Author Topic: WD Spectrometer Equations - Cameca & JEOL  (Read 1736 times)

Anette von der Handt

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WD Spectrometer Equations - Cameca & JEOL
« on: December 09, 2016, 08:53:42 am »
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


E = 12.396 / lambda
lambda = 12.396 / E

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.
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Ben Buse

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Re: WD Spectrometer Equations - Cameca & JEOL
« Reply #1 on: January 22, 2019, 02:19:16 am »
I sure this is mentioned elsewhere on the forum.

H-type uses the same L values as regular JEOL spectrometers. It has to otherwise it would be horrendously complicated Ti Ka would be at a different position on a H type and a regular spectrometer. Therefore H-type L values are converted to regular spectrometer L values.

The L value equation is the distance between crystal and source - but it assumes a 140mm radius. Therefore the H-type 100mm radius are converted into 140mm units.

Looking at the equations:

It can be seen that whilst the actual L value (distance from crystal to source [as oppose to software units used]) changes with radius, the theta angle is constant.
« Last Edit: January 22, 2019, 06:42:25 am by Ben Buse »