M. Ishitsuka

Evaluation of 400 low background 10-in. photo-multiplier tubes for the Double Chooz experiment

The goal of Double Chooz experiment is a precise measurement of the last unknown mixing angle theta_13 using two identical detectors placed at far and near sites from Chooz reactor cores. The detector is optimized for reactor-neutrino detection using specially developed 10-inch PMTs. We developed two types of measurement systems and evaluated 400 PMTs before the installation. Those PMTs fulfill our requirements, and a half of those have been installed to the far detector in 2009. The character and performance data of the PMTs are stored in a database and will be referenced in analysis and MC simulation.

A Study of Reactor Neutrino Monitoring at Experimental Fast Reactor JOYO

We carried out a study of neutrino detection at the experimental fast reactor JOYO using a 0.76 tons gadolinium loaded liquid scintillator detector. The detector was s et up on the ground level at 24.3 m from the JOYO reactor core of 140 MW thermal power. The measured neutrino event rate from reactor on-off comparison was 1.11±1.24(stat.)±0.46(syst.) events/day. Although the statistical significance of the measureme nt was not enough, the background in such a compact detector at the ground level was studied in detail and MC simulation was found to describe the data well. A study for improvement of the detector for future such experiments is also shown.

The waveform digitiser of the Double Chooz experiment: performance and quantisation effects on photomultiplier tube signals

We present the waveform digitiser used in the Double Chooz experiment. We describe the hardware and the custom-built firmware specifically developed for the experiment. The performance of the device is tested with regards to digitising low light level signals from photomultiplier tubes and measuring pulse charge. This highlights the role of quantisation effects and leads to some general recommendations on the design and use of waveform digitisers.

Online monitoring system for Double Chooz experiment

Double Chooz is a reactor-neutrino experiment at Chooz nuclear power plant in France to measure the unknown neutrino mixing angle θ13 with a better sensitivity than the current best limit. A remote-monitoring framework has been developed to check status of DAQ systems, which enables collaborators off-site to access online monitoring data through the internet. As for these graphical user interfaces (GUI) are developed with platform independent technologies to be available through the internet. As fault tolerant monitoring systems in Double Chooz, Gaibu (external in Japanese) system and Log-Message system have been developed. Gaibu system works as an alarm message provider working outside DAQs and Log-Message system is a log file manager. Developments of these systems are almost finished and we are preparing software commissioning at the far detector site now.

Detailed performance evaluation of a new 20-inch photomultiplier tube with a Box and Line dynode

Yasuhiro Nishimuraa, Ryosuke Akutsua, Yusuke Sudab, Miao Jiangc, Seiko Hirotac, Daisuke Fukudad , Masahiro Kuzee, Masaki Ishitsukae, Masayuki Nakahataa, Masato Shiozawaa, Yoshinari Hayatoa, Shoei Nakayamaa, Hidekazu Tanakaa, Masashi Yokoyamab, Tsuyoshi Nakayac, Akihiro Minaminoc, Akimichi Taketa f , Yoshihiko Kawaig, Takayuki Ohmurag, Masatoshi Suzukig a Institute for Cosmic Ray Research, University of Tokyo b Department of Physics, University of Tokyo c Department of Physics, Kyoto University d Department of Physics, Okayama University e Department of Physics, Tokyo Institute of Technology f Earthquake Research Institute, University of Tokyo g Hamamatsu Photonics K.K.

Calibration of the Double Chooz Detector

The Double Chooz experiment is observing reactor neutrinos for the precise measurement of neutrino oscillation and neutrino mixing angle θ13 using a detector at 1050m away from reactor cores. θ13 is measured to be sin2 2θ13 = 0.109 ± 0.030(stat) ± 0.025(syst) using data set with live time of 227.93 days. Not only the number of events but also the energy spectrum are used in a fit to extract θ13. Therefore, it is important to evaluate the energy and the systematic uncertainty to realize precise measurement of θ13. In this article, details of calibration of the Double Chooz detector is described putting the focus on photo-multiplier (PMT) gain measurement.