LUDLUM 2360, User Manual

Page: 23 / 72

Model 2360 Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-2 July 2016

Depress the
HV
switch and adjust the
HV
potentiometer for 0.4 to
0.5 kV on the 0-2.0 kV scale. Connect the scintillator and switch to
the
β only position. Place an alpha source on the detector face.

Slowly increase the
HV
potentiometer to observe an increase, then
decrease, and increase again in count as the
HV
is increased.
Decrease the
HV
until the ratemeter is in the "dip" of the observed
count rate-versus-
HV
plot just performed. Depress the
HV
switch
and note the
HV
setting.

Plot a
HV
versus count rate plateau in 25 V increments, 50 V each
side of the
HV
reading found in the above step (i.e.,
HV
setting for
count "dip" in the above step = 675 V, start the plot at 625 V and
increase in 25 V steps until 725 V is reached). Plot alpha source, beta
source, and background counts for both
α and β channel positions.

Find the optimum operating voltage from the plot, which gives the
greatest alpha and beta source efficiency while maintaining no
greater than the maximum acceptable level of cross talk between
channels.

Select the desired count channel display, and proceed to use
instrument.
M
ETER
C
ALIBRATION
A Ludlum Model 500 Pulser or equivalent is required. If the pulser does not
have high-voltage readout, use a high-impedance voltmeter with at least
1000 megohm input resistance to measure the detector voltage.
Ensure that the meter movement has proper mechanical zero. The
adjustment is on the front of the meter bezel. It must be adjusted to
˝
0
˝
with
the
ON
/
OFF
selector switch in the
OFF
position.
Connect the Model 500 Pulser to the Model 2360 with the appropriate
cable. Rotate the Model 2360 range multiplier switch to the ×100 position.
Select the
α + β channel position.
Adjust the Pulser for 40,000 cpm and adjust the pulse amplitude to at least
twice the beta threshold level (i.e.; beta threshold = 3.5 mV, adjust the pulser
to 7-10 mV).
Remove the instrument cover and adjust the
MTR
potentiometer until the
meter reads 400 cpm. Adjust the pulser to 10,000 cpm and ensure ratemeter
reads 100
±
10%. Decade the pulser and Model 2360 range multiplier switch