[Question] Would BC412 plastic scintillator be suitable?

[jtomes123]

Hi, would a plastic scintillator be suitable for the detector of would the output be too weak? I can get a cube of 50x50x10mm of BC412 for a reasonable price shipped to EU. I know that plastic scintillator have weaker output than NaI(Tl) or CsI(Tl), however the volume of the scintillator would also be greater. Or if you have other good scintillator source suggestion in EU it would be welcome.

But I like the BC412 since it should be pretty indestructible and moisture resistant.

Thanks!

[NuclearPhoenixx]

Hi there, I don't know any scintillator source in the EU. If somebody has one, please let me know as well 😄

BC412 is okay in theory. However, there are two things to keep in mind:

1. No spectrometry, plastic scintillators have very poor energy resolution so you won't get any useful info out of them.
2. The size you chose is not particularly great for a SiPM. For the best results you'd want a crystal face that has a comparable surface area to the SiPMs, otherwise you'll lose some of the light from the scintillator.

Not to say it wouldn't work just counting pulses, but it's not that ideal. You'll have to try it out. Hope that helps!

[NuclearPhoenixx]

Not really an issue, therefore I moved the topic to the Q&A discussions.

[jtomes123]

No problem, yeah sadly I don’t have any good place to source the crystals here in EU, they are apparently pretty rare even at my uni which sucks 😅.

The sources I found on ebay were:
LYSO from US (4x4x22mm)
CsI from US (6x6x30mm)
NaI from Ukraine (various but some seemed to be yellowed)

Of the ones I mentioned what do you think would be the best? I am strongly considering the LYSO, since it technically comes with it’s own check source.

[NuclearPhoenixx]

Cool, let me know if you hear from him 😉

Shipping for LYSO is not a problem, especially these tiny sticks. The activity is waaay below anything that would be considered problematic and it's all "natural" radiation anyways (if that helps). Even with a 1"x1" scintillator up close to two of these LYSO crystals, I only get around 50 cps or so vs 30 background. Nobody's going to bother checking that. But yeah, it got way more expensive. Couple of years ago I could get two of these crystals for like $35 delivered.

[jtomes123]

Yeah I missed out on this, I remember I saw SiPM coupled crystals for around 50 USD before the war in ukraine. This LYSO is about 25 USD but the shipping is additional 50.

[jtomes123]

I’ve contacted the guy through his email on the forum. He is really helpful and has pretty good prices. I can fully recommend him. I am now waiting for a cut to size CsI crystal 😄. Do you also sell completed sipm boards? I’ve noticed you have carrier boards on tindie.

[NuclearPhoenixx]

Very nice. I normally don't sell complete SiPM board, just because of the pretty high inventory cost to stock them. What do you need, though? If you want I can just make you one personally. It's not a lot of trouble to solder the SiPMs if that's what's holding you back, depends on what PCB you want.

[jbeale1]

I'm curious what method is best to get more than one SiPM on a board co-planar, without a professional reflow system. My first attempt to do this with hand soldering did not go well, and for the price of these parts it is painful to make mistakes- including that the 99% isopropyl alcohol which I've used without issue on PCBs for several decades, is no good for these delicate parts (although that was my fault for not studying the complete data sheet).

[dc1rdb]

I've achieved good results using small reverse tweezers with rubberized tips to fix the SiPMs to the board and then carefully soldering them in place. IMO it is vital to not put any solder on the pads or on the SiPM before placing the SiPM on the board. Coplanarity can then be checked with a suitable light source.
Regarding isopropyl alcohol: been there, done that, bought a new SiPM.

[NuclearPhoenixx]

Yeah I'm pretty much doing the same. Put on the SiPMs and then carefully solder one leg at a time making sure that it stays exactly in place using some tweezers. In my experience though, it doesn't matter all too much for the results if they're not 100% exactly co-planar down to like 0.1mm. Just make sure that you're not putting any more pressure onto the SiPMs than you absolutely need to. Optical coupling can take care of your tiny gap. That doesn't mean that they shouldn't be as flat and uniform as possible obviously. @jbeale1

Also it helps to have ENIG finish on the PCB as that tends to be a lot more flat and uniform on the pads than just your standard HASL.

[jbeale1]

Thank you both for these tips! I am ready to construct another SiPM board, so I will try this advice. I would not have guessed it was possible or likely to get a good solder joint without having at least some solder on the pad to start with, but in light of this report I am encouraged to believe it is possible.