Focal Plane Development for the Transition-Edge EBIT Microcalorimeter Spectrometer

The success of future X-ray missions that employ X-ray microcalorimeters and other highresolution spectrometers depends heavily on legwork done in the laboratory today. The project I undertook as an NSTRF fellow addressed both scientific and technological needs to meet this goal. Scientifically, I focused on an X-ray emission process called Charge Exchange (CX), which occurs constantly in the solar system and can be both a confusing and diagnostic foreground in many X-ray observations that we make. Though we recognize that CX is an important process, it is difficult to characterize its signature in order to both identify the CX component in observations, as well as to harness its diagnostic power. This is because many of the details of the process, at the atomic level, are unknown and extremely difficult to model. I addressed this challenge by performing CX experiments in the laboratory using the Electron Beam Ion Trap (EBIT) facility at the Lawrence Livermore National Laboratory (LLNL) in Livermore, CA. I performed and analyzed data from several experiments simulating conditions relevant to some astrophysical systems in order to understand the atomic physics behind the CX process. I also developed an analytical pipeline to take our experimental data and extract the relevant quantum mechanical properties; this was previously mainly possible through relatively complicated computational models. I found that current models do not adequately describe the spectral signatures of CX we measure in our experiments; our pipeline performs much better. I also identified specific spectral diagnostics for the presence of CX in several types of astrophysically relevant ions. On the technological side, it is important to have a working prototype of future flight instruments operating on the ground in order to fully characterize the system and identify any problems that may arise. To this end, I supported the development of an instrument that will be delivered to the EBIT facility that will be much like the X-IFU on Athena. The Transition-Edge EBIT Microcalorimeter Spectrometer (TEMS) will be the first flight-like system similar to the X-IFU that will be under constant operation in the laboratory. I helped with detector and system testing for TEMS, including vetting potential detector chips for installation in TEMS, upgrading the cryostat, Page 2 – Revised 04/2017 operating, testing, and characterizing the readout electronics, and analyzing new data. Progress on TEMS has been excellent, and we hope to deliver the system to the EBIT facility soon.