Subject: Calculations of BBI effects at 5.3 GeV and 1.9 GeV
From: "James A. Crittenden"
Date: Fri, 29 Jul 2005 14:28:40 -0400
To: Dave Rice , David Rubin , Stu Peck , Sasha Temnykh , mjf7 , Mike Billing , John Sikora , Mark Palmer sag , David Sagan , Jessica Darland

As advertised in yesterday's message, Stu's suggestion to
calculate the pretzel separations for the lattice in use
in June, 2001, prompted me to extend the comparison to
the positron current dependence of global lattice parameters.

The result is a lode of information which I can't fully
describe here. I will cover some isolated results which
I found particularly interesting, but I encourage
those of you with better intuition than I to page through
these plots to see if any of them strike
you as worthy of further investigation.

If you put the following two links on adjacent browser
pages, you can easily see how the various lattice
characteristics depend on positron current in the
weak/strong approximation:

5.3 GeV as of 6/2001:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855

1.9 GeV present operation
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851

These plots include the effect of the BBI at the IP.
For purposes of assessing the impact of the parasitic crossings,
it can be useful to compare the above plots to calculations
with the IP BBI turned off:

5.3 GeV as of 6/2001 with IP BBI off:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_854

1.9 GeV present operation with IP BBI off:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_850

Beta blowup
-----------
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851/P003.html
At 1.9 GeV the maximum beta goes from 40 to 140 m between 0 and 2 mA/bunch.
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855/P003.html
At 5.3 GeV the maximum beta goes from 65 to 100 m between 0 and 6 mA/bunch.
In both cases most of the effect comes from the IP BBI.
Without it:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_850/P003.html
At 1.9 GeV the maximum beta goes from 43 to 50 m between 0 and 2 mA/bunch.
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_854/P003.html
At 5.3 GeV the maximum beta changes little, staying at 68 m between 0 and 6 mA/bunch.

Horizontal emittance
--------------------
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851/P011.html
At 1.9 GeV the horiz emittance goes from 140 to 360 nm between 0 and 2 mA/bunch.
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855/P011.html
At 5.3 GeV the horiz emittance goes from 205 to 235 nm between 0 and 6 mA/bunch.

Vertical emittance (calculated from radiation integrals)
--------------------------------------------------------
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851/P012.html
At 1.9 GeV the vert emittance goes from 0.045 to 0.055 nm between 0 and 2 mA/bunch.
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855/P012.html
At 5.3 GeV the vert emittance goes from 0.018 to 0.026 nm between 0 and 6 mA/bunch.

Horizontal beta*
--------------------------------------------------------
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851/P016.html
At 1.9 GeV the vert emittance goes from 90 to 20 cm between 0 and 2 mA/bunch.
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855/P016.html
At 5.3 GeV the vert emittance goes from 90 to 60 nm between 0 and 6 mA/bunch.

Vertical beta*
--------------------------------------------------------
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851/P017.html
At 1.9 GeV the vert emittance goes from 1.1 to 0.9 cm between 0 and 2 mA/bunch.
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855/P017.html
At 5.3 GeV the vert emittance goes from 1.8 to 1.4 nm between 0 and 6 mA/bunch.

Yesterday I found the bug which had led me to think the vertical orbit position depended
on positron current at the level of 100 microns. The dependence turns out to be
at the level of 1 micron, and varies quite a bit from bunch to bunch. It is smaller
at 1.9 GeV:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_851/P010.html
than at 5.3 GeV:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bunch_855/P010.html

The dynamic aperture calculations are also interesting:
5.3 GeV as of 6/2001:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/dynap_855/P019.html
shows that the degradation at 5.3 GeV from 0 to 6 mA is from 10 to 8 sigma (at design tunes)
rather than to 2-3 sigma as shown during the MiniMAC at 1.9 GeV.

Finally, it is interesting to note that the horizontal BBI kick at the IP for
e- t1.b1 changes sign from 5.3 (6 mA/bunch) to 1.9 GeV (2 mA/bunch). The kicks at the parasitic
crossings are  similar for the two energies, ranging from 1 to 4 microradians, but the IP BBI kick
is -5 microradians at 1.9 GeV:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bbikicks_851/P001.html
and +20 microradians at 5.3 GeV:
http://www.lepp.cornell.edu/~critten/cesr/injection/notes/28jul05/bbikicks_855/P001.html

-- Jim

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