I constantly misplace these conversions so this is part sticky note for me but may also be useful for other people. I got the following off Mike Matthews excellent periodic table that is available on the EMAS web page.
WD Spectrometer Equations
Spectrometer units
JEOL units = 24.792 x R / (2d x E)
Cameca units = sin(theta) x 100000
Conversion JEOL XCE and FCE spectrometers vs Cameca
JEOL units = 0.0028 x Cameca units
Cameca units = 357.143 x JEOL units
Conversion JEOL H-type spectrometers vs Cameca
JEOL units = 0.002 x Cameca units
Cameca units = 500 x JEOL units
Rowland circle dimensions of different spectrometers
Cameca spectrometers R = 160
JEOL XCE/FCE spectrometers R = 140
JEOL H-type spectrometers = 100
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E = 12.396 / lambda
or
lambda = 12.396 / E
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E = X-ray energy in keV
R = WDS Rowland circle in mm
d = Diffracting crystal lattice spacing in A
lambda = X-ray wavelength in A.