Hard X-ray Telescope (HXT)
The Hard X-ray Telescope (HXT) is a separate telescope from the Soft X-ray Telescope (SXT), and will be sensitive to higher-energy light (or light with shorter wavelength) than the SXT. Both the X-ray Microcalorimeter Spectrometer (XMS) and X-ray Grating Spectrometer (XGS) use light that enters through the SXT, while the HXT has a separate detector and mirror system. The specific implementation of the HXT has yet to be selected.
The HXT, like the SXT, will have a set of nested, grazing-incidence mirrors (see SXT page for more on grazing-incidence X-ray mirrors), but the diameter of the largest shell will only be 0.7 meters, smaller than the SXT mirrors.
One of the Swift CZT detector modules. The Constellation-X HXT will likely use CZT detectors, but the exact implementation has not been selected yet.
The photons that enter the HXT mirrors will be focussed onto a semi-conductor detector, likely made of cadmium-zinc-telluride (or CZT). When an X-ray interacts with a semiconductor, it causes an electron to be knocked off of an atom. When that electron is knocked free, an electric current will form if the detector has a voltage applied to it. This is the type of detector used on the Swift Burst Alert Telescope.
