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Conroy, Sean
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Publications (10 of 166) Show all publications
Hellesen, C., Mantsinen, M., Conroy, S., Ericsson, G., Eriksson, J., Kiptily, V. & Nabais, F. (2018). Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy. Nuclear Fusion, 58(5), Article ID 056021.
Open this publication in new window or tab >>Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy
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2018 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 5, article id 056021Article in journal (Refereed) Published
Abstract [en]

ICRF heating at the fundamental cyclotron frequency of a hydrogen minority ion species also gives rise to a partial power absorption by deuterium ions at their second harmonic resonance. This paper studies the deuterium distributions resulting from such 2nd harmonic heating at JET using neutron emission spectroscopy data from the time of flight spectrometer TOFOR. The fast deuterium distributions are obtained over the energy range 100 keV to 2 MeV. Specifically, we study how the fast deuterium distributions vary as ICRF heating is used alone as well as in combination with NBI heating. When comparing the different heating scenarios, we observed both a difference in the shapes of the distributions as well as in their absolute level. The differences are most pronounced below 0.5 MeV. Comparisons are made with corresponding distributions calculated with the code PION. We find a good agreement between the measured distributions and those calculated with PION, both in terms of their shapes as well as their amplitudes. However, we also identified a period with signs of an inverted fast ion distribution, which showed large disagreements between the modeled and measured results. Resonant interactions with tornado modes, i.e. core localized toroidal alfven eigenmodes (TAEs), are put forward as a possible explanation for the inverted distribution.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-319414 (URN)10.1088/1741-4326/aab4ab (DOI)000428454700003 ()
Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2018-06-20Bibliographically approved
Binda, F., Ericsson, G., Conroy, S. & Andersson Sundén, E. (2017). Calculation of the profile-dependent neutron backscatter matrix for the JET neutron camera system. Paper presented at 29th Symposium on Fusion Technology (SOFT), SEP 05-09, 2016, Prague, CZECH REPUBLIC. Fusion engineering and design, 123, 865-868
Open this publication in new window or tab >>Calculation of the profile-dependent neutron backscatter matrix for the JET neutron camera system
2017 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 865-868Article in journal (Refereed) Published
Abstract [en]

We investigated the dependence of the backscatter component of the neutron spectrum on the emissivity profile. We did so for the JET neutron camera system, by calculating a profile-dependent backscatter matrix for each of the 19 camera channels using a MCNP model of the JET tokamak. We found that, when using a low minimum energy for the summation of the counts in the neutron pulse height spectrum, the backscatter contribution can depend significantly on the emissivity profile. The maximum variation in the backscatter level was 24% (8.0% when compared to the total emission). This effect needs to be considered when a correction for the backscatter contribution is applied to the measured profile.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
Neutron, Profile monitor, Backscatter, mcnp
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-341822 (URN)10.1016/j.fusengdes.2017.03.124 (DOI)000418992000181 ()
Conference
29th Symposium on Fusion Technology (SOFT), SEP 05-09, 2016, Prague, CZECH REPUBLIC
Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-03-13Bibliographically approved
Cufar, A., Batistoni, P., Conroy, S., Ghani, Z., Lengar, I., Milocco, A., . . . Snoj, L. (2017). Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 847, 199-204
Open this publication in new window or tab >>Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator
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2017 (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. 847, p. 199-204Article in journal (Refereed) Published
Abstract [en]

At the Joint European Torus (JET) the ex-vessel fission chambers and in-vessel activation detectors are used as the neutron production rate and neutron yield monitors respectively. In order to ensure that these detectors produce accurate measurements they need to be experimentally calibrated. A new calibration of neutron detectors to 14 MeV neutrons, resulting from deuterium tritium (DT) plasmas, is planned at JET using a compact accelerator based neutron generator (NG) in which a D/T beam impinges on a solid target containing T/D, producing neutrons by DT fusion reactions. This paper presents the analysis that was performed to model the neutron source characteristics in terms of energy spectrum, angle energy distribution and the effect of the neutron generator geometry. Different codes capable of simulating the accelerator based DT neutron sources are compared and sensitivities to uncertainties in the generator's internal structure analysed. The analysis was performed to support preparation to the experimental measurements performed to characterize the NG as a calibration source. Further extensive neutronics analyses, performed with this model of the NG, will be needed to support the neutron calibration experiments and take into account various differences between the calibration experiment and experiments using the plasma as a source of neutrons.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2017
Keywords
Compact DT neutron generator, MCNP, Modelling
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-320412 (URN)10.1016/j.nima.2016.12.009 (DOI)000394396800027 ()
Available from: 2017-04-19 Created: 2017-04-19 Last updated: 2017-04-19Bibliographically approved
Batistoni, P., Popovichev, S., Conroy, S., Lengar, I., Cufar, A., Abhangi, M., . . . Horton, L. (2017). Calibration of neutron detectors on the Joint European Torus. Review of Scientific Instruments, 88(10), Article ID 103505.
Open this publication in new window or tab >>Calibration of neutron detectors on the Joint European Torus
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2017 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, no 10, article id 103505Article in journal (Refereed) Published
Abstract [en]

The present paper describes the findings of the calibration of the neutron yield monitors on the Joint European Torus (JET) performed in 2013 using a Cf-252 source deployed inside the torus by the remote handling system, with particular regard to the calibration of fission chambers which provide the time resolved neutron yield from JET plasmas. The experimental data obtained in toroidal, radial, and vertical scans are presented. These data are first analysed following an analytical approach adopted in the previous neutron calibrations at JET. In this way, a calibration function for the volumetric plasma source is derived which allows us to understand the importance of the different plasma regions and of different spatial profiles of neutron emissivity on fission chamber response. Neutronics analyses have also been performed to calculate the correction factors needed to derive the plasma calibration factors taking into account the different energy spectrum and angular emission distribution of the calibrating (point) Cf-252 source, the discrete positions compared to the plasma volumetric source, and the calibration circumstances. All correction factors are presented and discussed. We discuss also the lessons learnt which are the basis for the on-going 14 MeV neutron calibration at JET and for ITER.

National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-340954 (URN)10.1063/1.4991780 (DOI)000414174000015 ()29092477 (PubMedID)
Available from: 2018-02-14 Created: 2018-02-14 Last updated: 2018-02-14Bibliographically approved
Hellesen, C., Andersson Sundén, E., Conroy, S., Dzysiuk, N., Ericsson, G., Hjalmarsson, A., . . . Marcinkevicius, B. (2017). Conceptual design of a BackTOF neutron spectrometer for fuel ion ratio measurements at ITER. Nuclear Fusion, 57(6), Article ID 066021.
Open this publication in new window or tab >>Conceptual design of a BackTOF neutron spectrometer for fuel ion ratio measurements at ITER
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 6, article id 066021Article in journal (Refereed) Published
Abstract [en]

In this paper we present a conceptual design of a back scattering neutron time of flight spectrometer (BackTOF) for use at ITER. The proposed BackTOF design aims at fulfilling the requirements set on a neutron spectrometer system to be used for inferring the core fuel ion ratio in a DT plasma. Specifically we have investigated the requirements on the size, energy resolution, count rate capability, efficiency and signal to background ratio. These requirements are a compact size that fits in roughly 1 m3, an energy resolution of 4% or better, a count rate capability of at least 100 kHz, an efficiency of at least 10−5 and a signal to background ratio of 1000 or better.

Using a Monte Carlo model of the BackTOF spectrometer we find that the proposed BackTOF design is compact enough to be installed at ITER while being capable of achieving a resolution of about 4% FWHM with a count rate capability of 300 kHz and an efficiency at 1.25 10−3. This is sufficient for achieving the requirements on the fuel ion ratio at ITER. We also demonstrate how data acquisition systems capable of providing both timing and energy information can be used to effectively discriminate random background at high count rates.

Keywords
neutron spectroscopy, time of flight, burning plasma, fuel ion ratio
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-348803 (URN)10.1088/1741-4326/aa6937 (DOI)000425870000001 ()
Available from: 2018-05-04 Created: 2018-05-04 Last updated: 2018-05-04Bibliographically approved
Binda, F., Eriksson, J., Ericsson, G., Hellesen, C., Conroy, S., Nocente, M. & Andersson Sundén, E. (2017). Generation of the neutron response function of an NE213 scintillator for fusion applications. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 866, 222-229
Open this publication in new window or tab >>Generation of the neutron response function of an NE213 scintillator for fusion applications
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2017 (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. 866, p. 222-229Article in journal (Refereed) Published
Abstract [en]

In this work we present a method to evaluate the neutron response function of an NE213 liquid scintillator. This method is particularly useful when the proton light yield function of the detector has not been measured, since it is based on a proton light yield function taken from literature, MCNPX simulations, measurements of gammarays from a calibration source and measurements of neutrons from fusion experiments with ohmic plasmas. The inclusion of the latter improves the description of the proton light yield function in the energy range of interest (around 2.46 MeV). We apply this method to an NE213 detector installed at JET, inside the radiation shielding of the magnetic proton recoil (MPRu) spectrometer, and present the results from the calibration along with some examples of application of the response function to perform neutron emission spectroscopy (NES) of fusion plasmas. We also investigate how the choice of the proton light yield function affects the NES analysis, finding that the result does not change significantly. This points to the fact that the method for the evaluation of the neutron response function is robust and gives reliable results.

Keywords
NE213 scintillator, Neutron spectroscopy, Response function, Proton light yield
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-330537 (URN)10.1016/j.nima.2017.04.023 (DOI)000407863700029 ()
Available from: 2017-10-04 Created: 2017-10-04 Last updated: 2018-04-23Bibliographically approved
Cecconello, M., Conroy, S., Marocco, D., Moro, F. & Esposito, B. (2017). Neural network implementation for ITER neutron emissivity profile recognition. Paper presented at 29th Symposium on Fusion Technology (SOFT), SEP 05-09, 2016, Prague, CZECH REPUBLIC. Fusion engineering and design, 123, 637-640
Open this publication in new window or tab >>Neural network implementation for ITER neutron emissivity profile recognition
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2017 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 637-640Article in journal (Refereed) Published
Abstract [en]

The ITER Radial Neutron Camera (RNC) is a neutron diagnostic intended for the measurement of the neutron emissivity radial profile and the estimate of the total fusion power. This paper presents a proof of-principle method based on neural networks to estimate the neutron emissivity profile in different ITER scenarios and for different RNC architectures. The design, optimization and training of the implemented neural network is presented together with a decision algorithm to select, among the multiple trained neural networks, which one provides the inverted neutron emissivity profile closest to the input one. Examples are given for a selection of ITER scenarios and RNC architectures. The results from this study indicate that neural networks for the neutron emissivity recognition in ITER can achieve an accuracy and precision within the spatial and temporal requirements set by ITER for such a diagnostic.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
ITER, RNC, Neural network, Real time, Fusion power
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-341820 (URN)10.1016/j.fusengdes.2017.02.058 (DOI)000418992000132 ()
Conference
29th Symposium on Fusion Technology (SOFT), SEP 05-09, 2016, Prague, CZECH REPUBLIC
Funder
Swedish Research Council, VR 826-2012-5116
Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-02-15Bibliographically approved
Moro, F., Marocco, D., Esposito, B., Flammini, D., Podda, S., Villari, R. & Conroy, S. (2017). Nuclear analysis of the ITER radial neutron camera architectural options. Paper presented at 29th Symposium on Fusion Technology (SOFT), SEP 05-09, 2016, Prague, CZECH REPUBLIC. Fusion engineering and design, 123, 1033-1038
Open this publication in new window or tab >>Nuclear analysis of the ITER radial neutron camera architectural options
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2017 (English)In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 1033-1038Article in journal (Refereed) Published
Abstract [en]

The ITER Radial Neutron Camera (RNC) is a multichannel detection system hosted in the Equatorial Port Plug 1 (EPP 1) designed to provide information on the neutron source total strength arid emissivity profiles. It consists of two sub-systems: the ex-port line-of-sights (LOSs), covering the plasma core, embedded in a massive shielding block located in the Port Interspace, and the in-port LOSs distributed in two removable cassettes integrated inside the Port Plug. Presently, the RNC layout development process is undergoing a System Level Design phase: several preliminary architectural options based on a System Engineering work have been defined: a detailed nuclear analysis of these options has been performed through radiation transport calculations with the MCNP Monte Carlo code. The radiation environment at the detectors positions has been fully characterized through the evaluation of the expected neutron spectra and the secondary gamma background and the analysis of the 3D radiation maps. MoreOver, the impact of a reduced ex-port shielding block on the neutron and gamma spectra has been investigated. The results of the present study provide guidelines for the development of the RNC final design and the necessary data for the measurement performance analysis.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
ITER, Radial neutron camera, Neutronics, Equatorial port plug, Design, Analysis
National Category
Accelerator Physics and Instrumentation
Identifiers
urn:nbn:se:uu:diva-341824 (URN)10.1016/j.fusengdes.2017.01.031 (DOI)000418992000217 ()
Conference
29th Symposium on Fusion Technology (SOFT), SEP 05-09, 2016, Prague, CZECH REPUBLIC
Available from: 2018-02-16 Created: 2018-02-16 Last updated: 2018-02-16Bibliographically approved
Kirk, A., Adamek, J., Akers, R. J., Allan, S., Appel, L., Lucini, F. A., . . . Zoletnik, S. (2017). Overview of recent physics results from MAST. Nuclear Fusion, 57(10), Article ID 102007.
Open this publication in new window or tab >>Overview of recent physics results from MAST
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 10, article id 102007Article in journal (Refereed) Published
Abstract [en]

New results from MAST are presented that focus on validating models in order to extrapolate to future devices. Measurements during start-up experiments have shown how the bulk ion temperature rise scales with the square of the reconnecting field. During the current ramp-up, models are not able to correctly predict the current diffusion. Experiments have been performed looking at edge and core turbulence. At the edge, detailed studies have revealed how filament characteristics are responsible for determining the near and far scrape off layer density profiles. In the core the intrinsic rotation and electron scale turbulence have been measured. The role that the fast ion gradient has on redistributing fast ions through fishbone modes has led to a redesign of the neutral beam injector on MAST Upgrade. In H-mode the turbulence at the pedestal top has been shown to be consistent with being due to electron temperature gradient modes. A reconnection process appears to occur during edge localized modes (ELMs) and the number of filaments released determines the power profile at the divertor. Resonant magnetic perturbations can mitigate ELMs provided the edge peeling response is maximised and the core kink response minimised. The mitigation of intrinsic error fields with toroidal mode number n > 1 has been shown to be important for plasma performance.

Keywords
MAST upgrade, DBS system, edge and core turbulence
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-348940 (URN)10.1088/1741-4326/aa65e0 (DOI)000425866000001 ()
Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-04-26Bibliographically approved
Litaudon, X., Abduallev, S., Abhangi, M., Abreu, P., Afzal, M., Aggarwal, K. M., . . . Zychor, I. (2017). Overview of the JET results in support to ITER. Nuclear Fusion, 57(10), Article ID 102001.
Open this publication in new window or tab >>Overview of the JET results in support to ITER
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 10, article id 102001Article in journal (Refereed) Published
Abstract [en]

The 2014-2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L-H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at beta(N) similar to 1.8 and n/n(GW) similar to 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D-T campaign and 14 MeV neutron calibration strategy are reviewed.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
JET, plasma, fusion, ITER
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-340063 (URN)10.1088/1741-4326/aa5e28 (DOI)000416419100001 ()
Available from: 2018-01-25 Created: 2018-01-25 Last updated: 2018-04-23Bibliographically approved
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