See Jay's entry (https://logbooks.jlab.org/entry/3814154) it was decided to proceed under the assumption the turbo pump had tripped and a larger scroll pump was needed. M. Drury will contact Frank Humphrey and TJ to come in. Once they are on the way the NL will go to Restricted so the pump can be moved into position and connected. Scroll pump will also be attached to the waveguides.
OPS (Freeman) will contact cryo on-call and update.
THOMAS JEFFERSON NATIONAL ACCELERATOR FACILITY
ACCELERATOR OPERATIONS CREW CHIEF SIGN IN FORM
Date : 07-11-20
Time : 07:19:48
Day : Saturday
Shift : Day
Crew Chief : Freeman
Program Deputy: McGuckin
Team : -
This stamp certifies that the above Crew Chief has read/reviewed/received the following:
As first linked entry reports, the access around 2130 showed tuners still frozen. Heater heat was left on at 50 W (green in bottom panel) until I asked the SSO to turn it off a few minutes ago. The four Minco heaters are at least 10 cm square each and are good for 1 W/cm^2 in air, so 12.5 W each in helium gas below 200K will not have damaged them.
As the top panel indicates, diodes are reading mean of about 160K so the tuners should be free by now.
Figure 1 shows the whole day. Upper pane is "cooldown" diodes. Middle is beamline and waveguide vacuum. Bottom is cryo signals. The variations around 1300 were caused by L-tube and RT valve work. JT closed about 1750. I don't know why the 2K outlet temp (1260) went to 180K during the L-tube work.
Figure 2 shows the last four hours. One sees in the lowest pane the JT closing in steps starting at 1750. Liquid level rises because the electric heaters were putting out 225 W and there was lots of cold gas moving by the sensor.