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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
1. you can check for leakage qualitatively with a Geiger counter.
2. Is the issue just slight non-flatness of the cover plate or the area it overlaps?
If you take the cutout from 5x5 hole, and attach that to bottom of the 7x7 cover, you will block the geometric line of sight even without pressing things flat.
How 'bout overlapping and/or filling the gaps with flexible magnet sheets. The stuff used to make business cards that stick on refrigerators, and signs that stick on doors of trucks. I'm sure it contains enough iron to significantly attenuate soft x-rays, especially oblique or parallel to the sheet.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I'd go with Klugesmiths's suggestion, and cut out a 5X5 square and fix it to the 7X7 square. That should block all radiation.
Lead wool is far less dense than either lead or steel, and can't be relied upon to block radiation.
EDIT: Even better would be a lead cover. Cut a 7X7 piece of lead sheet and a 5X5 lead sheet, fix them together, and it will still be flexible enough to press to fit the contours of the steel box. Job done.
Registered Member #3637
Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
Lead handling is going to be the least of your worries if you don't get enough shielding in there. And really, just wash your hands after you handle lead. It's not as toxic as most people make it out to be, you don't instantly get lead poisoning after touching it.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Well, if the lead wool is rolled up tightly it will be pretty dense, but then you may as well just use lead sheet.
I assumed the lead wool wouldn't be very dense in a silicone matrix, so that it would be more flexible. The silicone won't offer much resistance to 30kV X-rays.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Hi there Russkie,
x-ray reflection occurs mostly at 'glancing' angles < 2° so possible leakage channels at these angles should be taken care of.
Beam quality: If you are confident that 30 kV /1mA is the maximum anode voltage and current, then the effective energy of the output will be ~ 10 keV of low fluence, and easily stopped. The amount of radiation actually emitted at 30 keV will be less than 1 % of the total flux.
There is no reason not to use steel shielding at these energies and fluences. 3.5 mm steel will reduce such radiation outside the shield to lower than background, and for ordinary purposes, it will be undetectable.
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