[Esr-users] ESR Hall update

[Stuart Henderson]

Jonathan,
  Thanks for the summary.  As you know we're pursuing the ESR-II plan with 
high priority, for all the reasons outlined below.  Thanks again for your 
and your team's response.
Stuart


-----Original Message-----
From: Jonathan Creel [mailto:creel at jlab.org]
Sent: Wednesday, February 7, 2018 3:12 PM
To: esr-users <esr-users at jlab.org>
Cc: Will Oren <oren at jlab.org>; Michael Maier <mmaier at jlab.org>; Stuart 
Henderson <stuart at jlab.org>; Rolf Ent <ent at jlab.org>; 'Bob McKeown' 
<bmck at jlab.org>; Allison Lung <lung at jlab.org>
Subject: ESR Hall update

There seemed to be some confusion over the ESR/Hall problem last night.

The original 12GeV plan was Hall D plus any two other Halls. The projected 
loads in the Halls matched well with the capacity of the ESR.
When the proposal was changed to support Hall D plus three Halls it was 
determined the ESR would likely need to run at its very highest capacity and 
would also require constant support from the CHL to meet the needs of the 
loads. There would be no margin.

It has been widely disseminated that this would have a several side effects.

First, operating the ESR at full capacity will lower its reliability.
The ESR was originally build in 1978 for the ESCAR project and was 
decommissioned and installed here at JLab in 1994. The plant is aging and 
operating it at its highest capacity for extended periods will have an 
impact.

Second, the Halls are all essentially manifolded together at the ESR.
Operating the system at the highest capacity makes the ESR and the Halls 
very susceptible to collateral problems in any one Hall. With the warm 
compressors processing the large quantities of helium gas molecules flowing 
through the system there is little compressor margin to instantly react to 
process the extra gas molecules that are generated during magnet quenches or 
fast dumps. The result is that a significant event in one Hall will 
instantly raise the helium return pressures for all Halls and the ESR plant. 
If this pressure rise is high enough the magnets in the other Halls will 
shutdown or fast dump. If the disturbance is large enough the increased 
return pressures effect the ESR plant operation and pressurizes the dewar 
which leads to turbine shutdowns to protect the equipment from damage. This 
is the scenario that occurred last night.

Third, following a ESR trip, it has been disseminated that two of the Halls 
would be recovered fairly quickly but as the load increases on the plant the 
third Hall does not have access to any extra capacity to cooldown fast. For 
this reason the the third Hall will require from one to several days to 
recover depending on the length of time the plant was shutdown. This is the 
scenario that happened overnight with Hall C. We pre-determine the recovery 
priorities based on an email sent to us by Physics.

In summary, the events at the end station essentially followed the 
predictions and recovery went as expected. We are working with Physics to 
see if there are any lessons learned can be applied to the future.

Thanks

--
Jonathan Creel
Cryogenics Engineering and Operations Department Head and Senior Electrical 
Engineer Thomas Jefferson National Accelerator Facility
12000 Jefferson Avenue, Newport News, Virginia, 23602 Phone (757)269-5925