[Tpe] TPE shielding
Larry Weinstein
weinstei at jlab.org
Thu Jan 27 08:44:15 EST 2011
Yes, that is correct.
David Kashy wrote:
> Larry,
> If I understand correctly you want to add shielding on to the platform
> that supports the pairspectrometer magnet..
> Is this correct?
>
> Dave
>
>
> On 1/26/2011 5:26 PM, Larry Weinstein wrote:
>> 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
>>> <https://www.spamtrap.odu.edu/b.php?i=438400204&m=903a77671a30&t=20110126&c=s>
>>> Not spam
>>> <https://www.spamtrap.odu.edu/b.php?i=438400204&m=903a77671a30&t=20110126&c=n>
>>> 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 <mailto:weinstein at odu.edu>
>> http://www.lions.odu.edu/~lweinste/ <http://www.lions.odu.edu/%7Elweinste/>
>
>
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--
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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