Log entry time 01:33:51 on July 03, 2010

Entry number 329522

(See TOSP's for details, and ask spokespeople or RC if you have questions).

In its present configuration, the PREX septum has a dipole field along
the beamline, and bends the beam.  Two new compensating magnets were
added in Hall A to keep the beam directed toward the dump: the "permanent
magnet" in the sieve box and a "corrector magnet" whose current and field
are controlled by MCC.  They must tune the corrector magnet current
depending on the momentum setting of the PREX septum.

NEVER start beam or change the septum current (or the PREX P0 setting)
without coordinating with MCC. When in doubt, you probably should not be
changing the septum momentum -- call the RC to confirm before you do it.

You can ONLY run the septum at the three set-points established during
beamline commissioning (friday July 2 swing-shift):

PREX P0 set   |  Septum current setpoint   |  Corrector current setpoint
1.131 GeV     |   775.6 A                  |  9 A
0.9   GeV     |   617.2 A                  |  1 A
0.7   GeV     |   480.0 A                  | -4 A

You may also find the setpoints at:
http://ntoro.stanford.edu/APEX/wiki/index.php/Special_Procedures_for_Modified_Beamline#Setpoints

MCC operators will probably refer to the settings by the septum current.
 Please verbally confirm both the septum current and the corrector
current setpoint before any switch.