Direct measurement of x-ray producing electrons in the Caltech solar loop experiment

The Caltech solar loop experiment produces a 50 - 100 µs pulsed plasma that models a solar coronal loop. Previous experiments have demonstrated that the plasma loop is highly braided and is susceptible to kink and Rayleigh-Taylor instabilities which constrict, snap, and reorganize the strands. The reorganization process is associated with bursts of ~ 6 keV x-rays from the ~ 2 eV plasma, which are thought to originate from energetic electrons accelerated by inductive electric fields that form when the strands break. A current probe has been developed to directly measure the flux of energetic electrons. The probe, which consists of a biased electrode placed inside the vacuum chamber, collects electrons expelled from the plasma. The electrode can be biased up to 108 V to screen out low-energy electrons which constitute the bulk current. An x-ray emission event would be identified by correlating current spikes measured by the probe with x-ray photon detections from a 2D x-ray camera developed at Caltech, described in a companion poster. These measurements will test the inductive-acceleration hypothesis and provide insight into the processes which produce x-ray bursts in the solar corona and analogous astrophysical environments.