RHIC Magnets for JLEIC Yuhong Zhang May 11, 2018

Motivation We were asked recently by the lab management to explore Whether the RHIC magnets can be used to build the JLEIC ion collider ring without any constraint (dimensions and fit to site, etc.)

Basic Information about RHIC Magnets Magnetic length m 9.45 Physical length 9.7 Magnetic field T 0.4 – 3.46 (3.78) Bending radius 243 Bending angle deg 2.23 Mechanical sagitta mm 48.5 Good field width 66 Ramp rate T/s 0.042 Temperature K 4.6 FODO cell length 29.62 Packing factor 0.638 Proton energy GeV 29 – 250 (275)

JLEIC Proton Ring with RHIC Magnets by RHIC Magnets JLEIC baseline Dipole bending radius m 243 177 133 90 Max. proton energy GeV 275 200 151 102 100 Figure-8 angle deg 130 115 77 77.4 Arc radius 381 277 209 141 Arc length M 1197 2061 1428 1019 633 823 Straight length 240x6 355 354 350 292 Conference 3833 4832 3564 2737 1975 2230 Footprint: length 1220 2443 1871 1505 1189 762 555 417 282 Electron spin rotators and CCB in arc are not considered/included

Deep Tunnel R. Rimmer 2.25 times p 275 GeV

Small Apertures for Cooled Beam design orbit (0=243 m) 0 0 d L0 L d0 (9.45 m, bent w/ 4.85 cm sagitta) new orbit   Good field RHIC proton beam has no cooling  emittance is large (~20 µm 95%)  Average beam size 4 mm JLEIC ion beam is cooled, beam size at injection is < 1.6 mm JLEIC requirement of physical aperture could be a factor of 2 smaller than RHIC With a same aperture, magnet bending radius can be reduced substantially, to give more room for sagitta  243 m  139 m

JLEIC Proton Ring with RHIC Magnets by RHIC Magnets JLEIC baseline Dipole bending radius m 243 177 133 90 Max. proton energy GeV 275 200 151 102 100 Figure-8 angle deg 130 115 77 77.4 Arc radius 381 277 209 141 Arc length M 1197 2061 1428 1019 633 823 Straight length 240x6 355 354 350 292 Conference 3833 4832 3564 2737 1975 2230 ratio 2.2 1.6 1.2 ~1 Footprint: length 1220 2443 1871 1505 1189 762 555 417 282

Deep Tunnel Site-Filler R. Rimmer P: ~200 GeV 1.5 times

Cut-open Tunnel 1.2 times P: ~150 GeV

DESY Experience: Straighten the HEAR SC Magnet Cold Mass A. Hutton HERA SC magnets: 8.8 m, curved dipole. vacuum chamber 55 mm For ALPS (Any Light Particle Search) project: effective aperture is only 35 mm using HERA SC magnets To increase aperture, the magnet cold mass is straightened using mechanical force Idea: bend the RHIC dipole cold mass to gain more aperture, thus the bending radius can be reduced RHIC magnet can reach up to 4.6 T (33% more) HERA Magnet RHIC Magnet

Summary The “direct” use of RHIC SC magnets for the JLEIC ion collider requires a very large footprint, its circumference is about 4.8 km, 2.2 times of the present JLEIC baseline and also large than the RHIC circumference. This can only be realized by a deep tunnel using a tunneling machine Taking advantage of a pre-cooled JLEIC beam (thus requiring smaller physical aperture), the RHIC SC magnets can be used creatively with a smaller footprint To reach 200 GeV, the ring circumference is about 3.6 km, 1.6 times of the JLEIC baseline, and similar than the RHIC tunnel, could be a site filler with deep tunnel To reach 150 GeV, the ring circumference is about 2.7 km, 1.2 times of the JLEIC baseline, it could be a site filler with a normal depth tunnel done by a cut-and-cover method To reach 100 GeV, the ring circumference is similar to the present JLEIC baseline An new idea of physically bending the RHIC SC magnet cold mass was discussed for enlarging the aperture while strongly bending the ion beams