| 1. |
- Andersson, Peter, 1981-, et al.
(författare)
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Coincidence spectroscopy for increased sensitivity in radionuclide monitoring
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The majority of the energy in a nuclear explosion is released in the immediate blast and the initial radiation accounts. The remaining fraction is released through radioactive decay of the explosion's fission products and neutron activation products over a longer time span. This allows for the detection of a nuclear explosion by detecting the presence of residual decay. Radionuclide monitoring stations for detection of radioactive emissions to the atmosphere is thereby an important tool in the verification of compliance with nuclear disarmament treaties. In particular, the globally spanning radionuclide station network of the International Monitoring System (IMS) has been implemented for verification of the Comprehensive Nuclear-Test-Ban Treaty.High Purity Germanium (HPGe) detectors are workhorses in radionuclide monitoring. The detection of characteristic gamma rays can be used to disclose the presence of signature nuclides produced innuclear weapon tests. A particular development that has potential to improve the sensitivity of radionuclide monitoring is the coincidence technique where decaying nuclides that emit several coincident gamma rays can be detected at much smaller activity concentrations than with conventional gamma spectroscopy.In this project, dedicated gamma-gamma coincidence detectors are being developed, utilizing electronically segmented HPGe detectors. These detectors are expected to be highly sensitive to low-activity samples of nuclides that present coincident emissions of gamma rays. In this paper we present the concept, define performance parameters, and explore the performance of such detectors to a subset of radionuclides of particular CTBT relevance. In addition, we discuss the path forward in developing a next generation gamma-gamma coincidence spectroscopy system of segmented HPGe.
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| 2. |
- Barucca, G., et al.
(författare)
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Feasibility studies for the measurement of time-like proton electromagnetic form factors from (p)over-barp -> mu(+)mu(-) at PANDA at FAIR
- 2021
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Ingår i: European Physical Journal A. - NEW YORK, USA : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, vertical bar G(E)vertical bar and vertical bar G(M)vertical bar, using the (p) over barp -> mu(+)mu(-) reaction at PANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at PANDA, using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is (p) over barp -> pi(+)pi(-), due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented.
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| 3. |
- Barucca, G., et al.
(författare)
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PANDA Phase One
- 2021
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Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:6
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Tidskriftsartikel (refereegranskat)abstract
- The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or PANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton-nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper.
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| 4. |
- Barucca, G., et al.
(författare)
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Precision resonance energy scans with the PANDA experiment at FAIR : Sensitivity study for width and line shape measurements of the X(3872)
- 2019
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Ingår i: European Physical Journal A. - : SPRINGER. - 1434-6001 .- 1434-601X. ; 55:3
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like X(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from JPC=1--.
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| 5. |
- Barucca, G., et al.
(författare)
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Study of excited Ξ baryons with the P¯ ANDA detector
- 2021
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Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
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Tidskriftsartikel (refereegranskat)abstract
- The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards N∗ and Δ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the N∗ and Δ spectra. The future antiproton experiment P¯ANDA will provide direct access to final states containing a Ξ¯ Ξ pair, for which production cross sections up to μb are expected in p¯p reactions. With a luminosity of L= 10 31 cm- 2 s- 1 in the first phase of the experiment, the expected cross sections correspond to a production rate of ∼106events/day. With a nearly 4 π detector acceptance, P¯ANDA will thus be a hyperon factory. In this study, reactions of the type p¯p → Ξ¯ +Ξ∗ - as well as p¯p → Ξ¯ ∗ +Ξ- with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between 3 and 5%. This allows high statistics data to be collected within a few weeks of data taking.
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| 6. |
- Barucca, G., et al.
(författare)
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The potential of Λ and Ξ- studies with PANDA at FAIR
- 2021
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Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
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Tidskriftsartikel (refereegranskat)abstract
- The antiproton experiment PANDA at FAIR is designed to bring hadron physics to a new level in terms of scope, precision and accuracy. In this work, its unique capability for studies of hyperons is outlined. We discuss ground-state hyperons as diagnostic tools to study non-perturbative aspects of the strong interaction, and fundamental symmetries. New simulation studies have been carried out for two benchmark hyperon-antihyperon production channels: p¯ p→ Λ¯ Λ and p¯ p→ Ξ¯ +Ξ-. The results, presented in detail in this paper, show that hyperon-antihyperon pairs from these reactions can be exclusively reconstructed with high efficiency and very low background contamination. In addition, the polarisation and spin correlations have been studied, exploiting the weak, self-analysing decay of hyperons and antihyperons. Two independent approaches to the finite efficiency have been applied and evaluated: one standard multidimensional efficiency correction approach, and one efficiency independent approach. The applicability of the latter was thoroughly evaluated for all channels, beam momenta and observables. The standard method yields good results in all cases, and shows that spin observables can be studied with high precision and accuracy already in the first phase of data taking with PANDA.
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| 7. |
- Branger, Erik, 1988-, et al.
(författare)
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Combining DCVD measurements at different alignments for enhanced partial defect detection performance
- 2021
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Ingår i: Proceedings of the INMM & ESARDA Joint Virtual Annual Meeting August 23-26 & August 30-September 1, 2021.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the current Digital Cherenkov Viewing Device (DCVD) measurement methodology, the DCVD is aligned over the centre of a fuel assembly when measuring emitted Cherenkov light. Due to the collimation of light, and due to the lifting handle of PWR fuel assemblies covering the fuel periphery, the DCVD is more sensitive to partial defects near the fuel assembly centre than near the periphery. Here, we investigate the sensitivity of the DCVD for detecting partial defects for different instrument alignments. By performing measurements at both the centre and near the assembly periphery, more accurate measurements near the periphery can be obtained.DCVD images were simulated for different partial defect scenarios with 30% of the fuel rods removed or replaced with low, medium or high-density rods. Simulations were run with different DCVD alignments, and the Cherenkov light distribution in the images were quantitatively analysed and compared to simulated images for a fuel assembly without defects. The simulation results were also compared with measurements of intact spent fuel assemblies.The simulations show that the local Cherenkov light intensity deviation due to a partial defect is not sensitive to the alignment. Hence, the current methodology is robust, and will not benefit from measuring at different alignments. Regarding the signal-to-noise ratio, combining measurements at different alignments can improve the measurements. However, the improvement is modest, and for the DCVD it may be preferred to simply use the current methodology and make longer measurements. For future autonomous Cherenkov measuring systems, combining images can be a way of improving the quality of the measurements.
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| 8. |
- Branger, Erik, 1988-, et al.
(författare)
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Effects of modelling assumptions on Cherenkov light intensity predictions
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is one of the instruments available to IAEA inspectors to verify spent nuclear fuel in wet storage. The DCVD can be used for partial defect verification, verifying that 50% or more of a fuel assembly has not been diverted. The partial defect verification relies on a comparison between measured and predicted intensities, based on operator fuel declarations. Recently, IAEA inspectors have encountered spent fuels with short cooling times where there were systematic differences between predictions and measurements. Through the Swedish support program, this deviation was investigated, by studying various modelling assumptions that could cause the discrepancy.The predominant cause of the discrepancy was beta-decay electrons, passing through the fuel cladding and entering the water with sufficient energy to directly produce Cherenkov light. Analysis of measurement data for a set of fuels where the discrepancy was found to be pronounced revealed that for modern fuel designs with thin claddings the beta contribution is enhanced, and for short-cooled fuels additional beta-decaying isotopes are abundant and must be considered. Furthermore, the data showed that for nuclear fuels that had not reached the discharge burnup, the fuel irradiation history may cause a relative enhancement of the abundance of beta-decaying isotopes relative to other isotopes causing Cherenkov light. Other studied modelling assumptions, such as void, burnable absorbers and using binned gamma spectra, showed that they only introduced a modest bias, and proper default values and data handling can mitigate it. A method to predict the direct beta contribution to the Cherenkov light intensity was developed, which can ensure that the observed biases will be eliminated from future verification campaigns. It is advised that this enhanced prediction method be included in the DCVD software, and made available to inspectors.
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| 9. |
- Branger, Erik, 1988-, et al.
(författare)
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Image analysis to support DCVD verification
- 2023
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Ingår i: Proceedings of the INMM & ESARDA Joint Annual Meeting, May 22-26, 2023. - : Institute of Nuclear Materials Management (INMM).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is one instrument available to authority inspectors for verifying spent fuel assemblies in wet storage. The measurements result in images of the Cherenkov light emissions from the fuel assembly under study. This work presents research on applying image analysis and statistical methods to improve data quality and to extract more information from the measurements, extending the use of these methods beyond what is currently implemented in the DCVD software. The goal of this project is to apply template matching and statistical analysis to the images. However, before such techniques can be applied, effort is needed to ensure that the measurements are directly comparable. Two main issues are investigated here, the first being the positioning of the Region-Of-Interest. By developing an automated Region-Of-Interest placer, a consistent and reproducible Region-Of-Interest placement can be achieved. The second is automatic identification of fuel type, to support a later comparison with a template. We demonstrate that a method based on Principal Component Analysis can be used to determine the fuel type. Finally, we present the first results regarding template matching, comparing a measured image to a template, aiming to identify regions in the image where the two differ. Such differences could be due to a partial defect located in that region, but also due to other reasons such as debris covering the fuel top. Automatically identification of such regions can in the future be used to focus inspector attention to features requiring expert judgement, supporting efficient use of the measurement data and inspector effort. The first results demonstrate the feasibility of the method, but also that more work is required before the method is robust.
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| 10. |
- Branger, Erik, 1988-, et al.
(författare)
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Investigating the sensitivity to irradiation history when predicting fuel parameters using random forest regression
- 2021
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Ingår i: ESARDA Bulletin. - : European Commission Joint Research Centre. - 1977-5296. ; 62, s. 2-10
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Tidskriftsartikel (refereegranskat)abstract
- Safeguards verification of spent nuclear fuel assemblies is frequently done by performing non-destructive measurements, which are used to verify the completeness and correctness of operator declarations such as initial enrichment (IE), burnup (BU) and cooling time (CT) of the fuel. However, different irradiation histories may result in the same combination of CT, BU and IE, and such fuels may behave differently despite identically declared values. The goal of this work is to investigate what effect the irradiation history has on the ability to predict the fuel parameters using random forest regression. Random forest regression models were trained to predict the fuel parameters IE, BU and CT based on combinations of radiation signatures calculated from a previously modelled Pressurised Water Reactor (PWR) spent nuclear fuel library. The radiation signatures studied were the relative gamma-ray activities of Cs137, Cs134 and Eu154, their total gamma-ray activity, the total neutron emission rate and the parametrized early die-away time ? from the Differential Die-away Self Interrogation (DDSI) instrument. The performance of the models were tested on simulations of 2192 PWR fuel assemblies from the Ringhals 3 and 4 nuclear power plants in Sweden, which were simulated based on their documented irradiation histories. Despite significant differences in irradiation history between the training and testing data sets, the Ringhals assembly parameters could be predicted with similar accuracy as for assemblies in the training set. The relative gamma-ray activities were sufficient to predict the CT with an RMSE of 2 years, and adding a total gamma or total neutron signature allowed the BU to be predicted with an RMSE of 1.4 MWd/kgU. The DDSI early die-away time ? enabled an accurate IE prediction, with an RMSE of 0.16 w%. The differences between irradiation histories introduced a systematic bias where CT was overestimated by about 1 year and the BU by about 1.5 MWd/kgU.
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