Beam beam tune shifts for 36 bunch operation in the Tevatron

International Nuclear Information System (INIS)

Bagley, P.

1996-10-01

We are preparing to upgrade the Tevatron Collider from 6 to 36 bunch operation. The 36 bunches are in 3 ''trains'' of 12 bunches. The spacing between bunches within a train is 21 RF buckets (53.106 MHz) and 139 empty buckets separate the trains. Because the 36 bunches are not evenly spaced around the machine, the different bunches within a train pass the opposing bunches at different points in the ring and so feel different beam beam effects. Through most of the machine the beams have helical separation, so these are mainly long range beam beam effects. As a first, very simple step, we've looked at the differences in the tunes of the different anti-proton (anti p) bunches. During the 36 bunch studies in Fall 1995, we used a new tune measurement system to measure these in several different machine conditions. We compare these measurements to calculations of the tunes for a anti p with zero transverse and longitudinal oscillation amplitudes. We discuss experimental problems, and the assumptions, approximations, and effects included in the calculations. Our main intent is to gain confidence that we can accurately model beam beam effects in the Tevatron

Sensitive beam-bunch phase detector

Energy Technology Data Exchange (ETDEWEB)

Takeuchi, S; Shepard, K W

1984-11-15

A sensitive heavy-ion beam-bunch phase detector has been developed by first examining the relationship between the sensitivity of an rf resonant cavity as a particle bunch detector and the shunt impedance of the same cavity as an accelerating structure. Then the various high shunt impedance rf cavities previously developed for accelerating heavy ions were evaluated for use as bunch detectors. A spiral-loaded geometry was chosen, built, and tested with beam. The sensitivity obtained, 14 V per electrical nA of beam, is a factor 3 higher than previously reported. (orig.).

Sensitive beam-bunch phase detector

Energy Technology Data Exchange (ETDEWEB)

Takeuchi, S; Shepard, K W [Argonne National Lab., IL (USA). Physics Div.

1984-11-15

A sensitive heavy-ion beam-bunch phase detector has been developed by first examining the relationship between the sensitivity of an RF resonant cavity as a particle bunch detector and the shunt impedance of the same cavity as an accelerating structure. Then the various high shunt impedance RF cavities previously developed for accelerating heavy ions were evaluated for use as bunch detectors. A spiral-loaded geometry was chosen, built, and tested with beam. The sensitivity obtained, 14 ..mu.. V per electrical nA of beam, is a factor 3 higher than previously reported.

Emerging terawatt picosecond CO{sub 2} laser technology

Energy Technology Data Exchange (ETDEWEB)

Pogorelsky, I V [Accelerator Test Facility, Brookhaven National Lab., Upton, NY (United States)

1998-03-01

The first terawatt picosecond (TWps) CO{sub 2} laser is under construction at the BNL Accelerator Test Facility (ATF). TWps-CO{sub 2} lasers, having an order of magnitude longer wavelength than the well-known table-top terawatt solid state lasers, offer new opportunities for strong-field physics research. For laser wakefield accelerators (LWFA) the advantage of the new class of lasers is due to a gain of two orders of magnitude in the ponderomotive potential. The large average power of CO{sub 2} lasers is important for the generation of hard radiation through Compton back-scattering of the laser off energetic electron beams. We discuss applications of TWps-CO{sub 2} lasers for LWFA modules of a tentative electron-positron collider, for {gamma}-{gamma} (or {gamma}-lepton) colliders, for a possible `table-top` source of high-intensity x-rays and gamma rays, and the generation of polarized positron beams. (author)

Improvement of bunch-by-bunch beam current detection system in Hefei light source

International Nuclear Information System (INIS)

Zheng Kai; Wang Junhua; Liu Zuping; Li Weimin; Zhou Zeran; Yang Yongliang; Huang Longjun; Chen Yuanbo

2006-01-01

Bunch-by-bunch beam current detection system is an important facility in the multibunch storage ring. In this paper, the established bunch-by-bunch beam current detection systems for the accelerator such as Cornell, SLAC and KEKB were compared and studied. The design of the bunch-by-bunch beam current detection system for HLS, which was based on the bunch-by-bunch tracing measurement system in HLS was given. Both demodulation by sine wave and square were applied in this paper, the deviation of the detect system was determined by the longitudinal oscillation. Compared the data acquired from ADC with the data from DCCT, the ADC data was scaled by the bunch current. The standard deviations of linear fit were about 1%, and the standard deviations of polynomial fit were less than 0.5% in both sine wave and square wave demodulation. Some analysis of the measurement results also had been shown in this paper. (authors)

Single bunched beam generation without subharmonic prebuncher

International Nuclear Information System (INIS)

Kobayashi, T.; Tagawa, S.

1995-01-01

The intensity of the accelerated single bunched electron beam depends on the performance of the electron gun and the fast cathode pulser. The electron beam is emitted by a Y-796 cathode assembly with a cathode of 2 cm 2 (8 A/cm 2 ), and an extracted voltage of 90 kV. The maximum charge of the single bunched beam was attained at 1.5 nC/pulse using SHB. Recently, a single bunched beam has been generated by an ultrafast cathode pulser (rise and fall time <100 ps pulse height -2 kV at 50 Ω) without SHB. The charge of the accelerated electron beam is about 40 pC/pulse (pulse width <10 ps) without the production of a satellite beam. This result show that a single bunched beam can be produced by the linear accelerator without SHB. ((orig.))

Real-Time, Single-Shot Temporal Measurements of Short Electron Bunches, Terahertz CSR and FEL Radiation

CERN Document Server

Berden, G; Van der Meer, A F G

2005-01-01

Electro-optic detection of the Coulomb field of electron bunches is a promising technique for single-shot measurements of the bunch length and shape in the sub-picosecond time domain. This technique has been applied to the measurement of 50 MeV electron bunches in the FELIX free electron laser, showing the longitudinal profile of single bunches of around 650 fs FWHM [Phys. Rev. Lett. 93, 114802 (2004)]. The method is non-destructive and real-time, and therefore ideal for online monitoring of the longitudinal shape of single electron bunches. At FELIX we have used it for real-time optimization of sub-picosecond electron bunches. Electro-optic detection has also been used to measure the electric field profiles of far-infrared (or terahertz) optical pulses generated by the relativistic electrons. We have characterised the far-infrared output of the free electron laser, and more recently, we have measured the temporal profile of terahertz optical pulses generated at one of the bending magnets.

Fast infrared detectors for beam diagnostics with synchrotron radiation

International Nuclear Information System (INIS)

Bocci, A.; Marcelli, A.; Pace, E.; Drago, A.; Piccinini, M.; Cestelli Guidi, M.; De Sio, A.; Sali, D.; Morini, P.; Piotrowski, J.

2007-01-01

Beam diagnostic is a fundamental constituent of any particle accelerators either dedicated to high-energy physics or to synchrotron radiation experiments. All storage rings emit radiations. Actually they are high brilliant sources of radiation: the synchrotron radiation emission covers from the infrared range to the X-ray domain with a pulsed structure depending on the temporal characteristics of the stored beam. The time structure of the emitted radiation is extremely useful as a tool to perform time-resolved experiments. However, this radiation can be also used for beam diagnostic to determine the beam stability and to measure the dimensions of the e - or e + beam. Because of the temporal structure of the synchrotron radiation to perform diagnostic, we need very fast detectors. Indeed, the detectors required for the diagnostics of the stored particle bunches at third generation synchrotron radiation sources and FEL need response times in the sub-ns and even ps range. To resolve the bunch length and detect bunch instabilities, X-ray and visible photon detectors may be used achieving response times of a few picoseconds. Recently, photon uncooled infrared devices optimized for the mid-IR range realized with HgCdTe semiconductors allowed to obtain sub-nanosecond response times. These devices can be used for fast detection of intense IRSR sources and for beam diagnostic. We present here preliminary experimental data of the pulsed synchrotron radiation emission of DAΦNE, the electron positron collider of the LNF laboratory of the INFN, performed with new uncooled IR detectors with a time resolution of a few hundreds of picoseconds

Coupled-Beam and Coupled-Bunch Instabilities

Energy Technology Data Exchange (ETDEWEB)

Burov, Alexey [Fermilab

2016-06-23

A problem of coupled-beam instability is solved for two multibunch beams with slightly different revolution frequencies, as in the Fermilab Recycler Ring (RR). Sharing of the inter-bunch growth rates between the intra-bunch modes is described. The general analysis is applied to the RR; possibilities to stabilize the beams by means of chromaticity, feedback and Landau damping are considered.

Longitudinal Diagnostics for Short Electron Beam Bunches

Energy Technology Data Exchange (ETDEWEB)

Loos, H.; /SLAC

2010-06-11

Single-pass free electron lasers require high peak currents from ultra-short electron bunches to reach saturation and an accurate measurement of bunch length and longitudinal bunch profile is necessary to control the bunch compression process from low to high beam energy. The various state-of-the-art diagnostics methods from ps to fs time scales using coherent radiation detection, RF deflection, and other techniques are presented. The use of linear accelerators as drivers for free electron lasers (FEL) and the advent of single-pass (SASE) FELs has driven the development of a wide range of diagnostic techniques for measuring the length and longitudinal distribution of short and ultra-short electron bunches. For SASE FELs the radiation power and the length of the undulator needed to achieve saturation depend strongly on the charge density of the electron beam. In the case of X-ray FELs, this requires the accelerator to produce ultra-high brightness beams with micron size transverse normalized emittances and peak currents of several kA through several stages of magnetic bunch compression. Different longitudinal diagnostics are employed to measure the peak current and bunch profile along these stages. The measurement techniques can be distinguished into different classes. Coherent methods detect the light emitted from the beam by some coherent radiation process (spectroscopic measurement), or directly measure the Coulomb field traveling with the beam (electro-optic). Phase space manipulation techniques map the time coordinate onto a transverse dimension and then use conventional transverse beam diagnostics (transverse deflector, rf zero-phasing). Further methods measure the profile or duration of an incoherent light pulse emitted by the bunch at wavelengths much shorted than the bunch length (streak camera, fluctuation technique) or modulate the electron beam at an optical wavelength and then generate a narrow bandwidth radiation pulse with the longitudinal profile of

Generating picosecond x-ray pulses in synchrotron light sources using dipole kickers

Directory of Open Access Journals (Sweden)

W. Guo

2007-02-01

Full Text Available The duration of the x-ray pulse generated at a synchrotron light source is typically tens of picoseconds. Shorter pulses are highly desired by the users. In electron storage rings, the vertical beam size is usually orders of magnitude less than the bunch length due to radiation damping; therefore, a shorter pulse can be obtained by slitting the vertically tilted bunch. Zholents proposed tilting the bunch using rf deflection. We found that tilted bunches can also be generated by a dipole magnet kick. A vertical tilt is developed after the kick in the presence of nonzero chromaticity. The tilt was successfully observed and a 4.2-ps pulse was obtained from a 27-ps electron bunch at the Advanced Photon Source. Based on this principle, we propose a short-pulse generation scheme that produces picosecond x-ray pulses at a repetition rate of 1–2 kHz, which can be used for pump-probe experiments.

Beam bunch feedback

International Nuclear Information System (INIS)

Lambertson, G.

1995-09-01

When the electromagnetic fields that are excited by the passage of a bundle of charged particles persist to act upon bunches that follow, then the motions of the bunches are coupled. This action between bunches circulating on a closed orbit can generate growing patterns of bunch excursions. Such growth can often be suppressed by feedback systems that detect the excursion and apply corrective forces to the bunches. To be addressed herein is feedback that acts on motions of the bunch body centers. In addition to being useful for suppressing the spontaneous growth of coupled-bunch motions, such feedback can be used to damp transients in bunches injected into an accelerator or storage ring; for hadrons which lack strong radiation damping, feedback is needed to avoid emittance growth through decoherence. Motions excited by noise in magnetic fields or accelerating rf can also be reduced by using this feedback. Whether the action is on motions that are transverse to the closed orbit or longitudinal, the arrangement is the same. Bunch position is detected by a pickup and that signal is processed and directed to a kicker that may act upon the same bunch or some other portion of the collective beam pattern. Transverse motion is an oscillation with angular frequency ν perpendicular ω o where ω o is the orbital frequency 2π line-integral o. Longitudinal synchrotron oscillation occurs at frequency ω s = ν s ω o . The former is much more rapid, ν perpendicular being on the order of 10 while ν s is typically about 10 minus 1 to 10 minus 2

Velocity bunching of high-brightness electron beams

Directory of Open Access Journals (Sweden)

S. G. Anderson

2005-01-01

Full Text Available Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly

Absolute beam-charge measurement for single-bunch electron beams

International Nuclear Information System (INIS)

Suwada, Tsuyoshi; Ohsawa, Satoshi; Furukawa, Kazuro; Akasaka, Nobumasa

2000-01-01

The absolute beam charge of a single-bunch electron beam with a pulse width of 10 ps and that of a short-pulsed electron beam with a pulse width of 1 ns were measured with a Faraday cup in a beam test for the KEK B-Factory (KEKB) injector linac. It is strongly desired to obtain a precise beam-injection rate to the KEKB rings, and to estimate the amount of beam loss. A wall-current monitor was also recalibrated within an error of ±2%. This report describes the new results for an absolute beam-charge measurement for single-bunch and short-pulsed electron beams, and recalibration of the wall-current monitors in detail. (author)

Coasting beam theory applied to bunches

International Nuclear Information System (INIS)

Hereward, H.

1975-01-01

It is plausible to apply coasting beam criteria to bunches if one has short wavelength disturbances of the bunch and short memory wake fields, where short means short compared with a bunch length, for then one can argue that a piece of the bunch near the middle does not even know that the bunch has ends. Some other conditions probably required to validate this approach are discussed. The local Keil-Schnell criterion is derived from the local dispersion integral

Matching sub-fs electron bunches for laser-driven plasma acceleration at SINBAD

Energy Technology Data Exchange (ETDEWEB)

Zhu, J., E-mail: jun.zhu@desy.de [Deutsches Elektronen-Synchrotron, DESY, Hamburg (Germany); Universität Hamburg, Hamburg (Germany); Assmann, R.W.; Dorda, U.; Marchetti, B. [Deutsches Elektronen-Synchrotron, DESY, Hamburg (Germany)

2016-09-01

We present theoretical and numerical studies of matching sub-femtosecond space-charge-dominated electron bunch into the Laser-plasma Wake Field Accelerator (LWFA) foreseen at the SINBAD facility. The longitudinal space-charge (SC) effect induced growths of the energy spread and longitudinal phase-space chirp are major issues in the matching section, which will result in bunch elongation, emittance growth and spot size dilution. In addition, the transverse SC effect would lead to a mismatch of the beam optics if it were not compensated for. Start-to-end simulations and preliminary optimizations were carried out in order to understand the achievable beam parameters at the entrance of the plasma accelerator.

Coherent spontaneous radiation from highly bunched electron beams

International Nuclear Information System (INIS)

Berryman, K.W.; Crosson, E.R.; Ricci, K.N.

1995-01-01

Coherent spontaneous radiation has now been observed in several FELs, and is a subject of great importance to the design of self-amplified spontaneous emission (SASE) devices. We report observations of coherent spontaneous radiation in both FIREFLY and the mid-infrared FEL at the Stanford Picosecond FEL Center. Coherent emission has been observed at wavelengths as short as 5 microns, and enhancement over incoherent levels by as much as a factor of 4x10 4 has been observed at longer wavelengths. The latter behavior was observed at 45 microns in FIREFLY with short bunches produced by off-peak acceleration and dispersive compression. We present temporal measurements of the highly bunched electron distributions responsible for the large enhancements, using both transition radiation and energy-phase techniques

Studies on laser material processing with nanosecond and sub-nanosecond and picosecond and sub-picosecond pulses

Science.gov (United States)

Zhang, Jie; Tao, Sha; Wang, Brian; Zhao, Jay

2016-03-01

In this paper, laser ablation of widely used metal (Al, Cu. stainless-steel), semiconductor (Si), transparent material (glass, sapphire), ceramic (Al2O3, AlN) and polymer (PI, PMMA) in industry were systematically studied with pulse width from nanosecond (5-100ns), picosecond (6-10ps) to sub-picosecond (0.8-0.95ps). A critical damage zone (CDZ) of up to 100um with ns laser, efficiency were also investigated. This is to explore how to provide industry users the best laser solution for device micro-fabrication with best price. Our studies of cutting and drilling with ns, ps, and sub-ps lasers indicate that it is feasible to achieve user accepted quality and speed with cost-effective and reliable laser by optimizing processing conditions.

Parallel Beam-Beam Simulation Incorporating Multiple Bunches and Multiple Interaction Regions

CERN Document Server

Jones, F W; Pieloni, T

2007-01-01

The simulation code COMBI has been developed to enable the study of coherent beam-beam effects in the full collision scenario of the LHC, with multiple bunches interacting at multiple crossing points over many turns. The program structure and input are conceived in a general way which allows arbitrary numbers and placements of bunches and interaction points (IP's), together with procedural options for head-on and parasitic collisions (in the strong-strong sense), beam transport, statistics gathering, harmonic analysis, and periodic output of simulation data. The scale of this problem, once we go beyond the simplest case of a pair of bunches interacting once per turn, quickly escalates into the parallel computing arena, and herein we will describe the construction of an MPI-based version of COMBI able to utilize arbitrary numbers of processors to support efficient calculation of multi-bunch multi-IP interactions and transport. Implementing the parallel version did not require extensive disruption of the basic ...

Generation of slow positron beam and beam bunching

International Nuclear Information System (INIS)

Azuma, O.; Satoh, T.; Shitoh, M.; Kaneko, N.; Kawaratani, T.; Hara, O.

1994-01-01

Two items are described in this report. One is about the outline of our slow positron beam system, which has been fabricated as a commercial prototype. The other is about the calculation result of positron beam bunching, which will be an additional function to the system. (author)

Electron cooling of a bunched ion beam in a storage ring

Science.gov (United States)

Zhao, He; Mao, Lijun; Yang, Jiancheng; Xia, Jiawen; Yang, Xiaodong; Li, Jie; Tang, Meitang; Shen, Guodong; Ma, Xiaoming; Wu, Bo; Wang, Geng; Ruan, Shuang; Wang, Kedong; Dong, Ziqiang

2018-02-01

A combination of electron cooling and rf system is an effective method to compress the beam bunch length in storage rings. A simulation code based on multiparticle tracking was developed to calculate the bunched ion beam cooling process, in which the electron cooling, intrabeam scattering (IBS), ion beam space-charge field, transverse and synchrotron motion are considered. Meanwhile, bunched ion beam cooling experiments have been carried out in the main cooling storage ring (CSRm) of the Heavy Ion Research Facility in Lanzhou, to investigate the minimum bunch length obtained by the cooling method, and study the dependence of the minimum bunch length on beam and machine parameters. The experiments show comparable results to those from simulation. Based on these simulations and experiments, we established an analytical model to describe the limitation of the bunch length of the cooled ion beam. It is observed that the IBS effect is dominant for low intensity beams, and the space-charge effect is much more important for high intensity beams. Moreover, the particles will not be bunched for much higher intensity beam. The experimental results in CSRm show a good agreement with the analytical model in the IBS dominated regime. The simulation work offers us comparable results to those from the analytical model both in IBS dominated and space-charge dominated regimes.

LHC Report: 1,033 bunches per beam and counting

CERN Multimedia

Jorg Wenninger for the LHC team

2015-01-01

Following the second technical stop, the first beams were injected into the LHC in the early evening of Saturday, 5 September. About ten days later, the machine was operated with around 1,000 bunches per beam.    Evolution of the stored energy per LHC beam, over time.   The first step after a technical stop consists of running through a full LHC cycle, from injection to collisions and beam dump, with a low-intensity bunch (“probe”) to check all machine settings and equipment. This is followed by a series of collimation and absorber validation tests at different points in the LHC cycle. Low-intensity beams – typically the equivalent of three nominal bunches (3 x 1011 protons) – are expanded transversely or longitudinally, or de-bunched to verify that the collimators and absorbers are correctly intercepting lost particles. The techniques for those validations have been progressively improved, and t...

Measuring the electron beam energy in a magnetic bunch compressor

Energy Technology Data Exchange (ETDEWEB)

Hacker, Kirsten

2010-09-15

Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 {mu}m precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

Measuring the electron beam energy in a magnetic bunch compressor

International Nuclear Information System (INIS)

Hacker, Kirsten

2010-09-01

Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 μm precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

Beam-Beam Interaction, Electron Cloud and Intrabeam Scattering for Proton Super-bunches

CERN Document Server

Ruggiero, F; Rumolo, Giovanni; Papaphilippou, Y

2003-01-01

Super-bunches are long bunches with a flat longitudinal profile, which could potentially increase the LHC luminosity in a future upgrade. We present example parameters and discuss a variety of issues related to such superbunches, including beam-beam tune shift, tune footprints, crossing schemes, luminosity, intrabeam scattering, and electron cloud. We highlight the benefits, disadvantages and open questions.

Successful Beam-Beam Tuneshift Compensation

Energy Technology Data Exchange (ETDEWEB)

Bishofberger, Kip Aaron [Univ. of California, Los Angeles, CA (United States)

2005-01-01

The performance of synchrotron colliders has been limited by the beam-beam limit, a maximum tuneshift that colliding bunches could sustain. Due to bunch-to-bunch tune variation and intra-bunch tune spread, larger tuneshifts produce severe emittance growth. Breaking through this constraint has been viewed as impossible for several decades. This dissertation introduces the physics of ultra-relativistic synchrotrons and low-energy electron beams, with emphasis placed on the limits of the Tevatron and the needs of a tuneshift-compensation device. A detailed analysis of the Tevatron Electron Lens (T<sub>E>L) is given, comparing theoretical models to experimental data whenever possible. Finally, results of Tevatron operations with inclusion of the T<sub>E>L are presented and analyzed. It is shown that the T<sub>E>L provides a way to shatter the previously inescapable beam-beam limit.

Short bunch length detector for ion beam with high bunch density

International Nuclear Information System (INIS)

Tron, A.M.; Shako, V.V.

1993-01-01

The secondary electron rf monitors for short ion bunch phase distribution measurements are presented. Construction particularities of the monitors, influence of space charge of both the primary and the secondary electron beams on the phase resolution, thermal regime of the target during beam-target interaction are considered

Instability during bunch shortening of an electron-cooled beam

Directory of Open Access Journals (Sweden)

M. Takanaka

2003-10-01

Full Text Available Bunch shortening causes an electron-cooled beam to be space charge dominated at low energies. Instability during the bunch shortening has been studied using a particle-tracking program where the 3D space-charge field due to the beam is calculated with a simplifying model.

Observation of coherent Smith-Purcell and transition radiation driven by single bunch and micro-bunched electron beams

Science.gov (United States)

Liang, Yifan; Du, Yingchao; Su, Xiaolu; Wang, Dan; Yan, Lixin; Tian, Qili; Zhou, Zheng; Wang, Dong; Huang, Wenhui; Gai, Wei; Tang, Chuanxiang; Konoplev, I. V.; Zhang, H.; Doucas, G.

2018-01-01

Generation of coherent Smith-Purcell (cSPr) and transition/diffraction radiation using a single bunch or a pre-modulated relativistic electron beam is one of the growing research areas aiming at the development of radiation sources and beam diagnostics for accelerators. We report the results of comparative experimental studies of terahertz radiation generation by an electron bunch and micro-bunched electron beams and the spectral properties of the coherent transition and SP radiation. The properties of cSPr spectra are investigated and discussed, and excitations of the fundamental and second harmonics of cSPr and their dependence on the beam-grating separation are shown. The experimental and theoretical results are compared, and good agreement is demonstrated.

Nonlinear coherent beam-beam oscillations in the rigid bunch model

International Nuclear Information System (INIS)

Dikansky, N.; Pestrikov, D.

1990-01-01

Within the framework of the rigid bunch model coherent oscillations of strong-strong colliding bunches are described by equations which are specific for the weak-strong beam case. In this paper some predictions of the model for properties of nonlinear coherent oscillations as well as for associated limitations of the luminosity are discussed. 14 refs.; 6 figs

High Charge PHIN Photo Injector at CERN with Fast Phase switching within the Bunch Train for Beam Combination

CERN Document Server

Csatari Divall, M; Bolzon, B; Bravin, E; Chevallay, E; Dabrowski, A; Doebert, S; Drozdy, A; Fedosseev, V; Hessler, C; Lefevre, T; Livesley, S; Losito, R; Olvegaard, M; Petrarca, M; Rabiller, A N; Egger, D; Mete, O

2011-01-01

The high charge PHIN photo-injector was developed within the framework of the European CARE program to provide an alternative to the drive beam thermionic gun in the CTF3 (CLIC Test Facility) at CERN. In PHIN 1908 electron bunches are delivered with bunch spacing of 1.5 GHz and 2.33 nC charge per bunch. Furthermore the drive beam generated by CTF3 requires several fast 180 deg phase-shifts with respect to the 1.5 GHz bunch repetition frequency in order to allow the beam combination scheme developed at CTF3. A total of 8 subtrains, each 140 ns long and shifted in phase with respect to each other, have to be produced with very high phase and amplitude stability. A novel fiber modulator based phase-switching technique developed on the laser system provides this phase-shift between two consecutive pulses much faster and cleaner than the base line scheme, where a thermionic electron gun and sub-harmonic bunching are used. The paper describes the fiber-based switching system and the measurements verifying the schem...

Obtaining the Bunch Shape in a Linac from Beam Spectrum Measurements

International Nuclear Information System (INIS)

Bane, Karl LF

1999-01-01

In linacs with high single-bunch charge, and tight tolerances for energy spread and emittance growth, controlling the short-range wakefield effects becomes extremely important. The effects of the wakefields, in turn, depend on the bunch length and also on the bunch shape. It was shown in the linac of the Stanford Linear Collider (SLC), for example, that by shaping the bunch, the final rms energy spread could be greatly reduced, compared to for the standard Gaussian bunch shape[1]. Therefore, in machines with high single-bunch charge, a method of measuring bunch shape can be an important beam diagnostic. In a linac with low single-bunch charge, the longitudinal bunch shape can be obtained relatively easily from a single measurement of the beam's final energy spectrum, provided that the final to initial energy ratio is large. One merely shifts the average phase of the beam, so that it rides off-crest sufficiently to induce an energy variation that is monotonic with longitudinal position. Then, by knowing the initial and final energies, the rf wave number, and the average beam phase, one can directly map the spectrum into the bunch shape. In a linac with high single-bunch charge, however, due to the effect of the longitudinal wakefield, this method either does not work at all, or it requires such a large shift in beam phase as to become impractical. In earlier work[2],[3] it was shown that, even when wakefields are important, if one measures the final beam spectrum for two different (properly chosen) values of beam phase, then one can again obtain the bunch shape, and--as a by-product--also the form of the wakefield induced voltage; this method was then illustrated using data from the linac of the SLC. These SLC measurements, however, had been performed with the machine in a special configuration, where the current was low; in addition, the noise the data was low and the measured spectra were smooth distributions. Under normal SLC conditions, however, the currents

Commissioning of an electro-optic electron bunch length monitor at FLASH

International Nuclear Information System (INIS)

Breunlin, Jonas

2011-03-01

The demands on the electron beam qualities for free-electron lasers (FEL) are challenging in terms of high peak currents. At FLASH, the high-gain FEL in Hamburg, longitudinal bunch compression is performed to achieve the requested high charge densities in short bunches. The precise control of the bunch compression process requires advanced diagnostics on the longitudinal bunch profile. The bunch length monitor presented in this thesis is based on a non-destructive detection using the electro-optic effect. The focus is on a compact and reliable system for permanent bunch diagnostics. The monitor provides single-shot measurements of the longitudinal bunch profiles with lengths of a few picoseconds by spectrally encoding their charge distribution. First measurements for characterization purpose have been performed. It has been shown that the monitor is suitable for monitoring the longitudinal bunch profile behind the first bunch compressor at FLASH. Electron bunch profiles with slopes corresponding to a full width half maximum of about 1.4 ps have been detected. That is the intrinsic resolution limit of the utilized method. (orig.)

Simulations of Bunch Merging in a Beta Beam Decay Ring

CERN Document Server

Heinrich, Daniel Christopher; Chance, Antoine

2011-01-01

To further study neutrino oscillation properties a Beta Beam facility has been proposed. Beta decaying ions with high kinetic energy are stored in a storage ring ("Decay Ring") with straight sections to create pure focused (anti) electron neutrino beams. However to reach high sensitivity to neutrino oscillation parameters in the experiment the bunched beam intensity and duty cycle in the DR have to be optimized. The first CERN-based scenario, using 6He and 18Ne as neutrino sources, has been studied using a bunch merging RF scheme. Two RF cavities at different frequencies are used to capture newly injected bunches and then merge them into the stored bunches. It was shown that this scheme could satisfy the requirements on intensity and duty cycle set by the experiment. This merging scheme has now been revised with new simulation software providing new results for 6He and 18Ne. Furthermore bunch merging has been studied for the second CERN-based scenario using 8Li and 8B.

Evaluation of Temporal Diagnostic Techniques for Two-Bunch Facet Beam

Energy Technology Data Exchange (ETDEWEB)

Litos, M.D.; Bionta, M.R.; Dolgashev, V.A.; England, R.J.; Fritz, D.; Gilevich, S.; Hering, Ph.; Hogan, M.J.; /SLAC

2011-08-19

Three temporal diagnostic techniques are considered for use in the FACET facility at SLAC, which will incorporate a unique two-bunch beam for plasma wakefield acceleration experiments. The results of these experiments will depend strongly on the the inter-bunch spacing as well as the longitudinal profiles of the two bunches. A reliable, singleshot, high resolution measurement of the beam's temporal profile is necessary to fully quantify the physical mechanisms underlying the beam driven plasma wakefield acceleration. In this study we show that a transverse deflecting cavity is the diagnostic which best meets our criteria. Based on our laboratory testing, numerical calculations, and simulations of the three single-shot temporal diagnostic devices, the X-band TCAV system is the best candidate for resolving FACET's two-bunch beam, with an estimated resolution of 7 {micro}m. Both the S-band TCAV system and the EO system could resolve the peak-to-peak separation of the two bunches in the FACET beam with estimated resolutions of 25 {micro}m and 30 {micro}m, respectively, but would be unable to resolve the temporal profiles of the individual bunches themselves. Because the TCAV signal is more easily interpreted and because the reliability of the EO system is less well known, however, the S-band TCAV system would be the next preferred option after the X-band TCAV system. The Fesca-200 streak camera, though simple, compact, and reliable, is unable to achieve a resolution that would be of use to FACET.

Emittance growth of bunched beams in bends

International Nuclear Information System (INIS)

Carlsten, B.E.; Raubenheimer, T.O.

1995-01-01

Talman [Phys. Rev. Lett. 56, 1429 (1986)] has proposed a novel relativistic effect that occurs when a charged particle beam is bent in the magnetic field from an external dipole. The consequence of this effect is that the space-charge forces from the particles do not exhibit the usual inverse-square energy dependence and some part of them are, in fact, independent of energy. This led to speculation that this effect could introduce significant emittance growth for a bending electron beam. Subsequently, it was shown that this effect's influence on the beam's transverse motion is canceled for a dc beam by a potential depression within the beam (to first order in the beam radius divided by the bend radius). In this paper, we extend the analysis to include short bunch lengths (as compared to the beam pipe dimensions) and find that there is no longer the cancellation for forces both transverse to and in the direction of motion. We provide an estimate for the emittance growth as a function of bend angle, beam radius, and current, and for magnetic compression of an electron bunch

Beam transfer functions for relativistic proton bunches with beam–beam interaction

Energy Technology Data Exchange (ETDEWEB)

Görgen, P., E-mail: goergen@temf.tu-darmstadt.de [Institut für Theorie Elektromagnetischer Felder (TEMF), Technische Universität Darmstadt, Schloßgartenstr. 8 64289 Darmstadt (Germany); Boine-Frankenheim, O. [Institut für Theorie Elektromagnetischer Felder (TEMF), Technische Universität Darmstadt, Schloßgartenstr. 8 64289 Darmstadt (Germany); Fischer, W. [Brookhaven National Laboratory, Upton, NY 11973 (United States)

2015-03-21

We present a method for the recovery of the transverse tune spread directly from the beam transfer function (BTF). The model is applicable for coasting beams and bunched beams at high energy with a tune spread from transverse nonlinearities induced by the beam–beam effect or by an electron lens. Other sources of tune spread can be added. A method for the recovery of the incoherent tune spread without prior knowledge of the nonlinearity is presented. The approach is based on the analytic model for BTFs of coasting beams, which agrees very well with simulations results for bunched beams at relativistic energies with typically low synchrotron tune. A priori the presented tune spread recovery method is usable only in the absence of coherent modes, but additional simulation data shows its applicability even in the presence of coherent beam–beam modes. Finally agreement of both the analytic and simulation models with measurement data obtained at RHIC is presented. The proposed method successfully recovers the tune spread from analytic, simulated and measured BTF.

Multiphoton ionization of (Xe)/sub n/ and (NO)/sub n/ clusters using a picosecond laser

International Nuclear Information System (INIS)

Smith, D.B.; Miller, J.C.

1989-01-01

In an effort to extend the application of multiphoton ionization (MPI) spectroscopy to the study of weakly bound systems, we have begun a systematic investigation of picosecond MPI in van der Waals molecules and clusters. To our knowledge no previous picosecond MPI studies of weakly bound systems have been reported. We present here results of picosecond MPI of Xe/sub n/(n = 1-20) and (NO)/sub n/(n = 1-4) clusters. Previous MPI studies using nanosecond lasers have not detected the NO cluster series, presumably because of fast dissociation channels. The use of high peak-power allows resonant and non-resonant photon absorption to the ionization limit to compete effectively with fast dissociative processes. 10 refs., 2 figs

Nonlinear space charge effect of bunched beam in linac

International Nuclear Information System (INIS)

Chen Yinbao

1992-02-01

The nonlinear space charge effect due to the nonuniform particle density distribution in bunched beam of a linac is discussed. The formulae of nonlinear space charge effect and nonlinear focusing forces were derived for the bunched beam with Kapchinskij-Vladimirskij (K-V) distribution, waterbag (WB) distribution, parabolic (PA) distribution, and Gauss (GA) distribution in both of the space charge disk model and space charge cylinder model in the waveguide of a linac

Longitudinal schottky spectra of a bunched Ne10+ ion beam at the CSRe

International Nuclear Information System (INIS)

Wen Weiqiang; Ma Xinwen; Zhang Dacheng

2013-01-01

The longitudinal Schottky spectra of a radio-frequency (RF) bunched and electron cooled 22Ne 10+ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring (CSRe), at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of Δp/p=1.6 × 10 -5 has been reached with less than 107 stored ions. The reduction of momentum spread compared with a coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25 th , 50 th and 75 th harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe. (authors)

Beam simulations with initial bunch noise in superconducting RF proton linacs

CERN Document Server

Tückmantel, J

2010-01-01

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

Bunch-length and beam-timing monitors in the SLC final focus

International Nuclear Information System (INIS)

Zimmermann, F.; Yocky, G.; Whittum, D.H.; Seidel, M.; Ng, C.K.; McCormick, D.; Bane, K.L.F.

1998-07-01

During the 1997/98 luminosity run of the Stanford Linear Collider (SLC), two novel RF-based detectors were brought into operation, in order to monitor the interaction-point (IP) bunch lengths and fluctuations in the relative arrival time of the two colliding beams. Both bunch length and timing can strongly affect the SLC luminosity and had not been monitored in previous years. The two new detectors utilize a broad-band microwave signal, which is excited by the beam through a ceramic gap in the final-focus beam pipe and transported outside of the beam line vault by a 160-ft long X-Band waveguide. The authors describe the estimated luminosity reduction due to bunch-length drift and IP timing fluctuation, the monitor layout, the expected responses and signal levels, calibration measurements, and beam observations

Ultra-short coherent terahertz radiation from ultra-short dips in electron bunches circulating in a storage ring

International Nuclear Information System (INIS)

Yamamoto, N.; Shimada, M.; Adachi, M.; Zen, H.; Tanikawa, T.; Taira, Y.; Kimura, S.; Hosaka, M.; Takashima, Y.; Takahashi, T.; Katoh, M.

2011-01-01

Terahertz (THz) coherent synchrotron radiation (CSR) is emitted not only from ultra-short electron bunches, but also from electron bunches with micro-structures. Formation of micro-structures at the sub-picosecond scale in electron bunches by a laser slicing technique is experimentally studied through observation of the THz CSR. The THz CSR spectrum was found to depend strongly on the intensity and the pulse width of the laser. The results agreed qualitatively with a numerical simulation. It was suggested that the evolution of the micro-structure during CSR emission is important under some experimental conditions.

High-quality beam generation using an RF gun and a 150 MeV microtron

Science.gov (United States)

Kuroda, R.; Washio, M.; Kashiwagi, S.; Kobuki, T.; Ben-Zvi, I.; Wang, X. J.; Hori, T.; Sakai, F.; Tsunemi, A.; Urakawa, J.; Hirose, T.

2000-11-01

Low-emittance sub-picosecond electron pulses are expected to be used in a wide field, such as free electron laser, laser acceleration, femtosecond X-ray generation by Inverse Compton scattering, pulse radiolysis, etc. In order to produce the low-emittance sub-picosecond electron pulse, we are developing a compact Racetrack Microtron (RTM) with a new 5 MeV injection system adopting a laser photo cathode RF gun (Washio et al., Seventh China-Japan Bilateral Symposium on Radiation Chemistry, October 28, Cengdu, China, 1996). The operation of RTM has been kept under a steady state of beam loading for long pulse mode so far (Washio et al., J. Surf. Sci. Soc. Jpn. 19 (2) (1998) 23). In earlier work (Washio et al., PAC99, March 31, New York, USA, 1999), we have succeeded in the numerical simulation for the case of single short pulse acceleration. Finally, the modified RTM was demonstrated as a useful accelerator for a picosecond electron pulse generation under a transient state of beam loading. In the simulation, a picosecond electron pulse was accelerated to 149.6 MeV in RTM for the injection of 5 MeV electron bunch with a pulse length of 10 ps (FWHM), a charge of 1 nC per pulse, and an emittance of 3 πmm mrad.

Emittance preservation during bunch compression with a magnetized beam

Energy Technology Data Exchange (ETDEWEB)

Stratakis, Diktys [Brookhaven National Lab. (BNL), Upton, NY (United States)

2015-09-02

The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based on combining a finite solenoid field where the beam is generated together with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

Micro-Bunched Beam Production at FAST for Narrow Band THz Generation Using a Slit-Mask

Energy Technology Data Exchange (ETDEWEB)

Hyun, J. [Sokendai, Tsukuba; Crawford, D. [Fermilab; Edstrom Jr, D. [Fermilab; Ruan, J. [Fermilab; Santucci, J. [Fermilab; Thurman-Keup, R. [Fermilab; Sen, T. [Fermilab; Thangaraj, J. C. [Fermilab

2018-04-01

We discuss simulations and experiments on creating micro-bunch beams for generating narrow band THz radiation at the Fermilab Accelerator Science and Technology (FAST) facility. The low-energy electron beamline at FAST consists of a photoinjector-based RF gun, two Lband superconducting accelerating cavities, a chicane, and a beam dump. The electron bunches are lengthened with cavity phases set off-crest for better longitudinal separation and then micro-bunched with a slit-mask installed in the chicane. We carried out the experiments with 30 MeV electron beams and detected signals of the micro-bunching using a skew quadrupole magnet in the chicane. In this paper, the details of micro-bunch beam production, the detection of micro-bunching and comparison with simulations are described.

Diffractive sub-picosecond manipulation of x-rays

International Nuclear Information System (INIS)

Adams, B.

2004-01-01

A class of X-ray optical elements for the sub-picosecond manipulation of X-rays is proposed. The design of these elements is based upon a time-dependent dynamical diffraction theory that synthesizes the eikonal theory with the Takagi-Taupin theory. A brief outline of the theory is given

Beam induced heating reduction by bunch flattening

CERN Document Server

Argyropoulos, T; Esteban Müller, JF; Jakobsen, S; Mastoridis, T; Metral, E; Mounet, N; Papotti, G; Pieloni, T; Salvant, B; Shaposhnikova, E; Timko, H

2014-01-01

The main purpose of this MD was to modify the beam induced heating on some critical LHC components by flattening the bunch distribution by applying an RF phase modulation. In this way, the beam spectrum was modified so that the power spectral density is reduced at low frequencies (below 1.1 GHz), which is the band of frequencies where the beam interaction with different component impedances is most critical. We present temperature measurements showing the beneficial effect of this latter distribution on some of the monitored devices. Longitudinal peak detected Schottky spectrum was also acquired during the first part of the MD with the intention of estimating the synchrotron frequency shift due to the reactive part of the longitudinal impedance. In the second part of the MD, an attempt to cure the transverse instability during the beta-squeeze was done by reducing the RF voltage to lengthen the bunches and enhance Landau Damping.

Emittance preservation during bunch compression with a magnetized beam

Energy Technology Data Exchange (ETDEWEB)

Stratakis, Diktys

2016-03-01

The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based in combining a finite solenoid field where the beam is generated with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth from CSR can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

Single bunch beam loading on the SLAC three-kilometer accelerator

International Nuclear Information System (INIS)

Koontz, R.F.; Loew, G.A.; Miller, R.H.; Wilson, P.B.

1977-03-01

Since the report on single bunch beam loading experiments at SLAC at the 1975 Particle Accelerator Conference, it has been possible to obtain a much better understanding and agreement of theoretical and experimental results related to this problem. These improvements were made possible by two developments: the generation of a ''wake-field'' function for the SLAC 3-km slow-wave structure and the use of this function to calculate single bunch energy spectra. The wake-field function which gives the time decay of the fields generated by the passage of a delta-function beam was derived by summing all the TM cylindrically symmetrical modes of an equivalent accelerator cavity. By multiplying this wake-field function by a measured bunch density function and integrating along the bunch, it is possible to calculate the energy of each electron in the bunch. This in turn enables one to predict the energy spectrum for any given phase angle of the bunch with respect to the crest of the rf accelerating wave. Agreement between these calculations and experimental measurements is very good. These results are presented, and the possible sources of some of the remaining discrepancies are discussed

Single bunch beam loading on the SLAC three-kilometer accelerator

International Nuclear Information System (INIS)

Koontz, R.F.; Loew, G.A.; Miller, R.H.; Wilson, P.B.

1977-01-01

Since the report on single bunch beam loading experiments at SLAC at the 1975 Particle Accelerator Conference, it has been possible to obtain a much better understanding and agreement of theoretical and experimental results related to this problem. These improvements have been made possible by two developments: the generation of a ''wake-field'' function for the SLAC 3-km slow-wave structure and the use of this function to calculate single bunch energy spectra. The wake-field function which gives the time decay of the fields generated by the passage of a delta-function beam was derived by summing all the TM cylindrically symmetrical modes of an equivalent accelerator cavity. By multiplying this wake-field function by a measured bunch density function and integrating along the bunch, it is possible to calculate the energy of each electron in the bunch. This in turn enables one to predict the energy spectrum for any given phase angle of the bunch with respect to the crest of the rf accelerating wave. Agreement between these calculations and experimental measurements is very good. These results are presented and the possible sources of some of the remaining discrepancies are discussed

Transient analysis of a bunched beam free electron laser

International Nuclear Information System (INIS)

Wang, J.M.; Yu, L.H.

1985-01-01

The problem of the bunched beam operation of a free electron laser was studied. Assuming the electron beam to be initially monoenergetic, the Maxwell-Vlasov equations describing the system reduce to a third order partial differential equation for the envelope of the emitted light. The Green's function corresponding to an arbitrary shape of the electron bunch, which describes the transient behavior of the system, is obtained. The Green's function was used to discuss the start up problem as well as the power output and the power specrum of a self-amplified spontaneous emission

Comparison between coasting and bunched beams on optimum stochastic cooling and signal suppression

International Nuclear Information System (INIS)

Wei, J.

1991-01-01

A comparison has been performed between coasting and bunched particle beams pertaining to the mechanism of stochastic cooling. In the case that particles occupy the entire sinusoidal rf bucket, the optimum cooling rate for the bunched beam is shown to be the same as that predicted from the coasting-beam theory using local particle density. However, in the case that particles occupy only the center of the bucket, the optimum rate decreases in proportion to the ratio of the bunch area to the bucket area. Furthermore, it has been shown for both coasting and bunched beams that particle motion is stable upon signal suppression if the amplitude of the gain is less than twice the optimum value over the entire frequency bandwidth of the cooling system. 7 refs., 1 fig

Generation and measurement of velocity bunched ultrashort bunch of pC charge

Directory of Open Access Journals (Sweden)

X. H. Lu

2015-03-01

Full Text Available In this paper, we discuss the velocity compression in a short rf linac of an electron bunch from a rf photoinjector operated in the blowout regime. Particle tracking simulations shows that with a beam charge of 2 pC an ultrashort bunch duration of 16 fs can be obtained at a tight longitudinal focus downstream of the linac. A simplified coherent transition radiation (CTR spectrum method is developed to enable the measurement of ultrashort (sub-50 fs bunches at low bunch energy (5 MeV and low bunch charges (<10  pC. In this method, the ratio of the radiation energy selected by two narrow bandwidth filters is used to estimate the bunch length. The contribution to the coherent form factor of the large transverse size of the bunch suppresses the radiation signal significantly and is included in the analysis. The experiment was performed at the UCLA Pegasus photoinjector laboratory. The measurement results show bunches of sub-40 fs with 2 pC of charge well consistent with the simulation using actual experimental conditions. These results open the way to the generation of ultrashort bunches with time-duration below 10 fs once some of the limitations of the setup (rf phase jitter, amplitude instability and low field in the gun limited by breakdown are corrected.

A coupled bunch instability due to beam-photoelectron interactions in KEKB-LER

Energy Technology Data Exchange (ETDEWEB)

Ohmi, Kazuhito [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

1996-08-01

LER of KEKB is designed to storage the positron beam of 2.6 A with multibunch operation. Nb = 3.3 x 10{sup 10} positrons are filled in a bunch and the bunch passes every 2ns through a beam chamber. The photoelectron instability may be serious for KEKB-LER. We consider a motion of photoelectrons produced by a bunch with a computer simulation technic. A cylindrical chamber with a diameter of 10 cm was used as a model chamber. About 15 times of the photoelectrons were produced by a bunch. The wake force was calculated for the loading bunches with displacements of 0.5 mm and 1 mm. The wake characteristics seems to be caused by the trapped electrons kicked by the loading bunch. The wake was saturated with the loading displacement of 0.5 mm. We obtained a growth rate by the wake force. It is very high rate, 2500s{sup -1} which exceeds damping rates of various mechanism, radiation, head-tail and feedback. Perhaps it is essential to remove the photoelectrons around the positron beam explicitly. If we apply magnetic field fo about 20 G, the growth rate will be reduced. (S.Y.)

Phase measurement and control of bunched beams

International Nuclear Information System (INIS)

Lewis, R.N.

1978-01-01

An ion bean buncher was developed at ANL for bunching all ion species through a tandem accelerator. Transit time variations through the tandem, caused by ripple and fluctuations in the injection and lens power supplies and terminal voltage, and to varying voltage distributions in the accelerating tube, cause a beam-phase variation at the output of the tandem. A beam-phase measurement and control system was designed and installed in conjunction with the ion beam buncher to control beam phase at the tandem output. That system is described

CSR Effects in a Bunch Compressor influence of the Beam Frame Transverse Force

CERN Document Server

Bassi, G

2005-01-01

We study the influence of coherent synchrotron radiation (CSR) on particle bunches traveling on arbitrary planar orbits between parallel conducting plates (shielding) with a Vlasov approach. [1] The fields excited by the bunch are computed in the lab frame using a formula simpler than that based on retarded potentials. The Vlasov equation is solved in the beam frame interaction picture. In recent numerical investigations we solved the Vlasov equation for a bunch compressor using the Liouville-Maxwell approximation (LMA), where the bunch density is evolved under the fields produced by the unperturbed density (subject to external fields only), neglecting the beam frame transverse force. [2] Here we report on the influence of the beam frame transverse force on the equations of motion.

On-line Observation Of Electron Beam Bunches In The Large Storage Ring Of Kurchatov Srs

CERN Document Server

Ioudin, L I; Krylov, Y V; Rezvov, V A; Stirin, A I; Valentinov, A G; Yupinov, Y L

2004-01-01

A complex of instrumentation for visual quantitative estimation of electron beam bunches in the big storage ring of Kurchatov Synchrotron Radiation Centre (KSRC) is tested. The bunches pass through a cylindrical electrostatic sensor whose signal is recorded by a wide-band oscillograph. The TV camera reads the optical image of the signal from the oscillograph screen. The TV signal numbering board inputs the video image to the computer memory. The monitor displays the beam bunch structure. A special program provides on-line visualisation of bunch behaviour on the beam orbit. The images of beam structure and a series of images showing the beam behaviour in the regimes of accumulation, acceleration and in the stationary regime a full power are numbered and stored.

Multi-bunch energy spread induced by beam loading in standing wave structure

International Nuclear Information System (INIS)

Ferrario, M.; Tazzioli, F.

1995-04-01

The interaction of a relativistic beam with the modes of the TM 010 pass-band of a multicell cavity does not cause any problem: although all the modes are excited by the RF (radiofrequency) generator, resulting in different cell excitations during the cavity filling and the beam pulse, the net accelerating field exhibits negligible fluctuations from bunch to bunch. However, when the beam is not fully relativistic, this is no more true. The phase slippage occurring in the first cells, between the non relativistic beam and the lower pass-band modes, produces an effective enhancement of the shunt impedances, which is usually negligible for a relativistic beam in a well tuned cavity. Moreover, the voltage jumps (amplitude and phase) occurring at each bunch passage, as well as the beam detuning caused by the off-crest bunches, vary from cell to cell. These effects enhance dramatically the fluctuation of the accelerating voltage, with a dominant beating provided by the pass-band mode nearest to the pi-mode. The induced beam energy spread has been estimated by the help of two distinct codes, developed at Frascati (Italy) and (Saclay), with results in good agreement. While an interaction integral is computed at each bunch passage, the cavity refilling is calculated by solving coupled differential equations of the modes of the pass-band, driven by a generator linked to one end-cell. It is shown also that the intermode coupling arises from the external Q of the drive end-cell, and not from the wall losses. For illustration, the authors applied the method to the beam-loading problem in the SC capture cavity of the low charge injector of the TESLA test facility installed at DESY

Transport of dc and bunched beams through a 25 MV folded tandem accelerator

International Nuclear Information System (INIS)

Milner, W.T.; Alton, G.D.; Hensley, D.C.; Jones, C.M.; King, R.F.; Larson, J.D.; Moak, C.D.; Sayer, R.O.

1975-01-01

Studies of beam transport through the planned ORNL 25 MV folded tandem accelerator demonstrate efficient utilization of phase-space acceptance and the feasibility of injecting bunched beams from the tandem accelerator into the Oak Ridge Isochronous Cyclotron (ORIC). Use of a 180 0 bending magnet in the terminal provides outstanding charge state selection and permits better control of the high-energy beam transport than has previously been possible in conventional tandem accelerators. Time spreads introduced in bunched beams by the 180 0 magnet are kept within a 6 0 RF acceptance window at ORIC provided the beam has a crossover in the center of the 180 0 magnet. Ion masses from 12 to 240 amu, preinjection energies from 150 to 500 keV and terminal voltages from 7.5 to 25 MV were studied for dc beams and beams bunched by various modulation techniques. (U.S.)

A robust fibre laser system for electro-optic electron bunch profile measurements at FLASH

Energy Technology Data Exchange (ETDEWEB)

Wissmann, Laurens-Georg

2012-08-15

For the electro-optic measurement of electron bunch profiles at FLASH a robust ytterbium doped fibre laser (YDFL) system has been developed consisting of a laser oscillator and a two-staged amplifier. The oscillator is designed to meet the specifications of high reliability and low noise operation. The amplifier makes use of tailored nonlinearity to enhance the spectral bandwidth of the output laser pulses. Active repetition rate control enables sub-picosecond synchronisation of the laser to the accelerator reference RF. Using a two-stage gating scheme the output pulse train repetition rate is adopted to the accelerator repetition rate. An experimental site used for electro-optic electron bunch diagnostics has been redesigned to support single-shot bunch profile measurements based on spectral decoding. An existing bunch profile monitor with a similar laser system was upgraded and electro-optic bunch profile measurements were conducted, allowing for a comparison with measurements done with other longitudinal electron bunch diagnostics and with former measurements.

A robust fibre laser system for electro-optic electron bunch profile measurements at FLASH

International Nuclear Information System (INIS)

Wissmann, Laurens-Georg

2012-08-01

For the electro-optic measurement of electron bunch profiles at FLASH a robust ytterbium doped fibre laser (YDFL) system has been developed consisting of a laser oscillator and a two-staged amplifier. The oscillator is designed to meet the specifications of high reliability and low noise operation. The amplifier makes use of tailored nonlinearity to enhance the spectral bandwidth of the output laser pulses. Active repetition rate control enables sub-picosecond synchronisation of the laser to the accelerator reference RF. Using a two-stage gating scheme the output pulse train repetition rate is adopted to the accelerator repetition rate. An experimental site used for electro-optic electron bunch diagnostics has been redesigned to support single-shot bunch profile measurements based on spectral decoding. An existing bunch profile monitor with a similar laser system was upgraded and electro-optic bunch profile measurements were conducted, allowing for a comparison with measurements done with other longitudinal electron bunch diagnostics and with former measurements.

Independent component analysis applied to long bunch beams in the Los Alamos Proton Storage Ring

Science.gov (United States)

Kolski, Jeffrey S.; Macek, Robert J.; McCrady, Rodney C.; Pang, Xiaoying

2012-11-01

Independent component analysis (ICA) is a powerful blind source separation (BSS) method. Compared to the typical BSS method, principal component analysis, ICA is more robust to noise, coupling, and nonlinearity. The conventional ICA application to turn-by-turn position data from multiple beam position monitors (BPMs) yields information about cross-BPM correlations. With this scheme, multi-BPM ICA has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch revealing correlations of particle motion within the beam bunch. We digitize beam signals of the long bunch at the Los Alamos Proton Storage Ring with a single device (BPM or fast current monitor) for an entire injection-extraction cycle. ICA of the digitized beam signals results in source signals, which we identify to describe varying betatron motion along the bunch, locations of transverse resonances along the bunch, measurement noise, characteristic frequencies of the digitizing oscilloscopes, and longitudinal beam structure.

Independent component analysis applied to long bunch beams in the Los Alamos Proton Storage Ring

Directory of Open Access Journals (Sweden)

Jeffrey S. Kolski

2012-11-01

Full Text Available Independent component analysis (ICA is a powerful blind source separation (BSS method. Compared to the typical BSS method, principal component analysis, ICA is more robust to noise, coupling, and nonlinearity. The conventional ICA application to turn-by-turn position data from multiple beam position monitors (BPMs yields information about cross-BPM correlations. With this scheme, multi-BPM ICA has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch revealing correlations of particle motion within the beam bunch. We digitize beam signals of the long bunch at the Los Alamos Proton Storage Ring with a single device (BPM or fast current monitor for an entire injection-extraction cycle. ICA of the digitized beam signals results in source signals, which we identify to describe varying betatron motion along the bunch, locations of transverse resonances along the bunch, measurement noise, characteristic frequencies of the digitizing oscilloscopes, and longitudinal beam structure.

Improved Bunch Splitting for the 75ns LHC Beam

CERN Document Server

Damerau, H

2011-01-01

The 75ns variant was added to the PS arsenal of LHC-type beams by adapting the 20MHz cavity used to produce the 25 and 50ns variants to operate at a switchable 13MHz. This permitted splitting from harmonic 14 to 28, but at a cost in adiabaticity compared with the h=2142 splitting of the other two cases. Consequently, a delicate empirical optimization was necessary to bring the 75ns beam inside specification. More recently the speed at which the bunches, once fully distinct, are moved apart has been revisited and further optimization achieved. As a by-product, deliberately degrading the splitting by moving the bunches apart too quickly led to sufficient coherent motion in the resultant bunch pair to permit a voltage calibration of the 13MHz cavity by means of the influence on convergence of the rf voltage input into the iterative algorithm of the Tomoscope [1,2].

Can coherent Smith-Purcell radiation be used to determine the shape of an electron bunch?

International Nuclear Information System (INIS)

Doria, A.; Gallerano, G.P.; Giovenale, E.; Messina, G.; Doucas, G.; Kimmitt, M.F.; Andrews, H.L.; Brownell, J.H.

2002-01-01

Recent measurements at Frascati of the Smith-Purcell radiation emitted from the interaction of a 2.3 MeV (total) electron beam with a 2.5 mm grating show clear evidence of coherent enhancement of the radiation, with power levels exceeding 100 mW at emission angles around 90 deg. relative to the beam direction. The experimental results are in reasonable agreement with theoretical predictions and suggest that Smith-Purcell radiation may offer a simple way of determining the shape and duration of short (picosecond) electron bunches

Effect of nonuniform radial density distribution on the space charge dominated beam bunching

International Nuclear Information System (INIS)

Sing Babu, P.; Goswami, A.; Pandit, V. S.

2011-01-01

Beam dynamics of a space charge dominated beam during the bunch compression is studied self consistently for the case of fixed shape non-uniform bell shape and hollow shape density distributions in the transverse direction. We have used thick slices at different parts of the beam to account for variation in the beam radius in the study of the transverse dynamics. The longitudinal dynamics has been studied using the disc model. The axial variation of the radius of the slices and emittance growth arising from the phase dependence of the transverse rf forces are also included in the simulation. We have modified the beam envelope equation to take into account the longitudinal space charge effect on the transverse motion which arises due to the finite bunch size. To demonstrate the application of the theoretical formulations developed, we have studied a sinusoidal beam bunching system and presented detailed numerical results.

Application of Metal-Semiconductor-Metal (MSM) Photodetectors for Transverse and Longitudinal Intra-Bunch Beam Diagnostics

CERN Document Server

Steinhagen, R J; Boland, M J; Lucas, T G; Rassool, R P

2013-01-01

The performance reach of modern accelerators is often governed by the ability to reliably measure and control the beam stability. In high-brightness lepton and high-energy hadron accelerators, the use of optical diagnostic techniques is becoming more widespread as the required bandwidth, resolution and high RF beam power level involved limit the use of traditional electro-magnetic RF pick-up based methods. This contribution discusses the use of fibre-coupled ultra-fast Metal-Semiconductor-Metal Photodetectors (MSM-PD) as an alternative, dependablemeans to measure signals derived from electro-optical and synchrotron-light based diagnostics systems. It describes the beam studies performed at CERN’s CLIC Test Facility (CTF3) and the Australian Synchrotron to assess the feasibility of this technology as a robust, wide-band and sensitive technique for measuring transverse intra-bunch and bunch-by-bunch beam oscillations, longitudinal beam profiles, un-bunched beam population and beam-halo profiles. The amplifica...

Longitudinal halo in beam bunches with self-consistent 6-D distributions

International Nuclear Information System (INIS)

Gluckstern, R. L.; Fedotov, A. V.; Kurennoy, S. S.; Ryne, R. D.

1998-01-01

We have explored the formation of longitudinal and transverse halos in 3-D axisymmetric beam bunches by starting with a self-consistent 6-D phase space distribution. Stationary distributions allow us to study the halo development mechanism without being obscured by beam redistribution and its effect on halo formation. The beam is then mismatched longitudinally and/or transversely, and we explore the rate, intensity and spatial extent of the halos which form, as a function of the beam charge and the mismatches. We find that the longitudinal halo forms first because the longitudinal tune depression is more severe than the transverse one for elongated bunches and conclude that it plays a major role in halo formation

Initial Measurements of CSR from a Bunch-Compressed Beam at APS

CERN Document Server

Lumpkin, Alex H; Borland, M; Sereno, N S

2005-01-01

The interest in bunch compression to generate higher peak current electron beams with low emittance continues in the free-electron laser (FEL) community. At the Advanced Photon source (APS) we have both an rf thermionic gun and an rf photocathode (PC) gun on the S-band linac. At the 150-MeV point in the linac, we have a flexible chicane bunch compressor whose four dipoles bend the beam in the horizontal plane. There is also a vertical bend dipole after the chicane that allows measurement of energy and horizontal beam size at the imaging screen station to study possible effects on emittance due to coherent synchrotron radiation (CSR) in the chicane. A far-infrared (FIR) coherent radiation monitor is located downstream of the chicane as well. We have begun recommissioning of this device with coherent transition radiation (CTR), but we also have directly observed CSR from the bunch-compressed beam as it transits the vertical dipole and goes into the down leg. The unique geometry allows simultaneous tracking of b...

Thresholds of a bunched beam longitudinal instability in proton synchrotrons

International Nuclear Information System (INIS)

Balbekov, V.I.; Ivanov, S.V.

1986-01-01

The formulas and graphs for calculating instability thresholds arising during the interaction of a bunched proton beam with narrow-band resonator are given. The instabilities of three types with oscillations of a definite multipolarity, oscillations of some bound multipoles and with microwave oscillations arising as a result of addition of a great number of multipoles. The analysis of the above data shows that the increase of oscillations nonlinearity is accompanied by the growth of instability threshold only in the zone of separated and weakly bound multipoles. The increase of spread of synchrotron frequencies reduces the zone separated multipoles owing to which the microwave bunch instability can be caused by more and more low-frequency resonators. In the microwave zone practically there is no stabilizing effect of synchrotron frequencies spread. The instability threshold of the bunched beam now - where exceeds the microwave level

Controlling nonlinear longitudinal space charge oscillations for high peak current bunch train generation

Directory of Open Access Journals (Sweden)

P. Musumeci

2013-10-01

Full Text Available The evolution of picosecond modulations of the longitudinal profile of an electron beam generated in an rf photoinjector is analyzed and optimized with the goal of obtaining high peak current electron bunch trains at very high frequencies (≥THz. Taking advantage of nonlinear longitudinal space charge forces, it is found that more than 500 A peak current 1 THz bunch trains can be generated using a standard 1.6 cell SLAC/UCLA/BNL rf gun. Postacceleration is used to freeze the longitudinal phase space dynamics after one half plasma oscillation. Applications range from tunable narrow bandwidth THz radiation generation to drivers for high frequency high gradient accelerators.

Towards highest peak intensities for ultra-short MeV-range ion bunches

Science.gov (United States)

Busold, Simon; Schumacher, Dennis; Brabetz, Christian; Jahn, Diana; Kroll, Florian; Deppert, Oliver; Schramm, Ulrich; Cowan, Thomas E.; Blažević, Abel; Bagnoud, Vincent; Roth, Markus

2015-01-01

A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 108 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches. PMID:26212024

Towards highest peak intensities for ultra-short MeV-range ion bunches

Science.gov (United States)

Busold, Simon; Schumacher, Dennis; Brabetz, Christian; Jahn, Diana; Kroll, Florian; Deppert, Oliver; Schramm, Ulrich; Cowan, Thomas E.; Blažević, Abel; Bagnoud, Vincent; Roth, Markus

2015-07-01

A laser-driven, multi-MeV-range ion beamline has been installed at the GSI Helmholtz center for heavy ion research. The high-power laser PHELIX drives the very short (picosecond) ion acceleration on μm scale, with energies ranging up to 28.4 MeV for protons in a continuous spectrum. The necessary beam shaping behind the source is accomplished by applying magnetic ion lenses like solenoids and quadrupoles and a radiofrequency cavity. Based on the unique beam properties from the laser-driven source, high-current single bunches could be produced and characterized in a recent experiment: At a central energy of 7.8 MeV, up to 5 × 108 protons could be re-focused in time to a FWHM bunch length of τ = (462 ± 40) ps via phase focusing. The bunches show a moderate energy spread between 10% and 15% (ΔE/E0 at FWHM) and are available at 6 m distance to the source und thus separated from the harsh laser-matter interaction environment. These successful experiments represent the basis for developing novel laser-driven ion beamlines and accessing highest peak intensities for ultra-short MeV-range ion bunches.

Concept of a tunable source of coherent THz radiation driven by a plasma modulated electron beam

Science.gov (United States)

Zhang, H.; Konoplev, I. V.; Doucas, G.; Smith, J.

2018-04-01

We have carried out numerical studies which consider the modulation of a picosecond long relativistic electron beam in a plasma channel and the generation of a micro-bunched train. The subsequent propagation of the micro-bunched beam in the vacuum area was also investigated. The same numerical model was then used to simulate the radiation arising from the interaction of the micro-bunched beam with a metallic grating. The dependence of the radiation spectrum on the parameters of the micro-bunched beam has been studied and the tunability of the radiation by the variation of the micro-bunch spacing has been demonstrated. The micro-bunch spacing can be changed easily by altering the plasma density without changing the beam energy or current. Using the results of these studies, we develop a conceptual design of a tunable source of coherent terahertz (THz) radiation driven by a plasma modulated beam. Such a source would be a potential and useful alternative to conventional vacuum THz tubes and THz free-electron laser sources.

Emittance growth caused by nonuniform charge distribution of bunched beam in linac

International Nuclear Information System (INIS)

Chen Yinbao; Zhang Zhenhai

1993-09-01

The nonlinear space charge effect of bunched beam in linac is one of the important reasons that induces the emittance growth because of the conversion of the field energy to kinetic energy. The authors have worked out the internal field energies associated with some nonuniform space change distributions of a bunched beam, such as Gaussian distribution, waterbag distribution and parabolic distribution. And the emittance growths caused by these nonuniformities are obtained

Femtosecond resolved diagnostics for electron beam and XUV seed temporal overlap at sFLASH

Energy Technology Data Exchange (ETDEWEB)

Tarkeshian, Roxana

2012-02-15

sFLASH is a seeded experiment at the Free-Electron Laser FLASH in Hamburg. It uses a 38 nm High-Harmonic-Generation (HHG) scheme to seed the FEL-process in a 10m long variable-gap undulator. The temporal overlap between the electron and HHG pulses is critical to the seeding process. The use of a 3{sup rd} harmonic accelerating module provides a high current electron beam with {proportional_to} (400 fs){sub FWHM} bunch duration. The duration of the HHG laser pulse is {<=} (30 fs){sub FWHM}. The desired overlap is achieved in two steps. Firstly, the HHG drive laser is brought to temporal overlap with the incoherent spontaneous radiation from an upstream undulator with picosecond resolution. The temporal overlap is periodically monitored using a streak camera installed in the linear accelerator tunnel. Next, the coherent radiation from an undulator is used to determine the exact overlap of the electron beam in a modulator-radiator set-up with sub-picosecond resolution. The physical and technical principles of the setup providing the temporal overlap are described. Results of the system are analyzed. An analytical approach and simulation results for the performance of the seeding experiment are presented. First attempts at demonstration of seeding are discussed. Strategies for optimizing overlap conditions are presented. (orig.)

ELECTRON BUNCH CHARACTERIZATION WITH SUBPICOSECOND RESOLUTION USING ELECTRO-OPTIC TECHNIQUE

International Nuclear Information System (INIS)

SEMERTZIDIS, Y.K.; CASTILLO, V.; LARSEN, R.; LAZARUS, D.M.; NIKAS, D.; OZBEN, C.; SRINIVASAN-RAO, T.; STILLMAN, A.; TSANG, T.; KOWALSKI, L.

2001-01-01

In the past decade, the bunch lengths of electrons in accelerators have decreased dramatically and are in the range off a few millimeters. Measurement of the length as well as the longitudinal profile of these short bunches have been a topic of research in a number of institutions. One of the techniques uses the electric field induced by the passage of electrons in the vicinity of a birefringent crystal to change its optical characteristics. Well-established electro-optic techniques can then be used to measure the temporal characteristics of the electron bunch. The inherent fast response of the crystal facilitates the measurement to femtosecond time resolution. However, the resolution in experiments so far has been limited to 70 ps, by the bandwidth of the detection equipment. Use of a streak camera can improve this resolution to a few picoseconds. In this paper we present a novel, non-invasive, single-shot approach to improve the resolution to tens of femtoseconds so that sub mm bunch length can be measured

Stability of longitudinal modes in a bunched beam with mode coupling

International Nuclear Information System (INIS)

Satoh, K.

1981-06-01

In this paper we study a longitudinal coherent bunch instability in which the growth time is comparable to or less than the period of synchrotron oscillations. Both longitudinal and transverse bunch instabilities have been studied. In most treatments, however, the coherent force is assumed to be small and is treated as a perturbation compared with the synchrotron force. This makes the problem simpler because an individual synchrotron mode is decoupled. As bunch current increases, the coherent force is no longer small and the mode frequency shift becomes significant compared with the synchrotron frequency. Therefore in this case it is necessary to include coupling of the synchrotron modes. Recently a fast blow-up instability which comes from mode coupling was studied. Their method is to derive a dispersion relation for a bunched beam using the Vlasov equation and to analyze it as in a coasting beam. They showed that if mode coupling is included the Vlasov equation predicts a fast microwave instability with a stability condition similar to that for a coasting beam. In this paper we will partly follow their method and present a formalism which includes coupling between higher-order radial modes as well as coupling between synchrotron modes. The formalism is considered to be generalization of the Sacherer formalism without mode coupling. This theory predicts that instability is induced not only by coupling between different synchrotron modes, but also by coupling between positive and negative modes, since negative synchrotron modes are included in the theory in a natural manner. This formalism is to be used for a Gaussian bunch and a parabolic bunch, and is also useful for transverse problems

Transverse modes of a bunched beam with space charge dominated impedance

Directory of Open Access Journals (Sweden)

V. Balbekov

2009-12-01

Full Text Available Transverse coherent oscillations of a bunched beam in a ring accelerator are considered with space charge dominated impedance, taking into account linear synchrotron oscillations. A general equation of the bunch eigenmodes is derived, its exact analytical solution is presented for boxcar bunch, and numerical solutions are found for several realistic models. Both low and high synchrotron frequency approximations are considered and compared, fields of their applicability are determined, and some estimations are developed in the intermediate region. It is shown that most of the bunch eigenmodes are stabilized by Landau damping due to the space charge produced tune spread.

Nonrelativistic electron bunch train for coherently enhanced terahertz radiation sources

International Nuclear Information System (INIS)

Li Yuelin; Kim, Kwang-Je

2008-01-01

We propose to generate a train of prebunched electron beams for producing coherently enhanced Smith-Purcell radiation [S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953)] in the terahertz wavelength range. In this scheme, a train of picosecond laser pulses is produced to drive a photoemission gun to generate a train of 50 keV electron pulses. The parameters are chosen so that the space-charge effect does not destroy the pulse time structure. Smith-Purcell radiation from the electron pulse train is enhanced due both to the short length of the individual electron bunch and to the repetitive structure of the beam. Example systems producing coherent terahertz power at about 1 mW are described

The impact of coherent synchrotron radiation on the beam transport of short bunches

International Nuclear Information System (INIS)

Li, R.

1999-01-01

Designs for next-generation accelerator, such as future linear colliders and short-wavelength FEL drivers, require beams of short (mm-length or smaller) bunches and high charge (nC-regime). As such a high charge microbunch traverses magnetic bends, the curvature effect on the bunch self-interaction, by way of coherent synchrotron radiation (CSR) and space charge force, may cause serious emittance degradation. This impact of CSR on the beam transport of short bunches has raised significant concern in the design of future machines and led to extensive investigations. This paper reviews some of the recent progress in the understanding of the CSR effect, presents analysis of and computational work on the CSR impact on short bunch transport, and addresses remaining issues

Measurement of electron beam bunch phase length by rectangular cavities

International Nuclear Information System (INIS)

Afanas'ev, V.D.; Rudychev, V.G.; Ushakov, V.I.

1976-01-01

An analysis of a phase length of electron bunches with the help of crossed rectangular resonators with the Hsub(102) oscillation type has been made. It has been shown that the electron coordinates after the duplex resonator are described by an ellipse equation for a non-modulated beam. An influence of the initial energy spread upon the electron motion has been studied. It has been ascertained that energy modulation of the electron beam results in displacement of each electron with respect to the ellipse which is proportional to modulation energy, i.e. an error in determination of the phase length of an electron bunch is proportional to the beam energy spread. Relations have been obtained which enable to find genuine values of phases of the analyzed electrons with an accuracy up to linear multipliers

Turn-by-Turn and Bunch-by-Bunch Transverse Profiles of a Single Bunch in a Full Ring

International Nuclear Information System (INIS)

Kraus, R.; Fisher, A.S.

2005-01-01

The apparatus described in this paper can image the evolution of the transverse profile of a single bunch, isolated from a full PEP-II ring of 1500 bunches. Using this apparatus there are two methods of single bunch imaging; bunch-by-bunch beam profiling can image every bunch in the ring a single bunch at a time with the images of sequential bunches being in order, allowing one to see variations in beam size along a train. Turn-by-turn beam profiling images a single bunch on each successive turn it makes around the ring. This method will be useful in determining the effect that an injected bunch has on a stable bunch as the oscillations of the injected bunch damp out. Turn-by-turn imaging of the synchrotron light uses a system of lenses and mirrors to image many turns of both the major and minor axis of a single bunch across the photocathode of a gateable camera. The bunch-by-bunch method is simpler: because of a focusing mirror used in porting the light from the ring, the synchrotron light from the orbiting electrons becomes an image at a certain distance from the mirror; and since the camera does not use a lens, the photocathode is set exactly at this image distance. Bunch-by-bunch profiling has shown that in the Low Energy Ring (LER) horizontal bunch size decreases along a train. Turn-by-turn profiling has been able to image 100 turns of a single bunch on one exposure of the camera. The turn-by-turn setup has also been able to image 50 turns of the minor axis showing part of the damping process of an oscillating injected charge during a LER fill. The goal is to image the damping of oscillations of injected charge for 100 turns of both the major and minor axis throughout the damping process during trickle injection. With some changes to the apparatus this goal is within reach and will make turn-by-turn imaging a very useful tool in beam diagnostics

Stability of higher-order longitudinal modes in a bunched beam without mode coupling

International Nuclear Information System (INIS)

Satoh, K.

1981-05-01

The theory of longitudinal instabilities of bunched beams was proposed by F. Sacherer. Starting from the Vlasov equation, he derived the integral equation for the perturbed distribution function. While the general method to solve the integral equation was given by Sacherer, a number of other papers discussing longitudinal bunched beam instability have also been published. Here we want to propose another formalism with which we can treat the integral equation without mode coupling for the case of a Gaussian bunch. We then generalize the formalism for the other bunch distributions, and derive a practical method to analyze the instability for the case of a parabolic bunch. While the solution of the Sacherer equation that we find is not new, we present another approach to solve it. Since the integral equation for the transverse instability is similar to that for the longitudinal instability, this formalism is also useful for the transverse case. 12 figs., 4 figs

Simulation of Transverse Multi-Bunch Instabilities of Proton Beams in LHC

CERN Document Server

Koschik, Alexander; Zotter, Bruno

The CERN Large Hadron Collider (LHC) is designed for highest luminosity and therefore requires operation with a large number of bunches and high intensities. Its performance could be limited by the electromagnetic interaction between the charged particle beam and its surroundings which cause collective instabilities. This thesis describes methods of simulating and analyzing multi-bunch instabilities in circular accelerators and storage rings. The simulation models as well as analyzing tools presented here, also facilitate the interpretation of measurements in multi-bunch machines. The 3-dimensional, multi-bunch tracking program MultiTRISIM was developed, based on its single-bunch predecessor TRISIM3D. It allows the exploration of longrange effects in round or flat vacuum chambers for equidistant or uneven filling schemes. Previous computer simulations of collective effects concentrated mainly on instabilities of single or few bunches in electron storage rings. There, the strong radiation damping reduces the r...

Theoretical analysis and simulation of the influence of self-bunching effects and longitudinal space charge effects on the propagation of keV electron bunch produced by a novel S-band Micro-Pulse electron Gun

Science.gov (United States)

Zhao, Jifei; Lu, Xiangyang; Zhou, Kui; Yang, Ziqin; Yang, Deyu; Luo, Xing; Tan, Weiwei; Yang, Yujia

2016-06-01

As an important electron source, Micro-Pulse electron Gun (MPG) which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR), Free Electron Laser (FEL). The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY) curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC) effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.

Theoretical analysis and simulation of the influence of self-bunching effects and longitudinal space charge effects on the propagation of keV electron bunch produced by a novel S-band Micro-Pulse electron Gun

Energy Technology Data Exchange (ETDEWEB)

Zhao, Jifei; Lu, Xiangyang, E-mail: xylu@pku.edu.cn; Yang, Ziqin; Yang, Deyu; Tan, Weiwei; Yang, Yujia [Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, 100871 (China); Zhou, Kui; Luo, Xing [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China)

2016-06-15

As an important electron source, Micro-Pulse electron Gun (MPG) which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR), Free Electron Laser (FEL). The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY) curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC) effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.

Theoretical analysis and simulation of the influence of self-bunching effects and longitudinal space charge effects on the propagation of keV electron bunch produced by a novel S-band Micro-Pulse electron Gun

Directory of Open Access Journals (Sweden)

Jifei Zhao

2016-06-01

Full Text Available As an important electron source, Micro-Pulse electron Gun (MPG which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR, Free Electron Laser (FEL. The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.

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...

Generation and transport of double-bunch electron beams in the FLASH beamline

International Nuclear Information System (INIS)

Entrena Utrilla, Carlos Manuel

2014-10-01

The Free Electron Laser in Hamburg (FLASH) is part of the Deutsches Elektronen-Synchrotron (DESY) research center. Its linear accelerator produces high-quality electron bunches of up to about 1.2 GeV that are used in its undulator to generate short, intense, high-brilliance soft-X ray pulses with a wavelength from 4.2 nm to 45 nm with the SASE process. This characteristics make FLASH a leading facility worldwide in photon science and linear accelerator technologies, along with the Linac Coherent Light Source (in SLAC, Standford, USA), the FERMI rate at Elettra in Trieste (Italy) and SACLA (Japan). For several reasons, there is a substantial interest to accelerate two electron bunches with a final temporal distance of several hundreds of femtoseconds. These two bunches are generated on the photocathode within picoseconds from each other and accelerated within the same RF bucket (the same period of the RF (radio-frequency) accelerating fields). These experiments are of interest for two-color FEL for pump-probe experiments, and for the external injection of electrons in the future particle-driven plasma wakefield accelerator experiment, called FLASHForward, which will start in early 2016. This work analyzes the longitudinal dynamics of said double-bunches, from generation on the photocathode to the transport and compression through the linac. It is shown how a working point for a desired compression scenario (shape and final current of the bunches, and final distance between them) can be found with different numerical tracking procedures, and how the electrons can be experimentally generated and transported through the accelerator in the current layout, which was confirmed in a proof-of-concept experiment in late May 2014.

Development and testing of an ion probe for tightly-bunched particle beams

Energy Technology Data Exchange (ETDEWEB)

Ngo, M.; Pasour, J.

1996-06-01

Many high-energy physics experiments require a high-quality and well-diagnosed charged-particle beam (CPB). Precise knowledge of beam size, position, and charge distribution is often crucial to the success of the experiment. It is also important in many applications that the diagnostic used to determine the beam parameters be nonintercepting and nonperturbing. This requirement rules out many diagnostics, such as wire scanners, thin foils which produce Cerenkov or transition radiation, and even some rf cavity diagnostics. Particularly difficult to diagnose are tightly-focused (r{sub b} << 1 mm), short-duration (psec) beams, such as those in state-of-the-art or next-generation particle colliders. In this paper we describe an ion probe that is capable of penetrating the space-charge field of densely bunched CPBs without perturbation, thereby enabling the measurement of the microstructure of the bunch. This diagnostic probe uses a finely-focused stream of ions to interact with the CPB. Related techniques have been discussed in the literature. In fact, the present work evolved from an electron deflection diagnostic for CPBs that we previously described. A similar electron probe was tested even earlier at TRIUMF and in the Former Soviet Union. Electron probes have also been used to measure plasma sheaths and potentials and the neutralization of heavy ion beams. Also, Mendel has used an ion beam (22 keV He{sup +}) to probe rapidly varying fields in plasmas. The probe ions are injected across the beam tube and into the path of the high-energy CPB. The ions are deflected by the CPB, and the direction and magnitude of the deflection are directly related to the spatial and temporal charge distribution of the CPB. Easily-resolved deflections can be produced by microbunches having total charge on the order of a nCoul and pulse durations of a few psec. The deflected ions are monitored with a suitable detector, in this case a microchannel plate capable of detecting single ions.

Fast pulse beam generation systems for electron accelerators

International Nuclear Information System (INIS)

Koontz, R.F.

1977-01-01

The fast pulse beam generation system to supply the SLAC storage ring, SPEAR, by the two one nanosecond bunch electron beam pulses is described. Generation of these pulses is accomplished with a combination of a fast pulsed grided gun and a synchronized transverse beam chopper. Fast gun based on spherical cathode-grid assembly has output current up to 2As. Fast pulse amplifier system can handle trains of short pulses with repetition rates up to 40 MHz during the 1.6 μs normal accelerating time. Chopping deflector system consists of a resonant coaxial line with the deflecting plates. The resonator frequency is 39.667 MHz. A schematic diagram of the resonant system is shown. The fast beam pickup system has a one hundred picosecond rise time overrall. Fast beam generation and chopper systems permit to generate almost any short or single bunch beam profile needed for experiments

Bunch by bunch beam monitoring in 3rd and 4th generation light sources by means of single crystal diamond detectors and quantum well devices

Science.gov (United States)

Antonelli, M.; Di Fraia, M.; Tallaire, A.; Achard, J.; Carrato, S.; Menk, R. H.; Cautero, G.; Giuressi, D.; Jark, W. H.; Biasiol, G.; Ganbold, T.; Oliver, K.; Callegari, C.; Coreno, M.; De Sio, A.; Pace, E.

2012-10-01

New generation Synchrotron Radiation (SR) sources and Free Electron Lasers (FEL) require novel concepts of beam diagnostics to keep photon beams under surveillance, asking for simultaneous position and intensity monitoring. To deal with high power load and short time pulses provided by these sources, novel materials and methods are needed for the next generation BPMs. Diamond is a promising material for the production of semitransparent in situ X-ray BPMs withstanding the high dose rates of SR rings and high energy FELs. We report on the development of freestanding, single crystal CVD diamond detectors. Performances in both low and radio frequency SR beam monitoring are presented. For the former, sensitivity deviation was found to be approximately 2%; a 0.05% relative precision in the intensity measurements and a 0.1-μm precision in the position encoding have been estimated. For the latter, single-shot characterizations revealed sub-nanosecond rise-times and spatial precisions below 6 μm, which allowed bunch-by-bunch monitoring in multi-bunch operation. Preliminary measurements at the Fermi FEL have been performed with this detector, extracting quantitative intensity and position information for FEL pulses (~ 100 fs, energy 12 ÷ 60 eV), with a long-term spatial precision of about 85 μm results on FEL radiation damages are also reported. Due to their direct, low-energy band gap, InGaAs quantum well devices too may be used as fast detectors for photons ranging from visible to X-ray. Results are reported which show the capability of a novel InGaAs/InAlAs device to detect intensity and position of 100-fs-wide laser pulses.

Development of picosecond pulsed electron beam monitor

International Nuclear Information System (INIS)

Hosono, Y.; Nakazawa, M.; Ueda, T.; Kobayasi, T.; Yosida, Y.; Ohkuma, J.; Okuda, S.; Suemine, S.

1993-01-01

For the picosecond pulsed electron beam of a linear accelerator a simple monitor using an electric connector has been developed which is constructed with SMA, BNC, N type electric connector through pipe (inner diameter = 50 mm or 100 mm). Under the measurement conditions of peak current (26A-900A) and narrow pulse width (Pw = 10 ps(FWHM), Pw = 30 ps(FWHM)), the following characteristics of this monitor were obtained, (A) rise time is less than 25 ps (B) the amplitude of the monitor output pulse is proportional directly to the area of cross section of the electrode. (author)

Evolution of dense spatially modulated electron bunches

Science.gov (United States)

Balal, N.; Bratman, V. L.; Friedman, A.

2018-03-01

An analytical theory describing the dynamics of relativistic moving 1D electron pulses (layers) with the density modulation affected by a space charge has been revised and generalized for its application to the formation of dense picosecond bunches from linear accelerators with laser-driven photo injectors, and its good agreement with General Particle Tracer simulations has been demonstrated. Evolution of quasi-one-dimensional bunches (disks), for which the derived formulas predict longitudinal expansion, is compared with that for thin and long electron cylinders (threads), for which the excitation of non-linear waves with density spikes was found earlier by Musumeci et al. [Phys. Rev. Lett. 106(18), 184801 (2011)] and Musumeci et al. [Phys. Rev. Spec. Top. -Accel. Beams 16(10), 100701 (2013)]. Both types of bunches can be used for efficiency enhancement of THz sources based on the Doppler frequency up-shifted coherent spontaneous radiation of electrons. Despite the strong Coulomb repulsion, the periodicity of a preliminary modulation in dense 1D layers persists during their expansion in the most interesting case of a relatively small change in particle energy. However, the period of modulation increases and its amplitude decreases in time. In the case of a large change in electron energy, the uniformity of periodicity is broken due to different relativistic changes in longitudinal scales along the bunch: the "period" of modulation decreases and its amplitude increases from the rear to the front boundary. Nevertheless, the use of relatively long electron bunches with a proper preliminary spatial modulation of density can provide a significantly higher power and a narrower spectrum of coherent spontaneous radiation of dense bunches than in the case of initially short single bunches with the same charge.

Femtosecond single electron bunch generation by rotating longitudinal bunch phase space in magnetic field

International Nuclear Information System (INIS)

Yang, J.; Kondoh, T.; Kan, K.; Kozawa, T.; Yoshida, Y.; Tagawa, S.

2006-01-01

A femtosecond (fs) electron bunching was observed in a photoinjector with a magnetic compressor by rotating the bunch in longitudinal phase space. The bunch length was obtained by measuring Cherenkov radiation of the electron beam with a femtosecond streak camera technique. A single electron bunch with rms bunch length of 98 fs was observed for a 32 MeV electron beam at a charge of 0.17 nC. The relative energy spread and the normalized transverse emittance of the electron beam were 0.2% and 3.8 mm-mrad, respectively. The effect of space charge on the bunch compression was investigated experimentally for charges from 0.17 to 1.25 nC. The dependences of the relative energy spread and the normalized beam transverse emittance on the bunch charge were measured

COMMISSIONING OF THE DIGITAL TRANSVERSE BUNCH-BY-BUNCH FEEDBACK SYSTEM FOR THE TLS

International Nuclear Information System (INIS)

HU, K.H.; KUO, C.H.; CHOU, P.J.; LEE, D.; HSU, S.Y.; CHEN, J.; WANG, C.J.; HSU, K.T.; KOBAYASHI, K.; NAKAMURA, T.; CHAO, A.W.; WENG, W.T.

2006-01-01

Multi-bunch instabilities degrade beam quality through increased beam emittance, energy spread and even beam loss. Feedback systems are used to suppress multi-bunch instabilities associated with the resistive wall of the beam ducts, cavity-like structures, and trapped ions. A new digital transverse bunch-by-bunch feedback system has recently been commissioned at the Taiwan Light Source, and has replaced the previous analog system. The new system has the advantages that it enlarges the tune acceptance and improves damping for transverse instability at high currents, such that top-up operation is achieved. After a coupled-bunch transverse instability was suppressed, more than 350 mA was successfully stored during preliminary commissioning. In this new system, a single feedback loop simultaneously suppresses both horizontal and vertical multi-bunch instabilities. Investigating the characteristics of the feedback loop and further improving the system performances are the next short-term goals. The feedback system employs the latest generation of field-programmable gate array (FPGA) processor to process bunch signals. Memory has been installed to capture up to 250 msec of bunch oscillation signal, considering system diagnostics suitable to support various beam physics studies

Single-bunch beam loading on the SLAC two-mile accelerator

International Nuclear Information System (INIS)

Koontz, R.F.

1976-05-01

The experiments described were initially prompted by interest in the radiation loss of relativistic electron rings passing through periodic structures. Later the same experiments became relevant to the theory of energy loss of electrons in large storage rings. In both of these cases energy loss to the higher order modes of the respective structures could seriously limit their effective operation. In these experiments, single bunches of electrons with intensities up to 7 x 10 8 electrons per bunch are accelerated through the SLAC three-kilometer accelerator, and their energy spectra are analyzed. Early experiments over a wide energy range (900 MeV to 19 GeV) demonstrated that the energy loss was proportional to the total charge in the bunch but was independent of beam energy. The average energy loss of a single bunch normalized to 10 9 electrons was initially measured to be 38 MeV

Beam-induced heating / bunch length / RF and lessons for 2012

International Nuclear Information System (INIS)

Metral, E.

2012-01-01

Beam-induced heating has been observed here and there during the 2011 run when the bunch/beam intensity was increased and/or the bunch length was reduced. These observations are first reviewed before mentioning the recent news/work performed during the shutdown. In fact, several possible sources of heating exist and only the RF heating (i.e. coming from the real part of the longitudinal impedance of the machine components) is discussed in some detail in the present paper: 1) comparing the case of a Broad-Band (BB) vs. a Narrow-Band (NB) impedance; 2) discussing the beam spectrum; 3) reminding the usual solutions to avoid/minimize the RF heating; 4) reviewing the different heat transfer mechanisms; 5) mentioning that the synchronous phase shift is a measurement of the power loss and effective impedance. The three current 'hot' topics for the LHC performance, which are the VMTSA, TDI and MKI, are then analyzed in detail and some lessons for 2012 (and after) are finally drawn

Amplification of picosecond pulse by electron-beam pumped KrF laser amplifiers. Denshi beam reiki KrF laser zofukuki ni yoru piko byo pulse no zofuku

Energy Technology Data Exchange (ETDEWEB)

Okuda, I.; Tomie, T.; Owadano, Y.; Yano, M. (Electrotechnical Laboratory, Tsukuba (Japan))

1991-08-20

Experiments on the amplification of a picosecond pulse by electron-beam pumped KrF laser amplifiers were carried out for the purpose of its application to the field such as excitation light source for soft X-ray laser which requires large energy besides peak power. The picosecond pulse was amplified by a discharge pumped KrF amplifier and two electron-beam pumped KrF amplifiers(at the middle stage and the final stage). The energy of 4J, which was the largest energy for short pulse excimer laser so far, was obtained by these devices. About 90% of the window area of the final amplifier with 29cm diameter was filled by the input beam, and energy density of the picosecond beam reached 3.9 times saturation energy density. Measured energy of amplified spontaneous emission(ASE) showed good agreement with the theoretically estimated value. Most of ASE was derived from the discharge pumped laser as the first amplifier. As for the focused power density, the power density ratio of the picosecond pulse to ASE was estimated to be as large as 10{sup 5}. 11 refs., 4 figs.

Multi-bunch energy compensation in the NLC bunch compressor

International Nuclear Information System (INIS)

Zimmermann, F.; Raubenheimer, T.O.; Thomson, K.A.

1996-06-01

The task of the NLC bunch compressor is to reduce the length of each bunch in a train of 90 bunches from 4 mm, at extraction from the damping ring, to about 100 μm, suitable for injection into the X-band main linac. This task is complicated by longitudinal long-range wake fields and the multi-bunch beam loading in the various accelerating sections of the compressor. One possible approach to compensate the multi-bunch beam loading is to add two RF systems with slightly different frequencies (' Δf' scheme) to each accelerating section, as first proposed by Kikuchi. This paper summarizes the choice of parameters for three such compensating sections, and presents simulation results of combined single- and multi-bunch dynamics for four different NLC versions. The multi-bunch energy compensation is shown to be straightforward and its performance to be satisfactory

Nonlinear Delta-f Particle Simulations of Collective Effects in High-Intensity Bunched Beams

CERN Document Server

Qin, Hong; Hudson, Stuart R; Startsev, Edward

2005-01-01

The collective effects in high-intensity 3D bunched beams are described self-consistently by the nonlinear Vlasov-Maxwell equations.* The nonlinear delta-f method,** a particle simulation method for solving the nonlinear Vlasov-Maxwell equations, is being used to study the collective effects in high-intensity 3D bunched beams. The delta-f method, as a nonlinear perturbative scheme, splits the distribution function into equilibrium and perturbed parts. The perturbed distribution function is represented as a weighted summation over discrete particles, where the particle orbits are advanced by equations of motion in the focusing field and self-consistent fields, and the particle weights are advanced by the coupling between the perturbed fields and the zero-order distribution function. The nonlinear delta-f method exhibits minimal noise and accuracy problems in comparison with standard particle-in-cell simulations. A self-consistent 3D kinetic equilibrium is first established for high intensity bunched beams. The...

Electron Cloud Cyclotron Resonances in the Presence of a Short-bunch-length Relativistic Beam

International Nuclear Information System (INIS)

Celata, Christine; Celata, C.M.; Furman, Miguel A.; Vay, J.-L.; Wu, Jennifer W.

2008-01-01

Computer simulations using the 2D code 'POSINST' were used to study the formation of the electron cloud in the wiggler section of the positron damping ring of the International Linear Collider. In order to simulate an x-y slice of the wiggler (i.e., a slice perpendicular to the beam velocity), each simulation assumed a constant vertical magnetic field. At values of the magnetic field where the cyclotron frequency was an integral multiple of the bunch frequency, and where the field strength was less than approximately 0.6 T, equilibrium average electron densities were up to three times the density found at other neighboring field values. Effects of this resonance between the bunch and cyclotron frequency are expected to be non-negligible when the beam bunch length is much less than the product of the electron cyclotron period and the beam

Commissioning of FPGA-based Transverse and Longitudinal Bunch-by-Bunch Feedback System for the TLS

International Nuclear Information System (INIS)

Hu, K. H.; Kuo, C. H.; Lau, W. K.; Yeh, M. S.; Hsu, S. Y.; Chou, P. J.; Wang, M. H.; Lee, Demi; Chen, Jenny; Wang, C. J.; Hsu, K. T.; Kobayashi, K.; Nakamura, T.; Dehler, M.

2006-01-01

Multi-bunch instabilities deteriorate beam quality, increasing beam emittance, or even causing beam loss in the synchrotron light source. The feedback system is essential to suppress multi-bunch instabilities caused by the impedances of beam ducts, and trapped ions. A new FPGA based transverse and longitudinal bunch-by-bunch feedback system have been commissioned at the Taiwan Light Source recently, A single feedback loop is used to simultaneously suppress the horizontal and the vertical multi-bunch instabilities. Longitudinal instabilities caused by cavity-like structures are suppressed by the longitudinal feedback loop. The same FPGA processor is employed in the transverse feedback and the longitudinal feedback system respectively. Diagnostic memory is included in the system to capture the bunch oscillation signal, which supports various studies

Single-bunch beam breakup in a dielectric-lined waveguide

International Nuclear Information System (INIS)

Ng, King-Yuen.

1992-08-01

We examine beam breakup of a 100 nC I mm-long (rms) source bunch inside a cylindrical dielectric waveguide, with dielectric ε = 2.65 filling the radius between 7.5 and 9.0 mm. Only ∼ 78% of the bunch with an initial offset of 0.3 mm survives the passage of the 3.75 m waveguide. The loss is mainly due to the large deflections of some particles that are slowed down to nearly zero velocity. As a result, quadrupole focussing of any sort will not help. However, if the waveguide is shortened to 3.3 m, the loss reduces to only 5.5%

Considerations of bunch-spacing options for multi-bunch operation of the Tevatron Collider

International Nuclear Information System (INIS)

Dugan, G.

1989-01-01

This discussion will consider a number of points relevant to limitations, advantages and disadvantages of various arrangements of bunches in the Tevatron proton-antiproton collider. The considerations discussed here will be limited to: (a) bunch spacing symmetry and relation to the relative luminosity at B0 and D0 and the beam-beam interaction with separated beams; (b) bunch spacing constraints imposed by Main Ring RF coalescing and the optics of beam separation at B0 and D0; and (c) bunch spacing constraints imposed by injection and abort kicker timing requirements, and by the Antiproton Source RF unstacking process. 20 figs., 17 tabs

CEBAF Upgrade Bunch Length Measurements

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Mahmoud [Old Dominion Univ., Norfolk, VA (United States)

2016-05-01

Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

CORNELL: Bunch trains provide higher luminosity

Energy Technology Data Exchange (ETDEWEB)

Anon.

1995-09-15

The new colliding beam technique - ''bunch trains'' - at Cornell's electron-positron Storage Ring (CESR) has led to a new world record for colliding beam luminosity - 3.3 x 10{sup 32} cm{sup -2}s{sup -1}. In the bid to increase reaction rate for any particular process, this luminosity is pushed as high as possible. Once all other luminosityincreasing cards have been played, the only practical way of making a large gain in luminosity is to increase the frequency of bunch-bunch collisions by increasing the number of bunches stored in the ring. However this is not without its own problems: • If the two beams travel the same orbit, the n bunches in one beam collide with the n bunches of the other at 2n points around the ring, and the resulting cumulative nonlinear beam-beam effect (tune shift) severely limits the luminosity attainable at any interaction point. • The destabilizing wakefield effects of bunches on each other increase as the number of bunches increases and the spacing between them decreases. • The synchrotron radiation emitted by the beams becomes a severe problem as the total beam current is raised: to overcome these effects means supplying radiofrequency power to maintain the beam energy, carrying away heat from the vacuum chamber walls, pumping out desorbed gases, and controlling Xray backgrounds in the experiment. In 1979, CESR was designed to run with a single bunch of electrons and a single bunch of positrons circulating on the same orbit and colliding head-on at two diametrically opposite points in the ring, where the CLEO and CUSB experiments were then located. Ideally one could store multiple bunches and solve the multiple collision point problem by using separate rings for the two beams, as in the CERN ISR proton-proton collider and in the original DORIS two-ring configuration at DESY, Hamburg, making the two beams intersect only at the experiments. A less expensive version of this two-ring scheme was accomplished at CESR in 1983, using

Monolithic millimeter-wave and picosecond electronic technologies

International Nuclear Information System (INIS)

Talley, W.K.; Luhmann, N.C.

1996-01-01

Theoretical and experimental studies into monolithic millimeter-wave and picosecond electronic technologies have been undertaken as a collaborative project between the Lawrence Livermore National Laboratory (LLNL) and the University of California Department of Applied Science Coherent Millimeter-Wave Group under the auspices of the Laboratory Directed Research and Development Program at LLNL. The work involves the design and fabrication of monolithic frequency multiplier, beam control, and imaging arrays for millimeter-wave imaging and radar, as well as the development of high speed nonlinear transmission lines for ultra-wideband radar imaging, time domain materials characterization and magnetic fusion plasma applications. In addition, the Coherent Millimeter-Wave Group is involved in the fabrication of a state-of-the-art X-band (∼8-11 GHz) RF photoinjector source aimed at producing psec high brightness electron bunches for advanced accelerator and coherent radiation generation studies

Single-bunch beam loading on the SLAC two-mile accelerator

International Nuclear Information System (INIS)

Koontz, R.F.

1976-01-01

The experiments described were initially prompted by interest in the radiation loss of relativistic electron rings passing through periodic structures. Later, the same experiments became relevant to the theory of energy loss of electrons in large storage rings. In both of these cases, energy loss to the higher order modes of the respective structures could seriously limit their effective operation as acceleration devices. In these experiments, single bunches of electrons with intensities up to 7 x 10 8 electrons per bunch are accelerated through the SLAC three-kilometer accelerator, and their energy spectra are analyzed. Early experiments over a wide energy range (900 MeV to 19 GeV) demonstrated that the energy loss was proportional to the total charge in the bunch but was independent of beam energy. The average energy loss of a single bunch normalized to 10 9 electrons was initially measured to be 38 MeV. The experiments, including much of the equipment development, are described and are compared with theoretical predictions made to date

Theory of longitudinal instability for bunched electron and proton beams

International Nuclear Information System (INIS)

Ruggiero, A.G.

1977-01-01

A discussion is given of an original approach for the treatment of the longitudinal stability of high-intensity proton and electron bunches. The general analysis is divided in three steps. First, a search is made for a stationary bunch distribution which is matched to the external rf forces as well as to the current dependent induced fields. The existence of such distribution is questioned. Second, the stability of the stationary solution is checked by applying a small perturbation and observing whether this is initially damped or not. At this point a stability condition is derived in terms of current, surrounding impedance and bunch size. In the last step one should question what happens to the beam in case the stability condition is not satisfied. The problem here is the determination of the final bunch configuration. The originality of the approach stays in the combination of the three steps. All previous theories either consider only the first step or combine the second and third ones but disregard the first

Overall comparison of subpicosecond electron beam diagnostics by the polychromator, the interferometer and the femtosecond streak camera

CERN Document Server

Watanabe, T; Yoshimatsu, T; Sasaki, S; Sugiyama, Y; Ishi, K; Shibata, Y; Kondo, Y; Yoshii, K; Ueda, T; Uesaka, M

2002-01-01

Measurements of longitudinal bunch length of subpicosecond and picosecond electron beams have been performed by three methods with three radiation sources at the 35 MeV S-band twin liner accelerators at Nuclear Engineering Research Laboratory, University of Tokyo. The methods we adopt are the femtosecond streak camera with a nondispersive reflective optics, the coherent transition radiation (CTR) Michelson interferometer and the 10 ch polychromator that detects the spectrum of CTR and coherent diffraction radiation (CDR). The measurements by the two CTR methods were independently done with the streak camera and their results were consistent with one another. As a result, the reliability of the polychromator for the diagnostics of less than picosecond electron bunch and the usefulness of the diagnostics for the single shot measurement were verified. Furthermore, perfect nondestructive diagnostics for subpicosecond bunches was performed utilizing CDR interferometry. Then the good agreement between CDR interfero...

Effect of focusing field error during final beam bunching in heavy-ion-beam driven inertial confinement fusion

International Nuclear Information System (INIS)

Kikuchi, T.; Kawata, S.; Kawata, S.; Nakajima, M.; Horioka, K.

2006-01-01

Emittance growth due to the transverse focusing field error is investigated during the final beam bunching in the energy driver system of heavy ion inertial fusion. The beam bunch is longitudinally compressed during the transport with the field error in the continuous focusing (CF) or the alternating gradient (AG) field lattices. Numerical calculation results show the only 2% difference of the emittance growth between the cases with and without field error in the CF lattice. In the case of the AG lattice model with the field error of 10%, the emittance growth of 2.4 times is estimated, and the major difference between the CF and AG models is indicated from the numerical simulations. (author)

SuperB Bunch-By-Bunch Feedback R&D

Energy Technology Data Exchange (ETDEWEB)

Drago, A.; Beretta, M.; /Frascati; Bertsche, K.; Novokhatski, A.; /SLAC; Migliorati, M.; /Rome U.

2011-08-12

The SuperB project has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e{sup +}/e{sup -} Super Flavor Factory to achieve a peak luminosity > 10**36 cm{sup -2} s{sup -1}. The SuperB design is based on collisions with extremely low vertical emittance beams and high beam currents. A source of emittance growth comes from the bunch by bunch feedback systems producing high power correction signals to damp the beams. To limit any undesirable effect, a large R&D program is in progress, partially funded by the INFN Fifth National Scientific Committee through the SFEED (SuperB Feedback) project approved within the 2010 budget. The SuperB project [1] has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e{sup +}/e{sup -} Super Flavor Factory to achieve a peak luminosity > 10**36 cm{sup -2} s{sup -1}. In the last and current years, the machine layout has been deeply modified, in particular the main rings are now shorter and an option with high currents has been foreseen. In the fig.1 the new SuperB layout is shown. From bunch-by-bunch feedback point of view, the simultaneous presence in the machine parameters, of very low emittance, of the order of 5-10 pm in the vertical plane, and very high currents, at level of 4 Ampere for the Low Energy Ring, asks for designing very carefully the bunch-by-bunch feedback systems. The parameter list is presented in Fig. 2. The bunch-by-bunch feedback design must take care of the risky and exciting challenges proposed in the SuperB specifications, but it should consider also some other important aspects: flexibility in terms of being able to cope to unexpected beam behaviours [2], [3] legacy of previous version experience [4], [5] and internal powerful diagnostics [6] as in the systems previously used in PEP-II and DAFNE [7].

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 bunch shape monitor for high-intensity beam on the China ADS proton LINAC Injector II

Science.gov (United States)

Zhu, Guangyu; Wu, Junxia; Du, Ze; Zhang, Yong; Xue, Zongheng; Xie, Hongming; Wei, Yuan; Jing, Long; Jia, Huan

2018-05-01

The development, performance, and testing of the longitudinal bunch shape monitor, namely, the Fast Faraday Cup (FFC), are presented in this paper. The FFC is an invasive instrument controlled by a stepper motor, and its principle of operation is based on a strip line structure. The longitudinal bunch shape was determined by sampling a small part of the beam hitting the strip line through a 1-mm hole. The rise time of the detector reached 24 ps. To accommodate experiments that utilize high-intensity beams, the materials of the bunch shape monitor were chosen to sustain high temperatures. Water cooling was also integrated in the detector system to enhance heat transfer and prevent thermal damage. We also present an analysis of the heating caused by the beam. The bunch shape monitor has been installed and commissioned at the China ADS proton LINAC Injector II.

BUNCHED BEAM STOCHASTIC COOLING SIMULAITONS AND COMPARISON WITH DATA

Energy Technology Data Exchange (ETDEWEB)

BLASKIEWICZ,M.; BRENNAN, J.M.

2007-09-10

With the experimental success of longitudinal, bunched beam stochastic cooling in RHIC it is natural to ask whether the system works as well as it might and whether upgrades or new systems are warranted. A computer code, very similar to those used for multi-particle coherent instability simulations, has been written and is being used to address these questions.

Results on the interaction of an intense bunched electron beam with resonant cavities at 35 GHz

CERN Document Server

Gardelle, J; Rullier, J L; Vermare, C; Wuensch, Walter; Lidia, S M; Westenskow, G A; Donohue, J T; Meurdesoif, Y; Lekston, J M; MacKay, W W

1999-01-01

The Two-Beam Accelerator (TBA) concept is currently being investigated both at Lawrence Berkeley National Laboratory (LBNL) and at CERN. As part of this program, a 7 MeV, 1-kA electron beam produced by the PIVAIR accelerator at CESTA has been used to power a free electron laser (FEL) amplifier at 35 GHz. At the FEL exit, the bunched electron beam is transported and focused into a resonant cavity built by the CLIC group at CERN. The power and frequency of the microwave output generated when the bunched beam traverses two different cavities are measured. (7 refs).

CORNELL: Bunch trains provide higher luminosity

International Nuclear Information System (INIS)

Anon.

1995-01-01

The new colliding beam technique - ''bunch trains'' - at Cornell's electron-positron Storage Ring (CESR) has led to a new world record for colliding beam luminosity - 3.3 x 10 32 cm -2 s -1 . In the bid to increase reaction rate for any particular process, this luminosity is pushed as high as possible. Once all other luminosityincreasing cards have been played, the only practical way of making a large gain in luminosity is to increase the frequency of bunch-bunch collisions by increasing the number of bunches stored in the ring. However this is not without its own problems: • If the two beams travel the same orbit, the n bunches in one beam collide with the n bunches of the other at 2n points around the ring, and the resulting cumulative nonlinear beam-beam effect (tune shift) severely limits the luminosity attainable at any interaction point. • The destabilizing wakefield effects of bunches on each other increase as the number of bunches increases and the spacing between them decreases. • The synchrotron radiation emitted by the beams becomes a severe problem as the total beam current is raised: to overcome these effects means supplying radiofrequency power to maintain the beam energy, carrying away heat from the vacuum chamber walls, pumping out desorbed gases, and controlling Xray backgrounds in the experiment. In 1979, CESR was designed to run with a single bunch of electrons and a single bunch of positrons circulating on the same orbit and colliding head-on at two diametrically opposite points in the ring, where the CLEO and CUSB experiments were then located. Ideally one could store multiple bunches and solve the multiple collision point problem by using separate rings for the two beams, as in the CERN ISR proton-proton collider and in the original DORIS two-ring configuration at DESY, Hamburg, making the two beams intersect only at the experiments. A less expensive version of this two-ring scheme was accomplished at CESR in

Picosecond, single pulse electron linear accelerator

International Nuclear Information System (INIS)

Kikuchi, Riichi; Kawanishi, Masaharu

1979-01-01

The picosecond, single pulse electron linear accelerators, are described, which were installed in the Nuclear Engineering Laboratory of the University of Tokyo and in the Nuclear Radiation Laboratory of the Osaka University. The purpose of the picosecond, single pulse electron linear accelerators is to investigate the very short time reaction of the substances, into which gamma ray or electron beam enters. When the electrons in substances receive radiation energy, the electrons get high kinetic energy, and the energy and the electric charge shift, at last to the quasi-stable state. This transient state can be experimented with these special accelerators very accurately, during picoseconds, raising the accuracy of the time of incidence of radiation and also raising the accuracy of observation time. The outline of these picosecond, single pulse electron linear accelerators of the University of Tokyo and the Osaka University, including the history, the systems and components and the output beam characteristics, are explained. For example, the maximum energy 30 -- 35 MeV, the peak current 1 -- 8 n C, the pulse width 18 -- 40 ps, the pulse repetition rate 200 -- 720 pps, the energy spectrum 1 -- 1.8% and the output beam diameter 2 -- 5 mm are shown as the output beam characteristics of the accelerators in both universities. The investigations utilizing the picosecond single pulse electron linear accelerators, such as the investigation of short life excitation state by pulsed radiation, the dosimetry study of pulsed radiation, and the investigation of the transforming mechanism and the development of the transforming technology from picosecond, single pulse electron beam to X ray, vacuum ultraviolet ray and visual ray, are described. (Nakai, Y.)

Influence of laser parameters on the relativistic short electron bunches dynamics in linear accelerators based on RF-guns and development of associated diagnostics

International Nuclear Information System (INIS)

Vinatier, T.

2015-01-01

My thesis investigates dynamics and diagnostics related to short electron bunches, namely whose rms duration is not directly measurable by an electronic method locating the border at a few tens of picoseconds. The short nature of the bunch and the necessity of a high peak current for the applications imply strong space-charge forces leading to a degradation of beam properties, as its transverse emittance and duration. The main difficulty is to characterize, model and take into account these effects. The chapter 2 consists in the measurements of several properties of these bunches: charge, transverse emittance, energy and duration. The originality of my work is that I use simple methods, both on the theoretical (analytical at maximum) and technological (using only common elements of electron accelerators) point of view. I have developed a method of charge measurement from the measurement of the light intensity emitted by a scintillating screen following the interaction with an electron beam. I have also developed a method to measure the bunch mean energy with a steering magnet and a scintillating screen, via the displacement of the bunch centroid as a function of the field of the steering magnet. I have also adapted multi-parametric methods to measure the transverse emittance and duration of electron bunches. These indirect methods allow the determination of these properties from the measurement of other more accessible properties: the transverse dimensions for the transverse emittance and the energy spread for the duration. The chapter 3 consists in the comparison of the properties of short electron beams, single or longitudinally modulated, generated by 3 different methods: Injection of a short or longitudinally modulated laser pulse in an RF-gun; Magnetic compression in a chicane; and RF-compression in an accelerating structure (Velocity Bunching). I have shown that, at equal conditions of charge, the generation of short bunches thanks to a short laser pulse

Electro-Optic Sampling of Transient Electric Fields from Charged Particle Beams

Energy Technology Data Exchange (ETDEWEB)

Fitch, Michael James [Rochester U.

2000-01-01

The passage of a relativistic charged particle beam bunch through a structure is accompanied by transient electromagnetic fields. By causality, these fields must be behind the bunch, and are called "wakefields." The wakefields act back on the beam, and cause instabilities such as the beam break-up instability, and the headtail instability, which limit the luminosity of linear colliders. The wakefields are particularly important for short bunches with high charge. A great deal of effort is devoted to analytical and numerical calculations of wakefields, and wakefield effects. Experimental numbers are needed. In this thesis, we present measurements of the transient electric fields induced by a short high-charge electron bunch passing through a 6-way vacuum cross. These measurements are performed in the time domain using electro-optic sampling with a time resolution of approximately 5 picoseconds. With different orientations of the electro-optic crystal, we have measured different vector components of the electric field. The Fourier transform of the time-domain data yields the product of the beam impedance with the excitation spectrum of the bunch. Since the bunch length is known from streak camera measurements, the k loss factor is directly obtained. There is reasonably good agreement between the experimental k loss factor with calculations from the code MAFIA. To our knowledge, this is the first direct measurement of the k loss factor for bunch lengths shorter than one millimeter ( nns). We also present results of magnetic bunch compression (using a dipole chicane) of a high-charge photoinjector beam for two different UV laser pulse lengths on the pholocalhode. Al best compression, a 13.87 nC bunch was compressed to 0.66 mm (2.19 ps) rms, or a peak current of 3 kA. Other results from the photoinjeclor are given, and the laser system for pholocalhode excitation and electro-optic sampling is described.

A high resolution, single bunch, beam profile monitor

International Nuclear Information System (INIS)

Norem, J.

1992-01-01

Efficient linear colliders require very small beam spots to produce high luminosities with reasonable input power, which limits the number of electrons which can be accelerated to high energies. The small beams, in turn, require high precision and stability in all accelerator components. Producing, monitoring and maintaining beams of the required quality has been, and will continue to be, difficult. A beam monitoring system which could be used to measure beam profile, size and stability at the final focus of a beamline or collider has been developed and is described here. The system uses nonimaging bremsstrahlung optics. The immediate use for this system would be examining the final focus spot at the SLAC/FFTB. The primary alternatives to this technique are those proposed by P. Chen / J. Buon, which analyses the energy and angular distributions of ion recoils to determine the aspect ratio of the electron bunch, and a method proposed by Shintake, which measures intensity variation of compton backscattered photons as the beam is moved across a pattern of standing waves produced by a laser

A Main Ring bunch length monitor by detecting two frequency components of the beam

International Nuclear Information System (INIS)

Ieiri, T.; Jackson, G.

1989-01-01

The bunch length is measured by detecting two revolution frequency harmonics of the beam and taking the ratio of their amplitudes. Two heterodyne receivers have been made to direct them, one at 53MHz and the other at 159MHz. These signals are picked-up by a stripline detector. An analog circuit provides a signal proportional to the bunch length. The monitor measures variation of the bunch length as a function of time in the Main Ring. The measured signal, which sometimes shows that the bunches are tumbling in phase space, can be damped by feedback to the RF amplitude modulator. 9 refs., 12 figs., 1 tab

Design Studies for a High Current Bunching System for CLIC Test Facility (CTF3) Drive Beam

CERN Document Server

Thiery, Y.; Le Duff, J.

2000-01-01

A bunching system is proposed for the initial stage of CTF3 which consists of one (two) 3 GHz prebunchers and one 3 GHz travelling wave (TW) buncher with variable phase velocities. The electron beam is emitted from a 140 KV DC gun. Since the macropulse beam current (3.5 A) at the exit of the TW buncher is rather high, inside the TW buncher one has to take the beam loading effect into consideration. By using PARMELA, it is shown numerically that the bunching system can provide the bunches whose properties satisfy the design requirement of CTF3. The 0.8 m long TW buncher working at 2pi/3 mode has two phase velocities, 0.75 and 1. The dimensions of the caities in the two phase velocity regions are proposed considering the beam loading effect. The transient beam loading effect and the multibunch transverse instabilities are studied numerically, and it is concluded that higher order mode couplers should be installed in the TW buncher with the loaded quality factor of the dipole mode lower than 80.

The beam bunching and transport system of the Argonne positive ion injector

International Nuclear Information System (INIS)

Den Hartog, P.K.; Bogaty, J.M.; Bollinger, L.M.; Clifft, B.E.; Pardo, R.C.; Shepard, K.W.

1989-01-01

A new positive ion injector (PII) is currently under construction at Argonne that will replace the existing 9-MV tandem electrostatic accelerator as an injector into ATLAS. It consists of an electron-cyclotron resonance-ion source on a 350-kV platform injecting into a superconducting linac optimized for very slow (β ≤ .007 c) ions. This combination can potentially produce even higher quality heavy-ion beams than are currently available from the tandem since the emittance growth within the linac is largely determined by the quality of the bunching and beam transport. The system we have implemented uses a two-stage bunching system, composed of a 4-harmonic gridded buncher located on the ECR high-voltage platform and a room temperature spiral-loaded buncher of novel design. A sinusoidal beam chopper is used for removal of tails. The beam transport is designed to provide mass resolution of M/ΔM > 250 and a doubly-isochronous beamline is used to minimize time spread due to path length differences. 4 refs., 2 figs

The beam bunching and transport system of the Argonne positive ion injector

Energy Technology Data Exchange (ETDEWEB)

Den Hartog, P.K.; Bogaty, J.M.; Bollinger, L.M.; Clifft, B.E.; Pardo, R.C.; Shepard, K.W.

1989-01-01

A new positive ion injector (PII) is currently under construction at Argonne that will replace the existing 9-MV tandem electrostatic accelerator as an injector into ATLAS. It consists of an electron-cyclotron resonance-ion source on a 350-kV platform injecting into a superconducting linac optimized for very slow (..beta.. less than or equal to .007 c) ions. This combination can potentially produce even higher quality heavy-ion beams than are currently available from the tandem since the emittance growth within the linac is largely determined by the quality of the bunching and beam transport. The system we have implemented uses a two-stage bunching system, composed of a 4-harmonic gridded buncher located on the ECR high-voltage platform and a room temperature spiral-loaded buncher of novel design. A sinusoidal beam chopper is used for removal of tails. The beam transport is designed to provide mass resolution of M/..delta..M > 250 and a doubly-isochronous beamline is used to minimize time spread due to path length differences. 4 refs., 2 figs.

Analysis of the high frequency longitudinal instability of bunched beams using a computer model

International Nuclear Information System (INIS)

Messerschmid, E.; Month, M.

1976-01-01

The effects of high frequency longitudinal forces on bunched beams are investigated using a computer model. These forces are thought to arise from the transfer of energy between the beam and various structures in the vacuum chamber, this coupling being characterized by a longitudinal impedance function. The simulation is performed with a passive cavity-like element. It is found that the instability can be generated if three conditions are fulfilled: (1) the impedance must be sufficiently large, (2) the induced field must have a fast wake, and (3) the frequency of the induced field must be high enough. In particular, it is shown that the coasting beam threshold criterion for the longitudinal impedance accurately describes the onset of instability, if local values along the bunch of energy spread and current are used. It is also found that the very fast initial growth rate is in good agreement with linear theory and that the coasting beam overshoot expression may be used as a rough guide of the limiting growth for unstable bunches. Concerning the wake field, it is shown how the instability tends to disappear as the fields persist longer. It is furthermore demonstrated that as the wavelength of the unstable mode is increased, initially unstable conditions begin to weaken and vanish. This, it should be emphasized, is primarily a result of the strong correlation between the unstable mode frequency and the time rate of attenuation of the induced fields. ISR parameters are used throughout and a correspondence between the microwave instability observed in the ISR bunches and the simulated instability is suggested. (Auth.)

Electro-optic methods for longitudinal bunch diagnostics at FLASH

International Nuclear Information System (INIS)

Steffen, B.R.

2007-07-01

Precise measurements of the temporal profile of sub-picosecond electron bunches are of high interest for the optimization and operation of VUV and X-ray free electron lasers. In this thesis, the shortest electro-optic signals measured so far for electron bunch diagnostics are presented, reaching a time resolution of better than 50 fs (rms). The e ects that introduce signal distortions and limit the time resolution are studied in numerical simulations for different electro-optic detection materials and techniques. The time resolution is mainly limited by lattice resonances of the electro-optic crystal. Electro-optic signals as short as 54 fs (rms) are obtained with gallium phosphide (GaP) crystals in a crossed polarizer detection scheme using temporally resolved electro-optic detection. Measuring near crossed polarization, where the electro-optic signal is proportional to the velocity field of the relativistic electron bunch, the shortest obtained signal width is 70 fs (rms). The electro-optic signals are compared to electron bunch shapes that are measured simultaneously with a transverse deflecting structure with 20 fs resolution. Numerical simulations using the bunch shapes as determined with the transverse deflecting cavity as input data are in excellent agreement with electro-optical signals obtained with GaP, both for temporally and spectrally resolved measurements. In the case of zinc telluride (ZnTe) the observed signals are slightly broader and significantly smaller than expected from simulations. These discrepancies are probably due to the poor optical quality of the available ZnTe crystals. (orig.)

Electro-optic methods for longitudinal bunch diagnostics at FLASH

Energy Technology Data Exchange (ETDEWEB)

Steffen, B.R.

2007-07-15

Precise measurements of the temporal profile of sub-picosecond electron bunches are of high interest for the optimization and operation of VUV and X-ray free electron lasers. In this thesis, the shortest electro-optic signals measured so far for electron bunch diagnostics are presented, reaching a time resolution of better than 50 fs (rms). The e ects that introduce signal distortions and limit the time resolution are studied in numerical simulations for different electro-optic detection materials and techniques. The time resolution is mainly limited by lattice resonances of the electro-optic crystal. Electro-optic signals as short as 54 fs (rms) are obtained with gallium phosphide (GaP) crystals in a crossed polarizer detection scheme using temporally resolved electro-optic detection. Measuring near crossed polarization, where the electro-optic signal is proportional to the velocity field of the relativistic electron bunch, the shortest obtained signal width is 70 fs (rms). The electro-optic signals are compared to electron bunch shapes that are measured simultaneously with a transverse deflecting structure with 20 fs resolution. Numerical simulations using the bunch shapes as determined with the transverse deflecting cavity as input data are in excellent agreement with electro-optical signals obtained with GaP, both for temporally and spectrally resolved measurements. In the case of zinc telluride (ZnTe) the observed signals are slightly broader and significantly smaller than expected from simulations. These discrepancies are probably due to the poor optical quality of the available ZnTe crystals. (orig.)

A linear radiofrequency quadrupole ion trap for the cooling and bunching of radioactive ion beams

CERN Document Server

Kellerbauer, A G; Dilling, J; Henry, S; Herfurth, F; Kluge, H J; Lamour, E; Moore, R B; Scheidenberger, C; Schwarz, S; Sikler, G; Szerypo, J

2002-01-01

A linear radiofrequency quadrupole ion guide and beam buncher has been installed at the ISOLTRAP mass spectrometry experiment at the ISOLDE facility at CERN. The apparatus is being used as a beam cooling, accumulation, and bunching system. It operates with a buffer gas that cools the injected ions and converts the quasicontinuous 60- keV beam from the ISOLDE facility to 2.5-keV beam pulses with improved normalized transverse emittance. Recent measurements suggest a capture efficiency of the ion guide of up to 40% and a cooling and bunching efficiency of at least 12% which is expected to still be increased. The improved ISOLTRAP setup has so far been used very successfully in three on-line experiments. (12 refs).

Extremely short relativistic-electron-bunch generation in the laser wakefield via novel bunch injection scheme

Directory of Open Access Journals (Sweden)

A. G. Khachatryan

2004-12-01

Full Text Available Recently a new electron-bunch injection scheme for the laser wakefield accelerator has been proposed [JETP Lett. 74, 371 (2001JTPLA20021-364010.1134/1.1427124; Phys. Rev. E 65, 046504 (2002PLEEE81063-651X10.1103/PhysRevE.65.046504]. In this scheme, a low energy electron bunch, sent in a plasma channel just before a high-intensity laser pulse, is trapped in the laser wakefield, considerably compressed and accelerated to an ultrarelativistic energy. In this paper we show the possibility of the generation of an extremely short (on the order of 1   μm long or a few femtoseconds in duration relativistic-electron-bunch by this mechanism. The initial electron bunch, which can be generated, for example, by a laser-driven photocathode rf gun, should have an energy of a few hundred keVs to a few MeVs, a duration in the picosecond range or less and a relatively low concentration. The trapping conditions and parameters of an accelerated bunch are investigated. The laser pulse dynamics as well as a possible experimental setup for the demonstration of the injection scheme are also considered.

Higher-order photon bunching in a semiconductor microcavity

DEFF Research Database (Denmark)

Assmann, M.; Veit, F.; Bayer, M.

2009-01-01

Quantum mechanically indistinguishable particles such as photons may show collective behavior. Therefore, an appropriate description of a light field must consider the properties of an assembly of photons instead of independent particles. We have studied multiphoton correlations up to fourth order...... in the single-mode emission of a semiconductor microcavity in the weak and strong coupling regimes. The counting statistics of single photons were recorded with picosecond time resolution, allowing quantitative measurement of the few-photon bunching inside light pulses. Our results show bunching behavior...

Effects of energy chirp on bunch length measurement in linear accelerator beams

Science.gov (United States)

Sabato, L.; Arpaia, P.; Giribono, A.; Liccardo, A.; Mostacci, A.; Palumbo, L.; Vaccarezza, C.; Variola, A.

2017-08-01

The effects of assumptions about bunch properties on the accuracy of the measurement method of the bunch length based on radio frequency deflectors (RFDs) in electron linear accelerators (LINACs) are investigated. In particular, when the electron bunch at the RFD has a non-negligible energy chirp (i.e. a correlation between the longitudinal positions and energies of the particle), the measurement is affected by a deterministic intrinsic error, which is directly related to the RFD phase offset. A case study on this effect in the electron LINAC of a gamma beam source at the Extreme Light Infrastructure-Nuclear Physics (ELI-NP) is reported. The relative error is estimated by using an electron generation and tracking (ELEGANT) code to define the reference measurements of the bunch length. The relative error is proved to increase linearly with the RFD phase offset. In particular, for an offset of {{7}\\circ} , corresponding to a vertical centroid offset at a screen of about 1 mm, the relative error is 4.5%.

Simultaneous detection of longitudinal and transverse bunch signals at ANKA

Energy Technology Data Exchange (ETDEWEB)

Kehrer, Benjamin; Blomley, Edmund; Brosi, Miriam; Bruendermann, Erik; Hiller, Nicole; Mueller, Anke-Susanne; Steinmann, Johannes; Schedler, Manuel; Schuh, Marcel; Schoenfeldt, Patrik; Smale, Nigel [Karlsruhe Institute of Technology, Karlsruhe (Germany); Schuetze, Paul [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany)

2016-07-01

The ANKA storage ring offers different operation modes including the short-bunch mode with bunch lengths tuned down to a few picoseconds. This can lead to the occurrence of microwave instabilities coupled to the emission of coherent synchrotron radiation (CSR) in the so-called 'bursts'. To study this CSR instability we use several turn-by-turn enabled detector systems to synchronously measure both the THz signal as well as bunch profiles. The different detectors are placed at different locations around the storage ring. Here we discuss the experimental setup and calibration of the various systems' synchronisation.

Production of high-quality electron bunches by dephasing and beam loading in channeled and unchanneled laser plasma accelerators

International Nuclear Information System (INIS)

Geddes, C.G.R.; Toth, Cs.; Tilborg, J. van; Esarey, E.; Schroeder, C.B.; Bruhwiler, D.; Nieter, C.; Cary, J.; Leemans, W.P.

2005-01-01

High-quality electron beams, with a few 10 9 electrons within a few percent of the same energy above 80 MeV, were produced in a laser wakefield accelerator by matching the acceleration length to the length over which electrons were accelerated and outran (dephased from) the wake. A plasma channel guided the drive laser over long distances, resulting in production of the high-energy, high-quality beams. Unchanneled experiments varying the length of the target plasma indicated that the high-quality bunches are produced near the dephasing length and demonstrated that channel guiding was more stable and efficient than relativistic self-guiding. Consistent with these data, particle-in-cell simulations indicate production of high-quality electron beams when trapping of an initial bunch of electrons suppresses further injection by loading the wake. The injected electron bunch is then compressed in energy by dephasing, when the front of the bunch begins to decelerate while the tail is still accelerated

Multi-bunch feedback systems

CERN Document Server

Lonza, M

2008-01-01

Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. The advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. The lecture will first introduce coupled-bunch instabilities analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedbacks systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback sy...

Multi-bunch Feedback Systems

CERN Document Server

Lonza, M.

2014-12-19

Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. We first introduce coupled-bunch instabilities, analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedback systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback systems. The main co...

Single bunch beam breakup in linacs and BNS damping

International Nuclear Information System (INIS)

Toyomasu, Takanori

1991-12-01

We study a single-bunch beam breakup (BBU) problem by a macro-particle model. We consider both the BBU solution and the Landau damping solution which includes the Balakin-Novokhatsky-Smirnov (BNS) damping. In the BBU solution, we get an analytic solution which includes both the Chao-Richter-Yao solution and the two-particle model solution and which agrees well with simulation. The solution can also be used in a multi-bunch case. In the Landau damping solution, we can be see the mechanism of Landau damping formally and can get some insights into BNS damping. We confirm that a two-particle model criterion for BNS damping is a good one. We expect that the two-particle model criterion is represented by the first order interaction in Landau damping solution of a macro-particle model. (author)

Effect of the long-term memory on the beam break-up instability of a single bunch in storage rings

International Nuclear Information System (INIS)

Pestrikov, D.V.

2009-01-01

We study modifications of the beam break-up instability of transverse coherent oscillations of a single bunch which occur in storage rings due to weak wakefields decaying longer than the revolution period of particles. The long-term part of the wake results in the eigenmode spectra of coherent oscillations. Both stable and unstable modes are found for coherent oscillations of a monochromatic bunch. The single turn wakefields result in the beam break-up coherent oscillations of the bunch. The found eigenmode spectrum does not contain a leading unstable mode. Despite the exponential increase in time of the eigenmodes, both self-consistent and the beam break-up parts of the coherent oscillations indicate similar and non-exponential time dependencies. The beam break-up behavior dominates, if the wake memory is weak.

Femtosecond resolved diagnostics for electron beam and XUV seed temporal overlap at sFLASH

International Nuclear Information System (INIS)

Tarkeshian, Roxana

2012-02-01

sFLASH is a seeded experiment at the Free-Electron Laser FLASH in Hamburg. It uses a 38 nm High-Harmonic-Generation (HHG) scheme to seed the FEL-process in a 10m long variable-gap undulator. The temporal overlap between the electron and HHG pulses is critical to the seeding process. The use of a 3 rd harmonic accelerating module provides a high current electron beam with ∝ (400 fs) FWHM bunch duration. The duration of the HHG laser pulse is ≤ (30 fs) FWHM . The desired overlap is achieved in two steps. Firstly, the HHG drive laser is brought to temporal overlap with the incoherent spontaneous radiation from an upstream undulator with picosecond resolution. The temporal overlap is periodically monitored using a streak camera installed in the linear accelerator tunnel. Next, the coherent radiation from an undulator is used to determine the exact overlap of the electron beam in a modulator-radiator set-up with sub-picosecond resolution. The physical and technical principles of the setup providing the temporal overlap are described. Results of the system are analyzed. An analytical approach and simulation results for the performance of the seeding experiment are presented. First attempts at demonstration of seeding are discussed. Strategies for optimizing overlap conditions are presented. (orig.)

Demonstration of cathode emittance dominated high bunch charge beams in a DC gun-based photoinjector

Energy Technology Data Exchange (ETDEWEB)

Gulliford, Colwyn, E-mail: cg248@cornell.edu; Bartnik, Adam, E-mail: acb20@cornell.edu; Bazarov, Ivan; Dunham, Bruce; Cultrera, Luca [CLASSE, Cornell University, 161 Synchrotron Drive Ithaca, New York 14853-8001 (United States)

2015-03-02

We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9–9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers.

Hollow bunches production

CERN Document Server

Hancock, S

2017-01-01

Hollow bunches address the issue of high-brightnessbeams suffering from transverse emittance growth in a strongspace charge regime. During the Proton Synchrotron (PS)injection plateau, the negative space charge tune shift canpush the beam onto theQy=6integer resonance. Modify-ing the longitudinal bunch profile in order to reduce the peakline charge density alleviates the detrimental impact of spacecharge. To this end we first produce longitudinally hollowphase space distributions in the PS Booster by exciting aparametric resonance with the phase loop feedback system.These inherently flat bunches are then transferred to the PS,where the beam becomes less prone to the emittance growthcaused by the integer resonance.During the late 2016 machine development sessions inthe PS Booster we profited from solved issues from 2015and managed to reliably extract hollow bunches of1.3eVsmatched longitudinal area. Furthermore, first results to cre-ate hollow bunches with larger longitudinal emittances to-wards the LHC Inject...

Experimental investigation of the longitudinal beam dynamics in a photoinjector using a two-macroparticle bunch

Directory of Open Access Journals (Sweden)

P. Piot

2006-05-01

Full Text Available We have developed a two-macroparticle bunch to explore the longitudinal beam dynamics through various components of the Fermilab/NICADD photoinjector. Such a two-macroparticle bunch is generated by splitting the ultraviolet pulse from the photocathode drive laser. The presented method allows the exploration of radio-frequency-induced compression in the 1.625 cell radio frequency gun and the booster cavity. It also allows a direct measurement of the momentum compaction of the magnetic bunch compressor. The measurements are compared with analytical and numerical models.

Longitudinal bunch deformation of a multi-bunched beam in the TRISTAN Accumulation Ring

International Nuclear Information System (INIS)

Obina, T.; Satoh, K.; Kasuga, T.; Funakoshi, Y.; Tobiyama, M.

1997-01-01

A remarkable bunch deformation has been observed in the TRISTAN Accumulation Ring (AR) during multi-bunch operations. When two bunches that have different populations are stored in the ring, the bunch length of the weaker bunch is longer than that of the stronger one. The phenomenon can be explained as an effect of wake fields due to higher-order modes (HOMs) of accelerating cavities. We tried to find out the frequency of the mode and the strength of the wake field, and introduced a new technique called a test bunch measurement. The estimated field strength from the experiment shows a reasonable agreement with the calculation of HOM impedance. copyright 1997 American Institute of Physics

High-brightness electron beam diagnostics at the ATF

International Nuclear Information System (INIS)

Wang, X.J.; Ben-Zvi, I.

1996-01-01

The Brookhaven Accelerator Test Facility (ATF) is a dedicated user facility for accelerator physicists. Its design is optimized to explore laser acceleration and coherent radiation production. To characterize the low-emittance, picoseconds long electron beam produced by the ATF's photocathode RF gun, we have installed electron beam profile monitors for transverse emittance measurement, and developed a new technique to measure electron beam pulse length by chirping the electron beam energy. We have also developed a new technique to measure the ps slice emittance of a 10 ps long electron beam. Stripline beam position monitors were installed along the beam to monitor the electron beam position and intensity. A stripline beam position monitor was also used to monitor the timing jitter between the RF system and laser pulses. Transition radiation was used to measure electron beam energy, beam profile and electron beam bunch length

A multi-channel THz and infrared spectrometer for femtosecond electron bunch diagnostics by single-shot spectroscopy of coherent radiation

Energy Technology Data Exchange (ETDEWEB)

Wesch, Stephan; Schmidt, Bernhard; Behrens, Christopher; Delsim-Hashemi, Hossein; Schmueser, Peter

2011-08-15

The high peak current required in free-electron lasers (FELs) is realized by longitudinal compression of the electron bunches to sub-picosecond length. In this paper, a frequency-domain diagnostic method is described that is capable of resolving structures in the femtosecond regime. A novel in-vacuum spectrometer has been developed for spectroscopy of coherent radiation in the THz and infrared range. The spectrometer is equipped with five consecutive dispersion gratings and 120 parallel readout channels; it can be operated either in short wavelength mode (5-44 {mu}m) or in long wavelength mode (45-430 {mu}m). Fast parallel readout permits the spectroscopy of coherent radiation from single electron bunches. Test measurements at the soft X-ray free-electron laser FLASH, using coherent transition radiation, demonstrate excellent performance of the spectrometer. The high sensitivity down to a few micrometers allows study of short bunch features caused for example by microbunching e ects in magnetic chicanes. The device is planned for use as an online bunch profile monitor during regular FEL operation. (orig.)

A multi-channel THz and infrared spectrometer for femtosecond electron bunch diagnostics by single-shot spectroscopy of coherent radiation

International Nuclear Information System (INIS)

Wesch, Stephan; Schmidt, Bernhard; Behrens, Christopher; Delsim-Hashemi, Hossein; Schmueser, Peter

2011-08-01

The high peak current required in free-electron lasers (FELs) is realized by longitudinal compression of the electron bunches to sub-picosecond length. In this paper, a frequency-domain diagnostic method is described that is capable of resolving structures in the femtosecond regime. A novel in-vacuum spectrometer has been developed for spectroscopy of coherent radiation in the THz and infrared range. The spectrometer is equipped with five consecutive dispersion gratings and 120 parallel readout channels; it can be operated either in short wavelength mode (5-44 μm) or in long wavelength mode (45-430 μm). Fast parallel readout permits the spectroscopy of coherent radiation from single electron bunches. Test measurements at the soft X-ray free-electron laser FLASH, using coherent transition radiation, demonstrate excellent performance of the spectrometer. The high sensitivity down to a few micrometers allows study of short bunch features caused for example by microbunching e ects in magnetic chicanes. The device is planned for use as an online bunch profile monitor during regular FEL operation. (orig.)

FEL research and development at the SLAC sub-picosecond photon source, SPPS

International Nuclear Information System (INIS)

Bentson, L.; Bolton, P.; Bong, E.; Emma, P.; Galayda, J.; Hastings, J.; Krejcik, P.; Rago, C.; Rifkin, J.; Spencer, C.M.

2003-01-01

An upgrade project to the SLAC linac allows ultra-short electron bunches to be interleaved with the routine high-energy physics program operation, for use with an undulator to produce short-pulse, high-brightness X-rays. The linac upgrade comprises of the installation in the summer of 2002 of a bunch compressor chicane of similar design to the Linac Coherent Light Source (LCLS) project. A final compression stage in the high-energy Final Focus Test Beam (FFTB) line compresses the 28 GeV, 3.4 nC electron bunch to 80 fs FWHM, where a 5 m section of undulator (K=4.45) will produce 1.5 A X-rays with 3x10 7 photons per pulse and a peak brightness of 4x10 24 photons mm -2 mrad -2 s -1 (0.1% BW). The facility will allow us to test the dynamics and associated technology of bunch compression and gain valuable experience for the LCLS using the SLAC linac. New ultra-short electron bunch diagnostic techniques will be developed hand in hand with the same ultra-fast laser technology to be used for LCLS. Issues of high peak power (27 GW) X-ray transport and optics can be addressed at this facility as well as pump-probe and ultra-fast laser timing and stability issues

LHC Report: spring cleaning over, bunches of luminosity

CERN Multimedia

CERN Bulletin

2011-01-01

Scrubbing was completed on Wednesday 13 April. The run had seen over 1000 bunches per beam successfully circulating at 450 GeV. Measurements showed that electron cloud activity in the cold regions had been suppressed. A decrease of vacuum activity in the warm regions demonstrated that the cleaning had also achieved the required results there. As discussed in the last Bulletin, the scrubbing was performed with high intensity bunches with 50 nanosecond spacing. Given the potential luminosity performance with this spacing (more bunches, higher bunch intensity from the injectors) and in the light of the results of the scrubbing run, the decision was taken to continue the 2011 physics run with this bunch spacing.   A few issues with 50 nanosecond spacing had to be resolved when standard operations for luminosity production resumed. Once things had been tidied up, stable beams were provided for the experiments, firstly with 228 bunches per beam and then with 336 bunches per beam. The 336 bunch fill that w...

Analysis of bunch by bunch oscillations with bunch trains at injection into LHC at 25 ns bunch spacing

CERN Document Server

Bartosik, H

2012-01-01

An MD on August 26, 2011 was dedicated to injection studies of bunch trains with 25 ns spacing and nominal intensity of approximately 1×10(11) protons per bunch. Due to an electrical glitch, the MD was stopped after two attempts of injecting a train of 48 bunches for beam 2. Both injections were aborted after less than 0.1 s. In particular, the first attempt with transverse damper on was dumped after 1000 turns while the second attempt with transverse damper off was dumped after 500 turns only. In this note, an analysis of the bunch by bunch oscillation data recorded with the post-mortem system from the transverse damper is presented. The presented data clearly shows the presence of instabilities that affect mainly the second half of the batch. This is compatible with what would be expected qualitatively in the presence of the electron cloud effect.

Multiple-bunch-length operating mode design for a storage ring using hybrid low alpha and harmonic cavity method

Energy Technology Data Exchange (ETDEWEB)

Gao, Weiwei, E-mail: gaomqr@mail.ustc.edu.cn [College of Mathematics and Physics, Fujian University of Technology, Fuzhou 350118 (China); Wang, Lin; Li, Heting [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029 (China)

2017-03-11

In this paper we design a simultaneous three bunch length operating mode at the HLS-II (Hefei Light Source II) storage ring by installing two harmonic cavities and minimizing the momentum compaction factor. The short bunches (2.6 mm) presented in this work will meet the requirement of coherent millimeter-wave and sub-THz radiation experiments, while the long bunches (20 mm) will efficiently increase the total beam current. Therefore, this multiple-bunch-length operating mode allows present synchrotron users and coherent millimeter-wave users (or sub THz users) to carry out their experiments simultaneously. Since the relatively low energy characteristic of HLS-II we achieve the multiple-bunch-length operating mode without multicell superconducting RF cavities, which is technically feasible.

Long bunch trains measured using a prototype cavity beam position monitor for the Compact Linear Collider

Directory of Open Access Journals (Sweden)

F. J. Cullinan

2015-11-01

Full Text Available The Compact Linear Collider (CLIC requires beam position monitors (BPMs with 50 nm spatial resolution for alignment of the beam line elements in the main linac and beam delivery system. Furthermore, the BPMs must be able to make multiple independent measurements within a single 156 ns long bunch train. A prototype cavity BPM for CLIC has been manufactured and tested on the probe beam line at the 3rd CLIC Test Facility (CTF3 at CERN. The transverse beam position is determined from the electromagnetic resonant modes excited by the beam in the two cavities of the pickup, the position cavity and the reference cavity. The mode that is measured in each cavity resonates at 15 GHz and has a loaded quality factor that is below 200. Analytical expressions for the amplitude, phase and total energy of signals from long trains of bunches have been derived and the main conclusions are discussed. The results of the beam tests are presented. The variable gain of the receiver electronics has been characterized using beam excited signals and the form of the signals for different beam pulse lengths with the 2/3  ns bunch spacing has been observed. The sensitivity of the reference cavity signal to charge and the horizontal position signal to beam offset have been measured and are compared with theoretical predictions based on laboratory measurements of the BPM pickup and the form of the resonant cavity modes as determined by numerical simulation. Finally, the BPM was calibrated so that the beam position jitter at the BPM location could be measured. It is expected that the beam jitter scales linearly with the beam size and so the results are compared to predicted values for the latter.

Long bunch trains measured using a prototype cavity beam position monitor for the Compact Linear Collider

Science.gov (United States)

Cullinan, F. J.; Boogert, S. T.; Farabolini, W.; Lefevre, T.; Lunin, A.; Lyapin, A.; Søby, L.; Towler, J.; Wendt, M.

2015-11-01

The Compact Linear Collider (CLIC) requires beam position monitors (BPMs) with 50 nm spatial resolution for alignment of the beam line elements in the main linac and beam delivery system. Furthermore, the BPMs must be able to make multiple independent measurements within a single 156 ns long bunch train. A prototype cavity BPM for CLIC has been manufactured and tested on the probe beam line at the 3rd CLIC Test Facility (CTF3) at CERN. The transverse beam position is determined from the electromagnetic resonant modes excited by the beam in the two cavities of the pickup, the position cavity and the reference cavity. The mode that is measured in each cavity resonates at 15 GHz and has a loaded quality factor that is below 200. Analytical expressions for the amplitude, phase and total energy of signals from long trains of bunches have been derived and the main conclusions are discussed. The results of the beam tests are presented. The variable gain of the receiver electronics has been characterized using beam excited signals and the form of the signals for different beam pulse lengths with the 2 /3 ns bunch spacing has been observed. The sensitivity of the reference cavity signal to charge and the horizontal position signal to beam offset have been measured and are compared with theoretical predictions based on laboratory measurements of the BPM pickup and the form of the resonant cavity modes as determined by numerical simulation. Finally, the BPM was calibrated so that the beam position jitter at the BPM location could be measured. It is expected that the beam jitter scales linearly with the beam size and so the results are compared to predicted values for the latter.

A modified space charge routine for high intensity bunched beams

International Nuclear Information System (INIS)

Lapostolle, P.; Garnett, R.W.; Wangler, T.P.

1996-01-01

In 1991 a space charge calculation for bunched beam with a three-dimensional ellipsoid was proposed, replacing the usual SCHEFF routines. It removes the cylindrical symmetry required in SCHEFF and avoids the point to point interaction computation, whose number of simulation points is limited. This routine has now been improved with the introduction of two or three ellipsoids giving a good representation of the complex non-symmetrical form of the bunch (unlike the 3-d ellipsoidal assumption). The ellipsoidal density distributions are computed with a new method, avoiding the difficulty encountered near the centre (the axis in 2-d problems) by the previous method. It also provides a check of the ellipsoidal symmetry for each part of the distribution. Finally, the Fourier analysis reported in 1991 has been replaced by a very convenient Hermite expansion, which gives a simple but accurate representation of practical distributions. Comparisons with other space charge routines have been made, particularly with the ones applying other techniques such as SCHEFF. Introduced in the versatile beam dynamics code DYNAC, it should provide a good tool for the study of the various parameters responsible for the halo formation in high intensity linacs. (orig.)

High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

Science.gov (United States)

Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

2018-04-01

High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

DC-SC Photoinjector with Low Emittance at Peking University

CERN Document Server

Xiang Rong; Hao, J; Huang, Senlin; Lu Xiang Yang; Quan, Shengwen; Zhang, Baocheng; Zhao, Kui

2005-01-01

High average power Free Electron Lasers require the high quality electron beams with the low emittance and the sub-picosecond bunches. The design of DC-SC photoinjector, directly combining a DC photoinjector with an SRF cavity, can produce high average current beam with moderate bunch charge and high duty factor. Because of the DC gun, the emittance increases quickly at the beginning, so a carefully design is needed to control that. In this paper, the simulation of an upgraded design has been done to lower the normalized emittance below 1.5mm·mrad. The photoinjector consists of a DC gap and a 2+1/2-cell SRF cavity, and it is designed to produce 4.2 MeV electron beams at 100pC bunch charge and 81.25MHz repetition rate (8 mA average current).

Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

Energy Technology Data Exchange (ETDEWEB)

Piot, Philippe [Northern Illinois U.

2015-12-01

Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

Multi-bunch Feedback Systems

International Nuclear Information System (INIS)

Lonza, M; Schmickler, H

2014-01-01

Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides important advantages in terms of flexibility and reproducibility, digital systems open the way to the use of novel diagnostic tools and additional features. We first introduce coupled-bunch instabilities, analysing the equation of motion of charged particles and the different modes of oscillation of a multi-bunch beam, showing how they can be observed and measured. Different types of feedback systems will then be presented as examples of real implementations that belong to the history of multi-bunch feedback systems. The main components of a feedback system and the related issues will also be analysed. Finally, we shall focus on digital feedback systems, their characteristics, and features, as well as on how they can be concretely exploited for both the optimization of feedback performance and for beam dynamics studies

Investigation of transient processes at the DELTA electron storage ring using a digital bunch-by-bunch feedback system

Energy Technology Data Exchange (ETDEWEB)

Hoener, Markus

2015-07-01

At the 1.5-GeV synchrotron radiation source DELTA, operated by the TU Dortmund University, intensive synchrotron radiation in the spectral range from hard X-rays to THz radiation is generated by the circular deflection of highly relativistic electron bunches. Interacting with the vacuum chamber wall, the electron bunches create electric fields, which can act back on subsequent bunches. With increasing beam current, the excitation is enhanced so that the electron beam is unstable, which means that the electron bunches oscillate longitudinally or transversely relative to their reference position. The oscillations reduce the quality of the synchrotron radiation and limit the maximum storable beam current. Within the scope of this thesis, the beam instabilities at the storage ring were systematically investigated. A digital bunch-by-bunch feedback system was installed and commissioned, which allows to detect and digitize the position of each electron bunch at each turn. Based on the input signal, a correction signal is calculated in order to suppress transverse and longitudinal oscillation of the bunches. In addition, it is possible to excite dedicated bunches. The systematic excitation of all coupled-bunch modes allowed for the first time to determine the damping rates of all 192 eigenmodes of the electron beam. The current dependence of the damping rates was investigated and an instability threshold was found. Besides the investigation of multibunch instabilities, single-bunch instabilities are discussed. In addition, the acquisition unit of the digital feedback system can be triggered on external events. This was used to investigate the injection process and beam losses. It was shown that the transverse feedback system increases the injection efficiency. Another aspect of this thesis is the improvement of the signal quality of ultrashort coherent synchrotron radiation pulses, which are generated by the short-pulse facility at DELTA. The short-pulse facility is based

Electro-optical Detection of Charged Particles

International Nuclear Information System (INIS)

Lazarus, D.M.

2001-01-01

The electric field of charged particles can induce transient changes in the polarization of light that produce sub-picosecond modulation of a laser beam. This is a consequence of the electro-optical effect in which the presence of the electric field in an electro-optical medium produces a change in the index of refraction of the medium resulting in a phase retardation between polarization components parallel and perpendicular to the electric field. We have observed the electro-optical effect due to 10 picosecond electron beam bunches with rise times that were limited by the bandwidth of our data acquisition system. This technology is being applied to particle beam diagnostics and has the potential to produce charged particle detectors combining excellent spatial resolution with unprecedented temporal precision.

Spontaneous and stimulated emission induced by an electron, electron bunch, and electron beam in a plasma

International Nuclear Information System (INIS)

Kuzelev, M V; Rukhadze, A A

2008-01-01

Two fundamental mechanisms - the Cherenkov effect and anomalous Doppler effect - underlying the emission by an electron during its superluminal motion in medium are considered. Cherenkov emission induced by a single electron and a small electron bunch is spontaneous. In the course of spontaneous Cherenkov emission, the translational motion of an electron is slowed down and the radiation energy grows linearly with time. As the number of radiating electrons increases, Cherenkov emission becomes stimulated. Stimulated Cherenkov emission represents a resonance beam instability. This emission process is accompanied by longitudinal electron bunching in the beam or by the breaking of an electron bunch into smaller bunches, in which case the radiation energy grows exponentially with time. In terms of the longitudinal size L e of the electron bunch there is a transition region λ e 0 -1 between the spontaneous and stimulated Cherenkov effects, where λ is the average radiation wavelength, and δ 0 is the dimensionless (in units of the radiation frequency) growth rate of the Cherenkov beam instability. The range to the left of this region is dominated by spontaneous emission, whereas the range to the right of this region is dominated by stimulated emission. In contrast to the Vavilov-Cherenkov effect, the anomalous Doppler effect should always (even for a single electron) be considered as stimulated, because it can only be explained by accounting for the reverse action of the radiation field on the moving electron. During stimulated emission in conditions where anomalous Doppler effect shows itself, an electron is slowed down and spins up; in this case, the radiation energy grows exponentially with time. (reviews of topical problems)

Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier

Energy Technology Data Exchange (ETDEWEB)

Wu, Y. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China); Science and Technology on High Power Microwave Laboratory, Mianyang 621900 (China); Xu, Z.; Li, Z. H. [Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900 (China); Tang, C. X. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2012-07-15

In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.

Study of nonlinear interaction between bunched beam and intermediate cavities in a relativistic klystron amplifier

Science.gov (United States)

Wu, Y.; Xu, Z.; Li, Z. H.; Tang, C. X.

2012-07-01

In intermediate cavities of a relativistic klystron amplifier (RKA) driven by intense relativistic electron beam, the equivalent circuit model, which is widely adopted to investigate the interaction between bunched beam and the intermediate cavity in a conventional klystron design, is invalid due to the high gap voltage and the nonlinear beam loading in a RKA. According to Maxwell equations and Lorentz equation, the self-consistent equations for beam-wave interaction in the intermediate cavity are introduced to study the nonlinear interaction between bunched beam and the intermediate cavity in a RKA. Based on the equations, the effects of modulation depth and modulation frequency of the beam on the gap voltage amplitude and its phase are obtained. It is shown that the gap voltage is significantly lower than that estimated by the equivalent circuit model when the beam modulation is high. And the bandwidth becomes wider as the beam modulation depth increases. An S-band high gain relativistic klystron amplifier is designed based on the result. And the corresponding experiment is carried out on the linear transformer driver accelerator. The peak output power has achieved 1.2 GW with an efficiency of 28.6% and a gain of 46 dB in the corresponding experiment.

Electron bunch length measurement at the Vanderbilt FEL

Energy Technology Data Exchange (ETDEWEB)

Amirmadhi, F.; Brau, C.A.; Mendenhall, M. [Vanderbilt Free-Electron-Laser Center, Nashville, TN (United States)] [and others

1995-12-31

During the past few years, a number of experiments have been performed to demonstrate the possibility to extract the longitudinal charge distribution from spectroscopic measurements of the coherent far-infrared radiation emitted as transition radiation or synchrotron radiation. Coherent emission occurs in a spectral region where the wavelength is comparable to or longer than the bunch length, leading to an enhancement of the radiation intensity that is on the order of the number of particles per bunch, as compared to incoherent radiation. This technique is particularly useful in the region of mm and sub-mm bunch lengths, a range where streak-cameras cannot be used for beam diagnostics due to their limited time resolution. Here we report on experiments that go beyond the proof of principle of this technique by applying it to the study and optimization of FEL performance. We investigated the longitudinal bunch length of the Vanderbilt FEL by analyzing the spectrum of coherent transition radiation emitted by the electron bunches. By monitoring the bunch length while applying a bunch-compression technique, the amount of the compression could be easily observed. This enabled us to perform a systematic study of the FEL performance, especially gain and optical pulse width, as a function of the longitudinal electron distribution in the bunch. The results of this study will be presented and discussed.

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...

Present status of high quality beam facility at Waseda University

International Nuclear Information System (INIS)

Washio, M.; Kawai, H.; Hama, Y.; Kudo, N.; Kobayashi, M.; Kuribayasi, T.; Kawaguchi, M.; Kuroda, R.; Maeda, K.; Nagasawa, F.; Ueyama, D.; Hizume, K.; Wang, X.J.; Hayano, H.; Urakawa, J.; Kashiwagi, S.

2004-01-01

A research project named High-Tech Research Center Project has been conducted at Waseda University. In this project, an RF gun system has been used for production of low emittance and short bunched electron beam. The experiments for the electron beam quality measurement have been carried out by slit scan techniques, etc. Short pulsed x-ray with the energy range of so-called water window has been generation by the inverse compton scattering. Further, the pulse radiolysis system has been constructed, and the stroboscopic pulse radiolysis has been applied for the detection of hydrated electron in picosecond time region. (author)

Use of an INR-style bunch-length detector in the Fermilab Linac

International Nuclear Information System (INIS)

McCrory, E.S.; Schmidt, C.W.; Feschenko, A.V.

1993-01-01

Device to accurately measure the phase extent of a linac beam is being developed for use in the Fermilab 400 MeV Linac Upgrade. Prototypes have been and are being tested. We have attempted to improve the original design from the Institute for Nuclear Research in Moscow (INR) to increase the resolution for adequate operation at 805 MHz. The device incorporating a new arrangement of lens and deflector, reported previously, cannot achieve the desired resolution. This paper describes the operation and the strengths and weaknesses of the three types of bunch-length detectors (BLDs) and the measurements made at this time. The differences among these devices is delineated by the relative position of the rf deflector and the electrostatic einsel lens, as follows: INR--Lens before deflector; Fermilab--Lens after deflector; H- beam; and FNAL/INR--Lens and deflector combined. To satisfy the goals of commissioning the new linac, a resolution of about 5 picoseconds (1 degree at 805 MHz) is desired

Development of a coherent transition radiation-based bunch length monitor with application to the APS RF thermionic gun beam optimization

CERN Document Server

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

2001-01-01

We report further development of an EPICS-compatible bunch length monitor based on the autocorrelation of coherent transition radiation (CTR). In this case the monitor was used to optimize the beam from the S-band thermionic RF gun on the Advanced Photon Source (APS) linac. Bunch lengths of 400-500 fs (FWHM) were measured in the core of the beam, which corresponded to about 100-A peak current in each micropulse. The dependence of the CTR signal on the square of the beam charge for the beam core was demonstrated. We also report the first use of the beam accelerated to 217 MeV for successful visible wavelength SASE FEL experiments.

Intense Ion Beam for Warm Dense Matter Physics

Energy Technology Data Exchange (ETDEWEB)

Coleman, Joshua Eugene [Univ. of California, Berkeley, CA (United States)

2008-01-01

The Neutralized Drift Compression Experiment (NDCX) at Lawrence Berkeley National Laboratory is exploring the physical limits of compression and focusing of ion beams for heating material to warm dense matter (WDM) and fusion ignition conditions. The NDCX is a beam transport experiment with several components at a scale comparable to an inertial fusion energy driver. The NDCX is an accelerator which consists of a low-emittance ion source, high-current injector, solenoid matching section, induction bunching module, beam neutralization section, and final focusing system. The principal objectives of the experiment are to control the beam envelope, demonstrate effective neutralization of the beam space-charge, control the velocity tilt on the beam, and understand defocusing effects, field imperfections, and limitations on peak intensity such as emittance and aberrations. Target heating experiments with space-charge dominated ion beams require simultaneous longitudinal bunching and transverse focusing. A four-solenoid lattice is used to tune the beam envelope to the necessary focusing conditions before entering the induction bunching module. The induction bunching module provides a head-to-tail velocity ramp necessary to achieve peak axial compression at the desired focal plane. Downstream of the induction gap a plasma column neutralizes the beam space charge so only emittance limits the focused beam intensity. We present results of beam transport through a solenoid matching section and simultaneous focusing of a singly charged K⁺ ion bunch at an ion energy of 0.3 MeV. The results include a qualitative comparison of experimental and calculated results after the solenoid matching section, which include time resolved current density, transverse distributions, and phase-space of the beam at different diagnostic planes. Electron cloud and gas measurements in the solenoid lattice and in the vicinity of intercepting diagnostics are also presented. Finally

Bunching and phase focusing of laser generated proton beams

Energy Technology Data Exchange (ETDEWEB)

Schumacher, Dennis; Hofmann, Ingo; Blazevic, Abel; Deppert, Oliver [GSI Helmholtzzentrum fuer Schwerionenforschung (Germany); Busold, Simon; Roth, Markus; Boine-Frankenheim, Oliver [TU Darmstadt (Germany); Brabetz, Christian [Universitaet Frankfurt, Frankfurt am Main (Germany); Zielbauer, Bernhard [HI Jena (Germany); Collaboration: LIGHT-Collaboration

2013-07-01

Laser accelerated proton beams can reach very high intensities and very low emittances. Therefore they are suitable as ion sources for many applications. One is the coupling into common ion accelerator structures to replace pre accelerators that are used so far. The LIGHT (Laser Ion Generation, Handling and Transport) collaboration has been founded to develop ion optics and targets and optimize laser parameter to make this coupling most efficient. In a first step a short pulse beam line for the PHELIX-laser at GSI to the experiment site Z6 has been build in order to laser accelerate protons here. In a second step a pulsed solenoid has been established to collimate the divergent ion beam. In a third step this collimated beam will be coupled into a bunching unit, which consists of a spiral resonator with three gaps which leads to an overall acceleration voltage of 1 MV. With this cavity it is not only possible to avoid the broadening of the pulse, but also to phase focus it. This talk presents also the progress towards the operation of the spiral resonator as buncher for a laser accelerated ion beam e.g. simulations, tests and performance data and shows the next steps of the beam shaping efforts.

Study of the laser-induced damage of reflective components in the sub-picosecond regime

International Nuclear Information System (INIS)

Sozet, Martin

2016-01-01

In this thesis, laser-induced damage phenomenon of reflective components is investigated in the sub-picosecond regime. These components, made of stacks of dielectric materials, are widely used in powerful laser facilities such as PETAL laser. PETAL laser has been built at the CEA-CESTA in France to deliver multi-kJ/500 fs pulses at 1053 nm and reach a power higher than 6 PW. For this kind of laser systems, reflective components are commonly used instead of optics operating in transmission to limit the accumulation of non-linear phase along the beam propagation due to the high intensities. Optical components irradiated by the highest power densities are the pulse compression gratings, transport mirrors and the focusing parabola, located at the end of the laser chain. Nowadays, laser-induced damage is the main factor that limits the overall performances of powerful laser systems. This manuscript presents three study axes to better understand and control damage phenomenon. The first one concerns the conception of reflective optics for the peta-watt applications. The design of new structures has been investigated to reach high diffraction efficiencies in the case of pulse compression gratings and a high reflectivity in the case of mirrors, while reducing the Electric-field enhancement which is one of the causes of the laser-induced damage. The second axis deals with the development of a precise damage metrology with new testing tools which brings new perspectives and a new viewpoint for the assessment of the laser resistance of optical components. Finally, the third axis concerns the study the damage growth after several irradiations in the sub-picosecond regime. The evolution of the damage area during growth sequences is observed and compared to numerical simulations. It enables to improve the understanding in the growth phenomenon. In the end, these studies will allow to develop predictive models of the laser-induced damage and new tools for the conception of

Luminosity geometric reduction factor from colliding bunches with different lengths

Energy Technology Data Exchange (ETDEWEB)

Verdu-Andres, S. [Brookhaven National Lab. (BNL), Upton, NY (United States)

2017-09-29

In the interaction point of the future electron-Ion collider eRHIC, the electron beam bunches are at least one order of magnitude shorter than the proton beam bunches. With the introduction of a crossing angle, the actual number of collisions resulting from the bunch collision gets reduced. Here we derive the expression for the luminosity geometric reduction factor when the bunches of the two incoming beams are not equal.

Multi-bunch effect of resistive wall in the Beam Delivery System of the Compact Linear Collider

CERN Document Server

Mutzner, R; Rumolo, G; Tomas, R; Pieloni, T

2010-01-01

Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present work focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Our simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. The two cases of 3 TeV and 500 GeV have been examined.

Overview of bunch length measurements

International Nuclear Information System (INIS)

Lumpkin, A. H.

1999-01-01

An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed

A hybrid approach for generating ultra-short bunches for advanced accelerator applications

Energy Technology Data Exchange (ETDEWEB)

Stratakis, Diktys [Brookhaven National Lab. (BNL), Upton, NY (United States)

2015-09-01

Generation of electron beams with high phase-space density, short bunch length and high peak current is an essential requirement for future linear colliders and bright electron beam sources. Unfortunately, such bunches cannot be produced directly from the source since forces from the mutual repulsion of electrons would destroy the brilliance of the beam within a short distance. Here, we detail a beam dynamics study of an innovative two-stage compression scheme that can generate ultra-short bunches without degrading the beam quality. In the first stage, the beam is compressed with an advanced velocity bunching technique in which the longitudinal phase space is rotated so that electrons on the bunch tail become faster than electrons in the bunch head. In the second stage, the beam is further compressed with a conventional magnetic chicane. With the aid of numerical simulations we show that our two-staged scheme is capable to increase the current of a 50 pC bunch to a notable factor of 100 while the emittance growth can be suppressed to 1% with appropriate tailoring of the initial beam distribution.

Intensity and bunch length measurement for lepton beam in the injection lines of the SPS and LEP

CERN Document Server

Boccard, C; Papis, J P; Vos, L

1995-01-01

We describe a system which is used operationally to measure the absolute intensity of single lepton bunches in a beam transfer line. It is based on the detailed knowledge of every single item of a complex measuring chain that comprises a beam coupler on one end and an acquisition system on the other end. This knowledge can be acquired by a well tested theoretical model and careful measurement of the transfer function of each processing module. A precision better than 3 % can be obtained and no external calibration is required. A value for the bunch length can be deduced from a spectral intensity measurement at two well chosen frequencies.

''High intensity per bunch'' working group

International Nuclear Information System (INIS)

2001-01-01

Third Generation Light Sources are supposed to store high intensity beams not only in many tightly spaced bunches (multibunch operation), but also in few bunch or even single lunch modes of operation, required for example for time structure experiments. Single bunch instabilities, driven by short-range wake fields, however spoil the beam quality, both longitudinally and transversely. Straightforward ways of handling them, by pushing up the chromaticity (ζ = ΔQ/(Δp/p)) for example, enabled to raise the charge per bunch, but to the detriment of beam lifetime. In addition, since the impedance of the vacuum chamber deteriorates with the installation of new insertion devices, the current thresholds tend to dope down continuously. The goal of this Working Group was then to review these limitations in the existing storage rings, where a large number of beam measurements have been performed to characterise them, and to discuss different strategies which are used against them. About 15 different laboratories reported on the present performance of storage rings, experiences gained in high charge per bunch, and on simulation results and theoretical studies. More than 25 presentations addressed the critical issues and stimulated the discussion. Four main topics came out: - Observation and experimental data; - Impedance studies and tracking codes; - Theoretical investigations; - Cures and feedback. (author)

Luminosity with more bunches in PEP

International Nuclear Information System (INIS)

Corbett, W.J.

1990-12-01

The near term accelerator physics program for PEP includes experiments in a collider mode with up to 9 bunches in each beam. In this memo, luminosity data from the 3 x 3 configuration is first used to calculate vertical beam size, emittance and tune shift as a function of current. The data is then used to extrapolate to the case with either 6 x 6 or 9 x 9 bunches colliding in PEP. Vertical emittance growth from the separated bunch optics and dispersion at the IP are included in the calculations. The conclusion is that given a 90 mA current drive limitation in PEP, operating with 6 x 6 bunches yields the maximum luminosity. 9 refs., 6 figs

Multi-Bunch effect of resistive wall in the beam delivery system of the Compact Linear Collider

CERN Document Server

Mutzner, Raphael; Pieloni, Tatiana; Rivkin, Leonid

2010-01-01

Wake fields in the CLIC Beam Delivery System (BDS) can cause severe single or multi-bunch effects leading to luminosity loss. The main contributors in the BDS are geometric and resistive wall wake fields of the collimators and resistive wall wakes of the beam pipe. The present master thesis focuses only on the multi-bunch effects from resistive wall. Using particle tracking with wake fields through the BDS, we have established the aperture radius, above which the effect of the wake fields becomes negligible. Simulations were later extended to include a realistic aperture model along the BDS as well as the collimators. We examine the two cases of 3 TeV and 500 GeV in this work, for stainless steel and copper pipes.

Bunch identification module

International Nuclear Information System (INIS)

Fox, J.D.

1981-01-01

This module provides bunch identification and timing signals for the PEP Interaction areas. Timing information is referenced to the PEP master oscillator, and adjusted in phase as a function of region. Identification signals are generated in a manner that allows observers in all interaction regions to agree on an unambiguous bunch identity. The module provides bunch identification signals via NIM level logic, upon CAMAC command, and through LED indicators. A front panel ''region select'' switch allows the same module to be used in all regions. The module has two modes of operation: a bunch identification mode and a calibration mode. In the identification mode, signals indicate which of the three bunches of electrons and positrons are interacting, and timing information about beam crossing is provided. The calibration mode is provided to assist experimenters making time of flight measurements. In the calibration mode, three distinct gating signals are referenced to a selected bunch, allowing three timing systems to be calibrated against a common standard. Physically, the bunch identifier is constructed as a single width CAMAC module. 2 figs., 1 tab

Fabrication of sub-micron surface structures on copper, stainless steel and titanium using picosecond laser interference patterning

Energy Technology Data Exchange (ETDEWEB)

Bieda, Matthias, E-mail: matthias.bieda@iws.fraunhofer.de [Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Winterbergstr. 28, 01277 Dresden (Germany); Siebold, Mathias, E-mail: m.siebold@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Bautzner Landstr. 400, 01328 Dresden (Germany); Lasagni, Andrés Fabián, E-mail: andres_fabian.lasagni@tu-dresden.de [Fraunhofer-Institut für Werkstoff- und Strahltechnik (IWS), Winterbergstr. 28, 01277 Dresden (Germany); Technische Universität Dresden, Institut für Fertigungstechnik, 01062 Dresden (Germany)

2016-11-30

Highlights: • Laser interference patterning is introduced to generate sub-micrometer surface pattern. • The two-temperature model is applied to ps-laser interference patterning of metals. • Line-like structures with a pitch of 0.7 μm were fabricated on SAE 304, Ti and Cu. • The process is governed by a photo-thermal mechanism for a pulse duration of 35 ps. • A “cold”-ablation process for metals requires a pulse duration shorter than 10 ps. - Abstract: Picosecond direct laser interference patterning (ps-DLIP) is investigated theoretically and experimentally for the bulk metals copper, stainless steel and titanium. While surface texturing with nanosecond pulses is limited to feature sizes in the micrometer range, utilizing picosecond pulses can lead to sub-micrometer structures. The modelling and simulation of ps-DLIP are based on the two-temperature model and were carried out for a pulse duration of 35 ps at 515 nm wavelength and a laser fluence of 0.1 J/cm{sup 2}. The subsurface temperature distribution of both electrons and phonons was computed for periodic line-like structures with a pitch of 0.8 μm. The increase in temperature rises for a lower absorption coefficient and a higher thermal conductivity. The distance, at which the maximum subsurface temperature occurs, increases for a small absorption coefficient. High absorption and low thermal conductivity minimize internal heating and give rise to a pronounced surface micro topography with pitches smaller than 1 μm. In order to confirm the computed results, periodic line-like surface structures were produced using two interfering beams of a Yb:YAG-Laser with 515 nm wavelength and a pulse duration of 35 ps. It was possible to obtain a pitch of 0.7 μm on the metallic surfaces.

Self-bunching electron guns

CERN Document Server

Mako, F; Weilhammer, Peter

1999-01-01

We report on three electron gun projects that are aimed at power tube and injector applications. The purpose of the work is to develop robust electron guns which produce self-bunched, high-current-density beams. We have demonstrated cold emission, long life, and tolerance to contamination. The cold emission process is based on secondary electron emission. FMT has studied this resonant bunching process which gives rise to high current densities (0.01-5 kA/cm/sup 2/), high charge bunches (up to 100 nC/bunch), and short pulses (1-100 ps) for frequencies from 1 to 12 GHz. The beam pulse width is nominally ~5% of the RF period. The first project is the L-Band Micro-Pulse Gun (MPG). Measurements show ~40 ps long microbunches at ~20 A/cm/sup 2/ without contamination due to air exposure. Lifetime testing has been carried out for about 18 months operating at 1.25 GHz for almost 24 hours per day at a repetition rate of 300 Hz and 5 mu s-long macro- pulses. About 5.8*10/sup 13/ micro-bunches or 62,000 coulombs have pass...

New diagnostics and cures for coupled-bunch instabilities

International Nuclear Information System (INIS)

Prabhakar, S.

2000-01-01

Electromagnetic interaction between a charged particle beam and its surroundings causes collective instabilities, which must be controlled if the new light sources and colliders are to meet their design goals. Control requires a combination of passive damping and fast active feedback on an unprecedented technological scale. Efficient instability diagnosis techniques are also needed for machines with large numbers of bunches. This thesis describes new methods of measuring and analyzing coupled-bunch instabilities in circular accelerators, and demonstrates the existence of a new cure. A new technique is demonstrated for simultaneous measurement of growth rates, damping rates and coherent tune shifts of all unstable coupled-bunch eigenmodes from a single 10-25-ms transient snapshot of beam motion. The technique has been used to locate and quantify beam impedance resonances at PEP-II, ALS and SPEAR. This method is faster than existing spectral scan methods by at least an order of magnitude, and has the added advantage of revealing coupled-bunch dynamics in the linear small-signal regime. A method is also presented for estimating beam impedance from multi-bunch fill shape and synchronous phase measurements. Phase space tracking of multi-bunch instabilities is introduced as a ''complete instability diagnostic.'' Digitized multi-bunch data is analyzed offline, to estimate the phase space trajectories of bunches and modes. Availability of phase space trajectories is shown to open up a variety of possibilities, including measurement of reactive impedance, and diagnosis of the fast beam-ion instability. Knowledge gained from longitudinal measurements (all made using a digital longitudinal feedback system) has been used to optimize cavity temperatures, tuner positions and feedback parameters, and also to identify sources of beam noise at the three machines. A matrix-based method is presented for analyzing the beneficial effect of bunch-to-bunch tune variation on instability

Electron beam sub-harmonics chopping system for linear accelerator injector

International Nuclear Information System (INIS)

Bourat, Christophe

1988-01-01

The need of a 100 % duty cycle electron accelerator for use in nuclear physics, has led in 1981 the CEN Saclay Linear Accelerator Group, to study a machine using the existing linac associated with a pulse stretcher ring. The production of electron bunches at the ring RF frequency (600 MHz) requires the design of a new injector including a chopping beam System with a deflecting electromagnetic cavity and a collimator. A comparison between four transverse magnetic modes, led to choose a TM110 parallelepiped chopper. The construction of a prototype and of a vacuum-tight cavity followed by microwave measurements has permitted to solve several mechanical problems and to specify the cavity electrical properties. In a first step, the beam line, including - focusing, offset deflection coils, chopping with a rectangular collimator - has been studied, for zero intensity beam current, on the basis of a matrix model. An experimental 40 keV beam line, has been assembled to measure the bunch length. The method was based on a spectral analysis of the signal delivered by a large band, 50 ohms adapted beam collector. The bunch shape in the time domain was reconstructed by inverse Fourier transform. The beam dynamics has been studied with a 3D space charge model which has been introduced into the PARMELA tracking code. Simulations showed that a 150 keV, 2 A beam could be chopped with the same deflecting lay-out. (author) [fr

Down sampled signal processing for a B Factory bunch-by-bunch feedback system

International Nuclear Information System (INIS)

Hindi, H.; Hosseini, W.; Briggs, D.; Fox, J.; Hutton, A.

1992-03-01

A bunch-by-bunch feedback scheme is studied for damping coupled bunch synchrotron oscillations in the proposed PEP II B Factory. The quasi-linear feedback systems design incorporates a phase detector to provide a quantized measure of bunch phase, digital signal processing to compute an error correction signal and a kicker system to correct the energy of the bunches. A farm of digital processors, operating in parallel, is proposed to compute correction signals for the 1658 bunches of the B Factory. This paper studies the use of down sampled processing to reduce the computational complexity of the feedback system. We present simulation results showing the effect of down sampling on beam dynamics. Results show that down sampled processing can reduce the scale of the processing task by a factor of 10

Beam-beam effects in high energy e+e- storage rings: resonant amplification of vertical dimensions for flat beams

International Nuclear Information System (INIS)

Bambade, P.

1984-06-01

In this thesis, we present a phenomenological study of the beam-beam effect in e + e - storage rings. We are in particular interested in the blow-up of the vertical dimension observed in this kind of accelerator. A detailed analysis of the electromagnetic field generated by the very flat bunches stored, and seen by the counter-rotating particles shows that two-dimensional non-linear resonances, which couple vertical and horizontal betatron oscillations, play a very important role. Moreover, the ''weak beam-strong beam'' approximation holds rather well in the case of very flat bunches. Perturbative analysis enables us to predict the effects from the strongest coupling resonance: 20sub(x)-20sub(y) = integer. We find that mainly the tails of the vertical distribution are affected, and we give a criterion concerning the optimal distance to this resonance in the case of a storage ring such as LEP. Finally, the results and in particular the validity of the single resonance approximation are checked through a numerical simulation [fr

Design of a Multi-Bunch BPM for the Next Linear Collider

International Nuclear Information System (INIS)

Young, Andrew

2003-01-01

The Next Linear Collider (NLC) design requires precise control of colliding trains of high-intensity (1.4 x 10 10 particles/bunch) and low-emittance beams. High-resolution multi-bunch beam position monitors (BPMs) are required to ensure uniformity across the bunch trains with bunch spacing of 1.4ns. A high bandwidth (∼350 MHz) multi-bunch BPM has been designed based on a custom-made stripline sum and difference hybrid on a Teflon-based material. High bandwidth RF couplers were included to allow injection of a calibration tone. Three prototype BPMs were fabricated at SLAC and tested in the Accelerator Test Facility at KEK and in the PEP-II ring at SLAC. Tone calibration data and single-bunch and multi-bunch beam data were taken with high-speed (5Gsa/s) digitizers. Offline analysis determined the deconvolution of individual bunches in the multi-bunch mode by using the measured single bunch response. The results of these measurements are presented in this paper

Commissioning of a compact laser-based proton beam line for high intensity bunches around 10Â MeV

Science.gov (United States)

Busold, S.; Schumacher, D.; Deppert, O.; Brabetz, C.; Kroll, F.; Blažević, A.; Bagnoud, V.; Roth, M.

2014-03-01

We report on the first results of experiments with a new laser-based proton beam line at the GSI accelerator facility in Darmstadt. It delivers high current bunches at proton energies around 9.6 MeV, containing more than 109 particles in less than 10 ns and with tunable energy spread down to 2.7% (ΔE/E0 at FWHM). A target normal sheath acceleration stage serves as a proton source and a pulsed solenoid provides for beam collimation and energy selection. Finally a synchronous radio frequency (rf) field is applied via a rf cavity for energy compression at a synchronous phase of -90 deg. The proton bunch is characterized at the end of the very compact beam line, only 3 m behind the laser matter interaction point, which defines the particle source.

Results of Preliminary Tests of PAR Bunch Cleaning

CERN Document Server

Yao, Chihyuan; Grelick, Arthur; Lumpkin, Alex H; Sereno, Nicholas S

2005-01-01

A particle accumulator ring (PAR) is used at the Advanced Photon Source (APS) to collect multiple linac bunches and compress them into a 0.3-ns (rms) single bunch for booster injection. A 9.77-MHz fundamental rf system and a 117.3-MHz harmonic rf system are employed for initial beam capture and bunch length compression. Satellite bunches with very low charge form due to rf phase drifts or beam loading change. These satellites, when injected into the booster and then into the storage ring (SR), cause bunch impurity at three buckets from the target bucket. Storage ring and booster bunch cleaning was tried but proved to be difficult due to the top-up mode of operation in the storage ring and tune drift in the booster synchrotron. Recently we implemented a PAR bunch-cleaning system with tune-modulated harmonic rf knockout. Preliminary tests gave a measured SR bunch purity of better than 10

Operation and performance of bunch pre-compression for increased transmission at the SLC

International Nuclear Information System (INIS)

Minty, M.G.; Akre, R.; Decker, F.J.; Turner, J.

1997-11-01

As the beam currents at the SLC are increased, transverse aperture restrictions in the ring-to-linac transport line (RTL) become increasingly important. The RTL contains a bunch compressor which introduces a large energy variation across the bunch and hence a larger transverse beam size. Since 1994 the compressor amplitude has been operating at higher than design voltage. While advantageous for shaping the bunch distribution, this increased the bunch energy spread and therefore resulted in more beam loss. Moreover, due to current-dependent bunch lengthening in the damping ring, the higher the beam current, the more the current loss. To avoid such losses, the bunch length may be precompressed in the damping ring. Until recently, bunch precompression with high beam currents was not stable. In this paper the authors identify the reasons for the difficulties, describe the changes made to accommodate bunch precompression, and discuss performance aspects after implementation. The estimated increase in current at the interaction point is 15%

Operational performance of a bunch by bunch digital damper in the Fermilab Main Injector

International Nuclear Information System (INIS)

Adamson, P.; Ashmanskas, W.J.; Foster, G.W.; Hansen, S.; Marchionni, A.; Nicklaus, D.; Semenov, A.; Wildman, D.; Kang, H.

2005-01-01

We have implemented a transverse and longitudinal bunch by bunch digital damper system in the Fermilab Main Injector, using a single digital board for all 3 coordinates. The system has been commissioned over the last year, and is now operational in all MI cycles, damping beam bunched at both 53MHz and 2.5MHz. We describe the performance of this system both for collider operations and high-intensity running for the NuMI project

Micro-bunching diagnostics for the IFEL by coherent transition radiation

International Nuclear Information System (INIS)

Liu, Y.; Cline, D.B.

1996-10-01

Here, we propose an effective method for detecting micro-bunching effects (10 fs bunch length) produced by the IFEL interaction, by measuring the CTR spectrum. The pre-bunching of an initially energy- modulated c- beam passing through a wiggler (IFEL interaction) is studied. Simulation shows that more than 40% of electrons are pre- bunched in the micro-bunches. The longitudinal distribution of an optically pre-bunched beam is Fourier analyzed to find the dominant harmonics contributing to the CTR. The CTR spectrum is calculated analytically for the IFEL situation. A detection system has been built to demonstrate this technique

Analysis for extraction and bunching of ion beam from spherical reflex triode

International Nuclear Information System (INIS)

Kawata, Shigeo; Abe, Takashi; Kasuya, Koichi; Niu, Keishiro.

1978-11-01

Since an ion beam is hoped to impinge on a target in a spherically symmetric way for inertial confinement fusion, an analysis is developed here for the intense ion beam which is extracted from a spherical reflex triode. The basic equations are the Poisson equation for the electric potential and the conservation equations of energies for the ion and electron velocities. According to the asymptotic solution, the extracted ion-beam-current density is proportional to the power of 3/2 of the voltage imposed on the triode. This dependence of the current density on the voltage is improved to be the power of 1.6 by the numerical analysis. A special time-dependence of the ion-beam power at the target surface is required for an optimal implosion of the target. Using the bunching theory for the ion beam, we derive numerically an optimal time-dependence of the voltage imposed on the triode. Asymptotic forms are also obtained analytically for the voltage. (author)

Bunch length measurements using electro-optical sampling at the SLS linac

International Nuclear Information System (INIS)

Winter, A.

2004-07-01

A mode-locked titanium-sapphire laser with 15 fs pulse width is used to determine the time profile of the picosecond electron bunches in the Swiss light source linac of the Paul Scherrer Institute, Villigen Switzerland. This was done using the electro-optic effect in Zinc-Telluride crystals and sampling the change induced by coherent transition radiation with the TiSa laser. The development, implementation and results of an analogue synchronisation system to synchronise the repetition rate of the TiSa laser to the radio frequency of the accelerator with a short term stability of 40 fs is presented. The experimental setup of the bunch length measurements is described and results are presented on the coincidence measurements between the laser pulses and the coherent transition radiation pulses generated by the electron bunches. (orig.)

Measurement of short bunches

International Nuclear Information System (INIS)

Wang, D.X.

1996-01-01

In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, and advanced accelerators such as laser or plasma wakefield accelerators. One would like to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, and accurate timing. Meanwhile, recent development and advances in RF photoinjectors and various bunching schemes make it possible to generate very short electron bunches. Measuring the longitudinal profile and monitoring bunch length are critical to understand the bunching process and longitudinal beam dynamics, and to commission and operate such short bunch machines. In this paper, several commonly used measurement techniques for subpicosecond bunches and their relative advantages and disadvantages are discussed. As examples, bunch length related measurements at Jefferson Lab are presented. At Jefferson Lab, bunch lengths as short as 84 fs have been systematically measured using a zero-phasing technique. A highly sensitive Coherent Synchrotron Radiation (CSR) detector has been developed to noninvasively monitor bunch length for low charge bunches. Phase transfer function measurements provide a means of correcting RF phase drifts and reproducing RF phases to within a couple of tenths of a degree. The measurement results are in excellent agreement with simulations. A comprehensive bunch length control scheme is presented. (author)

Measurement of short bunches

International Nuclear Information System (INIS)

Wang, D.X.

1996-01-01

In recent years, there has been increasing interest in short electron bunches for different applications such as short wavelength FELs, linear colliders, and advanced accelerators such as laser or plasma wakefield accelerators. One would like to meet various requirements such as high peak current, low momentum spread, high luminosity, small ratio of bunch length to plasma wavelength, and accurate timing. Meanwhile, recent development and advances in RF photoinjectors and various bunching schemes make it possible to generate very short electron bunches. Measuring the longitudinal profile and monitoring bunch length are critical to understand the bunching process and longitudinal beam dynamics, and to commission and operate such short bunch machines. In this paper, several commonly used measurement techniques for subpicosecond bunches and their relative advantages and disadvantages are discussed. As examples, bunch length related measurements at Jefferson lab are presented. At Jefferson Lab, bunch lengths s short as 84 fs have been systematically measured using a zero-phasing technique. A highly sensitive Coherent Synchrotron Radiation (CSR) detector has been developed to noninvasively monitor bunch length for low charge bunches. Phase transfer function measurements provide a means of correcting RF phase drifts and reproducing RF phases to within a couple of tenths of a degree. The measurement results are in excellent agreement with simulations. A comprehensive bunch length control scheme is presented

POSITION DETERMINATION OF CLOSELY SPACED BUNCHES USING CAVITY BPMs

CERN Document Server

Joshi, N; Cullinan, F; Lyapin, A

2011-01-01

Radio Frequency (RF) Cavity Beam Position Monitor (BPM) systems form a major part of precision position measurement diagnostics for linear accelerators with low emittance beams. Using cavity BPMs, a position resolution of less than 100 nm has been demonstrated in single bunch mode operation. In the case of closely spaced bunches, where the decay time of the cavity is comparable to the time separation between bunches, the BPM signal from a bunch is polluted by the signal induced by the previous bunches in the same bunch-train. This paper discusses our ongoing work to develop the methods to extract the position of closely spaced bunches using cavity BPMs. A signal subtraction code is being developed to remove the signal pollution from previous bunches and to determine the individual bunch position. Another code has been developed to simulate the BPM data for the cross check. Performance of the code is studied on the experimental and simulated data. Application of the analysis techniques to the linear colliders,...

Commissioning of a compact laser-based proton beam line for high intensity bunches around 10 MeV

Directory of Open Access Journals (Sweden)

S. Busold

2014-03-01

Full Text Available We report on the first results of experiments with a new laser-based proton beam line at the GSI accelerator facility in Darmstadt. It delivers high current bunches at proton energies around 9.6 MeV, containing more than 10^{9} particles in less than 10 ns and with tunable energy spread down to 2.7% (ΔE/E_{0} at FWHM. A target normal sheath acceleration stage serves as a proton source and a pulsed solenoid provides for beam collimation and energy selection. Finally a synchronous radio frequency (rf field is applied via a rf cavity for energy compression at a synchronous phase of -90  deg. The proton bunch is characterized at the end of the very compact beam line, only 3 m behind the laser matter interaction point, which defines the particle source.

Bunch Length Measurements using Coherent Radiation

CERN Document Server

Ischebeck, Rasmus; Barnes, Christopher; Blumenfeld, Ian; Clayton, Chris; Decker, Franz Josef; Deng, Suzhi; Hogan, Mark; Huang Cheng Kun; Iverson, Richard; Johnson, Devon K; Krejcik, Patrick; Lu, Wei; Marsh, Kenneth; Oz, Erdem; Siemann, Robert; Walz, Dieter

2005-01-01

The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10kA will be delivered at a particle energy of 28GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts ...

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...

Measurements and analysis of a high-brightness electron beam collimated in a magnetic bunch compressor

Science.gov (United States)

Zhou, F.; Bane, K.; Ding, Y.; Huang, Z.; Loos, H.; Raubenheimer, T.

2015-05-01

A collimator located in a magnetic bunch compressor of a linear accelerator driven x-ray free electron laser has many potential applications, such as the removal of horns in the current distribution, the generation of ultrashort beams, and as a diagnostic of the beam slice emittance. Collective effects, however, are a major concern in applying the technique. Systematic measurements of emittance and analysis were performed using a collimator in the first bunch compressor of the Linac Coherent Light Source (LCLS). In the nominal, undercompressed configuration using the collimator we find that the y emittance (nonbending plane) is not increased, and the x emittance (in the bending plane) is increased by about 25%, in comparison to the injector emittance. From the analysis we conclude that the parasitic effects associated with this method are dominated by coherent synchrotron radiation (CSR), which causes a "systematic error" for measuring slice emittance at the bending plane using the collimation method. In general, we find good agreement between the measurements and simulations including CSR. However, for overcompressed beams at smaller collimator gaps, an extra emittance increase is found that does not agree with 1D simulations and is not understood.

Design, construction and measurements of an alpha magnet as a solution for compact bunch compressor for the electron beam from Thermionic RF Gun

Science.gov (United States)

Rajabi, A.; Jazini, J.; Fathi, M.; Sharifian, M.; Shokri, B.

2018-03-01

The beam produced by a thermionic RF gun has wide energy spread that makes it unsuitable for direct usage in photon sources. Here in the present work, we optimize the extracted beam from a thermionic RF gun by a compact economical bunch compressor. A compact magnetic bunch compressor (Alpha magnet) is designed and constructed. A comparison between simulation results and experimental measurements shows acceptable conformity. The beam dynamics simulation results show a reduction of the energy spread as well as a compression of length less than 1 ps with 2.3 mm-mrad emittance.

Flat bunch creation and acceleration: a possible path for the LHC luminosity upgrade

International Nuclear Information System (INIS)

Bhat, C.M.

2009-01-01

Increasing the collider luminosity by replacing bunches having Gaussian line-charge distribution with flat bunches, but with same beam-beam tune shift at collision, has been studied widely in recent years. But, creation of 'stable' flat bunches (and their acceleration) using a multiple harmonic RF system has not been fully explored. Here, we review our experience with long flat bunches in the barrier RF buckets at Fermilab.We presentsome preliminary results from beam dynamics simulations and recent beam studies in the LHC injectors to create stable flat bunches using double harmonic RF systems. The results deduced from these studies will be used to model the necessary scheme for luminosity upgrade in the LHC. We have also described a viable (and economical) way for creation and acceleration of flat bunches in the LHC. The flat bunch scheme may have many advantages over the LHC baseline scenario, particularly because of the reduced momentum spread of the bunch for increased intensities.

On the preservation of single- and multi-bunch emittance in linear accelerators

International Nuclear Information System (INIS)

Drevlak, M.

1995-11-01

This document is concentrated on the investigation of the dynamics of a particle beam in a linear accelerator. We numerically simulate a number of effects and evaluate the severity of their impact on the beam. Furthermore, we examine the applicability of several correction techniques aiming at the suppression or correction of the effects diluting the beam emittance. First, there is the issue of single-bunch dynamics : we see that wake field effects and dispersive errors can cause a significant emittance growth. Secondly, long range dipole wakes and dispersive effects arising from the energy spread between different bunches will cause relative offsets between the individual bunches and likewise result in emittance growth. Finally, we observe interactions between the single-bunch and multi-bunch dynamics in a bunch train, which further aggravate these effects. The corrective measures against emittance growth are first tested with respect to individual effects relating to issues of single- or multi-bunch dynamics. Later, these different correction techniques are joined to one machine tuning procedure that will be applied in order to achieve good emittance preservation for operation of the accelerator with a full beam consisting of the full number of bunches. The performance of this procedure is tested in simulations of the combined single- and multi-bunch dynamics. Finally, tolerances on the machine alignment as well as machine and beam parameters are established. (orig.)

Computer modelling of bunch-by-bunch feedback for the SLAC B-factory design

International Nuclear Information System (INIS)

Briggs, D.; Fox, J.D.; Hosseini, W.; Klaisner, L.; Morton, P.; Pellegrin, J.L.; Thompson, K.A.; Lambertson, G.

1991-05-01

The SLAC B-factory design, with over 1600 high current bunches circulating in each ring, will require a feedback system to avoid coupled-bunch instabilities. A computer model of the storage ring, including the RF system, wave fields, synchrotron radiation loss, and the bunch-by-bunch feedback system is presented. The feedback system model represents the performance of a fast phase detector front end (including system noise and imperfections), a digital filter used to generate a correction voltage, and a power amplifier and beam kicker system. The combined ring-feedback system model is used to study the feedback system performance required to suppress instabilities and to quantify the dynamics of the system. Results are presented which show the time development of coupled bunch instabilities and the damping action of the feedback system. 3 refs., 5 figs., 2 tabs

Creation and storage of long and flat bunches in the LHC

Energy Technology Data Exchange (ETDEWEB)

Damerau, H.

2005-09-01

To maximize the luminosity of the Large Hadron Collider (LHC), the collision of particle bunches with a uniform longitudinal particle density is considered for a future upgrade. The benefits of such bunches and their generation by means of special longitudinal beam manipulations are presented in this report. Three possible options are analyzed with respect to their potential luminosity gain at the beam-beam limit: short rectangular bunches held by radio frequency (RF) harmonics using multiples of the nominal RF frequency of 400.8 MHz, long and flat bunches held by multiples of 40.08 MHz, and so-called superbunches, confined by barrier buckets. The comparison of the three different approaches shows that flat bunches, with an intermediate bunch length of the order of several meters, are capable of producing a comparable luminosity to superbunches, while avoiding most of their inherent disadvantages. Possible schemes to create the bunches with uniform line density are studied and a longitudinal manipulation to combine a batch of ordinary bunches into a long and flat bunch is proposed. These RF gymnastics are based on well-proven techniques such as batch compression and bunch pair merging. Their advantages and disadvantages, including optimization with respect to degradation of the longitudinal particle density, are discussed in detail. Special attention is paid to the investigation of collective effects due to the large line charge density and the influence of the beam on the RF installation is also studied. (Orig.)

Creation and Storage of Long and Flat Bunches in the LHC

CERN Document Server

Damerau, H

2005-01-01

To maximize the luminosity of the Large Hadron Collider (LHC), the collision of particle bunches with a uniform longitudinal particle density is considered for a future upgrade. The benefits of such bunches and their generation by means of special longitudinal beam manipulations are presented in this report. Three possible options are analyzed with respect to their potential luminosity gain at the beam-beam limit: short rectangular bunches held by radio frequency (RF) harmonics using multiples of the nominal RF frequency of 400.8MHz, long and flat bunches held by multiples of 40.08MHz, and so-called superbunches, confined by barrier buckets. The comparison of the three different approaches shows that flat bunches, with an intermediate bunch length of the order of several meters, are capable of producing a comparable luminosity to superbunches, while avoiding most of their inherent disadvantages. Possible schemes to create the bunches with uniform line density are studied and a longitudinal manipulation to com...

The ATLAS beam pick-up based timing system

International Nuclear Information System (INIS)

Ohm, C.; Pauly, T.

2010-01-01

The ATLAS BPTX stations are composed of electrostatic button pick-up detectors, located 175 m away along the beam pipe on both sides of ATLAS. The pick-ups are installed as a part of the LHC beam instrumentation and used by ATLAS for timing purposes. The usage of the BPTX signals in ATLAS is twofold: they are used both in the trigger system and for LHC beam monitoring. The BPTX signals are discriminated with a constant-fraction discriminator to provide a Level-1 trigger when a bunch passes through ATLAS. Furthermore, the BPTX detectors are used by a stand-alone monitoring system for the LHC bunches and timing signals. The BPTX monitoring system measures the phase between collisions and clock with a precision better than 100 ps in order to guarantee a stable phase relationship for optimal signal sampling in the sub-detector front-end electronics. In addition to monitoring this phase, the properties of the individual bunches are measured and the structure of the beams is determined. On September 10, 2008, the first LHC beams reached the ATLAS experiment. During this period with beam, the ATLAS BPTX system was used extensively to time in the read-out of the sub-detectors. In this paper, we present the performance of the BPTX system and its measurements of the first LHC beams.

Vertical beam size measurement in the CESR-TA e{sup +}e{sup −} storage ring using x-rays from synchrotron radiation

Energy Technology Data Exchange (ETDEWEB)

Alexander, J.P.; Chatterjee, A.; Conolly, C.; Edwards, E.; Ehrlichman, M.P.; Fontes, E. [Cornell University, Ithaca, NY 14853 (United States); Heltsley, B.K., E-mail: bkh2@cornell.edu [Cornell University, Ithaca, NY 14853 (United States); Hopkins, W.; Lyndaker, A.; Peterson, D.P.; Rider, N.T.; Rubin, D.L.; Savino, J.; Seeley, R.; Shanks, J. [Cornell University, Ithaca, NY 14853 (United States); Flanagan, J.W. [High Energy Accelerator Research Organization (KEK), Tsukuba (Japan)

2014-06-01

We describe the construction and operation of an X-ray beam size monitor (xBSM), a device measuring e{sup +} and e{sup −} beam sizes in the CESR-TA storage ring using synchrotron radiation. The device can measure vertical beam sizes of 10–100μm on a turn-by-turn, bunch-by-bunch basis at e{sup ±} beam energies of ∼2GeV. At such beam energies the xBSM images X-rays of ϵ≈1–10keV (λ≈0.1–1nm) that emerge from a hard-bend magnet through a single- or multiple-slit (coded aperture) optical element onto an array of 32 InGaAs photodiodes with 50μm pitch. Beamlines and detectors are entirely in-vacuum, enabling single-shot beam size measurement down to below 0.1 mA (2.5×10{sup 9} particles) per bunch and inter-bunch spacing of as little as 4 ns. At E{sub b}=2.1GeV, systematic precision of ∼1μm is achieved for a beam size of ∼12μm; this is expected to scale as ∝1/σ{sub b} and ∝1/E{sub b}. Achieving this precision requires comprehensive alignment and calibration of the detector, optical elements, and X-ray beam. Data from the xBSM have been used to extract characteristics of beam oscillations on long and short timescales, and to make detailed studies of low-emittance tuning, intra-beam scattering, electron cloud effects, and multi-bunch instabilities.

Formation of a single-bunch beam in the booster synchrotron at SPring-8

CERN Document Server

Suzuki, H; Ego, H; Hara, M; Hosoda, N; Kawashima, Y; Ohashi, Y; Ohshima, T; Tani, N; Yabashi, M; Yonehara, H

2000-01-01

In order to fill a radio frequency (rf) bucket with an electron beam in the storage ring at SPring-8, an rf knockout system was installed in the booster synchrotron. With this system, the energy of the electron beam injected from the linac was increased from 1 to 8 GeV. The time width of multi-bunch beams from the linac operated at 2856 MHz rf can be selected as 1 or 40 ns. The beam injected from the linac is distributed in rf buckets of the booster synchrotron operated at 508.58 MHz rf. To fill a single rf bucket with a beam, the rf knockout system is operated at a minimum beam energy of 1 GeV. By using the rf knockout system, the electron beam is effectively kept in a single rf bucket. Then the beam is injected into a targeted rf bucket in the storage ring with a precise timing system. The beam intensity of satellite rf buckets in the storage ring was measured with a photon counting method and determined to be 10 sup - sup 6 less than that of the main rf bucket. In this paper, we describe the rf knockout sy...

Beam measurement of the high frequency impedance sources with long bunches in the CERN Super Proton Synchrotron

Directory of Open Access Journals (Sweden)

A. Lasheen

2018-03-01

Full Text Available Microwave instability in the Super Proton Synchrotron (SPS at CERN is one of the main limitations to reach the requirements for the High Luminosity-LHC project (increased beam intensity by a factor 2. To identify the impedance source responsible of the instability, beam measurements were carried out to probe the SPS impedance. The method presented in this paper relies on measurements of the unstable spectra of single bunches, injected in the SPS with the rf voltage switched off. The modulation of the bunch profile gives information about the main impedance sources driving microwave instability, and is compared to particle simulations using the SPS impedance model to identify the most important contributions. This allowed us to identify the vacuum flanges as the main impedance source for microwave instability in the SPS, and to evaluate possible missing impedance sources.

Beam measurement of the high frequency impedance sources with long bunches in the CERN Super Proton Synchrotron

Science.gov (United States)

Lasheen, A.; Argyropoulos, T.; Bohl, T.; Esteban Müller, J. F.; Timko, H.; Shaposhnikova, E.

2018-03-01

Microwave instability in the Super Proton Synchrotron (SPS) at CERN is one of the main limitations to reach the requirements for the High Luminosity-LHC project (increased beam intensity by a factor 2). To identify the impedance source responsible of the instability, beam measurements were carried out to probe the SPS impedance. The method presented in this paper relies on measurements of the unstable spectra of single bunches, injected in the SPS with the rf voltage switched off. The modulation of the bunch profile gives information about the main impedance sources driving microwave instability, and is compared to particle simulations using the SPS impedance model to identify the most important contributions. This allowed us to identify the vacuum flanges as the main impedance source for microwave instability in the SPS, and to evaluate possible missing impedance sources.

Note on polarized RHIC bunch arrangement

International Nuclear Information System (INIS)

Underwood, D.

1996-01-01

We discuss what combinations of bunch polarization in the two RHIC rings are necessary to do the physics measurements at various interaction regions. We also consider the bunches for both the pion inclusive and p-p elastic polarization measurements. Important factors to consider are the direction of the polarization with respect to the momentum in each bunch, the beam gas backgrounds, and the simulation of zero - polarization in one beam by averaging + and - helicity, and luminosity monitoring for normalization. These considerations can be addressed by setting the relative number of each of the 9 combinations possible at each of the 6 interaction regions. The combinations are (+ empty -) yellow X (+ empty -)blue, where yellow and blue are the counter-rotating rings

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

Bunch compression efficiency of the femtosecond electron source at Chiang Mai University

International Nuclear Information System (INIS)

Thongbai, C.; Kusoljariyakul, K.; Saisut, J.

2011-01-01

A femtosecond electron source has been developed at the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University (CMU), Thailand. Ultra-short electron bunches can be produced with a bunch compression system consisting of a thermionic cathode RF-gun, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. To obtain effective bunch compression, it is crucial to provide a proper longitudinal phase-space distribution at the gun exit matched to the subsequent beam transport system. Via beam dynamics calculations and experiments, we investigate the bunch compression efficiency for various RF-gun fields. The particle distribution at the RF-gun exit will be tracked numerically through the alpha-magnet and beam transport. Details of the study and results leading to an optimum condition for our system will be presented.

Bunch compression efficiency of the femtosecond electron source at Chiang Mai University

Science.gov (United States)

Thongbai, C.; Kusoljariyakul, K.; Saisut, J.

2011-07-01

A femtosecond electron source has been developed at the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University (CMU), Thailand. Ultra-short electron bunches can be produced with a bunch compression system consisting of a thermionic cathode RF-gun, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. To obtain effective bunch compression, it is crucial to provide a proper longitudinal phase-space distribution at the gun exit matched to the subsequent beam transport system. Via beam dynamics calculations and experiments, we investigate the bunch compression efficiency for various RF-gun fields. The particle distribution at the RF-gun exit will be tracked numerically through the alpha-magnet and beam transport. Details of the study and results leading to an optimum condition for our system will be presented.

Collisions with 1200 proton bunches in each beam recorded by the CMS detector April 2018

CERN Multimedia

Mc Cauley, Thomas

2018-01-01

These images depict collisions recorded by the CMS detector on 28 April 2018 from 1200 proton bunches in each circulating beam. The yellow lines represents reconstructed particle trajectories in the tracker. The green and blue rectangles represent energy deposits in the electromagnetic and hadronic calorimeters, respectively. The long red lines represent reconstructed muon trajectories.

The 'Fresh-Bunch' technique in FELs

International Nuclear Information System (INIS)

Ben-Zvi, I.; Yang, K.M.; Yu, L.H.

1991-01-01

The 'Fresh Bunch' technique is being proposed as a method of increasing the gain and power of FEL amplifiers in which the length of the optical radiation pulse is shorter than the length of the electron bunch. In multi-stage FEL, electron beam energy spread is increased by the FEL interaction in the early stages. In the 'Fresh Bunch' technique, the low energy spread of the electron beam is recovered by shifting the radiation pulse to an undisturbed part of the electron bunch, thus improving the gain and trapping fraction in later stages. A test case for the application of the Fresh Bunch method is demonstrated by numerical simulation. In this particular example we examine a subharmonically seeded VUV Free-Electron Laser. We begin with the generation of harmonic radiation, which takes place over one part of the electron bunch. Then the radiation is shifted by means of a strong dispersive section to a fresh part of the bunch for exponential amplification and tapered wiggler amplification. By starting over with a new ensemble of electrons, the energy spread introduced by the bunching in the fundamental is removed, leading to an increased gain. Furthermore, it is possible to use a much stronger seed in the fundamental without incurring the penalty of a large energy spread later on. We note that more than a single application of the 'Fresh Bunch' method may be done in a single FEL multiplier-amplifier. Thus x-ray wavelengths may be reached by successive multiplication in a chain of FEL amplifiers starting from a tunable seed laser. 5 refs., 2 figs., 2 tabs

Bunch-motion feedback for B-factories

International Nuclear Information System (INIS)

Lambertson, G.R.

1992-09-01

The colliding electron and positron beams in a B-factory must have average current of one ampere or more to produce the required luminosity. The high current interacts with structures in the beam tube to drive strong coupled-bunch (c.b.) instabilities. To suppress these instabilities requires negative feedback of the bunch motions. Beam impedances arising from strong rf cavity modes should first be reduced to make the required feedback damping rate practical and the cost economical. In what follows, control of transverse motions will be discussed first, then longitudinal. We shall use the parameters of the 3.1 GeV ring of PEP-II to illustrate the general requirements

Time-domain diagnostics in the picosecond regime

International Nuclear Information System (INIS)

Lumpkin, A.H.

1995-01-01

The measurement of bunch length and longitudinal profile for microbunches of electrons and positrons in the ps and sub-ps regime will be a critical part of validating performance of proposed facilities. Data will be presented showing single-sweep streak camera results at σ res ∼ 68 fs and projected synchroscan sweep resolution at σ ∼ 600 fs. Additionally, an rf cavity operating in a transverse magnetic mode has recently been shown to produce σ res ∼ 280 fs when used with a low-emittance beam. The potential for dual-sweep streak work with σ res < 1 ps on the fast axis is also described

Micro-bunching diagnostics for the ICA by coherent transition radiation

International Nuclear Information System (INIS)

Liu, Y.; Bogacz, S.A.; Cline, D.B.; Wang, X.J.; Pogorelsky, I.V.; Kimura, W.D.

1995-01-01

Here, the authors propose an effective method to detect micro-bunching effects (10 fs bunch length), produced by the ICA interaction, by using the CTR spectrum. The re-bunching of initially energy modulated e-beam passing through a Hydrogen gas cell (ICA interaction) is studied via a Monte Carlo simulation code (STI), as well as in a space-charge dominated region by a multi-particle time domain tracking code (PARMELA). The results show that even in a strong space-charge dominated region the re-bunching effect is still very pronounced. The erosion of bunching due to the space-charge defocusing washes out the final bunching peak only by about 10% (FWHM). The longitudinal distribution of a micro-bunched beam is Fourier analyzed to find the dominant harmonics contributing to the CTR. The CTR spectrum is calculated analytically for the ICA situation. A schematic of the experimental set up is also proposed

'Electron compression' of beam-beam footprint in the Tevatron

International Nuclear Information System (INIS)

Shiltsev, V.; Finley, D.A.

1997-08-01

The beam-beam interaction in the Tevatron collider sets some limits on bunch intensity and luminosity. These limits are caused by a tune spread in each bunch which is mostly due to head-on collisions, but there is also a bunch-to-bunch tune spread due to parasitic collisions in multibunch operation. We describe a counter-traveling electron beam which can be used to eliminate these effects, and present general considerations and physics limitations of such a device which provides 'electron compression' of the beam-beam footprint in the Tevatron

Interferometrically enhanced sub-terahertz picosecond imaging utilizing a miniature collapsing-field-domain source

Science.gov (United States)

Vainshtein, Sergey N.; Duan, Guoyong; Mikhnev, Valeri A.; Zemlyakov, Valery E.; Egorkin, Vladimir I.; Kalyuzhnyy, Nikolay A.; Maleev, Nikolai A.; Näpänkangas, Juha; Sequeiros, Roberto Blanco; Kostamovaara, Juha T.

2018-05-01

Progress in terahertz spectroscopy and imaging is mostly associated with femtosecond laser-driven systems, while solid-state sources, mainly sub-millimetre integrated circuits, are still in an early development phase. As simple and cost-efficient an emitter as a Gunn oscillator could cause a breakthrough in the field, provided its frequency limitations could be overcome. Proposed here is an application of the recently discovered collapsing field domains effect that permits sub-THz oscillations in sub-micron semiconductor layers thanks to nanometer-scale powerfully ionizing domains arising due to negative differential mobility in extreme fields. This shifts the frequency limit by an order of magnitude relative to the conventional Gunn effect. Our first miniature picosecond pulsed sources cover the 100-200 GHz band and promise milliwatts up to ˜500 GHz. Thanks to the method of interferometrically enhanced time-domain imaging proposed here and the low single-shot jitter of ˜1 ps, our simple imaging system provides sufficient time-domain imaging contrast for fresh-tissue terahertz histology.

Diode-pumped passively mode-locked sub-picosecond Yb:LuAG ceramic laser

International Nuclear Information System (INIS)

Zhu Jiang-Feng; Liu Kai; Wang Jun-Li; Yang Yu; Wang Hui-Bo; Gao Zi-Ye; Jiang Li; Xie Teng-Fei; Chao-Yu Li; Pan Yu-Bai; Wei Zhi-Yi

2017-01-01

In this paper the laser activities of a diode-pumped Yb:LuAG ceramic which was prepared by the solid-state reactive sintering method were reported. The maximum output power was 1.86 W in the continuous wave (CW) laser operation, corresponding to a slope efficiency of 53.6%. The CW laser could be tuned from 1030 to 1096 nm by inserting a prism in the cavity. With the assist of a semiconductor saturable absorber mirror (SESAM), passive mode-locking was realized, delivering sub-picosecond pulses with 933 fs duration and an average power of 532 mW at a repetition rate of 90.35 MHz. (paper)

Initial Observations of Micropulse Elongation of Electron Beams in a SCRF Accelerator

Energy Technology Data Exchange (ETDEWEB)

Lumpkin, A. H. [Fermilab; Thurman-Keup, R. [Fermilab; Edstrom Jr., D. [Fermilab; Ruan, J. [Fermilab; Santucci, J. [Fermilab

2016-10-09

Commissioning at the SCRF accelerator at the Fermilab Accelerator Science and Technology (FAST) Facility has included the implementation of a versatile bunch-length monitor located after the 4-dipole chicane bunch compressor for electron beam energies of 20-50 MeV and integrated charges in excess of 10 nC. The team has initially used a Hamamatsu C5680 synchroscan streak camera to assess the effects of space charge on the electron beam bunch lengths. An Al-coated Si screen was used to generate optical transition radiation (OTR) resulting from the beam’s interaction with the screen. The chicane bypass beamline allowed the measurements of the bunch length without the compression stage at the downstream beamline location using OTR and the streak camera. We have observed electron beam bunch lengths from 5 to 16 ps (sigma) for micropulse charges of 60 pC to 800 pC, respectively. We also report a compressed sub-ps micropulse case.

On some properties of longitudinal and transverse coupled-bunch instabilities

International Nuclear Information System (INIS)

Kamiya, Yukihide.

1983-02-01

Some properties of longitudinal and transverse coupled-bunch instabilities have been investigated theoretically and computationally, mainly based on a rigid-bunch model. In this report, we will study Robinson's stability, sum rules of the instabilities and the cure of instabilities by producing the oscillation frequencies different from bunch to bunch, and also give the numerical examples for KEK-PF storage ring. KEYWORD: storage ring, accelerator, bunched beam, longitudinal instability, transverse instability, coupled-bunch instability. (author)

Production of high power microwaves for particle acceleration with an FEL bunched electron beam

CERN Document Server

Gardelle, J; Marchese, G; Padois, M; Rullier, J L; Donohue, J T

1999-01-01

Among the studies in the framework of high gradient linear electron-positron collider research, the Two-Beam Accelerator (TBA) is a very promising concept, and two projects are in progress, the Compact Linear Collider project at CERN (W. Schnell, Report no. CERN SL/92-51 and CLIC note 184; K. Huebner, CERN/PS 92-43, CLIC note 176; S. Van der Meer, CERN/PS 89-50, CLIC note 97.) and the Relativistic Klystron-TBA project at LBNL (Technical Review Committee, International Linear Collider Technical Review Committee Report 1995, SLAC-R-95-471, 1995). In a TBA an extremely intense low-energy electron beam, called the drive beam, is bunched at the desired operating frequency, and upon passing through resonant cavities generates radio-frequency power for accelerating the main beam. Among the different approaches to the production of a suitable drive beam, the use of an FEL has been proposed and is under active study at CEA/CESTA.

Experimental observation of IFEL micro-bunching using coherent transition radiation

International Nuclear Information System (INIS)

Liu, Y.; Cline, D.B.; Wang, X.J.; Babzien, M.

1997-01-01

Electron beam bunching in the optical wavelength was observed experimentally for the first time at the Brookhaven Accelerator Test Facility (ATF) using the Inverse Free Electron (IFEL) accelerator. The micro-bunched electron beam has been studied by measuring the coherent transition radiation (CTR). The authors have experimentally observed a quadratic dependency of the CTR signal with the charge of the electron beam and the observation distance

Self-bunching electron guns

Science.gov (United States)

Mako, Frederick M.; Len, L. K.

1999-05-01

We report on three electron gun projects that are aimed at power tube and injector applications. The purpose of the work is to develop robust electron guns which produce self-bunched, high-current-density beams. We have demonstrated, in a microwave cavity, self-bunching, cold electron emission, long life, and tolerance to contamination. The cold process is based on secondary electron emission. FMT has studied using simulation codes the resonant bunching process which gives rise to high current densities (0.01-5 kA/cm2), high charge bunches (up to 500 nC/bunch), and short pulses (1-100 ps) for frequencies from 1 to 12 GHz. The beam pulse width is nominally ˜5% of the rf period. The first project is the L-Band Micro-Pulse Gun (MPG). Measurements show ˜40 ps long micro-bunches at ˜20 A/cm2 without contamination due to air exposure. Lifetime testing has been carried out for about 18 months operating at 1.25 GHz for almost 24 hours per day at a repetition rate of 300 Hz and 5 μs-long macro-pulses. Approximately 5.8×1013 micro-bunches or 62,000 coulombs have passed through this gun and it is still working fine. The second project, the S-Band MPG, is now operational. It is functioning at a frequency of 2.85 GHz, a repetition rate of 30 Hz, with a 2 μs-long macro-pulse. It produces about 45 A in the macro-pulse. The third project is a 34.2 GHz frequency-multiplied source driven by an X-Band MPG. A point design was performed at an rf output power of 150 MW at 34.2 GHz. The resulting system efficiency is 53% and the gain is 60 dB. The system efficiency includes the input cavity efficiency, input driver efficiency (a 50 MW klystron at 11.4 GHz), output cavity efficiency, and the post-acceleration efficiency.

A fifth harmonic rf bunch monitor for the ANL-APS electron linac

International Nuclear Information System (INIS)

Nassiri, A.; Grelick, A.

1993-01-01

The function of a fifth harmonic (14.28 GHz) bunch monitor is to provide a signal which is proportional to the electron beam bunch size. The monitoring of the rf power signal at 14.28 GHz enables the operator to optimize the rf bunching of the beam at the end of the first accelerating section where the full bunching has been formed and remains mainly constant in size throughout the rest of the electron linac. A modified version of the SLAC original bunch monitor has been fabricated and its rf properties measured. This paper describes the design and the initial measurement results

A fifth harmonic RF bunch monitor for the ANL-APS electron linac

International Nuclear Information System (INIS)

Nassiri, A.; Grelick, A.

1993-01-01

The function of a fifth harmonic (14.28 GHz) bunch monitor is to provide a signal which is proportional to the electron beam bunch size. The monitoring of the rf power signal at 14.28 GHz enables the operator to optimize the rf bunching of the beam at the end of the first accelerating section where the full bunching has been formed and remains mainly constant in size throughout the rest of the electron linac. A modified version of the SLAC original bunch monitor has been fabricated and its rf properties measured. This paper describes the design and the initial measurements results

Implementation of the Electronics Chain for the Bunch by Bunch Intensity Measurement Devices for the LHC

CERN Document Server

Belohrad, D; Ludwig, M; Savioz, J J; Thoulet, S

2009-01-01

The fast beam intensity measurements for the LHC are provided by eight Fast Beam Current Transformers (FBCT). Four FBCTs installed in the LHC rings are capable of providing both bunch-by-bunch and total turn-by-turn beam intensity information. A further four FBCTs, two in each of the LHC dump lines, are used to measure the total extracted beam intensity. In addition to providing intensity information the ring FBCTs also send signals to the machine protection system. This increases the complexity of both the RF front-end and the digital acquisition parts of the signal processing chain. The aim of this paper is to discuss the implemented hardware solution for the FBCT system, in particular with respect to the signal distribution, FPGA signal processing, calibration, and interaction of the FBCTs with the machine protection chain.

Enhanced coherent undulator radiation from bunched electron beams

International Nuclear Information System (INIS)

Berryman, K.W.; Crosson, E.R.; Ricci, K.N.; Smith, T.I.

1996-01-01

When energetic bunches of electrons traverse an undulator field, they can spontaneously emit radiation both coherently and incoherently. Although it has generally been assumed that undulator radiation is incoherent at wavelengths short compared to the longitudinal size of the electron bunch, several recent observations have proved this assumption false. Furthermore, the appearance of coherent radiation is often accompanied by a significant increase in radiated power. Here we report observations of strongly enhanced coherent spontaneous radiation together with direct measurements, using transition radiation techniques, of the electron distributions responsible for the coherent emission. We also report demonstrated enhancements in the predicted spontaneous radiated power by as much as 6x10 4 using electron bunch compression. copyright 1996 American Institute of Physics

Acceleration of a high-current single bunch in a linear accelerator

International Nuclear Information System (INIS)

Takeda, Seishi

1984-01-01

Some problems associated with the feasibility of an electron-positron linear collider with colliding energy of about 1x1 TeV are discussed. The first problem is related to the generation of high-current single bunch. A quasi-relativistic electron beam from an electron gun is injected into one bucket of the accelerating fields, in opposition to the longitudinal defocusing due to the space-charge effect. For generating a high-current single bunch, the beam bunching by means of the velocity modulation with a subharmonic prebuncher (SHPB) is indispensable. Three existing second generation single bunch electron linear accelerators (SLC, ANL and ISLR-Osaka Univ.) are briefly described. The results of the simulation of subharmonic-bunching is also reported. The second problem is associated with the physics of accelerating high-current single bunch. The longitudinal and transverse wake fields generated by a bunch-cavity interaction and the energy spread of the single bunch are analyzed and discussed. (Aoki, K.)

Direct experimental observation of the gas density depression effect using a two-bunch X-ray FEL beam.

Science.gov (United States)

Feng, Y; Schafer, D W; Song, S; Sun, Y; Zhu, D; Krzywinski, J; Robert, A; Wu, J; Decker, F J

2018-01-01

The experimental observation of the depression effect in gas devices designed for X-ray free-electron lasers (FELs) is reported. The measurements were carried out at the Linac Coherent Light Source using a two-bunch FEL beam at 6.5 keV with 122.5 ns separation passing through an argon gas cell. The relative intensities of the two pulses of the two-bunch beam were measured, after and before the gas cell, from X-ray scattering off thin targets by using fast diodes with sufficient temporal resolution. At a cell pressure of 140 hPa, it was found that the after-to-before ratio of the intensities of the second pulse was about 17% ± 6% higher than that of the first pulse, revealing lower effective attenuation of the gas cell due to heating by the first pulse and subsequent gas density reduction in the beam path. This measurement is important in guiding the design and/or mitigating the adverse effects in gas devices for high-repetition-rate FELs such as the LCLS-II and the European XFEL or other future high-repetition-rate upgrades to existing FEL facilities.

Method and apparatus for control of coherent synchrotron radiation effects during recirculation with bunch compression

Science.gov (United States)

Douglas, David R; Tennant, Christopher

2015-11-10

A modulated-bending recirculating system that avoids CSR-driven breakdown in emittance compensation by redistributing the bending along the beamline. The modulated-bending recirculating system includes a) larger angles of bending in initial FODO cells, thereby enhancing the impact of CSR early on in the beam line while the bunch is long, and 2) a decreased bending angle in the final FODO cells, reducing the effect of CSR while the bunch is short. The invention describes a method for controlling the effects of CSR during recirculation and bunch compression including a) correcting chromatic aberrations, b) correcting lattice and CSR-induced curvature in the longitudinal phase space by compensating T.sub.566, and c) using lattice perturbations to compensate obvious linear correlations x-dp/p and x'-dp/p.

Main Ring bunch spreaders: Past, 1987/1988 fixed target run, and proposed future

International Nuclear Information System (INIS)

Jackson, G.P.

1989-01-01

During the last 1987--1988 fixed target running period beam intensity was limited many times by coherent instabilities in both the Main Ring and in the Tevatron. The intensity thresholds for instabilities are generally inversely proportional to the proton bunch length. Since fixed target operations are insensitive to the longitudinal phase space emittance of the beam, bunch spreaders are employed to increase this emittance, and hence the bunch length. As a result, more beam intensity can be delivered to the fixed target experiments. This paper starts with a short history behind the old Main Ring bunch spreader. After discussing the physics of stimulated emittance growth, the design and performance of the 1987--1988 fixed target run Main Ring bunch spreader is discussed. Finally, designs of improved Main Ring and Tevatron bunch spreaders for the next fixed target run are proposed. 23 figs

Developing electron beam bunching technology for improving light sources

International Nuclear Information System (INIS)

Carlsten, B.E.; Chan, K.C.D.; Feldman, D.W.

1997-01-01

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project was to develop a new electron bunch compression technology, experimentally demonstrate subpicosecond compression of bunches with charges on the order of 1 nC, and to theoretically investigate fundamental limitations to electron bunch compression. All of these goals were achieved, and in addition, the compression system built for this project was used to generate 22 nm light in a plasma-radiator light source

Temporal dynamics of the longitudinal bunch profile in a laser wakefield accelerator

International Nuclear Information System (INIS)

Heigoldt, Matthias

2017-01-01

This thesis deals with the temporal characterisation of electron bunches produced by a laser plasma accelerator. In the so-called laser wakefield acceleration (LWFA) scheme, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m, thus exceeding the fields attainable by current state-of-the-art radio frequency (RF) accelerators by four orders of magnitude, offering the prospect of downsizing both the size and cost of such machines. Furthermore, by intrinsically confining the accelerated electron beam to the μm-scale size of the plasma wave, LWFAs provide ultra-short and highly brilliant beams, sparking great scientific interest for their application as a driver for compact sources of ultra-short X-ray pulses, e.g. Thomson-scattering, betatron sources or table-top free-electron lasers (FELs). The bunch profile is an important quantity for the application of these sources. With particular regard to the envisioned table-top FELs, it also determines the available peak current, an import input parameter for an appropriate undulator design that is optimized to support the self-amplified spontaneous emission (SASE) process. The experiments presented in this thesis comprise the measurement of the temporal profile of electron bunches produced by LWFA and further investigation of the evolution of the temporal profile in dependence of the acceleration distance and the plasma density. By measuring the intensity spectrum of coherent transition radiation (CTR) emitted by LWFA-driven electron bunches in the frequency domain, the experiments allow a reconstruction of the longitudinal bunch profiles with unprecedented resolution. Compared to earlier work, a key improvement is the single-shot coverage of a broadband spectral range of more than four octaves, which yields a time resolution of the reconstructed bunch profile in the sub-femtosecond region. This work further inspired the development of a new

Temporal dynamics of the longitudinal bunch profile in a laser wakefield accelerator

Energy Technology Data Exchange (ETDEWEB)

Heigoldt, Matthias

2017-05-19

This thesis deals with the temporal characterisation of electron bunches produced by a laser plasma accelerator. In the so-called laser wakefield acceleration (LWFA) scheme, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m, thus exceeding the fields attainable by current state-of-the-art radio frequency (RF) accelerators by four orders of magnitude, offering the prospect of downsizing both the size and cost of such machines. Furthermore, by intrinsically confining the accelerated electron beam to the μm-scale size of the plasma wave, LWFAs provide ultra-short and highly brilliant beams, sparking great scientific interest for their application as a driver for compact sources of ultra-short X-ray pulses, e.g. Thomson-scattering, betatron sources or table-top free-electron lasers (FELs). The bunch profile is an important quantity for the application of these sources. With particular regard to the envisioned table-top FELs, it also determines the available peak current, an import input parameter for an appropriate undulator design that is optimized to support the self-amplified spontaneous emission (SASE) process. The experiments presented in this thesis comprise the measurement of the temporal profile of electron bunches produced by LWFA and further investigation of the evolution of the temporal profile in dependence of the acceleration distance and the plasma density. By measuring the intensity spectrum of coherent transition radiation (CTR) emitted by LWFA-driven electron bunches in the frequency domain, the experiments allow a reconstruction of the longitudinal bunch profiles with unprecedented resolution. Compared to earlier work, a key improvement is the single-shot coverage of a broadband spectral range of more than four octaves, which yields a time resolution of the reconstructed bunch profile in the sub-femtosecond region. This work further inspired the development of a new

Application of a Low-Energy Electron Beam as a Tool for ultrashort bunch length measurement in circular machines

CERN Document Server

Nikiforov, D A; Malyutin, D; Matveenko, A; Rusinov, K; Starostenko, A A

2017-01-01

A new diagnostic device designed for non-destructive ultrashort bunch length measurement is described. The operating principle of the device and the measuring technique are described. The possible scheme of arrangement of the device elements are described. The results of simulations of EBP application for different beams under investigation are presented. The quality requirements of the low energy testing beam are considered and resolving detector ability is determined.

Focusing and bunching of ion beam in axial injection channel of IPHC cyclotron TR24

Science.gov (United States)

Adam, T.; Ivanenko, I.; Kazarinov, N.; Osswald, F.; Traykov, E.

2017-07-01

The CYRCe cyclotron (CYclotron pour la ReCherche et l’Enseignement) is used at IPHC (Institut Pluridisciplinaire Hubert Curien) for the production of radio-isotopes for diagnostics, medical treatments and fundamental research in radiobiology. The TR24 cyclotron produced and commercialized by ACSI (Canada) delivers a 16-25 MeV proton beam with intensity from few nA up to 500 μA. The solenoidal focusing instead of existing quadrupole one is proposed in this report. The changing of the focusing elements will give the better beam matching with the acceptance of the spiral inflector of the cyclotron. The parameters of the focusing solenoid are found. Additionally, the main parameters of the bunching system are evaluated in the presence of the beam space charge. This system consists of the buncher installed in the axial injection beam line of the cyclotron. The using of the grid-less multi harmonic buncher may increase the accelerated beam current and will give the opportunity to new proton beam applications.

Multi-bunch Feedback Systems

OpenAIRE

Lonza, M.; Schmickler, H.

2016-01-01

Coupled-bunch instabilities excited by the interaction of the particle beam with its surroundings can seriously limit the performance of circular particle accelerators. These instabilities can be cured by the use of active feedback systems based on sensors capable of detecting the unwanted beam motion and actuators that apply the feedback correction to the beam. Advances in electronic technology now allow the implementation of feedback loops using programmable digital systems. Besides importa...

Design of BEPCII bunch current monitor system

International Nuclear Information System (INIS)

Zhang Lei; Ma Huizhou; Yue Junhui; Lei Ge; Cao Jianshe; Ma Li

2008-01-01

BEPC II is an electron-positron collider designed to run under multi-bunches and high beam current condition. The accelerator consists of an electron ring, a positron ring and a linear injector. In order to achieve the target luminosity and implement the equal bunch charge injection, the Bunch Current Monitor (BCM) system is built on BEPC II. The BCM system consists of three parts: the front-end circuit, the bunch current acquisition system and the bucket selection system. The control software of BCM is based on VxWorks and EPICS. With the help of BCM system, the bunch current in each bucket can be monitored in the Central Control Room. The BEPC II timing system can also use the bunch current database to decide which bucket needs to refill to implement 'top-off' injection. (authors)

''High intensity per bunch'' working group

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-07-01

Third Generation Light Sources are supposed to store high intensity beams not only in many tightly spaced bunches (multibunch operation), but also in few bunch or even single lunch modes of operation, required for example for time structure experiments. Single bunch instabilities, driven by short-range wake fields, however spoil the beam quality, both longitudinally and transversely. Straightforward ways of handling them, by pushing up the chromaticity ({zeta} = {delta}Q/({delta}p/p)) for example, enabled to raise the charge per bunch, but to the detriment of beam lifetime. In addition, since the impedance of the vacuum chamber deteriorates with the installation of new insertion devices, the current thresholds tend to dope down continuously. The goal of this Working Group was then to review these limitations in the existing storage rings, where a large number of beam measurements have been performed to characterise them, and to discuss different strategies which are used against them. About 15 different laboratories reported on the present performance of storage rings, experiences gained in high charge per bunch, and on simulation results and theoretical studies. More than 25 presentations addressed the critical issues and stimulated the discussion. Four main topics came out: - Observation and experimental data; - Impedance studies and tracking codes; - Theoretical investigations; - Cures and feedback. (author)

Different charges in the same bunch train at the European XFEL

Energy Technology Data Exchange (ETDEWEB)

Kot, Yauhen; Limberg, Torsten; Zagorodnov, Igor

2013-11-15

The injector of the European XFEL was initially designed for the operation with 1nC bunch charges. Later the flexibility of the nominal design of the injector with respect to the bunch charge was studied and extended also for smaller bunch charges down to 20 pC. A very tempting upgrade of this extension would be the operation of the European XFEL with different charges in the same train. It would make it suitable also for the experiments which require simultaneously different SASE pulse length or radiation power. Operation of two bunches within the same train sets new requirements on the working points of the injector which are to be satisfied additionally to the ones of a single charge operation. From the beam dynamics point of view here is to mention the similarity of the beam optical functions after the first accelerating module and suitable for lasing shapes of both bunches in the train at the end of the linac. Due to different charges and thus to different space charge forces which act on bunches during the passage of the linac the last condition cannot be easily satisfied even if the similarity of optical functions at the beginning of the linac is achieved. A more subtle analysis of the interplay between mismatch of beam optical functions, emittance growth in the injector and different 6D beam dynamics in the linac is needed with the final goal of successful lasing of both charges. In this paper we have investigated the possibility of the operation of different charges in the bunch train for the nominal design of the injector and for the case that it is extended by an additional laser system on the cathode. We have examined the problem of similarity of beam optical functions for different bunches in a train. We report also about the sensitivity of the beam optical functions on the chosen compression scenario and give an overview over the working points for the settings at the injector for single charge operation as well as combined working points for

Different charges in the same bunch train at the European XFEL

International Nuclear Information System (INIS)

Kot, Yauhen; Limberg, Torsten; Zagorodnov, Igor

2013-11-01

The injector of the European XFEL was initially designed for the operation with 1nC bunch charges. Later the flexibility of the nominal design of the injector with respect to the bunch charge was studied and extended also for smaller bunch charges down to 20 pC. A very tempting upgrade of this extension would be the operation of the European XFEL with different charges in the same train. It would make it suitable also for the experiments which require simultaneously different SASE pulse length or radiation power. Operation of two bunches within the same train sets new requirements on the working points of the injector which are to be satisfied additionally to the ones of a single charge operation. From the beam dynamics point of view here is to mention the similarity of the beam optical functions after the first accelerating module and suitable for lasing shapes of both bunches in the train at the end of the linac. Due to different charges and thus to different space charge forces which act on bunches during the passage of the linac the last condition cannot be easily satisfied even if the similarity of optical functions at the beginning of the linac is achieved. A more subtle analysis of the interplay between mismatch of beam optical functions, emittance growth in the injector and different 6D beam dynamics in the linac is needed with the final goal of successful lasing of both charges. In this paper we have investigated the possibility of the operation of different charges in the bunch train for the nominal design of the injector and for the case that it is extended by an additional laser system on the cathode. We have examined the problem of similarity of beam optical functions for different bunches in a train. We report also about the sensitivity of the beam optical functions on the chosen compression scenario and give an overview over the working points for the settings at the injector for single charge operation as well as combined working points for

LHC MD 652: Coupled-Bunch Instability with Smaller Emittance (all HOMs)

CERN Document Server

AUTHOR|(CDS)2081238; Timko, Helga; CERN. Geneva. ATS Department

2017-01-01

The aim of the MD was to measure the coupled-bunch stability from all HOM impedances, with a reduced longitudinal emittance in order to explore the HL-LHC conditions. The acceleration ramp was performed with the nominal beams of 2016, but a reduced target bunch length and RF voltage. With this reduced emittance, the beam remained close but above the single-bunch stability threshold. No coupled-bunch oscillations were observed, so we can conclude that the stability threshold for coupled-bunch instability is not lower than the single-bunch threshold. An interesting observation in the MD was the long-lasting injection oscillations, whose traces can still be seen at arrival to flat top; in agreement with observations in earlier MDs. The measurements took place between 28th October 20:00 and 29th October 05:10.

Coherent beam-beam effect

International Nuclear Information System (INIS)

Chao, A.W.; Keil, E.

1979-06-01

The stability of the coherent beam-beam effect between rigid bunches is studied analytically and numerically for a linear force by evaluating eigenvalues. For a realistic force, the stability is investigated by following the bunches for many revolutions. 4 refs., 13 figs., 2 tabs

Preservation of low slice emittance in bunch compressors

Directory of Open Access Journals (Sweden)

S. Bettoni

2016-03-01

Full Text Available Minimizing the dilution of the electron beam emittance is crucial for the performance of accelerators, in particular for free electron laser facilities, where the length of the machine and the efficiency of the lasing process depend on it. Measurements performed at the SwissFEL Injector Test Facility revealed an increase in slice emittance after compressing the bunch even for moderate compression factors. The phenomenon was experimentally studied by characterizing the dependence of the effect on beam and machine parameters relevant for the bunch compression. The reproduction of these measurements in simulation required the use of a 3D beam dynamics model along the bunch compressor that includes coherent synchrotron radiation. Our investigations identified transverse effects, such as coherent synchrotron radiation and transverse space charge as the sources of the observed emittance dilution, excluding other effects, such as chromatic effects on single slices or spurious dispersion. We also present studies, both experimental and simulation based, on the effect of the optics mismatch of the slices on the variation of the slice emittance along the bunch. After a corresponding reoptimization of the beam optics in the test facility we reached slice emittances below 200 nm for the central slices along the longitudinal dimension with a moderate increase up to 300 nm in the head and tail for a compression factor of 7.5 and a bunch charge of 200 pC, equivalent to a final current of 150 A, at about 230 MeV energy.

Emittance Growth during Bunch Compression in the CTF-II

Energy Technology Data Exchange (ETDEWEB)

Raubenheimer, Tor O

1999-02-26

Measurements of the beam emittance during bunch compression in the CLIC Test Facility (CTF-II) are described. The measurements were made with different beam charges and different energy correlations versus the bunch compressor settings which were varied from no compression through the point of full compression and to over-compression. Significant increases in the beam emittance were observed with the maximum emittance occurring near the point of full (maximal) compression. Finally, evaluation of possible emittance dilution mechanisms indicate that coherent synchrotron radiation was the most likely cause.

Observed Orbit Effects during Long Range Beam-Beam Studies

CERN Document Server

Alemany, R; Buffat, X; Calaga, R; Fitterer, M; Giachino, R; Hemelsoet, GH; Herr, W; Papotti, G; Pieloni, T; Poyer, M; Schaumann, M; Trad, G; Wollmann, D

2012-01-01

Possible limitations due to long range beam-beam effects at the LHC have been studied and are presented in this note. With a larger number of bunches and collisions in all interaction points, the crossing angles were reduced to enhance long range beam-beam effects. The analysis of the effects on the dynamic aperture and losses are documented in [1]. This note concentrates on the bunch-by-bunch orbit effects observed during the experiment.

A sub-picosecond pulsed 5 MeV electron beam system

International Nuclear Information System (INIS)

Farrell, J. Paul; Batchelor, K.; Meshkovsky, I.; Pavlishin, I.; Lekomtsev, V.; Dyublov, A.; Inochkin, M.; Srinivasan-Rao, T.

2001-01-01

Laser excited pulsed, electron beam systems that operate at energies from 1 MeV up to 5 MeV and pulse width from 0.1 to 100 ps are described. The systems consist of a high voltage pulser and a coaxial laser triggered gas or liquid spark gap. The spark gap discharges into a pulse forming line designed to produce and maintain a flat voltage pulse for 1 ns duration on the cathode of a photodiode. A synchronized laser is used to illuminate the photocathode with a laser pulse to produce an electron beam with very high brightness, short duration, and current at or near the space charge limit. Operation of the system is described and preliminary test measurements of voltages, synchronization, and jitter are presented for a 5 MeV system. Applications in chemistry, and accelerator research are briefly discussed

Much Ado about Microbunching: Coherent Bunching in High Brightness Electron Beams

Energy Technology Data Exchange (ETDEWEB)

Ratner, Daniel [Stanford Univ., CA (United States)

2011-05-01

The push to provide ever brighter coherent radiation sources has led to the creation of correspondingly bright electron beams. With billions of electrons packed into normalized emittances (phase space) below one micron, collective effects may dominate both the preservation and use of such ultra-bright beams. An important class of collective effects is due to density modulations within the bunch, or microbunching. Microbunching may be deleterious, as in the case of the Microbunching Instability (MBI), or it may drive radiation sources of unprecedented intensity, as in the case of Free Electron Lasers (FELs). In this work we begin by describing models of microbunching due to inherent beam shot noise, which sparks both the MBI as well as SLAC's Linac Coherent Light Source, the world's first hard X-ray laser. We first use this model to propose a mechanism for reducing the inherent beam shot noise as well as for predicting MBI effects. We then describe experimental measurements of the resulting microbunching at LCLS, including optical radiation from the MBI, as well as the first gain length and harmonic measurements from a hard X-ray FEL. In the final chapters, we describe schemes that use external laser modulations to microbunch light sources of the future. In these sections we describe coherent light source schemes for both both linacs and storage rings.

Space-charge calculation for bunched beams with 3-D ellipsoidal symmetry

International Nuclear Information System (INIS)

Garnett, R.W.; Wangler, T.P.

1991-01-01

A method for calculating 3-D space-charge forces has been developed that is suitable for bunched beams of either ions or relativistic electrons. The method is based on the analytic relations between charge-density and electric fields for a distribution with 3-D ellipsoidal symmetry in real space. At each step we use a Fourier-series representation for the smooth particle-density function obtained from the distribution of the macroparticles being tracked through the elements of the system. The resulting smooth electric fields reduce the problem of noise from artificial collisions, associated with small numbers of interacting macroparticles. Example calculations will be shown for comparison with other methods. 4 refs., 2 figs., 1 tab

Suppression of resistive instability of a bunched beam in the UNK first stage using a digital recursive filter in the feedback circuit

International Nuclear Information System (INIS)

Zhabitskij, V.M.; Korenev, I.L.; Yudin, L.A.

1993-01-01

Technique and new fast system of proton bunch beam coherent betatron oscillations suppression in the UNK first stage are suggested. The system comprises two beam monitors and two pushers. Differential equations are reduced to linear difference matrix equation which is investigated for stability using unilateral Z-transformation. 10 refs

Measurement and analysis of SPS kicker magnet heating and outgassing with Different Bunch Spacing

CERN Document Server

Barnes, M J; Cornelis, K; Ducimetière, L; Mahner, E; Papotti, G; Rumolo, G; Senaj, V; Shaposhnikova, E

2010-01-01

Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, over several hours, even above the Curie temperature of the ferrite. At present the nominal bunch spacing in the SPS is 25 ns, however for an early stage of LHC operation it is preferable to have 50 ns bunch spacing. Machine Development (MD) studies have been carried out with an inter-bunch spacing of 25 ns, 50 ns or 75 ns. For some of the SPS kicker magnets the 75 ns bunch spacing resulted in considerable beam induced heating. In addition the MDs showed that 50 ns bunch spacing could result in a very rapid pressure rise in the kicker magnet and thus cause an interlock. This paper discusses the MD observations of the SPS kickers and analyses the available d...

Longitudinal coupled-bunch instability studies in the PS

CERN Document Server

Damerau, H

2017-01-01

The main longitudinal limitation for LHC-type beams inthe PS are coupled-bunch instabilities. A dedicated proto-typefeedbacksystemusingaFinemetcavityasalongitudinalkicker has been installed. Extensive tests with beam havebeen performed to explore the intensity reach with this feed-back. The maximum intensity with nominal longitudinalemittance at PS extraction has been measured, as well as theemittance required to keep the beam longitudinally stableat the design intensity for the High-Luminosity LHC (HL-LHC). A higher-harmonic cavity is a complementary op-tion to extend the intensity reach beyond the capabilities ofthe coupled-bunch feedback. Preliminary machine develop-ment (MD) studies operating one20MHzor one40MHzRF system as a higher harmonic at the flat-top indicate thebeneficial effect on longitudinal beam stability

Application accelerator system having bunch control

Science.gov (United States)

Wang, Dunxiong; Krafft, Geoffrey Arthur

1999-01-01

An application accelerator system for monitoring the gain of a free electron laser. Coherent Synchrotron Radiation (CSR) detection techniques are used with a bunch length monitor for ultra short, picosec to several tens of femtosec, electron bunches. The monitor employs an application accelerator, a coherent radiation production device, an optical or beam chopping device, an infrared radiation collection device, a narrow-banding filter, an infrared detection device, and a control.

Stability of longitudinal oscillations of a bunch propagating through an evacuated chamber with reactive impedance

International Nuclear Information System (INIS)

Besnier, G.

1979-01-01

The longitudinal space-charge force is assumed to vary like the derivative of the longitudinal beam density. Solutions of the linearized Vlasov equation are then given as an expansion of normal modes for the longitudinal phase-space density of a bunched beam. For a given bunch intensity, the method allows calculation of the required synchrotron frequency spread inside a parabolic bunch, in order to stabilize the beam against coherent oscillations by Landau-damping. (Auth.)

Controlling multi-bunches by a fast phase switching

International Nuclear Information System (INIS)

Decker, F.J.; Jobe, R.K.; Merminga, N.; Thompson, K.A.

1990-09-01

In linear accelerators with two or more bunches the beam loading of one bunch will influence the energy and energy spread the following bunches. This can be corrected by quickly changing the phase of a traveling wave-structure, so that each bunch receives a slightly different net phase. At the SLAC Linear Collider (SLC) three bunches, two (e + ,e - ) for the high energy collisions and one (e - -scavenger) for producing positrons should sit at different phases, due to their different tasks. The two e - -bunches are extracted from the damping ring at the same cycle time about 60 ns apart. Fast phase switching of the RF to the bunch length compressor in the Ring-To-Linac (RTL) section can produce the necessary advance of the scavenger bunch (about 6 degree in phase). This allows a low energy spread of this third bunch at the e + -production region at 2/3 of the linac length, while the other bunches are not influenced. The principles and possible other applications of this fast phase switching as using it for multi-bunches, as well as the experimental layout for the actual RTL compressor are presented

The mirror symmetric centroid difference method for picosecond lifetime measurements via {gamma}-{gamma} coincidences using very fast LaBr{sub 3}(Ce) scintillator detectors

Energy Technology Data Exchange (ETDEWEB)

Regis, J.-M., E-mail: regis@ikp.uni-koeln.d [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany); Pascovici, G.; Jolie, J.; Rudigier, M. [Institut fuer Kernphysik, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)

2010-10-01

The ultra-fast timing technique was introduced in the 1980s and is capable of measuring picosecond lifetimes of nuclear excited states with about 3 ps accuracy. Very fast scintillator detectors are connected to an electronic timing circuit and detector vs. detector time spectra are analyzed by means of the centroid shift method. The very good 3% energy resolution of the nowadays available LaBr{sub 3}(Ce) scintillator detectors for {gamma}-rays has made possible an extension of the well-established fast timing technique. The energy dependent fast timing characteristics or the prompt curve, respectively, of the LaBr{sub 3}(Ce) scintillator detector has been measured using a standard {sup 152}Eu {gamma}-ray source. For any energy combination in the range of 200keVsub {gamma}<}1500keV, the {gamma}-{gamma} fast timing characteristics is calibrated as a function of energy with an accuracy of 2-4 ps. An extension of the centroid shift method providing very attractive features for picosecond lifetime measurements is presented. The mirror symmetric centroid difference method takes advantage of the symmetry obtained when performing {gamma}-{gamma} lifetime measurements using a pair of almost identical very fast scintillator detectors. In particular cases, the use of the mirror symmetric centroid difference method also allows the direct determination of picosecond lifetimes, hence without the need of calibrating the prompt curve.

Halo formation in three-dimensional bunches

International Nuclear Information System (INIS)

Gluckstern, R.L.; Fedotov, A.V.; Kurennoy, S.; Ryne, R.

1998-01-01

We have constructed, analytically and numerically, a class of self-consistent six-dimensional (6D) phase space stationary distributions. Stationary distributions allow us to study the halo development mechanism without it being obscured by beam redistribution and its effect on halo formation. The beam is then mismatched longitudinally and/or transversely, and we explore the formation of longitudinal and transverse halos in 3D axisymmetric beam bunches. We find that the longitudinal halo forms first for comparable longitudinal and transverse mismatches because the longitudinal tune depression is more severe than the transverse one for elongated bunches. Of particular importance is the result that, due to the coupling between longitudinal and transverse motion, a longitudinal or transverse halo is observed for a mismatch less than 10% if the mismatch in the other plane is large. copyright 1998 The American Physical Society

Space Charge Mitigation by Hollow Bunches

CERN Multimedia

Oeftiger, AO

2014-01-01

To satisfy the requirements of the HL-LHC (High Luminosity Large Hadron Collider), the LHC injector chain will need to supply a higher brightness, i.e. deliver the same transverse beam emittances \\epsilon_{x,y} while providing a higher intensity N. However, a larger number of particles per bunch enhances space charge effects. One approach to mitigate the impact of space charge is to change the longitudinal phase space distribution: hollow bunches feature a depleted bunch centre and a densely populated periphery. Thus, the spatial line density maximum is depressed which ultimately decreases the tune spread imposed by space charge. Therefore, a higher intensity can be accepted while keeping the same overall space charge tune shift. 3 different methods to create hollow bunches in the PSBooster are simulated.

Sub-picosecond Resolution Time-to-Digital Converter

Energy Technology Data Exchange (ETDEWEB)

Bratov, Vladimir [Advanced Science and Novel Technology Company, Rancho Palos Verdes, CA (United States); Katzman, Vladimir [Advanced Science and Novel Technology Company, Rancho Palos Verdes, CA (United States); Binkley, Jeb [Advanced Science and Novel Technology Company, Rancho Palos Verdes, CA (United States)

2006-03-30

Time-to-digital converters with sub-picosecond resolutions are needed to satisfy the requirements of time-on-flight measurements of the next generation of high energy and nuclear physics experiments. The converters must be highly integrated, power effective, low cost, and feature plug-and-play capabilities to handle the increasing number of channels (up to hundreds of millions) in future Department of Energy experiments. Current state-off-the-art time-to-digital converter integrated circuits do not have the sufficient degree of integration and flexibility to fulfill all the described requirements. During Phase I, the Advanced Science and Novel Technology Company in cooperation with the nuclear physics division of the Oak Ridge National Laboratory has developed the architecture of a novel time-to-digital converter with multiple channels connected to an external processor through a special interfacing block and synchronized by clock signals generated by an internal phase-locked loop. The critical blocks of the system including signal delay lines and delay-locked loops with proprietary differential delay cells, as well as the required digital code converter and the clock period counter have been designed and simulated using the advanced SiGe120 BiCMOS technological process. The results of investigations demonstrate a possibility to achieve the digitization accuracy within 1ps. ADSANTEC has demonstrated the feasibility of the proposed concept in computer simulations. The proposed system will be a critical component for the next generation of NEP experiments.

A beam-synchronous gated peak-detector for the LHC beam observation system

CERN Document Server

Levens, T E; Wehrle, U

2013-01-01

Measurements of the bunch peak amplitude using the longitudinal wideband wall-current monitor are a vital tool used in the Large Hadron Collider (LHC) beam observation system. These peak-detected measurements can be used to diagnose bunch shape oscillations, for example coherent quadrupole oscillations, that occur at injection and during beam manipulations. Peak-detected Schottky diagnostics can also be used to obtain the synchrotron frequency distribution and other parameters from a bunched beam under stable conditions. For the LHC a beam-synchronous gated peak detector has been developed to allow individual bunches to be monitored without the influence of other bunches circulating in the machine. The requirement for the observation of both low intensity pilot bunches and high intensity bunches for physics requires a detector front-end with a high bandwidth and a large dynamic range while the usage for Schottky measurements requires low noise electronics. This paper will present the design of this detector s...

Study of CSR longitudinal bunch compression cavity

International Nuclear Information System (INIS)

Yin Dayu; Li Peng; Liu Yong; Xie Qingchun

2009-01-01

The scheme of longitudinal bunch compression cavity for the Cooling Storage Ring (CSR)is an important issue. Plasma physics experiments require high density heavy ion beam and short pulsed bunch,which can be produced by non-adiabatic compression of bunch implemented by a fast compression with 90 degree rotation in the longitudinal phase space. The phase space rotation in fast compression is initiated by a fast jump of the RF-voltage amplitude. For this purpose, the CSR longitudinal bunch compression cavity, loaded with FINEMET-FT-1M is studied and simulated with MAFIA code. In this paper, the CSR longitudinal bunch compression cavity is simulated and the initial bunch length of 238 U 72+ with 250 MeV/u will be compressed from 200 ns to 50 ns.The construction and RF properties of the CSR longitudinal bunch compression cavity are simulated and calculated also with MAFIA code. The operation frequency of the cavity is 1.15 MHz with peak voltage of 80 kV, and the cavity can be used to compress heavy ions in the CSR. (authors)

Tunable Subpicosecond Electron-Bunch-Train Generation Using a Transverse-To-Longitudinal Phase-Space Exchange Technique

International Nuclear Information System (INIS)

Sun, Y.-E; Piot, P.; Maxwell, T. J.; Johnson, A.; Lumpkin, A. H.; Ruan, J.; Thurman-Keup, R.

2010-01-01

We report on the experimental generation of a train of subpicosecond electron bunches. The bunch train generation is accomplished using a beam line capable of exchanging the coordinates between the horizontal and longitudinal degrees of freedom. An initial beam consisting of a set of horizontally separated beamlets is converted into a train of bunches temporally separated with tunable bunch duration and separation. The experiment reported in this Letter unambiguously demonstrates the conversion process and its versatility.

Double Emittance Exchanger as a Bunch Compressor for the MaRIE XFEL electron beam line at 1GeV

Energy Technology Data Exchange (ETDEWEB)

Malyzhenkov, Alexander [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Northern Illinois Univ., DeKalb, IL (United States); Yampolsky, Nikolai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carlsten, Bruce Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-09-22

We demonstrate an alternative realization of a bunch compressor (specifically the second bunch compressor for the MaRIE XFEL beamline, 1GeV electron energy) using a double emittance exchanger (EEX) and a telescope in the transverse phase space.We compare our results with a traditional bunch compressor realized via chicane, taking into account the nonlinear dynamics, Coherent Synchrotron Radiation (CSR) and Space Charge (SC) effects. In particular, we use the Elegant code for tracking particles through the beam line and analyze the eigen-emittances evolution to separate the influence of the CSR/SC effects from the nonlinear dynamics effects. We optimize the scheme parameters to reach a desirable compression factor and minimize the emittance growth. We observe dominant CSR-effects in our scheme resulting in critical emittance growth and introduce alternative version of an emittance exchanger with a reduced number of bending magnets to minimize the impact of CSR effects.

Application accelerator system having bunch control

International Nuclear Information System (INIS)

Wang, D.; Krafft, G.A.

1999-01-01

An application accelerator system for monitoring the gain of a free electron laser is disclosed. Coherent Synchrotron Radiation (CSR) detection techniques are used with a bunch length monitor for ultra short, picosec to several tens of femtosec, electron bunches. The monitor employs an application accelerator, a coherent radiation production device, an optical or beam chopping device, an infrared radiation collection device, a narrow-banding filter, an infrared detection device, and a control. 1 fig

Beam loading effects for two-beam ring

International Nuclear Information System (INIS)

Wang Lanfa; Lin Yuzheng; Tong Dechun

1999-01-01

An analytic treatment of multi-bunch potential well distortion for a two-beam storage ring is presented. The longitudinal wake effects are separated into: the mode loss, the synchrotron tune shift (both due to potential well distortion) and the coherent multi-bunch coupling. Here, only the first two effects are studied. Resulting simple analytic formulas describe the mode loss and the synchrotron tune shift experienced by a given bunch within the two-beam, as a function of the high order mode's parameters. One can get immediately a simple quantitative answer in term of the mode loss and the synchrotron tune shift experienced by each bunch from these formulas, so the authors can know how to modify the existing configuration of parasitic cavity resonance (via frequency tuning) so that the resulting potential well distortion effects are minimized. When the RF cavities are symmetrically distributed about the interaction points, the two beams will have same beam loading effects, so the authors can compensate the phase shift of the two beam using the same method as in one beam case

Optimization of a train of bunches for plasma wakefield acceleration

Energy Technology Data Exchange (ETDEWEB)

Martorelli, Roberto

2016-05-10

Particle accelerators are a fundamental instrument for the understanding of fundamental mechanism in nature. The need of always higher energies for the particle beams requires a huge increase of the sizes of the accelerators using the actual technology. Moreover the highest energies are achieved nowadays by circular colliders, not perfectly suitable for acceleration of electrons and positrons due to the radiation losses. In order to overcome this problem a new branch of physics studying alternative technique for particle acceleration has been developed. Among the various alternatives a promising one is the plasma wakefield acceleration (PWFA), in which a driver bunch interacts with a cold background plasma, exciting a plasma wave. The electric field of the plasma wave is then used for the acceleration of a second bunch. Such a mechanism allows to reach fields strength far beyond currently available, limited by the dielectric strength of the material. Among the different driver configurations, a promising one is the use of a modulated beam, namely a train of bunches, that provides a coherent interference among the electric fields generated by the single bunches. Such mechanism is subjected to a renewed interest in view of the forthcoming AWAKE experiment at CERN in which the long proton beam produced at the SPS facility is used as a driver. This possibility is achieved thanks to the onset of the self-modulation instability that modulates the long beam in a train of approximately 100 bunches. In order to accelerate the witness bunch to high energies is necessary on the other hand an efficient exchange of energy from the driver to the accelerated bunch, as well as a long duration of the driver so that can propagates for kilometers. This thesis deals with this two last aspects. The aim of this work is to provide an optimization for the modulated driver in order to improve specific features of the PWFA. This work shows the possibility to achieve an improved efficiency

Bunch arrival time monitors; Concepts towards improving the sensitivity for low charge operation for FLASH II and XFEL

Energy Technology Data Exchange (ETDEWEB)

Penirschke, Andreas; Angelovski, Aleksandar; Jakoby, Rolf [TU Darmstadt, Institut fuer Mikrowellentechnik und Photonik, Merckstr. 25, 64283 Darmstadt (Germany); Sydlo, Cezary; Bousonville, Michael; Czwalinna, Marie Kristin; Schlarb, Holger [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kuhl, Alexander [University of Hamburg, Physics Department, Accelerator Physics Group (Germany); Weiland, Thomas [Technische Univ. Darmstadt (Germany). Inst. fuer Theorie Elektromagnetischer Felder

2013-07-01

High gain Free-Electron Lasers can generate ultra short X-ray pulses in the femtosecond range. For a stable operation of the FEL, the precise knowledge of the bunch arrival time is crucial. A novel high bandwidth Bunch Arrival time Monitor was recently installed at FLASH to allow a low charge operation mode with a sub-10 fs resolution for bunch charges of 20 pC or more. The BAM is equipped with cone shaped pickups for the precise measurement of both, the high and low bunch charge operation mode. For the extension of FLASH facility to FLASH II new pickups for the high bandwidth BAMs need to be developed. The new BAM needs to maximize the voltage level of the beam induced signal for low charge operation mode in order to provide sufficient signal strength for the subsequent electronics. In this talk, we present concepts to improve the signal strength at the electro-optic modulators for low charge operation at FLASH II and XFEL.

Growth and apoptosis of HeLa cells induced by intense picosecond pulsed electric field

Directory of Open Access Journals (Sweden)

Yuan-yuan HUA

2011-07-01

Full Text Available Objective To investigate the growth and apoptosis of HeLa cells induced by intense picosecond pulsed electric field(PEF in vitro.Methods HeLa cells cultured in vitro were divided into experimental group and control group(with or without intense picosecond PEF.With constant pulse width,frequency and voltage,the cells in experimental group were divided into 6 sub-groups according to the number of pulse(100,200,500,1000,1500,2000,the growth inhibition of HeLa cells by PEF and the dose-effect relationship were analyzed by MTT.Caspase 3 protein activity was detected in the cells in 500,1000 and 2000 sub-groups.Mitochondrial transmembrane potential was detected by rhodamine 123 staining with the cells in 2000 sub-groups.Results MTT assay demonstrated that intense picosecond PEF significantly inhibited the proliferation of HeLa cells in dose-dependent manner.The survival rates of cells declined along with the increase in pulse number,and were 96.23%±0.76%,94.11%±2.42%,90.31%±1.77%,64.59%±1.59%,32.95%±0.73%,23.85%±2.38% and 100%,respectively,in 100,200,500,1000,1500,2000 sub-groups and control group(P < 0.01.The Caspase 3 protein activity was significantly enhanced by intense picosecond PEF,and the absorbancy indexes(A were 0.174±0.012,0.232±0.017,0.365±0.016 and 0.122±0.011,respectively,in 500,1000,2000 sub-groups and control group(P < 0.05.The mitochondrial transmembrane potential of HeLa cells was significantly inhibited by intense picosecond PEF,and the fluorescence intensity in 2000 sub-group(76.66±13.38 was much lower than that in control group(155.81±2.33,P < 0.05.Conclusion Intense picosecond PEF may significantly inhibit the growth of HeLa cells,and induce cell apoptosis via mitochondrial pathway.

Performance of the transverse coupled-bunch feedback system in the SRRC

International Nuclear Information System (INIS)

Hsu, K.T.; Kuo, C.C.; Kuo, C.H.; Lin, K.K.; Ueng, T.S.; Weng, W.T.

1996-01-01

A transverse feedback system has been implemented and commissioned in the SRRC storage ring to suppress transverse coupled-bunch oscillations of the electron beam. The system includes transverse oscillation detectors, notch filter, baseband quadrature processing circuitry, power amplifiers, and kickers. To control a large number of transverse coupled-bunch modes, the system is broad-band, bunch-by- bunch in nature. Because the system is capable of bunch-by-bunch correction, it can also be useful for suppressing instabilities introduced by ions. The sextupole strength was then reduced to improve dynamic aperture and hence lifetime of the storage ring

Bunch coalescing in the Fermilab Main Ring

International Nuclear Information System (INIS)

Wildman, D.; Martin, P.; Meisner, K.; Miller, H.W.

1987-01-01

A new RF system has been installed in the Fermilab Main Ring to coalesce up to 13 individual bunches of protons or antiprotons into a single high-intensity bunch. The coalescing process consists of adiabatically reducing the h=1113 Main Ring RF voltage from 1 MV to less than 1 kV, capturing the debunched beam in a linearized h=53 and h=106 bucket, rotating for a quarter of a synchrotron oscillation period, and then recapturing the beam in a single h=1113 bucket. The new system is described and the results of recent coalescing experiments are compared with computer-generated particle tracking simulations

Anticrab cavities for the removal of spurious vertical bunch rotations caused by crab cavities

Directory of Open Access Journals (Sweden)

G. Burt

2008-09-01

Full Text Available Many particle accelerators are proposing the use of crab cavities to correct for accelerator crossing angles or for the production of short bunches in light sources. These cavities produce a rotation to the bunch in a well-defined polarization plane. If the plane of the rotation does not align with the horizontal axis of the accelerator, the bunch will receive a small amount of spurious vertical bunch rotation. For accelerators with small vertical beam sizes and large beam-beam effects, this can cause significant unwanted effects. In this paper we propose the use of a 2nd smaller crab cavity in the vertical plane in order to cancel this effect and investigate its use in numerical simulations.

Simulations of the effects of a superconducting damping wiggler on a short bunched electron beam at ANKA

Energy Technology Data Exchange (ETDEWEB)

Gethmann, Julian; Bernhard, Axel; Blomley, Edmund; Hillenbrand, Steffen; Mueller, Anke-Susanne; Smale, Nigel [Karlsruher Institut fuer Technologie (KIT) (Germany); Zolotarev, Konstantin [Budker Institute of Nuclear Physics (Russian Federation)

2016-07-01

(As a part of the CLIC collaboration) A CLIC damping wiggler prototype has been installed at the ANKA synchrotron light source in order to validate the technical design of the 3 T superconducting conduction cooled wiggler and its cryostat and to cary out studies on beam dynamical aspects including collective effects. The latter one will be the main focus in this talk. Collective effects that will occur in damping rings are an issue in ANKA's short bunch operation as well. To simulate these effects the accelerator's model including its insertion device has to be very accurate. Such a model of the ANKA storage ring in short bunch operation mode has been developed in elegant. Simulations with the damping wiggler switched on and off have been performed in order to investigate effects of the wiggler on different machine parameters. These new results will be discussed with regard to the question if on the one hand the wiggler could be used for diagnostic purposes and if on the other hand the wiggler's impact on the beam dynamics is changed by the collective effects.

High bandwidth beam current monitor

International Nuclear Information System (INIS)

Baltrusaitis, R.M.; Ekdahl, C.A.; Cooper, R.G.; Peterson, E.; Warn, C.E.

1993-01-01

A stripline directional coupler beam current monitor capable of measuring the time structure of a 30-ps electron beam bunch has been developed. The time response performance of the monitor compares very well with Cherenkov light produced in quartz by the electron beam. The four-pickup monitor is now used on a routine basis for measuring the beam duration, tuning for optimized beam bunching, and centering the bunch in the beam pipe

On measuring charged particle bunch duration in linear accelerators

International Nuclear Information System (INIS)

Lomize, L.G.; Malykh, N.I.; Khizhnyj, V.I.; Yampol'skij, E.S.

1977-01-01

The process of measuring short bunches is simulated by means of cavity resonators in which HF fields are excited by both positive and negative ion bunches flying through them. The simulation is aimed to assess optimum operation of a linear accelerator. A set of bunches of chance form and duration is simulated. Then the simulation of the process of restoring the duration and shape of a bunch according to data obtained from a limited number of resonators is realized. The use of 3-4 resonators tuned to 3, 6, 9 and 12-th harmonics of bunch repetition rate is shown to be sufficient for determining bunch duration with an accuracy of several per cent. When data on harmonic phases is available, one can obtain information on beam asymmetry

A rotationally symmetric electron beam chopper for picosecond pulses

International Nuclear Information System (INIS)

Oldfield, L.C.

1976-01-01

The chopper was designed for dynamic electron optical experiments where it is necessary to provide pulses of high quality with respect to both width and energy spread. The chopping action relies on the optical properties of a microwave cavity; these are exploited such that the time dependent space focusing causes a small circular aperture on the axis of rotational symmetry to transmit strongly for a single band of phase angles in each cycle of the excitation. Unless the pulses are to be used near the aperture plane, an 'energy correcting' cavity that operates in phase synchronism with the chopper is added to the system. The theoretical treatment is oriented towards computer display, and is novel in that it follows the progress of individual electron packets throughout the system. In contrast to conventional chopping and bunching theory, it is possible to analyse with ease the pulsing properties of a multicavity device. For a typical two-cavity design the pulse quality may range from 10 0 width and negligible energy spread, to 0.25% energy spread and negligible pulse width, depending on the second cavity excitation; in either situation 7.5% of the original steady beam is transmitted. (author)

A better beam quality

CERN Multimedia

CERN Bulletin

2010-01-01

Progress has been made on two fronts, providing physics data and preparing for higher intensities. Over the Whitsun weekend of May 22 to 24, 5 fills for physics provided almost 30 hours of stable colliding beams, all with bunch intensities around 2x1010 protons and at a β* of 2m. The first three of these fills were with 6 bunches per beam, giving 3 pairs of collisions in all experiments. For the other two fills, the number of bunches per beam was increased to 13, giving 8 pairs of colliding bunches, and for the first time luminosities were pushed above 1029 cm-2s-1, 2 orders of magnitude higher than first collisions in March. In between and after these physics fills, nominal bunches of 1011 protons were successfully ramped and brought into collision in ATLAS and CMS for the first time (not in stable beam conditions and without squeeze). Event rates seen by the experiments were in the expected range for these conditions. In the middle of this work, a short fill with beams of 7 nominal bunches was ...

Determination of Longitudinal Electron Bunch Lengths on Picosecond Time Scales

CERN Document Server

Martínez, C; Calviño, F

1999-01-01

At CERN (European Laboratory for Particle Physics) the CLIC (Compact Linear Collider) study is pursuing the design of an electron-positron high-energy linear collider using an innovative concept for the RF (Radio Frequency) power production, the socalled two-beam acceleration scheme. In order to keep the length of the collider in a reasonable range while being able of accelerating electrons and positrons up to 5 TeV, the normal-conducting accelerating structures should operate at very high frequency (in this case 30 GHz). The RF power necessary to feed the accelerating cavities is provided by a second electron beam, the drive beam, running parallel to the main beam. The CLIC Test Facility (CTF) was build with the main aim of studying and demonstrating the feasibility of the two beam acceleration scheme and technology. It is composed of two beams, the drive beam that will generate the 30 GHz RF power and the main beam which will be accelerated by this power. In order to have a good efficiency for the power gen...

Emittance control and RF bunch compression in the NSRRC photoinjector

International Nuclear Information System (INIS)

Lau, W.K.; Hung, S.B.; Lee, A.P.; Chou, C.S.; Huang, N.Y.

2011-01-01

The high-brightness photoinjector being constructed at the National Synchrotron Radiation Research Center is for testing new accelerator and light-source concepts. It is the so-called split photoinjector configuration in which a short solenoid magnet is used for emittance compensation. The UV-drive laser pulses are also shaped to produce uniform cylindrical bunches for further reduction of beam emittance. However, limited by the available power from our microwave power system, the nominal accelerating gradient in the S-band booster linac is set at 18 MV/m. A simulation study with PARMELA shows that the linac operating at this gradient fails to freeze the electron beam emittance at low value. A background solenoid magnetic field is applied for beam emittance control in the linac during acceleration. A satisfactory result that meets our preliminary goal has been achieved with the solenoid magnetic field strength at 0.1 T. RF bunch compression as a means to achieve the required beam brightness for high-gain free-electron laser experiments is also examined. The reduction of bunch length to a few hundred femtoseconds can be obtained.

A method for ultrashort electron pulse-shape measurement using coherent synchrotron radiation

International Nuclear Information System (INIS)

Geloni, G.; Yurkov, M.V.

2003-03-01

In this paper we discuss a method for nondestructive measurements of the longitudinal profile of sub-picosecond electron bunches for X-ray free electron lasers (XFELs). The method is based on the detection of the coherent synchrotron radiation (CSR) spectrum produced by a bunch passing a dipole magnet system. This work also contains a systematic treatment of synchrotron radiation theory which lies at the basis of CSR. Standard theory of synchrotron radiation uses several approximations whose applicability limits are often forgotten: here we present a systematic discussion about these assumptions. Properties of coherent synchrotron radiation from an electron moving along an arc of a circle are then derived and discussed. We describe also an effective and practical diagnostic technique based on the utilization of an electromagnetic undulator to record the energy of the coherent radiation pulse into the central cone. This measurement must be repeated many times with different undulator resonant frequencies in order to reconstruct the modulus of the bunch form-factor. The retrieval of the bunch profile function from these data is performed by means of deconvolution techniques: for the present work we take advantage of a constrained deconvolution method. We illustrate with numerical examples the potential of the proposed method for electron beam diagnostics at the TESLA test facility (TTF) accelerator. Here we choose, for emphasis, experiments aimed at the measure of the strongly non-Gaussian electron bunch profile in the TTF femtosecond-mode operation. We demonstrate that a tandem combination of a picosecond streak camera and a CSR spectrometer can be used to extract shape information from electron bunches with a narrow leading peak and a long tail. (orig.)

Longitudinal Bunch Position Control for the Super-B Accelerator

International Nuclear Information System (INIS)

Bertsche, Kirk; Rivetta, Claudio; Sullivam, Michael K.; SLAC; Drago, Alessandro; Frascati

2009-01-01

The use of normal conducting cavities and an ion-clearing gap will cause a significant RF accelerating voltage gap transient and longitudinal phase shift of the individual bunches along the bunch train in both rings of the SuperB accelerator. Small relative centroid position shifts between bunches of the colliding beams will have a large adverse impact on the luminosity due to the small β* y at the interaction point (IP). We investigate the possibility of minimizing the relative longitudinal position shift between bunches by reducing the gap transient in each ring and matching the longitudinal bunch positions of the two rings at the IP using feedback/feedforward techniques in the LLRF. The analysis is conducted assuming maximum use of the klystron power installed in the system

Multiple bunch-splitting in the PS results and plans

CERN Document Server

Garoby, R

2001-01-01

The nominal longitudinal characteristics of the PS proton beam for the LHC were attained during the year 2000, using a sequence of triple- and double-splittings to divide each PS Booster (PSB) bunch into 12. This method minimizes longitudinal emittance blow-up and preserves a gap, free of particles, in the bunch train. Some of the ideas for alternative bunch trains have also been tested. The performance achieved is described and the sources of limitations are discussed together with the foreseen improvements.

Picosecond X-ray streak camera dynamic range measurement

Energy Technology Data Exchange (ETDEWEB)

Zuber, C., E-mail: celine.zuber@cea.fr; Bazzoli, S.; Brunel, P.; Gontier, D.; Raimbourg, J.; Rubbelynck, C.; Trosseille, C. [CEA, DAM, DIF, F-91297 Arpajon (France); Fronty, J.-P.; Goulmy, C. [Photonis SAS, Avenue Roger Roncier, BP 520, 19106 Brive Cedex (France)

2016-09-15

Streak cameras are widely used to record the spatio-temporal evolution of laser-induced plasma. A prototype of picosecond X-ray streak camera has been developed and tested by Commissariat à l’Énergie Atomique et aux Énergies Alternatives to answer the Laser MegaJoule specific needs. The dynamic range of this instrument is measured with picosecond X-ray pulses generated by the interaction of a laser beam and a copper target. The required value of 100 is reached only in the configurations combining the slowest sweeping speed and optimization of the streak tube electron throughput by an appropriate choice of high voltages applied to its electrodes.

Two frequency beam-loading compensation in the drive-beam accelerator of the CLIC Test Facility

CERN Document Server

Braun, Hans Heinrich

1999-01-01

The CLIC Test Facility (CTF) is a prototype two-beam accelerator, in which a high-current "drive beam" is used to generate the RF power for the main-beam accelerator. The drive-beam accelerator consists of two S-band structures which accelerate a bunch train with a total charge of 500 nC. The substantial beam loading is compensated by operating the two accelerating structures at 7.81 MHz above and below the bunch repetition frequency, respectively. This introduces a change of RF phase from bunch to bunch, which leads, together with off-crest injection into the accelerator, to an approximate compensation of the beam loading. Due to the sinusoidal time-dependency of the RF field, an energy spread of about 7% remains in the bunch train. A set of idler cavities has been installed to reduce this residual energy spread further. In this paper, the considerations that motivated the choice of the parameters of the beam-loading compensation system, together with the experimental results, are presented.

Ultrashort electron bunch length measurement with diffraction radiation deflector

Science.gov (United States)

Xiang, Dao; Huang, Wen-Hui

2007-01-01

In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR) deflector which is composed of a DR radiator and three beam position monitors (BPMs). When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

Ultrashort electron bunch length measurement with diffraction radiation deflector

Directory of Open Access Journals (Sweden)

Dao Xiang

2007-01-01

Full Text Available In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR deflector which is composed of a DR radiator and three beam position monitors (BPMs. When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

Beam-beam effects under the influence of external noise

International Nuclear Information System (INIS)

Ohmi, K

2014-01-01

Fast external noise, which gives fluctuation into the beam orbit, is discussed in connection with beam-beam effects. Phase noise from crab cavities and detection devices (position monitor) and kicker noise from the bunch by bunch feedback system are the sources. Beam-beam collisions with fast orbit fluctuations with turn by turn or multi-turn correlations, cause emittance growth and luminosity degradation. We discuss the tolerance of the noise amplitude for LHC and HL-LHC

Operational experience with nanocoulomb bunch charges in the Cornell photoinjector

Directory of Open Access Journals (Sweden)

Adam Bartnik

2015-08-01

Full Text Available Characterization of 9–9.5 MeV electron beams produced in the dc-gun based Cornell photoinjector is given for bunch charges ranging from 20 pC to 2 nC. Comparison of the measured emittances and longitudinal current profiles to optimized 3D space charge simulations yields excellent agreement for bunch charges up to 1 nC when the measured laser distribution is used to generate initial particle distributions in simulation. Analysis of the scaling of the measured emittance with bunch charge shows that the emittance scales roughly as the square root of the bunch charge up to 300 pC, above which the trend becomes linear. These measurements demonstrate that the Cornell photoinjector can produce cathode emittance dominated beams meeting the emittance and peak current specifications for next generation free electron lasers operating at high repetition rate. In addition, the 1 and 2 nC results are relevant to the electron ion collider community.

A low-frequency high-voltage rf-barrier-bunching system for high-intensity neutron source compressor rings

International Nuclear Information System (INIS)

Hardek, T.W.; Ziomek, C.; Rees, D.

1995-01-01

A Los Alamos design for a 1-MW pulsed neutron source incorporates a ring utilizing an rf-barrier bunching system. This bunching concept allows uniform longitudinal beam distributions with low momentum spread. Bunching cavities are operated at the revolution frequency (1.5 MHz in this case) and each of the 2nd, 3rd, 4th, and 5th revolution frequency harmonics. Their effects combine to maintain a beam free gap in the longitudinal distribution of the accumulated beam. The cavities are driven by low-plate-resistance common-cathode configured retrode amplifiers incorporating local rf feedback. Additional adaptive feed-forward hardware is included to reduce the beam-induced bunching-gap voltages well below that achievable solely with rf feedback. Details of this system are presented along with a discussion of the various feed-back and feed-forward techniques incorporated

Refinements to longitudinal, single bunch, coherent instability theory

Energy Technology Data Exchange (ETDEWEB)

Koscielniak, S R

1995-06-01

For the case of a bunched beam confined to a quadratic potential well, we demonstrate the necessity for considering mode-coupling to correctly obtain the threshold current for the d.c. instability. Further we find the effect upon growth rate and coherent tune shift of evaluating the impedance at a complex frequency. For the case of a bunched beam confined to a cosine potential well, we give an exact analytic expression for the dispersion integral, and calculate (with no approximations), the stability diagram for the Robinson instability taking into account Landau damping. This paper comprises extracts from a lengthy internal report. (author). 2 refs., 4 figs.

Three-dimensional nonstationary dynamics of a charged bunches-ellipsoids

International Nuclear Information System (INIS)

Budanov, Yu.A.

2000-01-01

The work is aimed at studying the changes in the beam dynamics at the beginning of acceleration, when the zero longitudinal emittance is transformed into the final longitudinal phase volume. This process is studied on the bunch-ellipsoid self-consistent model with the charge uniform distribution. The results obtained present the evaluation of the parameters, whereby the longitudinal dynamics in the bunch significantly changes, namely, the particles bunch with increase in the spatial charge transfers into a new state with doubled frequency of the longitudinal oscillations [ru

Preliminary Study on Two Possible Bunch Compression Schemes at NLCTA

International Nuclear Information System (INIS)

Sun, Yipeng

2011-01-01

In this paper, two possible bunch compression configurations are proposed and evaluated by numerical simulation in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. A bunch compression ratio up to 20 could be achieved under a perfect condition, without consideration for the timing jitter and other error sources. The NLCTA is a test accelerator built at SLAC, which is approximately 42 meters long and composed of X-band acceleration structures. The main aim of building NLCTA is to develop and demonstrate the X-band rf acceleration technologies for the next generation linear collider, with a relatively high acceleration gradient between 50 MV/m and 100 MV/m. The current operation configuration of NLCTA features a thermionic-cathode electron gun at its starting point which generates an electron beam with an energy of 5 MeV. This is followed by a roughly 1.5 meter long X-band acceleration structure which boosts the electron beam energy to 60 MeV. Then there is a four-dipole magnetic chicane which is 6 meters long and provides a first order longitudinal dispersion of R 56 = -73mm. Next the electron beam passes by several matching quadrupoles and can be accelerated further to 120 MeV through another one-meter-long X-band acceleration structure. After that, there are three small chicanes downstream, with a total first order longitudinal dispersion of R 56 = -10mm. A sketch of the main components of NLCTA is shown in Figure 1, where the total length of this accelerator is 45 meters. Free Electron Lasers (FELs), proposed by J. Madey and demonstrated for the first time at Stanford University in 1970s (2) (3), use the lasing of relativistic electron beam traveling through a magnetic undulator, which can reach high power and can be widely tunable in wavelength. Linac based FEL source can provide sufficient brightness, and a short X-ray wavelength down to angstrom scale, which promises in supporting wide range of research experiments. In order to have an electron beam

Compensation of longitudinal coupled-bunch instability in the advanced photon source storage ring

International Nuclear Information System (INIS)

Harkay, K.C.; Nassiri, A.; Song, J.J.; Kang, Y.W.; Kustom, R.L.

1997-01-01

A longitudinal couple-bunch (CB) instability was encountered in the 7-GeV storage ring. This instability was found to depend on the bunch fill pattern as well as on the beam intensity. The beam spectrum exhibited a coupled-bunch signature, which could be reproduced by an analytical model. The oscillations were also observed on a horizontal photon monitor. The beam fluctuations exhibited two periodicities, which were found to be correlated with the rf cavity temperatures. This correlation is consistent with the measured temperature dependence of the higher-order mode (HOM) frequencies. The HOM impedance drives the beam when brought into resonance with the CB mode by the temperature variation. Increasing the inlet cavity water temperature suppressed the instability. The experimental results are compared to an analytical model which characterizes the fill-pattern dependence. Studies to identify the offending HOMs are also presented

Electron bunch structure in energy recovery linac with high-voltage dc photoelectron gun

Directory of Open Access Journals (Sweden)

Y. M. Saveliev

2016-09-01

Full Text Available The internal structure of electron bunches generated in an injector line with a dc photoelectron gun is investigated. Experiments were conducted on the ALICE (accelerators and lasers in combined experiments energy recovery linac at Daresbury Laboratory. At a relatively low dc gun voltage of 230 kV, the bunch normally consisted of two beamlets with different electron energies, as well as transverse and longitudinal characteristics. The beamlets are formed at the head and the tail of the bunch. At a higher gun voltage of 325 kV, the beam substructure is much less pronounced and could be observed only at nonoptimal injector settings. Experiments and computer simulations demonstrated that the bunch structure develops during the initial beam acceleration in the superconducting rf booster cavity and can be alleviated either by increasing the gun voltage to the highest possible level or by controlling the beam acceleration from the gun voltage in the first accelerating structure.

MD1831: Single Bunch Instabilities with Q" and Non-Linear Corrections

CERN Document Server

Carver, Lee Robert; De Maria, Riccardo; Li, Kevin Shing Bruce; Amorim, David; Biancacci, Nicolo; Buffat, Xavier; Maclean, Ewen Hamish; Metral, Elias; Lasocha, Kacper; Lefevre, Thibaut; Levens, Tom; Salvant, Benoit; CERN. Geneva. ATS Department

2017-01-01

During MD1751, it was observed that both a full single beam and 964 non-colliding bunches in Beam 1 (B1) and Beam 2 (B2) were both stable at the End of Squeeze (EOS) for 0A in the Landau Octupoles. At ß* = 40cm there is also a significant Q" arising from the lattice, as well as uncorrected non-linearities in the Insertion Regions (IRs). Each of these effects could be capable of fully stabilising the beam. This MD made first use of a Q" knob through variation of the Main Sextupoles (MS) by stabilising a single bunch at Flat Top, before showing at EOS that the non-linearities were the main contributors to the beam stability.

Beam Techniques - Beam Control and Manipulation

International Nuclear Information System (INIS)

Minty, Michiko G

2003-01-01

We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The different procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization

Beam Techniques - Beam Control and Manipulation

Energy Technology Data Exchange (ETDEWEB)

Minty, Michiko G

2003-04-24

We describe commonly used strategies for the control of charged particle beams and the manipulation of their properties. Emphasis is placed on relativistic beams in linear accelerators and storage rings. After a brief review of linear optics, we discuss basic and advanced beam control techniques, such as transverse and longitudinal lattice diagnostics, matching, orbit correction and steering, beam-based alignment, and linac emittance preservation. A variety of methods for the manipulation of particle beam properties are also presented, for instance, bunch length and energy compression, bunch rotation, changes to the damping partition number, and beam collimation. The different procedures are illustrated by examples from various accelerators. Special topics include injection and extraction methods, beam cooling, spin transport and polarization.

Observation of the substructure in the electron bunch on the ACO storage ring

International Nuclear Information System (INIS)

Bergher, M.; Velghe, M.; Mialocq, J.P.

1984-09-01

In the future, one interesting point of the SRFEL at Orsay will be the microtemporal analysis of the laser beam correlated with that of the electron bunch. In a first time, we have only analysed the temporal structure of the electron bunch with an Electrophotonic streak camera. The first results seem to indicate that the bunch is not an homogeneous bunch but presents a substructure. We discuss with details this data

Beam energy loss to parasitic modes in SPEAR II

International Nuclear Information System (INIS)

Allen, M.A.; Paterson, J.M.; Rees, J.R.; Wilson, P.B.

1975-01-01

The energy loss due to the excitation of parasitic modes in the SPEAR II rf cavities and vacuum chamber components was measured by observing the shift in synchronous phase angle as a function of circulating beam current and accelerating cavity voltage. The resulting parasitic mode loss resistance is 5 M OMEGA at a bunch length of 6.5 cm. The loss resistance varies with bunch length sigma/sub z/ approximately as exp(-0.3 sigma/sub z/). If the measured result is compared with reasonable theoretical predictions, it may be inferred that the major portion of the parasitic loss takes place in ring vacuum components rather than in the rf cavities. (auth)

Investigations and Applications of Field- and Photo-emitted Electron Beams from a Radio Frequency Gun

Energy Technology Data Exchange (ETDEWEB)

Panuganti, SriHarsha [Northern Illinois Univ., DeKalb, IL (United States)

2015-08-01

Production of quality electron bunches using e cient ways of generation is a crucial aspect of accelerator technology. Radio frequency electron guns are widely used to generate and rapidly accelerate electron beams to relativistic energies. In the current work, we primarily study the charge generation processes of photoemission and eld emission inside an RF gun installed at Fermilab's High Brightness Electron Source Laboratory (HBESL). Speci cally, we study and characterize second-order nonlinear photoemission from a Cesium Telluride (Cs<sub>2sub>Te) semiconductor photocathode, and eld emission from carbon based cathodes including diamond eld emission array (DFEA) and carbon nanotube (CNT) cathodes located in the RF gun's cavity. Finally, we discuss the application experiments conducted at the facility to produce soft x-rays via inverse Compton scattering (ICS), and to generate uniformly lled ellipsoidal bunches and temporally shaped electron beams from the Cs<sub>2sub>Te photocathode.

A novel source of MeV positron bunches driven by energetic protons for PAS application

Energy Technology Data Exchange (ETDEWEB)

Tan, Zongquan, E-mail: tqq1123@mail.ustc.edu.cn [State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xu, Wenzhen; Liu, Yanfen; Xiao, Ran; Kong, Wei [State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Ye, Bangjiao, E-mail: bjye@ustc.edu.cn [State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2014-11-01

This paper proposes a novel methodology of MeV positrons generation for PAS application. Feasibility of this proposal analyzed by G4Beamline and Transport have shown reasonable success. Using 2 Hz, 1.6 GeV, 100 ns and 1.5 μC/bunch proton bunches for bombarding a graphite target, about 100 ns e{sup +} bunches are generated. Quasi-monochromatic positrons in the range of 1–10 MeV included in these bunches have a flux of >10{sup 7}/s, peak brightness of 10{sup 14}/s. A magnetic-confinement beamline is utilized to transport the positrons and a “Fast Beam Chopper” is unprecedentedly extended to chop those relativistic bunches. The positron beam can be finally characterized by the energy range of 1–10 MeV and bunch width from one hundred ps up to 1 ns. Such ultrashort bunches can be useful in tomography-type positron annihilation spectroscopy (PAS) as well as other applications.

A novel source of MeV positron bunches driven by energetic protons for PAS application

Science.gov (United States)

Tan, Zongquan; Xu, Wenzhen; Liu, Yanfen; Xiao, Ran; Kong, Wei; Ye, Bangjiao

2014-11-01

This paper proposes a novel methodology of MeV positrons generation for PAS application. Feasibility of this proposal analyzed by G4Beamline and Transport have shown reasonable success. Using 2 Hz, 1.6 GeV, 100 ns and 1.5 μC/bunch proton bunches for bombarding a graphite target, about 100 ns e+ bunches are generated. Quasi-monochromatic positrons in the range of 1-10 MeV included in these bunches have a flux of >107/s, peak brightness of 1014/s. A magnetic-confinement beamline is utilized to transport the positrons and a "Fast Beam Chopper" is unprecedentedly extended to chop those relativistic bunches. The positron beam can be finally characterized by the energy range of 1-10 MeV and bunch width from one hundred ps up to 1 ns. Such ultrashort bunches can be useful in tomography-type positron annihilation spectroscopy (PAS) as well as other applications.

Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

Energy Technology Data Exchange (ETDEWEB)

Nguyen, D.C.

1997-05-12

The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime.

Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

International Nuclear Information System (INIS)

Nguyen, D.C.

1997-01-01

The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime

Disruption effects on the beam size measurement

Energy Technology Data Exchange (ETDEWEB)

Raimondi, P.; Decker, F.J.; Chen, P.

1995-06-01

At the SLC Final Focus with higher currents and smaller beam sizes, the disruption parameter D{sub y} is close to one and so the pinch effect should produce a luminosity enhancement. Since a flat beam-beam function is fit to deflection scan data to measure the beam size, disruption can affect the measurement. Here the authors discuss the quantitative effects of disruption for typical SLC beam parameters. With 3.5 10{sup 10} particles per pulse, bunch length of 0.8 mm and beam sizes of 2.1 {mu}m horizontally and 0.55 {mu}m vertically, the measured vertical size can be as much as 25% bigger than the real one. Furthermore during the collision the spot size actually decrease, producing an enhancement factor H{sub D} of about 1.25. This would yield to a true luminosity which is 1.6 times that which is estimated from the beam-beam deflection fit.

Analytic model of bunched beams for harmonic generation in the low-gain free electron laser regime

Directory of Open Access Journals (Sweden)

G. Penn

2006-06-01

Full Text Available One scheme for harmonic generation employs free electron lasers (FELs with two undulators: the first uses a seed laser to modulate the energy of the electron beam; following a dispersive element which acts to bunch the beam, the second undulator radiates at a higher harmonic. These processes are currently evaluated using extensive calculations or simulation codes which can be slow to evaluate and difficult to set up. We describe a simple algorithm to predict the output of a harmonic generation beam line in the low-gain FEL regime, based on trial functions for the output radiation. Full three-dimensional effects are included. This method has been implemented as a Mathematica® package, named CAMPANILE, which runs rapidly and can be generalized to include effects such as asymmetric beams and misalignments. This method is compared with simulation results using the FEL code GENESIS, both for single stages of harmonic generation and for the LUX project, a design concept for an ultrafast x-ray facility, where multiple stages upshift the input laser frequency by factors of up to 200.

Studies of Longitudinal Coupled-Bunch Instabilities in the LHC Injectors Chain

CERN Document Server

AUTHOR|(CDS)2087149; Migliorati, M

Among several challenging objectives of the LHC Injectors Upgrade project, one aim is to double the beam intensity of the CERN Proton Synchrotron (PS) in order to achieve the integrated luminosity target of the High-Luminosity LHC project. A known limitation to reach the required high intensity is caused by the longitudinal coupled-bunch (CB) oscillations developing above the PS transition energy. The unwanted oscillations induce large bunch-to-bunch intensity variations not compatible with the specifications of the future LHC-type beams. In 2014 a new longitudinal kicker cavity has been installed, the Finemet cavity, as a part of the new digital coupled-bunch feedback (FB) system. The Finemet cavity allows with its large frequency bandwidth, to damp all the expected oscillation modes simultaneously. In the framework of this PhD study the impedance contribution of this equipment has been analyzed starting from the present knowledge of the machine impedance. A model of both the 10 MHz and the Finemet has been ...

Halo formation in three-dimensional bunches with various phase space distributions

Directory of Open Access Journals (Sweden)

A. V. Fedotov

1999-01-01

Full Text Available A realistic treatment of halo formation must take into account 3D beam bunches and 6D phase space distributions. We recently constructed, analytically and numerically, a new class of self-consistent 6D phase space stationary distributions, which allowed us to study the halo development mechanism without being obscured by the effect of beam redistribution. In this paper we consider nonstationary distributions and study how the halo characteristics compare with those obtained using the stationary distribution. We then discuss the effect of redistribution on the halo development mechanism. In contrast to bunches with a large aspect ratio, we find that the effect of coupling between the r and z planes is especially important as the bunch shape becomes more spherical.

Principles of longitudinal beam diagnostics with coherent radiation

Energy Technology Data Exchange (ETDEWEB)

Grimm, O.; Schmueser, P.

2006-04-24

The FLASH facility requires novel techniques to characterize the longitudinal charge distribution of the electron bunches that drive the free-electron laser. Bunch features well below 30 {mu}m need to be resolved. One technique is based on the measurement of the far-infrared radiation spectrum and reconstruction of the bunch shape through Fourier analysis. Currently, experiments using synchrotron, transition and diffraction radiation are operating at FLASH, studying the emission spectra with various instruments. This report describes the basic physics, the measurement principles, and gives explicit mathematical derivations. References to more comprehensive discussions of practical problems and experiments are listed. After a brief introduction in Sect. 1, the radiation spectrum emitted by an electron bunch is calculated in Sect. 2 in far-field approximation. The technique to reconstruct the bunch shape from the spectrum and its basic limitations are then explained in Sect. 3. Practical examples are given. The typical radiation pulse duration ranges from less than 100 femtoseconds to several picoseconds. (orig.)

Resistive theory of bunch lengthening

International Nuclear Information System (INIS)

Month, M.; Messerschmid, E.

1977-01-01

A new theory of bunch lengthening in electron storage rings is proposed. The equilibrium bunch length is that length which stabilizes the bunch against the onset of ''fast'' resistive instability, caused by the combination of many high frequency resonators such as vacuum flanges. The heat dissipated in these impedance sources follows immediately from the bunch length. It is found that the anomalous bunch length is determined by a scaling parameter g = (hVcos phi/sub s/)/I. Data taken in SPEAR I and II, data in which g extends in value by more than three orders of magnitude, can be fit with an appropriate choice of high frequency, large width coupling impedance. The impedance functions for SPEAR I and II are taken to be the same, a reflection of the fact that the high frequency sources are chamber discontinuities rather than structures connected with the rf systems. A parameter search leads to an impedance characterized by a central frequency approximately 5 GHz, a width (FWHM) approximately 1.8 GHz and a peak impedance approximately 0.2 M OMEGA. The expected and observed higher mode resistance (i.e., heat dissipated) for SPEAR are compared and found to be in agreement. Predictions are given for PEP and PETRA

Fast digital transverse feedback system for bunch train operation in CESR

International Nuclear Information System (INIS)

Rogers, J.T.; Billing, M.G.; Dobbins, J.A.

1996-01-01

We have developed a time domain transverse feedback system with the high bandwidth needed to control transverse instabilities when the CESR e + e - collider is filled with trains of closely spaced bunches. This system is based on parallel digital processors and a stripline driver. It is capable of acting on arbitrary patterns of bunches having a minimum spacing of 14 ns. Several simplifying features have been introduced. A single shorted stripline kicker driven by one power amplifier is used to control both counter-rotating beams. The desired feedback phase is achieved by sampling the bunch position at a single location on two independently selectable beam revolutions. The system adapts to changes in the betatron tune, bunch pattern, or desired damping rate through the loading of new parameters into the digital processors via the CESR control system. The feedback system also functions as a fast gated bunch current monitor. Both vertical and horizontal loops are now used in CESR operation. The measured betatron damping rates with the transverse feedback system in operation are in agreement with the analytical prediction and a computer simulation developed in connection with this work. (author)

Fast digital transverse feedback system for bunch train operation in CESR

Energy Technology Data Exchange (ETDEWEB)

Rogers, J T; Billing, M G; Dobbins, J A [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies; and others

1996-08-01

We have developed a time domain transverse feedback system with the high bandwidth needed to control transverse instabilities when the CESR e{sup +}e{sup -} collider is filled with trains of closely spaced bunches. This system is based on parallel digital processors and a stripline driver. It is capable of acting on arbitrary patterns of bunches having a minimum spacing of 14 ns. Several simplifying features have been introduced. A single shorted stripline kicker driven by one power amplifier is used to control both counter-rotating beams. The desired feedback phase is achieved by sampling the bunch position at a single location on two independently selectable beam revolutions. The system adapts to changes in the betatron tune, bunch pattern, or desired damping rate through the loading of new parameters into the digital processors via the CESR control system. The feedback system also functions as a fast gated bunch current monitor. Both vertical and horizontal loops are now used in CESR operation. The measured betatron damping rates with the transverse feedback system in operation are in agreement with the analytical prediction and a computer simulation developed in connection with this work. (author)

Method of controlling coherent synchroton radiation-driven degradation of beam quality during bunch length compression

Science.gov (United States)

Douglas, David R [Newport News, VA; Tennant, Christopher D [Williamsburg, VA

2012-07-10

A method of avoiding CSR induced beam quality defects in free electron laser operation by a) controlling the rate of compression and b) using a novel means of integrating the compression with the remainder of the transport system: both are accomplished by means of dispersion modulation. A large dispersion is created in the penultimate dipole magnet of the compression region leading to rapid compression; this large dispersion is demagnified and dispersion suppression performed in a final small dipole. As a result, the bunch is short for only a small angular extent of the transport, and the resulting CSR excitation is small.

Electron bunch length measurement with a wakefield radiation decelerator

Directory of Open Access Journals (Sweden)

Weiwei Li

2014-03-01

Full Text Available In this paper, we propose a novel method to measure the electron bunch length with a dielectric wakefield radiation (DWR decelerator which is composed of two dielectric-lined waveguides (DLWs and an electron spectrometer. When an electron beam passes through a DLW, the DWR is excited which leads to an energy loss of the electron beam. The energy loss is found to be largely dependent on the electron bunch length and can be easily measured by an electron spectrometer which is essential for a normal accelerator facility. Our study shows that this method has a high resolution and a great simplicity.

Dynamic behaviour of nominal and PACMAN bunches for different LHC crossing schemes

CERN Document Server

Herr, Werner

2005-01-01

To avoid unwanted beam-beam interactions, the two LHC beams cross at an angle in all experimental interaction regions. The choice of the crossing plane in the different areas has fundamental consequences on the effects of the long range beam-beam interaction. An alternating crossing scheme, i.e. horizontal and vertical crossing planes in the two high luminosity experiments, is presently foreseen to partly compensate and minimize first order effects on PACMAN bunches. Recent studies with a simplified model of the machine suggested that an alternating crossing scheme may be less favourable due to a reduced dynamic aperture. In this report I investigate this assertion with a detailed tracking study. The head on and long range beam-beam effects are taken into account as well as machine imperfections. The effects on the dynamic aperture of nominal and PACMAN bunches are evaluated.

On bunch lengthening using the fourth harmonic cavity in the NSLS VUV ring

International Nuclear Information System (INIS)

Wachtel, J.M.

1988-02-01

It has been suggested that the phase of the beam excited voltage in the harmonic cavity can be controlled by detuning its resonant frequency from the beam current harmonic. Unfortunately the detuning needed to flatten the acceleration waveform also corresponds to the region of Robinson instability for the harmonic cavity. Therefore, lengthening the bunch may be followed by large amplitude synchrotron oscillation of the bunch center of mass. Bunch lengthening is discussed in this note from several points of view. There follows a simple review of single electron oscillations in a quartic potential. Then equations are developed for the coupled oscillations of a cavity and a rigid bunch as a fully nonlinear, time dependent initial value problem. Next, a computer program that solves these equations for one, two or more cavities, with and without externally driven fields, is described and some simulations of the harmonic cavity interaction are shown. Finally, the fully nonlinear equations are linearized to derive a dispersion relation for the case of beam excitation in the harmonic cavity. 6 refs., 5 figs

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

Science.gov (United States)

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

2017-04-01

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

A 40 MHz Bunch by Bunch Intensity Measurement for the CERN SPS and LHC

CERN Document Server

Jakob, H; Jones, R; Jensen, L

2003-01-01

A new acquisition system has been developed to allow the measurement of the individual intensity of each bunch in a 40MHz bunch train. Such a system will be used for the measurement of LHC type beams after extraction from the CERN-PS right through to the dump lines of the CERN-LHC. The method is based on integrating the analogue signal supplied by a Fast Beam Current Transformer at a frequency of 40MHz. This has been made possible with the use of a fast integration ASIC developed by the University of Clermont-Ferrand, France, for the LHC-b pre-shower detector. The output of the integrator is digitised using a 12-bit ADC and fed into a Digital Acquisition Board (DAB) that was originally developed by TRIUMF, Canada, for use in the LHC orbit system. A full system set-up was commissioned during 2002 in the CERN-SPS, and following its success will now be extended in 2003 to cover the PS to SPS transfer lines and the new TT40 LHC extraction channel.

Resistive wall wakefields of short bunches at cryogenic temperatures

Directory of Open Access Journals (Sweden)

G. Stupakov

2015-03-01

Full Text Available We present calculations of the longitudinal wakefields at cryogenic temperatures for extremely short bunches, characteristic for modern x-ray free electron lasers. The calculations are based on the equations for the surface impedance in the regime of the anomalous skin effect in metals. This paper extends and complements an earlier analysis of B. Podobedov, Phys. Rev. ST Accel. Beams 12, 044401 (2009. into the region of very high frequencies associated with bunch lengths in the micron range. We study in detail the case of a rectangular bunch distribution for parameters of interest of LCLS-II with a superconducting undulator.

Beam-beam collisions and crossing angles in RHIC

International Nuclear Information System (INIS)

Peggs, S.

1999-01-01

This paper evaluates the strength of head on and parasitic beam-beam collisions in RHIC when the crossing angle is zero. A non-zero crossing angle is not required in normal operation with 120 bunches, thanks to the early separation of the two beams. The RHIC lattice is shown to easily accommodate even conservatively large crossing angles, for example in beam dynamics studies, or in future operational upgrades to as many as 360 bunches per ring. A modest loss in luminosity is incurred when gold ions collide at an angle after 10 hours of storage

Simulation of beam-beam effects in tevatron

International Nuclear Information System (INIS)

Mishra, C.S.; Assadi, S.; Talman, R.

1995-08-01

The Fermilab accelerator complex is in the middle of an upgrade plan Fermilab III. In the last phase of this upgrade the luminosity of the Tevatron will increase by at least one order of magnitude. In order to keep the number of interactions per crossing manageable for experiments, the number of bunches will be increased from 6 x 6 to 36 x 36 and finally to ∼100 x 100 bunches. The beam dynamics of the Tevatron has been studied from Beam-Beam effect point of view in a ''Strong-Weak'' representation with a single particle being tracked in presence of other beam. This paper describes the beam-beam effect in 6 x 6 operation of Tevatron

Use beam steering dipoles to minimize aberrations associated with off-centered transit through the induction bunching module. Design an improved NDCX-I drift compression section to make best use of the new bunching module to optimize planned initial NDCX-I target experiments

International Nuclear Information System (INIS)

HIFS-VNL; Seidl, Peter; Seidl, P.; Barnard, J.; Bieniosek, F.; Coleman, J.; Grote, D.; Leitner, M.; Gilson, E.; Logan, B.G.; Lund, S.; Lidia, S.; Ni, P.; Ogata, D.; Roy, P.; Waldron, W.; Welch, D.; Wooton, C.

2008-01-01

This milestone has been met by: (1) calculating steering solutions and implementing them in the experiment using the three pairs of crossed magnetic dipoles installed in between the matching solenoids, S1-S4. We have demonstrated the ability to center the beam position and angle to < 1 mm and < 1 mrad upstream of the induction bunching module (IBM) gap, compared to uncorrected beam offsets of several millimeters and milli-radians. (2) Based on LSP and analytic study, the new IBM, which has twice the volt-seconds of our first IBM, should be accompanied by a longer drift compression section in order to achieve a predicted doubling of the energy deposition on future warm-dense matter targets. This will be accomplished by constructing a longer ferro-electric plasma source. (3) Because the bunched current is a function of the longitudinal phase space and emittance of the beam entering the IBM we have characterized the longitudinal phase space with a high-resolution energy analyzer

Ultra-Short Electron Beam Compression and Phase Locking Using an Inverse Free Electron Laser Interaction in the THz Regime

International Nuclear Information System (INIS)

Moody, J. T.; Musumeci, P.; Scoby, C. M.; To, H.; Marcoux, C.

2010-01-01

The concept of a THz-based IFEL compressor at the UCLA Pegasus photoinjector laboratory is explored. A 3.5 MeV sub-picosecond electron beam generated in the photoinjector blowout regime can be compressed to femtosecond timescales by a THz IFEL interaction.

Multi-bunch energy distribution due to higher order modes in a travelling-wave constant gradient structure

International Nuclear Information System (INIS)

Yamamoto, M.; Higo, T.; Matsumoto, H.; Takeda, S.; Oide, K.; Takata, K.

1993-01-01

In order to accept the beam from an injector linac to a damping ring of Accelerator Test Facility (ATF), a multi-bunch energy distribution must be within ±0.3% of the beam energy. Most of the multi-bunch energy distribution linear by depends on a bunch number and this linear term can be corrected by the energy conpesention cavities. So non-linear term was calculated. It was found that the non-linear term is within ±0.3%. (author)

Choice of parameters for linear colliders in multi-bunch mode

International Nuclear Information System (INIS)

Claus, J.

1987-01-01

The energy efficiency of a linear collider in multi-bunch mode is calculated for the case that the bunches in each of the two interacting beams are identical in all interaction points, a configuration which can be realized by taking advantage of the beam-beam effect between beams of opposite electric charge. The maximization of the efficiency is discussed, the maximum appears to increase nearly linearly with beam brightness and accelerating gradient, and about quadratically with the length of the ir. The optimum operating frequency for the linacs increases also, while the pulse repetition rate and the beam current needed for fixed luminosity, decrease. The increasing brightness and the decreasing current needed for higher efficiency lead to smaller transverse spotsizes in the crossing points; this imposes tighter tolerances on the relative transverse coordinates of the two beam-axes. Pillbox or similar resonators, excited in the TM01 mode, may be preferable to quadrupoles for transverse focusing, at the high frequencies and gradients that seem desirable, particularly in the final focus. 4 refs., 7 figs

Measurement of self-shaped ellipsoidal bunches from a photoinjector with postacceleration

Directory of Open Access Journals (Sweden)

Brendan O’Shea

2011-01-01

Full Text Available Recent work has shown the possibility of generating self-shaped ellipsoidal beams with properties commensurate with the requirements of future light sources such as free-electron lasers and inverse Compton sources. In this so-termed “blowout” regime, short laser bunches are transformed via photoemission into short electron bunches which then self-consistently evolve into nearly uniform-density ellipsoids under space-charge forces. We report here on the first blowout studies conducted in collaboration between the UCLA Particle Beam Physics Lab and the Photo Injector Test Facility, Zeuthen (PITZ. The measurements conducted at the PITZ photoinjector facility examine the evolution of 750 pC, 2.7 ps FWHM electron bunches born in an L-band photoinjector and subsequently accelerated through a nine-cell L-band booster for a resulting energy of 12 MeV. These measurements represent the first observations of self-shaped ellipsoid evolution under postinjector acceleration, a key step in demonstrating the utility of such self-shaped beams at higher energy, where the advantages in both transverse and longitudinal and transverse phase space may be exploited in creating very high brightness beams.

Acceleration of a trailing positron bunch in a plasma wakefield accelerator

International Nuclear Information System (INIS)

Doche, A.; Beekman, C.; Corde, S.

2017-01-01

High gradients of energy gain and high energy efficiency are necessary parameters for compact, cost-efficient and high-energy particle colliders. Plasma Wakefield Accelerators (PWFA) offer both, making them attractive candidates for next-generation colliders. Here in these devices, a charge-density plasma wave is excited by an ultra-relativistic bunch of charged particles (the drive bunch). The energy in the wave can be extracted by a second bunch (the trailing bunch), as this bunch propagates in the wake of the drive bunch. While a trailing electron bunch was accelerated in a plasma with more than a gigaelectronvolt of energy gain, accelerating a trailing positron bunch in a plasma is much more challenging as the plasma response can be asymmetric for positrons and electrons. We report the demonstration of the energy gain by a distinct trailing positron bunch in a plasma wakefield accelerator, spanning nonlinear to quasi-linear regimes, and unveil the beam loading process underlying the accelerator energy efficiency. A positron bunch is used to drive the plasma wake in the experiment, though the quasi-linear wake structure could as easily be formed by an electron bunch or a laser driver. Finally, the results thus mark the first acceleration of a distinct positron bunch in plasma-based particle accelerators.

Beam loading in high-energy storage rings

International Nuclear Information System (INIS)

Wilson, P.B.

1974-06-01

The analysis of beam loading in the RF systems of high-energy storage rings (for example, the PEP e/sup /minus//e/sup +/ ring) is complicated by the fact that the time, T/sub b/, between the passage of successive bunches is comparable to the cavity filling time, T/sub b/. In this paper, beam loading expressions are first summarized for the usual case in which T/sub b/ /much lt/ T/sub f/. The theory of phase oscillations in the heavily-beam-loaded case is considered, and the dependence of the synchrotron frequency and damping constant for the oscillations on beam current and cavity tuning is calculated. Expressions for beam loading are then derived which are valid for any value of the ratio T/sub b//T/sub f/. It is shown that, for the proposed PEP e/sup /minus//e/sup +/ ring parameters, the klystron power required is increased by about 3% over that calculated using the standard beam loading expressions. Finally, the analysis is extended to take into account the additional losses associated with the excitation of higher-order cavity modes. A rough numerical estimate is made of the loss enhancement to be expected for PEP RF system. It is concluded that this loss enhancement might be substantial unless appropriate measures are taken in the design and tuning of the accelerating structure

Effect of empty buckets on coupled bunch instability in RHIC Booster: Longitudinal phase-space simulation

International Nuclear Information System (INIS)

Bogacz, S.A.; Griffin, J.E.; Khiari, F.Z.

1988-05-01

Excitation of large amplitude coherent dipole bunch oscillations by beam induced voltages in spurious narrow resonances are simulated using a longitudinal phase-space tracking code (ESME). Simulation of the developing instability in a high intensity proton beam driven by a spurious parasitic resonance of the rf cavities allows one to estimate the final longitudinal emittance of the beam at the end of the cycle, which puts serious limitations on the machine performance. The growth of the coupled bunch modes is significantly enhanced if a gap of missing bunches is present, which is an inherent feature of the high intensity proton machines. A strong transient excitation of the parasitic resonance by the Fourier components of the beam spectrum resulting from the presence of the gap is suggested as a possible mechanism of this enhancement. 10 refs., 4 figs., 1 tab

Longitudinal study of group a bunch of electrons in a linear accelerator

International Nuclear Information System (INIS)

Ben Taghalline, Ines; Ben Khedher, Rihab

2009-01-01

For an effective use of the electron beam, the energy dispersion shall have to be the weakest possible on the other hand the beam intensity owes shall be the biggest possible. In the practice these parameters depended of the bunching elements in the accelerator. The first part of our work presents studies concerning the influence of the modulation tension in the cavity and the drift space length on the bunching quality. The second part of this study is related to development an algorithm dedicated to determine the RF and geometrical parameters which influence the bunching quality. The studied case is a cavity followed by a drift space. The result obtained by application this algorithm is in good agreement with the others simulations result.

Beam physics design strategy for a high-current rf linac

Energy Technology Data Exchange (ETDEWEB)

Reiser, M. [Univ. of Maryland, College Park, MD (United States)

1995-10-01

The high average beam power of an rf linac system for transmutation of nuclear waste puts very stringent requirements on beam quality and beam control. Fractional beam losses along the accelerator must be kept at extremely low levels to assure {open_quotes}hands-on{close_quotes} maintenance. Hence, halo formation and large-amplitude tails in the particle distribution due to beam mismatch and equipartitioning effects must be avoided. This implies that the beam should ideally be in near-perfect thermal equilibrium from injection to full energy - in contrast to existing rf linacs in which the transverse temperature, T {sub {perpendicular}}, is higher than the longitudinal temperature, T{sub {parallel}}. The physics and parameter scaling for such a system will be reviewed using the results of recent work on high-intensity bunched beams. A design strategy for a high-current rf linac with equilibrated beam will be proposed.

Mode-coupling theory and bunch lengthening in SPEAR II

International Nuclear Information System (INIS)

Suzuki, T.; Chin, Y.; Satoh, K.

1983-01-01

A mode-coupling theory of bunched-beam instabilities is developed for a Gaussian bunch. The theory converts Sacherer's integral equation with mode coupling into a matrix eigenvalue problem. The present theory assumes well-defined azimuthal modes and takes into account radial modes which are expressed as superpositions of orthogonal functions. The theory is applied to bunch lengthening observed at SPEAR II. The theory explains qualitative features of the experimental results fairly well, but quantitative agreement is not too good. This is ascribed to insufficient knowledge of the coupling impedance of SPEAR II or to the possibility that such effects as radiation damping and quantum excitation should be included. (author)

Bunch monitor for an S-band electron linear accelerator

International Nuclear Information System (INIS)

Otake, Yuji; Nakahara, Kazuo

1991-01-01

The measurement of bunch characteristics in an S-band electron linear accelerator is required in order to evaluate the quality of accelerated electron beams. A new-type bunch monitor has been developed which combines micro-stripline technology with an air insulator and wall-current monitoring technology. The obtained time resolution of the monitor was more than 150 ps. This result shows that the monitor can handle the bunch number of an S-band linac. The structure of the monitor is suitable for being installed in the vacuum area, since it is constructed of only metal and ceramic parts. It can therefore easily be employed in an actual machine

Compensating effect of the coherent synchrotron radiation in bunch compressors

Science.gov (United States)

Jing, Yichao; Hao, Yue; Litvinenko, Vladimir N.

2013-06-01

Typical bunch compression for a high-gain free-electron laser (FEL) requires a large compression ratio. Frequently, this compression is distributed in multiple stages along the beam transport line. However, for a high-gain FEL driven by an energy recovery linac (ERL), compression must be accomplished in a single strong compressor located at the beam line’s end; otherwise the electron beam would be affected severely by coherent synchrotron radiation (CSR) in the ERL’s arcs. In such a scheme, the CSR originating from the strong compressors could greatly degrade the quality of the electron beam. In this paper, we present our design for a bunch compressor that will limit the effect of CSR on the e-beam’s quality. We discuss our findings from a study of such a compressor, and detail its potential for an FEL driven by a multipass ERL developed for the electron-Relativistic Heavy Ion Collider.

CSR Interaction for a 2D Energy-Chirped Bunch on a General Orbit

International Nuclear Information System (INIS)

Li, Rui

2009-01-01

When an electron bunch with initial linear energy chirp traverses a bunch compression chicane, the bunch interacts with itself via coherent synchrotron radiation (CSR) and space charge force. The effective longitudinal CSR force for such kind of 2D bunch on a circular orbit has been analyzed earlier (1). In this paper, we present the analytical results of the effective longitudinal CSR force for a 2D energy-chirped bunch going through a general orbit, which includes the entrance and exit of a circular orbit. In particular, we will show the behavior of the force in the last bend of a chicane when the bunch is under extreme compression. This is the condition when bifurcation of bunch phase space occurs in many CSR measurements. (1) R. Li, Phys. Rev. ST Accel. Beams 11, 024401 (2008)

The SPS Individual Bunch Measurement System

CERN Document Server

Guerrero, A; Jones, R; Savioz, J J

2001-01-01

The Individual Bunch Measurement System (IBMS) allows the intensity of each bunch in an LHC batch to be the measured both in the PS to SPS transfer lines and in the SPS ring itself. The method is vased on measuring the peak and valley of the analogue signal supplied by a Fast Beam Current Transformer at a frequency of 40 MHz. A 12 bit acquisition system is required to obtain a 1% resolution for the intensity range of 5X10`9 to 1.7X10`11 protons per bunch, corresponding to the pilot and ultimate LHC bunch intensities. The acquisition selection and external trigger adjustment system is driven by the 200MHz RF, which is distributed using a single-mode fibre-optic link. A local oscilloscope, controlled via a GPIB interface, allows the remote adjustment of the timing signals. The low-level software consists of a real-time task and a communication server run on a VME Power PC, which is accessed using a graphical user interface. This paper describes the system as a whole and presents some recent uses and results fro...

Transparent lattice characterization with gated turn-by-turn data of diagnostic bunch train

Science.gov (United States)

Li, Yongjun; Cheng, Weixing; Ha, Kiman; Rainer, Robert

2017-11-01

Methods of characterization of a storage ring's lattice have traditionally been intrusive to routine operations. More importantly, the lattice seen by particles can drift with the beam current due to collective effects. To circumvent this, we have developed a novel approach for dynamically characterizing a storage ring's lattice that is transparent to operations. Our approach adopts a dedicated filling pattern which has a short, separate diagnostic bunch train (DBT). Through the use of a bunch-by-bunch feedback system, the DBT can be selectively excited on demand. Gated functionality of a beam position monitor system is capable of collecting turn-by-turn data of the DBT, from which the lattice can then be characterized after excitation. As the DBT comprises only about one percent of the total operational bunches, the effects of its excitation are negligible to users. This approach allows us to localize the distributed quadrupolar wakefields generated in the storage ring vacuum chamber during beam accumulation. While effectively transparent to operations, our approach enables us to dynamically control the beta beat and phase beat, and unobtrusively optimize performance of the National Synchrotron Light Source-II accelerator during routine operations.

OBSERVATION OF STRONG - STRONG AND OTHER BEAM - BEAM EFFECTS IN RHIC

International Nuclear Information System (INIS)

FISCHER, W.; BLASKIEWICZ, M.; BRENNAN, J.M.; CAMERON, P.; CONNOLLY, R.; MONTAG, C.; PEGGS, S.; PILAT, F.; PTITSYN, V.; TEPIKIAN, S.; TRBOJEVIC, D.; VAN ZEIJTS, J.

2003-01-01

RHIC is currently the only hadron collider in which strong-strong beam-beam effects can be seen. For the first time, coherent beam-beam modes were observed in a bunched beam hadron collider. Other beam-beam effects in RHIC were observed in operation and in dedicated experiments with gold ions, deuterons and protons. Observations include measurements of beam-beam induced tune shifts, lifetime and emittance growth measurements with and without beam-beam interaction, and background rates as a function of tunes. During ramps unequal radio frequencies in the two rings cause the crossing points to move longitudinally. Thus bunches experience beam-beam interactions only in intervals and the tunes are modulated. In this article we summarize the most important beam-beam observations made so far

High power industrial picosecond laser from IR to UV

Science.gov (United States)

Saby, Julien; Sangla, Damien; Pierrot, Simonette; Deslandes, Pierre; Salin, François

2013-02-01

Many industrial applications such as glass cutting, ceramic micro-machining or photovoltaic processes require high average and high peak power Picosecond pulses. The main limitation for the expansion of the picosecond market is the cost of high power picosecond laser sources, which is due to the complexity of the architecture used for picosecond pulse amplification, and the difficulty to keep an excellent beam quality at high average power. Amplification with fibers is a good technology to achieve high power in picosecond regime but, because of its tight confinement over long distances, light undergoes dramatic non linearities while propagating in fibers. One way to avoid strong non linearities is to increase fiber's mode area. Nineteen missing holes fibers offering core diameter larger than 80μm have been used over the past few years [1-3] but it has been shown that mode instabilities occur at approximately 100W average output power in these fibers [4]. Recently a new fiber design has been introduced, in which HOMs are delocalized from the core to the clad, preventing from HOMs amplification [5]. In these so-called Large Pitch Fibers, threshold for mode instabilities is increased to 294W offering robust single-mode operation below this power level [6]. We have demonstrated a high power-high efficiency industrial picosecond source using single-mode Large Pitch rod-type fibers doped with Ytterbium. Large Pitch Rod type fibers can offer a unique combination of single-mode output with a very large mode area from 40 μm up to 100μm and very high gain. This enables to directly amplify a low power-low energy Mode Locked Fiber laser with a simple amplification architecture, achieving very high power together with singlemode output independent of power level or repetition rate.

Beam Induced Pressure Rise at RHIC

CERN Document Server

Zhang, S Y; Bai, Mei; Blaskiewicz, Michael; Cameron, Peter; Drees, Angelika; Fischer, Wolfram; Gullotta, Justin; He, Ping; Hseuh Hsiao Chaun; Huang, Haixin; Iriso, Ubaldo; Lee, Roger C; Litvinenko, Vladimir N; MacKay, William W; Nicoletti, Tony; Oerter, Brian; Peggs, Steve; Pilat, Fulvia Caterina; Ptitsyn, Vadim; Roser, Thomas; Satogata, Todd; Smart, Loralie; Snydstrup, Louis; Thieberger, Peter; Trbojevic, Dejan; Wang, Lanfa; Wei, Jie; Zeno, Keith

2005-01-01

Beam induced pressure rise in RHIC warm sections is currently one of the machine intensity and luminosity limits. This pressure rise is mainly due to electron cloud effects. The RHIC warm section electron cloud is associated with longer bunch spacings compared with other machines, and is distributed non-uniformly around the ring. In addition to the countermeasures for normal electron cloud, such as the NEG coated pipe, solenoids, beam scrubbing, bunch gaps, and larger bunch spacing, other studies and beam tests toward the understanding and counteracting RHIC warm electron cloud are of interest. These include the ion desorption studies and the test of anti-grazing ridges. For high bunch intensities and the shortest bunch spacings, pressure rises at certain locations in the cryogenic region have been observed during the past two runs. Beam studies are planned for the current 2005 run and the results will be reported.

Bunch Compressor Beamlines for the Tesla and S Band Linear Colliders

CERN Document Server

Emma, P

2003-01-01

A detailed design for a single stage beam bunch length compressor for both the TESLA and the S-Band Linear Collider (SBLC) is presented. Compression is achieved by introducing an energy-position correlation along the bunch with an rf section at zero-crossing phase followed by a short bending section with energy dependent path length (momentum compaction). The motivation for a wiggler design is presented and many of the critical single bunch tolerances are evaluated. A solenoid based spin rotator is included in the design and transverse emittance tuning elements, diagnostics and tuning methods are described. Bunch length limitations due to second order momentum compaction and sinusoidal rf shape are discussed with options for compensation. Finally, the disadvantages of bunch compression using a 180 sup o arc are discussed.

RF acceleration of intense laser generated proton bunches

Energy Technology Data Exchange (ETDEWEB)

Almomani, Ali

2012-07-13

With respect to laser-accelerated beams, the high current capability of the CH-DTL cavity has been investigated. Beam simulations have demonstrated that 10{sup 10} protons per bunch can be accelerated successfully and loss free along the structure. It was shown that, the maximum number of protons per bunch that can be accelerated in the first cavity by exploiting about 1% of the stored field energy is 2.02 x 10{sup 11} protons. One further aspect is the total number of protons arriving at the linac entrance. One main aspect of an rf postacceleration experiment is the rf operation stability under these beam load conditions. Detailed simulations from the target along the solenoid and down to the linac entrance were presented, applying adapted software. Special care was taken on the time steps, especially close to the target, and on the collective phenomena between electron and proton distributions. The effect of comoving electrons on the beam dynamics has been investigated in detail. A CH-linac with high space charge limit and large transverse and longitudinal acceptance was designed to accept a maximum fraction of the laser generated proton bursts. Due to well-known transformations of the injected beam emittances along the CH-cavity, it is aimed to derive parameters of the laser generated beam by measuring the beam properties behind of the CH-cavity. With respect to the linac development it is intended to realize the first cavity of the proposed CH-DTL and to demonstrate the acceleration of a laser generated proton bunch with the LIGHT project. The first cavity consists of 7 gaps within a total length of about 668 mm. It is operated at 325 MHz and has an effective accelerating field gradient of about 12.6 MV/m. The study on the surface electric field for this cavity shows, that maximum surface fields of about 94 MV/m and 88 MV/m on the third and sixth drift tubes are reachable, respectively.

Characterisation of weld zone reactions in dissimilar glass-to-aluminium pulsed picosecond laser welds

Energy Technology Data Exchange (ETDEWEB)

Ciuca, Octav P., E-mail: octav.ciuca@manchester.ac.uk [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Carter, Richard M. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom); Prangnell, Philip B. [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Hand, Duncan P. [Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS (United Kingdom)

2016-10-15

Precision welded joints, produced between fused silica glass and aluminium by a newly-developed picosecond-pulse laser technique, have been analysed for the first time using a full range of electron microscopy methods. The welds were produced as lap joints by focusing a 1.2 μm diameter laser beam through the transparent glass top sheet, slightly below the surface of the metal bottom sheet. Despite the extremely short interaction time, extensive reaction was observed in the weld zone, which involved the formation of nanocrystalline silicon and at least two transitional alumina phases, γ- and δ-Al{sub 2}O{sub 3}. The weld formation process was found to be complex and involved: the formation of a constrained plasma cavity at the joint interface, non-linear absorption in the glass, and the creation of multiple secondary keyholes in the metal substrate by beam scattering. The joint area was found to expand outside of the main interaction volume, as the energy absorbed into the low conductivity and higher melting point silica glass sheet melted the aluminium surface across a wider contact area. The reasons for the appearance of nanocrystalline Si and transitional alumina reaction products within the welds are discussed. - Highlights: •Pulsed laser welding of dissimilar materials causes extensive chemical reactivity. •Metastable Al{sub 2}O{sub 3} phases form due to laser-induced highly-transient thermal regime. •Fused silica is reduced by Al to form nanocrystalline Si. •Mechanism of joint formation is discussed.

Bunch-by-bunch feedback for PEP II

International Nuclear Information System (INIS)

Oxoby, G.; Claus, R.; Eisen, N.; Fox, J.; Hindi, H.; Hoeflich, J.; Olsen, J.; Sapozhnikov, L.; Linscott, I.

1993-01-01

The proposed PEP II B factory at SLAC requires a feedback to damp out longitudinal synchrotron oscillations. A time domain, downsampled, bunch-by-bunch feedback system in which each bunch is treated as an oscillator being driven by disturbances from other bunches is presented as we review the evolution of the system design. Results from a synchrotron oscillation damping experiment conducted at the SLAC/SSRL/SPEAR ring are also presented in this paper

The role of space charge in the performance of the bunching system for the ATLAS Positive Ion Injector

International Nuclear Information System (INIS)

Pardo, R.C.; Smith, R.

1995-01-01

The bunching system of the ATLAS Positive Ion Injector consists of a four-frequency harmonic buncher, a beam-tail removing chopper, and a 24.25 MHz spiral resonator sine-wave rebuncher. The system is designed to efficiently create beam pulses of approximately 0.25 nsec FWHM for injection into mid acceleration by the ATLAS superconducting linac. Studies of the effect of space charge on the performance of the system have been undertaken and compared to simulations as part of the design process for a new bunching system to be developed for a second ion source. Results of measurements and modeling studies indicate that the present system suffers significant bunching performance deterioration at beam currents as low as 5 eμA for 238 U 26+ at a velocity of β=0.0085. The low beam current tolerance of the present system is in reasonable agreement with computer simulation. Studies of two alternatives to the present bunching system are discussed and their limitations are explored

Calculation of coupled bunch effects in the synchrotron light source BESSY VSR

Energy Technology Data Exchange (ETDEWEB)

Ruprecht, Martin

2016-02-22

In the scope of this thesis, the strength of coupled bunch instabilities (CBIs) driven by longitudinal monopole higher order modes (HOMs) and transverse dipole and quadrupole HOMs is evaluated for the upgrade project BESSY Variable Pulse Length Storage Ring (BESSY VSR) at Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH (HZB), based on analytic calculations and tracking simulations, and compared to the performance of an active bunch-by-bunch feedback (BBFB). Algorithms for tracking codes are derived, and a semi-empirical formula for the estimation of transverse quadrupole CBIs is presented. CBI studies are an integral part of the benchmarking of the cavity models for BESSY VSR and have been accompanying and influencing their entire design process. Based on the BESSY VSR cavity model with highly advanced HOM damping, beam stability is likely to be reached with a BBFB system, independent of the bunch fill pattern. Additionally, measurements of CBIs have been performed at BESSY II and the Metrology Light Source of the Physikalisch-Technische Bundesanstalt (MLS), where the longitudinal long range impedance was characterized. Transient beam loading is evaluated by means of analytic formulas and new experimentally verified tracking codes. For the baseline bunch fill pattern of BESSY VSR, it is shown that the particular setup of cavity frequencies amplifies the transient effect on the long bunch, limiting its elongation and potentially resulting in increased Touschek losses.

Beam-Beam Interaction Studies at LHC

CERN Document Server

Schaumann, Michaela; Alemany Fernandez, R

2011-01-01

The beam-beam force is one of the most important limiting factors in the performance of a collider, mainly in the delivered luminosity. Therefore, it is essential to measure the effects in LHC. Moreover, adequate understanding of LHC beam-beam interaction is of crucial importance in the design phases of the LHC luminosity upgrade. Due to the complexity of this topic the work presented in this thesis concentrates on the beam-beam tune shift and orbit effects. The study of the Linear Coherent Beam-Beam Parameter at the LHC has been determined with head-on collisions with small number of bunches at injection energy (450 GeV). For high bunch intensities the beam-beam force is strong enough to expect orbit effects if the two beams do not collide head-on but with a crossing angle or with a given offset. As a consequence the closed orbit changes. The closed orbit of an unperturbed machine with respect to a machine where the beam-beam force becomes more and more important has been studied and the results are as well ...

Design study of longitudinal dynamics of the drive beam in 1 TeV relativistic klystron two-beam accelerator

International Nuclear Information System (INIS)

Li, H.; Yu, S.S.; Sessler, A.M.

1994-10-01

In this paper the authors present a design study on the longitudinal dynamics of a relativistic klystron two-beam accelerator (RK-TBA) scheme which has been proposed as a power source candidate for a 1 TeV next linear collider (NLC). They address the issue of maintaining stable power output at desired level for a 300-m long TBA with 150 extraction cavities and present their simulation results to demonstrate that it can be achieved by inductively detuning the extraction cavities to counter the space charge debunching effect on the drive beam. They then carry out simulation study to show that the beam bunches desired by the RK-TBA can be efficiently obtained by first chopping an initially uniform beam of low energy into a train of beam bunches with modest longitudinal dimension and then using the open-quotes adiabatic captureclose quotes scheme to bunch and accelerate these beam bunches into tight bunches at the operating energy of the drive beam. The authors have also examined the open-quotes after burnerclose quotes scheme which is implemented in their RK-TBA design for efficiency enhancement

Simulations of the ILC Electron Gun and Electron Bunching System

International Nuclear Information System (INIS)

Haakonsen, C.B.; McGill U.

2006-01-01

The International Linear Collider (ILC) is a proposed electron-positron collider, expected to provide insight into important questions in particle physics. A part of the global R and D effort for the ILC is the design of its electron gun and electron bunching system. The present design of the bunching system has two sub-harmonic bunchers, one operating at 108 MHz and one at 433MHz, and two 5-cell 1.3 GHz (L-band) bunchers. This bunching system has previously been simulated using the Phase and Radial Motion in Electron Linear Accelerators (PARMELA) software, and those simulations indicated that the design provides sufficient bunching and acceleration. Due to the complicated dynamics governing the electrons in the bunching system we decided to verify and expand the PARMELA results using the more recent and independent simulation software General Particle Tracer (GPT). GPT tracks the motion and interactions of a set of macro particles, each of which represent a number of electrons, and provides a variety of analysis capabilities. To provide initial conditions for the macro particles, a method was developed for deriving the initial conditions from detailed simulations of particle trajectories in the electron gun. These simulations were performed using the Egun software. For realistic simulation of the L-band bunching cavities, their electric and magnetic fields were calculated using the Superfish software and imported into GPT. The GPT simulations arrived at similar results to the PARMELA simulations for sub-harmonic bunching. However, using GPT it was impossible to achieve an efficient bunching performance of the first L-band bunching cavity. To correct this, the first L-band buncher cell was decoupled from the remaining 4 cells and driven as an independent cavity. Using this modification we attained results similar to the PARMELA simulations. Although the modified bunching system design performed as required, the modifications are technically challenging to implement

The CMS Beam Halo Monitor Electronics

CERN Document Server

AUTHOR|(CDS)2080684; Fabbri, F.; Grassi, T.; Hughes, E.; Mans, J.; Montanari, A.; Orfanelli, S.; Rusack, R.; Torromeo, G.; Stickland, D.P.; Stifter, K.

2016-01-01

The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes. The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few ns resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and receives data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is readout by IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed in real time and published to CMS and the LHC, providi...

Observation of Beam Size Flip-Flop in PEP-II

International Nuclear Information System (INIS)

Holtzapple, Robert luther

2002-01-01

The asymmetric B-factory, PEP-II, has delivered a peak luminosity of 4.6 x 10 33 cm -2 s -1 with less than half the design number of bunches, requiring a luminosity per bunch crossing more than three times larger than the design. As a result, strong beam-beam effects are present. The strong beam-beam forces between colliding electron and positron bunches can result in a ''flip-flop'' of the transverse beam size of some bunches. Focusing on one positron-electron colliding bunch pair, a flip-flop occurs when the transverse size of the positron bunch shrinks and the electron bunch grows. The flip-flop accounts for a reduction in luminosity, a lower positron lifetime, and increased background in the BABAR detector. The flip-flop phenomenon occurs not for all of the colliding bunches, but for the bunches at the front of a mini-train. Once a colliding pair has flipped to its reduced luminosity state it can be changed back to its normal state by raising the horizontal tune in the low-energy ring (LER, positrons) by 0.01. Afterwards the LER x-tune can be reduced nearly back to its original point, resulting in higher luminosity. These observations were verified and quantified with a new time-gated camera with a resolution of 2 ns, making it possible to observe single bunches

LHC Beam Instrumentation: Beam Profile Measurements (2/3)

CERN Document Server

CERN. Geneva

2014-01-01

The LHC is equipped with a full suite of sophisticated beam instrumentation which has been essential for rapid commissioning, the safe increase in total stored beam power and the understanding of machine optics and accelerator physics phenomena. These lectures will introduce these systems and comment on their contributions to the various stages of beam operation. They will include details on: the beam position system and its use for real-time global orbit feedback; the beam loss system and its role in machine protection; total and bunch by bunch intensity measurements; tune measurement and feedback; diagnostics for transverse beam size measurements, abort gap monitoring and longitudinal density measurements. Issues and problems encountered along the way will also be discussed together with the prospect for future upgrades.

State orthogonality, boson bunching parameter and bosonic enhancement factor

International Nuclear Information System (INIS)

Marchewka, A.; Granot, E.

2016-01-01

Bosons bunching is the tendency of bosons to bunch together with respect to distinguishable particles. It is emphasized that the bunching parameter β = p_B/p_D, i.e. the ratio between the probability to measure 2 bosons and 2 distinguishable particles at the same state, is a constant of motion and depends only on the overlap between the initial wavefunctions. This ratio is equal to β = 2/(1 + l"2), where l is the overlap integral between the initial wavefunctions. That is, only when the initial wavefunctions are orthogonal this ratio is equal to 2, however, this bunching ratio can be reduced to 1, when the two wavefunctions are identical. This simple equation explains the experimental evidences of a beam splitter. A straightforward conclusion is that by measuring the local bunching parameter β (at any point in space and time) it is possible to evaluate a global parameter l (the overlap between the initial wavefunctions). The bunching parameter is then generalized to arbitrary number of particles, and in an analogy to the two-particles scenario, the well-known bosonic enhancement appears only when all states are orthogonal

Stochastic cooling of bunched beams from fluctuation and kinetic theory

International Nuclear Information System (INIS)

Chattopadhyay, S.

1982-09-01

A theoretical formalism for stochastic phase-space cooling of bunched beams in storage rings is developed on the dual basis of classical fluctuation theory and kinetic theory of many-body systems in phase-space. The physics is that of a collection of three-dimensional oscillators coupled via retarded nonconservative interactions determined by an electronic feedback loop. At the heart of the formulation is the existence of several disparate time-scales characterizing the cooling process. Both theoretical approaches describe the cooling process in the form of a Fokker-Planck transport equation in phase-space valid up to second order in the strength and first order in the auto-correlation of the cooling signal. With neglect of the collective correlations induced by the feedback loop, identical expressions are obtained in both cases for the coherent damping and Schottky noise diffusion coefficients. These are expressed in terms of Fourier coefficients in a harmonic decomposition in angle of the generalized nonconservative cooling force written in canonical action-angle variables of the particles in six-dimensional phase-space. Comparison of analytic results to a numerical simulation study with 90 pseudo-particles in a model cooling system is presented

Simulations of Bunch Precompression at High Currents in the SLC Damping Rings

International Nuclear Information System (INIS)

Bane, K.L.F.; Minty, M.G.; Chao, A.W.

2011-01-01

In the Stanford Linear Collider (SLC) each beam, after leaving a damping ring, is compressed in the Ring-to-Linac (RTL) transfer line before entering the linear accelerator. At a bunch population of 4.0 x 10 10 particles, due to the limited energy acceptance of the RTL, approximately 15% of the beam has normally been lost. During the 1996 run, however, to eliminate this loss the bunch was partially precompressed in the damping ring, just before extraction; the beam loss in the RTL was reduced to almost zero. The operation and performance of precompression are presented by Minty et al. (1999). Also given is an analysis which, however, does not include the effects of the longitudinal wakefield on the beam dynamics. In this report we extend that analysis to include these effects.

Production of a monoenergetic electron bunch in a self-injected laser-wakefield accelerator

International Nuclear Information System (INIS)

Chang, C.-L.; Hsieh, C.-T.; Ho, Y.-C.; Chen, Y.-S.; Lin, J.-Y.; Wang, J.; Chen, S.-Y.

2007-01-01

Production of a monoenergetic electron bunch in a self-injected laser-wakefield accelerator is investigated with a tomographic method which resolves the electron injection and acceleration processes. It is found that all the electrons in the monoenergetic electron bunch are injected at the same location in the plasma column and then accelerated with an acceleration gradient exceeding 2 GeV/cm. The injection position shifts with the position of pump-pulse focus, and no significant deceleration is observed for the monoenergetic electron bunch after it reaches the maximum energy. The results are consistent with the model of transverse wave breaking and beam loading for the injection of monoenergetic electrons. The tomographic method adds a crucial dimension to the whole array of existing diagnostics for laser beams, plasma waves, and electron beams. With this method the details of the underlying physical processes in laser-plasma interactions can be resolved and compared directly to particle-in-cell simulations

Instrumental development of a quasi-relativistic ultrashort electron beam source for electron diffractions and spectroscopies.

Science.gov (United States)

Shin, Young-Min; Figora, Michael

2017-10-01

A stable femtosecond electron beam system has been configured for time-resolved pump-probe experiments. The ultrafast electron diffraction (UED) system is designed with a sub-MeV photoelectron beam source pulsed by a femtosecond UV laser and nondispersive beamline components, including a bunch compressor-a pulsed S-band klystron is installed and fully commissioned with 5.5 MW peak power in a 2.5 μs pulse length. A single-cell RF photo-gun is designed to produce 1.6-16 pC electron bunches in a photoemission mode with 150 fs pulse duration at 0.5-1 MeV. The measured RF system jitters are within 1% in magnitude and 0.2° in phase, which would induce 3.4 keV and 0.25 keV of ΔE, corresponding to 80 fs and 5 fs of Δt, respectively. Our particle-in-cell simulations indicate that the designed bunch compressor reduces the time-of-arrival jitter by about an order of magnitude. The transport and focusing optics of the designed beamline with the bunch compressor enables an energy spread within 10 -4 and a bunch length (electron probe) within quasi-relativistic UED system.

Space-charge effects on bunching of electrons in the CEBAF injector

International Nuclear Information System (INIS)

Liu, H.

1997-01-01

The main injector for the 4 GeV CEBAF accelerator at Thomas Jefferson national accelerator facility was designed to deliver simultaneously three CW electron beams for nuclear physics research. The maximum design current for a single beam from the injector is 100 μA, or 0.2 pC per microbunch at a repetition rate of 499 MHz. It was found through computer simulation that space charge even at a subpicocoulomb level can spoil the bunching of electrons significantly, and some unexpected phenomena observed experimentally could be explained accordingly. This problem arises because of the low-momentum tilt allowed for bunching to preserve low-momentum spread. In this paper, we analyze in detail the space-charge effects on bunching of electrons with the CEBAF injector as an example. Conditions for effective matching of longitudinal phase space in the presence of space charge are discussed. (orig.)

Beam instability during high-current heavy-ion beam transport

International Nuclear Information System (INIS)

Kikuchi, T.; Someya, T.; Kawata, S.; Nakajima, M.; Horioka, K.

2005-01-01

In driver system for heavy ion inertial fusion, beam dynamics is investigated by particle-in-cell simulations during final beam bunching. The particle simulations predict that the beam is transported with the localized transverse charge distribution induced by the strong space charge effect. The calculation results also show that the emittance growth during the longitudinal bunch compression for various particle distributions at the initial conditions and with two types of transverse focusing model, which are a continuous focusing and an alternating gradient focusing lattice configurations. (author)

LHC Report: 25 ns spacing yields record beam intensity

CERN Multimedia

The LHC team

2012-01-01

Over the weekend the LHC broke two records: a record number of 2,748 proton bunches were injected into the accelerator giving a record beam intensity of around 2.7 x 1014 protons in both beams. These beams have yet to face the challenge of "ramping" to high energy.   These very good results were made possible by a new beam configuration: the design value of 25 nanosecond spacing between proton bunches replaced - for the first time – the typical 50 nanosecond spacing. This test run was done at 450 GeV with no collisions. Up to now, the LHC has been running with around 1,380 bunches with 50 nanoseconds between bunches. By going to 25 nanoseconds, the LHC operations team can double the number of bunches to around 2,800. One of the main limitations for this mode of operation is the so-called electron cloud (see Bulletin 15-16/2011) that is strongly enhanced by the reduced spacing among bunches.  The electron cloud has nasty effects on the beam (beam size increase...

Self-modulation instability of a long proton bunch in plasmas

CERN Document Server

Kumar, Naveen; Lotov, Konstantin

2010-01-01

An analytical model for the self-modulation instability of a long relativistic proton bunch propagating in uniform plasmas is developed. The self-modulated proton bunch resonantly excites a large amplitude plasma wave (wake field), which can be used for acceleration of plasma electrons. Analytical expressions for the linear growth rate and the number of exponentiations are given. We use the full three-dimensional particle-in-cell (PIC) simulations to study the beam self-modulation and the transition to the nonlinear stage. It is shown that the self-modulation of the proton bunch competes with the hosing instability which tends to destroy the plasma wave. A method is proposed and studied through PIC simulations to circumvent this problem which relies on the seeding of the self-modulation instability in the bunch.

Picosecond image-converter diagnostics

International Nuclear Information System (INIS)

Schelev, M.Ya.

1975-01-01

A brief review is presented of the improvements in picosecond image-converter diagnostics carried out since the previous Congress in 1972. The account is given under the following headings: picosecond image converter cameras for visible and x-ray radiation diagnostics; Nd:glass and ruby mode-locked laser measurements; x-ray plasma emission diagnostics; computer treatment of pictures produced by picosecond cameras. (U.K.)

Design of bunch compressing system with suppression of coherent synchrotron radiation for ATF upgrade

International Nuclear Information System (INIS)

Jing, Yichao; Fedurin, Mikhail; Stratakis, Diktys

2015-01-01

One of the operation modes for Accelerator Test Facility (ATF) upgrade is to provide high peak current, high quality electron beam for users. Such operation requires a bunch compressing system with a very large compression ratio. The CSR originating from the strong compressors generally could greatly degrade the quality of the electron beam. In this paper, we present our design for the entire bunch compressing system that will limit the effect of CSR on the e-beam@s quality. We discuss and detail the performance from the start to end simulation of such a compressor for ATF.

Minimizing the energy spread within a single bunch by shaping its charge distribution

International Nuclear Information System (INIS)

Loew, G.A.; Wang, J.

1984-06-01

When electrons or positrons in a bunch pass through the periodic structure of a linear accelerator, they leave behind them energy in the form of longitudinal wake fields. The longitudinal fields left behind by early particles in a bunch decrease the energy of later particles. For a linear collider, the energy spread introduced within the bunches by this beam loading effect must be minimized because it limits the degree to which the particles can be focused to a small spot due to chromatic effects in the final focus system. For example, for the SLC, the allowable energy spread is +-0.5%. It has been known for some time that partial compensation of the longitudinal wake field effects can be obtained for any bunch by placing it ahead of the accelerating crest (in space), thereby letting the positive rising sinusoidal field offset the negative beam loading field. The work presented in this report shows that it is possible to obtain complete compensation, i.e., to reduce the energy spread essentially to zero by properly shaping the longitudinal charge distribution of the bunch and by placing it at the correct position on the wave

Programmable high power beam damper for the Tevatron

International Nuclear Information System (INIS)

Crisp, J.; Goodwin, R.; Gerig, R.

1985-06-01

A bunch-by-bunch beam damper has been developed for the Fermilab Tevatron. The system reduces betatron oscillation amplitudes and incorporates some useful machine diagnostics. The device is programmable via look-up tables so the output is an arbitrary function, on a bunch-by-bunch basis, of the beam displacement. We are presently using this feature to measure the betatron tune throughout the acceleration cycle. 4 refs

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.

Longitudinal phase-space manipulation of ellipsoidal electron bunches in realistic fields

Directory of Open Access Journals (Sweden)

S. B. van der Geer

2006-04-01

Full Text Available Since the recent publication of a practical recipe to create “pancake” electron bunches which evolve into uniformly filled ellipsoids, a number of papers have addressed both an alternative method to create such ellipsoids as well as their behavior in realistic fields. So far, the focus has been on the possibilities to preserve the initial “thermal” transverse emittance. This paper addresses the linear longitudinal phase space of ellipsoidal bunches. It is shown that ellipsoidal bunches allow ballistic compression at subrelativistic energies, without the detrimental effects of nonlinear space-charge forces. This in turn eliminates the need for the large correlated energy spread normally required for longitudinal compression of relativistic particle beams, while simultaneously avoiding all problems related to magnetic compression. Furthermore, the linear space-charge forces of ellipsoidal bunches can be used to reduce the remaining energy spread even further, by carefully choosing the beam transverse size, in a process that is essentially the time-reversed process of the creation of an ellipsoid at the cathode. The feasibility of compression of ellipsoidal bunches is illustrated with a relatively simple setup, consisting of a half-cell S-band photogun and a two-cell booster compressor. Detailed GPT simulations in realistic fields predict that 100 pC ellipsoidal bunches can be ballistically compressed to 100 fs, at a transverse emittance of 0.7   μm, with a final energy of 3.7 MeV and an energy spread of only 50 keV.

High Harmonic Inverse Free-Electron-Laser Interaction at 800 NM

CERN Document Server

Sears, Chris M S; Colby, Eric R; Cowan, Benjamin; Plettner, Tomas; Siemann, Robert; Spencer, James

2005-01-01

The inverse Free Electron Laser (IFEL) interaction has recently been proposed and used as a short wavelength modulator forμbunching of beams for laser acceleration experiments*,**. These experiments utilized the fundamental of the interaction between the laser field and electron bunch. In the current experiment, we explore the higher order resonances of the IFEL interaction from a 3 period, 1.8 centimeter wavelength undulator with a picosecond, 0.25 mJ/pulse laser at 800 nm. The resonances are observed by adjusting the gap of the undulator while keeping the beam energy constant. We will also discuss diagnostics for obtaining beam overlap and statistical techniques used to account for machine drifts and analyze the data.

Electro-Magnetic Bunch Length Measurement in LEP

CERN Document Server

Vos, L

1998-01-01

Bunch lengths between 3 and 12 mm have been measured routinely in LEP in 1997 with a small (7 mm diameter) button electrode. The measurement method is based on the spectral analysis of the electrode signal and relies on the fact that the transfer function of the complete set-up, including the signal cable, can be computed rather exactly thus eliminating the need for external calibration. The information of beam intensity is recovered as a by-product. It provides an interesting internal validation of the measurement by comparison with the normal intensity measurement. The system has been used to detect subtle but real bunch length changes with bunch intensity which can be attributed to the inductive impedance in LEP. A value for the imaginary (inductive) longitudinal impedance is derived from the observations. An indication for the resistive part of the impedance is given as well.

Elemental fractionation in 785 nm picosecond and femtosecond laser ablation inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

Shaheen, M.E.; Gagnon, J.E.; Fryer, B.J.

2015-01-01

Elemental fractionation and ICP-MS signal response were investigated for two different pulse width laser beams originating from the same laser system. Femtosecond and picosecond laser beams at pulse widths of 130 fs and 110 ps, respectively, and wavelength of 785 nm were used to ablate NIST 610 synthetic glass and SRM 1107 Naval Brass B at the same spot for 800 to 1000 laser pulses at different repetition rates (5 to 50 Hz). Elemental fractionation was found to depend on repetition rate and showed a trend with femtosecond laser ablation that is opposite to that observed in picosecond laser ablation for most measured isotopes. ICP-MS signal intensity was higher in femtosecond than picosecond LA-ICP-MS in both NIST 610 and naval brass when ablation was conducted under the same fluence and repetition rate. The differences in signal intensity were partly related to differences in particle size distribution between particles generated by femtosecond and picosecond laser pulses and the consequent differences in transport and ionization efficiencies. The main reason for the higher signal intensity resulting from femtosecond laser pulses was related to the larger crater sizes compared to those created during picosecond laser ablation. Elemental ratios measured using 66 Zn/ 63 Cu, 208 Pb/ 238 U, 232 Th/ 238 U, 66 Zn/ 232 Th and 66 Zn/ 208 Pb were found to change with the number of laser pulses with data points being more scattered in picosecond than femtosecond laser pulses. Reproducibility of replicate measurements of signal intensities, fractionation and elemental ratios was better for fs-LA-ICP-MS (RSD ~ 3 to 6%) than ps-LA-ICP-MS (RSD ~ 7 to 11%). - Highlights: • Fractionation and ICP-MS signal response were investigated for two different pulse widths using NIST 610 and Naval Brass. • Dependence of fractionation indices on repetition rate and pulse width. • Higher ablation rate was observed in picosecond compared to femtosecond laser ablation of NIST 610 and Brass

Beam dynamics in linear colliders

International Nuclear Information System (INIS)

Ruth, R.D.

1990-09-01

In this paper, we discuss some basic beam dynamics issues related to obtaining and preserving the luminosity of a next generation linear collider. The beams are extracted from a damping ring and compressed in length by the first bunch compressor. They are then accelerated in a preaccelerator linac up to an energy appropriate for injection into a high gradient linac. In many designs this pre-acceleration is followed by another bunch compression to reach a short bunch. After acceleration in the linac, the bunches are finally focused transversely to a small spot. 27 refs., 1 fig

Beam-chopping system for LNS superconducting cyclotron

International Nuclear Information System (INIS)

Calabretta, L.; Caruso, A.; Raia, G.; Sparta, A.; Zappala, E.; Zingale, A.; Khemka, P.; Wei, C.Y.

1999-01-01

Several experiments which foresee the measurement of time of flight require a bunched beam with a FWHM smaller that 1 ns and a temporal separation from 100 to 200 ns. An H.E. Chopper that achieves this temporal separation between the impulses has been installed along the beam extraction line of the cyclotron. The two electrodes, which deflect the beam and the inductance coil are both under vacuum. The operating frequency range of the LC resonant circuit is from 4.5 to 9 MHz and the maximum design voltage is 70 kV. The chopper selects only the beam bunches which cross the device at peak voltage, one bunch for cycle. A steerer magnet to recover the selected bunches on the beam axis is used. All the tests, measurements and chopper's performance, will be presented. (authors)

Beam-chopping system for LNS superconducting cyclotron

Energy Technology Data Exchange (ETDEWEB)

Calabretta, L.; Caruso, A.; Raia, G.; Sparta, A.; Zappala, E.; Zingale, A. [INFN-LNS, Catania (Italy); Khemka, P. [VEEC, Calcutta (India); Wei, C.Y. [Institute of Modern Physics, Lanzhou (China)

1999-07-01

Several experiments which foresee the measurement of time of flight require a bunched beam with a FWHM smaller that 1 ns and a temporal separation from 100 to 200 ns. An H.E. Chopper that achieves this temporal separation between the impulses has been installed along the beam extraction line of the cyclotron. The two electrodes, which deflect the beam and the inductance coil are both under vacuum. The operating frequency range of the LC resonant circuit is from 4.5 to 9 MHz and the maximum design voltage is 70 kV. The chopper selects only the beam bunches which cross the device at peak voltage, one bunch for cycle. A steerer magnet to recover the selected bunches on the beam axis is used. All the tests, measurements and chopper's performance, will be presented. (authors)

Operational beams for the LHC

CERN Document Server

Papaphilippou, Y.; Rumolo, G.; Manglunki, D.

2014-01-01

The variety of beams, needed to set-up in the injectors as requested in the LHC, are reviewed, in terms of priority but also performance expectations and reach during 2015. This includes the single bunch beams for machine commissioning and measurements (probe, Indiv) but also the standard physics beams with 50 ns and 25 ns bunch spacing and their high brightness variants using the Bunch Compression Merging and Splitting (BCMS) scheme. The required parameters and target performance of special beams like the doublet for electron cloud enhancement and the more exotic 8b$\\oplus$4e beam, compatible with some post-scrubbing scenarios are also described. The progress and plans for the LHC ion production beams during 2014-2015 are detailed. Highlights on the current progress of the setting up of the various beams are finally presented with special emphasis on potential performance issues across the proton and ion injector chain.

Performance of the CMS Beam Halo Monitor

CERN Document Server

CMS Collaboration

2015-01-01

The CMS Beam Halo Monitor has been successfully installed in the CMS cavern in LHC Long Shutdown 1 for measuring the machine induced background for LHC Run II. The system is based on 40 detector units composed of radiation hard synthetic quartz Cherenkov radiators coupled to fast photomultiplier tubes for a direction sensitive measurement. The readout electronics chain uses many components developed for the Phase 1 upgrade to the CMS Hadronic Calorimeter electronics, with dedicated firmware and readout adapted to the beam monitoring requirements. The PMT signal is digitized by a charge integrating ASIC (QIE10), providing both the signal rise time, with few ns resolution, and the charge integrated over one bunch crossing. The backend electronics uses microTCA technology and received data via a high-speed 5 Gbps asynchronous link. It records histograms with sub-bunch crossing timing resolution and is readout by IPbus using the newly designed CMS data acquisition for non-event based data. The data is processed i...

A Symplectic Beam-Beam Interaction with Energy Change

International Nuclear Information System (INIS)

Moshammer, Herbert

2003-01-01

The performance of many colliding storage rings is limited by the beam-beam interaction. A particle feels a nonlinear force produced by the encountering bunch at the collision. This beam-beam force acts mainly in the transverse directions so that the longitudinal effects have scarcely been studied, except for the cases of a collision with a crossing angle. Recently, however, high luminosity machines are being considered where the beams are focused extensively at the interaction point (IP) so that the beam sizes can vary significantly within the bunch length. Krishnagopal and Siemann have shown that they should not neglect the bunch length effect in this case. The transverse kick depends on the longitudinal position as well as on the transverse position. If they include this effect, however, from the action-reaction principle, they should expect, at the same time, an energy change which depends on the transverse coordinates. Such an effect is reasonably understood from the fact that the beam-beam force is partly due to the electric field, which can change the energy. The action-reaction principle comes from the symplecticity of the reaction: the electromagnetic influence on a particle is described by a Hamiltonian. The symplecticity is one of the most fundamental requirements when studying the beam dynamics. A nonsymplectic approximation can easily lead to unphysical results. In this paper, they propose a simple, approximately but symplectic mapping for the beam-beam interaction which includes the energy change as well as the bunch-length effect. In the next section, they propose the mapping in a Hamiltonian form, which directly assures its symplecticity. Then in section 3, they study the nature of the mapping by interpreting its consequences. The mapping itself is quite general and can be applied to any distribution function. They show in Section 4 how it appears when the distribution function is a Gaussian in transverse directions. The mapping is applied to the