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

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

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, 0.80 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. Electron Collider Ring Magnets

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

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 Electron Collider Ring Magnets

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. Electron Collider Ring Magnets

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 Electron Collider Ring Magnets

Sextupole – Higher Gradient Design High Current Design, 588 T/m^2 @2080, 11% Sat Summary – ‘Draft Design’ chosen to further optimize PEPPII, 220 T/m^2 @ 260 amps, 0.4% Sat Draft Design, 590 T/m^2 @ 780 amps, 13% Sat Chosen Design Electron Collider Ring Magnets

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

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

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 17.7 T/m @ 330 amps, 5.9% Sat 18.1 T/m @ 550 amps, 1.7% Sat Electron Collider Ring Magnets

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 0.0054 Tm (email from F. Lin) BPM’s (Monitor) 0.05 m long # 386 RF Cavity # 1(?) Drifts # 3751 of various lengths Includes coil end drifts lengths so actual # will be less Electron Collider Ring Magnets

Backup Electron Collider Ring Magnets

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

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