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Radioactive Source Tests at OSU

Radioactive Source Tests at OSU. Tests were performed on large cell tubes 10,12,13. Our source tests are made using three Cs137 sources 10 m C sources (~15 years old, t1/2 Cs137=30.2yrs) Cs137 gives off: e’s (0.51MeV/94%, 1.2MeV/6%) g ’s (0.662 MeV/85%)

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Radioactive Source Tests at OSU

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  1. Radioactive Source Tests at OSU Tests were performed on large cell tubes 10,12,13 Our source tests are made using three Cs137 sources 10mC sources (~15 years old, t1/2 Cs137=30.2yrs) Cs137 gives off: e’s (0.51MeV/94%, 1.2MeV/6%) g’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 All source tests were done using ZEUS gas mix

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

  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 > 1mA over the length of the wire tube 10, wires 3, 4, tube 12 wire 4 3) I jumps up to > 1mA over a region of the wire tube 12 wires 5, 7, tube 13 wire 2 happens near the HV end of the tube V=5700V OK=low current, I<~1mA uniform along wire EXAMPLES on FOLLOWING PAGES All 8 wires looked OK after a second scan ! Cycled HV, waited a few minutes and scanned NOTE: on scan plots “400” is the voltage input end of tube

  4. Scan tests Tube 10 wire 6 “Problem #1” “hot” regions First scan Second scan “400” is the voltage input end

  5. Scan Tests Tube 10 wire 4 “Problem #2” 1mA Second scan I<200nA First scan I>1mA “400” is the voltage input end

  6. Scan test Tube 12 Wire 5 “Problem # 3” Second scan: I<1mA First scan: I jumps >1mA “400” is the voltage input end

  7. 9/8 Scan Test

  8. 9/8 Scan Test

  9. 9/8 Scan Test

  10. Lateral Scan (3 tubes)

  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 200-300nA 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…..

  12. Source Induced Current ! If I put a source on the purple dot the current rises from <100nA to > 3mA in 30-60 seconds !! The effect is reproducible with HV > 5700V Could this be a problem with the wire termination or resistor pc board??

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