data acquisition what choices need to be made?
DESCRIPTION
Data Acquisition What choices need to be made?. Data Acquisition What choices need to be made?. Specimen type and preparation Radiation source Wavelength Instrument geometry Detector type Instrument setup Scan parameters. Data Acquisition What choices need to be made?. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/1.jpg)
1
Data Acquisition
What choices need to be made?
![Page 2: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/2.jpg)
2
Data Acquisition
What choices need to be made?
Specimen type and preparation
Radiation source
Wavelength
Instrument geometry
Detector type
Instrument setup
Scan parameters
![Page 3: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/3.jpg)
3
Data Acquisition
What choices need to be made?
Specimen type and preparation
Slide mount
Front loading cavity
Back loading cavity
Side drifting cavity
Low backgrd plate
Several spherical particle techniques
![Page 4: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/4.jpg)
4
Data Acquisition
What choices need to be made?
Specimen type and preparation
Slide mount
Front loading cavity
Back loading cavity
Side drifting cavity
Low backgrd plate
Several spherical particle techniques
Preferred orientation is worst prep problem
![Page 5: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/5.jpg)
5
Data Acquisition
Preferred orientation
![Page 6: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/6.jpg)
6
Data Acquisition
Preferred orientation
![Page 7: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/7.jpg)
7
Data Acquisition
What choices need to be made?
Specimen type and preparation
Slide mount
Front loading cavity
Back loading cavity
Side drifting cavity
Low backgrd plate
Several spherical particle techniques
Low angle problem - fixed divergence slit:
specimen
X
![Page 8: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/8.jpg)
8
Data Acquisition
Specimen type and preparation
To get good particle statistics, generally want size < 10
Poorly ground sample:
![Page 9: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/9.jpg)
9
Data Acquisition
What choices need to be made?
Specimen type and preparation
Slide mount
Front loading cavity
Back loading cavity
Side drifting cavity
Low backgrd plate
Several spherical particle techniques
Neutron diffraction requires larger specimens
![Page 10: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/10.jpg)
10
Data Acquisition
What choices need to be made?
Radiation sources
Lab x-rays
Rotating anode x-rays
Synchrotron x-rays
Constant wavelength neutrons
TOF neutrons
![Page 11: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/11.jpg)
11
Data Acquisition
What choices need to be made?
X-rays vs neutrons
X-rays - atomic scatt
power (ƒ) decreases w/
2
Neutrons - atom scatt
cross sections constant
w/ 2
![Page 12: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/12.jpg)
12
Data Acquisition
What choices need to be made?
X-rays vs neutrons
X-rays - low atomic no.
ƒs very small
Neutrons - little variation
of atom scatt cross
sections w/ atomic no.
![Page 13: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/13.jpg)
13
Data Acquisition
What choices need to be made?
X-rays vs neutrons
X-rays - low atomic no.
ƒs very small
Neutrons - little variation
of atom scatt cross
sections w/ atomic no.
magnetic spin – use for
magnetic structure detn
![Page 14: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/14.jpg)
14
Data Acquisition
What choices need to be made?
X-rays vs neutrons
X-rays - usually 1-2 doublet used (not w/ synchrotron x-rays)
![Page 15: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/15.jpg)
15
Data Acquisition
What choices need to be made?
X-rays vs neutrons
![Page 16: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/16.jpg)
16
Data Acquisition
What choices need to be made?
Radiation sources
Lab x-rays
relatively low intensity
Rotating anode x-rays
much higher intensity
![Page 17: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/17.jpg)
17
Data Acquisition
What choices need to be made?
Radiation sources
Lab x-rays
relatively low intensity
Rotating anode x-rays
much higher intensity
Synchrotron x-rays
extremely high intensity
monochromatic
continuously variable wavelength
very tiny beam
![Page 18: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/18.jpg)
18
Data Acquisition
What choices need to be made?
Radiation sources
Lab x-rays
relatively low intensity
Rotating anode x-rays
much higher intensity
Synchrotron x-rays
extremely high intensity
monochromatic
continuously variable wavelength
very tiny beam
very high resolution
![Page 19: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/19.jpg)
19
Data Acquisition
What choices need to be made?
Radiation sources
Reactor neutrons
continuous wave-
length distribution –
monochromator
req'd
![Page 20: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/20.jpg)
20
Data Acquisition
What choices need to be made?
Radiation sources
Reactor neutrons
continuous wave-
length distribution –
monochromator
req'd
generally low flux,
low resolution
![Page 21: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/21.jpg)
21
Data Acquisition
What choices need to be made?
Radiation sources
Spallation source
(pulsed)
time-of-flight (TOF)
energy (wavelength)
analysis used
![Page 22: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/22.jpg)
22
Data Acquisition
What choices need to be made?
Radiation sources
Spallation source
(pulsed)
time-of-flight (TOF)
energy (wavelength)
analysis used
very high flux,
high resolution
![Page 23: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/23.jpg)
23
Data Acquisition
What choices need to be made?
Radiation sources
Spallation source
(pulsed)
time-of-flight (TOF)
energy (wavelength)
analysis used
very high flux,
high resolution
![Page 24: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/24.jpg)
24
Data Acquisition
What choices need to be made?
Wavelength
Shorter wavelengths – more Bragg peaks
more peak overlap
![Page 25: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/25.jpg)
25
Data Acquisition
What choices need to be made?
Wavelength
Shorter wavelengths – more Bragg peaks
more peak overlap
(keep in mind peak broadening due to sample
and/or no. phases present)
![Page 26: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/26.jpg)
26
Data Acquisition
What choices need to be made?
Wavelength
Shorter wavelengths – more Bragg peaks
more peak overlap
(keep in mind peak broadening due to sample
and/or no. phases present)
X-rays – most atom types have very strong absorption
of characteristic wavelengths
![Page 27: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/27.jpg)
27
Data Acquisition
Instrument geometry
Choices:
a. conventional Bragg-Brentano diffractometer (includes -)
b. Guinier camera or diffractometer
c. diffractometer w/ curved PSD
d. TOF neutron instrument
e. 4-circle diffractometer
![Page 28: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/28.jpg)
28
Data Acquisition
Instrument geometry
Choices:
a. conventional Bragg-Brentano diffractometer (includes -)
b. Guinier camera or diffractometer
c. diffractometer w/ curved PSD
d. TOF neutron instrument
e. 4-circle diffractometer
Generally want good resolution & high intensity – can be
obtained w/ all but (c) above, & (a) w/reactor neutrons (CW)
![Page 29: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/29.jpg)
29
Data Acquisition
Instrument geometry
Choices:
a. conventional Bragg-Brentano diffractometer (includes -)
b. Guinier camera or diffractometer
c. diffractometer w/ curved PSD
d. TOF neutron instrument
e. 4-circle diffractometer
Generally want good resolution & high intensity – can be
obtained w/ all but (c) above, & (a) w/reactor neutrons (CW)
Instrument geometry affects instrument file
![Page 30: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/30.jpg)
30
Data Acquisition
What choices need to be made?
Detector type
Conventional – scintillation or proportional counterenergy resolution not high – usuallyneed monochromator
![Page 31: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/31.jpg)
31
Data Acquisition
What choices need to be made?
Detector type
Conventional – scintillation or proportional counterenergy resolution not high – usuallyneed monochromator
Also common – solid state detector – very high energy resolution – monochromator not needed
![Page 32: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/32.jpg)
32
Data Acquisition
What choices need to be made?
Detector type
Conventional – scintillation or proportional counterenergy resolution not high – usuallyneed monochromator
Also common – solid state detector – very high energy resolution – monochromator not needed
Neutrons – He counter
![Page 33: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/33.jpg)
33
Data Acquisition
What choices need to be made?
Detector type
Conventional – scintillation or proportional counterenergy resolution not high – usuallyneed monochromator
Also common – solid state detector – very high energy resolution – monochromator not needed
Neutrons – He counter
What about image plates? – poor resolution, hi bkgrd
![Page 34: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/34.jpg)
34
Data Acquisition
What choices need to be made?
Instrument setup
Divergence and receiving slit sizes
![Page 35: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/35.jpg)
35
Data Acquisition
What choices need to be made?
Instrument setup
Divergence and receiving slit sizes
Theta-compensating divergence slit keeps irradiated area constant,But changes intensity distribution vs 2
![Page 36: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/36.jpg)
36
Data Acquisition
What choices need to be made?
Instrument setup
Divergence and receiving slit sizes
![Page 37: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/37.jpg)
37
Data Acquisition
What choices need to be made?
Instrument setup
Divergence and receiving slit sizes
![Page 38: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/38.jpg)
38
Data Acquisition
What choices need to be made?
Instrument setup
Divergence and receiving slit sizes
Use of monochromator changes polarization correctionin LP factor
Integrated intensities of Bragg reflections:
Ihkl = scale factor x mult factorhkl x LP x absorb factor xpref orient factorhkl x extinction factorhkl x | Fhkl | 2
![Page 39: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/39.jpg)
39
Data Acquisition
What choices need to be made?
Scan setup
Scan range
no. of reflections – want >5 x no. parameters refined wavelength dependent low angle reflections may not be useful due to
specimen configurationlarger inherent instrumental errorsextinction effects
![Page 40: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/40.jpg)
40
Data Acquisition
What choices need to be made?
Scan setup
Step size
sample dependent - peak widths need 5 observations across top of peak usually 0.01 - 0.05° 2
![Page 41: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/41.jpg)
41
Data Acquisition
What choices need to be made?
Scan setup
Step size
sample dependent - peak widths need 5 observations across top of peak usually 0.01 - 0.05° 2
Count time
longer times ––> higher intensities ––> greater precision at some point, little improvement in refinement process for longer count times
![Page 42: Data Acquisition What choices need to be made?](https://reader036.vdocument.in/reader036/viewer/2022062423/5681449e550346895db155bf/html5/thumbnails/42.jpg)
42
Data Acquisition
What choices need to be made?
Specimen type and preparation
Radiation source
Wavelength
Instrument geometry
Detector type
Instrument setup
Scan parameters
Choose according to objective(s) of experiment