In any of the modern 4/spl pi/ particle detector array improvements of the measured parameters have been envisaged. Pulse shape discrimination (PSD) is an efficient electronic tool which can be ...applied to a single detector to achieve atomic number Z separation of the particles comparable to the /spl Delta/E - E telescopes. In the present study, a simple PSD device based on commercially available modules has been discussed with the motivation of future improvement in CHIMERA detector system without sacrificing time resolution in time of flight (TOF) measurement. In beam studies of PSD have been carried out following the ejected particles from /sup 19/F + /sup 12/C reaction at tandem energies with 2 large area - 300 /spl mu/m - silicon detectors of CHIMERA multi-detector. Front-side and rear-side entry of the detected ions were explored. Performance of the PSD set up has been discussed.
Several neutrino detectors, KamLAND, Daya Bay, Double Chooz, RENO, and the forthcoming large-scale JUNO, rely on liquid scintillator to detect reactor antineutrino interactions. In this context, ...inverse beta decay represents the golden channel for antineutrino detection, providing a pair of correlated events, thus a strong experimental signature to distinguish the signal from a variety of backgrounds. However, given the low cross-section of antineutrino interactions, the development of a powerful event selection algorithm becomes imperative to achieve effective discrimination between signal and backgrounds. In this study, we introduce a machine learning (ML) model to achieve this goal: a fully connected neural network as a powerful signal-background discriminator for a large liquid scintillator detector. We demonstrate, using the JUNO detector as an example, that, despite the already high efficiency of a cut-based approach, the presented ML model can further improve the overall event selection efficiency. Moreover, it allows for the retention of signal events at the detector edges that would otherwise be rejected because of the overwhelming amount of background events in that region. We also present the first interpretable analysis of the ML approach for event selection in reactor neutrino experiments. This method provides insights into the decision-making process of the model and offers valuable information for improving and updating traditional event selection approaches.
The optical and radiochemical purification of the scintillating liquid, which will fill the central detector of the JUNO experiment, plays a crucial role in achieving its scientific goals. Given its ...gigantic mass and dimensions and an unprecedented target value of about 3% @ 1 MeV in energy resolution, JUNO has set severe requirements on the parameters of its scintillator, such as attenuation length (Lat>20 m at 430 nm), transparency, light yield, and content of radioactive contaminants (238U,232Th<10-15 g/g). To accomplish these needs, the scintillator will be processed using several purification methods, including distillation in partial vacuum and gas stripping, which are performed in two large scale plants installed at the JUNO site. In this paper, layout, operating principles, and technical aspects which have driven the design and construction of the distil- lation and gas stripping plants are reviewed. The distillation is effective in enhancing the optical properties and removing heavy radio-impurities (238U,232Th, 40K), while the stripping process exploits pure water steam and high-purity nitrogen to extract gaseous contaminants (222Rn, 39Ar, 85Kr, O2) from the scintillator. The plant operating parameters have been tuned during the recent com- missioning phase at the JUNO site and several QA/QC measurements and tests have been performed to evaluate the performances of the plants. Some preliminary results on the efficiency of these purification processes will be shown.
In the field of rare event physics, it is common to have huge masses of
organic liquid scintillator as detection medium. In particular, they are widely
used to study neutrino properties or ...astrophysical neutrinos. Thanks to its
safety properties (such as low toxicity and high flash point) and easy
scalability, linear alkyl benzene is the most common solvent used to produce
liquid scintillators for large mass experiments. The knowledge of the
refractive index is a pivotal point to understand the detector response, as
this quantity (and its wavelength dependence) affects the Cherenkov radiation
and photon propagation in the medium. In this paper, we report the measurement
of the refractive index of the JUNO liquid scintillator between 260-1064 nm
performed with two different methods (an ellipsometer and a refractometer),
with a sub percent level precision. In addition, we used an interferometer to
measure the group velocity in the JUNO liquid scintillator and verify the
expected value derived from the refractive index measurements.
Nuclear reactors are a source of electron antineutrinos due to the presence of unstable fission products that undergo \(\beta^-\) decay. They will be exploited by the JUNO experiment to determine the ...neutrino mass ordering and to get very precise measurements of the neutrino oscillation parameters. This requires the reactor antineutrino spectrum to be characterized as precisely as possible both through high resolution measurements, as foreseen by the TAO experiment, and detailed simulation models. In this paper we present a benchmark analysis utilizing Serpent Monte Carlo simulations in comparison with real pressurized water reactor spent fuel data. Our objective is to study the accuracy of fission fraction predictions as a function of different reactor simulation approximations. Then, utilizing the BetaShape software, we construct fissile antineutrino spectra using the summation method, thereby assessing the influence of simulation uncertainties on reactor antineutrino spectrum.
Isotopic identification of nuclear products in heavy-ion physics with stable and exotic beams (RIB) is of crucial importance for understanding the behaviour of nuclear matter far away from normal ...density. This is true for both nuclear structure and nuclear reaction studies. The recent upgrading of the 4pi CHIMERA detector by pulse shape methods in silicon detectors in connection with the time of flight (TOF) and the energy loss (DE-E) methods allows for light charged particles and light fragments (Z < 10) identification in a broad kinetic energy range from the Coulomb barrier up to tens of MeV/nucleons. After a brief discussion of the experimental methodology used in the detector to identify the particles some relevant applications in the field of nuclear reaction studies with stable and exotic beams.
Intermediate energy heavy ion collisions are unique probes to study the properties of nuclei far away from the nuclear ground state. The CHIMERA detector is a powerful second generation 4/spl pi/ ...array conceived to study nuclear reactions at intermediate energies. The array has 1192 detection cells covering almost 95% of total solid angle. The CHIMERA device operated at the Laboratori Nazionali del Sud in Catania in four campaigns in 2000, 2003, 2004 and 2005, showing very good performances in the detection and identification capabilities. Experimental results are presented, together with the improvement in progress to extend further the detection and identification capabilities.
Abstract
In the frame of the CleanSky 2 MONNALISA project, a wind-tunnel campaign is planned to test a tail-plane model of a large passenger aircraft by using different measurement techniques. ...Wind-tunnel test results obtained over a systematic series of model geometries will be used to thoroughly validate a low-order numerical method based on physical modelling that will be developed in the project to evaluate the non-linear aerodynamic characteristics of aircraft lifting surfaces. The present paper describes the main results of the infrared thermography measurements performed in the first wind-tunnel entry to be used to tune RANS solvers and for the fine calibration of the low-order numerical method.
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