August 11, 2004SPEAR3 Chicane Lattice Review Lifetime and injection efficiency vs. Dynamic and physical aperture; Measurement & simulation

August 11, 2004SPEAR3 Chicane Lattice Review Touschek and brehmsstrahlung lifetime reduction For 0.04 % decrease in Bremsstrahlung lifetime decreases by 0.5 %; ~ln(  p/p). Touschek lifetime decreases by 4 %; ~(  p/p) 3. Bremsstrahlung & Touschek decreases by ~2 %.

August 11, 2004SPEAR3 Chicane Lattice Review Dynamic aperture simulations Baseline opticsChicane optics Plots show median over many error seeds.

August 11, 2004SPEAR3 Chicane Lattice Review Measured dynamic aperture Measured dynamic aperture better than median tracking on energy, and worse off energy.

August 11, 2004SPEAR3 Chicane Lattice Review 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. Kickers are designed to kick the beam to 3 mm from septum chamber. Stored beam starts scraping if beam is pushed ~1 mm closer to septum. simulationmeasurement

August 11, 2004SPEAR3 Chicane Lattice Review Kicker calibration, 2 Decking, Portmann calibration. Kicker amplitude to loose stored beam on septum vs. septum closed orbit. Calibration within 5 % of previous method.

August 11, 2004SPEAR3 Chicane Lattice Review Measured energy aperture Lifetime vs. V gap 8 mA, single bunch –Touschek regime –  1/3 ~ rf acceptance 2 % energy aperture (agrees w/ measured dynamic aperture). ID gaps closed

August 11, 2004SPEAR3 Chicane Lattice Review Coulomb scattering; BL12 gap 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 Orbit bump at BL9 12 mm aperture.

August 11, 2004SPEAR3 Chicane Lattice Review 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

August 11, 2004SPEAR3 Chicane Lattice Review 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.

August 11, 2004SPEAR3 Chicane Lattice Review Dynamic aperture required for injection Baseline optics (IDs closed) 20 mm dynamic aperture should be more than enough for injection. Should still get good injection with a 5 mm reduction in dynamic aperture. septum magnet iron Stored beamInjected beam

August 11, 2004SPEAR3 Chicane Lattice Review 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

August 11, 2004SPEAR3 Chicane Lattice Review Possible obstacle? septum magnet iron Mirror plate –Downstream of septum and phosphor screen –Upstream of window –Same x-section as septum –Last minute addition –Was not aligned

August 11, 2004SPEAR3 Chicane Lattice Review Injection with reduced y-aperture Tracking says not a problem. Measurement shows efficiency reduction. Need scraper! Injection rate vs. BL9 y-bump

August 11, 2004SPEAR3 Chicane Lattice Review 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.