375 research outputs found
The Ramsey method in high-precision mass spectrometry with Penning traps: Experimental results
The highest precision in direct mass measurements is obtained with Penning
trap mass spectrometry. Most experiments use the interconversion of the
magnetron and cyclotron motional modes of the stored ion due to excitation by
external radiofrequency-quadrupole fields. In this work a new excitation
scheme, Ramsey's method of time-separated oscillatory fields, has been
successfully tested. It has been shown to reduce significantly the uncertainty
in the determination of the cyclotron frequency and thus of the ion mass of
interest. The theoretical description of the ion motion excited with Ramsey's
method in a Penning trap and subsequently the calculation of the resonance line
shapes for different excitation times, pulse structures, and detunings of the
quadrupole field has been carried out in a quantum mechanical framework and is
discussed in detail in the preceding article in this journal by M. Kretzschmar.
Here, the new excitation technique has been applied with the ISOLTRAP mass
spectrometer at ISOLDE/CERN for mass measurements on stable as well as
short-lived nuclides. The experimental resonances are in agreement with the
theoretical predictions and a precision gain close to a factor of four was
achieved compared to the use of the conventional excitation technique.Comment: 12 pages, 14 figures, 2 table
A multi-reflection time-of-flight mass spectrometer for the offline ion source of the PUMA experiment
The antiProton Unstable Matter Annihilation experiment (PUMA) at CERN aims at
investigating the nucleon composition in the matter density tail of radioactive
as well as stable isotopes by use of low-energy antiproton-nucleon annihilation
processes. For this purpose, antiprotons provided by the Extra Low ENergy
Antiproton (ELENA) facility will be trapped together with the ions of interest.
While exotic ions will be obtained by the Isotope mass Separator On-Line DEvice
(ISOLDE), stable ions will be delivered from an offline ion source setup
designed for this purpose. This allows the proposed technique to be applied to
a variety of stable nuclei and for reference measurements. For beam
purification, the ion source setup includes a multi-reflection time-of-flight
mass spectrometer (MR-ToF MS). Supported by SIMION simulations, an earlier
MR-ToF MS design has been modified to meet the requirements of PUMA. During
commissioning of the new MR-ToF device with Ar ions, mass resolving powers
in excess of 50,000 have been obtained after 150 revolutions, limited by the
chopping of the continuous beam from an electron impact ionisation source
Production and trapping of carbon clusters for absolute mass measurements at ISOLTRAP
Singly-charged carbon clusters C/sub n//sup +/ (n >or= 1) have been produced by laser-induced desorption and fragmentation of C/sub 60/ fullerenes and have been injected into and stored in the Penning trap system of the ISOLTRAP mass spectrometer at ISOLDE/CERN. The present study is the first step to extend the until now direct mass measurements at ISOLTRAP to absolute mass measurements by using clusters of /sup 12/C. (10 refs)
High-precision mass measurements of nickel, copper, and gallium isotopes and the purported shell closure at N=40
High-precision mass measurements of more than thirty neutron-rich nuclides
around the Z=28 closed proton shell were performed with the triple-trap mass
spectrometer ISOLTRAP at ISOLDE/CERN to address the question of a possible
neutron shell closure at N=40. The results, for 57,60,64-69Ni (Z=28),
65-74,76Cu (Z=29), and 63-65,68-78Ga (Z=31), have a relative uncertainty of the
order of 10^8. In particular, the masses of 72-74,76Cu have been measured for
the first time. We analyse the resulting mass surface for signs of magicity,
comparing the behavior of N=40 to that of known magic numbers and to mid-shell
behavior. Contrary to nuclear spectroscopy studies, no indications of a shell
or sub-shell closure are found for N=40.Comment: 14 figure
Evidence for a breakdown of the Isobaric Multiplet Mass Equation: A study of the A=35, T=3/2 isospin quartet
Mass measurements on radionuclides along the potassium isotope chain have
been performed with the ISOLTRAP Penning trap mass spectrometer. For 35K
T1/2=178ms) to 46K (T1/2=105s) relative mass uncertainties of 2x10-8 and better
have been achieved. The accurate mass determination of 35K (dm=0.54keV) has
been exploited to test the Isobaric Multiplet Mass Equation (IMME) for the
A=35, T=3/2 isospinquartet. The experimental results indicate a deviation from
the generally adopted quadratic form.Comment: 8 pages, 4 figure
Separated Oscillatory Fields for High-Precision Penning Trap Mass Spectrometry
Ramsey's method of separated oscillatory fields is applied to the excitation
of the cyclotron motion of short-lived ions in a Penning trap to improve the
precision of their measured mass. The theoretical description of the extracted
ion-cyclotron-resonance line shape is derived out and its correctness
demonstrated experimentally by measuring the mass of the short-lived Ca
nuclide with an uncertainty of using the ISOLTRAP Penning
trap mass spectrometer at CERN. The mass value of the superallowed beta-emitter
Ca is an important contribution for testing the conserved-vector-current
hypothesis of the electroweak interaction. It is shown that the Ramsey method
applied to mass measurements yields a statistical uncertainty similar to that
obtained by the conventional technique ten times faster.Comment: 5 pages, 4 figures, 0 table
Electric and magnetic field optimization procedure for Penning trap mass spectrometers
Significant systematic errors in high-precision Penning trap mass
spectrometry can result from electric and magnetic field imperfections. An
experimental procedure to minimize these uncertainties is presented for the
on-line Penning trap mass spectrometer ISOLTRAP, located at ISOLDE/CERN. The
deviations from the ideal magnetic and electric fields are probed by measuring
the cyclotron frequency and the reduced cyclotron frequency, respectively, of
stored ions as a function of the time between the ejection of ions from the
preparation trap and their capture in the precision trap, which influences the
energy of their axial motion. The correction parameters are adjusted to
minimize the frequency shifts.Comment: 25 pages, 9 figure
Shape oscillation of a rotating Bose-Einstein condensate
We present a theoretical and experimental analysis of the transverse monopole
mode of a fast rotating Bose-Einstein condensate. The condensate's rotation
frequency is similar to the trapping frequency and the effective confinement is
only ensured by a weak quartic potential. We show that the non-harmonic
character of the potential has a clear influence on the mode frequency, thus
making the monopole mode a precise tool for the investigation of the fast
rotation regime
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