Date April 20, 2000
Attendees S. Danilov, M. Doleans, J. Galambos, J. Holmes, D. Jeon, S. Kim, J.G. Wang, J. Wei
 
J. Wei discussed the possibility of summer students and asked about possible 
LINAC 2K abstracts. Sang ho will submit one on the cavity parameters and J. 
Galambos will draft an abstract on linac architecture for J. Stovall's possible 
use. At the ring review last week this issue of more BPMs in the HEBT came up. 
Dong O will work on the HEBT transport to scope out the impact of reduce the 
phase advance per period below 90 degrees. Jie noted that B. Kustom is 
requesting that the RF partitioning scheme be addressed. The 1 on 1 klystron per 
cavity case has about 12 klystrons per power supply, and will not be able to 
keep running in the event of a power supply failure. The 12 cavities per 
klystron case offers the possibility of using a hot swappable spare klystron, on 
a common waveguide. This scheme offers the possibility of almost continuous beam 
in the event of a power supply failure. This issue needs to be addressed. R. 
Sundelin says CEBAF has a 1% downtime from power supply problems (out of a total 
of 20% downtime).

S. Kim and J. Galambos discussed the JLab cavity workshop on 4/12-13. The beta = 
0.61 cavity shape is finalized, similar to Sang ho's proposed shape. The high 
berta cavities  will have a beta_g of 0.81 to facilitate higher energy operation 
with higher gradients. Also the number of medium beta cryo-modules is increased 
from 8 to 11, to offer more physics margin by offering an increase in the 
transition energy. 

Sang ho discussed his recent trip. He first went to INFN and discussed cavity 
design with C. Pagani's group. Then he attended a TTF meeting in France where 
results of different cavity processing techniques were reported. Single cell 
beta=1 cavities with heat treatment and chemical processing achieved upo to 55 
MV/m. A new electro-polishing technique achieved slightly higher values, but is 
to novel to use in the SNS cavity processing. Tesla is considering 1 MW 
couplers, and is doing HOM studies to calculate the transverse kick. Sang ho 
also went to Sacaly France and met with H. Safa, and toured their facility. They 
are testing several low beta cavities, and observing different multipacting 
behaviour for cavities that have very similar design, and comparable processing. 
It is felt that the prediction of multi-pactoring is difficult. Finally Sang ho 
went to DESY and met with S. Simrock to discuss the LLRF. In the immediate 
future, Sang ho will wrap up the beta_g = 0.81 cavity shape work, and start the 
HOM work using MAFIA. Marc Doleans will work with Sang ho.


Dong O will begin benchmarking the linac codes, with particular emphasis on 
understanding the space charge modeling accuracy.

Regarding checking of the drawings, Jeff found no problems with the Ring and transfer line drawings. The linac drawings are presently being redone, to 
reflect the change in linac architecture.

S. Danilov noted that S. Kurennoy verified the presence of longitudinal magnetic 
field inside the kicker ferrite using a 3-D MAFIA model. This is consistent with 
Slava's prediction, and helps explain the possible high impedance from the 
kicker. Slava will discuss his ideas at BNL next week.

J. Wei noted that E. Tanke has accepted a position with our group. 

J. Wang discussed the Target interface. He attended the target review. Regarding 
protection of the accelerator from water damage in the event of a window 
breakage, a fast valve is planned upstream from the window. The 2 second 
response time of the valve was questioned. The radiation damage to the last harp 
is being addressed and the back-streaming neutron flux appears to be 1000 times lower than the proton flux. Transport analysis is being done to optimize the 
location of the final quads, focusing the beam on the target.