[Halla_running] update

[KiJun Park]

Dear All,

Here is more precise info. from the Jay.

https://logbooks.jlab.org/entry/3331242 explains the problems with CHL1
(4K) connected to SCM 2KM cold box. This has been cooling the South
Linac. CC4 was spinning at 500 Hz and came to an abrupt halt.  No one
has a hypothesis which augurs a quick fix.  All the plausible hypotheses
take 3-6 months to fix.

I can't find the clog entry which discusses contamination in the heat
exchanger linking CHL2 (4K) and SCN 2KN cold box.  This combo has been
cooling the North Linac. This system is being warmed to ~90K in the hope
that the contamination is predominantly air, not C02 or H20.  An attempt
will be made to unclog the heat exchanger with warm gas and move the
impurities into the sub-system designed to immobilize them so the box
doesn't have to be warmed all the way to 300K now.  The long term
concern is that the contamination must have entered through systems in
the tunnel or the piping from tunnel to CHL.


Sincerely,
Kijun