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Ions in an electrostatic ion beam trap Oded Heber Weizmann Institute of Science Israel Physics: Daniel Zajfman Henrik Pedersen (now at MPI) Michael Rappaport.

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Presentation on theme: "Ions in an electrostatic ion beam trap Oded Heber Weizmann Institute of Science Israel Physics: Daniel Zajfman Henrik Pedersen (now at MPI) Michael Rappaport."— Presentation transcript:

1 Ions in an electrostatic ion beam trap 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 4th LEIF meeting Belfast 2003

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

3 Optical resonatorParticle resonator Trapping of fast ion beams using electrostatic field Photon optics - ion optics L M VV E k, q V>E k /q

4 L=407 mm Entrance mirror Exit mirror Field free region

5 V1V1 V4V4 V2V2 V3V3 VzVz V1V1 V4V4 V2V2 V3V3 VzVz Trapping ion beams at keV energies No magnetic fields No RF fields No mass limit Large field free region Simple to operate Directionality External ion source Easy beam detection Why is this trap different from the other traps? Detector (MCP) EkEk Neutrals Physics with the electrostatic ion beam trap Metastable states Bi-molecules Clusters Photon induced processes Electron collisions Beam dynamics …

6 Lifetime of the metastable 1 S 0 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

7 Photon count rate  =4.46  0.08 ms 3P13P1 1S01S0 =380 nm

8 Beam lifetime: 4.2 keV, Xe ++.  =310  2 ms. Since the beam lifetime is much longer than the 1 S 0 state lifetime, there are no corrections due to collisions or quenching. 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

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

10 E k, m, q W0W0 Pickup electrode WnWn E k =4.2 keV Ar + (m=40) T 2W n 2930 ns 280 ns (f=340 kHz) Induced signal on the pickup electrode.

11 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

12 Time evolution of the bunch width ΔT: Dispersion coefficient

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

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

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

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

17 Trajectory simulation for the real system. Trajectories in the real field of the ion trap Without Coulomb interaction With Coulomb interaction E1>E2E1>E2

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

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

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

21 Delta-kick cooling (focusing in velocity space) S. Chu et al., Opt. Lett. 11, 73 (1986) Phase space before kick: x p x p 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, (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) γ

22 γ Phase space simulation using 20 ions with equivalent charges of 5 x 10 5 ions Phase space correlation builds up very fast because of the strong Coulomb interaction at the turning points (trap mirrors) dT/dv<0 !!

23 Delta-kick cooling on strongly interacting particles: Beating the Coulomb force Ingredients for delta-kick cooling in the trap: Wave form generator Trigger Kicker Bunch motion 1)Dispersive mode: dT/dv<0 2)Fast build up of phase space correlation 3)Small bunches t U(t) U0U0 Optimum pulse -T p TpTp γ: correlation angle Ek: beam energy τ: half transition time through the cooling electrodes β: Geometrical factor

24 If the velocity spread is reduced, the bunch size increase should be slower Bunch size without kick Bunch size with δ-kick Apply cooling pulse How is “cooling” observed? ΔWΔW Experiment: 5 x 10 5 Ar +, E k = 4.2 keV β ≈ 0.78 T p =0.5 μs γ ≈ 0.01 μs eV 10.7 eV

25 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 , 87 (2001). Phys. Rev. A., pp , 65 (2002). Phys. Rev. A, pp , 65 (2002). Phys. Rev. Lett., pp , 89 (2002) Delta Kick Cooling Submitted to Phys. Rev. A


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