Spacecharge simulations and experiments at Hiroshima University

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Space-charge simulations and experiments at
Hiroshima University

• Hiromi Okamoto
• AdSM, Hiroshima University, Japan

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Recent Activities

• Resonance analysis
• Cooling simulations
• Beam ordering crystallization
• Plasma trap experiments
• Nanobeam generation
• Laser-matter interactions
• Laser wake field acceleration

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Resonance Analysis (1D)

• Dispersion relation
• The resonance condition of the coupling of
  modes

FODO (50 fill) ?0 108 deg.
H. Okamoto K.Yokoya, NIM A 482 (2002) p.51.
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Resonance Simulation (1D)

• Sheet-beam simulation
• number of particles in
• number of particles in

FODO (50 fill) ?0 60 deg.
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Resonance Analysis (2D)

• Basic equations

I. Hofmann et al., Part. Accel. 13 (1983) p.145.
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Test lattice

• Lattice TARN II
• Circumference 77.7 m
• Superperiodicity 6
• Betatron tunes 1.4 - 2.1
• Ion species
• Kinetic energy 1 MeV

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Resonance Simulation (2D)
?084 deg.
?0108 deg.
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Stopbands Cooling (1)
PIC simulation
Vlasov prediction
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Stopbands Cooling (2)
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Dispersive Resonance
Betatron Hamiltonian
KEK-PS
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Plasma Trap Experiments
Charged-particle beam in a strong-focusing channel
Single-species plasma in a linear trap
?
Use this equivalence for the systematic study of
space-charge effects !
First proposal H. Okamoto and H. Tanaka, NIM A
437 (1999) p.178. H.
Okamoto, Y. Wada and R. Takai, NIM A485 (2002)
p.244.
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Why traps ?

• Very compact
• Low cost
• High flexibility of fundamental parameters
• High resolution high precision measurements
• No radio-activation

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Segmented Paul Trap
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S-POD Simulator for Particle Orbit Dynamics
NOTE A similar experimental project is in
progress at Princeton University.
See, E.P. Gilson, et al., PRL 92 (2004) 155002.
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Molecular Dynamics Method

• In the reference cell, use real particles.
• Apply the periodic boundary condition for
  long-range interactions.

The Ewald-type summation
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Beam-Frame Hamiltonian
Coulomb potential
RF
J. Wei, X.-P. Li, and A. M. Sessler, BNL Report,
BNL-52381 (1993)
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Laser Cooling
Basic cycle
Doppler cooling
Cooling force
Detuning
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S-LSR

• Circumference 22.6 m
• Superperiodicity 6
• Betatron tunes (2.067, 1.073)
• Length of a straight section 2.66 m
• Length of the solenoid 0.8 m
• RF harmonic number 100
• RF amplitude lt 30 V
• Ion species
• Kinetic energy 35 keV
• Saturation parameter (on axis) 1.0
• Saturation intensity 254 mW/cm2
• Minimum spot size 5 mm

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MD result

• The photon pressure operates only upon the
  longitudinal beam motion.
• No damping of the betatron motion, except for the
  sympathetic cooling, takes place in general.
• It is possible to extend a one-dimensional
  cooling force to the other two degrees of
  freedom
• RCM equalizes the cooling rates of all three
  directions.

BUT
Resonant Coupling Method (RCM)
H. Okamoto, A. M. Sessler and D. Möhl, PRL 72
(1994) p. 3977. H. Okamoto, PRE 50 (1994) p.4982.
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Future plans

• Space-charge experiments with S-POD
• Coherent resonance
• Halo formation
• Short-bunch effects
• Others
• More MD studies
• Cooling simulations
• Coulomb crystallization
• Experiments at S-LSR
• Electron and laser cooling
• Application of RCM
• Instabilities in space-charge-dominate
  d beams

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MD
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Dancing string in S-LSR