Electromagnetic Properties of Indium Isotopes Elucidate the Doubly Magic Character of ¹⁰⁰Sn

Understanding the nuclear properties in the vicinity of 100Sn – suggested to be the heaviest doubly magic nucleus with equal proton number Z and neutron number N – has been a long-standing challenge for experimental and theoretical nuclear physics. In particular, contradictory experimental evidence exists regarding the role of nuclear collectivity in this region of the nuclear chart. Here, we provide additional evidence for the doubly-magic character of 100Sn by measuring the ground-state electromagnetic moments and nuclear charge radii of indium (Z = 49) isotopes as N approaches 50 from above using precision laser spectroscopy. Our results span almost the complete range between the two major neutron closed shells at N = 50 and N = 82 and reveal parabolic trends as a function of the neutron number, with a clear reduction toward these two neutron closed-shells. A detailed comparison between our experimental and numerical results from two complementary nuclear many-body frameworks, density functional theory and ab initio methods, exposes deficiencies in nuclear models and establishes a benchmark for future theoretical developments.<br/

Ground-level neutron monitoring survey over the United Kingdom

Space weather events impose a threat on critical infrastructures such as electrical power grids, global navigation satellite systems, satellite operations, aviation technology and radio communication channels at various frequencies. We present an update on a new ground-level neutron monitor (NM-2023) which will be used to monitor space weather events, namely the detection and alert of ground-level enhancement (GLE) events. The NM-2023 will provide data to entities such as the United Kingdom Meteorological Office, the Neutron Monitor Database (NMDB), and the University of Surrey. We also report on a neutron monitoring survey conducted using a pair of subsystems deployed at several UK field sites. The data collected by these subsystems will be compared across the various sites, to data collected using a partial NM-2023 instrument and with data from established NMDB instruments with similar geomagnetic cutoff rigidities

Use of a commercial neutron counting module to validate neutron-particle transport code simulation of a new cosmic radiation neutron monitor design

This paper reports on one of several experiments used to validate MCNP models and processes employed to define a cosmic radiation (CR) neutron source and benchmark to optimise a new ground level neutron monitor (NM) design. The new NM design aims to be more compact, non-toxic and capable of producing comparable counting efficiencies to the NM-64; a monitor standardised in 1964 and which makes up most of the established global network. A broad-energy neutron monitor, the N50L, originally designed for nuclear material accountancy and safeguards, is used to provide primary data in support of our new NM design. Ambient count rate data from the N50L were acquired from it bare and inside a lead (Pb) sarcophagus to boost the neutron signal. Measured data were compared with calculations made using a Monte Carlo N-Particle (MCNP) transport code model of the setup. The calculated compared to the measured count rate for the monitor inside the Pb sarcophagus are in good agreement with a ratio close to one. However, overpredictions (by almost a factor of two) of the calculated rate for the bare monitor suggest inadequacies of the model for high-energy physics. Pressure corrected count rate data were also compared with data from several existing NM-64s over the same period. Our data are in good agreement with variations observed by these existing monitors on the global network. The N50L uses helium-3 (3He) counters and roughly equates to about 1/17th of the proposed final NM design in terms of detector volume. Scaled count rates from the N50L are within 73% of the rates derived from an NM-64 for a similar latitude, geomagnetic cutoff rigidity and altitude, and differs b