Status : Fridge couldn't get to base temperature.
Probable reasons and diagnostics:
1K pot? : Now seems to be the main culprit. After closing completely closing the needle valve, the 1K pot pressure shows 2mbar (is it okay?). However, 1K pot P max-out when I try to open event a VERY LITTLE. Not good!
Incorrect mix amount in the lines? : Forgot to mention on Tuesday, but the still pressure did not fall below 0.25 mbar (except when I started single-shot mode where the pressure went as low as 0.12 mbar). Looking at previous run diaries, the nominal value of still pressure at base temp was about 0.13 mbar.
Not good vacuum in the IVC? : Checked the pressure in the IVC, does seem to be a leak. BUT the current pressure gauge does not go below 400 nbar even while pumping with new [old] turbo continuously with IVC valved off. Nominal IVC pressure remains at few tens of nBar max when fully pumped out.
Not optimal circulation of the mix? : Checked the run diary. Himangshu had done a throughput test in the beginning of the run at 77K and it was fine.
Clogged traps? : We should clean it before the next cooldown.
