Ben Freemire Northern Illinois University IOTA ... · April 5, 2018 B. Freemire - IOTA...

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Transcript of Ben Freemire Northern Illinois University IOTA ... · April 5, 2018 B. Freemire - IOTA...

  • Beam-Jet Interaction Update

    Ben FreemireNorthern Illinois University

    IOTA Instrumentation MeetingApril 5, 2018

  • April 5, 2018 B. Freemire - IOTA Instrumentation 2

    Simulation Parameters● Transverse beam distribution Gaussian, σx,y = 3.5 mm● 500 macroparticles injected per time step● 1 macroparticle proton = 900 real proton● 1 macroparticle ion/electron = 81 ions/electrons● x (-3.5,3.5) cm, y (-3.0,5.0) cm, z (-3.5,3.5) cm

    – 70x80x350 simulation grid– 1 mm x, 1 mm y, 0.2 mm z grid spacing

    ● 9 ps time step● 1.8306 μs simulated (203,400 time steps)● Electrodes all annuli 2.5 cm ID, 3.0 cm OD, 0.5 cm lenth

    – Base at y = -2.5 cm, 500 V– E1 at y = 2.5 cm, -500 V– E2 at y = 3.5 cm, -1000 V– E3 at y = 4.5 cm, -1500 V

  • April 5, 2018 B. Freemire - IOTA Instrumentation 3

    Potential Contours

    [m] [m]

    [m]

    [m]

  • April 5, 2018 B. Freemire - IOTA Instrumentation 4

    Ionization Parameters● Nitrogen gas density 4.0e11 cm-3 ● Ionization cross section 7.19e-17 cm2 ● 150 thin columns of nitrogen gas 7 cm x 0.2

    mm x 0.2 mm arranged in step pattern– From (-1.5,-1.5) cm in y and z to (1.5,1.5) cm in y

    and z

  • April 5, 2018 B. Freemire - IOTA Instrumentation 5

    Ion Animation

    Beam

  • April 5, 2018 B. Freemire - IOTA Instrumentation 6

    Geometry / Comments● Beam imparting longitudinal momentum to ions

    – Currently, momenta are equal, but ion momentum can be specified in Warp– Results in non-Gaussian distribution of ions in z plane (see next slides)

    ● If the gas jet is rotated 45 degrees with respect to the beam, y profile of beam is z profile of jet– Jet thickness introduces some smearing

    PRAB 20, 062801 (2017)

  • April 5, 2018 B. Freemire - IOTA Instrumentation 7

    Profile Comparison● Every proton

    present at 1.757 μs (last file before beam ends)

    ● Bin size = simulation grid size

    ● Every ion to have ever been within 2.39 < y < 2.50 cm

    ● Integration window chosen so as to not miss ions (based on ions’ y velocity)

  • April 5, 2018 B. Freemire - IOTA Instrumentation 8

    Ion Profile● Ion distribution more closely matches beam (σ = 0.35 cm) closer

    to sheet● Still somewhat distorted vertical distribution

  • April 5, 2018 B. Freemire - IOTA Instrumentation 9

    Ion Profile● Ion distribution more closely matches beam (σ = 0.35 cm) closer

    to sheet● Still somewhat distorted vertical distribution

  • April 5, 2018 B. Freemire - IOTA Instrumentation 10

    Remarks● Realistic beam distribution implemented

    – Can be improved by adding transverse momentum● “Tilted” gas sheet implemented● Daughter products energies not realistic

    – Relatively easy fix possible– Will affect measured vertical profile

    ● Electrodes affecting ion transverse distributions– Worse match further from beam– Scan of electrode strengths may shed some light on magnitude of effect

    ● Space charge of beam is significant; some estimation of effect on ions should be made● By end of simulation (i.e. beam revolution period, 1.83 μs), only half of all ions created

    reach 2.5 cm above beam center– Pile up in detector from consecutive turns likely

    ● Longer simulation needed

    – How do we mitigate this?● Simulation diagnostics may be possible to improve by introducing virtual detector at fixed

    y– I’ve contacted Jean-Luc Vay, awaiting response

    Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10