Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak

Liu, X.; Zhao, Hailin; Liu, Y.; Li, E. Z.; Han, Xiang; Domier, Calvin; Luhmann, N.C.; Ti, Ang; Hu, Liqun; Zhang, X. D.

doi:10.1063/1.4896047

Cited by 22 publications

(20 citation statements)

References 18 publications

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“…In-situ absolute intensity calibration has been carried out independently for the radiometer systems and the Michelson interferometer since 2014 [8]. Two types of hot sources have been developed for the calibration on EAST.…”

Section: In-situ Intensity Calibrationmentioning

confidence: 99%

Overview of the ECE measurements on EAST

et al. 2019

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Radiometer systems and a Michelson interferometer, have been operated routinely to detect the elec-tron cyclotron emission (ECE) from EAST plasmas for diagnosing the local electron temperature. A common quasi-optical antenna placed inside the vacuum vessel is employed to collect and focus the plasma emission, and the line of sight is along a radial chord. All of the systems are located in a diagnostic room where the plasma emission is transmitted by overmoded corrugated waveguide. In-situ absolute intensity calibration has been carried out for both the radiometer systems and the Michelson interferometer independently, to ensure that the ECE diagnostic provides an independent electron temperature measurement. In order to diagnose the small-amplitude electron temperature fluctuation, a correlation ECE (CECE) diagnostic has been designed and commissioned recently. The CECE diagnostic employs an independent antenna system which has improved poloidal resolution. A synthetic diagnostic is realized by using the simulation code SPECE to interpret the ECE data in plasmas with non-Maxwellian distribution, and preliminary results imply that the ECE data could be still useful as a localized measurement in plasmas with non-thermal electrons, such as the LHW-heated plasmas on EAST.

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Section: In-situ Intensity Calibrationmentioning

confidence: 99%

Overview of the ECE measurements on EAST

et al. 2019

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“…For the EAST campaign in 2014, there are two ECE measurement systems in operation: a 32channel heterodyne radiometer [16,17] and a Michelson interferometer.…”

Section: Diagnostic Systemmentioning

confidence: 99%

“…Roughly, the total length of the transmission line is 45 m having 8 miter bends (the mode in this kind of waveguide is HE 11 ). In the laboratory, the transmission line houses a power divider (wire grid) with variable splitting ratio to feed the interferometer and the radiometer [16,17] .…”

Section: Quasi-optical Antenna and Transmission Linementioning

confidence: 99%

“…Fig. 6(a)-(c) illustrate the temporal evolution of some plasma parameters: the plasma current, the line averaged electron density measured by a HCN interferometer [25] , and the electron temperature around the major radius 1.77 m measured by a heterodyne radiometer [16,17] . At the beginning of the pulse (t < 0.2 s), the lower hybrid wave heating (LHW) of roughly 200 kW is adopted for pre-ionization.…”

Section: Derivation Of the Electron Temperature Profilementioning

confidence: 99%

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Impurity Emission Behavior in the Soft X-Ray and Extreme Ultraviolet Range on EAST

Shen

Lyu

2015

Plasma Sci. Technol.

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A Michelson interferometer, on loan from EFDA-JET (Culham, United Kingdom) has recently been commissioned on the experimental advanced superconducting tokamak (EAST, ASIPP, Hefei, China). Following a successful in-situ absolute calibration the instrument is able to measure the electron cyclotron emission (ECE) spectrum, from 80 GHz to 350 GHz in extraordinary mode (X-mode) polarization, with high accuracy. This allows the independent determination of the electron temperature profile from observation of the second harmonic ECE and the possible identification of non-Maxwellian features by comparing higher harmonic emission with numerical simulations. The in-situ calibration results are presented together with the initial measured temperature profiles. These measurements are then discussed and compared with other independent temperature profile measurements. This paper also describes the main hardware features of the diagnostic and the associated commissioning test results.

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“…Microwave radiometers are applied in a wide range of research areas, ranging from atmospheric physics 1 , radio astronomy 2 to nuclear fusion research 3,4 . A common way to absolutely calibrate the radiometers is the hot/cold calibration method, which uses two reference temperatures to determine the calibration factors 4 , although often only a relative calibration with respect to a Michelson interferometer or a Thomson scattering diagnostic is done 5 . Due to the amount of components used in a radiometer it is challenging to get appropriate uncertainties for each component up to the data acquisition system (DAQ).…”

Section: Introductionmentioning

confidence: 99%

Bayesian modeling of microwave radiometer calibration on the example of the Wendelstein 7-X electron cyclotron emission diagnostic

Hoefel

Hirsch

Kwak

et al. 2019

Review of Scientific Instruments

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This paper reports about a novel approach to the absolute intensity calibration of an electron cyclotron emission (ECE) spectroscopy system. Typically, an ECE radiometer consists of tens of separated frequency channels corresponding to different plasma locations. An absolute calibration of the overall diagnostic including near plasma optics and transmission line is achieved with blackbody sources at LN 2 temperature and room temperature via a hot/cold calibration mirror unit. As the thermal emission of the calibration source is typically a few thousand times lower than the receiver noise temperature, coherent averaging over several hours is required to get a sufficient signal to noise ratio. A forward model suitable for any radiometer calibration using the hot/cold method and a periodic switch between them has been developed and used to extract the voltage difference between the hot and cold temperature source via Bayesian analysis. In contrast to the classical analysis which evaluates only the reference temperatures, the forward model takes into account intermediate effective temperatures caused by the finite beam width and thus uses all available data optimally. This allows the evaluation of weak channels where a classical analysis would not be feasible, is statistically rigorous and provides a measurement of the beam width. By using a variance scaling factor a model sensitive adaptation of the absolute uncertainties can be implemented, which will be used for the combined diagnostic Bayesian modelling analysis.

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Absolute intensity calibration of the 32-channel heterodyne radiometer on experimental advanced superconducting tokamak

Cited by 22 publications

References 18 publications

Overview of the ECE measurements on EAST

Overview of the ECE measurements on EAST

Impurity Emission Behavior in the Soft X-Ray and Extreme Ultraviolet Range on EAST

Bayesian modeling of microwave radiometer calibration on the example of the Wendelstein 7-X electron cyclotron emission diagnostic

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