PMT Shielding Questions

[Tom Dressel]

Well, I got the EMI 9856 today, so it is time to think about putting this thing together. I know it needs light, magnetic, and electronic shielding. I have seen Richard Hull's vidio featuring the exact same PMT that I have using mu metal and copper foil shielding.

I have the necessary power supplies (0-10 KV, +15 V and -15 V), high voltage and BNC connectors and NIM components, so all that is left is the PMT enclosure and the appropriate scintillation plastic.

Could some one comment on enclosures in general and possible enclosure materials (mu metal, aluminun, copper) Is it possible to make an enclosure out of PVC pipe? How about sources for mu metal cans or foil, copper foil etc.

Tom Dressel

[guest]

Mc Master Carr, has mu metal foil for magnetic shielding, though it is a bit pricey. I would opt for ss pipe for the enclosure if you can find a piece big enough. You will get some shielding, and according to Knoll, the residual radioactivity is lower than for aluminum. Copper would be a good second. You'd want to put the lead on the outside of the copper/ss pipe.

[guest]

I could be wrong on this but I think mu metal has to be annealed or heat treated or something after it has been worked, most shields I have seen have a sticker warning about bending or denting the shield. A dead CRO would be a good source of it in sheet form from around the cathode ray tube.

regards
Mark Harriss
Thomas Dressel wrote:
> Well, I got the EMI 9856 today, so it is time to think about putting this thing together. I know it needs light, magnetic, and electronic shielding. I have seen Richard Hull's vidio featuring the exact same PMT that I have using mu metal and copper foil shielding.
>
> I have the necessary power supplies (0-10 KV, +15 V and -15 V), high voltage and BNC connectors and NIM components, so all that is left is the PMT enclosure and the appropriate scintillation plastic.
>
> Could some one comment on enclosures in general and possible enclosure materials (mu metal, aluminun, copper) Is it possible to make an enclosure out of PVC pipe? How about sources for mu metal cans or foil, copper foil etc.
>
> Tom Dressel

[Richard Hull]

PVC can be used as a housing, but it would have to be completely plated or covered with cover foil. I have done this and it works. If not covered, the tube will give you a FIT with electrostatic buildup. The advantages are low cost and super machinablitiy/tappability.

Richard Hull

[Tom Dressel]

It just so happens that I had to junk a 15" computer monitor that I had at the office today. It was 14 years old and my staff couldn't use it to type letters any more because it was too dim. Is there enough mu metal in it to make a PMT shield?

Interesting link reguarding durability of mu metal:http://cdms.physics.ucsb.edu/bunker/shi ... metal.html

Tom Dressel

[guest]

I don't think I've ever seen a monitor with a shield on the CRT. Mostly you'll see them for oscilloscope tubes and such. It would probably be a good idea to cruise the older surplus outfits that deal in tube paraphenalia to see if you can pick up something on the cheap.