Physics Colloquium: The Application of Low-Temperature Physics to High-Energy Astrophysics
Dr. Caroline A. Kilbourne from Goddard Space Flight Center, NASA
High-resolution x-ray spectroscopy is a powerful tool for studying the hot (1 – 100 MK) and dynamic universe. Although the grating x-ray spectrometers on the XMM and Chandra satellites have been powerful tools in this pursuit, there remains a need for instrumentation that can provide higher spectral resolution with high throughput in the Fe-K band (around 6 keV) and for extended sources. What is needed is a non-dispersive imaging spectrometer – essentially a 15-bit x-ray color camera. And what is needed for a non-dispersive spectrometer to provide eV-scale spectral resolution is a temperature below 0.1 K. The required spectral resolution and the constraints of thermodynamics and practicality dictate the temperature regime nearly independently of the details of the sensor or the read-out technology.
In this colloquium, I will discuss the physics of both the low-temperature sensors and the high-temperature universe they have been designed to study. In order to understand phenomena such as the feedback due to active galaxies in galaxy clusters and the production of the elements in the Universe, we first need to understand phenomena such as x-ray thermalization in HgTe and weak-link superconductivity. I will also present the breakthrough results from the Soft X-ray Spectrometer (SXS) instrument that was launched on the Hitomi satellite in 2016. SXS was the third attempt to place a microcalorimeter x-ray spectrometer in orbit; the first two were lost to unrelated failures. The Hitomi satellite was itself lost a month after launch in a completely different manner, but this time the spectrometer was operated long enough to teach us something about the Universe. The Hitomi SXS data resulted in two Nature papers and ten papers in other publications thus far, showing the power of the technology, hinting at other surprises high-resolution x-ray spectra may provide, and motivating the next attempt.
Tuesday, April 17 at 3:15pm
Regents Hall, 109
3700 O St. NW