TABLE I.

Example instrument x-ray bandwidths.

Source	Typical bandwidth ( $\Delta \lambda /\lambda$ or $\Delta E/E$, FWHM) (%)	Typical pulse duration
Si 111 monochromator	<0.01	Continuous
Cu anode (K $\alpha$) with multilayer mirrorsa	5	Continuous
Synchrotron multilayer monochromators (CHESS)54	0.6–1.3	Continuous
Synchrotron undulator (ESRF ID-09)55	1–3	ps
Synchrotron dual undulators (BioCARS)56	5.5	ps
SASE at XFELs57	0.1–0.3	fs
Pink SSX (Pohang)58	1.2	fs
SwissFEL pink59	1.8–2.2	fs
Inverse Compton sources (MuCLS)60	3	Continuous
Compact femtosecond Compton sources (CXLS)61	0.1–5	fs
Compact x-ray light sourceb	3, 10	fs
Betatron source62	<100	fs

^a Based on personal communication with Dr. J. Graf, Oncoatec (Bruker).

^b Based on personal communication with Dr. W. G. Graves, Arizona State University.