[Tpe] TPE shielding

Wed Jan 26 17:26:40 EST 2011

Dear Dave,

The wall is 10' wide.  That is the approximate distance from the short 
ladder at the pair spectrometer to the upstream end of that platform.  
The wall height would then be beam height plus one foot.  (I did not 
measure the height so I am not sure whether it would be 4' or 5'.)

I completely agree that we should not rush into this.  I think that the 
radiation experience since Thursday indicates that we do not need to do 
this immediately.

- Larry

David Kashy wrote:
> Hi Larry,
> Is this wall 10' high or wide?
> If it is 10 ft wide then I guess we need to start it above the floor 
> level and need to design a beam structure to support it.
>
> If it is 10 ft tall we will still need to design a structure to keep 
> it from toppling.
>
> This wall will weight about 8000 lbs (similar to HYCAL) not a trivial 
> load and thus we must do it correctly.
>
> Thanks
> Dave
>
>
>
> On 1/26/2011 4:55 PM, Larry Weinstein wrote:
>> 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  <mailto:weinstein at odu.edu>
>> http://www.lions.odu.edu/~lweinste/  <http://www.lions.odu.edu/%7Elweinste/>
>
> ------------------------------------------------------------------------
>
> Spam 
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> Forget previous vote 
> <https://www.spamtrap.odu.edu/b.php?i=438400204&m=903a77671a30&t=20110126&c=f>

-- 
				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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