Speaker: Luis Delgado-Aparicio, PPPL

Title: Energy-sensitive X-ray Cameras for Thermal and Non-Thermal Plasmas: A 12-Year Journey Towards Real-Time Solutions

Abstract: Versatile multi-energy soft and hard X-ray (SXR & HXR) pinhole cameras have been developed, calibrated, and deployed at MST, Alcator C-Mod, and WEST tokamaks with metal walls. These cutting-edge instruments, serving as enabling technologies, have facilitated investigations into a wide array of phenomena including particle, impurity, and thermal transport, heating and RF current-drive mechanisms, equilibria, MHD physics, and the diagnosis of non-Maxwellian effects such as runaway electrons (RE). This innovative imaging diagnostic leverages a pixelated X-ray detector capable of independently adjusting the lower energy threshold for photon detection on each pixel. Through meticulous trimming and calibration of the lower energy thresholds, our team has successfully mitigated contributions from radiative recombination and line emissions from medium to high-Z impurities like Al, Mo, and W. Central electron temperature values are derived by modeling the slope of continuum radiation, extracted from ratios of inverted radial emissivity profiles across multiple energy ranges, without relying on  a-priori assumptions of plasma profiles, magnetic field reconstructions, high- density limitations, or shot-to-shot reproducibility. Recent breakthroughs include  the temporal evolution measurement of central electron temperature during the C9 campaign at WEST, encompassing long-pulse L-modes lasting up to 364 seconds with 1.14 GJ of injected energy. Additionally, novel applications for diagnosing non-Maxwellian tails have been demonstrated, such as observing the birth, exponential growth, and saturation of runaway electrons (Ee~100×Te,0) at MST as well as characterizing fast-electron losses near the W strike point and emission anisotropies at the edge and core in LHCD plasmas at WEST. Several applications and potential collaborations will be discussed.

This talk will be offered in a hybrid format. If you wish to participate remotely, please send an email to cr2090@columbia.edu.