[Dsg-halla_ecal] ECal heater prototype

[Donald Jones]

Hi Folks,
I would like to report that the ECal heater prototype has been operating for the past 24+hrs and has more or less stabilized. The controls software is working well. Since we are feeding back on the aluminum plate temperature where the heaters are attached and not the crystal, it take some time and manual adjustment to get the crystal temperature right. Yesterday and today the Hall ambient temperature has ranged from 68 to 70 degF meaning the heaters must work harder than they did in Physics Storage where it was typically much warmer. Right now the supermodule front plate temperatures that create a crystal temperature in the desired 220-225degC range are: top row 280degC, middle row 242 degC and bottom row 296 degC. The middle row is essentially off and getting enough heat from its neighbors. The aluminum heater walls are set to 232 degC. The crystal temperatures on the front are in the 220-225degC range and on the backside are in the 180-190degC range. One backside thermocouple reads 195degC but it has been reading suspiciously high from the beginning so I suspect the reading does not represent reality.
We will continue running in this way until the end of A_LL at which point we will decide how to proceed.
-Don

Donald Jones
Hall A/C Staff Scientist
Jefferson Lab
Newport News, VA
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