Double-beta decay Q values of 130Te, 128Te, and 120Te

The double-beta decay Q values of 130Te, 128Te, and 120Te have been determined from parent-daughter mass differences measured with the Canadian Penning Trap mass spectrometer. The 132Xe-129Xe mass difference, which is precisely known, was also determined to confirm the accuracy of these results. The 130Te Q value was found to be 2527.01(32) keV which is 3.3 keV lower than the 2003 Atomic Mass Evaluation recommended value, but in agreement with the most precise previous measurement. The uncertainty has been reduced by a factor of 6 and is now significantly smaller than the resolution achieved or foreseen in experimental searches for neutrinoless double-beta decay. The 128Te and 120Te Q values were found to be 865.87(131) keV and 1714.81(125) keV, respectively. For 120Te, this reduction in uncertainty of nearly a factor of 8 opens up the possibility of using this isotope for sensitive searches for neutrinoless double-electron capture and electron capture with positron emission.Comment: 5 pages, 2 figures, submitted to Physical Review Letter

Mass measurements near the rr-process path using the Canadian Penning Trap mass spectrometer

The masses of 40 neutron-rich nuclides from Z = 51 to 64 were measured at an average precision of $\delta m/m= 10^{-7}$ using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a $^{252}$Cf spontaneous fission source in a helium gas catcher, approach the predicted path of the astrophysical $r$ process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in $\beta$-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.Comment: 15 pages, 16 figures. v2 updated, published in Physical Review

Measurement of radiative proton capture on F 18 and implications for oxygen-neon novae reexamined

Background: The rate of the F18(p,γ)Ne19 reaction affects the final abundance of the radioisotope F18 ejected from novae. This nucleus is important as its abundance is thought to significantly influence the first-stage 511-keV and continuum γ-ray emission in the aftermath of novae. No successful measurement of this reaction existed prior to this work, and the rate used in stellar models had been calculated based on incomplete information from contributing resonances. Purpose: Of the two resonances thought to provide a significant contribution to the astrophysical reaction rate, located at Ec.m.=330 and 665 keV, the former has a radiative width estimated from the assumed analog state in the mirror nucleus, F19, while the latter resonance does not have an analog state assignment, resulting in an arbitrary radiative width being assumed. As such, a direct measurement was needed to establish what role this resonance plays in the destruction of F18 at nova temperatures. This paper extends and takes the place of a previous Letter which reported the strength of the Ec.m.=665 keV resonance. Method: The DRAGON recoil separator was used to directly measure the strength of the important 665-keV resonance in this reaction, in inverse kinematics, by observing Ne19 reaction products. A radioactive F18 beam was provided by the ISAC facility at TRIUMF. R-matrix calculations were subsequently used to evaluate the significance of the results at astrophysical energies. Results: We report the direct measurement of the F18(p,γ)Ne19 reaction with the reevaluation of several detector efficiencies and the use of an updated Ne19 level scheme in the reaction rate analysis. The strength of the 665-keV resonance (Ex=7.076 MeV) is found to be an order of magnitude weaker than currently assumed in nova models. An improved analysis of the previously reported data is presented here, resulting in a slightly different value for the resonance strength. These small changes, however, do not alter the primary conclusions. Conclusions: Reaction rate calculations definitively show that the 665-keV resonance plays no significant role in the destruction of F18 at nova temperatures

The ethics of uncertainty for data subjects

Modern health data practices come with many practical uncertainties. In this paper, I argue that data subjects’ trust in the institutions and organizations that control their data, and their ability to know their own moral obligations in relation to their data, are undermined by significant uncertainties regarding the what, how, and who of mass data collection and analysis. I conclude by considering how proposals for managing situations of high uncertainty might be applied to this problem. These emphasize increasing organizational flexibility, knowledge, and capacity, and reducing hazard

The abundance of 44Ti in core collapse supernovae : Measuring the 44Ti(α, p)47V reaction

Publisher PD

The risk to relatives of patients with sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a neurodegenerative disease of motor neurons with a median survival of 2 years. Most patients have no family history of amyotrophic lateral sclerosis, but current understanding of such diseases suggests there should be an increased risk to relatives. Furthermore, it is a common question to be asked by patients and relatives in clinic. We therefore set out to determine the risk of amyotrophic lateral sclerosis to first degree relatives of patients with sporadic amyotrophic lateral sclerosis attending a specialist clinic. Case records of patients with sporadic amyotrophic lateral sclerosis seen at a tertiary referral centre over a 16-year period were reviewed, and pedigree structures extracted. All individuals who had originally presented with sporadic amyotrophic lateral sclerosis, but who subsequently had an affected first degree relative, were identified. Calculations were age-adjusted using clinic population demographics. Probands (n = 1502), full siblings (n = 1622) and full offspring (n = 1545) were identified. Eight of the siblings and 18 offspring had developed amyotrophic lateral sclerosis. The unadjusted risk of amyotrophic lateral sclerosis over the observation period was 0.5% for siblings and 1.0% for offspring. Age information was available for 476 siblings and 824 offspring. For this subset, the crude incidence of amyotrophic lateral sclerosis was 0.11% per year (0.05–0.21%) in siblings and 0.11% per year (0.06–0.19%) in offspring, and the clinic age-adjusted incidence rate was 0.12% per year (0.04–0.21%) in siblings. By age 85, siblings were found to have an 8-fold increased risk of amyotrophic lateral sclerosis, in comparison to the background population. In practice, this means the risk of remaining unaffected by age 85 dropped from 99.7% to 97.6%. Relatives of people with sporadic amyotrophic lateral sclerosis have a small but definite increased risk of being affected

Direct measurement of resonance strengths in S 34 (α,γ) Ar 38 at astrophysically relevant energies using the DRAGON recoil separator

Background: Nucleosynthesis of mid-mass elements is thought to occur under hot and explosive astrophysical conditions. Radiative α capture on S34 has been shown to impact nucleosynthesis in several such conditions, including core and shell oxygen burning, explosive oxygen burning, and type Ia supernovae. Purpose: Broad uncertainties exist in the literature for the strengths of three resonances within the astrophysically relevant energy range (ECM=1.94-3.42MeV at T=2.2GK). Further, there are several states in Ar38 within this energy range which have not been previously measured. This work aimed to remeasure the resonance strengths of states for which broad uncertainty existed as well as to measure the resonance strengths and energies of previously unmeasured states. Methods: Resonance strengths and energies of eight narrow resonances (five of which had not been previously studied) were measured in inverse kinematics with the DRAGON facility at TRIUMF by impinging an isotopically pure beam of S34 ions on a windowless He4 gas target. Prompt γ emissions of de-exciting Ar38 recoils were detected in an array of bismuth germanate scintillators in coincidence with recoil nuclei, which were separated from unreacted beam ions by an electromagnetic mass separator and detected by a time-of-flight system and a multianode ionization chamber. Results: The present measurements agree with previous results. Broad uncertainty in the resonance strength of the ECM=2709keV resonance persists. Resonance strengths and energies were determined for five low-energy resonances which had not been studied previously, and their strengths were determined to be significantly weaker than those of previously measured resonances. Conclusions: The five previously unmeasured resonances were found not to contribute significantly to the total thermonuclear reaction rate. A median total thermonuclear reaction rate calculated using data from the present work along with existing literature values using the STARLIB rate calculator agrees with the NON-SMOKER statistical model calculation as well as the REACLIB and STARLIB library rates at explosive and nonexplosive oxygen-burning temperatures (T=3-4GK and T=1.5-2.7GK, respectively)

Study of the Ti-44(alpha, p)V-47 reaction and implications for core collapse supernovae

Peer reviewe