The paper explores the feasibility of using machine learning techniques, in particular neural networks, for classification of the experimental data from the joint natC(n,p) and natC(n,d) reaction ...cross section measurement from the neutron time of flight facility n_TOF at CERN. Each relevant ΔE−E pair of strips from two segmented silicon telescopes is treated separately and afforded its own dedicated neural network. An important part of the procedure is a careful preparation of training datasets, based on the raw data from Geant4 simulations. Instead of using these raw data for the training of neural networks, we divide a relevant 3-parameter space into discrete voxels, classify each voxel according to a particle/reaction type and submit these voxels to a training procedure. The classification capabilities of the structurally optimized and trained neural networks are found to be superior to those of the manually selected cuts.
Neutron dark-field imaging (DFI) was used to investigate the microstructure of additive manufactured steels. Several DFI methods were combined to assess the microstructure over more than two orders ...of magnitude in size. Different degrees of porosity and other building features were found depending on the parameters of the selective laser melting additive manufacturing process. A sample built with processing parameters yielding the lowest porosity was deformed which induced a phase transformation of the austenitic phase (fcc) into the martensitic phase (bcc). In the deformed sample an increased dark-field contrast was observed which can only be explained by accounting for the fcc-bcc phase distribution and the magnetic properties of the martensitic phase. We demonstrate that neutron dark-field imaging is well suited to not only detect build flaws like cracks but quantitatively characterize the microstructure in additive manufactured steels.
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•Porosity study in additively manufactured steels via neutron dark field imaging.•Three set-ups cover nearly three orders of magnitude in microstructure size•Successful merging of data from different experimental set-ups•Deformation induced phase transformation of the steel causes strong contrast.•Dark field imaging allows to determine the phase ratio in the steel.
At the neutron time-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of ...challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beam line and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump.
The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgrounds.
One of the critical aspects for the accurate determination of neutron capture cross sections when combining time-of-flight and total energy detector techniques is the characterization and control of ...systematic uncertainties associated to the measuring devices. In this work we explore the most conspicuous effects associated to harsh count rate conditions: dead-time and pile-up effects. Both effects, when not properly treated, can lead to large systematic uncertainties and bias in the determination of neutron cross sections. In the majority of neutron capture measurements carried out at the CERN n_TOF facility, the detectors of choice are the C6D6 liquid-based either in form of large-volume cells or recently commissioned sTED detector array, consisting of much smaller-volume modules. To account for the aforementioned effects, we introduce a Monte Carlo model for these detectors mimicking harsh count rate conditions similar to those happening at the CERN n_TOF 20 m flight path vertical measuring station. The model parameters are extracted by comparison with the experimental data taken at the same facility during 2022 experimental campaign. We propose a novel methodology to consider both, dead-time and pile-up effects simultaneously for these fast detectors and check the applicability to experimental data from 197Au(n, γ), including the saturated 4.9 eV resonance which is an important component of normalization for neutron cross section measurements.
A synchronization method for the multi-channel silicon telescope Žugec, P.; Barbagallo, M.; Andrzejewski, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2020, Letnik:
983
Journal Article
Recenzirano
Odprti dostop
A simple method is presented for the simultaneous off-line synchronization of the digitally recorded data-streams from a multi-channel silicon telescope. The method is based both on the ...synchronization between the separate pairs of silicon strips and on the synchronization relative to an external timing device. Though only a reduced subset of these constraints is necessary in ideal circumstances, it is shown that this minimal set of conditions may not be sufficient for adequate synchronization in all cases. All available sources of information are therefore considered, in order to constrain the final synchronization as well as possible.
This article presents a few selected developments and future ideas related to the measurement of
(
n
,
γ
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data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use ...of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with
γ
-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate
i
neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area.
Abstract FOOT (FragmentatiOn Of Target) is an applied nuclear physics experiment with the aim of performing high precision cross section measurements for fragmentation reactions of interest in ...hadrontherapy and radiation protection in space. The physics program of the experiment foresees a set of measurements with light ion beams, such as C and O, in the energy range of 100–800 MeV/u interacting with tissue-like and shielding material targets. The setup was initially conceived for the detection of charged fragments and, in 2021, the Collaboration started the study of possible solutions for neutron detection. Two detection systems have been proposed: one based on BC-501A liquid scintillators with neutron/ γ discrimination capabilities and a system based on BGO crystals operated in phoswich mode. In 2022, a dedicated data acquisition campaign was carried out at the n_TOF facility at CERN to evaluate the capabilities of the two systems. First, the neutron/ γ discrimination efficiency of the BC-501A system was studied using radioactive sources. Then, the two systems were placed in the n_TOF experimental area to study their neutron detection efficiency under a well characterized neutron beam. In this work, the first preliminary results concerning the characterization of the two possible neutron detectors of FOOT are presented.
Abstract The average energy and multiplicity of prompt $$\gamma $$ γ -rays from slow neutron-induced fission of $$^{235}$$ 235 U have been measured using the STEFF spectrometer at the neutron ...time-of-flight facility n_TOF. The individual responses from 11 NaI scintillators were corrected for multiple $$\gamma $$ γ -ray interactions, prompt fission neutrons and background counts before being deconvolved to estimate the emitted spectrum of prompt fission $$\gamma $$ γ -rays. The results give an average $$\gamma $$ γ -ray energy $${\bar{E}}_{\gamma }$$ E ¯ γ of 1.71(5) MeV and multiplicity $$\bar{\nu }_{\gamma }$$ ν ¯ γ of 2.66(18) considering $$\gamma $$ γ -rays emitted within the energy range 0.8–6.8 MeV. The n_TOF data has a slightly larger $${\bar{E}}_{\gamma }$$ E ¯ γ and smaller $$\bar{\nu }_{\gamma }$$ ν ¯ γ than other recent measurements, however the product of the two is in agreement within quoted uncertainties.
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