| 1. |
- Jaworski, G., et al.
(författare)
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The New Neutron Multiplicity Filter NEDA and Its First Physics Campaign with AGATA
- 2019
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Ingår i: Acta Physica Polonica B. - 0587-4254 .- 1509-5770. ; 50:3, s. 585-590
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Tidskriftsartikel (refereegranskat)abstract
- A new neutron multiplicity filter NEDA, after a decade of design, R&D and construction, was employed in its first physics campaign with the AGATA spectrometer. Properties and performance of the array are discussed.
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| 2. |
- Sherratt, K., et al.
(författare)
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Predictive performance of multi-model ensemble forecasts of COVID-19 across European nations
- 2023
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Ingår i: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Methods: We used open-source tools to develop a public European COVID-19 Forecast Hub. We invited groups globally to contribute weekly forecasts for COVID-19 cases and deaths reported by a standardised source for 32 countries over the next 1–4 weeks. Teams submitted forecasts from March 2021 using standardised quantiles of the predictive distribution. Each week we created an ensemble forecast, where each predictive quantile was calculated as the equally-weighted average (initially the mean and then from 26th July the median) of all individual models’ predictive quantiles. We measured the performance of each model using the relative Weighted Interval Score (WIS), comparing models’ forecast accuracy relative to all other models. We retrospectively explored alternative methods for ensemble forecasts, including weighted averages based on models’ past predictive performance.Results: Over 52 weeks, we collected forecasts from 48 unique models. We evaluated 29 models’ forecast scores in comparison to the ensemble model. We found a weekly ensemble had a consistently strong performance across countries over time. Across all horizons and locations, the ensemble performed better on relative WIS than 83% of participating models’ forecasts of incident cases (with a total N=886 predictions from 23 unique models), and 91% of participating models’ forecasts of deaths (N=763 predictions from 20 models). Across a 1–4 week time horizon, ensemble performance declined with longer forecast periods when forecasting cases, but remained stable over 4 weeks for incident death forecasts. In every forecast across 32 countries, the ensemble outperformed most contributing models when forecasting either cases or deaths, frequently outperforming all of its individual component models. Among several choices of ensemble methods we found that the most influential and best choice was to use a median average of models instead of using the mean, regardless of methods of weighting component forecast models.Conclusions: Our results support the use of combining forecasts from individual models into an ensemble in order to improve predictive performance across epidemiological targets and populations during infectious disease epidemics. Our findings further suggest that median ensemble methods yield better predictive performance more than ones based on means. Our findings also highlight that forecast consumers should place more weight on incident death forecasts than incident case forecasts at forecast horizons greater than 2 weeks.
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| 3. |
- Valiente-Dobon, J. J., et al.
(författare)
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NEDA-NEutron Detector Array
- 2019
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 927, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- The NEutron Detector Array, NEDA, will form the next generation neutron detection system that has been designed to be operated in conjunction with gamma-ray arrays, such as the tracking-array AGATA, to aid nuclear spectroscopy studies. NEDA has been designed to be a versatile device, with high-detection efficiency, excellent neutron-gamma discrimination, and high rate capabilities. It will be employed in physics campaigns in order to maximise the scientific output, making use of the different stable and radioactive ion beams available in Europe. The first implementation of the neutron detector array NEDA with AGATA 1 pi was realised at GANIL. This manuscript reviews the various aspects of NEDA.
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| 4. |
- Fahlander, Claes, et al.
(författare)
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Excited States in 103Sn: Neutron Single-particle Energies with Respect to 100Sn
- 2001
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 63:2
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray lines from Sn-103 have been identified for the first time using EUROBALL and ancillary detectors. The level scheme of Sn-103 has been established by means of particle-gated gamma gamma coincidences. The energy spacing between the g(7/2) and d(5/2) neutron single-particle orbitals is determined from the excited states in Sn-103.
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| 5. |
- Egea Canet, F. J., et al.
(författare)
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A New Front-End High-Resolution Sampling Board for the New-Generation Electronics of EXOGAM2 and NEDA Detectors
- 2015
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 62:3, s. 1056-1062
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the final design and results of the FADC Mezzanine for the EXOGAM (EXOtic GAMma array spectrometer) and NEDA (Neutron Detector Array) detectors. The measurements performed include those of studying the effective number of bits, the energy resolution using HP-Ge detectors, as well as timing histograms and discrimination performance. Finally, the conclusion shows how a common digitizing device has been integrated in the experimental environment of two very different detectors which combine both low-noise acquisition and fast sampling rates. Not only the integration fulfilled the expected specifications on both systems, but it also showed how a study of synergy between detectors could lead to the reduction of resources and time by applying a common strategy.
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| 6. |
- Egea Canet, F. J., et al.
(författare)
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Digital Front-End Electronics for the Neutron Detector NEDA
- 2015
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 62:3, s. 1063-1069
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design of the NEDA (Neutron Detector Array) electronics, a first attempt to involve the use of digital electronics in large neutron detector arrays. Starting from the front-end modules attached to the PMTs (PhotoMultiplier Tubes) and ending up with the data processing workstations, a comprehensive electronic system capable of dealing with the acquisition and pre-processing of the neutron array is detailed. Among the electronic modules required, we emphasize the front-end analog processing, the digitalization, digital pre-processing and communications firmware, as well as the integration of the GTS (Global Trigger and Synchronization) system, already used successfully in AGATA (Advanced Gamma Tracking Array). The NEDA array will be available for measurements in 2016.
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| 7. |
- Luo, X. L., et al.
(författare)
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Pulse pile-up identification and reconstruction for liquid scintillator based neutron detectors
- 2018
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER SCIENCE BV. - 0168-9002 .- 1872-9576. ; 897, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- The issue of pulse pile-up is frequently encountered in nuclear experiments involving high counting rates, which will distort the pulse shapes and the energy spectra. A digital method of off-line processing of pile-up pulses is presented. The pile-up pulses were firstly identified by detecting the downward-going zero-crossings in the first-order derivative of the original signal, and then the constituent pulses were reconstructed based on comparing the pile-up pulse with four models that are generated by combining pairs of neutron and.. standard pulses together with a controllable time interval. The accuracy of this method in resolving the pile-up events was investigated as a function of the time interval between two pulses constituting a pile-up event. The obtained results show that the method is capable of disentangling two pulses with a time interval among them down to 20 ns, as well as classifying them as neutrons or gamma rays. Furthermore, the error of reconstructing pile-up pulses could be kept below 6% when successive peaks were separated by more than 50 ns. By applying the method in a high counting rate of pile-up events measurement of the NEutron Detector Array (NEDA), it was empirically found that this method can reconstruct the pile-up pulses and perform neutron-gamma discrimination quite accurately. It can also significantly correct the distorted pulse height spectrum due to pile-up events.
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| 8. |
- Moszynski, A., et al.
(författare)
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Intrinsic energy resolution and light yield nonproportionality of BGO
- 2004
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 51:3, s. 1074-1079
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic energy resolution and nonproportionality of the light yield as a function of gamma ray energies, in the energy range of 14 keV to 1.33 MeV, were studied for small BGO (Bi4Ge3O12) crystals at room and liquid nitrogen (LN2) temperatures. The study showed that the intrinsic resolution of BGO and the light yield nonproportionality, as a function of energy do not depend on the crystal temperature. High light outputs of 14000 +/- 300 electron-hole pairs and energy resolution of 6.5% +/- 0.2% for 662 keV gamma rays were measured with the 9 mm diameter, 4 mm thick crystals, coupled to large area avalanche photodiodes and cooled down to LN2 temperature. Special attention was paid to analyzing the energy resolution of the escape peaks, which were well separated from the full-energy peaks due to the good energy resolution of BGO at LN2 temperatures and the energy of bismuth KX-rays. The intrinsic energy resolution of the BGO crystal for escape peaks does not show deviations from analysis of total energy absorption photopeaks. This is in spite of the fact that the contributions of X-rays and Auger electron cascade in creation of escape peaks are much smaller than in full-energy peaks. In the small volume crystal, mainly electrons produced in the photoelectric absorption create the escape peaks.
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| 9. |
- Palacz, M., et al.
(författare)
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Investigations of Neutron Deficient Nuclei Close to 100Sn with EUROBALL
- 2001
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Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254 .- 1509-5770. ; 32, s. 999-1003
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Tidskriftsartikel (refereegranskat)abstract
- Excited states of nuclei in the vicinity of Sn-100 have been studied using: the EUROBALL detector array. Gamma-ray lines from Sn-103 have been identified for the first time, and a level scheme of low-lying excited states of Sn-103 has been established. New constraints on energies of single particle orbitals with respect to the Sn-100 core are obtained.
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| 10. |
- Perot, B., et al.
(författare)
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The EURITRACK project : Development of a tagged neutron inspection system for cargo containers
- 2006
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 0819462691 - 9780819462695
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Konferensbidrag (refereegranskat)abstract
- The EURopean Illicit TRAfficing Countermeasures Kit project is part of the 6th European Union Framework Program, and aims at developing a neutron inspection system for detecting threat materials (explosives, drugs, etc.) in cargo containers. Neutron interaction in the container produces specific gamma-rays used to determine the chemical composition of the inspected material. An associated particle sealed tube neutron generator is developed to allow precise location of the interaction point by direction and time-of-flight measurements of the neutrons tagged by alpha-particles. The EURITRACK project consists in developing: a transportable deuterium-tritium neutron generator including a position sensitive alpha detector (8×8 matrix of YAP:Ce crystals coupled to a multi-anode photomultiplier), fast neutron and gamma-ray detectors, front-end electronics to perform coincidence and spectroscopic measurements, and an integrated software which manages neutron generator and detectors positioning, data acquisition and analysis. Hardware components have been developed and tested by the consortium partners. Current status of this work and provisional performances of the system assessed by Monte Carlo calculations are presented.
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