Experimental Energy Spectra Research Articles

Evaluation of measurements of pre-equilibrum nucleon-induced light ion emission from 100 to 200 MeV

The mutual consistency of experimental continuum energy spectra observed in nucleon-induced inclusive reactions in the incident energy range from 100 to 200 MeV, which lead to emission of light composite ejectiles such as 3He and α particles, is investigated. Studies to determine details of the reaction mechanism of pre-equilibrium reactions such as (p,α) often require experimental data which come from various sources. The accuracy of the measurements depends on the choice of experimental techniques and detectors employed, therefore it would be expected that the reliability of the generated data could vary. These issues are discussed and it is found that the fairly large sample of data from independent sources are reassuringly consistent. Interesting agreement between results induced by neutron and proton projectiles is found.

Coexistence of planar and aplanar rotations in 195Tl

The chirality suggested for the doublet bands B2 and B2a in 195Tl in A∼190 region is reexamined. The potential-energy curves and the configurations together with the deformation parameters are obtained by the constrained covariant density functional theory. The corresponding experimental energy spectra, energy differences between doublet bands, and the available B(M1)/B(E2) values are investigated by the fully quantal particle rotor model. Analysis on the basis of the angular momentum components, the K-plots, and the azimuthal plots suggest a planar rotation interpretation for the bands B2 and B2a. Hence, it coexists with the aplanar rotation in the other doublet bands B4 and B4a in 195Tl.

Radionuclide spatial distribution and dose deposition for in vitro assessments of 212 Pb-αVCAM-1 targeted alpha therapy.

Targeted alpha therapy (TAT) takes advantage of the short-range and high-linear energy transfer of α-particles and is increasingly used, especially for the treatment of metastatic lesions. Nevertheless, dosimetry of α-emitters is challenging for the very same reasons, even for in vitro experiments. Assumptions, such as the uniformity of the distribution of radionuclides in the culture medium, are commonly made, which could have a profound impact on dose calculations. In this study we measured the spatial distribution of α-emitting 212 Pb coupled to an anti-VCAM-1 antibody (212 Pb-αVCAM-1) and its evolution over time in the context of in vitro irradiations. Two experimental setups were implemented without cells to measure α-particle count rates and energy spectra in culture medium containing 15kBq of 212 Pb-α-VCAM-1. Silicon detectors were placed above and below cell culture dishes for 20h. One of the dishes had a 2.5-µm-thick mylar-base allowing easy detection of the α-particles. Monte Carlo simulations were performed to analyze experimental spectra. Experimental setups were modeled and α-energy spectra were simulated in the silicon detectors for different decay positions in the culture medium. Simulated spectra were then used to deconvolute experimental spectra to determine the spatial distribution of 212 Pb-αVCAM-1 in the medium. This distribution was finally used to calculate the dose deposition in cell culture experiments. Experimental count rates and energy spectra showed differences in measurements taken at the top and the bottom of dishes and temporal variations that did not follow 212 Pb decay. The radionuclide spatial distribution was shown to be composed of a uniform distribution and concentration gradients at the top and the bottom, which were subjected to temporal variations that may be explained by gravity and electrostatic attraction. The absorbed dose in cells calculated from this distribution was compared with the dose expected for a uniform and static distribution and found to be 1.75 times higher, which is highly significant to interpret biological observations. This study demonstrated that accurate dosimetry of α-emitters requires the experimental determination of radionuclide spatial and temporal distribution and highlighted that in vitro assessment of dose for TAT cannot only rely on a uniform distribution of activity in the culture medium. The reliability and reproducibility of future experiments should benefit from specifically developed dosimetry tools and methods.

Two quasiparticle wobbling in the even-even nucleus 130Ba

Two newly observed bands built on a two-quasiparticle configuration in 130Ba have been investigated for the first time with the microscopic projected shell model. The experimental energy spectra and the available electromagnetic transition probabilities are well reproduced. The wobbling character of the higher band is revealed by the angular momentum projected wavefunctions via the K plot and the azimuthal plot. This provides the first strong microscopic evidence for wobbling motion based on a two-quasiparticle configuration in even-even nuclei.

Effects of Electromagnetic Fields over DNA of Hamsters with Implanted Graffi Tumor

Studies were conducted with model systems of bio influence (Drossinakis’ method) with electromagnetic (e.m.) fields and infrared thermal field (ITF) (Ignatov, Mosin, Niggli, Drossinakis, 2013). The purpose of research is to analyze effects over DNA. Analysis of effects over water and physiological saline is carried out in the report. Results are achieved with blood serum of hamsters and physiological processes in hamsters with tumors. The water analyses have been conducted with Nonequilibrium Energy Spectrum (NES) and Differential Nonequilibrium Energy Spectrum (DNES) methods (Antonov, 1992; Ignatov, 1998). Experiments were carried out about the influence on tumor cells of mice in water. Reduction of DNES spectrum according to the control sample of cells in healthy animals was observed. (Antonov, 1992). Reduction is also observed in DNES spectrum in blood serum of people having oncological diseases, compared to the one of healthy people (Ignatov, 2012). Such a reduction is most prevalent in (-0.1387 eV; 8.95 µm; 1117 cm -1 ). In research of the effects of e.m. fields in water and blood serum from hamsters the range is (-0.08 – -0.14 eV) (8.9 –15.5µm) (645–1129 cm -1 ). Research is conducted for the effects over Graffi tumor that was implanted in hamsters (Toshkova, Ignatov, Zvetkova, Ignatov, Gluhchev, Drossinakis, 2019). Studies are conducted with pH and oxidation redox potential (ORP) effects of e.m. fields over physiological saline (Gluhchev, Ignatov, Drossinakis, 2019). Keywords: Infrared thermal field (ITF), electromagnetic fields (e.m. fields), experimental Graffi solid tumor, energy spectrum, NES and DNES methods. DOI : 10.7176/JHMN/68-05 Publication date: November 30 th 2019

A comparison study of the pile-up correction algorithms

The pulse pile-up is a long-standing problem which deteriorates the energy, timing and spatial resolution of the radiation detection systems. Several algorithms have been developed for recovering the true pulse information using the available digital processing platforms. In this study, four well-established pile-up correction methods are numerically compared: single event reconstruction, template matching, maximum likelihood estimation and high-yield pile-up event recovery. Different pile-up waveforms are simulated by using the extracted parameters from the experimental data of a NaI(Tl) scintillation detector. The experimental pulses are taken from the charge sensitive preamplifier output, and therefore the methods are compared on the timescale of the RC constant of the preamplifier. Under such circumstance, the methods are compared with respect to their sensitivity to noise, variation of pulse shape, sampling rate and probable errors in time pick-off. In addition, their performance is assessed by calculating the experimental energy spectra of 137Cs at different high-count-rates. The results of the present study provide the benefits and limitations of each method, which can be used to select the best pile-up correction strategy for each specific application.

Accurate Magnetic Couplings in Chromium-Based Molecular Rings from Broken-Symmetry Calculations within Density Functional Theory.

We present a comprehensive analysis of magnetic coupling in a group of three popular chromium-based molecular rings, the homometallic Cr8 ring and the heterometallic Cr7Ni and Cr7Zn molecules. We show conclusively that the broken symmetry approach within density functional theory (DFT), based on suitable conventional or range-separated hybrid functionals, provides a quantitatively reliable tool to extract magnetic exchange coupling parameters in all rings considered, which opens a window for additional applications in molecular magnetism. We further show that a nonempirical model spin Hamiltonian, based on the parameters extracted from DFT, leads to excellent agreement with experimental susceptibility data and energy spectra. Moreover, based on an optimally tuned range-separated hybrid functional approach, we find that gas-phase gaps of the studied molecular rings are much larger than previously calculated and discuss the implications of the revised electronic structure to potential applications in molecular spintronics.

Effects of Electromagnetic Fields over DNA in Tumor Diseases, Biophysical and Biochemical Model Systems

Studies were conducted with model systems of influence of Drossinakis with electromagnetic (e.m.) fields and infrared thermal field (ITF) (Ignatov, Mosin, Niggli, Drossinakis, 2013). The purpose of research is to analyze effects over DNA. In the report is carried out analysis of effects over water and physiological saline. Results are achieved with blood serum of hamsters and physiological processes in hamsters with tumors. The analyses with water are conducted using the methods Nonequilibrium Energy Spectrum (NES) and Differential Nonequilibrium Energy Spectrum (DNES) (Antonov, 1992; Ignatov, 1998). Experiments are carried out with the influence of tumor cells of a mouse in water. It is observed reduction of DNES spectrum according to the control sample of cells in healthy animals. (Antonov, 1992). Reduction is also observed in DNES spectrum in blood serum of people having oncological diseases, compared to the one of healthy people (Ignatov, 2012). Such a reduction is most prevalent in (-0.1387 eV; 8.95 µm; 1117 cm -1 ). In research of the effects of e.m. fields in water and blood serum from hamsters the range is (-0.08 – -0.14 eV) (8.9 –15.5µm) (645–1129 cm -1 ). Research is conducted for the effects over Graffi tumor that was implanted in hamsters (Toshkova, Ignatov, Zvetkova, Ignatov, Gluhchev, Drossinakis, 2019). Studies are conducted with pH and oxidation redox potential (ORP) effects of e.m. fields over physiological saline (Gluhchev, Ignatov, Drossinakis, 2019). Keywords: Infrared thermal field (ITF), electromagnetic fields (e.m. fields), experimental Graffi solid tumor, energy spectrum, NES and DNES methods. DOI : 10.7176/JMPB/56-03 Publication date :May 31 st 2019

Possible chiral doublets in 60Ni

The open problem on whether or not the chirality exists in doublet bands M1 and M4 in light-mass even-even nucleus 60Ni is studied by adopting the recently developed fully quantal four-j shells triaxial particle rotor model. The corresponding experimental energy spectra, energy differences between doublet bands, and the available B(M1)/B(E2) values are successfully reproduced. The analyses on the basis of the angular momentum components, the azimuthal plots, and the K-plots suggest that the chiral modes exist at I≥12ħ in doublet bands M1 and M4.

Radial Flow in the Interaction of Relativistic Deuterons with a Gold Target

The kinetic energy spectra of intermediate mass fragments (IMF) has been studied for 4.4 GeV d + Au collisions at the Dubna Nuclotron with the 4π detector array FASA. Experimental kinetic energy spectra were compared to that obtained by the multi-body Coulomb trajectory calculations with the initial break-up conditions given by the combined model INC + SMM. It was found good agreement of measured and calculated kinetic energy spectra including a radial flow.

Behavior of the collective rotor in wobbling motion

The behavior of the collective rotor in wobbling motion is investigated within the particle-rotor model for the nucleus $^{135}$Pr by transforming the wave functions from the $K$-representation to the $R$-representation. After reproducing the experimental energy spectra and wobbling frequencies, the evolution of the wobbling mode in $^{135}$Pr, from transverse at low spins to longitudinal at high spins, is illustrated by the distributions of the total angular momentum in the intrinsic reference frame (azimuthal plot). Finally, the coupling schemes of the angular momenta of the rotor and the high-$j$ particle for transverse and longitudinal wobbling are obtained from the analysis of the probability distributions of the rotor angular momentum ($R$-plots) and their projections onto the three principal axes ($K_R$-plots).

Frequency-dependent polarizabilities of diatomic molecules: Density functional theory and ab initio methods compared with quantum-defect Green function technique

The choice of optimal calculation method for frequency-dependent polarizabilities (FDPs) is important for many applications. We compare some density functional theory (DFT) and ab initio methods with the quantum defect theory (QDT). Since QDT incorporates the experimental energy spectrum, it should yield more reliable results for FDP near the resonances at the excited states. We show that the DFT and ab initio methods which demonstrate the best accuracy for the static polarizabilities, have poor accuracy of the excited states energies. Such a behavior is a source of some discrepancies between these methods and QDT technique.

Laser wakefield acceleration in Kr–He plasmas and its application to positron beam generation

We present the generation of quasi-monoenergetic electron beams via ionization injection in a laser wakefield acceleration by using a krypton–helium plasma. We obtained higher-energy electron beams of low divergence as compared with beams from the nitrogen–helium plasma at low plasma densities. This is attributed to an immediate ionization, trapping and acceleration of many electrons from several inner shells of the krypton atoms. On the other hand, there are very high ionization potentials of the K-shell nitrogen electrons which require the pulse (in our laser-plasma parameters) to experience a self-focusing (after 1.6 mm of propagation) at first before any ionization injection and acceleration of those two electrons per atom can occur. Based on those high-quality electron beams from the Kr–He plasmas, we generated ultra-relativistic positron beams with energies up to 100 MeV by placing a lead slab converter with a thickness of the order of its radiation length in the electron beam path after the gas jet. Experimental and Mont-Carlo simulated energy spectra of the positron beams are compared for the energy range of 30 MeV ≤ Ee+ ≤ 100 MeV along with the positron yields. In addition, various parameters of the positrons are investigated against the primary electron beam parameters. Such electron–positron cascading experiment could be helpful in future development for the composition of an all-optical electron–positron collider.

Multiple chiral doublets in four-j shells particle rotor model: Five possible chiral doublets in [formula omitted]Nd76

A particle rotor model, which couples nucleons in four single-j shells to a triaxial rotor core, is developed to investigate the five pairs of nearly degenerate doublet bands recently reported in the even-even nucleus 136Nd. The experimental energy spectra and available B(M1)/B(E2) values are successfully reproduced. The angular momentum geometries of the valence nucleons and the core support the chiral rotation interpretations not only for the previously reported chiral doublet, but also for the other four candidates. Hence, 136Nd is the first even-even candidate nucleus in which the multiple chiral doublets exist. Five pairs of chiral doublet bands in a single nucleus is also a new record in the study of nuclear chirality.

Angular distribution measurement for 12C fragmentation via 12C + 12C scattering at 100 MeV/u**Supported by National Natural Science Foundation of China (11705123, 11475013, 11035007, 11175011), China Postdoctoral Science Foundation (2016M591911) and Natural Science Foundation of Jiangsu Province (BK20160306)

The angular distributions and energy spectra of 11B, 10B, and 9Be fragments of 12C in the angular range from 1.0° to 7.5° at 100 MeV/u were obtained via 12C + 12C scattering. Detailed comparisons are presented between the experimental data and the modified antisymmetrized molecular dynamics (AMD-FM), binary intranuclear cascade model (BIC) and Liège intranuclear cascade model (INCL++). The experimental angular distributions and energy spectra are well reproduced by the AMD-FM calculations but fail to be reproduced by the physical models installed in the Geant4 program, including the BIC and INCL++ models.

Low-lying states in even Gd isotopes studied with five-dimensional collective Hamiltonian based on covariant density functional theory

Five-dimensional collective Hamiltonian based on the covariant density functional theory has been applied to study the the low-lying states of even-even $^{148-162}$Gd isotopes. The shape evolution from $^{148}$Gd to $^{162}$Gd is presented. The experimental energy spectra and intraband $B(E2)$ transition probabilities for the $^{148-162}$Gd isotopes are reproduced by the present calculations. The relative $B(E2)$ ratios in present calculations are also compared with the available interacting boson model results and experimental data. It is found that the occupations of neutron $1i_{13/2}$ orbital result in the well-deformed prolate shape, and are essential for Gd isotopes.

Cluster correlation and fragment emission in C12+C12 at 95 MeV/nucleon

The impact of cluster correlations has been studied in the intermediate mass fragment (IMF) emission in $^{12}\mathrm{C}+^{12}\mathrm{C}$ at 95 MeV/nucleon, using antisymmetrized molecular dynamics (AMD) model simulations. In AMD, the cluster correlation is introduced as a process to form light clusters with $A\ensuremath{\le}4$ in the final states of a collision induced by the nucleon-nucleon residual interaction. Correlations between light clusters are also considered to form light nuclei with $A\ensuremath{\le}9$. This version of AMD, combined with GEMINI to calculate the decay of primary fragments, reproduces the experimental energy spectra of IMFs well overall with reasonable reproduction of light charged particles when we carefully analyze the excitation energies of primary fragments produced by AMD and their secondary decays. The results indicate that the cluster correlation plays a crucial role for producing fragments at relatively low excitation energies in the intermediate-energy heavy-ion collisions.

Possible “umbrella”-like antimagnetic rotation mode in odd- A Pd101,103 and even-even Pd102,104

The tilted-axis cranking model based on covariant density functional theory is used to study the candidate antimagnetic rotation (AMR) bands in $^{101,102,103,104}\mathrm{Pd}$. The experimental energy spectra and $B(E2)$ values are reproduced well in the self-consistent and microscopic calculations. By investigating microscopically the composition and orientation of angular momentum, an ``umbrella''-like antimagnetic rotation (UAMR) mode resulting from the coupling of four ${g}_{9/2}$ proton holes to neutron particles is clearly illustrated for the first time.

Energy-dependent dead-time correction in digital pulse processors applied to silicon drift detector's X-ray spectra.

Dead-time effects in X-ray spectra taken with a digital pulse processor and a silicon drift detector were investigated when the number of events at the low-energy end of the spectrum was more than half of the total, at counting rates up to 56 kHz. It was found that dead-time losses in the spectra are energy dependent and an analytical correction for this effect, which takes into account pulse pile-up, is proposed. This and the usual models have been applied to experimental measurements, evaluating the dead-time fraction either from the calculations or using the value given by the detector acquisition system. The energy-dependent dead-time model proposed fits accurately the experimental energy spectra in the range of counting rates explored in this work. A selection chart of the simplest mathematical model able to correct the pulse-height distribution according to counting rate and energy spectrum characteristics isincluded.

Yrast band of Ag109 described by tilted axis cranking covariant density functional theory with a separable pairing force

A separable form of the Gogny pairing force is implemented in tilted axis cranking covariant density functional theory for the description of rotational bands in open shell nuclei. The developed method is used to investigate the yrast sequence of 109Ag for an example. The experimental energy spectrum, angular momenta, and electromagnetic transition probabilities are well reproduced by taking into account pairing correlations with the separable pairing force. An abrupt transition of the rotational axis from the long-intermediate plane to the long-short one is obtained and discussed in detail.