1. 28-May-2008Non-linear Beam Dynamics WS1 On Injection Beam Loss at the SPring-8 Storage Ring Masaru TAKAO & J. Schimizu, K. Soutome, and H. Tanaka JASRI / SPring-8

2. 28-May-2008Non-linear Beam Dynamics WS2 Outline Motivation SPring-8 storage ring Injection efficiency measurement Tracking simulation Improvement of injection efficiency –Beam collimation in transport line –Low chromaticity operation –Beta-distortion correction Summary

3. 28-May-2008Non-linear Beam Dynamics WS3 Motivation Injection beam loss is a very important issue for top-up operation. –Demagnetization of insertion devices (ID) –Radiation safety Before introducing top-up operation, we intensively studied injection beam loss at the Spring-8 storage ring. –Effects of ID gap, chromaticity, beta-distortion, …

4. 28-May-2008Non-linear Beam Dynamics WS4 SPring-8 Storage Ring Parameters energy8 GeV circumference1.5 km horizontal / vertical betatron tune40.15 / 18.35 horizontal / vertical chromaticity8.0 / 8.3 natural emittance3.4 nmrad emittance coupling ratio0.002 synchrotron tune0.01 energy spread0.0011 bunch length (zero current limit)12.5 ps @ 2002.9 ~ 2003.7

5. 28-May-2008Non-linear Beam Dynamics WS5 Storage Ring Optics Modified Chasman-Green optics 4 magnet-free straight sections of 30 m long 36 normal cells, 4 long straight sections

6. 28-May-2008Non-linear Beam Dynamics WS6 Insertion Devices @ SPring-8 27 ID's –in-vacuum: 21, out-vacuum: 6. –One of in-vacuum undulators (ID19) is 25 m long. standard IDlong ID in-vacuum ID

7. 28-May-2008Non-linear Beam Dynamics WS7 Insertion Device Parameters ID19 (long)ID20 (standard) length25 m4.5 m minimum gap12 mm7 mm maximum gap50 mm vertical beta @ center14.1 m5.6 m vertical beta @ ends25.2 m6.5 m cf. vacuum chamber height: 40 mm

8. 28-May-2008Non-linear Beam Dynamics WS8 Injection Efficiency Measurement Turn-by-turn current monitor –ICT + oscilloscope. –Used for study. Voltage sum of 4 electrodes of turn-by-turn BPM –Influenced by synchrotron motion. (DCCT @ storage ring) - (BCM @ beam transport) –Monitoring in user operation.

9. 28-May-2008Non-linear Beam Dynamics WS9 Experiments Injection efficiency is measured for various ID gap. –Use ID as a scraper. Measured for ID19 (long), ID20, ID37 (standard). long undulator standard undulator

10. 28-May-2008Non-linear Beam Dynamics WS10 Dependence of injection efficiency on ID gap Gap where injection efficiency starts to decrease is different between long undulator and standard ones. The injection efficiencies corresponding to the same effective gaps of ID's coincide. The effective gap of injection efficiency starting to drop corresponds to the minimum effective height of the vacuum chamber. Injection efficiency is limited by transverse dynamics.

11. 28-May-2008Non-linear Beam Dynamics WS11 Tracking Simulation "Racetrack" based tracking code. 6 x 6 formalism. Symplectic integration. Using ring model (error fields) derived by response matrix analysis. With physical apertures. 1000 particles, 1000 revolutions.

12. 28-May-2008Non-linear Beam Dynamics WS12 Injection Beam Parameters horizontal emittance220 nmrad emittance coupling0.002 energy spread0.0013 bunch length63 ps off-set from stored beam orbit10 mm cf. booster synchrotron lattice: FODO. circumference: 400 m.

13. 28-May-2008Non-linear Beam Dynamics WS13 Simulation Results Decay rate of simulation is somewhat faster than that of experiment. Dependence of injection efficiency on ID gap is enough described by simulation. experimentsimulation

14. 28-May-2008Non-linear Beam Dynamics WS14 Lost Points of Injection Beam Loss points detected by simulation. ID 19 gap conditionmain loss points minimum (12 mm)ends of undulator maximum (50 mm) quadrupole magnets in matching section (highest vertical beta at upstream and down stream of long straight sections)

15. 28-May-2008Non-linear Beam Dynamics WS15 Lost Particle Distribution in Initial Phase Space Lost particle distribution in phase space of injection beam detected by simulation. Horizontal phase space: lost particles localize in large amplitude side. Vertical & longitudinal phase spaces: lost particles uniformly distributed.

16. 28-May-2008Non-linear Beam Dynamics WS16 Beam Collimation in Transport Line Beam collimator in horizontal direction was installed in transport line from booster to storage ring to eliminate unnecessary beam tail.  = 0. 544mm  = 1. 249mm booster SR

17. 28-May-2008Non-linear Beam Dynamics WS17 Influence of Chromaticity 1 Lowering the chromaticity improves injection efficiency. In low chromaticity condition, ID gap dependence of the injection efficiency is scarcely observed. high chromaticity ( 8, 8 ) low chromaticity ( 2, 2 )

18. 28-May-2008Non-linear Beam Dynamics WS18 Influence of Chromaticity 2 Particle distribution in vertical direction –long undulator entrance. –after 500 revolutions. –without aperture limit.

19. 28-May-2008Non-linear Beam Dynamics WS19 Beta-Distortion Correction Beta-distortion was corrected by using 48 auxiliary quadrupole magnet power supplies. Beta-distortion was measured by response matrix analysis. Correction performance was checked by re- measurement of beta-distortion after correction. It is observed beta-distortion correction improved injection efficiency by about 15 %.

20. 28-May-2008Non-linear Beam Dynamics WS20 Beta-Distortion Correction before (rms distortion: 7.4%) after (rms distortion: 1.9%) * Half of the Ring is shown.

21. 28-May-2008Non-linear Beam Dynamics WS21 Beta-Distortion Correction before (rms distortion: 7.3%) after (rms distortion: 1.5%)

22. 28-May-2008Non-linear Beam Dynamics WS22 Influence of Beta-Distortion Particle distribution in vertical direction –beta-distortion correction ON/OFF. –at long undulator entrance. –without aperture limit.

23. 28-May-2008Non-linear Beam Dynamics WS23 Summary Injection efficiency at the SPring-8 storage ring was investigated by experiments and simulations. Simulation well describes the experiments. Injection efficiency is mainly limited by vertical aperture. Following the implication by the simulation, we improved the injection efficiency. –Injection beam collimator. –Lowering chromaticity. –Correction of beta-distortion.