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Optimizing Particle Tracking for ILC Undulator-Based e+ Source Design

This study explores the design and particle tracking for the ILC undulator-based e+ source, covering system parameters and layout details to capture and accelerate positrons efficiently. The process involves multiple stages, from pre-acceleration to beam collimation, aiming at optimizing energy compression, beam transport, and polarization preservation. Various components are discussed, such as the PCAP and PPA systems, with a focus on multi-particle tracking from the target to the capture system. The analysis includes understanding energy losses, aperture considerations, and error corrections for accurate simulation results. Future outlook includes further optimizations, addressing losses, and defining tuning requirements for enhanced performance.

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Optimizing Particle Tracking for ILC Undulator-Based e+ Source Design

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  1. S2E optics design and particles tracking for the ILC undulator based e+ source Feng Zhou SLAC ILC e+ source meeting, Beijing, Jan. 31 – Feb. 2, 2007

  2. Main parameters

  3. Layout of the ILC e+ source • Target to capture system (125 MeV) • Target hall: 125 MeV dogleg,125-400 MeV NC pre-acceleration, and 400 MeV dogleg • 5.03 km 400 MeV transport • SC boost linac to 5 GeV • Linac-to-Ring: spin rotations, energy compression, and beam collimation. • 5-GeV beam dump

  4. Transport in Target hall • OMD (6T-0.5T): to transform e+ with small spot size and large divergence at the target into large size and small divergence at the capture cavities. • N.C. RF capture cavities system embedded in a 0.5 T of solenoid to accelerate e+ beam to 125 MeV. • PCAP - 125 MeV e+ beam dogleg: to separate e+ from e- and photons using a dogleg with 2.5 m of horiz. offset (by Nosochkov). • PPA - NC pre-accelerator consisting of L-band structures embedded in a 0.5 T of solenoid to accelerate e+ from 125 MeV to 400 MeV. • PPATEL - a 400-MeV horiz. and vert. dogleg to deflect the beam by 5 m and 2 m in the horiz. and vert. planes, respectively (by Nosochkov).

  5. PPATEL PCAP PPA PPATEL X (m) Y (m) PCAP PPA Z (m)

  6. 400 MeV 5-km Transport • PTRANa – to follow e- main linac tunnel for 4 km. • PTRANb – to bring e+ from e- main linac tunnel to e+ booster linac tunnel. • PTRANc – 479 m of transport to connect with booster linac. PTRANc PTRANb X (m) Y (m) PTRANa Z (m)

  7. 5-GeV e+ booster linac • Accelerate e+ beam from 400 MeV to 5 GeV. • Have 3 sections: - 400 MeV to 1.083 GeV (4 non-standard ILC CM, each CM has 6 9-cell cavities and 6 quads) - 1.083 GeV to 2.626 GeV (6 ILC CM, each has 2 quads) - 2.626 GeV to 5 GeV (12 standard ILC CM, each has 1 quad )

  8. LTR – Linac to Ring • Spin rotations to preserve polarization in DR: - Bending magnets: from longitudinal to horizontal plane =n7.929 at 5 GeV; here n=7 to get reasonable R56. - Solenoid: from horizontal to vertical, parallel or anti-parallel to the magnetic field in the DR: = 26.23 T.m at 5 GeV. • Energy compression: R56 and RF section • Collimations: to reduce beam loss in the DR • Emittance measurement, and 3 PPS stoppers • Matching section

  9. Emitt. station collimation solenoid RF 7X7.929 collimation solenoid Emitt. station 7X7.929 RF section

  10. 5-GeV e+ beam dump • As a beam dump: for 0.1% and 10% of energy spread, the half edge beam sizes x/y are 3.9cm/8.3cm and 14.3cm/8.3cm, respectively, which meet the dump window specifications (see D. Walz, Snowmass, 2005). • As an energy spectrometer: 0.1% of resolution. 1st Bend of PLTR arc, its power off for dump Dump bend Monitor for energy spectrometer Dump window

  11. Overall e+ source optics

  12. Overall e+ source geometry X (m) LTR Y (m) PCAP, PPA, and PPATEL PBSTR PTRAN Z (m)

  13. Multi-particle Tracking from the Target to the DR injection line • Multi-particle tracking from the Target to the capture system (125 MeV) (by Y. Batygin). • Elegant code is used to track the e+ beam through the rest of the beamline including the PCAP, PPA, PPATEL, PTRAN, PBSTR, and LTR. • Energy compression is optimized to accommodate more e+ within the DR 6-D acceptance: m, and (25MeV)(3.46cm)

  14. ILC e+ source physical apertures

  15. Target Target 125 MeV 125 MeV y’ (rad)  Time (s) y (m) • Undulator parameter: K=1, =1cm. • Target: 0.4 r.l., immersed B0=6T. • OMD: B=B0/(1+g.z), g=0.6/cm, z=18.3cm. Y. Batygin, www.slac.stanford.edu/~batygin/

  16. ILC e+ loss distribution along the beamline

  17. 50 MeV 2X3.46cm   With LTR, but w/o collimation W/o LTR Time (s) Time (s) 50 MeV 2X3.46cm  With LTR and collimation Time (s)

  18. RMS values of magnet errors for tracking

  19. No error No error x (rad) y (rad) y (m) x (m) with errors but no correction with errors but no correction y (rad) x (rad) x (m) y (m) With errors and correction With errors and correction y (rad) x (rad) x (m) y (m)

  20. Comparisons of capture efficiency

  21. Summary and outlook • S2E optics for e+ source is developed. • S2E tracking w/o and w/ errors is performed: 49.8% of e+ from the target are captured within the DR 6-D acceptance after energy compression. • e+ loss into DR is ~1% after LTR collimation; additional betatron collimators are needed to collimate 0.8% of e+. • Field and alignment errors and orbit correction are analyzed. • Toward EDR: optics and physical aperture optimizations; reducing e+ loss in the DR; modeling activation of the 5-GeV collimations; tolerances definition; and tuning requirements. F. Zhou, Y. Batygin, Y. Nosochkov, J, C.Sheppard, and M. D. Woodley, “Start-to-end optics development and multi-particle tracking for the ILC undulator-based positron source”, SLAC-PUB-12239, Jan. 2007.

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