Semiconductor Survey Meters

[glhansen]

I was just reading about deadtime (here, in case anyone is interested [broken link removed - Steven] and, when reading about semiconductors, suddenly wondered if there are survey meters, the kind typically used for radiation safety purposes or contamination checking, that use semiconductor probes instead of GM tubes. Or a semiconductor probe that could just be attached to a Ludlum 3 or something. Seems like there might at least be an advantage in comparison with a gas ion chamber since semiconductors have higher densities than even a pressurized gas. But I just suddenly liked the idea of buying a semiconductor probe to plug into one of our units.

[Sesselmann]

Greg,

I see no one has yet replied to your post. Unfortunately I can't be of much help as I haven't done much work with semiconductor detectors and SIPM's but it's on my list of things to do.

Semiconductors operate with a very different voltage and amplifier scheme and as far as I know there aren't any probes compatible with the old survey meters, but that doesn't mean it can't be done.

SIPM's are still fairly expensive compared to PMT's which I think is is a barrier for mass adoption of these devices, but watch this space it will happen.

Steven

[glhansen]

Thanks, Sesselman. I've seen semiconductor detectors in stationary science applications, like inside cryostats on beamlines. So totally different kind of application. It just tickled my fancy, and I thought I could see potentially an actual advantage over a gas ion chamber. But if they're not around, then I guess there's not much to say about them.

[sgt_bear]

My guess is that most modern manufactured Personal Radiation Detectors use SIPM Technology, especially those with Spectroscopic functions. But since these devices are usually sold to a limited market there is not much information about the interior of these devices.

One issue about SIPM is their temperature dependence, you have to either adjust the bias voltage or adjust the spectrum data to the current temperature.
I don't think the price is the problem here alone, it's the crystal size. You can easily read out a 3" Crystal with one PMT (1 Signal output), but with SIPM's you would need a cluster/array with probably multiple singal outs.

[glhansen]

I actually did come across a survey meter with semiconductor detectors: the Fluke RaySafe 452, $4290.
https://www.flukebiomedical.com/resourc ... w-approach
It says "The RaySafe 452 takes a different approach and seamlessly combines several measurement technologies in one instrument: Semiconductor diodes, scintillators, and a GM pancake", and then the article goes on to talk about the GM and the diodes but doesn't mention the scintillator again. It says the GM is used at low rates and the diodes at high rates -- maybe GM tubes remain popular because they're just more sensitive.

Looks like an interesting device, except that Fluke is expensive, has a long turnaround time, and every time I've dealt with them has been distasteful. I wouldn't want a unit that only they could calibrate.

[jneilson]

I have heard of a few places making semiconductor probes, especially with CZT. A few quick examples pulled from Google:

https://advatech-uk.co.uk/radiation_czt.html
[broken link removed - Steven]
[broken link removed - Steven]

I'm not certain exactly what the compatibility is like with conventional survey/ratemeter hardware, but it sounds like some of them may include some preamplifier electronics on-board which might open up compatibility with some systems.

It also sounds like there might be some confusion between SiPMs and true semiconductor detectors here. SiPMs (Silicon PhotoMultipliers) are semiconductor based, but achieve basically the same result as a PMT, and thus need to be paired with a scintillator for radiation detection purposes. A true semiconductor detector works quite differently, detecting directly in the semiconductor crystal (essentially radiation induced current in a reverse biased diode junction).

My guess is that most modern manufactured Personal Radiation Detectors use SIPM Technology, especially those with Spectroscopic functions.

I think things like the Radiacode are CsI scintillators and yes, presumably coupled to a SiPM; but I think a lot of the other manufactured devices that do dose rates just use PIN diodes; especially the EPD type devices (Electronic Personal Dosimeters), although I have heard of EPDs with a tiny scintillator for correcting for energy differences to produce an energy compensated dose.

PRDs is also a market where CZT semiconductors are also appearing now too.