  Calibration of X-ray detectors is very important to understand the
performance characteristics of the detectors and their variation with time and
changing operational conditions. This enables the most accurate translation of
the measurements to absolute and relative values of the incident X-ray photon
energy so that physical models of the source emission can be tested. It is a
general practice to put a known X-ray source (radio active source) in the
detector housing for the calibration purpose. This, however, increases the
background. Tagging the calibration source with the signal from a
simultaneously emitted charge particle (like alpha particle) can identify the
X-ray event used for calibration. Here in this paper, we present a new design
for an alpha-tagged X-ray source using Am^241 radio active source and describe
its performance characteristics. Its application for the upcoming Astrosat
satellite is also discussed.
