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A NOVEL LARGE AREA IMAGING NEXAFS SPECTROMETER FOR COMBINATORIAL CHEMICAL AND STRUCTURAL ANALYSIS
Large Area Combinatorial Near Edge X-ray Absorption Fine Structure Images: Parallel Process Determination of Molecular Bond Concentration and Orientation on Surfaces
POSTER: A NOVEL LARGE AREA IMAGING NEXAFS SPECTROMETER FOR COMBINATORIAL CHEMICAL AND STRUCTURAL ANALYSIS
LARIAT MKII Super Conducting NEXAFS Imaging Spectrometer (NISTSB134109SU1067)
The LARIAT MKI NEXAFS imaging spectrometers are currently in operational transition at Brookhaven National Laboratory NSLS II beamline operated by National Institute of Standards & Technology (NIST) and under the direction of Dr. Daniel Fischer.
LARIAT is an acronym for Large Area Rapid Imaging Analytical Tool. The rapid imaging capability is derived from two factors:
A high brightness tunable soft x-ray synchrotron radiation source rapidly scanned across the specimen surface stimulates emission of a large flux of secondary electrons and secondly;
The high flux of electrons emitted from the specimen surface are collected in parallel in an intense magnetic field from all emission angles (when no energy filtering is applied) across the entire field of view with a high depth of field and transmitted through the electron optics with nearly 100% efficiency to the imaging detector.
Image data collected with acquisition rates of up to 30 images per minute and 7um lateral resolution are processed to produce high signal-to-noise four-dimensional (X, Y, Z and photon energy) hyperspectral energy filtered images containing elemental and chemical contrast. Inherent design characteristics of the LARIAT spectrometer achieve a large effective numerical aperture (large collection angle) with minimal optical aberration.
The application image depicts a NEXAFS chemical contrast image of DNA patterned on a substrate. Note that the image contrast is produced from differences in the nitrogen chemistry between the substrate and the DNA containing adenine π* bonds.
LARIAT MKII is a second generation imaging NEXAFS spectrometer with a full field imaging area of 400mm2 and a minimum lateral resolution of <7um across the entire 20X20mm field of view. The LARIAT MKII is differentiated from its earlier embodiment, the LARIAT MK I, by implementation of a pair of superconducting magnets in the place of a single resistive magnet on the LARIAT MKI. The superconducting coils allow a 9x increase in the magnetic field at the sample surface: 8.5T versus 0.95T on the MKI. The higher magnetic field at the sample leads to reduction in the gyration radii distribution emitted from the sample surface, translating into dramatic improvement in the lateral image resolution of the spectrometer. Combined with the higher brightness of the NSLS II x-ray source; improved resolution will be accomplished without any anticipated reduction in throughput compared to the LARIAT MKI operating on the NSLS I.
A second major improvement in the LARIAT MKII is improved transmission due to grid-less electrostatic energy filtering elements. The new energy filter design both doubles the transmission efficiency and enhances energy filtering functionality considerably vs. the MKI. The imaging detection chain is functionally identical to the LARIAT MKI, consisting of an MCP, phosphor coated fiber optic and a CCD camera.
A complete acquisition and data reduction package, including beam control and advanced NEXAFS data processing is incorporated into each system. This is a turn-key spectrometer ready to conduct science
SRI 2018: Taiwan
LARIAT MKII Poster
Featuring Scanning Stage
NanoSpot Modality & Compressed Sensing