Nuclear moments and differences in mean square charge radii of short-lived neon isotopes by collinear laser spectroscopy

The nuclear moments and charge radii of short-lived neon isotopes were measured by the use of collinear laser spectroscopy at the on-line mass separator ISOLDE at CERN. After a general introduction the semiclassical theory of atomic spectra is given and the relevant properties are calculated for neon. The atomic physics section is followed by a description of the experimental setup of the collinear laser spectroscopy experiment at ISOLDE. From the mass separator an isotopically clean ion beam with a kinetic energy of 60 keV is delivered to the experiments. In collinear laser spectroscopy the incoming ion beam from the mass separator is superimposed to a single frequency cw laser beam. The frequency of the atomic transition $\nu\scriptstyle_{0}$ is given at resonance with the laser light frequency $\nu\scriptstyle_\textrm{L}$ by the Doppler shifted frequency $\nu\scriptstyle_\textrm{D}$ = $\nu\scriptstyle_{0}(1\pm\beta)$/$\scriptstyle\sqrt {1-\beta^2}$ = $\nu\scriptstyle_\textrm{L}$. Thus, the position of the resonance line is dependent on the kinetic enrgy of the incoming ion beam. The difference in the nuclear charge radii between two isotopes of an element causes the field shift contributing to the isotope shift which was measured in this experiment. As the field shift decreases with the nuclear charge Z, for neon a new method was needed to measure the kinetic beam energy to reach the required precision to determine the field shift / differences in nuclear charge radii. A variant of collinear laser spectroscopy using the Doppler shift caused by laser excitation in collinear and anticollinear geometry of closly lying atomic levels of neon was used to measure the ISOLDE ion beam energy with a precision of better than 1 V. The results of the measurements on the hyperfine structure parameters and the isotope shifts in the extended isotope chain $^{17-26,28}$Ne with the reference isotope $^{20}$Ne is discussed. From the hyerfine structure parameters of the odd-A neon isotopes the corresponding nuclear moments, from the isotope shifts the differences in the ms charge radii are calculated. The nuclear moments of the odd-A neon isotopes $^{19}$Ne, $^{21}$Ne, $^{23}$Ne and $^{25}$Ne are discussed in the framework of the nuclear shell model. $^{17}$Ne is an exception, beacuse it is a candidate of a proton-halo nucleus. Due to the lack of shell-model calculations its magentic moment is discussed in the framework of the isoscalar moment. The nuclear charge radii of $^{18-26,28}$Ne are compared with a number of collective models. Besided the comparison with data from the literature the droplet model is used to calculate charge radii as comparison, which gives surprisingly closely lying values compared to the experimental data. Again, the discussion for $^{17}$Ne is done separately and is compared with halo-theory calculations

Beam Current Monitors for FAIR

The FAIR (Facility for Antiproton and Ion Research) accelerator facility presently under construction at GSIwill supply a wide range of beam intensities for physicsexperiments. Design beam intensities range from 2.5×1013protons/cycle to be delivered to the pBar-target andseparator for production of antiprotons, to beams of e.g.109 ions/s in the case of slowly extracted beams. Thelarge intensity range demands for dedicated beam currentmonitors for precise, non-destructive beam intensitymeasurements in the synchrotrons, transport lines andstorage rings of the FAIR facility. This report describesGSI developments of purpose-built beam currentmonitors for the SIS100 synchrotron and high-energybeam transport lines (HEBT) of FAIR. Prototypemeasurements with a SQUID-based Cryogenic CurrentComparator and a resonant beam charge transformer arepresented, and possibilities for further upgrades arediscussed

Non-perturbative measurement of low-intensity charged particle beams

Non-perturbative measurements of low-intensity charged particle beams are particularly challenging to beam diagnostics due to the low amplitude of the induced electromagnetic fields. In the low-energy antiproton decelerator (AD) and the future extra low energy antiproton rings at CERN, an absolute measurement of the beam intensity is essential to monitor the operation efficiency. Superconducting quantum interference device (SQUID) based cryogenic current comparators (CCC) have been used for measuring slow charged beams in the nA range, showing a very good current resolution. But these were unable to measure fast bunched beams, due to the slew-rate limitation of SQUID devices and presented a strong susceptibility to external perturbations. Here, we present a CCC system developed for the AD machine, which was optimised in terms of its current resolution, system stability, ability to cope with short bunched beams, and immunity to mechanical vibrations. This paper presents the monitor design and the first results from measurements with a low energy antiproton beam obtained in the AD in 2015. These are the first CCC beam current measurements ever performed in a synchrotron machine with both coasting and short bunched beams. It is shown that the system is able to stably measure the AD beam throughout the entire cycle, with a current resolution of $30\,\mathrm{nA}$

A Squid-Based Beam Current Monitor For FAIR

A Cryogenic Current Comparator (CCC) wasdeveloped for the upcoming FAIR-Project, providing anon-destructive online monitoring of the beam current inthe nA-range. The CCC was optimized for a lowestpossible noise-limited current resolution together with ahigh system bandwidth. Therefore, the low temperatureproperties of ferromagnetic core materials used in thepick-up coil were investigated and differentSuperconducting Quantum Interference Device (SQUID)-systems were tested.In this contribution we present results of the completedCryogenic Current Comparator for FAIR working in alaboratory environment, regarding the improvements inresolution and bandwidth due to the use of suitableferromagnetic core materials and optimized SQUIDsystemcomponents

Calibration of the ISOLDE acceleration voltage using a high-precision voltage divider and applying collinear fast beam laser spectroscopy

A high-voltage divider with accuracy at the ppm level and collinear laser spectroscopy were used to calibrate the highvoltage installation at the radioactive ion beam facility ISOLDE at CERN. The accurate knowledge of this voltage is particularly important for collinear laser spectroscopy measurements. Beam velocity measurements using frequencycomb based collinear laser spectroscopy agree with the new calibration. Applying this, one obtains consistent results for isotope shifts of stable magnesium isotopes measured using collinear spectroscopy and laser spectroscopy on laser-cooled ions in a trap. The long-term stability and the transient behavior during recovery from a voltage dropout were investigated for the different power supplies currently applied at ISOLDE.Comment: 13 pages, 6 figure

Measurement of the magnetic moment of the one-neutron halo nucleus 11^{11}Be

The magnetic moment of $^{11}$Be was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a $^{11}$Be$^+$ ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal and observation of rf resonances in the asymmetric angular distribution of the $\beta$-decay ($\beta$-NMR). The nuclear magnetic moment $\mu(^{11}{\rm Be}) = -1.6816(8)\,\mu_N$ provides a stringent test for theoretical models describing the structure of the 1/2$^+$ neutron halo state

Theoretical study of the two-proton halo candidate 17^{17}Ne including contributions from resonant continuum and pairing correlations

With the relativistic Coulomb wave function boundary condition, the energies, widths and wave functions of the single proton resonant orbitals for $^{17}$Ne are studied by the analytical continuation of the coupling constant (ACCC) approach within the framework of the relativistic mean field (RMF) theory. Pairing correlations and contributions from the single-particle resonant orbitals in the continuum are taken into consideration by the resonant Bardeen-Cooper-Schrieffer (BCS) approach, in which constant pairing strength is used. It can be seen that the fully self-consistent calculations with NL3 and NLSH effective interactions mostly agree with the latest experimental measurements, such as binding energies, matter radii, charge radii and densities. The energy of $\pi$2s$_{1/2}$ orbital is slightly higher than that of $\pi1d_{5/2}$ orbital, and the occupation probability of the $(\pi$2s$_{1/2})^2$ orbital is about 20%, which are in accordance with the shell model calculation and three-body model estimation

TRIGA-SPEC: A setup for mass spectrometry and laser spectroscopy at the research reactor TRIGA Mainz

The research reactor TRIGA Mainz is an ideal facility to provide neutron-rich nuclides with production rates sufficiently large for mass spectrometric and laser spectroscopic studies. Within the TRIGA-SPEC project, a Penning trap as well as a beam line for collinear laser spectroscopy are being installed. Several new developments will ensure high sensitivity of the trap setup enabling mass measurements even on a single ion. Besides neutron-rich fission products produced in the reactor, also heavy nuclides such as 235-U or 252-Cf can be investigated for the first time with an off-line ion source. The data provided by the mass measurements will be of interest for astrophysical calculations on the rapid neutron-capture process as well as for tests of mass models in the heavy-mass region. The laser spectroscopic measurements will yield model-independent information on nuclear ground-state properties such as nuclear moments and charge radii of neutron-rich nuclei of refractory elements far from stability. This publication describes the experimental setup as well as its present status.Comment: 20 pages, 17 figure