This morning we went in chiller room to replace the filter of the chiller used to cool the head of the neovan in order to see if it has any positive effects on the temperature of the neovan and consequently on some figure of merit of PSL such has neovan output power, PSTAB residual rms noise, PMC throghtput....
We changed the filter but the chiller did not restart. It has the usual "flow sensor" problem that it sometimes has when it restarts. This time we could not go through it and we had to connect the filter the head to the spare chiller.
We restarts the neovan and PSL/INJ relocked without troubles.
The temperature of the head is lower than before (first plot attached) which is not completely explained since the measured flow is the same and the temperature setpoint of the chiller is the same.
Anyway it slightly improved the power at the output of the neovan and more noticeable the power in transmission of the PMC.
However it seems that there is a problem with the temperature stabilization, there is an oscillation of about 20 min (second plot attached) which can slightly be seen on the downstream power signals, IMC_TRA for example.
After switching from the main chiller to the spare unit two weeks ago, we observed a temperature oscillation in the neovan head. This fluctuation was also visible in the DC powers downstream: in the INJ/PSL ones and but also the ITF ones (see attached Figure 1).
This morning, we went back to the chiller room to reconnect the neovan head to the main chiller. We managed to perform the swap quickly enough to avoid triggering the Neovan head temperature safety.
Note for future interventions:
It is important to prime the chiller pump before switching it on by pulling the red priming handle on its front panel. It prevents the usual flow-error warning when powering the chiller back on.
After the swap, the temperature stabilized again around 29.6 °C (Figure 2). This value is higher than with the spare chiller, but without oscillations. We will continue monitoring the temperature over the next few days.
Part of Thursday’s shift will be dedicated to realigning the beam on the LB, particularly in the neovan head, which should slightly reduce the temperature.
