Simulations of the Electron Column in IOTA Ben Freemire Northern - - PowerPoint PPT Presentation
Simulations of the Electron Column in IOTA Ben Freemire Northern Illinois University May 9, 2018 Electron Lens vs Column Electron Lenses successful in compensating beam-beam effects & increasing beam lifetime Two operated at
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– Two operated at Tevatron with good effect
– Ions must be contended with
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2) ∝ np
2
2
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– Only 1 out of 40 m occupied by Electron Column →
R = η = 1 γ
2
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(Dimov & Chupriyanov, Part. Acc. 14, 1984)
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– Strong enough to prevent electrons from escaping transversely,
suppress e-p instabilities
– Weak enough to allow ions to escape
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traversed
p + H 2 → p + e
− + H 2 +
~ N = σ ng l
(Rudd, et al, Phys. Rev. A 1983)
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+:
++2H 2⇔ H n+2 + +H 2 n=3,5,7,...
++H 2→H3 ++H
(Johnsen, Huang & Biondi, J. Chem. Phys 1974)
+ ] = k [H 2 + ] [ H 2]
k = forward reaction rate
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+
– Along with diffusion out of ends of
– Ionization & recombination
(Glosik, et al, Plasma Sources Sci. Tech. 2003)
e
− + H 3 +→H 2 + H
− + H 3 + + H 2→H 3 + H 2
+ →3 H
+ important
– Electrons trapped by B-field, ions migrate out radially
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– Gas ionization – Forces on particles from
– Plasma oscillation – Electron-Ion Recombination – Plasma-gas scattering/collisions
– For example, gas density affects number of electrons produced,
which affects strength of electrodes needed to ensure desired longitudinal distribution
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Park, et al, NAPAC’16, THA3CO04
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macroparticle, 7 electrons or ions per macroparticle)
–
10 cm upstream of column
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– Single ionization of hydrogen by protons
p + 2 H 2→ p + H 3
+ + H + e −
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– With ionization (i.e. SCC) and without (i.e. no SCC)
force
– ~5% at end of beam pulse
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– Not a concern for higher energy machines, but
– Coulomb scattering dominant loss mechanism
−t τ
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– Partial pressures in table – Baseline beam lifetime ~30 minutes
Gas Pressure [10-11 torr] H2 4.6 H2O 3.8 CO2 1.8 CO 0.7 CH4 0.17 Ar 0.023 Other 0.21
Region of interest
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– Save beam & plasma distributions after one pass,
– Incorporate rest of IOTA lattice
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1 τES = ⟨β⟩ π β c k B T ϵA( q 2 ϵ0 γ m β c)
2
2
γ , β = relativistic factors c = speed of light k B = Boltzmann' sconstant m = protonmass T = gastemperature ϵ0 = vacuum permittivity q = electric charge Pi = pressure of ithgas species Qi = atomic numberof ith gas species ⟨β⟩ = averagebeta function ϵ A = ring acceptance
1 τIB = r
2 c N b λ 3
8 π γ
2 σ x σ y σz
D(ϵ)
r = classical protonradius Nb = numberof beam particles λ = momentumacceptance σx , y , z = beam ¿ x , y ,z D(ϵ) = Touschek function