X-ray Imaging of Plasma using a Fast 1D Coded Aperture Camera

Transient phenomena in fusion-relevant plasmas often generate x-rays originating from a compact region. The spatial and temporal distribution of these x-rays can provide useful information on the underlying plasma dynamics. A 1-D imaging system with < 50 ns time resolution capable of taking more than 1000 frames based on a coded aperture has been built to study these x-rays. This system uses a 128 channel, 1-D pixelated array of scintillators fiber-coupled to fast PMTs to achieve a detector sensitivity capable of single photon detection. The time response could be further improved by deconvolving the scintillator’s characteristic rise and fall time. To demonstrate the efficacy of the coded aperture scheme as compared to the more commonly used x-ray pinhole camera, this diagnostic is being tested on x-ray bursts observed in the Caltech MHD jet experiment. These bursts are generated during a current interruption resulting from a Rayleigh-Taylor instability. It is planned to image x-rays from magnetized target fusion devices such as MIFTI.