T. Konno

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.

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.