BNL: D. Davino, A. Fedotov, Y. Lee, D. Raparia, S. Tepikian, J. Wei
LANL: S. Nath, M. Plum, A. Regan, H. Takeda, L. Young
LBNL: R. Gough, J. Staples
Jlab:
ORNL: R. Cutler, S. Danilov, G. Dodson, E. Tanke, M. Doleans, P. Chu, M. Gianella, J. Galambos, S. Henderson, D. Jeon, T. Pelaia, A. Shishlo, M. White, S. Assadi
J. Wei introduced S. Tepikian, who will be doing lattice and application programming work for BNL.
D. Jeon reviewed the low energy collimation scheme: the proposed baseline approach includes adding 2 scrapers at the MEBT chopper (x direction) and adopting a modified MEBT optics (requires 3 new quad power supplies). DTL collimation is not effective, and not reccommended. Also, LEBT collimation is ineffective. J. Staples noted that the requirements for the additional MEBT scrapers need to be developed and an implementation plan formulated, and noted that horizontal windows at the MEBT chopper exist. It was decided to first get the ASAC reaction.
The DTL corrector power supply issue was discussed. The original PS bid (for 300 A supplies) came in well above the budgeted amount, and reducing to 200 A has minimal cost impact. Two alternatives are possible: 1) using the same type 20A supplies as all the other correctors use (linac + ring) and stacking them up to 140 A if needed, or 2) using unipolar 150 A supplies with reversing switches. The first alternative appears to be within cost. Estimates for option 2 will be available by Wed., when a decision will be made.
J. Wei showed results from the ring dipole measurement program, indicating at present three classes of transfer functions (10 coils measured, 6 OK, 2 high, and 1 low by 0.2% at 1.0 GeV). The spread was expected to be < 0.01%. The difference can be compensated by aligning the dipoles with horizontal offsets (utilizing the small change in transfer function as a function of position). However, the amount of compensation needed, is a function of energy. At 1.3 GeV, the measured difference in transfer magnets is smaller. It was noted that the dipole correctors could compensate the needed amount, but their use is preferrable reserved for other purposes (i.e. local bumps etc.).
D. Jeon reported on work related to the RF reference line stability requirements. Assuming a 0.1 degree cavity to cavity phase error has minimal effect on the beam dynamics (final phase shift) and is acceptable. Temperature control is needed, and the specification is 0.5 degrees F (equivilant to ~ 0.063 deg. cavity to cavity phase error). A. Regan noted that there will be a pressure controll system too (a simple stand-alone system). ORNL will be responsble for installation of the reference line, and responsibility for care of the reference line if the temperature control is ever shut off (i.e. concerns about the line breaking if it is fixed to the wall and shrinks). D. Raparia asked about the phase error at the energy corrector - only ~ 1 degree is required here, which should be achievable.
L. Young noted that the trip to the CCL cavity vendor was favorable, and that they appear to have someone who understands and is capable of the cavity tuning.S. Nath noted that running SCL cavities at their max. voltage (+- 10% variatio expected) and not adjusting the phase to compensate for continuous focusing results is a fairly well behaved beam (some small longitudinal growth, but not transverse). This was a surprising result, and somewhat simplifies the commissioning scheme, in that the target cavity phase need not be adjusted for the actual cavity performance. L. Young noted that the problem is more in setting the phase, not in determining what to set the phase to.
The end-to-end simulation is progressing. Staples' "measured" distribution has been transported through the RFQ, and passed to parmila for transport to the foil. This is refered to as the reference case, and is given to D. Raparia. Now, 10 mismatched cases are being run, using MEBT settings derived from expected setting capabilities.