Vibrational stability of a cryocooled horizontal double-crystal monochromator

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• 作者：Paw Kristiansen ; Ulf Johansson ; Thomas Ursby and Brian Norsk Jensen
• 关键词：horizontal double-crystal monochromator ; vibrational measurements ; vibrational performance ; monochromator cryocooling
• 刊名：Journal of Synchrotron Radiation
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：23
• 期：5
• 页码：1076-1081
• 全文大小：1029K
• ISSN：1600-5775

文摘

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.