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Ultra-Stable Horizontal DCM

installed on I14 Hard X-ray Nanoprobe beamline at Diamond Light Source

IDT have developed an ultra-stable horizontally deflecting Double Crystal Monochromator for the I14 Hard X-Ray Nanoprobe beamline at Diamond Light Source. I14 is a long beamline, extending beyond the main building for 175m. Due to the very long distances involved a highly stable DCM is critical to the beamline goal of a focused spot size of 30nm.

The I14 DCM has been designed and engineered with stability as the primary goal.

The first crystal cage has a novel kinematic mounting system to support the crystal on a stable platform about the centre of rotation to ensure no out-of-balance forces, minimising strain in the first crystal.

The DCM is cryo-cooled. The cooling scheme has been carefully designed to minimise vibration effects of turbulent coolant flow.

The mechanism is mounted on a massive granite block, which is supported on ultra-stiff adjustable wedges.

The I14 DCM features:

• 35mm fixed horizontal offset.
• Si(111) crystals with 4 keV - 26 keV energy range.
• Novel first crystal assembly for minimal crystal strain.
• Low mass & high stiffness components for high natural frequencies.
• High precision, ultra-stiff rotary table.
• Fast piezo feedback for fine control of 2nd crystal pitch & roll.
• High vacuum level <5×10-8 mbar.
• Mounting provisions for capacitance sensors.

The vibrational performance of the DCM has been measured with capacitance sensors and in-sit with an XBPM. No significant modes of vibration were found below 100 Hz. The first mode was found at 160 Hz with an amplitude of 25 nrad.