[Halld-tagger] Some results on electron acceptance

[Richard Jones]

Dan,

Some things to keep in mind:

 1. remember the quadrupole is vertically focusing, and can be tuned to improve things near the endpoint when the physics requires endpoint energies
 2. the gap is 3cm
 3. there is significant scraping at 11.7 GeV under GlueX running conditions
 4. we chose 11.7 GeV because things get impossible above that, even with the quad

-Richard J.

 1. On 6/27/2012 4:49 PM, Daniel Sober wrote:

> I have put the current tagger magnet into my old codes and come up with at least one interesting result that needs investigating: Using a realistic bremsstrahlung calculation integrated over photon angles (Maximon and Lepretre, 1985) for an amorphous gold radiator,
> the fraction of the bremsstrahlung electron cone clearing the 2 cm magnet gap gets bad rather quickly as k/E0 > 0.95, with only 81% transmitted at k/E0 = 0.98.  See the attached files, one for the full range and the other in fine steps near the endpoint. Some of the numbers in the header (especially "FULL-ENERGY ANGLE") may not make sense to you, but they generate what we need.  The second column (Gap frac.) gives the fraction of electrons clearing the 2 cm gap, neglecting the Rogowski chamfer which will make things a little better -- I will need a detailed drawing of the pole shape to account for this effect.  The subsequent columns give the fraction passing through a given detector full width.  (The "negative" fractions just flag the cases where the magnet gap is the limiting aperture.)
>
> I am not set up to calculate coherent bremsstrahlung or the effect of photon collimation, but with some work I could plug in the appropriate electron angular distributions if I had them.
>
> Dan
>
> -- 
> /Daniel Sober
> Professor
> Physics Department
> The Catholic University of America
> Washington, DC 20064
> Phone: (202) 319-5856, -5315
> E-mail: sober at cua.edu <mailto:sober at cua.edu>/


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