E. Jaeschke

First experiments with the heidelberg test storage ring TSR

Abstract The Heidelberg heavy ion test storage ring TSR started operation in May 1988. The lifetimes of the ion beams observed in the first experiments can be explained by interactions with the residual gas. Multiple Coulomb scattering, single Coulomb scattering, electron capture and electron stripping are the relevant processes. Electron cooling of ions as heavy as O 8+ has been observed for the first time. With increasing particle number, the longitudinal Schottky noise spectrum becomes dominated by collective waves for cooled beams, allowing a determination of velocities of sound. After correcting for these coherent distortions fo the Schottky spectrum, the longitudinal beam temperature could be extracted. The observed longitudinal equilibrium beam temperatures increase strongly with the charge of the ions. For a cooled C 6+ beam, temperatures a factor of 120 higher were measured compared to a proton beam with the same particle number. The shrinking of the beam diameter due to electron cooling was observed with detectors which measured the profile of charge-changed ions behind a bending magnet. A strong laser-induced fluorescence was detected when storing metastable 7 Li + ions in the ring. Via the Doppler effect a very accurate measurement of the ion velocity profile could be performed. First attempts to observe laser cooling failed, probably due to heating effects from intrabeam scattering and a coupling between longitudinal and transversal motion in the beam. Several experiments under preparation are outlined.

Electron cooling of heavy ions

Abstract The electron cooling device of the Heidelberg cooler storage ring has come into operation and for the first time has cooled ions heavier than protons. These experiments have proven that the cooling force is increasing with the charge of the ion. Cooling in the longitudinal and transverse phase space can increase the phase space density by up to four orders of magnitude. The usefulness of the method to increase the lifetime and the intensity of the stored particles was demonstrated resulting in a number of 3 × 10 10 carbon particles which were successfully cooled and stored.

The Heidelberg Heavy Ion Test Storage Ring TSR

The Heavy Ion Test Storage Ring TSR [1] is an experimental facility for accelerator, atomic and nuclear physics studies presently under construction at the Heidelberg Max-Planck-Institute. The storage ring is designed for heavy ions of up ∼ 30 MeV/u at a charge to mass ratio of qA = 0.5, corresponding to a magnetic rigidity of Bρ = 1.5 Tm. Phase space compression using electron cooling [2] will be applied in the TSR to produce ion beams of extreme quality and at the same time to reduce the large transverse emittances and momentum spread which build up in the sophisticated injection technique used to reach heavy ion currents in the mA range. The beams equilibrium emittance and momentum distribution after cooling will be limited just by intrabeam scattering and the interaction in an internal target. Furthermore the very broad rigidity acceptance of the TSR will permit operation with simultaneous storage of several neighboring charge states of ions. This report will review the major design features and give the status of the ring project.

Development of seven-gap resonators for the Heidelberg high current injector

Abstract A high current injector for the heavy ion storage ring TSR in Heidelberg is under construction. As a part of the injector eight seven-gap resonators with high shunt impedance are being developed. These resonators ( ƒ 0 = 108.48 MHz ) are designed for the synchronous velocities of β s = 3.7, 4.5, 5.1 and 5.7%. Low power models with scaling factors of 1:2.5 were built in order to study the characteristics of these new resonators. Following low level measurements to optimize the voltage distribution and eigenfrequency, a first power resonator was built and successfully tested at 80 kW (duty cycle of 25%). At this power, the resonator generated a maximum voltage (summation of all gap amplitude voltages) of 1.75 MV. This paper describes the design of the resonators and gives some details of the measurements.

Advanced stacking methods using electron cooling at the TSR Heidelberg

Using the new method of beam accumulation by stacking with electron cooling, intensities were enhanced by factors of several thousands compared with single-turn injection. With electron cooler stacking a current of 18 mA (3*10/sup 10/ particles) for /sup 12/C ions (E=73.3 MeV) was achieved.<<ETX>>

First atomic physics experiments with cooled stored ion beams at the Heidelberg heavy-ion ring TSR

An overview of atomic physics experiments at the heavy ion Test Storage Ring (TSR) is given. Highly charged ions up to fully stripped silicon have been stored at energies between 4 and 12 MeV/u. The enhancement of the beam intensity by stacking, the beam lifetime, and electron cooling of these ion beams are discussed. Radiative and state‐selective dielectronic recombination rates of hydrogen‐like oxygen ions with free electrons from the electron cooler were measured. Beam noise spectra are being investigated with regard to collective effects caused by the Coulomb interaction in the cold ion beams. Resonance fluorescence from stored single‐charged ions was observed using tunable narrow‐band lasers. First indications of laser cooling in a storage ring were seen.

The Heidelberg heavy ion cooler storage ring TSR

Commissioning of the Heidelberg Test Storage Ring (TSR) started in May 1988. The TSR is a low-energy cooler storage ring for heavy ions with energies up to 30 MeV/amu at a charge-to-mass ratio 1/A=0.5. Phase space cooling for coasting beams as well as for bunched beams is routinely done by electron cooling. As the ring is fed by a tandem linac combination, stored intensities of up to 1*10/sup 10/ particles are obtained by combined stacking into transversal and longitudinal phase space (multiturn injection and RF stacking). This stacking method gives 800 times the number of stored ions compared to single-turn injection. Cooling oxygen and carbon beams resulted in a typical emittance of 0.3 pi mm-mrad and a momentum spread of Delta p/p=10/sup -4/. The equilibrium was mainly determined by intrabeam scattering, and the heating in the residual gas was mainly determined by multiple scattering. An overall increase of phase space density by six orders of magnitude was observed, similar to cooling results at proton machines. Results on the first year of operation with heavy ions at the TSR are reported.<<ETX>>

Upgrading of the Heidelberg accelerator facility with a new high current injector

Abstract The existing accelerator facility at the Max-Planck-Institute in Heidelberg consists of a 12 MV tandem Van de Graaff accelerator, a post-accelerator and a heavy ion cooler storage ring TSR. Many experiments at the TSR, especially laser cooling, are limited by the low current delivered by the MP tandem. A new injector consisting of a high current source, two RFQs and eight seven-gap resonators will increase the currents for singly charged ions by up to three orders of magnitude. In a second phase, an ECR source for highly charged ions will be added and the high current injector will be used in combination with the Heidelberg heavy ion post-accelerator. This new system will deliver beams up to uranium with energies above the Coulomb barrier of the heaviest elements. In this paper the design and the status of the project are presented.

Laser and electron cooling of relativistic stored beams

Laser cooling of ions at relativistic energies was first observed at the TSR storage ring in Heidelberg. A 7Li+ ion beam moving at 6.4% the speed of light was overlapped with resonant co‐ and counter‐propagating laser beams. The longitudinal temperatures were found to pass below 190 mK. Limits and applications of laser cooled relativistic ion beams are discussed. Laser cooling and electron cooling of the ion beam were combined.