Operating Instructions
ComTec GmbH
5-1
5.
Operating Instructions
5.1. General
The purpose of this section is to familiarize the user with the Model CSP10...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 CSP10...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.
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 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
µ
s/div. Turn
Preamp power on.
5.4. Initial Checkout
Using the Test input BNC provided on the Model CSP10(...13), a detector input of approximately
100 MeV per input volt is simulated. Adjust the Pulser for -20 mV peak input signal and observe a
Preamplifier energy output of +130 mV peak (nominal). This is equivalent to a detector input of
2.1 MeV (nominal).
5.5. Common Operating Problems
The modern spectrometer is an extremly sensitive, state-of the-art system. Inexact performance
of other than the grossest type is generally due to subtle factors. It is the ability to determine and
correct these factors that constitutes the art in the science of spectroscopy instrumentation.
