[ RadSafe ] University of Michigan News Service...

Masi, Daniel (DESS) daniel.masi at smithsdetection.com
Fri Mar 14 12:28:49 CDT 2014

It's a system that uses CZT semiconductor detectors, and a considerable volume of them... two planes, with an array of 9 20x20x15mm detectors forming each plane.  Not exactly "pocket", as the detector box itself is a good 9 pounds or so I think.  Early prototypes I saw were about the form factor of a toaster oven with a handle.  And it's $100k.

Native resolution of the detectors is likely in the 1-2% FWHM range @662keV, but there's a question of how drift, thermal noise, and detector-to-detector calibration is achieved.

In terms of imaging, it operates via Compton scatter backprojection.  If a photon Compton-scatters in the front detector array and further interacts in the rear array, based on some assumptions about incident energy and the scatter angle between the two planes, you can form a "cone of direction" for the incident photon.  Overlay enough of them and you build statistics for the source direction (or multiple sources, if you separate them out by measured incident energy).

Efficiency is one of the tough nuts here, as you can only count events that multiple-scatter in your detectors.  There's also a sweet spot for what radionuclides this technique is most effective with; lower-energy gammas won't work because they will mostly do full-energy deposits in the front plane and not scatter, and high-energy gammas have both the issue of reduced interaction probability plus the fact that the second-plane interaction may also be a Compton scatter, carrying energy out of the detector after two scatters and thus making the energy assumption wrong for the incoming photon, which will blur your direction statistics.

This is all armchair-stuff on my part so take with a grain of salt.  Cool technology to be sure...

Dan Masi

Message: 1
Date: Thu, 13 Mar 2014 10:20:21 -0700
From: Ted de Castro <tdc at xrayted.com>
Subject: [ RadSafe ] University of Michigan News Service |
	Revolutionary nuclear radiation detector hits the market
To: 'Radsafe' <radsafe at health.phys.iit.edu>
Message-ID: <5321E8D5.9060307 at xrayted.com>
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Supposedly "A handheld radiation camera":

Has anyone seen one of these work??

It seems the source SHOULD be credible but I can think of so many reasons it just cannot work!!  I mean a pocket pho gam camera???? really????

Even if it did - it would most certainly only be for VERY high fields/sources - certainly not the kind of thing "if formerly took weeks to find" as they allege.

AND certainly not applicable to Fukushima as they imply at least not outside the plant itself.

IF in fact this IS true - it certainly is interesting.

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