uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Conroy, Sean
Alternative names
Publications (10 of 295) Show all publications
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
Show others...
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: 2019-03-08Bibliographically approved
Marcinkevicius, B., Andersson Sundén, E., Conroy, S., Ericsson, G. & Hjalmarsson, A. (2019). A Thin-foil Proton Recoil spectrometer for DT neutrons using annular silicon detectors. Journal of Instrumentation, 14, Article ID P03007.
Open this publication in new window or tab >>A Thin-foil Proton Recoil spectrometer for DT neutrons using annular silicon detectors
Show others...
2019 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id P03007Article in journal (Refereed) Published
Abstract [en]

The use of Thin-foil Proton Recoil (TPR) spectrometers to measure neutrons from Deuterium-Tritium (DT) fusion plasma has been studied previously and is a well established technique for neutron spectrometry. The study presented here focuses on the optimisation of the TPR spectrometer configurations consisting of Delta E and E silicon detectors. In addition an investigation of the spectrometer's ability to determine fuel ion temperature and fuel ion density ratio in ITER like DT plasmas has been performed. A Python code was developed for the purpose of calculating detection efficiency and energy resolution as a function of several spectrometer geometrical parameters. An optimisation of detection efficiency for selected values of resolution was performed regarding the geometrical spectrometer parameters using a multi-objective optimisation, a.k.a. Pareto plot analysis. Moreover, the influence of detector segmentation on spectrometer energy resolution and efficiency was investigated. The code also produced response functions for the two selected spectrometer configurations. The SPEC code was used to simulate the spectrometer's performance in determining the fuel ion temperature and fuel ion density ratio n(t)/n(d). The results presented include the selected spectrometer configuration with calculated energy resolution and efficiency. For a selected spectrometer resolution of 5% a maximum efficiency of around 0.003% was achieved. Moreover, the detector segmentation allows for a 20% increase in spectrometer efficiency for an energy resolution of 4.3%. The ITER requirements for a 20% accuracy on the n(t)/n(d) ratio determination and 10% on the temperature determination within a 100 ms sampling window can be achieved using a combination of several TPR's of same type, in order to boost efficiency.

Keywords
Neutron detectors (cold, thermal, fast neutrons), Spectrometers, Nuclear instruments and methods for hot plasma diagnostics
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-379926 (URN)10.1088/1748-0221/14/03/P03007 (DOI)000460721500004 ()
Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-28Bibliographically approved
Henderson, S. S., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Dzysiuk, N., . . . Zychor, I. (2019). An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor. Nuclear Materials and Energy, 18, 147-152
Open this publication in new window or tab >>An assessment of nitrogen concentrations from spectroscopic measurements in the JET and ASDEX upgrade divertor
Show others...
2019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 147-152Article in journal (Refereed) Published
Abstract [en]

The impurity concentration in the tokamak divertor plasma is a necessary input for predictive scaling of divertor detachment, however direct measurements from existing tokamaks in different divertor plasma conditions are limited. To address this, we have applied a recently developed spectroscopic N II line ratio technique for measuring the N concentration in the divertor to a range of H-mode and L-mode plasma from the ASDEX Upgrade and JET tokamaks, respectively. The results from both devices show that as the power crossing the separatrix, P-sep, is increased under otherwise similar core conditions (e.g. density), a higher N concentration is required to achieve the same detachment state. For example, the N concentrations at the start of detachment increase from approximate to 2% to approximate to 9% as P-sep, is increased from approximate to 2.5 MW to approximate to 7 MW. These results tentatively agree with scaling law predictions (e.g. Goldston et al.) motivating a further study examining the parameters which affect the N concentration required to reach detachment. Finally, the N concentrations from spectroscopy and the ratio of D and N gas valve fluxes agree within experimental uncertainty only when the vessel surfaces are fully-loaded with N.

Keywords
Impurity, Nitrogen, Divertor, Concentration, Spectroscopy, Tokamak
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-398542 (URN)10.1016/j.nme.2018.12.012 (DOI)000460107500026 ()
Note

For complete list of authors see http://dx.doi.org/10.1016/j.nme.2018.12.012

Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2019-12-09Bibliographically approved
Ström, P., Petersson, P., Rubel, M. J., Fortuna-Zaleśna, E., Widdowson, A. & Sergienko, G. (2019). Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall. Journal of Nuclear Materials, 516, 202-213
Open this publication in new window or tab >>Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall
Show others...
2019 (English)In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, p. 202-213Article in journal (Refereed) Published
Abstract [en]

Inconel-600 blocks and stainless steel covers for quartz microbalance crystals from remote corners in the JET-ILW divertor were studied with time-of-flight elastic recoil detection analysis and nuclear reaction analysis to obtain information about the areal densities and depth profiles of elements present in deposited material layers. Surface morphology and the composition of dust particles were examined with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The analysed components were present in JET during three ITER-like wall campaigns between 2010 and 2017. Deposited layers had a stratified structure, primarily made up of beryllium, carbon and oxygen with varying atomic fractions of deuterium, up to more than 20%. The range of carbon transport from the ribs of the divertor carrier was limited to a few centimeters, and carbon/deuterium co-deposition was indicated on the Inconel blocks. High atomic fractions of deuterium were also found in almost carbon-free layers on the quartz microbalance covers. Layer thicknesses up to more than 1 mu m were indicated, but typical values were on the order of a few hundred nm. Chromium, iron and nickel fractions were less than or around 1% at layer surfaces while increasing close to the layer-substrate interface. The tungsten fraction depended on the proximity of the plasma strike point to the divertor corners. Particles of tungsten, molybdenum and copper with sizes less than or around 1 mu m were found. Nitrogen, argon and neon were present after plasma edge cooling and disruption mitigation. Oxygen-18 was found on component surfaces after injection, indicating in-vessel oxidation. Compensation of elastic recoil detection data for detection efficiency and ion-induced release of deuterium during the measurement gave quantitative agreement with nuclear reaction analysis, which strengthens the validity of the results.

Keywords
Fusion, Tokamak, Plasma-wall interactions, ToF-ERDA, NRA, SEM
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-379019 (URN)10.1016/j.jnucmat.2018.11.027 (DOI)000458897100020 ()
Funder
Swedish Foundation for Strategic Research , RIF14-0053Swedish Research Council, 821-2012-5144Swedish Research Council, 2015-04884Swedish Research Council, 2017-00643
Note

Authors listed as Contributor / bidragsgivare above are part of EUROfusion Consortium, JET, Culham Science Centre, UK.

Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-04-24Bibliographically approved
Drenik, A., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Dzysiuk, N., . . . Zychor, I. (2019). Analysis of the outer divertor hot spot activity in the protection video camera recordings at JET. Fusion engineering and design, 139, 115-123
Open this publication in new window or tab >>Analysis of the outer divertor hot spot activity in the protection video camera recordings at JET
Show others...
2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 139, p. 115-123Article in journal (Refereed) Published
Abstract [en]

Hot spots on the divertor tiles at JET result in overestimation of the tile surface temperature which causes unnecessary termination of pulses. However, the appearance of hot spots can also indicate the condition of the divertor tile surfaces. To analyse the behaviour of the hot spots in the outer divertor tiles of JET, a simple image processing algorithm is developed. The algorithm isolates areas of bright pixels in the camera image and compares them to previously identified hot spots. The activity of the hot spots is then linked to values of other signals and parameters in the same time intervals. The operation of the detection algorithm was studied in a limited pulse range with high hot spot activity on the divertor tiles 5, 6 and 7. This allowed us to optimise the values of the controlling parameters. Then, the wider applicability of the method has been demonstrated by the analysis of the hot spot behaviour in a whole experimental campaign.

Keywords
JET, ITER-like wall, Plasma-wall interaction, Image analysis
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-378736 (URN)10.1016/j.fusengdes.2018.12.079 (DOI)000458939100016 ()
Note

For complete list of authors see http://dx.doi.org/10.1016/j.fusengdes.2018.12.079

Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved
Romazanov, J., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Dzysiuk, N., . . . Zychor, I. (2019). Beryllium global erosion and deposition at JET-ILW simulated with ERO2.0. Nuclear Materials and Energy, 18, 331-338
Open this publication in new window or tab >>Beryllium global erosion and deposition at JET-ILW simulated with ERO2.0
Show others...
2019 (English)In: Nuclear Materials and Energy, E-ISSN 2352-1791, Vol. 18, p. 331-338Article in journal (Refereed) Published
Abstract [en]

The recently developed Monte-Carlo code ERO2.0 is applied to the modelling of limited and diverted discharges at JET with the ITER-like wall (ILW). The global beryllium (Be) erosion and deposition is simulated and compared to experimental results from passive spectroscopy. For the limiter configuration, it is demonstrated that Be self-sputtering is an important contributor (at least 35%) to the Be erosion. Taking this contribution into account, the ERO2.0 modelling confirms previous evidence that high deuterium (D) surface concentrations of up to similar to 50% atomic fraction provide a reasonable estimate of Be erosion in plasma-wetted areas. For the divertor configuration, it is shown that drifts can have a high impact on the scrape-off layer plasma flows, which in turn affect global Be transport by entrainment and lead to increased migration into the inner divertor. The modelling of the effective erosion yield for different operational phases (ohmic, L- and H-mode) agrees with experimental values within a factor of two, and confirms that the effective erosion yield decreases with increasing heating power and confinement.

Keywords
Beryllium, Erosion, ER02.0, JET ITER-like wall
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-398544 (URN)10.1016/j.nme.2019.01.015 (DOI)000460107500056 ()
Note

For complete list of authors see http://dx.doi.org/10.1016/j.nme.2019.01.015

Available from: 2019-12-10 Created: 2019-12-10 Last updated: 2019-12-10Bibliographically approved
Lengar, I., Zohar, A., Batistoni, P., Popovichev, S. & Conroy, S. (2019). Characterization of JET neutron field in irradiation locations for DD, DT and TT plasmas. Fusion engineering and design, 146, 1967-1970
Open this publication in new window or tab >>Characterization of JET neutron field in irradiation locations for DD, DT and TT plasmas
Show others...
2019 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 146, p. 1967-1970Article in journal (Refereed) Published
Abstract [en]

The neutron fluxes and spectra were characterized for four locations close to the plasma and related to activation experiments, as the preparation for the upcoming experimental campaigns in JET. The focus was on the study of a variance reduction technique in order to obtain statistically significant results in the parts of the neutron energy spectra, important for irradiation experiments. The DD, DT and TT plasmas were studied with the Monte Carlo hybrid method and the use of the ADVANTG program for generation of weight windows as variance reduction method to accelerate Monte Carlo simulations. The calculations were optimized to obtain low statistical uncertainties for all energy bins in the 640 energy group structure and for all three plasma sources. This included the acceleration of calculations for reaction rates of capture reactions, i.e. in the thermal flux region in irradiation positions on the first wall. Speed-ups due to use of the hybrid method in excess of two orders of magnitude were found with respect to analog calculations despite the vicinity of the plasma source.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
JET, KN2 detector, Long-term irradiation station, Neutron transport calculations, ADVANTG
National Category
Fusion, Plasma and Space Physics Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-396639 (URN)10.1016/j.fusengdes.2019.03.078 (DOI)000488313700124 ()
Available from: 2019-11-07 Created: 2019-11-07 Last updated: 2019-11-07Bibliographically approved
Sahlberg, A., Eriksson, J., Conroy, S., Ericsson, G., Hellesen, C. & King, D. (2019). Component-wise deuterium-tritium fusion yield predictions with neutron emission spectrometry. Nuclear Fusion, 59(12), Article ID 126044.
Open this publication in new window or tab >>Component-wise deuterium-tritium fusion yield predictions with neutron emission spectrometry
Show others...
2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 12, article id 126044Article in journal (Refereed) Published
Abstract [en]

This paper uses neutron emission spectrometry (NES), with the spectrometer TOFOR, to estimate the deuterium-tritium (DT) equivalent fusion yields of deuterium-only (DD) pulses at the tokamak JET. A method for making DT predictions using parameters determined from the neutron energy spectrum is described and this method is compared to corresponding estimations done with the modeling codes JESTORR and TRANSP, as well as with results from the 1997 JET DT campaign. The method has been applied to a large number of JET DD pulses conducted after the installation of the ITER-like wall (ILW), and the results have been used to assess the prospects for the upcoming DT campaign (DTE2). DT predictions made by NES produces similar estimations as JESTORR and TRANSP, and the fusion power from studied DT pulses fall in line with the estimated power of similar DD discharges. Extrapolating the recent JET pulses to estimate what the fusion yields would be in DTE2, results indicate that reaching over 10 MW is achievable and that the highest performing ILW pulses to date could approach the desired fusion power of 15 MW.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
neutron spectroscopy, nuclear fusion, tokamak, JET, plasma diagnostics
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-397586 (URN)10.1088/1741-4326/ab45a6 (DOI)000494953500029 ()
Available from: 2019-11-25 Created: 2019-11-25 Last updated: 2019-11-25Bibliographically approved
Scholz, M., Hjalmarsson, A., Hajduk, L., Ericsson, G., Kotula, J., Woznicka, U., . . . Wojcik-Gargula, A. (2019). Conceptual design of the high resolution neutron spectrometer for ITER. Nuclear Fusion, 59(6), Article ID 065001.
Open this publication in new window or tab >>Conceptual design of the high resolution neutron spectrometer for ITER
Show others...
2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 6, article id 065001Article in journal (Refereed) Published
Abstract [en]

A high resolution neutron spectrometer (HRNS) system has been designed as a neutron diagnostic tool for ITER. The HRNS is dedicated to measurements of time resolved neutron energy spectra for both deuterium and deuterium-tritium (DT) plasmas. The main function of the HRNS is to determine the fuel ion ratio n(t)/n(d) in the plasma core with 20% uncertainty and a time resolution of 100ms for a range of ITER operating scenarios from 0.5 MW to 500 MW in fusion power. Moreover, neutron spectroscopy measurements should also be possible in the initial deuterium phase of ITER experiments. A supplementary function of the HRNS is to provide information on the fuel ion temperature. Furthermore, the HRNS can be used as an additional line-of-sight (LOS) for the radial neutron camera. To meet these requirements, a set of four spectrometers positioned after each other along a single LOS has been designed. The detector techniques employed include a thin foil proton recoil spectrometer (TPR), a neutron diamond detector (NDD), a back-scattering time-of-flight system (bToF) and a forward timeof-flight system (fToF). The TPR system, positioned closest to the plasma, provides data at high fusion powers. For plasma conditions producing intermediate fusion power two neutron spectrometers are installed: NDD and bToF. The NDD is installed as the second instrument along the HRNS LOS after the TPR. The fToF spectrometer is dedicated for low tritium densities and pure deuterium operation. The paper summarizes the current state of the art of neutron spectroscopy useful in plasma diagnostics and the possibility of installing a dedicated HRNS for ITER in the designated diagnostic port. We conclude that the proposed HRNS system can fulfil the ITER measurement requirements over a broad range of plasma operational scenarios, including full power DT, start-up, ramp-down and pure D operations.

Keywords
thermonuclear fusion, ITER, neutron diagnostics, high resolution neutron spectrometry, fuel ion ratio
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-384063 (URN)10.1088/1741-4326/abOdc1 (DOI)000466720800001 ()
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2019-06-20Bibliographically approved
Carvalho, D. D., Andersson Sundén, E., Binda, F., Cecconello, M., Conroy, S., Ericsson, G., . . . Zychor, I. (2019). Deep neural networks for plasma tomography with applications to JET and COMPASS. Paper presented at 3rd European Conference on Plasma Diagnostics (ECPD), MAY 06-10, 2019, Lisbon, PORTUGAL. Journal of Instrumentation, 14, Article ID C09011.
Open this publication in new window or tab >>Deep neural networks for plasma tomography with applications to JET and COMPASS
Show others...
2019 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id C09011Article in journal (Refereed) Published
Abstract [en]

Convolutional neural networks (CNNs) have found applications in many image processing tasks, such as feature extraction, image classification, and object recognition. It has also been shown that the inverse of CNNs, so-called deconvolutional neural networks, can be used for inverse problems such as plasma tomography. In essence, plasma tomography consists in reconstructing the 2D plasma profile on a poloidal cross-section of a fusion device, based on line-integrated measurements from multiple radiation detectors. Since the reconstruction process is computationally intensive, a deconvolutional neural network trained to produce the same results will yield a significant computational speedup, at the expense of a small error which can be assessed using different metrics. In this work, we discuss the design principles behind such networks, including the use of multiple layers, how they can be stacked, and how their dimensions can be tuned according to the number of detectors and the desired tomographic resolution for a given fusion device. We describe the application of such networks at JET and COMPASS, where at JET we use the bolometer system, and at COMPASS we use the soft X-ray diagnostic based on photodiode arrays.

Keywords
Computerized Tomography (CT) and Computed Radiography (CR), Plasma diagnostics - interferometry, spectroscopy and imaging
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-399021 (URN)10.1088/1748-0221/14/09/C09011 (DOI)000486989800011 ()
Conference
3rd European Conference on Plasma Diagnostics (ECPD), MAY 06-10, 2019, Lisbon, PORTUGAL
Funder
EU, Horizon 2020, 633053
Note

For complete list of authors see http://dx.doi.org/10.1088/1748-0221/14/09/C09011

Available from: 2019-12-11 Created: 2019-12-11 Last updated: 2019-12-11Bibliographically approved
Organisations

Search in DiVA

Show all publications