7 December, 2002
7 December, 2002
Up at the crack of dawn today ! I didn't have my computer - that's the only clock I have - and it looked very bright outside, so I got up. Things to do! Bai's waiting for me ! Don't want to miss breakfast! I asked the first guy I saw : 4 o'clock!
I'm up now. Over to the dome, take in some of that cool crisp air. The Jamesway where I'm sleeping is a fancy tent with a blasting heater that would dry out even Sponge Bob. 4 hours later (really, I had that much computer work to do, making movies, processing pictures, uploading, sending emails¯) it was time for breakfast. I hope you¸re looking at those movies.
Ran 2 experiments with the portable detector today. The solar experiment was pretty conclusive: no charged parcticles seem to reach us directly from the sun. Otherwise, the graph should have shown a rising trend at around 100 minutes, as the sun "moved" to a position directly perpendicular to the detectors. No direct parcticles, hmm, that's probably a good thing, health-wise.
See the graph in the picture section today for more on this. Solar parcticles are fairly low energy, and are pretty unlikely to penetrate through the atmosphere to where we are. That's true even at the pole, where the pressure altitude has hovered around 10,500 feet since I've been here. Question: why the downward trend in the graph? I have an idea, so check tomorrow.
I also ran a set of shielding experiments, based on an intriguing result from the first day of running the detector. First day: count rate inside the SPASE shack was higher than outside. 2 possibilities : colder PMTs create less background noise, lowering total counts, OR, roof of SPASE shack provides interaction medium for charged parcticles, and they create showers of secondaries inside the shack.
Bai suggested we borrow some metal plates from MAPO and run some shielding experiments. But they were inconclusive. They were only 10 minute experiments, and tomorrow, I'll run these again, and see if I can get some numbers that make more sense.
The ice tank occupied most of our day. We put it back together, covering it up and making it light tight so we could run some checks to make sure it's all working.
Badness! The two PMTs set into the top of the ice are not sending a signal. Lots of troubleshooting, one of us in the shack, one in the pit, testing resistances and voltages. No problems in the cables out to the pit is a big relief, as they are buried and nearly impossible to dig up. We finally traced it to the cable connector on the high voltage PMT supply. It seems these are getting warmed by the sun, the refreezing as soon as they¸re covered up again, and the ice prevents a connection.
We tried drying them with a heat gun, tried inserting extra wire in the holes to really get metal jammed onto metal. Each idea took a while to execute. Open the tank, fool around with the connectors, seal the tank back up. Fortunately, it was a warm windless day. To windless to fly a kite, even (we tried).
Very frustrating. We'd get signal briefly, then lose it. Tomorrow: we cut the connectors out and solder the cables together.
Not good. This tank is a prototype for nearly 200 in the ICETOP array, and the connectors are in general use in AMANDA. Hopefully, they perform better when frozen permanently into the ice.
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