CCR Status, 1/31/2012

1. CCR Status, 1/31/2012

2. Top Level Requirements • Deliver properly configured periodic train of bunches to cooling channel at appropriate repetition rate • 54 MeV • Few mm-mrad • 0.01% x ~ 1 cm • 2 nC • Rep rate of 750 MHz/N, N=1,10,100… • Manage stray power deposition, instabilities; preserve beam quality • Recover it Very similar to FEL requirements (but with longitudinal phase space rotated 90o)

3. Implementation Requirements • System configuration/geometry consistent with MEIC collider • 2 x 30 m 2 kG solenoids; figure X layout • ½ m vertical separation Perform design exercise to explore technology boundaries and beam dynamical limitations

4. Design Parameters

5. System Configuration • Three options • 750 MHz ERL (high risk source) • 75 MHz ERL (moderate risk source & beam transfer, high risk beam-beam interaction) • 7.5 MHz ERL (high risk beam transfer) • All three use common cooling channel geometry • All three use similar beam transfer system • Single DC dipole for 750 MHz ERL • Pair of RF separators/single septum for 75 MHz ERL • Pair of ultrafast kickers/single septum for 7.5 MHz ERL

6. recirculation/decompression transport dump CCR dechirper beam exchange system ERL cooling solenoids rechirper injector recovery/recompression transport System Layout

7. ERL Characteristics • 4 five-cell 750 MHz SRF cavities • Existing JLab high current design • Longitudinal aspect ratio at CCR imposes some degree of gymnastics • Harmonic RF problematic • Chirp/compress/dechirp before injection • Use transport system compactions for linear/nonlinear compensation • Chirp/decompress/energy compress during recovery • Use transport system compactions for linear/nonlinear compensation • Betatron matching between/amongst functional modules

8. Longitudinal Match – 1 cm

9. Longitudinal Match – 2 cm

10. BetatronMatching (1 cm)

11. CCR Concept • Use common figure-8 layout for all 3 ERL options • 2 x 30 m 20 kG cooling solenoids • Round beam matched to cooling channels • FODO arcs, asymmetric chicane vertical steps • Compactions cancel  isochronous transport • Betatron matching between/amongst segments • Beam transfer: 2 x 90 FODO cells • Single dipole at center in 750 MHz ERL option • RFS/fast kickers at ends, septum in center in 75, 7.5 MHz ERL option) • Cf. CEBAF beam distribution system

12. CCR layout • Figure 8, 30 m solenoids, ½ m vertical separation

13. CCR Optics

14. Rudimentary S2E: Injector to CCR

15. CCR: 1000(+) particles x 100 turns • Added a few outliers to probe aperture

16. Rudimentary S2E: CCR to Dump

17. Cheats, Swindles, Things Left Undone • Matching to/from CCR “figurative” • Simply set ERL match to 1 m into/out of exchange dipole/septum; adjusted using Twiss matrix into/out of CCR & started simulation in middle of central quad in beam exchange section Still have to construct details of transfer for each case… • Path lengths not properly set • ½ lRF for full ERL • Multi-turn CCR needs to be multiple of lRF • Haven’t started sensitivity/aberration analyses • Matching poorly optimized

18. Now, the bad news… • 2 nC x 54 MeV is nontrivial… • CW MHz, rep rate, nsec-rise/fall time kickers nontrivial