| 1. |
- Aartsen, M. G., et al.
(författare)
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Computational techniques for the analysis of small signals in high-statistics neutrino oscillation experiments
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 977
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Tidskriftsartikel (refereegranskat)abstract
- The current and upcoming generation of Very Large Volume Neutrino Telescopes - collecting unprecedented quantities of neutrino events - can be used to explore subtle effects in oscillation physics, such as (but not restricted to) the neutrino mass ordering. The sensitivity of an experiment to these effects can be estimated from Monte Carlo simulations. With the high number of events that will be collected, there is a trade-off between the computational expense of running such simulations and the inherent statistical uncertainty in the determined values. In such a scenario, it becomes impractical to produce and use adequately-sized sets of simulated events with traditional methods, such as Monte Carlo weighting. In this work we present a staged approach to the generation of expected distributions of observables in order to overcome these challenges. By combining multiple integration and smoothing techniques which address limited statistics from simulation it arrives at reliable analysis results using modest computational resources.
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| 2. |
- Bradbury, J., et al.
(författare)
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Lifetime measurements using a plunger device and the EUCLIDES Si array at the GALILEO gamma-ray spectrometer
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 979
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Tidskriftsartikel (refereegranskat)abstract
- The GALILEO gamma-ray spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), benefits from intense stable beams provided by the Tandem-ALPI-PIAVE accelerator complex and from radioactive beams to be delivered in the near future by the SPES facility. The spectrometer is complemented with a variety of ancillary devices to allow for nuclear structure and reaction studies. The 4 pi Si-ball array EUCLIDES coupled to the GALILEO gamma-ray spectrometer represents one of the commonly used setup for experiments aiming at spectroscopic studies. High-efficiency detection of light-charged particles in a fusion-evaporation reaction guarantees good discrimination of different reaction channels and provides essential information for the kinematic reconstruction. In this paper we discuss a configuration of the EUCLIDES array developed for the lifetime measurements of nuclear excited states populated in a fusion-evaporation reaction. In such a configuration a part of the EUCLIDES detectors is disassembled allowing for the installation of a plunger device in the reaction chamber. The reduced configuration of EUCLIDES provides high detection efficiency necessary for reliable light charged-particle discrimination. We report on the commissioning experiment focused on the Ni-58(Ni-58,3p)I-113 reaction. The lifetimes of 11/2(-) and 15/2(-) states were measured by applying the Recoil Distance Doppler Shift method to be equal to 206(20) ps and 7.9(12) ps correspondingly and were in good agreement with the values cited in the literature. Thus, the combination of the GALILEO and EUCLIDES arrays, and the plunger device has resulted in a powerful experimental setup to determine lifetimes of excited states in neutron-deficient nuclei in the picosecond range.
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| 3. |
- Charlton, M., et al.
(författare)
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Positron production using a 9 MeV electron linac for the GBAR experiment
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 985
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Tidskriftsartikel (refereegranskat)abstract
- For the GBAR (Gravitational Behaviour of Antihydrogen at Rest) experiment at CERN's Antiproton Decelerator (AD) facility we have constructed a source of slow positrons, which uses a low-energy electron linear accelerator (linac). The driver linac produces electrons of 9 MeV kinetic energy that create positrons from bremsstrahlung-induced pair production. Staying below 10 MeV ensures no persistent radioactive activation in the target zone and that the radiation level outside the biological shield is safe for public access. An annealed tungsten-mesh assembly placed directly behind the target acts as a positron moderator. The system produces 5 x 10(7) slow positrons per second, a performance demonstrating that a low-energy electron linac is a superior choice over positron-emitting radioactive sources for high positron flux.
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| 4. |
- Fabian, X., et al.
(författare)
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Artificial neural networks for neutron/gamma discrimination in the neutron detectors of NEDA
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 986
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Tidskriftsartikel (refereegranskat)abstract
- Three different Artificial Neural Network architectures have been applied to perform neutron/gamma discrimination in NEDA based on waveform and time-of-flight information. Using the coincident gamma-rays from AGATA, we have been able to measure and compare on real data the performances of the Artificial Neural Networks as classifiers. While the general performances are quite similar for the data set we used, differences, in particular related to the computing times, have been highlighted. One of the Artificial Neural Network architecture has also been found more robust to time misalignment of the waveforms. Such a feature is of great interest for online processing of waveforms.
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| 5. |
- Georgali, E., et al.
(författare)
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Using GEANT4 Monte Carlo simulations to resolve low energy γ-ray spectra : The study of 164Hog+m decay using a broad energy HPGe detector
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 985
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Tidskriftsartikel (refereegranskat)abstract
- Within the present work a peak analysis and unfolding method for low energy γ-ray spectroscopy is presented. This method can be used to facilitate the determination of the peak integral of a photopeak, when Ge X-ray escape peaks contaminate the latter and in parallel the source activity and the emission rate of the recorded photons which produce the escape peaks are unknown. It is based on extensive Monte Carlo simulations of the spectra by taking the full advantage of power and accuracy provided by the GEANT4 simulation toolkit.
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| 6. |
- Grape, Sophie, 1982-, et al.
(författare)
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Determination of spent nuclear fuel parameters using modelled signatures from non-destructive assay and Random Forest regression
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 969
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Tidskriftsartikel (refereegranskat)abstract
- Verification of fuel parameters is a central undertaking for nuclear inspectors aiming at verifying the completeness and correctness of operator declarations. Traditionally, such verification is done analysing data from one instrument at a time. Here we present a study based on simulated data from various non-destructive assay measurement techniques applied on modelled PWR nuclear fuel assemblies. The data comprised multiple signatures and were analysed using machine learning algorithms. These signatures included activities from gamma-ray emitting fission product radionuclides, the parametrised early die-away time.. from the prototype Differential Die-away Self-Interrogation (DDSI) instrument, as well as the total Cherenkov light intensity which is directly measurable. The objective of the work is to systematically explore the capability to predict values of the fuel parameters initial enrichment (IE), burnup (BU) and cooling time (CT) independently of operator declarations, using Random Forest regression and modelled pressurised water reactor (PWR) fuel. The results show that passive gamma-ray activities alone can be used to predict IE, BU and CT for CT<20 years, and that by adding a feature proportional to the total gamma-ray activity, the errors in the predictions are significantly reduced. In this work, two measures proportional to total gamma activity have been studied: the sum of all considered gamma-ray intensities, and the total Cherenkov light intensity. From this work it was concluded that for fuels with CTs between 20 and 70 years, CT can be well determined by a multivariate analysis of the activities of Cs-134, Cs-137, Eu-154. For a BU determination, an additional feature corresponding to total gamma activity is required. This is, however, not sufficient to determine IE, which requires inclusion of the neutron signature.. as well.
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| 7. |
- Holz, Michael, et al.
(författare)
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Envelope dynamics and stability with non-linear space-charge forces
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 951
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Tidskriftsartikel (refereegranskat)abstract
- We developed a model to calculate the stability of Gaussian beam distributionswith non-linear space-charge forces in the presence of random and skewquadrupoleerrors. The eect of the space-charge force on the beam matrix iscalculated analytically including full cross-plane coupling in 4D phase space,which allows us to perform fast parameter studies. For stability analysis, wend the xed points of the beam including the space-charge forces and constructa Jacobi-matrix by slightly perturbing the periodic solution. The stability ofenvelope oscillations is inferred by eigenvalue analysis. Furthermore, we employenvelope tracking as a complementary method and compare the results ofthe eigenvalue analysis with FFT data from the tracked envelope. The nonlinearityof the space-charge force in combination with lattice errors and beamcoupling opens up for envelope-lattice resonances and envelope coupling resonances.Hitting these resonances leads to envelope blow-up, causing an eectivebeam mismatch. Therefore, we nally examine the eect of beam mismatch onthe envelope tune-shift and its stability.
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| 8. |
- Husson, A., et al.
(författare)
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A pulsed high-voltage decelerator system to deliver low-energy antiprotons
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1002
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Tidskriftsartikel (refereegranskat)abstract
- The GBAR (Gravitational Behavior of Antihydrogen at Rest) experiment at CERN requires efficient deceleration of 100 keV antiprotons provided by the new ELENA synchrotron ring to synthesize antihydrogen. This is accomplished using electrostatic deceleration optics and a drift tube that is designed to switch from -99 kV to ground when the antiproton bunch is inside – essentially a charged particle “elevator” – producing a 1 keV pulse. We describe the simulation, design, construction and successful testing of the decelerator device at -92 kV on-line with antiprotons from ELENA.
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| 9. |
- Preston, Markus, et al.
(författare)
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A feature-extraction and pile-up reconstruction algorithm for the forward-spectrometer EMC of the PANDA experiment
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 1011
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Tidskriftsartikel (refereegranskat)abstract
- A digital algorithm for real-time feature extraction, i.e. determination of pulse amplitude and timing, has been developed for the forward-spectrometer electromagnetic calorimeter in the PANDA experiment. The algorithm, which is based on the well known optimal-filter algorithm, has been designed to allow reconstruction of pile-up signals in real time and to work in a free-running DAQ system such as PANDA. To benchmark the algorithm, a Geant4-based Monte Carlo model of photon interactions in the calorimeter has been developed to generate realistic detector signals which were used as inputs to a VHDL simulation of the algorithm. The results of this simulation study show that the developed algorithm improves the time resolution by almost 50% compared to a conventional linear constant fraction discriminator algorithm. For the PANDA calorimeter, this results in a time root resolution close to 100 ps/ GeV per detector element at high energies. The algorithm allows reconstruction of the amplitude and timing of pile-up pulses separated by as little as 30 ns with good efficiency, fulfilling the PANDA requirements.
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| 10. |
- Rathore, Vikram, et al.
(författare)
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Geometrical optimisation of a segmented HPGe detector for spectroscopic gamma emission tomography : A simulation study
- 2021
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 998
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Tidskriftsartikel (refereegranskat)abstract
- Segmented coaxial HPGe (High Purity Germanium) detectors have recently been shown to be feasible for Gamma Emission Tomography (GET). This type of detector allows for a combination of high efficiency and high energy resolution in gamma spectrometry of irradiated nuclear fuel. The ultimate aim of developing segmented HPGe for GET measurements is to achieve a high spatial resolution to facilitate imaging of rod-internal features and interrogation of smaller irradiated fuel samples.In this work, we present the optimisation of a segmented HPGe detector through a simulation study using the Monte Carlo particle transport code MCNP. Constraints to each dimension of the detector were identified, from manufacturing limitations and requirements arising from the use of a finite-sized collimator slit. In particular, a relationship between the minimum inner radius of the coaxial detector and the segments azimuthal dimension was derived based on the identified constraints. Segment azimuthal and radial dimensions have been varied (based on the derived relationship between the azimuthal and radial dimension) and the full energy efficiency and misidentification rate were evaluated to obtain the optimal dimensions. The optimal ranges of the segment dimensions were determined.
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