A photodiode amplifier system for pulse-by-pulse intensity measurement of an x-ray free electron laser

We have developed a single-shot intensity-measurement system using a silicon positive-intrinsic-negative (PIN) photodiode for x-ray pulses from an x-ray free electron laser. A wide dynamic range (10(3)-10(11) photons/pulse) and long distance signal transmission (>100 m) were required for this measurement system. For this purpose, we developed charge-sensitive and shaping amplifiers, which can process charge pulses with a wide dynamic range and variable durations (ns-μs) and charge levels (pC-μC). Output signals from the amplifiers were transmitted to a data acquisition system through a long cable in the form of a differential signal. The x-ray pulse intensities were calculated from the peak values of the signals by a waveform fitting procedure. This system can measure 10(3)-10(9) photons/pulse of ~10 keV x-rays by direct irradiation of a silicon PIN photodiode, and from 10(7)-10(11) photons/pulse by detecting the x-rays scattered by a diamond film using the silicon PIN photodiode. This system gives a relative accuracy of ~10(-3) with a proper gain setting of the amplifiers for each measurement. Using this system, we succeeded in detecting weak light at the developmental phase of the light source, as well as intense light during lasing of the x-ray free electron laser.     

A stator for a self-running, ultrasonically-levitated sliding stage

Here we propose a self-running, ultrasonically-levitated sliding stage and investigate the levitation and propulsion characteristics of its stator. The stator consists of two aluminum beams and four PZT plates, which have two-paired bimorph configurations. A flexural standing wave was generated along the beam by applying an input voltage to the PZTs, and the stator could be levitated from a flat substrate by the acoustic radiation force generated by its own vibrating beam. The size of the stator was optimized using finite-element analysis (FEA) to maximize the vibration displacement amplitude of the beam. The flexural vibration modes at 24.3 and 102 kHz were the most prominent vibration modes having large displacement amplitudes. The stator was levitated at 23.2 and 96.1 kHz, which are close to the frequencies predicted by the FEA results. A standing wave was observed along the beam. The experimental and the simulated results showed good agreement. The levitation distance h was measured by varying the vibration displacement amplitude of the beam u, and was found to be proportional to u. When a traveling wave was excited along the beam by controlling the temporal phase difference of the two transducers, the stator could be made to hover and to move in the opposite direction to the traveling wave. The stator moved in the positive direction when the phase difference was in the ranges 0 degrees to 200 degrees and 310 degrees to 360 degrees, and in the negative direction when the phase difference was between 220 degrees and 260 degrees.     

Relationship between tile exfoliation and moisture content

In Japan, tile exfoliation from external walls is a serious problem that must be prevented. In our previous study, a tiled concrete sample was dried at a temperature of 105 °C for preconditioning. Then, tile exfoliation occurred. Since this seemed to indicate a relationship between tile exfoliation and moisture content, it was further pursued in this study. First, drying experiments on concrete samples just after tiling were carried out under different ambient air temperatures. The following results were obtained. ●Tile exfoliation occurs even at the lower drying temperatures. ●Tile exfoliation starts at corner tiles (seen in all experiments). ●When the average moisture content of the tiled concrete sample becomes lower than a certain value, tile exfoliation occurs. Next, the experiments were analyzed using a three-dimensional model of simultaneous heat and moisture transport. The calculated moisture content agreed well with the measured results. By comparing the measurement and simulation results, it is considered that the tiles are exfoliated when the moisture content of the mortar on the back side of the tile becomes lower than a certain value. Therefore, the moisture content can serve as an index for evaluating the occurrence of the tile exfoliation.     

Insulation characteristics of GIS under nonstandard lightning impulse oscillations: Insulation characteristics under double‐frequency oscillations with various frequencies and damping ratios

To improve GIS insulation specifications, it is important to recognize the insulation characteristics under oscillatory overvoltage waveforms occurring in the field. This paper describes investigations of insulation characteristics for double‐frequency oscillatory waveforms with various frequencies and damping ratios. It was found that minimum breakdown voltages (V_min) were irrelevant to frequency changes in the range of experimental conditions under the same damping conditions. On the other hand, V_min rose with the damping ratio rising under the same frequency conditions. The insulation characteristics at a valley of oscillation were investigated using actual breakdown voltages. It was found that the insulation characteristics were treated all‐inclusively based on the characteristics of V_min for damping time. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 11–19, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10245     

Motion and size estimation of a free moving metallic particle in GIS based on propagation properties of acoustic waves

We have investigated the propagation properties of Lamb waves and motion characteristic of free moving metallic particle in a gas‐insulated switchgear (GIS) tank to diagnose the insulation performance of GIS. We have proposed a new identification technique for defect location in GIS based on the time–frequency analysis of the Lamb waves using the Wavelet Transform. In this paper, we measured the acoustic signals excited by a metallic particle colliding with the tank sheath. Furthermore, we measured the moving particles under a high electric field in GIS using a high‐speed video camera. As a result, we examined the relationship between maximum lifting height and the flight time during subsequent impacts of a moving particle. Moreover, we estimated particle size based on the propagation properties of Lamb waves. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 26–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20023     

Fiber optic surface topography measurement sensor and its design study

This paper presents some aspects of design approach, modeling, and experimental measurement results of a fiber optic-based surface topography measurement sensor that can measure surface roughness as well as the distance between the sensor tip and a surface and surface inclination angles. The working principle of the sensor is based on the detection of light intensity reflecting from the surface being measured. The sensor is very small and easy to operate. It can be attached to a coordinate measuring machine (CMM) to measure surface position coordinates, inclination angles, and surface roughness in a noncontact manner at one measurement setup. A theoretical model of intensity distribution and intensity detection has been established for the sensor. A three-factor and three-level experiment was designed to investigate the relationship between sensor performance and sensor design parameters. Two second-order regression models have been generated, which show that the central distance between the emitting and receiving fibers of a sensor has the strongest influence on the effective range of the sensor; whereas, the critical angle of a receiving fiber influences the sensitivity of the sensor most.     

Studies on the thermal degradation of synthetic polymers: 16. Estimation of the product yield on the basis of intensity function for thermal gasification of polyethylene

The kinetic equation for the pyrolysis gasification reaction of four kinds of polyethylene, differing from one another in average molecular weight, has been established. Differences in the molecular weight of the samples have no effect on the kinetic parameters when the molecular weight is 10⁴ or above. The intensity function, I_F=Tθ^a (K s^a), describing the severity of the decomposition conditions, has experimentally turned out to be a temperature throughout the residence time, θ, for reactions constrained by Arrhenius parameters A and E. The value of the exponent, a, may be found approximately from the kinetic parameters in this experiment. The values of the product yield calculated from the Arrhenius equation, $\text{k = A}\text{exp}\text{(}\text{?E}\text{RI}{}_{\mathrm{F}}\text{)}$, for a particular I_F, agree with the experimental values.     

Estimating Sediment Budget at a River Basin Scale Using a Process-Based Distributed Modelling Approach

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant’s principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels.