Wide dynamic range germanium detector for perturbation crystallography

Area of Science:

• Materials Science
• Crystallography
• Photonics

Background:

• X-ray diffraction (XRD) requires sensitive detectors for analyzing crystal structures.
• Existing detectors often have limitations in dynamic range, energy efficiency, or response time.
• Germanium-based photodetectors offer potential advantages over silicon for specific applications.

Purpose of the Study:

• To evaluate a cooled germanium photodetector for X-ray diffraction applications.
• To assess the detector's performance across a wide dynamic range and different operating modes.
• To demonstrate its utility in time-resolved crystallography and perturbation studies.

Main Methods:

• Testing a cooled germanium photodetector in both photon-counting and current modes.
• Measuring detector linearity at low (< 10^5 photons s^-1) and high (> 10^5 photons s^-1) photon fluxes.
• Evaluating the detector's response time (approx. 1 µs) and efficiency at energies > 25 keV.
• Coupling the detector with a lock-in amplifier for perturbation crystallography experiments.

Main Results:

• The germanium detector demonstrated a broad dynamic range from < 1 to 10^9 photons s^-1.
• High linearity was observed in both photon-counting (low flux) and current (high flux) modes.
• Germanium exhibited superior efficiency above 25 keV compared to silicon detectors.
• The detector's 1 µs response time proved suitable for time-resolved measurements.

Conclusions:

• The cooled germanium photodetector is a versatile and high-performance tool for X-ray diffraction.
• Its capabilities are well-suited for perturbation crystallography, as shown by measuring electric-field-induced shifts in LiNbO3.
• The detector's performance validates its use in advanced structural analysis requiring broad dynamic range and fast response.