphous silicon (a-Si) has been shown to have great promise as a negative electron affinity visible wavelength photocathode suitable for radio frequency (RF) gun systems. The specific operating wavelength can be shifted by growing it as a germanium alloy (a-Si(1-x)Ge(x)) rather than as pure silicon. This class of photoemitters has been shown to possess a high degree of immunity to charged particle flux. Such particle flux can be a significant problem in the operation of other photocathodes in RF gun systems. Its emission characteristics in the form of current per unit area, or current density, and emission angle, or beam spread are well matched for use in RF guns. Photocathodes made of a-Si can be fabricated on a variety of substrates including those most commonly employed in RF gun systems. Such photocathodes can be made for operation in either transmission or reflection mode. By growing them utilizing radio frequency plasma enhanced chemical vapor deposition, the unit cost is quite low, the quality is high and it is straightforward to grow custom size substrates and full or limited regions to confine the electron emission to the desired area. Quality emitters have been fabricated on tantalum, molybdenum, tungsten, titanium, copper, stainless steel, float glass, borosilicate glass and gallium arsenide. In addition to performing well in dedicated test chambers, a-Si photocathodes have been shown to function well in self-contained vacuum tubes. In this employment, they are subjected to a strenuous environment. Successful operation in this configuration provides additional confidence in their application to high energy linac photoinjectors and potentially as part of reliable, low cost photocathode driven RF gun systems that could become ready replacements for the diode and triode guns used on medical accelerators. Their applications in stand-alone vacuum tubes is just beginning to be explored.

Commissioning the Linac Coherent Light Source injector

Directory of Open Access Journals (Sweden)

R. Akre

2008-03-01

Full Text Available The Linac Coherent Light Source is a SASE x-ray free-electron laser (FEL project presently under construction at SLAC [J. Arthur et al., SLAC-R-593, 2002.]. The injector section, from drive laser and rf photocathode gun through first bunch compressor chicane, was installed in the fall of 2006. The initial system commissioning with an electron beam was completed in August of 2007, with the goal of a 1.2-micron emittance in a 1-nC bunch demonstrated. The second phase of commissioning, including second bunch compressor and full linac, is planned for 2008, with FEL commissioning in 2009. We report experimental results and experience gained in the first phase of commissioning, including the photocathode drive laser, rf gun, photocathode, S-band and X-band rf systems, first bunch compressor, and the various beam diagnostics.

Dark Current and Multipacting in the Photocathode RF Guns at PITZ

CERN Document Server

Hui-Han, Jang; Flöttmann, Klaus; Grabosch, H J; Hartrott, Michael; Krasilnikov, Mikhail; Michelato, Paolo; Miltchev, Velizar; Monaco, Laura; Oppelt, Anne; Petrosyan, Bagrat; Riemann, S; Roensch, Juliane; Schreiber, Siegfried; Sertore, Daniele; Staykov, Lazar; Stephan, Frank

2005-01-01

For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies.

Single-side electron multipacting at the photocathode in rf guns

Directory of Open Access Journals (Sweden)

Jang-Hui Han

2008-01-01

Full Text Available Multiple electron impacting (multipacting can take place in rf fields when the rf components are composed of materials with a secondary electron yield greater than one. In rf gun cavities, multipacting may change the properties of the vacuum components or even damage them. First systematic measurements of the multipacting occurring in a photocathode rf gun were made at the Fermilab/NICADD Photoinjector Laboratory in 2000. The multipacting properties were found to depend on the cathode material and the solenoid field configuration. In this study, we measure the multipacting properties in more detail and model the secondary electron generation for numerical simulation. Measurements and simulations for the photoinjectors at Fermilab and DESY are compared. The multipacting takes place at the photocathode in rf guns and is categorized as single-side multipacting. In a low rf field, the electrons emitted from the cathode area do not leave the gun cavity within one rf cycle and have an opportunity to travel back and hit the cathode. The solenoid field distribution in the vicinity of the cathode changes the probability of electron bombardment of the cathode and makes a major contribution to the multipacting behavior.

Femtosecond precision measurement of laser–rf phase jitter in a photocathode rf gun

International Nuclear Information System (INIS)

Shi, Libing; Zhao, Lingrong; Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhu, Pengfei; Xiang, Dao

2017-01-01

We report on the measurement of the laser–rf phase jitter in a photocathode rf gun with femtosecond precision. In this experiment four laser pulses with equal separation are used to produce electron bunch trains; then the laser–rf phase jitter is obtained by measuring the variations of the electron bunch spacing with an rf deflector. Furthermore, we show that when the gun and the deflector are powered by the same rf source, it is possible to obtain the laser–rf phase jitter in the gun through measurement of the beam–rf phase jitter in the deflector. Based on these measurements, we propose an effective time-stamping method that may be applied in MeV ultrafast electron diffraction facilities to enhance the temporal resolution.

Femtosecond precision measurement of laser–rf phase jitter in a photocathode rf gun

Energy Technology Data Exchange (ETDEWEB)

Shi, Libing; Zhao, Lingrong; Lu, Chao; Jiang, Tao; Liu, Shengguang; Wang, Rui; Zhu, Pengfei; Xiang, Dao, E-mail: dxiang@sjtu.edu.cn

2017-03-21

We report on the measurement of the laser–rf phase jitter in a photocathode rf gun with femtosecond precision. In this experiment four laser pulses with equal separation are used to produce electron bunch trains; then the laser–rf phase jitter is obtained by measuring the variations of the electron bunch spacing with an rf deflector. Furthermore, we show that when the gun and the deflector are powered by the same rf source, it is possible to obtain the laser–rf phase jitter in the gun through measurement of the beam–rf phase jitter in the deflector. Based on these measurements, we propose an effective time-stamping method that may be applied in MeV ultrafast electron diffraction facilities to enhance the temporal resolution.

Beam dynamics studies of a 30 MeV RF linac for neutron production

Science.gov (United States)

Nayak, B.; Krishnagopal, S.; Acharya, S.

2018-02-01

Design of a 30 MeV, 10 Amp RF linac as neutron source has been carried out by means of ASTRA simulation code. Here we discuss details of design simulations for three different cases i.e Thermionic , DC and RF photocathode guns and compare them as injectors to a 30 MeV RF linac for n-ToF production. A detailed study on choice of input parameters of the beam from point of view of transmission efficiency and beam quality at the output have been described. We found that thermionic gun isn't suitable for this application. Both DC and RF photocathode gun can be used. RF photocathode gun would be of better performance.

Lasertron, a pulsed RF-source using laser triggered photocathode

International Nuclear Information System (INIS)

Yoshioka, Masakazu.

1988-12-01

A new pulsed RF-source, 'Lasertron', are being developed as a possible RF-power source for future electron-positron linear colliders. In a series of systematic study, a prototype lasertron has been fabricated and tested. A peak power of 80 kW is attained at 2.856 GHz RF-frequency in 1-μs time duration. This paper describes the experimental results of the lasertron including the developments of the photocathode and the laser system. Test results are compared with the analysis of beam dynamics in the lasertron. (author)

Photocathodes in accelerator applications

International Nuclear Information System (INIS)

Fraser, J.S.; Sheffield, R.L.; Gray, E.R.; Giles, P.M.; Springer, R.W.; Loebs, V.A.

1987-01-01

Some electron accelerator applications require bursts of short pulses at high microscopic repetition rates and high peak brightness. A photocathode, illuminated by a mode-locked laser, is well suited to filling this need. The intrinsic brightness of a photoemitter beam is high; experiments are under way at Los Alamos to study the brightness of short bunches with high space charge after acceleration. A laser-illuminated Cs 3 Sb photoemitter is located in the first rf cavity of an injector linac. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a streak camera

RF photo-injector beam energy distribution studies by slicing technique

Science.gov (United States)

Filippetto, D.; Bellaveglia, M.; Musumeci, P.; Ronsivalle, C.

2009-07-01

The SPARC photo-injector is an R&D facility dedicated to the production of high brightness electron beams for radiation generation via FEL or Thomson scattering processes. It is the prototype injector for the recently approved SPARX project, aiming at the construction in the Frascati/University of Rome Tor Vergata area of a new high brightness electron linac for the generation of SASE-FEL radiation in the 1-10 nm wavelength range. The first phase of the SPARC project has been dedicated to the e-beam source characterization; the beam transverse and longitudinal parameters at the exit of the gun have been measured, and the photo-injector settings optimized to achieve best performance. Several beam dynamics topics have been experimentally studied in this first phase of operation, as, for example, the effect of photocathode driver laser beam shaping and the evolution of the beam transverse emittance. These studies have been made possible by the use of a novel diagnostic tool, the " emittance-meter" which enables the measurement of the transverse beam parameters at different positions along the propagation axis in the very interesting region at the exit of the RF gun. The new idea of extending the e-meter capabilities came out more recently. Information on the beam longitudinal phase space and correlations with the transverse planes can be retrieved by the slicing technique. In this paper, we illustrate the basic concept of the measurement together with simulations that theoretically validate the methodology. Some preliminary results are discussed and explained with the aid of code simulations.

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.

Design and modeling of a 17 GHz photocathode RF gun

International Nuclear Information System (INIS)

Lin, C.L.; Chen, S.C.; Wurtele, J.S.; Temkin, R.; Danly, B.

1991-01-01

The performance of a high-frequency (17 GHz), high accelerating gradient (250 MV/m) photocathode RF gun is studied with the particle-in-cell code MAGIC. For the parameter regime of interest, i.e. bunch charge smaller than 1 nC and bunch length shorter than 2 ps, space-charge forces and finite bunch length effects are less significant in determining the beam quality than nonlinear RF forces are. The cavity geometry, RF phase for photoemission, cathode size, and current density are being optimized to obtain high quality beams. Preliminary results are presented

Beam Dynamics Simulation of Photocathode RF Electron Gun at the PBP-CMU Linac Laboratory

Science.gov (United States)

Buakor, K.; Rimjaem, S.

2017-09-01

Photocathode radio-frequency (RF) electron guns are widely used at many particle accelerator laboratories due to high quality of produced electron beams. By using a short-pulse laser to induce the photoemission process, the electrons are emitted with low energy spread. Moreover, the photocathode RF guns are not suffered from the electron back bombardment effect, which can cause the limited electron current and accelerated energy. In this research, we aim to develop the photocathode RF gun for the linac-based THz radiation source. Its design is based on the existing gun at the PBP-CMU Linac Laboratory. The gun consists of a one and a half cell S-band standing-wave RF cavities with a maximum electric field of about 60 MV/m at the centre of the full cell. We study the beam dynamics of electrons traveling through the electromagnetic field inside the RF gun by using the particle tracking program ASTRA. The laser properties i.e. transverse size and injecting phase are optimized to obtain low transverse emittance. In addition, the solenoid magnet is applied for beam focusing and emittance compensation. The proper solenoid magnetic field is then investigated to find the optimum value for proper emittance conservation condition.

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.

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.

Deflecting cavity for beam diagnostics at Cornell ERL injector

International Nuclear Information System (INIS)

Belomestnykh, Sergey; Bazarov, Ivan; Shemelin, Valery; Sikora, John; Smolenski, Karl; Veshcherevich, Vadim

2010-01-01

A single-cell, 1300-MHz, TM110-like mode vertically deflecting cavity is designed and built for beam slice emittance measurements, and to study the temporal response of negative electron affinity photocathodes in the ERL injector at Cornell University. We describe the cavity shape optimization procedure, RF and mechanical design, its performance with beam.

High-power fiber lasers for photocathode electron injectors

Directory of Open Access Journals (Sweden)

Zhi Zhao

2014-05-01

Full Text Available Many new applications for electron accelerators require high-brightness, high-average power beams, and most rely on photocathode-based electron injectors as a source of electrons. To achieve such a photoinjector, one requires both a high-power laser system to produce the high average current beam, and also a system at reduced repetition rate for electron beam diagnostics to verify high beam brightness. Here we report on two fiber laser systems designed to meet these specific needs, at 50 MHz and 1.3 GHz repetition rate, together with pulse pickers, second harmonic generation, spatiotemporal beam shaping, intensity feedback, and laser beam transport. The performance and flexibility of these laser systems have allowed us to demonstrate electron beam with both low emittance and high average current for the Cornell energy recovery linac.

A proposed injector for the LCLS linac

International Nuclear Information System (INIS)

Yeremian, A.D.; Bharadwaj, V.K.; Emma, P.; Miller, R.H.; Palmer, D.T.; Woodley, M.D.

1996-11-01

The Linac Coherent Light Source (LCLS) will use the last portion of the SLAC accelerator as a driver for a short wavelength FEL. The injector must produce 1-nC, 3-ps rms electron bunches at a repetition rate of up to 120 Hz with a normalized rms emittance of about 1 mm-mrad. The injector design takes advantage of the photocathode rf gun technology developed since its conception in the mid 1980's, in particular the S-band rf gun developed by the SLAC/BNL/UCLA collaboration, and emittance compensation techniques developed in the last decade. The injector beamline has been designed using the SUPERFISH, POISSON, PARMELA, and TRANSPORT codes in a consistent way to simulate the beam from the gun up to the entrance of the main accelerator linac where the beam energy is 150 MeV. PARMELA simulations indicate that at 150 MeV, space charge effects are negligible

Electron linac injector developments

International Nuclear Information System (INIS)

Fraser, J.S.

1986-01-01

There is a continuing demand for improved injectors for electron linacs. Free-electron laser (FEL) oscillators require pulse trains of high brightness and, in some applications, high average power at the same time. Wakefield-accelerator and laser-acceleration experiments require isolated bunches of high peak brightness. Experiments with alkali-halide photoemissive and thermionic electron sources in rf cavities for injector applications are described. For isolated pulses, metal photocathodes (illuminated by intense laser pulses) are being employed. Reduced emittance growth in high-peak-current electron injectors may be achieved by linearizing the cavity electric field's radial component and by using high field strengths at the expense of lower shunt impedance. Harmonically excited cavities have been proposed for enlarging the phase acceptance of linac cavities and thereby reducing the energy spread produced in the acceleration process. Operation of injector linacs at a subharmonic of the main linac frequency is also proposed for enlarging the phase acceptance

Bevalac injector final stage RF amplifier upgrades

International Nuclear Information System (INIS)

Howard, D.; Calvert, J.; Dwinell, R.; Lax, J.; Lindner, A.; Richter, R.; Ridgeway, W.

1991-01-01

With the assistance of the DOE In-house Energy Management Program, the Bevalac injector final stage RF amplifier systems have been successfully upgraded to reduce energy consumption and operating costs. This recently completed project removed the energy-inefficient plate voltage modulator circuits that were used in conjunction with the final stage RF amplifiers. Construction, design, and operating parameters are described in detail

High power testing of a 17 GHz photocathode RF gun

International Nuclear Information System (INIS)

Chen, S.C.; Danly, B.G.; Gonichon, J.

1995-01-01

The physics and technological issues involved in high gradient particle acceleration at high microwave (RF) frequencies are under study at MIT. The 17 GHz photocathode RF gun has a 1 1/2 cell (π mode) room temperature cooper cavity. High power tests have been conducted at 5-10 MW levels with 100 ns pulses. A maximum surface electric field of 250 MV/m was achieved. This corresponds to an average on-axis gradient of 150 MeV/m. The gradient was also verified by a preliminary electron beam energy measurement. Even high gradients are expected in our next cavity design

Status of PPI (Pohang Photo-Injector) for PAL XFEL

CERN Document Server

Park, Sung-Ju; Oh, Jong-Seok; Park, Chong-Do; Park Jang Ho; Soo Ko In; Wang, Xijie; Woon Parc, Yong

2005-01-01

A X-Ray Free Electron Laser (XFEL) project based on the Self-Amplified Spontaneous Emission (SASE) is under progress at the Pohang Accelerator Laboratory (PAL). One of the critical R&D for the PAL XFEL* is to develop the Pohang Photo-Injector (PPI) which is required to deliver electron beams with normalized emittance < 1.5 mm-mrad. In order to achieve the required beam quality with high stability and reliability, we will use photocathode with quantum efficiency > 0.1 % and long lifetime. This will greatly lessen the laser energy requirement for producing flat-top UV pulses, and open the possibility of using only regenerative amplifiers (RGAs) to drive the photocathode RF gun. The RGAs can produce mJs output with much better stability than multi-pass amplifiers. Both the Cs2Te and Mg are under consideration for the possible photo-cathode. To demonstrate the suitability of the Mg and Cs2Te for the future 4th generation light source application, an improved BNL-type S-band RF gun with a high-pe...

Thermal Emittance Measurement of the Cs2Te Photocathode in FZD Superconducting RF

CERN Document Server

Xiang, R; Michel, P; Murcek, P; Teichert, J

2010-01-01

The thermal emittance of the photocathode is an interesting physical property for the photoinjector, because it decides the minimum emittance the photoinjector can finally achieve. In this paper we will report the latest results of the thermal emittance of the Cs2Te photocathode in FZD Superconducting RF gun. The measurement is performed with solenoid scan method with very low bunch charge and relative large laser spot on cathode, in order to reduce the space charge effect as much as possible, and meanwhile to eliminate the wake fields and the effect from beam halos.

Emittance Measurements from a Laser Driven Electron Injector

CERN Document Server

Reis, D

2003-01-01

The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 (angstrom), the LCLS requires an electron injector that can produce an electron beam with approximately 1 pi mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the ...

A photocathode rf gun design for a mm-wave linac-based FEL

Energy Technology Data Exchange (ETDEWEB)

Nassiri, A.; Berenc, T,; Foster, J.; Waldschmidt, G.; Zhou, J.

1995-07-01

In recent years, advances in the rf gun technology have made it possible to produce small beam emittances suitable for short period microundulators which take advantage of the low emittance beam to reduce the wavelength of FELs. At the Advanced Photon Source, we are studying the design of a compact 50-MeV superconducting mm-wave linac-based FEL for the production of short wavelengths ({approximately}300 nm) to carry out FEL demonstration experiments. The electron source considered for the linac is a 30- GHz, 3 1/2-cell {pi}-mode photocathode rf gun. For cold model rf measurements a 15-GHz prototype structure was fabricated. Here we report on the design, numerical modelling and the initial cold-model rf measurement results on the 15-GHz prototype structure.

A photocathode rf gun design for a mm-wave linac-based FEL

International Nuclear Information System (INIS)

Nassiri, A.; Berenc, T.; Foster, J.; Waldschmidt, G.; Zhou, J.

1995-01-01

In recent years, advances in the rf gun technology have made it possible to produce small beam emittances suitable for short period microundulators which take advantage of the low emittance beam to reduce the wavelength of FELs. At the Advanced Photon Source, we are studying the design of a compact 50-MeV superconducting mm-wave linac-based FEL for the production of short wavelengths (∼300 nm) to carry out FEL demonstration experiments. The electron source considered for the linac is a 30- GHz, 3 1/2-cell π-mode photocathode rf gun. For cold model rf measurements a 15-GHz prototype structure was fabricated. Here we report on the design, numerical modelling and the initial cold-model rf measurement results on the 15-GHz prototype structure

A low-power RF system with accurate synchronization for a S-band RF-gun using a laser-triggered photocathode

International Nuclear Information System (INIS)

Otake, Y.; Naito, T.; Shintake, T.; Takata, K.; Takeuchi, Y.; Urakawa, J.; Yoshioka, M.; Akiyama, H.

1992-01-01

An S-band RF-gun using a laser-triggered photocathode and its low-power RF system have been constructed. The main elements of the low-power RF system comprise a 600-W amplifier, an amplitude modulator, a phase detector, a phase shifter and a frequency-divider module. Synchronization between the RF fields for acceleration and the mode-locked laser pulses for beam triggering are among the important points concerning the RF-gun. The frequency divider module which down-converts from 2856 MHz(RF) to 89.25 MHz(laser), and the electrical phase-shifter were specially developed for stable phase control. The phase jitter of the frequency divider should be less than 10 ps to satisfy our present requirements. The first experiments to trigger and accelerate beams with the above-mentioned system were carried out in January, 1992. (Author) 6 figs., 5 refs

A high-gradient high-duty-factor Rf photo-cathode electron gun

International Nuclear Information System (INIS)

Rimmer, Robert A.; Hartman, Neal; Lidia, Steven M.; Wang, Shaoheng

2002-01-01

We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

A high-gradient high-duty-factor RF photo-cathode electron gun

International Nuclear Information System (INIS)

Rimmer, Robert; Hartman, N.; Lidia, S.; Wang, S.H.

2002-01-01

We describe the analysis and preliminary design of a high-gradient, high-duty factor RF photocathode gun. The gun is designed to operate at high repetition rate or CW, with high gradient on the cathode surface to minimize emittance growth due to space charge forces at high bunch charge. The gun may also be operated in a solenoidal magnetic field for emittance compensation. The design is intended for use in short-pulse, high-charge, and high-repetition rate applications such as linac based X-ray sources. We present and compare the results of gun simulations using different codes, as well as RF and thermal analysis of the structure

Optimization of RF Compressor in the SPARX Injector

CERN Document Server

Ronsivalle, Concetta; Ferrario, Massimo; Serafini, Luca; Spataro, Bruno

2005-01-01

The SPARX photoinjector consists in a rf gun injecting into three SLAC accelerating sections, the first one operating in the RF compressor configuration in order to achieve higher peak current. A systematic study based on PARMELA simulations has been done in order to optimize the parameters that influence the compression also in view of the application of this system as injector of the so called SPARXINO 3-5 nm FEL test facility. The results of computations show that peak currents at the injector exit up to kA level are achievable with a good control of the transverse and longitudinal emittance by means of a short SW section operating at 11424 MHz placed before the first accelerating section. Some working points in different compression regimes suitable for FEL experiments have been selected. The stability of these points and the sensitivity to various types of random errors are discussed.

Analysis of emittance compensation and simulation results to photo-cathode RF gun

CERN Document Server

LiuShengGuang

2002-01-01

The emittance compensation technology will be used on the photo-cathode RF gun for Shanghai SDUV-FEL. The space charge force and its effect on electron beam transverse emittance in RF gun is studied, the principle of emittance compensation in phase-space is discussed. The authors have designed a compensation solenoid and calculated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emittance for electron beam of 1.5 nC is 1.612 pi mm centre dot mrad, electron energy E = 5.71 MeV

The FERMI @ Elettra Technical Optimization Study: General Layoutand Parameters and Physics Studies of Longitudinal Space Charge, theSpreader, the Injector, and Preliminary FEL Performance

Energy Technology Data Exchange (ETDEWEB)

Byrd, John; Corlett, John; Doolittle, Larry; Fawley, William; Lidia, Steven; Penn, Gregory; Ratti, Alex; Staples, John; Wilcox,Russell; Wurtele, Jonathan; Zholents, Alexander

2005-09-01

The FERMI {at} Elettra facility will make use of the existing GeV linac at Sincrotrone Elettra, which will become available for dedicated FEL applications following the completion of construction of a new injector booster complex for the storage ring. With a new rf photocathode injector, and some additional accelerating sections, this linac will be capable of providing high brightness bunches at 1.2 GeV and up to 50 Hz repetition rates.

The FERMI (at) Elettra Technical Optimization Study: General Layout and Parameters and Physics Studies of Longitudinal Space Charge, the Spreader, the Injector, and Preliminary FEL Performance

International Nuclear Information System (INIS)

Byrd, John; Corlett, John; Doolittle, Larry; Fawley, William; Lidia, Steven; Penn, Gregory; Ratti, Alex; Staples, John; Wilcox, Russell; Wurtele, Jonathan; Zholents, Alexander

2005-01-01

The FERMI (at) Elettra facility will make use of the existing GeV linac at Sincrotrone Elettra, which will become available for dedicated FEL applications following the completion of construction of a new injector booster complex for the storage ring. With a new rf photocathode injector, and some additional accelerating sections, this linac will be capable of providing high brightness bunches at 1.2 GeV and up to 50 Hz repetition rates

Flat-beam Rf photocathode sources for linear collider applications

International Nuclear Information System (INIS)

Rosenzweig, J.B.

1991-01-01

Laser driven rf photocathodes represent a recent advance in high-brightness electron beam sources. The authors investigate here a variation on these devices, that obtained by using a ribbon laser pulse to illuminate the cathode, yielding a flat beam (σ x much-gt σ y ) which has asymmetric emittances at the cathode proportional to the beam size each transverse dimension. The flat-beam geometry mitigates space charge forces which lead to intensity dependent transverse and longitudinal emittance growth, thus limiting the beam brightness. The fundamental limit on achievable emittance and brightness is set by the transverse momentum distribution and peak current density of the photoelectrons (photon energy and cathode material dependent effects) and appears to allow, taking into account space charge and rf effects, normalized emittances ε x -5 m-rad and ε -6 m-rad, with Q = 5 nC and σ z = 1 mm. These source emittances are adequate for superconducting linear collider applications, and could preclude the use of a damping ring for the electrons in these schemes

Beam dynamics simulations in the photo-cathode RF gun for the CLIC test facility

International Nuclear Information System (INIS)

Marchand, P.; Rinolfi, L.

1992-01-01

The CERN CLIC Test Facility (CTF) uses an RF gun with a laser driven photo-cathode in order to generate electron pulses of high charge (≥10 nC) and short duration (≤20 ps). The RF gun consists of a 3 GHz 1 + 1/2 cell cavity based on the design originally proposed at BNL which minimizes the non-linearities in the transverse field. The beam dynamics in the cavity is simulated by means of the multiparticle tracking code PARMELA. The results are compared to previous simulations as well as to the first experimental data. (author). 4 refs., 4 tabs., 4 figs

High-quality electron pulse generation from a laser photocathode RF gun

International Nuclear Information System (INIS)

Yang, Jinfeng; Sakai, Fumio; Aoki, Yasushi

1999-01-01

A laser photocathode RF gun system was developed for ultra short X-ray pulse generation via the inverse Compton scattering. The gun is a BNL-type S-band RF gun and the performance test of the gun was performed at the Linear Accelerator Facility in the Institute of Scientific and Industries Research, Osaka University. The gun system produced 115 pC electron bunches with the energy of 1.6 MeV under the condition of RF peak power of 1.5 MW and laser pulse energy of 65 μJ. The quantum efficiency and dark current were obtained to be 10 -5 and 0.6 nA at the repetition rate of 10 Hz, respectively. The energy and charge of the electron bunch were measured as a function of laser injection phase. Furthermore, the electron bunches were accelerated up to 117 MeV by three s-band TW linacs and the energy monochromaticity (ΔE/E) of the beam was 1.2%. The transverse emittance was also experimentally investigated at the end of the linacs. (author)

Status of SPring-8 Photocathode Rf Gun for Future Light Sources

CERN Document Server

Tomizawa, H; Dewa, H; Hanaki, H; Kobayashi, T; Mizuno, A; Suzuki, S; Taniuchi, T; Yanagida, K

2005-01-01

We have been studying photocathode single-cell pillbox rf gun for future light sources since 1996. We achieved a rmaximum field gradient of 187 MV/m with chemical-etching processed cavity. We have been developed stable and highly qualified UV-laser source for the rf gun intensively last 3 years. The UV-laser pulse (10 Hz) energy is up to 850 uJ/pulse. The energy stability (rms) of laser has been improved down to 0.2~0.3 % at the fundamental and 0.7~1.3% at the third harmonic generation. This stability is held for two months continuously. In this improvement, we just passively stabilized the system in a humidity-controlled clean room. On the other hand, the ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from the rf gun. We prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. With a deformable mirror, we obtained an emittance of1.6

High power beam test and measurement of emittance evolution of a 1.6-cell photocathode RF gun at Pohang Accelerator Laboratory

International Nuclear Information System (INIS)

Park, Jang-Ho; Park, Sung-Ju; Kim, Changbum; Huang, Jung-Yun; Ko, In Soo; Parc, Yong-Woon; Hong, Ju-Ho; Xiang Dao; Wang, Xijie

2007-01-01

A Brookhaven National Laboratory (BNL) GUN-IV type photocathode rf gun has been fabricated to use in femtosecond electron diffraction (FED), femtosecond far infrared radiation (fs-FIR) facility, and X-ray free electron laser (XFEL) facilities at the Pohang Accelerator Laboratory (PAL). The gun consists of a 1.6-cell cavity with a copper cathode, a solenoid magnet, beam diagnostic components and auxiliary systems. We report here the measurement of the basic beam parameters which confirm a successful fabrication of the photocathode RF gun system. The emittance evolution is measured by an emittance meter and compared with the PARMELA simulation, which shows a good agreement. (author)

Investigations on the transverse phase space at a photo injector for minimized emittance

Energy Technology Data Exchange (ETDEWEB)

Miltchev, V.

2006-08-15

Radio frequency photoinjectors are electron sources able to generate beams of extremely high brightness, which are applicable to linac driven Free Electron Lasers (FEL). Because of the high phase space density, the dynamics of the electron beam is dominated by space charge interactions between the particles. This thesis studies the transverse phase space of space charge dominated electron beams produced by the Photo Injector Test Facility in Zeuthen (PITZ). The operation conditions for minimizing the transverse emittance are studied experimentally, theoretically and in simulations. The influence of the longitudinal profile of the driving UV laser pulse on the transverse emittance is investigated. Emphasis is placed on the experimental study of the emittance as a function of different machine parameters like the laser beam spot size, the amplitude of the focusing magnetic field, the rf phase and the electron bunch charge. First investigations on the thermal emittance for Cs{sub 2}Te photocathodes under rf operating conditions are presented. Measurements of the thermal emittance scaling with the photocathode laser spot size are analyzed. The significance of the applied rf field in the emittance formation process is discussed. (orig.)

Investigations on the transverse phase space at a photo injector for minimized emittance

International Nuclear Information System (INIS)

Miltchev, V.

2006-08-01

Radio frequency photoinjectors are electron sources able to generate beams of extremely high brightness, which are applicable to linac driven Free Electron Lasers (FEL). Because of the high phase space density, the dynamics of the electron beam is dominated by space charge interactions between the particles. This thesis studies the transverse phase space of space charge dominated electron beams produced by the Photo Injector Test Facility in Zeuthen (PITZ). The operation conditions for minimizing the transverse emittance are studied experimentally, theoretically and in simulations. The influence of the longitudinal profile of the driving UV laser pulse on the transverse emittance is investigated. Emphasis is placed on the experimental study of the emittance as a function of different machine parameters like the laser beam spot size, the amplitude of the focusing magnetic field, the rf phase and the electron bunch charge. First investigations on the thermal emittance for Cs 2 Te photocathodes under rf operating conditions are presented. Measurements of the thermal emittance scaling with the photocathode laser spot size are analyzed. The significance of the applied rf field in the emittance formation process is discussed. (orig.)

State-Of High Brightness RF Photo-Injector Design

Science.gov (United States)

Ferrario, Massimo; Clendenin, Jym; Palmer, Dennis; Rosenzweig, James; Serafini, Luca

2000-04-01

The art of designing optimized high brightness electron RF Photo-Injectors has moved in the last decade from a cut and try procedure, guided by experimental experience and time consuming particle tracking simulations, up to a fast parameter space scanning, guided by recent analytical results and a fast running semi-analytical code, so to reach the optimum operating point which corresponds to maximum beam brightness. Scaling laws and the theory of invariant envelope provide to the designers excellent tools for a first parameters choice and the code HOMDYN, based on a multi-slice envelope description of the beam dynamics, is tailored to describe the space charge dominated dynamics of laminar beams in presence of time dependent space charge forces, giving rise to a very fast modeling capability for photo-injectors design. We report in this talk the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector. During this work a new effective working point for a split RF photoinjector has been discovered by means of the previous mentioned approach. By a proper choice of rf gun and solenoid parameters, the emittance evolution shows a double minimum behavior in the drifting region. If the booster is located where the relative emittance maximum and the envelope waist occur, the second emittance minimum can be shifted at the booster exit and frozen at a very low level (0.3 mm-mrad for a 1 nC flat top bunch), to the extent that the invariant envelope matching conditions are satisfied.

Rf and space-charge induced emittances in laser-driven rf guns

International Nuclear Information System (INIS)

Kim, Kwang-Je; Chen, Yu-Jiuan.

1988-10-01

Laser-driven rf electron guns are potential sources of high-current, low-emittance, short bunch-length electron beams, which are required for many advanced accelerator applications, such as free-electron lasers and injectors for high-energy machines. In such guns the design of which was pioneered at Los Alamos National Laboratory and which is currently being developed at several other laboratories, a high-power laser beam illuminates a photo-cathode surface placed on an end wall of an rf cavity. The main advantages of this type of gun are that the time structure of the electron beam is controlled by the laser, eliminating the need for bunchers, and that the electric field in rf cavities can be made very strong, so that the effects due to space-charge repulsion can be minimized. In this paper, we present an approximate but simple analysis for the transverse and longitudinal emittances in rf guns that takes into account both the time variation of the rf field and the space-charge effect. The results are compared and found to agree well with those from simulation. 7 refs., 6 figs

Design of a high repetition rate S-band photocathode gun

International Nuclear Information System (INIS)

Han Janghui; Cox, Matthew; Huang, Houcheng; Pande, Shivaji

2011-01-01

Photocathode RF guns have been developed in many laboratories for generating high quality electron beams for free-electron lasers based on linear accelerators. Such guns can generate electron beams with an exceptionally high peak current as well as a small transverse emittance. Their applications have been recently expanded for ultrafast electron diffraction, coherent terahertz radiation, and X-ray or γ-ray radiation by Compton scattering. In this paper, we design an S-band normal-conducting gun with capabilities of high quality beam generation and high repetition rate operation. The RF design and thermal analysis of the gun cavity and coupler are introduced. Optimal position of the gun focusing solenoid for low emittance beam generation is found by performing particle tracking simulations. Then, the gun system is designed to be able to afford the optimal solenoid position. The cooling-water channel surrounding the gun cavity and coupler is designed and analyzed numerically. The pressure in the gun is simulated with a vacuum model containing the detailed inner structure of the gun. An injector for a free-electron laser application is designed by using this gun and the beam dynamics simulation is shown. A cold test with a prototype gun for confirmation of the RF design is reported. - Highlights: → We design an S-band gun for low emittance beam generation and high repetition rate operation. → The RF design and thermal analysis of the gun cavity and coupler are studied. → An FEL injector is designed by using this gun and the beam dynamics simulation is shown. → A cold test with a prototype gun for confirmation of the RF design is reported.

Experimental studies of emittance growth and energy spread in a photocathode RF gun

International Nuclear Information System (INIS)

Yang, J.; Sakai, F.; Okada, Y.; Yorozu, M.; Yanagida, T.; Endo, A.

2002-01-01

In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91±0.28 πmm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac

Experimental studies of emittance growth and energy spread in a photocathode RF gun

CERN Document Server

Yang, J; Okada, Y; Yorozu, M; Yanagida, T; Endo, A

2002-01-01

In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91+-0.28 pi mm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac.

Emittance measurement and optimization for the photocathode RF gun with laser profile shaping

International Nuclear Information System (INIS)

Liu Shengguang; Masafumi Fukuda; Sakae Araki; Nobuhiro Terunuma; Junji Urakawa

2010-01-01

The Laser Undulator Compact X-ray source (LUCX) is a test bench for a compact high brightness X-ray generator, based on inverse Compton Scattering at KEK, which requires high intensity multi-bunch trains with low transverse emittance. A photocathode RF gun with emittance compensation solenoid is used as an electron source. Much endeavor has been made to increase the beam intensity in the multi-bunch trains. The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects, so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough. A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform. In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance. With the uniform driving laser and the unbalanced RF gun, the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm·mrad. (authors)

High-charge s-band photocathode RF-gun and linac system for radiation research

Energy Technology Data Exchange (ETDEWEB)

Kobayashi, Tetsuya; Uesaka, Mitsuru; Katsumura, Yousuke [Univ. of Tokyo, Graduate School of Engineering, Nuclear Engineering Research Laboratory, Tokai, Ibaraki (JP)] (and others)

2002-01-01

For sub-picosecond pump-and-prove-type radiation chemistry work, a new synchronized electron linac and laser system was installed in the Nuclear Engineering Research Laboratory (NERL) of University of Tokyo. The new laser system, with a Ti:Sapphire oscillator (795 nm) and amplifiers, generates 300 ps pulses at 10 Hz. The laser is transported through the vacuum chamber and then split into two beams. The first is compressed and converted to the third harmonics (265 nm, <250 {mu}J, 4-11 ps) so as to drive the photocathode RF-gun and generate a pump-electron beam. The second is compressed to 100 fs and used for the probe light. The high-power RF, which is provided by a new 15 MW klystron, is divided into the gun and the accelerating section. Finally, a time jitter of 330 fs (rms) was achieved between the pump-electron beam and the probe laser, which is equivalent to the design value of 320 fs. A charge of 7 nC/bunch was observed at the exit of the gun from this new laser system. Improvement of the vacuum in the gun (<10{sup -9} Torr) is the most effective way to obtain such a high-charge beam. After about three years of operation, the Cu photocathode has shown no degradation of quantum efficiency. (author)

Generation of femtosecond electron single pulse using laser photocathode RF gun

Energy Technology Data Exchange (ETDEWEB)

Uesaka, M.; Kinoshita, K.; Watanabe, T. [Nuclear Engineering Research Laboratory, University of Tokyo, Tokai, Ibaraki (JP)] [and others

1998-11-01

A new laser photocathode RF electron gun was installed in the second linac of the S-band twin linac system of Nuclear Engineering Research Laboratory(NERL) of University of Tokyo in August in 1997. Since then, the behavior of the new gun has been tested and the characteristic parameters have been evaluated. At the exit of the gun, the energy is 4.7 MeV, the charge per bunch 1 nC, the pulse width is 10 ps(FWHM), respectively, for 6 MW RF power supply from a klystron. The electron bunch is accelerated up to 17 MeV. The horizontal normalized emittance is 1 {pi} mm.mrad. Then, the bunch is compressed to be 440 fs(FWHM) with 0.35 nC by the chicane-type magnetic pulse compressor. The gun is planned to be used for femtosecond X-ray generation via the head-on Thomson scattering and laser wakefield acceleration in 1998. (author)

Study on the drive laser system of the photocathode-injector used in high gain FEL

CERN Document Server

Lu Xiang Yang; Zhao Kui; Wang Li; Quan Sheng Wen; Hao Jian Kui; Zhang Bao Cheng; Chen J

2002-01-01

High gain FEL requires high quality electron beam which can be provided only by the RF photocathode gun. The drive laser for electron source plays the key role. In Institute of Heavy Ion Physics of Beijing University, the laser system is required to deliver a 500 mu J, 6-8 ps pulse of UV photons (260 nm) to the cathode. This system mainly consists of a CW, frequency-doubled, diode-pumped Nd:YAG laser, which provides energy to pump a CW mode-locked Ti:sapphire oscillator, Q-switched Nd:YaG pump lasers, a regenerative amplifier and harmonics crystals. To meet the low jitters of pulses (1.0 ps), cavity length of the oscillator should be adjustable to lock the pulse frequency with external RF reference, and a phase stability feedback system is also used

Design Study of Low-Emittance Injector for SASE-XFEL at Pohang Accelerator Laboratory

CERN Document Server

Park, Sungju J; Yun, H J; Kim, D E; Kim, E S; Ko, In Soo; Nam, S H; Oh, Jong Seok

2004-01-01

We report on the design study of the low-emittance injector for the SASE-XFEL that is being considered as a possible choice for the next-generation light sources at the Pohang Accelerator Laboratory, POSTECH. Using the PARMELA code, beam dynamics simulations were performed aiming to achieve the invariant-envelope matching at booster entrance, and to insure beam emittance < 1 mm.mrad (at 1-nC bunch charge) at the injector end. We also utilized the MAGIC code for analyzing beam dynamics inside the RF-gun cavities and to confirm the part of PARMELA simulations. Hardware design was done with possible implementation of high-Q.E. photocathode, which could reduce burdens imposed on laser system, thus improving overall system stability and reliability.

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.

Recent progress in photo-injectors

International Nuclear Information System (INIS)

Ben-Zvi, I.

1996-10-01

In photoinjector electron guns, electrons are emitted from a photocathode by a short laser pulse and then accelerated by intense RF fields in a resonant cavity. Photoinjectors are very versatile tools. Normally we think of them in terms of the production of high electron density in 6-D phase space, for reasons such as injection to laser accelerators, generation of x-rays by Compton scattering and short wavelength FELs. Another example for the use of photo-injectors is the production of a high charge in a short time, for wake- field acceleration, two-beam accelerators and high-power, long-wavelength FELs. There are other potential uses, such as the generation of polarized electrons, compact accelerators for industrial applications and more. Photoinjectors are in operation in many electron accelerator facilities and a large number of new guns are under construction. The purpose of this work is to present some trend setting recent results that have been obtained in some of these laboratories. In particular the subjects of high density in 6-D phase space, new diagnostic tools, photocathode advances and high-charge production will be discussed

SLAC collider injector, RF-drive synchronization and trigger electronics, and 15-AMP thermionic-gun development

International Nuclear Information System (INIS)

Koontz, R.; Miller, R.; McKinney, T.; Wilmunder, A.

1981-02-01

The rf drive system for the Collider Injector Development (EL CID) including laser timing, subharmonic buncher drive and phasing, and accelerator rf drive is described. The rf synchronized master trigger generation scheme for the collider is outlined. Also, a 15 amp peak, 200 kV short pulse gun being developed at SLAC as a backup to the Sinclair laser gun is described

Investigation of the Stability of the RF Gun of the SSRL Injector System

International Nuclear Information System (INIS)

Moore, J

2004-01-01

In the previous three years, Stanford Synchrotron Radiation Laboratory (SSRL) has experienced electron beam instabilities in the injector system of the Stanford Positron Electron Asymmetric Ring (SPEAR). Currently, for approximately the past four months the radio frequency (RF) gun of the linear accelerator injector system of the SPEAR at SSRL has become increasingly unstable. The current of the RF gun has become progressively sluggish and the lifetime of the cathode within the RF gun has been much shorter than expected. The cathode also sustains many unexplained damages. The instability of the RF gun affects the entire operation of SPEAR, creating substantial inconvenience. Through mechanical, design, and procedural analysis of the RF gun and the cathode that emits the electron beam of the linear accelerator, a solution to prolong the life of the cathode and secure the stability of the gun can be found. The thorough analysis of the gun and cathode involves investigation into the history of cathode installation and removal through the years of SPEAR operation as well as interviews with SSRL personnel involved with the upkeep of the gun and cathode. From speaking with SSRL employees and reviewing several articles many possible causes for beam instability were presented. The most likely cause of the SSRL gun instability is excessive back bombardment that can be attributed to running the cathode at too high a temperature

Evaluation of the photocathode laser transverse distribution

Energy Technology Data Exchange (ETDEWEB)

Saisa-ard, Chaipattana [DESY, Zeuthen (Germany); Chiang Mai Univ., Chiang Mai (Thailand); Krasilnikov, Mikhail; Vashchenko, Grygorii [DESY, Zeuthen (Germany)

2016-07-01

Many years experience of electron source developments at the photo injector test facility at DESY in Zeuthen (PITZ) show that the photocathode laser is the one of major tools to produce high brightness electron beams. The transverse distribution of the laser on the photocathode plays a significant role in the high brightness photo injector optimization. However, the imperfections in the laser beam profile according to the deviation from a radially homogeneous profile directly result in transversely distorted charged particle distributions. This includes inhomogeneous core as well as transverse halo which is due to not sharp edges around the core. The laser transverse distribution is measured at PITZ using a virtual cathode:this is a CCD camera located at the position which is optically equivalent to the photocathode position (so called virtual cathode). An algorithm is developed for the evaluation of the experimentally obtained transverse profiles. It fits a flat-top or an inhomogeneous rotational symmetric core with exponentially decaying tails to an experimental distribution. The MATLAB script with implemented algorithm is applied to a set of measured transverse laser distributions. Results of the analysis will be presented.

State-of-the-Art Electron Guns and Injector Designs for Energy Recovery Linacs (ERL)

CERN Document Server

Todd, Alan; Ben-Zvi, Ilan; Benson, Stephen V; Blüm, Hans; Burrill, Andrew; Calaga, Rama; Cameron, Peter; Campisi, Isidoro E; Chang, Xiangyun; Christina, Vincent; Cole, Michael; Colestock, Patrick L; Daly, Edward; Douglas, David; Dylla, Fred H; Falletta, Michael; Hahn, Harald; Hernandez-Garcia, Carlos; Hogan, John; Holmes, Douglas; Janssen, Dietmar; Kayran, Dmitry; Kelley, John P; Kewisch, Jorg; Kneisel, Peter; Kurennoy, Sergey; Lewellen, John W; Litvinenko, Vladimir N; Mammosser, John; McIntyre, Gary; Neil, George R; Nguyen, Dinh C; Nicoletti, Tony; Peterson, Ed; Phillips, Larry; Preble, Joseph P; Rank, Jim; Rao, Triveni; Rathke, John; Reass, William; Rees, Daniel; Rimmer, Robert; Rode, Claus; Russell, Steven; Scaduto, Joseph; Schrage, Dale L; Schultheiss, Tom; Sekutowicz, Jacek; Siggins, Tim; Warren Funk, L; Whitlach, Timothy; Wiseman, Mark; Wong, Robert; Wood, Richard L; Wu, Kuo-Chen; Young, Lloyd M; Zaltsman, Alex; Zhao, Yongxiang

2005-01-01

A key technology issue of ERL devices for high-power free-electron laser (FEL) and 4th generation light sources is the demonstration of reliable, high-brightness, high-power injector operation. Ongoing programs that target up to 1 Ampere injector performance at emittance values consistent with the requirements of these applications are described. We consider that there are three possible approaches that could deliver the required performance. The first is a DC photocathode gun and superconducting RF (SRF) booster cryomodule. Such a 750 MHz device is being integrated and will be tested up to 100 mA at the Thomas Jefferson National Accelerator Facility beginning in 2007. The second approach is a high-current normal-conducting RF photoinjector. A 700 MHz gun will undergo thermal test in 2006 at the Los Alamos National Laboratory, which, if successful, when equipped with a suitable cathode, would be capable of 1 Ampere operation. The last option is an SRF gun. A half-cell 703 MHz SRF gun capable of delivering 1.0...

Proceedings of the workshop on photocathodes for polarized electron sources for accelerators

International Nuclear Information System (INIS)

Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D.

1994-04-01

Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode

The SSRL linacs for injection to the storage ring and rf gun testing

International Nuclear Information System (INIS)

Park, Sanghyun; Weaver, James N.

1996-01-01

The Stanford Synchrotron Radiation Laboratory (SSRL) operates two linac systems. One has three SLAC type linac sections powered by two klystrons for injection of electrons at 120 MeV into the booster ring, boosting the energy to 2.3 GeV to fill the SPEAR. After the ramping, the SPEAR stores up to 100 mA of the beam at 3.0 GeV. The preinjector consists of a thermionic RF gun, an alpha magnet, and a chopper along with focusing magnets. The other has one 10 foot section powered by the injector klystron for the testing of RF gun with photocathode, which is driven by a separate klystron. This paper describes present systems with their operational parameters, followed by plans for the upgrades and RF gun development efforts at the SSRL. (author)

Proceedings of the workshop on photocathodes for polarized electron sources for accelerators. Revision

Energy Technology Data Exchange (ETDEWEB)

Chatwell, M.; Clendenin, J.; Maruyama, T.; Schultz, D. [eds.

1994-04-01

Application of the GaAs polarized electron source to studies of surface magnetism; thermal stability of Cs on NES III-V-Photocathodes and its effect on quantum efficiency; AFEL accelerator; production and detection of SPIN polarized electrons; emittance measurements on a 100-keV beam from a GaAs photocathode electron gun; modern theory of photoemission and its applications to practical photocathodes; experimental studies of the charge limit phenomenon in GaAs photocathodes; new material for photoemission electron source; semiconductor alloy InGaAsP grown on GaAs substrate; NEA photocathode surface preparation; technology and physics; metalorganic chemical vapor deposition of GaAs-GaAsP spin-polarized photocathodes; development of photocathodes injectors for JLC-ATF; effect of radiation trapping on polarization of photoelectrons from semiconductors; and energy analysis of electrons emitted by a semiconductor photocathode.

RF Processing Experience with the GTF Prototype RF Gun

International Nuclear Information System (INIS)

Schmerge, J.F.

2010-01-01

The SSRL Gun Test Facility (GTF) was built to develop a high brightness electron injector for the LCLS and has been operational since 1996. A total of five different metal cathodes (4 Cu and 1 Mg) have been installed on the GTF gun. The rf processing history with the different cathodes will be presented including peak field achieved at the cathode. The LCLS gun is intended to operate at 120 MV/m and fields up to 140 MV/m have been achieved in the GTF gun. After installing a new cathode the number of rf pulses required to reach 120 MV/m is approximately 5-10 million. Total emitted dark current and Fowler Nordheim plots are also shown over the life of the cathode. The GTF photo-injector gun is an S-band standing-wave structure, with two resonant cavities and an intervening thick washer (Figure 1). The flat, back wall of the first cavity is a copper plate that serves as photocathode when illuminated with ultraviolet light from a pulsed, high-power laser. RF power enters the gun through an iris on the outer wall of the second cavity, and is coupled to the first through the axial opening of the washer. The first cavity is often referred to as a half cell, because its full-cell length has been truncated by the cathode plate and the second cavity is called the full cell. The gun is designed to operate in a π mode, with the peak field on axis in each cell approximately equal. The maximum in the half cell occurs at the cathode, and in the full cell near the center of the cavity. The field profile and tuning procedures are discussed in a separate tech note (1).

Generation of quasiequally spaced ultrashort microbunches in a photocathode rf gun

International Nuclear Information System (INIS)

He, Zhigang; Xu, Yuanfang; Li, Weiwei; Jia, Qika

2015-01-01

A photocathode rf gun can generate trains of THz subpicosecond electron bunches by illuminating the cathode with trains of laser pulses, but it suffers from the increasing charge in the beam. The THz structure blurs and tends to disappear when the longitudinal space charge forces begin to play a significant role in the beam evolution. In this paper, we propose a scheme to restrain the space charge forces by expanding the transverse size of the laser pulses to reduce the charge density and adopting a multicell gun to increase the beam energy. Thus, quasiequally spaced ultrashort microbunches with relatively high charges can be generated according to our studies. Postacceleration can be used to freeze the longitudinal phase space dynamics. The proposed scheme is in principle able to generate intense multi-color narrow-band THz radiation and offers a promising way towards the tunable intense narrow-band THz sources

A novel scaling law relating the geometrical dimensions of a photocathode radio frequency gun to its radio frequency properties

Science.gov (United States)

Lal, Shankar; Pant, K. K.; Krishnagopal, S.

2011-12-01

Developing a photocathode RF gun with the desired RF properties of the π-mode, such as field balance (eb) ˜1, resonant frequency fπ = 2856 MHz, and waveguide-to-cavity coupling coefficient βπ ˜1, requires precise tuning of the resonant frequencies of the independent full- and half-cells (ff and fh), and of the waveguide-to-full-cell coupling coefficient (βf). While contemporary electromagnetic codes and precision machining capability have made it possible to design and tune independent cells of a photocathode RF gun for desired RF properties, thereby eliminating the need for tuning, access to such computational resources and quality of machining is not very widespread. Therefore, many such structures require tuning after machining by employing conventional tuning techniques that are iterative in nature. Any procedure that improves understanding of the tuning process and consequently reduces the number of iterations and the associated risks in tuning a photocathode gun would, therefore, be useful. In this paper, we discuss a method devised by us to tune a photocathode RF gun for desired RF properties under operating conditions. We develop and employ a simple scaling law that accounts for inter-dependence between frequency of independent cells and waveguide-to-cavity coupling coefficient, and the effect of brazing clearance for joining of the two cells. The method has been employed to successfully develop multiple 1.6 cell BNL/SLAC/UCLA type S-band photocathode RF guns with the desired RF properties, without the need to tune them by a tiresome cut-and-measure process. Our analysis also provides a physical insight into how the geometrical dimensions affect the RF properties of the photo-cathode RF gun.

The RF system for the 70 MeV linac injector

International Nuclear Information System (INIS)

Planner, C.W.

1975-12-01

The Radio Frequency System for the 70 MeV Linac Injector for Nimrod is required to power the four Accelerating Cavities and the Buncher and Debuncher Cavities. The frequency of operation is 202.5 MHz and is determined by the use of existing equipment from the redundant 50 MeV Proton Linac for the second and third accelerating cavities and the buncher and de-buncher cavities. The subject is discussed under the following headings: low power drive chain; RF feed lines; cavity field level stabilisation. Circuit diagrams are presented. (U.K.)

Synchronizaiton Between Laser and Electron Beam at Photocathode RF Gun

CERN Document Server

Sakumi, Akira; Fukasawa, Atsushi; Kumagai, Noritaka; Muroya, Yusa; Tomizawa, Hiromitsu; Ueda, T; Uesaka, Mitsuru; Urakawa, Junji; Yoshii, K

2005-01-01

The chemical reactions of hot, room temperature and critical water in a time-range of picosecond and sub-picosecond have been carried out by the 18 MeV S-band linac and a Mg photocathode RF gun with the irradiation of third harmonic Ti: Sapphire laser, at Nuclear Engineering Research Laboratory (NERL), the University of Tokyo. Although this short bunch and 100 fs laser light are enough to perform the experiment of radiation chemistry in the time-range of sub-picosecond, the total time-resolution become worse by the instability of synchronization between laser and radio frequency of linac. We found that the fluctuation of room temperature causes the instability, particularly the cycle of turning on/off of the air-conditioner. It is shown that 0.3 °C (peak-to-peak) fluctuation of the laser-room temperature have approximately corresponded to the instability of 6 ps. We are trying to decrease the fluctuation of the room temperature, together with the local temperature stability of the Ti: Sapphire crysta...

Performance of the PHIN High Charge Photo Injector

CERN Document Server

Petrarca, M; Doebert, S; Dabrowski, A; Divall, M; Fedoseev, V; Lebas, N; Lefevre, T; Losito, R; Egger, D; Mete, O

2010-01-01

The high charge PHIN photo injector is studied at CERN as an electron source for the CLIC Test Facility (CTF3) drive beam as an alternative to the present thermionic gun. The objective of PHIN is to demonstrate the feasibility of a laser-based electron source for CLIC. The photo injector operates with a 2.5 cell, 3 GHz RF gun using a Cs2Te photocathode illuminated by UV laser pulses generated by amplifying and frequency quadrupling the signal from a Nd:YLF oscillator running at 1.5GHz. The challenge is to generate a beam structure of 1908 micro bunches with 2.33nC per micro bunch at 1.5GHz leading to a high integrated train charge of 4446nC and nominal beam energy of 5.5MeV with current stability below 1%. In this paper we report and discuss the time resolved transverse and longitudinal beam parameters measurements. The performance of the photo cathodes made at CERN with a peak quantum efficiency of 18 % is shown as well. Laser pointing and amplitude stability results are discussed taking into account correla...

Elements of the system for RF power input into linear accelerator-injector for booster

International Nuclear Information System (INIS)

Mazurov, E.V.; Mal'tsev, I.G.; Shalashov, I.M.

1981-01-01

The elements of the original system for RF power input into 30 MeV linear accelerator-injector for the IHEP proton synchrotron booster are considered. A 3 dB coaxial directional coupler (T-bridge) is describedd. The characteristics of the bridge containing elements and the parameters of ballast matched load are given [ru

Design of a high charge (10 - 100 nC) and short pulse (2 - 5 ps) rf photocathode gun for wakefield acceleration

International Nuclear Information System (INIS)

Gai, W.

1998-01-01

In this paper we present a design report on a 1-1/2 cell, L Band RF photocathode gun that is capable of generating and accelerating electron beams with peak currents >10 kA. We have performed simulation for bunch intensities in the range of 10-100 nC with peak axial electrical field at the photocathode of 30-100 MV/m. Unlike conventional short electron pulse generation, this design does not require magnetic pulse compression. Based on numerical simulations using SUPERFISH and PARMELA, this design will produce 20-100 nC beam at 18 MeV with rms bunch length 0.6-1.25 mm and normalized transverse emittance 30-108 mm mrad. Applications of this beam for wakefield acceleration is also discussed

RF Design of the TW Buncher for the CLIC Drive Beam Injector (2nd report)

CERN Document Server

Shaker, Hamed

2016-01-01

CLIC is based on the two beams concept that one beam (drive beam) produces the required RF power to accelerate another beam (main beam). The drive beam is produced and accelerated up to 50MeV inside the CLIC drive beam injector. The drive beam injector main components are a thermionic electron gun, three sub-harmonic bunchers, a pre-buncher, a TW buncher, 13 accelerating structures and one magnetic chicane. This document is the second report of the RF structure design of the TW buncher. This design is based on the beam dynamic design done by Shahin Sanaye Hajari due to requirements mentioned in CLIC CDR. A disk-loaded tapered structure is chosen for the TW buncher. The axial electric field increases strongly based on the beam dynamic requirements. This second report includes the study of HOM effects, retuning the cells, study of dimensional tolerances and the heat dissipation on the surface.

Advanced 3D Photocathode Modeling and Simulations Final Report

International Nuclear Information System (INIS)

Dimitre A Dimitrov; David L Bruhwiler

2005-01-01

High brightness electron beams required by the proposed Next Linear Collider demand strong advances in photocathode electron gun performance. Significant improvement in the production of such beams with rf photocathode electron guns is hampered by the lack high-fidelity simulations. The critical missing piece in existing gun codes is a physics-based, detailed treatment of the very complex and highly nonlinear photoemission process

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.

Thermionic RF Gun and Linac Pre-Injector for SPEAR3

Energy Technology Data Exchange (ETDEWEB)

Park, S.

2003-08-11

Preparations are underway to upgrade the Spear2 to the third generation light source. Installation of all the subsystems will start in April 2003. Although the Spear3 RF system is entirely different from the present form, the pre-injector gun/linac and booster synchrotron will remain the same even after the upgrade. The thermionic rf gun reliability and stability are to be improved to inject 500 mA of stored current in shortest possible time. When a top-up mode is enforced, where the stored beam decay is replenished to maintain the constant current and thus constant light intensity, the Spear3 will take injection every few minutes. In that case the gun, linac, and booster must stay on at all times. In this report we will describe some improvements made on the gun and linac in the recent past, as well as their present performance and future upgrade to be made.

A pulsed electron injector using a metal photocathode irradiated by an excimer laser

International Nuclear Information System (INIS)

Kauppila, T.J.; Builta, L.A.; Crutcher, J.K.; Elliott, J.C.; Moir, D.C.

1987-01-01

The hot cathode of an electron gun is replaced by a metallic photocathode driven by an excimer laser. The current, current density, and emittance of the 500-kV electron beam produced by the photoelectron source are presented. In addition, the temperature of the photocathode is varied to study the possibility of a hybrid source

Simulations of S-band RF gun with RF beam control

Science.gov (United States)

Barnyakov, A. M.; Levichev, A. E.; Maltseva, M. V.; Nikiforov, D. A.

2017-08-01

The RF gun with RF control is discussed. It is based on the RF triode and two kinds of the cavities. The first cavity is a coaxial cavity with cathode-grid assembly where beam bunches are formed, the second one is an accelerating cavity. The features of such a gun are the following: bunched and relativistic beams in the output of the injector, absence of the back bombarding electrons, low energy spread and short length of the bunches. The scheme of the injector is shown. The electromagnetic field simulation and longitudinal beam dynamics are presented. The possible using of the injector is discussed.

Emittance studies of the BNL/SLAC/UCLA 1.6 cell photocathode rf gun

International Nuclear Information System (INIS)

Palmer, D.T.; Miller, R.H.; Wang, X.J.

1997-01-01

The symmetrized 1.6 cell S-band photocathode gun developed by the BNL/SLAC/UCLA collaboration is in operation at the Brookhaven Accelerator Test Facility (ATF). A novel emittance compensation solenoid magnet has also been designed, built and is in operation at the ATF. These two subsystems form an emittance compensated photoinjector used for beam dynamics, advanced acceleration and free electron laser experiments at the ATF. The highest acceleration field achieved on the copper cathode is 150 MV/m, and the guns normal operating field is 130 MV/m. The maximum rf pulse length is 3 micros. The transverse emittance of the photoelectron beam were measured for various injection parameters. The 1 nC emittance results are presented along with electron bunch length measurements that indicated that at above the 400 pC, space charge bunch lengthening is occurring. The thermal emittance, ε o , of the copper cathode has been measured

Emittance Measurements from a Laser Driven Electron Injector

Energy Technology Data Exchange (ETDEWEB)

Reis, David A

2003-07-28

The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 {angstrom}, the LCLS requires an electron injector that can produce an electron beam with approximately 1 {pi} mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the laser and electron beam at the GTF. A convolved measurement of the relative timing between the laser and the rf phase in the gun shows that the jitter is less than 2.5 ps rms. Emittance measurements of the electron beam at 35 MeV are reported as a function of the (Gaussian) pulse length and transverse profile of the laser as well as the charge of the electron beam at constant phase and gradient in both the gun and linac. At 1 nC the emittance was found to be {approx} 13 {pi} mm-mrad for 5 ps and 8 ps long laser pulses. At 0.5 nC the measured emittance decreased approximately 20% in the 5 ps case and 40% in the 8 ps case. These measurements are between 40-80% higher than simulations for similar experimental conditions. In addition, the thermal emittance of the electron beam was measured to be 0.5 {pi} mm-mrad.

Preliminary Results from a Superconducting Photocathode Sample Cavity

CERN Document Server

Kneisel, Peter; Lipski, Andrzej; Sekutowicz, Jacek

2005-01-01

Pure niobium has been proposed as a photocathode material and recently a successful test has been conducted with a niobium single cell cavity to extract photo-currents from the surface of this cavity. However, the quantum efficiency of niobium is ~2·10-4, whereas electrodeposited lead has a ~15 times higher quantum efficiency. We have designed and tested a photo-injector niobium cavity, which can be used to insert photo-cathodes made of different materials in the high electric field region of the cavity. Experiments have been conducted with niobium and lead, which show that neither the Q- values of the cavity nor the obtainable surface fields are significantly lowered. This paper reports about the results from these tests.

Femtosecond response time measurements of a Cs2Te photocathode

Science.gov (United States)

Aryshev, A.; Shevelev, M.; Honda, Y.; Terunuma, N.; Urakawa, J.

2017-07-01

Success in design and construction of a compact, high-brightness accelerator system is strongly related to the production of ultra-short electron beams. Recently, the approach to generate short electron bunches or pre-bunched beams in RF guns directly illuminating a high quantum efficiency semiconductor photocathode with femtosecond laser pulses has become attractive. The measurements of the photocathode response time in this case are essential. With an approach of the interferometer-type pulse splitter deep integration into a commercial Ti:Sa laser system used for RF guns, it has become possible to generate pre-bunched electron beams and obtain continuously variable electron bunch separation. In combination with a well-known zero-phasing technique, it allows us to estimate the response time of the most commonly used Cs2Te photocathode. It was demonstrated that the peak-to-peak rms time response of Cs2Te is of the order of 370 fs, and thereby, it is possible to generate and control a THz sequence of relativistic electron bunches by a conventional S-band RF gun. This result can also be applied for investigation of other cathode materials and electron beam temporal shaping and further opens a possibility to construct wide-range tunable, table-top THz free electron laser.

Polarization and charge limit studies of strained GaAs photocathodes

International Nuclear Information System (INIS)

Saez, P.J.

1997-03-01

This thesis presents studies on the polarization and charge limit behavior of electron beams produced by strained GaAs photocathodes. These photocathodes are the source of high-intensity, high-polarization electron beams used for a variety of high-energy physics experiments at the Stanford Linear Accelerator Center. Recent developments on P-type, biaxially-strained GaAs photocathodes have produced longitudinal polarization in excess of 80% while yielding beam intensities of ∼ 2.5 A/cm 2 at an operating voltage of 120 kV. The SLAC Gun Test Laboratory, which has a replica of the SLAC injector, was upgraded with a Mott polarimeter to study the polarization properties of photocathodes operating in a high-voltage DC gun. Both the maximum beam polarization and the maximum charge obtainable from these photocathodes have shown a strong dependence on the wavelength of illumination, on the doping concentration, and on the negative electron affinity levels. The experiments performed for this thesis included studying the effects of temperature, cesiation, quantum efficiency, and laser intensity on the polarization of high-intensity beams. It was found that, although low temperatures have been shown to reduce the spin relaxation rate in bulk semiconductors, they don't have a large impact on the polarization of thin photocathodes. It seems that the short active region in thin photocathodes does not allow spin relaxation mechanisms enough time to cause depolarization. Previous observations that lower QE areas on the photocathode yield higher polarization beams were confirmed. In addition, high-intensity, small-area laser pulses were shown to produce lower polarization beams. Based on these results, together with some findings in the existing literature, a new proposal for a high-intensity, high-polarization photocathode is given. It is hoped that the results of this thesis will promote further investigation on the properties of GaAs photocathodes

Technological Challenges for High-Brightness Photo-Injectors

CERN Multimedia

Suberlucq, Guy

2004-01-01

Many applications, from linear colliders to free-electron lasers, passing through light sources and many other electron sources, require high brightness electron beams, usually produced by photo-injectors. Because certain parameters of these applications differ by several orders of magnitude, various solutions were implemented for the design and construction of the three main parts of the photo-injectors: lasers, photocathodes and guns. This paper summarizes the different requirements, how they lead to technological challenges and how R&D programs try to overcome these challenges. Some examples of state-of-the-art parts are presented.

The linac and booster RF systems for a dedicated injector for SPEAR

International Nuclear Information System (INIS)

Weaver, J.N.; Baird, S.; Baltay, M.; Borland, M.; Nuhn, H.D.; Safranek, J.; Chavis, C.; Emery, L.; Genin, R.D.; Hettel, R.; Morales, H.; Sebek, J.; Voss, J.; Wang, D.; Wiedemann, H.; Youngmann, B.; Miller, R.H.

1991-01-01

A 120 MeV, 2,856 MHz, TW linac, with a microwave gun, alpha magnet, and chopper, has been built at SSRL as a preinjector for and along with a 3 GeV booster synchrotron ring. The resulting injector will be available on demand to fill SPEAR, which is a storage ring now dedicated to synchrotron light production. The linac sections were purchased from China, the XK-5 klystrons were obtained surplus from SLAC, the modulators are a variation on those at SLAC and were built by SSRL, the alpha magnet and chopper were designed and built at SSRL and the microwave gun was designed and built in collaboration with Varian Associates. The RF system for the booster ring is similar to those at SPEAR and PEP and was built by SSRL. Some of the interesting mechanical and electrical details are discussed and the operating characteristics of the linac and ring RF system are highlighted

The linac and booster RF systems for a dedicated injector for SPEAR

International Nuclear Information System (INIS)

Weaver, J.N.; Baird, S.; Baltay, M.; Borland, M.; Nuhn, H.D.; Safranek, J.; Chavis, C.; Emery, L.; Genin, R.D.; Hettel, R.; Morales, H.; Sebek, J.; Voss, J.; Wang, H.; Wiedemann, H.; Youngmann, B.

1991-05-01

A 120 MeV, 2856 MHz, TW linac, with a microwave gun, alpha magnet, and chopper, has been built at SSRL as a preinjector for and along with a 3 GeV booster synchrotron ring. The resulting injector will be available on demand to fill SPEAR, which is a storage ring now dedicated to synchrotron light production. The linac sections were purchased from China, the XK-5 klystrons were obtained surplus from SLAC, the modulators are a variation on those at SLAC and were built by SSRL, the alpha magnet and chopper were designed and built at SSRL and the microwave gun was designed and built in collaboration with Varian Associates. The rf system for the booster ring is similar to those at SPEAR and PEP and was built by SSRL. Some of the interesting mechanical and electrical details are discussed and the operating characteristics of the linac and ring rf system are highlighted. 8 refs., 6 figs

LCLS-II high power RF system overview and progress

Energy Technology Data Exchange (ETDEWEB)

Yeremian, Anahid Dian

2015-10-07

A second X-ray free electron laser facility, LCLS-II, will be constructed at SLAC. LCLS-II is based on a 1.3 GHz, 4 GeV, continuous-wave (CW) superconducting linear accelerator, to be installed in the first kilometer of the SLAC tunnel. Multiple types of high power RF (HPRF) sources will be used to power different systems on LCLS-II. The main 1.3 GHz linac will be powered by 280 1.3 GHz, 3.8 kW solid state amplifier (SSA) sources. The normal conducting buncher in the injector will use four more SSAs identical to the linac SSAs but run at 2 kW. Two 185.7 MHz, 60 kW sources will power the photocathode dual-feed RF gun. A third harmonic linac section, included for linearizing the bunch energy spread before the first bunch compressor, will require sixteen 3.9 GHz sources at about 1 kW CW. A description and an update on all the HPRF sources of LCLS-II and their implementation is the subject of this paper.

Fabrication and Measurement of Low Work Function Cesiated Dispenser Photocathodes

CERN Document Server

Moody, Nathan A; Jensen, Kevin

2005-01-01

Photoinjector performance is a limiting factor in the continued development of high powered FELs and electron beam-based accelerators. Presently available photocathodes are plagued with limited efficiency and short lifetime in an RF-gun environment, due to contamination or evaporation of a photosensitive surface layer. An ideal photocathode should have high efficiency at long wavelengths, long lifetime in practical vacuum environments, and prompt emission. Cathodes with high efficiency typically have limited lifetime, and vice versa, and the needs of the photocathode are generally at odds with those of the drive laser. A potential solution is the low work function dispenser cathode, where lifetime issues are overcome by periodic in situ regeneration that restores the photosensitive surface layer, analogous to those used in the microwave power tube industry. This work reports on the fabrication techniques and performance of cesiated metal photocathodes and cesiated dispenser cathodes, with a focus on understan...

Beam dynamics simulation of W-band photo injector

International Nuclear Information System (INIS)

Zhu Xiongwei

2002-01-01

The authors present a beam dynamics simulation study on 1.6 cell, high gradient W-Band photocathode RF gun which is capable of generating and accelerating 300 pC electron bunch. The design system is made up of 91.392 GHz photocathode RF gun and 91.392 GHz travelling wave linac cells. Based on the numerical simulation using SUPERFISH and PARMELA and the conventional RF linac scaling law, the design will produce 300 pC at 1.74 MeV with bunch length 0.72 ps and normalized transverse emittance 0.55 mm mrad. The authors study the beam dynamics in high frequency and high gradient; due to the high gradient, the ponderomotive effect plays an important role in beam dynamics; the authors found the ponderomotive effect still exist with only the fundamental space harmonics (synchrotron mode) due to the coupling of the transverse and longitudinal motion

A comparison of surface properties of metallic thin film photocathodes

CERN Document Server

Mistry, Sonal; Valizadeh, Reza; Jones, L.B; Middleman, Keith; Hannah, Adrian; Militsyn, B.L; Noakes, Tim

2017-01-01

In this work the preparation of metal photocathodes by physical vapour deposition magnetron sputtering has been employed to deposit metallic thin films onto Cu, Mo and Si substrates. The use of metallic cathodes offers several advantages: (i) metal photocathodes present a fast response time and a relative insensitivity to the vacuum environment (ii) metallic thin films when prepared and transferred in vacuum can offer smoother and cleaner emitting surfaces. The photocathodes developed here will ultimately be used in S-band Normal Conducting RF (NCRF) guns such as that used in VELA (Versatile Electron Linear Accelerator) and the proposed CLARA (Compact Linear Accelerator for Research and Applications) Free Electron Laser test facility. The samples grown on Si substrates were used to investigate the morphology and thickness of the film. The samples grown onto Cu and Mo substrates were analysed and tested as photocathodes in a surface characterisation chamber, where X-Ray Photoelectron spectroscopy (XPS) was emp...

High-brightness electron injectors

International Nuclear Information System (INIS)

Sheffield, R.L.

1987-01-01

Free-electron laser (FEL) oscillators and synchrotron light sources require pulse trains of high peak brightness and, in some applications, high-average power. Recent developments in the technology of photoemissive and thermionic electron sources in rf cavities for electron-linac injector applications offer promising advances over conventional electron injectors. Reduced emittance growth in high peak-current electron injectors may be achieved by using high field strengths and by linearizing the radial component of the cavity electric field at the expense of lower shunt impedance

Photocathode development

International Nuclear Information System (INIS)

Hinrichs, C.K.; Estrella, R.M.

1979-01-01

A research program for the development of photocathodes for use in streak image tubes is described. This is one task in the development of a high-resolution, high-speed x-ray streak camera system whose primary application is for diagnostics in underground nuclear testing. There are three objectives in the photocathode development program: (1) the development of new x-ray photocathodes compatible with the requirements of streak tubes; (2) the development of the capability to process high-quality visible light photocathodes as well as x-ray photocathodes; and (3) the design and construction of a transfer photocathode system. Design and construction of all the major components of the transfer photocathode system were completed. Assembly should be completed in early FY 80

Temporal laser pulse shaping for RF photocathode guns: the cheap and easy way using UV birefringent crystals

International Nuclear Information System (INIS)

Power, J.G.; Jing, C.

2009-01-01

We report experimental investigations into a new technique for achieving temporal laser pulse shaping for RF photocathode gun applications using inexpensive UV birefringent crystals. Exploiting the group velocity mismatch between the two different polarizations of a birefringent crystal, a stack of UV pulses can be assembled into the desired temporal pulse shape. The scheme is capable of generating a variety of temporal pulse shapes including: (i) flat-top pulses with fast rise-time and variable pulse duration. (ii) microbunch trains, and (iii) ramped pulse generation. We will consider two applications for beam generation at the Argonne Wakefield Accelerator (AWA) including a flat-top laser pulse for low emittance production and matched bunch length for enhanced transformer ratio production. Streak camera measurements of the temporal profiles generated with a 2-crystal set and a 4-crystal set are presented.

Experimental results of the ATF in-line injection system

International Nuclear Information System (INIS)

Wang, X.J.; Srinivasan-Rao, T.; Batchelor, K.

1995-01-01

The initial experimental results of the Brookhaven accelerator test facility (ATF) in-line injector is presented. The ATF in-line injector employed a full copper RF gun with a pair of solenoid magnets for emittance compensation. The maximum acceleration field of the RF gun was measured to be 130 MV/m. The electron yield from the copper cathode was maximized using p- polarized laser and the Schottky effect. The quantum efficiency under optimum conditions was measured to be 0.04%. The measured electron bunch length was less than 11 ps, which agreed with the laser pulse length measurement using a streak camera. The normalized rms. emittance for 0.25 nC charge is 0.9 ± 0.1 mm-mrad, which is almost four times smaller than the emittance predicted by the space-charge effect for a non-emittance compensation photocathode RF gun. The normalized rms for 0.6 nC charge was measured range from 1 to 3 mm-mrad. This measurement was first experimental demonstration of emittance compensation in a high-gradient, S-band photocathode RF gun

High Brightness Electron Guns for Next-Generation Light Sources and Accelerators

International Nuclear Information System (INIS)

H. Bluem; M.D. Cole; J. Rathke; T. Schultheiss; A.M.M. Todd; I. Ben-Zvi; T. Srinivasan-Rao; P. Colestock; D.C. Nguyen; R.L. Wood; L. Young; D. Janssen; J. Lewellen; G. Neil; H.L. Phillips; J.P. Preble

2004-01-01

Advanced Energy Systems continues to develop advanced electron gun and injector concepts. Several of these projects have been previously described, but the progress and status of each will be updated. The project closest to completion is an all superconducting RF (SRF) gun, being developed in collaboration with the Brookhaven National Laboratory, that uses the niobium of the cavity wall itself as the photocathode material. This gun has been fabricated and will shortly be tested with beam. The cavity string for a closely-coupled DC gun and SRF cavity injector that is expected to provide beam quality sufficient for proposed ERL light sources and FELs will be assembled at the Jefferson Laboratory later this year. We are also collaboration with Los Alamos on a prototype CW normal-conducting RF gun with similar performance, that will undergo thermal testing in late 2004. Another CW SRF gun project that uses a high quantum efficiency photocathode, similar to the FZ-Rossendorf approach, has just begun. Finally, we will present the RF design and cold test results for a fully axisymmetric, ultra-high-brightness x-band RF gun

RF Gun Optimization Study

International Nuclear Information System (INIS)

Alicia Hofler; Pavel Evtushenko

2007-01-01

Injector gun design is an iterative process where the designer optimizes a few nonlinearly interdependent beam parameters to achieve the required beam quality for a particle accelerator. Few tools exist to automate the optimization process and thoroughly explore the parameter space. The challenging beam requirements of new accelerator applications such as light sources and electron cooling devices drive the development of RF and SRF photo injectors. A genetic algorithm (GA) has been successfully used to optimize DC photo injector designs at Cornell University [1] and Jefferson Lab [2]. We propose to apply GA techniques to the design of RF and SRF gun injectors. In this paper, we report on the initial phase of the study where we model and optimize a system that has been benchmarked with beam measurements and simulation

Progress on a cryogenically cooled RF gun polarized electron source

Energy Technology Data Exchange (ETDEWEB)

Fliller, R.P., III; Edwards, H.; /Fermilab

2006-08-01

RF guns have proven useful in multiple accelerator applications. An RF gun capable of producing polarized electrons is an attractive electron source for the ILC or an electron-ion collider. Producing such a gun has proven elusive. The NEA GaAs photocathode needed for polarized electron production is damaged by the vacuum environment in an RF gun. Electron and ion back bombardment can also damage the cathode. These problems must be mitigated before producing an RF gun polarized electron source. In this paper we report continuing efforts to improve the vacuum environment in a normal conducting RF gun by cooling it with liquid nitrogen after a high temperature vacuum bake out. We also report on a design of a cathode preparation chamber to produce bulk GaAs photocathodes for testing in such a gun. Future directions are also discussed.

High-brightness electron beam evolution following laser-based cleaning of a photocathode

Directory of Open Access Journals (Sweden)

F. Zhou

2012-09-01

Full Text Available Laser-based techniques have been widely used for cleaning metal photocathodes to increase quantum efficiency (QE. However, the impact of laser cleaning on cathode uniformity and thereby on electron beam quality are less understood. We are evaluating whether this technique can be applied to revive photocathodes used for high-brightness electron sources in advanced x-ray free-electron laser (FEL facilities, such as the Linac Coherent Light Source (LCLS at the SLAC National Accelerator Laboratory. The laser-based cleaning was applied to two separate areas of the current LCLS photocathode on July 4 and July 26, 2011, respectively. The QE was increased by 8–10 times upon the laser cleaning. Since the cleaning, routine operation has exhibited a slow evolution of the QE improvement and comparatively rapid improvement of transverse emittance, with a factor of 3 QE enhancement over five months, and a significant emittance improvement over the initial 2–3 weeks following the cleaning. Currently, the QE of the LCLS photocathode is holding constant at about 1.2×10^{-4}, with a normalized injector emittance of about 0.3  μm for a 150-pC bunch charge. With the proper procedures, the laser-cleaning technique appears to be a viable tool to revive the LCLS photocathode. We present observations and analyses for the QE and emittance evolution in time following the laser-based cleaning of the LCLS photocathode, and comparison to the previous studies, the measured thermal emittance versus the QE and comparison to the theoretical model.

Solid state high power amplifier for driving the SLC injector klystron

International Nuclear Information System (INIS)

Judkins, J.G.; Clendenin, J.E.; Schwarz, H.D.

1985-03-01

The SLC injector klystron rf drive is now provided by a recently developed solid-state amplifier. The high gain of the amplifier permits the use of a fast low-power electronic phase shifter. Thus the SLC computer control system can be used to shift the phase of the high-power rf rapidly during the fill time of the injector accelerator section. These rapid phase shifts are used to introduce a phase-energy relationship in the accelerated electron pulse in conjunction with the operation of the injector bunch compressor. The amplifier, the method of controlling the rf phase, and the operational characteristics of the system are described. 5 refs., 4 figs

A numerical study of emittance growths in RF guns

CERN Document Server

Masuda, K; Sobajima, M; Kitagaki, J; Ohnishi, M; Toku, H; Yoshikawa, K

1999-01-01

A beam with greatly reduced emittance is required for further improvements of FELs, in particular, for FELs of shorter wavelengths, and of narrower bandwidths. From this viewpoint, the BNL/SLAC/UCLA 1.6-cell S-band photocathode RF gun performance characteristics were calculated, first in order to evaluate what may contribute to the emittance growths in photocathode RF guns. We developed an RF gun to produce an electron beam with an extremely low emittance, by using a 2-D simulation code. It is found that, by optimizing the laser injection phase, the drive laser spot radius and the cavity shape around the laser spot, the beam emittance by the 1.6-cell RF gun can be greatly reduced to 2.1 pi mm mrad, from the previous 4.4 pi mm mrad of the original shape.

Design of a low emittance and high repetition rate S-band photoinjector

Science.gov (United States)

Han, Jang-Hui

2014-09-01

As an electron beam injector of X-ray free-electron lasers (FELs), photoinjectors have been developed for the past few decades. Such an injector starting with a photocathode RF gun provides high brightness beams and therefore it is being adopted as an injector of X-ray FELs. In this paper we show how to improve photoinjector performance in terms of emittance and repetition rates by means of injector components optimization, especially with the gun. Transverse emittance at the end of an injector is reduced by optimizing the gun design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the gun. It is discussed that a repetition rate of 1 kHz at a normal-conducting S-band photoinjector is feasible by adopting a coaxial RF coupler and improving cooling-water channels surrounding the gun.

ROLE OF DIAMOND SECONDARY EMITTERS IN HIGH BRIGHTNESS ELECTRON SOURCES

International Nuclear Information System (INIS)

2005-01-01

In this paper we explore the possibility of using diamond secondary emitter in a high average current electron injector to amplify the current from the photocathode and to isolate the cathode and the injector from each other to increase the life time of the cathode and preserve the performance of the injector. Secondary electron yield of 225 and current density of 0.8 a/cm 2 have been measured in the transmission mode from type 2 a natural diamond. Although the diamond will be heated during normal operation in the injector, calculations indicate that by cryogenically cooling the diamond, the temperature gradient along the diamond can be maintained within the acceptable range. The electron energy and temporal distributions are expected to be narrow from this device resulting in high brightness beams. Plans are underway to measure the SEY in emission mode, fabricate photocathode-diamond capsule and test diamond and capsule in superconducting RF injector

NLCTA injector experimental results

International Nuclear Information System (INIS)

Yeremian, A.D.; Adolphsen, C.; Miller, R.H.; Nantista, C.D.; Wang, J.W.

1997-04-01

The purpose of the Next Linear Collider Test Accelerator (NLCTA) at SLAC is to integrate the new technologies of X-band accelerator structures and RF systems for the Next Linear Collider (NLC), demonstrate multibunch beam-loading energy compensation and suppression of high-order deflecting modes, measure the transverse components of the accelerating field, and measure the dark current generated by RF field emission in the accelerator. For beam loading R and D, an average current of about 1 A in a 120 ns long bunch train is required. The initial commissioning of the NLCTA injector, as well as the rest of the accelerator have been progressing very well. The initial beam parameters are very close to the requirement and they expect that injector will meet the specified requirements by the end of this summer

Recent advances in high-brightness electron guns at AES

International Nuclear Information System (INIS)

Bluem, H.; Todd, A.M.M.; Cole, M.D.; Rathke, J.; Schultheiss, T.

2003-01-01

We describe a number of active Advanced Energy Systems projects pertaining to the development of advanced, high-brightness electron guns for various applications. These projects include a fully superconducting, CW RF gun, nearing test, that utilizes the niobium surface as the photocathode material. An integrated 100 mA, low emittance DC/SRF gun, ideal as an injector for ERL-type light sources and intended as the injector for a 100 kW FEL, is in late design stage. A parallel high-power, CW, normal-conducting L-band RF gun project has just begun. The early performance analysis for this gun also shows good promise as an injector for ERL-type light sources. Lastly, a fully axisymmetric RF gun, operating in X-band, is being studied as a source of extremely bright electron bunches

Pulsed laser deposition of yttrium photocathode suitable for use in radio-frequency guns

Science.gov (United States)

Lorusso, A.; Trovò, M.; Demidovich, A.; Cinquegrana, P.; Gontad, F.; Broitman, E.; Chiadroni, E.; Perrone, A.

2017-12-01

Yttrium (Y) thin film was grown by pulsed laser deposition (PLD) on a copper (Cu) polycrystalline substrate. Ex situ morphological and structural characterisations of the circular Y film of 1.2 µm thickness and 3 mm diameter have shown a very low droplet density on the film surface and a crystalline feature with a preferred orientation along the Y (100) plane. Moreover, Y thin film resulted in being very adherent to the Cu substrate and more scratch resistant than Cu bulk. A twin thin film was deposited also on a Cu backflange of a radio-frequency (RF) gun to test the suitability of the metallic thin film as photocathode. It was observed that the Y-coated photocathode was characterised by a quantum efficiency ( QE) higher than that of the Cu bulk photocathode even if the presence of space charge effects didn't allow deriving the absolute maximum value of QE of Y photocathode.

Studies on a laser driven photoemissive high-brightness electron source and novel photocathodes

International Nuclear Information System (INIS)

Geng Rongli; Song Jinhu; Yu Jin

1997-01-01

A laser driven photoemissive high-brightness electron source at Beijing University is reported. Through a DC accelerating gap of 100 kV voltage, the device is capable of delivering high-brightness electron beam of 35-100 ps pulse duration when irradiated with a mode-locked YAG laser. The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON. The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given. The proposed laser driven superconducting RF gun is also discussed

Photocathode

Energy Technology Data Exchange (ETDEWEB)

Opachich, Yekaterina; MacPhee, Andrew

2017-12-05

A photocathode designs that leverage the grazing incidence geometry yield improvements through the introduction of recessed structures, such as cones, pyramids, pillars or cavities to the photocathode substrate surface. Improvements in yield of up to 20 times have been shown to occur in grazing incidence geometry disclosed herein due to a larger path length of the X-ray photons which better matches the secondary electron escape depth within the photocathode material. A photocathode includes a substrate having a first side and a second side, the first side configured to receive x-ray energy and the second side opposing the first side. A structured surface is associated with the second side of the substrate such that the structured surface includes a plurality of recesses from the second side of the substrate into the substrate.

Advanced laser technologies for high-brightness photocathode electron gun

International Nuclear Information System (INIS)

Tomizawa, Hiromitsu

2012-01-01

A laser-excited photocathode RF gun is one of the most reliable high-brightness electron beam sources for XFELs. Several 3D laser shaping methods have been developed as ideal photocathode illumination sources at SPring-8 since 2001. To suppress the emittance growth caused by nonlinear space-charge forces, the 3D cylindrical UV-pulse was optimized spatially as a flattop and temporally as squarely stacked chirped pulses. This shaping system is a serial combination of a deformable mirror that adaptively shapes the spatial profile with a genetic algorithm and a UV-pulse stacker that consists of four birefringent α-BBO crystal rods for temporal shaping. Using this 3D-shaped pulse, a normalized emittance of 1.4 πmm mrad was obtained in 2006. Utilizing laser's Z-polarization, Schottky-effect-gated photocathode gun was proposed in 2006. The cathode work functions are reduced by a laser-induced Schottky effect. As a result of focusing a radially polarized laser pulse with a hollow lens in vacuum, the Z-field (Z-polarization) is generated at the cathode. (author)

Advanced Laser Technologies for High-brightness Photocathode Electron Gun

Science.gov (United States)

Tomizawa, Hiromitsu

A laser-excited photocathode RF gun is one of the most reliable high-brightness electron beam sources for XFELs. Several 3D laser shaping methods have been developed as ideal photocathode illumination sources at SPring-8 since 2001. To suppress the emittance growth caused by nonlinear space-charge forces, the 3D cylindrical UV-pulse was optimized spatially as a flattop and temporally as squarely stacked chirped pulses. This shaping system is a serial combination of a deformable mirror that adaptively shapes the spatial profile with a genetic algorithm and a UV-pulse stacker that consists of four birefringent α-BBO crystal rods for temporal shaping. Using this 3D-shaped pulse, a normalized emittance of 1.4 π mm mrad was obtained in 2006. Utilizing laser's Z-polarization, Schottky-effect-gated photocathode gun was proposed in 2006. The cathode work functions are reduced by a laser-induced Schottky effect. As a result of focusing a radially polarized laser pulse with a hollow lens in vacuum, the Z-field (Z-polarization) is generated at the cathode.

Design and construction of a pre-injector for the Iranian Light Source Facility

Directory of Open Access Journals (Sweden)

A Sadeghipanah

2015-09-01

Full Text Available Every synchrotron accelerator requires a pre-injector for primary injection of the electrons into the booster ring. The Iranian Light Source Facility (ILSF pre-injector is a 150 MeV S-band linear accelerator with a thermionic cathode RF gun. The design of the pre-injector lattice and its beam dynamics calculation results together with the design of RF gun, alpha magnet, quadrupole magnets and linear accelerator structures are described in this article. The measurement results of the RF gun prototype fabricated in Iran demonstrate a dimension error less than 20 μm and a surface roughness of less than 0.8 μm

High-brightness injector modeling

International Nuclear Information System (INIS)

Lewellen, J.W.

2004-01-01

There are many aspects to the successful conception, design, fabrication, and operation of high-brightness electron beam sources. Accurate and efficient modeling of the injector are critical to all phases of the process, from evaluating initial ideas to successful diagnosis of problems during routine operation. The basic modeling tasks will vary from design to design, according to the basic nature of the injector (dc, rf, hybrid, etc.), the type of cathode used (thermionic, photo, field emitter, etc.), and 'macro' factors such as average beam current and duty factor, as well as the usual list of desired beam properties. The injector designer must be at least aware of, if not proficient at addressing, the multitude of issues that arise from these considerations; and, as high-brightness injectors continue to move out of the laboratory, the number of such issues will continue to expand.

Performances of the Alpha-X RF gun on the PHIL accelerator at LAL

Science.gov (United States)

Vinatier, T.; Bruni, C.; Roux, R.; Brossard, J.; Chancé, S.; Cayla, J. N.; Chaumat, V.; Xu, G.; Monard, H.

2015-10-01

The Alpha-X RF-gun was designed to produce an ultra-short (laser-driven plasma accelerator with a short wavelength accelerating medium. It has been demonstrated on PHIL (Photo-Injector at LAL) that the coaxial RF coupling, chosen to preserve the gun field cylindrical symmetry, is perfectly understood and allows reaching the required peak accelerating field of 100 MV/m giving beam energy of 6.3 MeV. Moreover, a quite low beam rms relative energy spread of 0.15% at 3.8 MeV has been measured, completely agreeing with simulations. Dark current, quantum efficiencies and dephasing curves measurements have also been performed. They all show high values of the field enhancement factor β, which can be explained by the preparation of the photocathodes. Finally, measurements on the transverse phase-space have been carried out, with some limitations given by the difficult modelization of one of the PHIL solenoid magnets and by the enlargement of the beam transverse dimensions due to the use of YAG screens. These measurements give a normalized rms transverse emittance around 5π mm mrad, which does not fulfill the requirement for the Alpha-X project.

An Injector for the CLIC Test Facility (CTF3)

CERN Document Server

Braun, H; Rinolfi, Louis; Zhou, F; Mouton, B; Miller, R; Yeremian, A D

2000-01-01

The CLIC Test Facility (CTF3) is an intermediate step to demonstrate the technical feasibility of the key concepts of the new RF power source for CLIC. CTF3 will use electron beams with an energy range adjustable from 170 MeV (3.5 A) to 380 MeV (with low current). The injector is based on a thermionic gun followed by a classical bunching system embedded in a long solenoidal field. As an alternative, an RF photo-injector is also being studied. The beam dynamics studies on how to reach the stringent beam parameters at the exit of the injector are presented. Simulations performed with the EGUN code showed that a current of 7 A can be obtained with an emittance less than 10 mm.mrad at the gun exit. PARMELA results are presented and compared to the requested beam performance at the injector exit. Sub-Harmonic Bunchers (SHB) are foreseen, to switch the phase of the bunch trains by 180 degrees from even to odd RF buckets. Specific issues of the thermionic gun and of the SHB with fast phase switch are discussed.

An Injector for the CLIC Test Facility (CTF3)

International Nuclear Information System (INIS)

Miller, Roger H.

2001-01-01

The CLIC Test Facility (CTF3) is an intermediate step to demonstrate the technical feasibility of the key concepts of the new RF power source for CLIC. CTF3 will use electron beams with an energy range adjustable from 170 MeV (3.5 A) to 380 MeV (with low current). The injector is based on a thermionic gun followed by a classical bunching system embedded in a long solenoidal field. As an alternative, an RF photo-injector is also being studied. The beam dynamics studies on how to reach the stringent beam parameters at the exit of the injector are presented. Simulations performed with the EGUN code showed that a current of 7 A can be obtained with an emittance less than 10 mm.mrad at the gun exit. PARMELA results are presented and compared to the requested beam performance at the injector exit. Sub-Harmonic Bunchers (SHB) are foreseen, to switch the phase of the bunch trains by 180 degrees from even to odd RF buckets. Specific issues of the thermionic gun and of the SHB with fast phase switch are discussed

An injector for the CLIC test Facility (CTF3)

CERN Document Server

Braun, Hans-Heinrich; Rinolfi, L.; Zhou, F.; Mouton, B.; Miller, R.; Yeremian, D.

2008-01-01

The CLIC Test Facility (CTF3) is an intermediate step to demonstrate the technical feasibility of the key concepts of the new RF power source for CLIC. CTF3 will use electron beams with an energy range adjustable from 170 MeV (3.5 A) to 380 MeV (with low current). The injector is based on a thermionic gun followed by a classical bunching system embedded in a long solenoidal field. As an alternative, an RF photo-injector is also being studied. The beam dynamics studies on how to reach the stringent beam parameters at the exit of the injector are presented. Simulations performed with the EGUN code showed that a current of 7 A can be obtained with an emittance less than 10 mm.mrad at the gun exit. PARMELA results are presented and compared to the requested beam performance at the injector exit. Sub-Harmonic Bunchers (SHB) are foreseen, to switch the phase of the bunch trains by 180 degrees from even to odd RF buckets. Specific issues of the thermionic gun and of the SHB with fast phase switch are discussed.

Development of a superconducting radio frequency photoelectron injector

International Nuclear Information System (INIS)

Arnold, A.; Buettig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W.D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Moeller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

2007-01-01

A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden-Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 312 cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity

Masked Photocathode for Photoinjector

International Nuclear Information System (INIS)

Qiang, Ji

2010-01-01

In this research note, we propose a scheme to insert a photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto the electrode, a masked electrode with small hole is used to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material very simple by rotating the photocathode behind the mask into the hole. This will significantly increase the usage lifetime of a photocathode. Furthermore, this also helps reduce the dark current or secondary electron emission from the photocathode. The hole on the mask also provides a transverse cut-off to the Gaussian laser profile which can be beneficial from the beam dynamics point of view.

Heat load of a P-doped GaAs photocathode in SRF electron gun

International Nuclear Information System (INIS)

Wang, E.; Ben-Zvi, I.; Kewisch, J.; Burrill, A.; Rao, T.; Wu, Q.; Jain, A.; Gupta, R.; Holmes, D.

2010-01-01

Many efforts were made over the last decades to develop a better polarized electron source for the high energy physics. Several laboratories operate DC guns with the Gallium-Arsenide photo-cathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved using a Superconducting RF electron gun, which delivers beams of higher brightness than DC guns does, because the field gradient at the cathode is higher. SRF guns with metal cathodes and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since the cathode will be normal conducting, the problem about the heat load stemming from the cathode arises. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and the verification by measuring the quality factor of the gun with and without cathode.

Progress on Using NEA Cathodes in an RF Gun

CERN Document Server

Fliller, Raymond P; Blüm, Hans; Edwards, Helen; Hüning, Markus; Schultheiss, Tom; Sinclair, Charles K

2005-01-01

RF guns have proven useful in multiple accelerator applications, and are an attractive electron source for the ILC. Using a NEA GaAs photocathode in such a gun allows for the production of polarized electron beams. However the lifetime of a NEA cathode in this environment is reduced by ion and electron bombardment and residual gas oxidation. We report progress made with studies to produce a RF gun using a NEA GaAs photocathode to produce polarized electron beams. Attempts to reduce the residual gas pressure in the gun are discussed. Initial measurements of ion flux through the cathode port are compared with simulations of ion bombardment. Future directions are also discussed.

Quantum efficiency and thermal emittance of metal photocathodes

Directory of Open Access Journals (Sweden)

David H. Dowell

2009-07-01

Full Text Available Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths with major advances occurring since the invention of the photocathode gun and the realization of emittance compensation. These state-of-the-art electron beams are now becoming limited by the intrinsic thermal emittance of the cathode. In both dc and rf photocathode guns details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance for metal cathodes using the Fermi-Dirac model for the electron distribution. We use a consistent theory to derive the quantum efficiency and thermal emittance, and compare our results to those of others.

Steady state neutral beam injector

International Nuclear Information System (INIS)

Mattoo, S.K.; Bandyopadhyay, M.; Baruah, U.K.; Bisai, N.; Chakbraborty, A.K.; Chakrapani, Ch.; Jana, M.R.; Bajpai, M.; Jaykumar, P.K.; Patel, D.; Patel, G.; Patel, P.J.; Prahlad, V.; Rao, N.V.M.; Rotti, C.; Singh, N.P.; Sridhar, B.

2000-01-01

Learning from operational reliability of neutral beam injectors in particular and various heating schemes including RF in general on TFTR, JET, JT-60, it has become clear that neutral beam injectors may find a greater role assigned to them for maintaining the plasma in steady state devices under construction. Many technological solutions, integrated in the present day generation of injectors have given rise to capability of producing multimegawatt power at many tens of kV. They have already operated for integrated time >10 5 S without deterioration in the performance. However, a new generation of injectors for steady state devices have to address to some basic issues. They stem from material erosion under particle bombardment, heat transfer > 10 MW/m 2 , frequent regeneration of cryopanels, inertial power supplies, data acquisition and control of large volume of data. Some of these engineering issues have been addressed to in the proposed neutral beam injector for SST-1 at our institute; the remaining shall have to wait for the inputs of the database generated from the actual experience with steady state injectors. (author)

Longitudinal beam instabilities in a double RF system

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00229208; Gazis, Evangelos

Operation with a double RF system is essential for many accelerators in order to increase beam stability, to change the bunch shape or to perform various RF manipulations. This is also the case for the operation of the CERN SPS as the LHC proton injector, where in addition to the main RF system, a fourth harmonic RF system is used in bunch shortening mode in order to increase the synchrotron frequency spread inside the bunch and thus to enhance Landau damping of the collective instabilities. In fact the double RF system operation in the SPS is one of the essential means, together with the controlled longitudinal emittance blow-up to significantly increase the longitudinal instability thresholds (single and multi-bunch) and deliver a good quality beam for the LHC. However, for the HiLumi-LHC (HL-LHC) and LHC injector upgrade (LIU) projects higher beam intensities are required. After all upgrades are in place, the main performance limitations of the LHC injector complex are beam instabilities and high intensity...

The Quantum Efficiency and Thermal Emittance of Metal Photocathodes

International Nuclear Information System (INIS)

Dowell, D.

2009-01-01

Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths, with the principle improvements occurring since the invention of the photocathode gun. The state-of-the-art normalized emittance electron beams are now becoming limited by the thermal emittance of the cathode. In both DC and RF photocathode guns, details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance of metal cathodes using the Fermi-Dirac model for the electron distribution. We derive the thermal emittance and its relationship to the quantum efficiency, and compare our results to those of others

A new two-step tuning procedure for a photocathode gun

International Nuclear Information System (INIS)

Lal, Shankar; Pant, K.K.; Krishnagopal, S.

2008-01-01

An important aspect of the development of multi-cell RF accelerating structures is tuning the resonant frequency f of the operating mode, field balance e b , and waveguide to cavity coupling coefficient β to the desired values. Earlier theoretical analyses have not been able to predict all three parameters simultaneously for a coupled-cavity system. We have developed a generalized circuit analysis to predict f, e b , and β of a coupled structure, based on the RF properties of the individual, uncoupled, cells. This has been used to develop a simplified two-step tuning procedure to tune a BNL/SLAC/UCLA type 1.6 cell S-band photocathode gun by varying RF properties of individual half and full cells, which are easily measurable. This procedure has been validated by tuning two true-to-scale prototypes made of aluminum and ETP copper to the desired values of the RF parameters

An introduction to photo-injector design

International Nuclear Information System (INIS)

Travier, C.

1993-07-01

A quick overview is given of the RF gun basic theory for photo-injectors and of the presently achievable technical parameters thus providing some guidelines to help the designer in his choices. Simple scaling laws and formulas for both beam dynamics and technical parameters are proposed and compared to corresponding values for existing photo-injectors. Various sophisticated schemes used to improve the performances beyond those given by a straightforward approach are reviewed. (author) 65 refs., 11 figs., 3 tabs

Discussion of high brightness rf linear accelerators

International Nuclear Information System (INIS)

Jameson, R.A.

1987-01-01

The fundamental aspects of high-brightness rf linacs are outlined, showing the breadth and complexity of the technology and indicating that synergism with advancements in other areas is important. Areas of technology reviewed include ion sources, injectors, rf accelerator structures, beam dynamics, rf power, and automatic control

The Development of the Linac Coherent Light Source RF Gun

International Nuclear Information System (INIS)

Dowell, D

2008-01-01

The Linac Coherent Light Source (LCLS) is the first x-ray laser user facility based upon a free electron laser (FEL) requiring extraordinary beam quality to saturate at 1.5 angstroms within a 100 meter undulator.[1] This new type of light source is using the last kilometer of the three kilometer linac at SLAC to accelerate the beam to an energy as high as 13.6 GeV and required a new electron gun and injector to produce a very bright beam for acceleration. At the outset of the project it was recognized that existing RF guns had the potential to produce the desired beam but none had demonstrated it. Therefore a new RF gun or at least the modification of an existing gun was necessary. The parameters listed in Table 1 illustrate the unique characteristics of LCLS which drive the requirements for the electron gun as given in Table 2. The gun beam quality needs to accommodate emittance growth as the beam is travels through approximately one kilometer of linac and two bunch compressors before reaching the undulator. These beam requirements were demonstrated during the recent commissioning runs of the LCLS injector and linac [2] due to the successful design, fabrication, testing and operation of the LCLS gun. The goal of this paper is to relate the technical background of how the gun was able to achieve and in some cases exceed these requirements by understanding and correcting the deficiencies of the prototype s-band RF photocathode gun, the BNL/SLAC/UCLA Gun III. This paper begins with a brief history and technical description of Gun III and the Gun Test Facility (GTF) at SLAC, and studies of the gun's RF and emittance compensation solenoid. The work at the GTF identified the gun and solenoid deficiencies, and helped to define the specifications for the LCLS gun. Section 1.1.5 describes the modeling used to compute and correct the gun RF fields and Section 1.1.6 describes the use of these fields in the electron beam simulations. The magnetic design and measurements of

Development of a Laser Driven Photocathode Injector and Femtosecond Scale Laser Electron Synchronization for Next Generation Light Sources

CERN Document Server

Le Sage, G P; Ditmire, T R; Rosenzweig, J

2000-01-01

A high brightness photoinjector has been developed at LLNL. This injector combined with the 100 TW FALCON laser and the LLNL 100 MeV S-Band RF linac will enable development of a high brightness, femtosecond-scale, tunable, hard x-ray probe for time-resolved material measurements, based on Thomson scattering. Short pulse x-rays enable time-resolved characterization of shock dynamics, and examination of materials under extremes of pressure and temperature. Examples include Equation of State characterization on high-density materials, Crystal disorganization and re-growth in shocked and heated materials, and measurement of short time scale phase transition phenomena. Single shot evaluation, requiring high peak flux, is important for complex experiments such as probing of laser shocked actinides. A low emittance electron beam synchronized with femtosecond accuracy to an intense laser will revolutionize x-ray dynamics studies of materials. This project will lead development of ultrafast x-ray dynamics research on ...

Beam-Based Procedures for RF Guns

CERN Document Server

Krasilnikov, Mikhail; Grabosch, H J; Hartrott, Michael; Hui Han, Jang; Miltchev, Velizar; Oppelt, Anne; Petrosyan, Bagrat; Staykov, Lazar; Stephan, Frank

2005-01-01

A wide range of rf photo injector parameters has to be optimized in order to achieve an electron source performance as required for linac based high gain FELs. Some of the machine parameters can not be precisely controlled by direct measurements, whereas the tolerance on them is extremely tight. Therefore, this should be met with beam-based techniques. Procedures for beam-based alignment (BBA) of the laser on the photo cathode as well as solenoid alignment have been developed. They were applied at the Photo Injector Test facility at DESY Zeuthen (PITZ) and at the photo injector of the VUV-FEL at DESY Hamburg. A field balance of the accelerating mode in the 1 ½ cell gun cavity is one of the key beam dynamics issues of the rf gun. Since no direct field measurement in the half and full cell of the cavity is available for the PITZ gun, a beam-based technique to determine the field balance has been proposed. A beam-based rf phase monitoring procedure has been developed as well.

Experimental study on the production of high density electron bunches from a GaAs photocathode

International Nuclear Information System (INIS)

Calabrese, R.; Masoli, F.; Gong, J.M.; Guidi, V.; Tecchio, L.

1991-01-01

In order to obtain a high charge, low emittance electron source, useful for FEL electron injector and for e + e - collider experiments, we performed a test experiment on a gallium arsenide photocathode, activated by negative electron affinity technique and illuminated with a 10 ns long laser pulse of 532 nm wavelength. We measured a maximum charge delivered, at relatively low potentials, of about 18 nC/bunch. The mean lifetime is greater than 60 h. (orig.)

Design and development of low level S-Band RF control system for IRFEL injector LINAC

International Nuclear Information System (INIS)

Mohania, Praveen; Mahawar, Ashish; Singh, Adarsh Pratap; Namdeo, Rajkumar; Baxy, Deodatta; Shrivastava, Purushottam

2015-01-01

A low level RF system has been designed and developed for phase and amplitude stabilization of S- Band microwave power being fed to fundamental buncher cavity and the injector LINAC structure of the Infra Red Free Electron Laser being developed at RRCAT Indore. The system uses analog phase shifters and voltage variable attenuators to control the phase and amplitude respectively, the control voltages for phase shifters and attenuators are generated using a 12 Bit ADC and is software controlled. The system has a slow feedback to correct phase and amplitude drifts occurring due to thermal variations and a fast feed forward mechanism to vary amplitude and phase of the output pulse to compensate beam loading and to shape the klystron output power. The present paper describes the design aspects of the LLRF system. (author)

Summary, Working Group 1: Electron guns and injector designs

International Nuclear Information System (INIS)

Ben-Zvi, I.; Bazarov, I.V.

2006-01-01

We summarize the proceedings of Working Group 1 of the 2005 Energy Recovery Linac (ERL) Workshop. The subject of this working group, the electron gun and injector design, is arguably the most critical part of the ERL as it determines the ultimate performance of this type of accelerators. Working Group 1 dealt with a variety of subjects: The technology of DC, normal-conducting RF and superconducting RF guns; beam dynamics in the gun and injector; the cathode and laser package; modeling and computational issues; magnetized beams and polarization. A short overview of these issues covered in the Working Group is presented in this paper

A review of radio-frequency photocathode electron sources

International Nuclear Information System (INIS)

Stovall, J.

1992-01-01

A review of this topic at the last conference in this series reported considerable progress in R and D programs aimed at producing high-current low-emittance electron beams using photocathode rf guns. At present at least 20 such projects are under way world wide and at least 6 photoinjectors are presently in operation. This paper reviews some of the choices that must be made in optimizing the design of the accelerating structure for a photoinjector based on the current state of knowledge. (Author) 5 refs., 9 figs., 3 tabs

New features of the MAX IV thermionic pre-injector

Energy Technology Data Exchange (ETDEWEB)

Andersson, J., E-mail: joel.andersson@maxiv.lu.se; Olsson, D., E-mail: david.olsson@maxiv.lu.se; Curbis, F.; Malmgren, L.; Werin, S.

2017-05-21

The MAX IV facility in Lund, Sweden consists of two storage rings for production of synchrotron radiation. The smaller 1.5 GeV ring is presently under construction, while the larger 3 GeV ring is being commissioned. Both rings will be operating with top-up injections from a full-energy injector. During injection, the electron beam is first delivered to the main injector from a thermionic pre-injector which consists of a thermionic RF gun, a chopper system, and an energy filter. In order to reduce losses of high-energy electrons along the injector and in the rings, the electron beam provided by the thermionic pre-injector should have the correct time structure and energy distribution. In this paper, the design of the MAX IV thermionic pre-injector with all its sub components is presented. The electron beam delivered by the pre-injector and its dependence on parameters such as optics, cathode temperature, and RF power are studied. Measurements are here compared with simulation results obtained by particle tracking and electromagnetic codes. The chopper system is described in detail, and different driving schemes that optimize the injection efficiency for the two storage rings are investigated. During operation, it was discovered that the structure of the beam delivered by the gun is affected by mode beating between the accelerating and a low-order mode. This mode beating is also studied in detail. Finally, initial measurements of the electron beam delivered to the 3 GeV ring during commissioning are presented.

Photocathodes for High Repetition Rate Light Sources

Energy Technology Data Exchange (ETDEWEB)

Ben-Zvi, Ilan [Stony Brook Univ., NY (United States). Dept. of Physics and Astronomy. Center for Accelerator Science and Education

2014-04-20

This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). Below details the Principal Investigators and contact information. Each PI submits separately for a budget through his corresponding institute. The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus is on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-­conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-­antimonide cathodes (BNL – LBNL) b) Development and testing of a diamond amplifier for photocathodes (SBU -­ BNL) c) Tests of both cathodes in superconducting RF photoguns (SBU) and copper RF photoguns (LBNL) Our work made extensive use of synchrotron radiation materials science techniques, such as powder-­ and single-­crystal diffraction, x-­ray fluorescence, EXAFS and variable energy XPS. BNL and LBNL have many complementary facilities at the two light sources associated with these laboratories (NSLS and ALS, respectively); use of these will be a major thrust of our program and bring our understanding of these complex materials to a new level. In addition, CHESS at Cornell will be used to continue seamlessly throughout the NSLS dark period and

RF guns: a review

International Nuclear Information System (INIS)

Travier, C.

1990-06-01

Free Electron Lasers and future linear colliders require very bright electron beams. Conventional injectors made of DC guns and RF bunchers have intrinsic limitations. The recently proposed RF guns have already proven their capability to produce bright beams. The necessary effort to improve further these performances and to gain reliability is now undertaken by many laboratories. More than twenty RF gun projects both thermionic and laser-driven are reviewed. Their specific characteristics are outlined and their nominal performances are given

Feasibility Study for the CERN "CLIC" Photo-Injector Laser System

CERN Document Server

Ross, I N

2000-01-01

This study is designed to contribute to the development of the Cern Linear Collider (CLIC). One route to the generation of the required electron injection into this system is through the use of photo-cathodes illuminated with a suitably designed laser system. The requirements of the accelerator and photo-cathodes have led to a specification for the laser system given in Table 1. Because CLIC will not be built directly but in stages, notably via CLIC Test Facilities (CTF), this table also includes the specification for a photo-injector laser system for CTF3 which will be required before the final system for CLIC. Although there are significant differences between these two specifications it will be necessary to design the CTF3 system such that it can be easily upgraded to the system for CLIC and will be able to check all the critical issues necessary for CLIC.

A hot-spare injector for the APS linac

International Nuclear Information System (INIS)

Lewellen, J. W.

1999-01-01

Last year a second-generation SSRL-type thermionic cathode rf gun was installed in the Advanced Photon Source (APS) linac. This gun (referred to as ''gun2'') has been successfully commissioned and now serves as the main injector for the APS linac, essentially replacing the Koontz-type DC gun. To help ensure injector availability, particularly with the advent of top-up mode operation at the APS, a second thermionic-cathode rf gun will be installed in the APS linac to act as a hot-spare beam source. The hot-spare installation includes several unique design features, including a deep-orbit Panofsky-style alpha magnet. Details of the hot-spare beamline design and projected performance are presented, along with some plans for future performance upgrades

Beam dynamics simulation of injector for high power CW electron linac in PNC

International Nuclear Information System (INIS)

Nomura, Masahiro; Yamazaki, Yoshio; Toyama, Shin-ichi

1994-01-01

The injector consists of a 200 kV DC gun, a RF chopper, a chopper slit, a prebuncher and a buncher. Solenoid coils covered from the exit of gun to accelerating tube 1 except between the RF chopper and chopper slit. Beam trajectories are simulated by PARMELA in order to design the injector. In this report, two simulation results are shown. One is for a beam trajectory from gun to solenoid coils. There is thick concrete wall between gun to RF chopper. Low energy electrons are transported through long solenoid coil area. The other is for a chopper part. The novel chopper system is designed to reduce the emittance growth. (author)

A Masked Photocathode in a Photoinjector

OpenAIRE

Qiang, Ji

2011-01-01

In this paper, we propose a masked photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto an electrode, an electrode with small hole is used as a mask to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material easy by rotating the photocathode behind the electrode into the hole. Furthermore, this helps reduce the dark current or seconda...

Reducing Energy Degradation Due to Back-bombardment Effect with Modulated RF Input in S-band Thermionic RF Gun

Science.gov (United States)

Kii, Toshiteru; Nakai, Yoko; Fukui, Toshio; Zen, Heishun; Kusukame, Kohichi; Okawachi, Norihito; Nakano, Masatsugu; Masuda, Kai; Ohgaki, Hideaki; Yoshikawa, Kiyoshi; Yamazaki, Tetsuo

2007-01-01

Energy degradation due to back-bombardment effect is quite serious to produce high-brightness electron beam with long macro-pulse with thermionic rf gun. To avoid the back-bombardment problem, a laser photo cathode is used at many FEL facilities, but usually it costs high and not easy to operate. Thus we have studied long pulse operation of the rf gun with thermionic cathode, which is inexpensive and easy to operate compared to the photocathode rf gun. In this work, to reduce the energy degradation, we controlled input rf power amplitude by controlling pulse forming network of the power modulator for klystron. We have successfully increased the pulse duration up to 4 μs by increasing the rf power from 7.8 MW to 8.5 MW during the macro pulse.

The design of a 3 GHz thermionic RF-gun and energy filter for MAX-lab

CERN Document Server

Anderberg, B; Demirkan, M; Eriksson, M; Malmgren, L; Werin, S

2002-01-01

A new pre-injector has been designed for the MAX-laboratory. It consists of an RF-gun and a magnetic energy filter. The newly designed RF-gun geometry will be operated at 3 GHz in the thermionic mode using a BaO cathode. The pre-injector will provide a 2.3 MeV electron beam in 3 ps micro pulses to a new injector system currently under construction.

Design, Fabrication and High Power RF Test of a C-band Accelerating Structure for Feasibility Study of the SPARC photo-injector energy upgrade

CERN Document Server

Alesini, D.; Di Pirro, G.; Di Raddo, R.; Ferrario, M.; Gallo, A.; Lollo, V.; Marcellini, F.; Higo, T.; Kakihara, K.; Matsumoto, S.; Campogiani, G.; Mostacci, A.; Palumbo, L.; Persichelli, S.; Spizzo, V.; Verdú-Andrés, S.

2011-01-01

The energy upgrade of the SPARC photo-injector from 160 to more than 260 MeV will be done by replacing a low gradient 3m S-Band structure with two 1.4m high gradient C-band structures. The structures are travelling wave, constant impedance sections, have symmetric waveguide input couplers and have been optimized to work with a SLED RF input pulse. A prototype with a reduced number of cells has been fabricated and tested at high power in KEK (Japan) giving very good performances in terms of breakdown rates (10^6 bpp/m) at high accelerating gradient (>50 MV/m). The paper illustrates the design criteria of the structures, the fabrication procedure and the high power RF test results.

Production and Studies of Photocathodes for High Intensity Electron Beams

CERN Document Server

Chevallay, E; Legros, P; Suberlucq, Guy; Trautner, H

2000-01-01

For short, high-intensity electron bunches, alkali-tellurides have proved to be a reliable photo-cathode material. Measurements of lifetimes in an rf gun of the CLIC Test Facility II at field strengths greater than 100 MV/m are presented. Before and after using them in this gun, the spectral response of the CS-Te and Rb-Te cathodes were determined with the help of an optical parametric oscillator. The behaviour of both materials can be described by Spicer's 3-step model. Whereas during the use the threshold for photo-emission in Cs-Te was shifted to higher proton energies, that of Rb-Te did not change. Our latest investigations on the stoichiometric ratio of the components are shown. The preparation of the photo-cathodes was monitored with 320 nm wavelength light , with the aim of improving the measurement sensitivity. The latest results on the protection of Cs-Te cathode surfaces with CsBr against pollution are summarized. New investigations on high mean current production are presented.,

Status of 174 MHz RF system for BEP

International Nuclear Information System (INIS)

Biryuchevsky, Yu.A.; Gorniker, E.I.; Kendjebulatov, E.K.; Krutikhin, S.A.; Kurkin, G.Ya.; Petrov, V.M.; Pilan, A.M.

2012-01-01

The new RF system for the BEP storage ring (which is an injector of VEPP-2000 accelerating complex) will increase the particles energy in the BEP from 0.9 to 1 GeV. RF system operates at a frequency of 174 MHz and consists of an accelerating cavity, RF power generator and control system.

rf beam-current, -phase, and -position monitors

International Nuclear Information System (INIS)

Young, L.

1984-01-01

A prototype rf beam monitor has been tested on the Racetrack Microtron's (RTM) 100 kV injector beam line at the National Bureau of Standards (NBS). This beam monitor is capable of measuring the current, the relative phase, and the position of the beam. The beam is bunched at 2380 MHz for acceleration by the linac in the injector beam line. This train of beam bunches passing through the beam monitor cavities excites the cavities at this resonance frequency of 2380 MHz. Probes in the cavities couple some of the beam-excited rf power out of the cavities. This rf power can be amplified if necessary and then analyzed by a double balanced mixer (DBM). The DBM can also be used as a phase detector. The effective shunt impedance of the cavities was measured with the CW beam. For the position monitor cavity, the shunt impedance is proportional to the displacement from the axis. The measured response of the prototype rf beam current monitor setup is a linear function of beam current. Response of the rf beam-position monitor is also shown

Development of Adaptive Feedback Control System of Both Spatial and Temporal Beam Shaping for UV-Laser Light Source for RF Gun

CERN Document Server

Tomizawa, H; Dewa, H; Hanaki, H; Kobayashi, T; Mizuno, A; Suzuki, S; Taniuchi, T; Yanagida, K

2004-01-01

The ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from a photo-cathode rf gun. We have been developing highly qualified UV-laser pulse as a light source of the rf gun for an injector candidate of future light sources. The gun cavity is a single-cell pillbox, and the copper inner wall is used as a photo cathode. The electron beam was accelerated up to 4.1 MeV at the maximum electric field on the cathode surface of 175 MV/m. For emittance compensation, two solenoid coils were used. As the first test run, with a microlens array as a simple spatial shaper, we obtained a minimum emittance value of 2 π·mm·mrad with a beam energy of 3.1 MeV, holding its charge to 0.1 nC/bunch. In the next test run, we prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. We applied the both adaptive optics to automatically shape the bot...

Engineering Design and Fabrication of an Ampere-Class Superconducting Photocathode Electron Gun

International Nuclear Information System (INIS)

Ben-Zvi, I.

2008-01-01

Over the past three years, Advanced Energy Systems and Brookhaven National Laboratory (BNL) have been collaborating on the design of an Ampere- class superconducting photocathode electron gun. BNL performed the physics design of the overall system and RF cavity under prior programs. Advanced Energy Systems (AES) is currently responsible for the engineering design and fabrication of the electron gun under contract to BNL. We will report on the engineering design and fabrication status of the superconducting photocathode electron gun. The overall configuration of the cryomodule will be reviewed. The layout of the hermitic string, space frame, shielding package, and cold mass will be discussed. The engineering design of the gun cavity and removable cathode will be presented in detail and areas of technical risk will be highlighted. Finally, the fabrication sequence and fabrication status of the gun cavity will be discussed

Carbon nanotube based photocathodes

International Nuclear Information System (INIS)

Hudanski, Ludovic; Minoux, Eric; Schnell, Jean-Philippe; Xavier, Stephane; Pribat, Didier; Legagneux, Pierre; Gangloff, Laurent; Teo, Kenneth B K; Robertson, John; Milne, William I

2008-01-01

This paper describes a novel photocathode which is an array of vertically aligned multi-walled carbon nanotubes (MWCNTs), each MWCNT being associated with one p-i-n photodiode. Unlike conventional photocathodes, the functions of photon-electron conversion and subsequent electron emission are physically separated. Photon-electron conversion is achieved with p-i-n photodiodes and the electron emission occurs from the MWCNTs. The current modulation is highly efficient as it uses an optically controlled reconfiguration of the electric field at the MWCNT locations. Such devices are compatible with high frequency and very large bandwidth operation and could lead to their application in compact, light and efficient microwave amplifiers for satellite telecommunication. To demonstrate this new photocathode concept, we have fabricated the first carbon nanotube based photocathode using silicon p-i-n photodiodes and MWCNT bunches. Using a green laser, this photocathode delivers 0.5 mA with an internal quantum efficiency of 10% and an I ON /I OFF ratio of 30

Multi-cell superconducting structures for high energy e+ e- colliders and free electron laser linacs

CERN Document Server

Sekutowicz, J

2008-01-01

This volume, which is the first in the EuCARD Editorial Series on “Accelerator Science and Technology”, is closely combined with the most advanced particle accelerators – based on Superconducting Radio Frequency (SRF) technology. In general, SRF research includes following areas: high gradient cavities, cavity prototyping, thin film technologies, large grain and mono-crystalline niobium and niobium alloys, quenching effects in superconducting cavities, SRF injectors, photo-cathodes, beam dynamics, quality of electron beams, cryogenics, high power RF sources, low level RF controls, tuners, RF power coupling to cavities, RF test infrastructures, etc. The monograph focuses on TESLA structures used in FLASH machine and planned for XFEL and ILC experiments.

Versatile rf controller

International Nuclear Information System (INIS)

Howard, D.

1985-05-01

The low level rf system developed for the new Bevatron local injector provides precise control and regulation of the rf phase and amplitude for three 200 MHz linac cavities. The main features of the system are: extensive use of inexpensive, off-the-shelf components, ease of maintenance, and adaptability to a wide range of operation frequencies. The system utilizes separate function, easily removed rf printed circuit cards interconnected via the edge connectors. Control and monitoring are available both locally and through the computer. This paper will describe these features as well as the few component changes that would be required to adapt the techniques to other operating frequencies. 2 refs

DARHT-II Injector Transients and the Ferrite Damper

Energy Technology Data Exchange (ETDEWEB)

Waldron, Will; Reginato, Lou; Chow, Ken; Houck, Tim; Henestroza, Enrique; Yu, Simon; Kang, Michael; Briggs, Richard

2006-08-04

This report summarizes the transient response of the DARHT-II Injector and the design of the ferrite damper. Initial commissioning of the injector revealed a rise time excited 7.8 MHz oscillation on the diode voltage and stalk current leading to a 7.8 MHz modulation of the beam current, position, and energy. Commissioning also revealed that the use of the crowbar to decrease the voltage fall time excited a spectrum of radio frequency modes which caused concern that there might be significant transient RF electric field stresses imposed on the high voltage column insulators. Based on the experience of damping the induction cell RF modes with ferrite, the concept of a ferrite damper was developed to address the crowbar-excited oscillations as well as the rise-time-excited 7.8 MHz oscillations. After the Project decided to discontinue the use of the crowbar, further development of the concept focused exclusively on damping the oscillations excited by the rise time. The design was completed and the ferrite damper was installed in the DARHT-II Injector in February 2006. The organization of this report is as follows. The suite of injector diagnostics are described in Section 2. The data and modeling of the injector transients excited on the rise-time and also by the crowbar are discussed in Section 3; the objective is a concise summary of the present state of understanding. The design of the ferrite damper, and the small scale circuit simulations used to evaluate the ferrite material options and select the key design parameters like the cross sectional area and the optimum gap width, are presented in Section 4. The details of the mechanical design and the installation of the ferrite damper are covered in Section 5. A brief summary of the performance of the ferrite damper following its installation in the injector is presented in Section 6.

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.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

Directory of Open Access Journals (Sweden)

M. Shevelev

2017-10-01

Full Text Available The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

Science.gov (United States)

Shevelev, M.; Aryshev, A.; Terunuma, N.; Urakawa, J.

2017-10-01

The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Rf System for the NLCTA

International Nuclear Information System (INIS)

Wang, J.W.; Adolphsen, C.; Eichner, J.; Fuller, R.W.; Gold, S.L.; Hanna, S.M.; Hoag, H.A.; Holmes, S.G.; Koontz, R.F.; Lavine, Theodore L.; Loewen, R.J.; Miller, R.H.; Nantista, C.D.; Pope, R.; Rifkin, J.; Ruth, R.D.; Tantawi, S.G.; Vlieks, A.E.; Wilson, Z.; Yeremian, A.

2011-01-01

This paper describes an X-Band RF system for the Next Linear Collider Test Accelerator. The RF system consists of a 90 MeV injector and a 540 MeV linac. The main components of the injector are two low-Q single-cavity prebunchers and two 0.9-m-long detuned accelerator sections. The linac system consists of six 1.8-m-long detuned and damped detuned accelerator sections powered in pairs. The rf power generation, compression, delivery, distribution and measurement systems consist of klystrons, SLEDII energy compression systems, rectangular waveguides, magic-T's, and directional couplers. The phase and amplitude for each prebuncher is adjusted via a magic-T type phase shifter/attenuator. Correct phasing between the two 0.9 m accelerator sections is obtained by properly aligning the sections and adjusting two squeeze type phase shifters. Bunch phase and bunch length can be monitored with special microwave cavities and measurement systems. The design, fabrication, microwave measurement, calibration, and operation of the sub-systems and their components are briefly presented.

Atlas positive-ion injector project

Energy Technology Data Exchange (ETDEWEB)

Pardo, R C; Bollinger, L M; Shepard, K W

1987-04-01

The goal of the Argonne Positive Ion Injector project is to replace the ATLAS tandem injector with a facility which will increase the beam currents presently available by a factor of 100 and to make beams of essentially all elements including uranium available at ATLAS. The beam quality expected from the facility will be at least as good as that of the tandem based ATLAS. The project combines two relatively new technologies - the electron cyclotron resonance ion source, which provides ions of high charge states at microampere currents, and rf superconductivity which has been shown to be capable of generating accelerating fields as high as 10 MV/m resulting in an essentially new method of acceleration for low-energy heavy ions.

Development of a Polarized Electron Gun Based on an S-Band PWT Photoinjector

CERN Document Server

Clendenin, J E; Yu, D; Newsham, D; Luo, Y; Smirnov, A

2003-01-01

An RF polarized electron gun utilizing the unique features of an integrated, plane-wave-transformer (PWT) photoelectron injector [1] is being developed by DULY Research Inc. in collaboration with SLAC. Modifications to a DULY S-band device [2] include: a re-design of the photocathode/RF backplane interface to accommodate a GaAs cathode; change in the design of the vacuum ports to provide 10-11 Torr operation; the inclusion of a load-lock photocathode replacement system to allow for reactivation and cessation of the GaAs photocathode in a vacuum; and alteration of the magnet field coils to make room for the load-lock. The use of a stainless steel outer tank and cooling rods without copper plating may also provide better vacuum performance at the expense of diminished Q factor. The effectiveness of both the standard cooling rods and synthetic diamond heat sinks for disk cooling is investigated for future linear collider applications operating at a rep rate of 180 Hz and a bunch charge of 2 nC.

CsI and some new photocathodes

International Nuclear Information System (INIS)

Anderson, D.F.; Kwan, S.; Peskov, V.

1993-06-01

A discussion of the possible sources of discrepancies in the measurements of the quantum efficiency of CsI photocathodes is presented. We propose that the major causes for disagreements in QE are due to the QE dependence on the current density extracted from the photocathode, on the electric field, and on the temperature of the photocathode. Preliminary results on TMAE enhanced GaAs and Si, plus TMAE protected CsTe and SbCs photocathodes, operated in gas, are also presented

Beam dynamics studies of the photo-injector in low-charge operation mode for the ERL test facility at IHEP

International Nuclear Information System (INIS)

Jiao Yi; Xiao Ouzheng

2014-01-01

The energy recovery linac test facility (ERL-TF), which is a compact ERL-FEL (free electron laser) two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector that started with a photocathode direct-current gun has been designed. In this paper, optimization of the injector beam dynamics in low-charge operation mode is performed with iterative scans using Impact-T. In addition, the dependencies between the optimized beam quality and the initial offset at cathode and element parameters are investigated. The tolerance of alignment and rotation errors is also analyzed. (authors)

Performances of the Alpha-X RF gun on the PHIL accelerator at LAL

Energy Technology Data Exchange (ETDEWEB)

Vinatier, T., E-mail: vinatier@lal.in2p3.fr [Laboratoire de l' Accélérateur Linéaire (LAL), Université Paris Sud, UMR 8607, bâtiment 200, 91898 Orsay Cedex (France); Bruni, C. [Laboratoire de l' Accélérateur Linéaire (LAL), Université Paris Sud, UMR 8607, bâtiment 200, 91898 Orsay Cedex (France); Roux, R. [Laboratoire de l' Accélérateur Linéaire (LAL), Université Paris Sud, UMR 8607, bâtiment 200, 91898 Orsay Cedex (France); Laboratoire d' Etude des Eléments Légers, CEA IRAMIS, bâtiment 524, 91191 Gif sur Yvette Cedex (France); Brossard, J. [Laboratoire de l' Accélérateur Linéaire (LAL), Université Paris Sud, UMR 8607, bâtiment 200, 91898 Orsay Cedex (France); Laboratoire Astroparticule et Cosmologie, Université Paris 7, UMR 7164, bâtiment Condorcet, 75205 Paris Cedex (France); Chancé, S.; Cayla, J.N.; Chaumat, V. [Laboratoire de l' Accélérateur Linéaire (LAL), Université Paris Sud, UMR 8607, bâtiment 200, 91898 Orsay Cedex (France); and others

2015-10-11

The Alpha-X RF-gun was designed to produce an ultra-short (<100 fs rms), 100 pC and 6.3 MeV electron beam with a normalized rms transverse emittance of 1π mm mrad for a gun peak accelerating field of 100 MV/m. Such beams will be required by the Alpha-X project, which aims to study a laser-driven plasma accelerator with a short wavelength accelerating medium. It has been demonstrated on PHIL (Photo-Injector at LAL) that the coaxial RF coupling, chosen to preserve the gun field cylindrical symmetry, is perfectly understood and allows reaching the required peak accelerating field of 100 MV/m giving beam energy of 6.3 MeV. Moreover, a quite low beam rms relative energy spread of 0.15% at 3.8 MeV has been measured, completely agreeing with simulations. Dark current, quantum efficiencies and dephasing curves measurements have also been performed. They all show high values of the field enhancement factor β, which can be explained by the preparation of the photocathodes. Finally, measurements on the transverse phase-space have been carried out, with some limitations given by the difficult modelization of one of the PHIL solenoid magnets and by the enlargement of the beam transverse dimensions due to the use of YAG screens. These measurements give a normalized rms transverse emittance around 5π mm mrad, which does not fulfill the requirement for the Alpha-X project.

ENERGY CORRECTION FOR HIGH POWER PROTON/H MINUS LINAC INJECTORS.

Energy Technology Data Exchange (ETDEWEB)

RAPARIA, D.; LEE, Y.Y.; WEI, J.

2005-05-16

High-energy proton/H minus energy (> GeV) linac injector suffer from energy jitter due to RF amplitude and phase stability. Especially in high power injectors this energy jitter result beam losses more than 1 W/m that require for hand on maintenance. Depending upon the requirements for next accelerator in the chain, this energy jitter may or may not require to be corrected. This paper will discuss the sources of this energy jitter, correction schemes with specific examples.

Experimental investigations on the influence of the photocathode laser pulse parameters on the electron bunch quality in an RF-photoelectron source

Energy Technology Data Exchange (ETDEWEB)

Haenel, Marc

2010-07-15

Free Electron Lasers based on the SASE principle like the European XFEL require electron bunches having peak currents of several kiloamperes as well as very low transverse emittance. While high peak currents can be generated using longitudinal bunch compression techniques, the transverse emittance must have values as low as 1mmmrad already at the source. The development of electron sources fulfilling these demanding specifications is the goal of the Photo Injector Test Facility (PITZ) in DESY, Zeuthen site. The key component of a photoinjector is the electron gun cavity where the electrons bunches are generated and immediately accelerated. The extraction of the electrons is based on the photoelectric effect of the cathode which requires a laser system having special capabilities. In the first part of the thesis, measurements are presented which were performed to investigate whether the laser and the laser transport system fulfill these requirements. The second part of the thesis is dedicated to simulations as well as experimental studies on the impact of the temporal and spatial parameters of the laser pulses on the electron bunch quality. This influence is possible because the response time of the Cs{sub 2}Te photocathode is short compared to the laser pulse duration. Based on these investigations, suggestions for improvements are given and tolerances for the laser pulse properties are defined. (orig.)

Experimental investigations on the influence of the photocathode laser pulse parameters on the electron bunch quality in an RF-photoelectron source

International Nuclear Information System (INIS)

Haenel, Marc

2010-06-01

Free Electron Lasers based on the SASE principle like the European XFEL require electron bunches having peak currents of several kiloamperes as well as very low transverse emittance. While high peak currents can be generated using longitudinal bunch compression techniques, the transverse emittance must have values as low as 1mmmrad already at the source. The development of electron sources fulfilling these demanding specifications is the goal of the Photo Injector Test Facility (PITZ) in DESY, Zeuthen site. The key component of a photoinjector is the electron gun cavity where the electrons bunches are generated and immediately accelerated. The extraction of the electrons is based on the photoelectric effect of the cathode which requires a laser system having special capabilities. In the first part of the thesis, measurements are presented which were performed to investigate whether the laser and the laser transport system fulfill these requirements. The second part of the thesis is dedicated to simulations as well as experimental studies on the impact of the temporal and spatial parameters of the laser pulses on the electron bunch quality. This influence is possible because the response time of the Cs 2 Te photocathode is short compared to the laser pulse duration. Based on these investigations, suggestions for improvements are given and tolerances for the laser pulse properties are defined. (orig.)

Properties of high current RFQ injectors

International Nuclear Information System (INIS)

Schempp, A.; Goethe, J.W.

1996-01-01

RFQ linacs are efficient, compact low energy ion structures, which have found numerous applications. They use electrical rf focusing and can capture, bunch and transmit high current ion beams. Some recent development and new projects like a heavy ion injectors for a cyclotron, and the status of the work on high current high duty factor RFQs will be discussed. (author)

Properties of high current RFQ injectors

Energy Technology Data Exchange (ETDEWEB)

Schempp, A.; Goethe, J.W. [Frankfurt Univ. (Germany). Inst. fuer Angewandte Physik

1996-12-31

RFQ linacs are efficient, compact low energy ion structures, which have found numerous applications. They use electrical rf focusing and can capture, bunch and transmit high current ion beams. Some recent development and new projects like a heavy ion injectors for a cyclotron, and the status of the work on high current high duty factor RFQs will be discussed. (author) 2 refs.

CTF3 Drive Beam Injector Optimisation

CERN Document Server

AUTHOR|(CDS)2082899; Doebert, S

2015-01-01

In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel to the main linac. The main feasibility issues of the two-beam acceleration scheme are being demonstrated at CLIC Test Facility 3 (CTF3). The CTF3 Drive Beam injector consists of a thermionic gun followed by the bunching system and two accelerating structures all embedded in solenoidal magnetic field and a magnetic chicane. Three sub-harmonic bunchers (SHB), a prebuncher and a travelling wave buncher constitute the bunching system. The phase coding process done by the sub-harmonic bunching system produces unwanted satellite bunches between the successive main bunches. The beam dynamics of the CTF3 Drive Beam injector is reoptimised with the goal of improving the injector performance and in particular decreasing the satellite population, the beam loss in the magnetic chicane and the beam emittance in transverse plane compare to the original model based on P. Ur...

SLC injector modeling

International Nuclear Information System (INIS)

Hanerfeld, H; Herrmannsfeldt, W.B.; James, M.B.; Miller, R.H.

1985-03-01

The injector for the Stanford Linear Collider is being studied using the fully electromagnetic particle-in-cell program MASK. The program takes account of cylindrically symmetrical rf fields from the external source, as well as fields produced by the beam and dc magnetic fields. It calculates the radial and longitudinal motion of electrons and plots their positions in various planes in phase space. Bunching parameters can be optimized and insights into the bunching process and emittance growth have been gained. The results of the simulations are compared to the experimental results

An rf modulated electron gun pulser for linacs

International Nuclear Information System (INIS)

Legg, R.; Hartline, R.

1991-01-01

Present linac injector designs often make use of sub-harmonic prebuncher cavities to properly bunch the electron beam before injection into a buncher and subsequent accelerating cavities. This paper proposes an rf modulated thermionic gun which would allow the sub-harmonic buncher to be eliminated from the injector. The performance parameters for the proposed gun are 120 kV operating voltage, macropulse duration-single pulse mode 2 nsec, multiple pulse mode 100 nsec, rf modularing frequency 500 MHz, charge per micropulse 0.4 nC, macropulse repetition frequency 10 Hz (max). The gun pulser uses a grid modulated planar triode to drive the gun cathode. The grid driver takes advantage of recently developed modular CATV rf drivers, high performance solid state pulser devices, and high-frequency fiber optic transmitters for telecommunications. Design details are presented with associated SPICE runs simulating operation of the gun

Heat load of a GaAs photocathode in an SRF electron gun

International Nuclear Information System (INIS)

Wang Erdong; Zhao Kui; Jorg Kewisch; Ilan Ben-Zvi; Andrew Burrill; Trivini Rao; Wu Qiong; Animesh Jain; Ramesh Gupta; Doug Holmes

2011-01-01

A great deal of effort has been made over the last decades to develop a better polarized electron source for high energy physics. Several laboratories operate DC guns with a gallium arsenide photocathode, which yield a highly polarized electron beam. However, the beam's emittance might well be improved by using a superconducting radio frequency (SRF) electron gun, which delivers beams of a higher brightness than that from DC guns because the field gradient at the cathode is higher. SRF guns with metal and CsTe cathodes have been tested successfully. To produce polarized electrons, a Gallium-Arsenide photo-cathode must be used: an experiment to do so in a superconducting RF gun is under way at BNL. Since a bulk gallium arsenide (GaAs) photocathode is normal conducting, a problem arises from the heat load stemming from the cathode. We present our measurements of the electrical resistance of GaAs at cryogenic temperatures, a prediction of the heat load and verification by measuring the quality factor of the gun with and without the cathode at 2 K. We simulate heat generation and flow from the GaAs cathode using the ANSYS program. By following the findings with the heat load model, we designed and fabricated a new cathode holder (plug) to decrease the heat load from GaAs. (authors)

Injector upgrade for the S-DALINAC

Energy Technology Data Exchange (ETDEWEB)

Kuerzeder, Thorsten; Brunken, Marco; Conrad, Jens; Eichhorn, Ralf; Graef, Hans-Dieter; Richter, Achim; Sievers, Sven [Institut fuer Kernphysik, TU Darmstadt (Germany); Ackermann, Wolfgang; Mueller, Wolfgang F.O.; Steiner, Bastian; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, TU Darmstadt (Germany); Fuerst, Joel [Argonne National Laboratory, Argonne (United States)

2009-07-01

The injector section of the S-DALINAC currently delivers beams of up to 10 MeV w ith a current of up to 60{mu}A. The upgrade aims to increase both parameters to 14 MeV and 150{mu}A in order to allow more demanding experiments. Therefor e, a modified cryostat module equipped with two new cavities is required. Due to an increase in rf power to 2 kW the old coaxial rf input couplers, being design ed for a maximum power of 500 W, have to be replaced by new waveguide couplers. We review the design principles and report on the fabrication of the cavities an d the whole module.

Absorption of optical power in an S-20 photocathode

CERN Document Server

Harmer, S W

2003-01-01

By considering a monochromatic plane wave obliquely incident upon a planar layer of S-20 photocathode material, deposited upon a non-absorbing glass substrate, the distribution of optical power absorbed within the layer can be resolved. This is important to the question of photocathode efficiency, as the absorbed light excites photoelectrons within the photocathode which then may pass from the photocathode into the vacuum of the photomultiplier tube and be collected and multiplied. The calculation uses the measured complex permittivity of an extended red S-20 photocathode in the wavelength range, 375-900 nm. The results show that thin film effects are important within the photocathode, as they give rise to interesting power absorption profiles. This information is invaluable in predicting optimum photocathode thickness for wavelength selective applications. Electromagnetic waves that are obliquely incident upon the photocathode are also considered in both transverse electric and transverse magnetic polarizati...

S1 photocathode image converter tubes

International Nuclear Information System (INIS)

Gex, F.; Bauduin, P.; Hammes, C.; Horville, P.; Fleurot, N.; Nail, M.

1984-08-01

The S1 photocathode was the first cathode available for practical applications; in spite of this its mechanism of photoemission has remained enigmatic. S1 semi-transparent photocathode is the only one that can be used to study the 1.06 μm neodynium laser pulses of less than 10 ps duration. This recent application and the difficulties to manufacture stable and sensitive S1 photocathode at this wavelength gave rise to new researches which aim is to have a better knowledge of this structure. We first review the recent results obtained at the Paris Observatory (research sponsored by the CEA) and report on the lifetime in the 1-μm range of the photocathodes processed four years ago. In a second part we will try to analyse the researches which have been investigated during these last ten years in different laboratories to determine the role of the main constituants (silver particles, Co oxydes) and their contributions to photoemission in order to improve the sensitivity and the stability of S1 photocathode

Measurements of Thermal Emittance for Cesium Telluride Photocathodes at PITZ

CERN Document Server

Miltchev, V; Grabosch, H J; Han, J H; Krasilnikov, M; Oppelt, A; Petrosian, B; Staykov, L; Stephan, F

2005-01-01

The thermal emittance determines the lower emittance limit and its measurement is of high importance to understand the ultimate injector performance. In this contribution we present results of thermal emittance measurements under rf operation conditions for various Cs2Te cathodes and different accelerating gradients. Measurements of thermal emittance scaling with the cathode laser spot size are presented and analysed. The significance of the Schottky effect in the emittance formation process is discussed.

Conceptual design of independently tunable cells RF gun with external injecting structure

International Nuclear Information System (INIS)

Liang Junjun; Feng Guangyao; Pei Yuanji; Pang Jian

2012-01-01

To obtain the micro-pulse bunch with the order of hundred femtoseconds length and high repetition rate, the pa- per proposes the independently tunable cells (ITC) RF gun, which has a double-cell structure with the cells being power fed independently. By choosing appropriate feeding power and phase of the two cells, this ITC-RF gun can achieve bunches of excellent characteristics. Additionally, the application of a-magnet and laser system can be avoided, which leads to more compact layout. An external injecting ITC-RF gun (DC-ITC-RF gun) structure is designed accordingly. The external injecting structure can increase beam current, decrease energy spread, and cancel the back-bombardment effect almost completely. By means of 1-D and 3- D beam dynamics calculation with different structure parameters, a group of RF parameters are obtained for better beam characteristics. Then the paper designs a pre-injector so that particles can be accelerated to 10 MeV. By choosing appropriate feeding power and incident particle phase for the pre-injector, the bunch length can be further compressed. (authors)

The RF Design of an HOM Polarized RF Gun for the ILC

International Nuclear Information System (INIS)

Wang, J.W.; Clendenin, J.E.; Colby, E.R.; Miller, R.A.; Lewellen, J.W.

2006-01-01

The ILC requires a polarized electron beam. While a highly polarized beam can be produced by a GaAs-type cathode in a DC gun of the type currently in use at SLAC, JLAB and elsewhere, the ILC injector system can be simplified and made more efficient if a GaAs-type cathode can be combined with a low emittance RF gun. Since this type of cathode is known to be extremely sensitive to vacuum contamination including back bombardment by electrons and ions, any successful polarized RF gun must have a significantly improved operating vacuum compared to existing RF guns. We present a new RF design for an L-Band normal conducting (NC) RF gun for the ILC polarized electron source. This design incorporates a higher order mode (HOM) structure, whose chief virtue in this application is an improved conductance for vacuum pumping on the cathode. Computer simulation models have been used to optimize the RF parameters with two principal goals: first to minimize the required RF power; second to reduce the peak surface field relative to the field at the cathode in order to suppress field emitted electron bombardment. The beam properties have been simulated initially using PARMELA. Vacuum and other practical issues for implementing this design are discussed

Acceleration characteristics of the injector Linacs for the Hyogo Hadrontherapy Center

International Nuclear Information System (INIS)

Inoue, J.; Sawada, K.; Sakata, T.

2000-01-01

Hyogo Hadrontherapy center in Harima Science Garden City is a cancer therapy facility with proton, helium and carbon beams. The beams are supplied by a synchrotron, which has manufactured by Mitsubishi Electric Corporation, with RF 1inacs as an injector, which has manufactured by Sumitomo Heavy Industries Ltd.(SHI). The injector consists of the identical ECR ion sources, a RFQ linac, and an Alvarez linac, which are connected by beam transport systems including vacuum systems, and some kinds of beam monitoring equipments. The results accomplished for the beam conditioning are described in this paper. (author)

Protection of cesium-antimony photocathodes

International Nuclear Information System (INIS)

Buzulutskov, A.; Breskin, A.; Chechik, R.; Prager, M.; Shefer, E.

1996-06-01

In order to operate gaseous photomultipliers in the visible range it was suggested to protect sensitive photocathodes against contact to air and counting gases by their coating with a thin solid dielectric film. We present data on coating of cesium- antimony photocathodes with alkali-halide (NaI, CsI, CsF, NaF), oxide (SiO) and organic (hexatriacontane, calcium stearate) films. The photoelectron transmission through these films and their protection capability have been studied in detail. Cesium-antimony photocathodes are shown to withstand exposure to considerable doses of oxygen and dry air when coated with Nal films. This opens ways to their operation in gas media. (authors), 11 refs., 6 figs

Preparations for Upgrading the RF Systems of the PS Booster

CERN Document Server

Albright, Simon; Shaposhnikova, Elena

2016-01-01

The accelerators of the LHC injector chain need to be upgraded to provide the HL-LHC beams. The PS Booster, the first synchrotron in the LHC injection chain, uses three different RF systems (first, second and up to tenth harmonic) in each of its four rings. As part of the LHC Injector Upgrade the current ferrite RF systems will be replaced with broadband Finemet cavities, increasing the flexibility of the RF system. A Finemet test cavity has been installed in Ring 4 to investigate its effect on machine performance, especially beam stability, during extensive experimental studies. Due to large space charge impedance Landau damping is lost through most of the cycle in single harmonic operation, but is recovered when using the second harmonic and controlled longitudinal emittance blow-up. This paper compares beam parameters during acceleration with and without the Finemet test cavity. Comparisons were made using beam measurements and simulations with the BLonD code based on a full PS Booster impedance model. Thi...

Three bunch energy stabilization for the SLC injector

International Nuclear Information System (INIS)

Sheppard, J.C.; Almog, I.; Bambade, P.S.; Clendenin, J.E.; Jobe, R.K.; Phinney, N.; Shoaee, H.; Stiening, R.F.; Thompson, K.A.

1986-09-01

Slow feedback has been developed to control the energy and energy spread of the beams which are injected into the SLC damping rings. Within a single RF pulse, two bunches of electrons and one bunch of positrons are accelerated to an energy of 1.21 GeV in the injector of the SLC. The two electron bunches are deflected into the north damping ring while the positrons are targeted into the south ring. In order to fit into the acceptance of the rings, the composite energy deviation and energy spread of the beams must be less than 2% full width. Control of the beam energy characteristics is accomplished with a set of computer controlled feedback loops which monitor the parameters of the three bunches and make adjustments to the available RF energy, RF phasing, and RF timing. This paper presents an overview of the feedback algorithms and of the special hardware developments, and reports on the operational status of the processes

Operation of the APS rf gun

International Nuclear Information System (INIS)

Lewellen, J. W.

1998-01-01

The Advanced Photon Source (APS) has a thermionic-cathode rf gun system capable of providing beam to the APS linac. The gun system consists of a 1.6-cell thermionic-cathode rf gun, a fast kicker for beam current control, and an alpha magnet for bunch compression and injection into the APS linac line. This system is intended for use both as an injector for positron creation, and as a first beam source for the Low-Energy Undulator Test Line (LEUTL) project [1]. The first measured performance characteristics of the gun are presented.

DESIGN OF A DC/RF PHOTOELECTRON GUN

International Nuclear Information System (INIS)

YU, D.; NEWSHAM, Y.; SMIRONOV, A.; YU, J.; SMEDLEY, J.; SRINIVASAN RAU, T.; LEWELLEN, J.; ZHOLENTS, A.

2003-01-01

An integrated dc/rf photoelectron gun produces a low-emittance beam by first rapidly accelerating electrons at a high gradient during a short (∼1 ns), high-voltage pulse, and then injecting the electrons into an rf cavity for subsequent acceleration. Simulations show that significant improvement of the emittance appears when a high field (∼ 0.5-1 GV/m) is applied to the cathode surface. An adjustable dc gap ((le) 1 mm) which can be integrated with an rf cavity is designed for initial testing at the Injector Test Stand at Argonne National Laboratory using an existing 70-kV pulse generator. Plans for additional experiments of an integrated dc/rf gun with a 250-kV pulse generator are being made

The Los Alamos photoinjector program

International Nuclear Information System (INIS)

Sheffield, R.L.; Gray, E.R.; Fraser, J.S.

1988-01-01

Free electron lasers (FELs) require electron beams of high peak brightness. In this presentation, we describe the design of a compact high-brightness electron source for driving short-wavelength FELs. The experiment uses a laser-illuminated Cs 3 Sb photoemitter located in the first rf cavity of an injector linac. The photocathode source and associated hardware are described. The doubled YAG laser (532 nm), which is used to drive the photocathode, produces 75 ps micropulses at 108 MHz repetition rate and peak powers of approximately 300 kW. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a 4 ps resolution streak camera. Present experiments give the following results: Micropulse current amplitudes of 100 mA to 400 A, beam emittances ranging from 10 π mm mrad to 40 π mm mrad, an energy spread of ±3%, and peak current densities of 600 A/cm 2 . The design of experiment has now been changed to include a separately phased rf cavity immediately following the first cavity. This modification enables us to study the effects of phasing with the possibility of improving the injector performance. Also, this change will improve the vacuum conditions in the photoelectron source with a consequent improvement in lifetime performance. A brief discussion on the possible applications of this very bright and compact electron source is presented. (orig.)

Status of the ATLAS Positive-Ion Injector Project

International Nuclear Information System (INIS)

Pardo, R.C.; Benaroya, R.; Billquist, P.J.

1987-01-01

The goal of the Argonne Positive Ion Injector project is to replace the ATLAS tandem injector with a facility which will increase the beam currents presently available by a factor of 100 and to make available at ATLAS essentially all beams including uranium. The beam quality expected from the facility will be at least as good as that of the tandem based ATLAS. The project combines two relatively new technologies - the electron cyclotron resonance ion source, which provides high charge state ions at microampere currents, and RF superconductivity which has been shown to be capable of generating accelerating fields as high as 10 MV/m, resulting in an essentially new method of acceleration for low-energy heavy ions. 5 refs., 7 figs., 1 tabs

RF Group Annual Report 2011

CERN Document Server

Angoletta, M E; Betz, M; Brunner, O; Baudrenghien, P; Calaga, R; Caspers, F; Ciapala, E; Chambrillon, J; Damerau, H; Doebert, S; Federmann, S; Findlay, A; Gerigk, F; Hancock, S; Höfle, W; Jensen, E; Junginger, T; Liao, K; McMonagle, G; Montesinos, E; Mastoridis, T; Paoluzzi, M; Riddone, G; Rossi, C; Schirm, K; Schwerg, N; Shaposhnikova, E; Syratchev, I; Valuch, D; Venturini Delsolaro, W; Völlinger, C; Vretenar, M; Wuensch, W

2012-01-01

The highest priority for the RF group in 2011 was to contribute to a successful physics run of the LHC. This comprises operation of the superconducting 400 MHz accelerating system (ACS) and the transverse damper (ADT) of the LHC itself, but also all the individual links of the injector chain upstream of the LHC – Linac2, the PSB, the PS and the SPS – don’t forget that it is RF in all these accelerators that truly accelerates! A large variety of RF systems had to operate reliably, often near their limit. New tricks had to be found and implemented to go beyond limits; not to forget the equally demanding operation with Pb ions using in addition Linac3 and LEIR. But also other physics users required the full attention of the RF group: CNGS required in 2011 beams with very short, intense bunches, AD required reliable deceleration and cooling of anti-protons, Isolde the post-acceleration of radioactive isotopes in Rex, just to name a few. In addition to the supply of beams for physics, the RF group has a num...

Graphene shield enhanced photocathodes and methods for making the same

Science.gov (United States)

Moody, Nathan Andrew

2014-09-02

Disclosed are graphene shield enhanced photocathodes, such as high QE photocathodes. In certain embodiments, a monolayer graphene shield membrane ruggedizes a high quantum efficiency photoemission electron source by protecting a photosensitive film of the photocathode, extending operational lifetime and simplifying its integration in practical electron sources. In certain embodiments of the disclosed graphene shield enhanced photocathodes, the graphene serves as a transparent shield that does not inhibit photon or electron transmission but isolates the photosensitive film of the photocathode from reactive gas species, preventing contamination and yielding longer lifetime.

Simplified RF power system for Wideroe-type linacs

International Nuclear Information System (INIS)

Fugitt, J.; Howard, D.; Crosby, F.; Johnson, R.; Nolan, M.; Yuen, G.

1981-03-01

The RF system for the SuperHILAC injector linac was designed and constructed for minimum system complexity, wide dynamic range, and ease of maintenance. The final amplifier is close coupled to the linac and operates in an efficient semilinear mode, eliminating troublesome transmission lines, modulators, and high level regulators. The system has been operated at over 250 kW, 23 MHz with good regulation. The low level RF electronics are contained in a single chassis adjacent to the RF control computer, which monitors all important operating parameters. A unique 360 0 phase and amplitude modular is used for precise control and regulation of the accelerating voltage

Integration of the PHIN RF Gun into the CLIC Test Facility

CERN Document Server

Döbert, Steffen

2006-01-01

CERN is a collaborator within the European PHIN project, a joint research activity for Photo injectors within the CARE program. A deliverable of this project is an rf Gun equipped with high quantum efficiency Cs2Te cathodes and a laser to produce the nominal beam for the CLIC Test Facility (CTF3). The nominal beam for CTF3 has an average current of 3.5 A, 1.5 GHz bunch repetition frequency and a pulse length of 1.5 ìs (2332 bunches) with quite tight stability requirements. In addition a phase shift of 180 deg is needed after each train of 140 ns for the special CLIC combination scheme. This rf Gun will be tested at CERN in fall 2006 and shall be integrated as a new injector into the CTF3 linac, replacing the existing injector consisting of a thermionic gun and a subharmonic bunching system. The paper studies the optimal integration into the machine trying to optimize transverse and longitudinal phase space of the beam while respecting the numerous constraints of the existing accelerator. The presented scheme...

Impedance budget and beam stability analysis of the Fermilab Main Injector

International Nuclear Information System (INIS)

Martens, M.A.; Ng, K.Y.

1993-05-01

The impedance budget of the Fermilab Main Injector (MI) is estimated, which includes the contributions from the resistive walls, bellows, rf cavities, steps, Lambertsons, etc. Beam stability during ramping and bunch coalescence is analyzed. The transverse resistive-wall coupled bunch growth is found to be somewhat worse than the situation in the Main Ring (MR)

Stable Solar-Blind Ultraviolet III-Nitride Photocathode for Astronomy Applications

Science.gov (United States)

Bell, Lloyd

In this effort, we propose to develop a new type of cesium-free photocathode using III- nitride materials (GaN, AlN, and their alloys) to achieve highly efficient, solar blind, and stable ultraviolet (UV) response. Currently, detectors used in UV instruments utilize a photocathode to convert UV photons into electrons that are subsequently detected by microchannel plate or CCD. The performance of these detectors critically depends on the efficiency and stability of their photocathodes. In particular, photocathode instability is responsible for many of the fabrication difficulties commonly experienced with this class of detectors. In recent years, III-nitride (in particular GaN) photocathodes have been demonstrated with very high quantum efficiency (>50%) in parts of UV spectral range; however, these photocathodes still rely on cesiation for activation. The proposed photocathode structure will achieve activation through methods for band structure engineering such as delta- doping and polarization field engineering. Compared to the current state-of-the-art in flight-ready microchannel plate/Cs2Te sealed tubes, photocathodes based on III-nitride materials will increase the quantum efficiency by nearly an order of magnitude and significantly enhance both fabrication yield and reliability, since they will not require cesium or other highly reactive materials for activation. This performance will enable a next-generation UV spectroscopic and imaging mission that is of high scientific priority for NASA. This photocathode uses near-surface band-structure engineering to create a permanently activated surface, with high efficiency and air-stable UV response. We will combine this III-nitride structure with our unique III-nitride processing technology to optimize the efficiency and uniformity of the photocathode. In addition, through our design, growth, and processing techniques, we will extend the application of these photocathodes into far UV for both semitransparent and

rf traveling-wave electron gun for photoinjectors

Science.gov (United States)

Schaer, Mattia; Citterio, Alessandro; Craievich, Paolo; Reiche, Sven; Stingelin, Lukas; Zennaro, Riccardo

2016-07-01

The design of a photoinjector, in particular that of the electron source, is of central importance for free electron laser (FEL) machines where a high beam brightness is required. In comparison to standard designs, an rf traveling-wave photocathode gun can provide a more rigid beam with a higher brightness and a shorter pulse. This is illustrated by applying a specific optimization procedure to the SwissFEL photoinjector, for which a brightness improvement up to a factor 3 could be achieved together with a double gun output energy compared to the reference setup foreseeing a state-of-the-art S-band rf standing-wave gun. The higher brightness is mainly given by a (at least) double peak current at the exit of the gun which brings benefits for both the beam dynamics in the linac and the efficiency of the FEL process. The gun design foresees an innovative coaxial rf coupling at both ends of the structure which allows a solenoid with integrated bucking coil to be placed around the cathode in order to provide the necessary focusing right after emission.

Imaging Hybrid Photon Detectors with a Reflective Photocathode

CERN Document Server

Ferenc, D

2000-01-01

Modern epitaxially grown photocathodes, like GaAsP, bring a very high inherent quantum efficiency, but are rather expensive due to the complicated manufacturing and mounting process. We argue that such photocathodes could be used in reflective mode, in order to avoid the risky and expensive removal of the epitaxial growth substrate. Besides that the quantum efficiency should increase considerably. In this paper we present results of the development of large imaging Hybrid Photon Detectors (HPDs), particularly designed for such reflective photocathodes.

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.)

Reactive magnetron sputtering of N-doped carbon thin films on quartz glass for transmission photocathode applications

Science.gov (United States)

Balalykin, N. I.; Huran, J.; Nozdrin, M. A.; Feshchenko, A. A.; Kobzev, A. P.; Sasinková, V.; Boháček, P.; Arbet, J.

2018-03-01

N-doped carbon thin films were deposited on a silicon substrate and quartz glass by RF reactive magnetron sputtering using a carbon target and an Ar+N2 gas mixture. During the magnetron sputtering, the substrate holder temperatures was kept at 800 °C. The carbon film thickness on the silicon substrate was about 70 nm, while on the quartz glass it was in the range 15 nm – 60 nm. The elemental concentration in the films was determined by RBS and ERD. Raman spectroscopy was used to evaluate the intensity ratios I D/I G of the D and G peaks of the carbon films. The transmission photocathodes prepared were placed in the hollow-cathode assembly of a Pierce-structure DC gun to produce photoelectrons. The quantum efficiency (QE) was calculated from the laser energy and cathode charge measured. The properties of the transmission photocathodes based on semitransparent N-doped carbon thin films on quartz glass and their potential for application in DC gun technology are discussed.

Embedded software for the CEBAF RF Control Module

International Nuclear Information System (INIS)

Lahti, G.; Ashkenazi, I.; West, C.; Morgan, B.

1991-01-01

The CEBAF accelerator control system employs a distributed computer strategy. As part of this strategy, the RF control sub-system uses 342 RF Control Modules, one for each of four warm section beam forming cavities (i.e., choppers, buncher, capture) and 338 superconducting accelerating cavities. Each control module has its own microprocessor, which provides local intelligence to automatically control over 100 parameters, while keeping the user interface simple. The microprocessor controls analog and digital I/O, including the phase and gradient section, high power amplifier (HPA), and interlocks. Presently, the embedded code is used to commission the 14 RF control modules in the injector. This paper describes the operational experience of this complex real-time control system

Technical Design and Optimization Study for the FERMI at Elettra FEL Photoinjector

International Nuclear Information System (INIS)

Lidia, Steven M.; Penco, Giuseppe; Trovo', Mauro

2006-01-01

The FERMI (at) Elettra FEL project will provide a novel, x-ray free electron laser user facility at Sincrotrone Trieste based on seeded and cascade FEL techniques. The electron beam source and injector systems play a crucial role in the success of the facility by providing the highest quality electron beams to the linac and FEL undulators. This Technical Note examines the critical technology components that make up the injector system, and demonstrates optimum beam dynamics solutions to achieve the required high quality electron beams. Section 2 provides an overview of the various systems and subsystems that comprise the photoinjector. The different operating modes of the injector are described as they pertain to the different linac configurations driven by the FEL and experimental design. For each mode, the required electron beam parameters are given. Sections 3 and 4 describe the critical beamline elements in the injector complex: the photocathode and drive laser, and the RF gun. The required drive laser parameters are given at the end of Section 3. Additional details on the design of the photoinjector drive laser systems are presented in a separate Technical Note. Design considerations for the RF gun are extensively presented in Section 4. There, we describe the variation of the cavity geometry to optimize the efficiency of the energy transfer to the electron beam. A study of the power coupling into the various cavity modes that interact within the bandwidth of the RF drive pulse is presented, followed by a study of the transient cavity response under several models and, finally, the effects on extracted beam quality. Section 5 describes the initial design for the low energy, off-axis diagnostic beamline. Beam dynamics simulations using ASTRA, elegant, and MAD are presented. Section 6 presents the optimization studies for the beam dynamics in the various operating modes. The optimized baseline configurations for the beamline and incident drive laser pulse are

A Stable, Non-Cesiated III-Nitride Photocathode for Ultraviolet Astronomy Application

Science.gov (United States)

Bell, Lloyd

In this effort, we propose to develop a new type of cesium-free photocathode using III-nitride (III-N) materials (GaN, AlN, and their alloys) and to achieve highly efficient, solar blind, and stable UV response. Currently, detectors used in UV instruments utilize a photocathode to convert UV photons into electrons that are subsequently detected by microchannel plate or CCD. The performance of these detectors critically depends on the efficiency and stability of their photocathodes. In particular, photocathode instability is responsible for many of the fabrication difficulties commonly experienced with this class of detectors. In recent years, III-N (in particular GaN) photocathodes have been demonstrated with very high QE (>50%) in parts of UV spectral range. Moreover, due to the wide bandgaps of III-nitride materials, photocathode response can be tailored to be intrinsically solar-blind. However, these photocathodes still rely on cesiation for activation, necessitating all-vacuum fabrication and sealed-tube operation. The proposed photocathode structure will achieve activation through methods for band structure engineering such as delta-doping and polarization field engineering. Compared to the current state-of-the-art in flight-ready microchannel plate sealed tubes, photocathodes based on III-N materials will yield high QE and significantly enhance both fabrication yield and reliability, since they do not require cesium or other highly reactive materials for activation. This performance will enable a ~4 meter medium class UV spectroscopic and imaging mission that is of high scientific priority for NASA. This work will build on the success of our previous APRA-funded effort. In that work, we demonstrated III-nitride photocathode operation without the use of cesium and stable response with respect to time. These accomplishments represent major improvements to the state-of-the-art for photocathode technologies. In the proposed effort, we will implement III

Cancellation of RF Coupler-Induced Emittance Due to Astigmatism

Energy Technology Data Exchange (ETDEWEB)

Dowell, David H.; /SLAC

2016-12-11

It is well-known that the electron beam quality required for applications such as FEL’s and ultra-fast electron diffraction can be degraded by the asymmetric fields introduced by the RF couplers of superconducting linacs. This effect is especially troublesome in the injector where the low energy beam from the gun is captured into the first high gradient accelerator section. Unfortunately modifying the established cavity design is expensive and time consuming, especially considering that only one or two sections are needed for an injector. Instead, it is important to analyze the coupler fields to understand their characteristics and help find less costly solutions for their cancellation and mitigation. This paper finds the RF coupler-induced emittance for short bunches is mostly due to the transverse spatial sloping or tilt of the field, rather than the field’s time-dependence. It is shown that the distorting effects of the coupler can be canceled with a static (DC) quadrupole lens rotated about the z-axis.

Jefferson Lab IR demo FEL photocathode quantum efficiency scanner

CERN Document Server

Gubeli, J; Grippo, A; Jordan, K; Shinn, M; Siggins, T

2001-01-01

Jefferson Laboratory's Free Electron Laser (FEL) incorporates a cesiated gallium arsenide (GaAs) DC photocathode gun as its electron source. By using a set of scanning mirrors, the surface of the GaAs wafer is illuminated with a 543.5nm helium-neon laser. Measuring the current flow across the biased photocathode generates a quantum efficiency (QE) map of the 1-in. diameter wafer surface. The resulting QE map provides a very detailed picture of the efficiency of the wafer surface. By generating a QE map in a matter of minutes, the photocathode scanner has proven to be an exceptional tool in quickly determining sensitivity and availability of the photocathode for operation.

Shunt impedance measurement of the APS BBC injector

International Nuclear Information System (INIS)

Sun, Y.E.; Lewellen, J.W.

2006-01-01

The injector test stand (ITS) at Advanced Photon Source (APS) presently incorporates a ballistic bunch compression (BBC) gun, and it is used as a beam source for a number of experiments, including THz generation, beam position monitor testing for the Linac Coherent Light Source (LCLS), novel cathode testing, and radiation therapy source development. The BBC gun uses three independently powered and phased rf cavities, one cathode cell, and two full cells to provide beam energies from 2 to 10 MeV with variable energy spread, energy chirp, and, to an extent, bunch duration. The shunt impedance of an rf accelerator determines how effectively the accelerator can convert supplied rf power to accelerating gradient. The calculation of the shunt impedance can be complicated if the beam energy changes substantially during its transit through a cavity, such as in a cathode cell. We present the results of direct measurements of the shunt impedance of the APS BBC gun on an individual cavity basis, including the cathode cell, and report on achieved gradients. We also present a comparison of the measured shunt impedance with theoretical values calculated from the rf models of the cavities.

The CH section of the 17 MeV injector for MYRRHA

International Nuclear Information System (INIS)

Maeder, Dominik

2015-01-01

The newly developed beam-dynamics design for the MYRRHA injector was optimized in view of a high reliability and availability and fulfills all requirements of the nuclear reactor. The basic concept of the EUROTRANS injector was revised and further developed. Ar result of this work among others the quality of the excite beam could be distrinctly improved. In the statistical error analysis the beam dynamics have been shown as extremely robust and yields even under most pessimistic error assumptions a transmission of above 99.9 %. The new injector concept offers essential advances against the injector design presented in ''MAX Referenzdesign 012'' and is applied as new ''MAX Referenzdesign 2014''. The development history until the new reference design was a successive process with numerous iterative intermediate steps. With the altrnative design (C1) and the consolidated alternative design (C2) in this thesis also the milestones of the injector development are described. The good beam-dynamical properties of the new injector design (C3) could be confirmed in comparison calculations with TraceWin at the IN2P3 rate at CNRS. Beside the beam dynamics the required accelerator cavities were developed and optimized for a high reliability and availability too. The RF design of the CH structures is layed out for a most possible breakdown safety in the operation with low electrical field gradients far below the technical power limits and possibilities of each cavity.

The transverse and longitudinal beam characteristics of the PHIN photo-injector at CERN

CERN Document Server

Mete, Ö; Dabrowski, A; Divall, M; Döbert, S; Egger, D; Elsener, K; Fedosseev, V; Lefèvre, T; Petrarca, M

2010-01-01

A new photo-injector, capable to deliver a long pulse train with a high charge per bunch for CTF3, has been designed and installed by a collaboration between LAL, CCLRC and CERN within the framework of the second Joint Research Activity PHIN of the European CARE program. The demonstration of the high charge and the stability along the pulse train are the important goals for CTF3 and the CLIC drive beam. The nominal beam for CTF3 has an average current of 3.5 A, a 1.5 GHz bunch repetation frequency and a pulse length of 1.27 μs (1908 bunches). The existing CTF3 injector consists of a thermionic gun and a subharmonic bunching system. The PHIN photo-injector is being tested in a dedicated test-stand at CERN to replace the existing CTF3 injector that is producing unwanted satellite bunches during the bunching process. A phase-coding scheme is planned to be implemented to the PHIN laser system providing the required beam temporal structure by CTF3. RF photo-injectors are high-brightness, low-emittance electron so...

Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

Energy Technology Data Exchange (ETDEWEB)

Wisniewski, Eric E., E-mail: ewisniew@anl.gov [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Velazquez, Daniel [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Yusof, Zikri, E-mail: zyusof@hawk.iit.edu [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States); Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Spentzouris, Linda; Terry, Jeff [Physics Department, Illinois Institute of Technology, 3300 South Federal Street, Chicago, IL 60616 (United States); Sarkar, Tapash J. [Rice University, 6100 Main, Houston, TX 77005 (United States); Harkay, Katherine [Accelerator Science Division, Argonne National Laboratory, 9700 S. Cass, Lemont, IL 60439 (United States)

2013-05-21

Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency (>1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch (≈50nC) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating. -- Highlights: ► The correlation between Quantum Efficiency (QE) and work function. ► How QE and work function evolve together. ► Rejuvenation of the photocathode via heating and the effect on work function. ► The effects on the work function due to exposure to UV light.

Improving the beam quality of rf guns by correction of rf and space-charge effects

International Nuclear Information System (INIS)

Serafini, L.

1992-01-01

In this paper we describe two possible strategies to attain ultra-low emittance electron beam generation by laser-driven RF guns. The first one is based on the exploitation of multi-mode resonant cavities to neutralize the emittance degradation induced by RF effects. Accelerating cigar-like (long and thin) electron bunches in multi-mode operated RF guns the space charge induced emittance is strongly decreased at the same time: high charged bunches, as typically requested by future TeV e - e + colliders, can be delivered by the gun at a quite low transverse emittance and good behaviour in the longitudinal phase space, so that they can be magnetically compressed to reach higher peak currents. The second strategy consists in using disk-like electron bunches, produced by very short laser pulses illuminating the photocathode. By means of an analytical study a new regime has been found, where the normalized transverse emittance scales like the inverse of the peak current, provided that the laser pulse intensity distribution is properly shaped in the transverse direction. Preliminary numerical simulations confirm the analytical predictions and show that the minimum emittance achievable is set up, in this new regime, by the wake-field interaction between the bunch and the cathode metallic wall

RF upgrade program in LHC injectors and LHC machine

International Nuclear Information System (INIS)

Jensen, E.

2012-01-01

The main themes of the RF upgrade program are: the Linac4 project, the LLRF-upgrade and the study of a tuning-free wide-band system for PSB, the upgrade of the SPS 800 MHz amplifiers and beam controls and the upgrade of the transverse dampers of the LHC. Whilst LHC Splice Consolidation is certainly the top priority for LS1, some necessary RF consolidation and upgrade is necessary to assure the LHC performance for the next 3- year run period. This includes: 1) necessary maintenance and consolidation work that could not fit the shorter technical stops during the last years, 2) the upgrade of the SPS 200 MHz system from presently 4 to 6 cavities and possibly 3) the replacement of one LHC cavity module. On the longer term, the LHC luminosity upgrade requires crab cavities, for which some preparatory work in SPS Coldex must be scheduled during LS1. (author)

Progress in ultrafast CsI-photocathode gaseous imaging photomultipliers

International Nuclear Information System (INIS)

Dagendorf, V.; Breskin, A.; Chechick, R.; Schmidt-Boecking, H.

1991-04-01

A large area low-pressure gas-filled UV-imaging photomultiplier with CsI photocathode is presented. The double step electron photomultiplier with a 10 torr CH 4 gas-filling enables stable high gain operation. The detection efficiency of photon in the wavelength range λ ∼ 170 nm (Xe scintilation light) is about 10% for 200 to 2000 nm thick photocathodes. We investigate the influence of various substrate materials, the thickness of the CsI-layer, the gas pressure and the gas composition on the performance of the photocathode. Furthermore we studied the stability of the photocathode under different operating conditions and its sensitivity to air. Measurements of the timing characteristic of the device yielded an ultimate time resolution of 350 ps (fwhm). (author)

Etude Experimentale du Photo-Injecteur de Fermilab

Energy Technology Data Exchange (ETDEWEB)

Carneiro, Jean-Paul [Orsay

2001-01-01

TESLA (TeV Superconducting Linear Accelerator) is an international collaboration which is studying the feasibility of an $e^+e^-$ collider of energy 0.8 TeV in the center of mass. One of the first goals of this collaboration was to construct a prototype linear accelerator at the DESY Laboratory in Hamburg, the TESLA Test Facility (TTF), in order to establish the technical basis for the collider. Two injectors were developed for TTF: a thermionic injector (developed by LAL-Orsay, IPN-Orsay, and CEA-Saclay) and a photo-injector (developed by Fermilab). The thermionic injector was used from February 1997 to October 1998, and then it was replaced by the photo-injector, which was first operated in December 1998. Another photo-injector, identical to the one delivered to TTF, was installed at Fermilab in the $A{\\emptyset}$ Building. The first beam from the latter was produced on 3 March 1999. The photo-injector consists of an RF gun, followed by a superconducting cavity. The RF gun is a 1.625-cell copper cavity with a resonant frequency of 1.3 GHz. The gun contains a cesium telluride ($C_{s_2}$Te) photo-cathode, which is illuminated by UV pulses from a Nd:YLF laser. The system can produce trains of 800 bunches of photo-electrons of charge 8 nC per bunch with spacing between bunches of 1$\\mu$s and 10 Hz repetition rate. Upon emerging from the RF gun, the beam energy is 4 to 5 MeV; the beam is then rapidly accelerated by the superconducting cavity to an energy of 17 to 20 MeV. Finally, a magnetic chicane, consisting of 4 dipoles, produces longitudinal compression of the electron bunches. This thesis describes the installation of the photo-injector at Fermilab and presents the experimentally-measured characteristics of the injector. The principal measurements were quantum eciency, dark current, transverse emittance, and bunch length. The conclusion from these studies is that the quality of the photo-injector beam fullls the design goals. The photo-injector at Fermilab is

The Brookhaven Accelerator Test Facility

International Nuclear Information System (INIS)

Batchelor, K.; Chou, T.S.; Fernow, R.C.

1988-01-01

The Brookhaven Accelerator Test Facility (ATF) will consist of a 50--100 MeV/c electron linac and a 100 GW CO 2 laser system. A high brightness RF-gun operating at 2856 MHz is to be used as the injector into the linac. The RF-gun contains a Nd:Yag-laser-driven photocathode capable of producing a stream of six ps electron pulses separated by 12.5 ns. The maximum charge in a micropulse will be one nano-Coulomb. The CO 2 laser pulse length will be a few picoseconds and will be synchronized with the electron pulse. The first experimental beam is expected in Fall 89. The design electron beam parameters are given and possible initial experiments are discussed. 9 refs., 1 fig., 3 tabs

rf traveling-wave electron gun for photoinjectors

Directory of Open Access Journals (Sweden)

Mattia Schaer

2016-07-01

Full Text Available The design of a photoinjector, in particular that of the electron source, is of central importance for free electron laser (FEL machines where a high beam brightness is required. In comparison to standard designs, an rf traveling-wave photocathode gun can provide a more rigid beam with a higher brightness and a shorter pulse. This is illustrated by applying a specific optimization procedure to the SwissFEL photoinjector, for which a brightness improvement up to a factor 3 could be achieved together with a double gun output energy compared to the reference setup foreseeing a state-of-the-art S-band rf standing-wave gun. The higher brightness is mainly given by a (at least double peak current at the exit of the gun which brings benefits for both the beam dynamics in the linac and the efficiency of the FEL process. The gun design foresees an innovative coaxial rf coupling at both ends of the structure which allows a solenoid with integrated bucking coil to be placed around the cathode in order to provide the necessary focusing right after emission.

Performance of an rf beam monitor on the NBS-Los Alamos racetrack microtron

International Nuclear Information System (INIS)

Young, L.M.; Cutler, R.I.

1985-01-01

A prototype rf beam-position, current, and phase monitor has been used on the 100-keV injector beamline of the racetrack microtron (RTM) where performance was measured with the chopped and bunched beam. This monitor works with both a pulsed beam and a cw beam. The pulsed beam consists of beam pulses with a FWHM of 40 ns. The rf beam monitor was tested with beam currents from approx. 50 to 600 μA. The rf beam monitor will be described and its performance will be reported. 6 refs., 5 figs

Development of a high current 250 kV photocathode dc gun

International Nuclear Information System (INIS)

Nishimori, Nobuyuki; Nagai, Ryoji; Sawamura, Masaru; Hajima, Ryoichi

2016-01-01

We have developed a high current photocathode dc gun at JAEA for the next generation light sources such as an energy recovery linac and high-repetition rate X-ray free electron laser. The gun is equipped with a multialkali photocathode preparation system. Quantum efficiency of 0.37% at 532 nm was obtained for a Cs_3Sb photocathode. The gun was high voltage conditioned up to 230 kV with a cathode electrode. Beam generation test from the multialkali photocathode will be performed by the end of FY2015. (author)

Development of highly qualified UV-laser light source for rf gun

International Nuclear Information System (INIS)

Tomizawa, H.; Dewa, H.; Taniuchi, T.

2004-01-01

We have been developing stable and highly qualified UV-laser pulse as a light source of the rf gun for an injector candidate of future light sources. Our gun cavity is a single-cell pillbox, and the copper inner wall is used as a photo cathode. In present status, the short pulse energy stability of laser has been improved down to 1.3∼1.5% (rms; 10pps; 10000 shots) at the third harmonic generation. The long stability depends on the stability of modelocking at oscillator. In this improvement we just passively stabilized the system. We considered environmental controls in clean room to reduce optical damage accidents and constructed a new humidity-controlled clean room in 2003. And we re-installed the total laser system in this room in 2004. The relative humidity of this new clean room at room temperature is in a region of 50∼60 % with a stability of less than 2% (p-p). On the other hand, the ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from a photo-cathode rf gun. This laser-shaping project has been started in two steps since 2002. As the first successful test run in 2002, with a microlens array as a simple spatial shaper, we obtained a minimum emittance value of 2π mm·mrad with a beam energy of 3.1 MeV, holding its charge to 0.1 nC/bunch. In the next test run in 2004, we prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. We are applying the both adaptive optics to automatically shape the both spatial and temporal UV-laser profiles with a feedback routine at the same time. We report herein the principle and developing process of our laser beam quality control system. (author)

Electron beam characterization of a combined diode rf electron gun

Directory of Open Access Journals (Sweden)

R. Ganter

2010-09-01

Full Text Available Experimental and simulation results of an electron gun test facility, based on pulsed diode acceleration followed by a two-cell rf cavity at 1.5 GHz, are presented here. The main features of this diode-rf combination are: a high peak gradient in the diode (up to 100  MV/m obtained without breakdown conditioning, a cathode shape providing an electrostatic focusing, and an in-vacuum pulsed solenoid to focus the electron beam between the diode and the rf cavity. Although the test stand was initially developed for testing field emitter arrays cathodes, it became also interesting to explore the limits of this electron gun with metallic photocathodes illuminated by laser pulses. The ultimate goal of this test facility is to fulfill the requirements of the SwissFEL project of Paul Scherrer Institute [B. D. Patterson et al., New J. Phys. 12, 035012 (2010NJOPFM1367-263010.1088/1367-2630/12/3/035012]; a projected normalized emittance below 0.4  μm for a charge of 200 pC and a bunch length of less than 10 ps (rms. A normalized projected emittance of 0.23  μm with 13 pC has been measured at 5 MeV using a Gaussian laser longitudinal intensity distribution on the photocathode. Good agreements with simulations have been obtained for different electron bunch charge and diode geometries. Emittance measurements at a bunch charge below 1 pC were performed for different laser spot sizes in agreement with intrinsic emittance theory [e.g. 0.54  μm/mm of laser spot size (rms for Cu at 274 nm]. Finally, a projected emittance of 1.25+/-0.2  μm was measured with 200 pC and 100  MV/m diode gradient.

Field assisted photoemission by silicon photocathodes

International Nuclear Information System (INIS)

Aboubacar, A.; Dupont, M.; El Manouni, A.; Querrou, M.; Says, L.P.

1991-01-01

Silicon photocathodes with arrays of tips have been prepared using microlithographic techniques. Current emission due to field effect has been measured in the case of heavy and weakly doped boron Silicon. An Argon continuous laser has been used to produce photocurrent. An instantaneous current (600 μA) with a moderate laser power (83 mW), has been produced on weakly doped photocathodes. This current corresponds to an average quantum yield (purely photoelectric) of about 1.7%, and a local current density in the range of a few 10 6 A m -2

General overview of the APS low-level rf control system

International Nuclear Information System (INIS)

Stepp, J.D.; Bridges, J.F.

1993-01-01

This paper describes the proposed low-level rf system of the positron accumulator ring (PAR), the injector synchrotron, and the storage ring of the 7-GeV Advanced Photon Source. Four rf systems are described since the PAR consists of a fundamental frequency system at 9.8 MHz and a harmonic system at 117 MHz. A block diagram of an accelerating unit is shown and descriptions of various control loops are made (including amplitude control, phase control, and cavity tuning control). Also, a brief overview of the computer interface is given

PIP-II Injector Test: Challenges and Status

Energy Technology Data Exchange (ETDEWEB)

Derwent, P. F. [Fermilab; Carneiro, J. P. [Fermilab; Edelen, J. [Fermilab; Lebedev, V. [Fermilab; Prost, L. [Fermilab; Saini, A. [Fermilab; Shemyakin, A. [Fermilab; Steimel, J. [Fermilab

2016-10-04

The Proton Improvement Plan II (PIP-II) at Fermilab is a program of upgrades to the injection complex. At its core is the design and construction of a CW-compatible, pulsed H- superconducting RF linac. To validate the concept of the front-end of such machine, a test accelerator known as PIP-II Injector Test is under construction. It includes a 10mA DC, 30 keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1 MeV CW RFQ, followed by a Medium Energy Beam Transport (MEBT) that feeds the first of 2 cryomodules increasing the beam energy to about 25 MeV, and a High Energy Beam Transport section (HEBT) that takes the beam to a dump. The ion source, LEBT, RFQ, and initial version of the MEBT have been built, installed, and commissioned. This report presents the overall status of the Injector Test warm front end, including results of the beam commissioning through the installed components, and progress with SRF cryomodules and other systems.

Properties of CsI and CsI-TMAE photocathodes

International Nuclear Information System (INIS)

Anderson, D.F.; Kwan, S.; Peskov, V.; Hoeneisen, B.

1992-06-01

The importance of heating the CsI or CsI-TMAE photocathodes during preparation, as well as the importance of the gas environment on the quantum efficiency is presented. The dependence of the aging characteristics of these photocathodes on the operating temperature, on the presence of gas, and on the charge amplification of the chamber is also discussed. For CsI photocathodes charges in excess of 2x10 14 e - /mm 2 can be collected with little degradation of performance. A timing resolution of 0.55 ns is also achieved for single photoelectrons suggesting a possible time-of-flight detector

The Grumman/Brookhaven high-brightness, high-duty factor RF gun

International Nuclear Information System (INIS)

Lehrman, I.S.; Birnbaum, I.A.; Cole, M.; Fixler, S.Z.; Heuer, R.L.; Siddiqi, S.; Sheedy, E.; Waren, G.D.

1992-01-01

Under a joint collaboration between Brookhaven National Laboratory and the Grumman Corporation, a high-duty (>1%) photocathode RF gun is under construction for use at the ATF facility at BNL. The gun will be capable of producing short ( 300 A (after compression) and a total bunch charge in excess of 3 nC. The gun consists of 3-1/2 cells constructed from GlidCop, an alumina dispersion strengthened copper alloy. Two individually phased waveguides are used to power the first two and final two cells. (Author) 10 refs., 8 figs., 2 tabs

Correlation of CsK2Sb photocathode lifetime with antimony thickness

Energy Technology Data Exchange (ETDEWEB)

Mamun, M. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Hernandez-Garcia, C. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA; The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA

2015-06-01

CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Correlation of CsK2Sb photocathode lifetime with antimony thickness

Directory of Open Access Journals (Sweden)

M. A. Mamun

2015-06-01

Full Text Available CsK2Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

A self-adaptive feedforward rf control system for linacs

International Nuclear Information System (INIS)

Zhang Renshan; Ben-Zvi, I.; Xie Jialin

1993-01-01

The design and performance of a self-adaptive feedforward rf control system are reported. The system was built for the linac of the Accelerator Test Facility (ATF) at Brookhaven National Laboratory. Variables of time along the linac macropulse, such as field or phase are discretized and represented as vectors. Upon turn-on or after a large change in the operating-point, the control system acquires the response of the system to test signal vectors and generates a linearized system response matrix. During operation an error vector is generated by comparing the linac variable vectors and a target vector. The error vector is multiplied by the inverse of the system's matrix to generate a correction vector is added to an operating point vector. This control system can be used to control a klystron to produce flat rf amplitude and phase pulses, to control a rf cavity to reduce the rf field fluctuation, and to compensate the energy spread among bunches in a rf linac. Beam loading effects can be corrected and a programmed ramp can be produced. The performance of the control system has been evaluated on the control of a klystron's output as well as an rf cavity. Both amplitude and phase have been regulated simultaneously. In initial tests, the rf output from a klystron has been regulated to an amplitude fluctuation of less than ±0.3% and phase variation of less than ±0.6deg. The rf field of the ATF's photo-cathode microwave gun cavity has been regulated to ±5% in amplitude and simultaneously to ±1deg in phase. Regulating just the rf field amplitude in the rf gun cavity, we have achieved amplitude fluctuation of less than ±2%. (orig.)

Cold electron beams from cryocooled, alkali antimonide photocathodes

Directory of Open Access Journals (Sweden)

L. Cultrera

2015-11-01

Full Text Available In this paper we report on the generation of cold electron beams using a Cs_{3}Sb photocathode grown by codeposition of Sb and Cs. By cooling the photocathode to 90 K we demonstrate a significant reduction in the mean transverse energy validating the long-standing speculation that the lattice temperature contributes to limiting the mean transverse energy or intrinsic emittance near the photoemission threshold, opening new frontiers in generating ultrabright beams. At 90 K, we achieve a record low intrinsic emittance of 0.2  μm (rms per mm of laser spot diameter from an ultrafast (subpicosecond photocathode with quantum efficiency greater than 7×10^{−5} using a visible laser wavelength of 690 nm.

Main injector synchronous timing system

International Nuclear Information System (INIS)

Blokland, W.; Steimel, J.

1998-01-01

The Synchronous Timing System is designed to provide sub-nanosecond timing to instrumentation during the acceleration of particles in the Main Injector. Increased energy of the beam particles leads to a small but significant increase in speed, reducing the time it takes to complete a full turn of the ring by 61 nanoseconds (or more than 3 rf buckets). In contrast, the reference signal, used to trigger instrumentation and transmitted over a cable, has a constant group delay. This difference leads to a phase slip during the ramp and prevents instrumentation such as dampers from properly operating without additional measures. The Synchronous Timing System corrects for this phase slip as well as signal propagation time changes due to temperature variations. A module at the LLRF system uses a 1.2 Gbit/s G-Link chip to transmit the rf clock and digital data (e.g. the current frequency) over a single mode fiber around the ring. Fiber optic couplers at service buildings split off part of this signal for a local module which reconstructs a synchronous beam reference signal. This paper describes the background, design and expected performance of the Synchronous Timing System. copyright 1998 American Institute of Physics

Main injector synchronous timing system

International Nuclear Information System (INIS)

Blokland, Willem; Steimel, James

1998-01-01

The Synchronous Timing System is designed to provide sub-nanosecond timing to instrumentation during the acceleration of particles in the Main Injector. Increased energy of the beam particles leads to a small but significant increase in speed, reducing the time it takes to complete a full turn of the ring by 61 nanoseconds (or more than 3 rf buckets). In contrast, the reference signal, used to trigger instrumentation and transmitted over a cable, has a constant group delay. This difference leads to a phase slip during the ramp and prevents instrumentation such as dampers from properly operating without additional measures. The Synchronous Timing System corrects for this phase slip as well as signal propagation time changes due to temperature variations. A module at the LLRF system uses a 1.2 Gbit/s G-Link chip to transmit the rf clock and digital data (e.g. the current frequency) over a single mode fiber around the ring. Fiber optic couplers at service buildings split off part of this signal for a local module which reconstructs a synchronous beam reference signal. This paper describes the background, design and expected performance of the Synchronous Timing System

SWCNT photocathodes sensitised with InP/ZnS core–shell nanocrystals

OpenAIRE

Macdonald, Thomas J.; Tune, Daniel D.; Dewi, Melissa R.; Bear, Joseph C.; McNaughter, Paul D.; Mayes, Andrew G.; Skinner, William M.; Parkin, Ivan P.; Shapter, Joseph G.; Nann, Thomas

2016-01-01

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes a...

SWCNT photocathodes sensitised with InP/ZnS core-shell nanocrystals

OpenAIRE

Macdonald, T. J.; Tune, D. D.; Dewi, M. R.; Bear, J. C.; McNaughter, P. D.; Mayes, A. G.; Skinner, W. M.; Parkin, I. P.; Shapter, J. G.; Nann, T.

2016-01-01

Increasing the light harvesting efficiency of photocathodes is an integral part of optimising the future efficiencies of solar technologies. In contrast to the more extensively studied photoanode systems, current state-of-the-art photocathodes are less efficient and are commonly replaced with rare and expensive materials such as platinum group metals. The significance of photocathodes is in the development of tandem electrodes, enhancing the performance of existing devices. Carbon nanotubes a...

Results of the SLAC LCLS Gun High-Power RF Tests

International Nuclear Information System (INIS)

Dowell, D.H.; Jongewaard, E.; Limborg-Deprey, C.; Schmerge, J.F.; Li, Z.; Xiao, L.; Wang, J.; Lewandowski, J.; Vlieks, A.

2007-01-01

The beam quality and operational requirements for the Linac Coherent Light Source (LCLS) currently being constructed at SLAC are exceptional, requiring the design of a new RF photocathode gun for the electron source. Based on operational experience at SLAC's GTF and SDL and ATF at BNL as well as other laboratories, the 1.6cell s-band (2856MHz) gun was chosen to be the best electron source for the LCLS, however a significant redesign was necessary to achieve the challenging parameters. Detailed 3-D analysis and design was used to produce near-perfect rotationally symmetric rf fields to achieve the emittance requirement. In addition, the thermo-mechanical design allows the gun to operate at 120Hz and a 140MV/m cathode field, or to an average power dissipation of 4kW. Both average and pulsed heating issues are addressed in the LCLS gun design. The first LCLS gun is now fabricated and has been operated with high-power RF. The results of these high-power tests are presented and discussed

The Brookhaven Accelerator Test Facility

International Nuclear Information System (INIS)

Batchelor, K.; Chou, T.S.; Fernow, R.C.; Fischer, J.; Gallardo, J.; Kirk, H.G.; Koul, R.; Palmer, R.B.; Pellegrini, C.; Sheehan, J.; Srinivasan-Rao, T.; Ulc, S.; Woodle, M.; Bigio, I.; Kurnit, N.; McDonald, K.T.

1989-01-01

The Brookhaven Accelerator Test Facility ATF will consist of a 50-100 MeV/c electron linac and a 100 GW CO 2 laser system. A high brightness RF-gun operating at 2,856 MHz is to be used as the injector into the linac. The RF-gun contains a Nd:Yag-laser-driven photocathode capable of producing a stream of six ps electron pulses separated by 12.5 ns. The maximum charge in a micropulse will be one nano-Coulomb. The CO 2 laser pulse length will be a few picoseconds and will be synchronized with the electron pulse. The first experimental beam is expected in Fall 89. The design electron beam parameters are given and possible initial experiments are discussed. 9 refs., 1 fig., 3 tabs

Recent development on RF-driven multicusp H- ion sources

International Nuclear Information System (INIS)

Leung, K.N.; De Vries, G.J.; Kunkel, W.B.; Perkins, L.T.; Pickard, D.S.; Saadatmand, K.; Wengrow, A.B.; Williams, M.D.

1996-06-01

The radio-frequency (rf) driven multicusp source was originally developed for use in the Superconducting Super Collider injector. The source routinely provided 35 keV, 30 mA of beam at 0.1% duty factor. By using a new cesium dispensing system, beam current in excess of 100 mA and e/H - ∼1 have been observed. For pulse mode operation, the rf discharge can be started by means of a xenon flash lamp. Extracted electrons in the beam can be efficiently removed by employing a permanent magnet insert structure. Chopping of the H - beam can be accomplished by applying a pulsed positive voltage on the plasma electrode

Refined beam measurements on the SNS H- injector

Science.gov (United States)

Han, B. X.; Welton, R. F.; Murray, S. N.; Pennisi, T. R.; Santana, M.; Stinson, C. M.; Stockli, M. P.

2017-08-01

The H- injector for the SNS RFQ accelerator consists of an RF-driven, Cs-enhanced H- ion source and a compact, two-lens electrostatic LEBT. The LEBT output and the RFQ input beam current are measured by deflecting the beam on to an annular plate at the RFQ entrance. Our method and procedure have recently been refined to improve the measurement reliability and accuracy. The new measurements suggest that earlier measurements tended to underestimate the currents by 0-2 mA, but essentially confirm H- beam currents of 50-60 mA being injected into the RFQ. Emittance measurements conducted on a test stand featuring essentially the same H- injector setup show that the normalized rms emittance with 0.5% threshold (99% inclusion of the total beam) is in a range of 0.25-0.4 mm.mrad for a 50-60 mA beam. The RFQ output current is monitored with a BCM toroid. Measurements as well as simulations with the PARMTEQ code indicate an underperforming transmission of the RFQ since around 2012.

Polarized Photocathode R&D for Future Linear Collliders

Energy Technology Data Exchange (ETDEWEB)

Zhou, F; Brachmann, A.; Maruyama, T.; Sheppard, J.C.; /SLAC

2009-01-23

It is a challenge to generate full charge electrons from the electron sources without compromising polarization for the proposed ILC and CLIC. It is essential to advance polarized photocathodes to meet the requirements. SLAC has worldwide unique dedicated test facilities, Cathode Test System and dc-Gun Test Laboratory, to fully characterize polarized photocathodes. Recent systematic measurements on a strained-well InAlGaAs/AlGaAs cathode at the facilities show that 87% polarization and 0.3% QE are achieved. The QE can be increased to {approx}1.0% with atomic hydrogen cleaning. The surface charge limit at a very low current intensity and the clear dependence of the polarization on the surface charge limit are observed for the first time. On-going programs to develop photocathodes for the ILC and CLIC are briefly introduced.

Correlation of CsK{sub 2}Sb photocathode lifetime with antimony thickness

Energy Technology Data Exchange (ETDEWEB)

Mamun, M. A., E-mail: mmamu001@odu.edu; Elmustafa, A. A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 (United States); The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, C.; Poelker, M. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2015-06-01

CsK{sub 2}Sb photocathodes with quantum efficiency on the order of 10% at 532 nm, and lifetime greater than 90 days at low voltage, were successfully manufactured via co-deposition of alkali species emanating from an effusion source. Photocathodes were characterized as a function of antimony layer thickness and alkali consumption, inside a vacuum chamber that was initially baked, but frequently vented without re-baking. Photocathode lifetime measured at low voltage is correlated with the antimony layer thickness. Photocathodes manufactured with comparatively thick antimony layers exhibited the best lifetime. We speculate that the antimony layer serves as a reservoir, or sponge, for the alkali.

Photocathode non-uniformity contribution to the energy resolution of scintillators

International Nuclear Information System (INIS)

Mottaghian, M.; Koohi-Fayegh, R.; Ghal-Eh, N.; Etaati, G. R.

2010-01-01

This paper introduces the basics of the light transport simulation in scintillators and the wavelength-dependencies in the process. The non-uniformity measurement of the photocathode surface is undertaken, showing that for the photocathode used in this study the quantum efficiency falls to about 4% of its maximum value, especially in areas far from the centre. The wavelength-and position-dependent quantum efficiency is implemented in the Monte Carlo light transport code, showing that, the contribution of the photocathode non-uniformity to the energy resolution is estimated to be around 18%, when all position-and wavelength-dependencies are included. (authors)

Particle Simulations of a Thermionic RF Gun with Gridded Triode Structure for Reduction of Back-Bombardment

CERN Document Server

Kusukame, K; Kii, T; Masuda, K; Nakai, Y; Ohgaki, H; Yamazaki, T; Yoshikawa, K; Zen, H

2005-01-01

Thermionic RF guns show advantageous features compared with photocathode ones such as easy operation and much higher repetition rate of micropulses, both of which are suitable for their application to high average power FELs. They however suffer from the back-bombardment effect [1], i.e., in conventional RF guns, electrons are extracted from cathode also in the latter half of accelerating phase and tend to back-stream to hit the cathode, and as a result the macropulse duration is limited down to severalμsec Against this adverse effect in thermionic RF guns, introduction of the triode structure has been proposed [2], where the accelerating phase and amplitude nearby the cathode can be controlled regardless of the phase of the first accelerating cell in the conventional RF gun. Our one-dimensional particle simulation results predict that the back-bombardment power can be reduced by 99 % only with 30-40 kW RF power fed to the grid in the present triode structure with an optimal phase difference from th...

Observation of Significant Quantum Efficiency Enhancement from a Polarized Photocathode with Distributed Bragg Reflector

Energy Technology Data Exchange (ETDEWEB)

Zhang, Shukui [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Stutzman, Marcy L. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Chen, Yiqiao [SVT Associates, Inc., Eden Prairie, MN (United States); Moy, Aaron [SVT Associates, Inc., Eden Prairie, MN (United States)

2015-09-01

Polarized photocathodes with higher Quantum efficiency (QE) would help to reduce the technological challenge associated with producing polarized beams at milliampere levels, because less laser light would be required, which simplifies photocathode cooling requirements. And for a given amount of available laser power, higher QE would extend the photogun operating lifetime. The distributed Bragg reflector (DBR) concept was proposed to enhance the QE of strained-superlattice photocathodes by increasing the absorption of the incident photons using a Fabry-Perot cavity formed between the front surface of the photocathode and the substrate that includes a DBR, without compromising electron polarization. Here we present recent results showing QE enhancement of a GaAs/GaAsP strained-superlattice photocathode made with a DBR structure. Typically, a GaAs/GaAsP strained-superlattice photocathode without DBR provides a QE of 1%, at a laser wavelength corresponding to peak polarization. In comparison, the GaAs/GaAsP strained-superlattice photocathodes with DBR exhibited an enhancement of over 2 when the incident laser wavelength was tuned to meet the resonant condition for the Fabry-Perot resonator.

Electron beam and rf characterization of a low-emittance X-band photoinjector

Directory of Open Access Journals (Sweden)

D. J. Gibson

2001-09-01

Full Text Available Detailed experimental studies of the first operation of an X-band (8.547 GHz rf photoinjector are reported. The rf characteristics of the device are first described, as well as the tuning technique used to ensure operation of the 11/2-cell rf gun in the balanced π-mode. The characterization of the photoelectron beam produced by the rf gun includes: measurements of the bunch charge as a function of the laser injection phase, yielding information about the quantum efficiency of the Cu photocathode ( 2×10^{-5} for a surface field of 100 MV/m; measurements of the beam energy (1.5–2 MeV and relative energy spread ( Δγ/γ_{0}=1.8±0.2% using a magnetic spectrometer; measurements of the beam 90% normalized emittance, which is found to be ɛ_{n}=1.65π mm mrad for a charge of 25 pC; and measurements of the bunch duration ( <2 ps. Coherent synchrotron radiation experiments at Ku-band and Ka-band confirm the extremely short duration of the photoelectron bunch and a peak power scaling quadratically with the bunch charge.

Electron beam bunch length characterizations using incoherent and coherent transition radiation on the APS SASE FEL project

CERN Document Server

Lumpkin, Alex H; Berg, W J; Lewellen, J W; Sereno, N S; Happek, U

2000-01-01

The Advanced Photon Source (APS) injector linac has been reconfigured with a low-emittance RF thermionic gun and a photocathode (PC) RF gun to support self-amplified spontaneous emission (SASE) free-electron laser (FEL) experiments. One of the most critical parameters for optimizing SASE performance (gain length) is the electron beam peak current, which requires a charge measurement and a bunch length measurement capability. We report here initial measurements of the latter using both incoherent optical transition radiation (OTR) and coherent transition radiation (CTR). A visible light Hamamatsu C5680 synchroscan streak camera was used to measure the thermionic RF gun beam's bunch length (sigma approx 2-3 ps) via OTR generated by the beam at 220 MeV and 200 mA macropulse average current. In addition, a CTR monitor (Michelson Interferometer) based on a Golay cell as the far-infrared (FIR) detector has been installed at the 40-MeV station in the beamline. Initial observations of CTR signal strength variation wi...

Optimization of cathodic arc deposition and pulsed plasma melting techniques for growing smooth superconducting Pb photoemissive films for SRF injectors

Science.gov (United States)

Nietubyć, Robert; Lorkiewicz, Jerzy; Sekutowicz, Jacek; Smedley, John; Kosińska, Anna

2018-05-01

Superconducting photoinjectors have a potential to be the optimal solution for moderate and high current cw operating free electron lasers. For this application, a superconducting lead (Pb) cathode has been proposed to simplify the cathode integration into a 1.3 GHz, TESLA-type, 1.6-cell long purely superconducting gun cavity. In the proposed design, a lead film several micrometres thick is deposited onto a niobium plug attached to the cavity back wall. Traditional lead deposition techniques usually produce very non-uniform emission surfaces and often result in a poor adhesion of the layer. A pulsed plasma melting procedure reducing the non-uniformity of the lead photocathodes is presented. In order to determine the parameters optimal for this procedure, heat transfer from plasma to the film was first modelled to evaluate melting front penetration range and liquid state duration. The obtained results were verified by surface inspection of witness samples. The optimal procedure was used to prepare a photocathode plug, which was then tested in an electron gun. The quantum efficiency and the value of cavity quality factor have been found to satisfy the requirements for an injector of the European-XFEL facility.

High energy gain electron beam acceleration by 100TW laser

International Nuclear Information System (INIS)

Kotaki, Hideyuki; Kando, Masaki; Kondo, Shuji; Hosokai, Tomonao; Kanazawa, Shuhei; Yokoyama, Takashi; Matoba, Toru; Nakajima, Kazuhisa

2001-01-01

A laser wakefield acceleration experiment using a 100TW laser is planed at JAERI-Kansai. High quality and short pulse electron beams are necessary to accelerate the electron beam by the laser. Electron beam - laser synchronization is also necessary. A microtron with a photocathode rf-gun was prepared as a high quality electron injector. The quantum efficiency (QE) of the photocathode of 2x10 -5 was obtained. A charge of 100pC from the microtron was measured. The emittance and pulse width of the electron beam was 6π mm-mrad and 10ps, respectively. In order to produce a short pulse electron beam, and to synchronize between the electron beam and the laser pulse, an inverse free electron laser (IFEL) is planned. One of problems of LWFA is the short acceleration length. In order to overcome the problem, a Z-pinch plasma waveguide will be prepared as a laser wakefield acceleration tube for 1 GeV acceleration. (author)

A 3 GHz photoelectron gun for high beam intensity

CERN Document Server

Bossart, Rudolf; Dehler, M; Godot, J C

1996-01-01

For the Compact Linear Collider Test Facility (CTF) at CERN a new rf gun with a laser driven photocathode is under construction. The new rf gun will replace the present 11/2 cell gun and will consist of 21/2 cells accelerating the beam to a momentum of 7.0 MeV/c with an electric field strength of 100 MV/m. The strong space-charge forces at low beam energy caused by the high charge density of the electron bunches are contained by radial and longitudinal rf focusing in the gun. The rf gun under construction has been optimized by MAFIA beam simulations for an injector assembly comprising a second accelerating rf structure and an intermediate solenoid magnet correcting the beam divergence of the 21/2 cell gun. The beam loading of the rf gun, by a train of 48 bunches with 21 nC charge each, causes a strong energy decay accompanied by an increase of the flight time for the bunches with lower energy. These effects can be corrected by slightly shifting the acceleration frequency of the gun. The experimental results...

A high-power rf linear accelerator for FELS [free-electron lasers

International Nuclear Information System (INIS)

Sheffield, R.L.; Watson, J.M.

1987-01-01

This paper describes the design of a high average current rf linear accelerator suitable for driving short-wavelength free-electron lasers (FEL). It is concluded that the design of a room-temperature rf linear acelerator that can meet the stringent requirements of a high-power short-wavelength FEL appears possible. The accelerator requires the use of an advanced photoelectric injector that is under development; the accelerator components, however, do not require appreciable development. At these large beam currents, low-frequency, large-bore room-temperature cavities can be highly efficient and give all specified performance with minimal risk. 20 refs

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

Development of a novel thermionic RF electron gun applied on a compact THz-FEL facility

Science.gov (United States)

Hu, T. N.; Pei, Y. J.; Qin, B.; Liu, K. F.; Feng, G. Y.

2018-04-01

The current requirements from civil and commercial applications lead to the development of compact free-electron laser (FEL)-based terahertz (THz) radiation sources. A picosecond electron gun plays an important role in an FEL-THz facility and attracts significant attention, as machine performance is very sensitive to initial conditions. A novel thermionic gun with an external cathode (EC) and two independently tunable cavities (ITCs) has been found to be a promising alternative to conventional electron sources due to its remarkable characteristics, and correspondingly an FEL injector can achieve a balance between a compact layout and high brightness benefitting from the velocity bunching properties and RF focusing effects in the EC-ITC gun. Nevertheless, the EC-ITC gun has not been extensively examined as part of the FEL injector in the past years. In this regard, to fill this gap, a development focusing on the experimental setup of an FEL injector based on an EC-ITC gun is described in detail. Before assembly, dynamic beam simulations were performed to investigate the optimal mounting position for the Linac associated with the focusing coils, and a suitable radio-frequency (RF) system was established based on a power coupling design and allocation. The testing bench proved to be fully functional through basic experiments using typical diagnostic approaches for estimating primary parameters. Associated with dynamic beam calculations, a performance evaluation for an EC-ITC gun was established while providing indirect testing results for an FEL injector.

Photoemission characteristics of thin GaAs-based heterojunction photocathodes

Energy Technology Data Exchange (ETDEWEB)

Feng, Cheng; Zhang, Yijun, E-mail: zhangyijun423@126.com; Qian, Yunsheng [Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094 (China); Shi, Feng [Science and Technology on Low-Light-Level Night Vision Laboratory, Xi' an 710065 (China); Zou, Jijun [Engineering Research Center of Nuclear Technology Application (East China Institute of Technology), Ministry of Education, Nanchang 330013 (China); Zeng, Yugang [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

2015-01-14

To better understand the different photoemission mechanism of thin heterojunction photocathodes, the quantum efficiency models of reflection-mode and transmission-mode GaAs-based heterojunction photocathodes are revised based on one-dimensional continuity equations, wherein photoelectrons generated from both the emission layer and buffer layer are taken into account. By comparison of simulated results between the revised and conventional models, it is found that the electron contribution from the buffer layer to shortwave quantum efficiency is closely related to some factors, such as the thicknesses of emission layer and buffer layer and the interface recombination velocity. Besides, the experimental quantum efficiency data of reflection-mode and transmission-mode AlGaAs/GaAs photocathodes are well fitted to the revised models, which confirm the applicability of the revised quantum efficiency models.

Experimental measurements and theoretical model of the cryogenic performance of bialkali photocathode and characterization with Monte Carlo simulation

Directory of Open Access Journals (Sweden)

Huamu Xie

2016-10-01

Full Text Available High-average-current, high-brightness electron sources have important applications, such as in high-repetition-rate free-electron lasers, or in the electron cooling of hadrons. Bialkali photocathodes are promising high-quantum-efficiency (QE cathode materials, while superconducting rf (SRF electron guns offer continuous-mode operation at high acceleration, as is needed for high-brightness electron sources. Thus, we must have a comprehensive understanding of the performance of bialkali photocathode at cryogenic temperatures when they are to be used in SRF guns. To remove the heat produced by the radio-frequency field in these guns, the cathode should be cooled to cryogenic temperatures. We recorded an 80% reduction of the QE upon cooling the K_{2}CsSb cathode from room temperature down to the temperature of liquid nitrogen in Brookhaven National Laboratory (BNL’s 704 MHz SRF gun. We conducted several experiments to identify the underlying mechanism in this reduction. The change in the spectral response of the bialkali photocathode, when cooled from room temperature (300 K to 166 K, suggests that a change in the ionization energy (defined as the energy gap from the top of the valence band to vacuum level is the main reason for this reduction. We developed an analytical model of the process, based on Spicer’s three-step model. The change in ionization energy, with falling temperature, gives a simplified description of the QE’s temperature dependence. We also developed a 2D Monte Carlo code to simulate photoemission that accounts for the wavelength-dependent photon absorption in the first step, the scattering and diffusion in the second step, and the momentum conservation in the emission step. From this simulation, we established a correlation between ionization energy and reduction in the QE. The simulation yielded results comparable to those from the analytical model. The simulation offers us additional capabilities such as calculation

Measurements of Compression and Emittance Growth after the First LCLS Bunch Compressor Chicane

International Nuclear Information System (INIS)

Emma, P.

2007-01-01

The Linac Coherent Light Source (LCLS) is a SASE xray free-electron laser project presently under construction at SLAC. The injector section from RF photocathode gun through first bunch compressor chicane was installed during the fall of 2006. The first bunch compressor is located at 250 MeV and nominally compresses a 1-nC electron bunch from an rms length of about 1 mm to 0.2 mm. Transverse phase space and bunch length diagnostics are located immediately after the chicane. We present preliminary measurements and simulations of the longitudinal and transverse phase space after the chicane in various beam conditions, including extreme compression with micron-scale current spikes

Surface science analysis of GaAs photocathodes following sustained electron beam delivery

Directory of Open Access Journals (Sweden)

V. Shutthanandan

2012-06-01

Full Text Available Degradation of the photocathode materials employed in photoinjectors represents a challenge for sustained operation of nuclear physics accelerators and high power free electron lasers (FEL. Photocathode quantum efficiency degradation is due to residual gases in the electron source vacuum system being ionized and accelerated back to the photocathode. These investigations are a first attempt to characterize the nature of the photocathode degradation, and employ multiple surface and bulk analysis techniques to investigate damage mechanisms including sputtering of the Cs-oxidant surface monolayer, other surface chemistry effects, and ion implantation. Surface and bulk analysis studies were conducted on two GaAs photocathodes, which were removed from the JLab FEL DC photoemission gun after delivering electron beam, and two control samples. The analysis techniques include helium ion microscopy, Rutherford backscattering spectrometry (RBS, atomic force microscopy, and secondary ion mass spectrometry (SIMS. In addition, two high-polarization strained superlattice GaAs photocathode samples, one removed from the continuous electron beam accelerator facility (CEBAF photoinjector and one unused, were also analyzed using transmission electron microscopy (TEM and SIMS. It was found that heat cleaning the FEL GaAs wafer introduces surface roughness, which seems to be reduced by prolonged use. The bulk GaAs samples retained a fairly well organized crystalline structure after delivering beam but show evidence of Cs depletion on the surface. Within the precision of the SIMS and RBS measurements, the data showed no indication of hydrogen implantation or lattice damage from ion back bombardment in the bulk GaAs wafers. In contrast, SIMS and TEM measurements of the strained superlattice photocathode show clear crystal damage in the wafer from ion back bombardment.

European contributions to the beam source design and R and D of the ITER neutral beam injectors

International Nuclear Information System (INIS)

Massmann, P.; Bayetti, P.; Bucalossi, J.

2001-01-01

The paper reports on the progress made by the European Home Team in strong interaction with the ITER JCT and JAERI regarding several key aspects of the beam source for the ITER injectors: integration of the SINGAP accelerator into the ITER injector design. This is a substantially simpler concept than the MAMuG accelerator of the ITER NBI 'reference design', which has potential for significant cost savings, and which avoids some of the weaknesses of the reference design such as the need for intermediate high voltage potentials from the HV power supply and pressurised gas insulation; high energy negative ion acceleration using a SINGAP accelerator; long pulse (i.e. >1000 s) negative ion source operation in deuterium; RF source development, which could reduce the scheduled maintenance of the ITER injectors (as it uses no filaments), and simplify the transmission line and the auxiliary power supplies for the ion source. (author)

European contributions to the beam source design and R and D of the ITER neutral beam injectors

International Nuclear Information System (INIS)

Massmann, P.; Bayetti, P.; Bucalossi, J.

1999-01-01

The paper reports on the progress made by the European Home Team in strong interaction with the ITER JCT and JAERI regarding several key aspects of the beam source for the ITER injectors: integration of the SINGAP accelerator into the ITER injector design. This is a substantially simpler concept than the MAMuG accelerator of the ITER NBI 'reference design', which has potential for significant cost savings, and which avoids some of the weaknesses of the reference design such as the need for intermediate high voltage potentials from the HV power supply and pressurised gas insulation; high energy negative ion acceleration using a SINGAP accelerator; long pulse (i.e. >1000 s) negative ion source operation in deuterium; RF source development, which could reduce the scheduled maintenance of the ITER injectors (as it uses no filaments), and simplify the transmission line and the auxiliary power supplies for the ion source. (author)

Photocathode Optimization for a Dynamic Transmission Electron Microscope: Final Report

Energy Technology Data Exchange (ETDEWEB)

Ellis, P; Flom, Z; Heinselman, K; Nguyen, T; Tung, S; Haskell, R; Reed, B W; LaGrange, T

2011-08-04

The Dynamic Transmission Electron Microscope (DTEM) team at Harvey Mudd College has been sponsored by LLNL to design and build a test setup for optimizing the performance of the DTEM's electron source. Unlike a traditional TEM, the DTEM achieves much faster exposure times by using photoemission from a photocathode to produce electrons for imaging. The DTEM team's work is motivated by the need to improve the coherence and current density of the electron cloud produced by the electron gun in order to increase the image resolution and contrast achievable by DTEM. The photoemission test setup is nearly complete and the team will soon complete baseline tests of electron gun performance. The photoemission laser and high voltage power supply have been repaired; the optics path for relaying the laser to the photocathode has been finalized, assembled, and aligned; the internal setup of the vacuum chamber has been finalized and mostly implemented; and system control, synchronization, and data acquisition has been implemented in LabVIEW. Immediate future work includes determining a consistent alignment procedure to place the laser waist on the photocathode, and taking baseline performance measurements of the tantalum photocathode. Future research will examine the performance of the electron gun as a function of the photoemission laser profile, the photocathode material, and the geometry and voltages of the accelerating and focusing components in the electron gun. This report presents the team's progress and outlines the work that remains.

Phase and amplitude stability of a pulsed RF system on the example of the CLIC drive beam LINAC

CERN Document Server

AUTHOR|(CDS)2132320; Prof. BANTEL, Michael

The CLIC drive beam accelerator consists of the Drive Beam Injector (DBI) and two Drive Beam Linacs (DBLs). The drive beam injector is composed of a thermionic electron source, 3 Sub Harmonic Bunchers (SHBs), a pre-buncher, and several acceleration structures. In the electron source the DC electron beam is produced from a thermionic cathode. The following buncher cavities group ("bunch") the electrons to be accelerated by RF later on. Each electron bunch has an energy of 140 keV, a length of 3 mm, and a charge qb = 8.4 nC. Afterwards the electrons are accelerated in the 1 GHz accelerating structures up to 50MeV. The pulsed Radio Frequency (RF) power for this acceleration is provided by 1 GHz, 20MW modulator-klystron units, one per acceleration structure. A klystron is an RF amplifier based on a linear-beam vacuum tube. The high voltage modulator supplies the acceleration voltage to this tube. A DC electron beam gets modulated with an input signal, the modulation enhances in a drift space, and finally the powe...

LHC Report: imaginative injectors

CERN Multimedia

Pierre Freyermuth for the LHC team

2016-01-01

A new bunch injection scheme from the PS to the SPS allowed the LHC to achieve a new peak luminosity record.   Figure 1: PSB multi-turn injection principle: to vary the parameters during injection with the aim of putting the newly injected beam in a different region of the transverse phase-space plan. The LHC relies on the injector complex to deliver beam with well-defined bunch populations and the necessary transverse and longitudinal characteristics – all of which fold directly into luminosity performance. There are several processes taking place in the PS Booster (PSB) and the Proton Synchrotron (PS) acting on the beam structure in order to obtain the LHC beam characteristics. Two processes are mainly responsible for the beam brightness: the PSB multi-turn injection and the PS radio-frequency (RF) gymnastics. The total number of protons in a bunch and the transverse emittances are mostly determined by the multi-turn Booster injection, while the number of bunches and their time spacin...

Ion Back-Bombardment of GaAs Photocathodes Inside DC High Voltage Electron Guns

CERN Document Server

Grames, Joseph M; Brittian, Joshua; Charles, Daniel; Clark, Jim; Hansknecht, John; Lynn Stutzman, Marcy; Poelker, Matthew; Surles-Law, Kenneth E

2005-01-01

The primary limitation for sustained high quantum efficiency operation of GaAs photocathodes inside DC high voltage electron guns is ion back-bombardment of the photocathode. This process results from ionization of residual gas within the cathode/anode gap by the extracted electron beam, which is subsequently accelerated backwards to the photocathode. The damage mechanism is believed to be either destruction of the negative electron affinity condition at the surface of the photocathode or damage to the crystal structure by implantation of the bombarding ions. This work characterizes ion formation within the anode/cathode gap for gas species typical of UHV vacuum chambers (i.e., hydrogen, carbon monoxide and methane). Calculations and simulations are performed to determine the ion trajectories and stopping distance within the photocathode material. The results of the simulations are compared with test results obtained using a 100 keV DC high voltage GaAs photoemission gun and beamline at currents up to 10 mA D...

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.)

Performance potential of the injectors after LS1

International Nuclear Information System (INIS)

Bartosik, H.; Carli, C.; Damerau, H.; Garoby, R.; Gilardoni, S.; Goddard, B.; Hancock, S.; Hanke, K.; Lombardi, A.; Mikulec, B.; Raginel, V.; Rumolo, G.; Shaposhnikova, E.; Vretenar, M.

2012-01-01

The main upgrades of the injector chain in the framework of the LIU Project will only be implemented in the second long shutdown (LS2), in particular the increase of the PSB-PS transfer energy to 2 GeV or the implementation of cures/solutions against instabilities/e-cloud effects etc. in the SPS. On the other hand, Linac4 will become available by the end of 2014. Until the end of 2015 it may replace Linac2 at short notice, taking 50 MeV protons into the PSB via the existing injection system but with reduced performance. Afterwards, the H - injection equipment will be ready and Linac4 could be connected for 160 MeV H - injection into the PSB during a prolonged winter shutdown before LS2. The anticipated beam performance of the LHC injectors after LS1 in these different cases is presented. Space charge on the PS flat-bottom will remain a limitation because the PSB-PS transfer energy will stay at 1.4 GeV. As a mitigation measure new RF manipulations are presented which can improve brightness for 25 ns bunch spacing, allowing for more than nominal luminosity in the LHC. (authors)

RF power source for the compact linear collider test facility (CTF3)

CERN Document Server

McMonagle, G; Brown, Peter; Carron, G; Hanni, R; Mourier, J; Rossat, G; Syratchev, I V; Tanner, L; Thorndahl, L

2004-01-01

The CERN CTF3 facility will test and demonstrate many vital components of CLIC (Compact Linear Collider). This paper describes the pulsed RF power source at 2998.55 MHz for the drive-beam accelerator (DBA), which produces a beam with an energy of 150 MeV and a current of 3.5 Amps. Where possible, existing equipment from the LEP preinjector, especially the modulators and klystrons, is being used and upgraded to achieve this goal. A high power RF pulse compression system is used at the output of each klystron, which requires sophisticated RF phase programming on the low level side to achieve the required RF pulse. In addition to the 3 GHz system two pulsed RF sources operating at 1.5 GHz are being built. The first is a wide-band, low power, travelling wave tube (TWT) for the subharmonic buncher (SHB) system that produces a train of "phase coded" subpulses as part of the injector scheme. The second is a high power narrow band system to produce 20 MW RF power to the 1.5 GHz RF deflectors in the delay loop situate...

Structured photocathodes for improved high-energy x-ray efficiency in streak cameras

Energy Technology Data Exchange (ETDEWEB)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Huffman, E.; Koch, J. A. [National Security Technologies, LLC, Livermore, California 94551 (United States); Bell, P. M.; Bradley, D. K.; Hatch, B.; Landen, O. L.; MacPhee, A. G.; Nagel, S. R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Chen, N.; Gopal, A.; Udin, S. [Nanoshift LLC, Emeryville, California 94608 (United States); Feng, J. [Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Hilsabeck, T. J. [General Atomics, San Diego, California 92121 (United States)

2016-11-15

We have designed and fabricated a structured streak camera photocathode to provide enhanced efficiency for high energy X-rays (1–12 keV). This gold coated photocathode was tested in a streak camera and compared side by side against a conventional flat thin film photocathode. Results show that the measured electron yield enhancement at energies ranging from 1 to 10 keV scales well with predictions, and that the total enhancement can be more than 3×. The spatial resolution of the streak camera does not show degradation in the structured region. We predict that the temporal resolution of the detector will also not be affected as it is currently dominated by the slit width. This demonstration with Au motivates exploration of comparable enhancements with CsI and may revolutionize X-ray streak camera photocathode design.

Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

CERN Document Server

Pompili, Riccardo; Bellaveglia, M; Biagioni, A; Castorina, G; Chiadroni, E; Cianchi, A; Croia, M; Di Giovenale, D; Ferrario, M; Filippi, F; Gallo, A; Gatti, G; Giorgianni, F; Giribono, A; Li, W; Lupi, S; Mostacci, A; Petrarca, M; Piersanti, L; Di Pirro, G; Romeo, S; Scifo, J; Shpakov, V; Vaccarezza, C; Villa, F

2017-01-01

The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC_LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations.

Femtosecond timing-jitter between photo-cathode laser and ultra-short electron bunches by means of hybrid compression

International Nuclear Information System (INIS)

Pompili, R; Anania, M P; Bellaveglia, M; Biagioni, A; Castorina, G; Chiadroni, E; Croia, M; Giovenale, D Di; Ferrario, M; Gallo, A; Gatti, G; Cianchi, A; Filippi, F; Giorgianni, F; Giribono, A; Lupi, S; Mostacci, A; Petrarca, M; Piersanti, L; Li, W

2016-01-01

The generation of ultra-short electron bunches with ultra-low timing-jitter relative to the photo-cathode (PC) laser has been experimentally proved for the first time at the SPARC-LAB test-facility (INFN-LNF, Frascati) exploiting a two-stage hybrid compression scheme. The first stage employs RF-based compression (velocity-bunching), which shortens the bunch and imprints an energy chirp on it. The second stage is performed in a non-isochronous dogleg line, where the compression is completed resulting in a final bunch duration below 90 fs (rms). At the same time, the beam arrival timing-jitter with respect to the PC laser has been measured to be lower than 20 fs (rms). The reported results have been validated with numerical simulations. (paper)

A kaon physics program at the Fermilab Main Injector

International Nuclear Information System (INIS)

Cooper, Peter

1997-11-01

In this paper we describe a triad of kaon experiments which will form the foundation of a kaon physics program at Fermilab in the Main Injector era. These three experiments; KAMI, CKM and CPT, span the range of experiment types discussed above. KAMI will use the existing neutral kaon beam and the KTeV detector as the basis of a search for the Standard Model ultra rare decay K L → π 0 ν anti ν decay mode is by far the theoretically cleanest measurement of the Standard Model parameter responsible for CP violation. CKM will measure the analogous charged kaon decay mode. Together these two experiments will determine the Standard Model contribution to CP violation independent of the B meson sector. The Standard Model parameters controlling CP violation must be observed to be the same in the K and B meson sectors in order to confirm the Standard Model as the sole source of CP violation in nature. CPT is a hybrid beam experiment using a high purity K + beam to produce a pure K 0 beam in order to search for violation of CPT symmetry at a mass scale up to the Planck mass. CPT also will measure new CP violation parameters to test the Standard Model and search for rare K S decays. The Fermilab infrastructure for such a physics program largely already exists. The Main Injector will be an existing accelerator by late 1998 with beam properties comparable to any of the previous ''kaon factory'' proposals. The KTeV detector and neutral kaon beamline are unsurpassed in the world and were originally designed to also operate with the 120 GeV Main Injector beam as KAMI. The Fermilab Meson laboratory was originally designed as an area for fixed target experiments using 200 GeV proton beams. The charged kaon beam experiments will naturally find a home there. Both charged kaon experiments, CKM and CPT, will share a new high purity RF separated charged kaon beam based on superconducting RF technology which will provide the highest intensity and purity charged kaon beam in the world

Research on the character and development of the neutral beam injector RF negative ion source

International Nuclear Information System (INIS)

Guan Liang

2011-01-01

The RF source is now an interesting alternative to the reference design with filamented sources due to its maintenance-free operation. Extensive R and D work on RF-driven negative hydrogen ion sources carried out at IPP Garching led to the decision of ITER to select this type of source as the new reference source for the ITER NBI system.The work is progressing with three test beds: BATMAN, MANITU and RADI, which are being used to carry out different investigations in parallel. The experimental results show that the RF source equals or surpasses the ITER requirements. (authors)

Linac4, a New Injector for the CERN PS Booster

CERN Document Server

Garoby, R; Gerigk, F; Hanke, K; Lombardi, A; Pasini, M; Rossi, C; Sargsyan, E; Vretenar, M

2006-01-01

The first bottle-neck towards higher beam brightness in the LHC injector chain is due to space charge induced tune spread at injection into the CERN PS Booster (PSB). A new injector called Linac4 is proposed to remove this limitation. Using RF cavities at 352 and 704 MHz, it will replace the present 50 MeV proton Linac2, and deliver a 160 MeV, 40 mA H- beam. The higher injection energy will reduce space charge effects by a factor of 2, and charge exchange will drastically reduce the beam losses at injection. Operation will be simplified and the beam brightness required for the LHC ultimate luminosity should be obtained at PS ejection. Moreover, for the needs of non-LHC physics experiments like ISOLDE, the number of protons per pulse from the PSB will increase by a significant factor. This new linac constitutes an essential component of any of the envisaged LHC upgrade scenarios. It is also designed to become the low energy part of a future 3.5 GeV, multi-megawatt superconducting linac (SPL). The present desig...

Start-to-end simulation of the injector for a compact THz source

OpenAIRE

Li, J.; Pei, Y. J.; Shang, L.; Feng, G.; Hu, T.; Chen, Q.; Li, C.

2013-01-01

Terahertz radiation has broad application prospect due to its ability to penetrate deep into many organic materials without damage caused by ionizing radiations. A FEL-based THz source is the best choice to produce high-power radiation. In this paper, a 14 MeV injector is introduced for generating high-quality beam for FEL, which is composed of an EC-ITC RF gun, compensating coils and a travelling-wave structure. Start-to-end simulation has been done with ASTRA code to verify the design and t...

Comparative research on the transmission-mode GaAs photocathodes of exponential-doping structures

International Nuclear Information System (INIS)

Chen Liang; Qian Yun-Sheng; Zhang Yi-Jun; Chang Ben-Kang

2012-01-01

Early research has shown that the varied doping structures of the active layer of GaAs photocathodes have been proven to have a higher quantum efficiency than uniform doping structures. On the basis of our early research on the surface photovoltage of GaAs photocathodes, and comparative research before and after activation of reflection-mode GaAs photocathodes, we further the comparative research on transmission-mode GaAs photocathodes. An exponential doping structure is the typical varied doping structure that can form a uniform electric field in the active layer. By solving the one-dimensional diffusion equation for no equilibrium minority carriers of transmission-mode GaAs photocathodes of the exponential doping structure, we can obtain the equations for the surface photovoltage (SPV) curve before activation and the spectral response curve (SRC) after activation. Through experiments and fitting calculations for the designed material, the body-material parameters can be well fitted by the SPV before activation, and proven by the fitting calculation for SRC after activation. Through the comparative research before and after activation, the average surface escape probability (SEP) can also be well fitted. This comparative research method can measure the body parameters and the value of SEP for the transmission-mode GaAs photocathode more exactly than the early method, which only measures the body parameters by SRC after activation. It can also help us to deeply study and exactly measure the parameters of the varied doping structures for transmission-mode GaAs photocathodes, and optimize the Cs-O activation technique in the future. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Experience with a radio frequency gun on the SSRL Injector Linac

International Nuclear Information System (INIS)

Weaver, J.N.; Genin, R.D.; Golceff, P.; Morales, H.; Sebek, J.

1993-04-01

A-SSRL/Varian-Associates-built, one-and-a-half cavity microwave, thermionic-cathode gun has operated on the SSRL Injector Linac reliably without changing the cathode for over 10,000 hours, with no significant decrease in emission. Thus, for a pulsed electron beam, with a maximum of 0.5 A peak at 2 to 3 MeV from a 3.5 MW peak rf pulse of 2 μs pulse width at 10 pps, the apparent but small amount of back bombardment of the cathode has been tolerable. Use of a bunch-compression alpha magnet and a stripline chopper after the gun produces the required S-band 3 to 5 microbunches of electrons for injection into a standard 10-m-long linac and on into a booster synchrotron, which in turn is used to fill SPEAR. Component limitations and operating characteristics of the gun and the linac's rf system are discussed

Beam emittance and the effects of the rf, space charge and wake fields: Application to the ATF photoelectron beam

International Nuclear Information System (INIS)

Parsa, Z.

1991-01-01

Laser driven photoelectron guns are of interest for use in new methods of accelerations, future development of Linear Colliders and new experiments such as Free Electron laser (IFEL). Such guns are potential source of low emittance-high current and short bunch length electron beams, where the emitted electrons are accelerated quickly to a relativistic energy by a strong rf, electric field in the cavity. We present a brief overview of the beam dynamic studies, e.g. emittance for the Brookhaven National Laboratory (BNL) ATF high brightness photocathode radio frequency gun (now in operation), and show the effects of the rf, Space Charge, and Wake fields on the photoelectrons. 4 refs., 7 figs

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)

Experimental program to build a multimegawatt lasertron for super linear colliders

International Nuclear Information System (INIS)

Garwin, E.L.; Herrmannsfeldt, W.B.; Sinclair, C.; Weaver, J.N.; Welch, J.J.; Wilson, P.B.

1985-04-01

A lasertron (a microwave ''triode'' with an RF output cavity and an RF modulated laser to illuminate a photocathode) is a possible high power RF amplifier for TeV linear colliders. As the first step toward building a 35 MW, S-band lasertron for a proof of principle demonstration, a 400 kV dc diode is being designed with a GaAs photocathode, a drift-tube and a collector. After some cathode life tests are made in the diode, an RF output cavity will replace the drift tube and a mode-locked, frequency-doubled, Nd:YAG laser, modulated to produce a 1 us-long comb of 60 ps pulses at a 2856 MHz rate, will be used to illuminate the photocathode to make an RF power source out of the device. This paper discusses the plans for the project and includes some results of numerical simulation studies of the lasertron as well as some of the ultra-high vacuum and mechanical design requirements for incorporating a photocathode

Advanced photoinjector experiment photogun commissioning results

Science.gov (United States)

Sannibale, F.; Filippetto, D.; Papadopoulos, C. F.; Staples, J.; Wells, R.; Bailey, B.; Baptiste, K.; Corlett, J.; Cork, C.; De Santis, S.; Dimaggio, S.; Doolittle, L.; Doyle, J.; Feng, J.; Garcia Quintas, D.; Huang, G.; Huang, H.; Kramasz, T.; Kwiatkowski, S.; Lellinger, R.; Moroz, V.; Norum, W. E.; Padmore, H.; Pappas, C.; Portmann, G.; Vecchione, T.; Vinco, M.; Zolotorev, M.; Zucca, F.

2012-10-01

The Advanced Photoinjector Experiment (APEX) at the Lawrence Berkeley National Laboratory is dedicated to the development of a high-brightness high-repetition rate (MHz-class) electron injector for x-ray free-electron laser (FEL) and other applications where high repetition rates and high brightness are simultaneously required. The injector is based on a new concept rf gun utilizing a normal-conducting (NC) cavity resonating in the VHF band at 186 MHz, and operating in continuous wave (cw) mode in conjunction with high quantum efficiency photocathodes capable of delivering the required charge at MHz repetition rates with available laser technology. The APEX activities are staged in three phases. In phase 0, the NC cw gun is built and tested to demonstrate the major milestones to validate the gun design and performance. Also, starting in phase 0 and continuing in phase I, different photocathodes are tested at the gun energy and at full repetition rate for validating candidate materials to operate in a high-repetition rate FEL. In phase II, a room-temperature pulsed linac is added for accelerating the beam at several tens of MeV to reduce space charge effects and allow the measurement of the brightness of the beam from the gun when integrated in an injector scheme. The installation of the phase 0 beam line and the commissioning of the VHF gun are completed, phase I components are under fabrication, and initial design and specification of components and layout for phase II are under way. This paper presents the phase 0 commissioning results with emphasis on the experimental milestones that have successfully demonstrated the APEX gun capability of operating at the required performance.

SLC polarized beam source ultra-high-vacuum design

International Nuclear Information System (INIS)

Lavine, T.L.; Clendenin, J.E.; Garwin, E.L.; Hoyt, E.W.; Hoyt, M.W.; Miller, R.H.; Nuttall, J.A.; Schultz, D.C.; Wright, D.

1991-05-01

This paper describes the design of the ultra-high vacuum system for the beam-line from the 160-kV polarized electron gun to the linac injector in the Stanford Linear Collider (SLC). The polarized electron source is a GaAs photocathode, requiring 10 -11 -Torr-range pressure for adequate quantum efficiency and longevity. The photo-cathode is illuminated by 3-nsec-long laser pulses. Photo-cathode maintenance and improvements require occasional substitution of guns with rapid restoration of UHV conditions. Differential pumping is crucial since the pressure in the injector is more than 10 times greater than the photocathode can tolerate, and since electron-stimulated gas desorption from beam loss in excess of 0.1% of the 20-nC pulses may poison the photocathode. Our design for the transport line contains a differential pumping region isolated by a pair of valves. Exchange of guns requires venting only this isolated region which can be restored to UHV rapidly by baking. The differential pumping is performed by non-evaporable getters (NEGs) and an ion pump. 3 refs., 3 figs

JAERI 200 kV electron gun with an NEA-GaAs photocathode

International Nuclear Information System (INIS)

Nishitani, Tomohiro; Minehara, Eisuke J.; Hajima, Ryoichi; Nagai, Ryoji; Sawamura, Masaru; Nishimori, Nobuyuki; Kikuzawa, Nobuhiro; Yamauchi, Toshihiko

2004-01-01

The photocathode DC-gun with high average current, low beam emittance and long operational lifetime is considered to be indispensable for ERL-FEL. We have started the development program of a 200 keV electron gun with the NEA-GaAs photocathode for the first time in JAERI. In order to long an NEA surface lifetime, the JAERI 200 kV electron gun system consists of a 200 kV DC-gun chamber on extreme high vacuum condition and an NEA activation chamber with load-lock system. We report the goal of photocathode DC-gun R and D and the schedule of a developmental program. (author)

53 MHZ Feedforward beam loading compensation in the Fermilab main injector

International Nuclear Information System (INIS)

Joseph E Dey et al.

2003-01-01

53 MHz feedforward beam loading compensation is crucial to all operations of the Main Injector. Recently a system using a fundamental frequency down converter mixer, a digital bucket delay module and a fundamental frequency up converter mixer were used to produce a one-turn-delay feedforward signal. This signal was then combined with the low level RF signal to the cavities to cancel the transient beam induced voltage. During operation they have shown consistently over 20 dB reduction in side-band voltage around the fundamental frequency during Proton coalescing and over 14 dB in multi-batch antiproton coalescing

Beam dynamics simulations of the injector for a compact THz source

Science.gov (United States)

Li, Ji; Pei, Yuan-Ji; Shang, Lei; Feng, Guang-Yao; Hu, Tong-Ning; Chen, Qu-Shan; Li, Cheng-Long

2014-08-01

Terahertz radiation has broad application prospects due to its ability to penetrate deep into many organic materials without the damage caused by ionizing radiations. A free electron laser (FEL)-based THz source is the best choice to produce high-power radiation. In this paper, a 14 MeV injector is introduced for generating high-quality beam for FEL, is composed of an EC-ITC RF gun, compensating coils and a travelling-wave structure. Beam dynamics simulations have been done with ASTRA code to verify the design and to optimize parameters. Simulations of the operating mode at 6 MeV have also been executed.

The light-ion injector

International Nuclear Information System (INIS)

Anon.

1983-01-01

In an extensive field mapping program the magnetic fields of the main coils and various pole-gap coils of the light-ion injector (SPC1) were measured. As a further test, the measured field maps were used to calculate the excitation currents through the various coils for a specific field shape. Orbit calculations, based on the electric potential fields measured is the electrolytic tank on the 3:1 scale model of the central region, made it possible to optimise the ion-source position, improve the axial focussing of the beam and specify an approximate position for the second axial. The coils for the first magnetic channel were manufactured and field measurements with the channel in position in the pole-gap have been performed. The radio-frequency system of SPC1 consists of three main sections, namely resonators, power amplifiers and the control systems. The purpose of the rf-system is to provide the accelerating voltages of up to 70 kV peak in the 8,6 to 26 MHz frequency range, which are required to accelerate the particle beams

Results from the CLIC Test Facility

CERN Document Server

Braun, H; Bossart, Rudolf; Chautard, F; Corsini, R; Delahaye, J P; Godot, J C; Hutchins, S; Kamber, I; Madsen, J H B; Rinolfi, Louis; Rossat, G; Schreiber, S; Suberlucq, Guy; Thorndahl, L; Wilson, Ian H; Wuensch, Walter

1996-01-01

In order to study the principle of the Compact Linear Collider (CLIC) based on the Two Beam Acceleration (TBA) scheme at high frequency, a CLIC Test Facility (CTF) has been set-up at CERN. After four years of successful running, the experimental programme is now fully completed and all its objectives reached, particularly the generation of a high intensity drive beam with short bunches by a photo-injector, the production of 30 GHz RF power and the acceleration of a probe beam by 30 GHz structures. A summary of the CTF results and their impact on linear collider design is given. This covers 30 GHz high power testing, study of intense, short single bunches; as well as RF-Gun, photocathode and beam diagnostic developments. A second phase of the test facility (CTF2) is presently being installed to demonstrate the feasibility of the TBA scheme by constructing a fully engineered, 10 m long, test section very similar to the CLIC drive and main linacs, producing up to 480 MW of peak RF power at 30 GHz and acceleratin...

Design and Results of a Time Resolved Spectrometer for the 5 MeV Photo-Injector Phin

CERN Document Server

Dabrowski, A; Egger, D; Mete, O; Lefevre, T

2010-01-01

The CLIC Test Facility 3 (CTF3) drive beam injector should provide high intensity and high quality electron beams. The present installation relies on a thermionic gun followed by a complex RF bunching system. As an upgrade to improve the beam emittance and the energy spread and to minimize the beam losses, a photo-injector is being developed and tested at CERN. One of the major challenges is to provide a 3.5A beam with a stable (0.1%) beam energy over 1.2 μs and a relative energy spread smaller than 1%. A 90◦ spectrometer line consisting of a segmented dump and an Optical Transition Radiation screen has been built in order to study these issues. The following paper describes its design and shows performances during the beam commissioning.

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

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.

Redirecting by Injector

Science.gov (United States)

Filman, Robert E.; Lee, Diana D.; Norvig, Peter (Technical Monitor)

2000-01-01

We describe the Object Infrastructure Framework, a system that seeks to simplify the creation of distributed applications by injecting behavior on the communication paths between components. We touch on some of the ilities and services that can be achieved with injector technology, and then focus on the uses of redirecting injectors, injectors that take requests directed at a particular server and generate requests directed at others. We close by noting that OIF is an Aspect-Oriented Programming system, and comparing OIF to related work.

High quantum efficiency photocathode simulation for the investigation of novel structured designs

Energy Technology Data Exchange (ETDEWEB)

Opachich, Y. P., E-mail: opachiyp@nv.doe.gov; Ross, P. W.; Huffman, E.; Koch, J. A. [National Security Technologies LLC, Livermore, California 94550 (United States); MacPhee, A. G.; Nagel, S. R.; Bell, P. M.; Bradley, D. K.; Landen, O. L. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Hilsabeck, T. J. [General Atomics, San Diego, California 92121 (United States)

2014-11-15

A computer model in CST Studio Suite has been developed to evaluate several novel geometrically enhanced photocathode designs. This work was aimed at identifying a structure that would increase the total electron yield by a factor of two or greater in the 1–30 keV range. The modeling software was used to simulate the electric field and generate particle tracking for several potential structures. The final photocathode structure has been tailored to meet a set of detector performance requirements, namely, a spatial resolution of <40 μm and a temporal spread of 1–10 ps. We present the details of the geometrically enhanced photocathode model and resulting static field and electron emission characteristics.

An RF driven H- source and a low energy beam injection system for RFQ operation

International Nuclear Information System (INIS)

Leung, K.N.; Bachman, D.A.; Chan, C.F.; McDonald, D.S.

1992-01-01

An RF driven H - source has been developed at LBL for use in the Superconducting Super Collider (SSC). To date, an H - current of ∼40 mA can be obtained from a 5.6-cm-diam aperture with the source operated at a pressure of about 12 m Torr and 50 kW of RF power. In order to match the accelerated H - beam into the SSC RFQ, a low-energy H - injection system has been designed. This injector produces an outgoing H - beam free of electron contamination, with small radius, large convergent angle and small projectional emittance

A compact rf driven H- ion source for linac injection

International Nuclear Information System (INIS)

Rymer, J.P.; Engeman, G.A.; Hamm, R.W.; Potter, J.M.

1991-01-01

A compact rf driven H - ion source has been developed for use as an injector for the AccSys radio frequency quadrupole (RFQ) linacs. A multicusp magnetic bucket geometry developed at Lawrence Berkeley Laboratory confines the plasma created by an antenna driven by 35 kW (peak) of pulsed rf power at 1.8 MHz. A three electrode system is used to extract and accelerate the H - beam, which is then focused into the RFQ by an einzel lens. Permanent magnets in the extraction region sweep electrons onto the second electrode at energies up to half of the full acceleration voltage. A fast pulsed valve allows the hydrogen gas supply to be pulsed, thus minimizing the average gas flow rate into the system. The design features and performance data from the prototype are discussed

Characterization of diamond film and bare metal photocathodes as a function of temperature and surface preparation

Energy Technology Data Exchange (ETDEWEB)

Shurter, R P; Moir, D C; Devlin, D J [Los Alamos National Laboratory, Los Alamos, NM (United States)

1997-12-31

High current photocathodes using bare metal and polycrystalline diamond films illuminated by ultraviolet lasers are being developed at Los Alamos for use in a new generation of linear induction accelerators. These photocathodes must be able to produce multiple 60 ns pulses separated by several to tens of nanoseconds. The vacuum environment in which the photocathodes must operate is {sup 1}0-5 torr. (author). 9 figs., 10 refs.

Beam dynamics simulations of the injector for a compact THz source

International Nuclear Information System (INIS)

Li Ji; Pei Yuanji; Shang Lei; Li Chenglong; Feng Guangyao; Hu Tongning; Chen Qushan

2014-01-01

Terahertz radiation has broad application prospects due to its ability to penetrate deep into many organic materials without the damage caused by ionizing radiations. A free electron laser (FEL)-based THz source is the best choice to produce high-power radiation. In this paper, a 14 MeV injector is introduced for generating high-quality beam for FEL, is composed of an EC-ITC RF gun, compensating coils and a travelling-wave structure. Beam dynamics simulations have been done with ASTRA code to verify the design and to optimize parameters. Simulations of the operating mode at 6 MeV have also been executed. (authors)

Effect of Sb thickness on the performance of bialkali-antimonide photocathodes

Energy Technology Data Exchange (ETDEWEB)

Mamun, Md Abdullah A., E-mail: mmamu001@odu.edu; Elmustafa, Abdelmageed A. [Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529 and The Applied Research Center, Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States); Hernandez-Garcia, Carlos; Mammei, Russell; Poelker, Matthew [Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States)

2016-03-15

The alkali species Cs and K were codeposited using an effusion source, onto relatively thick layers of Sb (50 nm to ∼7 μm) grown on GaAs and Ta substrates inside a vacuum chamber that was baked and not-vented, and also baked and vented with clean dry nitrogen but not rebaked. The characteristics of the Sb films, including sticking probability, surface roughness, grain size, and crystal properties were very different for these conditions, yet comparable values of photocathode yield [or quantum efficiency (QE)] at 284 V were obtained following codeposition of the alkali materials. Photocathodes manufactured with comparatively thick Sb layers exhibited the highest QE and the best 1/e lifetime. The authors speculate that the alkali codeposition enabled optimized stoichiometry for photocathodes manufactured using thick Sb layers, which could serve as a reservoir for the alkali materials.

3-D simulation study for a thermionic RF gun using an FDTD method

Energy Technology Data Exchange (ETDEWEB)

Hama, H. E-mail: hama@lns.tohoku.ac.jp; Hinode, F.; Shinto, K.; Miyamoto, A.; Tanaka, T

2004-08-01

Beam dynamics in a thermionic RF gun for a new pre-injector in a future synchrotron radiation facility at Tohoku university has been studied by developing a 3-D Maxwell's equation solver. Backbombardment (BB) effect on a cathode, which is a crucial problem for performance of the thermionic RF gun, has been investigated. It is found that an external dipole magnetic field applying around the cathode is effective to reduce high-energy backstreaming electrons from the accelerating cell. However, the low-energy electrons coming back from the first cell inevitably hit the cathode, so that characteristics of the cathode material seems to be crucial for reduction of the BB effect.

Engineering MoSx/Ti/InP Hybrid Photocathode for Improved Solar Hydrogen Production.

Science.gov (United States)

Li, Qiang; Zheng, Maojun; Zhong, Miao; Ma, Liguo; Wang, Faze; Ma, Li; Shen, Wenzhong

2016-07-19

Due to its direct band gap of ~1.35 eV, appropriate energy band-edge positions, and low surface-recombination velocity, p-type InP has attracted considerable attention as a promising photocathode material for solar hydrogen generation. However, challenges remain with p-type InP for achieving high and stable photoelectrochemical (PEC) performances. Here, we demonstrate that surface modifications of InP photocathodes with Ti thin layers and amorphous MoSx nanoparticles can remarkably improve their PEC performances. A high photocurrent density with an improved PEC onset potential is obtained. Electrochemical impedance analyses reveal that the largely improved PEC performance of MoSx/Ti/InP is attributed to the reduced charge-transfer resistance and the increased band bending at the MoSx/Ti/InP/electrolyte interface. In addition, the MoSx/Ti/InP photocathodes function stably for PEC water reduction under continuous light illumination over 2 h. Our study demonstrates an effective approach to develop high-PEC-performance InP photocathodes towards stable solar hydrogen production.

The PS 13.3-20 MHZ RF Systems for LHC

CERN Document Server

Garoby, R; Haase, M; Krusche, A; Maesen, P; Morvillo, M; Paoluzzi, M; Rossi, C

2003-01-01

As part of the preparation of the PS as an injector for the LHC, a prototype 20 MHz rf system has been used, to demonstrate that the nominal longitudinal performance of the proton beam for LHC can be obtained using multiple bunch-splittings. Based on these successful results obtained during 2000, the development of the operational rf system began in 2001. To allow the preparation of bunch trains with a bunch spacing of 25 or 75 ns, this system must operate either at 20 or 13.3 MHz respectively. Two new ferrite cavities and their associated amplifiers have been designed and built. Each one can provide a maximum voltage of 20 kV peak during 200 ms with a 10% duty cycle. The cavities are equipped with fast (~20 ms) gap shorting relays, and rf feedback reduces their Q below 10 at both frequencies. A single system is sufficient to generate the nominal beam for LHC. The second one will then be both a "hot spare" and a very valuable performance enhancement providing the possibility of handling a larger than nominal ...

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

CFD simulation of coaxial injectors

Science.gov (United States)

Landrum, D. Brian

1993-01-01

The development of improved performance models for the Space Shuttle Main Engine (SSME) is an important, ongoing program at NASA MSFC. These models allow prediction of overall system performance, as well as analysis of run-time anomalies which might adversely affect engine performance or safety. Due to the complexity of the flow fields associated with the SSME, NASA has increasingly turned to Computational Fluid Dynamics (CFD) techniques as modeling tools. An important component of the SSME system is the fuel preburner, which consists of a cylindrical chamber with a plate containing 264 coaxial injector elements at one end. A fuel rich mixture of gaseous hydrogen and liquid oxygen is injected and combusted in the chamber. This process preheats the hydrogen fuel before it enters the main combustion chamber, powers the hydrogen turbo-pump, and provides a heat dump for nozzle cooling. Issues of interest include the temperature and pressure fields at the turbine inlet and the thermal compatibility between the preburner chamber and injector plate. Performance anomalies can occur due to incomplete combustion, blocked injector ports, etc. The performance model should include the capability to simulate the effects of these anomalies. The current approach to the numerical simulation of the SSME fuel preburner flow field is to use a global model based on the MSFC sponsored FNDS code. This code does not have the capabilities of modeling several aspects of the problem such as detailed modeling of the coaxial injectors. Therefore, an effort has been initiated to develop a detailed simulation of the preburner coaxial injectors and provide gas phase boundary conditions just downstream of the injector face as input to the FDNS code. This simulation should include three-dimensional geometric effects such as proximity of injectors to baffles and chamber walls and interaction between injectors. This report describes an investigation into the numerical simulation of GH2/LOX coaxial

Advanced photoinjector experiment photogun commissioning results

Directory of Open Access Journals (Sweden)

F. Sannibale

2012-10-01

Full Text Available The Advanced Photoinjector Experiment (APEX at the Lawrence Berkeley National Laboratory is dedicated to the development of a high-brightness high-repetition rate (MHz-class electron injector for x-ray free-electron laser (FEL and other applications where high repetition rates and high brightness are simultaneously required. The injector is based on a new concept rf gun utilizing a normal-conducting (NC cavity resonating in the VHF band at 186 MHz, and operating in continuous wave (cw mode in conjunction with high quantum efficiency photocathodes capable of delivering the required charge at MHz repetition rates with available laser technology. The APEX activities are staged in three phases. In phase 0, the NC cw gun is built and tested to demonstrate the major milestones to validate the gun design and performance. Also, starting in phase 0 and continuing in phase I, different photocathodes are tested at the gun energy and at full repetition rate for validating candidate materials to operate in a high-repetition rate FEL. In phase II, a room-temperature pulsed linac is added for accelerating the beam at several tens of MeV to reduce space charge effects and allow the measurement of the brightness of the beam from the gun when integrated in an injector scheme. The installation of the phase 0 beam line and the commissioning of the VHF gun are completed, phase I components are under fabrication, and initial design and specification of components and layout for phase II are under way. This paper presents the phase 0 commissioning results with emphasis on the experimental milestones that have successfully demonstrated the APEX gun capability of operating at the required performance.

The LHC Lead Injector Chain

CERN Document Server

Beuret, A; Blas, A; Burkhardt, H; Carli, Christian; Chanel, M; Fowler, A; Gourber-Pace, M; Hancock, S; Hourican, M; Hill, C E; Jowett, John M; Kahle, K; Küchler, D; Lombardi, A M; Mahner, E; Manglunki, Django; Martini, M; Maury, S; Pedersen, F; Raich, U; Rossi, C; Royer, J P; Schindl, Karlheinz; Scrivens, R; Sermeus, L; Shaposhnikova, Elena; Tranquille, G; Vretenar, Maurizio; Zickler, T

2004-01-01

A sizeable part of the LHC physics programme foresees lead-lead collisions with a design luminosity of 1027 cm-2 s-1. This will be achieved after an upgrade of the ion injector chain comprising Linac3, LEIR, PS and SPS machines [1,2]. Each LHC ring will be filled in 10 min by almost 600 bunches, each of 7×107 lead ions. Central to the scheme is the Low Energy Ion Ring (LEIR) [3,4], which transforms long pulses from Linac3 into high-brilliance bunches by means of multi-turn injection, electron cooling and accumulation. Major limitations along the chain, including space charge, intrabeam scattering, vacuum issues and emittance preservation are highlighted. The conversion from LEAR (Low Energy Antiproton Ring) to LEIR involves new magnets and power converters, high-current electron cooling, broadband RF cavities, and a UHV vacuum system with getter (NEG) coatings to achieve a few 10-12 mbar. Major hardware changes in Linac3 and the PS are also covered. An early ion scheme with fewer bunches (but each at nominal...

Injector of the Utrecht EN tandem

Energy Technology Data Exchange (ETDEWEB)

Borg, K. van der; Haas, A.P. de; Hoogenboom, A.M.; Strasters, B.A.; Vermeer, A.; Zwol, N.A. van (Rijksuniversiteit Utrecht (Netherlands). Fysisch Lab.)

1984-02-15

An injector has been built to obtain improved beam transmission through the EN tandem. The injector has been provided with a 90/sup 0/ analysing magnet, m/..delta..m=300, and 130 kV preacceleration. Beam optics calculations have been made for the injector and tandem. The injector has been equipped with a fiber optics control and data acquisition system.

A DFT study on NEA GaN photocathode with an ultrathin n-type Si-doped GaN cap layer

Science.gov (United States)

Xia, Sihao; Liu, Lei; Kong, Yike; Diao, Yu

2016-10-01

Due to the drawbacks of conventional negative electron affinity (NEA) GaN photocathodes activated by Cs or Cs/O, a new-type NEA GaN photocathodes with heterojunction surface dispense with Cs activation are proposed. This structure can be obtained through the coverage of an ultrathin n-type Si-doped GaN cap layer on the p-type Mg-doped GaN emission layer. The influences of the cap layer on the photocathode are calculated using DFT. This study indicates that the n-type cap layer can promote the photoemission characteristics of GaN photocathode and demonstrates the probability of the preparation of a NEA GaN photocathode with an n-type cap layer.

Computation of electron cloud diagnostics and mitigation in the main injector

International Nuclear Information System (INIS)

Veitzer, S A; Cary, J R; Stoltz, P H; LeBrun, P; Spentzouris, P; Amundson, J F

2009-01-01

High-performance computations on Blue Gene/P at Argonne's Leadership Computing Facility have been used to determine phase shifts induced in injected RF diagnostics as a function of electron cloud density in the Main Injector. Inversion of the relationship between electron cloud parameters and induced phase shifts allows us to predict electron cloud density and evolution over many bunch periods. Long time-scale simulations using Blue Gene have allowed us to measure cloud evolution patterns under the influence of beam propagation with realistic physical parameterizations, such as elliptical beam pipe geometry, self-consistent electromagnetic fields, space charge, secondary electron emission, and the application of arbitrary external magnetic fields. Simultaneously, we are able to simulate the use of injected microwave diagnostic signals to measure electron cloud density, and the effectiveness of various mitigation techniques such as surface coating and the application of confining magnetic fields. These simulations provide a baseline for both RF electron cloud diagnostic design and accelerator fabrication in order to measure electron clouds and mitigate the adverse effects of such clouds on beam propagation.

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)

Methanol sensor for integration with GaP nanowire photocathode

Science.gov (United States)

Novák, J.; Laurenčíková, A.; Hasenohrl, S.; Eliáš, P.; Kováč, J.

2017-05-01

We proposed a new type of the methanol concentration sensor that may be integrated directly to the GaP nanostructured photocathode. Necessary attribute for this design is the possibility to make it compatible with p-type of semiconductor. This condition follows from the fact that photocathodes for the CO2 splitting are exclusively prepared from p-type of semiconductors. Design of methanol sensor emanates from this principle. On the GaP substrate is deposited thin Pt supporting layer (100-200 nm thick).This layer is covered by 500 nm thick Nafion membrane that serves as proton filter. On the top of Nafion layer is deposited top Pt contact layer covered by thin nanostructured Pt layer layer with various thickness (0.5 -5 nm). This nanostructured Pt is formed into small islands. It serves as an absorption layer for methanol. Sensor detection properties were estimated from monitoring of I-V characteristics. They were measured in dark and under various methanol concentrations. Dark current values are in order 10-9 A, and this current increases up to order of microamps for methanol of concentration more than 95%.These measurements proved high sensitivity of the GaP compatible sensor structure. Methanol sensors were realized in form of narrow stripe on the side of the photocathode.

Commissioning experience and beam physics measurements at the SwissFEL Injector test Facility

CERN Document Server

Schietinger, T.; Aiba, M.; Arsov, V.; Bettoni, S.; Beutner, B.; Calvi, M.; Craievich, P.; Dehler, M.; Frei, F.; Ganter, R.; Hauri, C. P.; Ischebeck, R.; Ivanisenko, Y.; Janousch, M.; Kaiser, M.; Keil, B.; Löhl, F.; Orlandi, G. L.; Ozkan Loch, C.; Peier, P.; Prat, E.; Raguin, J.-Y.; Reiche, S.; Schilcher, T.; Wiegand, P.; Zimoch, E.; Anicic, D.; Armstrong, D.; Baldinger, M.; Baldinger, R.; Bertrand, A.; Bitterli, K.; Bopp, M.; Brands, H.; Braun, H. H.; Brönnimann, M.; Brunnenkant, I.; Chevtsov, P.; Chrin, J.; Citterio, A.; Csatari Divall, M.; Dach, M.; Dax, A.; Ditter, R.; Divall, E.; Falone, A.; Fitze, H.; Geiselhart, C.; Guetg, M. W.; Hämmerli, F.; Hauff, A.; Heiniger, M.; Higgs, C.; Hugentobler, W.; Hunziker, S.; Janser, G.; Kalantari, B.; Kalt, R.; Kim, Y.; Koprek, W.; Korhonen, T.; Krempaska, R.; Laznovsky, M.; Lehner, S.; Le Pimpec, F.; Lippuner, T.; Lutz, H.; Mair, S.; Marcellini, F.; Marinkovic, G.; Menzel, R.; Milas, N.; Pal, T.; Pollet, P.; Portmann, W.; Rezaeizadeh, A.; Ritt, S.; Rohrer, M.; Schär, M.; Schebacher, L.; Scherrer, St.; Schlott, V.; Schmidt, T.; Schulz, L.; Smit, B.; Stadler, M.; Steffen, Bernd; Stingelin, L.; Sturzenegger, W.; Treyer, D. M.; Trisorio, A.; Tron, W.; Vicario, C.; Zennaro, R.; Zimoch, D.

2016-10-26

The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and test bed for the development and realization of SwissFEL, the x-ray Free Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including atransverse deflecting rf cavity. It delivered electron bunchesof up to200 pC chargeand up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of a FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultralow-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measureme...

Studies of Cs3Sb cathodes for the CLIC drive beam photo injector option

CERN Document Server

Martini, Irene; Doebert, Steffen; Fedosseev, Valentine; Hessler, Christoph; Martyanov, Mikhail

2013-01-01

Within the CLIC (Compact Linear Collider) project, feasibility studies of a photo injector option for the drive beam as an alternative to its baseline design using a thermionic electron gun are on-going. This R&D program covers both the laser and the photocathode side. Whereas the available laser pulse energy in ultra-violet (UV) is currently limited by the optical defects in the 4thharmonics frequency conversion crystal induced by the0.14 ms long pulse trains, recent measurements of Cs3Sbphotocathodes sensitive to green light showed their potential to overcome this limitation. Moreover, using visible laser beams leads to better stability of produced electron bunches and one can take advantages of the availability of higher quality optics. The studied Cs3Sbphotocathodes have been produced in the CERN photo emission laboratory using the co-deposition technique and tested in a DC gun set-up. The analysis of data acquired during the cathode production process will be presented in this paper, as well as the r...

Spectral response variation of a negative-electron-affinity photocathode in the preparation process

International Nuclear Information System (INIS)

Liu Lei; Du Yujie; Chang Benkang; Yunsheng Qian

2006-01-01

In order to research the spectral response variation of a negative electron affinity (NEA) photocathode in the preparation process, we have done two experiments on a transmission-type GaAs photocathode.First, an automatic spectral response recording system is described, which is used to take spectral response curves during the activation procedure of the photocathode. By this system, the spectral response curves of a GaAs:Cs-Ophotocathode measured in situ are presented. Then, after the cathode is sealed with a microchannel plate and a fluorescence screen into the image tube, we measure the spectral response of the tube by another measurement instrument. By way of comparing and analyzing these curves, we can find the typical variation in spectral-responses.The reasons for the variation are discussed. Based on these curves, spectral matching factors of a GaAs cathode for green vegetation and rough concrete are calculated. The visual ranges of night-vision goggles under specific circumstances are estimated. The results show that the spectral response of the NEA photocathode degraded in the sealing process, especially at long wavelengths. The variation has also influenced the whole performance of the intensifier tube

Effects of Surface Nonuniformities on the Mean Transverse Energy from Photocathodes

Science.gov (United States)

Karkare, Siddharth; Bazarov, Ivan

2015-08-01

The performance of photoinjectors is limited by the lowest value of the mean transverse energy of the electrons obtained from photocathodes. The factors that influence the mean transverse energy are poorly understood. In this paper, we develop models to calculate the effect of spatial work-function variations and subnanometer-scale roughness and surface defects on the mean transverse energy. We show that these can limit the lowest value of mean transverse energy achieved and that atomically perfect surfaces will be required to further reduce the mean transverse energy obtained from photocathodes.

Triaxial Swirl Injector Element for Liquid-Fueled Engines

Science.gov (United States)

Muss, Jeff

2010-01-01

A triaxial injector is a single bi-propellant injection element located at the center of the injector body. The injector element consists of three nested, hydraulic swirl injectors. A small portion of the total fuel is injected through the central hydraulic injector, all of the oxidizer is injected through the middle concentric hydraulic swirl injector, and the balance of the fuel is injected through an outer concentric injection system. The configuration has been shown to provide good flame stabilization and the desired fuel-rich wall boundary condition. The injector design is well suited for preburner applications. Preburner injectors operate at extreme oxygen-to-fuel mass ratios, either very rich or very lean. The goal of a preburner is to create a uniform drive gas for the turbomachinery, while carefully controlling the temperature so as not to stress or damage turbine blades. The triaxial injector concept permits the lean propellant to be sandwiched between two layers of the rich propellant, while the hydraulic atomization characteristics of the swirl injectors promote interpropellant mixing and, ultimately, good combustion efficiency. This innovation is suited to a wide range of liquid oxidizer and liquid fuels, including hydrogen, methane, and kerosene. Prototype testing with the triaxial swirl injector demonstrated excellent injector and combustion chamber thermal compatibility and good combustion performance, both at levels far superior to a pintle injector. Initial testing with the prototype injector demonstrated over 96-percent combustion efficiency. The design showed excellent high -frequency combustion stability characteristics with oxygen and kerosene propellants. Unlike the more conventional pintle injector, there is not a large bluff body that must be cooled. The absence of a protruding center body enhances the thermal durability of the triaxial swirl injector. The hydraulic atomization characteristics of the innovation allow the design to be

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 ...

Nonepitaxial Thin-Film InP for Scalable and Efficient Photocathodes.

Science.gov (United States)

Hettick, Mark; Zheng, Maxwell; Lin, Yongjing; Sutter-Fella, Carolin M; Ager, Joel W; Javey, Ali

2015-06-18

To date, some of the highest performance photocathodes of a photoelectrochemical (PEC) cell have been shown with single-crystalline p-type InP wafers, exhibiting half-cell solar-to-hydrogen conversion efficiencies of over 14%. However, the high cost of single-crystalline InP wafers may present a challenge for future large-scale industrial deployment. Analogous to solar cells, a thin-film approach could address the cost challenges by utilizing the benefits of the InP material while decreasing the use of expensive materials and processes. Here, we demonstrate this approach, using the newly developed thin-film vapor-liquid-solid (TF-VLS) nonepitaxial growth method combined with an atomic-layer deposition protection process to create thin-film InP photocathodes with large grain size and high performance, in the first reported solar device configuration generated by materials grown with this technique. Current-voltage measurements show a photocurrent (29.4 mA/cm(2)) and onset potential (630 mV) approaching single-crystalline wafers and an overall power conversion efficiency of 11.6%, making TF-VLS InP a promising photocathode for scalable and efficient solar hydrogen generation.

NLC electron injector beam dynamics

International Nuclear Information System (INIS)

Yeremian, A.D.; Miller, R.H.

1995-10-01

The Next Linear Collider (NLC) being designed at SLAC requires a train of 90 electron bunches 1.4 ns apart at 120 Hz. The intensity and emittance required at the interaction point, and the various machine systems between the injector and the IP determine the beam requirements from the injector. The style of injector chosen for the NLC is driven by the fact that the production of polarized electrons at the IP is a must. Based on the successful operation of the SLC polarized electron source a similar type of injector with a DC gun and subharmonic bunching system is chosen for the NLC

Electrostatic X-ray image recording device with mesh-base photocathode photoelectron discriminator means

International Nuclear Information System (INIS)

1977-01-01

An electrostatic X-ray image recording device having a pair of spaced electrodes with a gas-filled gap therebetween, and including discrimination means, having a conductive mesh supporting a photocathodic material, positioned in the gas-filled gap between a first electrode having a layer of ultraviolet-emitting fluorescent material and a second electrode having a plastic sheet adjacent thereto for receiving photoelectrons emitted by the photocathodic material and accelerated to the second electrode by an applied field. The photoconductor-mesh element discriminates against fast electrons, produced by direct impingement of X-rays upon the photocathode to substantially reduce secondary electron production and amplification, thereby increasing both the signal-to-noise and contrast ratios. The electrostatic image formed on the plastic sheet is developed by zerographic techniques after exposure. (Auth.)

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

Energy Technology Data Exchange (ETDEWEB)

Teng, J.; Gu, Y.Q., E-mail: tengjian@mail.ustc.edu.cn; Zhu, B.; Hong, W.; Zhao, Z.Q.; Zhou, W.M.; Cao, L.F.

2013-11-21

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

Science.gov (United States)

Teng, J.; Gu, Y. Q.; Zhu, B.; Hong, W.; Zhao, Z. Q.; Zhou, W. M.; Cao, L. F.

2013-11-01

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator.

Beam collimation and energy spectrum compression of laser-accelerated proton beams using solenoid field and RF cavity

International Nuclear Information System (INIS)

Teng, J.; Gu, Y.Q.; Zhu, B.; Hong, W.; Zhao, Z.Q.; Zhou, W.M.; Cao, L.F.

2013-01-01

This paper presents a new method of laser produced proton beam collimation and spectrum compression using a combination of a solenoid field and a RF cavity. The solenoid collects laser-driven protons efficiently within an angle that is smaller than 12 degrees because it is mounted few millimeters from the target, and collimates protons with energies around 2.3 MeV. The collimated proton beam then passes through a RF cavity to allow compression of the spectrum. Particle-in-cell (PIC) simulations demonstrate the proton beam transport in the solenoid and RF electric fields. Excellent energy compression and collection efficiency of protons are presented. This method for proton beam optimization is suitable for high repetition-rate laser acceleration proton beams, which could be used as an injector for a conventional proton accelerator

Repetitive Bunches from RF-Photo Gun Radiate Coherently

CERN Document Server

Van der Geer, C A J; Van der Geer, S B

2004-01-01

We consider to feed the laser wake field accelerator of the alpha-X project by a train of low charge pancake electron bunches to reduce undesired expansion due to space-charge forces. To this purpose the photo excitation laser of the rf-injector is split into a train of sub-pulses, such that each of the produced electron bunches falls into a successive ponderomotive well of the plasma accelerator. This way the total accelerated charge is not reduced. The repetitive photo gun can be tested, at low energy, by connecting it directly to the undulator and monitoring the radiation. The assertions are based on the results of new GPT simulations.

Temporal resolution limit estimation of x-ray streak cameras using a CsI photocathode

Energy Technology Data Exchange (ETDEWEB)

Li, Xiang; Gu, Li; Zong, Fangke; Zhang, Jingjin; Yang, Qinlao, E-mail: qlyang@szu.edu.cn [Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Institute of Optoelectronics, Shenzhen University, Shenzhen 518060 (China)

2015-08-28

A Monte Carlo model is developed and implemented to calculate the characteristics of x-ray induced secondary electron (SE) emission from a CsI photocathode used in an x-ray streak camera. Time distributions of emitted SEs are investigated with an incident x-ray energy range from 1 to 30 keV and a CsI thickness range from 100 to 1000 nm. Simulation results indicate that SE time distribution curves have little dependence on the incident x-ray energy and CsI thickness. The calculated time dispersion within the CsI photocathode is about 70 fs, which should be the temporal resolution limit of x-ray streak cameras that use CsI as the photocathode material.

Swirl Coaxial Injector Testing with LOX/RP-J

Science.gov (United States)

Greene, Sandra Elam; Casiano, Matt

2013-01-01

Testing was conducted at NASA fs Marshall Space Flight Center (MSFC) in the fall of 2012 to evaluate the operation and performance of liquid oxygen (LOX) and kerosene (RP ]1) in an existing swirl coaxial injector. While selected Russian engines use variations of swirl coaxial injectors, component level performance data has not been readily available, and all previously documented component testing at MSFC with LOX/RP ]1 had been performed using a variety of impinging injector designs. Impinging injectors have been adequate for specific LOX/RP ]1 engine applications, yet swirl coaxial injectors offer easier fabrication efforts, providing cost and schedule savings for hardware development. Swirl coaxial elements also offer more flexibility for design changes. Furthermore, testing with LOX and liquid methane propellants at MSFC showed that a swirl coaxial injector offered improved performance compared to an impinging injector. So, technical interest was generated to see if similar performance gains could be achieved with LOX/RP ]1 using a swirl coaxial injector. Results would allow such injectors to be considered for future engine concepts that require LOX/RP ]1 propellants. Existing injector and chamber hardware was used in the test assemblies. The injector had been tested in previous programs at MSFC using LOX/methane and LOX/hydrogen propellants. Minor modifications were made to the injector to accommodate the required LOX/RP ]1 flows. Mainstage tests were performed over a range of chamber pressures and mixture ratios. Additional testing included detonated gbombs h for stability data. Test results suggested characteristic velocity, C*, efficiencies for the injector were 95 ]97%. The injector also appeared dynamically stable with quick recovery from the pressure perturbations generated in the bomb tests.

The injector of the Utrecht EN tandem

International Nuclear Information System (INIS)

Borg, K. van der; Haas, A.P. de; Hoogenboom, A.M.; Strasters, B.A.; Vermeer, A.; Zwol, N.A. van

1984-01-01

An injector has been built to obtain improved beam transmission through the EN tandem. The injector has been provided with a 90 0 analysing magnet, m/Δm=300, and 130 kV preacceleration. Beam optics calculations have been made for the injector and tandem. The injector has been equipped with a fiber optics control and data acquisition system. (orig.)

Injector of solid indicator

Energy Technology Data Exchange (ETDEWEB)

Chernyshev, G.I.; Luk' yanov, E.P.; Pruslin, Y.A.; Zabrodin, P.I.

1981-04-25

The injector can be used with remote introduction of indicators into a borehole for study in an oil well of the parameters of movement of fluid currents, control of the state of the equipment, and study of the properties of the rocks. Proposed is a method of increasing the reliability of operation of the injector by stabilizing the rate of its dispersing. Introduced to the injector of a solid indicator are auxiliary brackets and a cathode made from nonmetallic electrical conducting material and reinforced at the end by an elastic bracket. The auxillary cathode is attached to the end surface of the anode and cathode.

Self-modulation of an intense electron beam in an injector of a linac with a feedback

International Nuclear Information System (INIS)

Ajzatskij, N.I.

1989-01-01

This paper reports the results of the analysis of the time structure of the beam versus the RF power supplied to the injector of the linac with a feedback. Using a nonstationary model of acceleration, we have performed a mathematical simulation of the dynamics of prebunched electron beam acceleration. The results of the mathematical simulation demonstrate that in the self-modulation acceleration regime of a linac with feedbacks there exists a possibility of adjusting the current pulse length, the pulse-to-pulse time being nearly the same. 4 refs., 2 figs

DIAGNOSTICS AND REGENERATION OF COMMON RAIL INJECTORS

Directory of Open Access Journals (Sweden)

Łukasz KONIECZNY

2015-03-01

Full Text Available The article presents the methodology of Common Rail injector diagnostic, regeneration and regulation with use of professional test stands. The EPS 815 machine can be used to test and repair all BOSCH injectors fully satisfying the producer requirements and standards. The article describes an example injector diagnosis with use of such test stand and additionally presents appropriate injector regeneration and encoding techniques

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

DC photogun vacuum characterization through photocathode lifetime studies

International Nuclear Information System (INIS)

Marcy Stutzman; Joseph Grames; Matt Poelker; Kenneth Surles-Law; Philip Adderley

2007-01-01

Excellent vacuum is essential for long photocathode lifetimes in DC high voltage photoelectron guns. Vacuum Research at Thomas Jefferson National Accelerator Facility has focused on characterizing the existing vacuum systems at the CEBAF polarized photoinjector and on quantifying improvements for new systems. Vacuum chamber preprocessing, full activation of NEG pumps and NEG coating the chamber walls should improve the vacuum within the electron gun, however, pressure measurement is difficult at pressures approaching the extreme-high-vacuum (XHV) region and extractor gauge readings are not significantly different between the improved and original systems. The ultimate test of vacuum in a DC high voltage photogun is the photocathode lifetime, which is limited by the ionization and back-bombardment of residual gasses. Discussion will include our new load-locked gun design as well as lifetime measurements in both our operational and new photo-guns, and the correlations between measured vacuum and lifetimes will be investigated

Study of the Quantum Efficiency of CsI Photocathodes Exposed to Oxygen and Water Vapour

CERN Document Server

Di Mauro, A; Piuz, François; Schyns, E M; Van Beelen, J B; Williams, T D

2000-01-01

The operation of CsI photocathodes in gaseous detectors requires special attention to the purity of the applied gas mixtures.We have studied the influence of oxygen and water vapour contaminations on the performance of CsI photocathodes for theALICE HMPID RICH prototype. Measurements were done through comparison of Cherenkov rings obtained from beamtests. Increased levels of oxygen and water vapour did not show any effect on the performance. The results of this studyfound a direct application in the way of storing CsI photocathodes over long periods nad in particular in the shipment of theHMPID prototype from CERN to the STAR experiment at BNL. (Abstract only available,full text to follow)

Operational Performance and Improvements to the RF Power Sources for the Compact Linear Collider Test Facility (CTF3) at CERN

CERN Document Server

McMonagle, Gerard

2006-01-01

The CERN CTF3 facility is being used to test and demonstrate key technical issues for the CLIC (Compact Linear Collider) study. Pulsed RF power sources are essential elements in this test facility. Klystrons at S-band (29998.55 GHz), in conjunction with pulse compression systems, are used to power the Drive Beam Accelerator (DBA) to achieve an electron beam energy of 150 MeV. The L-Band RF system, includes broadband Travelling Wave Tubes (TWTs) for beam bunching with 'phase coded' sub pulses in the injector and a narrow band high power L-Band klystron powering the transverse 1.5GHz RF deflector in the Delay Loop immediately after the DBA. This paper describes these different systems and discusses their operational performance.

Operational performance and improvements to the rf power sources for the Compact Linear Collider Test Facility (CTF3) at CERN

CERN Document Server

McMonagle, Gerard

2006-01-01

The CERN CTF3 facility is being used to test and demonstrate key technical issues for the CLIC (Compact Linear Collider) study. Pulsed RF power sources are essential elements in this test facility. Klystrons at S-band (29998.55 GHz), in conjunction with pulse compression systems, are used to power the Drive Beam Accelerator (DBA) to achieve an electron beam energy of 150 MeV. The L-Band RF system, includes broadband Travelling Wave Tubes (TWTs) for beam bunching with 'phase coded' sub pulses in the injector and a narrow band high power L-Band klystron powering the transverse 1.5 GHz RF deflector in the Delay Loop immediately after the DBA. This paper describes these different systems and discusses their operational performance.

Double-layered NiO photocathodes for p-type DSSCs with record IPCE

Energy Technology Data Exchange (ETDEWEB)

Li, Lin; Qin, Peng; Gorlov, Mikhail [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); Gibson, Elizabeth A.; Boschloo, Gerrit [Department of Physical and Analytical Chemistry, Uppsala University (Sweden); Hagfeldt, Anders [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); Department of Physical and Analytical Chemistry, Uppsala University (Sweden); DUT-KTH Joint Education and Research Center of Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian (China); Sun, Licheng [Center of Molecular Devices School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm (Sweden); DUT-KTH Joint Education and Research Center of Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian (China)

2010-04-18

A way to achieve a high-efficiency dye-sensitized solar cell is to combine an n-type TiO{sub 2}-based photoanode with a p-type photocathode in a tandem configuration. The development of an efficient photocathode is, at present, the key target. We have optimized the NiO, I{sub 3}{sup -}/I{sup -} p-DSSC system to obtain record photocurrent, giving 64% incident photon-to-current conversion efficiency (IPCE) and 5.48 mAcm{sup -2} J{sub SC}. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Automated installation for several photomultiplier photocathode activation by means of one vacuum facility

International Nuclear Information System (INIS)

Beschastnov, P.M.; Peryshkin, A.I.; Pyata, E.Eh.; Usov, Yu.V.

1989-01-01

An automated installation for simultaneous activation of up to four photocathodes of several photomultipliers by means of one vacuum station with the common furnace is described. Production technology of producing multialkaline photocathode makes up the basis for creating automated technology. The installation is produced on the base of the R110B industrial station and the Electronica-60 microcomputer. Software written in FORTRAN providing for control over all process stages is developed. 6 refs.; 2 figs

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.

CNG INJECTOR RESEARCH FOR DUAL FUEL ENGINE

Directory of Open Access Journals (Sweden)

Adam Majczak

2017-03-01

Full Text Available The article presents the tests results of the prototype design of hydraulically assisted injector, that is designed for gas supply into diesel engines. The construction of the injector allows for it positioning in the glow plug socket, so that the gas is injected directly into the combustion chamber. The cycle analysis of the four-cylinder Andoria ADCR engine with a capacity of 2.6 dm3 for different crankshaft rotational speeds allowed to determine the necessary time for fuel injection. Because of that, it was possible to determine the required mass flow rate of the injector, for replacing as much of the original fuel by gaseous fuel. To ensure a high value of flow inside the injector, supply pressure equal to 1 MPa was applied. High gas supply pressure requires high value of valve opening forces. For this purpose a injector with hydraulic control system, using a liquid under pressure for the opening process was designed. On the basis of air pressure measurements in the flow line after the injector, the analysis of opening and closing of the valve was made. Measurements of outflow mass of the injector were also carried out. The results showed that the designed injector meets the requirements necessary to supply ADCR engine by the CNG fuel.

Development of sub-100 femtosecond timing and synchronization system.

Science.gov (United States)

Lin, Zhenyang; Du, Yingchao; Yang, Jin; Xu, Yilun; Yan, Lixin; Huang, Wenhui; Tang, Chuanxiang; Huang, Gang; Du, Qiang; Doolittle, Lawrence; Wilcox, Russell; Byrd, John

2018-01-01

The precise timing and synchronization system is an essential part for the ultra-fast electron and X-ray sources based on the photocathode injector where strict synchronization among RF, laser, and beams are required. In this paper, we present an integrated sub-100 femtosecond timing and synchronization system developed and demonstrated recently in Tsinghua University based on the collaboration with Lawrence Berkeley National Lab. The timing and synchronization system includes the fiber-based CW carrier phase reference distribution system for delivering stabilized RF phase reference to multiple receiver clients, the Low Level RF (LLRF) control system to monitor and generate the phase and amplitude controllable pulse RF signal, and the laser-RF synchronization system for high precision synchronization between optical and RF signals. Each subsystem is characterized by its blocking structure and is also expansible. A novel asymmetric calibration sideband signal method was proposed for eliminating the non-linear distortion in the optical synchronization process. According to offline and online tests, the system can deliver a stable signal to each client and suppress the drift and jitter of the RF signal for the accelerator and the laser oscillator to less than 100 fs RMS (∼0.1° in 2856 MHz frequency). Moreover, a demo system with a LLRF client and a laser-RF synchronization client is deployed and operated successfully at the Tsinghua Thomson scattering X-ray source. The beam-based jitter measurement experiments have been conducted to evaluate the overall performance of the system, and the jitter sources are discussed.

Three-dimensional calculations for a 4 kA, 3.5 MV, 2 microsecond injector with asymmetric power feed

Directory of Open Access Journals (Sweden)

Thomas P. Hughes

1999-11-01

Full Text Available The DARHT-2 accelerator under construction at Los Alamos National Laboratory requires a long flattop (2μs 2–4 kA, 3.5 MV, low-emittance electron beam source. The injector is being constructed at Lawrence Berkeley National Laboratory and consists of a large-area thermionic cathode mounted atop a vertical column. The 90° bend between the horizontally emitted beam and the column produces dipole and higher-pole fields which must be corrected. In addition, the fast rise of the current flowing into the vacuum tank excites rf modes which cause transverse oscillations of the beam centroid. We have modeled these effects with the 3D electromagnetic code LSP. The code has models for pulsed power transmission lines, space-charge-limited emission and transport of charged particles, externally applied magnetic fields, and frequency-dependent absorption of rf. We calculate the transverse displacement of the beam as a function of time during the current pulse, and the positioning and thickness of ferrite absorber needed to damp the rf modes. The numerical results are compared to analytic calculations.

FERMILAB: Main Injector

International Nuclear Information System (INIS)

Anon.

1993-01-01

The Fermilab Main Injector (FMI) project is the centerpiece of the Laboratory's Fermilab III programme for the 1990s. Designed to support a luminosity of at least 5x10 31 cm -2 s -1 in the Tevatron collider, it will also provide new capabilities for rare neutral kaon decay and neutrino oscillation studies. The Fermilab Main Injector 8-150 GeV synchrotron is designed to replace the existing Main Ring which seriously limits beam intensities for the Tevatron and the antiproton production target. The project has passed several significant milestones and is now proceeding rapidly towards construction. The project received a $11.65M appropriation in 1992 and has been given $15M for the current fiscal year. Through the Energy Systems Acquisition Advisory Board (ESAAB) process, the US Department of Energy (DoE) has authorized funds for construction of the underground enclosure and service building where the Main Injector will touch the Tevatron, and to the preparation of bids for remaining project construction

Simulation of RF power and multi-cusp magnetic field requirement for H{sup −} ion sources

Energy Technology Data Exchange (ETDEWEB)

Pathak, Manish [Ion Source Lab., Proton Linac & Superconducting Cavities Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Senecha, V.K., E-mail: kumarvsen@gmail.com [Ion Source Lab., Proton Linac & Superconducting Cavities Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Homi Bhabha National Institute, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Kumar, Rajnish; Ghodke, Dharmraj V. [Ion Source Lab., Proton Linac & Superconducting Cavities Division, Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India)

2016-12-01

A computer simulation study for multi-cusp RF based H{sup −} ion source has been carried out using energy and particle balance equation for inductively coupled uniformly dense plasma considering sheath formation near the boundary wall of the plasma chamber for RF ion source used as high current injector for 1 Gev H{sup −} Linac project for SNS applications. The average reaction rates for different reactions responsible for H{sup −} ion production and destruction have been considered in the simulation model. The RF power requirement for the caesium free H{sup -} ion source for a maximum possible H{sup −} ion beam current has been derived by evaluating the required current and RF voltage fed to the coil antenna using transformer model for Inductively Coupled Plasma (ICP). Different parameters of RF based H{sup −} ion source like excited hydrogen molecular density, H{sup −} ion density, RF voltage and current of RF antenna have been calculated through simulations in the presence and absence of multicusp magnetic field to distinctly observe the effect of multicusp field. The RF power evaluated for different H{sup −} ion current values have been compared with the experimental reported results showing reasonably good agreement considering the fact that some RF power will be reflected from the plasma medium. The results obtained have helped in understanding the optimum field strength and field free regions suitable for volume emission based H{sup −} ion sources. The compact RF ion source exhibits nearly 6 times better efficiency compare to large diameter ion source.

Technology to Establish a Factory for High QE Alkali Antimonide Photocathodes

Energy Technology Data Exchange (ETDEWEB)

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

2015-11-16

Intense electron beams are key to a large number of scientific endeavors, including electron cooling of hadron beams, electron-positron colliders, secondary-particle beams such as photons and positrons, sub-picosecond ultrafast electron diffraction (UED), and new high gradient accelerators that use electron-driven plasmas. The last decade has seen a considerable interest in pursuit and realization of novel light sources such as Free Electron Lasers [1] and Energy Recovery Linacs [2] that promise to deliver unprecedented quality x-ray beams. Many applications for high-intensity electron beams have arisen in recent years in high-energy physics, nuclear physics and energy sciences, such as recent designs for an electron-hadron collider at CERN (LHeC) [3], and beam coolers for hadron beams at LHC and eRHIC [4,5]. Photoinjectors are used at the majority of high-brightness electron linacs today, due to their efficiency, timing structure flexibility and ability to produce high power, high brightness beams. The performance of light source machines is strongly related to the brightness of the electron beam used for generating the x-rays. The brightness of the electron beam itself is mainly limited by the physical processes by which electrons are generated. For laser based photoemission sources this limit is ultimately related to the properties of photocathodes [6]. Most facilities are required to expend significant manpower and money to achieve a workable, albeit often non-ideal, compromise photocathode solution. If entirely fabricated in-house, the photocathode growth process itself is laborious and not always reproducible: it involves the human element while requiring close adherence to recipes and extremely strict control of deposition parameters. Lack of growth reliability and as a consequence, slow adoption of viable photoemitter types, can be partly attributed to the absence of any centralized facility or commercial entity to routinely provide high peak current

Initial tests of the dual-sweep streak camera system planned for APS particle-beam diagnostics

International Nuclear Information System (INIS)

Lumpkin, A.; Yang, B.; Gai, W.; Cieslik, W.

1995-01-01

Initial tests of a dual-sweep streak system planned for use on the Advanced Photon Source (APS) have been performed using assets of the Argonne Wakefield Accelerator (AWA) facility. The short light pulses from the photoelectric injector drive laser in both the visible (λ=496 nm, Δt∼1.5 ps (FWHM)), and the ultraviolet (λ=248 nm, Δt∼5 ps (FWHM)) were used. Both a UV-visible S20 photocathode streak tube and a UV-to-x-ray Au photocathode streak tube were tested. Calibration data with an etalon were also obtained. A sample of dual-sweep streak data using optical synchrotron radiation on the APS injector synchrotron is also presented

The high peak current polarized electron source of the Stanford Linear Collider

International Nuclear Information System (INIS)

Schultz, D.; Alley, R.; Aoyagi, H.; Clendenin, J.; Frisch, J.; Garden, C.; Hoyt, E.; Kirby, R.; Klaisner, L.; Kulikov, A.; Mulhollan, G.; Prescott, C.; Saez, P.; Tang, H.; Turner, J.; Woods, M.; Yeremian, D.; Zolotorev, M.

1994-01-01

The Stanford Linear Collider injector requires two 2 ns pulses of 4.5-5.5 x 10 10 electrons, separated by 61 ns at 120 Hz, from its source. Since 1992, these currents have been provided by a polarized electron source based on GaAs photocathodes. A beam polarization of 76±4% has been measured at the end of the 50 GeV linac. At low photocathode quantum efficiencies, and for excitation near threshold, the maximum current delivered by the source is constrained, not by the space charge limit of the gun, but by a ''charge limit'' of the photocathode. The charge limited current is proportional to the photocathode quantum efficiency, but the proportionality varies for different photocathode types. Experience with high polarization strained GaAs photocathodes on a test beamline and on the SLC is presented. (orig.)

49 CFR 230.57 - Injectors and feedwater pumps.

Science.gov (United States)

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Injectors and feedwater pumps. 230.57 Section 230... Appurtenances Injectors, Feedwater Pumps, and Flue Plugs § 230.57 Injectors and feedwater pumps. (a) Water.... Injectors and feedwater pumps must be kept in good condition, free from scale, and must be tested at the...

Highly stable copper oxide composite as an effective photocathode for water splitting via a facile electrochemical synthesis strategy

KAUST Repository

Zhang, Zhonghai; Wang, Peng

2012-01-01

focused on n-type metal oxide semiconductors as photoanodes, whereas studies of p-type metal oxide semiconductors as photocathodes where hydrogen is generated are scarce. In this paper, highly efficient and stable copper oxide composite photocathode

Pellet injector research and development at ORNL

International Nuclear Information System (INIS)

Combs, S.K.; Barber, G.C.; Baylor, L.R.

1994-01-01

Oak Ridge National Laboratory has been developing pellet injectors for plasma fueling experiments on magnetic confinement devices for more than 15 years. Recent major applications of the ORNL development program include (1) a tritium-compatible four-shot pneumatic injector for the Tokamak Fusion Test Reactor, (2) a centrifuge pellet injector for the Tore Supra tokamak, and most recently (3) a three-barrel repeating pneumatic injector for the DIII-D tokamak. In addition to applications, ORNL is developing advanced technologies, including high-speed pellet injectors, tritium injectors, and long-pulse pellet feed systems. The high-speed research involves a collaboration between ORNL and ENEA-Frascati in the development of a repeating two-stage light gas gun based on an extrusion-type pellet feed system. Construction of a new tritium-compatible, extruder-based repeating pneumatic injector (8-mm-diam) is complete and will replace the pipe gun in the original tritium proof-of-principle experiment. The development of a steady-state feed system in which three standard extruders operate in tandem is under way. These research and development activities are relevant to the International Thermonuclear Experimental Reactor and are briefly described in this paper

An in-situ photocathode loading system for the SLC Polarized Electron Gun

International Nuclear Information System (INIS)

Kirby, R.E.; Collet, G.J.; Skarpaas, K.

1992-12-01

An ultra-high vacuum loadlock system capable of operating at high voltage has been added to the SLC Polarized Electron Gun. The unit incorporates facilities for heat cleaning, activating and measuring the quantum efficiency of photocathodes. A tray of up to four photocathodes can be exchanged without bringing the activation unit or gun up to atmosphere. Low voltage quantum efficiencies of 20% have been obtained for bulk GaAs at 633 nm and 6% for a 0.3 micron GaAs layer at 755 nm. Results for other cathodes as well as operational characteristics are discussed

Polarized Light Sources for photocathode electron guns at SLAC

International Nuclear Information System (INIS)

Woods, M.; Frisch, J.; Witte, K.; Zolotorev, M.

1992-12-01

We describe current and future Polarized Light Sources at SLAC for use with photocathode electron guns to produce polarized electron beams. The SLAC experiments SLD and E142 are considered, and are used to define the required parameters for the Polarized Light Sources

Numerical Simulation of Twin Nozzle Injectors

OpenAIRE

Milak, Dino

2015-01-01

Fuel injectors for marine applications have traditionally utilized nozzles with symmetric equispaced orifice configuration. But in light of the new marine emission legislations the twin nozzle concept has arisen. The twin nozzle differs from the conventional configuration by utilizing two closely spaced orifices to substitute each orifice in the conventional nozzle. Injector manufacturers regard twin nozzle injectors as a promising approach to facilitate stable spray patterns independent of t...

Modeling and simulation of RF photoinjectors for coherent light sources

Science.gov (United States)

Chen, Y.; Krasilnikov, M.; Stephan, F.; Gjonaj, E.; Weiland, T.; Dohlus, M.

2018-05-01

We propose a three-dimensional fully electromagnetic numerical approach for the simulation of RF photoinjectors for coherent light sources. The basic idea consists in incorporating a self-consistent photoemission model within a particle tracking code. The generation of electron beams in the injector is determined by the quantum efficiency (QE) of the cathode, the intensity profile of the driving laser as well as by the accelerating field and magnetic focusing conditions in the gun. The total charge emitted during an emission cycle can be limited by the space charge field at the cathode. Furthermore, the time and space dependent electromagnetic field at the cathode may induce a transient modulation of the QE due to surface barrier reduction of the emitting layer. In our modeling approach, all these effects are taken into account. The beam particles are generated dynamically according to the local QE of the cathode and the time dependent laser intensity profile. For the beam dynamics, a tracking code based on the Lienard-Wiechert retarded field formalism is employed. This code provides the single particle trajectories as well as the transient space charge field distribution at the cathode. As an application, the PITZ injector is considered. Extensive electron bunch emission simulations are carried out for different operation conditions of the injector, in the source limited as well as in the space charge limited emission regime. In both cases, fairly good agreement between measurements and simulations is obtained.

Detailed Measurement of ORSC Main Chamber Injector Dynamics

Science.gov (United States)

Bedard, Michael J.

Improving fidelity in simulation of combustion dynamics in rocket combustors requires an increase in experimental measurement fidelity for validation. In a model rocket combustor, a chemiluminescence based spectroscopy technique was used to capture flame light emissions for direct comparison to a computational simulation of the production of chemiluminescent species. The comparison indicated that high fidelity models of rocket combustors can predict spatio-temporal distribution of chemiluminescent species with trend-wise accuracy. The comparison also indicated the limited ability of OH* and CH* emission to indicate flame heat release. Based on initial spectroscopy experiments, a photomultiplier based chemiluminescence sensor was designed to increase the temporal resolution of flame emission measurements. To apply developed methodologies, an experiment was designed to investigate the flow and combustion dynamics associated with main chamber injector elements typical of the RD-170 rocket engine. A unique feature of the RD-170 injector element is the beveled expansion between the injector recess and combustion chamber. To investigate effects of this geometry, a scaling methodology was applied to increase the physical scale of a single injector element while maintaining traceability to the RD-170 design. Two injector configurations were tested, one including a beveled injector face and the other a flat injector face. This design enabled improved spatial resolution of pressure and light emission measurements densely arranged in the injector recess and near-injector region of the chamber. Experimental boundary conditions were designed to closely replicate boundary conditions in simulations. Experimental results showed that the beveled injector face had a damping effect on pressure fluctuations occurring near the longitudinal resonant acoustic modes of the chamber, implying a mechanism for improved overall combustion stability. Near the injector, the beveled geometry

{Ni4O4} Cluster Complex to Enhance the Reductive Photocurrent Response on Silicon Nanowire Photocathodes

Directory of Open Access Journals (Sweden)

Yatin J. Mange

2017-02-01

Full Text Available Metal organic {Ni4O4} clusters, known oxidation catalysts, have been shown to provide a valuable route in increasing the photocurrent response on silicon nanowire (SiNW photocathodes. {Ni4O4} clusters have been paired with SiNWs to form a new photocathode composite for water splitting. Under AM1.5 conditions, the combination of {Ni4O4} clusters with SiNWs gave a current density of −16 mA/cm2, which corresponds to an increase in current density of 60% when compared to bare SiNWs. The composite electrode was fully characterised and shown to be an efficient and stable photocathode for water splitting.

Pellet injector development and experiments at ORNL

International Nuclear Information System (INIS)

Baylor, L.R.; Argo, B.E.; Barber, G.C.; Combs, S.K.; Cole, M.J.; Dyer, G.R.; Fehling, D.T.; Fisher, P.W.; Foster, C.A.; Foust, C.R.; Gouge, M.J.; Jernigan, T.C.; Langley, R.A.; Milora, S.L.; Qualls, A.L.; Schechter, D.E.; Sparks, D.O.; Tsai, C.C.; Wilgen, J.B.; Whealton, J.H.

1993-01-01

The development of pellet injectors for plasma fueling of magnetic confinement fusion experiments has been under way at Oak Ridge National Laboratory (ORNL) for the past 15 years. Recently, ORNL provided a tritium-compatible four-shot pneumatic injector for the Tokamak Fusion Test Reactor (TFTR) based on the in situ condensation technique that features three single-stage gas guns and an advanced two-stage light gas gun driver. In another application, ORNL supplied the Tore Supra tokamak with a centrifuge pellet injector in 1989 for pellet fueling experiments that has achieved record numbers of injected pellets into a discharge. Work is progressing on an upgrade to that injector to extend the number of pellets to 400 and improve pellet repeatability. In a new application, the ORNL three barrel repeating pneumatic injector has been returned from JET and is being readied for installation on the DIII-D device for fueling and enhanced plasma performance experiments. In addition to these experimental applications, ORNL is developing advanced injector technologies, including high-velocity pellet injectors, tritium pellet injectors, and long-pulse feed systems. The two-stage light gas gun and electron-beam-driven rocket are the acceleration techniques under investigation for achieving high velocity. A tritium proof-of-principle (TPOP) experiment has demonstrated the feasibility of tritium pellet production and acceleration. A new tritium-compatible, extruder-based, repeating pneumatic injector is being fabricated to replace the pipe gun in the TPOP experiment and will explore issues related to the extrudability of tritium and acceleration of large tritium pellets. The tritium pellet formation experiments and development of long-pulse pellet feed systems are especially relevant to the International Tokamak Engineering Reactor (ITER)

A new slip stacking RF system for a twofold power upgrade of Fermilab's Accelerator Complex

Energy Technology Data Exchange (ETDEWEB)

Madrak, Robyn [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

2014-05-15

Fermilab's Accelerator Complex has been recently upgraded, in order to increase the 120 GeV proton beam power on target from about 400 kW to over 700 kW for NOvA and other future intensity frontier experiments. One of the key ingredients of the upgrade is the offloading of some Main Injector synchrotron operations - beam injection and RF manipulation called ''slip stacking'' - to the 8GeV Recycler Ring, which had until recently been used only for low-intensity antiproton storage and cooling. This required construction of two new 53 MHz RF systems for the slip-stacking manipulations. The cavities operate simultaneously at V_peak ≲150 kV, but at slightly different frequencies (Δf=1260 Hz). Their installation was completed in September 2013. This article describes the novel solutions used in the design of the new cavities, their tuning system, and the associated high power RF system. First results showing effective operation of the RF system, beam capture and successful slip-stacking in the Recycler Ring are presented.

Sawtooth-wave prebuncher with dual-gaps in Linac injector for HIRFL-SSC

Science.gov (United States)

Zhang, Xiaohu; Yuan, Youjin; Xia, Jiawen; Yin, Xuejun; Jin, Peng; Xu, Zhe; Du, Heng; Li, Zhongshan; Qiao, Jian; Wang, Kedong

2018-01-01

An RFQ structure is normally composed of radial matcher, shaper, gentle buncher and accelerator section with changing cell geometry. Bunching is started in the shaper, and adiabatic bunching is done in gentle buncher section. The beam preforms from DC beam to bunch beam through the RFQ and the longitudinal emittance for the ions linacs is defined initially in the RFQ, in which the beam bunch has been shaped. In the present SSC-Linac injector, an RFQ has been designed to accelerate the continuous beam from 3.728 keV/u to 143 keV/u. The heavy ions beam is injected into the SSC (Separated Sector Cyclotron) with the kinetic energy of 1.025 MeV/u after four IH DTLs. The rf frequency of the SSC is 13.417 MHz, and the frequency of the heavy ions RFQ is set to four times of the rf frequency of the SSC. In order to increase the longitudinal capture efficiency of the SSC and suppress the longitudinal emittance at the exit of RFQ, an external MHB (Multi-Harmonics Buncher) is proposed in front of the RFQ. The fundamental frequency of the MHB is the same as the rf frequency of the cyclotron. The scheme of dual-gaps prebuncher with the sawtooth waveform is firstly carried out through multi-harmonics synthetic technology. The multi-particle beam dynamic simulations of the MHB have been done by the BEAMPATH code.

FERMILAB: Main Injector

Energy Technology Data Exchange (ETDEWEB)

Anon.

1993-06-15

The Fermilab Main Injector (FMI) project is the centerpiece of the Laboratory's Fermilab III programme for the 1990s. Designed to support a luminosity of at least 5x10{sup 31} cm{sup -2} s{sup -1} in the Tevatron collider, it will also provide new capabilities for rare neutral kaon decay and neutrino oscillation studies. The Fermilab Main Injector 8-150 GeV synchrotron is designed to replace the existing Main Ring which seriously limits beam intensities for the Tevatron and the antiproton production target. The project has passed several significant milestones and is now proceeding rapidly towards construction. The project received a $11.65M appropriation in 1992 and has been given $15M for the current fiscal year. Through the Energy Systems Acquisition Advisory Board (ESAAB) process, the US Department of Energy (DoE) has authorized funds for construction of the underground enclosure and service building where the Main Injector will touch the Tevatron, and to the preparation of bids for remaining project construction.

High polarization photocathode R ampersand D at SLAC

International Nuclear Information System (INIS)

Maruyama, Takashi; Garwin, E.L.; Prepost, R.; Zaplac, G.H.

1993-01-01

This paper describes recent progress on the development of high polarization photocathodes for polarized electron sources. A strained InGaAs cathode has achieved a maximum electron-spin polarization of 71% and has demonstrated the strain enhancement of polarization for the first time. Strained GaAs cathodes have yielded polarizations as high as 90% with much higher quantum efficiency

Status of the positive-ion injector for ATLAS

International Nuclear Information System (INIS)

Bollinger, L.M.; Pardo, R.C.; Shepard, K.W.

1986-01-01

The planned positive-ion injector for ATLAS consists of an ECR ion source on a 350-kV platfrom and a superconducting injector linac of a new kind. The objective is to replace the present tandem injector with a system that can increase beam intensities by two orders of magnitude and extend the mass range up to uranium. In the first, developmental stage of the work, now in progress, the ECR source will be built, the technology of superconducting accelerating structures for low-velocity ions will be developed, and these structures will be used to form a 3-MV prototype injector linac. Even this small system, designed for ions with A < 130, will be superior to the present FN tandem as a heavy-ion injector. In later phases of the work, the injector linac will be enlarged enough to allow ATLAS to effectively accelerate uranium ions. The injector system is expected to provide exceptional beam quality. The status of the work, expected performance of the accelerator system, and the technical issues involved are summarized

Ion Sources and Injectors for HIF Induction Linacs

International Nuclear Information System (INIS)

Kwan, J.W.; Ahle, L.; Beck, D.N.; Bieniosek, F. M.; Faltens, A.; Grote, D.P.; Halaxa, E.; Henestroza, E.; Herrmannsfeldt, W.B.; Karpenko, V.; Sangster, T.C.

2000-01-01

Ion source and injector development is one of the major parts of the HIF program in the USA. Our challenge is to design a cost effective driver-scale injector and to build a multiple beam module within the next couple of years. In this paper, several current-voltage scaling laws are summarized for guiding the injector design. Following the traditional way of building injectors for HIF induction linac, we have produced a preliminary design for a multiple beam driver-scale injector. We also developed an alternate option for a high current density injector that is much smaller in size. One of the changes following this new option is the possibility of using other kinds of ion sources than the surface ionization sources. So far, we are still looking for an ideal ion source candidate that can readily meet all the essential requirements

Deuterium pellet injector gun design

International Nuclear Information System (INIS)

Lunsford, R.V.; Wysor, R.B.; Bryan, W.E.; Shipley, W.D.; Combs, S.K.; Foust, C.R.; Milora, S.L.; Fisher, P.W.

1985-01-01

The Deuterium Pellet Injector (DPI), an eight-pellet pneumatic injector, is being designed and fabricated for the Tokamak Fusion Test Reactor (TFTR). It will accelerate eight pellets, 4 by 4 mm maximum, to greater than 1500 m/s. It utilizes a unique pellet-forming mechanism, a cooled pellet storage wheel, and improved propellant gas scavenging

Status and future prospects of SRF gun developments

International Nuclear Information System (INIS)

Teichert, Jochen

2006-01-01

While the concepts of DC and normal-conducting photo-injectors are well proofed, the SRF gun development still possesses a high risk. Challenges are the thermal and contaminant isolation needed between the cathode and superconducting cavity, the choice of the right photocathode and its life time, the difficulty of coupling high-average power into the gun, and beam excitation of higher order cavity modes. But in combination with SRF linacs, the SRF guns are the best solution for high current and CW operation. Thus, several R and D projects of SRF gun have been launched. The talk will give an overview of the history and progress of the SRF gun development. In more detail the technical concept, performance, and status of the Rossendorf superconducting RF gun project, a collaboration of BESSY, DESY, MBI and FZR, will be presented. (author)

INEX simulations of the optical performance of the AFEL

International Nuclear Information System (INIS)

Goldstein, J.C.; Wang, T.S.F.; Sheffield, R.L.

1991-01-01

The AFEL (Advanced Free-Electron Laser) Project at Los Alamos National Laboratory is presently under construction. The project's goal is to produce a very high-brightness electron beam which will be generated by a photocathode injector and a 20 MeV rf-linac. Initial laser experiments will be performed with a 1-cm-period permanent magnet wiggler which will generate intense optical radiation near a wavelength of 3.7 μm. Future experiments will operate with ''slotted-tube'' electromagnetic wigglers (formerly called ''pulsed- wire'' wigglers). Experiments at both fundamental and higher-harmonic wavelengths are planned. This paper presents results of INEX (Integrated Numerical EXperiment) simulations of the optical performance of the AFEL. These simulations use the electron micropulse produced by the accelerator/beam transport code PARMELA in the 3-D FEL simulation code FELEX. 9 refs., 4 figs., 6 tabs

Modeling of classical swirl injector dynamics

Science.gov (United States)

Ismailov, Maksud M.

The knowledge of the dynamics of a swirl injector is crucial in designing a stable liquid rocket engine. Since the swirl injector is a complex fluid flow device in itself, not much work has been conducted to describe its dynamics either analytically or by using computational fluid dynamics techniques. Even the experimental observation is limited up to date. Thus far, there exists an analytical linear theory by Bazarov [1], which is based on long-wave disturbances traveling on the free surface of the injector core. This theory does not account for variation of the nozzle reflection coefficient as a function of disturbance frequency, and yields a response function which is strongly dependent on the so called artificial viscosity factor. This causes an uncertainty in designing an injector for the given operational combustion instability frequencies in the rocket engine. In this work, the author has studied alternative techniques to describe the swirl injector response, both analytically and computationally. In the analytical part, by using the linear small perturbation analysis, the entire phenomenon of unsteady flow in swirl injectors is dissected into fundamental components, which are the phenomena of disturbance wave refraction and reflection, and vortex chamber resonance. This reveals the nature of flow instability and the driving factors leading to maximum injector response. In the computational part, by employing the nonlinear boundary element method (BEM), the author sets the boundary conditions such that they closely simulate those in the analytical part. The simulation results then show distinct peak responses at frequencies that are coincident with those resonant frequencies predicted in the analytical part. Moreover, a cold flow test of the injector related to this study also shows a clear growth of instability with its maximum amplitude at the first fundamental frequency predicted both by analytical methods and BEM. It shall be noted however that Bazarov

Spray Modeling for Outwardly-Opening Hollow-Cone Injector

KAUST Repository

Sim, Jaeheon

2016-04-05

The outwardly-opening piezoelectric injector is gaining popularity as a high efficient spray injector due to its precise control of the spray. However, few modeling studies have been reported on these promising injectors. Furthermore, traditional linear instability sheet atomization (LISA) model was originally developed for pressure swirl hollow-cone injectors with moderate spray angle and toroidal ligament breakups. Therefore, it is not appropriate for the outwardly-opening injectors having wide spray angles and string-like film structures. In this study, a new spray injection modeling was proposed for outwardly-opening hollow-cone injector. The injection velocities are computed from the given mass flow rate and injection pressure instead of ambiguous annular nozzle geometry. The modified Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) breakup model is used with adjusted initial Sauter mean diameter (SMD) for modeling breakup of string-like structure. Spray injection was modeled using a Lagrangian discrete parcel method within the framework of commercial CFD software CONVERGE, and the new model was implemented through the user-defined functions. A Siemens outwardly-opening hollow-cone spray injector was characterized and validated with existing experimental data at the injection pressure of 100 bar. It was found that the collision modeling becomes important in the current injector because of dense spray near nozzle. The injection distribution model showed insignificant effects on spray due to small initial droplets. It was demonstrated that the new model can predict the liquid penetration length and local SMD with improved accuracy for the injector under study.

Pellet injectors for steady state plasma fuelling

International Nuclear Information System (INIS)

Vinyar, I.; Geraud, A.; Yamada, H.; Lukin, A.; Sakamoto, R.; Skoblikov, S.; Umov, A.; Oda, Y.; Gros, G.; Krasilnikov, I.; Reznichenko, P.; Panchenko, V.

2005-01-01

Successful steady state operation of a fusion reactor should be supported by repetitive pellet injection of solidified hydrogen isotopes in order to produce high performance plasmas. This paper presents pneumatic pellet injectors and its implementation for long discharge on the LHD and TORE SUPRA, and a new centrifuge pellet injector test results. All injectors are fitted with screw extruders well suited for steady state operation

MEMS-based, RF-driven, compact accelerators

Science.gov (United States)

Persaud, A.; Seidl, P. A.; Ji, Q.; Breinyn, I.; Waldron, W. L.; Schenkel, T.; Vinayakumar, K. B.; Ni, D.; Lal, A.

2017-10-01

Shrinking existing accelerators in size can reduce their cost by orders of magnitude. Furthermore, by using radio frequency (RF) technology and accelerating ions in several stages, the applied voltages can be kept low paving the way to new ion beam applications. We make use of the concept of a Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) and have previously shown the implementation of its basic components using printed circuit boards, thereby reducing the size of earlier MEQALACs by an order of magnitude. We now demonstrate the combined integration of these components to form a basic accelerator structure, including an initial beam-matching section. In this presentation, we will discuss the results from the integrated multi-beam ion accelerator and also ion acceleration using RF voltages generated on-board. Furthermore, we will show results from Micro-Electro-Mechanical Systems (MEMS) fabricated focusing wafers, which can shrink the dimension of the system to the sub-mm regime and lead to cheaper fabrication. Based on these proof-of-concept results we outline a scaling path to high beam power for applications in plasma heating in magnetized target fusion and in neutral beam injectors for future Tokamaks. This work was supported by the Office of Science of the US Department of Energy through the ARPA-e ALPHA program under contracts DE-AC02-05CH11231.

Resonant Frequency Control For the PIP-II Injector Test RFQ: Control Framework and Initial Results

Energy Technology Data Exchange (ETDEWEB)

Edelen, A. L. [Colorado State U.; Biedron, S. G.; Milton, S. V.; Bowring, D.; Chase, B. E.; Edelen, J. P.; Nicklaus, D.; Steimel, J.

2016-12-16

For the PIP-II Injector Test (PI-Test) at Fermilab, a four-vane radio frequency quadrupole (RFQ) is designed to accelerate a 30-keV, 1-mA to 10-mA, H- beam to 2.1 MeV under both pulsed and continuous wave (CW) RF operation. The available headroom of the RF amplifiers limits the maximum allowable detuning to 3 kHz, and the detuning is controlled entirely via thermal regulation. Fine control over the detuning, minimal manual intervention, and fast trip recovery is desired. In addition, having active control over both the walls and vanes provides a wider tuning range. For this, we intend to use model predictive control (MPC). To facilitate these objectives, we developed a dedicated control framework that handles higher-level system decisions as well as executes control calculations. It is written in Python in a modular fashion for easy adjustments, readability, and portability. Here we describe the framework and present the first control results for the PI-Test RFQ under pulsed and CW operation.

Equivalent Method of Solving Quantum Efficiency of Reflection-Mode Exponential Doping GaAs Photocathode

International Nuclear Information System (INIS)

Jun, Niu; Zhi, Yang; Ben-Kang, Chang

2009-01-01

The mathematical expression of the electron diffusion and drift length L DE of exponential doping photocathode is deduced. In the quantum efficiency equation of the reffection-mode uniform doping cathode, substituting L DE for L D , the equivalent quantum efficiency equation of the reffection-mode exponential doping cathode is obtained. By using the equivalent equation, theoretical simulation and experimental analysis shows that the equivalent index formula and formula-doped cathode quantum efficiency results in line. The equivalent equation avoids complicated calculation, thereby simplifies the process of solving the quantum efficiency of exponential doping photocathode

Pneumatic pellet injectors for TFTR and JET

International Nuclear Information System (INIS)

Combs, S.K.; Milora, S.L.

1986-01-01

This paper describes the development of pneumatic hydrogen pellet injectors for plasma fueling applications on the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET). The performance parameters of these injectors represent an extension of previous experience and include pellet sizes in the range 2-6 mm in diameter and speeds approaching 2 km/s. Design features and operating characteristics of these pneumatic injectors are presented

Modelling the High-speed Injector for Diesel ICE

Science.gov (United States)

Buryuk, V. V.; Kayukov, S. S.; Gorshkalev, A. A.; Belousov, A. V.; Gallyamov, R. E.; Zvyagintsev, V. A.

2018-01-01

The article describes the results of research on the option of improving the operation speed of the electro-hydraulically driven injectors (Common Rail) for diesel ICE. The injector investigated in this article is a modified serial injector Common Rail-type with solenoid. The model and the injector parameters are represented in the package LMS Imagine. Lab AMESim with the detailed description of the substantiation and background for the research. Following the research results, the advantages of the proposed approach to analysing the operation speed were detected with outlining the direction of future studies.

Application of advanced diagnostics to airblast injector flows

Science.gov (United States)

Mcvey, John B.; Kennedy, Jan B.; Russell, Sid

1987-01-01

This effort is concerned with the application of both conventional laser velocimetry and phase Doppler anemometry to the flow produced by an airblast nozzle. The emphasis is placed on the acquisition of data using actual engine injector/swirler components at (noncombusting) conditions simulating those encountered in the engine. The objective of the effort was to test the applicability of the instrumentation to real injector flows, to develop information on the behavior of injectors at high flow, and to provide data useful in the development of physical models of injector flows.

Design status of heavy ion injector program

International Nuclear Information System (INIS)

Ballard, E.O.; Meyer, E.A.; Rutkowski, H.L.; Shurter, R.P.; Van Haaften, F.W.; Riepe, K.B.

1985-01-01

Design and development of a sixteen beam, heavy ion injector is in progress at Los Alamos National Laboratory (LANL) to demonstrate the injector technology for the High Temperature Experiment (HTE) proposed by Lawrence Livermore Laboratory (LBL). The injector design provides for individual ion sources mounted to a support plate defining the sixteen beam array. The beamlets are electrostatically accelerated through a series of electrodes inside an evacuated (10 -7 torr) high voltage (HV) accelerating column

Direct Fuel Injector Power Drive System Optimization

Science.gov (United States)

2014-04-01

solenoid coil to create magnetic field in the stator. Then, the stator pulls the pintle to open the injector nozzle . This pintle movement occurs when the...that typically deal with power strategies to the injector solenoid coil. Numerical simulation codes for diesel injection systems were developed by...Laboratory) for providing the JP-8 test fuel. REFERENCES 1. Digesu, P. and Laforgia D., “ Diesel electro- injector : A numerical simulation code”. Journal of

Economic evaluation of epinephrine auto-injectors for peanut allergy.

Science.gov (United States)

Shaker, Marcus; Bean, Katherine; Verdi, Marylee

2017-08-01

Three commercial epinephrine auto-injectors were available in the United States in the summer of 2016: EpiPen, Adrenaclick, and epinephrine injection, USP auto-injector. To describe the variation in pharmacy costs among epinephrine auto-injector devices in New England and evaluate the additional expense associated with incremental auto-injector costs. Decision analysis software was used to evaluate costs of the most and least expensive epinephrine auto-injector devices for children with peanut allergy. To evaluate regional variation in epinephrine auto-injector costs, a random sample of New England national and corporate pharmacies was compared with a convenience sample of pharmacies from 10 Canadian provinces. Assuming prescriptions written for 2 double epinephrine packs each year (home and school), the mean costs of food allergy over the 20-year model horizon totaled $58,667 (95% confidence interval [CI] $57,745-$59,588) when EpiPen was prescribed and $45,588 (95% CI $44,873-$46,304) when epinephrine injection, USP auto-injector was prescribed. No effectiveness differences were evident between groups, with 17.19 (95% CI 17.11-17.27) quality-adjusted life years accruing for each subject. The incremental cost per episode of anaphylaxis treated with epinephrine over the model horizon was $12,576 for EpiPen vs epinephrine injection, USP auto-injector. EpiPen costs were lowest at Canadian pharmacies ($96, 95% CI $85-$107). There was price consistency between corporate and independent pharmacies throughout New England by device brand, with the epinephrine injection, USP auto-injector being the most affordable device. Cost differences among epinephrine auto-injectors were significant. More expensive auto-injector brands did not appear to provide incremental benefit. Copyright © 2017 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Understanding the spectrum of diesel injector deposits

Energy Technology Data Exchange (ETDEWEB)

Quigley, Robert; Barbour, Robert [Lubrizol Limited, Derby (United Kingdom); Arters, David; Bush, Jim [Lubrizol Corporation, Wickliffe, OH (United States)

2013-06-01

Understanding the origin of diesel fuel injector deposits used to be relatively simple; for the most part they were caused by the decomposition of fuel during the combustion process, were generally organic in nature and typically only affected the nozzle orifices. However, modem fuel injector designs appear to be both more severe in terms of generating conditions conducive to creating new and different types of deposits and more likely to have their operation affected by those deposits. Changes to fuel composition and type have in some cases increased the potential pool of reactive species or provided new potential deposit precursors. As a result, the universe of diesel injector deposits now range from the traditional organic to partially or fully inorganic in nature and from nozzle coking deposits to deposits which can seize the internal components of the injector; so called internal diesel injector deposits. Frequently, combinations of inorganic and organic deposits are found. While power loss is one well known issue associated with nozzle deposits, other field problems resulting from these new deposits include severe issues with drivability, emissions, fuel consumption and even engine failure. Conventional deposit control additive chemistries were developed to be effective against organic nozzle coking deposits. These conventional additives in many cases may prove ineffective against this wide range of deposit types. This paper discusses the range of deposits that have been found to adversely impact modem diesel fuel injectors and compares the performance of conventional and new, advanced deposit control additives against these various challenges to proper fuel injector functioning. (orig.)

Tritium pellet injector for TFTR

International Nuclear Information System (INIS)

Gouge, M.J.; Baylor, L.R.; Cole, M.J.; Combs, S.K.; Dyer, G.R.; Fehling, D.T.; Fisher, P.W.; Foust, C.R.; Langley, R.A.; Milora, S.L.; Qualls, A.L.; Wilgen, J.B.; Schmidt, G.L.; Barnes, G.W.; Persing, R.G.

1992-01-01

The tritium pellet injector (TPI) for the Tokamak Fusion Test Reactor (TFTR) will provide a tritium pellet fueling capability with pellet speeds in the 1- to 3-km/s range for the TFTR deuterium-tritium (D-T) phase. The existing TFTR deuterium pellet injector (DPI) has been modified at Oak Ridge National Laboratory (ORNL) to provide a four-shot, tritium-compatible, pipe-gun configuration with three upgraded single-stage pneumatic guns and a two-stage light gas gun driver. The TPI was designed to provide pellets ranging from 3.3 to 4.5 mm in diameter in arbitrarily programmable firing sequences at speeds up to approximately 1.5 km/s for the three single-stage drivers and 2.5 to 3 km/s for the two-stage driver. Injector operation is controlled by a programmable logic controller. The new pipe-gun injector assembly was installed in the modified DPI guard vacuum box, and modifications were made to the internals of the DPI vacuum injection line, including a new pellet diagnostics package. Assembly of these modified parts with existing DPI components was then completed, and the TPI was tested at ORNL with deuterium pellet. Results of the limited testing program at ORNL are described. The TPI is being installed on TFTR to support the D-D run period in 1992. In 1993, the tritium pellet injector will be retrofitted with a D-T fuel manifold and secondary tritium containment systems and integrated into TFTR tritium processing systems to provide full tritium pellet capability

Operation of the repeating pneumatic injector on TFTR and design of an 8-shot deuterium pellet injector

International Nuclear Information System (INIS)

Combs, S.K.; Milora, S.L.; Foust, C.R.

1985-01-01

The repeating pneumatic hydrogen pellet injector, which was developed at the Oak Ridge National Laboratory (ORNL), has been installed and operated on the Tokamak Fusion Test Reactor (TFTR). The injector combines high-speed extruder and pneumatic acceleration technologies to propel frozen hydrogen isotope pellets repetitively at high speeds. The pellets are transported to the plasma in an injection line that also serves to minimize the gas loading on the torus; the injection line incorporates a fast shutter valve and two stages of guide tubes with intermediate vacuum pumping stations. A remote, stand-alone control and data acquisition system is used for injector and vacuum system operation. In early pellet fueling experiments on TFTR, the injector has been used to deliver deuterium pellets at speeds ranging from 1.0 to 1.5 km/s into plasma discharges. First, single large (nominal 4-mm-dia) pellets provided high densities in TFTR (1.8 x 10 14 cm -3 on axis); after conversion to smaller (nominal 2.7-mm-dia) pellets, up to five pellets were injected at 0.25-s intervals into a plasma discharge, giving a line-averaged density of 1 x 10 14 cm -3 . Operating characteristics and performance of the injector in initial tests on TFTR are presented

Enhanced photoelectrochemical water splitting by oxides heterojunction photocathode coupled with Ag.

Science.gov (United States)

Lu, Xue; Liu, Zhifeng

2017-08-14

A novel one-dimensional Co 3 O 4 /CuO/Ag composite structure film was directly grown on indium tin oxide glass substrate by a simple hydrothermal method and electrodeposition method. The film was employed for the first time as a photocathode for photoelectrochemical (PEC) water splitting to generate hydrogen. The photocurrent density of the Co 3 O 4 /CuO/Ag composite structure achieved -5.13 mA cm -2 at -0.2 V vs. RHE, which is roughly 12.8 times that of 1D Co 3 O 4 nanowires and 3.31 times Co 3 O 4 /CuO heterojunction photocathodes. The enhanced PEC performance of this Co 3 O 4 /CuO/Ag composite structure ascribes increased light-harvesting and light-absorption, distensible photoresponse range, decreased interface charge transfer resistance, and improved photogenerated electron-hole pairs transfer and separation.

Design and fabrication of prototype 6×6 cm2 microchannel plate photodetector with bialkali photocathode for fast timing applications

International Nuclear Information System (INIS)

Xie, Junqi; Byrum, Karen; Demarteau, Marcel; Gregar, Joseph; May, Edward; Virgo, Mathew; Wagner, Robert; Walters, Dean; Wang, Jingbo; Xia, Lei; Zhao, Huyue

2015-01-01

Planar microchannel plate-based photodetectors with a bialkali photocathode are able to achieve photon detection with very good time and position resolution. A 6×6 cm 2 photodetector production facility was designed and built at Argonne National Laboratory. Small form-factor MCP-based photodetectors completely constructed out of glass were designed and prototypes were successfully fabricated. Knudsen effusion cells were incorporated in the photocathode growth chamber to achieve uniform and high quantum efficiency photocathodes. The thin film uniformity was simulated and measured for an antimony film deposition, showing uniformity of better than 10%. Several prototype devices with bialkali photocathodes have been fabricated with the described system and their characteristics were evaluated in the large signal (multi-PE) limit. A typical prototype device exhibits time-of-flight resolution of ~27 psec and differential time resolution of ~9 psec, corresponding to spatial resolution of ~0.65 mm

Low Emittance Guns for the ILC Polarized Electron Beam

International Nuclear Information System (INIS)

Clendenin, J. E.; Brachmann, A.; Ioakeimidi, K.; Kirby, R. E.; Maruyama, T.; Miller, R. H.; Wang, J. W.; Zhou, F.

2007-01-01

Polarized electron beams generated by DC guns are routinely available at several accelerators including JLAB, Mainz and SLAC. These guns operate with a cathode bias on the order of -100 kV. To minimize space charge effects, relatively long bunches are generated at the gun and then compressed longitudinally external to the gun just before and during initial acceleration. For linear colliders, this compression is accomplished using a combination of rf bunchers. For the basic design of the International Linear Collider (ILC), a 120 kV DC photocathode gun is used to produce a series of nanosecond bunches that are each compressed by two sub-harmonic bunchers (SHBs) followed by an L-band buncher and capture section. The longitudinal bunching process results in a significantly higher emittance than produced by the gun alone. While high-energy experiments using polarized beams are not generally sensitive to the source emittance, there are several benefits to a lower source emittance including a simpler more efficient injector system and a lower radiation load during transport especially at bends as at the damping ring. For the ILC, the SHBs could be eliminated if the voltage of the gun is raised sufficiently. Simulations using the General Particle Tracer (GPT) package indicate that a cathode bias voltage of ≥200 kV should allow both SHBs to be operated at 433 or even 650 MHz, while ≥500 kV would be required to eliminate the SHBs altogether. Simulations can be used to determine the minimum emittance possible if the injector is designed for a given increased voltage. A possible alternative to the DC gun is an rf gun. Emittance compensation, routinely used with rf guns, is discussed for higher-voltage DC guns

Low Emittance Guns for the ILC Polarized Electron Beam

International Nuclear Information System (INIS)

Clendenin, J.E.; Brachmann, A.; Ioakeimidi, K.; Kirby, R.E.; Maruyama, T.; Miller, R.H.; Wang, J.W.; Zhou, F.; SLAC

2006-01-01

Polarized electron beams generated by DC guns are routinely available at several accelerators including JLAB, Mainz and SLAC. These guns operate with a cathode bias on the order of -100 kV. To minimize space charge effects, relatively long bunches are generated at the gun and then compressed longitudinally external to the gun just before and during initial acceleration. For linear colliders, this compression is accomplished using a combination of rf bunchers. For the basic design of the International Linear Collider (ILC), a 120 kV DC photocathode gun is used to produce a series of nanosecond bunches that are each compressed by two sub-harmonic bunchers (SHBs) followed by an L-band buncher and capture section. The longitudinal bunching process results in a significantly higher emittance than produced by the gun alone. While high-energy experiments using polarized beams are not generally sensitive to the source emittance, there are several benefits to a lower source emittance including a simpler more efficient injector system and a lower radiation load during transport especially at bends as at the damping ring. For the ILC, the SHBs could be eliminated if the voltage of the gun is raised sufficiently. Simulations using the General Particle Tracer (GPT) package indicate that a cathode bias voltage of (ge)200 kV should allow both SHBs to be operated at 433 or even 650 MHz, while (ge)500 kV would be required to eliminate the SHBs altogether. Simulations can be used to determine the minimum emittance possible if the injector is designed for a given increased voltage. A possible alternative to the DC gun is an rf gun. Emittance compensation, routinely used with rf guns, is discussed for higher-voltage DC guns

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham M, Bruce; Heartmann, P.; Reza Kazimi; Hongxiu Liu; Poelker, B.M.; Price, J.S.; Rutt, P.M.; Schneider, W.J.; Sinclair K, Charles

1998-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughout. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion back-bombardment, and precise control of all of the electrons emitted from the cathode. In this paper, the authors will review recent results and discuss implications for future photocathode guns

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham, B. M.; Hartmann, P.; Kazimi, R.; Liu, H.; Poelker, B. M.; Price, J. S.; Rutt, P. M.; Schneider, W. J.; Sinclair, C. K.

1999-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughput. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, we will review recent results and discuss implications for future photocathode guns

Measurements of Photocathode Operational Lifetime at Beam Currents up to 10 mA using an Improved DC High Voltage GaAs Photogun

International Nuclear Information System (INIS)

Grames, J.; Poelker, M.; Adderley, P.; Brittian, J.; Clark, J.; Hansknecht, J.; Machie, D.; Stutzman, M. L.; Surles-Law, K.

2007-01-01

This work extends past research at Jefferson Lab aimed at better appreciating the mechanisms that limit photocathode operational lifetime at high current (> 1 mA). Specifically, the performance of an improved 100 kV DC high voltage load locked photogun will be described. Although difficult to measure directly, we believe the new gun has better vacuum conditions compared to the original gun, as indicated by enhanced photocathode lifetimes exceeding 2000 C using a 1.55 mm diameter drive laser spot at the photocathode. In addition, the dependence of the lifetime on the laser spot size at the photocathode was measured and a charge density lifetime exceeding 106 C/cm2 was measured with a 0.32 mm laser spot diameter

Measurements of photocathode operational lifetime at beam currents up to 10-mA using an improved DC high voltage GaAs photogun

International Nuclear Information System (INIS)

J. Grames; M. Poelker; P. Adderley; J. Brittian; J. Clark; J. Hansknecht; D. Machie; M.L. Stutzman; K. Surles-Law

2007-01-01

This work extends past research at Jefferson Lab aimed at better appreciating the mechanisms that limit photocathode operational lifetime at high current (> 1 mA). Specifically, the performance of an improved 100 kV DC high voltage load locked photogun will be described. Although difficult to measure directly, we believe the new gun has better vacuum conditions compared to the original gun, as indicated by enhanced photocathode lifetimes exceeding 2000 C using a 1.55 mm diameter drive laser spot at the photocathode. In addition, the dependence of the lifetime on the laser spot size at the photocathode was measured and a charge density lifetime exceeding 10 6 C/cm 2 was measured with a 0.32 mm laser spot diameter

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

International Nuclear Information System (INIS)

Li, S.; Alverson, S.; Bohler, D.; Egger, A.; Fry, A.

2017-01-01

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency. Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μm. In conclusion, our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

Science.gov (United States)

Li, S.; Alverson, S.; Bohler, D.; Egger, A.; Fry, A.; Gilevich, S.; Huang, Z.; Miahnahri, A.; Ratner, D.; Robinson, J.; Zhou, F.

2017-08-01

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency. Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μ m . Our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.

Status of the C-band RF System for the SPARC-LAB high brightness photo-injector

CERN Document Server

Boni, R.; Bellaveglia, M.; Di Pirro, G.; Ferrario, M.; Gallo, A.; Spataro, B.; Mostacci, A.; Palumbo, L.

2013-01-01

The high brightness photo-injector in operation at the SPARC-LAB facility of the INFN-LNF, Italy, consists of a 150 MeV S-band electron accelerator aiming to explore the physics of low emittance high peak current electron beams and the related technology. Velocity bunching techniques, SASE and Seeded FEL experiments have been carried out successfully. To increase the beam energy so improving the performances of the experiments, it was decided to replace one S-band travelling wave accelerating cavity, with two C-band cavities that allow to reach higher energy gain per meter. The new C-band system is in advanced development phase and will be in operation early in 2013. The main technical issues of the C-band system and the R&D activities carried out till now are illustrated in detail in this paper.

Synchrotron x-ray study of a low roughness and high efficiency K2CsSb photocathode during film growth

International Nuclear Information System (INIS)

Xie, Junqi; Demarteau, Marcel; Wagner, Robert; Schubert, Susanne; Gaowei, Mengjia; Attenkofer, Klaus; Walsh, John; Smedley, John; Ben-Zvi, Ilan; Wong, Jared; Feng, Jun; Padmore, Howard; Ruiz-Oses, Miguel; Ding, Zihao; Liang, Xue; Muller, Erik

2017-01-01

Reduction of roughness to the nm level is critical of achieving the ultimate performance from photocathodes used in high gradient fields. The thrust of this paper is to explore the evolution of roughness during sequential growth, and to show that deposition of multilayer structures consisting of very thin reacted layers results in an nm level smooth photocathode. Synchrotron x-ray methods were applied to study the multi-step growth process of a high efficiency K 2 CsSb photocathode. A transition point of the Sb film grown on Si was observed at the film thickness of ∼40 Å with the substrate temperature at 100 °C and the growth rate at 0.1 Å s −1 . The final K 2 CsSb photocathode exhibits a thickness of around five times that of the total deposited Sb film regardless of how the Sb film was grown. The film surface roughening process occurs first at the step when K diffuses into the crystalline Sb. The photocathode obtained from the multi-step growth exhibits roughness in an order of magnitude lower than the normal sequential process. X-ray diffraction measurements show that the material goes through two structural changes of the crystalline phase during formation, from crystalline Sb to K 3 Sb and finally to K 2 CsSb. (paper)

New developments of HIF injector

Directory of Open Access Journals (Sweden)

Liang Lu

2018-01-01

Full Text Available The ultra-high intensity heavy-ion beam is highly pursued for heavy-ion researches and applications. However, it is limited by heavy-ion production of ion source and space-charge-effect in the low energy region. The Heavy-ion Inertial Fusion (HIF facilities were proposed in 1970s. The HIF injectors have large cavity number and long total length, e.g., there are 27 injectors in HIDIF and HIBLIC is 30 km in length, and the corresponding HIF facilities are too large and too expensive to be constructed. Recently, ion acceleration technologies have been developing rapidly, especially in the low energy region, where the acceleration of high intensity heavy-ions is realized. Meanwhile, superconducting (SC acceleration matures and increases the acceleration gradient in medium and high energy regions. The length of HIF injectors can be shortened to a buildable length of 2.5 km. This paper will present a review of a renewed HIF injector, which adopts multi-beam linac-based cavities. Keywords: Heavy-ion inertial fusion (HIF, Radio frequency quadrupole (RFQ, IH cavity, Heavy-ion, Multi-beam accelerator, PACS Codes: 52.58.Hm, 28.52.Av, 29.20.Ej, 29.27.-a, 29.27.Ac, 41.75.Lx

Characterization of the transverse phase space at the photo-injector test facility in DESY, Zeuthen site

International Nuclear Information System (INIS)

Staykov, Lazar

2012-10-01

High brightness electron beams with charge of 1 nC and low transverse emittance are necessary for the functioning of advanced light sources such as the Free-electron Laser in Hamburg (FLASH) and the European X-ray FEL (XFEL). The photo-injector test facility at DESY, Zeuthen site (PITZ) is dedicated to the optimization of such electron beams. At PITZ the electrons are produced using an RF gun cavity operated at accelerating gradients of up to 60 MV/m. The gun is equipped with a pair of solenoids for the compensation of the emittance growth due to linear space charge forces. This solenoid compensation scheme is enhanced with a properly matched TESLA type normal conducting booster cavity. The main tool for the characterization of the transverse phase space of the electron beam at PITZ is the emittance measurement system (EMSY). It employs the single slit method for the measurement of the transverse phase space distribution of the electron beam. In this thesis, the performance of the EMSY was optimized for measurement of low emittances in a wide range of photo-injector parameters including such that result in electron beams close to the XFEL specifications. First results on the characterization of the PITZ photo-injector with a gun operated at maximum accelerating gradient of 60 MV/m are presented. This includes scans of the solenoid focusing strength, the initial beam size and the booster gradient. A comparison between results obtained at lower accelerating gradients is made with emphasize on the benefit of higher accelerating gradient.

Characterization of the transverse phase space at the photo-injector test facility in DESY, Zeuthen site

Energy Technology Data Exchange (ETDEWEB)

Staykov, Lazar

2012-10-15

High brightness electron beams with charge of 1 nC and low transverse emittance are necessary for the functioning of advanced light sources such as the Free-electron Laser in Hamburg (FLASH) and the European X-ray FEL (XFEL). The photo-injector test facility at DESY, Zeuthen site (PITZ) is dedicated to the optimization of such electron beams. At PITZ the electrons are produced using an RF gun cavity operated at accelerating gradients of up to 60 MV/m. The gun is equipped with a pair of solenoids for the compensation of the emittance growth due to linear space charge forces. This solenoid compensation scheme is enhanced with a properly matched TESLA type normal conducting booster cavity. The main tool for the characterization of the transverse phase space of the electron beam at PITZ is the emittance measurement system (EMSY). It employs the single slit method for the measurement of the transverse phase space distribution of the electron beam. In this thesis, the performance of the EMSY was optimized for measurement of low emittances in a wide range of photo-injector parameters including such that result in electron beams close to the XFEL specifications. First results on the characterization of the PITZ photo-injector with a gun operated at maximum accelerating gradient of 60 MV/m are presented. This includes scans of the solenoid focusing strength, the initial beam size and the booster gradient. A comparison between results obtained at lower accelerating gradients is made with emphasize on the benefit of higher accelerating gradient.

Influence of air exposure on CsI photocathodes

Energy Technology Data Exchange (ETDEWEB)

Xie, Yuguang, E-mail: ygxie@mail.ihep.ac.cn [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Zhang, Aiwu; Liu, Yingbiao [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Hongbang [Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Guangxi University, Naning 530004 (China); Hu, Tao; Zhou, Li; Cai, Xiao; Fang, Jian; Yu, Boxiang [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Ge, Yongshuai [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Lue, Qiwen [Shanxi University, Taiyuan 030006 (China); Sun, Xilei; Sun, Lijun; Xue, Zheng [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China); Xie, Yigang; Zheng, Yangheng [Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Lue, Junguang [State Key Laboratory of Particle Detection and Electronics, Institute of High Energy Physics, CAS and University of Science and Technology of China, Beijing 100049 (China)

2012-10-11

We investigate the influence of air exposure on the quantum efficiency (QE) and surface morphology of CsI photocathodes (PCs), at relative humidities (RH) higher than 80% down to nearly 3% (both at room temperature) and a 60 Degree-Sign C baking condition. By atomic force microscopy (AFM) surface analysis, it is clearly seen that RH >60% speeds up water film formation and CsI dissolution on the surface of the photocathode at the minute scale, while both grain size and QE change slowly at RH <30% at the hour scale. In the baking environment, the peak QE decreases less than 1.5% (absolute) within one week, and a stainless steel substrate and electron beam evaporation technique tend to effectively weaken the influence of air. With an Au-coated FR-4 substrate, the QE degradation is found to strongly depend on wavelength in the range of 120-210 nm. According to spectra of X-ray photoelectron spectroscopy (XPS), an excess of cesium was observed and the chemical reaction between water and CsI when exposed to humid air is proved. It is found that carbon, and not H{sub 2}O or O{sub 2}, is the main pollutant in the baking condition.

First measurements of electron-beam transit times and micropulse elongation in a photoelectric injector at the High-Brightness Accelerator FEL (HIBAF)

Energy Technology Data Exchange (ETDEWEB)

Lumpkin, A.H.; Carlsten, B.E.; Feldman, R.B.

1990-01-01

Key aspects of the dynamics of a photoelectric injector (PEI) on the Los Alamos High-Brightness Accelerator FEL (HIBAF) facility have been investigated using a synchroscan streak camera. By phase-locking the streak camera sweep to the reference 108.3 MHz rf signal, the variations of micropulse temporal elongations (30 to 80% over the drive-laser pulse length) and of transit times (25 ps for a 16{degree}-phase change) were observed for the first time. These results were in good agreement with PARMELA simulations. 2 refs., 8 figs.

Compact 250-kV injector system for PIGMI

International Nuclear Information System (INIS)

Hamm, R.W.; Stevens, R.R. Jr.; Mueller, D.W.; Lederer, H.M.

1978-01-01

A 250-kV proton injector to be used in the development of a linac suitable for medical applications has been constructed. This injector utilizes a spherical Pierce geometry to produce a converging beam. A gas insulated accelerating column is cantilevered on a grounded vacuum system, with a separate high voltage equipment dome connected to a 300-kV Cockcroft-Walton power supply. The injector can be operated locally or remotely, with the remote control accomplished by a microprocessor system linked to a central control minicomputer. This injector has been designed as a low-cost compact system. The design details and the data obtained during initial operation are presented

The SSRL injector beam position monitoring systems

International Nuclear Information System (INIS)

Lavender, W.; Baird, S.; Brennan, S.; Borland, M.; Hettel, R.; Nuhn, H.D.; Ortiz, R.; Safranek, J.; Sebek, J.; Wermelskirchen, C.; Yang, J.

1991-01-01

The beam position monitoring system of the SSRL injector forms a vital component of its operation. Several different types of instrumentation are used to measure the position or intensity of the electron beam in the injector. These include current toroids, fluorescent screens, Faraday cups, the 'Q' meter, a synchrotron light monitor, and electron beam position monitors. This paper focuses on the use of the electron beam position monitors to measure electron trajectories in the injector transport lines and the booster ring. The design of the beam position monitors is described in another paper to be presented at this conference. There are three different beam position monitor systems in the injector. One system consists of a set of five BPMs located on the injection transport line from the linac to the booster (known as the LTB line). There is a second system of six BPMs located on the ejection transport line (known as the BTS line). Finally, there is an array of 40 BPMs installed on the main booster ring itself. This article describes the software and processing electronics of the systems used to measure electron beam trajectories for the new SSRL injector for SPEAR

Photoemission spectroscopy study of a multi-alkali photocathode

CERN Document Server

Ettema, A R H

2000-01-01

In this paper a photoemission study of the highest core levels of the elements and the electron escape barrier (work function) in a multi-alkali photocathode are presented. The core levels indicate that the alkali atoms are in an oxidized state and therefore the compound Na sub 2 KSb can be regarded as an ionic semiconductor. The measured escape barrier of the Cs sub 2 O surface layer is determined as 2.3 eV.

Ignition Delay Properties of Alternative Fuels with Navy-Relevant Diesel Injectors

Science.gov (United States)

2014-06-01

nozzle tip. 8 Figure 3 EMD injector cross-sectional view, after [15]. c. Sturman Injector A Sturman research diesel injector was used to validate...PROPERTIES OF ALTERNATIVE FUELS WITH NAVY-RELEVANT DIESEL INJECTORS by Andrew J. Rydalch June 2014 Thesis Advisor: Christopher M. Brophy...Navy’s Green Fleet Initiative, this thesis researched the ignition characteristics for diesel replacement fuels used with Navy-relevant fuel injectors

Assembly process of the ITER neutral beam injectors

Energy Technology Data Exchange (ETDEWEB)

Graceffa, J., E-mail: joseph.graceffa@iter.org [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul lez Durance (France); Boilson, D.; Hemsworth, R.; Petrov, V.; Schunke, B.; Urbani, M. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul lez Durance (France); Pilard, V. [Fusion for Energy, C/ Josep Pla, n°2, Torres Diagonal Litoral, Edificio B3, 08019 Barcelona (Spain)

2013-10-15

The ITER neutral beam (NB) injectors are used for heating and diagnostics operations. There are 4 injectors in total, 3 heating neutral beam injectors (HNBs) and one diagnostic neutral beam injector (DNB). Two HNBs and the DNB will start injection into ITER during the hydrogen/helium phase of ITER operations. A third HNB is considered as an upgrade to the ITER heating systems, and the impact of the later installation and use of that injector have to be taken into account when considering the installation and assembly of the whole NB system. It is assumed that if a third HNB is to be installed, it will be installed before the nuclear phase of the ITER project. The total weight of one injector is around 1200 t and it is composed of 18 main components and 36 sets of shielding plates. The overall dimensions are length 20 m, height 10 m and width 5 m. Assembly of the first two HNBs and the DNB will start before the first plasma is produced in ITER, but as the time required to assemble one injector is estimated at around 1.5 year, the assembly will be divided into 2 steps, one prior to first plasma, and the second during the machine second assembly phase. To comply with this challenging schedule the assembly sequence has been defined to allow assembly of three first injectors in parallel. Due to the similar design between the DNB and HNBs it has been decided to use the same tools, which will be designed to accommodate the differences between the two sets of components. This reduces the global cost of the assembly and the overall assembly time for the injector system. The alignment and positioning of the injectors is a major consideration for the injector assembly as the alignment of the beamline components and the beam source are critical if good injector performance is to be achieved. The theoretical axes of the beams are defined relative to the duct liners which are installed in the NB ports. The concept adopted to achieve the required alignment accuracy is to use the

Study of residual gas adsorption on GaN nanowire arrays photocathode

Energy Technology Data Exchange (ETDEWEB)

Xia, Sihao; Liu, Lei, E-mail: liu1133_cn@sina.com.cn; Diao, Yu; Kong, Yike

2017-05-01

Highlights: • H{sub 2}O is more easily to absorb on the nanowire surface. • The work function increase after residual gas adsorption. • Bandgaps of the nanowire increase slightly. • Absorption coefficient is reduced and moves to higher energy side. - Abstract: In order to find out the influences of residual gas on GaN nanowire arrays photocathode, the optoelectronic properties of adsorption system are calculated on the basis of first principles. Results suggest that the residual gas adsorption will increase the work function and introduce a dipole moment with a direction from the nanowire to the adsorbates. The surface structures are changed and electrons transfer from nanowire to gas molecule. The bandgaps are enhanced after adsorption. Besides, the peak of absorption coefficients is reduced and moves to higher energy side. It is discovered that residual gas will drastically degrade the characteristics and lifetime of GaN nanowire arrays photocathode.

Photoemission using femtosecond laser pulses

International Nuclear Information System (INIS)

Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

1991-10-01

Successful operation of short wavelength FEL requires an electron bunch of current >100 A and normalized emittance < 1 mm-mrad. Recent experiments show that RF guns with photocathodes as the electron source may be the ideal candidate for achieving these parameters. To reduce the emittance growth due to space charge and RF dynamics effects, the gun may have to operate at high field gradient (hence at high RF frequency) and a spot size small compared to the aperture. This may necessitate the laser pulse duration to be in the subpicosecond regime to reduce the energy spread. We will present the behavior of metal photocathodes upon irradiation with femtosecond laser beams, comparison of linear and nonlinear photoemission, and scalability to high currents. Theoretical estimate of the intrinsic emittance at the photocathode in the presence of the anomalous heating of the electrons, and the tolerance on the surface roughness of the cathode material will be discussed

High-Average, High-Peak Current Injector Design

CERN Document Server

Biedron, S G; Virgo, M

2005-01-01

There is increasing interest in high-average-power (>100 kW), um-range FELs. These machines require high peak current (~1 kA), modest transverse emittance, and beam energies of ~100 MeV. High average currents (~1 A) place additional constraints on the design of the injector. We present a design for an injector intended to produce the required peak currents at the injector, eliminating the need for magnetic compression within the linac. This reduces the potential for beam quality degradation due to CSR and space charge effects within magnetic chicanes.

Tight comparison of Mg and Y thin film photocathodes obtained by the pulsed laser deposition technique

Energy Technology Data Exchange (ETDEWEB)

Lorusso, A. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Gontad, F., E-mail: francisco.gontad@le.infn.it [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Solombrino, L. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy); Chiadroni, E. [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, 00044 Frascati (Italy); Broitman, E. [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping (Sweden); Perrone, A. [Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento and Istituto Nazionale di Fisica Nucleare, 73100 Lecce (Italy)

2016-11-11

In this work Magnesium (Mg) and Yttrium (Y) thin films have been deposited on Copper (Cu) polycrystalline substrates by the pulsed laser ablation technique for photocathode application. Such metallic materials are studied for their interesting photoemission properties and are proposed as a good alternative to the Cu photocathode, which is generally used in radio-frequency guns. Mg and Y films were uniform with no substantial differences in morphology; a polycrystalline structure was found for both of them. Photoemission measurements of such cathodes based on thin films were performed, revealing a quantum efficiency higher than Cu bulk. Photoemission theory according to the three-step model of Spicer is invoked to explain the superior photoemission performance of Mg with respect to Y. - Highlights: • Mg and Y thin film photocathodes were successfully prepared by pulsed laser deposition. • Mg quantum efficiency is higher than Y, despite its higher work function. • The three-step model of Spicer justify the difference in quantum efficiency.

Commissioning of the RFQ1 injector

International Nuclear Information System (INIS)

Arbique, G.M.; Sheikh, J.Y.; Taylor, T.; Birney, L.F.; Davidson, A.D.; Wills, J.S.C.

1987-01-01

The RFQ1 accelerator is being developed at Chalk River to test the limits of the cw RFQ technology. A 50 kV injector has been built and is now being commissioned as the first phase of the program. This paper describes some of the innovative features of the RFQ1 injector and reports on initial operating experience

First operational tests of the positive-ion injector for ATLAS

International Nuclear Information System (INIS)

Bollinger, L.M.; Den Hartog, P.K.; Pardo, R.C.

1989-01-01

This paper summarizes the status and first operational experience with the positive-ion injector for ATLAS. The new injector consists of an ECR ion source on a 350-kV platform, followed by a superconducting injector linac of a new kind. In Phase I of this project, the ECR source, voltage platform, bunching system, beam-transport system, and a 3-MV injector linac were completed and tested in early 1989 by a successful acceleration of an 40 Ar 12+ beam. Most of the new system operated as planned, and the longitudinal emittance of the 36-MeV beam out of the injector was measured to be only 5 π keV-ns, much smaller than the emittance for the present tandem injector. When completed in 1990, the final injector linac will be enlarged to 12 MV, enough to allow the original ATLAS linac to accelerate uranium ions up to 8 MeV/u. 8 refs., 2 figs

First operational tests of the positive-ion injector for ATLAS

Energy Technology Data Exchange (ETDEWEB)

Bollinger, L.M.; Den Hartog, P.K.; Pardo, R.C.; Shepard, K.W.; Benaroya, R.; Billquist, P.J.; Clifft, B.E.; Markovich, P.; Munson, F.H. Jr.; Nixon, J.M.

1989-01-01

This paper summarizes the status and first operational experience with the positive-ion injector for ATLAS. The new injector consists of an ECR ion source on a 350-kV platform, followed by a superconducting injector linac of a new kind. In Phase I of this project, the ECR source, voltage platform, bunching system, beam-transport system, and a 3-MV injector linac were completed and tested in early 1989 by a successful acceleration of an /sup 40/Ar/sup 12 +/ beam. Most of the new system operated as planned, and the longitudinal emittance of the 36-MeV beam out of the injector was measured to be only 5 ..pi.. keV-ns, much smaller than the emittance for the present tandem injector. When completed in 1990, the final injector linac will be enlarged to 12 MV, enough to allow the original ATLAS linac to accelerate uranium ions up to 8 MeV/u. 8 refs., 2 figs.

SLC injector simulation and tuning for high charge transport

International Nuclear Information System (INIS)

Yeremian, A.D.; Miller, R.H.; Clendenin, J.E.; Early, R.A.; Ross, M.C.; Turner, J.L.; Wang, J.W.

1992-01-01

We have simulated the SLC injector from the thermionic gun through the first accelerating section and used the resulting parameters to tune the injector for optimum performance and high charge transport. Simulations are conducted using PARMELA, a three-dimensional space-charge model. The magnetic field profile due to the existing magnetic optics is calculated using POISSON, while SUPERFISH is used to calculate the space harmonics of the various bunchers and the accelerator cavities. The initial beam conditions in the PARMELA code are derived from the EGUN model of the gun. The resulting injector parameters from the PARMELA simulation are used to prescribe experimental settings of the injector components. The experimental results are in agreement with the results of the integrated injector model. (Author) 5 figs., 7 refs

Designing Liquid Rocket Engine Injectors for Performance, Stability, and Cost

Science.gov (United States)

Westra, Douglas G.; West, Jeffrey S.

2014-01-01

NASA is developing the Space Launch System (SLS) for crewed exploration missions beyond low Earth orbit. Marshall Space Flight Center (MSFC) is designing rocket engines for the SLS Advanced Booster (AB) concepts being developed to replace the Shuttle-derived solid rocket boosters. One AB concept uses large, Rocket-Propellant (RP)-fueled engines that pose significant design challenges. The injectors for these engines require high performance and stable operation while still meeting aggressive cost reduction goals for access to space. Historically, combustion stability problems have been a critical issue for such injector designs. Traditional, empirical injector design tools and methodologies, however, lack the ability to reliably predict complex injector dynamics that often lead to combustion stability. Reliance on these tools alone would likely result in an unaffordable test-fail-fix cycle for injector development. Recently at MSFC, a massively parallel computational fluid dynamics (CFD) program was successfully applied in the SLS AB injector design process. High-fidelity reacting flow simulations were conducted for both single-element and seven-element representations of the full-scale injector. Data from the CFD simulations was then used to significantly augment and improve the empirical design tools, resulting in a high-performance, stable injector design.

Fabrication, Tuning, Treatment and Testing of Two 3.5 Cell Photo-Injector Cavities for the ELBE Linac

International Nuclear Information System (INIS)

Arnold, A.; Murcek, P.; Teichert, J.; Xiang, R.; Eremeev, G. V.; Kneisel, P.; Stirbet, M.; Turlington, L.

2011-01-01

As part of a CRADA (Cooperative Research and Development Agreement) between Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Thomas Jefferson Lab National Accelerator Facility (TJNAF) we have fabricated and tested two 1.3 GHz 3.5 cell photo-injector cavities from polycrystalline RRR niobium and large grain RRR niobium, respectively. The cavity with the better performance will replace the presently used injector cavity in the ELBE linac. The cavities have been fabricated and pre-tuned at TJNAF, while the more sophisticated final field tuning, the adjustment of the external couplings and the field profile measurement of transverse electric modes for RF focusing was done at HZDR. The following standard surface treatment and the vertical test was carried out at TJNAF's production facilities. A major challenge turned out to be the rinsing of the cathode cell, which has small opening (O-slash10mm) to receive the cathode stalk. Another unexpected problem encountered after etching, since large visible defects appeared in the least accessible cathode cell. This contribution reports about our experiences, initial results and the on-going diagnostic work to understand and fix the problems

Commissioning experience and beam physics measurements at the SwissFEL Injector Test Facility

Directory of Open Access Journals (Sweden)

T. Schietinger

2016-10-01

Full Text Available The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and test bed for the development and realization of SwissFEL, the x-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of an FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultralow-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measurements performed during the operation of the test facility, including the results of the test of an in-vacuum undulator prototype generating radiation in the vacuum ultraviolet and optical range.

21 CFR 870.1670 - Syringe actuator for an injector.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Syringe actuator for an injector. 870.1670 Section 870.1670 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... actuator for an injector. (a) Identification. A syringe actuator for an injector is an electrical device...

Multiple beam envelope equations for electron injectors using a bunch segmentation model

Directory of Open Access Journals (Sweden)

A. Mizuno

2012-06-01

Full Text Available A new semianalytical method of investigating the beam dynamics for electron injectors was developed. In this method, a short bunched electron beam is assumed to be an ensemble of several segmentation pieces in both the longitudinal and the transverse directions. The trajectory of each electron in the segmentation pieces is solved by the beam envelope equations while taking into account the space charge fields produced by all the pieces, the electromagnetic fields of an rf cavity, and the image charge fields at a cathode surface. The shape of the entire bunch is consequently calculated, and thus the emittances can be obtained from weighted mean values of the solutions for the obtained electron trajectories. The advantage of this method is its unique assumption for the beam parameters. We assume that each segmentation slice is not warped in the calculations. Although if the beam energy is low and the charge density is large, this condition is not satisfied, in practice, this condition is usually satisfied. We have performed beam dynamics calculations to obtain traces in free space and in the BNL-type rf gun cavity by comparing the analytical solutions with those obtained by simulation. In most cases, the emittances obtained by the simulation become closer to those obtained analytically with increasing the number of particles used in the simulation. Therefore, the analytically obtained emittances are expected to coincide with converged values obtained by the simulation. The applicable range of the analytical method for the BNL-type rf gun cavity is under 0.5 nC per bunch. This range is often used in recently built x-ray free electron laser facilities.

Development of Technologies on Innovative-Simplified Nuclear Power Plant Using High-Efficiency Steam Injectors (11) Visualization Study on the Start-Up of the Steam Injector

International Nuclear Information System (INIS)

Koji Okamoto; Tadashi Narabayashi; Chikako Iwaki; Shuichi Ohmori; Michitsugu Mori

2006-01-01

The Steam Injector is the superior system to pump the fluid without rotating machine. Because the water column is surrounded by the saturated steam, very high heat transfer is also expected with direct condensation. The inside of the Steam Injector is very complicated. To improve the efficiency of the Steam Injector, the water column behavior inside the Injector is visualized using the Dynamic PIV system. Dynamic PIV system consists of the high-speed camera and lasers. In this study, 384 x 180 pixel resolution with 30,000 fps camera is used to visualize the flow. For the illumination CW green laser with 300 mW is applied. To view inside the Injector, relay lens system is set at the Injector wall. Very high speed water column during the starting up of Steam Injector had been clearly visualized with 30,000 fps. The wave velocity on the water column had been analyzed using PIV technique. The instability of the water column is also detected. (authors)

Status and Plans for a Superconducting RF Accelerator Test Facility at Fermilab

International Nuclear Information System (INIS)

Andrews, R.; Baffes, C.M.; Carlson, K.; Chase, B.; Church, M.D.; Harms, E.R.; Klebaner, A.L.; Leibfritz, J.R.; Martinez, A.; Nagaitsev, S.; Nobrega, L.E.

2012-01-01

The Advanced Superconducting Test Accelerator (ASTA) is being constructed at Fermilab. The existing New Muon Lab (NML) building is being converted for this facility. The accelerator will consist of an electron gun, injector, beam acceleration section consisting of 3 TTF-type or ILC-type cryomodules, multiple downstream beam lines for testing diagnostics and conducting various beam tests, and a high power beam dump. When completed, it is envisioned that this facility will initially be capable of generating a 750 MeV electron beam with ILC beam intensity. An expansion of this facility was recently completed that will provide the capability to upgrade the accelerator to a total beam energy of 1.5 GeV. Two new buildings were also constructed adjacent to the ASTA facility to house a new cryogenic plant and multiple superconducting RF (SRF) cryomodule test stands. In addition to testing accelerator components, this facility will be used to test RF power systems, instrumentation, and control systems for future SRF accelerators such as the ILC and Project-X. This paper describes the current status and overall plans for this facility.

Advances in DC photocathode electron guns

International Nuclear Information System (INIS)

Dunham, B.M.; Hartmann, P.; Kazimi, R.; Liu, H.; Poelker, B.M.; Price, J.S.; Rutt, P.M.; Schneider, W.J.; Sinclair, C.K.

1999-01-01

At Jefferson Lab, a DC photoemission gun using GaAs and GaAs-like cathodes provides a source of polarized electrons for the main accelerator. The gun is required to produce high average current with long operational lifetimes and high system throughput. Recent work has shown that careful control of the parameters affecting cathode lifetime lead to dramatic improvements in source operation. These conditions include vacuum and the related effect of ion backbombardment, and precise control of all of the electrons emitted from the cathode. In this paper, we will review recent results and discuss implications for future photocathode guns. copyright 1999 American Institute of Physics

A polarized photoluminescence study of strained layer GaAs photocathodes

International Nuclear Information System (INIS)

Mair, R.A.

1996-07-01

Photoluminescence measurements have been made on a set of epitaxially grown strained GaAs photocathode structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to ∼0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, ∼78 K and ∼12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminescence circular polarization data is compared with the measured electron spin polarization when the samples are used as electron photo-emitters with a negative electron affinity surface preparation. The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics and spin depolarization mechanisms of the photocathode structures. A simple model is used to describe the luminescence data, obtained for the set of samples. Within the assumptions of the model, the deformation potentials a, b and d for GaAs are determined. The measured values are a = -10.16±.21 eV, b = -2.00±.05 eV and d = -4.87±.29 eV. Good agreement with published values of the deformation potentials provides support for the model used to describe the data

SLC injector simulation and tuning for high charge transport

International Nuclear Information System (INIS)

Yeremian, A.D.; Miller, R.H.; Clendenin, J.E.; Early, R.A.; Ross, M.C.; Turner, J.L.; Wang, J.W.

1992-08-01

We have simulated the SLC injector from the thermionic gun through the first accelerating section and used the resulting parameters to tune the injector for optimum performance and high charge transport. Simulations are conducted using PARMELA, a three-dimensional ray-trace code with a two-dimensional space-charge model. The magnetic field profile due to the existing magnetic optics is calculated using POISSON, while SUPERFISH is used to calculate the space harmonics of the various bunchers and the accelerator cavities. The initial beam conditions in the PARMELA code are derived from the EGUN model of the gun. The resulting injector parameters from the PARMELA simulation are used to prescribe experimental settings of the injector components. The experimental results are in agreement with the results of the integrated injector model

CdTeO3 Deposited Mesoporous NiO Photocathode for a Solar Cell

Directory of Open Access Journals (Sweden)

Chuan Zhao

2014-01-01

Full Text Available Semiconductor sensitized NiO photocathodes have been fabricated by successive ionic layer adsorption and reaction (SILAR method depositing CdTeO3 quantum dots onto mesoscopic NiO films. A solar cell using CdTeO3 deposited NiO mesoporous photocathode has been fabricated. It yields a photovoltage of 103.7 mV and a short-circuit current density of 0.364 mA/cm2. The incident photon to current conversion efficiency (IPCE value is found to be 12% for the newly designed NiO/CdTeO3 solar cell. It shows that the p-type NiO/CdTeO3 structure could be successfully utilized to fabricate p-type solar cell.

Heat enhancement of radiation resistivity of evaporated CsI, KI and KBr photocathodes

CERN Document Server

Tremsin, A S

2000-01-01

The photoemissive stability of as-deposited and heat-treated CsI, KI and KBr evaporated thin films under UV radiation is examined in this paper. After the deposition, some photocathodes were annealed for several hours at 90 deg. C in vacuum and their performance was then compared to the performance of non-heated samples. We observed that the post-evaporation thermal treatment not only increases the photoyield of CsI and KI photocathodes in the spectral range of 115-190 nm, but also reduces CsI, KI and KBr photocurrent degradation that occurs after UV irradiation. KBr evaporated layers appeared to be more radiation-resistant than CsI and KI layers. Post-deposition heat treatment did not result in any significant variation of KBr UV sensitivity.

LTP fibre injector qualification and status

International Nuclear Information System (INIS)

Bogenstahl, J; Cunningham, L; Fitzsimons, E D; Hough, J; Killow, C J; Perreur-Lloyd, M; Robertson, D; Rowan, S; Ward, H

2009-01-01

This paper presents the current state of the LISA Technology Package (LTP) fibre injector qualification project in terms of vibration and shock tests. The fibre injector is a custom built part and therefore must undergo a full space qualification process. The mounting structure and method for sinusoidal vibration and random vibration tests as well as shock tests will be presented. Furthermore a proposal will be presented to use the fibre injector pair qualification model to build an optical prototype bench. The optical prototype bench is a full-scale model of the flight model. It will be used for development and rehearsal of all the assembly stages of the flight model and will provide an on-ground simulator for investigation as an updated engineering model.

Observation of Cherenkov rings using a low-pressure parallel-plate chamber and a solid cesium-iodide photocathode

International Nuclear Information System (INIS)

Lockyer, N.S.; Millan, J.E.; Lu, C.; McDonald, K.T.; Lopez, A.

1993-01-01

We have observed Cherenkov rings from minimum-ionizing particles using a low-pressure, parallel-plate pad-chamber with a cesium-iodide solid photocathode. This detector is blind to minimum-ionizing particles, and sensitive to Cherenkov photons of wavelengths 170-210 nm. An average of 5 photoelectrons per Cherenkov ring were detected using a 2-cm-thick radiator of liquid C 6 F 14 . This paper reports on the chamber construction, photocathode preparation and testbeam results. (orig.)

Structural transformation of CsI thin film photocathodes under exposure to air and UV irradiation

CERN Document Server

Tremsin, A S; Siegmund, O H W

2000-01-01

Transmission electron microscopy has been employed to study the structure of polycrystalline CsI thin films and its transformation under exposure to humid air and UV irradiation. The catastrophic degradation of CsI thin film photocathode performance is shown to be associated with the film dissolving followed by its re-crystallization. This results in the formation of large lumps of CsI crystal on the substrate surface, so that the film becomes discontinuous and its performance as a photocathode is permanently degraded. No change in the surface morphology and the film crystalline structure was observed after the samples were UV irradiated.

A compact 10 kW, 476 MHz solid state radio frequency amplifier for pre-buncher cavity of free electron laser injector linear accelerator

Energy Technology Data Exchange (ETDEWEB)

Mohania, Praveen; Mahawar, Ashish; Shrivastava, Purushottam; Gupta, P. D. [Raja Rammana Centre for Advanced Technology (RRCAT), Indore 452013 (India)

2013-09-15

A 10 kW, 476 MHz, 0.1% duty cycle solid state RF amplifier system for driving sub-harmonic, pre-buncher cavity of IR-FEL injector LINAC, has been developed at RRCAT. The 10 kW power is achieved by combining output of eight 1400 W amplifier modules using 8-way planar corporate combiner. The solid state amplifier modules have been developed using 50 V RF LDMOS transistors which although meant for push-pull operation are being used in single ended configuration with matching circuit developed on a thin (25 mils), high dielectric constant (9.7), low loss microwave laminate with an aim to have a compact structure. Ease of fabrication, modularity, small size, and low cost are the important features of this design which could be used as a template for low duty cycle medium to high pulsed power UHF amplifier system.

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.)

Experimental studies of the charge limit phenomenon in NEA GaAs photocathodes

International Nuclear Information System (INIS)

Tang, H.; Alley, R.K.; Aoyagi, H.; Clendenin, J.E.; Frisch, J.C.; Mulhollan, G.A.; Saez, P.J.; Schultz, D.C.; Turner, J.L.

1994-06-01

Negative electron affinity GaAs photocathodes have been in continuous use at SLAC for generating polarized electron beams since early 1992. If the quantum efficiency of a GaAs cathode is below a critical value, the maximum photoemitted charge with photons of energies close to the band gap in a 2-ns pulse is found to be limited by the intrinsic properties of the cathode instead of by the space charge limit. We have studied this novel charge limit phenomenon in a variety of GaAs photocathodes of different structures and doping densities. We find that the charge limit is strongly dependent on the cathode's quantum efficiency and the extraction electric field, and to a lesser degree on the excitation laser wavelength. In addition, we show that the temporal behavior of the charge limit depends critically on the doping density

The positive-ion injector of ATLAS: design and operating experience

Energy Technology Data Exchange (ETDEWEB)

Bollinger, L M [Physics Div., Argonne National Lab., IL (United States); Pardo, R C [Physics Div., Argonne National Lab., IL (United States); Shepard, K W [Physics Div., Argonne National Lab., IL (United States); Billquist, P J [Physics Div., Argonne National Lab., IL (United States); Bogaty, J M [Physics Div., Argonne National Lab., IL (United States); Clifft, B E [Physics Div., Argonne National Lab., IL (United States); Harkewicz, R [Physics Div., Argonne National Lab., IL (United States); Munson, F H [Physics Div., Argonne National Lab., IL (United States); Nolen, J A [Physics Div., Argonne National Lab., IL (United States); Zinkann, G P [Physics Div., Argonne National Lab., IL (United States)

1993-06-01

The recently completed positive-ion injector for the heavy-ion accelerator ATLAS is a replacement for the tandem injector of the present tandem-linac system. Unlike the tandem, the new injector provides ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and experience in the operation of ATLAS with its new injector is discussed. (orig.)

The positive-ion injector of ATLAS: Design and operating experience

International Nuclear Information System (INIS)

Bollinger, L.M.; Pardo, R.C.; Shepard, K.W.; Billquist, P.J.; Bogaty, J.M.; Clifft, B.E.; Harkewicz, R.; Munson, F.H.; Nolen, J.A.; Zinkann, G.P.

1992-01-01

The recently completed Positive-Ion Injector for the heavy-ion accelerator ATLAS is a replacement for the tandem injector of the present tandem-linac system. Unlike the tandem, the new injector provides ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and experience in the operation of ATLAS with its new injector is discussed

Pellet injector research and development at ORNL

International Nuclear Information System (INIS)

Combs, S.K.; Argo, B.E.; Baylor, L.R.; Cole, M.J.; Dyer, G.R.; Fehling, D.T.; Fisher, P.W.; Foster, C.A.; Foust, C.R.; Gouge, M.J.; Jernigan, T.C.; Langley, R.A.; Milora, S.L.; Qualls, A.L.; Schechter, E.; Sparks, D.O.; Tsai, C.C.; Wilgen, J.B.; Whealton, J.W.

1993-01-01

A variety of pellet injector designs have been developed at ORNL including single-shot guns that inject one pellet, multiple-shot guns that inject four and eight pellets, machine gun-types (single- and multiple-barrel) that can inject up to >100 pellets, and centrifugal accelerators (mechanical devices that are inherently capable of high repetition rates and long-pulse operation). With these devices, macroscopic pellets (1--6 mm in diameter) composed of hydrogen isotopes are typically accelerated to speeds of ∼1.0 to 2.0 km/s for injection into plasmas of experimental fusion devices. In the past few years, steady progress has been made at ORNL in the development and application of pellet injectors for fueling present-day and future fusion devices. In this paper, we briefly describe some research and development activities at ORNL, including: (1) two recent applications and a new one on large experimental fusion devices, (2) high-velocity pellet injector development, and (3) tritium injector research

Review on pressure swirl injector in liquid rocket engine

Science.gov (United States)

Kang, Zhongtao; Wang, Zhen-guo; Li, Qinglian; Cheng, Peng

2018-04-01

The pressure swirl injector with tangential inlet ports is widely used in liquid rocket engine. Commonly, this type of pressure swirl injector consists of tangential inlet ports, a swirl chamber, a converging spin chamber, and a discharge orifice. The atomization of the liquid propellants includes the formation of liquid film, primary breakup and secondary atomization. And the back pressure and temperature in the combustion chamber could have great influence on the atomization of the injector. What's more, when the combustion instability occurs, the pressure oscillation could further affects the atomization process. This paper reviewed the primary atomization and the performance of the pressure swirl injector, which include the formation of the conical liquid film, the breakup and atomization characteristics of the conical liquid film, the effects of the rocket engine environment, and the response of the injector and atomization on the pressure oscillation.

Development of Thin Film Amorphous Silicon Tandem Junction Based Photocathodes Providing High Open-Circuit Voltages for Hydrogen Production

Directory of Open Access Journals (Sweden)

F. Urbain

2014-01-01

Full Text Available Hydrogenated amorphous silicon thin film tandem solar cells (a-Si:H/a-Si:H have been developed with focus on high open-circuit voltages for the direct application as photocathodes in photoelectrochemical water splitting devices. By temperature variation during deposition of the intrinsic a-Si:H absorber layers the band gap energy of a-Si:H absorber layers, correlating with the hydrogen content of the material, can be adjusted and combined in a way that a-Si:H/a-Si:H tandem solar cells provide open-circuit voltages up to 1.87 V. The applicability of the tandem solar cells as photocathodes was investigated in a photoelectrochemical cell (PEC measurement set-up. With platinum as a catalyst, the a-Si:H/a-Si:H based photocathodes exhibit a high photocurrent onset potential of 1.76 V versus the reversible hydrogen electrode (RHE and a photocurrent of 5.3 mA/cm2 at 0 V versus RHE (under halogen lamp illumination. Our results provide evidence that a direct application of thin film silicon based photocathodes fulfills the main thermodynamic requirements to generate hydrogen. Furthermore, the presented approach may provide an efficient and low-cost route to solar hydrogen production.

Integrated MoSe2 with n+p-Si photocathodes for solar water splitting with high efficiency and stability

Science.gov (United States)

Huang, Guanping; Mao, Jie; Fan, Ronglei; Yin, Zhihao; Wu, Xi; Jie, Jiansheng; Kang, Zhenhui; Shen, Mingrong

2018-01-01

Many earth-abundant transition metal dichalcogenides (TMDs) have been employed as catalysts for H2 evolution reaction (HER); however, their impactful integration onto photocathodes for photoelectrochemical (PEC) HER is less developed. In this study, we directly sputtered a MoSe2 catalyst onto an n+p-Si photocathode for efficient and stable PEC-HER. An onset potential of 0.4 V vs. RHE, a saturated photocurrent of 29.3 mA/cm2, a fill factor of 0.32, and an energy conversion efficiency of 3.8% were obtained under 100 mA/cm2 Xe lamp illumination. Such superior PEC properties were ascribed to the nearly vertically standing two dimensional MoSe2 rough surface layer and the sharp interface between Si and MoSe2 with small charge transfer resistance. The balance between the reflectivity of the electrode surface and the absorptivity of MoSe2 was also discussed. In addition, the MoSe2 layer can protect the n+p-Si photocathode with a 120 h stability due to its initial growth on Si with high flatness and compactness. This study provides a path to the effective and scalable growth of TMDs onto the Si photocathode aiming for high efficiency and stability.

Pellet injectors for the tokamak fusion test reactor

International Nuclear Information System (INIS)

Combs, S.K.

1986-01-01

The repeating pneumatic injector is a device from the ORNL development program. A new eight-shot deuterium pellet injector has been designed and constructed specifically for the TFTR application and is scheduled to replace the repeating injector this year. The new device combines a cryogenic extruder and a cold wheel rotary mechanism to form and chamber eight pellets in a batch operation; the eight pellets can then be delivered in any time sequence. Another unique feature of the device is the variable pellet size with three pellets each of 3.0 and 3.5 mm diam and two each of 4.0 mm diam. The experience and technology that have been developed on previous injectors at ORNL have been utilized in the design of this latest pellet injection system

Spray Modeling for Outwardly-Opening Hollow-Cone Injector

KAUST Repository

Sim, Jaeheon; Badra, Jihad; Elwardani, Ahmed Elsaid; Im, Hong G.

2016-01-01

linear instability sheet atomization (LISA) model was originally developed for pressure swirl hollow-cone injectors with moderate spray angle and toroidal ligament breakups. Therefore, it is not appropriate for the outwardly-opening injectors having wide

Industrial RF Linac Experiences and Laboratory Interactions

CERN Document Server

Peiniger, M

2004-01-01

Since more than two decades ACCEL Instruments GmbH at Bergisch Gladbach (formerly Siemens/Interatom) is supplying the worldwide accelerator labs with key components like rf cavities and power couplers, s.c. magnets, insertion devices, vacuum chambers and x-ray beamline equipment. Starting with the design and production of turn key SRF accelerating modules in the late 80th, meanwhile ACCEL is engineering, manufacturing, on site commissioning and servicing complete accelerators with guaranteed beam performance. Today, with a staff of more than 100 physicists and engineers and about the same number of manufacturing specialists in our dedicated production facilities, ACCEL's know how and sales volume in this field has accumulated to more than 2000 man years and several hundred Mio €, respectively. Basis of our steady development is a cooperative partnership with the world leading research labs in the respective fields. As an example, for the supply of a turn key 100 MeV injector linac for the Swiss Ligh...

rf measurements and tuning of the 750 MHz radio frequency quadrupole

Science.gov (United States)

Koubek, Benjamin; Grudiev, Alexej; Timmins, Marc

2017-08-01

In the framework of the program on medical applications a compact 750 MHz RFQ has been designed and built to be used as an injector for a hadron therapy linac. This RFQ was designed to accelerate protons to an energy of 5 MeV within only 2 m length. It is divided into four segments and equipped with 32 tuners in total. The length of the RFQ corresponds to 5 λ which is considered to be close to the limit for field adjustment using only piston tuners. Moreover the high frequency, which is about double the frequency of existing RFQs, results in a sensitive structure and requires careful tuning. In this paper we present the tuning algorithm, the tuning procedure and rf measurements of the RFQ.

Engineering problems of future neutral beam injectors

International Nuclear Information System (INIS)

Fink, J.

1977-01-01

Because there is no limit to the energy or power that can be delivered by a neutral-beam injector, its use will be restricted by either its cost, size, or reliability. Studies show that these factors can be improved by the injector design, and several examples, taken from mirror reactor studies, are given

S-11 and S-20 photocathode research activity. Rev. 1

International Nuclear Information System (INIS)

Gex, F.; Huen, T.; Kalibjian, R.

1984-01-01

The S-1 semi-transparent photocathode is the only one that can be used to study the 1.06 μm neodynium laser pulses of less than 10 ps duration. We first reviewed the recent results obtained at the Paris Observatory (research sponsored by the CEA), and then we tried to determine the role of the main constituents and their contributions in photoemission

Performance of the 100 MeV injector linac for the electron storage ring at Kyoto University

International Nuclear Information System (INIS)

Shirai, T.; Sugimura, T.; Iwashita, Y.; Kakigi, S.; Fujita, H.; Tonguu, H.; Noda, A.; Inoue, M.

1996-01-01

An electron linear accelerator has been constructed as an injector of a 300 MeV electron storage ring (Kaken Storage Ring, KSR) at Institute for Chemical Research, Kyoto University. The output beam energy of the linac is 100 MeV and the designed beam current is 100 mA at the 1 μsec long pulse mode. The transverse and longitudinal emittance are measured to evaluate the beam quality for the beam injection into the KSR. They are observed by the profile monitors combined with quadrupole magnets or an RF accelerator. The results are that the normalized transverse emittance is 120 π.mm.mrad. The longitudinal emittance is 15 π.deg.MeV and the energy spread is ±2.2 %. (author)

352.2 MHz rf system for the ESRF

International Nuclear Information System (INIS)

Jacob, J.; David, C.

1988-01-01

This paper reports that ESRF's 352.2 MHz RF system that uses 1 MW-CW klystrons and five-cell LEP type cavities has been adopted. In the storage ring (SR), two klystrons will feed a total of four cavities in order to provide the maximum required accelerating voltage of 8.9 MV. In the injector synchrotron (SY), two cavities fed by one klystron in a cycling mode at 10 Hz will give the maximum needed accelerating voltage of 7.3 MV. In multibunch operation of the SR, coupled bunch oscillations will be driven by the higher order modes (HOMs) of the cavities, and may limit the maximum beam current to about 60 mA. Spare ports will allow to install HOM dampers on the cavities in order to raise the instability thresholds above the design current of 100 mA. In addition, active feed back systems may be implemented

RF Measurements and Tuning of the 750 MHz HF-RFQ

CERN Document Server

Koubek, Benjamin; Timmins, Marc; CERN. Geneva. ATS Department

2017-01-01

In the frame of the program on medical applications CERN has built a compact 750 MHz RFQ to be used as an injector for a hadron therapy linac. This RFQ was designed to accelerate protons to an energy of 5 {\\lambda} MeV within only 2 m length. It is divided into four segments and equipped with 32 tuners in total. The length of the RFQ corresponds to 5 which is considered to be close to the limit for field adjustment using only piston tuners. Moreover the high frequency, which is about double the frequency of existing RFQs, results in a sensitive structure and requires careful tuning by means of the alignment of the pumping ports and fixed tuners. This report summarises the tuning procedure, RF and bead pull measurements of the RFQ.

Rf-synchronized imaging for particle and photon beam characterizations

Energy Technology Data Exchange (ETDEWEB)

Lumpkin, A.H.

1993-07-01

The usefulness of imaging electro-optics for rf-driven accelerators can be enhanced by synchronizing the instruments to the system fundamental frequency or an appropriate subharmonic. This step allows one to obtain micropulse bunch length and phase during a series of linac bunches or storage ring passes. Several examples now exist of the use of synchroscan and dual-sweep streak cameras and/or image dissector tubes to access micropulse scale phenomena (10 to 30 ps) during linac and storage ring operations in the US, Japan, and Europe. As space permits, selections will be presented from the list of phase stability phenomena on photoelectric injectors, micropulse length during a macropulse, micropulse elongation effects, transverse Wakefield effects within a micropulse, and submicropulse phenomena on a stored beam. Potential applications to the subsystems of the Advanced Photon Source (APS) will be briefly addressed.

Necessary LIU studies in the injectors during 2012

International Nuclear Information System (INIS)

Rumolo, G.; Bartosik, H.; Papaphilippou, Y.

2012-01-01

A significant fraction of the Machine Development (MD) time in the LHC injectors in 2011 was devoted to the study of the intensity limitations in the injectors (e.g. space charge effects in PS and SPS, electron cloud effects in the PS and SPS, single bunch and multi-bunch instabilities in PS and SPS, emittance preservation across the injector chain, etc.). The main results achieved in 2011 are presented as well as the questions that still remain unresolved and are of relevance for the LHC Injector Upgrade (LIU) project. 2012 MD will also continue exploring the potential of scenarios that might become operational in the future, like the development of a low gamma transition optics in the SPS or alternative production schemes for the LHC beams in the PS. A tentative prioritized list of studies is provided. (authors)

Geometrical characterization and performance optimization of monopropellant thruster injector

Directory of Open Access Journals (Sweden)

T.R. Nada

2012-12-01

Full Text Available The function of the injector in a monopropellant thruster is to atomize the liquid hydrazine and to distribute it over the catalyst bed as uniformly as possible. A second objective is to place the maximum amount of catalyst in contact with the propellant in as short time as possible to minimize the starting transient time. Coverage by the spray is controlled mainly by cone angle and diameter of the catalyst bed, while atomization quality is measured by the Sauter Mean Diameter, SMD. These parameters are evaluated using empirical formulae. In this paper, two main types of injectors are investigated; plain orifice and full cone pressure swirl injectors. The performance of these two types is examined for use with blow down monopropellant propulsion system. A comprehensive characterization is given and design charts are introduced to facilitate optimizing the performance of the injector. Full-cone injector is a more suitable choice for monopropellant thruster and it might be available commercially.

Heavy ion fusion 2 MV injector

International Nuclear Information System (INIS)

Yu, S.; Eylon, S.; Henestroza, E.

1995-04-01

A heavy-ion-fusion driver-scale injector has been constructed and operated at Lawrence Berkeley Laboratory. The injector has produced 2.3 MV and 950 mA of K + , 15% above original design goals in energy and current. Normalized edge emittance of less than 1 π mm-mr was measured over a broad range of parameters. The head-to-tail energy flatness is less than ± 0.2% over the 1 micros pulse

ELECTRON BEAM ION SOURCE PRE-INJECTOR DIGNOSTICS

International Nuclear Information System (INIS)

WILINSKI, M.; ALESSI, J.; BEEBE, E.; BELLAVIA, S.; PIKIN, A.

2006-01-01

A new ion pre-injector line is currently under design at Brookhaven National Laboratory (BNL) for the Relativistic Heavy Ion Collider (RHIC) and the NASA Space Radiation Laboratory (NSRL,). Collectively, this new line is referred to as the EBIS project. This pre-injector is based on an Electron Beam Ion Source (EBIS), a Radio Frequency Quadrupole (R-FQ) accelerator, and a linear accelerator. The new EBIS will be able to produce a wide range of heavy ion species as well as rapidly switching between species. To aid in operation of the pre-injector line, a suite of diagnostics is currently proposed which includes faraday cups, current transformers, profile monitors, and a pepperpot emittance measurement device

Status and performance of PF injector linac

International Nuclear Information System (INIS)

Sato, Isamu

1994-01-01

PF injector linac has been improved on a buncher section for accelerating of intense electron beam, and reinforced a focusing system of the positron generator linac for the expansion of phase space. In this presentation, I shall report present status and performance of PF injector linac, and discuss its upgrade program for B-factory project. (author)

Digital Measuring Devices Used for Injector Hydraulic Test

Directory of Open Access Journals (Sweden)

S. N. Leontiev

2015-01-01

Full Text Available To ensure a high specific impulse of the LRE (liquid-propellant engine chamber it is necessary to have optimally organized combustion of the fuel components. This can be ensured by choosing the optimum geometry of gas-dynamic contour of the LRE combustor, as well as by improving the sputtering processes and mixing the fuel components, for example, by selection of the optimum type, characteristics, and location of injectors on the mixing unit of the chamber.These particular reasons arise the interest in the injector characteristics in terms of science, and technological aspects determine the need for control of underlying design parameters in their manufacture.The objective of this work is to give an experimental justification on used digital measurement instrumentation and research the hydraulic characteristics of injectors.To determine injector parameters most widely were used the units with sectional collectors. A technique to control injector parameters using the sectional collectors involves spraying the liquid by injector at a given pressure drop on it for a certain time (the longer, the higher the accuracy and reliability of the results and then determining the amount of liquid in each section to calculate the required parameters of injector.In this work the liquid flow through the injector was determined by high-precision flowmeters FLONET FN2024.1 of electromagnetic type, which have very high metrological characteristics, in particular a flow rate error does not exceed 0.5% in a range of water flow from Qmin= 0.0028 l/s to Qmax Qmax = 0.28 l/s. To determine the coefficient of uneven spray were used differential pressure sensors DMD 331-ASLX of company "DB Sensors RUS", which have an error of 0.075% with a range of differential pressure 0 ... 5 kPa. Measuring complex MIC-200 of company "NPP Measure" and WinPos software for processing array information provided entry, recording, and processing of all the data of the experiment.In this

HOM characterization for beam diagnostics at the european XFEL injector

CERN Document Server

Baboi, Nicoletta; Shi, Liangliang; Wamsat, Thomas, DESY; Jones, Roger M; Joshi, Nirav

2017-01-01

Higher Order Modes (HOM) excited by bunched electron beams in accelerating cavities carry information about the beam position and phase. This principle is used at the FLASH facility, at DESY, for beam position monitoring in 1.3 and 3.9 GHz cavities. Dipole modes, which depend on the beam offset, are used. Similar monitors are now under design for the European XFEL. In addition to beam position, the beam phase with respect to the accelerating RF will be monitored using monopole modes from the first higher order monopole band. The HOM signals are available from two couplers installed on each cavity. Their monitoring will allow the on-line tracking of the phase stability over time, and we anticipate that it will improve the stability of the facility. As part of the monitor designing, the HOM spectra in the cavities of the 1.3 and 3.9 GHz cryo-modules installed in the European XFEL injector have been measured. This paper will present their dependence on the beam position. The variation in the modal distribution f...

Linac pre-injector

CERN Multimedia

CERN PhotoLab

1965-01-01

New accelerating column of the linac pre-injector, supporting frame and pumping system. This new system uses two mercury diffusion pumps (in the centre) and forms part of the modifications intended to increase the intensity of the linac. View taken during assembly in the workshop.

First operational experience with the positive-ion injector of ATLAS

Energy Technology Data Exchange (ETDEWEB)

Bollinger, L M; Pardo, R C; Shepard, K W; Bogaty, J M; Clifft, B E; Munson, F H; Zinkann, G [Argonne National Lab., IL (United States)

1993-04-15

The recently completed positive-ion injector for the heavy-ion accelerator ATLAS was designed as a replacement for the tandem injector of the present tandem-linac system and, unlike the tandem, the positive-ion injector is required to provide ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and initial experience in the acceleration of heavy-ion beams through the entire ATLAS system is discussed. The unusually good longitudinal beam quality of ATLAS with its new injector is emphasized. (orig.).

First operational experience with the positive-ion injector of ATLAS

International Nuclear Information System (INIS)

Bollinger, L.M.; Pardo, R.C.; Shepard, K.W.; Bogaty, J.M.; Clifft, B.E.; Munson, F.H.; Zinkann, G.

1992-01-01

The recently completed positive-ion injector for the heavy-ion accelerator ATLAS was designed as a replacement for the tandem injector of the present tandem-linac system and, unlike the tandem, the positive-ion injector is required to provide ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and initial experience in the acceleration of heavy-ion beams through the entire ATLAS system is discussed. The unusually good longitudinal beam quality of ATLAS with its new injector is emphasized

First operational experience with the positive-ion injector of ATLAS

Energy Technology Data Exchange (ETDEWEB)

Bollinger, L.M.; Pardo, R.C.; Shepard, K.W.; Bogaty, J.M.; Clifft, B.E.; Munson, F.H.; Zinkann, G.

1992-08-01

The recently completed positive-ion injector for the heavy-ion accelerator ATLAS was designed as a replacement for the tandem injector of the present tandem-linac system and, unlike the tandem, the positive-ion injector is required to provide ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and initial experience in the acceleration of heavy-ion beams through the entire ATLAS system is discussed. The unusually good longitudinal beam quality of ATLAS with its new injector is emphasized.

First operational experience with the positive-ion injector of ATLAS

Energy Technology Data Exchange (ETDEWEB)

Bollinger, L.M.; Pardo, R.C.; Shepard, K.W.; Bogaty, J.M.; Clifft, B.E.; Munson, F.H.; Zinkann, G.

1992-01-01

The recently completed positive-ion injector for the heavy-ion accelerator ATLAS was designed as a replacement for the tandem injector of the present tandem-linac system and, unlike the tandem, the positive-ion injector is required to provide ions from the full range of the periodic table. The concept for the new injector, which consists of an ECR ion source on a voltage platform coupled to a very-low-velocity superconducting linac, introduces technical problems and uncertainties that are well beyond those encountered previously for superconducting linacs. The solution to these problems and their relationship to performance are outlined, and initial experience in the acceleration of heavy-ion beams through the entire ATLAS system is discussed. The unusually good longitudinal beam quality of ATLAS with its new injector is emphasized.

Integrated numerical modeling of a laser gun injector

International Nuclear Information System (INIS)

Liu, H.; Benson, S.; Bisognano, J.; Liger, P.; Neil, G.; Neuffer, D.; Sinclair, C.; Yunn, B.

1993-06-01

CEBAF is planning to incorporate a laser gun injector into the linac front end as a high-charge cw source for a high-power free electron laser and nuclear physics. This injector consists of a DC laser gun, a buncher, a cryounit and a chicane. The performance of the injector is predicted based on integrated numerical modeling using POISSON, SUPERFISH and PARMELA. The point-by-point method incorporated into PARMELA by McDonald is chosen for space charge treatment. The concept of ''conditioning for final bunching'' is employed to vary several crucial parameters of the system for achieving highest peak current while maintaining low emittance and low energy spread. Extensive parameter variation studies show that the design will perform beyond the specifications for FEL operations aimed at industrial applications and fundamental scientific research. The calculation also shows that the injector will perform as an extremely bright cw electron source

High-power rf pulse compression with SLED-II at SLAC

International Nuclear Information System (INIS)

Nantista, C.

1993-04-01

Increasing the peak rf power available from X-band microwave tubes by means of rf pulse compression is envisioned as a way of achieving the few-hundred-megawatt power levels needed to drive a next-generation linear collider with 50--100 MW klystrons. SLED-II is a method of pulse compression similar in principal to the SLED method currently in use on the SLC and the LEP injector linac. It utilizes low-los resonant delay lines in place of the storage cavities of the latter. This produces the added benefit of a flat-topped output pulse. At SLAC, we have designed and constructed a prototype SLED-II pulse-compression system which operates in the circular TE 01 mode. It includes a circular-guide 3-dB coupler and other novel components. Low-power and initial high-power tests have been made, yielding a peak power multiplication of 4.8 at an efficiency of 40%. The system will be used in providing power for structure tests in the ASTA (Accelerator Structures Test Area) bunker. An upgraded second prototype will have improved efficiency and will serve as a model for the pulse compression system of the NLCTA (Next Linear Collider Test Accelerator)

Design considerations for single-stage and two-stage pneumatic pellet injectors

International Nuclear Information System (INIS)

Gouge, M.J.; Combs, S.K.; Fisher, P.W.; Milora, S.L.

1988-09-01

Performance of single-stage pneumatic pellet injectors is compared with several models for one-dimensional, compressible fluid flow. Agreement is quite good for models that reflect actual breech chamber geometry and incorporate nonideal effects such as gas friction. Several methods of improving the performance of single-stage pneumatic pellet injectors in the near term are outlined. The design and performance of two-stage pneumatic pellet injectors are discussed, and initial data from the two-stage pneumatic pellet injector test facility at Oak Ridge National Laboratory are presented. Finally, a concept for a repeating two-stage pneumatic pellet injector is described. 27 refs., 8 figs., 3 tabs

Fundamental rocket injector/spray programs at the Phillips Laboratory

Science.gov (United States)

Talley, D. G.

1993-11-01

The performance and stability of liquid rocket engines is determined to a large degree by atomization, mixing, and combustion processes. Control over these processes is exerted through the design of the injector. Injectors in liquid rocket engines are called upon to perform many functions. They must first of all mix the propellants to provide suitable performance in the shortest possible length. For main injectors, this is driven by the tradeoff between the combustion chamber performance, stability, efficiency, and its weight and cost. In gas generators and preburners, however, it is also driven by the possibility of damage to downstream components, for example piping and turbine blades. This can occur if unburned fuel and oxidant later react to create hot spots. Weight and cost considerations require that the injector design be simple and lightweight. For reusable engines, the injectors must also be durable and easily maintained. Suitable atomization and mixing must be produced with as small a pressure drop as possible, so that the size and weight of pressure vessels and turbomachinery can be minimized. However, the pressure drop must not be so small as to promote feed system coupled instabilities. Another important function of the injectors is to ensure that the injector face plate and the chamber and nozzle walls are not damaged. Typically this requires reducing the heat transfer to an acceptable level and also keeping unburned oxygen from chemically attacking the walls, particularly in reusable engines. Therefore the mixing distribution is often tailored to be fuel-rich near the walls. Wall heat transfer can become catastrophically damaging in the presence of acoustic instabilities, so the injector must prevent these from occurring at all costs. In addition to acoustic stability (but coupled with it), injectors must also be kinetically stable. That is, the flame itself must maintain ignition in the combustion chamber. This is not typically a problem with main

Mechanical Design of a New Injector Cryomodule 2-Cell Cavity at CEBAF

Energy Technology Data Exchange (ETDEWEB)

Cheng, Guangfeng G. [JLAB; Henry, James E. [JLAB; Mammosser, John D. [JLAB; Rimmer, Robert A. [JLAB; Wang, Haipeng [JLAB; Wiseman, Mark A. [JLAB; Yang, Shuo [JLAB

2013-12-01

As a part of Jefferson Lab’s 12 GeV upgrade, a new injector superconducting RF cryomodule is required. This unit consists of a 2-cell and 7-cell cavity, with the latter being refurbished from an existing cavity. The new 2-cell cavity requires electromagnetic design and optimization followed by mechanical design analyses. The electromagnetic design is reported elsewhere. This paper aims to present the procedures and conclusions of the analyses on cavity tuning sensitivity, pressure sensitivity, upset condition pressure induced stresses, and structural vibration frequencies. The purposes of such analyses include: 1) provide reference data for cavity tuner design; 2) examine the structural integrity of the cavity; and 3) evaluate the 2-cell cavity’s resistance to microphonics. Design issues such as the location of stiffening rings, effect of tuner stiffness on cavity stress, choice of cavity wall thickness, etc. are investigated by conducting extensive finite element analyses. Progress in fabrication of the 2-cell cavity is also reported.

A light ion four rod RFQ injector

International Nuclear Information System (INIS)

Schempp, A.; Ferch, M.; Klein, H.

1987-01-01

The four-rod RFQ has been developed in Frankfurt as an alternative solution for ion injectors. A 202 MHz resonator has been built with design parameters taken from the HERA injector (18keV-750keV, 20mA H - ). Properties of this structure are described and applications as light ion accelerator for particles from an EBIS ion source are discussed

Initial use of the positive-ion injector of ATLAS

International Nuclear Information System (INIS)

Bollinger, L.M.; Billquist, P.J.; Bogaty, J.M.; Clifft, B.E.; Den Hartog, P.K.; Munson, F.H. Jr.; Pardo, R.C.; Shepard, K.W.; Zinkann, G.P.

1989-01-01

The positive-ion injector of ATLAS consists of an ECR heavy-ion source coupled to a 12-MV superconducting injector linac. The ECR source and a 3-MV version of the partially completed linac have been used to accelerate successfully several species of heavy ions. The operating experience is summarized, with emphasis on the excellent beam quality of beams from the new injector. Two new fast-timing detectors are described. 9 refs., 5 figs., 1 tab

Asymmetric focusing study from twin input power couplers using realistic rf cavity field maps

Directory of Open Access Journals (Sweden)

Colwyn Gulliford

2011-03-01

Full Text Available Advanced simulation codes now exist that can self-consistently solve Maxwell’s equations for the combined system of an rf cavity and a beam bunch. While these simulations are important for a complete understanding of the beam dynamics in rf cavities, they require significant time and computing power. These techniques are therefore not readily included in real time simulations useful to the beam physicist during beam operations. Thus, there exists a need for a simplified algorithm which simulates realistic cavity fields significantly faster than self-consistent codes, while still incorporating enough of the necessary physics to ensure accurate beam dynamics computation. To this end, we establish a procedure for producing realistic field maps using lossless cavity eigenmode field solvers. This algorithm incorporates all relevant cavity design and operating parameters, including beam loading from a nonrelativistic beam. The algorithm is then used to investigate the asymmetric quadrupolelike focusing produced by the input couplers of the Cornell ERL injector cavity for a variety of beam and operating parameters.

C-band RF-system development for e{sup +}e{sup -} linear collider

Energy Technology Data Exchange (ETDEWEB)

Shintake, T.; Akasaka, N.; Matsumoto, H. [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan); Oh, J.S.; Yoshida, M.; Watanabe, K.; Ohkubo, Y.; Yonezawa, H.; Baba, H.

1998-11-01

Hardware R and D on the C-band (5712 MHz) RF-system for an electron/positron linear collider started in 1996 at KEK. During two years R and D, we have developed a 50-MW C-band klystron (TOSHIBA E3746), a 'Smart Modulator', a traveling-wave resonator (TWR) and a cold model of the rf-pulse compressor. A C-band accelerating structure, which uses the choke-mode cavity, is under development. Its HOM damping performance will be tested using short-bunch beams of ASSET beam-line at SLAC in this year. The C-band system is able to accelerate a high-current beam at an accelerating gradient higher than that in a conventional S-band system, therefore, there will be various applications in the future beside the linear collider. For example, we can build an injector for a SR-ring and for various physics experiments within a short site-length. Additionally, since the C-band components are compact, it has a big potentiality to be widely used in various medical and industrial applications, such as an electron-beam radiotherapy machine, or a compact non-destructive X-ray imaging system. (author)

Design of injector section for SPring-8 linac

International Nuclear Information System (INIS)

Yoshikawa, Hiroshi; Nakamura, Naoki; Mizuno, Akihiko; Suzuki, Shinsuke; Hori, Toshihiko; Yanagida, Kenichi; Mashiko, Katsuo; Yokomizo, Hideaki

1993-07-01

In the SPring-8, we are planning to use positrons in order to increase the beam life time in the storage-ring. For the injector linac, though high current beam production to yield positrons is alternative with accurate low current beam production for commissioning, we designed the injector section to achieve both of the high current mode and the low current mode. In this paper, overview of some simulation codes for the design of electron accelerators are described and the calculation results by TRACE for the injector section of the linac are shown. That is useful not only for the design of machines but for the selection of sensitive parameters to establish the good beam quality. Now the injector section, which is settled at Tokai Establishment, is arranged for the case of the performance check of the electron gun. And we present that the layout of this section is needed to be rearranged for the high current mode operation. (author)

Characteristics of a high-power RF source of negative hydrogen ions for neutral beam injection into controlled fusion devices

Energy Technology Data Exchange (ETDEWEB)

Abdrashitov, G. F.; Belchenko, Yu. I.; Gusev, I. A.; Ivanov, A. A.; Kondakov, A. A.; Sanin, A. L.; Sotnikov, O. Z., E-mail: O.Z.Sotnikov@inp.nsk.su; Shikhovtsev, I. V. [Russian Academy of Sciences, Budker Institute of Nuclear Physics, Siberian Branch (Russian Federation)

2017-01-15

An injector of hydrogen atoms with an energy of 0.5–1 MeV and equivalent current of up to 1.5 A for purposes of controlled fusion research is currently under design at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. Within this project, a multiple-aperture RF surface-plasma source of negative hydrogen ions is designed. The source design and results of experiments on the generation of a negative ion beam with a current of >1 A in the long-pulse mode are presented.

Design of deuterium and tritium pellet injector systems for Tokamak Fusion Test Reactor

International Nuclear Information System (INIS)

Wysor, R.B.; Baylor, L.R.; Bryan, W.E.

1985-01-01

Three pellet injector designs developed by the Oak Ridge National Laboratory (ORNL) are planned for the Tokamak Fusion Test Reactor (TFTR) to reach the goal of a tritium pellet injector by 1988. These are the Repeating Pneumatic Injector (RPI), the Deuterium Pellet Injector (DPI) and the Tritium Pellet Injector (TPI). Each of the pellet injector designs have similar performance characteristics in that they deliver up to 4-mm-dia pellets at velocities up to 1500 m/s with a dsign goal to 2000 m/s. Similar techniques are utilized to freeze and extrude the pellet material. The injector systems incorporate three gun concepts which differ in the number of gun barrels and the method of forming and chambering the pellets. The RPI, a single barrel repeating design, has been operational on TFTR since April 1985. Fabrication and assembly are essentially complete for DPI, and TPI is presently on hold after completing about 80% of the design. The TFTR pellet injector program is described, and each of the injector systems is described briefly. Design details are discussed in other papers at this symposium

On the prediction of spray angle of liquid-liquid pintle injectors

Science.gov (United States)

Cheng, Peng; Li, Qinglian; Xu, Shun; Kang, Zhongtao

2017-09-01

The pintle injector is famous for its capability of deep throttling and low cost. However, the pintle injector has been seldom investigated. To get a good prediction of the spray angle of liquid-liquid pintle injectors, theoretical analysis, numerical simulations and experiments were conducted. Under the hypothesis of incompressible and inviscid flow, a spray angle formula was deduced from the continuity and momentum equations based on a control volume analysis. The formula was then validated by numerical and experimental data. The results indicates that both geometric and injection parameters affect the total momentum ratio (TMR) and then influence the spray angle formed by liquid-liquid pintle injectors. TMR is the pivotal non-dimensional number that dominates the spray angle. Compared with gas-gas pintle injectors, spray angle formed by liquid-liquid injectors is larger, which benefits from the local high pressure zone near the pintle wall caused by the impingement of radial and axial sheets.

Graphene-based copper oxide thin film nanostructures as high-efficiency photocathode for p-type dye-sensitized solar cells

Science.gov (United States)

Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Cebeci, Hulya; Urk, Deniz

2017-10-01

Graphene-based p-type dye-sensitized solar cells (p-DSSCs) have been proposed and fabricated using copper oxide urchin-like nanostructures (COUN) as photocathode with an FeS2 counter electrode (CE). COUN composed of Cu2O core sphere and CuO shell nanorods with overall diameters of 2 to 4 μm were grown by a simple hydrothermal method with self-assemble nucleation. It was figured out that the formation of copper oxide core/shell structures could be adjusted by an ammonia additive leading to pH change of the precursor solution. In addition to a photocathode, we also demonstrated FeS2 thin films as an efficient CE material alternative to the conventional Pt CEs in DSSCs. FeS2 nanostructures, with diameters of 50 to 80 nm, were synthesized by a similar hydrothermal approach. FeS2 nanostructures are demonstrated to be an outstanding CE material in p-DSSCs. We report graphene/COUN as photocathode and Pt/FeS2 as CE in p-DSSCs, and results show that the synergetic combination of electrodes in each side (increased interconnectivity between COUN and graphene layer, high surface area, and high catalytic activity of FeS2) increased the power conversion efficiency from 1.56% to 3.14%. The excellent performances of COUN and FeS2 thin film in working and CEs, respectively, make them unique choices among the various photocathode and CE materials studied.

Ultrathin MoS2-coated Ag@Si nanosphere arrays as an efficient and stable photocathode for solar-driven hydrogen production.

Science.gov (United States)

Zhou, Qingwei; Su, Shaoqiang; Hu, Die; Lin, Lin; Yan, Zhibo; Gao, Xingsen; Zhang, Zhang; Liu, Jun-Ming

2018-01-30

Solar-driven photoelectrochemical (PEC) water splitting has attracted a great deal of attention recently. Silicon (Si) is an ideal light absorber for solar energy conversion. However, the poor stability and inefficient surface catalysis of Si photocathodes for the hydrogen evolution reaction (HER) have remained key challenges. Alternatively, MoS 2 has been reported to exhibit excellent catalysis performance if sufficient active sites for the HER are available. Here, ultrathin MoS 2 nanoflakes are directly synthesized to coat arrays of Ag-core Si-shell nanospheres (Ag@Si NSs) by using chemical vapor deposition. Due to the high surface area ratio and large curvature of these NSs, the as-grown MoS 2 nanoflakes can accommodate more active sites. In addition, the high-quality coating of MoS 2 nanoflakes on the Ag@Si NSs protects the photocathode from damage during the PEC reaction. An photocurrent density of 33.3 mA cm -2 at a voltage of -0.4 V is obtained versus the reversible hydrogen electrode. The as-prepared nanostructure as a hydrogen photocathode is evidenced to have high stability over 12 h PEC performance. This work opens up opportunities for composite photocathodes with high activity and stability using cheap and stable co-catalysts.

Ultra-thin MoS2 coated Ag@Si nanosphere arrays as efficient and stable photocathode for solar-driven hydrogen production.

Science.gov (United States)

Zhou, Qingwei; Su, Shaoqiang; Hu, Die; Lin, Lin; Yan, Zhibo; Gao, Xingsen; Zhang, Zhang; Liu, Junming

2018-01-02

Solar-driven photoelectrochemical (PEC) water splitting has recently attracted much attention. Silicon (Si) is an ideal light absorber for solar energy conversion. However, the poor stability and inefficient surface catalysis of Si photocathode for hydrogen evolution reaction (HER) have been remained as the key challenges. Alternatively, MoS2 has been reported to exhibit the excellent catalysis performance if sufficient active sites for the HER are available. Here, ultra-thin MoS2 nanoflakes are directly synthesized to coat on the arrays of Ag-core Si-shell nanospheres (Ag@Si NSs) using the chemical vapor deposition (CVD). Due to the high surface area ratio and large curvature of these NSs, the as-grown MoS2 nanoflakes can accommodate more active sites. Meanwhile, the high-quality coating of MoS2 nanoflakes on the Ag@Si NSs protects the photocathode from damage during the PEC reaction. A high efficiency with a photocurrent of 33.3 mA cm-2 at a voltage of -0.4 V vs. the reversible hydrogen electrode is obtained. The as-prepared nanostructure as hydrogen photocathode is evidenced to have high stability over 12 hour PEC performance. This work opens opportunities for composite photocathode with high activity and stability using cheap and stable co-catalysts. © 2017 IOP Publishing Ltd.

Development of technologies on innovative-simplified nuclear power plant using high-efficiency steam injectors (5) operating characteristics of center water jet type supersonic steam injector

International Nuclear Information System (INIS)

Abe, Y.; Kawamoto, Y.; Iwaki, C.; Narabayashi, T.; Mori, M.; Ohmori, S.

2005-01-01

Next-generation reactor systems have been under development aiming at simplified system and improvement of safety and credibility. A steam injector has a function of a passive pump without large motor or turbo-machinery, and has been investigated as one of the most important component of the next-generation reactor. Its performance as a pump depends on direct contact condensation phenomena between a supersonic steam and a sub-cooled water jet. As previous studies of the steam injector, there are studies about formulation of operating characteristic of steam injector and analysis of jet structure in steam injector by Narabayashi etc. And as previous studies of the direct contact condensation, there is the study about the direct contact condensation in steam atmosphere. However the study about the turbulent heat transfer under the great shear stress is not enough investigated. Therefore it is necessary to examine in detail about the operating characteristic of the steam injector. The present paper reports the observation results of the water jet behavior in the super sonic steam injector by using the video camera and the high-speed video camera. And the measuring results of the temperature and the pressure distribution in the steam injector are reported. From observation results by video camera, it is cleared that the water jet is established at the center of the steam injector right after steam supplied and the operation of the steam injector depends on the throat diameter. And from observation results by high-speed video camera, it is supposed that the columned water jet surface is established in the mixing nozzle and the water jet surface movement exists. And from temperature measuring results, it is supposed that the steam temperature at the mixing nozzle is changed between about 80 degree centigrade and about 60 degree centigrade. Then from the pressure measuring results, it is confirmed that the pressure at the diffuser depends on each the throat diameter and

Impact of palm biodiesel blend on injector deposit formation

International Nuclear Information System (INIS)

Liaquat, A.M.; Masjuki, H.H.; Kalam, M.A.; Fazal, M.A.; Khan, Abdul Faheem; Fayaz, H.; Varman, M.

2013-01-01

Highlights: • 250 h Endurance test on 2 fuel samples; diesel fuel and PB20. • Visual inspection of injectors running on DF and PB20 showed deposit accumulation. • SEM and EDS analysis showed less injector deposits for DF compared to PB20 blend. • Engine oil analysis showed higher value of wear particles for PB20 compared to DF. - Abstract: During short term engine operation, renewable fuels derived from vegetable oils, are capable of providing good engine performance. In more extended operations, some of the same fuels can cause degradation of engine performance, excessive carbon and lacquer deposits and actual damage to the engine. Moreover, temperatures in the area of the injector tip due to advanced diesel injection systems may lead to particularly stubborn deposits at and around the injector tip. In this research, an endurance test was carried out for 250 h on 2 fuel samples; DF (diesel fuel) as baseline and PB20 (20% palm biodiesel and 80% DF) in a single cylinder CI engine. The effects of DF and PB20 on injector nozzle deposits, engine lubricating oil, and fuel economy and exhaust emissions were investigated. According to the results of the investigation, visual inspection showed some deposit accumulation on injectors during running on both fuels. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis showed greater carbon deposits on and around the injector tip for PB20 compared to the engine running with DF. Similarly, lubricating oil analysis presented excessive wear metal concentrations, decreased viscosity and increased density values when the engine was fuelled with PB20. Finally, fuel economy and emission results during the endurance test showed higher brake specific fuel consumption (bsfc) and NO x emissions, and lower HC and CO emissions, for the PB20 blend compared to DF

What factors affect the carriage of epinephrine auto-injectors by teenagers?

Science.gov (United States)

Macadam, Clare; Barnett, Julie; Roberts, Graham; Stiefel, Gary; King, Rosemary; Erlewyn-Lajeunesse, Michel; Holloway, Judith A; Lucas, Jane S

2012-02-02

Teenagers with allergies are at particular risk of severe and fatal reactions, but epinephrine auto-injectors are not always carried as prescribed. We investigated barriers to carriage. Patients aged 12-18 years old under a specialist allergy clinic, who had previously been prescribed an auto-injector were invited to participate. Semi-structured interviews explored the factors that positively or negatively impacted on carriage. Twenty teenagers with food or venom allergies were interviewed. Only two patients had used their auto-injector in the community, although several had been treated for severe reactions in hospital. Most teenagers made complex risk assessments to determine whether to carry the auto-injector. Most but not all decisions were rational and were at least partially informed by knowledge. Factors affecting carriage included location, who else would be present, the attitudes of others and physical features of the auto-injector. Teenagers made frequent risk assessments when deciding whether to carry their auto-injectors, and generally wanted to remain safe. Their decisions were complex, multi-faceted and highly individualised. Rather than aiming for 100% carriage of auto-injectors, which remains an ambitious ideal, personalised education packages should aim to empower teenagers to make and act upon informed risk assessments.

What factors affect the carriage of epinephrine auto-injectors by teenagers?

Directory of Open Access Journals (Sweden)

Macadam Clare

2012-02-01

Full Text Available Abstract Background Teenagers with allergies are at particular risk of severe and fatal reactions, but epinephrine auto-injectors are not always carried as prescribed. We investigated barriers to carriage. Methods Patients aged 12-18 years old under a specialist allergy clinic, who had previously been prescribed an auto-injector were invited to participate. Semi-structured interviews explored the factors that positively or negatively impacted on carriage. Results Twenty teenagers with food or venom allergies were interviewed. Only two patients had used their auto-injector in the community, although several had been treated for severe reactions in hospital. Most teenagers made complex risk assessments to determine whether to carry the auto-injector. Most but not all decisions were rational and were at least partially informed by knowledge. Factors affecting carriage included location, who else would be present, the attitudes of others and physical features of the auto-injector. Teenagers made frequent risk assessments when deciding whether to carry their auto-injectors, and generally wanted to remain safe. Their decisions were complex, multi-faceted and highly individualised. Conclusions Rather than aiming for 100% carriage of auto-injectors, which remains an ambitious ideal, personalised education packages should aim to empower teenagers to make and act upon informed risk assessments.

Water jet behavior in center water jet type supersonic steam injector

International Nuclear Information System (INIS)

Kawamoto, Y.; Abe, Y.

2005-01-01

Next-generation reactor systems have been under development aiming at simplified system and improvement of safety and credibility. A steam injector has a function of a passive pump without large motor or turbo-machinery, and has been investigated as one of the most important component of the next-generation reactor. Its performance as a pump depends on direct contact condensation phenomena between a supersonic steam and a sub-cooled water jet. As previous studies of the steam injector, there are studies about formulation of operating characteristic of steam injector and analysis of jet structure in steam injector by Narabayashi etc. And as previous studies of the direct contact condensation, there is the study about the direct contact condensation in steam atmosphere. However the study about the turbulent heat transfer under the great shear stress is not enough investigated. Therefore it is necessary to examine in detail about the operating characteristic of the steam injector. The present paper reports the observation results of the water jet behavior in the super sonic steam injector by using the video camera and the high-speed video camera. And the measuring results of the temperature and the pressure distribution in the steam injector are reported. From observation results by video camera, it is cleared that the water jet is established at the center of the steam injector right after steam supplied and the operation of the steam injector depends on the throat diameter. And from observation results by high-speed video camera, it is supposed that the columned water jet surface is established in the mixing nozzle and the water jet surface movement exists. Furthermore and effect of the non-condensable gas on the steam injector is investigated by measuring the radial temperature distributions in the water jet. From measuring results, it is supposed the more the air included in the steam, the more the temperature fluctuation of both steam and discharge water

Repeating pneumatic pellet injector in JAERI

Energy Technology Data Exchange (ETDEWEB)

Kasai, Satoshi; Hasegawa, Kouichi; Suzuki, Sadaaki; Miura, Yukitoshi (Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment); Oda, Yasushi; Onozuka, Masanori; Tsujimura, Seiichi.

1992-09-01

A repeating pneumatic pellet injector has been developed and constructed at Japan Atomic Energy Research Institute. This injector can provide repetitive pellet injection to fuel tokamak plasmas for an extended period of time, aiming at the improvement of plasma performance. The pellets with nearly identical speed and mass can be repeatedly injected with a repetition rate of 2-3.3 Hz and a speed of up to 1.7 km/s by controlling the temperature of the cryogenic system, the piston speed and the pressure of the propellant gas. (author).

Mechanical design for TMX injector system

International Nuclear Information System (INIS)

Calderon, M.O.; Chen, F.F.K.; Denhoy, B.S.

1977-01-01

The injector system for the Tandem Mirror Experiment (TMX) contains the components required to create and maintain a high-temperature, high-density plasma. These components include a streaming-plasma gun in each of the plug tanks to form the target-plasma, 24 neutral-beam source modules for injecting neutral deuterium atoms to heat and replace losses from the plasma, and a gas box system that applies a streaming cold gas to the plasma to stabilize it. This paper discusses the mechanical design problems and solutions for this injector system

Repeating pneumatic pellet injector in JAERI

International Nuclear Information System (INIS)

Kasai, Satoshi; Hasegawa, Kouichi; Suzuki, Sadaaki; Miura, Yukitoshi; Oda, Yasushi; Onozuka, Masanori; Tsujimura, Seiichi.

1992-09-01

A repeating pneumatic pellet injector has been developed and constructed at Japan Atomic Energy Research Institute. This injector can provide repetitive pellet injection to fuel tokamak plasmas for an extended period of time, aiming at the improvement of plasma performance. The pellets with nearly identical speed and mass can be repeatedly injected with a repetition rate of 2-3.3 Hz and a speed of up to 1.7 km/s by controlling the temperature of the cryogenic system, the piston speed and the pressure of the propellant gas. (author)

Papa, a Particle Tracing Code in Pascal

NARCIS (Netherlands)

Haselhoff, E.H.; Haselhoff, Eltjo H.; Ernst, G.J.

1990-01-01

During the design of a 10 ¿m high-gain FEL oscillator (TEUFEL Project) we developed a new particle-tracing code to perform simulations of thermionic- and photo-cathode electron injectors/accelerators. The program allows predictions of current, energy and beam emittance in a user-specified linac

Effect of injector geometry on the performance of an internally mixed liquid atomizer