| Paper |
Title |
Page |
| WG1000 |
ERL2011 Summaries of Working Group 1 |
10 |
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- B.M. Dunham
CLASSE, Ithaca, New York, USA
- A. Arnold
HZDR, Dresden, Germany
- S.A. Belomestnykh, T. Rao
BNL, Upton, Long Island, New York, USA
- S.V. Benson, C. Hernandez-Garcia, R. Suleiman
JLAB, Newport News, Virginia, USA
- D.C. Nguyen
LANL, Los Alamos, New Mexico, USA
- N. Nishimori
JAEA, Ibaraki-ken, Japan
- T. Quast
HZB, Berlin, Germany
- M. Yamamoto
KEK, Ibaraki, Japan
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Slides WG1000 [0.035 MB]
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WG1004 |
Laser System for the BNL ERL |
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- T. Rao
BNL, Upton, Long Island, New York, USA
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The laser system for the BNL ERL is a custom made, commercial diode pumped Nd:YVO MOPA that can deliver up to 20 W at 1064 nm, 10 W at 532 nm and > 5 W at 355 nm at 9.38 MHz. Three motion stages in the cavity, namely one stepper motor, one 100 μm range piezo and one 10 μm range piezo stage, maintain the synchronism with the RF master clock. A pulse picker after the amplifier enables selection of arbitrary length of the pulse train and number of pulses in the train. Noncritically phase matched LBO and critically phase matched LBO are used for second and third harmonic conversion respectively. The third harmonic crystal is contained in a sealed envelope purged with dry air to reduce its degradation and associated damage. The UV parameters are as follows: Amplitude stability: < 1% rms, power in pre/post pulse and pedestal: < 1 ppm., beam profile: Gaussian, beam quality: TEM00 with M2 < 1.5, pointing stability: 25 μrad, synchronization deviation to maser oscillator: < 1 ps, Pulse duration: ~ 5-12 ps, jitter in pulse duration: < 0.1 ps. 3 dimensional shaping of the 532 nm beam has been accomplished using beam stacking and pi shaper in another laser with similar beam parameters. The operation of the laser, results of beam shaping and the laser control system for the ERL will be presented.
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Slides WG1004 [4.189 MB]
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WG1016 |
Progress at BNL Towards Development of Efficient, Robust Photocathodes for High Average Current Operation |
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- T. Rao, S.A. Belomestnykh, I. Ben-Zvi, X. Chang, J. Smedley, E. Wang, Q. Wu
BNL, Upton, Long Island, New York, USA
- X. Liang, M. Ruiz-Osés, T. Xin
Stony Brook University, Stony Brook, USA
- R.R. Mammei, J.L. McCarter, M. Poelker, R. Suleiman
JLAB, Newport News, Virginia, USA
- E.M. Muller
SBU, Stony Brook, New York, USA
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The photocathode research at BNL is proceeding along two parallel paths, characterizing the cathodes as they are being fabricated and testing them in a variety of guns. Using modern surface science techniques such as X-Ray Reflection (XRR), X-Ray Diffraction (XRD) and X-Ray photoemission spectroscopy (XPS), we have investigated Sb and K-Cs-Sb layers as a function of the deposition technique, substrate material and deposition recipes. The talk will cover the latest results of these investigations. Cathode insertion section for the 112 MHz SRF gun is being designed for testing multialkali and diamond secondary emission cathodes. The status of the designs will also be presented. In addition, the multialkali cathode, fabricated at BNL and transported to JLab, has been tested for high current operation in a DC injector at JLab. The performance of this cathode when irradiated 440 nm and 532 nm radiation, under different bias voltages and average currents will be presented.
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Slides WG1016 [4.189 MB]
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| PSP019 |
Charge Lifetime, Emittance, and Surface Analysis Studies of K2CsSb Photocathode in a JLab DC High Voltage Gun |
133 |
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- J.L. McCarter
UVa, Charlottesville, Virginia, USA
- R.R. Mammei, M. Poelker, R. Suleiman
JLAB, Newport News, Virginia, USA
- T. Rao, J. Smedley
BNL, Upton, Long Island, New York, USA
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Funding: DOE Grant # DE-FG02-97ER41025
For the past year, BNL and JLab groups have been collaborating to study the characteristics of K2CsSb photocathodes inside a DC high voltage photogun. Although the first set of runs at 1 mA and at 100 kV bias voltage indicated disappointing charge lifetime, comparable to values obtained with GaAs photocathodes, subsequent measurements indicate that both the QE and charge life time increased significantly. This improvement could be attributed to the change in the chemical composition of the cathode due to UV irradiation. The charge life time measurements do not indicate any QE decay for currents of 10 mA over 350 micron FWHM spot, slight decay at 16 mA and significant decay at 20 mA for this spot size. When the spot size is increased to 850 micron, the lifetime at 20 mA increased significantly, implying local heating due to high laser intensity. Additional measurements with laser alone, without the HV, support this argument. These results as well as emittance and surface science measurements will be presented.
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