Prime pagine RA2010FUS:Copia di Layout 1 - ENEA - Fusione

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018 progress report 2010 dW/dt (Arb. units) 6 5 4 3 2 Collision stopping power Radiative stopping power Total stopping power eE R rad νII e E II ν II 1 W c1 W c2 0 0 1 2 3 4 5 Energy (MeV) Figure 1.13 – Collision, radiation, and total stopping powers for an electron. For an energy gain below (eE ν ) no runaways can be found. Electrons with energies W c1
magnetic confinement (cont’d.) progress report 2010 019 (see fig.1.15, blue symbols). Moreover we observe that, at high ν eff values, a well detectable delay between density and temperature rise (re)appears. The interaction between ITER like plasmas and the EC heating have to be investigated also under the profile of the effect of the heating system on the particle–energy confinement time with dedicated experiments extended to H–mode regimes and in conjunction with different heating systems. Sawteeth (de)stabilization by ECH and ECCD in FTU. In FTU the destabilization of sawteeth (ST) has been investigated using ECH and electron cyclotron current drive (ECCD) as a powerful tool for the shortening of ST period τ saw . This is a critical issue for the plasma confinement in fusion devices. In fact, long–period sawteeth give rise to large crashes that can trigger seed islands, thus destabilizing neoclassical tearing modes (NTM) that, on turn, degrade the plasma performances at high β. This programme was included in the work plan of the International Tokamak Physical Activity (ITPA) MHD working group on ST control for the empirical scaling of power requirement for avoiding the onset of NTMs. The sawteeth crash induced by ECH and co–ECCD was performed by using 500 ms of repetitive pulses (10 ms EC on, 40 ms EC off) from two 12 8 ×10 5 gyrotrons, up 0.8 MW total power. As the ST crash happens when the local magnetic shear s=rq’/q exceeds a critical value, ECH/co–ECCD, increasing the current density inside the inversion radius (q=1), can shorten the ST period by sharpening the q profile and enhancing the local shear. ST destabilization has been performed in plasmas at 500 kA with toroidal field ramping from 5.1 to 5.9 T in order to scan the EC absorption radius r abs from the plasma centre to well outside the q=1 radius and find the magnetic field value at which the sawteeth crash is induced by the EC trigger. Preliminary results are shown in figure 1.16, where the time delay t EC,on – t ST,crash is plotted during the EC modulation. For EC absorption inside the q=1 radius the ST periods are reduced from 6 ms (ohmic value) to about 2–4 ms, while for EC absorption outside the q=1 (t>0.8 s) the EC power plays an opposite effect, thus lengthening τ saw up to 10 ms. These results show that 0.8 MW of EC power can destabilize the ST by shortening their periods when EC absorption occurs inside the q=1 radius, where the ECH/co–ECCD increase the magnetic shear thus inducing the sawteeth crash. The next experiments should be devoted to investigating the EC power threshold for destabilization. Tests of the new ECRH launcher for FTU. The new EC antenna for real time control experiment on FTU tokamak was tested at the Istituto di Fisica del Plasma (IFP)–Consiglio Nazionale Ricerche (CNR) – Milano at the beginning of 2010. A series of tests concerning specific design issues and the launcher assembly were performed in order to validate the technical solutions adopted and to characterize the antenna in its final configuration, with low power measurements. A test facility was installed for the launcher tests (fig. 1.17). The mechanical tests involved the cardanic joints of the driving system, based on rotational movements, which are transferred, via vacuum–compatible rabs/rinv τsaw(ms) B t (T) 10 8 6 6 ×10 5 4 ×10 5 4 2 ×10 5 2 q=1 0 0 0.5 0.6 0.7 0.8 0.9 1 Time (s) ECRH Figure 1.16 – Combined effects of ECH/co–ECCD on τ saw (green circles) in the discharge with ramped B t (black solid line). For B t > 5.4 T the absorption is outside q=1 and the ST periods are greater than the ohmic ones (dashed line). The ratio between the EC power absorption minor radius rabs and the inversion radius is also marked (red line) during the 500 ms EC power modulation (10 ms on/40 ms off, blue line) Figure 1.17 – Experimental setup used to test the plug-in launcher at IFP mm-wave laboratory. The two launching lines (symmetric as to the equatorial plane) are visible and the low power mm–wave source can be seen on the top left
Page 1 and 2: PROGRESS REPORT Euratom-ENEA Associ
Page 3 and 4: progress report 2010 001 2010 Progr
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084 progress report 2010 Arb. units
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086 progress report 2010 12.500 lit
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088 progress report 2010 chapter 4
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092 progress report 2010 Critical c
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094 progress report 2010 Intensity
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102 progress report 2010 AND JET-EF
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104 progress report 2010 LITAUDON,
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106 progress report 2010 S. VENTICI
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108 progress report 2010 R. VILLARI
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110 progress report 2010 A. ROMANO,
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112 progress report 2010 J. DECKER,
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116 progress report 2010 A. BIERWAG
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Organization Chart The activities o
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Abbreviation and Acronyms A ac ACCC
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126 progress report 2010 GEM GRS GS
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128 progress report 2010 TF TF TFC
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