1) Discussion of radiation physics work plan, coordination, schedule and
Present: Mokhov (Fermilab), Striganov (Fermilab), Parker (BNL), Asiri, Corwin, Fasso, Keller, Maruyama, Rokni, Seryi, Spencer, et al.
The group discussed the RDR schedule (see
here, Tor's talk) and
radiation physics tasks
as well as the strategy of joint work by Fermilab and SLAC groups
on these questions.
The post-meeting action items compiled by Lew Keller are below.
See slides for
introduction. Below are Actions that need resolution within a month or two for
the Design Cost Group.
Beam conditions at IP and extraction line dumps: 1 TeV CM, 18 MW each beam
Start with deep FNAL site, look at other sites later.
Action A (SLAC and FNAL groups).
Two IR hall questions:
1. Detector is in the garage area and there is a concrete wall between the garage and the beam. We assume the beam is being commissioned and it strikes a thick target at various points along the beam line near the IR hall and in the hall. Assume the inside wall surface starts 10 m from the beamline.
What thickness wall is required to keep the instantaneous dose rate below 400 mrem/hr?
(We assume this condition will only last a short time before various interlocks turn off the beam).
2. Detector is on beamline with no wall. There is a "pac-man" shield, ala SLD, around the beam line between the tunnel and the detector - this is the so-called self-shielding condition. Assume the inside surface of pac-man starts 1 m from the beamline - it can be made of an inner layer of steel followed by concrete.
What thickness of pac-man is required to keep the instantaneous dose rate below 400 mrem/hr?
For now assume the following very simple tunnel and detector parameters:
Tunnel: 4 m square, beam 1 m from wall, 0.75 m from floor
Experiment hall: 28 m between walls along beam direction, centered on IP beam line 10 m above floor.
Detector centered on IP, assume cylinders centered on IP:
L = 5.6 m
R_inner = 2.5 m
R_outer = 2.9 m
Steel barrel: for now assume solid
L = 5.6 m
R_inner = 3.3 m
R_outer = 6.4 m
Steel endcaps, each, (from IP): for now assume solid
Z_inner = 2.8 m
Z_outer = 5.9 m
R_inner = 0.3 m
R_outer = 6.4 m
Action B (FNAL group).
1. Specify concrete floor and wall thickness around the two 18 MW extraction line and the 18 MW tuneup dumps.
2. Specify steel/concrete shield between dump and incoming beam tunnel.
3. Repeat for the 3 MW beamstrahlung dump in the 2 mrad crossing angle IR.
Action C (SLAC group).
1. Estimate air activation near the two 18 MW extraction dumps and estimate beam-off time before occupancy to the extraction line area is allowed.
2. Repeat for the 18 MW tuneup dump region.
Action D (F. Asiri)
1. Provide sketches/drawings of the extraction line dump and tuneup dump regions.
Action E (L. Keller)
1. Propose a set of beam containment interlocks to allow occupancy of one IR hall while the other IR is operating or occupancy of both IR halls when the beam is on the linac tuneup dump.
2. Reach consensus between FNAL and SLAC about what instantaneous dose rate in occupied areas is allowed in mis-steering and worst-case accident scenarios (see Action A).
Andrei Seryi, 01/25/06