OSU 9/7/03 1 Radioactive Source Tests at OSU Our source tests are made using three Cs137 sources 10  C sources (~15 years old, t1/2 Cs137=30.2yrs) Cs137 gives off: e’s (0.51MeV/94%, 1.2MeV/6%)  ’s (0.662 MeV/85%) We did two types of sources tests “scan” test (V=5700V) moved the 3 sources sources (by hand) ~1 cm/sec “long term” test (V=5500V) let a source sit in same location on tube for > 8hrs Set HV and monitor the current using CAEN system Tests were performed on large cell tubes 10,12,13 All source tests were done using ZEUS gas mix

OSU 9/7/03 2 Sources test setup Cs source A Cs source The bar holding the 3 sources was moved by hand along the wire ~1 cm/s

OSU 9/7/03 3 Cs137 Scan Tests Each wire was scanned with a source. Initial Study found: 16 wires “ok” 8 wires suspect types of Problems: 1) I increases in a few regions of wire tube 10, wires 2, 6 2) I > 1  A over the length of the wire tube 10, wires 3, 4, tube 12 wire 4 3) I jumps up to > 1  A over a region of the wire tube 12 wires 5, 7, tube 13 wire 2 happens near the HV end of the tube OK=low current, I<~1  A uniform along wire All 8 wires looked OK after a second scan ! Cycled HV, waited a few minutes and scanned V=5700V EXAMPLES on FOLLOWING PAGES NOTE: on scan plots “400” is the voltage input end of tube

OSU 9/7/03 4 Scan tests Tube 10 wire 6 “Problem #1” First scanSecond scan “400” is the voltage input end “hot” regions

OSU 9/7/03 5 Scan Tests Tube 10 wire 4 “Problem #2” First scan I>1  A Second scan I<200nA “400” is the voltage input end 1A1A

OSU 9/7/03 6 Scan test First scan: I jumps >1  A Second scan: I<1  A Tube 12 Wire 5 “Problem # 3” “400” is the voltage input end

OSU 9/7/03 7 9/8 Scan Test

OSU 9/7/03 8 9/8 Scan Test

OSU 9/7/03 9 9/8 Scan Test

OSU 9/7/03 10 Lateral Scan (3 tubes)

OSU 9/7/03 11 “Long Term” Source Test We let a source sit in one spot on tube for > 8hrs and monitored the current Lowered voltage to 5500V so current in a cell would typically be nA We have sampled 12 spots so far 4 spots on each tube, ~L/5, 2L/5, 3L/5, 4L/5 Current is very stable in each region HOWEVER…..

OSU 9/7/03 12 Source Induced Current ! If I put a source on the purple dot the current rises from 3  A in seconds !! The effect is reproducible with HV > 5700V Could this be a problem with the wire termination or resistor pc board??