Canberra 2015A, User Manual

Page: 14 / 56

to 93 ohms. The 2015A is shipped with the front panel output impedance set
for
≤
1 ohm. The rear output has a fixed output impedance of approximately
93 ohms, series connected.
When using the front panel low impedance output, short lengths of
interconnecting coaxial cable need not be terminated. To prevent possible
oscillations, longer cable lengths should be terminated at the receiving end in
a resistive load equal to the cable impedance (93 ohms for type RG-62
cable).
The rear panel 93 ohm output may be safely used with RG-62 cable up to a
few hundred feet. However, the 93 ohm output impedance is in series with
the load impedance, and a decrease in the total signal range may occur. For
example, a 50% loss will result if the load impedance is 93 ohms.
2. Insert the 2015A into a standard NIM BIN. Preamp power is provided by a 9
pin connector located on the 2015A rear panel. Allow the total system to
warm up and stabilize.
3. Set the 2015A controls as indicated below:
SHAPING: 2 ms (internal)
COARSE GAIN: 16
FINE GAIN: 2.2
This will give approximately 9 volts output when using a preamp gain of 100
mV/MeV and
60
Co radioactive source.
4. Install a “tee” connector on the 2015A AMP OUTPUT. Connect one end of
the “tee” connector to the analyzer ADC input. To fully exploit the count rate
capabilities of the Model 2015A Amplifier the ADC should be direct
coupled. All Canberra ADC’s are dc coupled. Connect the second end of the
“tee” connector to an oscilloscope and monitor the AMP OUTPUT.
Performance Adjustments
1. The pole/zero is extremely critical for good high count rate resolution. See
note 1 on page 11. Adjust the radiation source count rate between 2 kcps and
25 kcps. While observing the AMP OUTPUT on the scope, adjust the
pole/zero so that the trailing edge of the unipolar pulse returns to the baseline
with no over or undershoots.
8
Operating Instructions