Alpha sources

[segelfam]

Hi,
today I got the static master I ordered at Ebay one week ago. The device is unused but old, the ionisator should have been replaced in april 2010. I don't know how many halflifes have gone, but it was rather cheap (~ 13 US$).
I placed a small piece of the strip in my cloud chamber to compare with a smoke detector am241 source and a source with a tiny piece of radium dial paint save from a WW2 airplane clock.
http://www.rapp-instruments.de/temp/polonium.jpg
http://www.rapp-instruments.de/temp/americium.jpg
http://www.rapp-instruments.de/temp/radium.jpg
It looks like the activity of the static master has gone it is now even less than the 30 kBeq of the smoke detector. Still lower is the activity of the dial paint but it shows long range, high energy alphas, and from time to time a very long range tiny electron track
http://www.rapp-instruments.de/temp/electron.jpg
So older static masters maybe to weak for neutron experiments but nice for testing all kinds of radiation detectors

Thomas

[Doug Coulter]

Nice pics! We think we've figured out that the code date on these is about two half lives from new, for what it's worth. The ones we just got (new, theoretically) are about 1 half life old, and give some 10's of thousands of cpm each on a pancake geiger counter here. They make some neutrons with the Be foil we use, not a ton, but enough to put bubbles into a BTI bubble detector or count a 3He tube.

Looks like the thing to do with these is stay in touch with the vendor and get them before they've sat on the shelf for long. I'm supposing one could put a source on each side of the same Be foil to get a few more neutrons output, and more isotropically to boot -- the sources are a nice form factor to do that with, just thin layer over some Al foil stuck to the thing with double-sided tape.

You can upload pictures directly to this board and they'll stick around -- look at the upload attachment -- once added, they can be placed inline where-ever you want them in your text. That way, our host provides the long term storage -- and we have "unlimited" if we don't abuse it too badly (think of others who may not have high speed internet, mainly).

[segelfam]

Hi Dough,
like You proposed I use the two strips of the static master on both sides of the Be folie and wrapped the whole in a thin PTFE folie to held it together. After about 200 shots I didn't see any evidence of neutrons.
I also used a simple sandwich and bent away a small part of the active surface. Here the alphas a readly seen but nothing hidden by a neutron
But I don't wonder about because the chamber I use is a Wilson chamber which has a sensitive of about 0.2 seconds and a repetion rate of about 2 minutes, so the active time is short. I have to do much more shoots. I also have a longtime sensitive diffusion chamber, perhaps I should make a try with this device, although it's less sensitive than the Wilson chamber

Thomas

[Doug Coulter]

Here we can see counts on neutron-only detectors, but even a very thin amount of anything moderating them for our fast neutron detectors based on proton recoil kills that, for example with the BTI dosimeters (which get about 25 bubbles overnight at a sensitivity of 33 bubbles per millirem) or our plastic scintillators. Of course, using a 3He or BF3 tube, you still use the moderator.

Could it be that a cloud chamber just isn't dense enough with protons to see small amounts of neutrons reliably (or easily as you say -- more shots may tell)?
These never impressed me with being especially hot sources, but are enough to get us out of background for neutron detector tests. Even a poorly operating fusor makes tons more neutrons.
But a fusor also makes everything else, from Gammas to EMI, so we liked these as first tests for sensitive detectors.

[segelfam]

Of course the cross section of the atmosphere, mostly air, in the chamber is low. Perhaps I should make a try with some other gas, perhaps even deuterium, if I'm realy shure that there are no leaks in the chamber.
But for the next I will buy a power supply for my nikon kamera (I can't build it myself because the camera has a very strange conector) so I can run the chamber for some longer time. Because the chamber and the camera are controlled by a PIC processor I can run it for some days and make some thousand shots if I use a external power supply for the camera until the sd-card is full.

Thomas