title: Image Evaluation of the High Resolution VUV Spectrometer at SURF II by Ray Tracing.
abstract: A high resolution VUV spectroscopic facility has been in use for several years at SURF II, the Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology in Gaithersburg, Maryland. At this facility, a combination of three cylindrical mirrors is utilized to focus the light originating in the storage ring onto the horizontal entrance slit of the spectrometer. The spectrometer uses a 6.65 m concave grating having a groove density of 4800 lines/mm in the off-plane Eagle mounting. In preparation for the installation of an array detector in the exit image plane, a ray tracing program has been formulated and spot diagrams have been constructed by plotting the coordinates of the points of intersection of the diffracted rays with the image plane, which is tangent to the Rowland circle. In creating the spot diagrams, we have considered both parallel and tilted configurations of the entrance slit with respect to the grating grooves. It is shown that the line widths of the spectral images can be reduced when the entrance slit is properly tilted. Finally, we have estimated the spectral widths of the images when they are recorded on an array detector placed tangent to the Rowland circle. We conclude that an image spectral width of 0.41 pm to 0.88 pm in first order can be achieved over the wavelength region of 40 nm to 120 nm.
authors.affiliation: Spectroscopy Division, Bhabha Atomic Research Center, Bombay2400 085, India.
authors.forename: N C
authors.initials: NC
authors.lastname: Das
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
authors.forename: R P
authors.initials: RP
authors.lastname: Madden
authors.affiliation: Department of Physics, University of the District of Columbia, Washington, DC 20008.
authors.forename: H M
authors.initials: HM
authors.lastname: Seyoum
keywords: SURF II; high resolution; off-plane Eagle; ray tracing; spectrometer