= Diffraction thermal-expansion thermometry
{title2=$d(2\theta)/dT=-2\alpha_L\tan\theta$}
At fixed radiation <wavelength>, differentiating <Bragg's law> for an isotropically expanding cubic specimen gives the displayed angular sensitivity, with angles in radians. Accurate <temperature> inference requires a calibrated lattice-parameter versus <temperature> curve, stable <wavelength> and angular zero, and separation of thermal expansion from <stress> or composition shifts. Counting statistics can permit centroid precision finer than the observed diffraction-line width.
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