Radioactive Source Tests at OSU

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
Cs13730.2yrs) Cs137 gives off es
(0.51MeV/94, 1.2MeV/6) gs (0.662 MeV/85) We
did two types of sources tests scan test
(V5700V) moved the 3 sources sources (by
hand) 1 cm/sec long term test (V5500V)
let a source sit in same location on tube for gt
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 gt
1mA over the length of the wire tube 10, wires
3, 4, tube 12 wire 4 3) I jumps up to gt 1mA over
a region of the wire tube 12 wires 5, 7, tube
13 wire 2 happens near the HV end of the tube
V5700V
OKlow current, Ilt1mA 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
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Scan Tests
Tube 10 wire 4 Problem 2
1mA
Second scan Ilt200nA
First scan Igt1mA
400 is the voltage input end
6
Scan test
Tube 12 Wire 5 Problem 3
First scan I jumps gt1mA
Second scan Ilt1mA
400 is the voltage input end
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9/8 Scan Test
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9/8 Scan Test
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9/8 Scan Test
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Lateral Scan (3 tubes)
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Long Term Source Test
We let a source sit in one spot on tube for gt
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 lt100nA to gt 3mA in 30-60 seconds !!
The effect is reproducible with HV gt 5700V Could
this be a problem with the wire termination or
resistor pc board??