2015 cameca users meeting background characterization – must account for background shape...
TRANSCRIPT
2015 Cameca Users Meeting
Background characterization – must account for background shape
CurvatureSpectrometer efficiencyNatural Bremsstrahlung shape
InterferencesFrom elements in the excitation volumeFrom elements fluoresced from a distance – can be 10s to 100s of microns
Absorption edges
S K edge
S Kb S Ka
Bi Mα
Background characterization – must account for background shape
‘Holes’
Compositional variation within phase of interest
2012 Workshop: Dating Tectonic Events using Monazite/Xenotime
2015 Cameca Users Meeting
Background characterization – must account for background shape
‘Holes’
Compositional variation within phase of interest
2015 Cameca Users Meeting
Curvature and interferences…
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
54000 55000 56000 57000 58000 59000 60000 61000 62000 63000 640000.80
1.00
1.20
1.40
1.60
1.80
2.00
PbMb
f(x) = 174.740050889563 exp( − 8.39654354896111E-05 x )f(x) = 261.71092066823 exp( − 9.07497725717837E-05 x )
f(x) = NaN exp( NaN x )f(x) = NaN exp( NaN x )f(x) = NaN exp( NaN x )f(x) = NaN exp( NaN x )f(x) = NaN exp( NaN x )Pb-M region on GdPO4
Ultrachron VLPETExponential (Ultrachron VLPET)Ultrachron LPETExponential (Ultrachron LPET)Ultrachron PET (1 bar Poly)
wavelength (sin-q * 105)
inte
ns
ity
(c
ps
/nA
)
Intensity Scaling Curvature 1.0 -7.238 2.42 -8.465 5.14 -4.369 5.10 -5.161 4.00 -7.652 5.52 -9.075 1.67 -8.466
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
Ti Kα1 (2)
Th Mα
Th Mβ
High net intensity (pk-bkg) and large pk/bkg
Major element analysis is primarily characterization of peaks…
2015 Cameca Users Meeting
Measured net Int.20% error, ~350ppm error
Correct net Int.
Trace element analysis is primarily characterization of background…
2015 Cameca Users Meeting
Curvature and interferences…
2015 Cameca Users Meeting
2015 Cameca Users Meeting
How do we know the analysis is correct ?
Analysis of elemental concentration
Test against secondary standard of “known” composition
Secondary must be appropriate for monazite, etc.
REE phosphateThU
Very difficult to find or make homogeneous trace element secondary standard
2015 Cameca Users Meeting
If you can’t check against a known value, then try for a zero result in something appropriate that doesn’t have any of the trace element of interest (blank).
Clearly,“If you can’t analyze something, then see if you can analyze nothing…”
“Because, if you can’t do nothing right, then you can’t do anything.”
A start for assessing accuracy…Blank analysis
2015 Cameca Users Meeting
Test for Pb in synthetic GdPO4 (no Pb flux!)Savitsky – Golay low pass filter
2015 Cameca Users Meeting
Savitsky – Golay low pass filter
2015 Cameca Users Meeting
Blank test for Pb
2015 Cameca Users Meeting
Blank test for Pb
Background offsets Pb
(sinθ*105) ppm sd
+/- 200 2 12
+/- 500 -40 14
+/- 1000 -79 7
+/- 2000 -54 6
Regressed -4 10
2015 Cameca Users Meeting
Determination of background intensity by the multipoint method
Fit via exponential or polynomial regression
2015 Cameca Users Meeting
Determination of background intensity by the multipoint methodBlank testing…
GdPO4 PrPO4Avg all Std dev. Avg all Std dev.
0.0041 0.0048 -0.0059 0.00330.0117 0.0024 0.0123 0.00180.0004 0.0027 0.0006 0.0016
0.0033 0.0096 -0.0086 0.00280.0133 0.0015 0.0129 0.00190.0012 0.0042 -0.0022 0.0016
-0.0019 0.0096 -0.0130 0.00260.0093 0.0015 0.0102 0.0019
-0.0089 0.0044 -0.0126 0.0017
Multipt bkg
UTh
Pb
2-pts bkg, EXP.
UThPb
2-pts bkg, LIN.
UThPb
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
Interferences and absorption edges…It’s not just background, but background on interference correction measurements also
2015 Cameca Users Meeting
Interferences and absorption edges…
2015 Cameca Users Meeting
Interferences and absorption edges…How do we measure the interference correction?
2015 Cameca Users Meeting
Interferences and absorption edges…How do we measure the interference correction?
2015 Cameca Users Meeting
Interferences and absorption edges…How do we measure the interference correction?
2015 Cameca Users Meeting
Interferences and absorption edges…How do we measure the interference correction?
2015 Cameca Users Meeting
Interferences and absorption edges…
2015 Cameca Users Meeting
Interferences and absorption edges…
2015 Cameca Users Meeting
Interferences and absorption edges…
2015 Cameca Users Meeting
Interferences and absorption edges…
2015 Cameca Users Meeting
Interferences and absorption edges…
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting
2015 Cameca Users Meeting