Model PAS-2 PREAMPLIFIER/AMPLIFIER/TSCA
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FEATURES
Preamplifier/ Amplifier/Timing Single Channel Analyzer
Amplifier and TSCA output
Compact design
Designed for use with Proportional Counters
APPLICATIONS
Mössbauer Spectroscopy
other general purpose use
DESCRIPTION
The PAS-2 combines a Preamplifier for Proportional Counters, an Amplifier and a Timing Single Channel Analyzer. The bipolar Amplifier is designed for counting rates which are typical in Mössbauer Spectroscopy. Both a linear output from the Amplifier and a timing output from the TSCA are available for spectroscopy and counting purposes. A built-in pulse generator can be used for testing of a spectroscopy system.
SPECIFICATIONS
Preamplifier
Gain: -0,8 V/pC
Noise: <6*10-17 Coulomb (at 0 pF)
<1*10-16 Coulomb (at 100 pF)
Detector Input: MHV
HV Input: SHV, max. 3000 Volts DC
Amplifier
Gain: +70 V/V
Shaping time: 2 μsec. bipolar
Amplitude: up to 10V, positive lobe leading
Output connector: BNC, 50 Ohm
Timing Single Channel Analyzer
LLD: 0,4 to 10V, settable by 10 turn
locking dial potentiometer
ULD: 0,4 to 10V, settable by 10 turn
locking dial potentiometer
Output: logic pulse 5V, 1 μsec. width,
BNC, 50 Ohm
Pulse Generator
internal jumper setting. Can be used to test the functioning of the system
Monitor Output
(sum of AMP/TSCA outputs) for convenient setting of LLD and ULD.
Amplitude 200 mV, BNC, 50 Ohm
Power Amphenol 17-20090 connector for external
+12V supply, load 150 mA. Cable 3m lenghts
provided
Size 17 x 10 x 5 cm
PERFORMANCE
Stability: 0.01% /oC
Integral Nonlinearity:
>0,5%, 0.2 to 10 V
Setup using an oscilloscope
A typical pulse-height spectrum 57Co looks like this: a) with a detector filled with Xenon gas, b) with a Krypton gas
The output of the Amplifier looks like this - the example is for a detectoer filled with Krypton gas
The monitor output with lower level setting at minimum and upper level setting at maximum
A typical monitor output signal after setting the lower- and upper level to the 14.4 keV line which is significant for Mossbauer work
An oscilloscope must be used for proper setup.The monitor output shows three (two with a Xenon gas filled detector) clearly separated energy lines. By adjusting the lower level and upper level potentiometers the 14.4 keV energy line can be clearly set. Setting the potentiometers to the 6.4 keV line will not produce the desired Mossbauer effect. Some hints: The monitor output should be set to 5 to 7 Volts for the 14.4 keV line. Use the HV potentiometer to make this adjustment. Make sure the trigger level of the oscilloscope is setjust slightly above the zero level as you otherwise do
not see the rising edge of the pulses correctly. An alternative is to connect the OUT pulse to input 1 of a scope, the SCA pulse to input 2 and set the scope to "add". You will see the same kind of displays as above but because of the higher output level you will find it easier to trigger the oscilloscope. If a MCA is available the setup can also be made in pulse height analysis using the Amplifier output of the PAS-2 as the input to the ADC and the SCA output as a gate signal of the ADC. The internal switch should be in pos. 1 for setup as otherwise the output pulses of the amplifier will be inverted and therefore difficult to setup.
Component view of the printed circuit board showing the solder bridge setting for positive amplifier output
