Interesting DIY cosmic tube

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billwcf
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Interesting DIY cosmic tube

Post by billwcf » Tue Sep 22, 2009 2:04 am

Hi, Seeing the post about the silver covered geiger tube made me remember this link about a copper covered fluorescent counter tube. Not really related to neutron detection as such, but a novel idea I thought. -bill

http://hardhack.org.au/cosmic_ray_detector_2

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Carl Willis
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Re: Interesting DIY cosmic tube

Post by Carl Willis » Tue Sep 22, 2009 8:09 am

Hi Bill,

Nice find. Certainly a budget winner if it works. One big disadvantage would seem to be that the fluorescent tubes have no quenchant in the gas. They also don't have very much gas for low-LET or indirectly-ionizing particles to interact with. Since there are no closely-spaced or thin or sharp electrodes that produce concentrated fields, getting to the Geiger plateau on such a thing might be impossible.

Another budget option that I recall seeing sometime was the Geiger "point counter": a fine ball-tipped thin anode is brought near a grounded aperture, the whole thing open to air. Particles are detected when they pass through the aperture and ionize the air in the strong fields around the anode tip. The sensitive volume is tiny, but I'm sure it's a viable approach to some rudimentary particle-detection capability if the budget is tight.

-Carl
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Re: Interesting DIY cosmic tube

Post by billwcf » Tue Sep 22, 2009 2:39 pm

Carl, Hi. Yeah I was just impressed about how low-budget it is and how easy the parts would be to obtain. A perfect science fair project for someone. See you @ HEAS. -bill

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Re: Interesting DIY cosmic tube

Post by hardhack » Wed Sep 23, 2009 1:42 am

Yes your right, the florescent tube detector is not very suitable for radiation detection particularly low energy or alpha radiation, for the reasons you describe. Also it is still very much a work in progress and I'm currently working on some other electronic quenching circuit. Which is yet to be written up to my website.

It is in essence the florescent tube detector is a quirky Spark Chamber which is triggered by an unstable relaxation oscillator. It requires careful adjustment of the voltage so that the voltage is set just before the tube goes into free oscillation.

Its like a kind of Regenerative Radio for muons

In this unstable state it generates random pulses and when exposed to penetrating ionising radiation like eg xrays or gamma rays the pulse rate increases. However, it is very unstable and results vary greatly with temperature and the type/brand/wattage tube used.

I have been experimenting with arrays of actual Geiger tubes, but the aim in the florescent tube project is to develop a very low cost muon detector with a large surface area.

Regards

Robert
http://www.hardhack.org.au

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Doug Coulter
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Re: Interesting DIY cosmic tube

Post by Doug Coulter » Fri Sep 25, 2009 3:41 pm

I'll suggest an even cheaper and lower tech cosmic detector I've made and tested here.
One thing to remember -- cosmics are LOUD. We're trying to detect hand grenades, not
the noise of a gnat fart here.

What I did was so simple it's ridiculous, but it worked quite well. I took two sheets of
common sheet metal (not galvanized, and they were a little rusty) and spaced them with
some 3/6" OD soda lime glass tubing from my chemistry supplies. I grounded the bottom one,
and put around +1200v on the top one through a 1 meg or so resistor, and coupled from
there to a scope probe with a 47 pf capacitor. I got pulses of several volts at the right
rate to have been cosmic rays though I didn't do a co-incidence test with a "real" detector
to prove what it was. It sure looked right, and was numb to the normal lab radiation
sources I tested. The interplate capacity and the resistor set the time
constant at some microseconds, fast enough for what I was looking at then. I was using
about a square foot of metal plates, and held it together with one rubber band, and good
old gravity. I'd planned to use these as a trigger for a spark chamber I never got
around to building -- fusors were more fun. I may build another large area one though,
to veto counts from my fusor detectors when they are cosmic ray induced.

Yes, air at STP will work. Fluorescent light tubes (which BTW, DO have a quenchant-like
mix, though not for that reason), and a ton of other things work. Procedures in experimental
Physics shows some nice ones made of big honking pieces of pipe, with big glass bowls
used as endcaps and feedthough, and that works too. Proceedures mentions the
difference between fast (quenched) and slow counters as well -- slow ones DO work,
they're just, um, slow, and need real big series R to not go into arc/relaxation mode, as in
10 megs and more. I believe that source even mentions R's in the gig region.

This is so way not-hard it's silly. You don't need the finest large-diaphragm electrostatic pattern controlled microphone with corrected transient response at a Ghz data aquisition system to just tell if a grenade went off...And that would only work the one time anyway.
All you need is a pretty numb shrapnel detector.
Why guess when you can know? Measure!

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Doug Coulter
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Re: Interesting DIY cosmic tube

Post by Doug Coulter » Fri Sep 25, 2009 6:03 pm

Do you know what kind of scintillator it is? I could use some if it's a good type for
something I am interested in, and I'd be interested in a largish piece.
Why guess when you can know? Measure!

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Re: Interesting DIY cosmic tube

Post by hardhack » Sat Sep 26, 2009 2:15 am

It seems there "could be" a number of easy ways to detect cosmic rays. The problem is having some valid way to confirm that what is actually being detected is a cosmic ray (muon) and some other effect like coronal discharge, RFI etc.

Consequently, I've been tinkering with a few configurations of Geiger Muller Tube arrays,
http://www.hardhack.org.au/geiger_muller_detector

Unfortunately even these tend to have a number of false detections. Currently, I'm trying to source some PMT and Scintillators, to use as a reference to test the validity of other types of detectors including Fluorescent tubes, ion chambers, resistance plates, etc etc.

Robert

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Re: Interesting DIY cosmic tube

Post by science fair » Thu Dec 03, 2009 5:17 pm

My name is Oluwamide. l am a sophomore in highschool, and I'm really interested in using this approach as a an unsual way to measure cosmic rays. I want to use the project for the Chicago Science Fair, but I dont quite understand everything. Can you please e-mail me back with an elaborate explanation in layman's terms? (E-mail: MILE1994@gmail.com) I also wanted to know where I can get the materials, and exactly what materials I need. Im working with siome sponsors at Northeastern University, so some of the supplies are taken care of. Please e-mail me, anyone (If you can explain what's going on and help me reproduce it).

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Carl Willis
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Re: Interesting DIY cosmic tube

Post by Carl Willis » Thu Dec 03, 2009 6:43 pm

Olu,

Did you follow the link to Robert's website and spend some time reading it? It probably offers what is as close as you're going to get to an "elaborate explanation in layman's terms".

A basic conceptual understanding falls short of a working technical understanding, and so a few household analogies pitched at the "layman's" level of interest and comprehension won't cut it for you. There are prerequisite physics concepts to be familiar with, and the pragmatic wherewithal that is needed to engineer circuits, locate parts, and realize the project must largely be developed through personal experience. I'd recommend that if you are a complete novice, you look up a project design for a Geiger counter and build that first. You'll learn a lot in the process, after which a muon detector like Robert's experimental scheme will make more sense and will be far more approachable.

-Carl
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Re: Interesting DIY cosmic tube

Post by hardhack » Sat Dec 05, 2009 9:41 pm

Just a note to say I have started work on a Scintillator PHT detector http://www.hardhack.org.au/scintillator_detector

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