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Gas jet based diagnostics for beam monitoring

This overview discusses the use of gas jet-based diagnostics for monitoring high-intensity/energy beams, including techniques such as synchrotron radiation, ionization profile monitoring, beam-induced fluorescence, and gas sheet monitoring. It also highlights the challenges in separating radiation from the beam and achieving high resolution. The potential benefits of gas jet and beam-induced fluorescence for beam profiling are explored.

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Gas jet based diagnostics for beam monitoring

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  1. Gas jet based diagnostics for beam monitoring Carsten P. Welsch

  2. Overview

  3. Profile of High Intensity/EnergyBeams • Damage caused by the beam • Ideally: Non-invasive.

  4. Synchrotron Radiation • In the visible ? Problem: Resolution (LHC).

  5. Interferometry or Masking • Goal: Overcome diffraction limit. • Coronograph ? • DMD-based system ? Thanks to G. Trad, A. Jeff

  6. SOHO *Solar and Heliospheric Observatory

  7. Halo Monitoring: Core Masking (1) Aquire profile (2) Define core (4) Re-Measure (3) Generate mask J. Egberts, et al., JINST 5 P04010 (2010) H. Zhang, et al., Phys. Rev. STAB 15 (2012)

  8. From Synchrotron Light Sources • Fresnel zone plates • Compound refractive lens

  9. Challenges • Need to separate radiation from beam • Large bending radius = large distances (> 100 m) • Depth of field issues: ~ r/g • Requires undulator to produce (soft) X-rays

  10. Ionization Profile Monitor (IPM) • Souce: J. Egberts, CEA • Based on ionization of rest gas • Challenges • Required residual gas pressure • 1D beam profile ‚only‘

  11. Beam InducedFluorescence (BIF) • Measures light from rest gas, excited by beam • Challenges: • Very low cross sections • Isotropic light emission • Rest gas pressure requirements

  12. N2-fluorescent gas equally distributed Vacuum gauge Blackened walls Valve 150mm flange Ionbeam Viewport Lens, Image-Intensifier and CCD FireWire-Camera Fluorescence Monitor Principle • Gas molecules are excited by the beam and emit a photon when returning to the ground state. • Emission wavelength is determined by the gas species • The relaxation time is typically 10s or 100s of ns. P. Forck et al., Beam induced fluorescence profile monitor developments, Proc. HB2010

  13. Gas Sheet Monitor • Generate thin atom gas curtain, • Ionize atoms with primary particle beam, • Extract ions via electric field, • Monitor on MCP, P screen. Y. Hashimoto et al., Proc. Part. Acc. Conf., Chicago (2001)

  14. How to Generate the Jet ? Y. Hashimoto et al., Proc. Part. Acc. Conf., Chicago (2001)

  15. Experimental Data Y. Hashimoto et al., Proc. Part. Acc. Conf., Chicago (2001)

  16. Setup @ Cockcroft Institute ^^

  17. Zoom: Main chamber MCP Extraction electrodes Phosphor coated window e- gun

  18. Setup

  19. Ionization Cross Sections • Can be exotic, e.g. single ionization of helium by antiproton impact H. Knudsen, Hyperfine Interactions 109 (1997) 133–143 H. Knudsen, Journal of Physics:Conf. Series 194 (2009) 012040

  20. Results @ CI e- beam Residual gas signal Gas Jet Jet signal V. Tzoganis, et al., APL 104 204104 (2014) V. Tzoganis, et al., VACUUM (2015)

  21. Example Measurement 1 1.8 mm 7.2 mm X Y

  22. Example Measurement 2 0.4 mm 4.0 mm X Y

  23. Understanding the Jet • Simulations using the CST and WARP codes H. Zhang, et al., Phys. Rev. AB (2016), submitted

  24. External field and image broadening 200V -2200V

  25. Jet Studies • Apply 3D movable ion gauge to scan through jet Vertical scan – yields profile Identify Mach disk location H. Zhang, et al., Phys. Rev. AB (2016), submitted

  26. sCCD= 90 mm sMCP= 80 mm Jet thickness Resolution

  27. Benefit from Jet and BIF ! • Generate light in collision between gas jet and beam • Detect photons and measure profile • R&D challenges: • Monitor integration (location, cryostat,…) • Optimum location, e.g. do we have to measure inside the solenoid? • Gas condensation, extraction and choice of species,… • Achievable resolution of optics and anticipated signal levels • Weareoptimizingthisideatowards HLLHC applicationwith CERN and GSI. • 2 monitorsplannedfor 2017 and 2019.

  28. Mechanic Design (DRAFT) ① ③ ④ ⑤ ② ③ ⑥ ① ④ ① ③ Differential gauge ② ② ⑤ ③ ④ ④ ④

  29. Also considered: Gas Jet Wire ? • Similar idea to laser wire • Challenge mm focus Fresnel Zone Plate Preliminary

  30. Summary Thanks for your attention !

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