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Summary of QE Measurements

Summary of QE Measurements. HBD Working Group Meeting 8/31/05 B. Azmoun BNL. Past and Present Chicklet QE Measurements. QE in CF4 at High and Low Collection Fields. Photocathode Production Notes. 1 st USB Chicklet Produced @ Big Mac

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Summary of QE Measurements

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  1. Summary of QE Measurements HBD Working Group Meeting 8/31/05 B. Azmoun BNL

  2. Past and Present Chicklet QE Measurements B. Azmoun, BNL

  3. QE in CF4 at High and Low Collection Fields B. Azmoun, BNL

  4. Photocathode Production Notes • 1st USB Chicklet Produced @ Big Mac • 1.  Big Mac Vac = 2.2 x 10-6 Torr2.  No heating of substrate before, during or after evap., No pre-evaporation of CsI3. Thickness target = 2000Angstroms • 4. The chicklet was transferred to a paint can while still within Big Mac, in an Ar environment (little contact with air)5.  Chicklet was transferred to BNL within an hour of evap. within Ar filled can6.  Chicklet was mounted to QE testing flange and put under Vac with ~10min exposure to air (had to solder on HV connector).7.  QE was measured in Vac (after 2 hours of pumping), Spectrometer Vac = 1.0 E-5 Torr. 2nd USB Chicklet Produced @ Big Mac 1. Big Mac Vac = 2.1 x 10-6 Torr. 2. Galvanized steel replaced with polished stainless steel. 3. No Chimney used 4. Pre-evap done ~ 10 min before deposition.  5. 5000 angstroms (instead of 2000) with about a 5% error 6. ~5 min elapsed before chicklet was vacuum sealed in the desiccator. (Desiccator sat in Ar as the PC was placed within it.) 7. Used glass dessicator to transport PC8. Used glove box (under N2 purge) to transport PC from dessicator to test flange: ~2 min. exposure to air total 9. QE was measured in Vac (after 2 hours of pumping), Spectrometer Vac = 1.0 E-5 Torr. Initial Chicklet Produced @ USB in Andrzej’s Lab 1. Bell Jar Vac ~ 7.5.0 x 10-8 Torr 2. Thickness Target = 5000Angstroms 3. Heated substrate before, during, and after evap 4. Pre-Evap of CsI 5. Placed PC in glass dissicator while in Ar atmosphere, pumped out dissicator, and transported to BNL 6. PC mounted onto test flange in air, total air exposure ~ 7min. 7. QE was measured in Vac (after 2 hours of pumping), Spectrometer Vac = 1.0 E-5 Torr. B. Azmoun, BNL

  5. Gas Purity Vs Collection Efficiency • While the Lamp monitor measures ~100% • gas transmittance, the ratio of the Chicklet • current in gas to Vac is ~80%. • The lamp monitor and Chicklet current is • measured simultaneously Newer Measurements confirm older ones. B. Azmoun, BNL

  6. Collection Efficiency Vs Applied Field Collection Efficiency = Ratio of PC Current to Current Measured in Vac at high Field Newer Measurements confirm older ones. B. Azmoun, BNL

  7. Miscellaneous B. Azmoun, BNL

  8. UV Photon Detection-CsI PHOTOCATHODE D. Mörmann et al, Nucl. Instrum. Methods A471(2001)333 A. Breskin et al, Nucl. Instrum. Methods A483(2001)670 B. Azmoun, BNL

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