Re: [TCML] ion chamber use near Tesla coils?

[Michael Baumann <baumann@xxxxxxxxxxxxx>]

I'm curious about your ion chambers -  it just so happens I use those
regularly in my job. And I'll try and answer your questions about TC effects
on them, but that's a different issue.
First the answers: Don't even remotely consider trying to get reasonable
reading from your non-shielded chamber, without providing your own
shielding.  I'm assuming what you have are parallel plate chambers. The RF
field from the coil will play havoc with the measurements. Depending on your
bias voltages, and the construction of the chamber, you may still have some
issues due to charging of the chamber, cables from the HV and  signal lines.
 Assuming the chamber you are using does not operate in multiplication mode
(gieger/mueller tubes do) you may not have enough intensity from the tubes
to indicate. Especially since the shielding will attenuate the intensity.

So far as your dosimeter - I'd be a little concerned about the electrostatic
charging effects of the coil. Most pen type dosimeters measure the discharge
of the stored voltage.

I'm assuming you got your chambers as surplus? I'd be curious about from
where - I have some experiments I want to try that my employer doesn't think
worthy enough of funding. So I do my stuff in parallel with the "sanctioned"
work. But since I am also working on a shoestring then - cheap supplies
sound interesting.

In my work, we have some extremely sensitive chambers we are working with -
that have to be extensively shielded. Even with the shielding, when we are
directing the beam into another room, we have elevated background, despite
5-14 ft of concrete shielding around the test chamber. but then we are
measuring nanoamp currents. We also use film badges for all staff.

On Sat, Aug 29, 2009 at 5:46 AM, Jon Iverson <ji425bt@xxxxxxxxxxx> wrote:

> I recently acquired a couple of ion chambers for monitoring possible x-rays
> produced when vacuum tubes are operated on or near a Tesla coil.  One
> chamber is RF shielded, the other not and digital (but more sensitive than
> the RF one).  My coil is a small one, 100 KV maximum output.  How are RF/
> non-RF ion chambers affected by Tesla fields when testing vacuum tubes and
> what is the best placement for each device?  Also, I also wear a conductive
> plastic 200 mR pen dosimeter- can it also be affected by Tesla coil output
> say at 3-6 foot distance?
>
> Thanks in advance,
> Jon
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