Collimation in the ILC BDS

Collimation in the ILC BDS Carl Beard ASTeC Daresbury Laboratory • People • Requirement • Recent Successes • Future Aims

People • Task Leader – Nigel Watson (B’ham) • Damage Studies • L. Fernandez (ASTeC), A.Bungau (Manc) R. Barlow (Manc) G. Elwood (RAL), J. Greenhaulgh (RAL). • Wakefield Simulation and TDR • C. Beard (ASTeC), J. Smith (Lanc), R. Jones (Manc), R.Carter (Lanc), S Jamison (ASTeC), P Corlett (ASTeC)… • I. Zagorodnov (DESY), • M.Kärkkäinen, W.Müller, T.Weiland (TEMF) • Beam Tests (T-480 Experiment) • Frank Jackson…plus most of the above • SLAC ESA Team – Steven Malloy, Mike Woods… Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Need for Collimation • Reduce the background levels in the detector, by removing halo particles built up over the long linac. • Machine Protection, in the event of a beam miss-steer. Collimators are introduced, as a result of this the change in impedance has detrimental effects to the beam quality. The collimators have to be robust to withstand the full impact of several ILC Bunches. Design / optimisation of spoiler jaws (geometry and materials) for wakefield and beam damage performance Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Objectives • Development of Advanced EM modelling methods • Benchmarking of wakefield calculations against experiments • SLAC ESA beam test / data analysis • RF bench tests (training/code comparisons) • Tracking simulations with best models of wakefields • Simulations of beam damage to spoilers • Material studies using beam test Submitted 7 papers at EPAC, several EUROTeV reports/memos Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Collimator Parameter and Beam Parameters Copper Fracture temperature ~200 °C (473 K) Melting temperature 1085 °C (1357.77 K) Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Collimator Proposals 250, 500 GeV e- 2 mm, 10mm Ti/C 0.6 Xo of Ti alloy leading taper (gold), graphite (blue), 1 mm thick layer of Ti alloy 0.3 Xo of Ti alloy each side, central graphite part (blue). Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Cu+Graphite spoiler Carbon zones Cu zones 250 GeV: σx = 111 µm, σy= 9 µm 500 GeV: σx = 79.5 µm, σy= 6.36 µm Fracture temp. Melting temp. Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Ti / Graphite Spoiler Temperature data in the left only valid the Ti-alloy material. Top increase of temp. in the graphite ~400 K. Dash box: graphite region. 540 K 405 K 400 K 270 K ∆Tmax = 575 K per a bunch of 2E10 e- at 500 GeV σx = 79.5 µm, σy= 6.36 µm 2 mm deep from top Ti alloy and graphite spoiler [L.Fernandez, ASTeC] Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Fluka Benchmark Fluka Prediction of beam Damage (Evaporated material not considered Measurements of Beam damage crater in cooper on the FFTB. Measurements courtesy of SLAC, Marc Ross et al. Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Damage Studies • Beam tests are being planned to benchmark the Fluka/Geant Simulations • No electron beam is available with sufficient intensity • Or probability to hit the same point due to beam jitter. • Dynamic Simulations in ANSYS are being studied in support of the FLUKA/GEANT Simulations Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Wakefield Analysis Instant solution for only simple geometry Analytical Formula Simulation Bench Tests (TDR) Fast Results – Limited by Resolution/ confidence Good indicator – poor resolution Tests with Beam Real life measurements, slow turnaround time for measurements Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Simulation and Wire tests TDR and TDT are being used to measure the Impedance of a vessel and its loss factor Current TDR and TDT measurements are limited to 10 ps Pulse lengths. Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Achieving a 1 ps Pulse (In development) Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

MAFIA Simulations Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Limitations / Advances Limiting the simulations to short structures or only sufficient resolution for >>300 um bunch length. MAFIA/HFSS A new technique is being applied to allow full structures to be simulated with substantially higher resolution GDFIDL / ECHO 2 &3D Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Beam Tests in ESA • Simple Shapes to allow benchmarking with Calculations/Code • Geometric Wakefields • Resistive Wall Wakefields • Surface Roughness Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

2 doublets Two triplets BPM BPM BPM BPM ~40m ~16m T-480 Experiment Vertical mover • Wakefields measured in running machines: move beam towards fixed collimators • Problem • Beam movement  oscillations • Hard to separate wakefield effect • Solution • Beam fixed, move collimators around beam • Measure deflection from wakefields vs. beam-collimator separation • Many ideas for collimator design to test… Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

1500mm Wakefield Box Ebeam=28.5GeV ESA sz ~ 300mm – ILC nominal sy ~ 100mm (Frank/Deepa design) Magnet mover, y range = 1.4mm, precision = 1mm Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Initial Comparison of Results Analytical: 0.562 V/pC/mm MAFIA: 0.408 V/pC/mm Beam Test 0.556 V/pC/mm Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Future Work • Continue study into beam damage/materials • In the process of designing a 4th beam test • Collimators designed and built in EU, to be installed at SLAC ESA. • 3rd Physics run Mar/April 2007 • Application of the Moving Mesh Technique • TDR Measurements with Optically generated 1 ps Pulse. • Combine information on geometry, material, construction, to find acceptable baseline design regarding all of • Wakefield optimisation • Collimation efficiency • Damage mitigation Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006

Collimation in the ILC BDS