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The tiniest of detectors

Posted: Fri Apr 10, 2015 4:11 am
by jaaz95
Hello all. Been a few years.
I'm working with a group and we're hoping to create the smallest radiation detector we possible can. I thought who better to ask than the fusion boards.

The requirments are thus:
must run on a small watch battery that can be recharged
must be no thicker than a quarter inch but ideally far smaller
must detect the widest range of particles possible
cannot give off any ionizing radiation in an of itself, only detect it.
Output doesn't need to be to anything more than relative. think blinking LED maybe 2 or three to give some idea of scale (1x 10 x etc.)

we were thinking of using a layered chunk of bc408 and bc412 with a photodiode as the detector. boost and filter the signal.


Re: The tiniest of detectors

Posted: Fri Apr 10, 2015 5:16 am
by Richard Hull
There is alaready an app for a smart phone, and that kind of thing that uses it's camera chip as the detector. I have a friend who showed it to me at an ANS meeting earlier this year. It give direct gamma readings and doses on screen. Not a pro instrument at all but it works provided you have a warm enough source. He used a 5uCi CS137 calibration disc as his source.

Such a tiny sensor as the camera chip or a thin sanwich wafer of scintillator will never be of much value beyond letting you know you are in a very dangerous field. I doubt a common photo diode would be sensitive to stock BC material scintillation.

Richard Hull

Re: The tiniest of detectors

Posted: Fri Apr 10, 2015 5:36 am
by jaaz95
As I mentioned it doesn't need to be professional. More of an indication of radiation more than anything. Something to let you know if theres a sudden spike or you're near something really warm. Ideally this needs a far smaller footprint than a phone. Think size of a quarter ideally.

Re: The tiniest of detectors

Posted: Fri Apr 10, 2015 10:32 am
by John Futter
small thin detectors can miss high energy sources as they do not have the stopping power. Even sodium iodide has problems and huge lumps of this is required for energetic photons ie 4 to 6 inches long
Solid stae detectors miss the high 100's keV upwards and these suckers are the most dangerous plenty of penetration and hard to shield against.Silicon based detectors have run their course by about 50keV.
This is why exotic materials such as CZT have been developed but these are useless after about 150keV

Why not use the humble geiger tube it still senses the higher energy photons albeit with reduced sensitivity.

Re: The tiniest of detectors

Posted: Fri Apr 10, 2015 4:33 pm
by jaaz95
The reason it needs to be small is because it is potentially being inserted into a bioproof container and implanted into a person. It wasn't my idea, im simply asking for the guy who thought it'd be cool. He wants a tiny geiger counter he can implant into himself. So I'm looking into how it could be done properly such that it's small and comfortable for him and will still provide some amount of interesting data. If a geiger tube comes in a small enough size then sure but you'd need a tiny one. I suggested the size of a quarter to make implanting it easier but i've seen implants that are far larger. I like solid state since it at least in my head seemed like the smaller option, even if it's missing some of the higher energy particles. SO I guess it's probably best then to make it pick up the most common energy levels from fairly sources rather than all levels from more exotic sources. Since it's implanted I will advise the guy from going anywhere near super hot sources anyway.

Re: The tiniest of detectors

Posted: Fri Apr 10, 2015 5:06 pm
by JakeJHecla
While I realize you're not looking for a high-sensitivity detector, a great option for your purposes would be a SiPM based scintillation detector. I built a simple one based around a 3x3mm active-area B-series unit from SensL and a 4x4x15mm LYSO(Ce) crystal. They require minimal processing electronics, and give reasonably good sensitivity and energy resolution for their size. Below is a plot of a spectrum taken with the detector:

LYSO crystal on detector
Spectrum from 1uCi Cs-137 source at 10cm. ~10% FWHM

Re: The tiniest of detectors

Posted: Fri Apr 10, 2015 5:08 pm
by jaaz95
That is perfect honestly! I've passed it along to the biohacker guys to see what they think but that really does seem like the perfect size. And seemingly it has fairly good resolution for something so tiny.