1. 08/01/2007Juan Luis Fernandez-Hernando End Station A Measurements on Collimator Wakefields 4th Wakefield Interest Group - CI 05/03/2008 Luis Fernandez-Hernando, CCLRC DL, ASTeC Adriana Bungau, Manchester University Jonathan Smith, Lancaster University

2. 08/01/2007Juan Luis Fernandez-Hernando Content: ESA Set up and collimators Analysis of T480 Results Conclusion

3. 08/01/2007Juan Luis Fernandez-Hernando Wakefields deteriorate the beam quality. A final collimator design should minimise this effect. Studies on wakefields generated by different collimator geometries. Comparison to analytic predictions and simulations in order to improve both methods.

4. 08/01/2007Juan Luis Fernandez-Hernando Beam Parameters at SLAC ESA and ILC ParameterSLAC ESAILC-500 Repetition Rate10 Hz5 Hz Energy28.5 GeV250 GeV Bunch Charge2.0 x 10 10 Bunch Length 300  m Energy Spread0.2%0.1% Bunches per train1 (2*)2820 Microbunch spacing- (20-400ns*)337 ns *possible, using undamped beam

5. 08/01/2007Juan Luis Fernandez-Hernando Magnet mover, y range =  mm, precision = 1  m E beam =28.5GeV

6. 08/01/2007Juan Luis Fernandez-Hernando 1500mm

7. 08/01/2007Juan Luis Fernandez-Hernando T480 “wakefield box” ESA beamline

8. 08/01/2007Juan Luis Fernandez-Hernando

9. 08/01/2007Juan Luis Fernandez-Hernando 1000mm OFE Cu, ½ gap 1.4mm

10. 08/01/2007Juan Luis Fernandez-Hernando

11. 08/01/2007Juan Luis Fernandez-Hernando Designed Collimators

12. 08/01/2007Juan Luis Fernandez-Hernando BPM A run with the beam going through the middle of the collimator (or without the collimator) is used as reference for the next run where the collimator will be moved vertically. This run also serves to calculate the resolution of each BPM. BPM The analysis will do a linear fit to the upstream and downstream BPM data separately, per each pulse (bunch). For this fit the data is weighted using the resolution measured for each BPM.

13. 08/01/2007Juan Luis Fernandez-Hernando BPM Vertical mover ~15 m 2 triplets ~40 m 2 doublets Wakefield measurement: –Move collimators around beam (in steps of 0.2 mm, from -1.2 mm to +1.2 mm, being 0 mm the centre of the collimator). –Measure deflection from wakefields vs. beam-collimator separation

14. 08/01/2007Juan Luis Fernandez-Hernando BPM Vertical mover ~15 m 2 triplets ~40 m 2 doublets Wakefield measurement: –Move collimators around beam (in steps of 0.2 mm, from -1.2 mm to +1.2 mm, being 0 mm the centre of the collimator). –Measure deflection from wakefields vs. beam-collimator separation

15. 08/01/2007Juan Luis Fernandez-Hernando The slopes of each linear fit are subtracted obtaining a deflection angle. This angle is transformed into V/pC units using the charge reading and the energy of the beam. All the reconstructed kicks are averaged per each of the different collimator positions and a cubic fit of the form: y’ = A 3 ·y 3 + A 1 ·y + A 0 is done to the result. The error in the kick reconstruction at each collimator position weights the different points for the fit. The kick factor is defined as the linear term of the cubic fit (A 1 ). BPM

16. 08/01/2007Juan Luis Fernandez-Hernando Col. 12  = 166 mrad r = 1.4 mm Angular kick (V/pC) Collimator y (mm) T480 (prelim.) 2007 data T480 (prelim.) 2007 data Luis Fernandez - Daresbury Data analysis

17. 08/01/2007Juan Luis Fernandez-Hernando Slot 1 Slot 4 Slot 2 Slot 3 L=1000 mm  = 324 mrad r = 2 mm  = 324 mrad r = 1.4 mm  =  /2 r = 3.8 mm  = 324 mrad r = 1.4 mm (r = ½ gap)

18. 08/01/2007Juan Luis Fernandez-Hernando Collim No Experimental measurements (V/pC/mm) Analytic predictions (V/pC/mm) 3-D Modeling prediction kick (V/pC/mm) 1 1.2  0.3 2.27 1.63  0.37 2 1.9  0.2 4.63 2.88  0.84 3 4.4  0.3 5.25 5.81  0.94 4 0.6  0.4 0.56 9.09  0.06 5 4.9  0.3 4.59 6.88  0.58 6 1.0  0.1 4.65 2.12  1.14 7 1.4  0.3 4.59 2.87  0.53 8 1.0  0.2 4.59 2.39  0.89 10 1.4  0.2 11 1.7  0.1 12 1.7  0.1 13 1.9  0.2 3.57  0.98 14 2.6  0.1 3.57  0.98 15 1.6  0.1 2.51  1.16 16 1.6  0.2 2.35  1.50 Measured and calculated kick factor Note: quoted errors are estimates Assuming 500 um bunch lenght Colimators 4-5 and 13-16 do not include the resistive component of the kick

19. 08/01/2007Juan Luis Fernandez-Hernando SWMD: Deliverable Summary “Engineering design for ILC mechanical spoiler, including prototype evaluations of wakefield and beam-damage performance.”  Wakefields: T480 at SLAC to evaluate wakefield performance of candidate spoiler designs, benchmarking calculations/modelling  16 jaw designs studied  Outcome of ongoing wakefield optimisation likely to require further iteration on candidate designs  First conceptual design for mechanical spoiler design available, to report at EPAC’08.