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Photomultiplier - Cherenkov detector success! - soldering questions

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richnormand:
@ChristofferB
You mentioned optical coupling in the above post. Yes you need it otherwise the acceptance angle for photons from the scintillator to the PMT surface will be severely limited.

For optical coupling between several 5" PMTs with plastic and 3" PMTs with xtal scintillators I have used:

Temporary: for testing up to a month: KY Gel from the pharmacy.... works quite well, good index of refraction, and water soluble so it is easy to clean 8)
Usual stuff: remote control cars differential oil. Clear and viscous. Good index. Get the highest viscosity you can get. Got mine from hobby and RC shops. Been there for ten years on my two muon detectors. Make sure you have a strong adhesive tape around the scintillator and PMT to avoid leakage over time. :)
Better: is a pro index matching gel. The real stuff is about $70 for a few cc from the likes of 3M and such. This might be a better cost alternative, as an example, https://www.ebay.com/itm/Silicone-Optical-Coupling-Compound-for-PMT-Photomultiplier-Scintillator-Detector-/261918290249 but I have no idea how good it is compared to the industrial stuff.

ChristofferB:
Ha.. KY gel.. how great it would be to get that into a published journal  ;D

I suppose any viscous and clear liquid could really be used, right? Glycerine or microscopy immersion oil might work as well, optically wise, but both probably a little too liquid.

I wonder if the diff oil is a silicone oil or a petroleum based one? Maybe I'll check out my local hobby store.

Yeah I know the Iradinc guy on ebay. I was actually considering getting his complete kits, since that humongous heat shrink he sells is pretty ideal for light proofing.


I'm still working on how to best make a counting setup, since just building a lead castle is a little much. I can't find any sources to whether the entire PMT should be lead shielded or just the scintillator. Either way, a lot of high end scintillation probes also has a mu-metal shield, so maybe I should try making the probe in a 'scope CRT mu-metal shielding tube?

thanks for the advice!


 

profdc9:
If the pins are small enough, you might be able to use Nixie tube pins and make a socket PCB to solder them into.  For example:

https://www.ebay.com/itm/100-pcs-NIXIE-TUBE-Socket-Pins-Gold-Plated/153513091292

You can design a PCB that could have holes for the pins and solder the pins into the holes.   Then you insert the tube into the pins.   You could leave a hole in the PCB for the protrusion in the bottom.

Also, maybe plumber's silicone grease would work as a temporary index matching gel if it was a thin layer?

Kleinstein:
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. The shield from an old analog scope should be well good enough, if it fits.

The PMT does not directly needs a lead shield, however as the scintillator would be open to the PMT side otherwise the lead shield should extend somewhat over the PMT, up to fully covering the PMT. The shielding part would probably be one of the late stages, but it can help to keep the housing of the PMT small and round.

For the first tests one can even get away without index matching grease - this is more about the last 10%. A thin PE foil could avoid direct glass to glass contact.  I would do the first test with a LED dummy anyway.

ChristofferB:
I agree, shielding is secondary, and can always be added later in layers if it turns out to be needed.

A 6 cm long cylinder of copper sheet with a back plate for connectors that can be slipped over the back end of the tube to shield /protect the divider is probably the first thing I will add, also for an electrical safety point of view.

For pmt coupling, I also found some light curing optical coupling glue used for fiber optics and lens assemblies. This would probably be ideal since it holds the xtal onto the tube by itself, and also provide the desired coupling. Probably expensive though.


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