Alpha-particle spark detector

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Doug Coulter
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Re: Alpha-particle spark detector

Post by Doug Coulter » Thu May 26, 2011 7:05 pm

Thanks for the link! I was checking to see if I was in any of those pix myself. At the time I was being allowed to do the presentation for Melpar's speech synthesizer/vocoder nearby so the booth babe could take a break (I was a kid then, but my Dad was the project manager, so they cut me some slack -- and I knew more than the babe anyway). Did you see the (Swiss? Nordic at any rate) electrostatic/HV displays too? They were killer-cool E-Motors and they ran them up to sparking to make them look cooler yet.

Yeah, I'm in about the same state, pile of parts and no spare time...rats. But I suppose we're getting a little off topic here, oops.
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Winston
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Re: Alpha-particle spark detector

Post by Winston » Mon Jul 04, 2011 3:26 pm

Unfortunately, the link to http://jamsci.org that was referenced in the older thread you linked to seems to be dead. Anyone have a copy of the the construction details, testing, diagram and references that were available at that site?

Carl Willis wrote:
> I recently completed a wire spark detector for alpha particles, following the technique of Tim Raney. Thanks to him for sharing many of his design notes and experiences. An early thread of his here on the forums mentions spark counters, but I think the details and wonderful results of his work are known only to those of us who have been privileged to observe them at Richard Hull's HEAS meetups.
>
> viewtopic.php?f=13&t=5494#p33938
>
> My interest in this simple open-air counter--a close relative of the Geiger "point counter"--was spurred recently by the need for additional hands-on activities for a program on lightning I presented for the local public television station. I put my device together from metal and plastic scraps on hand and a bit of tungsten wire from eBay. My audience yesterday seemed fascinated with it (and nobody got shocked). To appreciate these things, they really have to be experienced in person. The next best thing is a video (see the description for further details on construction and operation):
>
> http://www.youtube.com/watch?v=-8GlzUjYazs
>
> The attached photos show the vigorous reaction to 5-mCi Po-210 and ~10-uCi Ra-226 sources, respectively.
>
> -Carl

Joe Jarski
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Re: Alpha-particle spark detector

Post by Joe Jarski » Sun Feb 26, 2012 2:18 am

I thought this was a cool piece for demonstrations when Carl originally posted it and finally got around to building my own.

Wire size and spacing is the same as what Carl used. I have 8 wires on mine and the HV supply (~5kV) is mounted in the box to the bottom of the FR4 and I use a wall wart for power.
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Carl Willis
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Re: Alpha-particle spark detector

Post by Carl Willis » Sun Feb 26, 2012 8:22 am

Hi Joe,

Nice craftsmanship. Is it working properly for you? One important trick is getting the right load resistance between the power supply and the spark detector. I use a 10M Caddock HV resistor for this function.

-Carl
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Joe Jarski
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Re: Alpha-particle spark detector

Post by Joe Jarski » Sun Feb 26, 2012 4:43 pm

Hi Carl,
Thanks for the compliment! It seems to work well. The sensitivity appears to be about the same as yours, as best as I can judge from your video. I'm using a 50M resistor that's similar to Caddock's. The sparks may be somewhat on the weak side - they're a little difficult to see in a sunlit room, but I'm happy with the way it works. Here's an action shot (I don't have the "super" alpha sources that you have)...
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Carl Willis
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Re: Alpha-particle spark detector

Post by Carl Willis » Sun Feb 26, 2012 5:14 pm

Nice operation, Joe. Is your 5-kV supply a commercial item? I like the compactness you've managed to achieve and might like to make mine a bit smaller too.

-Carl
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Joe Jarski
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Re: Alpha-particle spark detector

Post by Joe Jarski » Sun Feb 26, 2012 7:01 pm

Carl, My HV supply is built on some generic boards that I had made. They use a CCFL inverter for the HV and can be stuffed for a one or two stage multiplier and either polarity. I keep several on hand and built them up as needed for GM tubes and neutron detectors. The 5kV is about the limit for these particular boards and inverter. I'm getting some others for another project that'll go up to 10kV.

This is what the inside looks like. The PS is kind of ugly because of the 50M resistor placement and the HV section having a coating slopped on it. I didn't intend to use these boards at 5kV so the big resistor is hooked in there kinda funny because of the size. If you want a PCB or bag of parts for the PS, let me know.
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Steven Sesselmann
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Re: Alpha-particle spark detector

Post by Steven Sesselmann » Sun Feb 26, 2012 8:13 pm

Joe,

Compliments, a very neat project...

Steven
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jcs78227
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Re: Alpha-particle spark detector

Post by jcs78227 » Mon Feb 27, 2012 3:39 am

Joe,

I have to echo some other's observations: you did an excellent job. If I didn't know better, I'd swear you bought it.

I've had a roll of tungsten wire sitting around since seeing Carl's build last year and still haven't put together the PS yet. For sure, it will look nowhere near as good as yours. That's slick!

-Jonathan

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Carl Willis
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Re: Alpha-particle spark detector

Post by Carl Willis » Mon Feb 27, 2012 5:51 am

Hi Joe,

I like your little board. It will fit conveniently in the plastic base of my detector, according to my best abilities to size it up in the photo. I'll contact you off-list about getting a parts kit. What's the circuit over to the right of the inverter? Is that an input voltage regulator?

Thanks,
Carl
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