SUPERNOVA!

About 21 million years ago, a type IA supernova exploded in M101 (the Pinwheel Galaxy).  Due to the speed-of-light delay, it just became visible to our telescopes this past week.  I heard about it Saturday morning, and rushed into the lab to try to get an experiment up and running to see if we could detect any high-energy cosmic rays from it.  Ray says the particle flux should increase as the remnant nebula develops, so we are not too late.  After some fiddling, I got the system working with raw pulse data streaming from 2 input-capture datapaths. For some reason, the pulse rate in the 2nd PMT is higher than the first.  I adjusted the voltages on their HV supplies to be the same (1,200 V) but the difference is persisting.  The pulse rate on PMT 2 was so high I kept getting hardware FIFO overflows; I increased the size of the FIFO from 4 to 8 pulses which helped a little.  I shifted down the top end of the voltage ladder to -400 mV (from -300 mV) to filter out more pulses, which brought the pulse rate down to a manageable level.  Then I set up an experiment with the two test PMTs on opposite sides of the room on a North-South axis, in hopes of gathering evidence for an excess of northerly showers between the hours of 7:30 am and 3:00 am (when the supernova is above our horizon).

Unfortunately, the system crashed after a few hours, and did not keep running overnight.  However, we do at least have several hours worth of data that we can analyze looking for coincidences.  I tried restarting the run on Sunday, but now the 2nd datapath is not working for some reason (but that PMT is still producing pulses).  Could have been a heating problem.  Try again with the power on the thermoelectric cooler turned up.

Note to self:  Also try turning up the speed of the system clock, to clear the FIFO more quickly.  I think fmax for the system clock is something like 80 MHz.

After a quick skim through the data, it looks like the pulse rate was highest when the supernova was highest in the sky.  But I'm not sure about this yet; need to do a real plot.

Note to self:  Need to log the DAC settings to the server at the start of the run so that information will be included the data file.