Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach in order to investigate the presence of those Dark Matter (DM) candidates inducing nuclear recoils. In fact, their use can overcome the difficulty of detecting extremely short nuclear recoil traces. In this paper we present recent measurements performed on the anisotropic response of a ZnWO 4 crystal scintillator to nuclear recoils, in the framework of the ADAMO project. The anisotropic features of the ZnWO 4 crystal scintillators were initially measured with α particles; those results have been also confirmed by the additional measurements presented here. The experimental nuclear recoil data were obtained by using a neutron generator at ENEA-CASACCIA and neutron detectors to tag the scattered neutrons; in particular, the quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different neutron scattering angles (i.e. nuclear recoils energies). From these measurements, the anisotropy of the light response for nuclear recoils in the ZnWO 4 crystal scintillator has been determined at 5.4 standard deviations.

Background: the gamma-emitting radionuclide Technetium-99m (99mTc) is still the workhorse of Single Photon Emission Computed Tomography (SPECT) as it is used worldwide for the diagnosis of a variety of phatological conditions. 99mTc is obtained from 99Mo/99mTc generators as pertechnetate ion, which is the ubiquitous starting material for the preparation of 99mTc radiopharmaceuticals. 99Mo in such generators is currently produced in nuclear fission reactors as a by-product of 235U fission. Here we investigated an alternative route for the production of 99Mo by irradiating a natural metallic molybdenum powder using a 14-MeV accelerator-driven neutron source. Methods: after irradiation, an efficient isolation and purification of the final 99mTc-pertechnetate was carried out by means of solvent extraction. Monte Carlo simulations allowed reliable predictions of 99Mo production rates for a newly designed 14-MeV neutron source (New Sorgentina Fusion Source). Results: in traceable metrological conditions, a level of radionuclidic purity consistent with accepted pharmaceutical quality standards, was achieved. Conclusions: we showed that this source, featuring a nominal neutron emission rate of about 1015 s−1, may potentially supply an appreciable fraction of the current 99Mo global demand. This study highlights that a robust and viable solution, alternative to nuclear fission reactors, can be accomplished to secure the long-term supply of 99Mo.

A: The ZnWO 4 is an anisotropic crystal scintillator; for its peculiar characteristics, it is a very promising detector to exploit the so-called directionality approach in the investigation of those Dark Matter (DM) candidates inducing nuclear recoils. Recently, in the framework of the ADAMO project, an R&D to develop high quality and ultra-radiopure ZnWO 4 crystal scintillators has been carried out. In the present paper the measurements to study the anisotropic response of a ZnWO 4 to α particles and to nuclear recoils induced by neutron scattering are reported. Monochromatic neutrons have been produced by a neutron generator at ENEA-CASACCIA. The quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different nuclear recoils energies. These results open the possibility to realize a pioneer experiment to investigate the above mentioned DM candidates by means of the directionality. K: Dark Matter detectors (WIMPs, axions, etc.); Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators) 1Corresponding author.

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In the frame of the MICADO H2020 project, a passive and active neutron measurement system is being developed to estimate the nuclear material mass inside legacy waste drums of low and intermediate radioactivity levels. Monte-Carlo simulations have been performed to design a new modular and transportable neutron system, with the main objective to reach a good tradeoff between the performances in passive mode, i.e. neutron coincidence counting, and in active interrogation mode with the Differential Die-away Technique. Different designs are compared, which mainly differ in their moderation materials, graphite and polyethylene. This parametric study allowed us to define a prototype taking into account practical constraints in view of its final implementation in a wide range of in-situ locations and nuclear facilities. The total neutron detection efficiency of the prototype is 6.75%, as calculated for an empty drum, i.e. without waste matrix. The detection limit in terms of nuclear material equivalent mass have also been estimated based on assumptions for a homogeneous distribution of nuclear materials inside the drum, filled with four types of matrices covering the range of nuclear waste drums defined in the frame of the project. The most favorable matrix is made of stainless steel in passive mode and of polyethylene in active mode, with an apparent density of 0.7 g.cm -3 and 0.1 g.cm -3 , respectively. The calculated mass detection limits are respectively 68 mg of 240 Pu, 62 mg of 235 U and 39 mg of 239 Pu. The most penalizing matrix is made of polyethylene with an apparent density of 0.7 g.cm -3 , which leads to a mass detection limit of 519 mg of 240 Pu in passive mode, and 564 mg of 235 U or 349 mg of 239 Pu in active mode. Measurement time is 30 min for both passive and active modes. Next steps will be a complete investigation of matrix effects based on intensive Monte-Carlo calculations and an experimental design to figure out the appropriate corrections. Experiments will also be conducted at CEA Cadarache Nuclear Measurement Laboratory with the construction and the assembly of the neutron system prototype, and the measurement of mock-up drums filled with different matrices. I.