Decrease In Detection Efficiency Research Articles

A railway fastener inspection method based on lightweight network

To ensure the safety of train operations, regular inspection and maintenance of railway fastener is crucial. Currently, computer vision-based fastener inspection has become the primary method. However, to improve detection accuracy, model complexity has been continuously increasing, leading to a decrease in detection efficiency and seriously affecting real-time fastener inspection task. To address this issue, we propose a fastener inspection method based on lightweight network. First, we introduce YOLOv5n-Faster, where this model selects YOLOv5n as the base network for fastener localization and uses partial convolution (PConv) from FasterNet for lightweight design, while using CoordConv to improve localization accuracy, thereby achieving efficient fastener localization task. Then, we perform lightweight design on the overall network structure and Block module of the ConvNeXt-T to propose the fastener state inspection model, Light ConvNeXt, for rapid fastener classification. Experimental results show that our proposed fastener localization model achieves a mean average precision (mAP) of 84.7%, a detection speed of 161 FPS. The fastener state inspection model achieves an accuracy of 99.7%.

The effect of varying collimator geometry in alpha spectrometry of environmental analysis

Assessment of radioactive aerosols in the atmosphere has always been an important field of study due to its effects on many biological systems. The efficiency in measuring these aerosols is therefore critical to research and industrial practice, thus; the principles and methods of geometry development to improve efficiency and resolution is paramount. The aim of this study is to use numerical simulation with MATLAB to improve the resolution and detection efficiency of an alpha spectrometer with varying collimator geometries. A collimator between a radiation source and a detector plays a very important role in identifying specific radionuclides among various species in a radioactive environment. The geometric model of the collimator being considered here is that of a triangular and a hexagonal shape. To evaluate the counts, randomly obtained data using Microsoft excel was used, considering the specified boundary conditions in a two-dimensional plane. Various counts ranging from 100 to 100,000 were analyzed to obtain the results of a log efficiency curve using MATLAB. Subsequent counting efficiency curves were then determined relative to the dimensions. An average value of 0.44 ± 0.1106 was determined for the efficiency. With emphases on the apothem of the geometries being studied, the triangular shaped collimator has theoretically shown to produce a higher resolution though with a possible decrease in detection efficiency.

Nanodosimetry of light ions in targets of different size

Nanodosimetry measures the frequency distribution of the number of ionizations produced by primary particles in target volumes of nanometric size. At the Legnaro National Laboratories of INFN, a large measurement campaign was carried out with the Startrack nanodosimetric counter, which showed a consistent characterization of the ionization yield produced by different primary particles when the counter is filled at the design gas pressure of 300 Pa, corresponding to a mass thickness of 2.0 μg/cm2, i.e. about 20 nm at unit density. In order to investigate the operative limits of the Startrack counter and analyse the stochastics of the ionization yield also in targets of other sizes, new measurements were carried out at lower gas pressure. A first set of measurement was carried out with different primary ions at pressures of 200 Pa and 170 Pa, corresponding to a site size in mass per area of 1.4 μg/cm2 and 1.1 μg/cm2, respectively. A second set of measurements was carried out with low-energy lithium ions, varying the pressure in the range 150–300 Pa, i.e. down to a site size of 1.0 μg/cm2 (10 nm at unit density). The measured ionization cluster-size distributions were compared with Monte Carlo simulations performed with the MC-Startrack track structure code, in order to obtain a first estimation of the decrease in detection efficiency with decreasing gas pressure. The new results and their consistency with previous measurements are presented and discussed in this paper.

Microchannel plate detector detection efficiency to monoenergetic electrons between 3 and 28 keV.

An unshielded microchannel plate (MCP) detector with an ultrafine pore diameter of 2 μm was irradiated by an electron beam to determine the detection efficiency of electrons for creating detector signals, or counts. Tested electron energies spanned a range of 3 kiloelectron volts (keV) to 28 keV. Higher detection efficiencies were measured at the lower end of this energy range, 0.376 counts per incident electron at 3 keV down to 0.155 at 15 keV with an increase to 0.217 at 18 keV and then another decrease down to 0.15 counts per incident electron at 28 keV. The increase at 18 keV is attributed to primary electron interaction with the L shell electrons of lead (Pb), leading to an increase in secondary electron and X-ray generation within the MCP and thus an increase in detection efficiency. For the electron beam directed normal to the MCP surface, the lowest efficiency of 0.15 counts per incident electron was observed at 28 keV. Detection efficiency was also tested as a function of incident angle with angular steps of 5°. Detection efficiency was more sensitive to the angle of incidence as the incident electron energy decreased. The detection efficiency at 3 keV decreased from 0.376 counts per electron at the zero degree angle (normal incidence to MCP surface) to 0.027 counts per electron at an incident angle of 50° (average in both orientations). At 28 keV, the decrease in detection efficiency as a function of increasing angle was less pronounced, ranging from 0.15 counts per electron at zero degrees to 0.08 counts per electron at 50° (average in both orientations). Experimental data showed lower detection efficiencies compared with previously published data.

Three-dimensional imaging lidar system based on high speed pseudorandom modulation and photon counting

High speed pseudorandom modulation and photon counting techniques are applied to a three-dimensional imaging lidar system. The specific structure and working principle of the lidar system is described. The actual detector efficiency of a single-photon detector in an imaging system is discussed, and the result shows that a variety of reasons lead to the decrease in detection efficiency. A series of ranging and imaging experiments are conducted, and a series of high-resolution three-dimensional images and a distance value of 1200 m of noncooperative targets are acquired.

A high-resolution magnetic bottle electron spectrometer and its application to a photoelectron–Auger electron coincidence measurement of the L2,3VV Auger decay in CS2

The energy resolution and the detection efficiency of a magnetic bottle electron spectrometer equipped with an electrostatic retarder are examined, with a particular focus on its application to electron coincidence measurements. The electrostatic retardation properly improves the energy resolving power of the spectrometer. No significant decrease in detection efficiency is observed when retardation voltages are applied. Photoelectron–Auger electron coincidence measurement of the L2,3VV Auger decay in CS2 is performed by using the magnetic bottle spectrometer, which reveals Auger transition intensities varying for the different core holes.

Effects of proton escape on detection efficiency in thin scintillator elements and its consequences for optimization of fast-neutron imaging

Abstract Plastic scintillators are commonly used for neutron detection in the MeV energy range, based on n–p scattering and the subsequent deposition of recoil proton's kinetic energy in the detector material. This detection procedure gives a quasi-rectangular energy deposition distribution for mono-energetic neutrons, extending from zero to the neutron energy. However, if the detector sensitive element (DSE) is small, the energy deposition may be incomplete due to the recoil proton escape. In the application of neutron imaging, here exemplified by fast-neutron tomography, two conflicting requirements have been identified: (1) thin DSEs are required to obtain high spatial resolution and (2) energy discrimination may be required to reduce the influence of neutrons being scattered into the DSEs, which generally occurs at lower energies. However, at small DSE widths, the reduction of energy deposition due to recoil proton escape may cause a significant decrease in detection efficiency when energy discrimination is applied. In this work, energy deposition distributions in small-size DSEs have been simulated for Deuterium–Deuterium (DD; 2.5 MeV) and Deuterium–Tritium (DT; 14.1 MeV) fusion neutrons. The intrinsic efficiency has been analyzed as a function of energy discrimination level for various detector widths. The investigations show that proton recoil escape causes a significant drop in intrinsic detection efficiency for thin DSEs. For DT neutrons, the drop is 10% at a width of 3.2 mm and 50% at a width of 0.6 mm, assuming an energy threshold at half the incident neutron energy. The corresponding widths for a DD detector are 0.17 and 0.03 mm, respectively. Finally, implications of the proton escape effect on the design of a fast-neutron tomography device for void distribution measurements at Uppsala University are presented. It is shown that the selection of DSE width strongly affects the instrument design when optimizing for image unsharpness.

Effect of adding Ar gas on the pulse height distribution of BF3-filled neutron detectors

Boron trifluoride (BF3) proportional counters are used as detectors for thermal neutrons. They are characterized by high neutron sensitivity and good gamma discriminating properties. Most practical BF3 counters are filled with pure boron trifluoride gas enriched up to 96% 10B. But BF3 is not an ideal proportional counter gas. Worsening of plateau characteristics is observed with increasing radius due to impurities in gas. To overcome this problem, counters are filled with BF3 with an admixture of a more suitable gas such as argon. The dilution of BF3 with argon causes a decrease in detection efficiency, but the pulse height spectrum shows sharper peaks and more stable plateau characteristics than counters filled with pure BF3. The present investigations are undertaken to study the pulse height distribution and other important factors in BF3+Ar filled signal counters for neutron beam applications. Tests are performed with detectors with cylindrical geometry filled with BF3 gas enriched in 10B to 90%, and high purity Ar in different proportions. By analysing pulse height spectra, a value of 6.1 ± 0.2 has been obtained for the branching ratio of the 10B(n,α) reaction.

Feasibility study of absolute activity measurement with metallic magnetic microcalorimeters

We report on a feasibility study on precise determination of mass-specific activity of low-energy emitting radioisotopes. Conventional methods of activity measurement suffer from source self-absorption and a strong decrease in detection efficiency for low-energy electrons and photons. We propose a new method based on metallic magnetic microcalorimeters with the source embedded in the detector target in a 4π geometry. First results with a 55Fe source show that electrons and photons are detected with a detection efficiency close to unity and with little loss of energy for electrons. The aim of this study is to provide standards of activity with very low uncertainties in the framework of radiation metrology.

Solid scintillation proximity membranes. II. Use in wipe test assays for radioactive contamination

Membranes containing the inorganic fluor cerium-activated yttrium silicate were prepared using three different coagulation techniques and were subsequently evaluated for their suitability in cocktail-less wipe tests for radioactive ( 3 H -cortisol) contamination. Wipe tests employing fluor-containing membranes that were prepared by direct vitrification were nearly as efficient as the conventional wipe test assays that require the use of scintillation cocktails at detecting radioactive contamination on tile surfaces. The sensitivity of detecting radioactivity on the contaminated surfaces was significantly greater when the side of the membrane exposed to air during coagulation was used in the wipe tests compared to the side of the membrane exposed to the glass. Treatment of the membranes with DMF induced a change in surface morphology which allowed more radioactivity to be transferred from the surface, but also caused the leaching of the fluor from the membrane. This resulted in an overall decrease in detection efficiency.

Monitoring the performance of energy dispersive spectrometer detectors at low energy

AbstractThe performance of the energy dispersive spectrometer (EDS) detectors has to be established in its original state and monitored periodically to ensure the stability and long‐term performance of the system. Because EDS detectors are cooled by liquid nitrogen and because the environment is not an ultra‐high vacuum, ice and contaminants will buld up in front of the detector crystal, decreasing the detection efficiency at low energy. Few performance tests are suitable for the specifics problems found at low energy. The proposed test is based on a new procedure for the modelling of the decrease of detection efficiency (DODE) with time (Hovington et al. 1993). It was found that the deposition rate of both ice and carbon increased significantly when porous uncoated samples were observed. Significant difference between spectra acquired immediately after different conditioning was also found. The proposed procedure can be used to determine the optimum time before a conditioning cycle, to detect an abnormal accumulation of contaminant both in front of the detector and at the sample surface, and to diagnose a broken window and a malfunction in the conditioning apparatus.

Performance characteristics of transmission imaging using a uniform sheet source with parallel-hole collimation.

Transmission imaging is receiving increasing attention in SPECT due to the need to compensate for nonuniform attenuation in cardiac-chest SPECT. The quality of a transmission image has an important effect on the measured attenuation distribution. To improve image quality, knowledge of the performance characteristics of a transmission imaging system is essential. The characteristics, spatial resolution, detection efficiency, photon flux, and exposure to the object, of a transmission imaging system consisting of a gamma camera and a uniform sheet source have been studied. The results demonstrate that spatial resolution of a transmission imaging system can be improved by use of a high-resolution source collimator at the price of a moderate decrease in detection efficiency, in comparison to the uncollimated case. Also, the source collimator significantly reduces the photon flux and exposure to the object. This investigation suggests that a high-resolution collimator be used with an intense sheet source to improve spatial resolution and reduce statistical noise with low exposure to the patient. This research further suggests that the amount of source activity is determined by the requirement of image quality, detection geometry, and allowed absorbed dose to the patient.

Mass dependence of searches for fractional charge in matter using ion-beam techniques.

If free quarks or other fractionally charged particles can exist, they should be present as a low primordial or cosmic-ray-produced concentration in terrestrial matter. The most sensitive searches have been dependent on the detection of anomalous ions by silicon-barrier or electron-multiplier detection systems, in which the dependence of energy transfer on ion velocity results in a decrease of detection efficiency with increasing mass, leading to a cutoff in observable particle mass for a given accelerating voltage. The factors governing this mass dependence are discussed, with illustrative calculations for a number of typical experiments. It is shown that the reported concentration limits are valid up to typically 10--100 proton masses for anomalous particles either in the free state or attached to low-Z atoms, but with lower sensitivity and reduced mass limits if bound to heavier atoms. The prospects for improving mass limits in future fractional charge searches are discussed. It is concluded that the detectable mass range could in principle be extended by several orders of magnitude in this type of experiment, and that in the case of positive ions of sufficiently high electron affinity the ``potential mechanism'' of electron ejection might provide a basis for fully mass-independent detection (although at the expense of a direct fractional-charge signature). The problem of pre-enrichment of the sample material is also considered, and a general method of estimating the mass dependence of electrical extraction techniques is given.