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Beam Physics and Operations Support at Fermilab Institutional Review, June 6-9, 2011

This review addresses the goals and strategies of beam dynamics support at Fermilab, focusing on areas with general value and meeting the needs of individual programs. The achievements highlighted include operational support, beam physics research, development of simulation tools, and optimization of the MI collimation system. Additional topics discussed are Booster optics, LHC abort gap cleaning simulations, and electron cloud experiments in the Main Injector. The comparison of TiN and a-C coatings for electron cloud suppression is also covered.

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Beam Physics and Operations Support at Fermilab Institutional Review, June 6-9, 2011

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  1. Beam Physicsand Operations Support Alexander ValishevFermilab Institutional ReviewJune 6-9, 2011

  2. Addressing the Charge Contribute to the fundamental understanding of beam dynamics through experiment, simulation and theory Provide beam dynamics support for the operating accelerator complex at Fermilab, and the Large Hadron Collider at CERN Fermilab Institutional Review, June 6-9, 2011

  3. Goals and Strategy Develop and maintain core expertise and tools • Focus on topics having general value • Create scientific infrastructure, enabling efficient use of the expertise and tools • Address the needs of individual programs Provide beam dynamics support for the operating accelerators • Enabled by the core capabilities Fermilab Institutional Review, June 6-9, 2011

  4. Highlighted Achievements Operational Support • High intensity operation: Collimation system in MI • Beam physics: Booster optics • High intensity operation: Abort gap cleaning in the LHC Electron Cloud: Studies in MI Collective Effects: Dancing Bunches at Tevatron Tevatron as a test bed for new collimation technology • Crystal collimation • Collimation with Hollow Electron Beam Development of simulation tools • Tools used for real world applications Fermilab Institutional Review, June 6-9, 2011

  5. Optimization of MI Collimation System STRUCT Simulations (A.Drozhdin) Fermilab Institutional Review, June 6-9, 2011

  6. Booster Optics from Fourier Analysis of Turn-by-Turn Data • Tune measurement • Continuous Fourier Transformation • Phased Sum of measurements • Linear betatron coupling evaluation • Beta-functions Yu.Alexahin, IPAC’10, p. 1179 (2010) Fermilab Institutional Review, June 6-9, 2011

  7. Booster Tune Measurement Single BPM Phased Sum E. Gianfelice-Wendt Fermilab Institutional Review, June 6-9, 2011

  8. Booster Coupling Measurement Difference Resonance Harmonics Sum Resonance Harmonics 9,000 turns E. Gianfelice-Wendt Fermilab Institutional Review, June 6-9, 2011

  9. LHC Abort Gap Cleaning Simulations • Owing to the large energy stored in the beam (362 MJ with 0.5 A at 7 TeV), the problem of particles leaking into the AG is particularly serious for the LHC. AG cleaning by resonant excitation with dampers was studied. Simulations were performed to develop an efficient cleaning strategy. The role of Synchrotron Radiation at 7 TeV was investigated. • At injection energy, it is possible to clean the un-bunched beam even w/o excitation frequency modulation. • At 7 TeV (and 3.5), ramping of excitation frequency is necessary to cover the tune spectrum of the un-bunched beam. Step duration and size were worked out. • Despite SR, active cleaning is necessary at 7 TeV when buckets close to the AG are filled. E. Gianfelice-Wendt, work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  10. LHC Abort Gap Cleaning Experiments • AG is populated by decreasing the RF voltage and cleaned by exciting the dampers following simulation recipe. Black traces show the signal on the synchrotron light monitor produced by the particles entering the 3 us AG (grey band). When the particles reach the portion targeted by the kickers (the second half of the gap) they are quickly lost (faster than the acquisition time 0.1 s) • AG cleaning is crucial for day-to-day operation of LHC E. Gianfelice-Wendt, work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  11. LHC Abort Gap Pre-Cleaning at Injection • During the relatively long time necessary for filling the machine for physics, the build-up of un-bunched beam was observed. • Cleaning of AG at injection was implemented in operations. E. Gianfelice-Wendt, work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  12. Electron Cloud Experiments in Main Injector • Experimental Station in MI • 2 New experimental Chambers (TiN and SS) • Test TiN coating for EC suppression • Measure spatial extinction of EC • 3 Fermilab and 1 Argonne RFA • Retarding Field Analyzers • Directly measure electron flux • 3 microwave antennas and 2 absorbers • Measure EC density by phase delay of microwaves • 2010: TiN chamber replaced with a-C chamber from CERN • CERN Chambers show similar behavior to TiN • Appear vulnerable to vacuum issues R.Zwaska Fermilab Institutional Review, June 6-9, 2011

  13. Comparison of Coatings • TiN Coating • TiN validated as suppression technique in Main Injector • Depending on intensity and conditioning, suppression was between 5x and 1000x • Suppression evolved with beam exposure (conditioning) • TiN conditioned much more quickly than stainless • Suppression continued to the highest beam intensities with TiN • a-C Coating • Initial behavior similar to TiN • Superior to stainless, and rapid conditioning • Problem with vacuum issue • Leak developed near the pipe • Appears to have damaged the material • Indicates that α-C may be vulnerable to typical accelerator issues R.Zwaska Fermilab Institutional Review, June 6-9, 2011

  14. Dancing Bunches in Tevatron • Longitudinal coherent oscillations of bunches in Tevatron explained by Loss of Landau Damping of van Kampen modes • Successfully suppressed the oscillations by longitudinal RF shaking A. Burov, PAC’11 Fermilab Institutional Review, June 6-9, 2011

  15. Collimation with Bent CrystalsExperiments at Tevatron • Deflect halo particles by a large angle using bent crystals • Multi-strip crystal • Repeated Volume Reflections in an array of parallel crystals results in larger deflection (up to 64 urad at Tevatron) D.Still, et al work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  16. Collimation with Bent CrystalsExperiments at Tevatron D.Still, et al. work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  17. Collimation with Hollow Electron BeamExperiments at Tevatron • In high intensity accelerators primary collimators cannot be placed close to beam • Enhance diffusion with hollow e- beam G.Stancari, et al work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  18. Collimation with Hollow Electron BeamExperiments at Tevatron G.Stancari, et al work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  19. Collimation with Hollow Electron BeamExperiments at Tevatron • Successfully demonstrated slow halo particle removal and suppression of loss spikes! • Only solution for beam scraping in LHC. Support from CERN G.Stancari, et al work partially supported by US LARP Fermilab Institutional Review, June 6-9, 2011

  20. Accelerator Physics Modeling Tool Development: MARS • The MARS15 code system by Nikolai Mokhov is a set of Monte Carlo programs for the simulation of hadronic and electromagnetic cascades which is used for shielding, accelerator design, and detector studies. • Recent developments: • Improvements of the LAQGSM quark-gluon string model • New module for cross-sections of light nuclear projectiles • Arbitrary light materials are now allowed (deuterium, tritium, D2O etc.) • Graphical-User Interface (GUI) further extended • Adjusted to run in a machine-independent fashion on 32- and 64-bit platforms. • 10 more… • 300 registered users world-wide Fermilab Institutional Review, June 6-9, 2011

  21. Accelerator Physics Modeling Tool Development: Synergia and CHEF • Synergia: Beam dynamics Framework with fully 3D Particle in Cell capabilities • Incorporates many physics modules, either developed at Fermilab or by ComPASS collaborators • Runs on desktops and supercomputers • Sample application: simulation of • beam-beam effects in the Tevatron in • the presence of machine impedance. • Successful application to control • proton losses in squeeze. • CHEF: Single particle optics with • full dynamics P.Spentzouris et al, work partially supported by ComPASS and SciDAC Fermilab Institutional Review, June 6-9, 2011

  22. Conclusion Fermilab developed and maintains a world-class program in accelerator and beam physics • Numerous new developments in theory and experiment • Advanced simulation tools • Efficient use of Fermilab’s accelerator complex for development of novel concepts The core capabilities are successfully applied at existing accelerators to improve their performance Looking forward to address new challenges in beam intensity, energy and brightness Fermilab Institutional Review, June 6-9, 2011

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