Workshop on Polarized Electron Sources and Polarimeters

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Status of 200keV Beam Operations at Nagoya University M. Yamamoto a , T. Konomi a , S. Okumi a , Y. Nakagawa a , N. Yamamoto b , M. Tanioku b , X. Jin b , T. Ujihara b , Y. Takeda b , F. Furuta c , H. Matsumoto c , M. Yoshioka c , M. Kuriki d , C. Shonaka d , and T. Nakanishi a a Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan 464-8602 b Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan 464-8603 c High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki, Japan 305-0801 d Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, Japan 739-8530 Abstract. We have developed a 200keV polarized electron source for generating high bunch charge of >3.2nC within ~1ns bunch duration for the International Linear Collider (ILC) and >7.7pC within 30ps bunch duration for a basic source study of an Energy Recovery Linac (ERL). In order to improve gun operation voltage and an operational lifetime, we have employed new electrode materials of molybdenum and titanium to eliminate field emission dark current, and restructured a beam transport vacuum systems. As a beam generation for the ERL, bunch charge of up to 28pC was generated by irradiating with sliced laser pulse trains. The details are described in this report. Keywords: Electron source; Polarized beams; Vacuum systems PACS: 29.25.Bx; 29.27.Hj; 07.30.Kf 200KEV GUN AND BEAM TRANSPORT SYSTEM A 200-keV polarized electron source has been developed for generating highly polarized electron beams with high bunch charge for requirements of ILC [1]. Remaining problems of this source are photocathode QE lifetime in the condition with actual beam current of more than 50 A and stable gun high voltage operation. An ultra high vacuum (≤10 -9 Pa) environment of a beam transport system as well as of the gun is important to maintain NEA surface during beam operation. In order to avoid vacuum increase due to outgassing from a beam dump, we have applied four NEG modules (WP950) and a 100 L/s ion pump to the beam dump system, and two NEG pumps (GP100MK5) to a differential pumping system (DPS). The vacuum pressure of the beam transport line is important information for a photocathode QE lifetime measurement. The DPS vacuum pressure was monitored by an extractor-type
vacuum gauge (AxTRAN X-11,ULVAC). By comparison of the DPS base pressure with and without NEG modules in a condition with 20 A beam dumping for ~10 minutes, the DPS base pressure of 1.2x10 -9 Pa was increased to 1.7x10 -9 Pa and 1.4x10 -8 Pa, respectively. FIGURE 1. Schematic view of the 200keV polarized electron source and beam transport system. To reduce the dark current in a high field gradient condition, we have employed a molybdenum cathode and titanium anode (Mo-Ti) [2]. A result of Mo-Ti electrode conditioning is shown in Fig. 2a. (a) (b) FIGURE 2. Result of electrode conditioning (a). Red circles, blue squares and green diamonds show high voltage duration less than 1 minute, 10 minutes and 1 hour respectively. The pictures show molybdenum cathode electrode fabrication processes of hot squeezing (b) and finished electrode (c). The gradual increase of dark current observed before a breakdown in the SUS electrode was hardly detectable at a resolution of 1 nA, and breakdowns occurred (b) (c)
Page 1 and 2: Workshop on Polari
Page 3 and 4: Surface Analysis of Damaged Superla
Page 5 and 6: High Brightness and High Polarizati
Page 7 and 8: FIGURE 1. Schematic drawing of the
Page 9: To be independent from possible ins
Page 13 and 14: In order to research QE degradation
Page 15 and 16: Polarized Photocathode R&D for Futu
Page 17 and 18: charge limitation can be measured.
Page 19 and 20: SUMMARY AND PLANS It is challenging
Page 21 and 22: The most difficult task is to achie
Page 23 and 24: The run with a small laser spot cen
Page 25 and 26: Hydrogen Cleaning of Superlattice P
Page 27 and 28: HABS Prep Load UHV Vessel Ion Pump
Page 29 and 30: FIGURE 4. Comparison of results ach
Page 31 and 32: Heidelberg photoelectron target and
Page 33 and 34: However, it is emphasized here that
Page 35 and 36: Atomic Hydrogen Treatment Atomic hy
Page 37 and 38: Rydberg binding energy. In many cas
Page 39 and 40: the ring dispersion and from fluctu
Page 41 and 42: The valence band splitting ∆Ehh-l
Page 43 and 44: will be achieved by taking the last
Page 45 and 46: A Study of the Activated GaAs Surfa
Page 47 and 48: diffraction (LEED) and auger electr
Page 49 and 50: FIGURE 4. LEED pattern of the GaAs
Page 51 and 52: HIGH POLARIZATION PHOTOEMITTER IMMU
Page 53 and 54: QE (%) 10 9 8 7 6 5 4 3 2 1 650 Cs
Page 55 and 56: Superlattice Photocathode Damage An
Page 57 and 58: and reactivated between February 11
Page 59 and 60: Discussion of SIMS data and Compari
Page 61 and 62:
MBE Growth of Graded Structures for
Page 63 and 64:
conduction miniband is higher that
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GRADED ALUMINUM GALLIUM ARSENIDE SU
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Three wafers were grown with differ
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FIGURE 10. Polarization and QE as a
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PHOTOCATHODE WITH NEA SURFACE USING
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FIGURE 2. Dependence of DOS on exci
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High Brightness and high polarizati
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Laser Substrate GaP 355 μm Zoom Bu
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process of NEA-PC with SL layers, o
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FIGURE 1. (a) Band-graded photocath
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Left (a): Homogeneous (HM) layer Ri
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K2CsSb Cathode Development John Sme
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for the potassium deposition. 40nm
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ias of 500V, with 60µA of emitted
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analyzing chamber are used for samp
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spectrum of the film was observed a
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Demo Free Electron Laser (FEL) [1]
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hours, or if the emitter returns at
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neon or argon would have helped pro
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for emittance compensation solenoid
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If one can make electrodes that do
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The last important parameter is cat
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Status of the ALICE Energy Recovery
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TABLE 1. Booster & main linac gradi
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• The beam was fully-characterise
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photocathode. This limitation means
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whilst focusing the heat onto the p
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Development of an electron gun for
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FIGURE 2. Preparation, loading, and
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may help to avoid electric field co
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from its neighbors. The core-to-win
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series connection and the output cu
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Low Emittance Electron Gun for XFEL
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FIGURE 3. Copper cathode and corres
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current in the secondary which oppo
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Equation (2) shows that the effect
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Generally, the equation for the rad
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High-Fidelity RF Gun Simulations wi
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Causal Moving Window The methods us
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(a) y / mm y / mm Transverse Distri
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studies like long term studies of p
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ehavior of the curves is independen
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In Fig. 4 the curve shows an ASTRA
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TABLE 1. RF cavity parameters calcu
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PASSBAND AND ON-AXIS FIELD DISTRIBU
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If the frequency shift on crest is
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In order to increase the quality fa
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THE EXPERIMENT The experimental set
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FIRST COOL-DOWN In the first cool-d
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Non Evaporable Getter (NEG) Pumps:
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Examples of Applications NEG pumps
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isotherms in a controlled and repro
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chemical gettering that results whe
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inside the photogun remains very go
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High Brightness and High Polarizati
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focusing lens is mounted on a trans
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of electron polarization obtained b
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FIGURE 7. Reduced brightness depend
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FIGURE 1. Mott polarimeter with two
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� ��
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Compton Polarimetry at ELSA Wolfgan
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In order to be detected, the Compto
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monitored after the interaction by
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where n + and n - are the counting
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Our test cavity (Figure 3.) consist
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Polarimetry at the Superconducting
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30-130 MEV MØLLER POLARIMETER A 30
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Benchmark studies among own and com
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d2z = ds2 d2x = ds2 eQ eQ 4πε0 m0
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ments of his tracing cord developin
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all requires a slot in the side for
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simulations in GPT show that these
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Polarized Positrons at Jefferson La
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GEANT4 [11]. Using Stokes parameter
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Ultimately, the shower of particles
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It was gratifying to hear about the
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gun/photocathode, and likely repres
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induced emittance growth, especiall
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PESP Workshop Prog
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PESP Posters Posters (17 total) •
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Clendenin, James SLAC National Acce
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McCarter, James Jefferson Lab 12000
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Surles-Law, Ken Jefferson Lab 12050
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Workshop on Polarized Electron Sources and Polarimeters

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