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Weiszflog, Matthias
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Publications (10 of 436) Show all publications
Eriksson, B., Conroy, S., Ericsson, G., Eriksson, J., Hjalmarsson, A., Weiszflog, M., . . . Maslov, M. (2023). TOFu: A fully digital data acquisition system upgrade for the neutron time-of-flight spectrometer TOFOR. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1049, Article ID 168126.
Open this publication in new window or tab >>TOFu: A fully digital data acquisition system upgrade for the neutron time-of-flight spectrometer TOFOR
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2023 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 1049, article id 168126Article in journal (Refereed) Published
Abstract [en]

TOFOR is a time-of-flight (TOF) neutron spectrometer located at the Joint European Torus (JET) with a vertical sightline of the JET plasma. It consists of 5 start (denoted S1) and 32 stop (denoted S2) plastic scintillation detectors which can be used in coincidence to generate a TOF spectrum. Spectroscopic analysis of the neutron TOF spectra produced by the JET plasma is regularly performed to determine, e.g., the fuel ion ratio and the presence of fast ion species in the fusion plasma. TOFOR has been upgraded with a new digital data acquisition (DAQ) system, denoted TOFu, which consists of 10 waveform digitizers with a total of 40 channels, 37 of which are connected to the photomultiplier output of the different S1 and S2 detectors. This paper presents a technical overview of the TOFu system and describes the offline analysis capabilities of TOFu which were not available with the previous DAQ system. Two experimental JET discharges are studied and used to show that the signal-to-background ratio is improved by almost 200% for the 2.5 MeV neutron signal and almost 400% for the 14 MeV neutron signal using the new offline analysis capabilities.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
TOFOR, Data acquisition system, TOFu, Time-of-flight, Neutron spectrometry, Joint European Torus
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-504964 (URN)10.1016/j.nima.2023.168126 (DOI)000997950400001 ()
Funder
EU, European Research Council, 101052200-EUROfusion
Available from: 2023-06-16 Created: 2023-06-16 Last updated: 2023-10-18Bibliographically approved
Marcinkevicius, B., Eriksson, J., Hjalmarsson, A., Conroy, S. & Ericsson, G. (2022). Fuel ion ratio determination using the 14 MeV Tandem neutron spectrometer for JET DTE1 campaign discharges. Fusion engineering and design, 184, Article ID 113259.
Open this publication in new window or tab >>Fuel ion ratio determination using the 14 MeV Tandem neutron spectrometer for JET DTE1 campaign discharges
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2022 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 184, article id 113259Article in journal (Refereed) Published
Abstract [en]

This paper investigates the determination of the fuel ion ratio nT/ntot in fusion experiments using two different approaches. The methods are applied to plasma discharges from the deuterium-tritium campaign at the Joint European Torus (JET) in 1997. Multiple discharges have been analysed using data acquired with the Tandem (KM2) neutron spectrometer, using a new neutron spectrometer response function and improved line-of-sight information.The two different approaches were generally similar with the exception of the beam slowing down modelling, handled by two different particle transport codes, namely, TRANSP and PENCIL.The results show that nT/ntot can be determined using Tandem neutron spectrometer data; nT/ntot using both of the approaches are consistent and within the uncertainty for a range of studied discharges.The obtained results support previous studies on nT/ntot determination using neutron spectroscopy. In addition, we have shown that PENCIL can be used instead of TRANSP for a range of discharges which could simplify and speed up the estimation of nT/ntot. The possible limitations of the approach using PENCIL could be investigated using different neutron spectrometer data from the 2021 JET deuterium-tritium campaign.A similar spectrometer like Tandem is planned to be operational at ITER and the results of this paper form the first experimental verification of the capability for nT/ntot measurements with such spectrometers. Further research on this could lead to better understanding of these instruments and their limitations before the start of experiments at ITER.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Neutron spectrometer, Hot plasma, JET, Tokamak, Fuel ion ratio
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-487891 (URN)10.1016/j.fusengdes.2022.113259 (DOI)000869406200006 ()
Note

JET (Joint European Torus) medarbetare står som gruppförfattare i artikeln.

Här har de affilierade vid Uppsala Universitet tagits med.

Available from: 2022-11-08 Created: 2022-11-08 Last updated: 2022-11-08Bibliographically approved
Mailloux, J., Andersson Sundén, E., Cecconello, M., Conroy, S., Ericsson, G., Eriksson, B., . . . Zychor, I. (2022). Overview of JET results for optimising ITER operation. Nuclear Fusion, 62(4), Article ID 042026.
Open this publication in new window or tab >>Overview of JET results for optimising ITER operation
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2022 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 62, no 4, article id 042026Article in journal (Refereed) Published
Abstract [en]

The JET 2019–2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major neutral beam injection upgrade providing record power in 2019–2020, and tested the technical and procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle (α) physics in the coming D–T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed shattered pellet injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design and operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D–T benefited from the highest D–D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2022
Keywords
overview, D-T preparation, tritium operations, plasma facing components (PFC), nuclear technology, JET with ITER-like wall, isotope
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-482515 (URN)10.1088/1741-4326/ac47b4 (DOI)000829648300001 ()
Funder
European Commission, 633053
Note

For complete list of authors see http://dx.doi.org/10.1088/1741-4326/ac47b4

Available from: 2022-08-25 Created: 2022-08-25 Last updated: 2022-09-30Bibliographically approved
Weiszflog, M. & Goetz, I. K. (2022). Transforming laboratory experiments for digital teaching: remote access laboratories in thermodynamics. European journal of physics, 43(1), Article ID 015701.
Open this publication in new window or tab >>Transforming laboratory experiments for digital teaching: remote access laboratories in thermodynamics
2022 (English)In: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 43, no 1, article id 015701Article in journal (Refereed) Published
Abstract [en]

Laboratories in an undergraduate physics course were adapted to remote learning while conserving a high degree of student autonomy regarding the experimental work. The commencement of the COVID-19 pandemic in 2020 and the resulting restrictions for large groups enforced the immediate development and implementation of new teaching concepts. This article describes laboratories, which have been redesigned in order to give the students the possibility to remotely steer and control the experiments by instructing their teachers, who were on site in the laboratory. This interactive approach allowed for a high degree of autonomy and freedom in the experimental design. The assessment of the laboratories, oral presentations by the students, was carried out in a similar format as in previous years, but remotely. The presentations indicated that the students reached a comparable level of understanding of the underlying physics concepts as in years with on-site laboratories. The experiences gathered with this concept can be beneficial beyond the described one-time implementation and allow adaptation for other scenarios of remote courses.

Place, publisher, year, edition, pages
IOP Publishing, 2022
Keywords
remote access, student laboratory, remote teaching
National Category
Didactics
Identifiers
urn:nbn:se:uu:diva-459001 (URN)10.1088/1361-6404/ac3193 (DOI)000716733900001 ()
Available from: 2021-11-29 Created: 2021-11-29 Last updated: 2021-11-29Bibliographically approved
Eriksson, B., Conroy, S., Ericsson, G., Eriksson, J., Giacomelli, L., Hjalmarsson, A. & Weiszflog, M. (2021). New method for time alignment and time calibration of the TOFOR time-of-flight neutron spectrometer at JET. Review of Scientific Instruments, 92(3), Article ID 033538.
Open this publication in new window or tab >>New method for time alignment and time calibration of the TOFOR time-of-flight neutron spectrometer at JET
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2021 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 92, no 3, article id 033538Article in journal (Refereed) Published
Abstract [en]

The TOFOR time-of-flight (TOF) neutron spectrometer at the Joint European Torus (JET) is composed of 5 start (S1) and 32 stop (S2) scintillation detectors. Recently, the data acquisition system (DAQ) of TOFOR was upgraded to equip each of the 37 detectors with its own waveform digitizer to allow for correlated time and pulse height analysis of the acquired data. Due to varying cable lengths and different pulse processing pathways in the new DAQ system, the 160 (5.32) different TOF pairs of start-stop detectors must be time-aligned to enable the proper construction of a summed TOF spectrum. Given the time (energy) resolution required by the entire spectrometer system to measure different plasma neutron emission components, it is of importance to align the detector pairs to each other with sub-nanosecond precision. Previously, the alignment partially depended on using fusion neutron data from Ohmic heating phases of JET experimental pulses. The dependence on fusion neutron data in the time alignment process is, however, unsatisfactory as it involves data one would wish to include in an independent analysis for physics results. In this work, we describe a method of time-aligning the detector pairs by using gamma rays. Given the known geometry and response of TOFOR to gamma rays, the time alignment of the detector pairs is found by examining gamma events interacting in coincidence in both S1-S1 and S1-S2 detector combinations. Furthermore, a technique for separating neutron and gamma events in the different detector sets is presented. Finally, the time-aligned system is used to analyze neutron data from Ohmic phases for different plasma conditions and to estimate the Ohmic fuel ion temperature.

Place, publisher, year, edition, pages
American Institute of Physics (AIP)AMER INST PHYSICS, 2021
National Category
Fusion, Plasma and Space Physics Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-440893 (URN)10.1063/5.0041126 (DOI)000631023100002 ()
Available from: 2021-04-28 Created: 2021-04-28 Last updated: 2024-01-15Bibliographically approved
Tardocchi, M., Giacomelli, L., Gorini, G., Muraro, A., Nocente, M., Rebai, M., . . . Popovichev, S. (2020). High rate neutron and gamma ray spectroscopy of magnetic confinement fusion plasmas. Paper presented at 3rd European Conference on Plasma Diagnostics (ECPD), MAY 06-10, 2019, Lisbon, PORTUGAL. Journal of Instrumentation, 15, Article ID C01010.
Open this publication in new window or tab >>High rate neutron and gamma ray spectroscopy of magnetic confinement fusion plasmas
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2020 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 15, article id C01010Article in journal (Refereed) Published
Abstract [en]

An important instrumental development work has been done in the last two decades in the field of neutron and gamma ray spectroscopic measurements of magnetic confinement plasmas. Starting from the present state of the art instrumentation installed at JET, this paper reviews the recent development that has been carried out within the EUROFUSION programme for the forthcoming high power JET D and DT campaign. This development was dedicated to the realization of new compact neutron and gamma-ray spectrometers which combine very high energy resolution (typically better than 5%) and MHz counting rate capabilities allowing for time resolution in the 10 ms time scale. One of the advantages offered by the compact dimensions of these spectrometers is to make possible their use in multiple sight-line camera configurations, such as for future burning plasma reactors (ITER and DEMO). New compact neutron spectrometers based on single crystal diamond detectors have been developed and installed at JET for measurements of the 14MeV neutron spectrum. Measurements on a portable DT neutron generator have shown that neutron spectroscopy of the accelerated beam ions at unprecedented energy resolution (similar to 1% at 14 MeV) is possible, which opens up new opportunities for diagnosing DT plasmas. For what concerns gamma ray measurements, the JET gamma ray camera has been recently upgraded with new compact spectrometers based on a LaBr3 scintillator coupled to Silicon Photomultiplier with the dual aim to improve the spectroscopic and rate capabilities of the detectors. The upgrade camera system will reconstruct the spatial gamma ray emissivity from the plasma in the MeV energy range at MHz counting rates and energy resolution in the 2-4% range. This will allow physics studies of gamma rays produced by the interaction of fast ions with impurities in the plasma and bremsstrahlung emission from runaway electrons.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2020
Keywords
Diamond Detectors, Gamma detectors (scintillators, CZT, HPG HgI etc), Neutron detectors (cold, thermal, fast neutrons), Nuclear instruments and methods for hot plasma diagnostics
National Category
Accelerator Physics and Instrumentation Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-410968 (URN)10.1088/1748-0221/15/01/C01010 (DOI)000525449100010 ()
Conference
3rd European Conference on Plasma Diagnostics (ECPD), MAY 06-10, 2019, Lisbon, PORTUGAL
Available from: 2020-05-28 Created: 2020-05-28 Last updated: 2020-05-28Bibliographically approved
Sias, G., Cecconello, M., Klimek, I., Wodniak, I., Yadykin, D., Andersson Sundén, E., . . . Zychor, I. (2019). A locked mode indicator for disruption prediction on JET and ASDEX upgrade. Fusion engineering and design, 138, 254-266
Open this publication in new window or tab >>A locked mode indicator for disruption prediction on JET and ASDEX upgrade
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2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 138, p. 254-266Article in journal (Refereed) Published
Abstract [en]

The aim of this paper is to present a signal processing algorithm that, applied to the raw Locked Mode signal, allows us to obtain a disruption indicator in principle exploitable on different tokamaks. A common definition of such an indicator for different machines would facilitate the development of portable systems for disruption prediction, which is becoming of increasingly importance for the next tokamak generations. Moreover, the indicator allows us to overcome some intrinsic problems in the diagnostic system such as drift and offset. The behavior of the proposed indicator as disruption predictor, based on crossing optimized thresholds of the signal amplitude, has been analyzed using data of both JET and ASDEX Upgrade experiments. A thorough analysis of the disruption prediction performance shows how the indicator is able to recover some missed and tardy detections of the raw signal. Moreover, it intervenes and corrects premature or even wrong alarms due to, e.g., drifts and/or offsets.

Keywords
Tokamak, Disruption prediction, Locked mode signal, Disruption indicators, Feature extraction
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-377710 (URN)10.1016/j.fusengdes.2018.11.021 (DOI)000457663100032 ()
Note

For complete list of authors see http://dx.doi.org/10.1016/j.fusengdes.2018.11.021

Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2023-10-31Bibliographically approved
Pau, A., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Dzysiuk, N., . . . Zychor, I. (2019). A machine learning approach based on generative topographic mapping for disruption prevention and avoidance at JET. Nuclear Fusion, 59(10), Article ID 106017.
Open this publication in new window or tab >>A machine learning approach based on generative topographic mapping for disruption prevention and avoidance at JET
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 10, article id 106017Article in journal (Refereed) Published
Abstract [en]

The need for predictive capabilities greater than 95% with very limited false alarms are demanding requirements for reliable disruption prediction systems in tokamaks such as JET or, in the near future, ITER. The prediction of an upcoming disruption must be provided sufficiently in advance in order to apply effective disruption avoidance or mitigation actions to prevent the machine from being damaged. In this paper, following the typical machine learning workflow, a generative topographic mapping (GTM) of the operational space of JET has been built using a set of disrupted and regularly terminated discharges. In order to build the predictive model, a suitable set of dimensionless, machine-independent, physics-based features have been synthesized, which make use of 1D plasma profile information, rather than simple zero-D time series. The use of such predicting features, together with the power of the GTM in fitting the model to the data, obtains, in an unsupervised way, a 2D map of the multi-dimensional parameter space of JET, where it is possible to identify a boundary separating the region free from disruption from the disruption region. In addition to helping in operational boundaries studies, the GTM map can also be used for disruption prediction exploiting the potential of the developed GTM toolbox to monitor the discharge dynamics. Following the trajectory of a discharge on the map throughout the different regions, an alarm is triggered depending on the disruption risk of these regions. The proposed approach to predict disruptions has been evaluated on a training and an independent test set and achieves very good performance with only one tardive detection and a limited number of false detections. The warning times are suitable for avoidance purposes and, more important, the detections are consistent with physical causes and mechanisms that destabilize the plasma leading to disruptions.

Keywords
disruption prevention and avoidance, machine learning, artificial intelligence, dimensionless physics-based indicators, unsupervised learning and clustering of high-dimensional spaces, disruption classification and causes, JET tokamak real-time opearation and control
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-399009 (URN)10.1088/1741-4326/ab2ea9 (DOI)000482571700001 ()
Note

For complete list of authors see http://dx.doi.org/10.1088/1741-4326/ab2ea9

Available from: 2019-12-13 Created: 2019-12-13 Last updated: 2019-12-13Bibliographically approved
Garcia, J., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Ericsson, G., . . . Zychor, I. (2019). A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E x B shearing. Plasma Physics and Controlled Fusion, 61(10), Article ID 104002.
Open this publication in new window or tab >>A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E x B shearing
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2019 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 10, article id 104002Article in journal (Refereed) Published
Abstract [en]

Developing successful tokamak operation scenarios, as well as confident extrapolation of present-day knowledge requires a rigorous understanding of plasma turbulence, which largely determines the quality of the confinement. In particular, accurate particle transport predictions are essential due to the strong dependence of fusion power or bootstrap current on the particle density details. Here, gyrokinetic turbulence simulations are performed with physics inputs taken from a JET power scan, for which a relatively weak degradation of energy confinement and a significant density peaking is obtained with increasing input power. This way physics parameters that lead to such increase in the density peaking shall be elucidated. While well-known candidates, such as the collisionality, previously found in other studies are also recovered in this study, it is furthermore found that edge E x B shearing may adopt a crucial role by enhancing the inward pinch. These results may indicate that a plasma with rotational shear could develop a stronger density peaking as compared to a non-rotating one, because its inward convection is increased compared to the outward diffusive particle flux as long as this rotation has a significant on E x B flow shear stabilization. The possibly significant implications for future devices, which will exhibit much less torque compared to present day experiments, are discussed.

Keywords
turbulence, transport, plasma
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-399008 (URN)10.1088/1361-6587/ab31a4 (DOI)000482602800002 ()
Note

For complete list of authors see http://dx.doi.org/10.1088/1361-6587/ab31a4

Available from: 2019-12-13 Created: 2019-12-13 Last updated: 2019-12-13Bibliographically approved
Zanca, P., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Dzysiuk, N., . . . Zychor, I. (2019). A power-balance model of the density limit in fusion plasmas: application to the L-mode tokamak. Nuclear Fusion, 59(12), Article ID 126011.
Open this publication in new window or tab >>A power-balance model of the density limit in fusion plasmas: application to the L-mode tokamak
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 12, article id 126011Article in journal (Refereed) Published
Abstract [en]

A power-balance model, with radiation losses from impurities and neutrals, gives a unified description of the density limit (DL) of the stellarator, the L-mode tokamak, and the reversed field pinch (RFP). The model predicts a Sudo-like scaling for the stellarator, a Greenwald- like scaling, alpha I-p(8/9), for the RFP and the ohmic tokamak, a mixed scaling, alpha (PIp4/9)-I-4/9, for the additionally heated L-mode tokamak. In a previous paper (Zanca et al 2017 Nucl. Fusion 57 056010) the model was compared with ohmic tokamak, RFP and stellarator experiments. Here, we address the issue of the DL dependence on heating power in the L-mode tokamak. Experimental data from high-density disrupted L-mode discharges performed at JET, as well as in other machines, arc taken as a term of comparison. The model fits the observed maximum densities better than the pure Greenwald limit.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Keywords
magnetohydrodynamics, transport, radiation
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-399086 (URN)10.1088/1741-4326/ab3b31 (DOI)000488059900001 ()
Funder
EU, Horizon 2020, 633053
Note

For complete list of authors see http://dx.doi.org/10.1088/1741-4326/ab3b31

Available from: 2019-12-16 Created: 2019-12-16 Last updated: 2019-12-16Bibliographically approved
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