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Lvovskiy A, Paz-Soldan C, Eidietis N, Dal Molin A, Nocente M, Cooper C, Rigamonti D, Tardocchi M, Taussig D. Upgrades to the gamma ray imager on DIII-D enabling access to high flux hard x-ray measurements during the runaway electron plateau phase (invited). Rev Sci Instrum 2022; 93:113524. [PMID: 36461541 DOI: 10.1063/5.0101690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Accepted: 09/07/2022] [Indexed: 06/17/2023]
Abstract
The Gamma Ray Imager (GRI) is a pinhole camera providing 2D imaging of MeV hard x-ray (HXR) bremsstrahlung emission from runaway electrons (REs) over the poloidal cross section of the DIII-D tokamak. We report a series of upgrades to the GRI expanding the access to RE scenarios from the diagnosis of a trace amount of REs to high flux HXR measurements during the RE plateau phase. We present the implementation of novel gamma ray detectors based on LYSO and YAP crystals coupled to multi-pixel photon counters, enabling a count rate in excess of 1 MHz. Finally, we highlight new insights into the RE physics discovered during the current quench and RE plateau phase experiments as the result of these upgrades.
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Affiliation(s)
- A Lvovskiy
- General Atomics, P.O. Box 85608, San Diego, California 92186, USA
| | - C Paz-Soldan
- General Atomics, P.O. Box 85608, San Diego, California 92186, USA
| | - N Eidietis
- General Atomics, P.O. Box 85608, San Diego, California 92186, USA
| | - A Dal Molin
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - M Nocente
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - C Cooper
- Oak Ridge Associated Universities, Oak Ridge, Tennessee 37830, USA
| | - D Rigamonti
- Istituto per la Scienza e Tecnologia dei Plasmi, CNR, 20126 Milan, Italy
| | - M Tardocchi
- Istituto per la Scienza e Tecnologia dei Plasmi, CNR, 20126 Milan, Italy
| | - D Taussig
- General Atomics, P.O. Box 85608, San Diego, California 92186, USA
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2
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Dal Molin A, Fumagalli L, Nocente M, Rigamonti D, Tardocchi M, Giacomelli L, Panontin E, Lvovskiy A, Paz-Soldan C, Edietis NW, Gorini G. Novel compact hard x-ray spectrometer with MCps counting rate capabilities for runaway electron measurements on DIII-D. Rev Sci Instrum 2021; 92:043517. [PMID: 34243482 DOI: 10.1063/5.0043762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 03/18/2021] [Indexed: 06/13/2023]
Abstract
A novel compact spectrometer optimized for the measurement of hard x rays generated by runaway electrons is presented. The detector is designed to be installed in the fan-shaped collimator of the gamma-ray imager diagnostic at the DIII-D tokamak. The spectrometer is based on a 1 × 1 cm2 cerium doped yttrium aluminum perovskite scintillator crystal coupled with a silicon photomultiplier. The detector dynamic energy range is in excess of 10 MeV, with an energy resolution of ∼10% at 661.7 keV. The fast detector signal (≈70 ns full width at half maximum) allows for operation at counting rates in excess of 1 MCps. The gain stability of the system can be monitored in real time using a light-emitting diode embedded in the instrument. The detector is expected to be deployed in the forthcoming DIII-D runaway electron experimental campaign.
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Affiliation(s)
- A Dal Molin
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - L Fumagalli
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - M Nocente
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - D Rigamonti
- Istituto per la Scienza e Tecnologia dei Plasmi, CNR, 20126 Milan, Italy
| | - M Tardocchi
- Istituto per la Scienza e Tecnologia dei Plasmi, CNR, 20126 Milan, Italy
| | - L Giacomelli
- Istituto per la Scienza e Tecnologia dei Plasmi, CNR, 20126 Milan, Italy
| | - E Panontin
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
| | - A Lvovskiy
- General Atomics, San Diego, California 92127, USA
| | - C Paz-Soldan
- General Atomics, San Diego, California 92127, USA
| | - N W Edietis
- General Atomics, San Diego, California 92127, USA
| | - G Gorini
- Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, 20126 Milan, Italy
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Dal Molin A, Martinelli L, Nocente M, Rigamonti D, Abba A, Giacomelli L, Gorini G, Lvovskiy A, Muraro A, Tardocchi M. Development of a new compact gamma-ray spectrometer optimised for runaway electron measurements. Rev Sci Instrum 2018; 89:10I134. [PMID: 30399979 DOI: 10.1063/1.5038803] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Accepted: 06/25/2018] [Indexed: 06/08/2023]
Abstract
A new compact gamma-ray spectrometer was developed in order to optimise the measurement of bremsstrahlung radiation emitted from runaway electrons in the MeV range. The detector is based on a cerium doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator coupled to a silicon photomultiplier and is insensitive to magnetic fields. A dedicated electronic board was developed to optimise the signal readout as well as for online control of the device. The detector combines a dynamic range up to 10 MeV with moderate energy non-linearity, counting rate capabilities in excess of 1 MHz, and an energy resolution that extrapolates to a few % in the MeV range, thus meeting the requirements for its application to runaway electron studies by bremsstrahlung measurements in the gamma-ray energy range.
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Affiliation(s)
- A Dal Molin
- Dipartimento di Fisica "G. Occhialini," Università degli Studi di Milano-Bicocca, Milano, Italy
| | - L Martinelli
- Dipartimento di Fisica "G. Occhialini," Università degli Studi di Milano-Bicocca, Milano, Italy
| | - M Nocente
- Dipartimento di Fisica "G. Occhialini," Università degli Studi di Milano-Bicocca, Milano, Italy
| | - D Rigamonti
- Istituto di Fisica del Plasma "P. Caldirola," CNR, Milano, Italy
| | - A Abba
- Nuclear Instruments, Lambrugo, Italy
| | - L Giacomelli
- Istituto di Fisica del Plasma "P. Caldirola," CNR, Milano, Italy
| | - G Gorini
- Dipartimento di Fisica "G. Occhialini," Università degli Studi di Milano-Bicocca, Milano, Italy
| | - A Lvovskiy
- Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA
| | - A Muraro
- Istituto di Fisica del Plasma "P. Caldirola," CNR, Milano, Italy
| | - M Tardocchi
- Istituto di Fisica del Plasma "P. Caldirola," CNR, Milano, Italy
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Spong DA, Heidbrink WW, Paz-Soldan C, Du XD, Thome KE, Van Zeeland MA, Collins C, Lvovskiy A, Moyer RA, Austin ME, Brennan DP, Liu C, Jaeger EF, Lau C. First Direct Observation of Runaway-Electron-Driven Whistler Waves in Tokamaks. Phys Rev Lett 2018; 120:155002. [PMID: 29756886 DOI: 10.1103/physrevlett.120.155002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Indexed: 06/08/2023]
Abstract
DIII-D experiments at low density (n_{e}∼10^{19} m^{-3}) have directly measured whistler waves in the 100-200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with runaway intensity (hard x-ray emission level), occurs in novel discrete frequency bands, and exhibits nonlinear limit-cycle-like behavior. The measured frequencies scale with the magnetic field strength and electron density as expected from the whistler dispersion relation. The modes are stabilized with increasing magnetic field, which is consistent with wave-particle resonance mechanisms. The mode amplitudes show intermittent time variations correlated with changes in the electron cyclotron emission that follow predator-prey cycles. These can be interpreted as wave-induced pitch angle scattering of moderate energy runaways. The tokamak runaway-whistler mechanisms have parallels to whistler phenomena in ionospheric plasmas. The observations also open new directions for the modeling and active control of runaway electrons in tokamaks.
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Affiliation(s)
- D A Spong
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - W W Heidbrink
- University of California-Irvine, Irvine, California 92697, USA
| | - C Paz-Soldan
- General Atomics, San Diego, California 92186-5608, USA
| | - X D Du
- University of California-Irvine, Irvine, California 92697, USA
| | - K E Thome
- Oak Ridge Associated Universities, P.O. Box 117, Oak Ridge, Tennessee 37831, USA
| | | | - C Collins
- General Atomics, San Diego, California 92186-5608, USA
| | - A Lvovskiy
- Oak Ridge Associated Universities, P.O. Box 117, Oak Ridge, Tennessee 37831, USA
| | - R A Moyer
- University of California-San Diego, La Jolla, California 92093, USA
| | - M E Austin
- University of Texas, Austin, Texas 78705, USA
| | - D P Brennan
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - C Liu
- Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA
| | - E F Jaeger
- XCEL Engineering, Oak Ridge, Tennessee 37830, USA
| | - C Lau
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Paz-Soldan C, Cooper CM, Aleynikov P, Pace DC, Eidietis NW, Brennan DP, Granetz RS, Hollmann EM, Liu C, Lvovskiy A, Moyer RA, Shiraki D. Spatiotemporal Evolution of Runaway Electron Momentum Distributions in Tokamaks. Phys Rev Lett 2017; 118:255002. [PMID: 28696735 DOI: 10.1103/physrevlett.118.255002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Indexed: 06/07/2023]
Abstract
Novel spatial, temporal, and energetically resolved measurements of bremsstrahlung hard-x-ray (HXR) emission from runaway electron (RE) populations in tokamaks reveal nonmonotonic RE distribution functions whose properties depend on the interplay of electric field acceleration with collisional and synchrotron damping. Measurements are consistent with theoretical predictions of momentum-space attractors that accumulate runaway electrons. RE distribution functions are measured to shift to a higher energy when the synchrotron force is reduced by decreasing the toroidal magnetic field strength. Increasing the collisional damping by increasing the electron density (at a fixed magnetic and electric field) reduces the energy of the nonmonotonic feature and reduces the HXR growth rate at all energies. Higher-energy HXR growth rates extrapolate to zero at the expected threshold electric field for RE sustainment, while low-energy REs are anomalously lost. The compilation of HXR emission from different sight lines into the plasma yields energy and pitch-angle-resolved RE distributions and demonstrates increasing pitch-angle and radial gradients with energy.
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Affiliation(s)
- C Paz-Soldan
- General Atomics, San Diego, California 92186, USA
| | - C M Cooper
- Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA
| | - P Aleynikov
- Max-Planck Institute for Plasma Physics, Greifswald, Germany
| | - D C Pace
- General Atomics, San Diego, California 92186, USA
| | - N W Eidietis
- General Atomics, San Diego, California 92186, USA
| | - D P Brennan
- Princeton University, Princeton, New Jersey 05764, USA
| | - R S Granetz
- Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - E M Hollmann
- University of California-San Diego, La Jolla, California 92093, USA
| | - C Liu
- Princeton University, Princeton, New Jersey 05764, USA
| | - A Lvovskiy
- Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA
| | - R A Moyer
- University of California-San Diego, La Jolla, California 92093, USA
| | - D Shiraki
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Zeng L, Koslowski HR, Liang Y, Lvovskiy A, Lehnen M, Nicolai D, Pearson J, Rack M, Jaegers H, Finken KH, Wongrach K, Xu Y. Experimental observation of a magnetic-turbulence threshold for runaway-electron generation in the TEXTOR tokamak. Phys Rev Lett 2013; 110:235003. [PMID: 25167504 DOI: 10.1103/physrevlett.110.235003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Indexed: 06/03/2023]
Abstract
Magnetic turbulence is observed at the beginning of the current quench in intended TEXTOR disruptions. Runaway electron (RE) suppression has been experimentally found at magnetic turbulence larger than a certain threshold. Below this threshold, the generated RE current is inversely proportional to the level of magnetic turbulence. The magnetic turbulence originates from the background plasma and the amplitude depends strongly on the toroidal magnetic field and plasma electron density. These results explain the previously found toroidal field threshold for RE generation and have to be considered in predictions for RE generation in ITER.
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Affiliation(s)
- L Zeng
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany and Institute of Plasma Physics, Chinese Academy of Sciences, 230031 Hefei, China
| | - H R Koslowski
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - Y Liang
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - A Lvovskiy
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - M Lehnen
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany and ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance, France
| | - D Nicolai
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - J Pearson
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - M Rack
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - H Jaegers
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research-Plasma Physics (IEK-4), Association EURATOM-FZJ, Trilateral Euregio Cluster, 52425 Jülich, Germany
| | - K H Finken
- Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - K Wongrach
- Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Y Xu
- Laboratoire de Physique des Plasmas-Laboratorium voor Plasmafysica, Association 'Euratom-Belgian state', Ecole Royale Militaire-Koninklijke Militaire School, Trilateral Euregio Cluster, 1000 Brussels, Belgium
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