Hall A Dump

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The configuration of the Hall A dump is being evaluated.



Official JLab documents with the current state

  • Beamline folder documentation
  • Hall A Dump configuration pdf
  • Hall C Dump configuration pdf
  • Dump apperture pdf
  • Dump beam line neck down: pdf
  • Thermal calculation for dump apperture pdf

Meetings where this was discussed


Keith Welch

From: Keith Welch <welch@jlab.org>

Date: Wed, May 31, 2017 at 3:45 PM

Subject: Fwd: Aperture plate looks good to go in 5052-O

To: Ciprian Gal <ciprian@jlab.org>, Dave Gaskell <gaskelld@jlab.org>

Cc: George Kharashvili <georgek@jlab.org>

Dave, Ciprian,

Here's the Ansys analysis done on the aperture plate. I did model the plate with a 10% RL target, 1 GeV and got a total power deposition of about 9.5 Watt/uA (total almost 2 kW with 200 uA beam). This is with the "stepped" plate design, which lowers the overall power deposition non-trivially (less interaction in the thinner area). But it of course does not take into account the colimator. Seems like with these things in mind we have pretty good agreement. The power density, along the inner edge of the hole was about 1.5 Watt/cm^3 (this value was actually lower with the 10% target, compared to 5% target, due to spreading the beam out more).

The Ansys analysis (done by Bill Crahen) shows that the heating from this condition is acceptable and doesn't put the aluminum in jeopardy. It would produce pretty significant activation in the plate of course. We have not modeled the activation specifically. Maybe that is something George and/or I can look at.

Tim Michalsi

Subject: Re: Hall A beam dump vacuum pipe

Date: Tue, 6 Jun 2017 11:17:40 -0400 (EDT)

From: Tim Michalski <michalsk@jlab.org>

To: Dave Gaskell <gaskelld@jlab.org>

CC: Anthony DiPette <dipette@jlab.org>


We would have to look in detail at the beam size you are projecting for the PREX/CREX experiments. One thought is to turn off the MPS (or increase the alarm threshold) for the aperture plate ion chambers. However, this may increase the activation and thereby the residual radiation in the entrance to the dump tunnel.

The Hall A vacuum pipe was made as one piece, thereby limiting access to the aperture plate which is located near the midpoint. I have attached the drawing for reference. The aperture plate is bolted in, but not feasible to access it to unbolt the assembly.

I would expect the cost to "rework" the current assembly would be much more cost effective than procuring a replacement vacuum pipe. I expect it can be cut and a flange set added, if desired. The cost for the Hall C vacuum pipe, while a bit longer, was quite a bit more costly than the Hall A vacuum pipe. I would imagine $2k-$4k for a new set of flanges and time to cut and weld new flanges. I assume this work would be done in house either with Machine Shop + Welder personnel or could be done with Hall personnel. The flex seal is an additional expense.

Hall A vacuum pipe - $34k

Hall C vacuum pipe - $110k

Helico-Flex Seal - $1.5k each.

Let me know if you need more information or want to discuss any details presented here.