Detectors for radioactivity come in many forms. The most common are Geiger-Mueller tube based but they are not as sensivitive as the scintillation counter (Wiki) type, like this PDR-56F.
When a radioactive particle hits an atom of the crystal (scintillator) a photon of light is emitted. The crystal must be in a light tight housing so the only light is from the crystal. Typically the light is detected by a photomultiplier tube (Wiki). The electrical pulse that comes out of the photomultiplier tube has a pulse amplitude that is proportional to the energy of the particle that generated it. The PDR-56 is designed to detect the X-Ray (medium energy Gamma Rays (Wiki)) that come from Plutonium 239 (Wiki). More generalized detectors can be used in Multi-Channel Analyzers (MCA) to display a graph of the energy magnitude vs. energy level thus allowing analysis of radioactive materials.
The PDR-56 might be called a Single Channel Analyzer since the X-Ray (Wiki) probe (DT-590A) is optimized for detecting 239P.
The PDR-56 set consists of the meter and three probes (main, auxiliary and X-Ray) as well as some related items like a storage case, carrying strap and probe extended.
The crystal used for the DT-590A X-Ray Probe is CaF2(Eu) in order to detect 14-21 keV gamma radiation from 239P. See the Links below for a modification that uses a NaI(T1) crystal and readjustment of the trim pots so for a general use gamma detector, like for use in an MCA.
The main probe and auxiliary probe share the same 931 photomultiplier tube and are just different sensing crystals.
Fig 1 Radiacmeter w/ Main Probe
Fig 2 Cable (always needed)
Fig 3 Main Probe Telescoping Extension
Fig 4 Carry Strap
Fig 5 H-43B Headphones
CAGE: 96696 Canberra Ind.
Fig 6 DT-228A Aux Probe
Fig 8 DT-590A 239P X-Ray Probe
Fig 9 DT-224B Main Probe
Fig 12 IM-160F Radiacmeter
Fig 13 CY-7375 Storage Case
Fig 14 "D" battery positions
Fig 15 Missing Test Source?
Fig 16 Main Probe opened & DT-228A Aux Probe
931A Photomultiplier tube
Fig 17 Aux Probe on Extension
Handle shows on meter, but when in use is held in the hand
that's not carrying the meter.
Instead of zeroing on the 10K range the needle is pinned to the right (past full scale), but does zero on the other ranges.
RelatedRADIAC CALIBRATOR SET AN/UDM-7( )
Bicron Surveyor 50
The Polonium Pen (Tech Lib web page)
LinksHome-Built Radiac (Radiation Detector and Meter) for a Surplus DT-590A/PDR-56F Scintillation Probe
Converting a DT-590A/PDR-56F “X-Ray” Probe into a General-Purpose NaI(Tl) Gamma Probe
PRC68, Products for Sale, Alphanumeric index to web pages
This page created 15 Jan 2013