Description
A multi-view soft x-ray (SXR) diagnostic based on multiwire proportional chambers (MW-PCs) is being developed for the Tokamak à Configuration variable to provide soft x-ray emission from the plasma, 2D investigations of magnetohydrodynamic (MHD) activity and core electron temperature (Te) dynamics.
The diagnostic consists of four discrete cameras placed on the high-field side and low-field side, at both upper and lower locations, to cover of the plasma core cross-section of most TCV’s magnetic configurations. Each camera comprises two superimposed curved MWPC detectors arranged in a dual-layer configuration, separated by a metallic filter foil combination (Be/Al), to provide the simultaneous acquisition of SXR signals over two spectral ranges. Each chamber has 64 readout channels, corresponding to an intended sub-centimetre spatial resolution at the vertical location z = 0 cm. The target time resolution is 10 μs, enabling measurements of fast dynamics associated with MHD events such as sawteeth and tearing modes which typically evolve on milliseconds timescales. The dual-layer concept is expected to provide ratio measurements that can be interpreted as a Te measurement — with the intensity of each signal being dependant on the electron density ne and the impurity content with good signal-to-noise, even at high time resolution.
Te will be inferred from the ratio of simultaneously measured SXR signals acquired with two different metallic filters, using precomputed ratio–Te lookup curves. These curves are generated from a spectral continuum model folded with the detector response and foil transmission. This approach is designed to provide Te for thermialised plasmas. In addition to Te inference, the system will also operate as a standard multi-view 2D SXR diagnostic for emissivity reconstruction and MHD mode localisation.
The diagnostic design is complete and a prototype is being prepared for laboratory testing, including gain, linearity, and count-rate characterisation. Installation of the diagnostic on TCV
is planned for the upcoming experimental campaign in summer 2026.