Re: PS target issues (fwd)

[Richard Jones <richard.t.jones@uconn.edu>]

Hrachya,

Are you proposing that we move the position of the converter from its 
current position ~2m upsteam of the PS magnet, and then envision a 
second converter somewhere else when we get around to designing the 
polarimeter?  We should consider this possibility, but I am skeptical 
that it makes much difference.  Can you tell us quantitatively what gain 
we get in final energy resolution by moving the converter downstream a 
couple of meters from its present position?  At least at its present 
position it is possible to think about doing polarimetry with the same 
converter.  We are never going to find anything like 19 m of space for 
doing polarimetry in the way we did at YERPHI.  To use that system, we 
would need to scale that distance up by another factor to account for 
the higher energies involved.  Whatever we do (and I have some ideas) we 
will need to do within a few meters space that we have between the 
second sweeping magnet and the PS.

If we move the converter to the entrance of the PS magnet, we probably 
double the cost of adding a polarimeter at some point in the future, and 
certainly make installing it much more disruptive to the running 
schedule of the hall.  We could do that, but we need a compelling reason 
for it.

Richard Jones


Hrachya.Hakobyan wrote:
> Dear  Sasha,
>
> I'm sending this email with some delay due to my local over-occupancy 
> yesterday. Thank you for calculations of MS influence. I ve already  
> seen them
> and I ve sent slightly earlier my evaluation of MS effects to Richard 
> (see below) and  would remark on the distance of converter from 
> Magnet. Richard has  suggested the need in large distance, seems  for 
> direct polarimetry needs. At YeRPHI  we applied even a 19m upstream 
> setting. But for the ordinary PS functioning  and aim to decrease the 
> angular divergence influence, including that of MS , I suggest the use 
> a  converter insert at the entrance of the magnet, which corresponds 
> to 3.5m long distance to FSF and WSF hodoscopes.  For direct 
> polarimetry needs the distance should be choosen big enough to provide 
> a domonance of the pairs  angular divergence over the beam spot size 
> at the magnet entrance..
>
> Cheers, Hrachya