R. C. Barber

A high resolution mass spectrometer for atomic mass determinations

A high resolution, second‐order double‐focusing mass spectrometer has been constructed for the precise determination of atomic mass differences. The instrument has a mean radius of curvature in the electrostatic analyzer of 1 m and has operated with a resolving power at the base of the peaks of ∼200 000. Details of current operation are given. The best precision achieved to date is 2.5×10−9, corresponding to ∼250 eV at M = 100 amu; typical precision is ∼5×10−9.

Precise atomic mass difference determinations between some stable isotopes of Ge, As and Se

Abstract The 1 m radius, high-resolution mass spectrometer at the University of Manitoba (“Manitoba II”) has been used to determine 11 atomic mass differences between some stable isotopes of Ge, As and Se. These values are of greater accuracy and precision than existing data. Their consistency has been checked by a major least-squares adjustment involving relevant data in the region. Results include improved S2n values for several nuclides and the energies available for the ββ decays of 76Ge and 74Se, respectively.

Energy available for the double beta-decay of 76Ge

Abstract The Manitoba II high-resolution mass spectrometer has been used to determine the atomic mass difference 76 Ge − 76 Se = 2040.71 ± 0.52 keV . This result, which is superior in precision and accuracy to previous values, should facilitate current searches for the neutrinoless double beta-decay of 76Ge.

Precise atomic mass differences using peak-matching by computer

Abstract A high resolution mass spectrometer has been used to obtain precise atomic mass differences by means of an improved peak-matching technique in which off-line computer analysis is used to determine the matching condition. The procedure retains the improved signal-to-noise ratio achieved with a signal averager, but offers improved precision in a given operating time and removes further human judgment of the matched condition. Moreover, it makes possible a comparison between the precision obtained experimentally and the theoretical limit (derived here) determined by the instrument resolution and the number of ions detected. Representative results for doublet spacings are presented for which the precision (δM/M ∼ 5 × 10−9) approaches the statistical limit.

A High Precision Ratio Potentiometer

A high precision potentiometer has been constructed to determine the ratio of two voltages presented by the University of Manitoba second order mass spectrometer. The ratio can be determined to a precision of 0.4/ΔV ppm, where ΔV is the smaller of the two voltages. ΔV is variable from a few millivolts to several volts. For ΔV>4 V the precision remains near 0.1 ppm.

Precise determination of the mass difference 76Ge76Se and a derived upper limit on the Majorana mass of the electron neutrino

Abstract Recent improvements to both the instrumentation and data analysis techniques associated with the Manitoba II high resolution mass spectrometer have led to greater precision and accuracy. The mass difference between 76 Ge and 76 Se has been redetermined to be 2038.58 (31) keV. When the new 76 Ge double-beta decay Q -value is used to examine recent spectra reported by groups searching for the characteristic sharp peak expected for neutrinoless double-beta decay, no evidence for the occurrence of such a decay is found. New upper limits can be derived for the electron neutrino mass. Reanalysis of earlier data is also presented, leading to a value for the mass difference 74 Se 74 Ge of 1209.53 (48) keV.

Energies available for the double-beta decay of 130Te and 128Te

Abstract The high resolution mass spectrometer at the University of Manitoba (Manitoba II) has been used to determine the spacings of four mass spectral doublets involving selected isotopes of Xe and Te. These mass differences were combined with existing data, in a least squares analysis, to yield “best” values for the double-beta decay Q -values for 128 Te and 130 Te, viz. 867.2±1.0 and 2528.8±1.3 keV, respectively.

Atomic mass of 180Ta, a naturally occurring isomer

Abstract The Manitoba II high-resolution mass spectrometer has been used to determine atomic mass differences between isotopes of Hf, Ta and W. The new values confirm that the 10 13 y state of 180 Ta is a naturally occurring excited state.

Direct mass measurements at the TASCC facility: The Manitoba-Chalk River on-line mass spectrometer

Abstract The Chalk River On-line Isotope Separator has been used by itself to determine the masses of unstable nuclei. The addition of a high-resolution mass spectrometer for the further analysis of beams from the separator, currently on-line at the TASCC facility at Chalk River, offers an improvement in the accuracy and sensitivity of the mass measurement system. The characteristics and projected performance of the proposed apparatus are described.

Atomic mass differences in gadolinium and terbium and the K-capture of 158Tb as an indicator of neutrino mass☆

Abstract A high-resolution mass spectrometer has been used to determine six precise atomic mass differences in gadolinium and terbium. These are combined with nuclear reaction and decay Q -values in a least-squares adjustment to give “best” values for the mass differences. The Q EC -value of 1220.64±0.83 keV for 158 Tb precludes K-capture to the 1187 keV state in 158 Gd.