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Beam Loss Technology

Beam Loss Technology. Eduardo Nebot del Busto (1) CERN, Geneva, Switzerland (2) The University of Liverpool, Department of physics, Liverpool, U. K (3) The Cockcroft Institute, Warrington, U.K. ACAS School for Accelerator Physics. Outlook. Introduction Detector technologies

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Beam Loss Technology

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  1. Beam Loss Technology Eduardo Nebot del Busto (1) CERN, Geneva, Switzerland (2) The University of Liverpool, Department of physics, Liverpool, U. K (3) The Cockcroft Institute, Warrington, U.K ACAS School for Accelerator Physics

  2. Outlook • Introduction • Detector technologies • Detector location • Machine protection implementation • State of the art • Challenging environments E. Nebot del Busto ASAP 2016 - BLM Technology 1

  3. A graphical introduction

  4. Introduction • What are Beam Loss Monitors? Particle detector Vacuum Chamber Wall E. Nebot del Busto ASAP 2016 - BLM Technology 2

  5. Detector technologies

  6. Ionization • Energy loss described by Bethe-Bloch • Concept of MIP • Scintillation • Ionizing radiation detectors located around an accelerator • Secondary Emission • Cherenkov Effect Sources of BLM signal MIP dE/dxMIP = (1-5) MeV cm2 g-1 Y = dL/dx = R dE/dx MIP YMIP = (0.01-0.05) e/primary E. Nebot del Busto ASAP 2016 - BLM Technology 3

  7. Incident particle produces e-/ion: • Fast electrons and slow ions collected via Bias voltage to produce a measurable current • Typical ionization potentials (25-100) eV/pair Ionization - Gas detectors Ionization potential Incident particle Energy Quad E. Nebot del Busto ASAP 2016 - BLM Technology 4

  8. Ionization Chambers Ionization - Gas detectors Quad Quad Quad No dependence on Bias Voltage E. Nebot del Busto ASAP 2016 - BLM Technology 5

  9. Ionization - Gas detectors • Saturation effects: • Large number of e/ion pairs generated • Field generated by ions shields bias field • Charge recombination Quad 10-3 Gy 10-4 Gy Quad Charge collection efficiency 10-5 Gy Instantaneous pulse FNAL Ionization chamber Bias Voltage (V) • Ionization Chambers: PROs/CONs • Very robust, radiation hard, require low mantainance • No dependence on Bias Voltage • Large Dynamic range • Slow time response (~0.1 - 1 ms) E. Nebot del Busto ASAP 2016 - BLM Technology 6

  10. Ionization - Solid state detectors • Semiconductor based detectors (Si, Diamond, ...) • Incident particles produce electron/holes as charge carriers (3-10eV/pair) • thole ≳ telectron ~ 1-10 ns • smaller size Quad Quad • Solid state Ionization Chambers: PROs/CONs • No dependence on Bias Voltage • Fast response (1-10 ns) • Radiation hardness (1 MGy) E. Nebot del Busto ASAP 2016 - BLM Technology 7

  11. Scintillators • Light produced by de-excitation of atomic/molecular levels • Multiple types • Inorganic crystals: NaI, CsI ... • Organic (plastic): NE103, Antracene • Liquid Quad Quad • Photo Multiplier Tube: active photon sensor • Light from scintillator to PMT via waveguides E. Nebot del Busto ASAP 2016 - BLM Technology 8

  12. Scintillators • Considerations • Photon Yield • Collection efficiency • Photocathode quantum efficiency • PMT gain GPMT= δn = (10+5 -10+8) • δ = (2-10) number of secondary electrons • n = (8-15) number of dynodes Quad Quad • Scintillators: PROs/CONs • High sensitivity • Fast response: ~ (1-10) ns for plastic/liquid • Slow response: ~ (0.1 - 1)μs for inorganic • Limited radiation hardness (1-10 MGy) • PMT gain control E. Nebot del Busto ASAP 2016 - BLM Technology 9

  13. Secondary Emission Monitors • Sensitivity defined by SEM Yield • 0.01- 0.05 e-/primary • Two possible uses • No amplification (needs current integration) • Amplification • broadband current amplifiers • PMT INCIDENT RADIATION • SEM: PROs/CONs • Fast (< 10 ns) e transit • Very linear • Very radiation hard (no PMT) • Low sensitivity SEM Electrons E. Nebot del Busto ASAP 2016 - BLM Technology 10

  14. Cherenkov detectors • Considerations (similar to scintillators) • Photon Yield (continuous) • Collection efficiency (directionality) • Photocathode quantum efficiency (match cherenkov spectrum) • PMT gain GPMT= δn = (10+5 -10+8) • δ = (2-10) number of secondary electrons • n = (8-15) number of dynodes • Cherenkov: PROs/CONs • Fast (only limited by PMT response) • Insensitive to neutral radiation • Low sensitivity • Limited radiation hardness (10 - 100 MGy) E. Nebot del Busto ASAP 2016 - BLM Technology 11

  15. BLMs across different machines SEM - LHC Ion chamber LHC Quad Plastic scintillator Flash Diamond SEM + PMT Quartz + PMT CTF3 Cherenkov radiator - CEBAF E. Nebot del Busto ASAP 2016 - BLM Technology 12

  16. Technology choice • No universal rule • detector choice depends on main properties of the machine • Intensity, energy, particle type, timing, length ... • Main considerations • Sensitivity/Dynamic Range • Time response • Expected type of radiation • Shield-ability (from unwanted radiation) • Physical size • Test ability • Calibration techniques • Cost E. Nebot del Busto ASAP 2016 - BLM Technology 13

  17. BLM location

  18. Particle tracking codes (SixTrack, MadX, ...): • implementation of accelerator optics • Mapping of the aperture limits along the machine BLM location • Monte Carlo simulation codes: (SixTrack, MadX, ...): • Geometry of accelerator components • Mapping of the aperture limits along the machine E. Nebot del Busto ASAP 2016 - BLM Technology 14

  19. BLM location E. Nebot del Busto ASAP 2016 - BLM Technology 15

  20. Machine Protection

  21. BLM location Signal pre-processing: Integration, amplification... Threshold comparison Abort request BLM • Depends on the technology of your magnets, cavities, ... • Normal conducting. Damage of components • Superconducting. Quench protection (T < TC) • Linear accelerators (Linac) vs storage ring • Storage rings require protection for single turn/multi turn losses with different threshold level • How we protect • Safe beam extraction (storage rings) • Subsequent injection inhibit (linac) E. Nebot del Busto ASAP 2016 - BLM Technology 16

  22. Geant 4 simulation of horizontal losses in bending magnet Abort thresholds calculations • Complicated dependences with loss duration and beam energy E. Nebot del Busto ASAP 2016 - BLM Technology 17

  23. Complicated readout with multiple inputs and connected to interlock Read out and processing electronics E. Nebot del Busto ASAP 2016 - BLM Technology 18

  24. Data driven approach for threshold tuning Abort thresholds optimiztion E. Nebot del Busto ASAP 2016 - BLM Technology 19

  25. Complicated applications for handling and monitoring of signals and thresholds Threshold handling E. Nebot del Busto ASAP 2016 - BLM Technology 20

  26. State of the art: examples

  27. Diamond detectors at the LHC Quad Diamond Bunch by bunch Losses Ionization Chamber Avg. Losses (1/2 turn) E. Nebot del Busto ASAP 2016 - BLM Technology 21

  28. Fill pattern Diamond detectors at the LHC 12 pilot bunches 144 nominal bunches Quad 0.2 us SPS injection gap 1 us injection gap 3 us beam abort gap Single bunch instability 1 LHC Turn E. Nebot del Busto ASAP 2016 - BLM Technology 22

  29. Light (scintillation or Cherenkov) generated in fiber core • Full coverage of beam lines • Potential position reconstruction via photon Time of Flight Optical fibres E. Nebot del Busto ASAP 2016 - BLM Technology 23

  30. Optical fibre: Position reconstruction • KEK-PF • 2.5 GeV electrons E. Nebot del Busto ASAP 2016 - BLM Technology 24

  31. Optical fibre: Dosimetry • Location vi Optical Time Domain Reflectometry • Total dose via Radiation Induced Attenuation E. Nebot del Busto ASAP 2016 - BLM Technology 25

  32. Beam Loss Monitors in high background environments

  33. Particles accelerated by surfing the wave RF structure related background • Electrons released from inner surface of cavities • Full coverage of beam lines • Xrays generated in the cavity may limit the BLM sensitivity E. Nebot del Busto ASAP 2016 - BLM Technology 26

  34. Location vi Optical Time Domain Reflectometry • Total dose via Radiation Induced Attenuation Synchrotron radiation ESRF: Quartz rods as Cherenkov radiators Fermi@Elettra Quartz core optical fibers E. Nebot del Busto ASAP 2016 - BLM Technology 27

  35. High EM noise • Ground Loop • Bad shielding • Ripple (power supplies, magnets...) Electromagnetic noise E. Nebot del Busto ASAP 2016 - BLM Technology 28

  36. High EM noise • Ground Loop • Bad shielding • Ripple (power supplies, magnets...) Electromagnetic noise MAGIC! GHOSTS!! SABOTAGE!!! E. Nebot del Busto ASAP 2016 - BLM Technology 28

  37. High EM noise • Ground Loop • Bad shielding • Ripple (power supplies, magnets...) Electromagnetic noise MAGIC! GHOSTS!! SABOTAGE!!! • Keep scratching your head for days/months ..... and finally BLAME OTHERS!!! E. Nebot del Busto ASAP 2016 - BLM Technology 28

  38. References

  39. K. Wittenburg. “Beam Loss Monitors” CAS2008. • A. Zukov. “Beam Loss Monitors: Physics, Simulations and Applications in accelerators”. BIW2010. • E. B. Holzer. “Beam Loss Monitoring for demanding environments”. IBIC2015 • E. Nebot. “An overview on Beam Loss Monitoring”. Advanced oPAC school on Acceleration optimization 2014. • T. Obina. “Optical fiber based loss monitors for electron storage rings”. IBIC2013. • Particle data group: • “Review of particle physcis”. Phys Rev. D 86. 010001 (2012) 30. Passage of Particles though matter • “Particle Physics Booklet”. http://pdg.lbl.gov/

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