title: Imaging crystal spectrometer for high-resolution x-ray measurements on electron beam ion traps and tokamaks.
abstract: We describe a crystal spectrometer implemented on the Livermore electron beam ion traps that employ two spherically bent quartz crystals and a cryogenically cooled back-illuminated charge-coupled device detector to measure x rays with a nominal resolving power of λ/Δλ ≥ 10 000. Its focusing properties allow us to record x rays either with the plane of dispersion perpendicular or parallel to the electron beam and, thus, to preferentially select one of the two linear x-ray polarization components. Moreover, by choice of dispersion plane and focussing conditions, we use the instrument either to image the distribution of the ions within the 2 cm long trap region, or to concentrate x rays of a given energy to a point on the detector, which optimizes the signal-to-noise ratio. We demonstrate the operation and utility of the new instrument by presenting spectra of Mo34+, which prepares the instrument for use as a core impurity diagnostic on the NSTX-U spherical torus and other magnetic fusion devices that employ molybdenum as plasma facing components.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: P
authors.initials: P
authors.lastname: Beiersdorfer
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: E W
authors.initials: EW
authors.lastname: Magee
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: N
authors.initials: N
authors.lastname: Hell
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: G V
authors.initials: GV
authors.lastname: Brown