[Halld-tagger] neutron background in the Hall D tagger hall

[Richard Jones]

Pavel,

Greetings from Connecticut.  I am writing to you to follow up on a 
discussion that took place in our HallD Photon Beam working group 
meeting this morning.  You are aware of recent measurements that were 
carried out in Hall A to test the radiation hardness of silicon 
photomultiplier (SiPM) devices.  The results of those measurements have 
shown that we need to be extremely careful about the radiation levels in 
areas where we want to use SiPM's to read out detectors.

We are planning to use SiPM's to read out the tagger microscope in the 
Hall D tagger hall.  Before we go to full-scale production of this 
readout system, our collaboration would like to see updated simulations 
of the tagger hall backgrounds in the area of the microscope detector.  
About 5 years ago we went through this exercise to measure tagger 
backgrounds coming back from the dump.  At that time we were more 
interested in the electromagnetic component.  Now we would like to go 
back and look at the neutron component as well.  The geometry of the 
tagger has changed somewhat (we now have a single-dipole design instead 
of two) but that should not make much difference to the neutron 
backgrounds that we should see.  What would it take to resurrect that 
simulation and run a few milliseconds of beam through it?  I would do it 
myself, except that we need to make sure that we have libraries that are 
certified by you to be more or less accurate for low-energy neutron 
fluxes in halls with electron beam present.

I have plenty of cpu time available on my cluster, and am willing to run 
the code and do the analysis myself here at UConn.

-Richard Jones

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