Hydrogen and Ultra-High Vacuum Jefferson Lab Photo-Electron Gun • Baked Stainless chamber • Base pressure ~1e-11 Torr • Pumped with Ion and NEG pumps • Hydrogen.
Download ReportTranscript Hydrogen and Ultra-High Vacuum Jefferson Lab Photo-Electron Gun • Baked Stainless chamber • Base pressure ~1e-11 Torr • Pumped with Ion and NEG pumps • Hydrogen.
Hydrogen and Ultra-High Vacuum Jefferson Lab Photo-Electron Gun • Baked Stainless chamber • Base pressure ~1e-11 Torr • Pumped with Ion and NEG pumps • Hydrogen dominates residual gas Marcy Stutzman 26 September 2003 Thomas Jefferson National Accelerator Facility Photocathode Lifetime ~2.5E-11 Torr ~5.0E-11 Torr >15.0E-11 Torr J. Grames, Jefferson Lab Cathode Degradation Lifetime vs. Pressure Marcy Stutzman 26 September 2003 Thomas Jefferson National Accelerator Facility Vacuum Improvements Rate of Rise Outgassing Measurement 3.0E-04 2.5E-04 304 Stainless 2.0E-04 1.5E-04 316L Stainless 1.0E-04 6061 Aluminum 5.0E-05 340 320 300 280 260 240 220 200 180 160 140 120 100 80 60 40 0 0.0E+00 20 Pressure (Torr) •Chamber material Al, 304SS, 316L SS •Coatings TiN, SiO2, Getter •Pump Speed measurements at UHV Time (hours) Marcy Stutzman 26 September 2003 Thomas Jefferson National Accelerator Facility Conclusions •Vacuum quality directly affects photocathode lifetime •Hydrogen is the primary residual gas in UHV/XHV systems •We are researching diffusion barriers and pumping for UHV Marcy Stutzman 26 September 2003 Thomas Jefferson National Accelerator Facility Gun 2 after bakeout, 15 September 2003 Torr 1.0x10 -10 1.0x10 -11 1.0x10 -12 1.0x10 -13 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 Atomic Mass Units Marcy Stutzman 26 September 2003 Thomas Jefferson National Accelerator Facility