[Tpe] TPE shielding

[Larry Weinstein]

Dear Folks,

Recommendation: In order to be very conservative, build a concrete wall 
on the beam left side of the collimator box, frascati magnet 1, and PS 
magnet.  The wall would be about 10' x 5' x 1' and require 200 blocks.  
It should be built during the next extended down time (Tuesday?) so as 
not to interfere with taking data.

Details:  I spoke to Pavel Degtiarenko, the radiation and shielding 
expert.  He says that there is very little useful data about the effect 
of radiation on electronics because the response of electronics to 
radiation is highly variable.  He also noted that the existing BPM 
amplifiers have probably already suffered some radiation damage and that 
this damage is cumulative.  He also said that most of the radiation is 
probably high energy particles that can be shielded by a shield wall (if 
we know the approximate source location.)

This means that we probably want to add shielding to reduce the 
probability of catastrophic BPM failure.

RadCon gave us the badge readings today (thanks, Becky!).

66016 	331 	1' from top of Acc IOC rack 	
66017 	197 	2.5' from top of Acc IOC rack, in front of concrete wall
66018 	220 	2.5' from bottom of Acc IOC rack, in front of concrete wall
66019 	66 	2.5 from top of Acc IOC rack, behind concrete wall
66020 	73 	2' from bottom of Acc IOC rack, behind concrete wall
66023 	92 	on ioc ptarg 			
66024 	254 	in front of new lead wall, 5' from floor 	
66025 	191 	L1-15 on left (upstream) side of IOC 	
66026 	632 	on railing opposite PS 		
66027 	230 	upstream, beam side of lead wall on ioctorus
66028 	126 	downstream, outside of lead wall on ioc torus

The first column is the badge number, the second is the radiation dose, 
and the third is the location.

A few notes: Badge 66026 with a reading of 632 mr is located where the 
radcon photon probe was located before 1/20, on the railing of the space 
frame close to the pair spectrometer.  The probe was reading about 50 
mr/hr at that location.

Badge 66019, behind the concrete wall, is located directly on top of the 
accelerator BPM amplifiers and right next to the radcon photon probe 
which is currently reading 5 mr/hr.  This is consistent with badge 66026.

badges 66016, 7, and 8 are located on the accelerator BPM amplifier 
rack.  The highest one (66016) has the highest dose and has much less of 
the lead shielding on the lead wall between it and the beam line.  The 
concrete wall (either 6" or 12") reduces the rate from about 200 mr to 
70 mr (comparing badges 17 and 18 with 19 and 20).  (Note that the 
badges were placed before the BPE shielding was added.)

The maximum thickness of the lead wall reduces the dose from 254 (badge 
66024) to 92 (badge 66023).

The radiation level is not much less a little further down-beam on rack 
L1-15 (191 mr at badge 25).

The dose decreases about a factor of two between the upstream beam side 
of the lead wall on ioctorus to the downstream outside of the lead wall.

Summary: The dose at iocptarg, ioctorus and the accelerator BPM 
amplifiers are within a factor of two.  The shielding reduces the dose 
significantly.

There is floor space or floor weight capacity to place any more 
shielding near the racks.  THis means that the only place to add 
shielding is near the source.  Since the source probably includes the 
collimator box, convertor and chicane, we should build a concrete wall 
on the beam left side from the PS magnet going as far upstream as possible.

-- 
				Sincerely,
				Larry

-----------------------------------------------------------
Lawrence Weinstein
University Professor
Physics Department
Old Dominion University
Norfolk, VA 23529
757 683 5803
757 683 3038 (fax)
weinstein at odu.edu
http://www.lions.odu.edu/~lweinste/

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