D. Forkel-Wirth

COMPLIS experiments: COllaboration for spectroscopy Measurements using a Pulsed Laser Ion Source

Laser spectroscopy measurements have been carried out on very neutron-deficient isotopes of Au, Pt and Ir, produced as daughter elements from a Hg ISOLDE beam. For these transitional region nuclides, the hyperfine structure (HFS) and isotope shift (IS) were measured by Resonance Ionization Spectroscopy (RIS). Magnetic moments μ, spectroscopic quadrupole moments Qs and changes of the nuclear mean square charge radius δ〈rc2〉along isotopic series have been extracted. For some results, a detailed comparison with theoretical predictions is presented.

Measurements of the spectroscopic quadrupole moments of the 112− isomers 193mAu, 195mAu and 197mAu with MAPON

Abstract With measurements of modulated adiabatic passage on oriented nuclei (MAPON) of the 11 2 − isomers 193m Au ( T 1 2 = 3.9 s ), 195m Au ( T 1 2 = 30.6 s ) and 197m Au ( T 1 2 = 7.7 s ) in hcp-Co, the electric quadrupole splitting frequencies eQV zz h were determined to be −46.82(11), −44.29(11) and −39.78(11) MHz for 193m Au, 195m Au and 197m Au, respectively. With the known electric field gradient of Au in hcp-Co, eq = −0.977(29) × 10 17 V/cm 2 , the spectroscopic quadrupole moments are deduced to be Q ( 193m Au) = +1.98(6) b, Q ( 195m Au) = +1.87(6) b and Q ( 197m Au) = +1.68(5) b. Theoretical quadrupole moments calculated within the asymmetric rotor model are in moderate agreement with the experimental values.

Radioactive isotopes in solid state physics

Abstract A wide range of solid state physics techniques is using radioactive ion beams, both from on-line and off-line separators. The different techniques can be roughly subdivided into two classes: one, including the hyperfine techniques like Mosbauer spectroscopy (MS), Perturbed Angular Correlation (PAC) spectroscopy, β-NMR and the ion-beam technique of Emission Channeling (EC). They all crucially depend on the availability of radioactive isotopes with very specific decay properties. The second group comprises radio-tracer techniques which combine radioactive probe atoms with conventional semiconductor physics methods like Deep Level Transient Spectroscopy (DLTS), Capacitance Voltage measurements (CV), Hall-effect measurements or Photoluminescence Spectroscopy (PL). They are perfectly feasible without any radioactive probe atom, however, using such isotopes enables the unambiguous chemical identification of impurities. The present paper gives an overview on the potential of nuclear techniques by describing some typical experiments.

High-resolution measurements of low-energy conversion electrons

High-resolution measurements of low-energy conversion electrons have been performed in odd and odd–odd nuclei with masses around A=182. The experimental setup, a magnetic spectrograph coupled to a specific tape transport system, is described. Three experiments have been performed and the main results are presented.

DEVIATION OF THE IMPURITY MAGNETIC HYPERFINE FIELDS AT BR AND KR FROM THE HOST LATTICE MAGNETIZATION IN NI

Abstract The magnetic hyperfine fields at Br and Kr nuclei in nickel have been measured by heavy ion implantation techniques. Extrapolating to 0 K, H = −0.7(1) T is obtained for Kr and H = +8.0(1) T for Br, in qualitative agreement with theoretical values. The temperature dependences deviate strongly from that of the lattice magnetization.

Generic Studies of Radioactivity Induced by High-Energy Beams in Different Absorber Materials

Abstract The FLUKA code is used to simulate the residual dose rates around a typical beam absorber considering various scenarios. The latter include carbon, copper, and tungsten as jaw materials, different beam energies, protons, and lead ion beams as well as different irradiation and cooling times. Using the dose rate maximum close to the absorber surface, the study investigates the cooling time dependence for the different scenarios. It is found to be similar for all jaw materials and beam energies. The dose rate scales with energy as E0.83 and with the number of nucleons when comparing proton beam with lead ions. After a sufficiently long cooling time, a few radionuclides produced in the steel tank, such as 56Co, 58Co, 48V, and 54Mn, dominate the dose rate. The study can be easily extended to other materials or irradiation scenarios and can be applied to first evaluations of given accelerator design options.

Traceable measurements of the activity concentration in air

Abstract The nuclear reactions induced by high energetic protons in heavy targets such as UC 2 and ThC cause a particular, complex radiation protection task at facilities like ISOLDE: the measurement of a mixture of different isotopes of the radioactive noble gas radon and the radon progenies in air. The knowledge of their respective activity concentration is fundamental for exposure assessments. Due to the complex mixture of activity concentrations in air, its precise determination is quite difficult. Therefore, a new procedure for taking reference samples was developed and implemented for the traceable measurement of the activity concentration of radioactive ions (e.g., radon progenies) in air. This technique is combined by measuring α -particles with a multi-wire ionization chamber for the parallel on-line determination of the activity concentration of different radon isotopes.

Surface and interface studies with ASPIC

Magnetic properties at surfaces and interfaces have been investigated performing Perturbed Angular Correlation (PAC) measurements in the UHV chamber ASPIC (Apparatus for Surface Physics and Interfaces at CERN) using different PAC probes. The results are: (i) determination of magnetic hyperfine fields of Se on Fe, Co, Ni which are explained by a theoretical study on the magnetic hyperfine fields of 4sp-elements in adatom position on Ni and Fe;(ii) static magnetic hyperfine fields in ultrathin Pd on Ni(0 0 1) which indicate an induced magnetic order in Pd;(iii) the observation of induced fluctuating magnetic interactions in Pd when thick Pd is in contact with Ni. Monolayer-resolved measurements of the magnetic hyperfine fields in magnetized Pd are in accordance with theoretical predictions of the layer dependence of the induced magnetic moments in Pd.

Radiation protection at CERN

This paper gives a brief overview of the general principles of radiation protection legislation; explains radiological quantities and units, including some basic facts about radioactivity and the biological effects of radiation; and gives an overview of the classification of radiological areas at CERN, radiation fields at high-energy accelerators, and the radiation monitoring system used at CERN. A short section addresses the ALARA approach used at CERN.

Monte Carlo-Based Field Calibration of Radiation Monitors for the Large Hadron Collider at CERN

Abstract Operating a high-energy accelerator like the Large Hadron Collider (LHC) requires a state-of-the-art monitoring system for radiation protection. In the vicinity of the accelerator as well as in the accessible areas behind thick shielding, a unique mixed radiation environment is encountered that consists of different particle types with energies ranging from fractions of electron volt up to several giga-electron-volts. Consequently, the correct assessment of ambient dose equivalent poses a challenging task and requires appropriate field-specific calibration methods, in particular as no adequate calibration sources exist. This circumstance motivated the development of a more accurate field calibration method for the LHC, based on benchmarked FLUKA Monte Carlo simulations. The method of obtaining such field calibration coefficients for IG5 high-pressure ionization chambers is exemplified in a case study for the LHCb experiment. Comparing these factors to calibration source–based values shows over- or underestimation of the actual dose by the source-based coefficient, depending on the location of the monitor.