To: Distribution

From: Martin Nordby

Subject: Minutes of the IR Engineering and Physics Meeting of 26 July 96

Hard-Copy Distribution:

Bob Bell	41	Jim Krebs	41
Lou Bertolini	LLNL L-287	Dave Kirkby	95
Gordon Bowden	26	Harvey Lynch	41
Pat Burchat	95	Tom Mattison	17
David Coward	95	James Osborn	LBL B71J
Scott Debarger	17	Eric Reuter	18
Hobey DeStaebler	17	Andy Ringwall	17
Jonathan Dorfan	17	Knut Skarpaas VIII	18
Stan Ecklund	17	John Seeman	17
Alex Grillo	95	Mike Sullivan	17
John Hodgson	12	Uli Wienands	17
Hank Hsieh	LBL B71J	Mike Zisman	LBL B71J
David Humphries	LBL 46-161
Roy Kerth	LBL 50-340

Electronic Distribution:

Catherine Carr	Nadine Kurita	Natalie Roe	Rick Wilkins
David Coupal	Georges London	Ross Schlueter	Fran Younger
Fred Goozen	Joseph Rasonn	Joe Stieber
Rick Iverson	Jeff Richman	Jack Tanabe

IR Magnets Final Configuration

Mike Sullivan discussed results of his final magnet optimization out to Q5. The final BH1 magnet design is about 1% lower than the 7/12 design, since a 0.5 mm assembly gap was added between slices. This reduces the parasitic crossing separation by 60 microns, or 0.1 sigma. It was deemed a small enough perturbation to be considered insignificant.

The harmonics for B1 were determined for standard block fabrication tolerances of +/- 0.005" and magnetization magnitude and orientation tolerances of +/- 2% and 2°, respectively. The harmonics were weighted by BSC for each slice, then summed for the entire magnet. Total harmonics are all less than 10^-4, except the sextupole term, which was 3 X 10^-4. Because the harmonics are weighted by BSC, they are worst at the ends of the magnet, where R1 of the P.M. material is closest to the BSC.

Mike increased the magnetization error tolerance by 50% and found a corresponding increase in harmonics of around 50%. This suggests that the mag. errors dominate harmonics. Thus, tightening dimensional tolerances would not significantly reduce harmonics.

For Q1, the final configuration of Q1A and Q1B radii is as follows:

Q1A Quad:

R1 = 57 mm (compared with 74 mm R1 for prototype design)

R2 = 89.0 mm

G = -118.02 kG/m (compared with -106.51 kG/m for prototype design)

Q1A Dipole:

R1 = 95.0 mm

R2 = 135.0 mm (4.3 cm smaller than the prototype design)

B = 3.3802 kG (increased from 2.13 kG from the prototype design)

Q1B Quad:

R1 = 74 mm (same as prototype design)

R2 = 123.0 mm (compared with 134.3 for prototype design)

G = -103.71 kG/m

Q1B does not have a dipole section, so the quad field is not offset.

Harmonics for this design have not changed much from the 7/12 design, so the Har. Corr. Ring sizing is unaffected. The last two slices of Q1B rotate to provide a +4.1% / -12.3% manual trim adjustment. This will be used to fine-tune the integrated gradient of the quad, and to trim it for changing running conditions (see below).

Q2 Magnet

Length = 62 cm (4 cm shorter than the baseline PDR design)

G = 68.2971 kG/m (solenoid OFF)

G = 84.8847 kG/m (solenoid ON)

At 2.8 m, the magnet centerline is offset from the LEB beamline by +6.5 mm. This is about 3.5 mm more than the baseine design, but is needed to increase separation through Q4 and Q5. Q2 yaw is 20 mrad.

(The assumed magnet length is the shortest expected length. James Osborn and David Humphries are working on finalizing this length based on z-space needed for the Q2 Har. Corr. Ring, and the peak current density of the Q2 coils. Nevertheless, the shorter magnet length is a more conservative assumption for Mike's analysis.)

SK1 Magnet

Length = 10 cm

G = 90.016 kG/m

The magnet is centered on the LEB orbit.

The difficult task in finalizing magnet configurations was to thread both beams through the magnet bores, using mostly existing magnet and chamber designs. To maintain separation at Q5, the Q2 Magnet center had to be moved further away from the HEB by 3.5 mm. Also, the Q4 and Q5 Magnets moved as a unit by 2 mm (relative position of Q4 to Q5 is unchanged). This produces the following beam separations:

Q2: + 3 mm

Q4: + 2 mm

Q5: 0 mm

This is for the solenoid OFF running configuration. To maintain separation and stay-clear for the Luminosity Monitor S.R. cone, the Detector Axis yaw with respect to the collision axis was changed to 20.5 mrads. The collision axis, itself, is unchanged with respect to the IR Reference Frame.

The next steps to finalize this configuration is to have Martin Donald run this MAGBENDS output in the latest MAD lattice, to look for closed-orbit distortions which can not be modelled in MAGBENDS.

Also, Mike will re-check all S.R. fans, power, and their affect on detector backgrounds. This will also serve to finalize the Near IR chamber sizes and mask positions.

Finally, when all magnet positions and strengths are confirmed by Martin Donald, Mike will re-visit the solenoid compensation scheme.

Q1 Quad and Dipole Trims Final Configuration

Stan Ecklund presented the final geometry and sizing for the quad and dipole trims for Q1. This fits with the Q1A and Q1B geometry presented by Mike. The quad trim function has been divided into an electric trim, providing +/- 1.5% trim on the main quad gradient, and a manually rotating set of P.M. slices, which can provide +4% / -12% trim range, but are only manually adjustable.

According to a tally of trim requirements put out by John Seeman, the total trim range needed for Q1 is +4.8% / -5.3%. Stan divided the constituents of this total into those needing on-line trimming, and those which could be done using the manual trim. The sum of those needing electric trimming was +1.54% / -1,38%, so the planned-for 1.5% trim fills the bill.

The quad trim uses two layers of 0.34" square, water-cooled copper conductor, with a max. current of 250 Amps, total power of 2800 Watts, and a peak gradient of 2.0 kG/m.

The dipole trims were sized to be large enough to compensate for the horizontal steering of the quad trim. This should minimize the loss of beam separation through Q2-Q5 when the quad trim is used. The trims produce a 39 G dipole field, which is equivalent to moving the quad 18 mm. Max current on the #8 conductor is 20 Amps, for a total power of 1140 W.

Additional dipole trim can be produced by moving the Support Tube. A 1 mm motion of the S.T. is equivalent to a 100 G dipole field, so leaving room for motion is a more efficient use of space than adding more dipole trim. Stan felt that the minimum range of motion should be +/- 3 mm at the outboard end of the S.T. This would be available to fix problems or modify beam separation or trajectories around the I.P. The only real S.R. problem this could produce is that of the B1 S.R. fan exiting the Q1 Chamber. Mike Sullivan will be looking at this soon.

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

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