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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
radhoo wrote ...
I don't think the parabolic path of the bremmstrahlung is what I've photographed
There is no parabolic path of bremmstrahlung.
The graphical curves are a way of illustrating the ratio of X-ray photons departing at any particular angle relative to the incident electron beam.
The lower the energy of the electrons, the more the X-ray photons tend towards an isotropic distribution - i.e. go in all directions of a sphere. The higher the energy, the more the photons will tend to continue in the same direction as the incident electrons.
At the relatively low energy levels of these experiments - between about 15keV - 40keV - there will be considerable photon emission at all angles related to the incident electron beam.
A Google search for "Bremsstrahlung angular distribution" will lead you to more detailed explanations of this phenomenon.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699
Thanks for the clarification. So this means I might see changes in the fluorescent band as recorded here... ...if I vary the voltage across the tube. With my current setup I should be able to go from 10KV to 70KV (with more stress on the components).
As a remark to , the fluorescent screen shows a more illuminated area to the left and some shadows in the right part. If the shield is the target, this might be related to the angle the shield is placed at (not perfectly parallel to the base, and so not parallel to the fluorescent screen)
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
radhoo wrote ...
Thanks for the clarification. So this means I might see changes in the fluorescent band as recorded here... ...if I vary the voltage across the tube. With my current setup I should be able to go from 10KV to 70KV (with more stress on the components).
As a remark to , the fluorescent screen shows a more illuminated area to the left and some shadows in the right part. If the shield is the target, this might be related to the angle the shield is placed at (not perfectly parallel to the base, and so not parallel to the fluorescent screen)
By George, he's got it!
Now as for your fluorescent bands, as you say, Radu, we may see a redistribution of the light intensity as you vary the tube voltage but the tube geometry, the non-linear energy response of both the phosphors and the human eye, the filtration of the rays by the glass envelope, etc, may make the effect hard to see across our voltage range.
So - when it comes to your turn to explain the angular distribution of bremmstrahlung, you only need mention the Koch and Motz bremsstrahlung double differential cross-section to see people's eyes glaze over, and bring the conversation to a speedy end!
I'm just getting the Sunday roast into the oven now, but hope that I might have some preliminary results tonight, if I'm quick, or by tomorrow anyway.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699
Anders M. wrote ...
Don't give up on the 2X2s though, there a lot of good science being done in this thread.
I won't. As per the thread's title, I still need to come with a final enclosure/setup for the tube, easy to deploy and use. Eirik might finish his first, maybe he'll post some pictures here later.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Is it a samovar? Is it a funeral urn for Chernobyl victims?
Just when I thought I'd be getting round to making some measurements, various shortfalls in the shielding regime became apparent, so I ended up spending my spare time making this:
2X2A Project: Baseplate and Shielding Assembly
I riveted 1.8mm lead sheet onto a length of 20cm dia. MDPE sewage pipe, which wasn't easy to cut square. The Pb joint is lapped together, and further sealed with self-adhesive Pb tape. The thick dielectric lining will hopefully reduce the incidence of unwelcome streamers trying to find a weakness in the EHT insulation.
Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
Steve McConner wrote ...
Excellent pics, Les! This has been the most interesting thread in a long time. I can recommend the X-Ray Studies book, that's where I read about the pinhole camera technique.
Thanks, I will check that out!
For those interested in the pics of the pinhole camera (its really not that exciting to look at though):
Above is the lead cone that fits onto the intensifier assembly.
The tip of the cone is truncated to mount the pinhole. The pinhole is made from a thinner piece of lead, and is simply taped in place.
The intensified fluoroscope is a Mullard (now Phillips) XX1332, with Gd2O2S:Tb scintillator bonded to its large 50mm diameter faceplate.
The cone sits neatly on the front. I still need to make a suitable mount for it, so I can set it up on a tripod for long exposures, I expect I will have some more pinhole pics by the end of the week.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699
Proud Mary wrote ...
I riveted 1.8mm lead sheet onto a length of 20cm dia. MDPE sewage pipe, which wasn't easy to cut square. The Pb joint is lapped together, and further sealed with self-adhesive Pb tape. The thick dielectric lining will hopefully reduce the incidence of unwelcome streamers trying to find a weakness in the EHT insulation.
No need for gym when you move that thing around the house. Very nice setup!
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
radhoo wrote ...
Proud Mary wrote ...
I riveted 1.8mm lead sheet onto a length of 20cm dia. MDPE sewage pipe, which wasn't easy to cut square. The Pb joint is lapped together, and further sealed with self-adhesive Pb tape. The thick dielectric lining will hopefully reduce the incidence of unwelcome streamers trying to find a weakness in the EHT insulation.
No need for gym when you move that thing around the house. Very nice setup!
You know me by now, Radu - even the smallest indication above background outside the shield and I'll worry away at it and won't proceed further until the leak is stopped. Cable glands need special thought.
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Vacuum Rectifiers X-rays report
