The 14C(n,g) cross section between 10 keV and 1 MeV

The neutron capture cross section of 14C is of relevance for several nucleosynthesis scenarios such as inhomogeneous Big Bang models, neutron induced CNO cycles, and neutrino driven wind models for the r process. The 14C(n,g) reaction is also important for the validation of the Coulomb dissociation method, where the (n,g) cross section can be indirectly obtained via the time-reversed process. So far, the example of 14C is the only case with neutrons where both, direct measurement and indirect Coulomb dissociation, have been applied. Unfortunately, the interpretation is obscured by discrepancies between several experiments and theory. Therefore, we report on new direct measurements of the 14C(n,g) reaction with neutron energies ranging from 20 to 800 keV

Search for superradiant emission states in nuclear isomer crystals

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective was to verify the stimulated emission of gamma rays from {sup 125m}Te, as claimed by Russian scientists. The reported cross section for stimulated emission was sufficiently large to allow gain in a single-pass gamma-ray laser. The stimulated emission of gamma rays from a nuclear isomer is expected to result in collinear photons and, therefore, should be observable as a sum peak in the gamma-ray spectrum. Skorobogatov and Dzevitskii reported an increase of an order of magnitude in the sum peak (218.56 keV) when a sample of beryllium telluride containing {sup 125m}Te was cooled from room temperature to near-liquid-helium temperatures. The authors have repeated their experiment and have observed no increase in the sum peak above accidental summing. The upper limit for the stimulated-emission cross section based on the three-standard-deviation statistical error is 6.8 x 10 {sup {minus}21} cm{sup 2}. This result is one order of magnitude lower than the cross section reported by Skorobogatov and Dzevitskii. The cross section would not allow gain in a single-pass gamma-ray laser. Their results support the position of Baldwin and Solem rather than that of Kamenov

First bromine doped cryogenic implosion at the National Ignition Facility

We report on the first experiment dedicated to the study of nuclear reactions on dopants in a cryogenic capsule at the National Ignition Facility (NIF). This was accomplished using bromine doping in the inner layers of the CH ablator of a capsule identical to that used in the NIF shot N140520. The capsule was doped with 3$\times$10$^{16}$ bromine atoms. The doped capsule shot, N170730, resulted in a DT yield that was 2.6 times lower than the undoped equivalent. The Radiochemical Analysis of Gaseous Samples (RAGS) system was used to collect and detect $^{79}$Kr atoms resulting from energetic deuteron and proton ion reactions on $^{79}$Br. RAGS was also used to detect $^{13}$N produced dominantly by knock-on deuteron reactions on the $^{12}$C in the ablator. High-energy reaction-in-flight neutrons were detected via the $^{209}$Bi(n,4n)$^{206}$Bi reaction, using bismuth activation foils located 50 cm outside of the target capsule. The robustness of the RAGS signals suggest that the use of nuclear reactions on dopants as diagnostics is quite feasible

Preparation of radioactive rare earth targets for neutron capture study

The understanding of thc details of nucleosynthesis in stars remains a great challenge. Though the basic mechanisms governing the processes have been known since the pioneering work of Burbidge, Burbidge, Fowler and Hoyle (l), we are now evolving into a condition where we can ask more specific questions. Of particular interest are the dynamics of the s ('slow') process. In this process the general condition is one in which sequential neutron captures occur at time scales long compared with the beta decay half lives of the capturing nuclides. The nucleosynthesis period for C or Ne burning stellar shells is believed to be in the year to few year time frame (2). This means that radionuclides with similar half lives to this burning period serve as 'branch point' nuclides. That is, there will be a competition between a capture to the next heavier isotope and a beta decay to the element of nexl higher atomic number. By understanding the abundances of these competing reactions we can learn about the dynamics of the nucleosynthesis process in the stellar medium. Crucial to this understanding is that we have a knowledge of the underlying neutron reaction cross sections on these unstable nuclides in the relevant stellar energy regions (neutrons of 0.1-100 KeV). Tm (1.9 years) and ls'Sm (90 ycws) have decay properties that permit their handling in an open fume hood. These Iwo were therefore selected to be the first radionuclides for neutron capture study in what will be an ongoing effort

Social inequalities and correlates of psychotropic drug use among young adults: a population-based questionnaire study

<p>Abstract</p> <p>Background</p> <p>Use of psychotropic drugs is widespread in Europe, and is markedly more common in France than elsewhere. Young adults often fare less well than adolescents on health indicators (injury, homicide, and substance use). This population-based study assessed disparities in psychotropic drug use among people aged 18–29 from different socio-occupational groups and determined whether they were mediated by educational level, health status, income, health-related behaviours, family support, personality traits, or disability.</p> <p>Methods</p> <p>A total of 1,257 people aged 18–29, randomly selected in north-eastern France completed a post-mailed questionnaire covering sex, date of birth, height, weight, educational level, occupation, smoking habit, alcohol abuse, income, health-status, diseases, reported disabilities, self-reported personality traits, family support, and frequent psychotropic medication for tiredness, nervousness/anxiety or insomnia. The data were analyzed using the adjusted odds ratios (ORa) computed with logistic models.</p> <p>Results</p> <p>Use of psychotropic drugs was common (33.2%). Compared with upper/intermediate professionals, markedly high odds ratios adjusted for sex were found for manual workers (2.57, 95% CI 1.02–6.44), employees (2.58, 1.11–5.98), farmers/craftsmen/tradesmen (4.97, 1.13–21.8), students (2.40, 1.06–5.40), and housewives (3.82, 1.39–10.5). Adjusting for all the confounders considered reduced the estimates to a pronounced degree for manual workers (adjusted OR 1.49, non-significant) but only slightly for the other socio-occupational groups. The odds ratio for unemployed people did not reach statistical significance. The significant confounders were: sex, not-good health status, musculoskeletal disorders and other diseases, being worried, nervous or sad, and lack of family support (adjusted odds ratios between 1.60 and 2.50).</p> <p>Conclusion</p> <p>There were marked disparities among young adults from different socio-occupational groups. Sex, health status, musculoskeletal diseases, family support, and personality traits were related to use of psychotropic drugs. These factors mediated the higher risk strongly among manual workers and slightly among the other groups.</p