Light yield studies for SoLid phase I

International audienceThe SoLid experiment is searching for sterile neutrinos at the BR2 nuclear research reactor. Anti-neutrinos are detected through inverse beta decays (producing a positron and a neutron in delayed coincidence) with a very segmented detector made of thousands of scintillating cubes. SoLid has a very innovative hybrid technology with two different scintillators which have different temporal signature: polyvynil-toluene cubes (PVT) to detect the positrons and 6LiF:ZnS sheets to detect the neutrons. The 288 kg detector prototype (SM1) took data in 2015. It demonstrated the detection principle and background rejection efficiency. The construction of SoLid phase I (∼ 1.6 t) is now finished and data taking has started. To improve the energy resolution of SoLid phase I, we have tried to increase the light yield studying the PVT scintillator design. To study the positron light yield on the PVT, we have built a test bench with a 207Bi source. We have improved the design of the cubes, their wrapping or the type and the configuration of the fibers. After its construction, the SoLid detector has been calibrated with a 22Na source and preliminary results seem to show that the light yield has increased by a factor 3 compared to SM1 so it should improve the energy resolution of the positron from 21% for SM1 down to 12% for SoLid