electrostatic ion beam trap Ions in an electrostatic ion beam trap 4th LEIF meeting Belfast 2003 Oded Heber Weizmann Institute of Science Israel Physics: Daniel Zajfman Henrik Pedersen (now at MPI) Michael Rappaport Sarah Goldberg Adi Naaman Daniel Strasser Peter Witte (also MPI) Nissan Altstein Daniel Savin Chemistry: Yinon Rudich Irit Sagi

TALK SUBJECTS INTRODUCTION: ELETROSTATIC LINEAR TRAP AND LAB DYNAMICS OF ION BUNCHES IN THE TRAP LONG TIME SYNCRONIZATION MODE DIFFUSION MODE

Photon optics - ion optics Optical resonator Particle resonator Ek, q V V V>Ek/q L M Trapping of fast ion beams using electrostatic field

Entrance mirror L=407 mm Field free region Exit mirror

Trapping ion beams at keV energies Detector (MCP) Field free region Neutrals Ek V1 V1 V2 V2 V3 V3 V4 V4 Vz Vz Why is this trap different from the other traps? Physics with the electrostatic ion beam trap No magnetic fields No RF fields No mass limit Large field free region Simple to operate Directionality External ion source Easy beam detection Metastable states Bi-molecules Clusters Photon induced processes Electron collisions Beam dynamics …

Lifetime of the metastable 1S0 state of Xe++ Theory Garstang: 4.4 ms Hansen: 4.9 ms Experiments Calamai: 4.6  0.3 ms Walch: 4.5  0.3 ms

Photon count rate 1S0 =4.46  0.08 ms 3P1  =380 nm

Beam lifetime: 4.2 keV, Xe++ . Since the beam lifetime is much longer than the 1S0 state lifetime, there are no corrections due to collisions or quenching. =310  2 ms. Theory Garstang: 4.4 ms Hansen: 4.9 ms Experiments Calamai: 4.6  0.3 ms Walch: 4.5  0.3 ms Present: 4.46  0.08 ms

control room Linear trap Laser room Bent trap Ion sources Source control

Ek=4.2 keV Ar+ (m=40) Pickup electrode Wn Ek, m, q W0 Induced signal on the pickup electrode. 2Wn T 280 ns 2930 ns Ek=4.2 keV Ar+ (m=40) (f=340 kHz)

Time evolution of the bunch length The bunch length increases because: Not all the particles have exactly the same velocities (v/v5x10-4). Not all the particles travel exactly the same path length per oscillation. The Coulomb repulsion force pushes the particles apart. After 1 ms (~350 oscillations) the packet of ions is as large as the ion trap

Time evolution of the bunch width ΔT: Dispersion coefficient

Harmonic Oscillator Linear Trap Oscillation time: “Time focusing”,”space focusing”, “momentum focusing”

Is dT/dv>0 a valid condition in the “real” trap? Characteristic time spread as a function of voltage on the last electrode of the trap. Synch. Diffusion dT/dv > 0 Dispersion calculated for the real potential in the 3D ion trap K dT/dv dT/dv < 0 Kinematical condition for motion synchronization: dT/dv > 0

T=1 ms T=5 ms T=15 ms T=30 ms T=50 ms T=90 ms

“Synchronization motion” Expected “Synchronization motion” Dispersion Observation: No time dependence! Shouldn’t the Coulomb repulsion have spread the particles? What happened to the initial velocity distribution? No-dispersion

E1>E2 Trajectory simulation for the real system. Trajectories in the real field of the ion trap Without Coulomb interaction With Coulomb interaction E1>E2

Fourier Transform of the Pick-up Signal . Non-synchronizing mode: dT/dv < 0 Resolution: 1.3 kHz, f/f1/300 4.2 keV Ar+ f

Application to mass spectrometry: Injection of more than one mass Ek m<m FFT

Is dT/dv>0 a valid condition in the “real” trap? Characteristic time spread as a function of voltage on the last electrode of the trap. Synch. Diffusion dT/dv > 0 Dispersion calculated for the real potential in the 3D ion trap K dT/dv dT/dv < 0 Kinematical condition for motion synchronization: dT/dv > 0

Delta-kick cooling (focusing in velocity space) S. Chu et al., Opt. Lett. 11, 73 (1986) x p x p γ Phase space before kick: Phase space after kick: Condition for delta-kick cooling: A correlation in phase space must exist Experiments performed on neutral atoms or molecules F. Crompvoets et al., Phys. Rev. Lett., 89, 093004 (2002) E. Marechal et al., Phys. Rev. A, 59, 4636 (1999) Proposal for charged particles (weakly interacting particles): Y. Kishimoto et al., Phys. Rev. E, 55, 5948 (1997)

dT/dv<0 !! γ Phase space simulation using 20 ions with equivalent charges of 5 x 105 ions dT/dv<0 !! γ Phase space correlation builds up very fast because of the strong Coulomb interaction at the turning points (trap mirrors)

τ: half transition time Delta-kick cooling on strongly interacting particles: Beating the Coulomb force Ingredients for delta-kick cooling in the trap: Dispersive mode: dT/dv<0 Fast build up of phase space correlation Small bunches U(t) Bunch motion U0 -Tp Tp t Optimum pulse Kicker γ: correlation angle Ek: beam energy τ: half transition time through the cooling electrodes β: Geometrical factor Wave form generator Trigger

Experiment: 5 x 105 Ar+, Ek= 4.2 keV β ≈ 0.78 Tp=0.5 μs γ ≈ 0.01 μs-1 How is “cooling” observed? If the velocity spread is reduced, the bunch size increase should be slower Apply cooling pulse Bunch size without kick 13 eV Bunch size with δ-kick 10.7 eV ΔW

Ion bunch motion in the electrostatic trap can be Summery: Ion bunch motion in the electrostatic trap can be in a synchronization mode when dT/dv>0 Application: high resolution mass spectrometry When dT/dv<0 the bunch is in an enhanced diffusion mode Application: delta kick cooling Ion Motion Synchronization in an Ion-Trap Resonator, Phys. Rev. Lett., pp. 55001, 87 (2001). Phys. Rev. A., pp. 42703, 65 (2002). Phys. Rev. A, pp. 42704, 65 (2002). Phys. Rev. Lett., pp. 283204, 89 (2002) Delta Kick Cooling Submitted to Phys. Rev. A