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5 Operating Instructions
5.1 General
The purpose of this section is to familiarize the user with the Model CSPA10...13 Preamplifier and to
check that the unit is operating correctly. Since it is difficult to determine the exact system configuration in
which the unit will be used, explicit operating instructions cannot be given. However, if the following
procedure is carried out the user will gain sufficient familiarity with the instrument to permit its proper use
in the system at hand.
The instructions which follow may be best carried out with the preamplifier on latest bench, seperated
from the detector.
Because the input is charge sensitive, and ultra high impedances are involved, the Preamplifier is
inherently somewhat microphonic. For best results, testing should be done with the Preamplifier chassis
cushioned on a block of foam rubber, and the cover securely fastened to the frame.
5.2 Test Input
The Model CSPA10...13 accommodate a TEST input via a BNC connector on the front panel introduces
the externally applied signal (preferably a negative tail pulse of -1 to -5 volt peak amplitude) to a charge
injection capacitor to the summing junction of the inegrator. The test signal voltage is usually adjusted in
amplitude by the user so as to give a reference peak signal in his data spectrum at a convinient location
so as to normalize multiple detectors. This input does provide a resistive terminating impedance.
In the endless mode data acquisition is started only once, e.g. by a software start i.e. asynchronously to
the rest of the experiment. Then all arriving events are recorded and stored with an absolute time relative
only to the initial start. Since the dynamic range is up to 53 bit or 8.3 days the available absolute time
range will be sufficient for every imaginable experiment.
5.3 Initial Setup
1. Connect the Preamp to a source of low voltage power such as a FAST ComTec Spectroscopy
Amplifier using the five foot cable provided.
2. Using the RG-58C/U coax, connect the Preamp output to channel 1 of a dual trace
Oscilloscope.
3. Connect the negative, attenuated output of a tail pulse generator (such as the Berkeley
Nucleonics Corp.: BH-1, PB-5 Tail Pulser) to channel 2 using RG-58C/U and a „tee" at the
Scope input.
4. The other side of the „tee" should be connected to the Test input BNC connector through a
length of RG-58C/U coax.
5. Select Scope vertical sensitivities of 50 mV/div. And set the time base to 10 µs/div. Turn
Preamp power on.
5.4 Initial Checkout
Using the Test input BNC provided on the Model CSPA10...13, a detector input of approximately 100 MeV
per input volt is simulated. Adjust the pulse generator for -100 mV peak input signal and observe a
Preamplifier energy output of +150 mV peak (nominal). This is equivalent to a detector input of 2.4 MeV
(nominal).
For the CSPA11, you should get about +16 mV from a –100 mV test signal and for the CSPA12, you
should get about +16 mV from a –1000 mV test signal.
12
Operating Instructions
ComTec GmbH
F
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