1. X-ray detectors single photon detectors
scintillation detectors
(gas-filled) proportional counters
semiconductor detectors
linear (position-sensitive) detectors
gas-filled (wire) detectors
charge-coupled devices (CCD’s)
area detectors
2-D wire detectors
CCD area detectors
X-ray film

2. Gas-filled proportional counter
A proportional counter consists of the following main components:
a gas-filled cylindrical envelope (usually Ar, Kr, or Xe)
a central anode wire
a grounded coaxial cylinder (the cathode)
an X-ray transparent window
Cullity (cathode at high voltage?)
Klug & Alexander (grounded cathode)

4. Gas-filled proportional counter
When an X-ray photon ionizes a gas molecule, the ejected photoelectrons are accelerated to the anode
low voltages – photoelectrons don’t have enough energy to ionize other molecules
intermediate voltages – gas amplification occurs (photo-electrons ionize gas molecules on the way to the anode
high voltages – discharge occurs throughout the gas volume

5. The scintillation detector
most common detector in materials analysis by X-ray diffraction
the detector has two basic elements:
a crystal that fluoresces visible light (scintillates) when struck by X-ray photons
a photomultiplier tube (PMT) that converts the light to electrical pulses
gain ~5 per dynode (total gain with ten dynodes is  107)
NaI(Tl) scintillator (very sensitive to moisture) – emits
around 4200Å
CsSb photocathode – ejects electrons

6. Semiconductor detectors
Semiconductor detectors are solid-state proportional counters – each photon produces electron-hole (e/h) pairs
The detection of e/h pairs would not be possible if the semiconductor has free carriers (n-type or p-type) so it must be intrinsic – this can be done by “lithium drifting” p n p n
apply V
p--Si
heat
Li+ i
lithium
lightly p-doped
Si has Li plated
heat to have the Li diffuse
apply a reverse bias to cause Li+ ions to “drift
a wide central intrinsic region is formed

7. Random aspects of semiconductor detectors
originally: Si(Li) and Ge(Li) – “silly” and “jelly”
now intrinsic Si and intrinsic Ge are available (Ge better due to higher absorption and better energy resolution)
energy resolution about 2%
small signal requires a charge-sensitive preamp integrated with the detector
due to thermal e/h generation and noise in the preamp, cooling to 77K is needed
new detectors use Si p-i-n photodiodes and large bandgap materials (CdTe and CdZnTe) for room-temperature operation

8. Random aspects of semiconductor detectors
originally: Si(Li) and Ge(Li) – “silly” and “jelly”
now intrinsic Si and intrinsic Ge are available (Ge better due to higher absorption and better energy resolution)
energy resolution about 2%
small signal requires a charge-sensitive preamp integrated with the detector
due to thermal e/h generation and noise in the preamp, cooling to 77K is needed
new detectors use Si p-i-n photodiodes and large bandgap materials (CdTe and CdZnTe) for room-temperature operation

9. Diffractometer operation
The steps taken in diffractometer operation depends on whether the system is being used for powder analyses or single crystal analyses

10. Neutrons and electron diffraction
Louis de Broglie: h= ×10−34 J.s

11. X-ray Fluorescence Spectrometry (XRF)

12. Energy dispersive spectrometry
schematic arrangement of EDX spectrometer

14. Wavelength dispersive spectrometry (WDS)

16. Crystals The desirable characteristics of a diffraction crystal are:
High diffraction intensity
High dispersion
Narrow diffracted peak width
High peak-to-background
Absence of interfering elements
Low thermal coefficient of expansion
Stability in air and on exposure to X-rays
Ready availability
Low cost

17. Normally, the maximum achievable θ angle in a WDS system is about 73◦
Normally, the maximum achievable θ angle in a WDS system is about 73◦. Thus, the maximum λ of characteristic X-rays being diffracted is about 1.9d of the analyzing crystal.

18. Crystals with simple structure tend to give the best diffraction performance. Crystals containing heavy atoms can diffract well, but also fluoresce themselves, causing interference. Crystals that are water-soluble, volatile or organic tend to give poor stability.
Commonly used crystal materials include LiF (lithium fluoride), ADP (ammonium dihydrogen phosphate), Ge (germanium), graphite, InSb (indium antimonide), PE (tetrakis-(hydroxymethyl)-methane: penta-erythritol), KAP (potassium hydrogen phthalate), RbAP (rubidium hydrogen phthalate) and TlAP (thallium(I) hydrogen phthalate). In addition, there is an increasing use of "layered synthetic microstructures", which are "sandwich" structured materials comprising successive thick layers of low atomic number matrix, and monatomic layers of a heavy element. These can in principle be custom-manufactured to diffract any desired long wavelength, and are used extensively for elements in the range Li to Mg.