To: Distribution 19 Feb 97

From: Martin Nordby

Subject: IR Engineering and Physics Meeting Minutes of 7 February 97

Hard-Copy Distribution:

Bob Bell 41 Nadine Kurita 18
Gordon Bowden 26 Jim Krebs 41
Pat Burchat 95 Harvey Lynch 41
Scott Debarger 17 Tom Mattison 17
Hobey DeStaebler 17 James Osborn LBL B71J
Jonathan Dorfan 17 Andy Ringwall 17
Stan Ecklund 17 John Seeman 17
John Hodgson 12 Mike Sullivan 17
Hank Hsieh LBL B71J Uli Wienands 17
David Humphries LBL 46-161 Mike Zisman LBL B71J
Lew Keller 41
Roy Kerth LBL 50-340
David Kirkby 95

Electronic Distribution:

Curt Belser Kay Fox Jeff Richman Joe Stieber
Lou Bertolini Fred Goozen Natalie Roe Jack Tanabe
Catherine Carr Alex Grillo Ross Schlueter Rick Wilkins
Al Constable J. Langton Knut Skarpaas VIII Fran Younger
David Coupal Georges London
David Coward Joseph Rasonn Ben Smith

Q2 Vacuum Chamber Update

Nadine Kurita and J. Langton reported on progress in laying out the final Q2 Chamber design. The LEB Chamber is squeezed between the BSC's and the pole inside of the Q2 Magnet. Since the BSC dimensions and positions change for running with our without solenoid compensation, and the orbit is different for incoming and outgoing LEB, there are 6 permutations of BSC positions for the chamber to fit around. Also, the Q2 Magnet is offset 5 mm vertically up on the incoming side, and 2 mm down on the outgoing. No "generic" LEB Chamber can fit around all of these permutations without hitting either the pole tip, the octupole trim windings, the main quad septum winding, or encroach on the BSC.

This is worsened by the proposal by James Osborn to displace the coil conductor by 4 mm toward the beam to improve Q2 harmonics. Currently, on the in-board end of the magnet, there is 3 mm of clearance between the chamber and the standard coil position., leaving only 2 mm of room for conductor displacement and 1 mm for alignment tolerance for the chamber.

J. is looking into making two different shaped LEB Chambers. This is not preferred, since it increases complexity and ED&I time. James will look at reducing the size of the octupole trim, and possibly moving it to clear the chamber (Stan will deliver a final spec. on octupole trim capacity, for James to work with). He felt that the trims could be flattened, and possibly reduced in cross-section, but their position is tied to the higher harmonics they produce.

Q2 Magnet Update

James Osborn reported on progress in the Q2 Magnet analysis. He has found that displacing the inner conductor on the split-plane and deleting the inner condutor on the face of the pole root can essentially eliminate n = 6, 10, and 14 harmonics. Moving the other conductors did not seem to help. This suggests that it may be hard to reduce the 4 mm of displacement expected for the inner conductor. However, the entire coil package may be able to be displaced into the HEB passage somewhat to avoid encroaching on the LEB Chamber.

Mike Sullivan reported that the half-aperture BSC's for the Q2 Magnet are thus (defined as 15 sigma + 2 mm):

In-board end
Out-board end
z
2.8 m
3.42m
BSCx
39.6 mm
47.6 mm
BSCy
25.7 mm
20.9 mm

At z = 3.5 m (the start of the Q4 LEB Chamber) the BSC is clipped by a 45 mm wide HER Arc Quad Chamber extrusion. This was needed to leave room for coil and support in the Q4 septum region. Since this is clipping the BSCx already, John Seeman and Mike Sullivan felt that extending this into the back end of the Q2 Magnet should not be an additional problem.

The following proposal and action plan was developed:

--Out-board end: reduce Q2 LEB Chamber half-width to 45 mm

--In-board end: reduce half-width by 1 mm (encroach BSCx by 1 mm)

--LEB Chamber: linearly taper chamber between in- and out-board ends

--Move Q2 coil conductor by 3.5 mm, max

--Add 0.5 mm alignment and fab tolerance to the Q2 LEB Chamber dim's.

--Flatten out skew octupole trims and look into moving them

These minutes, and agenda for future meetings, are available on the Web at:

http://www.slac.stanford.edu/accel/pepii/near-ir/home.html