The fast-ion collective Thomson scattering (CTS) receiver at ASDEX Upgrade can detect spectral po... more The fast-ion collective Thomson scattering (CTS) receiver at ASDEX Upgrade can detect spectral power densities of a few eV in the millimeter-wave range against the electron cyclotron emission (ECE) background on the order of 100 eV under presence of gyrotron stray radiation that is several orders of magnitude stronger than the signal to be detected. The receiver heterodynes the frequencies of scattered radiation (100-110 GHz) to intermediate frequencies (IF) (4.5-14.5 GHz). The IF signal is divided into 50 IF channels tightly spaced in frequency space which are terminated by square-law Schottky detector diodes. The performance of the entire receiver is determined by the main receiver components operating at mm-wave frequencies (notch-, bandpass-and lowpass filters, a voltage-controlled variable attenuator, and an isolator), a mixer, and the IF components (amplifiers, band-pass filters, and detector diodes). We discuss here the design of the entire receiver, focussing on its performance as a unit. The receiver has been disassembled, and the performance of its individual components has been characterized. Based on these individual component measurements we predict the spectral response of the receiver assembled as a unit. The measured spectral response of the assembled receiver is in reasonable agreement with this prediction.
Collective Thomson scattering (CTS) measurements provide information about the composition and ve... more Collective Thomson scattering (CTS) measurements provide information about the composition and velocity distribution of confined ion populations in fusion plasmas. The bulk ion part of the CTS spectrum is dominated by scattering off fluctuations driven by the motion of thermalized ion populations. It thus contains information about the ion temperature, rotation velocity, and plasma composition. To resolve the bulk ion region and access this information, we installed a fast acquisition system capable of sampling rates up to 12.5 GS/s in the CTS system at ASDEX Upgrade. CTS spectra with frequency resolution in the range of 1 MHz are then obtained through direct digitization and Fourier analysis of the CTS signal. We here describe the design, calibration, and operation of the fast receiver system and give examples of measured bulk ion CTS spectra showing the effects of changing ion temperature, rotation velocity, and plasma composition.
The collective Thomson scattering (CTS) diagnostic installed on ASDEX Upgrade uses millimeter wav... more The collective Thomson scattering (CTS) diagnostic installed on ASDEX Upgrade uses millimeter waves generated by the newly installed 1 MW dual frequency gyrotron as probing radiation at 105 GHz. It measures backscattered radiation with a heterodyne receiver having 50 channels (between 100 and 110 GHz) to resolve the one-dimensional velocity distribution of the confined fast ions. The steerable antennas will allow different scattering geometries to fully explore the anisotropic fast ion distributions at different spatial locations. This paper covers the capabilities and operational limits of the diagnostic. It then describes the commissioning activities carried out to date. These activities include gyrotron studies, transmission line alignment, and beam pattern measurements in the vacuum vessel. Overlap experiments in near perpendicular and near parallel have confirmed the successful alignment of the system. First results in near perpendicular of scattered spectra in a neutral beam i...
APS Bulletin of the American Physical Society. 49th Annual Meeting of the Division of Plasma Phys... more APS Bulletin of the American Physical Society. 49th Annual Meeting of the Division of Plasma Physics Volume 52, Number 11. Monday–Friday, November 12–16, 2007; Orlando, Florida. ... H. Bindslev (Risoe-DTU). SB Korsholm (Risoe-DTU). F. Leipold (Risoe-DTU). ...
Spatially resolved fast ion velocity distribution results from on-axis and off-axis NBI heated plasmas on ASDEX Upgrade using the Collective Thomson Scattering (CTS)
Risø-R-Report Engineering design of the ITER Collective Thomson Scattering diagnostic. Contract E... more Risø-R-Report Engineering design of the ITER Collective Thomson Scattering diagnostic. Contract EFDA 06-1478 PK Michelsen, V. Furtula, SB Korsholm, F. Leipold, F. Meo, M. Salewski, H. Bindslev, B. Lauritzen, M. Lucas, E. Nonbøl Risø-R-1717(EN) December 2009 Page 2. ...
A 105 GHz Notch Filter for mm-Wave Plasma Diagnostics
ABSTRACT Notch filters are the most important mm-wave components to protect front-end receivers f... more ABSTRACT Notch filters are the most important mm-wave components to protect front-end receivers from intensive gyrotron stray radiation in fusion plasmas. Here we describe a notch filter design with 105 GHz center frequency and 200 MHz rejection bandwidth. The design is based on a fundamental rectangular waveguide with cylindrical cavities coupled by narrow iris gaps, i.e. small elongated holes of negligible thickness. We use numerical simulations to study the sensitivity of the notch filter performance to changes in geometry and in material properties within a total bandwidth of ±10 GHz. The typical insertion loss in the passband is below 1.5 dB, and the attenuation in the stopband is approximately 40 dB.
Towards Bayesian Inference of the Fast-Ion Distribution Function
ABSTRACT The fast-ion distribution function (DF) has a complicated dependence on several phase-sp... more ABSTRACT The fast-ion distribution function (DF) has a complicated dependence on several phase-space variables. The standard analysis procedure in energetic particle research is to compute the DF theoretically, use that DF in forward modeling to predict diagnostic signals, then compare with measured data. However, when theory and experiment disagree (for one or more diagnostics), it is unclear how to proceed. Bayesian statistics provides a framework to infer the DF, quantify errors, and reconcile discrepant diagnostic measurements. Diagnostic errors and ``weight functions" that describe the phase space sensitivity of the measurements are incorporated into Bayesian likelihood probabilities, while prior probabilities enforce physical constraints. As an initial step, this poster uses Bayesian statistics to infer the DIII-D electron density profile from multiple diagnostic measurements. Likelihood functions for various fast-ion diagnostics are also described.
The fast-ion collective Thomson scattering (CTS) receiver at ASDEX Upgrade can detect spectral po... more The fast-ion collective Thomson scattering (CTS) receiver at ASDEX Upgrade can detect spectral power densities of a few eV in the millimeter-wave range against the electron cyclotron emission (ECE) background on the order of 100 eV under presence of gyrotron stray radiation that is several orders of magnitude stronger than the signal to be detected. The receiver heterodynes the frequencies of scattered radiation (100-110 GHz) to intermediate frequencies (IF) (4.5-14.5 GHz). The IF signal is divided into 50 IF channels tightly spaced in frequency space which are terminated by square-law Schottky detector diodes. The performance of the entire receiver is determined by the main receiver components operating at mm-wave frequencies (notch-, bandpass-and lowpass filters, a voltage-controlled variable attenuator, and an isolator), a mixer, and the IF components (amplifiers, band-pass filters, and detector diodes). We discuss here the design of the entire receiver, focussing on its performance as a unit. The receiver has been disassembled, and the performance of its individual components has been characterized. Based on these individual component measurements we predict the spectral response of the receiver assembled as a unit. The measured spectral response of the assembled receiver is in reasonable agreement with this prediction.
Collective Thomson scattering (CTS) measurements provide information about the composition and ve... more Collective Thomson scattering (CTS) measurements provide information about the composition and velocity distribution of confined ion populations in fusion plasmas. The bulk ion part of the CTS spectrum is dominated by scattering off fluctuations driven by the motion of thermalized ion populations. It thus contains information about the ion temperature, rotation velocity, and plasma composition. To resolve the bulk ion region and access this information, we installed a fast acquisition system capable of sampling rates up to 12.5 GS/s in the CTS system at ASDEX Upgrade. CTS spectra with frequency resolution in the range of 1 MHz are then obtained through direct digitization and Fourier analysis of the CTS signal. We here describe the design, calibration, and operation of the fast receiver system and give examples of measured bulk ion CTS spectra showing the effects of changing ion temperature, rotation velocity, and plasma composition.
The collective Thomson scattering (CTS) diagnostic installed on ASDEX Upgrade uses millimeter wav... more The collective Thomson scattering (CTS) diagnostic installed on ASDEX Upgrade uses millimeter waves generated by the newly installed 1 MW dual frequency gyrotron as probing radiation at 105 GHz. It measures backscattered radiation with a heterodyne receiver having 50 channels (between 100 and 110 GHz) to resolve the one-dimensional velocity distribution of the confined fast ions. The steerable antennas will allow different scattering geometries to fully explore the anisotropic fast ion distributions at different spatial locations. This paper covers the capabilities and operational limits of the diagnostic. It then describes the commissioning activities carried out to date. These activities include gyrotron studies, transmission line alignment, and beam pattern measurements in the vacuum vessel. Overlap experiments in near perpendicular and near parallel have confirmed the successful alignment of the system. First results in near perpendicular of scattered spectra in a neutral beam i...
APS Bulletin of the American Physical Society. 49th Annual Meeting of the Division of Plasma Phys... more APS Bulletin of the American Physical Society. 49th Annual Meeting of the Division of Plasma Physics Volume 52, Number 11. Monday–Friday, November 12–16, 2007; Orlando, Florida. ... H. Bindslev (Risoe-DTU). SB Korsholm (Risoe-DTU). F. Leipold (Risoe-DTU). ...
Spatially resolved fast ion velocity distribution results from on-axis and off-axis NBI heated plasmas on ASDEX Upgrade using the Collective Thomson Scattering (CTS)
Risø-R-Report Engineering design of the ITER Collective Thomson Scattering diagnostic. Contract E... more Risø-R-Report Engineering design of the ITER Collective Thomson Scattering diagnostic. Contract EFDA 06-1478 PK Michelsen, V. Furtula, SB Korsholm, F. Leipold, F. Meo, M. Salewski, H. Bindslev, B. Lauritzen, M. Lucas, E. Nonbøl Risø-R-1717(EN) December 2009 Page 2. ...
A 105 GHz Notch Filter for mm-Wave Plasma Diagnostics
ABSTRACT Notch filters are the most important mm-wave components to protect front-end receivers f... more ABSTRACT Notch filters are the most important mm-wave components to protect front-end receivers from intensive gyrotron stray radiation in fusion plasmas. Here we describe a notch filter design with 105 GHz center frequency and 200 MHz rejection bandwidth. The design is based on a fundamental rectangular waveguide with cylindrical cavities coupled by narrow iris gaps, i.e. small elongated holes of negligible thickness. We use numerical simulations to study the sensitivity of the notch filter performance to changes in geometry and in material properties within a total bandwidth of ±10 GHz. The typical insertion loss in the passband is below 1.5 dB, and the attenuation in the stopband is approximately 40 dB.
Towards Bayesian Inference of the Fast-Ion Distribution Function
ABSTRACT The fast-ion distribution function (DF) has a complicated dependence on several phase-sp... more ABSTRACT The fast-ion distribution function (DF) has a complicated dependence on several phase-space variables. The standard analysis procedure in energetic particle research is to compute the DF theoretically, use that DF in forward modeling to predict diagnostic signals, then compare with measured data. However, when theory and experiment disagree (for one or more diagnostics), it is unclear how to proceed. Bayesian statistics provides a framework to infer the DF, quantify errors, and reconcile discrepant diagnostic measurements. Diagnostic errors and ``weight functions" that describe the phase space sensitivity of the measurements are incorporated into Bayesian likelihood probabilities, while prior probabilities enforce physical constraints. As an initial step, this poster uses Bayesian statistics to infer the DIII-D electron density profile from multiple diagnostic measurements. Likelihood functions for various fast-ion diagnostics are also described.
Uploads
Papers by Mirko Salewski