Technology, Components, Subsystems

Particle Sources, Injectors

    
Paper Title Page
MO202 High-Intensity, High Charge-State Heavy Ion Sources 8
 
  • J. Alessi
    BNL, Upton, Long Island, New York
  
  There are many accelerator applications for high intensity heavy ion sources, with recent needs including dc beams for RIA, and pulsed beams for injection into synchrotrons such as RHIC and LHC. The present status of sources producing high currents of high charge state heavy ions will be reviewed. These sources include ECR, EBIS, and Laser ion sources. The benefits and limitations for these type sources will be described, for both dc and pulsed applications. Possible future improvements in these type sources will also be discussed.  
Transparencies
MOP73 Development of a Permanent Magnet ECR Source to Produce a 5 mA Deuteron Beam at CEA/Saclay 192
 
  • R. Gobin, D.D. De Menezes, O. Delferriere, R. Ferdinand, F. Harrault
    CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex
  • P.-Y. Beauvais, G. Charruau, Y. Gauthier
    CEA/DSM/DAPNIA, Gif-sur-Yvette
  • N. Comte
    CEA/Saclay, Gif-sur-Yvette
  • P. Lehérissier, J.Y. Pacquet
    GANIL, Caen
  
  The high intensity light ion source, SILHI, is an ECR ion source operating at 2.45 GHz which produces high intensity (over 100 mA) proton or deuteron beams at 95 keV. It has been moved in the IPHI building after a complete dismantling. At the beginning of 2003, after tuning the source parameters at standard values, the first extracted beam reached more than 70 mA within a few minutes. This encouraged us to propose a permanent magnet source based on the SILHI design to fit in with the injector of the Spiral2 project, requesting 5 mA of D+ beam with an energy of 40 keV and a normalized rms emittance lower than 0.2 π·mm·mrad. The new source has been recently assembled and the first beam (proton) extracted. After a brief source description, the preliminary results will be reported and discussed.  
MOP74 Recent Results of the 2.45 GHz ECR Source Producing H- Ions at CEA/Saclay 195
 
  • R. Gobin, K. Benmeziane, O. Delferriere, R. Ferdinand, F. Harrault
    CEA/DAPNIA-SACM, Gif-sur-Yvette Cedex
  • A. Girard
    CEA DSM Grenoble, Grenoble
  
  Low frequency ECR plasma sources have demonstrated their efficiency, reproducibility and long life time for the production of positive light ions. In 2003, the new 2.45 GHz ECR test stand based on a pure volume H- ion production, developed at CEA/Saclay, showed a dramatic increase of the H- extracted ion beam. In fact, a stainless steel grid now divides the plasma chamber in two different parts: the plasma generator zone and the negative ion production zone. By optimizing the grid position and its potential with respect to the plasma chamber, the negative ion current reached close to 1 mA. Ceramic plates, covering the plasma chamber walls help electron density and lead to an optimisation of the ion production. A 50 % improvement has been observed. A new 6 kW magnetron RF generator now replaces the 1.2 kW previous one and the current will be soon plotted versus the RF power. New Langmuir probe measurements are also expected on both sides of the grid. The last results will be reported and discussed.  
Transparencies
MOP75 Hminus Distribution in the HERA RF-Volume Source 198
 
  • J. Peters
    DESY, Hamburg
  
  The HERA RF-Volume Source is the only source available that delivers routinely an Hminus current of 40 mA without Cs. The production mechanism for Hminus ions in this type of source is still under discussion. Laser photodetachment measurements have been started at DESY in order to measure the Hminus distribution in the source. The measurements have also been done under extraction conditions at high voltage. The results of the measurements with and without extraction are a basis for the development of a theory for the transition between plasma and vacuum (sheath), a cornerstone for beam transport programs. Knowledge of the H- distribution and where they are produced makes further source improvements possible.  
MOP76 Ultra-High-Vacuum Problem for 200 keV Polarized Electron Gun with NEA-GaAs Photocathode 201
 
  • T. Nakanishi, F. Furuta, M. Kuwahara, K. Naniwa, S. Okumi, M. Yamamoto, N. Yamamoto, K. Yasui
    DOP Nagoya, Nagoya
  • H. Kobayakawa, Y. Takashima
    DOE Nagoya, Nagoya-City
  • M. Kuriki, H. Matsumoto, M. Yoshioka
    KEK, Ibaraki
  
  For a polarized electron source based on photoemission from GaAs, a NEA (Negative Electron Affinity) surface makes an indispensable role to extract polarized electrons in conduction band into vacuum. The NEA surface is also considered as a best surface to provide a beam with a minimum initial beam-emittance. However, the NEA surface state is realized by a mono-layer of electric dipole moment (that is Ga(-)-Cs(+)) formed at the surface and thus it is easily degraded by
  1. desorption of harmful residual gas,
  2. desorption of harmful gas created by field emission from HV-cathodes and
  3. ion back-bombardment.
In order to reduce the effects of (a) and (c), extremely good UHV is required. Presently total pressure of 4·10-12 torr and respective partial pressures of 3·10-13 torr and 4·10-13 torr for H2O and CO2 were achieved at our gun chamber. Field emission dark current must be extremely suppressed to reduce the effect of (c). The maximum field gradient of 7.8 MV/m is applied for electrode envelope (3.0 MV/m for cathode surface) at 200 kV DC bias-voltage, but total dark current was suppressed below 1 nA for our electrodes. The NEA lifetime under these conditions will be reported at the conference. 		 
MOP77 Design Parameters of the Normal Conducting Booster Cavity for the PITZ-2 Test Stand 204
 
  • V.V. Paramonov, N.I. Brusova, A.I. Kvasha, A. Menshov, O.D. Pronin, A.K. Skasyrskaya, A.A. Stepanov
    RAS/INR, Moscow
  • A. Donat, M. Krasilnikov, A. Oppelt, F. Stephan
    DESY Zeuthen, Zeuthen
  • K. Flöttmann
    DESY, Hamburg
  
  The normal conducting booster cavity is intended to increase the electron bunch energy in the Photo Injector Test (DESY, Zeuthen) stage 2 experiments. The normal conducting cavity is selected due to infrastructure particularities. The L-band cavity is designed to provide the accelerating gradient up to 14 MV/m with the total input RF power 8.6 MW, RF pulse length up to 900 mks and repetition rate 5 Hz. The multi-cell cavity is based on the CDS compensated accelerating structure with the improved coupling coefficient value. The main design ideas and decisions are described briefly together with cavity parameters - RF properties, cooling and pumping circuits.  
MOP80 Development of Adaptive Feedback Control System of Both Spatial and Temporal Beam Shaping for UV-Laser Light Source for RF Gun 207
 
  • H. Tomizawa, T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, A. Mizuno, S. Suzuki, T.  Taniuchi, K. Yanagida
    JASRI-SPring-8, Hyogo
  • F. Matsui
    FKLAB, Fukui City
  
  The ideal spatial and temporal profiles of a shot-by-shot single laser pulse are essential to suppress the emittance growth of the electron beam from a photo-cathode rf gun. We have been developing highly qualified UV-laser pulse as a light source of the rf gun for an injector candidate of future light sources. The gun cavity is a single-cell pillbox, and the copper inner wall is used as a photo cathode. The electron beam was accelerated up to 4.1 MeV at the maximum electric field on the cathode surface of 175 MV/m. For emittance compensation, two solenoid coils were used. As the first test run, with a microlens array as a simple spatial shaper, we obtained a minimum emittance value of 2 π·mm·mrad with a beam energy of 3.1 MeV, holding its charge to 0.1 nC/bunch. In the next test run, we prepared a deformable mirror for spatial shaping, and a spatial light modulator based on fused-silica plates for temporal shaping. We applied the both adaptive optics to automatically shape the both spatial and temporal UV-laser profiles with a feedback routine at the same time. We report herein the principle and developing process of our laser beam quality control system.  
THP03 DESIGN IMPROVEMENT OF THE RIA 80.5 MHZ RFQ 599
 
  • Q. Zhao, V. Andreev, M. Doleans, D. Gorelov, T.L. Grimm, W. Hartung, F. Marti, S.O. Schriber, X. Wu, R.C. York
    NSCL, East Lansing, Michigan
  
  An 80.5 MHz, continuous-wave, normal-conducting, radio-frequency quadrupole (RFQ) was designed for the front end of the Rare Isotope Accelerator (RIA) driver linac. It will accelerate various ion beams (hydrogen up to uranium) from 12 keV/u to about 300 keV/u. The 4-meter-long RFQ accepts the pre-bunched beam from the low energy beam transport (LEBT) and captures more than 80% with a current of ~0.3 mA. Beam dynamics simulations show that the longitudinal output emittance is small for both single- and two-charge-state ion beams with an external multi-harmonic buncher. A 4-vane resonator with magnetic coupling windows was employed in the cavity design to provide large mode separation, high shunt impedance, and a small transverse dimension. The results of beam dynamics as well as the electromagnetic simulations are presented.  
THP23 An Electrode With Molybdenum-Cathode and Titanium-Anode to Minimize Field Emission Dark Currents 645
 
  • T. Nakanishi, F. Furuta, T. Gotou, M. Kuwahara, K. Naniwa, S. Okumi, M. Yamamoto, N. Yamamoto, K. Yasui
    DOP Nagoya, Nagoya
  • H. Matsumoto, M. Yoshioka
    KEK, Ibaraki
  • K. Togawa
    RIKEN Spring-8 Harima, Hyogo
  
  A systematic study to minimize field emission dark currents from high voltage DC electrode has been continued. It is clearly demonstrated that much lower field emissions observed for Molybdenum (Mo) and Titanium (Ti) in comparison to Stainless-steel and Copper. Furthermore, by analyzing gap-length dependence data of the dark current from Mo and Ti, we can find a method to separate the primary field emission currents (FEC) from secondary induced currents (SIC). The latter currents will be created by possible bombardments of metal surface of anode or cathode by electrons or positive ions, respectively. From this data analysis, it is suggested that Mo is suitable for cathode due to its smallest FEC, and Ti is adequate for anode due to relatively small SIC. This prediction was confirmed by our experiment using a pair of Mo and Ti electrode, which showed the total dark current is suppressed below 1 nA at 105 MV/m applied for an area of 7 mm2 with a gap-length of 1.0 mm. Therefore this Mo-Ti electrode seems useful for a high field gradient DC gun, especially for a GaAs-photocathode gun using an NEA (Negative Electron Affinity) surface.  
THP24 Highly Polarized Electrons from GaAs-GaAsP and InGaAs-AlGaAs Strained Layer Superlattice Photocathodes 648
 
  • T. Nakanishi, F. Furuta, M. Kuwahara, K. Naniwa, T. Nishitani, S. Okumi, N. Yamamoto, K. Yasui
    DOP Nagoya, Nagoya
  • H. Horinaka, T. Matsuyama
    OPU, Osaka
  • H. Kobayakawa, Y. Takashima, Y. Takeda, O. Watanabe
    DOE Nagoya, Nagoya-City
  
  GaAs-GaAsP strained layer superlattice photocathode has been developed for highly polarized electron beams. This cathode achieved a maximum polarization of 92% with a quantum efficiency of 0.5%. Criteria for achieving the highest polarization together with high quantum efficiency using superlattice photocathodes are discussed based on experimental spin-resolved quantum efficiency spectra of GaAs-AlGaAs, InGaAs-AlGaAs and GaAs-GaAsP superlattice structures.  
THP25 Development of Field-Emission Electron Gun from Carbon Nanotubes 651
 
  • Y. Hozumi
    GUAS/AS, Ibaraki
  • M. Ikeda, S. Ohsawa, T. Sugimura
    KEK, Ibaraki
  
  Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2] was achieved with 8 kV acceleration voltage by applying short grid pulses between cathode-grid electrodes. In order to proof utility, 100 kV gun system had been designed and structured since last year. Then the value of 300 mA was obtained based on 10-5…10-6 [Pa] back ground pressures. With some improvements anode currents of Ampere order is expected.  
THP26 Comparison of 2 Cathode Geometries for High Current (2 kA) Diodes 654
 
  • N. Pichoff
    CEA/DAM, Bruyères-le-Châtel
  • F. Bombardier, M. Caron, E. Merle, C. Noël, O. Pierret, R. Rosol, C. Vermare
    CEA, Pontfaverger-Moronvilliers
  • D.C. Moir
    LANL, Los Alamos, New Mexico
  • A. Piquemal
    CEA/PTN, Bruyères-le-Châtel
  
  AIRIX (FRANCE) and DARHT axis-1 (USA) are two high current accelerators designed for flash X-ray radiography. The electron beam produced (2 kA, 3.5 to 3.8 MV, 60 ns) is extracted from a velvet cold cathode. Specific calculations have demonstrated the influence of the cathode geometry on the emitted beam profile [1]. To check this assumption we have made two different experiments (DARHT March 2003 – AIRIX March 2004). We have compared the beam characteristics with two different geometries both theoretically and experimentally. The beam simulations have been done with 3 codes: a home-made code (M2V) and 2 commercial codes (PBGUNS and MAGIC). The extracted beam current and transverse profiles, for the first experiment, have been measured and compared to simulations results. In the second one, we have compared the beam’s extracted current and the energy spread.

[1] E. Merle et al., "Efforts to Improve Intense Linear Induction Accelerator (LIA) Sources for Flash Radiography",Proceedings of the LINAC2002 conference. August 19-23, 2002 Gyeongju, Korea.

 
THP27 Ultra Low Emittance Electron Gun Project for FEL Application 657
 
  • R. Ganter, M. Dehler, J. Gobrecht, C. Gough, G. Ingold, S. Leemann, M. Paraliev, M. Pedrozzi, J.-Y. Raguin, L. Rivkin, V. Schlott, A. Streun, A. Wrulich
    PSI, Villigen
  • A. Candel, K. Li
    ETH, Zürich
  
  Most of the current 1Å Free-Electron Laser (FEL) projects are based on thermionic or photocathode guns aiming at an electron beam emittance of 0.5 to 1 mm·mrad. The design of a gun capable of producing a beam with an emittance one or two order of magnitude lower than the state of the art would reduce considerably the cost and size of such a FEL. Due to the recent advances in nanotechnologies and vacuum microelectronics, a field-emitter based gun is a promising alternative scheme. We present first measurements on commercial field emitter arrays as well as 3-D numerical simulations of the electron beam dynamics for typical bunch distributions generated from field emitters in realistic gun geometries. The design and some experimental results on a 500kV pulser is also presented.  
Transparencies
FR104 Overview on High-Brightness Electron Guns 842
 
  • J.W. Lewellen
    ANL, Argonne, Illinois
  
  In an electron storage ring, the quality of the electron beam is generally a function of the ring lattice parameters and has little to do with the source of the electrons. In most electron linear accelerators, the beam brightness is set by the beam source. It is very difficult to improve the overall beam brightness after it has been produced; on the other hand, providing a brighter beam source can provide an “instant upgrade” to the performance of a brightness-limited electron linac-based facility. The development and routine operation of high-brightness guns, therefore, is critical to the success of next-generation linac-based light sources. This includes sources already under construction, such as LCLS, as well as proposed and as-yet completely theoretical machines. In this talk I present a general overview of the state-of-the-art in high-brightness electron beam source development, discuss the concept of “situational brightness”, and highlight some interesting paths towards future devices. I conclude with thoughts on some possible alternate applications for high-brightness beams.  
Transparencies