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pointed to by val. An error is returned in case there is no argument or the
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Option.ArgVar takes a pointer to a variable that it sets on success. Its
Current X-ray lasers require facilities that are kilometres long. A cavity-based set-up about 66 metres in length has been developed that uses highly reflective mirrors to enable the generation of high-intensity pulses of narrow-band X-ray radiation. This promises to overcome the limitations of current X-ray lasers.