[Tpe] Beamline down stream of target

[Will Brooks]

Hi,

  I think without question the calorimeter will be positioned downstream 
of the forward carriage during special calibration runs, and elsewhere 
(probably just north of the sector 4 calorimeter) during the rest of the 
time. There was a discussion of a stand on the forward carriage at one 
point, but then it appeared the stand blocked egress; following that we 
discussed hanging it or putting it inside the support tube, which would 
require relocation of radiation detectors. In principle we could put it 
in the downstream alcove if there is a helium bag, but that is less 
desirable because the beam size is diverging and may become larger than 
the calorimeter face; however, in a pinch it will probably work, if 
aligned well with the beamline.

  Here is a proposal: can the engineering staff evaluate if it is 
feasible to hang the calorimeter downstream of the support ring or not. 
If hung, it needs to be removable in a short time, e.g. an hour or two 
(and if possible repositioned in a flexible location nearby). I picture 
using the floor supports from the upper level of the forward carriage 
for supporting this, and a come-along to lift it, supporting it from 
cables with turnbuckles for height adjustment. If it is NOT possible to 
hang it safely, then we should see what the simulation says about the 
beam spot size in the downstream alcove, and must plan on a helium bag 
with dimensions similar to those of the calorimeter.

  Someone else should address the rest of the questions. My guess is 
that we want helium to the Faraday cup; vacuum would be nicer but it 
would be quite a big beam pipe (20 cm diameter?) and will interfere with 
the calorimeter, and air will probably cause too much background.

Thanks,

  - Will


On 7/27/10 4:18 PM, David Kashy wrote:
> Hi All,
> I don't think we have settled what to do downstream of the target.
> We need to know if the calorimeter is going there and who is designing a
> stand and how it works.
> Also if we want helium, vacuum or air or a combo between the target and
> the Faraday cup or the calorimeter.
>
> Thanks
> Dave
>
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