M. Tanaka

Performance of multi-pixel photon counters for the T2K near detectors

We have developed a Multi-Pixel Photon Counter (MPPC) for the neutrino detectors of T2K experiment. About 64,000 MPPCs have been produced and tested in about a year. In order to characterize a large number of MPPCs, we have developed a system that simultaneously measures 64 MPPCs with various bias voltage and temperature. The performance of MPPCs are found to satisfy the requirement of T2K experiment. In this paper, we present the performance of 17,686 MPPCs measured at Kyoto University.

The silicon vertex detector for the super B factory

The silicon vertex detector (SVD2) of the Belle experiment at KEK (Tsukuba, Japan) is currently close to its limits in terms of the occupancy of the innermost layer and the readout dead time. In order to cope with further increase in luminosity, different levels of upgrades are proposed: small improvements are possible in the short term by tuning the current system at the cost of signal-to-noise and crosstalk. In 2007, the two inner layers of the SVD2 will be replaced by similar detectors with faster readout electronics (SVD2.5) and in the long term, a major upgrade of the full silicon vertex detector (SVD3) is envisaged for the KEK Super B Factory. These upgrade scenarios will be discussed in detail from the hardware point of view along with the options under study.

Development of a multi-pixel hybrid photodetector with high quantum efficiency and gain

A hybrid photo-detector (HPD) consisting of a photocathode and a multi-pixel avalanche diode (MP-AD) has been developed for these years. One of the features of the HPD is a good energy resolution, and it was shown in our previous study that the further improvement would be possible by reducing the fluctuation of charge loss in the dead layer at the entrance of the MP-AD. In this paper, we report on the result of the improvement with the newly developed HPD whose MP-AD encapsulated has a thinner dead layer than before. It is demonstrated that the new HPD has a much better energy resolution which enables the clear counting up to nine photoelectrons. Other features like a uniformity among the pixels or a photocathode sensitivity of the HPD are also presented.A hybrid photodetector (HPD) consisting of a photocathode and a multipixel avalanche diode (MP-AD) was developed a few years ago. Our previous studies showed that its inherent potential for high resolution photon counting could be further enhanced by reducing fluctuations in charge loss in the dead layer at the entrance of the MP-AD. In this paper, we report on the improvement with the newly developed HPD whose encapsulated MP-AD has a thinner dead layer than before. It is demonstrated that the new HPD has much better energy resolution, which enables clearer counting up to nine photoelectrons. Further enhancement of the photocathode sensitivity of the HPD is also discussed.

Mass production test of Hamamatsu MPPC for T2K neutrino oscillation experiment

Abstract In the T2K near neutrino detectors, about 60xa0000 Hamamatsu Multi-Pixel Photon Counters (MPPCs) will be used. The mass production of MPPC has started in February 2008. In order to perform quality assurance and to characterize each device, we have developed an MPPC test system. For each MPPC, gain, breakdown voltage, noise rate, photo detection efficiency, and cross-talk and after-pulse rate are measured as functions of the bias voltage and temperature. The design of the test system and the measurement procedure are described.

Readout Electronics Of Multi-anode Photomultiplier Tubes For Scintillation Fiber Calorimeter

A readout system of multianode photomultiplier tubes (PMT) was designed for a scintillation fiber calorimeter. A time-invariant method of charge measurement is applied. Key components of this system are a monolithic shaper amplifier using semicustom bipolar ASIC (application-specific integrated circuit) technology and an analogy memory hybrid made of full-custom nMOS VLSI. The readout circuits of a 256-channel readout system of multianode PMTs have also been fabricated and await final check out. Since heat dissipation is a critical issue, a special printed-circuit board, a lamination of an aluminum plate and FR-4, is used to achieve efficient heat removal. >