![]() ![]() The problem may be partly averted with toroidally bent crystal analysers (TBCA) which have different sagittal and meridional bending radii. ![]() However, as a significant disadvantage SBCAs suffer from spatial separation of meridional and sagittal foci (focal astigmatism) when taken out of the backscattering condition (angle of incident X-rays <90°) which can cause aberrations in imaging and issues with detectors with small active areas. Indeed, the portfolio of scientific cases, in which the laboratory instruments using SBCAs have proven to be a viable alternative to large-scale facilities, is expanding rapidly and spans already a vast cavalcade of interests in natural sciences such as fundamental materials research (Mortensen et al., 2017 ▸), electrochemistry (Wang et al., 2017 ▸ Kuai et al., 2018 ▸ Sun et al., 2019 ▸ Lutz & Fittschen, 2020 ▸), nanoparticle characterization (Davodi et al., 2019 ▸), in operando battery studies (Jahrman et al., 2018 ▸, 2019 c ▸), actinide research (Bès et al., 2018 ▸ Jahrman et al., 2019 b ▸ Mottram et al., 2020 b ▸), in situ catalysis studies (Moya-Cancino et al., 2019 a ▸, b ▸), geochemistry (Mottram et al., 2020 a ▸), and microbiology and enviromental research (Lusa et al., 2019 ▸). (2014 ▸) reported 4 photons W −1 s −1 for two high-resolution CBCA instruments with 2–3 eV energy resolution and 600–2000 photons W −1 s −1 for their 1 eV SBCA instrument depending on the crystal reflection used. Especially relevant to this work are the instrument designs based on SBCAs which, in conjunction with recent advances in the crystal technology (Verbeni et al., 2005 ▸ Rovezzi et al., 2017 ▸), have largely overcome the problem of low photon output per generating power limiting the previous generation of laboratory instruments (that were often based on cylindrically bent crystals, i.e. ![]() In addition to studying the structure and internal dynamics of matter via externally produced radition, SBCAs are also used to analyse X-rays in plasma research (Faenov et al., 1994 ▸ Aglitskiy et al., 1998 ▸ Sinars et al., 2003 ▸ Knapp et al., 2011 ▸).ĭue to high demand and limitations of synchrotron/free-electron access, a renewed interest towards laboratory-scale X-ray instrumentation based on conventional X-ray tubes has grown in recent years (Seidler et al., 2014 ▸ Anklamm et al., 2014 ▸ Németh et al., 2016 ▸ Holden et al., 2017 ▸ Honkanen et al., 2019 ▸ Jahrman et al., 2019 b ▸). It is no wonder that many inelastic X-ray scattering (IXS) and X-ray emission spectroscopy (XES) endstations at synchrotron and free-electron laser light sources worldwide, such as SOLEIL (Ablett et al., 2019 ▸), ESRF (Kvashnina & Scheinost, 2016 ▸ Huotari et al., 2017 ▸ Moretti Sala et al., 2018 ▸), APS (Fister et al., 2006 ▸), Spring-8 (Cai, 2004 ▸ Ishii et al., 2013 ▸), SSRF (Duan et al., 2016 ▸), SLS (Kleymenov et al., 2011 ▸), SSRL (Sokaras et al., 2012 ▸) and DESY (Welter et al., 2005 ▸), utilize SBCAs in their instrument designs. SBCAs also exhibit (approximate) point-to-point focusing allowing integration of imaging and tomography capabilities in spectroscopic instruments (Huotari et al., 2011 ▸). Especially with spherically bent crystal analysers (SBCA) one can efficiently cover and analyse photons collected over a large solid angle. The same basic principle, the diffraction of X-rays from the periodical crystal structure, has been used in a plethora of spectrometric designs in which curved crystal analysers are employed to increase the collected photon flux and to ensure their proper focusing on a detector (DuMond & Kirkpatrick, 1930 ▸ Johann, 1931 ▸ Johansson, 1932 ▸ Cauchois, 1932 ▸ von Hámos, 1932 ▸). ![]() Crystal analysers are the heart of most contemporary mid-to-high energy resolution X-ray spectrometers in the hard X-ray regime (Suortti & Schulze, 1995 ▸ Yamaoka et al., 1998 ▸). ![]()
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