1. JLEIC Collider Rings’ Geometry Options
Fanglei Lin, Vasiliy Morozov

2. Electron Ring Design History
2011 September January : had a 1.3 km ring with one short in each arc for Siberian snakes. Developed and studied ion chromaticity compensation scheme and DA.
2013 January : completed a 1.2 km electron ring, shorts were removed from arcs.
2013 February : completed a 1.5 km (60 crossing angle) electron ring (considering to lengthen the polarization lifetime).
2014 June – December : studied various arc cell design options, decided to construct a FODO-arc-cell lattice reusing PEPII magnets.
2015 January : completed a 2.2 km (2154 m, 81.7 crossing angle) ring using PEPII magnets for the cost review. Dedicated CCB is included, but had a large emittance contribution.
2015 February – 2016 August : still a 2.2 (2185m) km ring but optimized optics to reduce the emittance, explored different chromaticity compensation schemes.
2016 September – 2017 April : studied DA for a TME-like lattice.
2017 April : completed a 2.3 km (2276 m) ring using new magnets with an optimum SuperB- like CCB design and studied DA (presented at JLEIC collaboration meeting spring 2017).
2017 October : completed a 2.3 km (2336m, 81.7 crossing angle) ring (the one in svn now). However, IP is very close to the figure-8 crossing point, ~35 m.
2018 March : completed a 2.5 km (2498 m, 69  crossing angle) ring and presented at JLEIC collaboration meeting spring The distance between IP and crossing point is ~100 m.
2018 March : geometrically completed a 2.4 km (2365m) ring at the JLEIC collaboration meeting spring 2018.

3. JLEIC Collider Ring Geometry
2.2 km : at cost review in Jan 2015
2.5 km : at JLEIC collaboration meeting spring 2018
2.4 km : quick modified version at JLEIC collaboration meeting spring 2018
2.5km
2.4km
2.2km
Courtesy of Rusty Sprouse, David Fazenbaker

4. Exploration of Collider Ring Geometry
Option
Condition
Circ.
Figure-8 crossing angle
Arc length
Straight length
IP to crossing angle
To CEBAF m
degree ft 1
Current spin rotator1 + current CCB + straight. CCB replaces the second dipole set in spin rotator.
2343 69
971
200 50 2
Current spin rotator, no CCB2.
2323
795
367
130 30
2.1
Current spin rotator, no CCB.
2232
77.4
818
298
100 3
New spin rotator3 + current CCB + straight. (see more info about new spin rotator in slide 6)
2327
67.8
986
178 40 20 4
New spin rotator, no CCB.
2273
825
312
120 5
New spin rotator + current CCB + straight.
2277 72
998
141
111 6
2186
76.2
848
245 70
Current spin rotator only rotates the spin. Vertical dogleg is still needed in the ion ring.
Only global chromaticity compensation will be performed if no CCB.
New spin rotator has two functions : i) rotating the spin ii) bringing the electron beam to the ion beam plane for collision. The total bending angles in the new spin rotator are zero in both horizontal and vertical planes.

5. 1 (orange) 2 (green) 3 (blue) 4 (cyan) 5 (magenta) 6 (dark green)
2.154 km, 367ft to CEBAF
Option 2.1
Option 6 and 2.1 (no CCB) are promising, but need nonlinear dynamic study.
Option with CCB may deserve more exploration.

6. New Spin Rotator x : radial field y : vertical field
z : longitudinal field
Courtesy of Anatoly Kondratenko et al.

7. Summary of DA Study for a 2185m-long Ring (reuse PEP-II magnets)
Chromaticity Correction Schemes
x/x,0
DA: x/σx , y/σy
Range of (p/p)/σ
p/p=0
p/p=0.4%
Linear correction: conventional 2-family arc sextupoles (v1)
Non-linear: no dedicated correction 1
±20, ±48
0, 0
  9
Linear correction: conventional 2-family arc sextupoles
Non-linear: interleaved –I sext pairs in regular arc cells (v1a)
Non-linear: FODO type CCB with 2 non-interleaved –I sextupole pairs, optimized phase advance (v1b3)
2.1
±15, ±40
±4.5, ±10
  9
Non-linear: FODO type CCB with 2 non-interleaved –I sextupole pairs, optimized phase advance, reduced beta functions for lower emittance (v1d2)
1.7
±17, ±41
±5, ±10
Non-linear: compact CCB with 3 interleaved sextupoles, optimized phase advance
±8.5, ±18
±5, ±7.3
Non-linear: SuperB type scheme (SBCC) with regular length dipoles and large bending angles (scheme-3 )
1.4
±25, ±60
±10, ±15
Non-linear: SBCC with short dipoles and small bending angles (scheme-6, optimized, ring geometry not yet matched)
0.93
±23, ±72
±7, ±26
11
Will consider
chosen

8. Thank You for Your Attention !