Re: Tagger vacuum chamber (fwd)

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

Jim,

The 30mm is not the height of the window, it is the minimum required gap 
height of the magnet.  It is driven by the requirement to be able to tag 
up to within a few hundred MeV of the endpoint and keep background in 
the tagger from scraping of the beam halo on the poles to a minimum.  I 
think 30mm is about the right number for the minimum required tagger 
vacuum box height through the magnetic field region of the 
spectrometer.  It needs to be larger outside the magnetic field region, 
but that is a lot easier to arrange than increasing the gap between the 
poles.

Richard Jones

Jim Stewart wrote:
> Dear Richard and Elke
>
> I asked Tim to calculate how thick the wall thickness would have to be 
> if we were to design a vacuum chamber which fits into the poles of the 
> tagger magnet. Tim computed for a 550 mm wide chamber and a 6mm wall, 
> the wall would deflect 5mm due to vacuum forces. With an 8mm wall the 
> deflection would be ~2mm. This implies that we could build a chamber 
> with 8mm wall and fit it into a 45mm gap magnet. I believe this would 
> increase our power consumption by 50% but we would not have to worry 
> about vacuum leaks. We could also remove the vacuum chamber and re-map 
> or re-survey the magnet if we want. It is not clear to me how you 
> calculate power verses security.
>
> Do you know, Richard, what the gap in the magnet needs to be at the 
> middle of the magnet? I understand we need 30mm at the window. A 
> double arch structure could probably get by with somewhat thinner walls.
>
> Jim
>
>
> ---------- Forwarded message ----------
> Date: Mon, 12 May 2008 11:33:32 -0400
> From: Tim Whitlatch <whitey@jlab.org>
> To: Jim Stewart <jstewart@jlab.org>
> Subject: Tagger vacuum chamber
>
> Hi Jim,
>
> A rough calculation shows that the chamber wall would have to be 6mm 
> thick to deflect only 5mm. This means that the inside of the 2 walls 
> would be 8mm apart under vacuum (assuming outside dimension is still 
> 30mm).
>
> Cheers,
>
>       Tim
>