The first decade of science with Chandra and XMM-Newton

X-ray astronomy comes of age

The Chandra X-ray Observatory (Chandra) and the X-ray Multi-Mirror Mission (XMM-Newton) continue to expand the frontiers of knowledge about high-energy processes in the Universe. These groundbreaking observatories lead an X-ray astronomy revolution: revealing the physical processes and extreme conditions involved in producing cosmic X-rays in objects ranging in size from a few kilometres (comets) to millions of light years (clusters of galaxies), and particle densities ranging over 20 orders of magnitude. In probing matter under conditions far outside those accessible from Earth, they have a central role in the quest to understand our place in the Universe and the fundamental laws that govern our existence. Chandra and XMM-Newton are also part of a larger picture wherein advances in subarcsecond imaging and high-resolution spectroscopy across a wide range of wavelengths combine to provide a more complete picture of the phenomena under investigation. As these missions mature, deeper observations and larger samples further expand our knowledge, and new phenomena and collaborations with new facilities forge exciting, often unexpected discoveries. This Review provides the highlights of a wide range of studies, including auroral activity on Jupiter, cosmic-ray acceleration in supernova remnants, colliding neutron stars, missing baryons in low-density hot plasma, and supermassive black holes formed less than a billion years after the Big Bang.

Chromium/scandium multilayer mirrors for isolated attosecond pulses at 145 eV

Recent advances in the development of attosecond soft x-ray sources toward photon wavelengths below 10 nm are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. We demonstrate that current attosecond experiments in the sub-200-eV range benefit from these improved optics. We present our achievements in utilizing ion-beam-deposited chromium/scandium (Cr/Sc) multilayer mirrors, optimized by tailored material dependent deposition and interface polishing, for the generation of single attosecond pulses from a high-harmonic cut-off spectrum at a central energy of 145 eV. Isolated attosecond pulses have been measured by soft x-ray-pump/NIR-probe electron streaking experiments and characterized using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG/CRAB). The results demonstrate that Cr/Sc multilayer mirrors can be used as efficient attosecond optics for reflecting 600-attosecond pulses at a photon energy of 145 eV, which is a prerequisite for present and future attosecond experiments in this energy range.

Ion polished Cr/Sc attosecond multilayer mirrors for high water window reflectivity

Recent advances in the development of attosecond soft X-ray sources ranging into the water window spectral range, between the 1s states of carbon and oxygen (284 eV-543 eV), are also driving the development of suited broadband multilayer optics for steering and shaping attosecond pulses. The relatively low intensity of current High Harmonic Generation (HHG) soft X-ray sources calls for an efficient use of photons, thus the development of low-loss multilayer optics is of uttermost importance. Here, we report about the realization of broadband Cr/Sc attosecond multilayer mirrors with nearly atomically smooth interfaces by an optimized ion beam deposition and assisted interface polishing process. This yields to our knowledge highest multilayer mirror reflectivity at 300 eV near normal incidence. The results are verified by transmission electron microscopy (TEM) and soft/hard X-ray reflectometry.