Satoru Uozumi

Development of Multi-Pixel Photon Counters

The multipixel photon counter (MPPC) is a newly developed photodetector with an excellent photon counting capability. It also has many attractive features such as small size, high gain, low operation voltage and power consumption, and capability of operating in magnetic fields and in room temperature. The basic performance of samples has been measured. A gain of ~106 is achieved with a noise rate less than 500 kHz with 1 p.e. threshold, and cross-talk probability of less than 40% at room temperature. The photon detection efficiency for green light is twice or more that of the photomultiplier tubes. It is found that the basic performance of the MPPC is satisfactory for use in real experiments.

Fine Granular Calorimeter with Scintillator Strips and New Photon Sensor Readout

The Global Large Detector (GLD) is one of the detector concepts proposed for the future linear collider experiment. At the linear collider experiment Particle Flow Algorithm plays an important role in achieving excellent jet energy resolution (~30%/radicE). This method requires a finely segmented calorimeter able to separate individual particles inside jets in the calorimeter. The GLD calorimeter is a sampling calorimeter which consists of scintillator and absorber (tungsten for electromagnetic, lead or iron for hadron calorimeter) layers. It has a scintillator-strip structure; strips in successive scintillator layers are aligned in orthogonal directions to achieve effective 1 times cm2 segmentation. To read out the signal from all the individual scintillator strips, we adopt a new photon sensor, the Multi-Pixel Photon Counter (MPPC). The MPPC consists of 100-1600 APD pixels, each of which works in the limited Geiger mode. This new photon sensor has many excellent features (compact size, low cost, high gain and photon detection efficiency and insensitivity to magnetic fields) and is suitable for use in the GLD calorimeter readout. We have tested 800 samples of 1600-pixel MPPCs and confirmed that the performance is satisfactory for calorimetric use. We have also constructed an electromagnetic calorimeter test module with 468 scintillator strips and full MPPC readout, and performed a beam test using a 1-6 GeV positron beam to evaluate its performance. The test module was measured to have good performance (energy resolution is (13.45 plusmn 0.07)% / radicE oplus (2.87 plusmn 0.08)%, deviation from linearity is less than 4%), showing that the 1600-pixel MPPC is suitable for the readout of finely segmanted calorimeters.

Study and development of multi pixel photon counter for the GLD calorimeter readout

The Multi Pixel Photon Counter (MPPC) is a novel photon senso r manufactured by Hamamatsu Photonics. It has many advantages compared to other photon s ensors (compact size, low cost, high gain and detection efficiency, insensitivity to magnet ic fields). In the GLD calorimeter group, study of the MPPC properties is extensively ongoing aiming t o utilize it as the photon sensor of a finely segmented calorimeter. As a result of the study, we ha ve confirmed that the current 1600 pixel MPPC has almost satisfactory gain, photon detect ion efficiency and noise rate for our requirements. We have also found that the dynamic range o f the 1600 pixel MPPC can be enhanced thanks to its short recovery time, which is useful f or calorimetric use. As a practical test for use at the GLD calorimeter, we have constructed a prototy pe of a scintillator-strip calorimeter and exposed it to 1-6 GeV positron beams and validated its per formance. As a result of the test, we have observed a satisfactory linearity and energy resolu tion of the scintillator-strip calorimeter with full MPPC readout.