Oliver Kester

HITRAP: A Facility at GSI for Highly Charged Ions

Abstract An overview and status report of the new trapping facility for highly charged ions at the Gesellschaft fur Schwerionenforschung is presented. The construction of this facility started in 2005 and is expected to be completed in 2008. Once operational, highly charged ions will be loaded from the experimental storage ring ESR into the HITRAP facility, where they are decelerated and cooled. The kinetic energy of the initially fast ions is reduced by more than fourteen orders of magnitude and their thermal energy is cooled to cryogenic temperatures. The cold ions are then delivered to a broad range of atomic physics experiments.

Laser-driven ion acceleration with hollow laser beams

The laser-driven acceleration of protons from thin foils irradiated by hollow high-intensity laser beams in the regime of target normal sheath acceleration (TNSA) is reported for the first time. The use of hollow beams aims at reducing the initial emission solid angle of the TNSA source, due to a flattening of the electron sheath at the target rear side. The experiments were conducted at the PHELIX laser facility at the GSI Helmholtzzentrum fur Schwerionenforschung GmbH with laser intensities in the range from 1018u2009Wu2009cm−2 to 1020u2009Wu2009cm−2. We observed an average reduction of the half opening angle by (3.07±0.42)° or (13.2±2.0)% when the targets have a thickness between 12u2009μm and 14u2009μm. In addition, the highest proton energies were achieved with the hollow laser beam in comparison to the typical Gaussian focal spot.

The SPARC EBIT at GSI; commissioning and future plans at the HITRAP beamline

This contribution describes the current set-up and future plans for a small permanent magnet electron beam ion trap (EBIT) which has been installed at GSI. The EBIT is planned to serve as an off-line test ion source for experiments on the HITRAP project and also as a test-bed for instrumentation under development for the SPARC collaboration which is part of the new FAIR facility to be built at GSI. In order to increase the range of highly charged ion species which are produced by the source a charge breeding program has been initiated in which singly charged ions are externally injected into the EBIT with high efficiency. We describe recent results from the initial conditioning of the EBIT along with preliminary results of charge breeding tests.

The HITRAP facility for slow highly charged ions

At the GSI accelerator complex, behind the universal linear accelerator UNILAC and the synchrotron SIS, highly charged ions up to are produced at 400 MeV/nucleon. When this beam is sent through a copper foil all or nearly all remaining electrons are stripped. The HITRAP facility, a combination of a linear decelerator and a cryogenic Penning trap, is built to decelerate those ions to almost rest and to provide them for the experiments. In a number of commissioning beam times, the deceleration in the ESR, the extraction, bunching and, finally, deceleration to 6 keV/nucleon has been shown. The remaining steps, being capture and cooling in a cryogenic Penning trap, are presently tested off-line.

A transverse electron target for the investigation of electron–ion interaction processes

For the investigation of electron–ion interaction processes, a new transverse electron target is under development. It opens the perspective to new types of experiments with ions by applying the crossed beam technique for free electrons to a storage ring. The new target is suited for the UHV requirements of a storage ring and realizes an open geometry giving access to the interaction region for photon and electron spectroscopy under large solid angles. It is based on a simple design using only electrostatic fields for the focus of the sheet beam. The adjustable electron energy ranges between several tens of eV and a few keV. The electron target is dedicated to the storage rings of the Facility for Antiproton and Ion Research. First measurements are planned at a test bench, and subsequent tests at the Frankfurt Low Energy Storage Ring are envisaged.

HITRAP – Heavy, highly charged Ions at Rest: Status and experimental Opportunities

HITRAP, the facility for heavy, highly-charged ions at rest, is being commissioned at GSI in Darmstadt. The highly-charged ions are produced by stripping all electrons at 400 MeV/u and then decelerating the beam of bare, heavy nuclei in a storage ring, the ESR, and a linear decelerator. The first steps have been taken into operation successfully; about 105 ions have been decelerated to 0.5 MeV/u. The remaining deceleration and cooling in a RFQ decelerator structure and a Penning trap is prepared. For off-line tests of the experiments as well as the cooler Penning trap, a compact room-temperature EBIT has been installed and delivers beam already.

Status report on the Frankfurt EBIS research program

The Frankfurt superconducting EBIS has been run beyond the space-charge neutralization limit making use of the evaporative cooling technique showing a continuous transition between EBIS to EBIT operation. The experience gained on the performance of this more sophisticated source has been employed to develop simpler EBIS sources: The MEDEBIS using a warm solenoid will demonstrate rapid extraction of bare nuclei for single turn injection into a synchrotron for cancer therapy. The PPM-focused EBIS with permanent magnets and the XEBIS without any focusing magnetic field have been developed to demonstrate by its reduced power consumption and size to be more suitable to small laboratories. High emission current densities from a laser heated tip cathode offer the formation of a well-defined high current density beam. Several spectrometers have been built and installed to offer diagnostics for the EBIS operation as well as atomic physics research. Ionization measurements can be performed using the magnetic switchyard, an external electrostatic and magnetic spectrometer allows to study secondary electron emission by highly charged ions as well as to ionize and analyse sputtered atoms.

Demonstration of charge breeding in a compact room temperature electron beam ion trap

For the first time, a small room-temperature electron beam ion trap (EBIT), operated with permanent magnets, was successfully used for charge breeding experiments. The relatively low magnetic field of this EBIT does not contribute to the capture of the ions; single-charged ions are only caught by the space charge potential of the electron beam. An over-barrier injection method was used to fill the EBITs electrostatic trap with externally produced, single-charged potassium ions. Charge states as high as K(19+) were reached after about a 3 s breeding time. The capture and breeding efficiencies up to 0.016(4)% for K(17+) have been measured.

Construction, characterization and optimization of a plasma window based on a cascade arc design for FAIR at the GSI Hemholtz Center

Summary form only given. High intensity ion beams are important tools to investigate the interaction of ions with matter. Especially at GSI and for the new FAIR project it is important, to transport the ion beam from the UHV-accelerator into a gas filled target chamber. This is relevant for experiments concerning the generation of matter at high energy density matter. This is true also for gas stripper systems, where the pressure inside the stripper is significantly higher than inside the accelerator.

HITRAP - a facility for experiments on heavy highly charged ions and on antiprotons

HITRAP is a facility for very slow highly-charged heavy ions at GSI. HITRAP uses the GSI relativistic ion beams, the Experimental Storage Ring ESR for electron cooling and deceleration to 4 MeV/u, and consists of a combination of an interdigital H-mode (IH) structure with a radiofrequency quadrupole structure for further deceleration to 6 keV/u, and a Penning trap for accumulation and cooling to low temperatures. Finally, ion beams with low emittance will be delivered to a large variety of atomic and nuclear physics experiments. Presently, HITRAP is in the commissioning phase. The deceleration of heavy-ion beam from the ESR storage ring to an energy of 500 keV/u with the IH structure has been demonstrated and studied in detail. The commissioning of the RFQ structure and the cooler trap is ongoing.