dxc workshop challenges in xrf analysis: sample ... in xrf analysis.pdf · (7) wds(wdx) or...
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DXC WORKSHOPChallenges in XRF Analysis: Sample Preparation,
Spectral Interpretation, and Soft X‐ray Detection (Tuesday Morning 9:00am‐12 Noon@South Mammoth)
J. Kawai, Kyoto UniversityS. Ichikawa, Fukuoka UniversityU. Yasushi, Mitsubishi Electric Co.
This workshop provides a technical introduction on the following topics:1. The sample preparation (sample amount, particle size for e.g. rice as received or pulverized based on escape depth of fluorescent X‐ray, pressure to make a briquette, glass bead components and thickness, specimen diameter, synthetic standard for calibration curve, validation using reference materials ...)‐‐‐ S. Ichikawa2.Spectrometer settings (A/D conversion gain, smoothing, background subtraction, dwelling time, iteration time, WDX or EDX, X‐ray intensity and counting rate, sum peak, escape peak, diffraction peak, shaping time ...)‐‐‐ J. Kawai3. Measurement conditions (sample thickness, monochromatic X‐ray energy, incident X‐ray beam angle ...) which will affect the results of quantitative and even qualitative results of XRF. ‐‐‐ U. YasushiThough synchrotron radiation XRF and EPMA are compared with ordinary laboratory orhandheld XRF spectrometers, the workshop is intended to make use of ordinary laboratory XRF spectrometer’s high reliability. This workshop is intended not only for XRF beginners but also for those already familiar with XRF measurements.
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DXC WORKSHOPChallenges in XRF Analysis: Sample Preparation, Spectral Interpretation,
and Soft X‐ray Detection(Tuesday Morning 9:00am‐12 Noon
@South Mammoth)J. Kawai, Kyoto University
Spectrometer settings (A/D conversion gain, smoothing, background subtraction, dwelling time, iteration time, WDX or EDX, X‐ray intensity and counting rate, sum peak, escape peak, diffraction peak, shaping time ...)
Acknowledgements: Ryohei Tanaka, Kohei Yoshida 2
(1) SSD, Sold State Detector
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Energy (keV)C
ount
s/se
cond
Long distance between PHA-amplifier as synchrotron experiments, signal reflection makes
small peak at low energy side
Reflectedsignal
Terminator
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1m 5m 5m with terminator
Function Generator
1m/5m
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Function Generator
1m
Without terminator With terminator
When the electric contact was bad at a place.
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(Bad 1 m electric cable) + (another good 60 m cable)
Without terminator With terminator
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Without terminator With terminator
(73 Ω 3 m) + (50 Ω 60 m)
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Undershoot pulse form
Energy (keV)
Cou
nts/
seco
nd
time
Volta
ge
Pole zero (PZ) adjust
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Pure Si (Xerophy) spectrum of an equimolar sample of V, Mn, Co, and Cu.
Int 2 μs1st diff 2 μs2nd diff 0.5 μs.
Int 1 μs1st diff 5 μs2nd diff 1 μs
Int 1 μs1st diff 1 μs2nd diff 0.5 μs
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Xerophy spectrum of MnO2. The main amplifier condition was (a) int.=1 μs, 1st diff.=1 μs, and 2nd diff.=0.5 μs, (b) int.=2 μs, 1st diff.=2 μs, and 2nd diff.=0.5 μs, (c) int.=5 μs, 1st diff.=5 μs, and 2nd diff.=0.5 μs. The FWHM of Mn Kα is (a) 265, (b) 244, and (c) 345 eV. (b) is narrowest but the shape is worse than (a).
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Vanadium spectrum
Low energy tail(1) RAE: Radiative
Auger Effect(2) Detector response
Vanadium spectrum was monochromated
by a crystal.
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(2) Sum, escape, diffraction peaks
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(3) Proportional counter (1940s)
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Pulse height distribution curve of proportional counter. Monochromated V K.
Escape peak at 2 V. Wire cleaning is needed.
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Pulse height distribution curve of proportional
counter.
PR gas flow rate:150cm3/min80cm3/min20cm3/min
Pulse hight distribution does not change.
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Pulse height distribution curve of proportional counter.
Applied voltage1750 V1720 V1680 V1600 V
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Pulse height distribution curve of proportional
counter.
Counting rate:67cps998cps126cps
Gas amplification is larger for low counting rate.Monochromated Ti K
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PHA window and X‐ray spectral profileBroadest spectral profile: Window of 5‐10 VNarrowest spectral profile: Window 0.5‐5 V
Normalized at peak maximum
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K/K intensity ratio depends on kcps.
KEscaped from the window
Weak peak
Strong peak
window
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(1) SSD, Sold State Detector
(2) Sum, escape, diffraction peaks(3) Proportional counter (1940s)(4) Savitzky‐Golay smoothing(5) Fourier transform smoothing(6) Relation between concentration and sampling iterations of particles sampled(7) WDS(WDX) or EDS(EDX)?
(4) Savitzky‐Golay smoothing
5‐points7‐points 25
ChannelSolid line: Noise‐less Lorentzian functionDotted: Intensity dependent noise added
Intensity
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Savitzky‐Golay smoothing
Channel5‐point smoothing 1 time
Channel5‐point smoothing 10 times
Channel5‐point smoothing 100 times
Channel25‐point smoothing 1 time
Intensity
Inten
sity
Intensity
Inten
sity
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10, 100, 1000 iterations of 5‐points S‐G smoothingResponse to the function = Green’s function
Smoo
thing coefficients
Channel
Iterations
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Savitzky‐Golay smoothing
• 5 points 100 iterations = 25 points 1 iteration.• Point number should be less than 70 % of FWHM channel number.
• D/A conversion gain should be adjusted according to the XRF peak FWHM. If you want to use 7 points, FWHM should be 10 or more channels.
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Background line is determined by 5‐point average.
Noisy signal
Intensity
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Fourier transform
(5) Fourier transform smoothing
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ChannelSolid line: Noise‐less Lorentzian functionDotted: Intensity dependent noise added
Intensity
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Amplitu
de Amplitu
de
Frequency
Noise‐less Lorentzian function
Noisy Lorentzian function
Fourier Transform
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Low‐pass filtered as a window function
Frequency
Amplitu
de
Frequency
Low‐pass filter
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Intensity
Channel
Noise‐lessLorentzian function
Noisy Lorentzian function ‐> Fourier transformed‐> Low‐pass filtered ‐> Inverse FT
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50ppm
(6) Relation between concentration and sampling iterations of particles sampled
Number of particles sampled
Concen
tration (ppm
)
50ppm
• Produce 10 random numbers between 0 and 1,000,000.
• Count the times when the random number is less than 50.
• Produce additional 90 random numbers between 0 and 1,000,000.
• Count the times when the random number is less than 50, and add.
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(7) WDS(WDX) or EDS(EDX)?
• WDX is for process control in steel making.• EDX is for scrap classification in steel analysis.• The precision is completely different.• Usually EDX is enough.• The precision of SR‐WDX is worse than EDX.• EDX or WDX depends on sample preparation.
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Comparison between ICP‐AES and SR‐WDXRFPe
rkin‐Elm
er OPT
IMA
3000
XL (2
001)
Seiko SPS‐1700HVR(1998) 39
(8) Conclusions
• Intensity dependent pulse‐height distribution.• Savitzky‐Golay smoothing parameter.• Smoothing by Fourier transform.• Pole zero adjust.• Terminator is important when cable is long (100 m).• Electric circuit parameters.• Sampling amount is important for accurate concentration analysis.
• Usually EDX is enough.
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