6 results about "Mean free path" patented technology

The invention discloses a dynamic calculation method and system for a radiation field in the cutting process of an activity non-uniform radioactive source, and belongs to the field of radiation field calculation. The method comprises the following steps: acquiring three-dimensional activity distribution data of a radioactive source; constructing a voxelization model and coupling the voxelization model with an activity grid to distribute activity; establishing an LBVH hierarchical structure of the shielding body; a point kernel is generated in a self-adaptive mode through ray tracing and average free path comparison; carrying out radiation field calculation by adopting point nuclear integration, and realizing multilayer ray tracing in the radioactive source, between the sources and a shield in the process; on-line cutting and moving operation of the voxel model is supported, and the radiation field is dynamically updated. According to the method, the cutting operation of the activity non-uniform radioactive source can be simulated, the problem that the radioactive activity of each cutting product cannot be represented after cutting by a traditional method is solved, the radiation field dynamic calculation in the activity non-uniform radioactive source cutting process can be simulated, initial modeling of the radiation environment only needs to be carried out once, and the efficiency is improved. And repeated modeling is not needed.

The invention discloses a speckle pumping microscopic system for measuring the average free path of a photon-generated carrier. The speckle pumping microscopic system comprises a laser light source, a pumping light path, a detection light path, a signal acquisition module and an image processing module, the laser light source is used for outputting pump light and probe light with selected wavelengths, and the pump light and the probe light are combined to the signal acquisition module through a pump light path and a probe light path respectively; a beam shaping module is arranged on the pump light path and comprises two objective lenses and a diffusion sheet placed at the focal points of the two objective lenses; the signal acquisition module is used for exciting a signal on the surface of the sample and shooting a signal returned from the sample; and the image processing module is in communication connection with the camera and is used for performing Fourier amplitude spectrum processing on the shot signal to obtain the average free path, the service life and the bipolar diffusion coefficient of the photon-generated carrier of the sample. According to the invention, the pump light is shaped into speckles, so that the measurement covers a ballistic region and a diffusion region, and the technical problem of measuring the average free path in a non-equilibrium state by an experiment is solved.

The application discloses a simulation method for tokamak neutral beam injection and fast ion deposition. In the numerical simulation of the neutral beam particle injection and ionization process in a tokamak device, the physical parameters of the neutral beam injection device are determined first, then the injection source is simplified by using a narrow particle beam model, the neutral beam particle density of a reference point given under geometric conditions is calculated, the average free path of the neutral beam particle ionization is calculated after the parameters of the position of the reference point in the plasma interior are obtained, the ions in different regions are divided by using a non-uniform grid and are given different weights, and finally the simulation process of the neutral beam injection is realized. The application realizes the simulation of the injection process of the neutral beam particles by using the narrow particle beam model, can obtain the neutral particle and fast ion distribution at any position in the plasma, has high calculation efficiency and strong numerical stability, and is a stable and efficient numerical simulation method.

The application discloses a method for single-shot imaging of an internal target of a scattering medium based on near-infrared light. The method utilizes statistical characteristics of speckle and a conclusion that a square root of a covariance of the speckle is equal to an amplitude of autocorrelation of the target, realizes single-shot imaging of the internal target of the thick scattering medium based on the near-infrared light, and can realize imaging of an internal target of fresh chicken breast tissue with a maximum of 20 mean free paths and a maximum imaging resolution of 150 microns. The method only needs to shoot a speckle corresponding to the target to clearly reconstruct the image, which greatly reduces a calculation amount in scattering imaging; the near-infrared light is used as a light source to improve imaging depth, the maximum imaging depth can reach 20 mean free paths, and the method provides a new thought for applications in the fields of biomedicine and the like.

The application discloses a high-throughput calculation method of electric transport performance based on deformation potential approximation. In the method, the electron relaxation time involved in the calculation of the electric transport performance is only considered as the electric-acoustic interaction, and the electric-acoustic interaction is described by using the deformation potential approximation. A high-throughput calculation method of the deformation potential constant is developed, the average value of the first band is used as a reference state, and the obtained deformation potential constant dataset is used for high-throughput electric transport performance calculation. Compared with the constant relaxation time approximation and the constant mean free path approximation method, the method has higher precision, and compared with the precise electric-acoustic coupling method, the method is more suitable for high-throughput calculation in terms of cost and time. The method is based on the MatHub-3d database, 11993 semiconductor materials are screened from the database, the deformation potential constants of the 11993 semiconductor materials are high-throughput calculated, and the electric transport performance of 10195 semiconductor materials is high-throughput predicted by using the deformation potential constant dataset.

This invention discloses a method for selective epitaxy of the SiGe:C base region in high-speed silicon-germanium (HBT), comprising: providing a patterned substrate having a base region growth window; performing RCA cleaning on the patterned substrate; forming a low-pressure environment in the epitaxial chamber; and forming the SiGe:C base region in the base region growth window of the patterned substrate through selective epitaxy. In this invention, optimized pretreatment of the patterned substrate surface effectively suppresses the etching damage caused by highly reactive carbon atoms and their uncontrollable migration on the dielectric surface; thereby significantly widening the process window for selective SiGe:C epitaxy and improving process stability and repeatability; conducting the reaction under low pressure increases the mean free path of gas molecules and facilitates surface reaction control, strengthening the dependence of growth / etching on surface chemical properties and enhancing selectivity.