Sources and Injectors

Electron/Positron Sources

Paper Title Page
TPPE039 Development of Advanced Models for 3D Photocathode PIC Simulations 2583
 
  • D.A. Dimitrov, D.L. Bruhwiler, J.R. Cary, P. Messmer, P. Stoltz
    Tech-X, Boulder, Colorado
  • D.W. Feldman, P.G. O'Shea
    IREAP, College Park, Maryland
  • K. Jensen
    NRL, Washington, DC
 
  Funding: This work is supported by the U.S. DOE, use of NERSC supercomputer facilities, and the Joint Technology office (JTO).

Codes for simulating photocathode electron guns invariably assume the emission of an idealized electron distribution from the cathode, regardless of the particular particle emission model that is implemented. The output of such simulations, a relatively clean and smooth distribution with very little variation as a function of the azimuthal angle, is inconsistent with the highly irregular and asymmetric electron bunches seen in experimental diagnostics. To address this problem, we have implemented a recently proposed theoretical model* that takes into account detailed solid-state physics of photocathode materials in the VORPAL particle-in-cell code.** Initial results from 3D simulations with this model and future research directions will be presented and discussed.

*K.L. Jensen, D.W. Feldman, M. Virgo, and P.G. O'Shea, Phys. Rev. ST Accel. Beams, 6:083501, 2003. **C. Nieter and J.R. Cary, J. Comp. Phys. 196 (2004), p. 448.

 
TPPE040 RF and Magnetic Measurements on the SPARC Photoinjector and Solenoid at UCLA 2624
 
  • J.B. Rosenzweig, A.M. Cook, M.P. Dunning, P. Frigola, G. Travish
    UCLA, Los Angeles, California
  • D.T. Palmer
    SLAC, Menlo Park, California
  • C. Sanelli, F. Tazzioli
    INFN/LNF, Frascati (Roma)
 
  Funding: This work is supported by U.S. Dept. of Energy grant DE-FG03-92ER40693.

The rf photocathode gun and the solenoid for the SPARC project at INFN-LNF (Frascati) have been fabricated and undergone initial testing at UCLA. The advanced aspects of the design of these devices are detailed. Final diagnosis of the tuning of the RF gun performance, including operating mode frequency and field balance, is described. The emittance compensating solenoid magnet, which is designed to be tuned in longitudinal position by differential excitation of the coils, has been measured using Hall probe scans for field profiling, and pulsed wire methods to determine the field center.

 
TPPE041 Multi-Alkali Photocathode Development at Brookhaven National Lab for Application in Superconducting Photoinjectors 2672
 
  • A. Burrill, I. Ben-Zvi, D. Pate, T. Rao, Z. Segalov
    BNL, Upton, Long Island, New York
  • D. Dowell
    SLAC, Menlo Park, California
 
  In this paper we will report our progress on the development of cesium potassium antimonide photocathodes and their application in superconducting photoinjectors. Quantum efficiencies of 2-3 % at 545 nm, and 10% at 365 nm have been routinely obtained in the test stand, and electron emission uniformity, quantum efficiency at a variety of wavelengths, and lifetime under different vacuum conditions has been well characterized. The extraction of high charge per laser pulse will also be addressed in addition to the comparison of results from two different deposition techniques.  
TPPE042 Study of Secondary Emission Enhanced Photoinjector 2711
 
  • X.Y. Chang, I. Ben-Zvi, A. Burrill, P.D.J. Johnson, J. Kewisch, T. Rao, Z. Segalov, Y. Zhao
    BNL, Upton, Long Island, New York
 
  The secondary emission enhanced photoinjector (SEEP) is a very promising new approach to the generation of high-current, high-brightness electron beams. Primary electrons with a few thousand electron-volts of energy strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating proper of the “gun” through a Negative Electron Affinity (NEA) surface of the diamond (Hydrogen terminated). We present the calculation of heating power sources and the temperature distribution in details. Some properties of the secondary electron beam related to beam dynamics are also reported. The results show feasibility of this kind of cathode.  
TPPE043 Electron Beam Generation and Transport for the RHIC Electron Cooler 2774
 
  • J. Kewisch, I. Ben-Zvi, X.Y. Chang
    BNL, Upton, Long Island, New York
 
  Funding: Work performed under Contract Number DE-AC02-98CH10886 with the auspices of the U.S. Department of Energy.

An electron cooler, based on an Energy Recovery Linac (ERL) is under development for the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. This will be the first electron cooler operating at high energy with bunched beams. A better understanding of the cooling process and more accurate measurements of Intra Beam Scattering in RHIC have imposed increased requirements on the electron accelerator: Besides a doubling of the bunch charge to 20 nC, the strength of the cooling solenoid was increased five-fold to 5 Tesla. The magnetic field on the cathode should be increased to 500 Gauss to match the magnetization required in the cooling solenoid. This paper reports the measures taken to minimize the electron beam emittance in the cooling section. The front-to-end simulation using different tracking codes is presented.

 
TPPE044 Upgrade of the Fermilab/NICADD Photoinjector Laboratory 2848
 
  • P. Piot, H. Edwards
    Fermilab, Batavia, Illinois
  • M. Huening
    DESY, Hamburg
  • T. W. Koeth
    Rutgers University, The State University of New Jersey, Piscataway, New Jersey
  • J.L. Li, R. Tikhoplav
    Rochester University, Rochester, New York
 
  Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. DOE, and by NICADD.

The Femilab/NICADD photoinjector laboratory (FNPL) is a 16 MeV electron accelerator dedicated to beam dynamics and advanced accelerator studies. FNPL will soon be capable of operating at 50 MeV, after the installation of a high gradient TESLA cavity. In this paper we present the foreseen design for the upgraded facility along with its performance. We discuss the possible application of 50 MeV beam including the possible use of FNPL as an injector for the superconducting module and test facility (SM&TF).

 
TPPE045 Normal-Conducting High Current RF Photoinjector for High Power CW FEL 2866
 
  • S.S. Kurennoy, D.C. Nguyen, D.L. Schrage, R.L. Wood
    LANL, Los Alamos, New Mexico
  • V. Christina, J. Rathke, T. Schultheiss
    AES, Medford, NY
  • L.M. Young
    TechSource, Santa Fe, New Mexico
 
  An RF photoinjector capable of producing high average current with low emittance and energy spread is a key enabling technology for high power CW FEL. The design of a 2.5-cell, pi-mode, 700-MHz normal-conducting RF photoinjector cavity with magnetic emittance compensation is completed. With average gradients of 7, 7, and 5 MV/m in its three accelerating cells, the photoinjector will produce a 2.5-MeV electron beam with 3-nC charge per bunch and transverse rms emittance below 7 mm-mrad. Electromagnetic modeling has been used extensively to optimize ridge-loaded tapered waveguides and RF couplers, and led to a new, improved coupler iris design. The results, combined with a thermal and stress analysis, show that the challenging problem of cavity cooling can be successfully solved. Fabrication of a demo 100-mA (at 35 MHz bunch repetition rate) photoinjector is underway. The design is scalable to higher average currents by increasing the electron bunch repetition rate, and provides a path to a MW-class FEL. This paper presents the cavity design and details of RF coupler modeling.  
TPPE046 Computer Simulation of the UMER Gridded Gun 2908
 
  • I. Haber, S. Bernal, R.A. Kishek, P.G. O'Shea, Y. Zou
    IREAP, College Park, Maryland
  • A. Friedman, D.P. Grote
    LLNL, Livermore, California
  • M. Reiser
    University Maryland, College Park, Maryland
  • J.-L. Vay
    LBNL, Berkeley, California
 
  Funding: This work is supported by the U.S. DOE under contract Nos. DE-FG02-02ER54672 and DE-FG02-94ER40855 at the UMD, and DE-AC03-76SF00098 at LBNL and W-7405-ENG-48 at LLNL.

The electron source in the University of Maryland Electron Ring (UMER) injector employs a grid 0.15 mm from the cathode to control the current waveform. Under nominal operating conditions, the grid voltage during the current pulse is sufficiently positive relative to the cathode potential to form a virtual cathode downstream of the grid. Three-dimensional computer simulations have been performed that use the mesh refinement capability of the WARP particle-in-cell code to examine a small region near the beam center in order to illustrate some of the complexity that can result from such a gridded structure. These simulations have been found to reproduce the hollowed velocity space that is observed experimentally. The simulations also predict a complicated time-dependent response to the waveform applied to the grid during the current turn-on. This complex temporal behavior appears to result directly from the dynamics of the virtual cathode formation and may therefore be representative of the expected behavior in other sources, such as some photoinjectors, that are characterized by a rapid turn-on of the beam current.

 
TPPE047 Fabrication and Measurement of Low Work Function Cesiated Dispenser Photocathodes 2953
 
  • N.A. Moody, D.W. Feldman, P.G. O'Shea
    IREAP, College Park, Maryland
  • K. Jensen
    NRL, Washington, DC
 
  Funding: We gratefully acknowledge our funding agencies, the Joint Technology Office and the Office of Naval Research for their support.

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

*K. L. Jensen, et al., "Photoemission from Low Work Function Coated Metal Surfaces: A Comparison of Theory to Experiment" (this conference).

 
TPPE048 The Injection System of SAGA Light Source 3007
 
  • Y. Iwasaki, S. Koda, T. Okajima, Y. Takabayashi, T. Tomimasu, K. Yoshida
    Saga Synchrotron Light Source, Industry Promotion Division, Saga City
  • H. Ohgaki
    Kyoto IAE, Kyoto
 
  Saga light Source is a 1.4-GeV electron storage ring with a circumference of 75.6m. The injector is a 250-MeV linac producing 1 ms macro-pulse with a peak current of 12mA and repetition rate of 1Hz. The output beam from the linac is transported though a transport line, and injected into the ring though a septum magnet with a bending angle of 20-degree. The transport line consists of two bending magnets, two quadrupole doublelets, and a quadrupole singlet. The bump orbit is formed by four kicker magnets, two of which are installed at both sides of septum magnet, and other two are positioned apart by one magnet cell of the ring. They are excited by sinusoidal electric currents with a half width of 0.5 ms. The beam optics for the injection trajectory is computed and shown at control room, the parameters for which are provided directly from the power supply control server PC. The operator is able to see real-time result of the beam trajectory calculation. This tool is quite effective to optimize the magnets parameter setting. The commissioning of the light source was started in August 2004, and 250-MeV electrons ware stored first time on November 2004.  
TPPE049 Synchronizaiton Between Laser and Electron Beam at Photocathode RF Gun 3079
 
  • A. Sakumi, A. Fukasawa, Y. Muroya, T. Ueda, M. Uesaka, K. Yoshii
    UTNL, Ibaraki
  • K. Dobashi
    NIRS, Chiba-shi
  • N. Kumagai, H. Tomizawa
    JASRI/SPring-8, Hyogo
  • J.U. Urakawa
    KEK, Ibaraki
 
  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 crystal, the pumping laser. Furthermore, we will develop the feed back system for reducing the instability of the synchronization.  
TPPE050 Beam Injection in Recirculator SALO 3109
 
  • I.S. Guk, A. Dovbnya, S.G. Kononenko, F.A. Peev, A.S. Tarasenko
    NSC/KIPT, Kharkov
  • J.I.M. Botman, M.J. Van der Wiel
    TUE, Eindhoven
 
  Possible antetypes of injectors for electron recirculator SALO,* intended for nuclear-physical research, are analyzed. The plan injection of beams in recirculator is offered. Expected parameters of beams are designed.

*I.S. Guk, A.N. Dovbnya, S.G. Kononenko, A.S. Tarasenko, M. van der Wiel, J.I.M. Botman, NSC KIPT accelerator on nuclear and high energy physics, Proceedings of EPAC 2004, Lucerne, Switzerland, p. 761-764.

 
TPPE051 The Optimization of the Electron Injector Resonance System Based on the Evanescent Oscillations 3170
 
  • S.A. Perezhogin, M.I. Ayzatskiy, K. Kramarenko, V.A. Kushnir, V.V. Mytrochenko, Z.V. Zhiglo
    NSC/KIPT, Kharkov
 
  The report presents the results of the bunching system optimization and electrons motion simulation in the compact S – band injector. The injector consists of the low-voltage diode electron gun and optimized bunching system based on the resonant system with the evanescent oscillations. The amplitude of RF electrical field is increased along the axis of the bunching system. The resonance system optimization allows to obtain electron bunches with the phase length less than 10° (for 70 % particles) at the injector exit.  
TPPE052 Characteristics of Electron Beam Produced by Magnetron Diode with a Secondary-Emission Cathode 3197
 
  • N.G. Reshetnyak, N. Aizatsky, A. Dovbnya, N.A. Dovbnya, V.V. Mytrochenko, V. Zakutin
    NSC/KIPT, Kharkov
 
  The beam parameters were investigated using an azimuth-sectionalized 8-channel Faraday cup and a 12-channel computer-aided measuring system. The magnetron diode had a cathode (40 mm in diameter) and a 15 mm anode-cathode gap. At a cathode voltage amplitude of 50 kV and a cathode magnetic field of ~1200 Oe, the diode generates a tubular electron beam with an outer diameter of 50 mm, an inner diameter of 44 mm, a beam current of ~50 A. The short time instability of the total beam current, and of the current from each of eight segments of the Faraday cup was estimated to be ~2 … 3%, and long time instability (3 hours) was 57 %. Azimuthal distribution of beam current was investigated versus the amplitude, distribution and direction of the magnetic field. At a cathode magnetic field of 1200 Oe, that falls off inhomogeneity in the vicinity of the Faraday cup down to ~800 Oe, the azimuthal beam current distribution has a ± (3 … 5)%. As the magnetic field strength increases up to ~1700 Oe in the region of beam emergence from the gun and the Faraday cup, the azimuthal inhomogeneity of the beam current increases up to ± (100 … 150)%.  
TPPE053 Design Issues for the ILC Positron Source 3230
 
  • V. Bharadwaj, Y.K. Batygin, R. Pitthan, D.C. Schultz, J. Sheppard, H. Vincke, J.W. Wang
    SLAC, Menlo Park, California
  • J.G. Gronberg, W. Stein
    LLNL, Livermore, California
 
  Funding: Work supported by Department of Energy contract DE-AC02-76SF00515.

A positron source for the ILC can be designed using either a multi-GeV electron beam or a multi-MeV photon beam impinging on a metal target. The major issues are: the drive beam, choice of target material, the design of the target station, the capture section, the target vault, and beam transport to the damping ring. In this paper, positron source parameters for the various schemes are outlined and the advantages and disadvantages of each scheme are discussed.

 
TPPE054 Status of the Injection System for the Australian Synchrotron Project 3271
 
  • S.P. Møller, H. Bach, F. Bødker, T.G. Christiansen, A. Elkjaer, S. Friis-Nielsen, N. Hauge, J. Kristensen, L.K. Kruse, S.P. Møller, B.R. Nielsen
    Danfysik A/S, Jyllinge
 
  DANFYSIK A/S designs and builds the complete injection system for the Australian Synchrotron Project. The full-energy booster will accelerate the beam from the injection energy of 100 MeV. to a maximum of 3.0 GeV. The booster is using combined function magnets. The status of the project is presented.  
TPPE055 DC-SC Photoinjector with Low Emittance at Peking University 3325
 
  • R. Xiang, Y.T. Ding, J. Hao, S.L. Huang, X.Y. Lu, S.W. Quan, B.C. Zhang, K. Zhao
    PKU/IHIP, Beijing
 
  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).  
TPPE056 Emittance Measurement with Upgraded RF Gun System at SPring-8 3348
 
  • A. Mizuno, H. Dewa, H. Hanaki, T. Taniuchi, H. Tomizawa
    JASRI/SPring-8, Hyogo
  • M. Uesaka
    UTNL, Ibaraki
 
  A single cell S-band RFgun has been developed at the SPring-8 since 1996. The minimum normalized beam emittance, measured with double slits' scanning method in 2002, was 2.3 pi mm mrad at the exit of the gun cavity with charge of 0.1 nC/bunch. In 2004, we installed a following accelerator structure to investigate beam behavior of the whole injector system. In this paper, we report emittance measurement results of upgraded system, using variable quadrupole magnet method. The minimum emittance of 2.0 pi mm mrad with a net charge of 0.14 nC/bunch were able to be measured.  
TPPE057 An Experimental Study of the Quantum Efficiency and Topology of Copper Photocathode Due to Plasma Cleaning and Etching
 
  • D.T. Palmer, F. King, R.E. Kirby
    SLAC, Menlo Park, California
 
  We have developed an experimental research program to the study of the photoemission properties of copper photocathodes as a function of various plasma cleaning/etching parameters. The quantum efficiency, QE, and topology, Ra and Rpp, of Copper Photocathodes, , will be monitored while undergoing plasma cleaning/etching process. We will monitor the QE as a function of time for the various test coupons while we optimize the various plasma processing parameters. In addition, surface topology, will be studied to determine the suitability of the cleaning/etching process to produce an acceptable photoemitter. We propose to use two metrics in the evaluation of the plasma cleaning process as an acceptable cleaning method for metallic photocathodes, Quantum Efficiency versus Wavelength and Surface roughness: Ra and Rpp represent the Average Roughness and Peak to Peak Roughness parameters, respectively.  
TPPE058 Dual Feed RF Gun Design for the LCLS 3432
 
  • L. Xiao, R.F. Boyce, D. Dowell, Z. Li, C. Limborg-Deprey, J.F. Schmerge
    SLAC, Menlo Park, California
 
  Funding: Work supported by the U.S. DOE under contract DE-AC03-76SF00515.

In order to remove the dipole field introduced by the coupler in existing S-band BNL/SLAC/UCLA 1.6 cell rf gun, a dual feed design for the LCLS RF gun is proposed together with several significant changes. The improvements include adopting Z-coupling instead of ?-coupling for easier machining and reducing heating, increasing the 0-and ?-mode separation from 3.4 to 15 MHz to reduce the amplitude of the 0 mode, incorporating race-track cavity shape to minimize the quadruple fields, increased cooling for operation at 120Hz and other small changes to improve performance and diagnostic capabilities. The new design has been modeled with the parallel finite element eigenmode solver Omega3P to provide the desired RF parameters and to generate the gun cavity dimensions needed for fabrication.

 
TPPE059 New Electron Gun System for BEPCII
 
  • B. Liu, Y.L. Chi, M. Gu, C. Zhang
    IHEP Beijing, Beijing
 
  The new electron gun system for BEPCII has been put into operation since Nov. 2004. The article describes the design, experiment and operation of this new system. The design current of the gun is 10 A for the pulse lengths of 1 ns, 2.5 ns and 1 μs with repetition rate of 50 Hz. The gun is operated with a pulsed high voltage power supply which can provide up to 200 kV high voltage. Computer simulations have been carried out in the design stage, including simulation of the gun geometry and beam transportation. Some important relation curves are obtained during the experiment. Two-bunch operation is available and some elementary tests have been performed. New scheme of the gun control system based on EPICS is also presented. The real operation shows that the design and manufacturing is basically successful.  
TPPE060 Simulation Study of a Thermionic RF Gun for High Brightness and Short Pulse Beam 3499
 
  • T. Tanaka, H. Hama, F. Hinode, M. Kawai
    LNS, Sendai
  • A. Miyamoto
    HSRC, Higashi-Hiroshima
  • K. Shinto
    Tohoku University, Sendai
 
  Characteristics of thermionic RF guns are not understood completely. In particular, measured intense beam emittances extracted from thermionic RF guns do not agree well with simulated values so far. Most of simulation codes solve the equation of electron motion in an intrinsic mode of the RF field calculated by a separated code. The way of such simulation codes is not self-consistent completely. That is probably a major reason for the discrepancy between the experiments and the simulations. One of the other way for a self-consistent simulation codes is to use an FDTD (Finite Difference Time Domain) method. Since the FDTD method can take into account the microwave propagation including the space charge effect and the beam loading self-consistently, we have developed an FDTD code as 3-D Maxwell's equation solver and applied for a study of beam dynamics in a thermionic RF gun. The main purpose of simulaiton study is to obtain overall properties of the beam dynamics at the time. The goal of this simulation study of the thermionic RF gun is to understand correct characteristics of the thermionic RF gun for producing high brightness and short pulse beam.  
TPPE061 RF Design and Operating Performance of the BNL/AES 1.3 GHz Single Cell Superconducting RF Photocathode Electron Gun 3514
 
  • M.D. Cole
    AES, Medford, NY
  • I. Ben-Zvi, A. Burrill, H. Hahn, T. Rao, Y. Zhao
    BNL, Upton, Long Island, New York
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
 
  Over the past several years Advanced Energy Systems and BNL have been collaborating on the development and testing of a fully superconducting photocathode electron gun. Over the past year we have begun to realize significant results which have been published elsewhere.* This paper will review the RF design of the gun under test and present results of its performance under various operating conditions. Results for cavity quality factor will be presented for various operating temperatures and cavity field gradients. We will discuss various methods of determining the cavity fields and the extent of agreement between them. We will also discuss future plans for testing using this gun.

*Photoemission studies on BNL/AES all niobium, Superconducting RF injector, T. Rao, these proceedings.

 
TPPE062 Photoemission from Low Work Function Coated Metal Surfaces: A Comparison of Theory to Experiment
 
  • K. Jensen
    NRL, Washington, DC
  • D.W. Feldman, N.A. Moody, P.G. O'Shea
    IREAP, College Park, Maryland
 
  Funding: We gratefully acknowledge support provided by the Joint Technology Office and the Office of Naval Research.

The development of rugged and/or self rejuvenating photocathodes with high quantum efficiency (QE) using the longest wavelength drive laser is of paramount importance for RF photo-injectors for high power FELs and accelerators. We report on our program to develop advanced photocathodes and to develop and validate models of photoemission from coated metals to analyze experimental data,* provide emission models usable by beam simulation codes,** and project performance. The model accounts for the effects of laser heating, thermal evolution, surface conditions, laser parameters, and material characteristics, and predicts current distribution and QE. The photoemission and QE from metals and dispenser photocathodes is evaluated: the later introduces complications such as coverage non-uniformity and field enhancement. The performance of the models is compared to our experimental results for dispenser photocathodes and cesiated surfaces (e.g., tungsten, silver, etc.) in which the time-dependent models are shown to agree very well with experimental findings, but also to results in the literature. Extrapolations to performance regimes of interest shall be given.

*N. Moody et al., "Fabrication and Measurement of Low Workfunction Cesiated Dispenser Photocathodes" (this conference). **D.A. Dimitrov et al., "Development of Advanced Models for 3D Photocathode PIC Simulations" (this conference).

 
TPPE063 Improved Electron Yield and Spin-Polarization from III-V Photocathodes Via Bias Enhanced Carrier Drift 3603
 
  • G.A. Mulhollan, J.C.B. Bierman
    Saxet, Austin, Texas
  • A. Brachmann, J.E. Clendenin, E.G. Garwin, R.E. Kirby, D.-A.L. Luh, T.V.M. Maruyama
    SLAC, Menlo Park, California
  • R.X.P. Prepost
    UW-Madison/PD, Madison, Wisconsin
 
  Funding: Work at Saxet Surface Science, SLAC and the University of Wisconson is supported by the following U.S. DOE grants respectively: DE-FG02-04ER86231, DE-AC02-76SF00515 and DE-AC02-76ER00881.

Spin-polarized electrons are commonly used in high energy physics. Future work will benefit from greater polarization. Polarizations approaching 90% have been achieved at the expense of yield. The primary paths to higher polarization are material design and electron transport. Our work addresses the latter. Photoexcited electrons may be preferentially emitted or suppressed by an electric field applied across the active region. We are tuning this forward bias for maximum polarization and yield, together with other parameters, e.g., doping profile Preliminary measurements have been carried out on bulk GaAs. As expected, the yield change far from the bandgap is quite large. The bias is applied to the bottom (non-activated) side of the cathode so that the accelerating potential as measured with respect to the ground potential chamber walls is unchanged for different front-to-back cathode bias values. For a bias which enhances emission, the yield nearly doubles. For a bias which diminishes emission, the yield is approximately one half of the zero bias case. The size of the bias to cause an appreciable effect is rather small reflecting the low drift kinetic energy in the zero bias case.

 
TPPE064 Space-Charge Effects Near a Cathode 3629
 
  • V. Gorgadze
    UCB, Berkeley, California
  • J.S. Wurtele
    LBNL, Berkeley, California
 
  Funding: This work was supported by the Director, Office of Science of the U.S. DOE under Contract No. DE-AC03-76SF00098.

RF photocathode guns are excellent sources of high brightness electron bunches. In the limit of high-current short bunches the electron are complicated space-charge fields. To mitigate space charge effect downstream of the gun it is often desirable to produce electorn bunches with uniform distribution. Our goal is to understand to what extent the non-uniformity of the laser pulse intensity is responsible for a non-uniform electron distribution and to what extent this is due to the electron beam dynamics near to the cathode. We investigate these effects with particle-in-cell simulations and simple theory. These studies are focused on the regime where the peak current as well as the temporal current profile are influenced by the self-fields of the bunch. The simulation code XOOPIC has been employed. The critical current limitation for virtual cathode formation and current density profile at the exit of the injector have been found.

 
TPPE065 Calculating of Coupling Factor of Microwave Electron Gun 3656
 
  • X. Bian, H. Chen, S. Zheng
    TUB, Beijing
  • D. Li
    LBNL, Berkeley, California
 
  To design the coupler of a designing microwave electron gun, we use the "energy method" proposed by Derun Li, et al. The intrinsic Q of the electron gun cavity is very high: about 20000. The method calculates the intrinsic and external Q values of a cavity coupled to a waveguide using MAFIA code in time domain. The comparisons between simulation and experimental results are given for a set of different coupling iris apertures and height. The result shows that "energy method" works efficiently for high Q cavities.  
TPPE066 Geometry Optimization of DC/RF Photoelectron Gun 3679
 
  • P. Chen, R. Yi, D. Yu
    DULY Research Inc., Rancho Palos Verdes, California
 
  Funding: *Work supported by DOE SBIR Grant No. DE-FG02-03ER83878.

Pre-acceleration of photoelectrons in a pulsed, high voltage, short, dc gap and its subsequent injection into an rf gun is a promising method to improve electron beam emittance in rf accelerators. Simulation work has been performed in order to optimize the geometric shapes of a dc/rf gun and improve electron beam properties. Variations were made on cathode and anode shapes, dc gap distance, and inlet shape of the rf cavity. Simulations showed that significant improvement on the normalized emittance (< 1 mm-mrad), compared to a dc gun with flat cathode, could be obtained after the geometric shapes of the gun were optimized.

 
WPAP001 HELIOS, the Linac Injector of SOLEIL: Installation and First Results 755
 
  • B. Pottin, R. Chaput, J.-P. Pollina, M.-A. Tordeux
    SOLEIL, Gif-sur-Yvette
  • D. Jousse, J.-L. Pastre, A.S. Setty
    THALES, Colombes
 
  Funding: SOLEIL

HELIOS is the Hundred MeV Electron Linac Injector Of SOLEIL the new French SR facility. The Linac is constructed by THALES as a “turn key” equipment on the basis of SOLEIL’s APD design. The Linac injector is composed of a triode gun (90 kV, 500 mA), a prebuncher (10 kV, 200 W), a buncher (SW, 15 MeV, 5 MW) focalised by a solenoid and two accelerating sections (TW, 2pi/3, 45 MeV, 12 MW) feeded by 2 klystrons (35 MW). The major Linac components have been previously tested at THALES factory and the installation on the site has begun from October 2004. After a brief description of the building construction, the tests of the Linac components and operating modes will be detailed. The commissioning with beam is planned on March; the results on beam qualities will be presented: energy spread, emittance, and beam dynamics along the Linac.

 
WPAP003 Emission Mechanisms in a Photocathode RF Gun 856
 
  • J.H. Han, J.W. Baehr, H.-J. Grabosch, M. Krasilnikov, V. Miltchev, A. Oppelt, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • K. Floettmann, S. Schreiber
    DESY, Hamburg
  • M.V. Hartrott
    BESSY GmbH, Berlin
  • P. Michelato, L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI)
  • J.R. Roensch
    Uni HH, Hamburg
 
  In photocathode rf guns, emission mechanisms at the photocathode play a crucial role in the overall beam dynamics. A low bunch charge as well as a short Gaussian bunch profile allow us to study the beam dynamics depending on emission phase without space charge force. This paper presents experimental and simulation studies toward detailed understanding of the photo emission and secondary emission processes at the cathode.  
WPAP004 Dark Current and Multipacting in the Photocathode RF Guns at PITZ 895
 
  • J.H. Han, J.W. Baehr, H.-J. Grabosch, M. Krasilnikov, V. Miltchev, A. Oppelt, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • K. Floettmann, S. Schreiber
    DESY, Hamburg
  • M.V. Hartrott
    BESSY GmbH, Berlin
  • P. Michelato, L. Monaco, D. Sertore
    INFN/LASA, Segrate (MI)
  • J.R. Roensch
    Uni HH, Hamburg
 
  For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies.  
WPAP005 Beam-Based Procedures for RF Guns 967
 
  • M. Krasilnikov, J.W. Baehr, H.-J. Grabosch, J.H. Han, V. Miltchev, A. Oppelt, B. Petrosyan, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • M.V. Hartrott
    BESSY GmbH, Berlin
 
  A wide range of rf photo injector parameters has to be optimized in order to achieve an electron source performance as required for linac based high gain FELs. Some of the machine parameters can not be precisely controlled by direct measurements, whereas the tolerance on them is extremely tight. Therefore, this should be met with beam-based techniques. Procedures for beam-based alignment (BBA) of the laser on the photo cathode as well as solenoid alignment have been developed. They were applied at the Photo Injector Test facility at DESY Zeuthen (PITZ) and at the photo injector of the VUV-FEL at DESY Hamburg. A field balance of the accelerating mode in the 1 cell gun cavity is one of the key beam dynamics issues of the rf gun. Since no direct field measurement in the half and full cell of the cavity is available for the PITZ gun, a beam-based technique to determine the field balance has been proposed. A beam-based rf phase monitoring procedure has been developed as well.  
WPAP006 Recent Developments at PITZ 1012
 
  • M. Krasilnikov, K. Abrahamyan, G. Asova, J.W. Baehr, G. Dimitrov, U. Gensch, H.-J. Grabosch, J.H. Han, S. Khodyachykh, S. Liu, V. Miltchev, A. Oppelt, B. Petrosyan, S. Riemann, L. Staykov, F. Stephan
    DESY Zeuthen, Zeuthen
  • W. Ackermann, W.F.O. Müller, S. Schnepp, T. Weiland
    TEMF, Darmstadt
  • J.-P. Carneiro, K. Floettmann, S. Schreiber
    DESY, Hamburg
  • M.V. Hartrott, E. Jaeschke, D. Kraemer, D. Lipka, R. Richter
    BESSY GmbH, Berlin
  • P. Michelato, L. Monaco, C. Pagani, D. Sertore
    INFN/LASA, Segrate (MI)
  • J.R. Roensch, J. Rossbach
    Uni HH, Hamburg
  • W. Sandner, I. Will
    MBI, Berlin
  • I. Tsakov
    INRNE, Sofia
 
  The ability to produce high brightness electron beams as required for modern Free Electron Lasers (FELs) has been demonstrated during the first stage of the Photo Injector Test Facility at DESY Zeuthen (PITZ1). The electron source optimization at PITZ1 was successfully completed, resulting in the installation of the PITZ rf gun at the VUV-FEL (DESY, Hamburg). One of the main goals of the second stage of PITZ (PITZ2) is to apply higher gradients in the rf gun cavity in order to obtain smaller beam emittance by faster acceleration of the space charge dominated beams. In order to reach the required gradients a 10 MW klystron has to be installed and the gun cavity has to be conditioned for higher peak power. Another important goal of PITZ2 is a detailed study of the emittance conservation principle by using proper electron beam acceleration with a booster. Further photo injector optimization, including update of the photocathode laser and diagnostic tools, is foreseen as well. Recent progress on the PITZ developments will be reported.  
WPAP007 Status of the 3 Cell Superconducting RF Gun Project in Rossendorf 1081
 
  • R. Xiang, H. Buettig, P. Evtushenko, D. Janssen, U. Lehnert, P. Michel, K. Moeller, Ch. Schneider, R. Schurig, F. Staufenbiel, J. Teichert
    FZR, Dresden
  • T.  Kamps, D. Lipka
    BESSY GmbH, Berlin
  • W.-D. Lehmann
    IfE, Dresden
  • J. Stephan
    IKST, Drsden
  • V. Volkov
    BINP SB RAS, Novosibirsk
  • I. Will
    MBI, Berlin
 
  In the paper, we report on the status and progress of the superconducting rf gun project in Rossendorf. The gun is designed for cw operation mode with 1mA current and 10 MeV electron energy. The gun will be installed at the ELBE superconducting electron linear accelerator. It will have a 3 cell niobium cavity operating at 1.3 GHz. The cavity consists of three cells with TESLA geometry and a specially designed half-cell in which the photocathode will be placed. Two Nb cavities, with RRR 300 and 40 respectively, will be finished at the beginning of 2005. After delivery, the rf tests will be performed and the treatment of the cavities will be started. At the same time, the design of the cryostat is finished and the fabrication of its components is under way. Further activities are the design of the diagnostic beam line, the assembling of the new photocathode preparation system, and the upgrade of the 262 nm driver laser system.  
WPAP008 Simulation for a New Polarized Electron Injector (SPIN) for the S-DALINAC 1117
 
  • B. Steiner, W.F.O. Müller, T. Weiland
    TEMF, Darmstadt
  • J. Enders, H.-D. Gräf, A. Richter, M. Roth
    TU Darmstadt, Darmstadt
 
  Funding: Work supported in part by DFG under contract SFB 634 and DESY, Hamburg.

The Superconducting DArmstädter LINear ACcelerator (S-DALINAC) is a 130 MeV recirculating electron accelerator serving several nuclear and radiation physics experiments. For future tasks, the 250 keV thermal electron source should be completed by a 100 keV polarized electron source. Therefore a new low energy injection concept for the S-DALINAC has to be designed. The main components of the injector are a polarized electron source, an alpha magnet, a Wien filter spin-rotator and a Mott polarimeter. In this paper we report over the first simulation and design results. For our simulations we used the TS2 and TS3 modules of the CST MAFIA (TM) programme which are PIC codes for two and three dimensions and the CST PARTICLE STUDIO (TM).

 
WPAP009 Optimization of RF Compressor in the SPARX Injector 1144
 
  • C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
  • M. Boscolo, M. Ferrario, B. Spataro
    INFN/LNF, Frascati (Roma)
  • L. Serafini
    INFN-Milano, Milano
 
  The SPARX photoinjector consists in a rf gun injecting into three SLAC accelerating sections, the first one operating in the RF compressor configuration in order to achieve higher peak current. A systematic study based on PARMELA simulations has been done in order to optimize the parameters that influence the compression also in view of the application of this system as injector of the so called SPARXINO 3-5 nm FEL test facility. The results of computations show that peak currents at the injector exit up to kA level are achievable with a good control of the transverse and longitudinal emittance by means of a short SW section operating at 11424 MHz placed before the first accelerating section. Some working points in different compression regimes suitable for FEL experiments have been selected. The stability of these points and the sensitivity to various types of random errors are discussed.  
WPAP011 SPARC Working Point Optimization for a Bunch with Gaussian Temporal Profile 1248
 
  • M. Boscolo, M. Ferrario, V. Fusco, M.  Migliorati
    INFN/LNF, Frascati (Roma)
  • S. Reiche
    UCLA, Los Angeles, California
  • C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
 
  We present the optimization of the working point for the SPARC photoinjector with a Gaussian temporal profile. The implications of a Gaussian temporal profile are discussed here for the standard working conditions and for the RF compressor case in comparison with the nominal working point performances of a 10ps flat top pulse with rise time of 1ps. Comparisons with the upgraded version of the HOMDYN code including arbitrary bunch temporal profiles are also reported. Advantages and drawbacks of the Gaussian and flat top pulse shapes are discussed. For the standard working point, it is shown that the two cases provide the same saturation length and average power, but the higher current in the beam core of the Gaussian pulse gives a higher peak radiation power. As the laser pulse shape could be Gaussian at the first stage of the SPARC operation, it is clear the importance of these simulation results.  
WPAP012 Preliminary Results on Beam Dynamics of Laser Pulse Shaping Effects in SPARC 1315
 
  • M. Boscolo, M. Ferrario, M.  Migliorati
    INFN/LNF, Frascati (Roma)
  • F. Castelli, S. Cialdi, A.F. Flacco
    INFN-Milano, Milano
 
  In a photoinjector system the role played by the laser pulse shaping in achieving high quality electron beam is crucial, as it determines the distribution dependent space charge effects in the early stages of the acceleration. A dedicated code to simulate pulse shaping in a laser system and able to generate the corresponding initial electron beam distribution has been developed. Realistic deviations from the ideal flat top pulse give for example a ramp or multi-peaks shape with a raletive rise time, plateau deformation and ripples. The beam dynamics of electron beams with different initial temporal pulse characteristics along the SPARC photoinjector has also been studied with the code PARMELA. More exotic pulse shaping are also discussed. The study presented here gives some indications on the tolerances of the laser beam characteristics for the electron beam quality preservation.  
WPAP013 Magnesium Film Photocathodes for High Brilliance Electron Injectors 1350
 
  • F. Tazzioli, G. Gatti, C. Vicario
    INFN/LNF, Frascati (Roma)
  • I. Boscolo, S. Cialdi
    INFN-Milano, Milano
  • L. Cultrera, A. Perrone
    Lecce University, Lecce
  • S. Orlanducci, M.L. Terranova
    Università di Roma II Tor Vergata, Roma
  • M. Rossi
    Rome University La Sapienza, Roma
 
  Advanced high brilliance electron injectors require photocathodes having low thermal emittance, high quantum efficiency (QE) and prompt response. They should be easy to handle and capable of working in the very high electric fileds of a RF gun. Magnesium films deposited by laser ablation and sputtering techniques are discussed and QE measurements are presented.  
WPAP014 Development of Electron Gun of Carbon Nanotube Cathode 1392
 
  • Y. Hozumi
    GUAS/AS, Ibaraki
  • M. Ikeda, S. Ohsawa, T. Sugimura
    KEK, Ibaraki
 
  We are developing high brightness electron guns utilizing carbon nanotube (CNT) cathodes. Recently, we succeeded to achieved field emission currents to 0.2 A (3 A/cm2) from a triode type CNT cathode of 3 mm diameter. The emission tests were performed at DC100kV acceleration voltage in pulse operations of 50 Hz using 6 nsec pulses. The emission currents were very stable for long term periods of 3 weeks. Photo emission tests from CNT cathode by 266nm laser pulses is also due to be reported simultaneously.  
WPAP016 High Brightness Electron Gun for X-Ray Source 1488
 
  • S. Ohsawa, M. Ikeda, T. Sugimura, M. Tawada
    KEK, Ibaraki
  • Y. Hozumi
    GUAS/AS, Ibaraki
  • K. Kanno
    AET Japan, Inc., Kawasaki-City
 
  A new electron-gun system is under development in order to increase X-ray from a rotating target. In commercial X-ray sources electron beams usually hit targets at the outer part. Owing to deformation by centrifugal force, there has been a limit on electron beam intensities. In order to overcome this difficulty, we adopted a new injection system which strikes inside of a ring-shape projection on a rotating target. It has an advantage in that heated-up points have supports back side against centrifugal force. This merit allows us to raise electron beam to give stronger X-rays.  
WPAP017 Experimental Observation of a 100-Femtosecond Single Electron Bunch in Photocathode Linac with Longitudinal Emittance Compensation Technique 1546
 
  • J. Yang
    RCNP, Osaka
  • K. Kan, T. Kondoh, T. Kozawa, S. Tagawa, Y. Yoshida
    ISIR, Osaka
 
  The realization of a 100fs electron pulse is important for the studies of ultrafast physical/chemical phenoena with a pump-probe method. We have developed a photocathode linear accelerator (linac) to generate such electron pulse with a magnetic pulse compressor. The nonlinear effect of the magnetic fields in the pulse compression was compensated carefully by optimizing the magnetic fields and the booster linac RF phase. A 105fs(rms) electron bunch with electron charge of 0.1nC was observed experimentally by using a femtosecond streak camera. The beam energy was 35MeV, and the normalized teraservers emittance was lower than 3mm-mrad. The dependences of the pulse length and the emittance on the electron charge were also measured and compared with the theoretical calculations.  
WPAP018 Generation of Double-Decker Femtosecond Electron Beams in a Photoinjector 1604
 
  • J. Yang, K. Kan, T. Kondoh, T. Kozawa, Y. Kuroda, S. Tagawa, Y. Yoshida
    ISIR, Osaka
 
  The femtosecond electron beam is a practical source in the pump-probe experiment for studies of ultrafast physical/chemical reactions in materials, in which a mode-locked ultrashort laser light is used as a probe source. The synchronized time jitter between the electron beam and the laser light limits the time resolution in the experiment. In order to reduce the time jitter, a new concept of synchronized double-decker electron beam generation in a photoinjector was proposed. The double electron beams were observed in an S-band photocathode RF gun by injecting two laser beams which produced with a picosecond laser. The double electron beams were compressed into 400fs(rms) with a phase-space rotation technique in magnetic fields. The beams, which one is used as a pump source and another is used as a probe source, are expected for ultrafast reaction studies in femtosecond resolution.  
WPAP019 X-Band Thermionic Cathode RF Gun at UTNL 1646
 
  • A. Fukasawa, F. Ebina, T. Kaneyasu, H. Ogino, F. Sakamoto, M. Uesaka
    UTNL, Ibaraki
  • M. Akemoto, H. Hayano, T. Higo, J.U. Urakawa
    KEK, Ibaraki
  • K. Dobashi
    NIRS, Chiba-shi
  • K.M. Matsuo, H. Sakae
    IHI/Yokohama, Kanagawa
 
  The X-band (11.424 GHz) linac for compact Compton scattering hard X-ray source are under construction at Nuclear Engineering Research Laboratory, University of Tokyo. This linac designed to accelerate up to 35 MeV, and this electron beam will be used to produce hard X-ray by colliding with laser. It consists of a thermionic cathode RF gun, an alpha magnet, and a traveling wave tube. The gun has 3.5 cells (unloaded Q is 8250) and will be operated at pi-mode. A dispenser cathode is introduced. Since the energy spread of the beam from the gun is predicted to be broad due to the continuous emission from the thermionic cathode, a slit is placed in the alpha magnet to eliminate low energy electrons. The simulation on the injector shows the beam energy 2.9 MeV, the charge 23 pC/bunch, and the emittance less than 10 mm.mrad. The experiment on the gun is planed in the beginning of 2005, and the details will be discussed on the spot.  
WPAP021 Status of PPI (Pohang Photo-Injector) for PAL XFEL 1733
 
  • S.J. Park, C. Kim, I.S. Ko, J.-S. Oh, Y.W. Parc, P.C.D. Park, J.H. Park
    PAL, Pohang, Kyungbuk
  • X.J. Wang
    BNL, Upton, Long Island, New York
 
  Funding: Supported by the POSCO and the MOST, Korea.

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

*J.S. Oh, S.J. Park et al., "0.3-nm SASE-FEL at PAL," NIM A528, 582 (2004); S.J. Park, J.S. Oh et al., "Design Study of Low-Emittance Injector for SASE XFEL at Pohang Accelerator Laboratory," FEL2004, Italy, 2004.

 
WPAP022 Measurements of Transverse Emittance for RF Photocathode Gun at the PAL 1760
 
  • J.H. Park, I.S. Ko, J.-S. Oh, Y.W. Parc, S.J. Park
    PAL, Pohang, Kyungbuk
  • X.J. Wang
    BNL, Upton, Long Island, New York
  • D. Xiang
    TUB, Beijing
 
  Funding: Supported by the POSCO and the MOST, Korea.

A BNL GUN-IV type RF photo-cathode gun is under fabrication for use in the FIR (Far Infra-Red) facility being built at the Pohang Accelerator Laboratory (PAL). Performance test of the gun will include the measurement of transverse emittance profile along the longitudinal direction. Successful measurement of the emittance profile will provide powerful tool for the commissioning of the 4GLS (4th generation light source) injectors based on the emittance compensation principle. We are going to achieve this withthe use of pepper-pot based emittance meters that can be moved along the longitudinal direction. In this article, we present design considerations on the emittance meter with the resolution of 1 mm mrad.

 
WPAP023 Compact Source of Electron Beam with Energy of 200 kEv and Average Power of 2 kW 1832
 
  • I.V. Kazarezov, V. Auslender, V.E. Balakin, A.A. Bryazgin, A.V. Bulatov, I.I. Glazkov, I.V. Kazarezov, E.N. Kokin, G.S. Krainov, G.I. Kuznetsov, A.M. Molokoedov, A.F.A. Tuvik
    BINP SB RAS, Novosibirsk
 
  The paper describes a compact electron beam source with average electron energy of 200 keV. The source operates with pulse power up to 2 MW under average power not higher than 2 kW, pulsed beam current up to 10 A, pulse duration up to 2 mks, and repetition rate up to 5 kHz. The electron beam is extracted through aluminium-beryllium alloy foil. The pulse duration and repetition rate can be changed from control desk. High-voltage generator for the source with output voltage up to 220 kV is realized using the voltage-doubling circuit which consists of 30 sections. The insulation type - gas, SF6 under pressure of 8 atm. The cooling of the foil supporting tubes is provided by a water–alcohol mixture from an independent source. The beam output window dimensions are 180?75 mm, the energy spread in the beam +10/-30%, the source weight is 80 kg.  
WPAP027 RF Electron Gun with Driven Plasma Cathode 1991
 
  • I.V. Khodak, V.A. Kushnir
    NSC/KIPT, Kharkov
 
  It’s known that RF guns with plasma cathodes based on solid-state dielectrics are able to generate an intense electron beam. In this paper we describe results of experimental investigation of the single cavity S-band RF gun with driven plasma cathode. The experimental sample of the cathode based on ferroelectric ceramics has been designed. Special design of the cathode permits to separate spatially processes of plasma development and electron acceleration. It has been obtained at RF gun output electron beam with particle energy ~500 keV, pulse current of 4 A and pulse duration of 80 ns. Results of experimental study of beam parameters are referred in. The gun is purposed to be applied as the intense electron beam source for electron linacs.  
WPAP028 Modes of Electron Beam Generation in a Magnetron Diode with a Secondary-Emission Cathode 2027
 
  • V. Zakutin, A. Dovbnya, N.G. Reshetnyak
    NSC/KIPT, Kharkov
 
  Experiments have shown that the electron current direction can be varied along the diode axis or perpendicular to the axis, depending on the longitudinal magnetic field amplitude and distribution. The diode had a copper cathode diameter 40 mm and 15 mm anode-cathode gap. Several modes of electron beam generation are realized, namely, open, closed, and intermediate. In the first case, at a cathode magnetic field of ~ 1200 Oe, that falls off approaching the diode output down, and at a cathode voltage of 50 kV, the diode generates a tubular electron beam of a current 50 A and the anode current was about 1 % of the beam current. In the second case, the electron current was going to the anode, the secondary-emission multiplication of electrons being retained. At a cathode voltage of ~ 45 kV, the anode current was ~ 5 A, and the beam current was practically absent. This was attained by decreasing the magnetic field to ~ 1.11.2 of the Hell field value and by increasing the magnetic field towards the diode output. In the intermediate mode with a cathode voltage of ~ 45 kV the direct beam current measured was ~ 5 A, and the anode current was ~ 7 A.  
WPAP031 Use of Multiobjective Evolutionary Algorithms in High Brightness Electron Source Design 2188
 
  • I.V. Bazarov, C.K. Sinclair
    Cornell University, Department of Physics, Ithaca, New York
  • I. Senderovich
    Cornell University, Ithaca, New York
 
  Funding: Supported by Cornell University.

We describe the use of multiobjective evolutionary algorithms (MOEAs) for the design and optimization of a high average current, high brightness electron injector for an Energy Recovery Linac (ERL). By combining MOEAs with particle tracking, including space charge effects, and by employing parallel computing resources, we explored a multidimensional parameter space with 22 independent variables for a DC gun based injector which is being constructed at Cornell University. The simulated performance of the optimized injector is found to be excellent, with normalized rms emittances as low as 0.1 mm-mrad for a 77 pC bunch, and 0.7 mm-mrad for a 1 nC bunch. We detail the advantages and flexibility of MOEAs as a powerful tool well suited for wide application in solving various problems in the accelerator field.

 
WPAP032 Emittances Studies at the Fermilab/NICADD Photoinjector Laboratory
 
  • R. Tikhoplav, A.C. Melissinos
    Rochester University, Rochester, New York
  • J.L. Li, P. Piot
    Fermilab, Batavia, Illinois
 
  Funding: This work was supported by the Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. DOE, and by NICADD.

The Fermilab/NICADD photoinjector incorporates an L-band rf-gun capable of generating 1-10 nC bunches. The bunches are then accelerated to 16 MeV with a TESLA superconducting cavity. In the present paper we present parametric studies of transverse emittances and energy spread for a various operating points of the electron source (RF-gun E-field, laser length and spot size, and solenoid settings). We especially study the impact, on transverse emittance, of Gaussian and Plateau temporal distribution of the photocathode drive-laser.

 
WPAP033 State-of-the-Art Electron Guns and Injector Designs for Energy Recovery Linacs (ERL) 2292
 
  • A.M.M. Todd, A. Ambrosio, H. Bluem, V. Christina, M.D. Cole, M. Falletta, D. Holmes, E. Peterson, J. Rathke, T. Schultheiss, R. Wong
    AES, Princeton, New Jersey
  • I. Ben-Zvi, A. Burrill, R. Calaga, P. Cameron, X.Y. Chang, H. Hahn, D. Kayran, J. Kewisch, V. Litvinenko, G.T. McIntyre, T. Nicoletti, J. Rank, T. Rao, J. Scaduto, K.-C. Wu, A. Zaltsman, Y. Zhao
    BNL, Upton, Long Island, New York
  • S.V. Benson, E. Daly, D. Douglas, H.F.D. Dylla, L. W. Funk, C. Hernandez-Garcia, J. Hogan, P. Kneisel, J. Mammosser, G. Neil, H.L. Phillips, J.P. Preble, R.A. Rimmer, C.H. Rode, T. Siggins, T. Whitlach, M. Wiseman
    Jefferson Lab, Newport News, Virginia
  • I.E. Campisi
    ORNL, Oak Ridge, Tennessee
  • P. Colestock, J.P. Kelley, S.S. Kurennoy, D.C. Nguyen, W. Reass, D. Rees, S.J. Russell, D.L. Schrage, R.L. Wood
    LANL, Los Alamos, New Mexico
  • D. Janssen
    FZR, Dresden
  • J.W. Lewellen
    ANL, Argonne, Illinois
  • J.S. Sekutowicz
    DESY, Hamburg
  • L.M. Young
    TechSource, Santa Fe, New Mexico
 
  Funding: This work is supported by NAVSEA, NSWC Crane, the Office of Naval Research, the DOD Joint Technology Office and by the U.S. DOE.

A key technology issue of ERL devices for high-power free-electron laser (FEL) and 4th generation light sources is the demonstration of reliable, high-brightness, high-power injector operation. Ongoing programs that target up to 1 Ampere injector performance at emittance values consistent with the requirements of these applications are described. We consider that there are three possible approaches that could deliver the required performance. The first is a DC photocathode gun and superconducting RF (SRF) booster cryomodule. Such a 750 MHz device is being integrated and will be tested up to 100 mA at the Thomas Jefferson National Accelerator Facility beginning in 2007. The second approach is a high-current normal-conducting RF photoinjector. A 700 MHz gun will undergo thermal test in 2006 at the Los Alamos National Laboratory, which, if successful, when equipped with a suitable cathode, would be capable of 1 Ampere operation. The last option is an SRF gun. A half-cell 703 MHz SRF gun capable of delivering 1.0 Ampere will be tested to 0.5 Ampere at the Brookhaven National Laboratory in 2006. The fabrication status, schedule and projected performance for each of these state-of-the-art injector programs will be presented.

 
WPAP034 Positron Emulator for Commissioning ILC Positron Source 2321
 
  • H. Wang, W. Gai, K.-J. Kim, W. Liu
    ANL, Argonne, Illinois
 
  Funding: U.S. DOE.

It is apparent that the gamma-ray based positron source components including positron linac and damping rings for ILC can not be easily commissioned until the electron beam is fully conditioned at high energies (> 150 GeV). In this paper, we discuss a scheme that could use a short and energetic electron beam scattered through a set of carefully selected targets to simulate certain behaviors of the positron beam, such as beam emittance and energy spread. The basic idea is to make the phase space distribution of the scattered electron beam to reflect certain aspects of the positron beam distributions. Subsequently, the positron source elements such as capture optics, linacs and even damping ring could be effectively commissioned before ILC colliding electron beam is ready. The simulation results using EGS4 for beam scattering and PARMELA for beam dynamics are presented.

 
WPAP035 Emittance Compensation in Flat Beam Production in an RF Gun Linac 2399
 
  • S. Wang
    ANL, Argonne, Illinois
 
  Funding: This research is supported by the U.S. Department of Energy under contract DE-FG02-92ER40747 and the National Science Foundation under contract NSF PHY-0244793.

Ya. Derbenev Proposed a flat beam production method in RF gun Linac, which passes the electron beam through a matched skew quadrupole channel and transform the initially transversely round beam into a flat beam. Fermilab/NICADD Photoinjector Laboratory has performed a lot of experiments, a ratio of 50 of the transverse emittances in x and y plane has been achieved and the ratio of 100 and higher is underway of research. In this paper, the S-shaped flat beam, found both in experiments and simulations, is investigated. The nonlinear transverse force from the RF field when the beam passes the superconducting cavity is found to be one of the sources which produce the transverse S-shape distribution and increase the emittance. An extra solenoid located before the superconducting cavity is proposed to be added to adjust the beam transverse size when the beam passes through the cavity. The resulted transverse nonlinear space-charge force is used to counter-act against the nonlinear transverse force from the RF field. PARMELA simulations have shown that, with proper setup of the extra solenoid, the emittance ratio can be enhanced by a factor of 2 and the S-shaped transverse distribution can also be eliminated.

 
WPAP036 Determination of the Field Enhancement Factor on Photocathode Surface Via the Schottky Effect 2425
 
  • Z.M. Yusof, M.E. Conde, W. Gai
    ANL, Argonne, Illinois
 
  Funding: U.S. Department of Energy.

Using photons with energy that is less than the work function, we employ the Schottky effect to determine the field enhancement factor on the surface of a Mg photocathode. The Schottky effect is manifested via a shift in the threshold for photoemission as the amplitude of the RF in the photoinjector gun is varied. From the threshold condition, we can directly determine the field enhancement factor on the cathode surface. This is a viable technique to obtain the field enhancement factor of surfaces of other materials such as Nb and Cu.

 
WPAP037 Novel Method of Emittance Preservation in ERL Merging System in Presence of Strong Space Charge Forces 2512
 
  • D. Kayran, V. Litvinenko
    BNL, Upton, Long Island, New York
 
  Funding: Work performed under the auspices of the U.S. Department of Energy and partially funded by the US Department of Defence

Energy recovery linacs (ERLs) are potential candidates for the high power and high brightness electron beams sources. The main advantages of ERL are that electron beam is generated at relatively low energy, injected and accelerated to the operational energy in a ERL loop with a common linac, then is decelerated in the same loop down to injection energy and dumped. The intrinsic part of any ERL is a merging system for the low-energy beam with a high-energy beam passing around the ERL loop. One of the challenges for generating high charge high brightness e-beam in ERL is development of merging system, which provides achromatic condition for space charge dominated beam and which is compatible with the emittance compensation scheme. In this paper we present principles of operation of such merging system. We also describe an example of such system, which we call Zigzag or Z-system. We use a specific implementation for R&D ERL at Brookhaven for illustration.

 
WPAP038 Photoemission Studies on BNL/AES/JLab all Niobium, Superconducting RF Injector 2556
 
  • T. Rao, I. Ben-Zvi, A. Burrill, H. Hahn, D. Kayran, Y. Zhao
    BNL, Upton, Long Island, New York
  • M.D. Cole
    AES, Medford, NY
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
 
  Funding: Under contract with the U.S. DOE, Contract No. DE-AC02-98CH10886.

Photoemission from all niobium superconducting injector is of considerable interest for the development of higher average current electron sources. In the past year, we have generated photocurrent from such an injector by irradiating the back wall of the 1/2 cell cavity with 248 nm and 266 nm laser beams. In this paper, we present the results of these measurements including the quantum efficiency, and its dependence on the field and wavelength. Issues related to the quenching of the cavity by the laser radiation will also be addressed.

 
WPAP039 Progress on Lead Photocathodes for Superconducting Injectors 2598
 
  • J. Smedley, T. Rao
    BNL, Upton, Long Island, New York
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
  • J.L. Langner, P. Strzyzewski
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
  • R.S. Lefferts, A.R. Lipski
    SBUNSL, Stony Brook, New York
  • J.S. Sekutowicz
    DESY, Hamburg
 
  Funding: This work was supported by DOE contracts DE-AC02-98CH10886, DE-AC03-76SF00515 and DE-FG02-97ER82336.

We present the results of our investigation of bulk, electroplated and vacuum deposited lead as suitable photocathode materials for superconducting RF injectors. The quantum efficiency of each sample is presented as a function of the wavelength of the incident light, from 310 nm to 190 nm. Quantum efficiencies of 0.3% have been obtained. Production of a niobium cavity with a lead-plated cathode is underway.

 
WPAP041 Time Dependent Quantum Efficiency and Dark Current Measurements in an RF Photocathode Injector with a High Quantum Efficiency Cathode 2681
 
  • R.P. Fliller, H. Edwards
    Fermilab, Batavia, Illinois
  • W. Hartung
    NSCL, East Lansing, Michigan
 
  Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. DOE and by NICADD.

A system was developed at INFN Milano for preparing cesium telluride photo-cathodes and transferring them into an RF gun under ultra-high vacuum. This system has been in use at the Fermilab NICADD Photo-Injector Laboratory (FNPL) since 1997. A similar load-lock system is used at the TeSLA Test Facility at DESY-Hamburg. Two 1.625-cell high duty cycle RF guns have been fabricated for the project. Studies of the photo-emission and field emission ("dark current") behavior of both RF guns have been carried out. Unexpected phenomena were observed in one of the RF guns. In situ changes in the cathode's quantum efficiency and dark current with time were seen during operation of the photo-injector. These changes were correlated with the magnetostatic field at the cathode.* In addition, multipacting is observed in the RF guns under certain conditions. Recent measurements indicate a correlation between multipacting, anomalous photo-emission behavior, and anomalous field emission behavior. Results will be presented.

*W. Hartung, J.-P. Carneiro, H. Edwards, M. Fitch, M. Kuchnir, P. Michelato, D. Sertore, in Proceedings of the 2001 Particle Accelerator Conference, p. 2239-2241.

 
WPAP042 Progress on Using NEA Cathodes in an RF Gun 2708
 
  • R.P. Fliller, T. G. Anderson, H. Edwards
    Fermilab, Batavia, Illinois
  • H. Bluem, T. Schultheiss
    AES, Princeton, New Jersey
  • M. Huening
    DESY, Hamburg
  • C.K. Sinclair
    Cornell University, Department of Physics, Ithaca, New York
 
  Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. DOE and by NICADD. AES personnel were supported under DOE SBIR contract #DE-FG02-04ER838.

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

 
WPAP043 Production of Transverse Controllable Laser Density Distribution in Fermilab/NICADD Photoinjector 2783
 
  • J.L. Li, J.L. Li
    Rochester University, Rochester, New York
  • P. Piot, R. Tikhoplav
    Fermilab, Batavia, Illinois
 
  The Fermilab/NICADD photoinjector laboratory consist of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultrashort UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located ~20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controlled nonuniformity, yielding the production of an electron beam with various transverse densities patterns. Measuring the evolution of the artificial pattern on the electron bunch provides information that can be used to benchmark numerical simulations and investigate the impact of space charge. Preliminary data on these investigations are presented in the present paper.  
WPAP044 Advanced Electromagnetic Analysis for Electron Source Geometries 2815
 
  • M. Hess, C.S. Park
    IUCF, Bloomington, Indiana
 
  One of the challenging issues for analytically modeling electron sources, such as rf photoinjectors, is how to incorporate fully electromagnetic effects which are generated by the electron beam. The main difficulties that arise in finding an analytical solution of the electromagnetic fields are due to the complex shape of the conductor boundary, as well as the complicated structure of the beam density and current. Both of these problems can be handled self-consistently by using an electromagnetic Green’s function method. In this paper, we present a solution to the exact electromagnetic fields, which were derived from the Green’s function, for a simplified electron source conductor geometry, namely a semi-infinite circular pipe with an endcap. We assume that the beam currents are in the axial direction and satisfy the continuity equation in conjunction with the beam charge density, but may have arbitrary spatial and time dependency. We discuss how these analytical methods may be extended to include in the effect of one or multiple irises, which are found in rf photoinjector systems.  
WPAP045 Ion Back-Bombardment of GaAs Photocathodes Inside DC High Voltage Electron Guns 2875
 
  • J.M. Grames, P. Adderley, J. Brittian, D. Charles, J. Clark, J. Hansknecht, M. Poelker, M.L. Stutzman, K.E.L. Surles-Law
    Jefferson Lab, Newport News, Virginia
 
  Funding: This work was supported by U.S. DOE Contract No. DE-ACO5-84-ER40150.

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

 
WPAP046 Injection Options for 12 GeV CEBAF Upgrade 2911
 
  • R. Kazimi, J. F. Benesch, Y.-C. Chao, J.M. Grames, G.A. Krafft, M. Tiefenback, B.C. Yunn, Y. Zhang
    Jefferson Lab, Newport News, Virginia
 
  Funding: Work supported by DOE Contract DE-AC05-84ER40150.

Jefferson Lab is planning to upgrade the CEBAF accelerator from 6 to 12 GeV. In order to achieve this, the beam energy at injection into the main accelerator needs to increase from 67 MeV to either 123 or 134 MeV depending on the location of the new experimental hall relative to the accelerator. The present 100 keV electron source and beam formation to 5 MeV will remain unchanged; however, the present accelerating cryomodules in the injector cannot reach the higher injection energies. Consequently, two options for attaining these energies are considered: (1) replacing the present injector cryomodules with new, higher gradient cryomodules, or (2) re-circulating the beam through the existing cryomodules to achieve the necessary energy gain in two passes. In this paper we present simulation results and list the advantages and disadvantages of these two options.

 
WPAP047 Preliminary Results from a Superconducting Photocathode Sample Cavity 2956
 
  • P. Kneisel
    Jefferson Lab, Newport News, Virginia
  • R.S. Lefferts, A.R. Lipski
    SBUNSL, Stony Brook, New York
  • J.S. Sekutowicz
    DESY, Hamburg
 
  Funding: Work supported by the U.S. DOE Contract No DE-AC05-84ER40150.

Pure niobium has been proposed as a photocathode material and recently a successful test has been conducted with a niobium single cell cavity to extract photo-currents from the surface of this cavity. However, the quantum efficiency of niobium is ~210-4, whereas electrodeposited lead has a ~15 times higher quantum efficiency. We have designed and tested a photo-injector niobium cavity, which can be used to insert photo-cathodes made of different materials in the high electric field region of the cavity. Experiments have been conducted with niobium and lead, which show that neither the Q- values of the cavity nor the obtainable surface fields are significantly lowered. This paper reports about the results from these tests.

 
WPAP049 A High-Gradient CW RF Photo-Cathode Electron Gun for High Current Injectors 3049
 
  • R.A. Rimmer
    Jefferson Lab, Newport News, Virginia
 
  Funding: This manuscript has been authored by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy.

The paper describes the analysis and preliminary design of a high-gradient photo-cathode RF gun optimized for high current CW operation. The gun cell shape is optimized to provide maximum acceleration for the newly emitted beam while minimizing wall losses in the structure. The design is intended for use in future high-current high-power CW FELs but the shape optimization for low wall losses may be advantageous for other applications such as XFELs or Linear Colliders using high peak power low duty factor guns where pulse heating is a limitation. The concept allows for DC bias on the photocathode in order to repel ions and improve cathode lifetime.

 
WPAP050 A High Average Current DC GaAs Photocathode Gun for ERLs and FELs 3117
 
  • C. Hernandez-Garcia, S.V. Benson, D.B. Bullard, H.F.D. Dylla, K. Jordan, C. M. Murray, G. Neil, M.D. Shinn, T. Siggins, R.L. Walker
    Jefferson Lab, Newport News, Virginia
 
  Funding: This work supported by The Office of Naval Research under contract to the Dept. of Energy, the Air Force Research Lab, and the Commonwealth of Virginia.

The Jefferson Lab (JLab) 10 kW IR Upgrade FEL DC GaAs photocathode gun is presently the highest average current electron source operational in the U.S., delivering a record 9.1 mA CW, 350 kV electron beam with 122 pC/bunch at 75 MHz rep rate. Pulsed operation has also been demonstrated with 8 mA per pulse (110 pC/bunch) in 16 ms-long pulses at 2 Hz rep rate. Routinely the gun delivers 5 mA CW and pulse current at 135 pC/bunch for FEL operations. The Upgrade DC photocathode gun is a direct evolution of the DC photocathode gun used in the previous JLab 1 kW IR Demo FEL. Improvements in the vacuum conditions, incorporation of two UHV motion mechanisms (a retractable cathode and a photocathode shield door) and a new way to add cesium to the GaAs photocathode surface have extended its lifetime to over 500 Coulombs delivered between re-cesiations (quantum efficiency replenishment). With each photocathode activation quantum efficiencies above 6% are routinely achieved. The photocathode activation and performance will be described in detail.

 
WPAP055 A 3D Parallel Beam Dynamics Code for Modeling High Brightness Beams in Photoinjectors 3316
 
  • J. Qiang, S.M. Lidia, R.D. Ryne
    LBNL, Berkeley, California
  • C. Limborg-Deprey
    SLAC, Menlo Park, California
 
  Funding: This work was supported by a SciDAC project in accelerator physics which is supported by the U.S. DOE/SC Office of High Energy Physics and the Office of Advanced Scientific Computing Research.

In this paper we report on IMPACT-T, a 3D beam dynamics code for modeling high brightness beams in photoinjectors and rf linacs. IMPACT-T is one of the few codes used in the photoinjector community that has a parallel implementation, making it very useful for high statistics simulations of beam halos and beam diagnostics. It has a comprehensive set of beamline elements, and furthermore allows arbitrary overlap of their fields. It is unique in its use of space-charge solvers based on an integrated Green function to efficiently and accurately treat beams with large aspect ratio, and a shifted Green function to efficiently treat image charge effects of a cathode. It is also unique in its inclusion of energy binning in the space-charge calculation to model beams with large energy spread. Together, all these features make IMPACT-T a powerful and versatile tool for modeling beams in photoinjectors and other systems. In this paper we describe the code features and present results of IMPACT-T simulations of the LCLS and LUX photoinjectors. We also include a comparison of IMPACT-T and PARMELA results, and a comparison of IMPACT-T and ASTRA results.

 
WPAP057 Three-Dimensional Theory and Simulation of an Ellipse-Shaped Charged-Particle Beam Gun 3372
 
  • R. Bhatt, T. Bemis, C. Chen
    MIT/PSFC, Cambridge, Massachusetts
 
  Funding: U.S. DOE: Grant No. DE-FG02-95ER40919, Grant No. DE-FG02-01ER54662, Air Force Office of Scientific Research: Grant No. F49620-03-1-0230, and the MIT Deshpande Center for Technological Innovation.

A three-dimensional (3D) theory of non-relativistic, laminar, space-charge-limited, ellipse-shaped, charged-particle beam formation has been developed recently (Bhatt and Chen, PR:ST-AB, submitted Dec. 2004), whereby charged particles (electrons or ions) are accelerated across a diode by a static voltage differential and focused transversely by Pierce-type external electrodes placed along analytically specified surfaces. The treatment is extended to consider the perturbative effects of anode hole lensing, thermal isolation of the emitter, finiteness and nonuniformities of beam-forming electrodes, and an initial thermal spread. Analytic and semi-analytic results are presented along with 3D simulations utilizing the 3D trajectory code, OMNITRAK. Considerations with regard to beam matching into a periodic magnetic focusing lattice are discussed.

 
WPAP058 The ILC Polarized Electron Source 3420
 
  • A. Brachmann, J.E. Clendenin, E.G. Garwin, R.E. Kirby, D.-A.L. Luh, T.V.M. Maruyama, D.C. Schultz, J. Sheppard
    SLAC, Menlo Park, California
  • R.X.P. Prepost
    UW-Madison/PD, Madison, Wisconsin
 
  Funding: This work is supported by U.S. DOE contracts DE-AC02-76SF00515 (SLAC) and DE-AC02-76ER00881 (UW).

The SLC polarized electron source (PES) can meet the expected requirements of the International Linear Collider (ILC) for polarization, charge and lifetime. However, experience with newer and successful PES designs at JLAB, Mainz and elsewhere can be incorporated into a first-generation ILC source that will emphasize reliability and stability without compromising the photocathode performance. The long pulse train for the ILC may introduce new challenges for the PES, and in addition more reliable and stable operation of the PES may be achievable if appropriate R&D is carried out for higher voltage operation and for a simpler load-lock system. The outline of the R&D program currently taking shape at SLAC and elsewhere is discussed. The principal components of the proposed ILC PES, including the laser system necessary for operational tests, are described.