An experimental setup for studying spectra of β particles emitted by mixtures of 235U and 239Pu thermal neutron fission products

An experimental setup on the thermal neutron beam of the IR-8 reactor at the National Research Centre Kurchatov Institute is described. This setup has been designed to precisely measure the ratio of spectra of β particles emitted by mixtures of ²³⁵U and ²³⁹Pu fission products. The experiment is based on simultaneous measurements of β spectra from fissile isotopes ²³⁵U and ²³⁹Pu and the background spectrum in the same neutron beam. Measurements of the β spectra are taken by a high-selectivity β spectrometer in the time interval when the neutron beam is intercepted by a mechanical chopper. The evolution of the measurement technique is considered.     

A γ detector movement system of the spectrometer with a vertex detector setup

The system controlling movement of the γ detector in the spectrometer with a vertex detector (SVD) setup has been upgraded. The choice of circuitry components for designing the control interface, coordinate sensors, actuation mechanisms, and system of emergency shutdown is substantiated. The circuit designs allowing the reliability of the γ detector and its positioning accuracy to be increased are described. Commercially produced industrial controllers of asynchronous motors with frequency steering are used in the system. The software developed for controlling the γ detector movement is described. The system has been completely mounted and tested and now is ready for operation as a part of the SVD setup.     

A study of Xe 2β decay using the DEVIS tracking setup at the institute for theoretical and experimental physics

The DEVIS experiment aimed at searching for 2ν2β decay of ¹³⁶Xe isotope has been conducted for several years at the Institute for Theoretical and Experimental Physics. The DEVIS (DEtector for VISu-alization) tracking setup is a time projection chamber placed in a magnetic field. Xenon samples with a mass of 4 kg and different isotopic compositions have been sequentially exposed in it. An excess of events has been observed in the run with the sample enriched in ¹³⁶Xe. The stages of the experiment are described, and the background processes capable of simulating events of 2ν2β decay are analyzed. The limit on the half-life of ¹³⁶Xe 2ν2β decay is shown to be T _1/2 (2ν2β) > 2.1 × 10²⁰ years.     

Development of a Setup for the Discrimination of β+ and γ Rays

Abstract

A β⁺–γ discrimination set‐up was developed and applied to the ²²Na radioisotope. The radioisotope emits positrons (β⁺) and these positrons create γ rays by annihilating with electrons. These annihilation γ rays were used here, and the discrimination between these positrons and γ rays was investigated by the coincidence measurement between time signals and the energy signals. The detection system presented here uses a 3 inch (diameter) by 3 inch (length) NaI(Tl) inorganic scintillation detector for γ detection and 3 inch (diameter) by 3 inch (length) plastic scintillation detector for β⁺ detection.     

Evaluation of multi-holed orifice flowmeters under developing flow conditions – An experimental study

This study focuses on multi-holed orifice plates, which have superior flow measuring characteristics as compared to their conventional counterparts. However, literature is scant on quantitative parametric investigations. In this experimental study, the performance of a multi-holed orifice plate is evaluated for variable number of holes (n), equivalent diameter ratio (EDR), compactness ratio (C), plate thickness ratio (s/d) and upstream developing length (L/D) in developing flow regimes for the Reynolds number range of 24,500–55,500 by using Central Composite Design. A total number of 324 experiments were performed. It was found that EDR has the most significant effect on pressure loss coefficient, followed by ‘n’ and ‘C’. Moreover, it was found out that single orifice (SO) and multi-holed orifice (MO) have almost the same pressure losses for the same value of EDR/β. However, flow develops quickly for MOs. Higher values of coefficient of discharge were observed in the case of MOs as compared to the SOs with little effect of upstream disturbances. The effect of developing length is significant on the accuracy of orifice meter. However, when the multi-holed orifice plates are installed at 2D upstream length, the effect of upstream disturbances are diminished. This result provides the flexibility of installation, which means that multi-holed orifices can be installed at 2D. The experimental data is in good agreement with literature. Finally, an optimum orifice plate (5,0.4,0.7) was selected for flow developing region with minimum pressure loss coefficient based upon the experimental results.     

Analysis of precision deburring using a laser —An experimental study and FEM simulation

The purpose of this study is to develop an effective methods for automated deburring of precision components. A high power laser is proposed as a deburring tool for complex part edges and burrs. For the laser experiments, rectangular-shaped carbon steel and stainless steel machined specimens with burr along one side were prepared. A 1500 Watts CO₂ laser was used to remove burrs on the workpieces. The prediction of the heat affected zone (HAZ) and cutting profile of laser-deburred parts using finite element method is presented and compared with the experimental results. This study shows that the finite element method (FEM) analysis can effectively predict the thermal affected zone of the material and that the technique can be applied to precision components.     

An experimental analysis of effects of various material tool’s wear on burr during generator sheets blanking

Blanking is one of the most frequently used processes in sheet metal forming. Unlike other forming processes, such as stamping, blanking not only deforms the metal plastically to give the appropriate size and shape, but also ruptures the sheet metal in the desired zones. Among the others, blanking enables manufacturing of electric motor components, such as rotor or stator parts. The parts of the low power commutator motor of rotor and stator are made of generator sheets, which are really difficult to do from the machining point of view. The shock loads and high reaction of the sheet metal of separation surface to the punch surface are presented during the blanking process. In this paper, an investigation has been made to study the effects of punch–die clearance, tool materials, and tool coatings on the wear of blanking tools. In the paper, the feasibility analysis for various materials used for production of the tools for punching the generator sheets is presented.     

Application of a position-sensitive scintillation spectrometer for measuring the resonance absorption of γ rays in nitrogen-containing substances

A single-coordinate scintillation spectrometer for measuring the γ-ray resonance absorption in nitrogen-containing samples is described. The energy and coordinate characteristics of the spectrometer were measured. The results of experiments on the resonance absorption of γ radiation with an energy of 9.17 MeV in a carbamide sample are presented.     

Ultrasonic method for determination of elastic moduli—Numerical simulation and experimental results

In this work, a numerical simulation and experimental results using a modified prism technique are presented. It is based on pulse-echo technique and involves the measurement of both longitudinal and transversal waves velocities in trapezoidal-prism shaped specimens with only one transducer. Both longitudinal and transversal waves are generated through mode conversion at the interface between water and the specimen under test. Based on numerical simulation with the 2-D Elastodynamic Finite Integration Technique (EFIT), several snapshots are generated to illustrate the functionality of this new technique, and the experiment was performed on cement paste with various water/cement ratios.     

Machinability study of high speed steel for focused ion beam (FIB) milling process – An experimental investigation at micron/nano scale

Nowadays the attention is focused on machining of non-silicon materials for miniaturized devices. High speed steel (HSS) is a non-silicon tool material, which is used in metal cutting applications as well as in micro-medical applications. Focused ion beam (FIB) milling process is highly suited for the fabrication of micro tools and other micro devices manufactured from HSS material. This study investigates the machinability aspects of HSS for FIB milling process. Beam current, extraction voltage, angle of incidence, dwell time and percentage overlap between beam diameters are the FIB process parameters, which have been analyzed experimentally to optimize FIB milling process for maximum material removal rate and minimum surface roughness. Beam current is found as the most significant parameter for controlling the material removal rate and surface roughness.     

Theoretical–experimental evaluation of different biomaterials for parts obtaining by fused deposition modeling

Although microFDM (microFused Deposition Modeling) has been widely used with biomaterials, there is not enough information about their flow models and the appropriate values for operating conditions. The aim of this paper is to provide a criterion to establish feasible ranges of temperature and shear stress to carry out fused deposition of the biomaterials studied at microscale (hundreds of μm). Materials used were (acrylonitrile–butadiene–styrene), PLA (polylactic acid), and PCL (polycaprolactone). Polyvinyl alcohol was also included in this study, although its quick thermal degradation has led to poor dimensional stability parameters and, therefore, it has been considered inappropriate for this application. Viscosity models were obtained in a 300 μm nozzle microFDM device manufactured by electroforming techniques. These models were used in a simulation analysis whose results show a relationship between the convergence of the algorithm and the characteristics of the filament obtained in equivalent experimental testing.Besides, melt fracture and relevance of swelling was assessed by optical microscopy observation. This information allows to define operating conditions (in terms of temperature and shear rate) to obtain homogeneous morphological characteristics of the microextrudate. Furthermore, the procedure stated could be used in tissue engineering to delimit feasible operating conditions to manufacture scaffolds by fused deposition modeling.     

An experimental study of the hadron calorimeter module response to protons and pions with energies of 1–5 GeV

The design of the hadron calorimeter module is discussed. Such modules are expected to be used in the forward calorimeters of the Multi Purpose Detector (MPD) (Dubna, Russia) and Compressed Barionic Matter (CBM) (Darmstadt, Germany) experiments. The module has transverse dimensions of 20 × 20 cm² and is composed of 60 16-mm-thick lead layers interleaved with 4-mm-thick scintillator plates. Light from scintillator plates is captured by wavelength-shifting optical fibers. The module has longitudinal segmentation and consists of 10 sections. Light collected from each section is read out by micropixel photodiodes with a sensitive area of 3 × 3 mm². Test measurements of the energy resolution and linearity of the calorimeter module response in the hadron momentum range of 2–6 GeV/c have been performed. The longitudinal profiles of the hadron shower, obtained in the measurable energy range both for pion and proton beams, are discussed. The measured energy resolution and the linearity of the calorimeter module response at low energies are presented and compared to the data obtained at high energies.     

Experimental method of fabrication of a matched metal–dielectric structure for a sensor based on the effect of frustrated total internal reflection

An experimental method of fabrication of a sensor based on a metal–dielectric structure (Al + ZnS) and optimization of its characteristics is described. The coefficient of light reflection (p-polarization) from the aluminum layer is studied as a function of the layer thickness for different angles of incidence at the wavelength of 532 nm. Based on calculations, which are qualitatively consistent with experimental results, a structure consisting of matched layers of aluminum and zinc sulfide is fabricated; this structure has a higher angular resolution than the aluminum film with no dielectric coating. The detection limit of angular measurements by the sensor based on this structure is estimated as 2.6 · 10^-5 RIU (refraction index units).     

An improved algorithm for McDowell’s analytical model of residual stress

The analytical model for two-dimensional elastoplastic rolling/sliding contact proposed by McDowell is an important tool for predicting residual stress in rolling/sliding processes. In application of the model, a problem of low predicting precision near the surface layer of the component is found. According to the volumeconstancy of plastic deformation, an improved algorithm for McDowell’s model is proposed in order to improve its predicting accuracy of the surface residual stress. In the algorithm, a relationship between three normal stresses perpendicular to each other at any point within the component is derived, and the relationship is applied to McDowell’s model. Meanwhile, an unnecessary hypothesis proposed by McDowell can be eliminated to make the model more reasonable. The simulation results show that the surface residual stress predicted by modified method is much closer to the FEM results than the results predicted by McDowell’s model under the same simulation conditions.     

An experimental study on real–time analysis of two–phase peristaltic slug flows in dialysis machines

Two–phase flows appear in many industrial and biomedical applications. One of the most vital biomedical applications of two–phase flows is in hemodialysis machines due to air embolism and heparin injection. Since these flows have a very complex and intermittent nature, studying their dynamics is a very challenging and fundamental problem. The purpose of this article is to present an experimental study on the dynamics of two–phase peristaltic slug flows. The measurement strategy is based on the image processing technology. The characteristic parameters of the two–phase pulsatile slug flows, including the slug length, as well as the translational velocity and frequency of the slug motion, are measured, and the effect of the liquid flow rate and liquid superficial velocity is investigated. The results show that the average and maximum slug velocities, and also the dominant amplitude of the slug velocity increase with the flow rate and liquid superficial velocity, while it is not possible to clearly predict a correlation between the liquid superficial velocity and the slug length. The measurement strategy presented in this article can be used in the control and alarm systems of smart dialysis machines.     

An ion pulse ionization chamber for spectrometric measurements of low surface α activities

The design of a pulse ionization chamber for measuring the surface αactivity of various samples is described. When used together with the appropriate methods for recording and processing the signals, a low-background spectrometer based on this chamber is able to ensure a high sensitivity in direct measurements of ultralow surface α activities. This approach offers a solution to the problem of controlling superpure materials used in detectors for studying rare nuclear processes with a broken equilibrium in the decay chains of the uranium and thorium series. A procedure for modeling the shape of the current pulses according to the orientation of α-particle tracks and their location inside the chamber is described. Results obtained with an α source, as well as with copper and VM2000 light-reflecting film samples, are presented.     

An experimental study of process variables in turning operations of Ti–6Al–4V and Cr–Co spherical prostheses

Ti–6Al–4V and Cr–Co alloys are extensively used in manufacturing prostheses due to their biocompatibility, high strength-to-weight ratio and high resistance to corrosion and wear. However, machining operations involving Ti–6Al–4V and Cr–Co alloys face a series of difficulties related to their low machinability which complicate the process of controlling the quality levels required in these parts. The main objective of this paper is to study the influence of cutting parameters, machine tool control accuracy and metrology procedures on surface roughness parameters and form errors in contouring operations of Ti–6Al–4V and Cr–Co workpieces. The machining performance of the two biocompatible materials is compared, focusing the study on part quality at low feed per revolution and the stochastic nature of plastic deformations at this regime. The results showed a better surface roughness control for Ti–6Al–4V, whereas for Cr–Co alloys, the performance presents high variability. In the case of form errors (sphericity), contouring errors and metrology procedures are important factors to be considered for quality assurance. In addition, the study analyses the correlation of the machining performance with different sensor signals acquired from a low cost non-intrusive multi-sensor, showing a high correlation of signals from acoustic emission sensors and accelerometers in the machining of spherical features on Ti–6Al–4V parts. The findings of this research work can be taken into account when designing prostheses components and planning their manufacturing processes.     

A multichannel spectrometer for detecting γ rays in a wide range of time intervals during pulse neutron irradiation

A versatile spectrometer has been developed for measuring the nuclear radiation spectrum in discrete time intervals. The design and operating principle of the spectrometer are described. Since the main logical part is based on a field programmable gate array, time intervals may be tuned in a wide range without changing the spectrometer hardware. The test experiments have demonstrated the spectrometer applicability for measuring the amplitude and timing parameters of the γ response when an analyzed sample is irradiated with a pulsed neutron flux. This device can be used to solve many problems of nondestructive testing, e.g., spectrometric neutron logging, detection of explosives, identification and characterization of fissile materials.     

A theoretical model of slider–disk interaction and AE sensing process for studying interface phenomena and estimating unknown parameters

Theoretical models were developed for comprehensively accounting for the AE sensing process in the measurement of interfaces between different sliders and magnetic rigid disks. The models include tribological factors and system dynamics factors such as contact force, sliding velocity, lubricant thickness, topographic parameters, mechanical parameters, system transfer functions and filter design parameters. The theoretical models agree well with the experimental results conducted for different slider–disk interfaces. The models are also well correlated with extensively published experimental results. This revised version was published online in July 2006 with corrections to the Cover Date.