This paper presents a 120-GHz-band 10-Gbit/s quadrature phase-shift-keying (QPSK) modulator and demodulator. To reduce system complexity, the modulator employs direct modulation, and the demodulator uses differentially coherent detection. We fabricated the modulator monolithic microwave integrated circuit (MMIC) and demodulator MMIC with 0.1-μm-gate InP HEMTs. The test element of the modulator had a static error-vector magnitude of 10%. We mounted the modulator and demodulator MMICs in separate modules. The size of the modules was 20 mm × 8 mm × 25 mm. The main lobe in the spectrum of 10-Gbit/s QPSK signals ranged from 123 to 133 GHz. The bit error rate for 10-Gbit/s 2⁷ - 1 pseudorandom binary sequence data was smaller than 10^-10 at a received power of -38.5 dBm.

Electrical characteristics of poly(3-alkylthiophene) and metal interfaces have been studied. Good Schottky type diodes have been fabricated using aluminum and gold-tin electrodes vacuum-evaporated onto poly(3-alkylthiophene) films. Markedly large temperature dependences are observed for poly(3-alkylthio-phene) Schottky diodes and discussed in terms of a temperature-dependent electronic band scheme.

The architecture of a multi-channel front-end system is important for realizing a high-resolution PET system. We propose a novel front-end pulse processing scheme with pulse width modulation (PWM) and pulse train method for PET systems. Each channel of the proposed system consists of a preamplifier, a shaping amplifier, a comparator, and a digital circuit that generates a pulse train for each event. The preamplifier-shaper-discriminator module first generates a trigger pulse with time-over-threshold (ToT), which contains the energy information. The trigger pulse is then processed through a digital circuit that adds subsequent pulses to form a pulse train. These additional pulses encode channel information, timing information, etc. The digital signal output of each channel can be connected by simple wired-OR logic, and the output is read in one transmission line. This multi-channel, low power consumption front-end scheme can acquire enough pulse height (energy) and position information to realize a PET system with a significantly smaller number of output pins in the front-end ASIC. The pulse width encoding also simplifies the digital processing system. We designed a new ASIC based on this concept. The proposed architecture can be applied to high-resolution PET systems with multi-channel ASICs.

Spectroscopic studies of emissions released from tungsten ions combined with a pellet injection technique have been conducted in Large Helical Device for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. The spectral intensities of W⁵⁺, W²⁴⁺–W²⁸⁺, W³⁷⁺, W³⁸⁺, W⁴¹⁺–W⁴³⁺, W⁴⁵⁺, and W⁴⁶⁺ emission lines were measured simultaneously over a wide wavelength range from x-ray to visible. Time evolutions of the various tungsten line spectra indicate that the tungsten confinement time depends on the electron density of the plasma and is long in high density plasmas, on the order of seconds, and short in low density plasmas, on the order of sub-seconds. When the confinement time was long, the tungsten ions remained in the plasma until the end of the discharge, changing their dominant charge with the change in electron temperature. When the confinement time was short, the tungsten ions rapidly decreased in all charge states and disappeared. Space-resolved EUV and visible spectroscopy measurements have revealed that tungsten ions stayed in the core region of the plasma with changing their dominant charge state depending on the electron temperature in the discharges with the long confinement time. Detailed analysis of soft x-ray emission suggested that the confinement time increases with density and becomes saturated when the central electron density exceeds 2 × 10¹³ cm⁻³.