Zoran Andjelkovic Johannes Gutenberg Universität Mainz GSI Darmstadt Laser Spectroscopy of Highly Charged Ions and Exotic Radioactive Nuclei (Helmholtz Young Investigator Group) Laser cooling of Mg + and laser spectroscopy of SPECTRAP

Zoran Anđelković 2outline Introduction: –overview of SPECTRAP? –trapping cycle Results from ion trapping and laser cooling: –fast fourier transfom ion cyclotron resonance –single and multiple ion fluorescence –trapping time Further plans: –for the not so near future –and two immediate spectroscopy candidates

ion production and TOF trap acceptance up to 500 V TOF of produced Mg ions typical energy 100 eV to 1 keV

Zoran Anđelković 4 view of the trap and the magnet

injection of externally produced ions Zoran Anđelković 5 dynamic ion capture cycle low energy and TOF allow selection of captured ions Option with a cooling mechanism: Stacking of successive ion bunches 2  s gate up to 5 Hz almost no ion loss

Zoran Anđelković 6 ion motion in a Penning trap in a harmonic trap all three motions are independent energy transfer in a non-ideal trap

I t Zoran Anđelković 7 resistive cooling and non-destructive detection 1.Passive:- detects ion current - cools the ion cloud 2.Active:- excite ions and induce corr. motion - heats the ion cloud endcap C R L detect excite „FT-ICR“ Fourier-Transform Ion Cyclotron Resonance I f q/m spectrum ion current signal

reduced cyclotron frequency Zoran Anđelković 8 around 500 trapped and cooled 24 Mg ions, excitation ~ 100 mV pp measured via electronic pickup and fluorescence reduction a small frequency shift due to the magnetic field imperfection

fluorescence and line profile Zoran Anđelković 9 identified single ion signal via quantized fluorescence jumps natural linewidth 42 MHz => final temperature < 1 K if fully saturated => detection efficiency ~ 5*10 -5  ~ 1500 trapped ions a single trapped ion real line profile

trapping time Zoran Anđelković 10 if ejected after a long time the radial component gets too big fluorescence showed that the real trapping time is much longer estimated t1 ~ 100 s => in-trap vacuum ~ mbar Graph showing ions ejected and counted with an MCP fast switched ejection electrode (adiabatic ejection) additional einzel lense

further planned measurements Zoran Anđelković 11 TypeIonTransition [nm] A [1/s] low q 207 Pb +2 P 1/2 - 2 P 3/ B-like 40 Ar 13+2 P 1/2 - 2 P 3/ C-like 40 Ca 14+3 P P H-like 207 Pb 81+ F=0 - F= Bi 82+ F=4 - F= Li-like 209 Bi 80+ F=4 - F= final accuracy limited by the Doppler broadening with resistive cooling  / 0 ≈ to with sympathetic cooling  / 0 ≈ to 10 -8

Zoran Anđelković 12 Pb 1+ pro -well known transition - no “fancy” ion source needed - „short“ lifetime (41 ms) - improvement of the magnetic moment wavelength: nm contra - difficult to trap - invisible for pickup detection - „long“ lifetime (41 ms) - how many can we make? 3 P 0 6 P 1 F=2 F=1 F=0 208 Pb ( I=0 ) 207 Pb ( I=1/2 ) abdec T=1600 K X. Feng, …, G. Werth; PRA 46 (1992) candidate no. 1

candidate no. 2 Zoran Anđelković 13 Zoran Anđelković 13 Ca 14+ pro - known transition, but - accuracy can be increased by 3-4 orders of magnitude - “short” lifetime (10 ms) - easy to trap, easy to see wavelength: nm contra -need an EBIT - need a beamline from the EBIT - transported with 5 keV and needs large deceleration 3 P P 1... no hyperfine structure transition known from emission spectroscopy

Zoran Anđelković 14 pulsed elevator electrodes Zoran Anđelković 14 no mag field – phase space conservation makes life difficult with the magnetic field field – the ions are kept on axis by the field 300 eV; +200 V to -50 V; no mag. field 300 eV; +200 V to -50 V; with mag. field

Zoran Anđelković 15outlook current status: UHV system and superconducting magnet in operation ion trap with cryogenic electronics finished and working demonstrated laser cooling of Mg + to sub K temperature fluorescence detection functioning successfull ESR measurements of both Bi 82+ and Bi 80+ further plans: install a He recovery system improve the UHV system (cryopums) perform cooling and laser spectroscopy on Pb + new ion sources – EBIT, MEVVA, HITRAP measurements on forbidden transitions in mid-Z ions finally, high precision measurements on Bi 82+ and Bi 80+

HITRAP and its experiments Zoran Anđelković 16 from ESR 4 MeV/u HITRAP parameters: IH decelerationto 0.5 MeV/u RFQ decelerationto 6 keV/u cooler trap decel.to 4 K mass over charge≤ 3 N of extr. part.10 6