To: Distribution 20 Nov 95 From: Martin Nordby Subject: Minutes of Near IR Engineering Meeting of 17 Nov 95 Announcements On Thursday, 30 Nov 95, 1-3:00 pm, there will be a conceptual design review of the Q1 Quadrupole. This will include details of the magnetic and mechanical design, as well as a substantiation for the 45 cm diameter Support Tube. More on this will follow. There will be no IR Engineering and Physics Meeting on 24 November, due to the Thanksgiving Holiday. Next meeting will be on 1 Dec 95. Forward End While work on structural and magnetic analysis of the C-Hook support design and possible alternates continues, a list of issues regarding the small-radius region on the Forward (HEB downbeam) direction was generated: 1) Lengthening the Support Tube: this reduces the size requirements for any support design, but may end up wasting space in the region. This also requires adding 30%-50% more carbon to the center part of the tube. Dave Coward will follow-up on the effect on the D.C., while Martin Nordby will lay out the new length. 2) S.T. Movers: Independent of the support design, the S.T. will sit on remote movers, which will take up much of this small-radius space. Martin Nordby will block out space for these. 3) Tungsten Shielding: Approx 4 cm thick tungsten shielding is needed at the end of the S.T., but total coverage required and shape of the shielding is unspecified. Available space will fall out from the layout, and be reviewed by Dave Coupal in a few weeks. 4) SVT Cables: Cables exiting from the S.T. will most likely have connectors, with heavier-gauge ribbon cables running out of the detector. SVT people were at a workshop, so their input was missing, but they clearly need to help block out volume and access requirements in this area. 5) Aerogel cables: How and where are the ATC cables routed, and are connectors needed for them. Jim Krebs will follow-up on this. Q1 Trim Coils Stan Ecklund presented results of preliminary analysis of the Q1 Trim Coils. First, requirements for trim capacity, per a summary by John Seeman, are +/- 5%. The actual values of harmonics for the trims can be 33 times higher than for the Q1 quad, since the coil is that much weaker, and still produce a total quad + trim package with relative harmonics less than 1.0 E-4 of the total quad field (quad + trim). Stan's analysis shows that, for this air-core trim, uniform azimuthal conductor spacing produces a gradient which drops off quickly at 50% of the bore radius. By distributing the conductors to better simulate a cos(2*theta) distribution, the gradient can be maintained out to a larger radius. However, this requires tight tolerances on the positioning of the conductor. For a 5 cm square conductor, with 2.5 cm diameter hole, the current density is 1500 A/cm^2 (total current = 300 A). Resisitive power = 1000 W for each of 4 parallel coils, and for a water flow rate of 1.2 L/min, the temp rise is 11.5 degC. The dipole trim will be #16 gauge wire, cooled by being epoxied to the quad trim. This provides a kick angle of 0.25 mrads for the LEB with a 25 G total field, 6 A current, and 100 W power x 2 coils. Both designs need more attention, especially to maintain the harmonics, while making the coils build-able with realistic tolerances. Andy Ringwall will follow up on this with Stan. Q2 Quad Design Update Dave Humphries presented an updated design for the combined Q2/SK1 permanent magnet. This includes a 16-block Halbach quad with a 11.153 T/m gradient, a dipole with 33 kG-cm first integral on the front end, and an 8.1 kG total field skew quad. The main quad has 0-10% tuning capacity, and the skew quad has 0-100% variability. These are both accomplished with two independently rotatable tuning rings on the out-board end of the quad. Both rings rotate 90 degrees, so both tuning maximum's can be attained simultaneously. The entire package fits around the Q2 septum chamber, with enough room for a thermal shield to maintain temperature stability, and for cooling tubes for the chamber itself. Lou Bertollini is working with Dave to lay out this chamber. Most of the magnet can be split for assembly/removal around the beampipe, making assembly of both the chamber and magnet more straightforward. This Q2 design has a magnetic center about 13 cm outboard of the CDR design. According to Mike Sullivan, this increases beta at Q2 and SCX2, and requires a reduction of Q1 strength to compensate, which, in turn, decreases the beam separation through Q2, 4, and 5. Moving the dipole blocks of Q2 to the opposite end of the magnet would move the quad center back inboard, but also tends to decrease separation. Dave and Mike will look at the trade-offs of the possible options. However, none of the variations significantly alters the overall design concept and package envelope. Work on the details of the mechanical and magnetic design (including a tuning algorithm) will continue, in anticipation of a CDR in mid/-December. These minutes, and agenda for future meetings, are available on the Web at: http://www.slac.stanford.edu/accel/pepii/near-ir/home.html