The HITRAP Project at GSI

1. The HITRAP Project at GSI For the HITRAP collaboration: Frank Herfurth GSI Darmstadt

2. Content The aim is to create highly charged ions up to U92+ at low energies (eV) or at rest • Overview of the facility • Deceleration and cooling • Key experiments

3. experiments for slow particles post- decelerator SIS experiments with particles at rest cooler Penning trap U92+ stripper target Overview UNILAC 6 keV /u 400 MeV /u U73+ • EXPERIMENTS WITH HIGHLY CHARGED IONS AT EXTREMELY LOW ENERGIES: • collisions at very low velocitiesultra-accurate • surface studies and hollow-atom spectroscopy • laser and x-ray spectroscopy • g-factor measurements (tests of QED) • mass measurements 4 MeV /u U92+ ESR electron coolingand deceleration

4. Overview

5. HITRAP in the SIS reinjection channel Experiment:Precision trap northern wall of ESR hall Other experimental set-ups Re-injection channel 4 MeV/u 0.5 MeV/u  6 keV/u from ESR x/y steerers x/y steerers IH-LINACRFQ cooler trap x/y steerers x/y steerers profile grid, diagnostics profile grid, diagnostics wall diagnostics diagnostics 4 m valve solenoid solenoid four-gap buncher diffusion valve three-gap re-buncher QP Tripl. cryogenic valve 90o- bender QP Tripl. QP Tripl. diagnostics x/y steerers x/y steerers 1 m vacuum section 1 vacuum section 2 vac. section 3 vac. section 4

6. HITRAP: Deceleration Cycle UNILAC and SIS: acceleration of U73+ ions up to 400 MeV/u. Extraction towards ESR. Stripping up to uranium U92+. ESR: Two-stage deceleration with electron cooling down to 4 MeV/u. Rebunching and fast extraction of 6·105 ions every 10 s towards ESR-SIS reinjection channel. HITRAP decelerator:Prebunching in four-gap buncher. Deceleration in IH-Linac down to 0.5 MeV/u. Deceleration in RFQ down to 6 keV/u. HITRAP cooler trap: Electrostatic trapping in cryogenic Penning trap. Electron cooling down to 100 eV/u. Resistive cooling to T = 4 K. From cooler trap to HITRAP experimental area: Pulsed and slow extraction of ions from cooler trap. Delivery of 105 highly charged ions every 10 s at energies between 1 eV/u and 20 keV/u to precision trap experiment and other experimental set-ups.

7. ESR deceleration cycle – Efficiency E = 4 MeV/u Deceleration efficiency Number of ions

8. Decelerator LINAC for HITRAP • Operational Parameters: • Highly charged ions with M/q  3 • Operation frequency: 108 MHz • Emittance of extracted ESR beam  1 mm mrad • Emittance of decelerated beam  100 mm mrad • Beam intensity after decelerator linac: some 105 ions/pulse (for U92+) • Repetition time: 10 s • Decelerator can be used for antiprotons

9. The Cooler Penning Trap trap electrodes capturing and trapping of highly charged ions electron cooling of HCI separation of HCI and electrons resistive cooling of HCI

10. Collision Studies With Slow HCIs Reaction-Microscope HCI • Studies of reaction kinematics of slow HCI with Reaction-Microscope • Interaction of HCI with surfaces • Development of position-sensitive and multi-hit detectors • Strongly inverted systems

11. Collision Studies With Slow HCIs

12. Surface Studies With Slow HCIs

13. Surface Studies With Slow HCIs

14. Precision experiments • High-Precision Ion Trap Techniques: • Single highly charged ion stored in Penning trap at T = 4 K • Measurement of ion cyclotron frequency and of Larmor precession frequency of the bound electron with an accuracy on the 10-10 level • Bound-state QED and atomic-structure investigations: • g-Factor of the bound electron in hydrogen-like ions • up to U91+ • Fundamental constants (a, me) • Nuclear moments, diamagnetic shielding, charge radii • Determination of atomic binding energies via ion cyclotron frequencymeasurements in different charge states

15. -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 0 10 20 30 40 50 60 70 80 90 Bound State QED of e- g-Factor gbound/gfree 1 - (Za)2/3 +a(Za)2/4p + .... Dirac theory bound-state QED - Dirac (Breit 1928) T. Beier, S. Karshenboim, H. Persson, V. Shabaev, V. Yerokhin, et al. all orders in Za contribution to g-factor Grotch et al. 1970 nuclear size nuclear charge Z

16. g-Factor of the bound electron in hydrogen like ions Larmor precession frequency of the bound electron: Ion cyclotron frequency: B

17. Mass Measurements No contamination, very long storage times • High precision mass measurements: • Single highly charged ion stored in Penning trap at T = 4 K • The ion cyclotron frequency nc scales with q and relative statistical mass uncertainty ~ • í.e. a mass uncertainty dm/m < 10-10 can be reached for stable and radioactive nuclei • Example: Comparing masses of U92+ and U91+ gives the electron binding energy with an uncertainty below 20 eV! Low statistical uncertainty Investigation of electron correlation and QED in high fields

18. Laser and X-ray Spectroscopy Hyperfine-Transition in H-like Ions: • Nuclear properties (charge and magnetisation distributions) • QED effects • Atomic and nuclear polarization by optical pumping X-ray spectroscopy with HCI: • Precision Measurements of Lamb shift • Isotope shift, nuclear charge radii

19. Conclusions • HITRAP will be a unique facility for highly-charged ions up to U92+ at very low energies. • Design of decelerator linac and cooler Penning trap is under way. • Installation of HITRAP Facility at re-injection channel in the ESR hall at GSI. • GSI Future Facility: low-energy antiprotons will be • available at NESR with high intensity. • The future plans at GSI give a long-term perspective for HITRAP.