Ludlum Measurements 125559, Руководство пользователя

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MODEL 2224-1 Technical Manual
Section 6
Ludlum Measurements, Inc. Page 6-2 January 2012
3. Switch the channel selector switch to the α position. Adjust
the pulser for a 120 mV pulse output and vary the
AT
control until counts are detected on the ratemeter.
4. 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 s witch to the β only position. Place an alpha source on
the detector face.
5. 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.
6. Plot a
HV
versus count rate plateau in 25-volt increments, 50
volts each side of the
HV
reading found in the above step
(ie,
HV
setting for count "dip" in the above step = 675 volts,
start the plot at 625 volts and increase in 25-volt steps until
725 volts is reached). Plot alpha source, beta source, and
background counts for both the α and β channel positions.
7. 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.
8. Select the desired count channel display, and proceed with
use.
M
ETER
C
ALIBRATION
A Ludlum Model 500 Pulser or equivalent is required. If the pulser does not
have a high-voltage readout, use a high-impedance voltmeter with at least
1000 Megohm input resistance to measure the detector voltage.
1. Ensure that the meter movement has proper mechanical
zero. The adjustment is on the front of the meter bezel. It
must be adjusted to zero with the range selector switch in
the
OFF
position.
2. Connect the Model 500 Pulser to the Model 2224-1 with the
appropriate cable. Rotate the Model 2224-1 range selector
switch to the × 100 position. Select the α+β channel
position.