1 / 12

RF measurements during floating MD in Week 40 3 rd of October 2012

RF measurements during floating MD in Week 40 3 rd of October 2012. Participants : T. Argyropoulos , H. Bartosik , T. Bohl , J. Esteban Müller , H. Timko , E. Shaposhnikova CCC: G. Iadarola , Y. Papaphilippou , G. Rumolo Thanks to all SPS OP on shift. LIU-SPS BD WG 25/10/2012.

thao
Download Presentation

RF measurements during floating MD in Week 40 3 rd of October 2012

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. RF measurements during floating MD in Week 40 3rd of October 2012 Participants: T. Argyropoulos, H. Bartosik, T. Bohl, J. Esteban Müller,H. Timko, E. Shaposhnikova CCC: G. Iadarola, Y. Papaphilippou, G. Rumolo Thanks to all SPS OP on shift LIU-SPS BD WG 25/10/2012

  2. General • MD title: • Longitudinal set up of the 25 ns LHC beam with Q20 optics (nominal • ~1.25x1011 pb and high ~1.4x1011 p/b injected intensities) • MD aim: • Improve the bunch length distribution inside the batch (“U-shape”) • Improve the slope of the bunch lengths along the train • Achieve beam stability and acceptable beam parameters at flat top • Beam conditions: • 4 batches of 72 bunches • Intensities at injection: Np~1.25x1011 p/b and Np~1.45x1011 p/b • Varying parameters @SPS: • RF voltage amplitudes at FB (V200 and V800 - operation always in • double RF) • Controlled longitudinal emittance blow-up (Amplitude and scaling – always • on ) • Phase between the 2 RF systems at FT (first attempt to improve stability • by compensating for beam loading at 800 MHz)

  3. Outline • Losses • Nominal intensities (~1.25x1011 at injection) • Optimization of the controlled longitudinal emittance BUP to • reduce the “U-shape” of the bunch length distribution inside • the batches at FT • Modification of the RF voltage (V200) to improve the slope of • the bunch lengths along the batch trains at FT • High intensities (~1.45x1011 at injection) • Improve stability: mainly by optimizing the BUP (amplitude, • scale) • Summary

  4. Losses • Very good transmission for nominal intensities (~96 %) : not • affected by the changes in longitudinal parameters • Still low losses for the higher intensities (~6-7 %)

  5. Nominal intensities (~1.25x1011 at injection) • Beam was stable (with the 800 MHz RF system and • controlled emittance blow-up) • Decrease of average bunch length along the FB for constant • RF voltage (3 or 4.5 MV) + slight increase (~1%) of capture • losses not observed with the voltage dips • Bunch length distribution at FT: • “U-shape” inside the batch • slope along the batch train • Example of the best conditions: • V200 = 4.5 MV • V800 = 0.45 MV • ScaleBUP = 0.93 • VBUP = 35 mV

  6. U – shape of bunch length distribution Synchrotron frequency Distribution inside the bunch. Before BUP – V800/V200 = 0.1 • Due to beam loading the synchrotron • frequency distribution varies along the • batch • Different effect of the controlled BUP to • the bunches at the edges and the center of the • batch • Leads to the “U-shape” at FT • Reduce this by decreasing the scale • parameter in the BUP • Average of all acquisitions for different BUP scales: • V200 = 4.5 MV – V800 = 0.1V200 – VBUP = 30 mV • increasing the scale makes bunch lengths along the • batch more uniform • with scale=0.85 bunches a slightly unstable at FT • slightly better stability for scale=0.9 than 0.93 (mainly • dipole oscillations)

  7. Slope along the batch train • Correlation of the V200 at FB with the bunch length slope along the batch at FT • V800 = 0.45 MV – VBUP = 35 mV – ScaleBU = 0.93 • Not significant improvement with the different voltage settings that were tried • Small difference in stability

  8. Higher intensities (~1.45x1011 at injection) • Beam was unstable- with the 800 MHz RF system and controlled • emittance blow-up (same settings as in the low intensities) • Decrease of average bunch length along the FB for constant RF • voltage • Bunch length distribution at FT: “U-shape” inside the batch and slope • along the batch train still remain • Optimize the controlled emittance BUP: • increase the noise amplitude VBUP • lower the scale parameter • Limiting time with these intensities  only few acquisitions

  9. Higher intensities (~1.45x1011 at injection) • Increase VBUP while keeping the same high scale (0.9) didn’t show any • improvement V200 = 3 MV – V800 = 0.45 MV ScaleBUP = 0.9 – VBUP = 35 mV V200 = 3 MV – V800 = 0.45 MV ScaleBUP = 0.9 – VBUP = 60 mV

  10. Higher intensities (~1.45x1011 at injection) • Increase ScaleBUP while keeping the same high VBUP (60 mV) • improved stability • Still unstable with long bunches at FT V200 = 3 MV – V800 = 0.3 MV ScaleBUP = 0.85 – VBUP = 60 mV V200 = 3 MV – V800 = 0.45 MV ScaleBUP = 0.9 – VBUP = 60 mV Change of the ratio V800/V200 to 0.1 improved the situation but not significantly

  11. Higher intensities (~1.45x1011 at injection) • Increase RF voltage at FB improved stability • Still some bunches are unstable with very long bunches at FT V200 = 3 MV – V800 = 0.3 MV ScaleBUP = 0.85 – VBUP = 60 mV V200 = 4.5 MV – V800 = 0.45 MV ScaleBUP = 0.85 – VBUP = 60 mV

  12. Summary • Good transmission: • ~96-97 % for Np~1.25x1011 p/b • ~93-94 % for Np~1.45x1011 p/b • Stable beam always with the nominal intensities: • 800 MHz ON • controlled longitudinal emittance BUP ON • Decrease of average bunch length along the FB for constant RF voltage (3 or 4.5 MV) • not observed with the voltage dips • but slightly more unstable at FT • “U-shape” inside the batch : • improved with higher ScaleBUP • slope along the batch trainremains still •  further investigation is needed • Higher intensities • Beam unstable at FT • small improvement by optimizing the BUP • but bunches too long at FT •  More time is needed

More Related