Date May 25, 2000
Attendees M. Doleans,  S. Danilov, J. Galambos, D. Jeon, S. Kim,  J. Wei
 
J. Wei discussed initial results from space charge experiments at the IU CIS 
machine. The input beam of 7 MeV has similar space charge tune shift as SNS, 
and could be a useful tool. The beam profile diagnostic is in the extraction 
line though, and extraction of the non-accelerated 7 MeV beam was troublesome.
It appears that a significant portion of the beam is scraped on extraction, 
which masks the space charge effects. The diagnostics in the ring are limited.
A work-around using an in-ring diagnostic is being looked into. There will be 
an ASAC meeting in mid September, and a mini-ASAC meeting June 19 focusing on 
the linac RF architecture. The design is heading towards a one-on-one 
klystron/cavity configuration. Costs have been reduced, to make this approach 
more attractive. There is an ICAP meeting  in Sept. Dong- O will attend this 
meeting and  discuss the space charge comparison exercise for linac models. 

D. Jeon discussed his efforts in the HOM area. He is reading papers and using 
a rough analytic model which predicts that the SNS is below the threshold for 
beam breakup. Also he has ported a JLab beam breakup code to SNS, and is
presently constructing an SNS input file for it. He also presented plots of 
the beam size and aspect ratio at energies up to ~ 200 MeV. The beam real 
space aspect ratio varies from ~ 5 in the MEBT to ~ 3 in the CCL. 

Sang ho is doing a single cell MAFIA analysis of the beta_g = 0.61 interior 
cell for JLab. Results will be compared to measured values. A copper 
prototype is expected to be operational soon. Sang ho will be traveling and 
communicating with JLab regularly.

Slava presented MAFIA results for the extraction kicker. In particular, he 
is calculating the magnetic and electric field flux for the full geometry, 
including the copper plate and ferrite. Magnetic flux is seen to bend parallel
to the copper plate near the ends, leading to a higher magnetic energy in the 
ferrite than predicted by 2-D analysis. Presently, the MAFIA set up is not 
able to analyze high frequency modes, but Slava will consult with Sang ho on 
possibilities to address this by inputting the B/H cure data instead of 
assuming constant mu ferrite.

J. Galambos presented an update on the corrector / BPM study for the DTL. 
Results using 8/2 and 6/2 corrector to BPM ratios and 2 BPM's per tank, 
indicate most of the error induced beam displacement can be corrected. Using 
6/2, and 4/2 ratios (fewer correctors) also looks promising, except in tank 
6. These results will be discussed with LANL, for feedback. Issues on BPM / 
corrector reliability need to be addressed.