Fri·Jun 17, 2016Friday·June 17, 2016

1. 01*

   Improved limit on the ${}^{225}$Ra electric dipole moment

   Michael Bishof🇺🇸 · Richard H. Parker🇺🇸 · Kevin G. Bailey🇺🇸 · John P. Greene🇺🇸 · Roy J. Holt🇺🇸 · Mukut R. Kalita🇮🇳 · Wolfgang Korsch🇺🇸 · Nathan D. Lemke🇺🇸 · Zheng-Tian Lu🇺🇸 · Peter Mueller🇺🇸 · Thomas P. O'Connor🇺🇸 · Jaideep T. Singh🇺🇸 · Matthew R. Dietrich🇺🇸

   Background: Octupole-deformed nuclei, such as that of ${}^{225}$Ra, are expected to amplify observable atomic electric dipole moments (EDMs) that arise from time-reversal and parity-violating interactions in the nuclear medium. In 2015, we reported the first "proof-of-principle" measurement of the ${}^{225}$Ra atomic EDM. Purpose: This work reports on the first of several experimental upgrades to improve the statistical sensitivity of our ${}^{225}$Ra EDM measurements by orders of magnitude and evaluates systematic effects that contribute to current and future levels of experimental sensitivity. Method: Laser-cooled and trapped ${}^{225}$Ra atoms are held between two high voltage electrodes in an ultra high vacuum chamber at the center of a magnetically shielded environment. We observe Larmor precession in a uniform magnetic field using nuclear-spin-dependent laser light scattering and look for a phase shift proportional to the applied electric field, which indicates the existence of an EDM. The main improvement to our measurement technique is an order of magnitude increase in spin precession time, which is enabled by an improved vacuum system and a reduction in trap-induced heating. Results: We have measured the ${}^{225}$Ra atomic EDM to be less than $1.4\times 10^{-23}$ $e$ cm (95% confidence upper limit), which is a factor of 36 improvement over our previous result. Conclusions: Our evaluation of systematic effects shows that this measurement is completely limited by statistical uncertainty. Combining this measurement technique with planned experimental upgrades we project a statistical sensitivity at the $1\times 10^{-28}$ $e$ cm level and a total systematic uncertainty at the $4\times 10^{-29}$ $e$ cm level.

   nucl-exphysics.atom-phPRC(2016)·133 citations
2. 02*

   What is the theoretical time precision achievable using a dCFD algorithm ?

   Eric Delagnes🇫🇷

   The time precision achievable using standard analog methods is well known. Several expressions for timing methods using digitized signals have been recently proposed in workshops, conferences or training courses. Most of them are only partially exact. This paper presents a comprehensive calculation of the timing precision for algorithms using digital treatment of digitized signal to mimic analog discriminator-based methods. The results of these calculations are discussed for various cases of correlation between samples.

   ↳ physics.ins-dethep-exnucl-ex7 citations
3. 03*

   Conceptual design of the BRIKEN detector: A hybrid neutron-gamma detection system for nuclear physics at the RIB facility of RIKEN

   A. Tarifeño-Saldivia · J. L. Tain · C. Domingo-Pardo · F. Calviño · G. Cortes · V. H. Phong · A. Riego · The BRIKEN collaboration

   BRIKEN is a complex detection system to be installed at the RIB-facility of the RIKEN Nishina Center. It is aimed at the detection of heavy-ion implants, $\beta$-particles, $\gamma$-rays and $\beta$-delayed neutrons. The whole detection setup involves the Advanced Implantation Detection Array (AIDA), two HPGe Clover detectors and a large set of 166 counters of 3He embedded in a high-density polyethylene matrix. This article reports on a novel methodology developed for the conceptual design and optimisation of the 3He-tubes array, aiming at the best possible performance in terms of neutron detection. The algorithm is based on a geometric representation of two selected parameters of merit, namely, average neutron detection efficiency and efficiency flatness, as a function of a reduced number of geometric variables. The response of the detection system itself, for each configuration, is obtained from a systematic MC-simulation implemented realistically in Geant4. This approach has been found to be particularly useful. On the one hand, due to the different types and large number of 3He-tubes involved and, on the other hand, due to the additional constraints introduced by the ancillary detectors for charged particles and gamma-rays. Empowered by the robustness of the algorithm, we have been able to design a versatile detection system, which can be easily re-arranged into a compact mode in order to maximize the neutron detection performance, at the cost of the gamma-ray sensitivity. In summary, we have designed a system which shows, for neutron energies up to 1(5) MeV, a rather flat and high average efficiency of 68.6%(64%) and 75.7%(71%) for the hybrid and compact modes, respectively. The performance of the BRIKEN system has been also quantified realistically by means of MC-simulations made with different neutron energy distributions.

   ↳ physics.ins-detnucl-exJINST(2017)·35 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.