R-Process with Magnetized Nuclei at Dynamo-Explosive Supernovae and Neutron Star Mergers

Nucleosynthesis at latge magnetic induction levels relevant to core-collapse supernovae and neutron star mergers is considered. For respective magnetic fields of a strength up to ten teratesla, atomic nuclei exhibit a linear magnetic response due to the Zeeman effect. Such nuclear reactivity can be described in terms of magnetic susceptibility. Susceptibility maxima correspond to half-filled shells. The neutron component rises linearly with increasing shell angular momentum, while the contribution of protons grows quadratically due to considerable income from orbital magnetization. For a case j = l + 1/2, the proton contribution makes tens of nuclear magnetons and significantly exceeds the neutron values which give several units. In a case j = l − 1/2, the proton component is almost zero up to the g shell. A noticeable increase in the generation of corresponding explosive nucleosynthetic products with antimagic numbers is predicted for nuclei at charge freezing conditions. In the iron group region, new seeds are also created for the r-process. In particular, the magnetic enhancement of the volume of 44Ti isotopes is consistent with results from observations and indicates the substantial increase in the abundance of the main titanium isotope (48Ti) in the Galaxy’s chemical composition. Magnetic effects are proven to result in a shift of the r-process path towards smaller mass numbers, as well as an increase in the volume of low-mass nuclides in peaks of the r-process nuclei.

Effective exploitation of a geyser bubble-chamber equipment as a background-free fast neutron detector

The MOSCAB equipment, a geyser-concept bubble-chamber originally thought for the search of dark matter in the form of WIMPs, is employed for the detection of fast neutrons. Once the background-free operating conditions are determined such that the detector is sensitive only to neutrons, which occurs when the neutron energy threshold required for nucleation is higher than approximately 2.5 MeV, the detector response to fast neutrons is investigated using a $${^{241}}$$ 241 AmBe neutron source. Sets of detection efficiency functions are then produced via Monte Carlo simulations and post-processing, their validation being performed experimentally and discussed. Finally, the use of the detector to measure the fast neutron activity of very weak n-sources in low neutron background environments, as well as to monitor the cosmic ray variations through the neutron component of the Extensive Air Showers, is considered.

A Superfluid Perspective on Neutron Star Dynamics

As mature neutron stars are cold (on the relevant temperature scale), one has to carefully consider the state of matter in their interior. The outer kilometre or so is expected to freeze to form an elastic crust of increasingly neutron-rich nuclei, coexisting with a superfluid neutron component, while the star’s fluid core contains a mixed superfluid/superconductor. The dynamics of the star depend heavily on the parameters associated with the different phases. The presence of superfluidity brings new degrees of freedom—in essence we are dealing with a complex multi-fluid system—and additional features: bulk rotation is supported by a dense array of quantised vortices, which introduce dissipation via mutual friction, and the motion of the superfluid is affected by the so-called entrainment effect. This brief survey provides an introduction to—along with a commentary on our current understanding of—these dynamical aspects, paying particular attention to the role of entrainment, and outlines the impact of superfluidity on neutron-star seismology.

Observations of neutron radiation environment during Odyssey cruise to Mars

<p>In April 2001 Mars Odyssey spacecraft with High Energy Neutron Detector (HEND) onboard was launched to Mars. HEND/Odyssey was switched on measurement mode most of transit to Mars to monitor variations of spacecraft background and solar activity. Although HEND/Odyssey was originally designed to measure martian neutron albedo and to search for martian subsurface water/water ice, its measurements during cruise phase to Mars are applicable to evaluate spacecraft ambient radiation background. The biological impact of neutron component of this radiation background should be understood to take it into account in planning future manned missions to Mars.  We modeled spacecraft neutron spectral density and compare it with HEND measurements to estimate equivalent neutron dose rates during Odyssey cruise phase, which corresponds to the solar maxim period (23<sup>th</sup> solar cycle). It was found that Odyssey ambient neutron environment during May – September 2001 produces 6.3±1.0 mSv per day in energy range 0-15 MeV or about 23 mSv per day if extrapolated to 0-1000 MeV energy range for sun quiet intervals without Solar Particle Events (SPEs). The occurrence of SPEs may additionally increase the total neutron radiation dose accumulated for 6 months of Odyssey cruise phase up to 10%. We have also extrapolated HEND/Odyssey measurements to the different periods of solar cycle and found that during solar minimum (maximum of GCR flux) neutron equivalent rate during cruise to Mars could be as high as 40 mSv per day.  These values are in good agreement with results reported for a similar measurement made with an instrument aboard the Mars Science Laboratory during its cruise to Mars in 2011-2012.</p>

CALCULATION OF CONVERSION COEFFICIENTS FOR VOXELIZED PHANTOMS FOR CRITICALITY ACCIDENT DOSIMETRY

In the event of a criticality accident, not only the maximal doses received by the victims must be determined but it is also crucial to evaluate the doses to the different organs. With a neutron component, morphology is a key parameter in the organ dose calculation. As the simulation tools can be time consuming to proceed, especially if morphology is taken into account, for all the victims, it may be very useful to have a database of conversion coefficients that allow to obtain the organ doses from the dose measured in the dosemeter for different kinds of morphology. In this paper, we present a study performed to evaluate such conversion coefficients using voxelized anthropomorphic phantoms. These coefficients take into account two crucial parameters having an impact on the dose at the organs: the orientation of the victim in the radiation field and the morphology, that is to say the body mass index of the different victims.