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EMMA: FFAG Demonstration

This article discusses the successful demonstration of a linear non-scaling FFAG accelerator for muon acceleration at the Neutrino Factory. The advantages of this accelerator include fast acceleration, large dynamic aperture, and cost-effective operation. The principles of the non-scaling FFAG are currently being tested during the EMMA commissioning.

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EMMA: FFAG Demonstration

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  1. EMMA: FFAG Demonstration J. Pasternak, Imperial College London/RAL STFC on behalf of the EMMA collaboration 13.01.2012, PASI Workshop, Fermilab J. Pasternak

  2. IDS-NF Neutrino Factory Baseline 3000-5000 km 7000-8000 km

  3. NS-FFAG • Non-scaling FFAG is selected forthe final muon accelerationattheNeutrino Factory. • Advantages include: • Allows very fast acceleration (~12 turns). • Large dynamic aperture due to linear magnets + high degree of symmetry. • More turns than in RLA – more efficient use of RF – cost effective. • Quasi-isochronous – allows fixed frequency RF system. • Orbit excursion and hence magnet aperture smaller than in the case of a scaling FFAG – cost effective. • Principles of NS-FFAG are now being tested during ongoing EMMA commissioning.

  4. NS-FFAG parameters for the Neutrino Factory

  5. Beam Optics and Acceleration (simulations) H Tune per cell ToF [ns] V Kinetic Energy [GeV] [MeV] Kinetic Energy [GeV] • Beam optics has been checked • with independent codes. • ToF and tune as a function of energy • was reproduced. • Initial “serpentine” acceleration was • obtained (in simulations) time [ns] J. Pasternak

  6. ns-FFAG works as expected? • Demonstration of a linear non-scaling Fixed Field Alternating Gradient accelerator was long waited. • EMMA is • Electron Model for Many Applications • Although initial experiment more focuses on • Electron Model of Muon Acceleration

  7. Three main goals • Acceleration in serpentine channel (outside rf bucket) in around 10 turns. • Large tune variation due to natural chromaticity during acceleration. SFP Serpentine channel SFP • Large acceptance for huge (muon) beam emittance.

  8. ALICE/EMMA at Daresbury Accelerators and Lasers in Combined Experiments EMMA Parameter Value Particle electron Momentum 10.5 to 20.5 MeV/c Cell 42 doublet Circumference 16.57 m RF Frequency 1.301 GHz RF voltage 2 MV with 19 cavities

  9. EMMA in pictures FQUAD Cavity DQUAD Ion Pump Ion Pump Ion Pump Girder

  10. EMMA collaboration • Funded by CONFORM (EPSRC basic technology grant). • STFC provided significant support through ASTeC. • Institutions include • STFC/ASTeC • Cockcroft Institute • John Adams Institute • Imperial College London • Brunel University • Fermi National Accelerator Laboratory • Brookhaven National Laboratory • CERN • TRIUMF • ……

  11. Four sector commissioning • Beam image on screen at the end of 4 sectors. • 22:37 on 22 June 2010

  12. Complete ring • A beam circulates first for three turns and then for thousands turns a few day later. • 16 August 2010 Second Turn First Turn

  13. Measurement of basic parameters Betatron oscillations • Closed orbit Orbital period Closed orbit distortion

  14. Two major problems identified • Closed orbit distortion was rather large (~+/- 5 mm) in both horizontal and vertical. • rf vector sum of 19 cavities was lower than expected. Cavity phase was not correctly adjusted.

  15. Cavity phase adjustment with beam loading signal • Monitor amplitude • Monitor phase beam rf For each cavity, observe sign of loading signal as a function rf phase offset.

  16. Synchrotron oscillation in a bucket • Consistent synchrotron oscillation period in experiment and simulation suggests Vector sum ~ 19 (# of cavity) x voltage expected Experiment set1

  17. Source of COD • Misalignment turns out worse than expected. • Re-alignment during shutdown should have made COD less than +/- 1 mm. But…

  18. COD caused by septum • Kick with the strength of 0.0006 [Tm] at both septa makes a similar COD observed. • Source of vertical COD is not yet identified. injection septum extraction septum

  19. Conclusion from runs in 2010 • Stability of optics with very small dispersion function has been illustrated. • Dependence of orbital period on beam momentum is confirmed. • Optics is fine. • Large COD suggests integer tune crossing could be harder than initially thought. • Acceleration seems difficult.

  20. Quick and dirty? • Fast acceleration with maximum possible rf voltage • To overcome possible beam deterioration due to integer tune crossing. • Brute force, but why not. • Serpentine channel opens with 1 MV per turn. • Increase the voltage to ~ 2 MV and see what happen. • NAFF algorism is used to calculate instantaneous tune.

  21. with 1.9 MV rf (1) Rapid acceleration with large tune variation Tune decreases and hor. orbit increases monotonically in measurement.

  22. without rf • Beam position and tune with fixed momentum.

  23. with 1.9 MV rf (2) Serpentine channel acceleration outside rf bucket All three momentum calibration methods; (a) hor. and (b) ver. tune and (c) hor. orbit shows consistent evidence of acceleration. (a) (b) (c)

  24. with 1.9 MV rf (3) • Not much distortion to betatron oscillations with integer tune crossing.

  25. Momentum measurement • Beam image on screen in the extraction line. 18 April 2011 Second Turn First Turn 12.0+/-0.1 MeV/c beam is accelerated to 18.4+/-1.0 MeV/c.

  26. Conclusion from runs in 2011 • EMMA proves that a linear non-scaling FFAG works. • A big step forward to the muon acceleration in a neutrino factory as well as to other applications. • Two out of three main goals are achieved. • Still need to show large acceptance.

  27. Plan for the next year more EMMA run • Acceleration with varying phase advance • Effect of magnet errors and misalignments • Slowly cross individual resonance • Examine effects of space charge, etc. • Serpentine channel acceleration • Measure mapping of longitudinal phase space • Study parameter dependence of longitudinal phase space • Dependence of transverse amplitude, etc. • Show large longitudinal and transverse acceptance • Scan injected beam in horizontal, vertical and longitudinal phase space

  28. Synergies • Proof of principle of the muon acceleration -serpentine acceleration (demonstrated, but more lessons to be learned), -operation of NS-FFAG, • Extrapolation of the results to future muon machines. • Synergies mainly with IDS-NF and MAP, VLENF, PRISM (experimental test of phase rotation in NS-FFAG) ,VLENF, but also with a medical FFAG, ADSR etc. • It is important to extract as much output as possible from the EMMA commissioning (may be try to extend the EMMA life?)!

  29. Summary • EMMA proves that a linear non-scaling FFAG works. • So far, no big surprise. • We will gain much more knowledge in the next year, both design and operational view point, on a linear non-scaling FFAG.

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