Extended Energy Range Research Articles

Investigation of gamma-ray attenuation coefficients for solid boronized 304L stainless steel

In this study, mass attenuation coefficient (μ/ρ) and half value layer (HVL) at Eu-152 and Co-60 energies were used in measuring attenuation coefficients of the solid boronized AISI 304L stainless steel at 950 °C for 2, 4, 6 and 8 h. The experimental mass attenuation coefficients, μ/ρ, and HVL for these materials were compared to theoretical values obtained with WinXCOM. At the same time a new boriding agent (Baybora®-1) also developed for solid boriding method was used. The effects of boron layer size on radiation attenuation of boronized composites were evaluated in relation with gamma-ray transmission and the results of the experiments were interpreted. It could be understood that increased of boron layer in AISI 304L causes of increases in the attenuation coefficient values. The measured values agree with the theoretical values. The interaction parameters for selected samples have been computed and provided in the extended energy range 10−3–104 MeV. The shielding properties prepared stainless steel have also been compared with standard concretes as well as with the standard shielding stainless steel. It is found that the prepared stainless steel is the better shielding substitute to the conventional concretes as well as other standard shielding stainless steel. So, submicron size boron layer used composite materials are more convenient than micron size boron used composite materials as radiation shielding materials for nuclear applications.

Pressure dependence of structural, elastic, electronic, thermodynamic, and optical properties of van der Waals-type NaSn2P2 pnictide superconductor: Insights from DFT study

NaSn2P2 is a recently discovered superconducting system belonging to a particular class of materials with van der Waals (vdW) structure. There is enormous interest in vdW compounds because of their intriguing electrical, optical, chemical, thermal, and superconducting state properties. We have studied the pressure dependent structural, thermo-physical, electronic band structure, and superconducting state properties of this quasi-two dimensional system in details for the first time via ab initio technique. The optical properties are also investigated for different electric field polarizations for the first time. Structural, electronic, and optical properties were explored via density functional theory (DFT) calculations. Thermal properties were investigated using the quasi-harmonic Debye model. NaSn2P2 is found to be mechanically stable in the pressure range 0–3.0 GPa. The elastic anisotropy indices point towards high level of mechanical and bonding anisotropy in NaSn2P2 consistent with its highly layered structure. The elastic constants, moduli, and Debye temperature (θD) show non-monotonic variation with pressure, particularly close to 1.0 GPa. The pressure dependent superconducting transition temperature, Tc, of NaSn2P2 is predicted to vary strongly with the pressure dependent variation of θD. The electronic energy dispersion curves, E(k), reveal high level of direction dependence; the effective masses of charge carries are particularly high for the out-of-plane (c-axis) charge transport. The optical parameters compliment the underlying electronic energy density of states features and are weakly dependent on the polarization of the incident electric field. The reflectivity of NaSn2P2 is very high in the visible region and remains quite high and non-selective over an extended energy range in the ultraviolet region. The absorption coefficient is also high in the mid-ultraviolet band. All these optical features render NaSn2P2 suitable for optoelectronic device applications.

Extended Validity of the Energy Dependent Scattering Kernel within the Boltzmann Transport Equation

The scattering term within the Boltzmann equation was for decades approximated either through the Legendre polynomial for deterministic solvers or by /free gas model approach for Monte Carlo solvers. This, to some extent, inaccurate approach led to the assumption in several cases that the scattering term can be further “tuned” to simplify complex mathematical solver of the transport equation, mainly by reducing considerably the computation time, assuming no consequences on the physical results. The introduction of the resonant dependent scattering kernel to MONTE CARLO code and in particular the experimental validation within the resolved resonance range for Uranium and Thorium, in RPI (Renselear Polytechnic Institute), pointed out that the scattering term cannot be taken as a second order negligible term, but rather should be accurately regarded for any solution of the transport equation. Corollary to the considerable high impact of that “physical” scattering kernel, this study extends its importance beyond the epithermal resolved resonance range and aims to proof that the scattering kernel can and should be accurately dealt also at higher energies at least up to about several tens of keV. Moreover, in the debate between the purely quantum mechanics treatment known as the Optical Model -OM and the Doppler broadening based classical approach, the latter seems to be correct for this extended energy range. Strictly speaking, Newton’s Laws for the scattering kernel evaluation remain intact, yet in accordance to their quantum mechanics based integrated scattering cross section values as was shown for example by the well-known fundamental Breit Wigner formula.

Ultra-long gamma-ray bursts and ultra-soft gamma-ray bursts

Ultra-long gamma-ray bursts (ULGRBs) are special gamma-ray bursts (GRBs) lasting for several hours. However, their released energy is comparable with that of typical long GRBs. The observed flux of ULGRBs is typically low, making them hard to detect, and therefore, only a small sample of ULGRBs have been collected. Observationally, it remains a question of whether ULGRBs are a new population or just a tail distribution of long GRBs. Ultra-soft gamma-ray bursts (USGRBs) refer to another type of special GRBs with soft energy spectra. USGRBs include X-ray flashes (XRFs) and X-ray rich GRBs (XRRs). In this paper, we first review the observations and theoretical studies of ULGRBs and USGRBs and discuss their possible explosion mechanisms and progenitor models. We then consider the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM), which has some advantages in observing ULGRBs and USGRBs. The GECAM has a full-sky FOV, high sensitivity, good positioning accuracy, extensive energy range coverage (6 keV–5 MeV), and lower energy threshold, making it ideal to observe ULGRBs and USGRBs. Based on the provided GECAM response matrix and background simulation data, we simulate the energy spectrum of typical ULGRB (GRB 130925A) and USGRB (XRR 050525A). We then compare those spectra with those observed by Fermi/GBM and Swift/BAT. We found that the GECAM can provide a more accurate energy spectrum. Furthermore, we also discuss the detection rate of ULGRBs and USGRBs observed by GECAM. We found that GECAM should detect ~20 ULGRBs, ~50 XRFs, and ~300 XRRs per year.

Linear dichroism infrared resonance in overdoped, underdoped, and optimally doped cuprate superconductors

By measuring the polarization changes in THz, infrared, and visible radiation over an extended energy range (3-2330 meV), we observe symmetry-breaking in cuprate high temperature superconductors over wide energy, doping, and temperature ranges. We measure the polarization rotation and ellipticity of transmitted radiation though thin films as the sample is rotated. We observe a two-fold rotational symmetry in the Faraday angle, which is associated with linear dichroism (LD) and occurs when electromagnetic radiation polarized along one direction is absorbed more strongly than radiation polarized in the perpendicular direction. Such polarization anisotropies can be generally associated with symmetry breakings. We measure the amplitude of the LD signal and study its temperature, energy, and doping dependence. The LD signal shows a resonant behavior with a peak in the few hundred meV range, which is coincident with the mid-infrared optical feature that has been associated with the formation of the pseudogap state. The strongest LD signal is found in under-doped films, although it is also observed in optimally- and over-doped samples. The LD signal is consistent with nematic charge ordering as well as novel magnetoelectric effects.

Improving the accuracy of gamma radiation measurements in radiation monitoring

The article suggests the use of unmanned vehicles for monitoring the radiation situation. The paper analyzes data on the radiation situation at nuclear power plants and identifies the main factors of external radiation exposure. It is shown that the existing means of measuring gamma radiation in real conditions have to be used in an extended energy range. To improve the measurement accuracy while simultaneously expanding the energy range of gamma radiation levels, a method is proposed for automatically compensating for additional error due to the energy dependence of the sensitivity over the entire measurement range in real time by introducing pre-calculated correction coefficients. Simulation of the proposed circuit design is performed.

Excitation effect of d electrons on the electronic energy loss of energetic protons colliding with a Zn atom

By using a nonequilibrium approach based on real-time time-dependent density-functional theory combined with molecular dynamics simulations, the effects of $d$-electron excitation on the electronic energy loss of energetic protons colliding with atomic zinc target are studied. The results show that the semicore electrons play a crucial role in the electronic energy loss in an extended energy range. In the low-energy regime, the electronic energy loss displays the threshold effect before it is proportional to velocity, which is explained by the quantization of the energy levels of zinc atom, and the charge transfer contributes greatly to the electronic energy loss, especially at 0.1 a.u. In addition, due to the electron resonance excitation, the number of excited electrons and charge transfer is significantly increased at the velocity thresholds for electron excitation. In the high-energy regime, the electronic energy loss is greatly enhanced as the the impact parameter decreases, which is ascribed to the excitation of $3d$ electrons. We also calculated the stopping cross section for energetic protons colliding with atomic zinc, which is in a good agreement with the experimental values in both low- and high-velocity regimes.

ALD grown polycrystalline HfO2 dielectric layer on (−2 0 1) β-Ga2O3 for MOS capacitors

Polycrystalline HfO2 dielectrics grown on (−2 0 1) beta-gallium oxide (β-Ga2O3) using high temperature ALD process is investigated. A low capacitance–voltage (C-V) hysteresis of <60 mV is obtained, and the high quality interface is verified via the temperature-dependent C-V characterizations, showing low interface trap density (Dit < 1.3 × 1012 cm−2eV−1) distributions over the extended energy range. The proposed polycrystalline HfO2/(−2 0 1) β-Ga2O3 MOS structure can be an attractive candidate for β-Ga2O3 based MOSFET devices.

237Np reactions with fast neutrons: a phenomenological study

Neptunium presents various opportunities as nuclear fuel, especially in deep–space mission power generators. As it is part of the nuclear spent fuel in PWR, waste management concerns due to 237Np long α-emitting half-life have attracted some attention recently. The scarcity of experimental data in the fast neutron energy range highlights the necessity to investigate the radiative neutron capture and neutron–induced fission cross sections of this radioisotope. In the present work, statistical modeling of these reactions is performed using TALYS in an extended range of neutron energies between 10 keV and 20 MeV. In total, 72 different combinations of code parameters were selected to study the level density and γ-strength function dependence of the cross section in 238Np. Preequilibrium and compound nucleus formation phenomena are also examined. Theoretical calculations are compared to available experimental total cross section data found in literature in an attempt to investigate any discrepancies between experiment and theory and validate statistical uncertainties.

Injected coherence in the tunneling of ultracold atoms through a two-photon mazer in the squeezed vacuum and coherent field distributions

We examine the traversal aspect of ultracold two-level atoms through a high-quality two-photon mazer with squeezed vacuum and coherent field distributions. Here the net cavity potential is constituted by the coherent addition of multiple barriers and well potentials, which is quite different from the potential offered by a cavity in the Fock or vacuum state. For squeezed vacuum and coherent field distributions, one gets different phase times ( t p h ) for different modes of the distribution, which are then averaged by taking the weighted mean on the t p h over the n-dependent transmission probability. It is found that the nature, intensity of the field, and injected coherence of the incident atoms have a decisive role in controlling peak values and sub- and superclassical traversals of the tunneling atoms. For two of the system’s dressed states ( | Φ b 0 ⟩ , | Φ b 1 ⟩ ), the cavity offers reflectionless transmission, as the atoms experience zero potential due to the dark state formation. Moreover, for a somewhat intense cavity field, mazer action (scattering-type behavior) may be obtained for an extended range of energies due to increased cavity potential in the course of atom–cavity interaction.

Extension of the Energy Range Accessible with a TES Using Bath Temperature Variations

The energy range of transition-edge sensor (TES) X-ray microcalorimeters with a multiplexed readout depends upon the width and shape of the TES superconducting transition, and also on the dynamic range of the readout. In many detector systems, the multiplexed readout slew rate capability will be the limiting factor for the energy range. In these cases, if we are willing to accept some energy resolution degradation, we can significantly extend the energy range by increasing the bath temperature of operation, essentially creating a second “extended energy range” mode of operation. For example, if we require the very highest energy resolution up to 7 keV, and wish to optimize the design up to this energy, for some measurements it could be very beneficial to have a mode where we can extend the energy range to 15–20 keV even if some energy resolution is sacrificed. In this paper, we explore the trade-off between dynamic range and energy resolution from changing the bath temperature of the TES. We present measurements of TES resolution and slew rate as a function of bath temperature and compare to numerical simulations.

Burst-induced coronal cooling in GS 1826–24

Type I X-ray bursts in GS 1826–24, and in several other systems, may induce cooling of the hot inner accretion flow that surrounds the bursting neutron star. Given that GS 1826–24 remained persistently in the hard state over the period 2003–2008 and presented regular bursting properties, we stacked the spectra of the X-ray bursts detected by INTEGRAL (JEM-X and ISGRI) and XMM-Newton (RGS) during that period to study the effect of the burst photons on the properties of the Comptonizing medium. The extended energy range provided by these instruments allows the simultaneous observation of the burst and persistent emission spectra. We detect an overall change in the shape of the persistent emission spectrum in response to the burst photon shower. For the first time, we observe simultaneously a drop in the hard X-ray emission, together with a soft X-ray excess with respect to the burst blackbody emission. The hard X-ray drop can be explained by burst-induced coronal cooling, while the bulk of the soft X-ray excess can be described by fitting the burst emission with an atmosphere model, instead of a simple blackbody model. Traditionally, the persistent emission was assumed to be invariant during X-ray bursts, and more recently to change only in normalization but not in spectral shape; the observed change in the persistent emission level during X-ray bursts may thus trigger the revision of existing neutron star mass-radius constraints, as the derived values rely on the assumption that the persistent emission does not change during X-ray bursts. The traditional burst fitting technique leads to up to a 10% overestimation of the bolometric burst flux in GS 1826–24, which significantly hampers the comparisons of the KEPLER and MESA model against this “textbook burster”.

Fabrication, physical, optical characteristics and gamma-ray competence of novel bismo-borate glasses doped with Yb2O3 rare earth

New transparent bismuth borate glasses doped with ytterbium oxide (Yb2O3 = 0.0–5.0 mol%) have been fabricated. The amorphous nature of the glasses was checked via XRD measurements. The optical energy band gaps, and index of refraction of all fabricated glasses were determined with help of the absorbance spectra which measured from 200 to 1100 nm wavelength. The results revealed that the optical energy band gap for the glasses was between 2.56 eV for glass sample with Yb2O3 = 0.5 mol% and 2.84 for sample with Yb2O3 = 1.0 mol%. The refractive index was high (around 2.5). Moreover, gamma photons shielding factors have been evaluated for the glasses via mass attenuation coefficient (μ/ρ) which calculated using XCOM software over an extended energy range 0.015–15 MeV. The obtained μ/ρ for the glass samples were compared to some commercial glasses, concrete, and heavy metal oxides. Based on the (μ/ρ), another effective radiation shielding factors such as half value layer (HVL), effective atomic number (Zeff), and mean free path (MFP) were calculated. The shielding results showed that the HVL begin to increase and arranged in the order Yb0.0 > Yb0.1 > Yb0.5 > Yb1.0 > Yb3.0 > Yb5.0. Thus, the fabricated glasses can be used in different optical applications and as promising radiation shielding materials, especially Yb5.0, owns high μ/ρ and Zeff, low HVL and MFP.

Oxyfluoro-tellurite-zinc glasses and the nuclear-shielding ability under the substitution of AlF3 by ZnO

This paper examines radiation-shielding abilities of oxyfluoro-tellurite-zinc glasses in the chemical form of AlF3–TeO2–ZnO under the substitution of AlF3 by ZnO. Gamma-ray- and neutron-shielding properties were tested in terms of mass attenuation coefficient (μ/ρ), half value layer, mean free path, effective atomic numbers (Zeff), effective electron density (Neff) and removal cross-section (ΣR). The μ/ρ values of the glasses were generated by Geant4 simulations over an extended energy range and then the generated data were confirmed via XCOM software. The results showed that both gamma-ray- and neutron-shielding efficiencies of the selected glasses evolved by substituting of AlF3 by ZnO. Nuclear radiation-shielding abilities of the current glass systems were compared with that of some conventional shielding materials and newly developed HMO glasses. It can be concluded that oxyfluoro-tellurite-zinc glasses could be useful to design novel shields for radiation protection applications.

Influence of ZrO2 on gamma shielding properties of lead borate glasses

In this paper, new lead borate glass system in the chemical form of 40B2O3–40PbO–20Li2O3–xZrO2; where x = 0, 0.25, 0.50, 1, and 1.5 mol% has been synthesized. Gamma-ray shielding properties of these glasses have been tested in terms of mass attenuation coefficient (μ/ρ), half value layer (HVL), effective atomic number (Zeff), mean free path (MFP), and exposure build-up factor (EBF). The μ/ρ values of the prepared glasses were generated by FLUKA Monte Carlo simulations over an extended energy range of 0.015–15 MeV, and then, the generated data were verified using the calculated values of XCOM software. The results showed that gamma-ray shielding ability of BPLZ0.00 is superior among the other prepared glasses. Moreover, the gamma-ray shielding properties of the current glass system have been compared with that of some commercial glasses and newly developed HMO glasses. It can be concluded that the prepared glass system could be useful to design and/or develop novel shields for radiation protection applications.

Influence of Bi2O3/PbO on nuclear shielding characteristics of lead-zinc-tellurite glasses

This paper examines the nuclear shielding characteristics for two different lead-zinc-tellurite glass systems with the composition of TeO2–Bi2O3 – ZnO–PbO and TeO2–Na2O – ZnO–PbO coded as series A and series B, respectively. Nuclear shielding features of these glasses have been tested in terms of mass attenuation coefficient (μ/ρ), half value layer (HVL), removal cross section (∑R), exposure buildup factor (EBF), effective atomic number (Zeff), and mean free path (MFP). The μ/ρ values of these systems were generated by Geant4 Monte Carlo simulations over an extended energy range of 0.015–15 MeV. The generated data of μ/ρ were confirmed by XCOM calculations. The results show that the nuclear shielding ability of the lead-zinc-tellurite system increases as Bi2O3 content increases in the glasses of series A and as PbO content increases in the glasses of series B. Moreover, the nuclear shielding ability of the current glass systems have been compared with those of some conventional shielding materials and commercial glasses. It can be concluded that the present lead-zinc-tellurite glass systems could be useful to serve as novel shields for nuclear protection applications.

Evaluation of radiation shielding ability of boro-tellurite glasses: TeO2–B2O3–SrCl2–LiF–Bi2O3

This paper focuses on examining the radiation shielding features of seven boro-tellurite glasses in the form of TeO2–B2O3–SrCl2–LiF–Bi2O3. Gamma rays and neutrons shielding features of these glasses have been tested in terms of mass attenuation coefficient (μ/ρ), half value layer (HVL), mean free path (MFP), effective atomic number (Zeff), and removal cross section (∑R). The μ/ρ values of the present glasses were simulated by Geant4 Monte Carlo simulations over an extended energy range of 0.015 − 20 MeV and then the generated data were verified using the calculated values of WinXCOM software. Additionally, geometric progression (G–P) method was used to estimate gamma ray exposure buildup factor (EBF) for the prepared glasses. It is noted that μ/ρ and Zeff values increase, while MFP and HVL values decrease as TeO2 content increases in the glass sample. The EBF values would be useful to design or develop the present glasses for gamma shielding applications. Results reveal that the present glasses have good capability for gamma rays shielding compared with some commercial radiation shielding materials.

Simultaneous precision spectroscopy of pp , Be7 , and pep solar neutrinos with Borexino Phase-II

We present the first simultaneous measurement of the interaction rates of $pp$, $^7$Be, and $pep$ solar neutrinos performed with a global fit to the Borexino data in an extended energy range (0.19-2.93)$\,$MeV. This result was obtained by analyzing 1291.51$\,$days of Borexino Phase-II data, collected between December 2011 and May 2016 after an extensive scintillator purification campaign. We find: rate($pp$)$\,$=$\,$$134$$\,$$\pm$$\,$$10$$\,$($stat$)$\,$$^{\rm +6}_{\rm -10}$$\,$($sys$)$\,$cpd/100$\,$t, rate($^7$Be)$\,$=$\,$$48.3$$\,$$\pm$$\,$$1.1$$\,$($stat$)$\,$$^{\rm +0.4}_{\rm -0.7}$$\,$($sys$)$\,$cpd/100$\,$t, and rate($pep$)$\,$=$\,$$2.43$$\pm$$\,$$0.36$$\,$($stat$)$^{+0.15}_{-0.22}$$\,$($sys$)$\,$cpd/100$\,$t. These numbers are in agreement with and improve the precision of our previous measurements. In particular, the interaction rate of $^7$Be $\nu$'s is measured with an unprecedented precision of 2.7%, showing that discriminating between the high and low metallicity solar models is now largely dominated by theoretical uncertainties. The absence of $pep$ neutrinos is rejected for the first time at more than 5$\,$$\sigma$. An upper limit of $8.1$$\,$cpd/100$\,$t (95%$\,$C.L.) on the CNO neutrino rate is obtained by setting an additional constraint on the ratio between the $pp$ and $pep$ neutrino rates in the fit. This limit has the same significance as that obtained by the Borexino Phase-I (currently providing the tightest bound on this component), but is obtained by applying a less stringent constraint on the $pep$ $\nu$ flux.

The Endofullerene HF@C60: Inelastic Neutron Scattering Spectra from Quantum Simulations and Experiment, Validity of the Selection Rule, and Symmetry Breaking.

Accurate quantum simulations of the low-temperature inelastic neutron scattering (INS) spectra of HF@C60 are reported for two incident neutron wavelengths. They are distinguished by the rigorous inclusion of symmetry-breaking effects in the treatment and having the spectra computed with HF as the guest, rather than H2 or HD, as in the past work. The results demonstrate that the precedent-setting INS selection rule, originally derived for H2 and HD in near-spherical nanocavities, applies also to HF@C60, despite the large mass asymmetry of HF and the strongly mixed character of its translation-rotation eigenstates. This lends crucial support to the theoretical prediction made earlier that the INS selection rule is valid for any diatomic molecule in near-spherical nanoconfinement. The selection rule remains valid in the presence of symmetry breaking but is modified slightly in an interesting way. Comparison is made with the recently published experimental INS spectrum of HF@C60. The agreement is very good, apart from one peak for which our calculations suggest a reassignment. This reassignment is consistent with the measured INS spectrum presented in this work, which covers an extended energy range.

A novel synthetic diamond Cherenkov radiator for measuring space radiation

The measurement of cosmic rays and Solar energetic particles in space is basic to our understanding of the Galaxy, the Sun, phenomena in the Heliosphere and the emerging field of space weather . For these reasons, cosmic ray instruments are common on both scientific spacecraft and operational spacecraft such as weather satellites. Cosmic rays (CRs) and Solar energetic particles (SEPs) include ions over the full range of elements found in the Solar System. High-resolution measurements of the energy spectra of space radiation are key to understanding both acceleration and propagation processes. An inherent challenge is the large range of energies of such spectra. Cosmic ray energies range up to over 1 0 21 eV , while SEPs can reach a few GeV. Multi-instrument measurements are currently required to cover the full range of particle energies. Indeed, the highest energy particles, due to the rarity, can only be measured with ground-based instruments using the atmosphere as a calorimeter . Over limited energy ranges, SEP spectra are often approximated by a power law; however, over the full energy range, SEP events exhibit changing spectral shapes (e.g. “knees”, “roll-overs” and “cut-offs”). These features give information about the acceleration processes, such as size of the acceleration region, time of acceleration, morphology of the magnetic field during acceleration, and others, all of which can vary from event to event. Measurements of such features are often compromised by the need to combine measurements from more than one instrument, each with its own limited energy range. Even if there are no gaps between the energy intervals of the instruments, differing systematics can severely impact data analysis. A single instrument capable of measurements over a continuous and extended energy range would offer vastly more reliable measurement of the energy spectra of SEP events as well as replacing multiple instruments on resource-limited spacecraft. The most common method to measure GCRs and SEPs from a few to ∼ 100 MeV for protons, is Si Solid-State Detector (SSD) stacks. Above these energies, Cherenkov detectors are typically used together with SSDs. Ideally, to provide full energy coverage with no gaps, this requires a Cherenkov radiator with a threshold of ∼ 100 MeV. No suitable Cherenkov detector with such a low threshold has been developed. We are in the process of developing a synthetic diamond Cherenkov detector for this purpose. Diamond’s high index of refraction (2.42) results in a theoretical threshold of 92 MeV for protons. Even with a practical threshold of ∼ 110 MeV, this is ideal for extending the energy range from that of SSDs alone to that of sapphire Cherenkov detectors (202 MeV threshold) with higher energies attainable using plastic Cherenkov detectors. Both Sapphire and plastic Cherenkov radiators have spaceflight heritage.