1. RHIC Magnets for JLEIC
Yuhong Zhang
May 11, 2018

2. 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.)

3. 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)

4. 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

5. Deep Tunnel
R. Rimmer
2.25 times
p 275 GeV

6. 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

7. 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

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

9. Cut-open Tunnel
1.2 times
P: ~150 GeV

10. 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

11. 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