The GSI JetTarget Thomas Sthlker GSIDarmstadt and IKF

The GSI Jet-Target Thomas Stöhlker GSI-Darmstadt and IKF, Frankfurt University • The Jet-Target and its Environment at the ESR current experimental setup planned for 2005 required modifications for future experiments • Atomic Charge Exchange Cross-Sections and Beam Lifetimes • Target Developments at GSI • Synchronize the Various Efforts (EXL, NUSTAR, SPARC, …)

The Experiment Storage Ring ESR Key features / instrumentation: • Stochastic and electron cooling • Schottky and TOF mass and lifetime spectroscopy (single ion sensitivity) • Internal gas jet target • X ray and position sensitive particle detectors • Crystal spectrometer • Bolometric detectors • Collinear laser spectroscopy. • electron spectrometer • recoil ion spectrometer

The Jet-Target Supersonic jet, operates in ultra high vacuum environment (10 -11 mbar) Target densities 1012 – 1014 p/cm 3 Single collision conditions A. Krämer et al. , NIM B 174, 205 (2001)

Target Densities and Profile by cooling to LN 2 temperatures a density increase from 1010 p/cm 3 to 1013 p/cm 3 has been achieved for H 2 Target profile: A. Krämer et al. , NIM B 174, 205 (2001) FWHM: 5 mm

ESR – Target Environment

Scattering Chamber Currently Installed • Photon angular correlation studies • 0 -deg photon spectroscopy • X-X coincidence experiments • photon polarization experiments • precision photon spectroscopy, crystal spectrometer, calorimeter • electron spectrometer

Planned Modifications • Lower temperatures Density increase by an order of magnitude for H 2 • Variable/smaller jet-beam diameter (5 mm to 1 mm) Reduced Doppler broadening Very important: Because of the high gas load differential pumping along the beam line required => moveable collimators required (fast moving)

Recoil Ion Chamber Combined and 0 -deg Electron Spectrometer planned for 2005 Recoil ion spectrometer: A longitudinal B field and a electrostatic E field will allow to detect low momentum target electrons and target recoil ions

Measurements of K-shell Ionization in 260 Me. V/u Pb 81+ on Ar Collisions time of flight coincindece atomic gas target + 100 V recoil ions ion beam + 100 V impact parameter

Target Recoil in Coincidence with Projectile Electron Loss pulsed beam used inside the ESR (10 ns)

1 s Lamb-Shift Experiment

The HITRAP Project at the ESR experiments for slow particles experiments with particles at rest cooler Penning trap postdecelerator 400 Me. V/u UNILAC SIS U 92+ EXPERIMENTS WITH HIGHLY CHARGED IONS AT EXTREMELY LOW ENERGIES: stripper target U 73+ U 92+ · ultra-accurate mass measurements (atomic physics) · g-factor measurements (tests of QED) · laser and x-ray spectroscopy ESR · surface studies and hollow-atom spectroscopy · collisions at very low velocities planned for 2007 / 2008 electron cooling and deceleration down to 4 Me. V/u

Charge exchange rates and beam lifetimes 1/ = = target+ cooler+ residual gas Like in the jet-target, collisions with residual Gas atoms or moleculs may lead to beam losses For the ESR the assumed composition of the residual is 79% H 2 20% N 2 1% Ar

ZT scaling of cross sections

Beam life times with the gasjet target U 92+ => N 2 Th. Stöhlker et al. , Phys. Rev. A 58, 2043 (1998)

Beam life times with the gasjet target U 92+ capture

Beam lifetimes for ion beams in the NESR for a H 2 target at 740 Me. V/u 500 m. A cooler current; T=0. 1 e. V

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INFN Cluster-jet target (FNAL E 760, E 835) achived target thickness: 5 x 1014 atoms/cm 3 pumping system with turbo molecular pumps: 10 x 1000 l/s 2 x 3500 l/s vacuum chamber for cryogenic nozzle and skimmers cluster-jet beam dump p-beam JZ / GSI, June 2004

Lanzhou (internal target) Lanzhou Cluster Target cluster polarized density: 1013/cm 2 material: N 2, CH 4, Ne, Ar, etc. polarization: 0 2 x 1011/cm 2 H, D 90%, 95%

Beam life times for few-electron ions in the NESR interplay between ionization and capture ionization capture for heavy elements, a closed K-shell results in an increase of beam lifetime by a factor of two

Radiative Electron Capture of Quasifree Targetelectrons U 92+ => Ar, 358 Me. V/u REC photon energy Shape and width of REC lines are determined by the momentum distribution of the target electrons EKIN

Electron Pickup Processes of HCI in Collisions with Electrons (Dynamic Processes) Radiative Recombination/Electron Capture AZ+ + e- A(Z-1)+ + EKIN electron continuum bound states • Electron capture into a bound ionic state by emission of a photon • Time-reversed photionization • Only possible capture/recom-bination process for bare ions colliding with electrons Dielectron Recombination/Electron Capture EKIN electron continuum bound states • Resonant (non-radiative) capture of an electron into a bound state • Time-reversed Auger process • Important charge exchange process for multi-electron ions

experiment cycle at the target beam injection, cooling, deceleration data accumulation slow particle detector movement By fast particle detector movement, the overall efficiency has now been improved by up to a factor of two.

Radiative Recombination/Electron Capture at Cooler electron cooler dipole magnet Low velocity regime At low velocities RR populates high n, l states but no s-levels Electron beam M L Ly (delayed) K

Charge Exchange Processes for Bare Ions REC: Radiative Electron Capture photoionization) Z T ´ ZP REC µ 5/2 v 5 (High energy domain) (time reversed EKIN electron NRC: Kinematic or Non Radiative - Electron Capture (three body interaction where momentum and energy is shared between the collision partner) Z T ´ ZP NRC µ 11 v 5 5 Z T : Nuclear charge of the target Z P : Nuclear charge of the projectile V : Relative velocity between target electron and projectile continuum bound states

AP experiments at the Jet-Target Beam energies: 10 to 400 Me. V/u Charge states: bare to Li-like ions Photon detection: 10 -3 -10 -2 Photon energies: 2 ke. V – 1 Me. V x-ray/particle • Photon angular correlation studies • 0 -deg photon spectroscopy • X-X coincidence experiments • photon polarization experiments • precision photon spectroscopy coincidences

RECOIL ION MOMENTUM SPECTROSCOPY 3. 6 Me. V/u C 2+ He magnet C 2+ C 3+ target electron projectile electron coincidence projectile electrons recoil ions target Electrons tp=0 projectile electrons counts target electrons 0 TOF [channels] 50 100 150 200 350 TOF [ns] 4 -particle coincidence: C 3+, He 1+, projectile (cusp)- and target electron H. Kollmus et. al, 2002

Beam lifetimes for ion beams in the NESR Xe target at 500 Me. V/u 500 m. A cooler current T=0. 1 e. V cooler+jet [1014 p/cm 2] cooler+jet [1013 p/cm 2] electron cooler With a Xe target and for heavy projectiles, the beam life time is entirely dominated by charge exchange in the target

Beam life times for few-electron ions in the NESR interplay between ionization and capture ionization capture for heavy elements, a closed K-shell results in an increase of beam lifetime by a factor of two