This preamplifier is designed for Russian corona counters, but should also work with B10 and He3 neutron counters, it uses a Schmitt trigger to discriminate the noisy baseline typical of these detectors. The trigger point or the LLD is adjustable via a trimpot, a second trimpot is available for adjusting the level of hysteresis required. These two adjustments make it possible to tune this preamplifier to work with different tubes. 

Typical raw pulse from corona neutron counter

When the input signal (red trace) exceeds a set threshold, the schmitt trigger output goes high, simultaneously the input lifts to a new level thereby maintaining the higher level (grey trace)  until it falls below the threshold, causing the output to go low. The resulting output is a clean on off signal.

(note: due to the slew rate of the opamp and the short pulse time, the actual output pulse will look narrower at the top)

Some knowledge of electronics and preferably an oscilloscope and a DVM  is required to fine tune the preamp for use with your detector.

Connection Specifications

1. HV Positive Bias (GS-USB-PRO recommended)
2. HV ground 
3. Detector pos
4. 5 to 9V DC Power
5. Ground

Coupling Specifications

1. Coupling Resistor 100 M Ohm (4 x 25M Ohm)
2. Coupling capacitor 1 nF

Power Specifications

1. Input power 5 to 9V DC
2. Regulated circuit voltage 3.3V
3. Output pulse -  AC coupled 100 µs. 1 volt pulse 

* Coupling can be bypassed so the output is a logic pulse (3.3V square wave)

Dimensions

60 x 40 mm

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