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PDT10A and PDT20A compact neutron monitoring modules designed for high radiation environments connect directly He-3 detectors. Each instrument contains a precision wide band charge sensitive pre-amplifier followed by an amplifier, wave shaping and discriminator circuits. When connected to He-3 detectors, these instruments detect the presence of charged-sensitive particles. Our focus is to create a compact (1 inch diameter), simple to use, high performance instrument with a variety of features available.

Each instrument has an analog monitoring test point allowing direct monitoring of amplified charged events using an oscilloscope. A twelve turn trim pot is available to finely tune the amplifier sensitivity to the desired level so you can obtain a good HV plateau for your application.
In addition, when a charged event is detected, a TTL OUT pulse is produced.
The TTL OUT pulse width is adjustable from 40nSeconds to 500nSeconds..
Each instrument contains a TTL IN input allowing you to sum outputs from other modules in a system. This allows quick and easy interconnection from 1 to over 100 detectors for digital pulse counting measurements.
Each instrument contains a threshold control trim pot allowing you to control the discriminator level for your application. 
The PDT20 is equivalent in performance to the PDT10A but additionally contains a high performance high voltage generator that can be adjusted over a range of 0-2200 volts.
The PDT20 contains a HV MON test point that allows you to measure and adjust the high voltage setting.
The PDT10 is compact, housed in 1 inch diameter aluminum with a length of 1.5 inches.
The PDT20 is enclosed in 1 inch diameter aluminum with a length of 3 inches.

PDT10A and PDT20A modules have been designed for extended temperature and vibration environments. The products have been tested at temperatures ranging from 0-170 degrees Centigrade including vibration to 70g from 2Hz to 10kHz.This new generation of neutron monitoring modules allow new systems to be quickly configured and existing detector instruments to be easily upgraded. The charge sensitive amplifiers are designed for Helium-3, boron loaded, fission chamber, alpha-and proton-recoil neutron detector operation. Multiple modules can be easily interconnected providing a single digital counting channel that will process pulse rates exceeding 5 MHz. Engineered in a compact ruggedized aluminum housing that interfaces directly to gas filled detectors, these modules provide an efficient clean solution in difficult environments.

Additional Features
Additional features include a light emitting-diode (LED) and two trimpots. The LED provides visual indication when a neutron event has occurred. Two trimpots allow control of the amplifier sensitivity ("THRES ADJ ")and "TTL OUT " pulse width. The trimpots are located just beneath the hole locations labeled as "THRES ADJ " and "PW ADJ ".Refer to Figure 2 on the reverse side.

Specifications
TTL OUT Pulse Width Adjustment Range 50nSec to 500nSec
Pulse Pair Resolution 500nSeconds
Power Supply Options +5 Volts or +12 Volts
Power Supply Current Requirements @5V 30mA,@12V 20mA
Gain Sensitivity Adjustment Range 20:1
Threshold Adjustment Range .005pC to .05pC
HV BIAS Range:PDT20A Only 0 to 2200 Volts
HV BIAS Noise .02Volts at HV Output
HV BIAS Stability per hour .05 Volts at HV Output
HV BIAS Stability per 24 hour .1 Volts at HV Output
Maximum TTL IN summing capability 5,000,000 counts

Digital Cascade Summing
All PDT10A and PDT20A modules provide an input labeled "TTL IN " intended for cascade or summed pulse applications. For cascade operation, the "TTL OUT " of a PDT10A is connected to the "TTL IN " of another PDT10A.Suppose you have an application requiring three detectors. Three modules are interfaced directly to the HN connectors of three detectors. The bias supply and power supply cables are attached to the PDT110A "HV IN " and "Vcc " connectors, respectively. For cascade operation, the "TTL OUT " of one PDT110A instrument is cabled to the "TTL IN " of another PDT110A..In a similar manner, the "TTL OUT " of the second PDT110A is cabled to the remaining PDT110A "TTL IN " input. The "TTL OUT " of the final PDT110A is cabled to the monitoring equipment.

PDT10A and PDT20A Configurations
You can purchase PDT10A and PDT20A modules with a variety of connector interfaces for He-3 detectors. Modules have the capability to connect directly to Helium-3 gas filled detectors that us HN, MHV, or SHV type of connectors. If necessary, you can even cable directly from the PDT10A modules to the detector using a high voltage cable with the 10A-C.The 10A-C uses a miniature high voltage connector rated for 5000 volts allowing cable connection to the detector. PDT can provide the cable with the desired connectors for your application. Please contact us and we will discuss the cable length, type of connection on the detector to help simplify your setup. When using the 10A-C it is important that the cable length is kept as small as possible to minimize both capacitance and noise. Most PDT modules connect directly to He-3 detectors to minimize capacitance with the added advantage of providing a more ruggedized interface.

10A Detector Interface 20A Detector Interface Description
10A-HN 20A-HN HN interface to He-3
10A-SHV 20A-SHV SHV interface to He-3
10A-MHV 20A-MHV MHV interface to He-3
10A-C Cable interface to He-3


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