Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils

The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in $^{208}$Tl and $^{214}$Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 $m^2$ of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in $^{208}$Tl. After more than one year of background measurement, a surface activity of the scintillators of $\mathcal{A}$($^{208}$Tl) $=$ 1.5 $\mu$Bq/m$^2$ is reported here. Given this level of background, a larger BiPo detector having 12 m$^2$ of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of $\mathcal{A}$($^{208}$Tl) $<$ 2 $\mu$Bq/kg (90% C.L.) with a six month measurement.Comment: 24 pages, submitted to N.I.M.

Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors

We have constructed a GEANT4-based detailed software model of photon transport in plastic scintillator blocks and have used it to study the NEMO-3 and SuperNEMO calorimeters employed in experiments designed to search for neutrinoless double beta decay. We compare our simulations to measurements using conversion electrons from a calibration source of $\rm ^{207}Bi$ and show that the agreement is improved if wavelength-dependent properties of the calorimeter are taken into account. In this article, we briefly describe our modeling approach and results of our studies.Comment: 16 pages, 10 figure

Plastic scintillators for thermal neutrons detection

The new cadmium and gadolinium-loaded polymethylmethacrylate based plastic scintillators with the mass fraction of the metals up to 2 % and 4 %, respectively, are described in this article. There are presented the techniques of the new materials preparation and their main properties: transmission spectra, light output and thermal neutrons detection efficiency. The light output of Cd -loaded scintillator with 2 % of metal is 67 % relative to the unloaded sample; the light output of Gd -loaded plastic scintillator with 4 % of the metal is reduced to 67.6 %. There is regular increase of the thermal neutrons detection efficiency for the both series of the scintillation materials

A liquid scintillator for thermal neutrons detection

A novel gadolinium-loaded liquid scintillator based on linear alkylbenzene intended for use in a large-scale neutrino experiment Daya Bay has been studied. The study results show a high efficiency of thermal neutron detection using the novel liquid scintillator and make it possible to recommend this material in experiments on search for neutrino oscillations.Досліджено новий гадолінійвмісний рідкийо сцинтилятор на основі лінійного алкіл бензолу, призначеного для застосування у великомасштабному нейтринному експерименті Daya Вау. Отримані результати свідчать про високу ефективність реєстрації теплових нейтронів новим рідким сцинтилятором і дозволяють рекомендувати його для застосуванні у експериментах з пошуку нейтринних осциляцій.Исследован новый гадолинийсодержащий жидкий сцинтиллятор на основе линейного алкилбензола, предназначенного для использования в крупномасштабном нейтринном эксперименте Daya Вау. Полученные результаты свидетельствуют о высокой эффективности регистрации тепловых нейтронов новым жидким сцинтиллятором и позволяют рекомендовать его для использования в экспериментах по поиску нейтринных осцилляций

Boron-loaded liquid scintillator

The high thermal neutron capture cross-section of ¹⁰B nucleus enables to use the boron-loaded organic scintillators as a basis of the neutron detectors. The study results of the new liquid scintillator with mass concentration of boron up to 6 %, based on linear alkylbenzene and contained as a boron additive ortho-carborane, are presented in the paper. The transparency spectra, scintillation characteristics of the new material and the detection efficiency for thermal neutrons have been studied

Measurement of the background in the NEMO 3 double beta decay experiment

In the double beta decay experiment NEMO~3 a precise knowledge of the background in the signal region is of outstanding importance. This article presents the methods used in NEMO~3 to evaluate the backgrounds resulting from most if not all possible origins. It also illustrates the power of the combined tracking-calorimetry technique used in the experiment