134 research outputs found
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 is given at resonance with the laser light frequency by the Doppler shifted frequency = / = . 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 Ne with the reference isotope 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 Ne, Ne, Ne and Ne are discussed in the framework of the nuclear shell model. 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 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 Ne is done separately and is compared with halo-theory calculations
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
Measurement of the magnetic moment of the one-neutron halo nucleus Be
The magnetic moment of Be was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a 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 -decay (-NMR). The nuclear magnetic moment provides a stringent test for theoretical models describing the structure of the 1/2 neutron halo state
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
Theoretical study of the two-proton halo candidate 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 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 2s orbital is slightly higher than that
of orbital, and the occupation probability of the
2s orbital is about 20%, which are in accordance with the
shell model calculation and three-body model estimation
Improved accuracy of in-ring laser spectroscopy by in-situ electron cooler voltage measurement
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
Recent results on neutron rich tin isotopes by laser spectroscopy
Laser spectroscopy measurements have been performed on neutron rich tin isotopes using the COMPLIS experimental setup. The nuclear charge radii of the even-even isotopes from A=108 to 132 are compared to the results of macroscopic and microscopic calculations. The improvements and optimizations needed to perform the isotope shift measurement on Sn are presented
Regional Monitoring of Capital Flows and Coordination of Financial Regulation: Stakes and Options for Asia
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