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Dust-Beam interaction in the LHC vacuum chamber

Dust-Beam interaction in the LHC vacuum chamber. SUPERVISOR: FRANK ZIMMERMANN. Outline of the talk. Background Dust particle dynamics Beam lifetime Future work. Introduction.

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Dust-Beam interaction in the LHC vacuum chamber

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  1. Dust-Beam interaction in the LHC vacuum chamber SUPERVISOR: FRANK ZIMMERMANN ATHANASIA XAGKONI

  2. Outline of the talk • Background • Dust particle dynamics • Beam lifetime • Future work ATHANASIA XAGKONI

  3. Introduction in the 2008 incident some portions of the LHC beam pipe were contaminated with insulation parts, soot and metallic macro-particles charged “dust” or macro-particles are subjected to electrical forces in the beam field and electrical image forces, plus gravity; for various reasons they could start to move, if they come close to the beam local beam losses can lead to quenches of SC magnets, but the macro-particles will also further ionize, become positively charged, and then be repelled from the beam vicinity ATHANASIA XAGKONI

  4. fibers soot ATHANASIA XAGKONI

  5. dust particle dynamics • Electrical beam force • Electrical image force • Gravity • Charging rate due to ionization and secondary electron escape from the dust particle ATHANASIA XAGKONI

  6. vertical component modulus C: circumference (26.7 km), A: mass in units of proton mass, c : velocity of light, σ: rms beam size (0.3 mm), rp: proton radius, Np: number of protons (2808x1.15x1011) R(A):radius of round dust particle (R~0.1 mm for A~1010) ATHANASIA XAGKONI

  7. particle motion in the x-y plane, inside the pipe, starting from the top ; deflection by electric beam field y [m] b=2 cm charging rate vs vertical position dQ/dt [s-1] x [m] y [m] ATHANASIA XAGKONI

  8. vertical acceleration at the wall due to beam force, image force, and gravity, vs the mass of singly charged dust particle, for nominal LHC beam current (solid) and 10x this current (dashed) round “dust” particle at the wall Q=-1 top nominal LHC beam current 10x LHC design current bottom dust particles with masses larger than ~1011 proton masses can “fall” into the beam pipe, but the nominal beam cannot pick up any charged particles from bottom ATHANASIA XAGKONI

  9. beam lifetime beam lifetime vs vertical position (x=0, A=1013) sc: nuclear interaction cross section of protons and dust nucleons, ~1 barn ATHANASIA XAGKONI

  10. future work • combined solution of equation of motion, charging rate and beam lifetime {x(t), y(t), Q(t), T(t)} for different A and x0 • relate lifetime with quench limit for SC magnets • thermal stability of dust particles • different dust shapes ATHANASIA XAGKONI

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