title: Vibrational stability of a cryocooled horizontal double-crystal monochromator.
abstract: The vibrational stability of a horizontally deflecting double-crystal monochromator (HDCM) is investigated. Inherently a HDCM will preserve the vertical beam stability better than a `normal' vertical double-crystal monochromator as the vibrations of a HDCM will almost exclusively affect the horizontal stability. Here both the relative pitch vibration between the first and second crystal and the absolute pitch vibration of the second crystal are measured. All reported measurements are obtained under active cooling by means of flowing liquid nitrogen (LN2). It is found that it is favorable to circulate the LN2 at high pressures and low flow rates (up to 5.9 bar and down to 3 l min(-1) is tested) to attain low vibrations. An absolute pitch stability of the second crystal of 18 nrad RMS, 2-2500 Hz, and a relative pitch stability between the two crystals of 25 nrad RMS, 1-2500 Hz, is obtained under cryocooling conditions that allow for 1516 W to be adsorbed by the LN2 before it vaporizes.
authors: FMB Oxford Ltd, Unit 1 Ferry Mills, Oxford OX2 0ES, UK.
authors: Paw
authors: P
authors: Kristiansen
authors: MAX IV Laboratory, Lund University, Box 118, SE-221 00 Lund, Sweden.
authors: Ulf
authors: U
authors: Johansson
authors: MAX IV Laboratory, Lund University, Box 118, SE-221 00 Lund, Sweden.
authors: Thomas
authors: T
authors: Ursby
authors: MAX IV Laboratory, Lund University, Box 118, SE-221 00 Lund, Sweden.
authors: Brian Norsk
authors: BN
authors: Jensen
keywords: horizontal double-crystal monochromator; monochromator cryocooling; vibrational measurements; vibrational performance