Supernova notes from Saturday

[Drafted this post Saturday but only posting it now]

The news just broke that a Type IA supernova just exploded this week (yes, I'm using language loosely here) in the Pinwheel galaxy (M101), only 21 million light-years away (close in cosmic terms).  As the remnant nebula expands, there should be an increasing flux of high-energy particles coming from that vicinity.  If we get our 3-node detector LAN working soon, we might be able to identify an excess of UHECRs originating from that area of the sky!  This gives us additional motivation to get busy.

I came in to the lab and hooked up our 2nd test PMT to the board.  I can see the pulses on the scope, but the firmware is not reporting them yet.  I double-checked the pin assignments for the 2nd channel against the layout, and they are all correct.

I think the PLL frequency was just too high - after turning it down (and turning up the cooling) the 2nd channel started working.

The pulses on the 2nd channel seem larger (and more frequent) than those on the first one.  Ray said it might be because that PMT isn't wrapped in felt.  But these are too big to be pulses from single leaked-in optical-wavelength photons.  The histogram for those peaked at about 40 mV and these are over 300 mV.

I might just be imagining things, but it seems like the total pulse rate (even on PMT 1) is higher today than it was a few days ago.  Could it be because of the supernova?

OK, turns out one of the PMTs (#2) had its voltage set much higher than the other one.  (12,000 V?)  At some point the voltage readout stopped working and I had to switch bases.  Now, both PMT bases are set to 1.2V HV readout (1,200 V internal high voltage) and they are generating pulses at about the same rate.

I put one PMT at the far North end of the room, and the other one at the far South end of the room, so that if a significant proportion of UHECR-initiated showers comes from the direction of the supernova (which is in the Big Dipper), if we get coincidences, we will be able to see an excess one ones coming from the North in the relative time-of-arrival data.