QE: Quantum Efficiency
The quantum efficiency (QE) is the fraction of incident photons registered by a detector. For an ideal detector, this is 100% (every incoming photon results in a single count). In reality, however, no detector is 100% efficient. If, for instance, the detector is 70% efficient, then every 100 photons would result in 70 counts. The QE is a strong, highly-structured function of energy for both Chandra detectors, ACIS and HRC.
In the Chandra Calibration Database (CALDB), the QE of the detectors is divided into:
- the QE file: a mean curve (vs. energy)
- the quantum efficiency uniformity (QEU) file: a map of the deviations across the face of the detector