alpha-window GM tube, fifty bucks

Huh, cool. So if I buy one and the electronics are flaky can I build my own? (A high voltage, and count pulses? )

George H.

On a sunny day (Fri, 29 Jan 2021 14:00:14 -0800 (PST)) it happened Bill Beaty wrote in :

You could, for only 5 USD, buy a scintillation screen to detect alphas:

I have one (different source) somewhere. No 'tronics no baDteries

Some here could perhaps add a Camera .... ehh, use their [smart??] phone.... cameras get better all the time. app

// LOL

I bought a BGO (bismuth germanate) crystal on eBay last summer. It is 25 x 25 x 10 mm, and probably cost somebody a fortune. These make dandy Gamma detectors. We had a bunch of Silicon photomultipliers at work that we experimented with. I built up a little circuit to amplify and detect the pulses from this. I had to make a boost converter to get the 42 V bias for the photomultipier, and it is not really stable enough, but mostly works.

Jon

On a sunny day (Sat, 30 Jan 2021 10:08:22 -0600) it happened Jon Elson wrote in :

Nice, I tried to buy one of those silli-con multipliers but got 'we do not deliver to your country'. Probably changed now, was years ago. Have several plastic scintillation crystals from ebay, and a NaI(Tl) 30x30 crystal. Using a Russian PMT in my gamma spectrometer:

This one works too, but needs to be assembled some day, now in a cardboard box stored somewhere;

An NE2 neon can be a radiation detector.

There are some windowless photodiodes too, for soft x-rays, maybe energetic particles.

r_2_IMG_4185.JPG

s the 'tronics and 2 AA batteries,

d box stored somewhere;

Hey, anyone wanna make some big bucks?

Rather than basic hobby spectrometers, if anyone were to use these as the b asis of a tiny portable XRF ELEMENTAL ANALYZER, there is a huge market for them, since the current top product is around $20K usd (Thermo Scientific " gamma gun" handheld XRF units.) Or under half that price for various simil ar devices based on Cd or Iodine sources (only good for a year.)

They're very hot sellers for gold analysis (precious metals percentages,) e ven when priced way above $10K. Also for mineral ID of course, or even for detecting Pb paint and Pb water contamination, if one could build a versio n for low enough price. Yes it's fun to have a gamma spectrometer to sepa rate yer Ra226 clock dials and U-daughters fiestawares from yer neutron-act ivated human bones. But instead if we could detect, say, gold fluorescenc e lines, we'd have a simple yes/no Au-detector selling well at maybe $1K. A lot higher price if it can determine the Au percentage versus silver/copp er/nickel in the alloy. And if the price was low enough, then many thousa nds of coil shops, gold sellers, and metal-recycling centers could afford a modern metals-ID device.

Only trouble is, the XRF guns without radioisotopes instead use a little bi tty 30KeV x-ray tube. Not nearly as DOE regulated as a Cd source. But stil l! (Must avoid having the villiagers grabbing their torches and pitchfork s, if they find out that their neighbors are messing with RAY-DE-AATION!!!)

A hobbyist might sell diy XRF projects the in the same way we sell lethal T esla coils and 1-watt laser diodes: simply don't sell a unit with a workin g x-ray generator. The buyer must build the KeV photon source on their own . (re. the simple cold-cathod pulsed-needle X-ray tubes from Golden Engine ering. Use your glassblowing skills and some tungsten parts to make a Nyle Steiner tiny version? Pulse it as we do with N2 TEA lasers, just using a CW stack and a spark gap?)

I have a Niton gun here, heavily damaged inside, shattered window on the P. D., trying to re-build (without schematics from Thermo.) They're not all that complicated, in view of hobbyist spectrometers. ANd quite small, if y ou have a SiPM or even a wide area photodiode. A cheap "high-energy illum ination" device is the real trick. Heh you'd also need a hobbyist software community to develop some code for peak-judging and metals identification.

((((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))))) William J. Beaty Research Engineer wbeaty,uw,edu . . UW Chem Dept, Bagley Hall RM74 billb,eskimo,com . . Box 351700, Seattle, WA 98195-1700 ph x3-6195 . . http//staff.washington.edu/wbeaty/

Need an external quench circuit? Actually that would make a good beginner s diy project, if they needed lots of gm tubes for a big detector-array (as opposed to ion-chambers ...which don't make any headphone clicking.)

Years ago some guy was trying to make a gamma telescope using fluorescent t ubes. Racks of tubes with a big vertical gap, and coincidence detect, like an artificial spark-chamber detector. I don't know if it ever worked. For 3rd-grade science fair, do a cheap DIY version of the Luis Alvarez muon project:

Maybe to avoid fluorescence from x-rays interacting with the window? I've seen pyrolytic graphic windows used (might have less unwanted elements eve n than fused silica.)

On a sunny day (Sat, 30 Jan 2021 22:29:04 -0800 (PST)) it happened Bill Beaty wrote in :

I know nothing about that, but am now reading:

Seems their 'LIBS' system uses a laser to evaporate some material. have it form a plasma, that is then spectroscopely analyzed. I found this paper: AGiakoumakietal_AnBioCh2007.pdf Laser-induced breakdown spectroscopy (LIBS) in archaeological science-applications and prospects. That is a free download that sort of gives an overview, see page 3 and later. It seems to me, from the way they describe it, to have some advantages over XRF. And it does not use Xrays. High power laser modules are cheap on ebay, been a wile since I did do something with spectrographs in uni sort of curious about how they fit that in a small housing, maybe indeed a simple CDD [line?] sensor and prism would work? That would be cool!

A fun circuit (cite Popular Electronics roughly 1960) is a relaxation oscillator with two neons in parallel. One has lower ignition voltage so it blinks. But a small disturbance (ambient light, e-field, radiation) makes the other one start to blink.

Kids who like blinkey things had to do with neons before LEDs were invented.

Hey, pave a surface with neons and fire them with a projected image or an e-field. Neon pixels.

That one is used in a DUV (193 nm) eximer lithography laser system. I have some that work at EUV (13 nm, tin droplet) too. The EUV diodes are a couple hundred dollars each, Hamamatsu I recall.

I amplify them and time stamp the pulses, to help tune the laser systems. They have lots of capacitance so need Hobsonian levels of signal conditioning.

There are a number of patents on the Niton XRF guns. Start with US8982338B2, and look into the patents that it references, and that reference it. Type this into Google Advanced Patents to get a copy.

Joe Gwinn

PS if you wanted to gamble a bit, perhaps get this one:

either that chip has a build in temp sensor, then it needs a new chip or peltier element. or it is just a separate sensor and probably can be fixed for a few $, broken wire or open contact (connector) comes to mind too! For 'tronics 'xperts here, fixing it would be a piece of cak... ehhh mushrooms? eeeh chocolate???? oh well, s*it?? LOL

So 100$ repair and resell for 3000$?

Maybe I should....

That seller has some very cool stuff. They also seem to know what they're selling, which makes me nervous. If it were an easy repair, I have to suspect that the seller could (and would) have fixed it themselves.

-- john, KE5FX

On a sunny day (Mon, 1 Feb 2021 15:41:49 -0800 (PST)) it happened "John Miles, KE5FX" wrote in :

True look at the the picture of the defective sensor, it is in a plastic bag so a bit hard to see, but do I see a flex PCB there? He said It was mechanically damaged, Maybe just a broken track? Somebody here once described a way to fix those.. What was it ? silver glue or something?

Worst case you could order the spare part...

As to seller, not sure he has a workshop.

It is just that I do not really need that thing.... else..

Funnily enough I have one trapped in a 6cm plexiglass square on my desk. I think it was a 2MeV electron beam that did it.

Souvenir made for me from a visit to a largish linear accelerator.

You can do a not bad impression of one by squidging some acrylic paint between two pieces of thick plexiglass and then slowly prizing them apart without sliding. Not as fine as e-beam ones but still pretty.

The kynar thing is a piece of protective tape, to keep the delicate window clean.

Might be expensive repair. Shattered x-ray window (beryllium? carbon?) with defective sensor (photodiode? SiPM?) Also looks like thermocouple is dead, which suggests that maybe even the peltier cooling block is corroded.

But the photodiode gets chilled to -40C by peltier block. If the window over the sensor is shattered, then -40C touches the outside air, and a big wad of frost builds up. Then melts when power is off. Water gets into everything. When chilled again, ice might shatter things. The photodiode may be windowless, so comes in contact long-term with probably dirty water.

Might be weeks of work to repair. Or the entire sensor assy might need replace! Definitely useful as a low-level precision source of 30KV x-rays.

Exactly right. $1200 price is not tempting. Maybe Olympus charges few thousand bucks to repair, and won't provide the exotic window, maybe the actual sensor is a custom photodiode not available anywhere.