IM-156/PD Ion Chamber Survey Meter (ca. 1960) 

This example of the IM-156/PD was manufactured by Technical Associates of Burbank California.  It is obviously the military version of the Juno, but I have not been able to locate any specific references regarding the IM-156/PD.

The above photo shows the bottom of the case with the gamma and beta shields partially covering the window opening. The window itself has been broken and is not present.

Although the IM-156/PD can respond to alphas, betas and gamma rays, its response is only calibrated for the latter.

With the window uncovered, the instrument would respond to alpha particles, beta particles and gamma rays. With the beta shield (it actually screens out the alpha particles) in place, the instrument responds to betas and gamma rays. With the gamma shield (it actually screens out beta particles) in place, the instrument only responds to gamma rays. 

 

Detector: Ion Chamber, air filled.

Window: 3" x 4 1/2"   1 mg/cm2   (standard Juno specification)

Beta Shield: 50 mg/cm(standard Juno specification)

Gamma Shield:  3/32" aluminum  (standard Juno specification)

Range: 0 50, 0-500, and 0-5000 mR/hr.

Size:  9 3/4 x  5 3/4" x  4" high (not including handle)

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Last updated: 05/10/11
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