C. Kozhuharov

Charge states and energy loss of relativistic heavy ions in matter

Abstract Relativistic heavy-ion collisions of few-electron projectiles ranging from argon up to uranium have been investigated in solid and gaseous media. Electron-loss and electron-capture cross sections, charge-state distributions, as well as energy loss and energy deposition have been measured and are compared with theoretical predictions. Especially fully-ionized heavy projectiles represent a unique possibility to test atomic-collision theories.

First steps towards radioactive beams in the experimental storage ring at GSI

Abstract During the present commissioning phase of the new heavy-ion facilities at GSI first radioactive beams have been produced by the Projectile Fragment Separator, while beams of stable neon, argon, krypton, and bismuth ions have been stored and cooled in the Experimental Storage Ring. The connection between these two facilities has been installed, so that first tests of injecting radioactive fragments will soon be possible. This procedure and the available beam diagnostics are briefly described. Main emphasis is given to the description of gas-filled multiwire proportional chambers that serve as position-sensitive detectors to monitor the low-intensity radioactive beams.

Vavilov-Cherenkov radiation emitted by heavy ions near the threshold

Abstract The Vavilov–Cherenkov radiation (VChR) emitted by the heavy ions 79 Au was studied by the photography method. The photographs of the radiation near and below the VChR threshold are published for the first time.

LARGE-SCALE MASS MEASUREMENTS OF SHORT-LIVED NUCLIDES WITH THE ISOCHRONOUS MASS SPECTROMETRY AT GSI

Precise mass measurements of short-lived exotic nuclei are very important for the understanding of basic nuclear structure physics and astrophysical nucleosynthesis in nature, as well as for the test and the development of theoretical nuclear mass models. At GSI, the Isochronous Mass Spectrometry (IMS) dedicated to mass measurements of short-lived nuclides was developed. In this contribution, the IMS technique is briefly reviewed. Recently, the first large-scale measurement on the 238U fission fragment was done successfully. The measured mass values are in excellent agreement with the recent Penning trap data, however, they show a systematical deviation from the values in the latest atomic mass evaluation. Some representative results from this experiment will be presented, including their impact on nuclear structure physics and astrophysical r-process nucleosynthesis.

Isochronous Mass Measurements of Hot Exotic Nuclei

A novel method for mass measurements of short-lived exotic nuclides is presented. Exotic nuclides were produced and separated in flight at relativistic energies with the fragment separator (FRS) and were injected into the experimental storage ring (ESR). Operating the ESR in the isochronous mode we performed mass measurements of neutron deficient fragments of 84Kr with half-lives larger than 50 ms. However, this experimental technique is applicable in a half-life range down to a few μs. A mass resolving power of 110000 (FWHM) has been achieved. Results are presented for the masses of 68As, 70,71Se and 73Br.

Radiative double electron capture in heavy-ion atom collisions

Abstract Total cross sections for radiative double electron capture (RDEC) in collisions of fast highly charged ions with light target atoms were estimated. The applied method is based on the principle of detailed balance using the cross sections for the double photoionization process. Preliminary results of a dedicated RDEC experiment aiming at the observation of photons with twice the single REC photon energy, associated with double charge exchange, are discussed. Additionally, results of complementary measurements of double capture (without photon registration) by fully stripped U ions in collisions with C atoms at 295 MeV/u are presented. Here, a surprisingly enhanced cross section for double electron capture is found in accordance with observations reported in the literature.

Future experiments using forward electron spectroscopy to study the quantum dynamics of high-Z ions at the ESR/CRYRING storage rings

At the FAIR facility for antiproton and ion research, the new ESR + CRYRING combination of storage rings CRYRING@ESR opens up a wealth of opportunities for in-ring atomic physics experiments on few-body quantum dynamics. The low-energy storage ring CRYRING will serve in its new location at FAIR/ESR for experiments with decelerated antiprotons and highly charged ions. We will discuss selected new experiments in the field of quantum dynamics of high-Z ions, for example for adiabatic superheavy quasi-molecules transiently formed with bare and H-like projectiles. Such experiments will be for the first time possible at the future CRYRING at ESR.

Electron Screening Effects on a-decay

An open problem in Nuclear Astrophysics concerns the understanding of electron‐screening effects on nuclear reaction rates at stellar energies. In this framework, we have proposed to investigate the influence of the electron cloud on α‐decay by measuring Q‐values and α‐decay half‐lives of fully stripped, H‐like and He‐like ions. These kinds of measurements have been feasible just recently for highly‐charged radioactive nuclides by fragmentation of 238U at relativistic energies at the FRS‐ESR facility at GSI. In this way it is possible to produce, efficiently separate and store highly‐charged α‐emitters. Candidates for the proposed investigation were carefully selected and will be studied by using the Schottky Mass Spectroscopy technique. In order to establish a solid reference data set, lifetimes and Qα‐value measurements of the corresponding neutrals have been performed directly at the FRS, by implanting the separated ions into an active Silicon stopper.

Mass and Lifetime Measurements in Storage Rings

Masses of nuclides covering a large area of the chart of nuclides can be measured in storage rings where many ions circulate at the same time. In this paper the recent progress in the analysis of Schottky mass spectrometry data is presented as well as the technical improvements leading to higher accuracy for isochronous mass measurements with a time‐of‐flight detector. The high sensitivity of the Schottky method down to single ions allows to measure lifetimes of nuclides by observing mother and daughter nucleus simultaneously. In this way we investigated the decay of bare and H‐like 140Pr. As we could show the lifetime can be even shortened compared to those of atomic nuclei despite of a lower number of electrons available for internal conversion or electron capture.All these techniques will be implemented with further improvements at the storage rings of the new FAIR facility at GSI in the future.Masses of nuclides covering a large area of the chart of nuclides can be measured in storage rings where many ions circulate at the same time. In this paper the recent progress in the analysis of Schottky mass spectrometry data is presented as well as the technical improvements leading to higher accuracy for isochronous mass measurements with a time‐of‐flight detector. The high sensitivity of the Schottky method down to single ions allows to measure lifetimes of nuclides by observing mother and daughter nucleus simultaneously. In this way we investigated the decay of bare and H‐like 140Pr. As we could show the lifetime can be even shortened compared to those of atomic nuclei despite of a lower number of electrons available for internal conversion or electron capture.All these techniques will be implemented with further improvements at the storage rings of the new FAIR facility at GSI in the future.

Study of basic nuclear properties of highly-charged, unstable nuclei at the SIS-FRS-ESR complex

Recent progress in experiments with exotic nuclear beams at the SIS-FRS-ESR facility is summarized. New results on gross properties of exotic nuclei like binding energy, half-lives, and decay modes are presented. A brief outlook to future experiments is given.