Accelerator Physics Group Meeting

6/27/01
Present: J. Wei, J.Galambos, S. Aleksandov, S. Danilov, W. Wan, J. Holmes,
S. Kim, P. Chu, E. Tanke, M. Doleans, S. Cousineau, 
I. Hoffman, S. Valero, J. Qiang, 


(1) ring injection kicker coating: The 5 coating requirements are:
a) unperturbed penetration of kicker field (200 us, 0.1 T)
b) screen of beam field (from <200 kHz to ~ >5MHz) (we need to worry about impedance from sidebands)
c) tolerable heat load (LHC recently discovered an error in the resistivity formula)
d) low secondary electron yield
e) Practical feasibility.
LHC work on this recently indicates 

Jie proposed a dual-layer solution:
1) inner layer (contacting ceramic pipe) of striped coating of a material of
known,good conductivity, maybe gold? The striped coating avoids Eddy current, 
the thickness is balanced from kicker field penetration while allowing
image current at least to the 200 kHz sideband
2) outer layer of thin TiN, all-around to avoid electron production


(2) FE/RFQ/MEBT halo: the key is whether RFQ is a good emittance filter. 
 Staples + Sasha claims yes, Stovall + Takeda claims no. In the 
case of "no", then the only choice to me seems to find a back-pocket plan of
identifying two locations in MEBT with proper phase relation to have two sets
of scrapers -- tough. (one place is at the anti-damper) Sasha is 
working on this.
 
(3) rf power overhead -- short of reducing the Lorentz detuning coefficient
(stiffening rings and further measurements) a more elegant solution is
active tuning -- like using piezo tuner. The gain is huge. The uncertainty
is in the robustness of the piezo tuner in a radiation environement for 
many years. Radiation tests are planned at DESY. Sang-ho is looking out 
on this.

(4) We really ought to keep FE/MEBT diagnostics. The reports from LEDA 
experiments and also at the space charge mini- workshop are bothering. 
The lack of an emittance measurement complicates and clouds the 
interpretation of profile measurements. Presently RMS measured 
quantities do not match well with models.