Princeton Users See First light from Multi-Energy Soft-X-ray camera

A collaboration between Dr. Luis? Delgado-Aparicio (Princeton Plasma Physics Laboratory), Dr. Lisa Reusch, and Dr. Daniel Den Hartog (UW-Madison) has successfully installed and operated a new soft-x-ray camera based on the Pilatus3 detector made by DECTRIS Laboratories in Switzerland. The detector has the novel features of using a thick silicon layer bonded to a 100k pixel CMOS detector and per-pixel control of the pulse height comparator providing sharp energy thresholding. A pinhole in front of the detector allows it to be used as an x-ray camera with extremely high spatial resolution.? The combination of a large number of pixels with individual energy settings allows the camera to be operated with both high spatial and spectral? resolution enabling it to function as a high resolution Multi-Energy Soft-X-ray (ME-SXR) detector.

This ability to simultaneously set multiple energy thresholds enables ? simultaneous measurement of both continuum and line emission features in the 2-8 keV range where highly-charged ions contribte to the emission spectrum. The camera was installed in? the spring of 2018, and the first data collected with the system is shown in Figure 10. It shows the number of counts generated from x-ray photons with energy greater than? 4 keV. These x-rays were created by thermal electrons in a 500 kA MST discharge.

To get a sense of the spatial resolution o? f the camera, images were taken when fast electrons from the plasma were striking objects on the wall of the vessel, lighting them up with x-ray emission. In the image on the left, different structures are apparent in the image.

This camera will be used to measure temperature and density, structures in helical plasmas, detect fast electrons generated by fast magnetic reconnection events, and quantify resistive dissipation in? MST plasmas.




Compressible MHD turbulence studied in high-beta plasmas

In March, the Big Red Ball at WiPPL was operated for an investigation of compressible MHD turbulence proposed by a collaboration of Swarthmore College professor Mike Brown, Swarthmore undergraduate student Emma Suen-Lewis, and Bryn Mawr College professor David Schaffner. They proposed to measure the correlations between density and magnetic field fluctuations to distinguish between fast and slow waves in turbulent, high-beta magnetized plasmas. Suen-Lewis and Schaffner visited WiPPL to oversee the initial plasma run days. UW-Madison graduate students Doug Endrizzi and Ethan Peterson operated an array of biased plasma guns with a background axial magnetic field in order to create the experimental flux-rope plasmas, an example of which is seen in the video below. Endrizzi also designed, built, and operated a novel combination Langmuir and magnetic fluctuation probe to carry out the correlation measurements. Suen-Lewis is analyzing the experimental data for an undergraduate thesis at Swarthmore.