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We have measured the energy of each charged particle in carbon ion beam using a transition edge sensor (TES). The TES was irradiated by carbon ion beam of 100 MeV/u in Heavy Ion Medical Accelerator in Chiba. We have measured the energy of each charged particle in the carbon ion beam. This will contribute to the establishment of a new dosimetry method of carbon ion beam for radiotherapy.

We present the development of a frequency-domain multiplexing readout of kinetic inductance detectors (KIDs) for pulse signals with a self-trigger system. The KIDs consist of an array of superconducting resonators that have different resonant frequencies individually, allowing us to read out multiple channels in the frequency domain with a single wire using a microwave-frequency comb. The energy deposited to the resonators break Cooper pairs, changing the kinetic inductance and, hence, the amplitude and the phase of the probing microwaves. For some applications such as X-ray detections, the deposited energy is detected as a pulse signal shaped by the time constants of the quasiparticle lifetime, the resonator quality factor, and the ballistic phonon lifetime in the substrate, ranging from microseconds to milliseconds. A readout system commonly used converts the frequency-domain data to the time-domain data. For the short pulse signals, the data rate may exceed the data transfer bandwidth, as the short time constant pulses require us to have a high sampling rate. In order to overcome this circumstance, we have developed a KID readout system that contains a self-trigger system to extract relevant signal data and reduces the total data rate with a commercial off-the-shelf FPGA board. We have demonstrated that the system can read out pulse signals of 15 resonators simultaneously with about 10 Hz event rate by irradiating \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document}α particles from \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{241}$$\end{document}241Am to the silicon substrate on whose surface aluminum KID resonators are formed.

The quality factors and noise performances of superconducting resonators play an important role in microwave SQUID multiplexer (MW-MUX). Since we develop microwave SQUID multiplexer for transition edge sensor arrays, the operation temperature is around 100 mK where the effects of two level system (TLS) can be significant. In this paper, we have investigated the electrode-material or wafer dependence of noise performance of MW-MUX by characterizing four types of resonators. Although the temperature dependence of resonance frequency and the power dependence of ${{\boldsymbol{Q}}_{\boldsymbol{u}}}$ show clear difference among the materials, frequency noises which contribute the readout noise of MW-MUX are similar. Theoretical model predicts that not TLS but other loss dominates ${{\boldsymbol{Q}}_{\boldsymbol{u}}}$ in the power region suitable for the low-noise operation of our MW-MUX. Further, the estimated flux noise calculated from the measured frequency noise and the conversion coefficient from frequency to flux were 1–5 $({{{\mathbf \mu }}{{{\mathbf \Phi }}_0}/\sqrt {{{\mathbf Hz}}} })$ @ 1 Hz, 0.2–0.8 $({{{\mathbf \mu }}{{{\mathbf \Phi }}_0}/\sqrt {{{\mathbf Hz}}} })$ @ 3 kHz. These results indicate the noise of our MW-MUX has small material dependence and the compatible low noise operation to typical dc SQUIDs would be possible. Therefore, the MW-MUX with our materials would not suffer from the low frequency noise due to TLS.

In order to read out current signals from large-scale arrays of transition edge sensors (TES), microwave SQUID multiplexers (MW-MUX) have been developed by several groups. Reduction of crosstalk induced in the multiplexer is important in order to maintain the energy resolution or the noise equivalent power of detector arrays. In the present study, crosstalk between channels in MW-MUX with five different designs is experimentally evaluated. The resonance frequency separation is ten times as large as the resonator bandwidth. Without flux-ramp modulation, crosstalk between two adjacent channels neighboring in position decreases to ≍1 × 10–3 with increasing resonance frequency separation to ≍100 MHz. Crosstalk between SQUID channels neighboring in resonance frequency also decreases to 4 × 10–3 with increasing the distance to 2.5 mm. We show that nonlinear error can occur due to the crosstalk with flux-ramp modulation. Flux readings from a well-designed multiplexer exhibit crosstalk of less than 1 mΦ0 peak-to-peak and nonlinear errors of less than 2 mΦ0 peak-to-peak, which is sufficient for the readout of the gamma-ray TES arrays being developed. These results can provide guidelines for suppressing both the crosstalk and the nonlinear error to less than the criterion of TES spectrometers with typical energy-resolving ability.

The voltage multiplier (VM) is a principal component in high-precision digital-to-analog (D/A) converters based on rapid single flux quantum (RSFQ) circuits. Experimental confirmation of correct operation of the VM is important to guarantee the accuracy of the D/A converter. In this study, a circuit for direct comparison of the output voltages of VMs was designed and demonstrated. An on-chip SQUID sensor was utilized to detect the VM errors. Bit error rates of a single-stage VM were successfully measured down to 10/sup -12/ in the constant-voltage regions. A method of detecting errors during transients was also proposed and carried out.

A pulse-number multiplier (PNM) is a principal subsystem of our rapid single flux quantum digital-to-analog converter for metrology applications. The PNM circuit generates a high-speed pulse train from an input of a precise low-frequency clock signal. We designed, fabricated, and successfully tested a PNM test circuit. The PNM test circuit was implemented by using our standard cell library on 1.6 kA/cm/sup 2/ Nb trilayer technology. Fully functional operation was confirmed by low-speed testing. Experimental bias margins were wider than /spl plusmn/20%, and these results agreed with a simulation. We also tested the circuit by average-voltage measurements for estimating the frequencies of output pulse trains. Results of average-voltage measurements implied that the output frequency of the PNM circuit was tunable from 5 GHz to 17 GHz. The bit error rate (BER) of the PNM circuit was measured, and extrapolation of the error-function fits suggested a sufficiently small BER at the optimum bias point.

We present design and experimental results of a voltage multiplier (VM) that is a main component of a Josephson D/A converter based on single flux quantum pulses. We have analyzed the VM operation through detailed simulations and have re-designed the circuit. The amplitude of the constant-voltage step for a 64-stage VM with the new design is 80 /spl mu/A at 10 GHz of an input frequency, which is sufficiently large for D/A converter applications.

We are developing an X-ray microcalorimeter with high energy resolution and position sensitivity by using an Iridium transition edge sensor. The Ir-TES with a new pixel-type geometry has ten small pixel TES array. Each pixel size is 80 μm ×200 μm . This device has shown a good energy resolution of 26 eV (FWHM) at 5.9 keV . Furthermore, the Ir-TES film was scanned along each pixel by a collimated X-ray microbeam and signal pulses were measured at each incident position. The pulse height and rise time map has shown ten different regions where pulses are concentrated which correspond to each pixel. This might be useful for an imaging TES array.

We have developed superconducting calorimeters using transition edge sensors (TESs) for industrial X-ray microanalysis. To obtain high count rate, high reliability, and high energy resolution, a large format array of the sensors and an integration of a TES calorimeter and a SQUID amplifier are required. A novel calorimeter fabrication process has been established, in which a micro-machining technology using a silicon-on-insulator wafer was applied. A 4-pixel Au/Ti TESs calorimeter was fabricated using this process. SQUID amplifiers suitable for the calorimeter have also been designed and fabricated. It is expected to achieve a count rate per pixel of 7.1 kcps. The expected energy resolution including the SQUID contribution was estimated at 17-21 eV. It has been confirmed that the SQUID contribution for the current noise of our calorimeter can almost be ignored. It has also been confirmed that an array of 14 or more pixel are required that to achieve an effective count rate of more than 100 kcps.

For broadband data communication between Josephson and CMOS digital systems, amplification of small Josephson-output signals and synchronization between the systems are important issues. We present an interface circuit for a Josephson-CMOS hybrid digital system. The interface circuit consists of a parallel-in-parallel-out (PIPO) circuit and built-in Josephson-MOS amplifiers. The PIPO circuit, implemented based on 4JL latching logic technology, performs synchronized data transfer between the Josephson and CMOS circuits. The Josephson-MOS amplifiers consists of stacked Josephson junctions (Suzuki stacks) and MOS inverters which are monolithically integrated on a chip. The circuits have been designed, fabricated and tested. We have successfully confirmed correct operation of the circuits.

To realize imaging X-ray spectroscopy with high-energy resolution, we proposed a new pixellated array of Ir-TES. In this type of device, the bias point of each pixel is slightly modified. Therefore the analysis of the pulse shape parameter, such as the pulse height, the rise time and the fall time of a signal pulse, can identify the incident pixel position. We have obtained 13 eV (FWHM) at 3 keV energy resolution and 80 μm position resolution for 10 pixel devices. At this moment we could successfully operate a 20 pixel device.

Effects of parasitic capacitance in a magnetically-coupled voltage multiplier (VM) are described. We found that parasitic capacitance between SQUIDs and JTLs in a VM decreases its operating margin. We also found that separation of electric grounds for the output terminal of a VM from those for the JTLs is effective to improve the operating margin. Using this method, a 64-stage VM was fabricated and well-defined output voltage was obtained.

Atomically flat terraces and steps with a height of one c‐axis lattice parameter have been observed with atomic force microscopy (AFM) on the surface of a flux‐grown YBa2Cu3O7−δ (YBCO) single crystal. Homoepitaxial growth of YBCO on the flux‐grown single crystal has been investigated using reflection high‐energy electron diffraction (RHEED). Initial stage of the RHEED intensity oscillation without anomalous peaks usually observed in heteroepitaxial growth suggests epitaxial growth of YBCO on the substrate surface from the beginning of deposition. A surface image of AFM for the homoepitaxial film reveals coalescent step‐like structures and two‐dimensional islands of one c‐axis height on the growing surface of YBCO. The observed RHEED oscillation and AFM image are consistent with the two‐dimensional nucleation growth of the film.

Search for proximity effect between a-, c- and (103) oriented YBCO and Au was carried out using low temperature scanning tunneling microscopy at 4.2K. BCS-like conductance spectra were observed only at the small part of the surface of Au thin film deposited in-situ on the (103) oriented YBCO thin film made by coevaporation method

Digital-to-analog (D/A) converters based on rapid single flux quantum (RSFQ) technology are under development for ac voltage standard applications. We present design and test results on a prototype 10-bit version integrated on a single chip. The 10-bit chip includes over 6000 Josephson junctions and consumes a bias current exceeding 1 A. To reduce the effects of the high bias current on circuit operation, a custom design method was employed in part and large circuit blocks were divided into smaller ones. The 10-bit chips were fabricated and tested at low speed. The test results suggested that our design approach could manage large bias currents on the order of 1 A per chip.