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We developed an optically synchronized highly stable frequency-doubled Nd:YAG laser with sub-nanosecond pulse duration. The 1064 nm seed pulses generated by soliton self-frequency shift in a photonic crystal fiber from Ti:sapphire oscillator pulses were stabilized by controlling input pulse polarization. The seed pulses were amplified to 200 mJ by diode-pumped amplifiers with a high stability of only

We developed an optically synchronized highly stable frequency-doubled Nd:YAG laser with sub-nanosecond pulse duration. The 1064 nm seed pulses generated by soliton self-frequency shift in a photonic crystal fiber from Ti:sapphire oscillator pulses were stabilized by controlling input pulse polarization. The seed pulses were amplified to 200 mJ by diode-pumped amplifiers with a high stability of only

To improve the accessibility of emergency vehicles after a large earthquake, it is important to quantify the effects of risk mitigation strategies. In this paper, using a simulation model that describes the movement of emergency vehicles amidst property collapse after a large earthquake, we evaluate street network accessibility in the Tokyo Metropolitan Area. Moreover, by analyzing the relationships between local environments and street network accessibility, we discuss the effects of risk mitigation strategies on improving street network accessibility.

In order to realize a compact and high repetition rate plasma X-ray laser, we have developed a recombination scheme plasma X-ray laser. In particular, we focused on a laser oscillation of Li-like aluminum 3d-4f transition (15.5 nm), which was already demonstrated in a high-density and low-temperature Al laser plasma with a low gain coefficient. In this study, by using an Nd:YAG laser (500 ps, 3 J, 16 pulse-trains) we created the lasing media and succeeded in laser oscillation at 15.5 nm. The optimization of the pulse-train in terms of the pulse duration and its interval enhanced the gain coefficient to g = 4.3 cm−1.

At the time of a large earthquake, property collapse (e.g., building collapse and street blockage) will obstruct emergency activities (e.g., firefighting activity and ambulance service) and cause the expansion of secondary damage. For reducing the secondary damage of a large earthquake, it is important to assess the accessibility of emergency activity under property collapse. However, the accessibility index, which can evaluate the emergency activity considering the effect of property collapse, is not developed nor applied in actual urban area. In this paper, we propose the street network accessibility: indices of assessing the movement of emergency vehicles. Then, we construct a simulation model that describes property collapse and the movement of emergency vehicles. Performing the simulation in Tokyo Metropolitan Area, we evaluate the damage of each building/street and assess the street network accessibility after a large earthquake. Finally, analysing the relationships among indices, we indicate that it is important to evaluate the street network accessibility from multiple viewpoints.

It is difficult to evaluate the street network accessibility after a large earthquake occurs. In this paper, we construct a model to evaluate the street network accessibility for wide-area emergency behaviors under the condition of property damage in the Tokyo Metropolitan Area after a large earthquake. Additionally, we analyze the relationships between a local environment and street network accessibility by using multiple regression analysis. Finally, we discuss some important factors for evaluating risk mitigation strategies.

Changes in land use in established city areas generally arise when older style buildings are demolished and replaced by contemporary buildings. The direction and the speed of land use change are dependent on the possibility and probability that buildings will be demolished or will remain in the future. Hence, various studies about the life span of buildings have been carried out, and proposed statistical models that could estimate the value of probability that buildings would be demolished or would remain in a specific time interval, based on the age of buildings. However, in general it is not easy to acquire the necessary information about the age of buildings. In order to extend the application of the proposed model to these cases, we propose a method for estimating the number of buildings that will remain in the future when data about the age of buildings cannot be obtained.

The Metropolitan Tokyo Ordinance on Measures Concerning Stranded Persons (hereafter, the Tokyo Metropolitan Government Ordinance (TMGO)) was enacted in April, 2013 as part of efforts to encourage employers and schools to keep their employees, students, or young children in place, rather than freeing them set out for home when public transportation has been paralyzed by a major earthquake or other disaster. However, whether a person decides to return home or not depends on his or her individual attributes and other factors such as the presence of family members at home, and it is uncertain whether the TMGO will actually be effective in reducing the number of people attempting to return home. Therefore, a survey on individual courses of action after a major earthquake was conducted. This data was employed to construct a probabilistic model for predicting whether an individual will “try to walk home”, “try to return to, or stay in, his/her workplace or school”, or “try to take some other action”, based on the individual’s attributes and the walking distances. This model was applied to person-trip survey data in the Tokyo metropolitan area to estimate the numbers of people walking home after a major earthquake, after which a quantitative prediction of the effectiveness of the TMGO on attempts to return home was made.

To generate bright water-window (WW) soft x rays (2.3–4.4 nm), gold slab targets were irradiated with laser pulses (1064 nm, 7 ns, 1 J). Emission spectroscopy showed that the introduction of low-pressure nitrogen enhanced the soft x-ray yield emitted from the laser-produced Au plasma. The intensity of the WW x-ray transported in a 400-Pa N2 atmosphere from the laser-produced plasma increased by 3.8 times over that in vacuum. Considering a strong x-ray absorption, the x-ray yield emitted directly from the Au plasma in the N2 gas was evaluated to be 13 times higher than that in vacuum. Although similar measurements were made for various gases, only N2 gas causes an increase in a soft x-ray yield. The processes leading to this enhancement mechanism were revealed by using hydrodynamic simulation and atomic structure codes.

We present a systematic approach how to characterize the dynamics of a laser-produced Au plasma, generated with a commercial Joule-class laser system. By means of our diagnostic methods, we identify the dominant ionic species within the water-window spectral region, as well as the radiated energy, the x-ray emission duration and the total dimensions of the x-ray source. We present additional analysis through radiation hydrodynamic simulations to provide details about the electron temperature and density profiles and further show that the plasma exhibits nearly 20% self-absorption, while the electron temperature is limited to 400 eV. A comparison with the experimental data further allows us to verify the applied numerical code.

We present a systematic approach how to charactorize the dynamics of a laser-produced Au plasma, generated with a commercial Joule-class laser system. By means of our diagnostic methods, we identify the dominant ionic species within the water-window spectral region, as well as the radiated energy, the x-ray emission duration and the total dimensions of the x-ray source. We present additional analysis through radiation hydrodynamic simulations to provide details about the electron temperature and density profiles and further show that the plasma exhibits nearly 20% self-absorption, while the electron temperature is limited to 400 eV. A comparison with the experimental data further allows us to verify the applied numerical code.

A Li-like Al soft x-ray laser oscillation (15.47 nm) by means of recombination plasma scheme was investigated to enhance the gain coefficent of lasing medium. In this study, we employed a Nd:YAG laser pulse composed of 8-pulse train, in which each pulse width was 400 ps and its interpulse time was 400 ps. The laser beam was tightly line-focused into 50 μm in height and 12 mm in length on Al slab target by using prism lens array. The created cylindrical plasma showed that with increasing plasma length the lasing intensity at 15.47 nm increased expoentially up to 3.5 mm. For the laser energy of 3 J, the gain coefficient was 8.3 cm−1. Above 3.5 mm in length, the signals seemed to increase linearly, indicating that the lasing action reached the saturation regime.

A Li-like Al soft x-ray laser oscillation (15.47 nm) by means of recombination plasma scheme was investigated to enhance the gain coefficent of lasing medium. In this study, we employed a Nd:YAG laser pulse composed of 8-pulse train, in which each pulse width was 400 ps and its interpulse time was 400 ps. The laser beam was tightly line-focused into 50 μm in height and 12 mm in length on Al slab target by using prism lens array. The created cylindrical plasma showed that with increasing plasma length the lasing intensity at 15.47 nm increased expoentially up to 3.5 mm. For the laser energy of 3 J, the gain coefficient was 8.3 cm−1. Above 3.5 mm in length, the signals seemed to increase linearly, indicating that the lasing action reached the saturation regime.

Inorganic phosphate (Pi) is an essential nutrient for maintaining various biological functions, particularly during growth periods. Excess intake of dietary Pi increases the secretion of fibroblast growth factor 23 (FGF23) and parathyroid hormone to maintain plasma Pi levels. FGF23 is a potent phosphaturic factor that binds to the α-klotho/FGFR complex in the kidney to promote excretion of Pi into the urine. In addition, excess intake of dietary Pi decreases renal α-klotho expression. Down-regulation or lack of α-klotho induces a premature aging-like phenotype, resulting from hyperphosphatemia, and leading to conditions such as ectopic calcification and osteoporosis. However, it remains unclear what effects dietary Pi has on α-klotho expression at different life stages, especially during growth periods. To investigate this, we used C57BL/6J mice in two life stages during growing period. Weaned (3 weeks old) and periadolescent (7 weeks old) were randomly divided into seven experimental groups and fed with 0.02, 0.3, 0.6, 0.9, 1.2, 1.5, or 1.8% Pi diets for 7 days. As a result, elevated plasma Pi and FGF23 levels and decreased renal α-klotho expression were observed in weaned mice fed with a high Pi diet. In addition, a high Pi diet clearly induced renal calcification in the weaned mice. However, in the periadolescent group, renal calcification was not observed, even in the 1.8% Pi diet group. The present study indicates that a high Pi diet in weaned mice has much greater adverse effects on renal α-klotho expression and pathogenesis of renal calcification compared with periadolescent mice.

Mesoscopic polarization structures such as polar nanoregions and polarization domain walls are the key factors that connecting microscopic fundamental polarization structures with macroscopic practical dielectric properties. Snapshot observation of domain in the relaxor-ferroelectrics PMN-x%PT just vicinity of morphotropic phase boundary region was performed by use of 7 ps single shot soft X-ray laser pulse. A self-assembled evolution of oblique polarization domain was observed in PMN-27.8%PT under the sample temperature decreased with thermal equilibrium condition. Based on energetic discussion, anti-phase shift of domain wall pairs keeping with flat boundaries was proposed for the dielectric response. A sharp enhancement in dielectric response at the vicinity of morphotropic phase boundary region reported previously was recognized as an evidence for hierarchic nature of the present oblique polarization domain wall.

A laser-plasma soft X-ray microscope which is a combination of a highly intense laser-plasma soft X-ray source and a contact microscopy has been developed. We have proposed a correlative imaging method with the laser-plasma soft X-ray microscope and a fluorescence microscope to observe the same biological cells with the both microscopes at the same time. Live hydrated biological cells and cellular organelles have been observed with the correlative imaging method. Using the information of the cellular organelles obtained with the fluorescence microscope, inner structures obtained with the soft X-ray microscope are identified. Since the spatial resolution of the soft X-ray microscope is much higher than that of the fluorescence microscope, fine structures of the cellular organelles of the live biological cells have been visualized with the correlative imaging.

We report recent advances on the J-KAREN laser upgrade to provide an intensity capacity surpassing 1022 W/cm2 at 0.1 Hz. Currently, the high-spatiotemporal quality broadband pulses are amplified to over 55 J at 0.1 Hz.

Laser-matter interaction is defined by an electronic band structure of condensed matter and frequency ωL of electromagnetic radiation. In the range of moderate fluences, the energy absorbed by electrons from radiation finally thermalizes in the ion thermal energy. The thermalization processes are different for optical as compared with X-ray quanta and for metals relative to semiconductors and dielectrics, since the light absorption and electron-electron, electron-ion dynamics are sensitive to the electron population in a conduction band and the width of a forbidden gap. Although the thermalization processes are different, the final state is simply a heated matter. Laser heating creates powerful stresses in a target if duration of a laser pulse τL is short in acoustic time scale. Nucleation and material removal take place under such stresses. Such way of removal is called here the spallative ablation. Thus the spallative ablation is an ablation mechanism universally important for qualitatively different materials and quanta. c

Actin filaments in Leydig cells from mouse testes have been observed with a contact-type soft x-ray microscope with laser plasma x-ray source. The Leydig cells were fixed with paraformaldehyde, stained with Phalloidin, and observed with a confocal laser microscope prior to the observation with x-ray microscope. Obtained images by both of the confocal laser microscopy and the x-ray microscopy were directly compared and revealed that not only position of actin filaments but also the shapes can be identified each other. The actin filaments in the x-ray images were clearly recognized and their structures were obtained in more detail compared to those in the confocal laser microscope images.

The results of theoretical and experimental studies of ablation of LiF crystal by X-ray beam having photons with 89.3 eV and very short duration of pulse τ = 7 ps are presented. It is found that the crater is formed for fluences above the threshold Fabl ≈ 10mJ/cm2. Such a small threshold is one order of magnitude less than the one obtained for X-ray ablation by longer (nanoseconds) pulses. The theory explains this dramatic difference as a transition from more energy-consuming evaporative ablation to spallative ablation, when the pulse duration decreases from ns tops time ranges. Previously, the spallative mechanism of ablation was exclusively attributed to removal of target materials of metal and semiconductor by the short laser pulses with optical photons ∼ 1eV. We demonstrate that tensile stress created in dielectrics by short X-ray pulse can produce spallative ablation of target even for drastically small X-ray fluences (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We attempted the first measurement of the spectral width of the nickel-like molybdenum x-ray laser ( ${\lambda}\;=\;18.895\;nm$ ) by use of a high-resolution spectrometer in order to determine the strength of the magnetic field required for the generation of a circularly polarized x-ray laser. The spectral width was measured to be ${\Delta}{\lambda}\;=\;18\;m{\AA}$ under the substantial lasing condition. The magnetic field required for the generation of a circularly polarized x-ray laser was 40 T. The splitting of the x-ray laser line was clearly obtained under 15 T external magnetic field. The strength of the magnetic field estimated from the splitting of the x-ray laser line was large compared with the external magnetic field. It implies that there might be an alternative mechanism for enhancement of the magnetic field in the gain medium plasma.

We have recently reported the successful development of a fully coherent X-ray laser (XRL) at 13.9 nm by an oscillator-amplifier configuration with two targets. In the experiment, a seed XRL beam from the first target is injected into a plasma amplifier at the second target. The observed XRL beam has full spatial coherence and 0.2 mrad of nearly diffraction-limited divergence. In order to improve the output fluence, the amplification properties of the XRL beam have been investigated using various plasma lengths of the second amplifier target. The output energy has been improved by a factor of ten, increasing the length of the gain region to 10 mm, resulting in about 0.2 /spl mu/J of output energy.

Micrometer pixelated arrays comprised of different functional organic molecules were formed on a polymer film using a laser implantation and transfer dry processing technique. The spatial distribution of the implanted organic molecules and the extended pattern that they formed could be controlled with high resolution as determined using fluorescence microscopy. The individual molecular implant pixels had a diameter of less than 4 μm. This method of molecular manipulation is both precise and reproducible and could therefore be used in many applications such as molecular devices, molecular sensors, non-linear optical devices, drug delivery and opto-electronic displays.

A laser-pumped x-ray laser with full spatial coherence has been developed for the first time. This x-ray laser has a wavelength of 13.9 nm and a beam divergence of 0.2 mrad. In the experiment, a seeding light from the first laser medium was amplified in the second medium, which worked as an active spatial filter. The observed beam divergence was close to the diffraction limited value within a factor of two. The seeding light was amplified in the second medium without refraction influence. The gain region of the second medium was far away from the target surface compared with that of the first medium, and was located in a region of considerably low density. From the measurement of visibility, it was found that the spatial coherent length was longer than the beam diameter. This means that this xray laser beam has full spatial coherence.

In this paper, we report the first measurement of the time-integrated spatial coherence of the Ni-like Ag X-ray laser at 13.9 nm pumped by a 1.5 ps, 20 J Nd glass laser, in which the transient collisional excitation (TCE) pumping scheme is realized. The time-integrated complex coherence factor (CCF) of the X-ray laser has been determined from partially coherent diffraction patterns of a multislit array placed 1 m away from the X-ray laser source. The transverse coherence lengths in the directions horizontal and vertical to the Ag target surface are estimated respectively to be within 110 µm to 140 µm at a position 1 m from the X-ray laser source. We tried to explain the profile of the CCF with a quasi-monochromatic incoherent source model with various profiles.

兵庫, 奈良, 岡山の大学に通う19～24歳の大学生 (男子329名, 女子406名) を対象に健康と食生活に関するアンケート調査を実施した.1) 調査対象者の多くは健康に興味・関心をもっており, それらに関する知識の情報源は「テレビ・ラジオ」が多かった. しかし, 健康よりも男子では「遊び」「恋愛」に, 女子では「美容・ファッション」「遊び」に対する興味・関心の方が強かった.2) 健康のために心がけて摂取している食品群は「乳類・乳製品」, 「緑黄色野菜」や「淡色野菜」の野菜類で, 健康食品は「足りない栄養を補う」ためであったが, 利用頻度は低かった.3) 健康のために重要視するのは「睡眠時間」, 「栄養バランス」で, 「運動」は少なく, また, 女子では「特に運動をしていない」が約43%存在した.4) 外食の多くは昼食と夕食で, 男子では「洋食定食」を女子では「洋食一品料理」を選択し, 男女差があった.5)「健康に興味・関心がある」者ほど日常の食事に気をっけ, 積極的に情報を得ており, 食生活の自己評価が高かった. 自己評価の高い者ほど外食や市販菓子の摂取頻度が低かった.6) 食生活を充実させるという「強い意志」が食生活改善に必要であるとの回答が多かったことから, 若者では健康・栄養に関する知識があり, 健康の大切さを認識していてもそのための実践が伴わない者が多いことが示唆された.

Low frictional coatings made of copper, boron nitride, and oxygen on a stainless steel substrate were synthesized by magnetron cosputter deposition combined with excimer laser irradiation. The frictional force of the coating films was observed by a system developed for measuring vacuum friction. The coating properties were also observed by a conventional contact angle measuring system, a scanning Auger electron spectrometer, and a Vickers hardness measuring system. The surface layer of the coating films was oxidized by the excimer laser irradiation. Surface energy and film hardness were also modified by the laser irradiation. Frictional coefficients as low as 0.075 were achieved after irradiating the films under ultrahigh vacuum conditions. Since these coating films have already been oxidized and irradiated with high energy UV light they will be applicable for aerospace coatings.

A novel readout method using wavelength-shifting fibers aimed at real-time imaging for X-ray and neutron was developed. It is confirmed that the PSLs can be detected by wavelength-shifting fibers with sufficient sensitivity and a radiation image can be measured with good position resolution by the readout method.

J-KAREN-P is a high-power laser facility aiming at the highest beam quality and irradiance for performing state-of-the art experiments at the frontier of modern science. Here we approached the physical limits of the beam quality: diffraction limit of the focal spot and bandwidth limit of the pulse shape, removing the chromatic aberration, angular chirp, wavefront and spectral phase distortions. We performed accurate measurements of the spot and peak fluence after an f/1.3 off-axis parabolic mirror under the full amplification at the power of 0.3 PW attenuated with ten high-quality wedges, resulting in the irradiance of ~1022 W/cm2 and the Strehl ratio of ~0.5.

The wavelength region between the K-edges of carbon and oxygen is termed as the water window (λ = 2.3–4.5 nm) and is considered to be suitable for the observation of nanometer-scale structures composed of light elements in an aqueous solution because of both the short wavelength and transparency of the light. The nanometer-scale structures in an aqueous solution fluctuate owing to Brownian motion. Therefore, the observation of the nanometer-scale structures can be achieved by one-shot exposure of the light in the water window. To observe the nanometer-scale structures by the one-shot exposure, the light source of the microscope working in the water window should exhibit a high light-flux. One of the light sources used for the one-shot exposure is the laser-produced plasma (LPP) light source. The conversion efficiency of the LPP light source in the water window is 1% or less. Therefore, a high intensity laser or improvement of the conversion efficiency is required for the one-shot observation. In this stud...

Functional organic molecules have been manipulated into fluorescent features as small as 450 nm on a polymer film using a method derived from laser ablation and laser implantation. The technique utilizes a piezodriver to position a pipette, having a 100 nm aperture and doped at the tip with organic molecules, tens of nanometers above a polymer film. The pipette is subsequently irradiated using 3 ns (full width at half maximum) laser pulses guided down to the tip by a fiber optic. This method of ablation confinement gives fine spatial control for placing functional organic molecules in a designated region and will have applications in optoelectronics. It could also be applied to drug delivery or biotechnology, because in principle, different molecules of diverse function can be manipulated in the same way for various purposes.

The width of the mesa (and well) however is vital to the epitaxy. Epitaxial growth is nucleated by the edges of the mesas. If the width of the mesa is 5 lm or larger, the preferred alignment of the crystal near its edges does not persist for the entire width of the mesa, so the center of the stripe reverts to the polygrain structure of films on flat substrates. When the edges of the mesas are less than 5 lm apart, the grains on either side of the mesa join, creating a single grain across the entire width of the mesa (or well) as seen in Figure 2. In summary we have demonstrated that graphoepitaxy offers a facile, efficient way to produce thin film arrays of spherical block copolymer domains with good long range order. This method could be useful for controlling the orientation and registration of these domains for use as nanolithographic etching masks. The well-ordered mesoscopic structures that can be subsequently produced may lead to new devices for quantum electronics and optics.

Functional organic molecules can be space-selectively implanted into polymer films by pulsed laser irradiation. This method has been developed for fabricating nano- and micro-scale fluorescent patterns on polymer surfaces. Two approaches employing scanning probe microscopy and conventional optical microscopy have been demonstrated. The former used a glass pipette having aperture of 100 nm, doped with fluorescent organic molecules at the tip. The distance between the tip and a polymer surface was controlled by a piezo driver to within a few tens of nanometer. Then nanosecond pulsed laser light was guided into the pipette with a glass fiber producing a nano-jet of organic molecules that is ejected towards the polymer surface, resulting in disklike implantation with a diameter of a few hundred nanometers. It was also demonstrated that a conventional microscope is useful to manufacture micro-scale patterns with functional organic molecules. This mechanism of the microscopic implantation is discussed based on experimental parameters affecting implantation size.

The photostimulated luminescence (PSL) characteristics of an imaging plate (IP) irradiated with α-ray has been experimentally investigated in order to construct a theoretical model on PSL phenomenon. In this way the nonlinearity of PSL intensity to α-ray dose, the dependence of PSL intensity decay on PSL excitation light power and the saturation of PSL intensity with increasing PSL excitation light power have been found.We propose a rate equation that describes the time evolution of the number of holes and F centers in the phosphor with α-ray dose and show that the nonlinearity of the PSL intensity to α-ray dose is caused by hole and F center recombination losses.Next we construct a theoretical model for the interaction of the PSL excitation light photon with the F center and the recombination of the conduction band electron with the hole. This shows that the constructed PSL model reproduces the decay of PSL intensity and the relationship between α-ray dose, PSL excitation light power and PSL intensity.Finally, fading experiments of IP have been performed. With elapsed time there was a rapid decrease of PSL intensity with a corresponding increase in its fluctuation. We propose a theoretical model for the fading of the IP and thereby show that the fading phenomenon is caused by the production of a large and fluctuating number of unstable F (Br-) centers.

The readout characteristics of an imaging plate (IP) by fast laser pulses have been studied using an /spl alpha/ particle source. The total photostimulated luminescence (PSL) detected with the system was proportional to the /spl alpha/ particle irradiation time. It can be used for radiation dose measurement. The accumulated radiation information in the IP is decreased by reading PSL signal with the laser pulses. The PSL decay curve in each frequency is well fitted by a single exponential function. Linear dependency of the decay constant on the repeated frequency of the pulse was observed in a frequency range from 60 kHz to 200 kHz. The readout method with fast laser pulses will be useful for development of novel radiation detection system and investigation of successive repeated readout characteristics and fading effects of the IP.

We propose a novel signal processing method to improve the energy resolution of superconducting tunnel junction X-ray detectors with quasiparticle trapping. Current signals produced in the detectors are amplified by a fast current preamplifier with a bandwidth of 110 MHz, and divided into two parts, i.e., the rise part and the decay part. It was found that the best energy resolution was obtained by using the integrated charge of the rise part. This indicates that the charge of the decay parts has a charge scatter larger than that of the rise part.

We have developed a fast current readout system for STJ detectors with a fast current preamplifier by direct signal observation. The preamplifier has frequency bandwidth of 110 MHz with stable voltage bias operation. By the various experiments using a Ta STJ and Nb STJ, it is confirmed that the readout system is effective for the evaluation of STJs, research of the mechanism for signal production process and the X-ray detection with high counting rate. (C) 2000 Elsevier Science B.V. All rights reserved.

The electron collision cascade process of primary photoelectrons generated by absorbed X-rays was studied to develop a clear model of the signal producing process of a superconducting tunnel junction (STJ), and the intrinsic peak probability P I of the STJ was calculated as a function of X-ray energy. X-rays of 5–18 keV were measured by a 178 μ m×178 μ m Nb/AlAlO 2 /Al/Nb STJ with the Nb electrode thickness of 200 nm and P I was experimentally obtained. The calculated P I agreed well with the measured one for the range of X-ray energies of 5–12 keV. The numerical evaluation of P I with this model reveals that the increases of the electrode thickness is effective to increase P I .

A low-noise charge-sensitive preamplifier with cooled 4-JFETs was developed for an X-ray detector of a Nb-based superconducting tunnel junction with a large capacitance and a low leakage current. The low-noise characteristics for a wide range of shaping times were obtained by using a selected JFET, 2SK 190 in the first stage of the preamplifier. A new formula to simulate the preamplifier noise was developed and applied to the optimization of preamplifier design. A high-energy resolution of 66 eV for 5.9 keV X-ray and 51 eV for pulser signals was obtained by using the optimized preamplifier with an X-ray detector of a 178 μ m × 178 μ m Nb/Al-AlO 2 /Nb superconducting tunnel junction with a junction capacitance of 1900pF and a bias current of 1.44nA.

High quality Nb-based tunnel junctions with surface areas of 100 x 100 μm2 and 200 x 200 μm2 were tested by irradiating X-rays. According to the decrease in the disappearance of quasiparticles before tunneling, the 200 x 200 μm2 junction exhibited better X-ray response than that of 100 x 100 μm2 one. In the operation of the 200 x 200 μm2 junction, two kinds of stable operation modes with different pulse heights were found by applying a magnetic field with different ramping speeds. The higher pulse height mode was observed with a ramping-speed faster than about 200 G/s. After tuning of the bias current in the higher mode operation, the energy required for single electron collection was obtained to be 6.5meV and the junction detected 5.9keV X-rays of 55Mn with an energy resolution (FWHM) of 93eV. The 200 x 200 μm2 junction has the largest dimension among tunnel junctions exceeding silicon-semiconductor detectors in energy resolution.