[Halld] Hall D Solenoid Update

[Eugene Chudakov]

Dear colleagues,

The proposed modifications to the cooling systems have been discussed
with a group of local experts. Also, the information was sent to the
panel of the last solenoid review. That review had come to a
conclusion that the quenches were most likely caused by cooling
problems.  In summary, all the responses were positive. Although
nobody could guarantee that the modifications would solve all possible
problems with the cooling system, they are considered a substantial
improvement. We have a green light from the department management
(Patrizia Rossi) to go ahead.

The work schedule has been prepared. Finishing the work, cooling and
testing the magnet before the end of the 5-weeks Fall Run (about Dec
13) is very unlikely. The primary goal of the Fall Run is the
accelerator development (establishing 12 GeV operations) and it is
still unclear how much time would be dedicated physics. Our current
goal is to have the magnet cold and tested by the end of January.

The work will start when the magnet is warm enough, hopefully the next
week.

Regards,
Eugene

------------------------------------------------------
Eugene Chudakov
https://userweb.jlab.org/~gen/
phone (757) 269 6959  fax (757) 269 6331
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave, STE 4,
Newport News, VA 23606 USA

On Mon, 31 Aug 2015, Eugene Chudakov wrote:

> Dear colleagues,
>
> There is a new development concerning the problems with the Hall D
> solenoid. One of the engineers who built this solenoid at SLAC long
> ago - Steve St.Loren noticed a difference in the ways liquid He is
> provided to the coils between the SLAC and JLab implementations. He
> explained that one of the two 3/8" pipes, which go to the bottom of
> the coils, was used not for the cool-down (as we do) but was connected
> to the bottom of the Helium cold box and in fact provided a
> thermosyphon. The current implementation does not employ the
> thermosyphon effect, which is its obvious weakness. The finding was
> discussed with local experts and the general opinion is that the
> effect might be significant.
>
> We have come to a preliminary plan on making the proper modifications
> in order to get closer to the SLAC configuration. We would need to
> warm up the magnet and make modifications in the chimneys.  The work
> is not trivial but seems doable.  The time estimate is 2 months till
> the magnet is cold again.
>
> There is a broad agreement that the modifications should be done now
> rather than later. Today, the cryo group started warming
> up the magnet.
>
> Best regards,
> Eugene
>
>