Gabor Por | University of Dunaújváros (original) (raw)

Papers by Gabor Por

Carrying out fatigue testing of reactor vessel material 15H2MFA acoustic emission sensors were ap... more Carrying out fatigue testing of reactor vessel material 15H2MFA acoustic emission sensors were applied to follow changes. It is shown, that observed bursts can be explained only with appearance of acoustic Barkhausen Effect (ABE). Interesting source localization is shown during heat treatment and consecutive stress test, which can be explained acoustic emission due to material transition from martensite phase to bainite phase. Observed ABE opens the way to apply it in industry using magnetic stresses to provoke acoustic response for characterization of the state of the magnetic materials.

Introduction There is a long history of the use of continuous linear time-frequency transforms in... more Introduction There is a long history of the use of continuous linear time-frequency transforms in the analysis of transients detected in fusion plasma devices [1]. Despite the fact that numerous alternative methods of time-frequency analysis were proposed during the years, Fourier transform based solutions are still the standard method to approach transient wave-like phenomena. The reason for this continued popularity is that these linear time-frequency transforms do not produce any disturbing interference patterns between the time-frequency atoms, which are eigenfunctions of linear and quasi-linear theories [2]. This paper concentrates on continuous transforms that are time-shift invariant, thus ideal for the analysis of transient signals. The two well-known types of continuous linear time-frequency transforms, namely the shorttime Fourier transform (STFT) and the continuous wavelet transform with analytical wavelets (CWT), differ basically in their invariance properties, which determines their optimal field of use. Uncertainty estimation of transform values and derived quantities, like energy density distributions and phases, is also addressed shortly. Finally, the paper presents some advanced methods based on the time-frequency transforms that have been implemented in the recently developed NTI Wavelet Tools package [3] with practical fusion plasma applications. A mode number determination routine is a main feature that is based on fitting mode phases [4]. Time-frequency coherence and transfer functions are introduced briefly, and time-frequency bicoherence is discussed concentrating on consequences of the invariance properties of the transforms used. Continuous linear time-frequency transforms and their uncertainty Continuous linear time-frequency transforms can be derived from a more general family produced by smoothing the Wigner-Ville distributions of the signals [5]. Their linearity makes them unique in the sense that no non-linear interference patterns are produced between components of composite signals. Two examples are the STFT and the CWT differing only in their invariance properties: the STFT is frequency-invariant, while CWT is scale invariant-both are time-invariant, too. They are well-suited for studying transient signals, and their invariance properties determine their specific field of use: If it is need to resolve fluctuations with frequencies extending throughout many orders of magnitude, CWT should be used with logarithmic frequency axis. On the other hand, STFT is most often used to study fluctuations in a limited frequency range because of its 40 th EPS Conference on Plasma Physics P5.116

This work is based on the amplitude correlation analysis of the signals from a poloidal Mirnov-co... more This work is based on the amplitude correlation analysis of the signals from a poloidal Mirnov-coil array on the Wendelstein 7-Advanced Stellarator (W7-AS). The motivation behind this work is an earlier finding, that changes in the RMS amplitude of Mirnov-coil signals are correlated with the amplitude of small scale density turbulence measured by CO2 Laser Scattering. Based on this and other measurements, the hypothesis was set, that some of the magnetic fluctuations are caused by transient MHD modes excited by large turbulent structures. The statistical dependencies between the power modulations of different eigenmodes can provide information about the statistics of these structures. Our amplitude correlation method is based on linear continuous time-frequency representations of the signal, we use Short-Time Fourier Transformation (STFT) with Gabor-atoms to map the signal onto the time-frequency plane, as two dimensional power density distributions. From these transforms we can recover the power modulation of different frequency bands. Provided the selection of the resolution of the transforms and the limits of the frequency bands were correct, the time series calculated this way resembles the original power fluctuation of the selected eigenmode. The only distortion introduced is a convolution smoothing by the time-window used in the transformation. Detailed correlation analysis between different bandpowers of the Mirnov-coil array signals were carried out and presented in bad a nd good confinement states. In order to reveal the true structure and cause of magnetic fluctuations Mirnov-coil diagnostic signals were also compared with Lithium beam and CO2 Laser Scattering measurements. In our analysis we have found, that there was a strong and systematic difference in the cross-correlations of power bands between different confinement states.

Az általunk kifejlesztett Pásztázó akusztikus mikroszkópot kereskedelmi forgalomban kapható ultra... more Az általunk kifejlesztett Pásztázó akusztikus mikroszkópot kereskedelmi forgalomban kapható ultrahangos szenzorokból és berendezésekből állítottuk össze. A mozgatást ISEL léptető motorok segítségével végezzük. A berendezés első változatában a mérési-felbontás 1mm volt, - ma már a fókuszált ultrahangos fejnek köszönhetően 1mm alatt van. Jelenleg a mozgatásban a lépésközök 0,1 mm-el történnek, és meg tudjuk különböztetni a 0,1 mm-nél is kisebb felületi bemetszéseket. LabVIEW segítségével létrehozunk egy 3D-s modellt, amely lehetővé teszi a detektált hibák mozgatását, forgatását, valamint tomográfiás jellegű képeket is elő tudunk állítani a fémben észlelt folytonossági hiányokról. A mi rendszerünk a kereskedelmi forgalomban lévő rendszerek negyedébe, ötödébe kerül csupán. A rendszert először speciálisan kifejlesztett etalonokon teszteltük, amelyek furatokat és bemetszéseket tartalmaztak. Az autóiparban használt fröccsöntött elektronikai alkatrészekben lévő hiányok és légbuborékok vizsg...

e-Journal of Nondestructive Testing

Stresses born in the solid state may trigger acoustic emission (AE). Stresses are traditionally c... more Stresses born in the solid state may trigger acoustic emission (AE). Stresses are traditionally caused by mechanical forces and/or pressures implemented to the surface of the material. However, inner stresses in solid state may be born due to changing of magnetic field or due to temperature changes especially when cooling down the material, for example in structure changing. It is also well known that elongation of material structures due to rolling may lead to different AE bursts, which may be used for characterization of the structure of material due to cold forming. In the presentation we show in experiments that alternating magnetic field leads to AE burst, which have larger magnitude where the gradient of the changes of magnetic field is larger in absolute value. We also demonstrate correlation of the RMS of AE signals with the direction of the elongation of steel structure. This opens the way to investigate anisotropy in steel sheets. We also investigated the dependence of the...

A measurement based on the temperature noise analysis method was carried out in the Training Reac... more A measurement based on the temperature noise analysis method was carried out in the Training Reactor of the Budapest University of Technology and Economics. The main goals were the estimation of the flow velocity immediately above the reactor core and investigation of the thermal-hydraulical conditions of the reactor, mainly in the core. Subsequently 2D and 3D computations were carried out with the aid of the code CFX4.3. The main objective of the 2D calculation was to clarify the thermal-hydraulical conditions of the whole reactor tank with a reasonable computing demand. It was also necessary to accomplish 3D numerical investigations of the reactor core and the space above since three dimensional effects of the flow could only be studied in this way. In addition, obtaining certain boundary conditions of the 3D computations was another significant aim of the 2D investigations. It is important that the results of the noise analysis and the operational measuring system of the reactor ...

IOP Conference Series: Materials Science and Engineering, 2020

Experiments have been carried out using yoke for energizing alternating magnetic field in the ste... more Experiments have been carried out using yoke for energizing alternating magnetic field in the steel samples. We used acoustic emission sensors and ultrasound microphone for recording acoustic signal born in the steel material. Results of experiments clearly show the presence of Acoustic Barkhausen noise. We are introducing graphs presenting dependence of acoustic time response signal on magnetic signal (inductance) in form of Lissajous curve. It is claimed that this new method gives more in-sigh in the material than the widely used simple RMS measurement of acoustic response.

Cornell University - arXiv, Nov 7, 2018

Bicoherence analysis is a well established method for identifying the quadratic nonlinearity of s... more Bicoherence analysis is a well established method for identifying the quadratic nonlinearity of stationary processes. However, it is often applied without checking the basic assumptions of stationarity and convergence. The classic bicoherence, unfortunately, tends to give false positives-high bicoherence values without actual nonlinear coupling of different frequency components-for signals exhibiting rapidly changing amplitudes and limited length. The effect of false positive values can lead to misinterpretation of results, therefore a more prudent analysis is necessary in such cases. This paper analyses the properties of bispectrum and bicoherence in detail, generalizing these quantities to nonstationary processes. A step-by-step method is proposed to filter out false positives at a given confidence level for the case of nonstationary signals. We present a number of test cases, where the method is demonstrated on simple physics-based numerical systems. The approach and methodology introduced in the paper can be generalized to lower and higher order coherence calculations.

At the Wendelstein 7-X stellarator (W7-X), CMOS cameras will be used for the video survey diagnos... more At the Wendelstein 7-X stellarator (W7-X), CMOS cameras will be used for the video survey diagnostics. According to the present design, the sensor module of the cameras will be located at the plasma facing end of the selected angential ports. A dedicated camera system (EDICAM: Event Detection Intelligent CAMera) has been developed for the diagnostics, which should operate in a harsh environmen t u der neutron and gamma radiation. EDICAM (see fig.1.) is built up of three different modul es: (a) a Sensor Module (SM) with reduced hardware and functional elements to reach a small and compact size and robust action in a harsh environment as well; (b) an Image Pro cessing and Control Unit module handles all of the user predefined events and run image proce ssing algorithms to genera te trigger signals; (c) finally, a 10 Gigabit Ethernet compatible Imag e Readout Card serves a the network interface for the PC. In the present irradiation tests, a pr ototype of SM is used which contains only...

Introduction Over the past years data from several diagnostics of the Wendelstein 7-AS stellarato... more Introduction Over the past years data from several diagnostics of the Wendelstein 7-AS stellarator showed transients with some hundred microsecond characteristic lifetime. This timescale is an intermediate one between the energy confinement time (≈ 10ms) and the timescale of the turbulence in various regions in the plasma (1-50 μs). This ordering indicates that these events neither belong to the basic turbulence nor they are associated with global changes in the plasma. Although generally present, these transients showed high sensitivity to the magnetic configuration, therefore the question arises to what extent they can be responsible for anomalous transport, which is also known to be strongly dependent on the magnetic configuration[1]. A remarkable feature of these phenomena is that their statistical properties are very well reproducible and steerable by external parameters. This paper is devoted to a systematic study of these transient phenomena. We analyze exclusively 140 GHz ECRH heated discharges at 2.5 T toroidal magnetic field. The rotational transform was taken to be close (but not at) to either 1/3 or 1/2 and in some cases it was fine tuned by external fields or by an internal current[2] to study differences in the phenomena when the confinement changes nearly a factor of two in response to a minute rotational transform change. We collect all the information obtained from various diagnostics, and analyze correlations among them. Finally we investigate the transport relevance of these events.

The paper describes the measurement of the delayed signal of a Rh emitter Self Powered Neutron De... more The paper describes the measurement of the delayed signal of a Rh emitter Self Powered Neutron Detector (SPND) separately from other signal components originating from (n-gamma-e), (background gamma-e) and other effects. In order to separate the delayed signal, the detector was removed from the reactor core and placed to an adequately distant location during the measurement, where the radiation from the core was negligible. The experiment was carried out on the 100kW light water tank-type reactor of Technical University of Budapest and the results of the measurement were compared with the results of Monte Carlo calculations.

EPJ Web of Conferences, 2021

Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polyt... more Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polytechnique Federale de Lausanne and swissnuclear, an industrial partner, in order to determine the axial void distribution in a channel installed in the reflector of the zero power research reactor CROCUS, using neutron noise techniques. The main objective of the present paper is to report on the validation of the results against an alternative measurement technique using gamma-ray attenuation and simulations with the TRACE code. For the gamma-ray attenuation experiments, the channel used in CROCUS is installed out of the core in a Plexiglass water tank. The source and detector are fixed and the channel is moved axially to keep the geometry of the source/detector arrangement untouched. This is key to measure the void effect by gamma attenuation due to the low contrast of this technique. The paper compares the experimental results obtained with both techniques, with the outcomes of simulati...

The transient power load on plasma facing components caused by edge localised modes (ELMs) in H-m... more The transient power load on plasma facing components caused by edge localised modes (ELMs) in H-mode plasmas can be critically high for large size toroidal machines like ITER, therefore it is of high importance to develop methods to mitigate this effect. Pellet ELM pacemaking - the injection of frequent small and shallow penetrating cryogenic pellets - has been found to be a promising mitigation technique. Pellets injected into ELMy H-mode plasmas have been found to be able to trigger prompt ELMs. To be able to predict the capability of the pellet ELM triggering in future toroidal machines and to optimise the ELM pacemaking tool the understanding of the trigger mechanism is indispensable.

AIP Conference Proceedings, 2008

Journal de Physique, 1989

Progress in Nuclear Energy, 1999

ABSTRACT

Annals of Nuclear Energy, 1999

Carrying out fatigue testing of reactor vessel material 15H2MFA acoustic emission sensors were ap... more Carrying out fatigue testing of reactor vessel material 15H2MFA acoustic emission sensors were applied to follow changes. It is shown, that observed bursts can be explained only with appearance of acoustic Barkhausen Effect (ABE). Interesting source localization is shown during heat treatment and consecutive stress test, which can be explained acoustic emission due to material transition from martensite phase to bainite phase. Observed ABE opens the way to apply it in industry using magnetic stresses to provoke acoustic response for characterization of the state of the magnetic materials.

Introduction There is a long history of the use of continuous linear time-frequency transforms in... more Introduction There is a long history of the use of continuous linear time-frequency transforms in the analysis of transients detected in fusion plasma devices [1]. Despite the fact that numerous alternative methods of time-frequency analysis were proposed during the years, Fourier transform based solutions are still the standard method to approach transient wave-like phenomena. The reason for this continued popularity is that these linear time-frequency transforms do not produce any disturbing interference patterns between the time-frequency atoms, which are eigenfunctions of linear and quasi-linear theories [2]. This paper concentrates on continuous transforms that are time-shift invariant, thus ideal for the analysis of transient signals. The two well-known types of continuous linear time-frequency transforms, namely the shorttime Fourier transform (STFT) and the continuous wavelet transform with analytical wavelets (CWT), differ basically in their invariance properties, which determines their optimal field of use. Uncertainty estimation of transform values and derived quantities, like energy density distributions and phases, is also addressed shortly. Finally, the paper presents some advanced methods based on the time-frequency transforms that have been implemented in the recently developed NTI Wavelet Tools package [3] with practical fusion plasma applications. A mode number determination routine is a main feature that is based on fitting mode phases [4]. Time-frequency coherence and transfer functions are introduced briefly, and time-frequency bicoherence is discussed concentrating on consequences of the invariance properties of the transforms used. Continuous linear time-frequency transforms and their uncertainty Continuous linear time-frequency transforms can be derived from a more general family produced by smoothing the Wigner-Ville distributions of the signals [5]. Their linearity makes them unique in the sense that no non-linear interference patterns are produced between components of composite signals. Two examples are the STFT and the CWT differing only in their invariance properties: the STFT is frequency-invariant, while CWT is scale invariant-both are time-invariant, too. They are well-suited for studying transient signals, and their invariance properties determine their specific field of use: If it is need to resolve fluctuations with frequencies extending throughout many orders of magnitude, CWT should be used with logarithmic frequency axis. On the other hand, STFT is most often used to study fluctuations in a limited frequency range because of its 40 th EPS Conference on Plasma Physics P5.116

This work is based on the amplitude correlation analysis of the signals from a poloidal Mirnov-co... more This work is based on the amplitude correlation analysis of the signals from a poloidal Mirnov-coil array on the Wendelstein 7-Advanced Stellarator (W7-AS). The motivation behind this work is an earlier finding, that changes in the RMS amplitude of Mirnov-coil signals are correlated with the amplitude of small scale density turbulence measured by CO2 Laser Scattering. Based on this and other measurements, the hypothesis was set, that some of the magnetic fluctuations are caused by transient MHD modes excited by large turbulent structures. The statistical dependencies between the power modulations of different eigenmodes can provide information about the statistics of these structures. Our amplitude correlation method is based on linear continuous time-frequency representations of the signal, we use Short-Time Fourier Transformation (STFT) with Gabor-atoms to map the signal onto the time-frequency plane, as two dimensional power density distributions. From these transforms we can recover the power modulation of different frequency bands. Provided the selection of the resolution of the transforms and the limits of the frequency bands were correct, the time series calculated this way resembles the original power fluctuation of the selected eigenmode. The only distortion introduced is a convolution smoothing by the time-window used in the transformation. Detailed correlation analysis between different bandpowers of the Mirnov-coil array signals were carried out and presented in bad a nd good confinement states. In order to reveal the true structure and cause of magnetic fluctuations Mirnov-coil diagnostic signals were also compared with Lithium beam and CO2 Laser Scattering measurements. In our analysis we have found, that there was a strong and systematic difference in the cross-correlations of power bands between different confinement states.

Az általunk kifejlesztett Pásztázó akusztikus mikroszkópot kereskedelmi forgalomban kapható ultra... more Az általunk kifejlesztett Pásztázó akusztikus mikroszkópot kereskedelmi forgalomban kapható ultrahangos szenzorokból és berendezésekből állítottuk össze. A mozgatást ISEL léptető motorok segítségével végezzük. A berendezés első változatában a mérési-felbontás 1mm volt, - ma már a fókuszált ultrahangos fejnek köszönhetően 1mm alatt van. Jelenleg a mozgatásban a lépésközök 0,1 mm-el történnek, és meg tudjuk különböztetni a 0,1 mm-nél is kisebb felületi bemetszéseket. LabVIEW segítségével létrehozunk egy 3D-s modellt, amely lehetővé teszi a detektált hibák mozgatását, forgatását, valamint tomográfiás jellegű képeket is elő tudunk állítani a fémben észlelt folytonossági hiányokról. A mi rendszerünk a kereskedelmi forgalomban lévő rendszerek negyedébe, ötödébe kerül csupán. A rendszert először speciálisan kifejlesztett etalonokon teszteltük, amelyek furatokat és bemetszéseket tartalmaztak. Az autóiparban használt fröccsöntött elektronikai alkatrészekben lévő hiányok és légbuborékok vizsg...

e-Journal of Nondestructive Testing

Stresses born in the solid state may trigger acoustic emission (AE). Stresses are traditionally c... more Stresses born in the solid state may trigger acoustic emission (AE). Stresses are traditionally caused by mechanical forces and/or pressures implemented to the surface of the material. However, inner stresses in solid state may be born due to changing of magnetic field or due to temperature changes especially when cooling down the material, for example in structure changing. It is also well known that elongation of material structures due to rolling may lead to different AE bursts, which may be used for characterization of the structure of material due to cold forming. In the presentation we show in experiments that alternating magnetic field leads to AE burst, which have larger magnitude where the gradient of the changes of magnetic field is larger in absolute value. We also demonstrate correlation of the RMS of AE signals with the direction of the elongation of steel structure. This opens the way to investigate anisotropy in steel sheets. We also investigated the dependence of the...

A measurement based on the temperature noise analysis method was carried out in the Training Reac... more A measurement based on the temperature noise analysis method was carried out in the Training Reactor of the Budapest University of Technology and Economics. The main goals were the estimation of the flow velocity immediately above the reactor core and investigation of the thermal-hydraulical conditions of the reactor, mainly in the core. Subsequently 2D and 3D computations were carried out with the aid of the code CFX4.3. The main objective of the 2D calculation was to clarify the thermal-hydraulical conditions of the whole reactor tank with a reasonable computing demand. It was also necessary to accomplish 3D numerical investigations of the reactor core and the space above since three dimensional effects of the flow could only be studied in this way. In addition, obtaining certain boundary conditions of the 3D computations was another significant aim of the 2D investigations. It is important that the results of the noise analysis and the operational measuring system of the reactor ...

IOP Conference Series: Materials Science and Engineering, 2020

Experiments have been carried out using yoke for energizing alternating magnetic field in the ste... more Experiments have been carried out using yoke for energizing alternating magnetic field in the steel samples. We used acoustic emission sensors and ultrasound microphone for recording acoustic signal born in the steel material. Results of experiments clearly show the presence of Acoustic Barkhausen noise. We are introducing graphs presenting dependence of acoustic time response signal on magnetic signal (inductance) in form of Lissajous curve. It is claimed that this new method gives more in-sigh in the material than the widely used simple RMS measurement of acoustic response.

Cornell University - arXiv, Nov 7, 2018

Bicoherence analysis is a well established method for identifying the quadratic nonlinearity of s... more Bicoherence analysis is a well established method for identifying the quadratic nonlinearity of stationary processes. However, it is often applied without checking the basic assumptions of stationarity and convergence. The classic bicoherence, unfortunately, tends to give false positives-high bicoherence values without actual nonlinear coupling of different frequency components-for signals exhibiting rapidly changing amplitudes and limited length. The effect of false positive values can lead to misinterpretation of results, therefore a more prudent analysis is necessary in such cases. This paper analyses the properties of bispectrum and bicoherence in detail, generalizing these quantities to nonstationary processes. A step-by-step method is proposed to filter out false positives at a given confidence level for the case of nonstationary signals. We present a number of test cases, where the method is demonstrated on simple physics-based numerical systems. The approach and methodology introduced in the paper can be generalized to lower and higher order coherence calculations.

At the Wendelstein 7-X stellarator (W7-X), CMOS cameras will be used for the video survey diagnos... more At the Wendelstein 7-X stellarator (W7-X), CMOS cameras will be used for the video survey diagnostics. According to the present design, the sensor module of the cameras will be located at the plasma facing end of the selected angential ports. A dedicated camera system (EDICAM: Event Detection Intelligent CAMera) has been developed for the diagnostics, which should operate in a harsh environmen t u der neutron and gamma radiation. EDICAM (see fig.1.) is built up of three different modul es: (a) a Sensor Module (SM) with reduced hardware and functional elements to reach a small and compact size and robust action in a harsh environment as well; (b) an Image Pro cessing and Control Unit module handles all of the user predefined events and run image proce ssing algorithms to genera te trigger signals; (c) finally, a 10 Gigabit Ethernet compatible Imag e Readout Card serves a the network interface for the PC. In the present irradiation tests, a pr ototype of SM is used which contains only...

Introduction Over the past years data from several diagnostics of the Wendelstein 7-AS stellarato... more Introduction Over the past years data from several diagnostics of the Wendelstein 7-AS stellarator showed transients with some hundred microsecond characteristic lifetime. This timescale is an intermediate one between the energy confinement time (≈ 10ms) and the timescale of the turbulence in various regions in the plasma (1-50 μs). This ordering indicates that these events neither belong to the basic turbulence nor they are associated with global changes in the plasma. Although generally present, these transients showed high sensitivity to the magnetic configuration, therefore the question arises to what extent they can be responsible for anomalous transport, which is also known to be strongly dependent on the magnetic configuration[1]. A remarkable feature of these phenomena is that their statistical properties are very well reproducible and steerable by external parameters. This paper is devoted to a systematic study of these transient phenomena. We analyze exclusively 140 GHz ECRH heated discharges at 2.5 T toroidal magnetic field. The rotational transform was taken to be close (but not at) to either 1/3 or 1/2 and in some cases it was fine tuned by external fields or by an internal current[2] to study differences in the phenomena when the confinement changes nearly a factor of two in response to a minute rotational transform change. We collect all the information obtained from various diagnostics, and analyze correlations among them. Finally we investigate the transport relevance of these events.

The paper describes the measurement of the delayed signal of a Rh emitter Self Powered Neutron De... more The paper describes the measurement of the delayed signal of a Rh emitter Self Powered Neutron Detector (SPND) separately from other signal components originating from (n-gamma-e), (background gamma-e) and other effects. In order to separate the delayed signal, the detector was removed from the reactor core and placed to an adequately distant location during the measurement, where the radiation from the core was negligible. The experiment was carried out on the 100kW light water tank-type reactor of Technical University of Budapest and the results of the measurement were compared with the results of Monte Carlo calculations.

EPJ Web of Conferences, 2021

Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polyt... more Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polytechnique Federale de Lausanne and swissnuclear, an industrial partner, in order to determine the axial void distribution in a channel installed in the reflector of the zero power research reactor CROCUS, using neutron noise techniques. The main objective of the present paper is to report on the validation of the results against an alternative measurement technique using gamma-ray attenuation and simulations with the TRACE code. For the gamma-ray attenuation experiments, the channel used in CROCUS is installed out of the core in a Plexiglass water tank. The source and detector are fixed and the channel is moved axially to keep the geometry of the source/detector arrangement untouched. This is key to measure the void effect by gamma attenuation due to the low contrast of this technique. The paper compares the experimental results obtained with both techniques, with the outcomes of simulati...

The transient power load on plasma facing components caused by edge localised modes (ELMs) in H-m... more The transient power load on plasma facing components caused by edge localised modes (ELMs) in H-mode plasmas can be critically high for large size toroidal machines like ITER, therefore it is of high importance to develop methods to mitigate this effect. Pellet ELM pacemaking - the injection of frequent small and shallow penetrating cryogenic pellets - has been found to be a promising mitigation technique. Pellets injected into ELMy H-mode plasmas have been found to be able to trigger prompt ELMs. To be able to predict the capability of the pellet ELM triggering in future toroidal machines and to optimise the ELM pacemaking tool the understanding of the trigger mechanism is indispensable.

AIP Conference Proceedings, 2008

Journal de Physique, 1989

Progress in Nuclear Energy, 1999

ABSTRACT

Annals of Nuclear Energy, 1999