elenna.capote@LIGO.ORG - posted 17:37, Tuesday 28 July 2026 - last comment - 18:31, Tuesday 28 July 2026(91296)
JAC heater power set to zero
Gerardo pointed out that the HAM1 pressure had been rising for about an hour. Ryan checked that the JAC heater guardian was off. However, the JAC heater was still on at steady power. I called Jennie, and she turned the JAC heater power to zero. It had been set with a value of 0.749, which is not high compared to its usual value. We will monitor HAM1 pressure to see if it turns around.
HAM1 pressure appears to be dropping now.
As far as I can tell from trending Backhoff channels for the JAC heater we have been at the same set heater power all day (~0.7W).
So not sure how it was the heater causing this.
The last time we had this problem it was because we were dumping 3W of power into the heater.
Included are long term trends of the heater power set value in Watts and the JAC thermistor we use for control in degrees. I also included the HAM1 pressure.
There was a channel cut-out about 3 hours ago in all the JAC heater channels, but I assume this was something to do with the RCG upgrade.
They all went to 0 including the JAC heater guardian. Its on state is 1 and off is 20.
During the cut-out it went to 0 so should not have turned the heater control loop on.
This zoomed in picture of the time all these channels went to 0 is the second attachment.
Here is a long term trend showing the constant readback power from the JAC heater in the bottom left plot and the JAC guardian state in the bottom right.
The temperature on the JAC thermistor has been rising sharply for the last three hours.
Summary: This makes me suspicious that some Beckhoff channel cutting out caused this temperature spike and thus the pressure spike but not sure what.