1. Racetrack Booster Option & Initial Spin Tracking Results
A.M. Kondratenko, M.A. Kondratenko, and Yu.N. Filatov presented by V.S. Morozov
MEIC Weekly R&D Meeting
September 10, 2015
F. Lin

2. Racetrack Booster Motivation to consider racetrack booster
Shorter circumference better for space charge
Lower cost

3. Racetrack Booster Motivation Booster lattice
Reduction of space charge tune shift due to shorter circumference
Cost optimization
Convenient simplified model to benchmark theory and simulations
Booster lattice
Modified figure-8 lattice with arc sections removed
Injection in a straight, which should be okay for transverse phase-space painting

4. Ring Length Same straights Figure-8 Racetrack BL, Tm Ldip, m 267 89
188 63

5. Spin Resonances in Racetrack
Particles
Number of spin resonances
integer  = k
intrinsic  = k N  y
coupling  = k N  x
non-superperiodic  = k  y (k  mN)
protons 16 32
deuterons 1

6. Polarized Protons About 80 resonances for protons Siberian snake
Solenoidal snake
~34 Tm at 9 GeV/c: 2  4.6 m with Bmax = 3.7 T
Inserted in a straight
Ramped with energy
Optical effects
Compensate betatron tune shift adjusting two quadrupole families in triplets
Leave transverse coupling uncompensated as in Nuclotron

7. Optics with Siberian Snake

8. Polarized Deuterons Snake not practical (~100 Tm, ~30 m long)
Resonance crossing more adequate
Characteristic ramp time giving full depolarization
For Taccel = 0.01 T *, resonance w crossed fast with 1% depolarization
For Taccel = 100 T *, resonance w crossed adiabatically with 1% depolarization (not really practical due to weaker resonances)
For typical parameters
 fast crossing requires ~4 s ramp time (demonstrated in Nuclotron)
 at slower rates, easier to use figure-8

9. Tracking: Longitudinal Phase Space
Crossing of  = y – 5 resonance at 1 T/s
B from 5.3 to 5.53 Tm in 3104 turns
Benchmarking Zgoubi
Longitudinal phase space:
Option
Integration steps inside body (cm)
CPU time, total (s)
Quad
Bend A
1/10 = 0.1
1/8 = 0.125
1750 B
1/6 = 0.167
1/4 = 0.25
1200 C
1/3 = 0.333
1/2 = 0.5
500 D 1 2
160 A B C D

10. Tracking: Vertical Phase SpaceB C D

11. Tracking: Spin
 = y – 5 resonance induced by offsetting strength of one of the quads A B C D

12. Tracking: Slower Ramp Rate
Ramp rate of 510-3 T/s, largest integration step size (D)
~150 times greater polarization loss consistent with expectation

13. Summary & Conclusions
Racetrack shortens the circumference reducing space charge effect and potentially saves the cost
Acceleration of polarized protons in a racetrack requires Siberian snake
Polarized deuterons feasible with quickly-rampable Nuclotron-style magnets
Additional benefit of faster booster cycle
Simulations underway in Zgoubi, results consistent with expectations
Zgoubi convenient for testing, validation and optimization, longer-term simulations may need to be done with something else, e.g. GPU Spink
Next steps
Tracking proton polarization in racetrack booster with Siberian snake
Validating statistical model
Moving on to collider ring
Results with exception of spin tracking will be presented at DSPIN