| 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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WG1018 |
The Jefferson Lab 200 kV Inverted Gun: Lifetime Measurements Using Strained Superlattice GaAs and K2CsSb Photocathodes |
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- R. Suleiman
JLAB, Newport News, Virginia, USA
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A DC high voltage photoelectron gun has been built at Jefferson Lab based on a compact inverted insulator. The photogun with cathode electrode made of large-grain niobium has been high-voltage conditioned to 225 kV and operates reliably without field emission at 200 kV. Charge lifetime measurements at high average current were made using two different photocathodes: polarized beam operation using a strained superlattice GaAs photocathode at current up to 4 mA average current with RF-pulsed light at 780 nm and unpolarized beam operation using a K2CsSb photocathode at currents up to 20 mA with DC laser light at wavelengths 404, 440 and 532 nm laser light. A summary of beam-based observations are presented.
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Slides WG1018 [2.177 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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