Accelerator Video Conference Minutes - 01/14/03


Participants:

BNL: D. Raparia, Y.Y. Lee

LANL: M. Plum

LBNL: R. Keller, J. Staples

Jlab: 

ORNL: S. Henderson, N. Holtkamp, S. Henderson, S. Kim, M. Doleans, 
M. Stockli, S. Aleksandrov, S. Danilov, J.G. Wang, T. Hunter, 
R. Cutler, S. Cousineau, L. Kravchuk, W. Klotz , M. White


Agenda:

1) Front-End Re-Commissioning Status - S. Aleksandrov gave a progress 
report on front end commisioning:  

-MEBT beam emittance measurements resulted in an emittance of 0.27 mm*mrad 
for 32mA of beam current.  

-The extinction ratio of the LEBT chopper was measured versus chopper 
voltage; the chopping inefficiency was 1% at 1.8kV.  Slight emittance 
growth to 0.3 mm*mrad was observed with the chopper on.  

-Data has been collected but not analyzed for a number of items, including: 
DC LEBT chopping tests, hysterisis tests, output emittance vs. last 
quadrupole setting, and beam profile vs. quadrupole setting.

-Beam steering in MEBT requires full current in first corrector. Possible 
alignment problem from IS to LEBT.

-Future plans include increasing the source to 38 mA, reducing the beam 
gap to nominal valued (determined by Berkeley measurement), and a possible 
change of the Cs element.  Also, MEBT chopper test, Beam in Gap measurements 
using laser stripping and high power test. 


2) Final HEBT dipole magnetic measurements - J. G. Wang presented the 
finalized results of the HEBT dipole magnet measurements.  Conclusions
were that the performance characteristics of the magnets are satisfactory 
for SNS operation.  Magnets have been accepted by physics group for
installation.

3) HEBT dipole sorting and orbit distortion - D. Raparia talked about 
dipole magnet sorting and closed orbit distortion with unsorted, sorted, 
and sorted and corrected magnet schemes.  The results indicate that the 
magnet sorting reduces the COD by a factor of 3, which is well within the 
COD correction scheme capability.  Only 5% of corrector power is needed to 
achieve a good COD correction with the sorted magnets.