Time resolved radiated power during tokamak disruptions and spectral averaging of AXUV photodiode response in DIII-D

Gray, D.S.; Luckhardt, S.C.; Chousal, L.; Gunner, G.; Kellman, A.G.; Whyte, D.G.

doi:10.1063/1.1642745

Cited by 44 publications

(30 citation statements)

References 14 publications

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“…3 ͑lower inset͒, was located at the edge of the plasma in the midplane to provide fast ͑1 s͒ twodimensional ͑2-D͒ imaging of the density. The DISRAD2 14 measures absolutely calibrated photon intensity along 30 poloidally separated view chords, as shown in Fig. 4, at a toroidal angle of 225°at a rate of 100 kHz and a photon energy response of 1 eV to 5 keV.…”

Section: Methodsmentioning

confidence: 99%

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Edge-localized mode dynamics and transport in the scrape-off layer of the DIII-D tokamak

Boedo¹,

Rudakov²,

Hollmann³

et al. 2005

Physics of Plasmas

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High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge-localized modes ͑ELMs͒ are produced in the low field side, are poloidally localized and are composed of fast bursts ͑ϳ20 to 40 s long͒ of hot, dense plasma on a background of less dense, colder plasma ͑ϳ5 ϫ 10 18 m −3 , 50 eV͒ possibly created by the bursts themselves. The ELMs travel radially in the scrape-off layer ͑SOL͒, starting at the separatrix at ϳ450 m / s, and slow down to ϳ150 m / s near the wall, convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but quickly decay with radius in the SOL. The temperature decay length ͑ϳ1.2 to 1.5 cm͒ is much shorter than the density decay length ͑ϳ3 to 8 cm͒, and the latter decreases with increasing pedestal ͑and SOL͒ density. The local particle and energy flux ͑assuming T i = T e ͒ at the midplane wall during the bursts are 10% to 50% ͑ϳ1 to 2ϫ 10 21 m −2 s −1 ͒ and 1% to 2% ͑ϳ20 to 30 kW/ m 2 ͒, respectively, of the LCFS fluxes, indicating that particles are transported radially much more efficiently than heat. Evidence is presented suggesting toroidal rotation of the ELM plasma in the SOL. The ELM plasma density and temperature increase linearly with discharge/pedestal density up to a Greenwald fraction of ϳ0.6, and then decrease resulting in more benign ͑grassier͒ ELMs.

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Section: Methodsmentioning

confidence: 99%

“…The principal measurements were made by the fast radiometer array 14 ͑DISRAD2͒, a fast scanning probe, 15 beam emission spectroscopy 16 ͑BES͒, reflectometry 17 and the divertor current monitor tile array. 18 The fast scanning probe array features five tips ͑Fig.…”

Section: Methodsmentioning

confidence: 99%

Edge-localized mode dynamics and transport in the scrape-off layer of the DIII-D tokamak

Boedo¹,

Rudakov²,

Hollmann³

et al. 2005

Physics of Plasmas

Self Cite

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“…Therefore, the nonlinear wavelength dependence has to be taken into account, as it is presented for specific applications in references 5,6 . The references point out the strong impact of radiation in the VUV region, as anticipated from the initial diode responsivity.…”

Section: Comparison To Foil Measurementsmentioning

confidence: 99%

Application of AXUV diode detectors at ASDEX Upgrade

Bernert

Eich

Burckhart

et al. 2014

Review of Scientific Instruments

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In the ASDEX Upgrade tokamak a radiation measurement for a wide spectral range, based on semiconductor detectors, with 256 lines of sight (LOS) and a time resolution of 5 µs was recently installed. In combination with the foil based bolometry, it is now possible to estimate the absolutely calibrated radiated power of the plasma on fast timescales. This work introduces this diagnostic based on AXUV (Absolute eXtended UltraViolet) n-on-p diodes made by International Radiation Detectors, Inc. (IRD). The measurement and the degradation of the diodes in a tokamak environment is shown. Even though the AXUV diodes are developed to have a constant sensitivity for all photon energies (1 eV to 8 keV), degradation leads to a photon energy dependence of the sensitivity. The foil bolometry, which is restricted to a time resolution of less than 1 kHz, offers a basis for a time dependent calibration of the diodes. The measurements of the quasi-calibrated diodes are compared with the foil bolometry and found to be accurate on the kHz time scale. Therefore, it is assumed, that the corrected values are also valid for the highest time resolution (200 kHz). With this improved diagnostic setup, the radiation induced by edge localized modes (ELMs) is analyzed on fast timescales.

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“…where I is the average current produced in the photodiode, s is the ionization constant in silicon (3.63 eV/electron-hole pair (23,24), A is the area of the diode (1.0 cm 2 for both AXUV100LA and AXUV100Al), r is the diode detection efficiency (assumed a constant of 0.01), E is the average energy of Compton-recoil electrons in the detector (expressed in eV), and e is the electron charge (1.602 x 10 -19 coulombs). The quantity E can be estimated as 1/2 E max , where E max is derived from Compton's formula for the energy of a backscattered photon (i.e., a photon whose scattering angle is 180 o ) (24).…”

Section: Prototype Analysis and Proof Of Conceptmentioning

confidence: 99%

Inverse Analysis of Cavitation Impact Phenomena on Structures

Lambrakos

Tran

2007

J. of Materi Eng and Perform

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Standard Form 298 (Rev. 8-98)Prescribed by ANSI Std. Z39.18Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Inverse analysis of signals Spectral signature analysis A general methodology is presented for in situ detection of cavitation impact phenomena on structures based on inverse analysis of luminescent emissions resulting from the collapsing of bubbles onto surfaces. Following an inverse-analysis approach, luminescent emission signatures are correlated with the general structure of asymmetric bubble collapse onto a surface. This method suggests applications for detection of cavitation that can occur within different types of dynamic water environments of structures. Case study analyses using experimental data are used to demonstrate the fundamentals of various aspects of this methodology. The goal of this methodology is to establish a direct correlation of luminescent emissions with cavitation impact phenomena, and ultimately, with cavitation erosion of structures within turbulent water environments. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S ACRONYM(S) 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S REPORT NUMBER(S)

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Time resolved radiated power during tokamak disruptions and spectral averaging of AXUV photodiode response in DIII-D

Cited by 44 publications

References 14 publications

Edge-localized mode dynamics and transport in the scrape-off layer of the DIII-D tokamak

Edge-localized mode dynamics and transport in the scrape-off layer of the DIII-D tokamak

Application of AXUV diode detectors at ASDEX Upgrade

Inverse Analysis of Cavitation Impact Phenomena on Structures

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