Yoshikatsu Kuroda

Hard X-ray Detector (HXD) on board Suzaku

The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit back ground based on a combination of new techniques, including the concept of well-type active shield counter. With an effective area of 142 cm^2 at 20 keV and 273 cm2 at 150 keV, the background level at the sea level reached ~1x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 30 keV for the PI N diodes, and ~2x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 100 keV, and ~7x10^{-6} cts s^{-1} cm^{-2} keV^{-1} at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of ~4 cm thick BGO crystals, have a large effective area for sub-MeV to MeV gamma-rays. They work as an excellent gamma-ray burst monitor with limited angular resolution (~5 degree). The on-board signal-processing system and the data transmitted to the ground are also described.

High-resolution CdTe detector and applications to imaging devices

Using a high quality cadmium telluride (CdTe) wafer, we formed a Schottky junction and operated the detector as a diode (CdTe diode). The low leakage current of the CdTe diode allows us to apply a much higher bias voltage than was possible with the previous CdTe detectors. For a relatively thin detector of /spl sim/0.5 mm thick, the high bias voltage results in a high electric field in the device. Both the improved charge collection efficiency and the low-leakage current lead to an energy resolution of 1.1 keV FWHM at 60 keV for a 2/spl times/2 mm/sup 2/ device and 2 keV for a 10/spl times/10 mm/sup 2/ device at 5/spl deg/C without any charge-loss correction electronics. For astrophysical applications, we have developed a an initial prototype CdTe pixel detector based on the CdTe diode. The detector has 400 pixels with a pixel size of 625/spl times/625 /spl mu/m/sup 2/. Each pixel is gold-stud bonded to a fanout board and routed to a front end ASIC to measure pulse height information for each /spl gamma/-ray photon.

Improvement of the CdTe diode detectors using a guard-ring electrode

Recent results from the Schottky CdTe diode detectors employing a guard-ring (GR) electrode are reported. A cathode electrode, made of platinum, was separated into an active electrode(s) and a surrounding GR. Typical leakage current of a device with active area of 2 /spl times/ 2 mm/sup 2/ and 0.5 mm thickness surrounded by a GR, is 7 and 20 pA at a bias of 100 and 500 V, respectively, operated at 20/spl deg/C. Spectral resolution of this device is 0.93 and 1.2 keV (FWHM) at 59.5 and 122 keV, respectively, operated at 20/spl deg/C with a bias of 800 V. Detailed study of the characteristics of these devices working as a gamma-ray detector is presented.

SEU resistance in advanced SOI-SRAMs fabricated by commercial technology using a rad-hard circuit design

We fabricate 128 Kbit SRAMs using a rad-hard circuit design based on a mixed-mode three-dimensional simulation in a commercial silicon-on-insulator foundry with 0.2 /spl mu/m design rules. Appropriate design increases the critical linear energy transfer of single-event upset over 164.4 MeV/(mg/cm/sup 2/).

High Energy Resolution Hard X-Ray and Gamma-Ray Imagers Using CdTe Diode Devices

We developed CdTe double-sided strip detectors (DSDs or cross strip detectors) and evaluated their spectral and imaging performance for hard X-rays and gamma-rays. Though the double-sided strip configuration is suitable for imagers with a fine position resolution and a large detection area, CdTe diode DSDs with indium (In) anodes have yet to be realized due to the difficulty posed by the segmented In anodes. CdTe diode devices with aluminum (Al) anodes were recently established, followed by a CdTe device in which the Al anodes could be segmented into strips. We developed CdTe double-sided strip devices having Pt cathode strips and Al anode strips, and assembled prototype CdTe DSDs. These prototypes have a strip pitch of 400 mum. Signals from the strips are processed with analog ASICs (application specific integrated circuits). We have successfully performed gamma-ray imaging spectroscopy with a position resolution of 400 mum. Energy resolution of 1.8 keV (FWHM: full width at half maximum) was obtained at 59.54 keV. Moreover, the possibility of improved spectral performance by utilizing the energy information of both side strips was demonstrated. We designed and fabricated a new analog ASIC, VA32TA6, for the readout of semiconductor detectors, which is also suitable for DSDs. A new feature of the ASIC is its internal ADC function. We confirmed this function and good noise performance that reaches an equivalent noise charge of 110 e- under the condition of 3-4 pF input capacitance.

A Si/CdTe semiconductor Compton camera

We are developing a Compton camera based on Si and CdTe semiconductor imaging devices with high energy resolution. In this paper, results from the most recent prototype are reported. The Compton camera consists of six stacked double-sided Si strip detectors and CdTe pixel detectors, which are read out with low noise analog ASICs, VA32TAs. We obtained Compton reconstructed images and spectra of line gamma-rays from 80 keV to 662 keV. The energy resolution (FWHM) is 10 keV and 16 keV at 356 keV and 511 keV, respectively

Si/CdTe semiconductor compton camera

We are developing a Compton camera based on Si and CdTe semiconductor imaging devices with high energy resolution. In this paper, results from the most recent prototype are reported. The Compton camera consists of six layered double-sided Si Strip detectors and CdTe pixel detectors, which are read out with low noise analog ASICs, VA32TAs. We obtained Compton reconstructed images and spectra of line gamma-rays from 122 keV to 662 keV. The energy resolution is 9.1 keV and 14 keV at 356 keV and 511 keV, respectively.

Direct Measurement of SET Pulse Widths in 0.2-

Heavy-ion-induced SET-pulse widths in NOR-logic cells fabricated by a 0.2-mum FD-SOI technology are directly measured by using an on-chip self-triggering flip-flop circuit. The pulse widths are distributed from 0.3 to 1.0 ns under a constant LET of 40 MeVmiddot cm 2/mg

\mu

Abstract Stacking several ten layers of thin CdTe devices is a new concept of a gamma-ray detector, featuring both good energy resolution and high efficiency. We have developed prototype models of the CdTe stacked detector which consists of 10 layers and 40 layers based on a newly-developed large CdTe diode. The energy resolution of the detector is measured to be 1–2% (FWHM) from 500 keV to 6 MeV . In addition to the gamma-ray spectroscopy, we propose to use the stack detector as a new type of range finder for gamma-ray sources below a few hundred keV. We demonstrate that the distance of a 57 Co radio active source, which is located 5 cm from the detector surface, is measured within the accuracy of 1–2 mm .

m SOI Logic Cells Irradiated by Heavy Ions

The hard X-ray detector (HXD) aboard the X-ray satellite Suzaku is designed to have a good timing capability with a 61 � s time resolution. In addition to detailed descriptions of the HXD timing system, results of in-orbit timing calibration and the performance of the HXD are summarized. The relative accuracy of time measurements of the HXD event was confirmed to have an accuracy of 1:9 � 10 � 9 ss � 1 per day, and the absolute timing was confirmed to be accurate to 360 � s or better. The results were achieved mainly through observations of the Crab pulsar, including simultaneous ones with RXTE, INTEGRAL, and Swift.