Phase-space resolved measurement of 2nd harmonic ion cyclotron heating using FIDA tomography at the ASDEX Upgrade tokamak

Abstract

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Detection of neutral beam deuterons acceleration by 2nd harmonic radio frequency heating in ASDEX Upgrade via neutron spectrometry

“…This explanation seems confirmed by recent measurements with the Fast Ion D-Alpha (FIDA) diagnostics [11]. However, FIDA cannot measure accurately fast ions above energies of ∼ 150 keV, due to the charge exchange cross-section having a maximum around 60 keV, thus reducing the signal-to-noise ratio at high energies [11]. Moreover, such an increase of the neutron rate could be explained also with a lesser sensitivity of NBI-D ions to turbulence or in general to a reduction of turbulent transport in presence of fast ions [22].…”

“…It has been explained as direct absorption of RF waves by D-ions with a large Larmor radius, such as fast NBI-D ions [1] [5]. This explanation seems confirmed by recent measurements with the Fast Ion D-Alpha (FIDA) diagnostics [11]. However, FIDA cannot measure accurately fast ions above energies of ∼ 150 keV, due to the charge exchange cross-section having a maximum around 60 keV, thus reducing the signal-to-noise ratio at high energies [11].…”

Deuterium temperature, drift velocity, and density measurements in non-Maxwellian plasmas at ASDEX Upgrade

“…We find evidence for acceleration above the full NBI energy of 60 keV as expected for the 2 nd harmonic ICRF heating scenario which accelerates fast ions from NBI. These results are consistent with recent measurements of the fast-ion velocity distribution function in a comparable plasma scenario [62]. The central boron temperature and the neoclassically computed central deuterium temperature according to TRANSP in the NBI-only phase were about 2.3 keV.…”

Velocity-space tomography using prior information at MAST

“…[19][20][21] In order to find a stable solution, first-order Tikhonov regularization 22 has proven a useful tool in tomography studies. 7,12,13,23,24 Here the solution is regularized by introducing a penalty term that favours solutions with small gradients. The solution F * is then the distribution F that minimizes the sum of the residual norm of the original problem [Eq.…”