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This document presents a comprehensive study on the optics design and multi-particle tracking for the International Linear Collider (ILC) undulator-based positron source. Key parameters include a 125 MeV target capture system, 125-400 MeV non-conductive pre-acceleration, 400 MeV transport, and a superconducting linac boosting the beam to 5 GeV. The optical configurations aim to enhance capture efficiency, minimize electron loss, and optimize beam dynamics throughout the system. Analysis includes potential errors, beam alignment, and meticulous utilization of different components for effective positron production and transport.
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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
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
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).
PPATEL PCAP PPA PPATEL X (m) Y (m) PCAP PPA Z (m)
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)
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 )
LTR – Linac to Ring • Spin rotations to preserve polarization in DR: - Bending magnets: from longitudinal to horizontal plane =n7.929 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
Emitt. station collimation solenoid RF 7X7.929 collimation solenoid Emitt. station 7X7.929 RF section
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
Overall e+ source geometry X (m) LTR Y (m) PCAP, PPA, and PPATEL PBSTR PTRAN Z (m)
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)
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/
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)
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)
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.