html5-img
1 / 28

BEAM STUDIES AT THE SNS LINAC

BEAM STUDIES AT THE SNS LINAC. Yan Zhang On behalf of the SNS team. 42nd ICFA, HB2008, Nashville, USA, August 25-29, 2008. Outline. Introduction to the SNS Linac Longitudinal Beam Dynamics Studies Transverse Beam Dynamics Studies Unsolved Puzzles Summary. The SNS Linac. To Ring.

zena-odonnell
Download Presentation

BEAM STUDIES AT THE SNS LINAC

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. BEAM STUDIES AT THE SNS LINAC Yan Zhang On behalf of the SNS team 42nd ICFA, HB2008, Nashville, USA, August 25-29, 2008

  2. Outline • Introduction to the SNS Linac • Longitudinal Beam Dynamics Studies • Transverse Beam Dynamics Studies • Unsolved Puzzles • Summary Presentation_name

  3. The SNS Linac To Ring 402.5 MHz 805 MHz HEBT MEBT DTL CCL RFQ SCL, ß=0.61 SCL, ß=0.81 Linac dump Injector 2.5 MeV 86.8 MeV 186 MeV b=0.55 391 MeV b=0.71 1 GeV b=0.87 • Length ~260 m, 96 independently phased RF cavity/tanks • Normal conducting linac from the H- ion source to 186 MeV • Superconducting linac from 186 MeV to 1 GeV • Beam commissioning of the SCL began in August 2005 • Achieved the design repetition rate 60 Hz,maximum beam energy 1.01 GeV, peak beam current 40 mA, pulse length 1 ms, beam power on the mercury target 520 kW. Presentation_name

  4. Longitudinal Lattice RMS phase in the warm linac, linear map and zero current Presentation_name

  5. Y. Zhang, S. Henderson, this proceedings. Phase oscillation in one of the SCLcommissioning lattice Presentation_name

  6. Longitudinal beam emittance increase in the SCL commissioning lattice IMPACT, beam current 20 mA Presentation_name

  7. Y. Zhang, et. al., NIM B 261 (2007) Beam phase oscillation and damping are sensitive to RF errors Presentation_name

  8. SCL phase oscillation measured in February 2006 First cavity gradient 10% & 15% reduction, model & measurement Presentation_name

  9. A. V. Aleksandrov, et. al., EPAC2008 RF Shaker, warm linac model prediction and BPM measurement Presentation_name

  10. SCL phase oscillation, dominated by random errors (~2 phase, ~2% amplitude) and likely caused by RF driftings Presentation_name

  11. Longitudinal Beam Emittance Measurement A. V. Feschenko, et. al., PAC2007 Beam phase profile measured with a BSM in CCL1 Presentation_name

  12. Y. Zhang, et. al., submitted to PRST-AB Model predicted the SCL longitudinal acceptance BCM measured acceptance SCL longitudinal acceptance measurement with BCM and BLMs Presentation_name

  13. Bunch shape measurement Energy profile measurement Bunch shape and beam energy profile measured with BCM Presentation_name

  14. Longitudinal beam contours at the SCL entrance (Cav_01b) RMS emittance: 2.9 MeV*deg ~ 2.2 times the nominal design Cav_01a reference phase set at -85, -90 and -95 degree Presentation_name

  15. 12/23/2007 Phase tails > 40 deg 06/15/2008 Presentation_name

  16. 12/23/2007 Energy tails > 3 MeV 06/15/2008 Presentation_name

  17. Transverse Beam Dynamics Beam emittance and twiss parameter measurement at MEBT • Multiple wire scans measure beam profiles, and fit the measured beam RMS size with the accelerator models • On-line model in the XAL is based on TRACE3D. • Transverse – longitudinal phase space coupling. • Higher order effects: emittance growth in RF gaps, chromatic aberrations in “short” quadrupoles. Presentation_name

  18. Y. Zhang, J. Qiang, this proceedings MEBT beam parameter measurement using the IMPACT model Presentation_name

  19. Beam Trajectory Correction T. Pelaia, et. al., ICALEPCS 2007 Warm Linac SCL Presentation_name

  20. A. Shishlo, A. V. Aleksandrov, EPAC2008 x Before quads shaker Y x After quads shaker - model based alignment Y Presentation_name

  21. Unsolved Puzzles Linac residual activations after neutron productions Presentation_name

  22. SCL Longitudinal Acceptance and … SCL Acceptance, MEBT Particles and CCL Particles Presentation_name

  23. Longitudinal emittance in the warm linac The nc. linac could be a halo filter (scrapper) if no error existed Presentation_name

  24. RFQ Beam Tails plus Linac RF Errors ? Beam loss in the linac, No Error, RF Error, MEBT RBs gradients Presentation_name

  25. Beam Loss In the SNS Linac (500 kW) Presentation_name

  26. Partially chopped beams ? CCL1 BPM amplitude and phase measurement for 4 mini-pulse Presentation_name

  27. Increase the SCL acceptance ? s = -35 (design: -20), sacrifices ~100 MeV output energy Presentation_name

  28. Summary • Beam dynamics studies at the SNS linac are performed with several conventional and newly developed techniques. • Beam longitudinal tails/halo shown in the measurements, but the exact cause of the longitudinal halo is not fully understood. • Simulation study of halo in the linac does not have a complete picture, might need 3D particle tracking from the ion source. • Characterize beam halo in the order of 10-5 to 10-4 and reduce the fractional beam loss to below 10-4 in the SCL is a challenge, existing problems should be fixed first. E.g., MEBT rebuncher, LEBT and MEBT beam chopper, performance of the RFQ, and transverse beam matching through the entire linac correctly… • Beam loss in the linac especially in the SC linac is one of the major concerns to further ramp up the beam power, a factor of two to three beam loss reduction is needed. Suggestions and ideas are welcome. Presentation_name

More Related