8 December, 2002
8 December, 2002
Lots of news on many fronts:
Ice tank detector: Bai & I replaced the suspicious connector in the tank today. But after a lot more tests, the PMTs were clearly not behaving well. This is perplexing and frustrating, and we are beginning to suspect that they may have been damaged by thermal expansion when we first opened the tank lid and let them warm up. We heard a couple of "pops," but attributed those noises to the expansion of the ice.
Bai explained the whole situation to his colleagues by email last night, and is hoping for some fresh ideas. We are looking at possibly opening up the tank tomorrow and doing a visual inspection of the PMTs, which sit inside acrylic spheres. This may require opening up the spheres, which may require hacksawing the threaded rod which holds them together. But Bai's main PMT expert failed to understand the situation, in his email reply, so we're awaiting clarification.
Funny note: the expert is in Washington, DC, and offered to come over to check the problem first hand! He thought Bai was in Delaware! (Bai works for the Bartol Research Institute, which is associated with the University of Delaware in Newark)
To find out more about cosmic rays :
Kites: Got flying today! What I learned :
a) wind is much better aloft than at the surface, even though there's not many trees or hills here.
b) To lift the camera rig, both kites I brought are required. Using a caribiner, I improvised a second hitch for the smaller kite, and that provided enough force to get the rig up.
c) The camera is good for about 15 minutes in the cold. Ditto for the batteries that drive the servos.
d) The camera needs to go higher, and shoot with a wide field of view. Our main subject was the ice tank pit, and I got shots all around it, but not in it.
e) Kites make people nervous around here, with all the air traffic. Weekends are best. Flights stopped Saturday at noon, and will resume Sunday morning.
f) Station folks have been very accommodating and helpful.
g) Kites are a great way to meet people.
To find out more about kite aerial photography :
Portable detector: The solar experiment I ran yesterday? I expected that since the count rate went down, the AIR PRESSURE went up. More air over your detector blocks more parcticles. I checked with meteorology, and the pressure went DOWN during that interval!
Read specs on the PMTs. They have an operating minimum of +5 C ! So what the solar experiment may be showing is the PMTs cooling down to ambient outside temperature (-30 C)
So I brought them inside the SPASE shack, and ran a long experiment, and indeed, count rates climbed as they warmed up.
I also repeated the shielding experiment, and the results seem to indicate that the shielding lowered counts. Tomorrow : a spacing experiment.
To find out more about the portable detector :
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