Combined unfolding and spatial inversion of neutron camera measurements for ion temperature profile determination in ITER

Abstract

Measurements of the core ion temperature profile are required in ITER with ±10% accuracy and 100 ms time resolution. The ITER radial neutron camera (RNC), with 45 collimated lines of sight (spanning almost completely a poloidal plasma section) equipped with compact neutron spectrometers, has the potential to provide such spatially resolved temperature information. In this paper a novel technique for the ion temperature profile measurement based on the combination of unfolding and spatial inversion of RNC measurements is presented and applied to the ITER full power standard H-mode deuterium–tritium scenario, assuming the RNC to be equipped with liquid scintillators. Results based on synthetic data suggest that the target accuracy could be reached with a time resolution ⩾200 ms.

Neutron diagnostics for the physics of a high-field, compact, Q ≥ 1 tokamak

“…The fitted temperatures for both spectrometers are displayed in Table 6. Note that this calculation consistently overpredicts the uniform temperature by ∼10-20%, whereas an underprediction of ∼20% by a single line-of-sight radial spectrometer is reported in [52]. One probable cause for this is spectral broadening from energy down-scattered neutrons.…”

“…In JET, the neutron camera system measured the fuel ratio profile during a series of trace tritium experiments; sawtooth crashes were also observed as temperature and density profile flattening in the core caused drops in DT neutron rates [58]. Redundant measurements made by the neutron camera system include the total fusion neutron rate and T i profile [52], given adequate signal levels.…”

Exploration of ion temperature profile measurements at JET using the upgraded neutron profile monitor

“…The calibrated PHS were processed by successive application of forward fitting and spatial inversion algorithms (see Ref. 6). In the forward fitting a parametric model is assumed for the unknown line-integrated spectra; the model is folded with the RF and the difference between the measured and folded PHS is minimized using χ 2 statistics.…”

Current Research into Applications of Tomography for Fusion Diagnostics

“…Based on the observed robustness of the MFR method as well as on experience with spectral unfolding, a new approach to analyses of spatially resolved pulse height data from the RNC scintillation detectors at ITER can be proposed. In contrast to the step-by-step approach presented in [32], where tomography analyses is run for separate energy bins, it is recommended to directly combine the contribution (i.e. geometric) matrix and the response matrix of the energy calibrated detectors into a single inversion problem as follows:…”