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LARP Accelerator Systems

Explore the latest developments in the US LHC Accelerator Research Program (LARP), covering instrumentation, collimation, and accelerator physics. Get insights into ongoing projects and studies, including simulation efforts and system dynamics analysis.

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LARP Accelerator Systems

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  1. US LHC Accelerator Research Program BNL - FNAL- LBNL - SLAC LARP Accelerator Systems 16 November 2011 LARP CM17/HL-LHC at CERN Tom Markiewicz/SLAC

  2. The LARP Accelerator Systems Program • “Instrumentation” • Completed Schottky Monitor, Tune & Chromaticity FB, AC Dipole • Ongoing Commissioning Support for the Lumi Monitor • Support for modest LLRF and SLM collaboration • “Collimation” • Phase II Collimator “Rotatable Collimator” Prototype • Crystal Collimation at Tevatron (T980) and SPS (UA9) • “Accelerator Physics” • Simulation-dominated effort in Beam-Beam → Hollow Electron Beam Gun for use as a Collimation Scraper • Simulation-dominated study of Ecloud effects → High Bandwidth Feedback Control of Ecloud/TCMI in SPS • Crab cavity: Cavity Design and related Beam Physics • Hi-Lumi Accelerator Physics in support of Magnet Program • Completed PS2 Study & Hibernated PSB Study Accelerator Systems - T. Markiewicz

  3. Schedule for Accelerator Systems Parallel Session This Afternoon Accelerator Systems - T. Markiewicz

  4. In 2012 SPS Ecloud FB & Crab Cavity Are Largest LARP AS Budget Items * SUBSTANTIAL un-billed Labor from, especially, Fermilab NOT included Accelerator Systems - T. Markiewicz

  5. Pre-CC’11 Comments on the LARP CRAB CAVITY Program • Highlights of December 2010 CC’10 meeting at CERN • Design capable of crossing beams in either H or V preferable • No test of KEK-B Cavity in SPS • New SLAC Design to Satisfy H-V specification • “Compact Ridged Waveguide Deflector” • Tweaking of ODU/JLAB Parallel bar Design for H & V Crabbing • “Rigid Waveguide” and “Parallel Bar” designs beginning to look similar and agreement to merge designs made • SLAC offer to analyze all designs under consideration with Advanced Computing Division tool suite met with approval • Rama Calaga no longer LARP funded (Congratulations!!) • LARP Crab “Leadership” & Role of BNL under discussion • New full time postdoc for Old Dominion (plus previous student support) • Increased support for SLAC ACD • Still no consensus for how to “projectize” effort (& get engineering funds) Accelerator Systems - T. Markiewicz

  6. MultiPactering Analysis of SLAC Compact 1-D Half Wave Spoke Resonator Cavity Impressive Visualization of Resonant MP Z. Li Accelerator Systems - T. Markiewicz LOM/HOM-v HOM-h FPC

  7. SLAC Ridged Waveguide Deflector for H & V Crabbing Z. Li Accelerator Systems - T. Markiewicz

  8. Current ODU Crab Cavity Design Program ODU/Niowave Phase II STTR Current Design J. Delayen Accelerator Systems - T. Markiewicz

  9. Example of Multipacting Simulation Using Track3Pon ODU Prototype Cavity Z. Li Accelerator Systems - T. Markiewicz

  10. Transverse Wideband Feedback for Ecloud/TMCI in the SPSTask Leader: John Fox • SLAC Accelerator Research Department: • J. Cesaratto (newest LARP Toohig Fellow, November 2011) • J. D. Fox, M. Pivi, C. Rivetta • O. Turgut, S. Uemura (graduate students) • BE-RF Group, CERN: • G. Arduini, W. Hofle, K. Li, G. Rumolo, B. Salvant • LBL: • M. Furman, M. Venturini, S. De Santis, J.-L. Vay • R. Secondo (graduate student) Accelerator Systems - T. Markiewicz

  11. 2011 Ecloud/TMCI Progress • A vertical excitation system was developed, tested, and installed in the SPS • Existing pickups for driving bunch & measuring response • Four 100W 20-1000 MHz amplifier array • 4 Gsample/sec D/A synched to RF and software tools to drive individual bunches • Data collected during the July/August and November 2011 Machine Development runs at the SPS used to understand Ecloud/TMCI dynamics and to develop reduced models and numeric simulations • Modeling in WAP, CMAD and Head-Tail Codes • Extraction of system dynamics • Develop a simplified coupled-oscillator model for feedback design Accelerator Systems - T. Markiewicz

  12. Broadband 100W 20 - 1000 Mhz amplifiers under construction & test Sho Uemura Accelerator Systems - T. Markiewicz

  13. 4 GigaSample/s D/A Synched to RF and software tools to drive individual bunches Accelerator Systems - T. Markiewicz

  14. Amplifiers Shipped, Installed & Connected to SPS Kicker Accelerator Systems - T. Markiewicz

  15. Results from Excitation studies • A single bunch of stable beam is excited by the amplifier array • The excitation system drives the bunch at mode 0, mode 1, etc. frequencies • Bunch motion is studied via pickup array and receiver system, digitized at 40 GS/sec. • Barycentric, head-tail or higher modes are excited • Study dynamics as currents are increased towards instability thresholds • Movies ( time domain), and Spectrograms ( frequency domain) Accelerator Systems - T. Markiewicz

  16. Modeling • Extraction of system dynamics • Development of reduced (linear) coupled-oscillator model for feedback design • Inclusion of feedback models in WARP, CMAD and Head-Tail codes C-MAD result: Vertical displacement of center of the bunch Data: Vertical displacement of center of the bunch Kicker signal for all the slices: Vb = 4E-6sin(2π(0.185Turns)) eV-sec/m Accelerator Systems - T. Markiewicz

  17. 2012 Ecloud/TMCI Plan • Develop 4 GS/sec. proof of principle feedback system • Identify critical technology options, evaluate difficulty of technical implementation • Explore ’small prototype’ functional feedback channel for 2012 fab and MD use • Evaluation boards being used to explore feedback parameters • R. Secondo (LBL) is now working on a equalizer design to process the pickup signals: • part of the proof-of-principle system in development for tests at the SPS • Both a prototype and full scale feedback system are beyond scope of LARP’s budget • SPS Kicker Design Study: develop wideband prototype • Goal is prototype kicker & feedback installation in SPS in 2013-14 shutdown Accelerator Systems - T. Markiewicz

  18. Loss Maps & Energy Deposition Studies in Support of Nb3Sn Magnet Design • Funding began summer 2011 with FY11 contingency request and continued in FY12 at same level • In line with DOE reviewer comments for AP support of LARP magnet design • In line with HL-LHC Accelerator Physics task (Hi Lumi WP2) • General agreement by all AP parties that this is good • Led by Nikolai Mokhov/Fermilab with MARS-based tools • Led by Yunhai Cai/SLAC with suite of agreed upon AP codes • Communication with CERN (Bruning et al) and Magnet side required for success • This has begun within the context of Hi-Lum Work Package 2 • Subtask Leader: M. Giovannozzi Accelerator Systems - T. Markiewicz

  19. LHC Beam Dynamics and Collimation Studies at SLAC • SLAC members involved • Yunhai Cai, Yi Jiao, Yuri Nosochkov, Lanfa Wang, Min-Huey Wang, Yiton Yan • CERN members in contact and for discussion • M. Giovannozzi , R. Assmann, Y. Levinsen, E. Mcintosh, A. Rossi, F. Schmidt • Lattice: ATS collision scheme “4444” with b*=15/15 cm at IP1 and IP5 • Codes: SixTrack, MAD-X. • Proposed topics of studies • Field quality specifications for the new triplet quadrupoles . • Computation of collimation loss maps. • High order map analysis. • Chromatic effects on beam cleaning efficiency. • Chromatic aberrations for the collimation system. • 6-D beam-beam effects.

  20. Status and Highlight • Current studies: • Numerous dynamic aperture studies are carried out to declare the “first round” triplet tolerance error table based on global scaling of the field coefficients. • Preliminary calculation of the beam loss map is done for the ATS collision lattice “4444”. • Further studies: • Analysis of sources for dynamic aperture reduction (effects of arc beta beat and non-paired sextupoles). • The “Second round” triplet tolerance error table is to be based on relaxing field error coefficients one-by-one -- more realistic for the magnet design. • more detailed calculation of collimation beam loss map. • Future studies: Analyses of High-order maps, chromatic effects, and 6-D Beam-beam effects for the ATS lattice. • Highlight: “First round” tolerance table in the next slide.

  21. ATS “4444 First Round” IT Tolerance Error Table (Rref = 50 mm)

  22. Accelerator Systems - T. Markiewicz

  23. 15mm Hollow Electron Gun Accelerator Systems - T. Markiewicz

  24. Hollow Electron Beam Gun in Tevatron • 18 experiments 2010.10-2011.06 • Tail of selected bunch depopulated • Control bunches & core of selected bunch unaffected Accelerator Systems - T. Markiewicz

  25. Sample HEBC Results: Selected & Control Bunch Intensity vs. Beam Size • Excellent progress in understanding of hollow beam collimation • Many new observations: halo removal rates, effects on core, • diffusion, fluctuations in losses, collimation efficiencies, ... Accelerator Systems - T. Markiewicz

  26. Sample HEBC Results: Signal on Gated Loss Monitor for Selected & Control Bunch Accelerator Systems - T. Markiewicz

  27. New 25mm Hollow Gun for Stronger Scraping • 25 mm diameter cathode vs. 15 mm previously • 3A at 5 kV vs. 1A • Technical feasibility study • Currently assembled, • installed at test stand • Bakeout, cathode heating Accelerator Systems - T. Markiewicz

  28. Discussions of Bringing Electron Lens Hardware to CERN Underway Accelerator Systems - T. Markiewicz

  29. Luminosity Monitor Commissioning Status A.Ratti, H. Mathis, M. Stezelberger, M. Placidi LBNL

  30. Lumi Status • All four devices (two per IP) have been functioning very reliably since the beginning • As single bunch luminosity increases, we are moving from counting mode (saturating) to pulse height mode (not effective at lower lumi) • FLUKA modeling continues to provide useful support

  31. Lumi Update since the June DOE review Modeling • Completed integration of the FLUKA model of the IPs (from CERN) with the detailed LBL model of the TAN and BRAN • Summer Student (D. Nguyen – UT Austin) • Completed transition to FLUKA 2011 • Improved results of crossing angle calculations at 3.5, 5 and 7 TeV per beam

  32. Energy Deposition per p-p collisionvs crossing angle (from FLUKA) Ecross = (E1 + E4) – (E2 +E3) E1 + E2 + E3 + E4

  33. Operational Experience • Continued to develop operator user interface for use in the CCC • All software effort thanks to Elliott McCrory (FNAL) • Coordinated at CERN by Terri Lahey (SLAC) • This GUI is starting to be used in CCC • See example next • Becoming a tool for beam physics measurements. Can show: • Beam beam effects • Emittance growth

  34. GUI diagnostics example • Example from Aug. 6 (fill 2007) • Emittance blowup of one batch during injection • Disappointing early luminosity • GUI was used to identify which batch immediately

  35. New GUI for use in the CCC System Parameters Emittance Atlas and CMS Luminosity Atlas and CMS B by B lumi @ ATLAS B by B lumi @ CMS Bad Batch B by B Emitt.@ CMS B by B Emitt.@ ATLAS

  36. Synchrotron Light Based Halo Monitoring • LARP involved with SLM (Alan Fisher, SLAC) and Collimation • SLAC interest (SSRL) independent of LHC-tested October 2011 • Use a “Digital Micro Mirror Device” (DMD) as an ADJUSTABLE MASK to black out light from beam core so can see halo • Suggested by Karsten Welch, EU funded DITANET: students may be available Accelerator Systems - T. Markiewicz

  37. DMD Masking Experiments at SPEAR3 Oct-Nov 2011 Ralph Fiorito, A.Shkvarunets, H.Zhang –University of Maryland J.Corbett, A.Fisher, K.Tian – SLAC T.Mitsuhashi (KEK, Japan), W.Mok (Visiting scientist), J.Kamp (Summer student) Oscillating injected beam (~30pC) Intense stored beam (few nC) Airforce Target Calibration Incident beam DMD 5x Magnification Gated Camera w/intensifier J. Corbett Turn #6 Turn #3 Turn #4 Turn #5 Turn #2 Turn #1 mask diffraction injected beam

  38. Measuring the Size of Every Bunch Every Second • Slowly rotating wheel (0.25 Hz) scans 3 thin slots across the image of the beam • PMT after slot gives pulse for each bunch • As slot passes by, digitize 100 pulses for each bunch • Projects each bunch onto x, y, and 45° axes Y slot 45° slot X slot Beam A. Fisher X profile of a bunch in SPEAR3 15-µm wide slot in foil Al discs to support foil Accelerator Systems - T. Markiewicz

  39. LHC LLRF and Longitudinal Beam Dynamics Purpose: LHC non-linear beam dynamics-RF station simulation and system model. • The model captures engineering level implementation details. People: • SLAC: J.D.Fox, C. Rivetta, D. Van Winkle • CERN: P. Baudrenghien, A. Butterworth, T. Mastorides, J. Molendijk Results in 2009-2010: • The LLRF configuration tools have been used by the CERN BE-RF group to remotely commission the LLRF feedback loops of the RF stations during start up in both November 2009 / February 2010. • Tools reduced commissioning from 1.5 days/station to 1.5 hours/station. • Model based configuration adds consistency and reliability. • CERN BE-RF group have repeatedly expressed their support and proposes • Continue work to test the 1-turn feedback functionality of the commissioning tools • Expansion of the tools to control the smooth increase of the High Voltage and Klystron current with beam, from 450 GeV conditions to ramping/physics

  40. Beam Diffusion Studies and LLRF System Noise Contributions • RF Noise Effect on Beam Diffusion Studies • Developed theoretical formalism relating the equilibrium bunch length with beam dynamics, accelerating voltage noise, and RF system configurations. • Conducted measurements that • confirmed the formalism and models • identified performance-limiting components • RF reference noise introduced by controller in mod/demodulation process • Intrinsic noise in the controller feedback boards • set an allowable noise threshold for acceptable lifetime. • Predictions of beam longitudinal motion and RF station stability limits for future high current/higher energy LHC operations • Estimate longitudinal stability margin for 2012 operations. • Impact of future LLRF configurations on RF noise levels is being investigated.

  41. The LARP Rotatable Collimator PrototypeCandidate for a Phase II Secondary Collimator • Two jaw collimator made of Glidcop • Rotate jaw after 1MJoule beam abort failure accident occurs • Each jaw is a cylinder with an embedded brazed cooling coil • No vacuum-water braze; 12kW/jaw cooling; minimal thermal distortion • Maximum radius cylinder possible given beam pipe separation • 20 2cm wide facets provided for presumed rare beam abort accidents • Advantages: • Not exotic material • High Z for better collimation efficiency & more debris absorption • Low resistance for better impedance • Elemental for high radiation resistance • Disadvantages: • Glidcop WILL be damaged in asynchronous beam abort Accelerator Systems - T. Markiewicz

  42. Collimator Assembled 13-Mar-11Mechanical & Resistance Tests Good Accelerator Systems - T. Markiewicz

  43. Vacuum Tests • After welding tank to base and copper cooling tubes to feedthroughs at bottom of bellows discover major “water-to-vacuum” leak in each cooling tube • Each tube was tested at various stages in fabrication process but not at every stage of fabrication and not at final stage • Since then • Cap the tubes and: • Test rotation mechanism under vacuum – Good • 5 week vacuum bakeout, pressure test and RGA scan- few x E-9 torr • Test rotation mechanism after bakeout – • One gear jammed; repaired easily; cause understood • Cut open the tank, cut out the jaws & find leaks • Jaw A has crack in tube wall in stress free area: repaired • Jaw B leak isolated to small zone at rear of collimator • Jaw material being cut now to expose tube for repair • Discussions with CERN, SLAC, LARP & DOE as to best course of action Accelerator Systems - T. Markiewicz

  44. When Cooling Tubes Capped and Tank Pumped Vacuum IS Good Pressure: 1.9E-5 Torr (Cold Cathode Gauge on tank) Leak rate: 5.9E-10 mbar-l/sec (on the Adixen input) Pressure rate of rise Leak rate of ~1E-4 torr/hour Accelerator Systems - T. Markiewicz

  45. Final RGA after 5 week 250˚C bakeout(Blue bar is ideal level), P=4.4E-9 torr Accelerator Systems - T. Markiewicz

  46. Crack in Copper Magnet Conductor Used for Winding First Prototype Jaw • Tube is not Class 1 OFE • was thought to be OK for a prototype to get started • Suspect weakening in material at crystal grain boundaries after last of many high temperature firings Accelerator Systems - T. Markiewicz

  47. Leak in OFE Class 1 Copper Tubing Isolated to Area Indicated Suspect damage at tack welds used during assembly Accelerator Systems - T. Markiewicz

  48. Summary • Major shift in emphasis away from Luminosity Monitor and Rotatable Collimator to the SPS Wideband FB Control of Ecloud/TCMI and the Crab Cavity • New effort in Accelerator Physics in support of HL-LHC and the LARP magnet program • Superb new experimental results from the Hollow Beam Electron Gun and interest in bringing it to CERN • Continued excellent work in the Luminosity Monitor, LLRF, SLM, as well as the Crystal Collimation experiments & Schottky monitor (apology) • Continuing effort to recover the Rotatable Collimator Phase II Prototype program. Accelerator Systems - T. Markiewicz

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