Parallel recording of electron energy loss spectra

Two silicon photo diode array devices were tested as parallel recording detectors for electron energy loss spectrometry (EELS). The direct bombardment of a Reticon photodiode array detector with high energy electrons (80 keV) causes an irreversible increase in diode dark current. The dark current saturates the detector amplifier after a dose of 10(-6) C/diode making it unsuitable for EELS. A scintillator coupled SIT vidicon is sensitive enough to count two high energy electrons with a spatial resolution of 100 micrometers, corresponding to 5 eV energy resolution with the electron optical system described. The large pixel-to-pixel gain variation inherent in the scintillator and vidicon can be reduced by averaging the spectrum over a large area of the target perpendicular to the dispersion direction. The L-edge of calcium for a 4 X 10(-3) weight fraction concentration biological specimen is observable in a 40 s parallel recorded spectrum. The minimum detectable concentration of calcium is estimated to be ten times better for ELLS than EDS X-ray analysis.