Re: hall D optics June 2001

[Elton Smith <elton@jlab.org>]

Hi Jay,

Thanks for the update. The ability to offset the beam vertically and
horizontally without changing the angles will clearly be useful when it
comes to commissioning the beamline.

About the distance from tangency to radiator: At this point, even if the
optics allow for a slightly shorter distance than what we nominally have
reserved (119 m), I suggest that we keep the current distance with the
additional couple of meters as contingency for future use.

Thanks, Elton.


On Thu, 21 Jun 2001, Jay Benesch wrote:

> Richard and Elton,
>
> 	I've got a new design which shortens the ramp by 6 meters.  I began
> working with one I found which is shorter yet than the one in PDR
> version 3 and the one we discussed in March, a design I had misplaced.
> In any event, I now have pairs of correctors just after the last triplet
> and 2.5m upstream of the radiator; 9m between the pairs.  The radiator
> is 117m from the point of tangency.  I can offset the beam +/- 4mm
> horizontally or vertically at the collimator with standard correctors at
> these locations.  I also have more room for electron beam dianostics.
>
> 	At the collimator, beam envelope (one sigma) is x=0.45mm and y=0.4mm.
> Beam is diverging vertically at the collimator, but probably acceptable
> given the radius.  Horizontal sigma 1.65mm at radiator; y ~0.4mm there.
>
>
> 	Decrease in ramp length raised dipole field to 6.4 kG at 12 GeV, so
> upper energy capability is now ~18 GeV.
>
> 	I just had an idea which might allow a later vertical focus without
> screwing up the horizontal; I'll try it tomorrow.
>
> Jay
>

-- 
Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625