Meeting with Radcon

[Elton Smith <elton@jlab.org>]

Hall D,

Elliott and I met with Pavel Degtiarenko and Bob May this afternoon and
reviewed the civil drawings.

Here are some questions we need to pursue:

1. How much steel do we actually need behind the electron dump?
   - does the groundwater contamination, or muon production determine its
     transverse size?

2. Specify fail-safe path for electron beam (i.e. strength of permanent
   magnets)

3. It was decided that dirt shielding should be centered on the buildings
   (not the beam).

4. We should seriously consider a pre-collimator (about 70 m downstream of
   radiator) to reduce photon flux on collimator, thereby reducing
   radiation in Hall D.

Additions to drawing:

1. Add existing road to Canon Blvd. 
2. Add cyogenic building for magnet support.

Note:

At this time, there is no concern that the electron beam dump is on the
same side of the beamline as the Counting House.

Information of interest:

a. ~ 10**12 low-energy neutrons/KW of beam in steel.

b. Radiation in Hall C (due to neutron production backward direction) is
about 200 mrem/hr for 15 cm LH2 target and 50 microA beam.

f.y.i. elton.


Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625