1. The Feasibility of Using RHIC Magnets for MEIC and Cost Impact
Nov. 20, 2014

2. General Findings
Limited by the magnet sagitta, the RHIC dipoles alone can not be fitted into the MEIC figure-8 ion collider ring (the minimum circumference of such a ring is about 2800 m)
It seems not feasible to remanufacture RHIC dipoles for increasing their sagitta (P. McIntyre)
This difficult can be mitigated straightforwardly by introducing additional new dipoles with smaller bending radius (large bending angle per dipole).
There are several ways for mixing the RHIC dipoles with new dipoles for the MEIC ion ring. The most interesting one is illustrated in slide 4 and 5.
The new dipoles can be made of low field (super-ferric), medium field (RHIC-like) or high filed (LHC-like) magnets. The costs of different magnet types are unknown.
For various design schemes, number of new dipoles are approximately 50% of the total dipoles needed, or account for about 50% of total BDL (integration of magnetic field over the ring, which only depends on the beam energy).
Therefore, the cost reduction (dipole part) is up to 50% of the new construction (including the super-ferric one as the present MEIC baseline)

3. General Findings (cont)
The other beam-line elements of RHIC, such as quads, sextrupoles, BPM and correctors, in principle, can be reused for MEIC since there is no sagitta issue. The field range is large enough since the RHIC ring is for up to 250 GeV.
With some modest modifications, the RHIC-based MEIC ion ring can reach beam energies modestly higher than 100 GeV (up to 150 GeV)
There is no problem for an anticipated future upgrade to 250 GeV.

4. RHIC+Super-ferric Magnets (2.4 km)
This is perhaps the simplest & most practical scheme for reusing the RHIC magnets for MEIC
Half of the ring is RHIC dipoles, the other half is super-ferric magnets (up to 3.2 T). Both types of dipoles have same length
This should provide a 50% cost reduction of the dipoles on top of the super-ferric approach
In principle, all other RHIC magnets (quads, sextupoles) and diagnostics (kickers, BPM) can be reused (MEIC 100 GeV vs. RHIC 250 GeV). This provides another significant cost reduction
There are two types of layouts (symmetric/uniform and asymmetric/uniform) as shown below, both should work
Asymmetric cells but uniform lattice
RHIC magnet
9.45 m, up to 2.2 T
Super-ferric
9.45 m, up to 3.2 T
Symmetric cells but non-uniform lattice
RHIC magnet
9.45 m, up to 2.2 T
Super-ferric
9.45 m, up to 3.2 T

5. RHIC+Super-ferric Magnets (2.4 km)
Magnet type
RHIC
Super-ferric
High Field
Maximum kinetic energy
100 GeV
Upgrade to 250 GeV
Dipole length m
9.45
Dipole maximum field T
2.15
3.2
4.4 9
Dipole bending radius / angle
m / deg
155 / 3.5°
104 / 5.2°
190 / 2.9°
92.5 / 5.9°
Figure-8 crossing angle
deg
72°
FODO cells / dipoles in each arc
29 / 58
FODO cell length / packing factor
25.2 / 0.75
Arc length / radius
m / m
730 / 166
Straight length
457
Ring circumference
2374
The circumference was expanded to provide longer straights by lowering the figure- 8 crossing angle to 72 degree; the arc length has little change.
It should still fit the JLab site (new proposed boundary)
A similar design can be done for a 2.2 km ring