Diagnostic weight functions in constants-of-motion phase-space
M. Rud, D. Moseev, F. Jaulmes, K. Bogár, J. Eriksson, H. Järleblad, M. Nocente, G. Prechel, Bernard Reman, Bo Simmendefeldt Schmidt, A. Snicker, L. Stagner, A. Valentini, M. Salewski
Abstract
Abstract The fast-ion phase-space distribution function in axisymmetric tokamak plasmas is completely described by the three constants of motion: energy, magnetic moment and toroidal canonical angular momentum. In this work, the observable regions of constants-of-motion phase-space, given a diagnostic setup, are identified and explained using projected velocities of the fast ions along the diagnostic lines-of-sight as a proxy for several fast-ion diagnostics, such as fast-ion <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mtext>D</mml:mtext> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> </mml:msub> </mml:math> spectroscopy, collective Thomson scattering, neutron emission spectroscopy and gamma-ray spectroscopy. The observable region in constants-of-motion space is given by a position condition and a velocity condition, and the diagnostic sensitivity is given by a gyro-orbit and a drift-orbit weighting. As a practical example, 3D orbit weight functions quantifying the diagnostic sensitivity to each point in phase-space are computed and investigated for the future COMPASS-Upgrade and MAST-Upgrade tokamaks.