Tatsumi Mizogawa

New readout technique for two-dimensional position-sensitive detectors

Abstract A new simple technique for two-dimensional position readout from one electrode plane is proposed, which is applicable to a wide range of detector types such as a gas-filled counter and a microchannel plate. Combining the “backgammon” method with the “weighted coupling capacitor” method, the present technique has a simpler electrode pattern than the “wedge and strip” method and is free from thermal noise from which the “resistive layer” method suffers. An application of this technique to a position-sensitive proportional counter is reported.

Application of the “MBWC” two-dimensional position readout technique to a multiwire proportional counter

Abstract A two-dimensional position readout technique named “modified backgammon method with weighted coupling capacitors (MBWC)” has been applied to a multiwire proportional counter, and its image linearity and position resolution have been investigated. One of two types of the technique, the three-output MBWC method, has shown several kinds of image deformations. The sources of the deformation and the way to avoid them are clarified. On the other hand, an essentially linear image has been readily obtained by adopting the other type (four-output MBWC method). The overall spatial resolution parallel to the wire direction and the spatial resolution of the position encoding cathode for the direction perpendicular to the wire have been investigated with Fe K X-rays. The best values obtained are 130 and 110 μm (FWHM), respectively, which correspond to ∼600 × 600 pixels.

A two-dimensional position-sensitive anode for microchannel plates based on the “MBWC” technique

Abstract The modified backgammon method with weighted coupling capacitors (MBWC) has been applied to a tandemmicrochannel-plate charged-particle detector for two-dimensional position encoding. After some optimizing procedure a position resolution better than 40 μm (FWHM) is obtained for an avalanche size of ∼ 1 × 10 7 electrons. Individual microchannels with 15 μm spacing are clearly resolved at the avalanche size of ∼ 4 × 10 7 electrons. Acceptable image linearity over the whole MCP sensitive area of 20 mm ace gf is obtained.

A two-dimensional position-sensitive ion detector based on modified backgammon method with weighted-coupling capacitors

Abstract Properties of a two-dimensional position-sensitive charged-particle detector based on “modified backgammon method with weighted-coupling capacitors (MBWC)” are described. Procedure to optimize its position resolution and image linearity is discussed.

A proportional scintillation X-ray imaging chamber and its performance

Abstract We discuss the operational principle of a proportional scintillation X-ray imaging chamber, and report the performance of the first prototype constructed for SPring-8. Single X-ray photons have been successfully imaged with the prototype as bright spots of 1.4 mm in diameter, as expected. The absolute detection efficiency has been found to be 2.4%, consistent with the predicted value. The fluctuation in the light gain uniformity was less than 7% over the entire detection area. The linearity of response has been examined by measuring the gray value distribution of single X-ray photons detected. The spatial resolutions attained in analogue mode and in digital mode were around 1 mm and better than 170 μm, respectively.

Impact Parameter Dependent Probability of Au L3-Shell Ionization by 40.7 MeV Ar Ions

The ionization probability of Au–L 3 shell by 1 MeV/u Ar ions is measured as a function of impact parameter by a scattered projectile-x ray coincidence method. The result is compared with semi-classical approximation calculations with separated-atom and united-atom electron wave functions for the initial state of the ionized electron. It is close to or larger than the separated-atom values at impact parameter larger than the radius of Au–L shell and it approaches to the united-atom value at smaller impact parameters. This behavior is qualitatively consistent with the binding effect.

Charge-state distribution measurements of heavy ions

Abstract Charge-state distributions of Ar ions after single close collisions (impact parameter ∼1 × 10 −9 cm) with target gases of Ne, Ar, and Kr are measured. The impact parameters are selected so that the L-shell electrons of Ar ions play an important role in determining the resultant charge state. The experimental setup for the measurements of charge-state distributions of heavy ions consists of a magnet and a position-sensitive parallel-plate avalanche counter. Charge-state distributions of several kinds of ions (∼1 MeV/u) after passing through a carbon foil are also measured to test the experimental setup.

DEVELOPMENT OF A PROPORTIONAL SCINTILLATION X-RAY IMAGING CHAMBER FOR SYNCHROTRON RADIATION EXPERIMENTS

Proportional scintillation x‐ray imaging chamber (PSXIC) is a new type of two‐dimensional position‐sensitive x‐ray detector composed of a spherical drift chamber, a parallel plate avalanche counter, and an image‐intensifier‐associated charge coupled device camera. A prototype of PSXIC filled with xenon (97%)+triethylamine (3%) gaseous mixture has been stably operated under a high flux of x‐ray irradiation. The spatial resolution the prototype can attain has been found better than 800 μm. The time‐resolved imaging capability has also been examined by taking time‐varying x‐ray images of a test pattern with a time resolution of 1/30 s.

Target thickness dependence of projectile Ar K X-rays: L-shell nonequilibrium

Abstract We have measured the target-thickness dependence of the intensities of the argon Kα X-ray satellites emitted in collisions between 50-MeV argon ions (4+, 6+, 11+, 12+, and 13+) and carbon foils. An effect of the projectile L-shell configuration on the projectile K-vacancy formation in solid is discussed.