Search NASA⌕ Search

Engineering topics

Dillmann, I.

Publications and source records attributed to Dillmann, I..

45 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Conceptual design of a hybrid neutron-gamma detector for study of β-delayed neutrons at the RIB facility of RIKEN

Here, the conceptual design of the BRIKEN neutron detector at the radioactive ion beam factory (RIBF) of the RIKEN Nishina Center is reported. The BRIKEN setup is a complex system aimed at detecting heavy-ion implants, β particles, γ rays and β-delayed neutrons. The whole setup includes the Advanced Implantation Detection Array (AIDA), two HPGe Clover detectors and up to 166 3 He-filled counters embedded in a high-density polyethylene moderator. The design is quite complex due to the large number and different types of 3 He-tubes involved and the additional constraints introduced by the ancillary detectors for charged particles and γ rays. This article reports on a novel methodology developed for the conceptual design and optimisation of the 3 He-counter array, aiming for the best possible performance in terms of neutron detection. The algorithm is based on a geometric representation of two selected detector parameters of merit, namely, the average neutron detection efficiency and the efficiency flatness as a function of a reduced number of geometric variables. The response of the neutron detector is obtained from a systematic Monte Carlo simulation implemented in GEANT4. The robustness of the algorithm allowed us to design a versatile detection system, which operated in hybrid mode includes the full neutron counter and two clover detectors for high-precision gamma spectroscopy. In addition, the system can be reconfigured into a compact mode by removing the clover detectors and re-arranging the 3 He tubes in order to maximize the neutron detection performance. Both operation modes shows a rather flat and high average efficiency. In summary, we have designed a system which shows an average efficiency for hybrid mode ( 3 He tubes + clovers) of 68.6% and 64% for neutron energies up to 1 and 5 MeV, respectively. For compact mode (only 3 He tubes), the average efficiency is 75.7% and 71% for neutron energies up to 1 and 5 MeV, respectively. The performance of the BRIKEN detection system has been also quantified by means of Monte Carlo simulations with different neutron energy distributions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Proton Distribution Radii of 12-19 C Illuminate Features of Neutron Halos

We report proton radii of 12-19 C densities derived from first accurate charge changing cross section measurements at 900A MeV with a carbon target. A thick neutron surface evolves from ~0.5 fm in 15 C to ~1 fm in 19 C. Also, the halo radius in 19 C is found to be 6.4±0.7 fm as large as 11 Li. Ab initio calculations based on chiral nucleon-nucleon and three-nucleon forces reproduce the radii well.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Evaluation of Beta-Delayed Neutron Emission Probabilities and Half-Lives for Z = 2–28

We present an evaluation and compilation of β-delayed neutron probabilities and half-lives for nuclei in the region Z = 2–28 ({sup 8}He–{sup 80}Ni). This article includes the recommended values of these quantities as well as a compiled list of experimental measurements for each nucleus in the region for which β-delayed neutron emission is possible. The literature cut-off for this work is August 15{sup th}, 2015. Some notable cases as well as new standards for β-delayed neutron measurements in this mass region are also discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

First Compilation and Evaluation of Beta-Delayed Neutron Emission Probabilities and Associated Half-Lives for A ≤ 72 Nuclei

A comprehensive compilation and evaluation of beta-delayed neutron (β{sup −}n) emission probabilities, P{sub n}, and associated half-lives for A ≤ 72 nuclei has been performed for the first time. The recommended values have been used to analyze the systematics of β{sup −}n emission in this region. The ratio P{sub n}/T{sub 1/2} is better correlated with the Q-value of the β{sup −}n decay mode than the previously proposed Kratz-Herrmann Formula (KHF). The recommended values are also compared with theoretical quasi-particle random phase approximation (QRPA) calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

KADoNiS-p: The Astrophysical p-Process Database

The KADoNiS-p project is an online database for cross sections relevant to the p-process. All existing experimental data was collected and reviewed. With this contribution a user-friendly database using the KADoNiS (Karlsruhe Astrophysical Database of Nucleosynthesis in Stars) framework is launched, including all available experimental data from (p,γ), (p,n), (p,α), (α,γ), (α,n) and (α,p) reactions in or close to the respective Gamow window with cut-off date of August 2012 ( (http://www.kadonis.org/pprocess))

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

Neutron-induced fission cross section measurement of 233 U, 241 Am and 243 Am in the energy range 0.5 MeV En 20 MeV at n TOF at CERN

Neutron-induced fission cross section measurements of 233U, 243Am and 241Am relative to 235U have been carried out at the neutron time-of-flight facility n TOF at CERN. A fast ionization chamber has been employed. All samples were located in the same detector; therefore the studied elements and the reference 235U target are subject to the same neutron beam.

Belloni, F.↗
DOE OSTI2012

Resonance neutron-capture cross sections of stable magnesium isotopes and their astrophysical implications

We have measured the neutron capture cross sections of the stable magnesium isotopes {sup 24,25,26}Mg in the energy range of interest to the s process using the neutron time-of-flight facility n{_}TOF at CERN. Capture events from a natural metal sample and from samples enriched in {sup 25}Mg and {sup 26}Mg were recorded using the total energy method based on C{sub 6}{sup 2}H{sub 6} detectors. Neutron resonance parameters were extracted by a simultaneous resonance shape analysis of the present capture data and existing transmission data on a natural isotopic sample. Maxwellian-averaged capture cross sections for the three isotopes were calculated up to thermal energies of 100 keV and their impact on s-process analyses was investigated. At 30 keV the new values of the stellar cross section for {sup 24}Mg, {sup 25}Mg, and {sup 26}Mg are 3.8 {+-} 0.2 mb, 4.1 {+-} 0.6 mb, and 0.14 {+-} 0.01 mb, respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗