M. Pillon

New limits on particle dark matter search with a liquid Xenon target-scintillator

New results on WIMP-Xe-129 elastic scattering are presented. The target-detector is a pure liquid Xenon scintillator filled with Kr-free Xenon enriched in Xe-129 at 99.5%. Preliminary measurements with neutrons to estimate the quenching factor and to study a statistical pulse shape discrimination between electromagnetic background and recoils are also discussed

A diamond based neutron spectrometer for diagnostics of deuterium-tritium fusion plasmas

Single crystal Diamond Detectors (SDD) are being increasingly exploited for neutron diagnostics in high power fusion devices, given their significant radiation hardness and high energy resolution capabilities. The geometrical efficiency of SDDs is limited by the size of commercially available crystals, which is often smaller than the dimension of neutron beams along collimated lines of sight in tokamak devices. In this work, we present the design and fabrication of a 14 MeV neutron spectrometer consisting of 12 diamond pixels arranged in a matrix, so to achieve an improved geometrical efficiency. Each pixel is equipped with an independent high voltage supply and read-out electronics optimized to combine high energy resolution and fast signals (<30 ns), which are essential to enable high counting rate (>1 MHz) spectroscopy. The response function of a prototype SDD to 14 MeV neutrons has been measured at the Frascati Neutron Generator by observation of the 8.3 MeV peak from the (12)C(n, α)(9)Be reaction occurring between neutrons and (12)C nuclei in the detector. The measured energy resolution (2.5% FWHM) meets the requirements for neutron spectroscopy applications in deuterium-tritium plasmas.

Neutron Detectors Based Upon Artificial Single Crystal Diamond

This paper reports about state-of-the-art artificial Single Crystal Diamond (SCD) neutron detectors based on a multilayered structure and grown by chemical vapour deposition (CVD) technique. Multilayered SCD detectors covered with a thin layer of 6LiF allow the simultaneous detection of both slow and fast neutrons and can operate in pulse and current mode. These detectors can also be produced with a thin layer of Boron. Application of SCD detectors to neutron detection around fusion tokamak is reported. Some problems related to the processing of the very fast electrical pulse produced by diamond are addressed and the achieved and foreseen development of the processing electronics is reported as well.

Development of a mobile and repetitive plasma focus

A plasma focus device aimed at working in environmental conditions not tailored for nuclear equipment has been developed by ENEA. It can operate in deuterium at 1 Hz shot rate, with an average neutron production of 3 × 108 neutrons/shot at 6 kJ of capacitor energy. It is easy to transport and conceived for those industrial purposes where a rather intense neutron generator is required but the use of tritium is forbidden. The machine is designed to be reliable and uniform in emission and to be operated in the field by personnel who are not specialists, to meet the requirements of the possible transformation into a commercial product.

Neutronics experiments for uncertainty assessment of tritium breeding in HCPB and HCLL blanket mock-ups irradiated with 14 MeV neutrons

Two neutronics experiments have been carried out at 14 MeV neutron sources on mock-ups of the helium cooled pebble bed (HCBP) and the helium cooled lithium lead (HCLL) variants of ITER test blanket modules (TBMs). These experiments have provided an experimental validation of the calculations of the tritium production rate (TPR) in the two blanket concepts and an assessment of the uncertainties due to the uncertainties on nuclear data. This paper provides a brief summary of the HCPB experiment and then focuses in particular on the final results of the HCLL experiment. The TPR has been measured in the HCLL mock-up irradiated for long times at the Frascati 14 MeV Neutron Generator (FNG). Redundant and well-assessed experimental techniques have been used to measure the TPR by different teams for inter-comparison. Measurements of the neutron and gamma-ray spectra have also been performed. The analysis of the experiment, carried out by the MCNP code with FENDL-2.1 and JEFF-3.1.1 nuclear data libraries, and also including sensitivity/uncertainty analysis, shows good agreement between measurements and calculations, within the total uncertainty of 5.9% at 1σ level.

Silicon Photo-Multiplier radiation hardness tests with a beam controlled neutron source.

Abstract Radiation hardness tests were performed at the Frascati Neutron Generator on silicon Photo-Multipliers that were made of semiconductor photon detectors built from a square matrix of avalanche photo-diodes on a silicon substrate. Several samples from different manufacturers have been irradiated, integrating up to 7×1010 1-MeV-equivalent neutrons per cm2. Detector performance was recorded during the neutron irradiation, and a gradual deterioration of their properties began after an integrated fluence of the order of 108 1-MeV-equivalent neutrons per cm2 was reached.

Technological exploitation of Deuterium-Tritium operations at JET in support of ITER design, operation and safety

Abstract Within the framework of the EUROfusion programme, a work-package of technology projects (WPJET3) is being carried out in conjunction with the planned Deuterium–Tritium experiment on JET (DTE2) with the objective of maximising the scientific and technological return of DT operations at JET in support of ITER. This paper presents the progress since the start of the project in 2014 in the preparatory experiments, analyses and studies in the areas of neutronics, neutron induced activation and damage in ITER materials, nuclear safety, tritium retention, permeation and outgassing, and waste production in preparation of DTE2.

Benchmark Experiment for the Validation of Shut Down Activation and Dose Rate in a Fusion Device

A neutronics experiment has been performed at the 14 MeV Frascati Neutron Generator (FNG) and using a proper experimental set-up, with the objective to validate the calculations of shut down dose rate outside the ITER vacuum vessel. In the experiment, a shield mock up was irradiated for sufficiently long time that the level of induced activation was followed after shut down by dosemeters for a cooling time as required for allowing personal access. The measurements were analysed, using a rigorous, standard two-step method (MCNP transport / FISPACT inventory codes), and a new one-step method with an ad hoc modified version of MCNP code, developed within the ITER Project to provide a more straightforward tool for dose rate analysis outside the vessel. The results of the experiment are presented together with the analysis performed with both approaches and with different nuclear data.

Test of a resistive plate chamber under irradiation of photons and neutrons

Abstract A resistive plate chamber operated at low gas amplification has been exposed to photon and neutron sources to study the detection efficiency and the time response in conditions close to those expected in experiments at the Large Hadron Collider. Results on the sensitivity to photons and neutrons of energy around 1 MeV are presented.

Sensitivity and uncertainty analyses of 14 MeV neutron benchmark experiment on silicon carbide

Abstract A shielding experiment on a silicon carbide (SiC) composite, a potentially important low activation structural material for the fusion reactor, was performed at the 14 MeV Frascati Neutron Generator (FNG) in 2001 and analyzed using both deterministic and probabilistic transport, sensitivity and uncertainty methods. The objective of the experiment was to verify the nuclear cross section files, as well as the calculational methods, used in the design and shielding calculations for fusion reactor. Neutron activation reaction rates, neutron and photon flux spectra, and nuclear heating rates were measured at several positions inside the SiC block. Point-wise and group cross sections derived from the European Fusion File (EFF-2.4 and -3.0) and the Fusion Evaluated Nuclear Data Library (FENDL-2) were used in the analysis. Results indicate that the calculation based on the recent EFF-3.0 Si-28 nuclear data estimates the measured quantities with a reasonable uncertainty of ±(10–15)% for 1 σ.