Carlotta Scirè

Thermal neutron detection using a silicon pad detector and 6LiF removable converters

A semiconductor detector coupled with a neutron converter is a good candidate for neutron detection, especially for its compactness and reliability if compared with other devices, such as (3)He tubes, even though its intrinsic efficiency is rather lower. In this paper we show a neutron detector design consisting of a 3 cm × 3 cm silicon pad detector coupled with one or two external (6)LiF layers, enriched in (6)Li at 95%, placed in contact with the Si active surfaces. This prototype, first characterized and tested at INFN Laboratori Nazionali del Sud and then at JRC Ispra, was successfully shown to detect thermal neutrons with the expected efficiency and an outstanding gamma rejection capability.

Characterization of the silicon+

Abstract The worldwide need to replace 3 He for neutron detection has triggered research and development on new technologies and methods. A promising one is based on commercial solid state silicon detectors coupled with thin neutron converter layers containing 6 Li. After proving the feasibility of this technique, we characterized the behavior of such a detector with different converter layer thicknesses. In this paper we also disentangle other contributions to the overall spectrum shape observed with this kind of detector, proving that its detection efficiency can be made reasonably high and that the gamma/neutron discrimination capability is comparable to that of 3 He tubes.

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Abstract. A new detector technology was developed, particularly suitable for low-cost radioactivity monitoring in radwaste storage sites. It consists of a scintillating optical fiber coupled at each end to a silicon photomultiplier (SiPM). The single-photon sensitivity of the SiPM, along with the left-right coincidence constraint, allows the achievement of a reasonable sensitivity to gamma radiation even though a thin 1-mm-diameter plastic scintillating fiber is used. Simulation results are in perfect agreement with the measured behavior, and several implementations are under way. The possibility of choosing the fiber length and shape makes them very flexible both conceptually and mechanically. Any improvement in the SiPM development technology reflects immediately into an improvement in the detector performance.

LiF thermal neutron detection technique

A prototype array of modular sensors for online monitoring of radioactive waste was developed at INFN-LNS. We implemented a new kind of gamma mini-sensor, based on Silicon PhotoMultipliers and scintillating fibers, that behaves like a cheap scintillating Geiger-Muller counter. It can be placed in shape of a fine grid around each single waste drum in a repository. After simulating the counting response of thin scintillating fibers to gamma radiation, we verified our simulation results with measurements using radioactive sources. Front-end electronics and an FPGA-based counting system were developed to handle the field data, also implementing data transmission, a graphical user interface and a data storage system. A test of four sensors in a real radwaste storage site was performed with promising results.

Low-cost radioactivity monitoring with scintillating fibers and silicon photomultipliers

We propose a system for the on-line monitoring of short and medium term radioactive waste repositories. Such a system is distributed, fine-grained, robust, reliable, and must be based on low-cost components. It could, in principle, open new perspectives on the modality of waste packaging and storage. In particular we propose to employ a new family of cheap and powerful micro sensors to be placed in shape of a fine grid around each single drum.

Real-time online monitoring of radwaste storage: A proof-of-principle test prototype

We propose a technique for thermal neutron detection, based on a (6)Li converter placed in front of scintillating fibers readout by means of silicon photomultipliers. Such a technique allows building cheap and compact detectors and dosimeters, thus possibly opening new perspectives in terms of granular monitoring of neutron fluxes as well as space-resolved neutron detection.

An online monitoring system for nuclear waste storage

The Silicon Photomultiplier (SiPM) has become a solid playground for many applications requiring compact and well performing photon detectors. In particular, this is true when the detection of few photons with good time resolution is required. In this paper, we show how the SiPM features can be exploited to set up a compact neutron detector. By coupling two SiPMs to an inorganic scintillator strip, one can discriminate between gamma-rays and neutrons and, at the same time, determine the impact position with millimeter accuracy.