Subject: Pretzel effect on sync light source and BBI distortions
From: "James A. Crittenden"
Date: Wed, 17 May 2006 13:31:55 -0400
To: Donald Hartill , Mark Palmer , Eugene Tanke , mjf7 , Dave Rice , John Sikora , Stu Peck

My recent calculations (11 and 16 May) of the electron and positron
orbits at the sync light source points were done with
the design pretzel settings (2400 at 5 GeV and 3300
at 2 GeV.) However, at 2 GeV, we operate at a pretzel
setting of 2850.  It turns out that for this pretzel
the orbits at 2 GeV and 5 GeV are more similar.

I have also calculated the orbit and beta distortions
at the electron sync light source points which arise from
the BBI.  I used the operating positron configurations
of 4x5 10 mA/bunch at 5 GeV and 8x3 2 mA/bunch at 2 GeV.
The orbits and beta's vary with current and
are slightly different for each electron bunch, as
can be seen here:

2 Gev:
http://www.lns.cornell.edu/~critten/cesr/injection/notes/17may06/synclight_1307/

5 Gev:
http://www.lns.cornell.edu/~critten/cesr/injection/notes/17may06/synclight_1306/

Modulo the slight bunch-to-bunch differences, the
orbit and beta's for electrons in our present operating
conditions are about:

                2 GeV               5 GeV
                -----               -----

                e-                    e-
                --                    --

 X (cm)        1.2                   0.97
 Y (cm)        0.01                  0.0

 XP (mrad)     0.55                  0.50
 YP (mrad)     0.0                   0.01

 BetaX (m)     20                    12
 BetaY (m)     17                    12


I have updated the calculations of the source positions
and reflection angles at the primary mirror for these
operating conditions here:

http://www.lns.cornell.edu/~critten/cesr/synclight/16may06/all/

These results show that such effects do not account
for our difficulty in getting compatible mirror alignments
at the two energies.

-- jim

========================================================
James Crittenden                   Tel. (607) 255-9424
Wilson Synchrotron Laboratory      Fax  (607) 255-8062
Cornell University
Ithaca, New York 14853-8001
========================================================


James A. Crittenden wrote:
> Having found that the horizontal orbit angles at the source points
> differ in the 2 and 5 GeV optics by 40% (appended, mail of 11 May), I
> checked these
> angles in the SBP optics presently under design (chess_20060123).
> I found these angles have changed by a similar amount, but
> in the other direction. One can conclude that the horizontal
> orbit angles at the light source points are not constrained
> by the design procedure at the 0.2 mrad level.
>
>                 5 GeV (optics design in progress)
>                 ---------------------------------
>
>             e+          e-
>             --          --
>
> X (cm)     1.13        1.230
> Y (cm)    0.005        -0.0049
>
> XP (mrad)  -0.97        1.02
> YP (mrad)  0.013e-3       0.013e-3
>
> BetaX (m)  12.8        10.4
> BetaY (m)  11.0        10.9
>
>
> ===================================================================================
>
>
> I also calculated the effects on the source points and reflection angles
> arising from switching from 2 to 5 GeV, using the pretzel orbits found
> in the calculations from May 11. The difference in source points and
> angles can be seen here:
>
> http://www.lns.cornell.edu/~critten/cesr/synclight/16may06/all
>
> The source points move by 5 cm and the reflection angles by about 0.2 mrad.
> These difference don't seem large enough to explain why we have lost
> the electron light at 5 GeV.
>
> -- jim
>
> ========================================================
> James Crittenden                   Tel. (607) 255-9424
> Wilson Synchrotron Laboratory      Fax  (607) 255-8062
> Cornell University
> Ithaca, New York 14853-8001
> ========================================================
>
> Presenting operating lattices:
>
>                 2 GeV                           5 GeV
>                 -----                           -----
>
>             e+          e-                e+              e-
>             --          --                --              --
>
> X (cm)     1.15        1.20              0.95            0.95
> Y (cm)    -0.01        0.01              0.001          -0.001
>
> XP (mrad)  -0.77        0.78             -0.56            0.58
> YP (mrad)  0.7e-3       0.7e-3           2.2e-3           2.2e-3
>
> BetaX (m)  17.5        18.7              14.3            13.8
> BetaY (m)  16.2        15.5              11.1             8.1
>
>
>