Summary of the Muon Collider Targetry Workshop BNL, 1-5 pm, June 1, 1998 by K. McDonald This summary also appears at http://puhep1.princeton.edu/mumu/target/ Sends comments etc. to mcdonald@puphep.princeton.edu The agenda was: 1:00-1:30 K. McDonald, Overview of targetry R&D plans (including comments from Colin Johnson) 1:30-1:45 A. Carroll, Remarks on the FEB U-line 1:45-2:10 J. Hastings, Plans for spallation target tests 2:10-2:25 B. King, Moving solid targets 2:25-3:00 B. Weggel, the FSU High Field Magnet Lab and other magnet options 3:00-3:20 Break 3:20-4:00 H. Kirk + Y. Zhao, New scenarios for phase rotation; RF test stand for radiation studies 4:00-5:00 General discussion on R&D We agreed that the next 2 workshops will be held on Monday, June 29, 1998 at BNL Monday, Aug. 3, 1998 at BNL Some key points of the presentations: McDonald: see transparencies at http://puhep1.princeton.edu/mumu/target/ Identified 6 steps in the targetry/phase rotation R&D program. Steps 1-4 should be accomplished by the end of FY 99 1. Build a Ga-In liquid metal jet similar to the Hg jet of C. Johnson. 2. Test effects of eddy currents on the jet at the 20-T, 20-cm-bore resistive magnet at the FSU National High Field Magnet Lab. 3. Test effects of short beam pulses on liquid metals at the AGS 4. Test the liquid jet in the AGS beam 5. Test liquid jet + 20-T pulsed magnet in the AGS beam 6. Test rf cavity (+ superconducting magnet) downstream of the target in the AGS beam. Reported on C. Johnson's work with single-shot jets driven by a commercial air rifle. This might be sufficient for the FSU magnet test. Discussed simplified analytic model of shock heating: concluded that an energy deposition of 30 J/g in Ga-In is very close to that needed to `tear' the liquid apart. FEA modelling desired. Reviewed scenario of beam tests in the BNL FEB U-line. Will need different quads to get beam sigmas of 1-5 mm, as desired. Presented an AutoCAD sketch of a test setup including an open trough and a u-shaped pipe to be exposed to the U-line beam. A recirculating vertical free jet is also under consideration. Commented on the fiber-optic strain gauges used by the spallation target group; we should be able to share the readout system with that group (Duncan Earl). Carroll: Reviewed the FEB U-line. Clarified that the present quads just upstream of the blockhouse are not connected -- they are expensive to connect and will not produce a small beam spot. A proposal to replace these quads by smaller quads is encouraged. We should ask for what we want, not what we think the AGS might deliver. Hastings: Reviewed plans for spallation target tests in the next 9 months. These include running at 3 beam energies, but generally with big beam spots on the Hg target. A special run in Feb. '99 would emphasize a small beam spot on a solid target to study neutron production. This run would require different quads than those presently in place (but not connected). Instrumentation includes: Thermocouple arrays to measure temperature rise in the target => profile of energy deposition. Foils to determine neutron production via activation. Interferometric strain gauges of two types: USA (Duncan Earl) and Japanese. Simulation includes runs of the LLNL DYNA code (public domain) by Paul Montanez of BNL. Work on liquid simulation (as opposed to solids) is just beginning. King: Reported on discussions with Gerry Bunce on the g-2 target. Data was compared to FEA simulations. More details (people, codes) on the latter were desired. A bibliography on the g-2 target is being assembled. Weggel: Reported on last week's visit of Muon Collider personnel to the FSU magnet lab. They are quite keen on helping with high-field magnet design such as the 15-T superconducting magnets for the cooling channel, and the 20-T hybrid magnet for the target; they appeared lukewarm about helping with design of bent solenoids. It may be more natural to consult with the magnetic fusion community on the latter. The magnet lab facilities are excellent, and the lab was very welcoming of our testing the liquid jet in the (almost working) 20-T resistive magnet. Reviewed a design for a pulsed 20-T magnet with two coils, one of which is used in part as an energy storage device to permit quick excitation of the second coil (after appropriate switching). Kirk: Reviewed new designs for phase rotation rf cavities for which a 1.25-T superconducting magnet completely encloses the cavity. Stepped or slanted cavities did not seem as effective as earlier hoped. Fairly standard designs of cavities with large irises could accomplish our goals -- but they are rather power hungry. KTM asked that we consider cavities with foil electrodes that intercept them beam: these would be much more efficient, and somewhat more compact. Be foils would total less than 10% of a radiation length, less than 5% of an interaction length. The LBL 200-MHz rf test stand was visited in May, but found to be in very poor condition. However, a stand that operates at 70-90 MHz could be salvaged from the HILAC. Zhao: Reviewed the job of reconstructing a HILAC stand based on 4 1-MW tetrodes. KTM desired a cost comparison with building such a stand from scratch. General discussion: The targetry/phase rotation group needs to formulate budgets and schedules for its R&D program. A detailed version must be available by mid August to assist Bob Palmer in negociations with DOE for FY99 support. Proposals to BNL and the FSU magnet lab should be prepared and submitted on a similar time scale. The June 29 workshop will emphasize discussion of drafts of the budget and schedules. Designated to prepare the various drafts: K. McDonald: Construction of liquid jet; AGS beam tests (Input from C. Johnson highly desirable) B. Weggel: Pulsed magnet construction H. Kirk: RF cavity and test stand.