Search

We have been developing a monolithic active pixel sensor with the silicon-on-insulator (SOI) CMOS technology for use in future X-ray astronomical satellite missions. This sensor is called XRPIX. Our objective is to replace the X-ray CCD, which is currently the standard detector in the field, with the developed XRPIX, which offers high coincidence time resolution (~ 50 ns), superior hit-position readout time (~ 10 μs), and wide bandpass (0.5-40 keV), in addition to having comparable performance in terms of imaging spectroscopy. In our previous study, we built a prototype sensor called XRPIX1 and confirmed its basic X-ray imaging spectroscopy performance in a mode that read out the entire area (all pixels). The next step is to realize a high-speed, intelligent readout for X-ray detection. XRPIX1 comprises a trigger circuit for each pixel, so as to detect an X-ray photon injection; this system is capable of direct access to selected pixels to read out the signal amplitude. We describe the design of the trigger circuitry system and report on the first resolved X-ray spectra obtained in the trigger-driven readout mode.

We have been developing monolithic active pixel sensors with 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for high-speed wide-band X-ray imaging spectroscopy on future astronomical satellites. In this work, we investigate a revised chip (XRPIX1b) for soft X-rays used in frontside illumination. The Al Kα line at 1.5 keV is successfully detected and energy resolution of 188 eV (FWHM) is achieved from a single pixel at this energy. The responsivity is improved to 6 μV/electron and the readout noise is 18 electrons rms. Data from 3 ×3 pixels irradiated with 6.4 keV (Fe Kα) X-rays demonstrates that the circuitry crosstalk between adjacent pixels is less than 0.5%.

We have been developing a monolithic active pixel sensor with the 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for the wide-band X-ray imaging spectroscopy on future astronomical satellites. SOIPIX includes a thin CMOS-readout-array layer and a thick high-resistivity Si-sensor layer stacked vertically on a single chip. This arrangement allows for fast and intelligent readout circuitries on-chip, providing advantages over the charge-coupled device (CCD). We have designed and built a new SOIPIX prototype XRPIX1 for X-ray detection. XRPIX1 implements a correlated double sampling (CDS) readout circuit in each pixel to suppress the reset noise. We obtained an energy resolution of full width at half maximum of 1.2 keV (5.4%) at 22 keV with a chip having a 147 μm sensor depletion at a back bias of 100 V cooled to -50°C. Moreover, XRPIX1 offers intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. We also confirmed the trigger capability by irradiating a single pixel with laser light.

With an increase in the operation frequency of complimentary metal oxide semiconductor (CMOS) circuits, a radio-frequency system-on-a-chip (RF-SOC) that integrates GHz-RF and large-scale digital circuits becomes a key device for wireless systems and high-speed networks. To develop high-performance RF-SOCs, high quality voltage controlled oscillators (VCOs) are required as local oscillators or clock generators, which operate in noisy environments suffering from crosstalk noise generated by digital circuits. A 0.25 µm CMOS test chip for a new differential-input VCO and a conventional single-input VCO was designed with on-chip CMOS logic noise sources and substrate noise detectors. The jitter and phase noise of the VCOs were measured to investigate the effect of substrate crosstalk noise. We confirmed that the differential-input VCO is robust to low-frequency noise in comparison with a conventional single-input VCO.

We have developed a monolithic pixel detector with the silicon-on-insulator (SOI) pixel CMOS technology to use as radiation monitor, called RADPIX. The RADPIX intends to identify the type of radiation (α, β, γ, muon, etc.) by differences in hit pattern. The sensor is DC-coupled to the input of the pixel circuit so the leakage current I leak of a few pA for 40 µm × 40 µm at room temperature must be sunk by the pixel circuit for long time exposure. The RADPIX has the individual leakage compensation circuit. In addition to a digital output, the analog signal also can be read by using the comparator output as a store signal to latch the analog signal for the tracking accuracy enhancement. The prototype chip consists of 32 × 32 pixels with the pixel size of 40 µm × 40 µm (∼1 mm square sensitive area). We report the design and the result of the basic evaluation test.

We have been developing a monolithic active pixel sensor with the silicon-on-insulator (SOI) CMOS technology for use in future X-ray astronomical satellite mission. Our objective is to replace the X-ray Charge Coupled Device (CCD), which is the standard detector in the field, by offering high coincidence time resolution (∼ 50 ns), superior hit-position readout time (∼ 10 μs), and wider bandpass (0.5 – 40 keV) in addition to having comparable performances in imaging spectroscopy. In order to realize this detector, we have developed prototype detectors, called “XRPIX” series. XRPIX contains comparator circuit in each pixel to detect an X-ray photon injection; it offers intra-pixel hit trigger (timing) and two-dimensional hit-pattern (position) outputs. Therefore, XRPIX is capable of direct access to selected pixels to read out the signal amplitude. In our previous study, we evaluated its basic performance and obtained the X-ray spectra by this system. The next step is improvement in spectroscopic performance. Then, we designed a new prototype, called “XRPIX3”, which has charge sensitive amplifier (CSA) in each pixel. The pixel circuit with CSA works good. It is 3.4 times higher gain as compared with normal pixel circuit. Furthermore, XRPIX3 resolved Mn-K α and Mn-K β successfully for the first time in our series. The readout noise is 33 e- rms and the energy resolution is about 300 eV FWHM at 5.9 keV. In this paper, we report on the design and test results of this new device.

We have been developing a monolithic active pixel sensor with the Silicon-On-Insulator (SOI) CMOS technology, called SOIPIX, for future X-ray astronomical satellite missions. The goal of SOIPIX is to replace the X-ray CCD, which is the standard detector in the field, by offering superior time resolution (∼10 µs) and wider bandpass (0.5 keV – 40 keV) in addition to having comparable performances in imaging spectroscopy. In the previous work, we built a SOIPIX prototype, XRPIX1, and confirmed the basic X-ray performance of imaging spectroscopy in a mode reading out the whole area (all pixels). The next step is to realize a high-speed and intelligent readout for X-ray detection. XRPIX1 contains trigger circuit in each pixel to detect an X-ray photon and is capable of direct access to the local pixels to read out the signal amplitude. We report on the design and development of a trigger-driven readout system with XRPIX1. We present the first resolved X-ray spectra of Cu+Mo and Am-241 obtained in the trigger-driven mode.

We have been developing a novel X-ray astronomy detector combined with a CMOS readout circuit on a monolithic chip using the SOI CMOS technology. As a part of the development, we have fabricated a prototype of an analog-to-digital converter (ADC) component aiming for building it into the detector itself. We used the OKI 0.2 µm CMOS fully depleted Silicon-On-Insulator process. The prototype ADC consists of a pre-amplifier and two delta-sigma (ΔΣ) modulators. The two modulators process a series of analog input signal alternately to improve the readout speed (∼100 kHz), and output the digital bit-stream signal. An external Field Programmable Gate Array works as a decimation filter and converts the bit-stream signal into a 12-bit digital signal. We evaluated the prototype ADC and obtained the first results as follows: the power consumption of 40 mW, the equivalent input noise of ∼80 µV rms, and the integral non-linearity of less than 0.8%.

We have been developing a monolithic active pixel sensor with the 0.2 μm Silicon-On-Insulator (SOI) CMOS technology, i.e. SOIPIX, for the X-ray imaging spectroscopy on future astronomical satellites. SOIPIX includes a thin CMOS readout layer and a thick high-resistivity Si-sensor layer vertically on a single chip, which would provide advantages in capabilities of direct and flexible readout circuitries over charge-coupled device (CCD). We have built INTPIX2/3 (2008/2009) and XRPIX1(2010). We successfully confirmed the capability of X-ray imaging and spectroscopy in a photon-counting mode by irradiating INTPIX2/3 with monochromatic X-rays. To reduce the readout noise, we designed and built XRPIX1, which has a correlated double sampling (CDS) readout circuit in each pixel to suppress the reset noise. We obtained an energy resolution of FWHM ∼1.5 keV(7%)@22 keV with XRPIX1 cooled at 50 degree. Moreover, XRPIX1 offers intra-pixel hit trigger and one-dimensional hit-pattern outputs. We also confirmed the trigger capability by irradiating a single pixel of XRPIX1 with laser light.

A beam test was executed to evaluate the behavior of the first prototype radiation-hard double-sided silicon microstrip sensor for the SDC silicon tracking system. Pions of 4 GeV/c in a test bcamline at KEK illuminated three planes of detectors. Thc signals wcrc amplified, shaped, and discriminated with TEKZ bipolar analog LSI's, and the on-off levels were sampled at l0MHz clock with CMOS digiwl LSI's, asynchronously with beam triggers. The detectors were rotated in null and 1 .O Tesla magnetic fields. The efficiencies were found to be 98-9996. The position resolutions were 12.5pm. where the multi-strip hit fraction was 30-40%. There was no essential difference in the performance of the pand the n-sides. The multi-strip hit fraction showed a clear rotation and magnetic-field dependence. From the angles where the fractions were minimum in the 1T magnetic field, the Hall mobilities of the electrons and holes were obtained to be 1391k43 (clcctrons) and 325f30 (holes) cm2/Vs.

Activity controllable noise source and arrayed substrate voltage detectors use a 0.25-/spl mu/m, 2.5-V CMOS technology and enable substrate noise measurements with controlled logic density/activity distributions. These circuits are used for exploring effects of power-supply parasitic components on substrate noise generation in practical large-scale CMOS digital circuits. Spatially distributed parasitic impedances on power-supply and return wirings cause the noise generation locally, and moreover, screen the effect of noise attenuation by parasitic capacitances of logic elements working as charge reservoirs.

A double-sided silicon strip detector with a radiation-tolerant design was fabricated and characterized in a sequence of beam tests at KEK using 4 GeV/ c pions. The detectors were combined with newly designed, fast, lower power, bipolar amplifier-shaper-discriminator chips and CMOS digital pipeline chips to record hit-no hit signals in the strips. Efficiencies, noise occupancies, and spatial resolutions were measured before and after the proton irradiation at an equivalent fluence of 1 × 10 14 p/cm 2 , depending on angle of track incidence and strip-pitches. The median pulse height distribution, derived from the threshold scans of the efficiency, allowed to extract the response of the detector. A 1 T magnetic field enabled us to determine the Hall mobilities of electrons and holes.