Takeshi Matsuda

VOID FRACTION PROFILE IN TUBE-BANKS OF A SIMULATED FLUIDIZED-BED HEAT EXCHANGER

Abstract Flow visualization of cross-flow tube-banks in a simulated fluidized-bed was conducted by using the neutron radiography system of JRR-3M. Applying the image processing technique to the visualized image, the void fraction profile in the tube-bank was obtained. The observed flow pattern and the void fraction profile demonstrate the importance of the tube arrangement in fluidized-bed heat exchangers.

Large-particle movement and drag coefficient in a fluidized bed

Flow visualization studies of the behavior of a large particle in a fluidized bed were conducted using neutron radiography. The large particle moved according to the bed materials, especially in the wake of a bubblc. When the density of the large particle was high, the particle moved with a velocity different from that of a bubble, and in some cases the particle moved downward through a bubble. When the density was low enough, the particle moved on the surface of the bubble wake. The drag force of the large particle immersed in a fluidized bed was measured. The drag force increased with an increase in the volumetric gas flux as well as with an increase in the particle diameter. The drag coefficient was derived and was well correlated on the basis of a two-phase model and experimentally determined effective viscosity of the bed materials.

A FASTBUS digitizer system for TOPAZ TPC

Abstract A large scale digitzer system for 11000 channels of the TOPAZ TPC was constructed based on FASTBUS and installed for TRISTAN at KEK. Each digitizer card is equipped with 16 channels of CCD with a moderate speed of A/D converter. Output data are arithmetically corrected for pedestals, zero-suppressed and applied with a PRE/POST mechanism by an on-board sequencer; they are followed by a sparse data scan with an intelligent data scanner.

Simulation and first beam test of a single-sided two-dimensional detector using pMOS pixels

Abstract A strip-like two-dimensional readout single-sided detector using pMOS pixels is being developed at KEK, as part of the R&D for the BELLE experiment. It may be used in upgrades of the vertex detector. The pMOS pixel is composed of a double drain pMOS transistor, providing direct amplification on site, implanted in the n-well collecting electrode of the detecting silicon pin diode. We first briefly review the concept and principle of the pMOS pixel detector, before presenting simulation and test performed on the prototypes with a beam of minimum ionizing particles.

Preliminary test results from a single-sided two-dimensional detector using pMOS pixels

Abstract As a part of the R&D for the BELLE experiment at the KEK-B-factory a strip-like two-dimensional readout single-sided detector using pMOS pixels has been developed and tested. It may be used in upgrades of the vertex detector. A double drain pMOS transistor, implanted in the 100 × 100 μ m 2 n-well collecting electrode, amplifies the signal, while the low detector capacitance lowers the noise. A high signal-to-noise ratio is expected. Ganging the pixels at the drain nodes in a strip-like configuration provides a two-dimensional readout. The superior characteristics of the proposed device are attractive for charged particle detection as well as X- and γ-rays. We present here results from electrical and IR light tests of prototypes of the pMOS pixel.