We demonstrate a photodetector sensitive to both optical and x-ray picosecond pulses based on our in-house grown cadmium magnesium telluride (Cd,Mg)Te single crystal. Specifically, we developed In-doped Cd0.96Mg0.04Te material and discuss its femtosecond optical photoresponse, as well as the detector performance, such as <100-pA dark current and up to 0.22-mA/W responsivity for 780-nm wavelength optical radiation. The detector exposed to Ti fluorescence (K alpha) x-ray pulses at 4.5 keV, generated by a free-electron laser beam with the central energy of 9.8 keV and <100 fs pulse width, exhibited readout-electronics-limited 200-ps full-width-at-half-maximum photoresponse, demonstrating that it is suitable for coarse timing in free-electron laser x-ray/optical femtosecond pump–probe spectroscopy applications.

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Existing COTS inorganic scintillators all have the characteristic of being very good at certain desirable properties, but not sufficient at other desirable properties for HEP. The demand for suitable scintillators (with regards to both scintillation detector properties and suitable pricing), to be used for modern intensities frontier (Mu2e-II), energy frontier (High luminosity large hadron collider) and future e+e- collider projects (aimed as Higgs bosons factory, such as the International Linear Collider (ILC) and the Future Circular Collider (FCC) are putting even higher challenges on crystal scintillators. In this work, we report the development of a novel high-performance scintillators that can address the issues associated with existing scintillators, the activator doped Hg2Br2. Initial results are very encouraging on the detection of gamma and alpha particles using a solid-state photomultiplier (SSPM). The responses have been stable and repeatable. Hg2Br2 also has many advantages over existing COTS scintillators such as: high density, bright, fast, good energy resolution, no intrinsic radiation, radiation hard and cost-effectiveness. We present here why Hg2Br2 is the next generation scintillator for high energy physics experiments as well as other scientific and imaging applications such as planetary science and medical imaging.

We present a photodetector capable of detecting both optical and x-ray picosecond pulses, based on our in-house grown cadmium magnesium telluride (Cd,Mg)Te single crystals. We focused on a specific Cd0.97Mg0.03Te, In-doped crystal composition, because of its bandgap suitable for 800-nm-wavelength light detection and a single-picosecond optical photoresponse. The detector was fabricated as a planar metal-semiconductor-metal structure with interdigitated electrodes and exhibited a linear, Schottky-free, current-voltage characteristics with <40-pA dark current and up to 20-mA/W responsivity. The detector temporal resolution was measured to be ~200 ps full-width-at-half-maximum transient, in response of ~100-fs-wide pulses consisting of either optical (800 nm wavelength) or X-ray (4.5 keV) photons and was limited by the detector housing and 15-GHz bandwidth of the readout oscilloscope. The latter demonstrates the detector is suitable for coarse timing in X-ray free-electron laser/optical femtosecond pump-probe spectroscopy applications. We also demonstrated that due to its very high stopping power, the Cd0.97Mg0.03Te detector responded well to various nuclear gamma sources with energy ranging from 59.6 keV to 660 keV.