Soft X-ray 2-D imaging with time resolution of microseconds and continuous frame rate

Abstract

This paper will discuss soft X-ray imaging with time resolution in the range of tens to hundreds of microseconds, and continuous frame rate. A device operating in the range 0.2–10 keV (with capability to be extended to higher energy), has been developed for fast imaging of X-ray emissions of large magnetic fusion plasmas, at ENEA Frascati, Italy in collaboration with INFN-Pisa. It consists of a pinhole camera provided with a Micro Pattern Gas Detector (MPGD) detector, having a Gas Electron Multiplier (GEM) as amplifying stage, and a true 2-D pixel read out, working in photon counting mode. The front end electronics has independent channels for each pixel and the data acquisition system has been designed to allow for high framing rates (1 kHz to 1 MHz) at time intervals with different acquisition parameters.Continuous images of extended magnetically confined fusion plasmas have been acquired with framing rates from 1 to 100 kHz, revealing different types of instabilities. A few representative video clips are included for each case. The monitoring of the core plasma emission in the true 2-D cross section at high time resolution enables the study of MHD instabilities and the possibility of a more effective plasma control. It turns out that such a device has a good potential for applications in other fields of research outside fusion; in order to explore these capabilities, time resolved radiographies have been performed in the laboratory to prove the possibility of monitoring simple dynamic processes on the sub millisecond time scales (see included video clips).Finally, high pixel density developments of this detector will be described, together with a general discussion on this still unexplored domain of continuous sub millisecond soft X-ray imaging.