Notes from Main Injector/Recycler Group Meeting Wednesday, 25 September 2002 Bruce C. Brown Mike Syphers -- Beam Optics Effect of Transfer Line Vacuum Window Mike provided physics explanation and formulas for the effects on the beam optics of a vacuum window. In each plane, the position is unchanged but the angle is spread. If the optics were ideally matched to this new situation, the new emittance is the area of an ellipse which encloses the scattered beam. Without this matching, the ellipse will tumble in phase space and further dilution is inevitable. Mike can provide formulas for each case. If a 5 mil Ti window is inserted in an otherwise ideally matched 8 GeV beamline with a beta of 50 m in the plane under consideration, without optics changes, there will be an emittance growth of 7 pi-mm-mr. Nasty!! Both the RR20 and RR30 transfer lines have windows which separate the MI from the RR. Initially a thin Be window was used but one of them failed and both were replaced with Titanium windows from available materials. Ming-Jen observed that early rumors that the window was 5 mil Ti was inconsistent with beam measurement (Available measurements determine the emittance growth only with the assumption that beam losses can be neglected.) Cons consulted with Terry Anderson and they believe (at time of meeting) that the windows were 2 or 3 mil Ti, however it might be a 5 mil window. The option to improve the situation by optics changes has had little consideration. Some discussion ensued on the possibility of removing the window. The RR with 1.0E-10 design vacuum can be connected to the MI with a design vacuum more than two orders of magnitude higher only by having very good differential pumping between them. In fact the difference is vacuum is not as large as per design since the Recycler only approaches its design vacuum while the MI is better then the design specification. It was commented that to protect the high vacuum of the recycler, we would need in each of these lines a fast valve to cover accident conditions and lots of differential pumping. Fred Mills suggested that this might be a place to consider NEG (Non Evaporable Getter) pumps such as are used extensively at CERN. He suggested Noel Hilleret or Alain Poncet as a CERN experts (The also knows some retired experts from CERN).. Mike has made his work available as a Main Injector note. http://beamdocs.fnal.gov/DocDB/0003/000375/001/MI-0286.pdf For now I will also store a copy in the directory with these minutes. Please see http://www-ap.fnal.gov/~bcbrown/MtgNotes/MI-0286.pdf Ming-Jen Yang -- Lattice matching Verification The efforts to measure the lattice functions of the RR20 and RR30 transfer lines are made quite difficult by the fact that the MI can only measure beams with 53 MHz structure while the RR requires 2.5 MHz structure. The possibility of employing only a single pass around the RR and immediately transferring back to the MI is not possible because the VDPA magnets (main vertical bends in both lines) are powered in series for the two lines and different currents are needed. We ramp them to the required currents between the transfers (also note that the currents are too high to permit the DC operation at either current because of inadequate magnet cooling). Ming-Jen is exploring the option of running small cables and using a shunt on one magnet in each pair. The alternative of using separate supplies requires 350 MCM (large) cable and more rack space in an already crowded building. Other issues in trying to get lattice measurements were discussed. Shekhar Mishra -- plans Dan Broemmelsiek has provided a list of RR studies using protons which Shekhar showed. He will work with us to try to get this accomplished. The near-term plan is to get 1.0E12 pbars into the RR beginning immediately using pbars from the bottom of the Acc Stack initially. Goal is >80% transfer efficiency and >100 Hour lifetime with 1.0E12 pbars. Dan commented that the 0.5-1 GHz momentum cooling system will not be available for 10 days to 2 weeks. Shekhar said he chooses not to wait. Warren Schappert has additional data with the BLT BPM system. Filters (hardware) have improved the appearance of the signal near injection. Guan Wu is ready to try to exercise his software to use RR dipole and tune trombone correctors to hold RR orbit and tune constant against MI Ramping. Stan Pruss will work with Guan to try this with beam.