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Photomultiplier - Cherenkov detector success! - soldering questions

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ChristofferB:
Just found the perfect shielding for the pins/divider - the inner tube of a stainless thermos! There is even room for ~4mm foam padding around the tube!

I'll need to cut out a 40ish mm hole in the bottom for HV and SIG connectors, then bolt it on the back but I think this is pretty much ideal!

--Chris

Kleinstein:
Stainless steel does not provide a lot of magnetic shielding. So I would prefer normal steel.

For optical coupling I would start with something that is easy to remove, so more like silicone grease, Vaseline or just a plastic foil as a cushion.

ChristofferB:
This is not meant as magnetic shielding, this is just to hold / protect the electronics/user. A magnetic shield could be slid on top. My machining/fabricating capabilities arent the greatest so a favourable shape material to start out with is pretty important.

I think I will go with cling film as a cushion at the very beginning, just to verify that the tube actually works!

jmelson:

--- Quote from: ChristofferB on February 08, 2020, 10:29:56 pm ---The problem with negative HV is that anything earthed or conductive MUST be kept physically away from the tube, especially the window. Since scintillation crystals usually come in aluminum cans this is impractical for these.

--- End quote ---
Well, actually, this is VERY rarely any problem.  The window is not a problem, anything that is transparent to light is likely to be non-conductive, too.
Generally, the sides of the tube are not much affected by external fields, and usually PMTs are placed in Mu-Metal shields to exclude magnetic fields which can affect the electron paths.

I MUCH prefer the negative HV method for safety reasons.  Also, the 3 KV or whatever caps are somewhat difficult to find.

Jon

jmelson:

--- Quote from: Kleinstein on February 09, 2020, 10:17:35 am ---Some magnetic shielding of the PMT may be a good idea, but it depends on the tube. I got away without any magnetic shield.  I don't think one would really need Mu-metal. Something like transformer steel should be good enough for most cases. A little fixed residual field should not be a problem.

--- End quote ---
Transformer steel would be bad, as all soft iron is very susceptible to aquiring a permanent magnetization.  Mu Metal is good in that it is much less
susceptible to getting magnetized.

Jon

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