Friday, October 4, 2002 - Discuss John Johnstone's Idea for Cryo Solution ========================================================================= John Johnstone, Vladimir Shiltsev, PHG, Harry Cheung, Bruce Hanna, Jay Theilacker, Arkadiy Klebaner, Fritz Lange, Gerry Annala, Dave Augustine, Doug Allen 1 November 02: Meeting of Tevatron Department, John Johnstone, Mike Syphers, and I concluded that it is more optimal (less cryo and optics complications) to go with Conventional-Warm-FMI solution. Steve Holmes concurs and will present this option at Nov 5 meeting to determine shutdown schedule and duration. John Johnstone has come up with a possible approach to the C0 Lambertson Resplacment project which maintains the synchrotron light monitor, however, moves it to the B48 side from the C11 side. The basic idea is to remove the Lambertson and C magnets and B48 Abort Kicker magnets, replace the half dipole at C11 with a full dipole, and move that C11 half-dipole along with 3 dipole trims to the B48-B49 region. This will require the fabrication of two cryo powered spool pieces (0.582 and 0.564 meter slot lengths)(Jay and Arkadiy: check the exact lengths before starting to cut pipes!). The main beam optics questions are whether the close placement of two half-dipoles, with their poor sextupole components will be a problem, and whether the synchrotron light monitor will be able to deal with the separated orbit configuration at this location. Jay Theilacker said that it was NOT a problem to construct these two simple spools, provided that he be given the go ahead SOON. There would also need to be modifications of the warm gas return/quench header and it would be advantageous to have TD modify/upgrade some spools at the same time. Dave Augustine said this would add another week to the shutdown (6 weeks => 7 weeks for single shift operation) but would saturatue his people. They could only work on two cyro houses at a time and this would preclude doing the planned work at A0 (change high beta to a regular straight section, to increase apertures there, the next smallest after C0. This would also require warming up two cryo houses). Dave reports that this C0 work could be done on two shift operations over a 3 week shutdown, and both C0 and A0 could be done via two shift operations for 6 weeks, along with the work at MI30 PROVIDED: a. more skilled manpower could be provided to free up the key leaders for the two shift cryo operations, and b. Vladimir Shiltsev considers not accomplishing some of the following Tevatron tasks during this shutdown: rebuilding the shielding walls at CDF, installing the shottky device, and/or lots of vacuum improvements in many ares. On Monday, Oct 7, Peter and Vladimir met and discussed these issues with Steve Holmes. Steve had a favorable impression and asked for some of the impacts described above. We pressed Steve for a decision on which way to proceed at C0 within two weeks (by Oct 21) to give lead time for the fabrication of the two cryo spool pieces. Up to Steve's approval of this alternative C0 solution, we continue working on the previous FMI solution. 30 October 02: Dan Wolff says there are sufficient corrector power supply spares (50 Amps) to be able to supply for the dipole correctors whether we put them in series or 3 separate supplies. 30 October 02: Vladimir asks John Johnstone whether a design for B48-C12 is possible to allow placing the Second Tevatron Electron Lens somewhere in the C11 dipole string (has correct ratio of BetaY/BetaX). Since this would require the construction of new warm bypass, it is understood that this couldn't be implemented before Summer 03. 30-31 October 02: Jay Theilacker says that because of all the extra spools, Cryo will definitely require a recooler on the B49 side to insure that single phase gets to the JT valve. This could be positioned just before the Turn-Around Box (containing JT valve) dowonstream of the repositioned Half-Dipole (last element). There is plenty of longitudinal space to install a new box (needs design and fabrication) containing just this recooler. Producing this box will not be impossible (by stopping other important jobs) for a March 2003 shutdown and would be attainable for a June 2003 shutdown Action Items: (oct 4) - none, all completed ===================== Completed Action Items (Oct 4): ============================== John Johnstone: question of sextupole impact of two half-dipoles -------------- on same side of IR 13 October - John Johnstone response: MTF measurements show both half-dipoles to have about -16 units of sextupole at their top current of 4033 Amps. This is large by Tevatron standards but wouldn't be too exceptional in any other machine. With the half-dipoles separated by the long straight (as in the current lattice) there is some cancellation -- but not much -- between the sextupole contributions. With both magnets located on the B48/49 side the sextupoles largely add, but the chromaticities change by only +/-0.1 units. This is pretty small & can be corrected globally using the chromaticity sextupole families; adjusting the string currents by less than 20 mA from injection through to collision. In my simulations I used just the existing F & D sextupole strings for compensation. Although I think corrections probably could be implemented locally using only the 3 new spool pieces, I didn't explore the option. That approach seemed to be an unnecessary complication considering the small amount of chromatic adjustment involved, requiring as it would new, dedicated power supplie(s) & software. John Johnstone: can it be done with 1 extra full dipole (instead of -------------- 2 half-dipoles) and then compensate movement of bend point with extra trim dipoles? 13 October - John Johnstone response: In light of the result (on sextupole moments), there doesn't appear to be a good reason for going to full dipoles. However, it is possible, but now requires a minimum of 6 spool pieces [compared to the 3 trims used in (above)] to reclose the orbit -- 3 "anti"-bends intermingled with the dipoles on the B4 side & 3 dipole trims on the C1 side at the downstream end of the straight. Each of the six magnets bends by 119.5 urad @ 43 A -- the beam trajectory now looks like a piece of spaghetti. Jerry Annala (21 Oct): identify three 72 inch spools for cryo solution --------------------- they do not need operational sextupole correctors, only horizontal dipole correctors. 22 October - Jerry identified TSC266, TSE396, TSG196 spools. He said there are some problems with these spools, but they are well suited for this application. 1nov - Harry Cheung: need final OK from viewpoint of synchrotron light monitor? does it still work, beam-SR separations, and all that for flipping horizontal and vertical separated orbits ~18 October - Harry says moving to B48 will require internal optics change for synch light monitor. 1nov - decision by Tevatron Department to go warm FMI solution 5nov - Steve Holmes: need approval (by 21 Oct) to start cryo spools 21 Oct: Steve says decision will be made on November 5 but he is definitely leaning to the WARM solution at C0 so that manpower will be available to also perform the high Beta => standard straight section at A0 Steve instructs us to continue to work (spend $) on the warm solution, e.g. Mike May's question on flags hold off ~ 1/2 meter cryo spools until Nov 5 (see above 1nov decision on warm FMI dipoles) 5 nov: tentative decision for 3.5 week shutdown start 13 Jan