[en] We developed a silicon photodetector optically coupled with a crystal scintillator. The silicon photodetector consists of a single crystal and two silicon photo-strip sensors. The silicon photo-strip sensor is designed and manufactured based on a concept of an AC-coupled single-sided silicon strip sensor, but the back-side of the strip sensor is modified to detect scintillation light. One scintillator is sandwiched between two photo-strip sensors. The p⁺ strip arrays of the photo-strip sensors are oriented orthogonally to each other. This detector configuration provides the two-dimensional position information and the depth of interaction by measuring signal ratios between the first and the second photo-strip sensors. Theses sensors are fabricated on a 5 in., 380μm-thick, n-type and high resistivity silicon wafer. The leakage currents of the fabricated sensors are measured as a function of the reverse bias voltages. We also measured the photo response of the fabricated sensor for the wavelength range from 350 to 1000 nm. The energy resolution of the fabricated photodiode optically coupled with a CsI(Tl) crystal is obtained to be 13.8% for the ¹³⁷Cs (662 keV) γ-rays. The one-dimensional position information by the α-particles from ²⁴¹Am is obtained with the photo-strip sensor optically coupled with the CsI(Tl) crystal. We also measure the two-dimensional position of a LED light source with two photo-strip sensors.

[en] The AC-coupled double-sided silicon microstrip sensors are designed and 14 masks are used to produce prototype strip sensors. The biasing resistors are made of p-doped polysilicons and the coupling capacitors are built by separating implanted strips and readout strips by a thin oxide layer. The p-stops in the atoll patterns are introduced to disrupt an electron accumulation layer at the Si-SiO₂ interface on the ohmic side. The junction side has a double metal structure using two metal layers separated from each other by a thick insulator layer. The strip sensors are fabricated on a 5-in., high resistivity, <100>-orientation, and 380μm thick n-type double-sided polished silicon wafer. The prototype sensor with an area of 2.8x2.8cm² consists of 256(512) readout channels with a strip pitch of 100(50)μm. The leakage currents and the bulk capacitances as a function of the reverse bias voltage are measured to understand the fabrication process of the prototype sensors. The signal to noise ratios are measured by using a ⁹⁰Sr radioactive source in order to evaluate performance of the sensors. The design of the AC-coupled double-sided silicon strip sensor and its various components are described, and measurements of the electric characteristics and the signal to noise ratio are presented.

[en] Highlights: • Single-sided silicon photostrip sensors are designed and fabricated. • The fabricated photostrip sensors are sufficient enough to provide 2D position information. • Signal ratios between two photostrip sensors are well-separated. • 2D position and depth of interaction are measured using photostrip sensors and a scintillator. • The depth of interaction by gamma irradiation in the scintillator is simulated by using Geant4. The photoelectric absorption of gamma rays in silicon occurs with such low probability that scintillation material is employed in the photostrip detector. We fabricate single-sided photostrip sensors which are sensitive to visible light. Two photodetectors in a photon counting mode are optically coupled with the scintillator with a sandwich structure. The photostrip sensors have 128 strips, a $200\mathrm{\mu }\mathrm{m}$ strip pitch and a size of $3.8\times 2.8{\mathrm{cm}}^2$. Sensor signals are read by a 128-channel VA1TA3 readout chip. A CsI(Tl) crystal is then optically combined to measure both of depths of interaction (DOI) and 2-D images, while the position of the LED are varied. We also performed a simulation of gamma ray irradiation at different locations inside the scintillator using the GEANT4 Monte Carlo simulation tool. We measured the 2-D position of incoming light with two photostrip sensors, and also measured the DOI and 2-D position of scintillating light by placing a scintillator between the photostrip sensors. The DOI measurement results and the GEANT4 simulation results were compared.

[en] The aim of this work is to evaluate the performance of a strip sensor with a single photon counting data acquisition system based on VA1 readout chips to study the feasibility of a silicon microstrip detector for medical application. The sensor is an AC-coupled single-sided microstrip sensor and the active area of the sensor is 32.0 mmx32.0 mm with a thickness of 380 μm. The sensor has 64 readout strips with a pitch of 500 μm. The sensor was biased at 45 V and the experiment was performed at room temperature. Two silicon strip sensors were mounted perpendicularly one another to get two-dimensional position information with a 5 mm space gap. Two low noise analog ASICs, VA1 chips, were used for signal readout of the strip sensor. The assembly of sensors and readout electronics was housed in an Al light-tight box. A CsI(Tl) scintillation crystal and a 2-in. photomultiplier tube were used to trigger signal events. The data acquisition system was based on a 64 MHz FADC and control softwares for the PC-Linux platform. Imaging tests were performed by using a lead phantom with a ⁹⁰Sr radioactive source and a 45 MeV proton beam at Korea Institute of Radiological and Medical Science in Seoul, respectively. Results of the S/N ratio measurement and phantom images are presented

[en] The Cosmic Ray Energetics And Mass (CREAM) mission is planned for launch in 2015 to the International Space Station (ISS) to research high-energy cosmic rays. Its aim is to understand the acceleration and propagation mechanism of high-energy cosmic rays by measuring their compositions. The Top Counting Detector and Bottom Counting Detector (T/BCD) were built to discriminate electrons from protons by using the difference in cascade shapes between electromagnetic and hadronic showers. The T/BCD provides a redundant instrument trigger in flight as well as a low-energy calibration trigger for ground testing. Each detector consists of a plastic scintillator and two-dimensional silicon photodiode array with readout electronics. The TCD is located between the carbon target and the calorimeter, and the BCD is located below the calorimeter. In this paper, we present the design, assembly, and performance of the T/BCD

[en] We have been designing and developing DC- and AC-coupled double-sided and single-sided silicon strip detectors for tracking device in the international linear collider (ILC). We present the electrical characteristics of the fabricated sensors such as the leakage currents and the capacitances as a function of reverse bias voltage. We also discuss results of the radiation damage test with 45 MeV proton beam of a cyclotron in Korea Institute of Radiological and Medical Science (KIRAMS) in Seoul, Korea. The leakage currents and the full depletion voltage were measured to be less than 10 nA/strip and about 60 V, respectively. We conclude that developed sensors have an excellent safety margin of radiation hardness appropriate for the ILC. The results of the signal-to-noise ratio (SNR) of the fabricated silicon strip sensors with ⁹⁰Sr radioactive source and the proton beam of the KIRAMS are also presented. The SNRs of the strip sensor are measured to be 25.0 and 6.7-16.4 for the source test and for the proton beam test, respectively

[en] The Cosmic Ray Energetics and Mass (CREAM) experiment at the International Space Station (ISS) aims to elucidate the source and acceleration mechanisms of high-energy cosmic rays by measuring the energy spectra from protons to iron. The instrument is planned for launch in 2015 at the ISS, and it comprises a silicon charge detector, a carbon target, top and bottom counting detectors, a calorimeter, and a boronated scintillator detector. The top and bottom counting detectors are developed for separating the electrons from the protons, and each of them comprises a plastic scintillator and a 20×20 silicon photodiode array. Each photodiode is 2.3 cm×2.3 cm in size and exhibits good electrical characteristics. The leakage current is measured to be less than 20 nA/cm"2 at an operating voltage. The signal-to-noise ratio is measured to be better than 70 using commercial electronics, and the radiation hardness is tested using a proton beam. A signal from the photodiode is amplified by VLSI (very-large-scale integration) charge amp/hold circuits, the VA-TA viking chip. Environmental tests are performed using whole assembled photodiode detectors of a flight version. Herein, we present the characteristics of the developed photodiode along with the results of the environmental tests

[en] This paper describes an investigation into gluing and wire bonding for assembling the Silicon Vertex Detector (SVD) for the Belle II experiment at KEK in Japan. Optimizing the gluing of the silicon microstrip sensors, the support frame, and the readout flex cables is important for achieving the required mechanical precision. The wire bonding between the sensors and the readout electronic chips also needs special care to maximize the physics capability of the SVD. The silicon sensors and signal fan out flex circuits (pitch adapters) are glued and connected using wire bonding. We determine that gluing quality is important for achieving good bonding efficiency. The standard deviation in the glue thickness for the best result is measured to be 3.11 μm. Optimal machine parameters for wire bonding are determined to be 70 mW power, 20 gf force, and 20 ms for the pitch adapter and 60 mW power, 20 gf force, and 20 ms for the silicon strip sensors; these parameters provide a pull force of (10.92±0.72) gf. With these settings, 75% of the pitch adapters and 25% of the strip sensors experience the neck-broken type of break

[en] The Cosmic Ray Energetics And Mass (CREAM) experiment is designed to measure cosmic ray elemental spectra to help understand the source and acceleration mechanisms of ultra-high-energy cosmic rays. The payload is planned to launch in December 2004 from McMurdo Station, Antarctica as a balloon mission. A Silicon Charge Detector (SCD) was designed and constructed for the CREAM experiment to provide precision charge measurements of incident cosmic rays with a resolution of 0.2 charge unit or better. The SCD was exposed to heavy ion beams at CERN's H2 beam line in November 2003. The results reported here show the SCD performs as designed

[en] We report measurements of charmonia produced in two-photon collisions and decaying to four-meson final states, where the meson is either a charged pion or a charged kaon. The analysis is based on a 395 fb^-1 data sample accumulated with the Belle detector at the KEKB electron-positron collider. We observe signals for the three C-even charmonia η_c(1S), χ_c0(1P) and χ_c2(1P) in the π⁺π^-π⁺π^-, K⁺K^-π⁺π^- and K⁺K^-K⁺K^- decay modes. No clear signals for η_c(2S) production are found in these decay modes. We have also studied resonant structures in charmonium decays to two-body intermediate meson resonances. We report the products of the two-photon decay width and the branching fractions, Γ_γγB, for each of the charmonium decay modes. (orig.)