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Lifetime and injection efficiency vs. Dynamic and physical aperture; Measurement & simulation

Lifetime and injection efficiency vs. Dynamic and physical aperture; Measurement & simulation. Touschek and brehmsstrahlung lifetime reduction. For 0.04 % decrease in <energy acceptance> Bremsstrahlung lifetime decreases by 0.5 %; ~ln( D p/p).

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Lifetime and injection efficiency vs. Dynamic and physical aperture; Measurement & simulation

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  1. Lifetime and injection efficiency vs. Dynamic and physical aperture;Measurement & simulation SPEAR3 Chicane Lattice Review

  2. Touschek and brehmsstrahlung lifetime reduction • For 0.04 % decrease in <energy acceptance> • Bremsstrahlung lifetime decreases by 0.5 %; ~ln(Dp/p). • Touschek lifetime decreases by 4 %; ~(Dp/p)3. • Bremsstrahlung & Touschek decreases by ~2 %. SPEAR3 Chicane Lattice Review

  3. Dynamic aperture simulations Plots show median over many error seeds. Baseline optics Chicane optics SPEAR3 Chicane Lattice Review

  4. Measured dynamic aperture Measured dynamic aperture better than median tracking on energy, and worse off energy. SPEAR3 Chicane Lattice Review

  5. Stored beam starts scraping if beam is pushed ~1 mm closer to septum. Kickers are designed to kick the beam to 3 mm from septum chamber. Kicker calibration • Simulations indicate injection efficiency should drop off, if beam is kicked ~1 mm closer to septum. • Measurements show expected drop off. • This indicates injection bump is indeed kicking beam to 22 mm (3 mm from septum). • Kicker calibration from this measurement within 6% of design. simulation measurement SPEAR3 Chicane Lattice Review

  6. Kicker calibration, 2 • Decking, Portmann calibration. • Kicker amplitude to loose stored beam on septum vs. septum closed orbit. • Calibration within 5 % of previous method. SPEAR3 Chicane Lattice Review

  7. Measured energy aperture ID gaps closed • Lifetime vs. Vgap • 8 mA, single bunch • Touschek regime • t1/3 ~ rf acceptance • 2 % energy aperture (agrees w/ measured dynamic aperture). SPEAR3 Chicane Lattice Review

  8. Coulomb scattering; BL12 gap Orbit bump at BL9 12 mm aperture. • BL9 aperture scans • Lifetime vs. vertical orbit • Lifetime ~ constant over 4 mm • Systematic errors • Re-measure with scrapers, 11/2004 • BL12 gap, conservative • 12 – 2 = 10 mm at BL9 • Scales to 6.2 mm at BL12 • BL12 gap, aggressive • 12 – 4 = 8 mm at BL9 • Scales to 5.0 mm at BL12 SPEAR3 Chicane Lattice Review

  9. Aperture scans, systematic errors • Bump increases coupling (optimistic gap) • Included coupling correction in bump • Filled low current/bunch • Bump degrades vacuum (pessimistic gap) • Lifetime vs. bump in other straights also drops off. • Scans with low current, turned off ion pumps • Need scrapers SPEAR3 Chicane Lattice Review

  10. Aperture scans, conclusions • BL9 gap from 12 mm to 10 mm very likely OK. • 12 mm to 8 mm may be OK. • Further reduction not out of the question • Aperture scans plagued with systematic errors. • Scraper measurements this fall. SPEAR3 Chicane Lattice Review

  11. Dynamic aperture required for injection Baseline optics (IDs closed) 20 mm dynamic aperture should be more than enough for injection. septum magnet iron Stored beam Injected beam Should still get good injection with a 5 mm reduction in dynamic aperture. septum magnet iron SPEAR3 Chicane Lattice Review

  12. Measured injection efficiency • Simulate dynamic aperture reduction with closed orbit bump at septum. • Efficiency decreases sooner than expected. • Poor control/understanding of BTS optics. • Optics distortion from bump. • Possible obstacle. • Nonetheless, expected ~1 mm decrease in dynamic aperture is OK. Red = control study SPEAR3 Chicane Lattice Review

  13. Possible obstacle? • Mirror plate • Downstream of septum and phosphor screen • Upstream of window • Same x-section as septum • Last minute addition • Was not aligned septum magnet iron SPEAR3 Chicane Lattice Review

  14. Injection with reduced y-aperture • Tracking says not a problem. • Measurement shows efficiency reduction. • Need scraper! Injection rate vs. BL9 y-bump SPEAR3 Chicane Lattice Review

  15. Conclusions • Chicane lattice dynamic aperture meets requirements • Sufficient for injection • Minimal reduction in beam lifetime • Measurements show simulations (mostly) accurately predict optics performance • BL12 gap • Expect small lifetime and injection reduction. • Needs further measurements with scraper. SPEAR3 Chicane Lattice Review

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