WIP stilbene

[stamasd]

Inspired by the previous thread by Steven I have acquired a stilbene crystal and just got around to building a detector with it. Stilbene emission is mostly in violet/UV range with peak at 390nm. I have consequently built the detector with a UV-enhanced PMT.

The crystal I have is20mm diameter by 30mm length. It came already wrapped in PTFE and sealed. The PMT is a Hamamatsu R292 1.125-inch tube; the crystal is a bit small for it but I don't have any 1" UV-enhanced tubes. The R292 is otherwise very similar to the more common R6095. The catalog data is almost identical for the two, except for the spectral curve due to R292's fused silica window vs. low-K glass for R6095. As such, the spectral response extends down to 185nm though the peak sensitivity is still around 420nm.

I used my ghetto "pigtail" construction for the detector as I was in a hurry and my 3D printer needs a recalibration which will take several days (until then I'm unable to print a proper BNC cap). Essentially stuck the crystal to the window with optical grease, fixed it in place with strips of black electrical tape, added a socket with voltage divider that I had pre-built - same divider I use for R6095 - and a mu-metal shield around the tube. More electrical tape to insulate the BNC connector that hangs pigtail-style at the end, and extra layers over the crystal for optical shielding.

I will need a lot of testing to dial in parameters to make this useful; for now I'm attaching 2 screenshots, one is of the new detector with a Thorium mantle, at 650V, 100% sound volume; the other one is of the same Thorium mantle but with my NaI(Tl) detector based on a R6095 and similar size crystal (30*40mm), at 650V, 60% volume. Things are recognizable but not great. The data was acquired for only 20minutes with the stilbene vs. 30 minutes with the NaI. This was all done with a GS-2000 Pro at 192khZ, 24bits.

More work to be done, once I know this crystal better I will switch to a different acquisition system with much higher bandwidth and hopefully get some neutron detection going.

[stamasd]

Detector with pigtail