Koichiro Oba

Computer Analysis of the Timing Properties in Micro Channel Plate Photomultiplier Tubes

The timing properties of the micro channel plate photomultiplier tubes(MCP-PMT) have been studied by computer simulation. The calculated results were compared with experimental results obtained in a nonproximity focused and a proximity focused MCP-PMT and showed good agreement. The analysis also showed that the transit time spread(TTS) of the proximity type MCP-PMT can be improved from 60 psec to 40 psec increasing the secondary emission coefficient in first collision from 1 to 10.

Newly Developed Photomultiplier Tubes with Position Sensitivity Capability

This paper describes several newly developed PMTs which utilize Multi-Anode, segmented dynodes or resistive anodes. The triode tube with 4 segmented dynodes and the 20¿ dia. Hemispherical PMT with 4 segmented anode has been tested and shown excellent capability of spatial resolution and low cross talk. The Fine Mesh Dynode PMTs with Multi-Anode or resistive anode also have been developed and their performances have been tested showing good position sensitivity. These features seem to be useful tools especially for scintillation imaging applied to nuclear and medical instrumentation.

Characterization of a pulsed X-ray source for fluorescent lifetime measurements

To search for new, fast, inorganic scintillators, we have developed a bench-top pulsed X-ray source for determining fluorescent lifetimes and wavelengths of compounds in crystal or powdered form. This source uses a light-excited X-ray tube which produces X-rays when light from a laser diode strikes its photocathode. The X-ray tube has a tungsten anode, a beryllium exit window, a 30 kV maximum tube bias, and a 50 /spl mu/A maximum average cathode current. The laser produces 3/spl times/10/sup 7/ photons at 650 nm per /spl sim/100 ps pulse, with up to 10/sup 7/ pulses/sec. The time spread for the laser diode, X-ray tube, and a microchannel plate photomultiplier tube is less than 120 ps fwhm. The mean X-ray energy at tube biases of 20, 25, and 30 kV is 9.4, 10.3, and 11.1 keV, respectively. We measured 140, 230, and 330 X-ray photons per laser diode pulse per steradian, at tube biases of 20, 25, and 30 kV, respectively. Background X-rays due to dark current occur at a rate of 1/spl times/10/sup 6/ and 3/spl times/10/sup 6/ photons/sec/steradian at biases of 25 and 30 kV, respectively. Data characterizing the X-ray output with an aluminum filter in the X-ray beam are also presented. >

A 400 Anode Chevron Microchannel Plate PMT for High Energy Application

A proto type multianode photomultiplier tube incorporating a chevron type MCPs electron multiplier and 400 multi anodes was developed for high speed image pick-up at low light levels such as in detection of rings of Cherenkov light. The diameter of and mean spacing of each anode are 0.3mm and 0.65mm respectively in a rectangular array of 16mm×12mm. The MCP used in the tube were fabricated at HTV and had 24.9mm diameter, 20mm useful diameter, 15¿m pore diameter and 45 length to pore diameter ratio. Electron multiplication and dark current for each MCP were about 104 and 1pA at 1000v respectively. 0.6mm spatial resolution over anode surface and about 600psec rise time of output signal were obtained.

Photomultiplier tube of new dynode configuration

In spectroscopic analysis, radiation detection, and medical application fields, portable instruments requiring high accuracy and high sensitivity are being developed. Since conventional photomultiplier tube (PMT) envelopes are made of glass and are large in size, it is difficult to downsize instruments. PMTs are mainly used for high accuracy instruments, while solid state detectors are employed for general purpose, or compact instruments. Hamamatsu recently developed the compact PMT R5600 series, which is downsized to the same dimensions as a solid state detector while maintaining the same performance, high sensitivity and high speed as the conventional PMTs. >

Characteristics of the Newly Developed MCP and Its Assembly

Several types of MCP assemblies including 2-stage and 3-stage MCPs consist of 8¿m and 12¿m channel MCP having length to diameter ratio ¿ of 40 and 60 are tested relating to the gain and pulse height resolution. The 2-stage assembly with ¿=60 MCPs was incorporated in the proximity type MCP-PMT and showed capability to separate triple photon event clearly. Furthermore, 6¿m channel MCPs in 2-stage was tested in PMT configuration and showed drastic improvement of timing property. As for the life, new MCP showed residual gain of more than 50% at the accumulated output charge of 0.1 C/cm2.

Recent Development of Photomultiplier Tubes for Nuclear and Medical Applications

New type of photomultiplier tubes (PMTs) have been developed for the applications to high energy physics experiments, medical instruments and biophysics experiments. Remarkable features of these PMTs are fast time response and gating function, immunity to the magnetic field, position sensitivity, good pulse height resolution and so on. The performances and the test results of these PMTs are discussed in this paper.

CsI(Na) Scintillation Plate with High Spatial Resolution

A two dimensional CsI(Na) scintillation plate with high spatial resolution has been developed by growing CsI(Na) crystal on a special fiber plate with fiber size of 20 ¿m. The number of photons at the output were 34 photons for 55Fe and 260 photons for 129I respectively. The spatial resolution measured by electron beam excitation showed approximately 30 ¿m of FWHM. Detection efficiency of the plate with 120 ¿m crystal thickness was measured to be about 23 % for 129I referring to a standard NaI(Tl) scintillator.

Current Status of the Micro Channel Plate

More than one order of improvement of the saturation effect was achieved by developing low resistance channel wall material and improved H2-reduction processing condition and introducing non-uniform resistance distribution along the channel. The nonuniform resistance distribution was also found to improve life problem because it can compensate the resistance change near the output end of the channel caused by electron bombardment.

Performance of microchannel plates in high magnetic fields

Abstract The behaviour of microchannel plate (MCP) detectors in high magnetic fields has been investigated. Satisfactory performance in axial fields of up to 3 T has been observed.