Production of HCI with an electron beam ion trap

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Erin Gray
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charge total trap potential U trap 200 V (U trap ion charge)

1 Production of HCI with an electron beam ion trap I=450 ma E= 5 kev axially: electrodes radially: electron beam space charge total trap potential U trap 200 V (U trap ion charge) ev A/cm 2 n e e - /cm 3 AAMOP

2 Time evolution of the charge state Charge state fraction Hg 10+ Hg 20+ Hg 30+ Hg 40+ Hg 52+ Hg 70+ Hg Ionization time (s) Calculated for Hg ions at 50 kev electron beam energy by solving a numerically a set of coupled differential equations for the ionization and recombination processes: AAMOP

3 Evaporative cooling collisions with beam electrons heat up ion ensemble light, lesstightlytrappedions(e.g. Ne 10+ ) evaporate removing thermal energy: a single Ne 10+ takes away 2 kev (1 second additional life for a heavy ion) heavy, highly charged ions (e.g. Ba 53+ ) remain trapped indefinitely Ion temperatures from 1000 ev to 10 ev Doppler width Δλ/λ 1/ (Ba 53+ ) High resolution spectroscopy AAMOP

4 Section through the HD-EBIT I (1999) HD-EBIT III (2006) The first EBIT (LLNL,1986) AAMOP

5 Photoionization E=hν γ direct PI E kin + E=hν resonant PI L K E binding L K E res interference Fano profiles doubly excited autoionizing AAMOP

6 X-ray spectra of quasars indicate the presence of highly charged C, N, O, Ne and Fe ions M. Sako et al., Astron. Astrophys. Lett. 365, L168 (2001) AAMOP

Photoionized plasmas in astrophysics Around black holes or neutron stars, X rays generated by infalling matter photoionize the surroundings:

7 Photoionized plasmas in astrophysics Around black holes or neutron stars, X rays generated by infalling matter photoionize the surroundings: Photoabsorption lines appear Iron K-shell radiation is the last spectral signature of baryonic matter before crossing the event horizon AAMOP

8 Photoion extraction and charge analysis Fe14+ monochromator Wien filter Fe15+ extracted ions B position sensitive detector photon beam: 1013 photons/s E electrostatic deflector X-ray detector collector trap gun After interaction with photons, ions and photoions are extracted, mass selected and detected AAMOP

9 Fe 14+ photoionization AAMOP

10 Comparison with theory for Fe 14+ Magenta dots: our data Red curve: HULLAC Black curve: RMBPT Doppler shift depends on prediction Hypothetical two-phase outflows in NGC 3783 Results confirm RMBPT calculations:no two-phase outflows AAMOP

11 Doppler shift corrected based on experiment Precise measurements of HCI X-ray absorption line positions and cross sections are possible with EBITs AAMOP

EBITs are good to reproduce the conditions prevailing in astrophysical plasmas transient plasmas, strong density and temperature gradients EBITs: stationary, homogeneous

12 EBITs are good to reproduce the conditions prevailing in astrophysical plasmas transient plasmas, strong density and temperature gradients EBITs: stationary, homogeneous conditions Density and temperature space sampled by different spectroscopic light sources P. Beiersdorfer, Annu. Rev. Astron. Astrophys. 41 (2003) AAMOP

13 Recombination processes n= E 1 e beam t Dielectronic recombination DR resonant two-step process: capture of a free electron and bound electron excitation. radiative stabilization via photon emission. n=2 E 2 E γ e beam n=1 n= E γ Radiative recombination RR non-resonant process capture of a free electron with photon emission n=2 E 1 E 2 A + e A ( q ) q γ RR n=1 AAMOP

14 Dielectronic recombination A + e ( q 1) + ** ( q 1) [ A ] A q+ + * + γ E beam γ RR Resonance condition: E b +E 2l =E 1s -E 2l photon: Eγ~E 1s -E 2l E B 2p 2s γ DR 1s Radiative recombination E γ = E beam + E Binding q + ( q 1) + A + e A AAMOP γ

15 The bare uranium signal U 92+ at SuperEBIT 10 U 92+ ions trapped! AAMOP

16 Photorecombination of Hg 72 + bis Hg 78+ at 72.5 kev electron beam energy (Heidelberg) Intensity Hg K α2 n=4 Hg K α1 n=5 n=3 ion abundance (%) Hg ion charge state n=2 j=3/2 n=2 j=1/ Photon energy (kev) AAMOP

17 Experiment: varyelectron beam energy (x-coordinate) measure photon energy (y-coordinate) RR: as the electron beam energy changes: Photon energy shifts continuosly DR: as the electron beam energy changes: characteristic dielectronic resonances selectively excited lines AAMOP

18 He-like Ar 16+ Photon energy (ev) radiative recombination into n= n=2 n=1 direct excitation DR resonances Electron beam energy (ev) Two-photon continuum AAMOP

19 Hg, Li-like Hg+77 j= n=2, 1/2 j= n=2, AAMOP /2

20 The KLL resonances KL 1/2 L 1/2 KL 1/2 L 3/2 2s 1/2 2p 1/2 2p 3/2 2s 1/2 2p 1/2 2p 3/2 Be-like B-like 1s 1s and analogously the KL 3/2 L 3/2 AAMOP

21 Quantum interference between DR and RR initial state DR final state +? + RR Fano profile González et al., Phys. Rev. Lett. 94, (2005) AAMOP

22 More complex even: trielectronic and quadruelectronic recombination AAMOP

23 Dielectronic recombination AAMOP

24 Trielectronic and quadruelectronic recombination AAMOP

25 Contributions of trielectronic and quadruelectronic processes to resonant photorecombination AAMOP

26 Accelerators Acceleration schemes for ions Electrostatic accelerators RF accelerators AAMOP

27 Van de Graaff principle Purely electrostatic acceleration Ion source is installed at high voltage terminal Potential is caused by charging up the terminal with a mechanical charge transport chain AAMOP

28 Tandem van de Graaff accelerator (1930) Tank with insulating gas (SF 6 ) Potential negative ions stripping positive ions C - C MV 0 Volt 0 Volt Energy 20 kev MeV MeV AAMOP

Negative ion source Van de Graaff accelerator

29 Negative ion source Van de Graaff accelerator MPI-K: 12 MV tandem accelerator Tank (5.3 bar SF 6 ) Terminal inside the tank High voltage terminal van de Graaff principle Charge Rubber conveyor belt or metal/insulator chain (Pelletron) Ground AAMOP

The cyclotron In 1930 the New York Times announced that a

per second in an effort to obtain a long-sought goal the

30 The cyclotron In 1930 the New York Times announced that a "new apparatus to hurl particles at a speed of 37,000 miles per second in an effort to obtain a long-sought goal the breaking up of the atom was described here today by Professor Ernest O. Lawrence of the University of California." One of the original Lawrence cyclotrons AAMOP

31 The synchrotron Ring with bending magnets and RF cavity synchronously accelerate particle bunches Magnetic focusing by quadrupoles and by radial field gradients in the bending magnets AAMOP

32 HF linear accelerator structures Deliver bunched beams Use powerful RF generators High voltage generated by resonantly driven drift tubes Wideröe (1928) AAMOP

33 Heavy ion linear accelerators at the GSI Darmstadt AAMOP

Radio-frequency quadrupoles as accelerators RFQs do not use drift tubes but resonant waveguides at f 100-500 MHz - + + - Oscillating

34 Radio-frequency quadrupoles as accelerators RFQs do not use drift tubes but resonant waveguides at f MHz Oscillating electric field and shape of electrodes induces an longitudinal accelerating component in z direction GSI AAMOP

35 Ion accelerators: beam foil technique ion source accelerator stripper foil storage ring Storage ring = synchrotron without acceleration To produce higher charge states in accelerators, ions in low charge states pass through a very thin foil where electrons are stripped. Example: ion source produces a beam of 20 kev Ne 2+ accelerated to: 20 MeV Ne 2+ after passing stripper: 20 MeV Ne 10+ AAMOP

36 Electron cooling in storage rings I: ma U: kv Electrons Ions Ions Ions interact 10 6 times per second with a collinear beam of cold electrons at nearly the same speed. Thetransversal components of the ion motion are cooled. Momentum spread Δp/p : Beam diameter : 2 mm AAMOP

37 End AAMOP

free electron plus He-like ion

free electron plus He-like ion E e I p,n E 2 E 1 ΔE=E e +I p,n aber: ΔE=E 2 -E 1 n n n n n n=1 n=2 n=3 AAMOP 2011-2012 2011-11-16 1 dielectronic recombination E 2 E 1 n n n n n n=1 n=2 n=3 AAMOP 2011-2012