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User name dalton
Log entry time 09:52:04 on August 25, 2009
Entry number 285838
keyword=Beam energy measurement
The dipole mapper was finally made to work and the field was mapped. To
complete the arc measurement of beam energy, we would need to tune
dispersive optics and take harps scans before and after the arc, which
may take 4 hours. Due to problems with the accelerator and in the hall
over the last week we will have to forgo this measurement. The
accelerator has to be raised in energy by ~0.5% and this has been
scheduled for this morning.
The arc field measurement is still interesting. Below is a copy of Mike
Tiefenback's elog entry.
1482644 Hall A 9th dipole scanner run #968
24-Aug-2009 21:26 M_Tiefenback ELOG
After operations was able to bring the MBSY1C dipole back to its
operating point (MBSY1C.BDL=299044 G), we were able to lock the system
NMR probe using probe #1. The devide would not lock on field with the
default automatic locking algorithms. I set the search mode to
"DAC+/-5%" and used a DAC set point of 2780. The locked field was
unchanged for DAC set points across the range from 2730 to 2830, and lock
was lost quickly outside this set point range. I used the midpoint of
this span (2780) to guide the NMR probe field scan.
I executed the 9th dipole scanner and saved the result as file #968. The
fully corrected field integral was reported as 2391.025 Tesla-mm.
Converting this to a momentum for a beam perfectly matched to the ideal
bend angle for the Hall A transport line of 34.3 degrees results in an
uncorrected momentum of 1197.38 MeV/c. The Beam Energy Monitor table
conversion for the Hall A dipole set point results in 1197.41 MeV/c,
which appears to be adequately close.
It appears that the NMR probe is locking to a physically reasonable
value, in accord with past performance. This dipole set point was tuned
to agree with the 1st pass beam energy delivered to Hall A in recent days.