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Particle Beam Characterisation

This presentation by Pavel Karataev at the oPAC Advanced School outlines methodologies for characterizing particle beams, focusing on 6D phase space distribution. It covers key aspects, including transverse and longitudinal phase spaces, beam production, acceleration, and advanced measurement techniques. The discussion highlights the importance of measuring emittance through various invasive and non-invasive techniques such as wire scanners and laser methods. The talk also reviews the extraction line at KEK's ATF2 facility, emphasizing operational principles and practical applications in accelerator science.

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Particle Beam Characterisation

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  1. Particle Beam Characterisation Pavel Karataev John Adams Institute for Accelerator Science At Royal Holloway, University of London oPACAdvanced School on Accelerator Optimisation 7-11 July 2014, Royal Holloway College, Egham, UK

  2. Outline • 6D phase space distribution • Motivation • Transverse Phase-Space • Longitudinal Phase-Space • Accelerator Operation Principles • Accelerator Test Facility (ATF2 at KEK in Japan) • Beam production, pre-acceleration, injection, damping, extraction, delivery, characterization and main acceleration, application and termination • Summary

  3. High Luminosity Here Pb is the beam power ECM is the centre of mass energy N is the number of particles in the interaction x and y are the horizontal and vertical dimensions of the collision area HD is the luminosity enhancement factor determined by the inter-bunch focusing effect, bunch length, etc.

  4. Low divergence X-rays 3rd Generation Light Source 4th Generation Light Sources 500 MeV 1.2 GeV e-beam X01 RF-GUN  50 m UNDULATOR S01 S02 S03 BC1 S04 S05 S06 BC2 S07 S08 ...

  5. Low divergence X-rays Single bending magnet Undulator or wiggler

  6. Transverse Phase – Space

  7. Transverse Phase – Space b) e) c) a)

  8. Transverse Phase – Space

  9. Emittance CharacterizationDirect method

  10. Emittance CharacterizationQuadrupole Scan incoming beam beam size monitor quadrupole magnet

  11. Emittance CharacterizationQuadrupole Scan incoming beam beam size monitor quadrupole magnet ey = 41pm rad ey = 38pm rad

  12. Emittance CharacterizationMulti-BSM 3 Beam Profile Monitor ; 60 degrees of phase advance in between the monitors 4 Beam Profile Monitor ; 40-50 degrees of phase advance We can evaluate the error of the emittance measurement system. 5 beam Profile Monitor ; 30-50 degrees of phase advance are better setting. We can make a cross check of each measurement .

  13. Emittance CharacterizationMulti - BSM Emittance = 16.5 pm rad 5 wire scanners are used to measure the beam emittance

  14. Transverse beam size measurement techniques • Invasive: • Fluorescent Screens • OTR monitors • Wire scanners • Direct imaging • PSF technique • Non-Invasive: • Laser-Wire • e-beams – Compton scattering • H-beams – Photo-detachment • ODR monitor • Synchrotron Radiation • Direct imaging • Interferometers • Pin-hole camera

  15. Longitudinal Phase-Space

  16. Dispersion Function and Energy Spread Measurement Two particles in a dipole magnet p+Dp p Transverse Beam Size

  17. Dispersion Function and Energy Spread Measurement Two particles in a dipole magnet p+Dp p Beam Energy Spread measurement

  18. Dispersion Compression

  19. Bunch Length Characterization • RF techniques: • Streak Camera • External source • RF deflecting cavity • Destructive • RF Accelerating cavity • Laser based techniques: • Laser-Wire scanner • Beam-laser time jitter • Non-linear mixing • Destructive • E-O techniques • Coherent radiation spectrum: • Synchrotron radiation • Transition radiation • Diffraction radiation • Smith-Purcell radiation • Cherenkov Diffraction rad.

  20. Operation Principles • Beam production • Pre-acceleration • Injection • Damping, storage or accumulation • Extraction • Delivery • Characterization and main acceleration • Application and • Termination

  21. KEK-ATF2 facility in Japan ATF2 Extraction Line 1.28 GeV Linac

  22. Beam current monitors EXT IP BTE BTM DR GUN LN0 LNE

  23. RF GUN and 80MeV pre-accelerator 1-20 bunch with 2.8n spacing Charge : 1-3nC/bunch N. emittance : 5um.rad Energy: 80±0.8~2.4 MeV • Laser Phase • RF Gun Phase • LN0 Phase (2.8 GHz) Faraday Cup for initial Gun Tuning

  24. 1.3 GeV Linac • Beam Energy • RF is set wrtLN0 • Klystrons #1 - #8 • Beam trajectory • Instrumentation: BPMs, ICT, Wire Scanners, Screen monitor

  25. 1.3 GeV LinacKlystron #8 Right power level

  26. Trajectory in the Linac and in the Beam transport line

  27. Trajectory in the Linac and in the Beam transport line • 30 BPMs • 9 screens • 40 dipoles • 62 quadrupoles • Energy • Trajectory • Beta-function

  28. Septum area: injection and extraction Septum Kicker

  29. Damping Ring Extraction and Final Focus Test Beam Line Injector Linac

  30. Radiation Damping of Betatron Oscillations

  31. Excitation of Betatron Oscillations p -p

  32. Damping Ring Extraction and Final Focus Test Beam Line • Three Corrections: • Beam Based Alignment • Closed Orbit Distortion correction • Vertical COD-dispersion correction • Coupling correction • Beta-beat (optics) correction Injector Linac

  33. Damping Ring Extraction and Final Focus Test Beam Line Monitor: BPM - total 96 Corrector: Steering magnets (47 - H and 51 -V) Sextupoles with Skew Qaud (total 68) Injector Linac

  34. Beam based alignment

  35. Other instrumentation Extraction and Final Focus Test Beam Line Charge: Wall current monitor ICT Beam size: SR monitors: Optical SR interferometer, Fresnel zone plateXSR, Cavity Laser-Wire. Injector Linac

  36. Septum area: injection and extraction Septum Kicker

  37. Extraction line and Final Focus • 40 Cavity BPMs • Orbit tilt monitor • 5 wire scanners • 5 OTR monitors • Sub-um OTR monitor • Pulsed Laser-wire • Laser Interferometer • Intra-train FB • Beam loss monitor

  38. Extraction line and Final Focus • Corrections • Orbit correction • Dispersion correction • Beta-matching • Skew correction 67 nm beam was achieved: G. White, ATF2 Collaboration, PRL 112, 034802 (2014).

  39. Beam loss monitoring

  40. Beam loss monitoring 4) L3 input 1) Chicane or L0 2) Between MS3L to MS5L 3) L1 input

  41. Summary • The characterization begins from the source • Every Accelerator subsection should be equipped with a comprehensive set of diagnostics equipment • 6 D phase space and intensity, position, direction, arrival time, beam losses are equally important.

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