Model 43-68, 43-68/1, 43-68/2 Gas Proportional Detector
Ludlum Measurements, Inc.
Page 6
February 2011
Detector Performance
ALPHA PLATEAU:
Determine the plateau region of the
background and alpha source counting curves for the applied
voltage range of 1100-1400 volts. Use 50-volt increments and set
the counting instrument input sensitivity at 4 mV. The operating
voltage should be approximately 1250 volts. The background
count should be 3 cpm or less. The operating voltage will increase
with a higher input sensitivity. Check each quadrant of the detector
face for statistically uniform response; that is, ensure that each
quadrant reading is within
±
10% of the average of the readings. If
the count is not statistically uniform, check for light leaks in the
window and repeat flush procedures.
BETA-GAMMA PLATEAU:
Determine the plateau region in the
background and beta-gamma source counting curves for the
applied voltage range of 1550 volts to 1900 volts or from 1550
volts to when either the source or background count rate increases
dramatically. Use 50-volt increments and leave the input
sensitivity at 4 mV. The operating voltage should be approximately
1700-1750 volts, with the background count at 350 cpm or less.
Setting instrument input sensitivity greater than 4 mV will increase
the operating voltage.
Static Operation
Check detector for proper operation, for appropriate source
count, and gas leakage.
Disconnect output and input male quick connects.
