Meeting with Lew Keller / Agenda (fwd)

[Elton Smith <elton@jlab.org>]

---------- Forwarded message ----------
Date: Thu, 15 Jun 2000 12:25:21 -0400 (EDT)
From: Elton Smith <elton@jlab.org>
To: Hall D civil <areti@jlab.org>, benesch@jlab.org, chandra@jlab.org,
     Curtis Meyer <cmeyer@ernest.phys.cmu.edu>, domingo@jlab.org,
     Alex Dzierba <dzierba@indiana.edu>, elton@jlab.org, harwood@jlab.org,
     Lewis Keller <Keller@slac.stanford.edu>, mahoney@jlab.org, may@jlab.org,
     pavel@jlab.org, Richard Jones <jonesrt@uconnvm.uconn.edu>,
     Elliott Wolin <wolin@jlab.org>
Subject: Meeting with Lew Keller / Agenda



We will meet with Lew Keller tomorrow Fri Jun 16, 9:00 in A211.

Agenda Items
=======================================================================

1. Latest Drawings Review (Elton)  

Electron Beam Dump:
* Summarize ground water activation calculations for the BSY dump, which
can be used to predict the environment around the Hall D electron dump.
* Estimates of lateral distribution of muons (Lew)

2. Collimator Enclosure:
* Concept (Elton)
* Discussion (Richard)
* Muon background from collimator enclosure (Lew)
* Better estimate for shielding around collimator (not including forward 
shielding). Present estimate is 1.5m of concrete or 2 m of dirt. (Lew: how
does this sound?)

3. Photon Dump:
* Transverse size of dump? (Lew)

Service Buildings: Do we have enough?

4. Hall D:
* Cryolines from accelerator
* Radiation of individuals in the counting room?

5. Safety System:
* Work with Kelly Mahoney to define "maximum credible accident." One of
the scenarios should be related to the maximum photon flux which can be
transmitted down the beamline.
* Transfer permanent magnets from Fermilab (for photon line)?
* Require neutron background rates in hall due collimator setup. This
estimate can be extended to the region of the counting room during normal
operation. Calculations should be made as a function of photon flux (power
on collimator), so that personnel limits in the counting room can be
estimated during routine operation.



============================================================================
Below are notes of general interest
=============================================================================

Hall D Failure Scenarios:

* Failure of vertical beam transport, shooting electron beam into the sky.
The vertical-bend dipole magnets will be connected in series to a single
power supply, so that failure of the supply will result in all magnets
shutting down. In case of shorts in individual coils, the 1 inch beam pipe
apertures will prevent accidental trajectories from clearing the transport
line. Sufficient shielding surrounds the upstream portion of the photon
beamline to contain the mis-steered electron beam.

* Poor tuning or missteering of electron beam.

* Excessive current in electron beamline. Current monitors upstream of the
vertical transport will be interlocked to prevent high current from
reaching the tagger building.

* Tagger magnet failure, directing electrons down the photon line. The
tagger magnet must be interlocked so that if the magnet current falls
below some level the beam is turned off. Two permanent-magnet dipoles
located downstream from the tagger magnet, each with a small aperture
burn-through monitor at its entrance, ensure that the 60 KW beam will not
go down the photon channel.

* Excessive photon flux (this may result from obstructions in the electron
beamline, poor vacuum, etc). Beam halo monitors surrounding the upstream
end of the permanent magnets (or collimator area) can be used to check
that the electron beam is delivered cleanly to the thin radiator for the
photon hall.

Notes from meeting with Pavel:

* Need up-to-date model of hall to get accurate (factor of 2) estimates
for the boundary doses during normal operation.

Additional Miscellaneous:

* What is the effect of the residual magnetization of the tagger iron on
the beamline safety systems.

* What kind of access do we need along the beamline, i.e. a tunnel or just
bury the beam pipe.  If a tunnel, what are the safety concerns.

* Will add'l buildings be needed for cryo line?


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