A Study on Two-dimensional Spectrum Analysis System of Energy and Time

Proposed is a two-dimensional(2D)spectrum analysis system for acquiring the statistical information of radioactive particles on two dimensions,i.e.energy and time.Based on pulse width modulation readout circuit,such a system with 4-channels is designed,which converts the radiation signal into a rectangular pulse signal with pulse width modulated.The pulse width,occurrence time,and pulse count of the rectangular pulses are measured simultaneously with digital counters,so that the 2D spectra on energy and time of the radioactive particles can be obtained efficiently based on bi-parameter statistical analysis.A prototype of this 2D system is tested with gamma rays from 241Am isotopes,from which both the correlated 2D spectra and the independent spectra on energy and time are obtained.The energy spectra of four channels shows all characteristic peaks of 241Am gamma rays,among which the full-energy peak at 59.5keV exhibits energy resolution of about 5-6%,suggesting a good energy resolution and channel uniformity of the system.The regression of the time spectra of the characteristic peaks can give the time constants of each characteristic peak,revealing the time characteristics of the nuclear reactions in the radiative source.

An improved secondary electrons energy spectrum model and its application in multipactor discharge

Secondary electron emission （SEE） of metal and dielectric materials plays a key role in multipactor discharge, which is a bottle neck problem for high-power satelliate components. Measurements of both the secondary electron yield （SEY） and the secondary electron energy spectrum （SES） are performed on metal samples for an accurate description of the real SEE phenomenon. In order to simplify the fitting process and improve the simulation efficiency, an improved model is proposed for the description of secondary electrons （SE） emitted from the material surface, including true, elastic, and inelastic SE. Embedding the novel SES model into the electromagnetic particle-in-cell method, the electronic resonant multipactor in microwave components is simulated successfully and hence the discharge threshold is predicted. Simulation results of the SES variation in the improved model demonstrate that the multipactor threshold is strongly dependent on SES. In addition, the mutipactor simulation results agree quite well with the experiment for the practical microwave component, while the numerical model of SEY and SES fits well with the sample data taken from the microwave component.

Application of the wavelet packet and its energy spectrum to identify nugget splash during the aluminum alloys spot welding

Nugget splash during aluminum alloys spot welding has a detrimental effect on weld nugget integrity, strength and durability of the welded joints. This investigation is performed to identify nugget splash from voltage signals because these are easily accessible on-line. In the present work, we propose a novel method based on the wavelet packet transform and its energy spectrum for pattern recognition of splash signal. The result demonstrates that this novel method is more accuracy and a useful way of monitoring the spot welding quality.

The quantum Kirchhoff equation and quantum current and energy spectrum of a homogeneous mesoscopic dissipation transmission line

On the basis of quantization of charge, the loop equations of quantum circuits are investigated by using the Helsenberg motion equation for a mesoscopic dissipation transmission line. On the supposition that the system has a symmetry under translation in charge space, the quantum current and the quantum energy spectrum in the mesoscopic transmission llne are given by solving their eigenvalue equations. Results show that the quantum current and the quantum energy spectrum are not only related to the parameters of the transmission llne, but also dependent on the quantized character of the charge obviously.

Experimental Study of Wave Energy Spectrum in Shallow Water

Wave energy spectrum in shallow water can be studied in wind wave channel in combination with irregular wave- maker. Fetch length is successfully extended and by 'Relay' method the corresponding spectrum pattern and the wind velocity scale are obtained.

A novel approach for feature extraction from a gamma‑ray energy spectrum based on image descriptor transferring for radionuclide identification

This study proposes a novel feature extraction approach for radionuclide identification to increase the precision of identification of the gamma-ray energy spectrum set.For easier utilization of the information contained in the spectra,the vectors of the gamma-ray energy spectra from Euclidean space,which are fingerprints of the different types of radionuclides,were mapped to matrices in the Banach space.Subsequently,to make the spectra in matrix form easier to apply to image-based deep learning frameworks,the matrices of the gamma-ray energy spectra were mapped to images in the RGB color space.A deep convolutional neural network(DCNN)model was constructed and trained on the ImageNet dataset.The mapped gamma-ray energy spectrum images were applied as inputs to the DCNN model,and the corresponding outputs of the convolution layers and fully connected layers were transferred as descriptors of the images to construct a new classification model for radionuclide identification.The transferred image descriptors consist of global and local features,where the activation vectors of fully connected layers are global features,and activations from convolution layers are local features.A series of comparative experiments between the transferred image descriptors,peak information,features extracted by the histogram of the oriented gradients(HOG),and scale-invariant feature transform(SIFT)using both synthetic and measured data were applied to 11 classical classifiers.The results demonstrate that although the gamma-ray energy spectrum images are completely unfamiliar to the DCNN model and have not been used in the pre-training process,the transferred image descriptors achieved good classification results.The global features have strong semantic information,which achieves an average accuracy of 92.76%and 94.86%on the synthetic dataset and measured dataset,respectively.The results of the statistical comparison of features demonstrate that the proposed approach outperforms the peak-searching-based method,HOG,and SIFT on the synthetic and measured datasets.

Transformation of Wave Energy Spectrum in Shallow Water

Combined with irregular wave-maker, the growing process of Wave Energy Spectrum in shallow water can be studied in wind wave channel on different water depth conditions, and its transformation characteristics and rules can be obtained.

A Cell Condition-Sensitive Frequency Segmentation Method Based on the Sub-Band Instantaneous Energy Spectrum of Aluminum Electrolysis Cell Voltage

Cell voltage is a widely used signal that can be measured online from an industrial aluminum electrolysis cell.A variety of parameters for the analysis and control of industrial cells are calculated using the cell voltage.In this paper,the frequency segmentation of cell voltage is used as the basis for designing filters to obtain these parameters.Based on the qualitative analysis of the cell voltage,the sub-band instantaneous energy spectrum(SIEP)is first proposed,which is then used to quantitatively represent the characteristics of the designated frequency bands of the cell voltage under various cell conditions.Ultimately,a cell condition-sensitive frequency segmentation method is given.The proposed frequency segmentation method divides the effective frequency band into the[0,0.001]Hz band of lowfrequency signals and the[0.001,0.050]Hz band of low-frequency noise,and subdivides the lowfrequency noise into the[0.001,0.010]Hz band of metal pad abnormal rolling and the[0.01,0.05]Hz band of sub-low-frequency noise.Compared with the instantaneous energy spectrum based on empirical mode decomposition,the SIEP more finely represents the law of energy change with time in any designated frequency band within the effective frequency band of the cell voltage.The proposed frequency segmentation method is more sensitive to cell condition changes and can obtain more elaborate details of online cell condition information,thus providing a more reliable and accurate online basis for cell condition monitoring and control decisions.

Measurement of the Energy Spectrum of a 6 MV Linear Accelerator Using Compton Scattering Spectroscopy and Monte Carlo-Generated Corrections

Purpose: The energy spectrum of a linear accelerator used for dose calculations is determined during beam commissioning by iteratively adjusting the spectrum and comparing calculated and measured percent depth-dose curves. Direct measurement of the energy spectrum using pulse mode detectors is particularly challenging because of the high-energy, high fluence nature of these beams and limitations of the detector systems. This work implements a Compton scattering (CS) spectroscopy setup and presents detector corrections and spectral unfolding techniques to measure the spectrum of a 6 MV linear accelerator using a pulse mode detector. Methods: Spectral measurements were performed using a Varian Clinac 21EX linear accelerator and a high-purity germanium (HPGe) detector. To reduce fluence to the detector, a custom-built lead shield and a CS spectrometry setup were used. The detector was placed at CS angles of 46°, 89°, and 125°. At each of these locations, a detector response function was generated to account for photon interactions within the experimental geometry. Gold’s deconvolution algorithm was used to unfold the energy spectrum. The measured spectra were compared to simulated spectra, which were obtained using an experimentally benchmarked model of the Clinac 21EX in MCNP6. Results: Measurements were acquired and detector response corrections were calculated for all three CS angles. A comparison of spectra for all CS angles showed good agreement with one another. The spectra for all three angles were averaged and showed good agreement with the MCNP6 simulated spectrum, with all points above 400 keV falling within 4%, which was within the uncertainty of the measurement and statistical uncertainty. Conclusions: The measurement of the energy spectrum of a 6 MV linear accelerator using a pulse-mode detector is presented in this work. For accurate spectrum determination, great care must be taken to optimize the detector setup, determine proper corrections, and to unfold the spectrum.

Growth of deuterium clusters in a gas jet and ion energy spectrum of clusters in ultra-short laser field

Large deuterium clusters are generated using a cryogenic pulse valve with a cone nozzle （21 mm long, 4° open angle）. Rayleigh scattering experiment is carried out to obtain the scaling relation between scattering signal SR and backing pressure P0. A method using the Coulomb explosion model is proposed to verify that the clusters continue to grow after their leaving the nozzle. Our experiments suggest a tentatively optimized position for laser cluster interaction.

Reconstruction of Ionization Density Distribution in Hall Thruster Channel from Ion Energy Spectrum of Plasma Jet

Propellant ionization in the Hall thruster discharge channel is a significant process and has strong influence on the thruster＇s efficiency. In this work, the functional relation has been established between the ionization density distribution and the function of the ion energy distribution through the basic equations governing the ion flow in the Hall thruster channel and the method achieved for reconstructing the ionization density distribution inside the channel by ordinary plasma diagnosis of the potential distribution and ion energy spectrum of the plasma jet. The ionization density distributions of single and double charged ions in an ATON-thruster channel have been reconstructed according to the experimental data of the potential distribution along the axis of the channel and the ion energy spectrum of the plasma jet. The agreement between the calculation and experimental results of the percentage of double charged ions proves the validity of our method achieved in this work.

Statistical properties of the photoelectron energy spectrum generated by an intense laser pulse and a continuous X-ray

This study shows that the photoelectron energy spectrum generated by an intense laser pulse in the presence of a continuous X-ray has interesting and useful statistical properties. The total photoionization production is linearly propor- tional to the time duration of the laser pulse and the square of the beam size. The spectral double energy-integration is an intrinsic value of the laser-assisted X-ray photoionization, which linearly depends on the laser intensity and which quantita- tively reflects the strengths of the laser-field modulation and the quantum interference between photoelectrons. The spectral energy width also linearly depends on the laser intensity. These linear relationships suggest new methods for the in-situ measurement of laser intensity and pulse duration with high precision.

Energy spectrum and entanglement of two tunnelcoupled Bose-Einstein condensates

This paper obtains the energy-spectrum and eigenstate corrections of two-mode Bose-Einstein condensates （BECs） coupled by quantum tunnelling by perturbation method in both strong and weak tunnelling regions. The population imbalance between two BECs are then studied in terms of the low-lying eigenstates which also characterize the intrinsic entanglement between the two-mode BECs. The strong parity effect in the weak tunnelling region is also investigated.

Energy spectrum and superfluidity of spin-2 ultracold bosons in optical lattices

This paper studies the superfluidity of ultracold spin-2 Bose atoms with weak interactions in optical lattices by calculating the excitation energy spectrum using the Bogoliubov approach. The energy spectra exhibit the characteristics of the superfluid-phase explicitly and it finds the nonvanishing critical speeds of superfiuid. The obtained results display that the critical speeds of superfiuid are different for five spin components and can be controlled by adjusting the lattice parameters in experiments. Finally it discusses the feasibilities of implementing and measuring superfluid.

Role of Ordering Energy in Formation of Grain Structure and Special Boundaries Spectrum in Ordered Alloys with L12 Superstructure

It was revealed that an average energy of special boundaries is proportional to APB energy in the alloys with the L12 superstructure. This fact proves the appearance of the GAPBs in the planes of location of special boundaries in coincidence sites of ordered alloys. It was determined that the more energy of special boundaries in ordered alloys, the more energy of complex stacking fault. There is a correlation between the distribution of special boundaries as a function its relative energy and ordering energy: the more ordering energy, the more degree of washed away of distribution. The correlation between average relative energy of special boundaries and ordering energy was detected: the more ordering energy, the more average energy of special boundaries. The reverse dependence between ordering energy and average number of special boundaries in grains limited by boundaries of general type was discovered.

Coherent Features of Resonance-Mediated Two-Photon Absorption Enhancement by Varying the Energy Level Structure,Laser Spectrum Bandwidth and Central Frequency

The femtosecond pulse shaping technique has been shown to be an effective method to control the multi-photon absorption by the light–matter interaction. Previous studies mainly focused on the quantum coherent control of the multi-photon absorption by the phase, amplitude and polarization modulation, but the coherent features of the multi-photon absorption depending on the energy level structure, the laser spectrum bandwidth and laser central frequency still lack in-depth systematic research. In this work, we further explore the coherent features of the resonance-mediated two-photon absorption in a rubidium atom by varying the energy level structure, spectrum bandwidth and central frequency of the femtosecond laser field. The theoretical results show that the change of the intermediate state detuning can effectively influence the enhancement of the near-resonant part, which further affects the transform-limited （TL）-normalized final state population maximum. Moreover, as the laser spectrum bandwidth increases, the TL-normalized final state population maximum can be effectively enhanced due to the increase of the enhancement in the near-resonant part, but the TL-normalized final state population maximum is constant by varying the laser central frequency. These studies can provide a clear physical picture for understanding the coherent features of the resonance-mediated two-photon absorption, and can also provide a theoretical guidance for the future applications.

Monte Carlo simulation for bremsstrahlung and photoneutron yields in high-energy x-ray radiography

This paper reports on the results of calculations using a Monte Carlo code （MCNP5） to study the properties of photons, electrons and photoneutrons obtained in the converted target and their transportations in x-ray radiography. A comparison between measurements and calculations for bremsstrahlung and photoneutrons is presented. The radiographic rule and the effect of the collimator on the image are studied with the experimental model. The results provide exact parameters for the optimal design of radiographic layout and shielding systems.

Wave packet dynamics of nonlinear Gazeau–Klauder coherent states of a position-dependent mass system in a Coulomb-like potential

AD = 1 position-dependent mass approach to constructing nonlinear quantum states for a modified Coulomb potential is used to generate Gazeau–Klauder coherent states. It appears that their energy eigenvalues are scaled down by the quantum number and the nonlinearity coefficient. We study the basic properties of these states, which are found to be undefined on the whole complex plane, and some details of their revival structure are discussed.

The Theoretical Model of Atmospheric Turbulence Spectrum in Surface Layer

It is shown that the slope of energy spectrum obtained from the velocity solution of Kdv-Burgers equation lies between -5/3 and -2 in the dilogarithmic coordinates paper. The spectrum is very close to one of Kolmogorov's isotropic turbulence and Frisch's intermittent turbulence in inertial region. In this paper, the Kdv-Burgers equation to describe atmospheric boundary layer turbulence is obtained. In the-equation, the 1 / Re corresponds to dissipative coefficient v, Ri1/2 to dispersive coefficient β, then (v/2β)2 corresponds to 1 /Re2 ·Ri. We prove that the wave number corresponding to maximum energy spectrum S(k) decreases with the decrease of stability (i.e., the increase of (v / 2β)2 in eddy-containing region. And the spectrim amplitude decreases with the increase of (v / 2β)2 (i.e., the decrease of stability). These results are consistent with actual turbulence spectrum of atmospheric surface layer from turbulence data.

Rapid diagnostic method for transplutonium isotope production in high flux reactors

Transplutonium isotopes are scarce and need to be produced by irradiation in high flux reactors.However,their production is inefficient,and optimization studies are necessary.This study analyzes the physical nature of transplutonium isotope produc-tion using ^(252)Cf,^(244)Cm,^(242)Cm,and ^(238)Pu as examples.Traditional methods based on the Monte Carlo burnup calculation have the limitations of many calculations and cannot analyze the individual energy intervals in detail;thus,they cannot sup-port the refined evaluation,screening,and optimization of the irradiation schemes.After understanding the physical nature and simplifying the complexity of the production process,we propose a rapid diagnostic method for evaluating radiation schemes based on the concepts“single energy interval value(SEIV)”and“energy spectrum total value(ESTV)”.The rapid diagnostic method not only avoids tedious burnup calculations,but also provides a direction for optimization.The optimal irradiation schemes for producing ^(252)Cf,^(244)Cm,^(242)Cm,and ^(238)Pu are determined based on a rapid diagnostic method.Optimal irradiation schemes can significantly improve production efficiency.Compared with the initial scheme,the optimal scheme improved the production efficiency of ^(238)Pu by 7.41 times;^(242)Cm,11.98 times;^(244)Cm,65.20 times;and ^(252)Cf,15.08 times.Thus,a refined analysis of transplutonium isotope production is conducted and provides a theoretical basis for improving production efficiency.