1-2 µm2 beam from a compact focusing mirror assembly

Figure 6. General Purpose Table (16-ID-B)
Figure 6. General Purpose Table (16-ID-B)

HPCAT recently installed and commissioned a compact Kirkpatrick-Baez (KB) mirror assembly capable of delivering the smallest, most tightly focused beam yet at HPCAT’s General Purpose Table (16-ID-B) (Fig. 6).  The approximate beam dimensions – characterized by the full-width half-maximum intensity (FWHM) of the derivative of knife edge across the focal spot – are 1 µm in the vertical direction and 2 µm in the horizontal direction.  The assembly is mounted on a precision rail system which allows robust, efficient switching between the large and small KB assemblies.  An integrated pinhole positioning system is mounted directly to the helium-filled enclosure, ensuring maximum stability of the pinhole with respect to the focused beam.  A range of clean-up pinhole sizes down to approximately 10 µm in diameter allows for maximum flexibility in the pinhole location with respect to various diamond anvil cell designs. The focusing assembly was commissioned in Summer run of 2015 and is open for general users starting in October 2015 (Key personnel: Stas Sinogeikin, Jesse Smith)

 

Typical knife-edge scans of the focused beam in the vertical (left) and horizontal (right) directions.  The fitted parameters of a split Pseudo-Voigt profile function quantify the primarily Gaussian beam with a fitted beam spot size of 0.9 µm (v) x 2.3 µm (h)