Re: pair space

[Jim Stewart <jstewart@jlab.org>]

Hello Richard

I looked a bit at the civil drawings with Alex for the collimator 
extension and came to the conclusion we cannot use this space for the 
pair spectrometer if we go with the 24-8-72 magnet. The labyrinth to the 
collimator extension looks like it enters the collimator extension cave 
roughly  6' (+/- 1/4")  from the hall-d wall. If we want to move the 
concrete/lead  shielding farther into the hall than this then we will 
block the entrance. I assume for safety reasons we need a 1m path to 
flee the cave in emergency.   Therefore there is not enough space for 
the magnet and a labyrinth next to each other.

i think we need to plan that the concrete shielding starts flush with 
the entry of the labyrinth to the extension.

Jim

Tim Whitlatch wrote:
> This is dependent on the outcome of the sweep magnet requirements of 
> course.....
>
> Tim
>
> Richard Jones wrote:
>> Jim Stewart wrote:
>>> Hello Tim
>>> This starts to get a bit uncomfortable. If we go with the 24-8-72 
>>> then the magnet is 7'-6"= 2.3m long including the field clamp. 
>>> Hrachya  plans to use a 1.5m long vacuum chamber followed 
>>> immediately with the counter array. This means 4.5m are blocked not 
>>> counting space for working. Here I am assuming the radiator is about 
>>> 1m upstream so that Franz could install silicon  in front of the 
>>> magnet. Could we talk about this at the next tagger meeting? I think 
>>> we are missing a couple meters.
>>>
>>> Jim
>>>
>> One way to estimate space occupation in the collimator cave is to add 
>> up the lengths of the essential items.
>> primary collimator: 50 cm
>> first sweep: 100 cm ??
>> first iron block: 200 cm -- could be incorporated into a longer first 
>> sweep magnet with filled gap
>> first concrete block: 100 cm
>> second collimator: 50 cm
>> second sweep: 100 cm ??
>> second iron block: 100 cm
>> second concrete block: 100 cm
>> lead wall: 15 cm
>> total (irreducible) length: 815 cm
>> total length of cave: 1200 cm
>> We probably have something like 3 m max that we can squeeze out of 
>> the cave.
>>
>> Richard Jones