An Interesting Poster to look at from the Tri Alpha Energy Team in California

Abstract
FIDA System (FIDA Emission)
What is FIDA?
Camera (Beam Emission)
D-Alpha System (Halo & Beam Emission)
What is FIDASIM?
FIDASIM Inputs
Summary
First Fast-Ion D-Alpha (FIDA) Measurements and Simulations on C-2U
Nathan G. Bolte1, Deepak Gupta1, Luke Stagner2, Marco Onofri1, Sean Dettrick1, Erik M. Granstedt1
1 TRI ALPHA ENERGY, INC., P.O. Box 7010, Rancho Santa Margarita, CA 92688-7010 2 University of California, Irvine. Irvine, CA 92697
 Fast-camera Sanstreak Edgertronic
Camera*
 Typically operated using 192x192 frame size at 9527fps
 Fitted for a wide-angle, radial view near the C-2U midplane
 Views largely toward oncoming beam (NB5)
NB5 (SE)
* See also poster CP10.00077 “Fast imaging measurements and modeling of neutral and impurity density on C-2U” by E. Granstedt
Blue-shifted filter picks out beam emission from single beam (652.4 x 2 nm filter bandpass filter)
Un-shifted filter picks out un-shifted emission from all beams (656.1 x 1.5 nm filter bandpass filter)
Experimental
FIDASIM
APS/DPP/2016
In Tri Alpha Energy's C-2U experiment, advanced beam-driven field-reversed configuration (FRC) plasmas were sustained via tangential neutral beam injection1. The dominant fast ion population made a dramatic impact on the overall plasma performance. A fast-ion D-alpha (FIDA)2 diagnostic, which is based on the Doppler- shifted Balmer-alpha light from neutralized fast ions, was recently added to the C-2U fast-ion diagnostics suite. The first ever FIDA measurements on an FRC topology have been carried out. Bandpass-filtered FIDA measurements (>6 keV ions) were made with a photomultiplier tube and are forward modeled by FIDASIM. Line- integrated signals were taken at eight radial locations and eight times during the FRC lifetime. While the measurements share some salient features with the simulation, they are 4.5x larger, suggesting a higher fast-ion content than the Monte Carlo distribution. Highly Doppler-shifted beam radiation is also measured with a high- speed camera and is spatially well-correlated with FIDASIM. Having shown the feasibility of FIDA on C-2U, we will further explore the use of FIDA on the upgraded C- 2W machine to estimate fast-ion densities and to infer the local fast-ion distribution function.
1 M. Binderbauer et al, Phys. of Plasmas 22, 056110 (2015) 2 W.W. Heidbrink., Rev. Sci. Instr. 81, 10D727 (2010)
 1 movable line-averaged line-of-sight, 8 times, 8 unique views, 26-shot average
 652.4x2nm bandpass filter captures only FIDA (fully rejects halo and beam emission)
 FIDASIM inputs optimized for this data set
 Future plans include full spectra and several fixed views
 Measurements confirm Bremsstrahlung modulation causes <5% pollution of FIDA signal
Single, movable line of sight
X
NB5 (SE)
vfi
FIDA measurements are of Doppler-shifted D- alpha light from reneutrals born of the charge exchange (CX) between confined fast-ions and neutral beam or halo neutrals. The radiation occurs so quickly after CX that the location and velocity of the reneutral are effectively that of the confined fast ion. Viewing geometry and fast-ion velocities produce broad FIDA spectra detectable beyond the range of thermal emission. While a full beam deposition and collisional-radiative model (FIDASIM) is used to fully deconvolve the data, a control-room level interpretation is afforded as signals are proportional to fast-ion densities.
FIDASIM models neutral beam deposition and produces synthetic D-alpha and neutral particle analyzer signals. A collisional radiative model gives the Balmer-alpha emission from injected neutrals, thermal halo neutrals, and fast reneutrals.
 14 fixed line-averaged lines-of-sight, 9 times, 7-shot average
 Broad 10nm filter captures halo and beam emission
 FIDASIM inputs not optimized for this data set
 Future use of narrow 656.1nm filters will isolate halo emission and help verify plasma profiles
NB6 (NE)
Experimental plasma parameters compared to FIDASIM inputs
X
Inputs for FIDASIM for this work are produced using a mixture of experimental data and modeling values. Experimentally-obtained plasma radial profiles at the midplane are utilized. TAEs experimentally-validated simulation Q2D1, which is a two-temperature, 2D MHD model with an added neutral fluid component combined with a 3D Monte Carlo fast-particle code, provides the 2D E and B fields and the 3D fast-ion distribution. Experimental profiles are mapped onto radial and axial dimensions assuming them to be flux functions of the Q2D equilibrium.
1 M. Onofri et al, “Simulations of the C-2 and C-2U Field Reversed Configurations with the Q2D code”, APS DPP 2015 Conference
D-Alpha View Port
FIDA View Port
NB6
Camera View Port
NB5
 FIDA signals are measurable in beam-driven FRCs
 FIDASIM predicts spatial variation well
 Halo, beam, and FIDA light can be experimentally isolated  Measured FIDA signals much larger then predicted
 Validates plans to develop a FIDA spectrometer