Measurement of vertical atmospheric density profile from the X-ray Earth occultation of the Crab Nebula with Insight-HXMT

The X-ray Earth occultation sounding (XEOS) is an emerging method for measuring the neutral density in the lower thermosphere. In this paper, the X-ray Earth occultation (XEO) of the Crab Nebula is investigated by using the Insight-HXMT. The pointing observation data on the 30th September, 2018 recorded by the Low Energy X-ray telescope (LE) of Insight-HXMT are selected and analyzed. The extinction lightcurves and spectra during the X-ray Earth occultation process are extracted. A forward model for the XEO lightcurve is established and the theoretical observational signal for lightcurve is predicted. A Bayesian data analysis method is developed for the XEO lightcurve modeling and the atmospheric density retrieval. The posterior probability distribution of the model parameters is derived through the Markov Chain Monte Carlo (MCMC) algorithm with the NRLMSISE-00 model and the NRLMSIS 2.0 model as basis functions and the best-fit density profiles are retrieved respectively. It is found that in the altitude range of 105–200 km, the retrieved density profile is 88.8 % of the density of NRLMSISE-00 and 109.7 % of the density of NRLMSIS 2.0 by fitting the lightcurve in the energy range of 1.0–2.5 keV based on XEOS method. In the altitude range of 95–125 km, the retrieved density profile is 81.0 % of the density of NRLMSISE-00 and 92.3 % of the density of NRLMSIS 2.0 by fitting the lightcurve in the energy range of 2.5–6.0 keV based on XEOS method. In the altitude range of 85–110 km, the retrieved density profile is 87.7 % of the density of NRLMSISE-00 and 101.4 % of the density of NRLMSIS 2.0 by fitting the lightcurve in the energy range of 6.0–10.0 keV based on XEOS method. The measurements of density profiles are compared with the NRLMSISE-00/NRLMSIS 2.0 model simulations and the previous retrieval results with RXTE satellite. Finally, we find that the retrieved density profile from Insight-HXMT based on the NRLMSISE-00/NRLMSIS 2.0 models is qualitatively consistent with the previous retrieved results from RXTE. This study demonstrate that the XEOS from the X-ray astronomical satellite Insight-HXMT can provide an approach for the study of the upper atmosphere. The Insight-HXMT satellite can join the family of the XEOS. The Insight-HXMT satellite with other X-ray astronomical satellites in orbit can form a space observation network for XEOS in the future.

Examination of applicability of the ISO slab phantom as calibration phantom for the new ICRU 95 operational quantity personal dose

In this article, the proposal of ICRU/ICRP, that the ISO slab phantom should continue to be used as calibration phantom for the new ICRU Report 95 operational quantity personal dose should be legitimized by simulation and performance of experiments to determine backscatter factors on the ISO slab phantom and, in comparison, on an anthropomorphic Alderson Rando phantom. The scope of this work was restricted to the photon energy range of radiation qualities commonly used in X-ray diagnostics. For this purpose, a shadow-free diagnostic (SFD) ionization chamber was used to measure backscatter factors for X radiation in the energy range of 24 keV to 118 keV. The Monte Carlo code MCNP 6.2 was used to validate measurement results on the ISO slab phantom. Additionally, the influence of varying the SFD position on the Rando phantom on the backscatter factor was determined. Since backscatter factors on the ISO slab phantom differ only up to 5 % from those on the Rando phantom, it could be concluded that it is not necessary to develop a new phantom for calibrations in terms of personal dose. A position variation of the detector by few centimeters on the surface of the Rando phantom causes similarly large deviations and thus alone represents an equally large uncertainty contribution in practical personal dosimetry than that arising from the dissimilarity of the real human body to the ISO slab phantom.

Analyzing Transverse Momentum Spectra by a New Method in High-Energy Collisions

We analyzed the transverse momentum spectra of positively and negatively charged pions (π+ and π−), positively and negatively charged kaons (K+ and K−), protons and antiprotons (p and p¯), as well as ϕ produced in mid-(pseudo)rapidity region in central nucleus–nucleus (AA) collisions over a center-of-mass energy range from 2.16 to 2760 GeV per nucleon pair. The transverse momentum of the considered particle is regarded as the joint contribution of two participant partons which obey the modified Tsallis-like transverse momentum distribution and have random azimuths in superposition. The calculation of transverse momentum distribution of particles is performed by the Monte Carlo method and compared with the experimental data measured by international collaborations. The excitation functions of effective temperature and other parameters are obtained in the considered energy range. With the increase of collision energy, the effective temperature parameter increases quickly and then slowly. The boundary appears at around 5 GeV, which means the change of reaction mechanism and/or generated matter.

AGILE Observations of the LIGO-Virgo Gravitational-wave Events of the GWTC-1 Catalog

We present a comprehensive review of AGILE follow-up observations of the Gravitational Wave (GW) events and the unconfirmed marginal triggers reported in the first LIGO-Virgo (LV) Gravitational Wave Transient Catalog (GWTC-1). For seven GW events and 13 LV triggers, the associated 90% credible region was partially or fully accessible to the AGILE satellite at the T 0; for the remaining events, the localization region was not accessible to AGILE due to passages into the South Atlantic Anomaly, or complete Earth occultations (as in the case of GW170817). A systematic search for associated transients, performed on different timescales and on different time intervals about each event, led to the detection of no gamma-ray counterparts. We report AGILE MCAL upper limit fluences in the 400 keV–100 MeV energy range, evaluated in a time window of T 0 ± 50 s around each event, as well as AGILE GRID upper limit (UL) fluxes in the 30 MeV–50 GeV energy range, evaluated in a time frame of T 0 ± 950 s around each event. All ULs are estimated at different integration times and are evaluated within the portions of GW credible region accessible to AGILE at the different times under consideration. We also discuss the possibility of AGILE MCAL to trigger and detect a weak soft-spectrum burst such as GRB 170817A.

Offline computing resources for FCC-ee and related challenges

The international Future Circular Collider (FCC) study aims at designing $$\mathrm {pp}$$ pp , $$\mathrm {e^{+}e^{-}}$$ e + e - , $$\mathrm {e^{\pm }p}$$ e ± p colliders to be built in a new 100-km tunnel in the Geneva region. The electroweak, Higgs and top factory (FCC-ee) is designed to provide collisions at a centre-of-mass energy range between 90 (Z-pole) and 365 GeV ($$\mathrm {t}\bar{\mathrm {t}}$$ t t ¯ ) and unprecedented integrated luminosities, producing huge amounts of data which will pose significant challenges to data processing. In this study, we discuss the needs in terms of storage and CPU for the diverse phases of the project, and the possible solutions mostly based on the models developed for HL-LHC.

Impact of the gamma and neutron attenuation behaviors on the functionally graded composite materials

Gamma-ray and neutron shielding properties of the AA6082 + TiO2 (0-50wt.%) functionally graded composite materials (FGCMs) were investigated using the PSD software. The values of the mean free path (MFP), half-value layer (HVL), linear attenuation coefficients (LAC), mass attenuation coefficient (MAC), tenth-value layer (TVL), exposure buildup factors (EBF), effective atomic number (Zeff), effective conductivity (Ceff), and fast neutron removal cross-sections (FNRC) were found for the energy range between 0.015–15 MeV. The increase in the TiO2 content in the AA6082 composite material has raised the values of MAC and LAC. The calculations for the EBFs were carried out using the G-P fitting method for the energy range between 0.015–15 MeV and penetration depth of up to 40 mfp. The results revealed that HVL values ranged between 0.01-0.116 cm, TVL values ranged between 0.01-0.385 cm, FNRC values ranged between 7.918-10.017 cm-1, and Ceff values ranged between 5.67 x1010 and 9.85x1010 S/m. The AA6082 + TiO2 (50%) composite material was observed to provide the maximum photon and neutron shielding capacity since it offered the highest Zeff, MAC, and FNRC values, and the lowest HVL value. In terms of several aspects, the research is considered original. Besides contributing to several technologies including nanotechnology and space technologies, present research’s results may contribute to nuclear technology.