The fusion performance of ELMy H-mode 50–50 deuterium–tritium (DT) plasmas with 50–50 DT NBI inje... more The fusion performance of ELMy H-mode 50–50 deuterium–tritium (DT) plasmas with 50–50 DT NBI injection and q 95 ≈ 3 and β N ≈ 1.8 (also referred to as medium-β N baseline scenario in the rest of this paper) are predicted with the JINTRAC suite of codes and the QuaLiKiZ transport model. The predictions are based on the analysis of plasmas from the first DT campaign on JET in 1997 (DTE1) and pure deuterium plasmas developed at JET in preparation for the DT experimental campaign in 2021 (DTE2), after the installation of a Be/W ITER-like wall in 2011. The sensitivity of the predictions to plasma parameters such as current, toroidal field, pedestal confinement and impurity content are analysed together with the sensitivity to the amount of auxiliary heating power available. The simulations indicate that a fusion power of 10 MW should be achievable under a fairly wide range of assumptions, provided that the auxiliary heating power is around or above 38 MW. Higher fusion power approaching ...
In order to extend observations on the increase of electron density peaking in neon doped plasmas... more In order to extend observations on the increase of electron density peaking in neon doped plasmas, already reported in FTU Mazzotta et al (2015 Nucl. Fusion 55 073027), some sessions have been performed by injecting helium gas on the L-mode plasmas during the last two experimental campaigns. This favorable scenario, which can fall within so called ‘highly radiative’ or ‘plasma detachment’ themes, is investigated in this paper. The description of the impact of the helium injection on plasma behavior, by varying plasma parameters and shape, is exposed, especially with respect to the density peaking and edge conditioning. It has been recorded that, not only the total amount of puffed helium, but also the injection rate intervenes in triggering a particle inflow. Finally, by using VUV spectroscopy measurements, a model to estimate concentrations of impurities is outlined here for the first time, in this way the helium amount is deduced.
Results from the last FTU campaigns on RE mitigation strategies for quiescent and post-disruption... more Results from the last FTU campaigns on RE mitigation strategies for quiescent and post-disruption RE beams are presented. We provide experimental evidence that for some RE quiescent scenarios D2 solid pellets achieve complete RE suppression capability, mainly due to the induced burst MHD activity expelling RE seed, whereas in other cases we report clear indications of avalanche multiplication of RE. Results on the assimilation of solid deuterium pellets on RE quiescent scenarios are provided. Quantitative indications of dissipative effects of anomalous Doppler instabilities (ADI) and MHD activity, in terms of critical electric field increase, is introduced and supported by experimental evidence. Multiple analysis are provided to show the significant energy conversion/dissipation of large ADI on post-disruption RE beams suggesting new strategies for RE energy suppression. We also demonstrate experimentally that modulated ECRH could be used for ADI pacing.
The evidence of Parametric Decay Instabilities (PDI) excited by the ECH power injected in O-Mode ... more The evidence of Parametric Decay Instabilities (PDI) excited by the ECH power injected in O-Mode has been explored in FTU Tokamak, using the Collective Thomson Scattering (CTS) diagnostic. The experiments show evidences to support the hypothesis of low-threshold excitation of waves generated by PDI mechanisms, formerly proposed in the case of 2nd harmonic X-mode injection in TEXTOR and ASDEX-U. Theoretical analysis predicts low-threshold parametric decay also for O-mode pump-wave injection, which can be injected in FTU at frequencies close to the first Harmonic EC resonance. Experiments were made at different magnetic fields, injecting the 140 GHz probe and observing the emission from the second antenna of the EC launcher in poloidally symmetric and asymmetric configurations, in presence of MHD islands. The signal is detected by the CTS radiometers, with a fast digitizer allowing the spectral reconstruction at very fine time and frequency scales. Different types of emissions are stu...
Introduction. In order to improve the diagnostic performances in the Frascati Tokamak Upgrade (FT... more Introduction. In order to improve the diagnostic performances in the Frascati Tokamak Upgrade (FTU) for the advanced scenario experiments, a new scanning interferometer was installed. More than 30 chords through the observation port have been obtained, with a substantial increase of the spatial resolution for density profiles. The scanning time was 12 kHz (density profiles every 42μs) in the 2004 campaign. Now a more reliable oscillator is used that provides a density profile every 62.5 μs (scanning frequency 8 kHz). The diagnostic has been developed by the “Consorzio RFX” [1] and was implemented during the first FTU shut down in 2004. In the following, we will present some measurements made during the 2004 and first part of 2005 experimental campaigns, to show the diagnostic capability of the instrument. The scanning interferometer. A “two colours” interferometer uses two different lasers to compensate the mechanical vibration contribution to the phase. The density is obtained by the phase difference of two interferometers (n e~ λ1φ1−λ2φ2). In this case CO 2 laser (10 W, λ = 10.6μm) is used for the measurement, while a CO laser (1 W, λ = 5.5μm) is used to compensate vibrations. The wavelength choice was dictated by the attainment of very high densities (> of 10 21 m-3) with multiple pellet injection. Due to an obstruction in the middle of the port, two Scanner Mirror Focusing Mirror Beam splitter そ Selection filter Bragg cell CO CO2 detector
ABSTRACT Since the 2012 IAEA-FEC Conference, FTU operations have been largely devoted to runaway ... more ABSTRACT Since the 2012 IAEA-FEC Conference, FTU operations have been largely devoted to runaway electrons generation and control, to the exploitation of the 140 GHz electron cyclotron (EC) system and to liquid metal limiter elements. Experiments on runaway electrons have shown that the measured threshold electric field for their generation is larger than predicted by collisional theory and can be justified considering synchrotron radiation losses. A new runaway electrons control algorithm was developed and tested in presence of a runaway current plateau, allowing to minimize the interactions with plasma facing components and safely shut down the discharges. The experimental sessions with 140 GHz EC system have been mainly devoted to experiments on real-time control of magnetohydrodynamic (MHD) instabilities using the new EC launcher with fast steering capability. Experiments with central EC injection have shown the onset of 3/2 and 2/1 tearing modes, while EC assisted breakdown experiments have been focused on ITER start-up issues, exploring the polarization conversion at reflection from inner wall and the capability to assure plasma start-up even in presence of a large stray magnetic field. A new actively cooled lithium limiter has been installed and tested. The lithium limiter was inserted in the scrape-off layer, without any damage to the limiter surface. First elongated FTU plasmas with EC additional heating were obtained with the new cooled limiter. Density peaking and controlled MHD activity driven by neon injection were investigated at different plasma parameters. A full real-time algorithm for disruption prediction, based on MHD activity signals from Mirnov coils, was developed exploiting a large database of disruptions. Reciprocating Langmuir probes were used to measure the heat flux e-folding length in the scrape-off layer, with the plasma kept to lay on thea internal limiter to resemble the ITER start-up phase. New diagnostics were successfully installed and tested, as a diamond probe to detect Cherenkov radiation produced by fast electrons and a gamma camera for runaway electrons studies. Laser induced breakdown spectroscopy measurements were performed under vacuum and with toroidal magnetic field, so demonstrating their capability to provide useful information on the surface elemental composition and fuel retention in present and future tokamaks, such as ITER.
In magnetically confined fusion experiments interferometry is commonly used to measure plasma ele... more In magnetically confined fusion experiments interferometry is commonly used to measure plasma electron density. This because interferometry is a very reliable technique, not affected by calibration problem. The main drawbacks of interferometers are the integral characteristic of the measurement and the fringe loosing problem. Scanning beam interferometry can always overcome the former problem and in some cases the second as
The fusion performance of ELMy H-mode 50–50 deuterium–tritium (DT) plasmas with 50–50 DT NBI inje... more The fusion performance of ELMy H-mode 50–50 deuterium–tritium (DT) plasmas with 50–50 DT NBI injection and q 95 ≈ 3 and β N ≈ 1.8 (also referred to as medium-β N baseline scenario in the rest of this paper) are predicted with the JINTRAC suite of codes and the QuaLiKiZ transport model. The predictions are based on the analysis of plasmas from the first DT campaign on JET in 1997 (DTE1) and pure deuterium plasmas developed at JET in preparation for the DT experimental campaign in 2021 (DTE2), after the installation of a Be/W ITER-like wall in 2011. The sensitivity of the predictions to plasma parameters such as current, toroidal field, pedestal confinement and impurity content are analysed together with the sensitivity to the amount of auxiliary heating power available. The simulations indicate that a fusion power of 10 MW should be achievable under a fairly wide range of assumptions, provided that the auxiliary heating power is around or above 38 MW. Higher fusion power approaching ...
In order to extend observations on the increase of electron density peaking in neon doped plasmas... more In order to extend observations on the increase of electron density peaking in neon doped plasmas, already reported in FTU Mazzotta et al (2015 Nucl. Fusion 55 073027), some sessions have been performed by injecting helium gas on the L-mode plasmas during the last two experimental campaigns. This favorable scenario, which can fall within so called ‘highly radiative’ or ‘plasma detachment’ themes, is investigated in this paper. The description of the impact of the helium injection on plasma behavior, by varying plasma parameters and shape, is exposed, especially with respect to the density peaking and edge conditioning. It has been recorded that, not only the total amount of puffed helium, but also the injection rate intervenes in triggering a particle inflow. Finally, by using VUV spectroscopy measurements, a model to estimate concentrations of impurities is outlined here for the first time, in this way the helium amount is deduced.
Results from the last FTU campaigns on RE mitigation strategies for quiescent and post-disruption... more Results from the last FTU campaigns on RE mitigation strategies for quiescent and post-disruption RE beams are presented. We provide experimental evidence that for some RE quiescent scenarios D2 solid pellets achieve complete RE suppression capability, mainly due to the induced burst MHD activity expelling RE seed, whereas in other cases we report clear indications of avalanche multiplication of RE. Results on the assimilation of solid deuterium pellets on RE quiescent scenarios are provided. Quantitative indications of dissipative effects of anomalous Doppler instabilities (ADI) and MHD activity, in terms of critical electric field increase, is introduced and supported by experimental evidence. Multiple analysis are provided to show the significant energy conversion/dissipation of large ADI on post-disruption RE beams suggesting new strategies for RE energy suppression. We also demonstrate experimentally that modulated ECRH could be used for ADI pacing.
The evidence of Parametric Decay Instabilities (PDI) excited by the ECH power injected in O-Mode ... more The evidence of Parametric Decay Instabilities (PDI) excited by the ECH power injected in O-Mode has been explored in FTU Tokamak, using the Collective Thomson Scattering (CTS) diagnostic. The experiments show evidences to support the hypothesis of low-threshold excitation of waves generated by PDI mechanisms, formerly proposed in the case of 2nd harmonic X-mode injection in TEXTOR and ASDEX-U. Theoretical analysis predicts low-threshold parametric decay also for O-mode pump-wave injection, which can be injected in FTU at frequencies close to the first Harmonic EC resonance. Experiments were made at different magnetic fields, injecting the 140 GHz probe and observing the emission from the second antenna of the EC launcher in poloidally symmetric and asymmetric configurations, in presence of MHD islands. The signal is detected by the CTS radiometers, with a fast digitizer allowing the spectral reconstruction at very fine time and frequency scales. Different types of emissions are stu...
Introduction. In order to improve the diagnostic performances in the Frascati Tokamak Upgrade (FT... more Introduction. In order to improve the diagnostic performances in the Frascati Tokamak Upgrade (FTU) for the advanced scenario experiments, a new scanning interferometer was installed. More than 30 chords through the observation port have been obtained, with a substantial increase of the spatial resolution for density profiles. The scanning time was 12 kHz (density profiles every 42μs) in the 2004 campaign. Now a more reliable oscillator is used that provides a density profile every 62.5 μs (scanning frequency 8 kHz). The diagnostic has been developed by the “Consorzio RFX” [1] and was implemented during the first FTU shut down in 2004. In the following, we will present some measurements made during the 2004 and first part of 2005 experimental campaigns, to show the diagnostic capability of the instrument. The scanning interferometer. A “two colours” interferometer uses two different lasers to compensate the mechanical vibration contribution to the phase. The density is obtained by the phase difference of two interferometers (n e~ λ1φ1−λ2φ2). In this case CO 2 laser (10 W, λ = 10.6μm) is used for the measurement, while a CO laser (1 W, λ = 5.5μm) is used to compensate vibrations. The wavelength choice was dictated by the attainment of very high densities (> of 10 21 m-3) with multiple pellet injection. Due to an obstruction in the middle of the port, two Scanner Mirror Focusing Mirror Beam splitter そ Selection filter Bragg cell CO CO2 detector
ABSTRACT Since the 2012 IAEA-FEC Conference, FTU operations have been largely devoted to runaway ... more ABSTRACT Since the 2012 IAEA-FEC Conference, FTU operations have been largely devoted to runaway electrons generation and control, to the exploitation of the 140 GHz electron cyclotron (EC) system and to liquid metal limiter elements. Experiments on runaway electrons have shown that the measured threshold electric field for their generation is larger than predicted by collisional theory and can be justified considering synchrotron radiation losses. A new runaway electrons control algorithm was developed and tested in presence of a runaway current plateau, allowing to minimize the interactions with plasma facing components and safely shut down the discharges. The experimental sessions with 140 GHz EC system have been mainly devoted to experiments on real-time control of magnetohydrodynamic (MHD) instabilities using the new EC launcher with fast steering capability. Experiments with central EC injection have shown the onset of 3/2 and 2/1 tearing modes, while EC assisted breakdown experiments have been focused on ITER start-up issues, exploring the polarization conversion at reflection from inner wall and the capability to assure plasma start-up even in presence of a large stray magnetic field. A new actively cooled lithium limiter has been installed and tested. The lithium limiter was inserted in the scrape-off layer, without any damage to the limiter surface. First elongated FTU plasmas with EC additional heating were obtained with the new cooled limiter. Density peaking and controlled MHD activity driven by neon injection were investigated at different plasma parameters. A full real-time algorithm for disruption prediction, based on MHD activity signals from Mirnov coils, was developed exploiting a large database of disruptions. Reciprocating Langmuir probes were used to measure the heat flux e-folding length in the scrape-off layer, with the plasma kept to lay on thea internal limiter to resemble the ITER start-up phase. New diagnostics were successfully installed and tested, as a diamond probe to detect Cherenkov radiation produced by fast electrons and a gamma camera for runaway electrons studies. Laser induced breakdown spectroscopy measurements were performed under vacuum and with toroidal magnetic field, so demonstrating their capability to provide useful information on the surface elemental composition and fuel retention in present and future tokamaks, such as ITER.
In magnetically confined fusion experiments interferometry is commonly used to measure plasma ele... more In magnetically confined fusion experiments interferometry is commonly used to measure plasma electron density. This because interferometry is a very reliable technique, not affected by calibration problem. The main drawbacks of interferometers are the integral characteristic of the measurement and the fringe loosing problem. Scanning beam interferometry can always overcome the former problem and in some cases the second as
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