  We report on the successful sounding rocket flight of the high resolution
(R=3000-4000) J-PEX EUV spectrometer. J-PEX is a novel normal incidence
instrument, which combines the focusing and dispersive elements of the
spectrometer into a single optical element, a multilayer-coated grating. The
high spectral resolution achieved has had to be matched by unprecedented high
spatial resolution in the imaging microchannel plate detector used to record
the data. We illustrate the performance of the complete instrument through an
analysis of the 220-245A spectrum of the white dwarf G191-B2B obtained with a
300 second exposure. The high resolution allows us to detect a low-density
ionized helium component along the line of sight to the star and individual
absorption lines from heavier elements in the photosphere.
