ASTM E1172-87(2003)

Standard Practice for Describing and Specifying a Wavelength-Dispersive X-Ray Spectrometer

SIGNIFICANCE AND USE
This practice describes the essential components of a wavelength-dispersive X-ray spectrometer. This description is presented so that the user or potential user may gain a cursory understanding of the structure of an X-ray spectrometer system. It also provides a means for comparing and evaluating different systems as well as understanding the capabilities and limitations of each instrument.
SCOPE
1.1 This practice covers the components of a wavelength-dispersive X-ray spectrometer that are basic to its operation and to the quality of its performance. It is not the intent of this practice to specify component tolerances or performance criteria, as these are unique for each instrument. The document does, however, attempt to identify which of these are critical and thus which should be specified.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific safety hazard statements are given in 5.3.1.2 and 5.3.2.4, and in Section 7.
1.3 There are several books and publications from the National Institute of Standards Technology and the U.S. Government Printing Office which deal with the subject of X-ray safety. Refer also to Practice E416.

General Information

• Status: Historical
• Publication Date: 09-Jun-2003
• ICS: 17.180.30 - Optical measuring instruments
• Technical Committee: E01 - Analytical Chemistry for Metals, Ores, and Related Materials
• Drafting Committee: E01.20 - Fundamental Practices

Relations

• Replaces: ASTM E1172-87(2001) - Standard Practice for Describing and Specifying a Wavelength-Dispersive X-Ray Spectrometer
• Effective Date: 10-Jun-2003
• Replaced By: ASTM E1172-87(2011) - Standard Practice for Describing and Specifying a Wavelength-Dispersive X-Ray Spectrometer
• Effective Date: 15-Nov-2011
• Referred By: ASTM E539-19 - Standard Test Method for Analysis of Titanium Alloys by Wavelength Dispersive X-Ray Fluorescence Spectrometry
• Effective Date: 10-Jun-2003
• Referred By: ASTM D7085-04(2018) - Standard Guide for Determination of Chemical Elements in Fluid Catalytic Cracking Catalysts by X-ray Fluorescence Spectrometry (XRF)
• Effective Date: 10-Jun-2003
• Referred By: ASTM F2063-18 - Standard Specification for Wrought Nickel-Titanium Shape Memory Alloys for Medical Devices and Surgical Implants
• Effective Date: 10-Jun-2003

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E1172–87(Reapproved 2003)
Standard Practice for
Describing and Specifying a Wavelength-Dispersive X-Ray
Spectrometer
This standard is issued under the fixed designation E1172; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E416 Practice for Planning and Safe Operation of a Spec-
trochemical Laboratory
1.1 This practice covers the components of a wavelength-
E876 Practice for Use of Statistics in the Evaluation of
dispersive X-ray spectrometer that are basic to its operation
Spectrometric Data
and to the quality of its performance. It is not the intent of this
practice to specify component tolerances or performance
3. Terminology
criteria, as these are unique for each instrument.The document
3.1 For terminology relating to X-ray spectrometry, refer to
does, however, attempt to identify which of these are critical
Terminology E135.
and thus which should be specified.
1.2 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
4.1 This practice describes the essential components of a
responsibility of the user of this standard to establish appro-
wavelength-dispersive X-ray spectrometer. This description is
priate safety and health practices and determine the applica-
presented so that the user or potential user may gain a cursory
bility of regulatory limitations prior to use. Specific safety
understanding of the structure of an X-ray spectrometer sys-
hazard statements are given in 5.3.1.2 and 5.3.2.4, and in
tem. It also provides a means for comparing and evaluating
Section 7.
different systems as well as understanding the capabilities and
1.3 There are several books and publications from the
2 limitations of each instrument.
National Institute of Standards and Technology and the U.S.
3,4
Government Printing Office which deal with the subject of
5. Description of Equipment
X-ray safety. Refer also to Practice E416.
5.1 Types of Spectrometers—X-ray spectrometers can be
classified as sequential, simultaneous, or a combination of
2. Referenced Documents
these two (hybrid).
2.1 ASTM Standards:
5.1.1 Sequential Spectrometers—The sequential spectrom-
E135 Terminology Relating to Analytical Chemistry for
eter disperses and detects secondary X rays by means of an
Metals, Ores, and Related Materials
adjustable monochromator called a goniometer. In flat-crystal
instruments, secondary X rays are emitted from the specimen
and nonparallel X rays are eliminated by means of a Soller slit
This practice is under the jurisdiction of ASTM Committee E01 on Analytical
(collimator). The parallel beam of X rays strikes a flat
Chemistry for Metals, Ores and Related Materials and is the direct responsibility of
analyzing crystal which disperses the X rays according to their
Subcommittee E01.20 on Fundamental Practices.
wavelengths. The dispersed X rays are then measured by
Current edition approved June 10, 2003. Published July 2003. Originally
approved in 1987. Last previous edition approved in 2001 as E1172 – 87(2001). suitable detectors. Adjusting the goniometer varies the angle
DOI: 10.1520/E1172-87R03.
between the specimen, crystal, and detector, permitting the
NBS Handbook, X-Ray Protection, HB76, and NBS Handbook 111, ANSI
measurement of different wavelengths and therefore different
N43.2-1971, available from National Institute of Standards and Technology,
elements. Sequential instruments containing curved-crystal
Gaithersburg, MD 20899.
Radiation Safety Recommendations for X-Ray Diffraction and Spectrographic
optics are less common. This design substitutes curved for flat
Equipment, No. MORP 68-14, 1968, available from U.S. Department of Health,
crystals and entrance and exit slits for collimators.
Education, and Welfare, Rockville, MD 20850.
4 5.1.2 Simultaneous Spectrometers—Simultaneous spec-
U.S. Government Handbook 93, Safety Standards for Non-Medical X-Ray and
trometers use separate monochromators to measure each ele-
Sealed Gamma-Ray Sources, Part 1, General, Superintendent of Documents,
available from U.S. Government Printing Office, Washington, DC 22025.
ment. These instruments are for the most part of fixed
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Withdrawn. The last approved version of this historical standard is referenced
the ASTM website. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1172–87 (2003)
configuration, although some simultaneous instruments have a 5.3.1.2 X-ray tubes are rated according to maximum power,
scanning channel with limited function. A typical monochro- maximum current, and typical power settings. These should be
mator consists of an entrance slit, a curved (focusing) analyz- specified by the manufacturer. (Warning—It is important that
ing crystal, an exit slit, and a suitable detector. Secondary X the user be protected from exposure to harmful X rays.
rays pass through the entrance slit and strike the analyzing
Standardwarninglabelsshallwarntheuserofthepossibilityof
crystal, which diffracts the wavelength of interest and focuses exposure to X rays. Safety interlock circuits (7.3) shall shut
it through the exit slit where it is measured by the detector.
down power to the X-ray tube whenever protective shielding is
Some simultaneous instruments use flat crystals, but this is less removed.)
common.
5.3.2 High Voltage Generator—The high voltage generator
5.1.3 Hybrid Spectrometers—Hybrid spectrometers com-
supplies power to the X-ray tube. Its stability is critical to the
bine features found in sequential and simultaneous instru-
precision of the instrument.
ments. They have both fixed channels and one or more fully
5.3.2.1 The dc voltage output of the high voltage generator
functional goniometers.
istypicallyadjustablewithintherangeof10to100kV.Voltage
5.2 Spectrometer Environment:
stability, drift with temperature, and voltage ripple should be
5.2.1 Temperature Stabilization—A means for stabilizing
specified. Voltage repeatability should be specified for a
the temperature of the spectrometer shall be provided. The
programmable generator, which is frequently used in sequen-
degree of temperature control shall be specified by the manu-
tial systems.
facturer. Temperature stability directly affects instrument sta-
5.3.2.2 The current to the X-ray tube is typically adjustable
bility.
within the range of 5 to 100 mA. Current stability and thermal
5.2.2 Optical Path:
drift should be specified. Current repeatability should be
5.2.2.1 Avacuum path is generally preferred, especially for
specified for programmable generators.
the analysis of light elements (long wavelengths). Instruments
5.3.2.3 Voltage and current recovery times should be speci-
capable of vacuum operation shall have a vacuum gage to
fiedforprogrammablegenerators.Thesoftwareroutineswhich
indicate vacuum level. An airlock mechanism shall also be
control the generator must delay measurement until the gen-
provided to pump down the specimen chamber before opening
erator recovers from voltage or current changes.
it to the spectrometer. Pump down time shall be specified by
5.3.2.4 Input power requirements should be specified by the
the manufacturer.
manufacturer so the proper power can be supplied when the
5.2.2.2 A helium path is recommended when light element
instrument is installed. Maximum generator power output
analysis is required and the specimen (such as a liquid) would
should be stated. (Warning—Safety is a primary concern
be disturbed by a vacuum. Instruments equipped for helium
when dealing with high voltage. Safety interlock circuits (7.3)
operation shall have an airlock for flushing the specimen
and warning labels shall protect the user from coming in
chamber with helium before introducing the specimen into the
contact with high voltage. The interlock system shall shut
spectrometer. Helium flushing time shall be specified by the
down the generator when access to high voltage is attempted.
manufacturer. The manufacturer shall also provide a means for
CircuitsshallbeprovidedtoprotecttheX-raytubefrompower
accurately controlling the pressure of the helium within the
and current overloads.)
spectrometer.
5.3.3 Water Cooling Requirements—The X-ray tube and
5.2.2.3 An air path is an option when the instrument is not
some high voltage generators require cooling by either filtered
equipped for vacuum or helium operation. Light element
tap water or a closed-loop heat exchanger system.
analysis and some lower detection limits are sacrificed when
5.3.3.1 The manufacturer shall specify water flow and
operating with an air optical path.
quality requirements.
5.3 Excitation—A specimen is excited by X rays generated
5.3.3.2 To protect components from overheating, an inter-
by an X-ray tube which is powered by a high voltage generator
lock circuit that monitors either water coolant flow or tempera-
and is usually cooled by circulating water. The intensity of the
ture or both shall shut down power to the X-ray tube whenever
various wavelengths of X rays striking the specimen is varied
these requirements are not met.
bychangingthepowersettingstothetubeorbyinsertingfilters
into the beam path. 5.3.3.3 Water purity is especially critical in cathode-
grounded systems since this requires the coolant to be noncon-
5.3.1 X-Ray Tube—The X-ray tube may be one of two
ducting. A closed-loop heat exchanger is necessary to supply
types; end-window or side-window. Depending upon the in-
high purity cooling water. A conductivity gage shall monitor
strument, either the anode or the cathode is grounded. Cathode
water coolant purity in these systems and shall shut down
grounding permits the window of the X-ray tube to be thinner
power to the X-ray tube when coolant purity is below require-
and thus affords more efficient transmittance of the longer
ments.
excitation wavelengths.
5.3.1.1 X-ray tubes are produced with a variety of targets. 5.3.4 Primary Beam Filter—A primary beam filter is com-
The choice of the target material depends upon the wave- monly used in sequential spectrometers to filter out the
lengths that require excitation. X rays from certain materials characteristic emissions from the X-ray tube’s target when
excite the longer wavelengths more efficiently. Other materials these emissions might interfere with the measurement of an
are better for exciting the shorter wavelengths. Generally the analyte element. Primary beam filters are also useful for
choice of target material is a compromise. lowering the background in the longer wavelength portion of
E1172–87 (2003)
the spectrum. This serves to increase the peak to background 5.6.1.1 Soller slits may be present in several locations. A
ratio and offers greater detection of those longer wavelength X primarySollerslitisalwayspresentintheopticalpathbetween
rays.
the specimen and the analyzing crystal. Auxiliary slits may be
5.3.4.1 Primary beam filters are made of several different
installed at the detector windows between the detector and the
metals (depending upon the X-ray tube’s target) and come in analyzing crystal.
various thicknesses. The manufacturer should specify the type,
5.6.1.2 It is common for a sequential spectrometer to have
thickness, and location of the primary beam filter.
both coarse and fine primary Soller slits, installed and mounted
5.4 Sample Positioning—The process of positioning a
in a changer mechanism. Better resolution is achieved with a
specimen in a spectrometer for analysis involves several
fine slit, but at the expense of a loss of intensity.
components; the specimen holder, the specimen changer, and
5.6.1.3 The manufacturer should specify the location and
the specimen rotation mechanism (spinner).These components
plate spacing of all Soller slits installed in a particular
contribute collectively to the reproducibility of positioning the
instrument. A means shall be provided for adjusting (peaking)
specimen in the optical path and thus, to instrument precision.
each slit.
The design of these components should therefore be regarded
5.6.2 Entrance and Exit Slits—Both entrance and exit slits
critically.
are required in a curved-crystal spectrometer. The curved
5.4.1 Reproducibilityofthedistancebetweenthefaceofthe
crystal establishes a focusing circle that is similar to the
specimen and the window of the X-ray tube is especially
Rowland circle defined by a grating in an optical emission
critical and should be specified by the manufacturer.
spectrograph. In an X-ray spectrometer, however, proper fo-
5.4.2 The spinner rotates the specimen while it is being
cusingrequiresthatbothslitsnotonlybeonthefocusingcircle
exposed to the X-ray beam and thus helps to minimize the
but also have identical chordal distances from the slits to the
influence of surface defects and specimen inhomogeneity on
crystal. A detector is aimed at the crystal through the exit slit.
analytical results.
5.6.2.1 The manufacturer should specify the size of the
5.4.3 Imperfections in the surface of the specimen have the
entrance and exit slit for each monochromator and shall
greatest effect on analytical results in spectrometers with a
shallow angle of irradiation or take-off angle. The manufac- provide adjustments to peak each monochromator. Depending
upon the manufacturer, peaking may involve movement of the
turer shall specify these angles.
crystal, the exit slit, or both.
5.4.4 Other important specifications include maximum
specimen size (thickness and diameter) and the specimen
5.6.3 Apertures—In flat-crystal spectrometers, an aperture
rotation speed (if the instrument is equipped with a spinner).
is placed at the point in the optical path where the secondary X
5.5 Dispersion—The analyzing crystal is the dispersive
rays exit the specimen. The aperture limits the area of the
device in a wavelength-dispersive X-ray spectrometer. Various
specimen seen by the detector. In some instruments, the size of
crystals having a variety of interplanar spacings are used to
this aperture is fixed, but in most it can be varied, either by
disperse the specimen’s characteristic wavelengths.
manual replacement or a mechanical changer. The manufac-
5.5.1 Sequentialspectrometersmaycontainseveraldifferent
turer should specify the sizes of any apertures inst
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