1 / 24

Generating Picosecond X-ray Pulse at APS Through Beam Manipulation

Generating Picosecond X-ray Pulse at APS Through Beam Manipulation. Weiming Guo Accelerator Physics Group / ASD Advanced Photon Source. Acknowledgements. Michael Borland Katherine Harkay Vadim Sajaev Chunxi Wang Bingxin Yang. Outline. Brief review of short pulse generation methods.

pelham
Télécharger la présentation

Generating Picosecond X-ray Pulse at APS Through Beam Manipulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Generating Picosecond X-ray Pulse at APS Through Beam Manipulation Weiming Guo Accelerator Physics Group / ASD Advanced Photon Source

  2. Acknowledgements • Michael Borland • Katherine Harkay • Vadim Sajaev • Chunxi Wang • Bingxin Yang

  3. Outline • Brief review of short pulse generation methods. • Introduce idea of synchrobetatron coupling method. • Linear synchrobetatron coupling and decoherence beam dynamics. • Experimental results. • Conclusions.

  4. Longitudinal Phase Space Manipulation Methods I sd = 0.096% d t sDt = 20 ps • Lower ac • Increase ns: 2nd rf system, lower energy • 3. Voltage modulation

  5. Longitudinal Phase Space Manipulation Methods II dipole d D(s) t 0 Vrf = V0(1+ecosnmw0t)sin hw0t nm~2ns • Lower ac • Voltage modulation

  6. Tilt the Bunch to Get Shorter Pulses y z sy=8mm,0.03ps sz= 5.8mm,20ps sl= sy /q Initial bunch Tilted bunch Photons Slit Shorter Pulse Shorter Pulse

  7. Physics Limits Method Maximum Pulse length Limitation Comp. ratio (ps) Voltage modulation * ~ 2 10 Nonlinearity Increase ns, ns→0.5 ~60 0.3 cavity number Low ac ,fs→1/tE** ~65 0.3 ac,n, x-z coupling Vertical tilt *** ~660 0.03 Physical aper. * Glenn Decker ** Vadim Sajaev *** Michael Borland

  8. Deflecting Cavity and Synchrobetatron coupling y A(z) sin(nxq + y) y Cavity Kick Betatron Osci. A sin(nxq + y(z)) z Magnet Kick Synchrobetatron Coupling y′ y y y y′ y′ y′ ‹y›: Bunch centroid ‹y2›: Bunch height ‹y› (z): Slice centroid ‹y2› (z): Slice beam height

  9. Particle Motion After A Vertical Kick y′ y′ y y After Before the Kick Betatron Oscillation

  10. Tune Difference by Momentum Spread Vertical tune The phase advance due to chromaticity is Longitudinal motion d 2 3 1  Head Tail

  11. Phase Difference by Momentum Spread Vertical tune The phase advance in half synchrotron period Betatron Oscillation Average in one Slice

  12. 4 D Phase Space Simulation Initial distribution:Gaussian in both planes Longitudinal phase space: Transverse phase space: Synchrobetatron coupling: Note: simplified simulation, nonlinearity and damping not included.

  13. Simulation Result Bunch shape after ½ synchrotron period Centroid oscillation

  14. Decoherence Concept • If all particles have same oscillation frequency and phase, motion is coherent. • If the oscillation phase is uniformly distributed, the ensemble average is constant, and the particle motion is incoherent. • The progression from coherent motion to incoherent motion is called decoherence. • In accelerators decoherence is usually caused by tune spread, and is accompanied by emittance increase.

  15. Decoherence by Quantum Excitation I Quantum excitation effect Simulation by Elegant

  16. Decoherence by Quantum Excitation II Longitudinal map

  17. BPM Signal y x Turn Turn V=4kV, I=1.3mA, Cy=2.4, Cx=2.6, ns=0.0078 • X-y coupling • The modulation frequency • Fast decoherence; persistent motion in damping time scale. • The decoherence stops with modulation

  18. BPM Signal Envelop Fit V=4kV, I=1.3mA, Cy=3.5, ns=0.0078, nm=0.0035. • We believe the amplitude tune dependence is small; it has the same feature as quantum excitation decoherence; we hope for one slice under low current, small kick, quantum excitation decoherence dominates.

  19. Experiment Setups for Streak Camera Imaging • Cy was lowered to 4, Cx=6 was unchanged. • We were able to store 1.3 mA current. • The kicker strength applied to the beam was 4kV, or, 0.12 mr, which corresponds to 0.5 mm in the straight sections. The kicker frequency is 2 Hz. • The streak camera was set up to take images turn by turn, in (y,z) plane. Resolution: Y 0.43 ps(0.13mm), Z 2.2 ps. • Images were taken from 0 to 190 turns after the kick, from which we found the best turn to obtain shorter pulses. • The effective slit width was 100 mm.

  20. Streak Camera Measurement Results Pixel size:0.036mm*1.2ps Turn 83-87 Gaussian fit of one slice

  21. Streak Camera Measurement Results The center tilt angle The emittance of the center slice

  22. Shorter Pulse • The current was only 0.2 mA per bunch. • The profile is the overlap of 10 consecutive bunches. • The bunch length was 31 ps. • Streak camera resolution and optical effects are not subtracted. • Turn number • Longitudinal position • Kicker strength • longitudinal tune • Minimum achievable pulse length

  23. Conclusion • Linear synchrobetatron motion • Decoherence caused by quantum excitation • BPM and streak camera data • Effective and convenient • Shortest pulse 3 ps

  24. BPM signal fit

More Related