Thu·Aug 11, 2016Thursday·August 11, 2016

1. 01*

   Recent Experimental Results on Nuclear Cluster Physics

   C. Beck (IPHC Strasbourg)🇫🇷

   Knowledge on nuclear cluster physics has increased considerably since the pioneering discovery of 12C+12C resonances half a century ago and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. The occurrence of "exotic" shapes and/or Bose-Einstein alpha condensates in light N-Z alpha-conjugate nuclei is investigated. Evolution of clustering from stability to the drip-lines examined with clustering aspects persisting in light neutron-rich nuclei is consistent with the extension of the "Ikeda-diagram" to non alpha-conjugate nuclei.

   nucl-exnucl-thJ.Phys.Conf.Ser.(2017)·5 citations
2. 02*

   Nuclear charge radii: Density functional theory meets Bayesian neural networks

   Raditya Utama · Wei-Chia Chen🇺🇸 · Jorge Piekarewicz🇺🇸

   The distribution of electric charge in atomic nuclei is fundamental to our understanding of the complex nuclear dynamics and a quintessential observable to validate nuclear structure models. We explore a novel approach that combines sophisticated models of nuclear structure with Bayesian neural networks (BNN) to generate predictions for the charge radii of thousands of nuclei throughout the nuclear chart. A class of relativistic energy density functionals is used to provide robust predictions for nuclear charge radii. In turn, these predictions are refined through Bayesian learning for a neural network that is trained using residuals between theoretical predictions and the experimental data. Although predictions obtained with density functional theory provide a fairly good description of experiment, our results show significant improvement (better than 40%) after BNN refinement. Moreover, these improved results for nuclear charge radii are supplemented with theoretical error bars. We have successfully demonstrated the ability of the BNN approach to significantly increase the accuracy of nuclear models in the predictions of nuclear charge radii. However, as many before us, we failed to uncover the underlying physics behind the intriguing behavior of charge radii along the calcium isotopic chain.

   ↳ nucl-thnucl-exJ.Phys.G(2016)·136 citations
3. 03*

   High-rate axial-field ionization chamber for particle identification of radioactive beams

   J. Vadas🇺🇸 · Varinderjit Singh🇺🇸 · G. Visser🇺🇸 · A. Alexander🇺🇸 · S. Hudan🇺🇸 · J. Huston🇺🇸 · B. B. Wiggins🇺🇸 · A. Chbihi🇫🇷 · M. Famiano🇺🇸 · M.M. Bischak🇺🇸 · R. T. deSouza🇺🇸

   The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV/A) the detector presents only three 0.5 $\mu$m/cm${}^2$ foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate. Tests with an $\alpha$ source establish the detector energy resolution as $\sim$8 $\%$ for an energy deposit of $\sim$3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A ${}^{39}$K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3 x 10${}^5$ ions/s the energy resolution has degraded to 14% with a pileup of 12%. The good energy resolution of this detector at rates up to 3 x 10${}^5$ ions/s makes it an effective tool in the characterization of low-energy radioactive beams.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2016)·3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.