• RTV cookie/mold: Hakob asked for the mold we talked about last week. The meniscus is alright now, but the mold does not have round shapes on the edges which makes it hard to release the cookie once it's dry. I will take the mold project from there and ask for a new one.

 
• Cable handling issue: I need Eugene to give me the specs of the new HV cables as well as the usual lemo cables to get a new quotation. All this will probably happen before next week's meeting.

 
• Fast proton-arm trigger: Bogdan has talked to some people and they also seem interested in building a fast trigger from the proton-arm. The cost would definitely be lower than $3000 including everything, and Bogdan has preliminary drawings of a sealed structure (helium problem) for a fast phototube. I've looked into the data of 95001 to get an estimate of the single rates on the S1 and S2 (S3) counters at the kinematics we're interested in. I only managed to get estimates for the electron arm: up to a maximum of 8kHz for S2-left (run e95001.2596.00). I don't know what's causing that I can't get any reasonnable numbers from the hadron-arm, but I'll look into that for next week.

 
• Pb-glass radiation damage: Hakob has disassembled the 9-block prototype we used for the test run back last year. He then measured the transmission of blue light through the block at different places. He found out the front of the block (pointing to the target) was damaged: the transmission there is about 75% whereas it's about 95% at the other side of the block (it's actually the ratio of the transmission on a clear block to the transmission of the damaged block). The likely conclusion is that there is a flux of low energy (~40 MeV) photons and such coming from the target. It has been decided to install a block in the hall during HAPPEX, pointing at the target at some low (~10-20 degrees) angle and shielded on the sides. We will measure its transmission before installing it and make another measurement at the next maintenance period. This will help getting a better estimate of the dose and inferred damage to the block. Also, we will try to use a UV lamp to heal the damaged block to see if it does work properly. David offered his help on this issue. A dedicated page about the radiation damage is available.

 
• New 9-block array prototype: All the parts are ordered for a 25-block prototype. We will only be able to test a 9-block prototype in the Moller apparatus (25 blocks wouldn't fit in it) once it's completed. 

 
Franck Sabatie - 04/07/1999


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