1. Electron Collider Ring Magnets Preliminary Summary
Based on 6/26/18 Lattice file
Mark Wiseman
7/18/19

2. Outline Conductor choice – Copper vs Aluminum Dipoles
Superconducting Solenoids
Sextupoles
Quadrupoles
Correctors & Misc
In many places I compare the new (6/26/18) lattice to the (4/06/18) lattice but don’t always state that
Electron Collider Ring Magnets

3. PEP-II Magnets
As I understand it the PEP-II Magnets used aluminum conductor
Arc dipoles no longer match the PEPII dipole lengths
Could consider cutting the iron and reusing
Will need new coils
Sextupoles no longer match the PEPII sextupole lengths
Now 0.44 m vs 0.25 m
Will need all new magnets
Need total of 481 quads -
Could still use PEPII 0.56m and 0.73 m quadrupoles – but will need to buy more of each
0.56 m - Require 242 with 94 to 202 available
0.73 m - Require 178 with 81 available
Peak field requirements put both designs at up to ~30% saturation (more later)
198 to 306 all new magnets
61 of lengths greater than 0.73m, to 1.5 m long
Therefore, base all designs on copper conductor
Aluminum losses are ~1.6 times copper
Aluminum material cost ~9 to10 times less than copper
Eliminates the need for a second LCW system to cool magnets
Same plan for CEBAF to Collider transport line magnets, etc.
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4. Dipoles All dipoles look reasonable
Joe Meyer is looking at the detailed designs
Use PEPII gap to maintain compatibility with PEPII vacuum designs
Plan on all new magnets
Consider reusing PEPII arc dipole iron if cost effective (5.4 m length)
Do not have a field quality specification
Electron Collider Ring Magnets

5. Dipoles – Synchrotron Radiation
Arc dipoles (3.6 m) match the PEPII SR design values
Sixteen of the 3.6 m dipoles are slightly above this
BXSRx (twenty four 2 m ) SR is high ~3.3 times PEPII design value
Need to reduce SR and or explore other solutions to handle the increase power
BXSPx (four 3m and two 0.5 m) part of Compton Chicane ~1.6 times PEPII design value
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6. Solenoids
Spin Rotator solenoids, half the length, twice the number, stronger fields than the April lattice
At 7.6 T, shielding may drive fields above NbTi conductor capability
under study
Aperture requirement
Sized to hold PEPII quad chamber to absorb synchrotron radiation (upper right figure)
~7m downbeam of dipoles so SR requirements may be less
Shorter SC solenoid design with room temperature quad between
Doubles the number of cryostats and limited room for RT quads in layout - Need to look at layout design more closely
Two solenoids plus the detector solenoid are required for the Interaction Region and remain unchanged.
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7. Sextupoles New sextupole length of 0.44 m vs 0.25 m
All new magnets
Low strength design (273 T/m^2)
Based on PEPII design meets gradient with 8% saturation
New design could eliminate the saturation
Have generated power and cooling estimates based on the PEPII design
Should revisit assuming a new design that eliminates the saturation
High strength design (566 T/m^2)
Have a potential design that meets gradient with 12% saturation
New design will need a 6 (maybe 3?) piece pole design (vs 2 for PEPII) which increases the likely hood of assembly error terms
Still have room for some improvement but think we are near the limits for iron based magnets at this aperture
Have not looked at field quality and do not have a specification for field quality
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8. Sextupole – Higher Gradient Design
High Current Design, % Sat
Summary –
‘Draft Design’ chosen to further optimize
PEPPII, amps, 0.4% Sat
Draft Design, 590 T/m^2
@ 780 amps, 13% Sat
Chosen Design
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9. Quadrupoles – Gradients at 12 GeV
Quantity is down from 596 (April lattice) to 482
Plus six SC quadrupoles in the IR region (16.1 to 55 T/m) with skew quads
Three more will change to SC in the IR region (not reflected in table below)
Maximum gradients are lower and within the PEPII design range with saturation
18 T/m start of saturation, ~20 T/m around 20% saturation
279 quads specified over 18 T/m, 254 over 20 T/m, 24 over 21 T/m
Need a different size conductor for lengths 1.1 and 1.36 meter quads to keep temperature rise below 40 C - maximum temperature rise now at 25C
Electron Collider Ring Magnets

10. Quadrupoles – Gradients at 12 GeV
Maximum gradients are now within the PEPII design range with saturation (up to 30%)
Not very efficient to run this far into saturation
For the 0.73 m PEP II Quadrupole the power goes up 125% from 17.7 T/m to 21.5 T/m (7.7 to 17.4 kW) (~11.4 kW at 21.5 T/m without additional saturation)
Should develop a new design and/or increase magnet lengths to minimize or eliminate the saturation
Have started looking at a new design but not finished (next slide)
I think we are close to the practical limits for iron quads at this aperture
Additional for quads
Need to include enough room for coils beyond effective length
Now have 3 cm on each end and the PEPII design would require 7 cm
May be enough drift space any many areas to absorb this but need to look at it
Electron Collider Ring Magnets

11. Quadrupoles – Higher Gradient Design
First attempt, tried to maximize the pole area by reducing the number of turns
Added ~2.16” to the pole width, also increased return leg
Dropped two coil rows, 57 turns to 34 turns with same conductor
Results in a higher current design
Should be able to go to a smaller conductor, increase the turns to lower the current
4 row coil design gives 23.1 T/m at 830 amps with ~20% saturation
Vs 21.4 T/m at 495 amps with ~ 30% saturation
Gain of 1.7 T/m with reduced saturation
Gives a working margin above the required gradients
Further optimization still possible – Have not looked at field quality
PEPPII
amps, 5.9% Sat
amps, 1.7% Sat
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12. Correctors and Misc. Correctors (Kicker) 0.3 m long, strength TBD
# 386 (772 power supplies)
Each one is just one magnet, and can provide both horizontal and/or vertical correction
Only 30 cm allowed in beamline space so need to look at magnet designs or requirement
PEP II integral strength around Tm ( from F. Lin)
BPM’s (Monitor) m long
# 386
RF Cavity
# 1(?)
Drifts
# 3751 of various lengths
Includes coil end drifts lengths so actual # will be less
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13. Backup
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14. Quadrupoles – recommended changes to lattice
Original Lattice (6/26/18) requirements in table below
Change single 0.8 m Quad to 0.73 m
Change two 1.2 m length quads to 1.1 m length
One of these QFFBUS2TT2 so actually becomes 0.6 m SC Quad
Change single 1.5 m quad to two 0.85 m ones
QFFBUS2TT1 so actually becomes 0.6 m SC Quad
Change QFFBUS2TT1, QFFBUS2TT2, QFFBUS2TT3 to 0.6 m SC quads
Not enough room in IR region for normal magnets
Electron Collider Ring Magnets

15. Power Supply and LCW Requirements – E Collider Ring
Based on PEPII designs, copper conductor, and include saturation effects
Just for Quadrupoles and Sextupoles (so far)
11.4 MW and 2230 GPM
Quadrupoles
Sextupoles
Electron Collider Ring Magnets