Anode Target
Definition
The metal block (commonly Cu, Mo or Rh) that electrons strike inside an X-ray tube to produce the X-ray beam. Choice of anode sets the K-alpha wavelength used for excitation.
- Common materials
- Copper (Cu), molybdenum (Mo), rhodium (Rh)
- Function
- Struck by electrons to generate the X-ray beam
- Sets
- The K-alpha wavelength used for excitation
- Used in
- XRD and XRF instruments
Common questions
Why does the anode material matter for forensic analysis?+
Each target metal emits characteristic K-alpha radiation at a fixed wavelength, so the choice determines which elements or crystal structures the instrument can resolve well, and a mismatch between target and sample can wash out peaks the examiner needs.
How is anode target choice different between XRD and XRF work?+
XRD commonly uses copper for its wavelength suited to common crystal lattice spacings, while XRF instruments often use rhodium because its spectrum keeps interference away from the elements typically screened for in trace and gunshot-residue work.
Related terms
- Bragg's Law
- nλ = 2d sin(θ). A monochromatic X-ray beam diffracted off the parallel lattice planes of a crystal produces constructive interference only at...
- Characteristic X-Rays
- Sharp emission lines produced when an inner-shell vacancy in an atom is filled by an outer electron. Their energies are element-specific (Moseley's...
- Continuous (Bremsstrahlung) Radiation
- Smooth background X-ray spectrum produced when high-energy electrons decelerate in the anode. Element-independent. The 'hump' under the characteristic lines.
- D-Spacing
- The perpendicular distance between adjacent parallel planes of atoms in a crystal lattice, measured in angstroms or nanometres. Each set of planes...
- EDXRF
- Energy-dispersive X-ray fluorescence. A solid-state detector resolves the entire emission spectrum at once by photon energy. Cheap, portable, faster.
- K-Alpha Line
- The characteristic X-ray emitted when an electron drops from the L-shell to fill a K-shell vacancy. Brightest line for most elements; the...
- WDXRF
- Wavelength-dispersive X-ray fluorescence. An analyser crystal disperses fluorescence by wavelength (Bragg's law again). Slower, costlier, much higher resolution.