The use of passive personal neutron dosemeters to determine the neutron dose equivalent component of radiation fields in spacecraft

For the altitude range and inclination of the International Space Station (ISS), secondary neutrons can be a major contributor to dose equivalent inside a spacecraft. The exact proportion is very dependent on the amount of shielding of the primary galactic cosmic radiation and trapped particles, but is likely to lie in the range of 10-50%. Personal neutron dosemeters of simple design, processed using simple techniques developed for personal dosimetry, may be used to estimate this neutron component.     

Height-keeping reliability of aircraft at high altitude

Increasing congestion in high altitude air routes has led to an expectation of large financial benefits from a reduction in separation standards, which will enable more aircraft to fly closer to their optimal altitude. The safety of reduced separation depends mainly on the reliability of aircraft height-keeping, which is itself the product of a number of different airframe, instrument and pilot-related errors. This is the subject of an international programme of studies under way in Europe, Japan and the United States. A review of studies being carried out in Europe is presented, indicating some of the problems encountered.     

Boundary-based passive component inspection approach using eigenvalues of covariance matrices

A boundary-based scheme to inspect basic dimensions and surface defects on solder plates (terminations) of passive components by using the eigenvalues of covariance matrices was developed. The image of the passive component was initially processed to show only two terminations. The eigenvalues of covariance matrices for boundary points, which are equivalent to curvature measurements, then generate a one-dimensional representation describing the angle variations on termination boundaries. Since a single corner (intersection of two boundary edges) and jagged corners (a surface defect) are local deviations on termination boundaries, their locations will be represented as highly fluctuating eigenvalue waveforms. By setting an appropriate threshold on the eigenvalues, the surface defects and single corners on the termination boundaries can be identified. The basic dimensions of a passive component are determined simply by the distances between the detected single corners. Real passive components (0805 MLCCs) are testing samples to evaluate the performance of the proposed approach. Experimental results show that the proposed approach achieves precise identification for surface defects and measurement for the basic dimensions. The proposed approach is precise, rotation invariant and template free. Therefore, it is especially suitable for small batch production of various types of passive components.     

Analysis of the errors of active converters of passive electrical quantities

It is proposed that a vector relative error, which gives an upper estimate of the relative error of the conversion of the modulus and absolute argument, should be used. The relation between the vector error and the errors of converting the active and reactive components is established, which reveals the mechnism by which these errors are formed. __________ Translated from Izmeritel’naya Tekhnika, No. 7, pp. 50–51, July, 2006.     

Homogenous concept for the coupling of active and passive single-mode devices by utilizing planar gradient-index lenses and silicon-V grooves

A new concept for a common interface between passive and active single-mode devices is proposed. The submicrometer alignment accuracy necessary for efficient coupling of single-mode devices is extended to the range of some 10 mum by beam expansion with planar gradient-index microlenses; the increased angular sensitivity is satisfied by the use of planar surfaces. The imaging system is used off axis, resulting in a suppression of backreflections in the range >60 dB. Of many possible variations of components (fibers, waveguides, optoelectronic integrated circuits, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodiodes), the coupling of fibers and waveguides is examined in detail. Expected coupling efficiency and sensitivity to lateral misalignment are calculated by use of a modified beam-propagation method. In this way, the overall performance of the connector can be compared with existing connector concepts, and the feasibility of the concept is proven. Experimental results for the fiber-fiber connector are given.     

Estimating particle concentration using passive ultrasonic measurement of impact vibrations

A method of obtaining particle size and concentration information, from ultrasonic transducer measurements of particle-wall interactions in a particle laden fluid, is presented. A mathematical model of the flexural vibrations of the vessel wall due to the particle impact is constructed. The key component of this model is the derivation of an analytic expression for the impact force amplitude. An analytic expression for the power spectrum is then obtained that shows its explicit dependency on the system parameters. This spectrum is then integrated over a specific frequency range and a comparison with experimental results is reported.     

Surface tension measurement at the microscale by passive resonance of capillary waves

The properties of fluid interfaces increase in importance as the physical scale decreases and, hence, characterization of surface tension becomes all the more critical. However, there is to date no method to characterize this parameter on microscale surfaces. We propose here a simple method based on the resonance of capillary waves, which are naturally excited by thermal fluctuations, under one-dimensional spatial restrictions using single-beam dynamic light scattering. The principle was verified at methanol/air interfaces in polydimethylsiloxane (PDMS) microchannels having various widths. Characteristic comb-shape power spectra were experimentally obtained. Theoretical analysis showed that the spectral peaks correspond to the first or higher modes of the capillary wave resonance in the restricted space between the parallel channel walls. A useful relation between successive modes was derived to eliminate the effects of damping at the soft PDMS walls. Thus, for methanol, two values were calculated from three successive modes (24.8 and 21.2 mN/m); the literature value is 22.02 mN/m. For acetonitrile, the value obtained was 28.2 ± 5 mN/m, close to the literature value of 28.6 mN/m. Although accuracy and precision require further elucidation, this novel method is expected to become a powerful tool at the micro/nanoscale.     

Main inorganic component measurement of seawater using near-infrared spectroscopy

The potential of near-infrared (NIR) spectroscopy to measure the main inorganic components of seawater as salt-manufacturing materials was investigated. A total of 72 seawater samples collected from six locations was used, and spectra (1100-1800 nm) were acquired by a NIR spectrophotometer with a 1-mm path length. Principal component analysis (PCA), canonical correlation analysis (CCA), and partial least-squares (PLS) regression were performed based on the reference inorganic components. As a result, the principal component analysis and canonical correlation analysis showed that the near-infrared spectra could be related to the inorganic components of seawater. The partial least-squares regression analysis showed that the inorganic components (ion concentration of Cl, Na+, K+, SO4(2-), and Ca2+) could be predicted with good accuracy using NIR spectra and their second derivatives. For Cl ion and K+ ion concentrations, the accuracy was high.     

Wideband on-wafer noise measurement setup for noisecharacterization of active devices in the low VHF band

This paper addresses a new wideband on-wafer measurement test set designed for noise characterization of microwave active devices over the frequency range of 300 kHz to 150 MHz. Noise parameters obtained from the multiple impedance technique on a GaAlAs/GaAs heterojunction bipolar transistor (HBT) from 300 kHz to 70 MHz are reported and compared with low-frequency noise data. Investigation of the excess noise sources of III-V HBT's is performed well above the 100 kHz frequency limit of standard dynamic signal analyzers and noise modeling of these devices is reported     

Spectator detection for the measurement of proton–neutron interactions at ANKE

A telescope of three silicon detectors has been installed close to the internal target position of the ANKE spectrometer, which is situated inside the ultra-high vacuum of the COSY-Jülich light-ion storage ring. The detection and identification of slow protons and deuterons emerging from a deuterium cluster-jet target thus becomes feasible. A good measurement of the energy and angle of such a spectator proton (p_sp) allows one to identify a reaction as having taken place on the neutron in the target and then to determine the kinematical variables of the ion–neutron system on an event-by-event basis over a range of c.m. energies.

The system has been successfully tested under laboratory conditions. By measuring the spectator proton in the pd→p_spdπ⁰ reaction in coincidence with a fast deuteron in the ANKE Forward Detector, values of the pn→dπ⁰ total cross-section have been deduced. Further applications of the telescope include the determination of the luminosity and beam polarisation which are required for several experiments.     

Effect of wavelength-dependent attenuation on strain measurement using pulsed neutron diffraction

The measurement of stresses in engineering components and structures by neutron diffraction has traditionally been limited to depths of a few centimetres. However, recent developments in instrumentation open up the possibility of deeper measurements. It has been suggested that a systematic error may occur when measuring stresses deep in materials due to wavelength-dependent attenuation of the incident and/or diffracted beam. A series of experiments to evaluate the magnitude of this effect on ENGIN, a pulsed neutron strain scanner will be presented in this paper. It was found that the pseudo-strains induced by the attenuation of the diffracted beam were negligible, whereas there was a small but still noticeable effect produced by the attenuation in the incident beam. The possible causes of this shift and the consequences for deep measurements are discussed.     

Comparison of 24 GHz receiver front-ends using active and passive mixers in CMOS

This study compares the key parameters of two integrated receiver front-end architectures: low noise amplifier (LNA) with active mixer against LNA with passive mixer. The authors discuss the differences in the performance and their impact on system characteristics for radar applications. A low-IF down-conversion receiver implementation is considered. The results are compared in measurement for two 24 GHz receiver front-end chips realised in a 0.13 mm digital CMOS process. Both circuits have been characterised over automotive temperature range -40 to 125°C. The front-end with an active mixer offers lower LO power dependence and exhibits better temperature stability, whereas the front-end with a passive mixer has the advantage of better input-referred linearity and lower flicker noise.     

The measurement of humidity at high pressures

A humidity calibrator for measurements at pressures up to 15 MPa is designed. The effect of pressure on the characteristics of capacitive humidity sensors is demonstrated. A method of taking this effect into account is proposed. A procedure for calibrating humidity transducers with capacitive sensors at high pressure is described. __________ Translated from Izmeritel’naya Tekhnika, No. 2, pp. 61–64, February, 2008.     

Simulation and preliminary experimental results for an active neutron counter using a neutron generator for a fissile material accounting

An active neutron coincidence counter using a neutron generator as an interrogation source has been suggested. Because of the high energy of the interrogation neutron source, 2.5 MeV, the induced fission rate is strongly affected by the moderator design. MCNPX simulation has been performed to evaluate the performance achieved with these moderators. The side- and bottom-moderator are significantly important to thermalize neutrons to induce fission. Based on the simulation results, the moderators are designed to be adapted to the experimental system. Their preliminary performance has been tested by using natural uranium oxide powder samples. For a sample of up to 3.5 kg, which contains 21.7 g of ²³⁵U, 2.64 cps/g-²³⁵U coincidence events have been measured. Mean background error was 9.57 cps and the resultant coincidence error was 13.8 cps. The experimental result shows the current status of an active counting using a neutron generator which still has some challenges to overcome. However, the controllability of an interrogation source makes this system more applicable for a variety of combinations with other non-destructive methods like a passive coincidence counting especially under a harsh environment such as a hot cell. More precise experimental setup and tests with higher enriched samples will be followed to develop a system to apply it to an active measurement for the safeguards of a spent fuel treatment process.     

Extremely high dose neutron dosimetry using CR-39 and atomic force microscopy

Atomic force microscopy (AFM) has been applied to the analysis of CR-39 nuclear track detectors for high dose neutron dosimetry. As a feasible study to extract the neutron dose, we have employed a (239)Pu-Be neutron source with the traditional track density measurement of recoil proton etch pits from a high density polyethylene (CH(2)) radiator. After very short etching ( approximately 1 microm), etch pit densities were measured as a function of neutron fluence (neutron dose) up to 1.4 x 10(10) cm(-2) (6.6 Sv). Neutron sensitivity was also measured to be 6.6 x 10(-4). Maximum measurable neutron dose was estimated to be approximately 200 Sv by measuring the fraction of the total image area occupied by the etch pits.     

Non-destructive evaluation of nano-sized structure of thin film devices by using small angle neutron scattering

Nano-sized multi-layers copper-doped SrZrO3, platinum (Pt) and silicon oxide (SiO2) on silicon substrates were prepared by dense plasma focus (DPF) device with the high purity copper anode tip and analyzed by using small angle neutron scattering (SANS) to establish a reliable method for the non-destructive evaluation of the under-layer structure. Thin film was well formed at the time-to-dip of 5 microsec with stable plasma of DPF. Several smooth intensity peaks were periodically observed when neutron beam penetrates the thin film with multi-layers perpendicularly. The platinum layer is dominant to intensity peaks, where the copper-doped SrZnO3 layer next to the platinum layer causes peak broadening. The silicon oxide layer has less effect on the SANS spectra due to its relative thick thickness. The SANS spectra shows thicknesses of platinum and copper-doped SrZnO3 layers as 53 and 25 nm, respectively, which are well agreement with microstructure observation.     

A spectrometer for measurement of the neutron capture gamma multiplicity at a stationary research reactor

The multiplicity spectrometry technique of secondary emission of nuclei excited by thermal neutrons for the neutron cross sections measurements is developed. A multisectional NaI(Tl) scintillation detector for gamma-ray detection with high efficiency and 4π-geometry is used. The experiments are performed on a stationary 2 MW research reactor by the time-of-flight method. Such a method and apparatus are also to be used to measure the important neutron constant “alpha” (capture-to-fission ratio) for ²³⁵U.