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HESS Gamma-Ray Telescope Inaugurated This Week
Grandroyill writes "Most ground-based telescopes with lenses and mirrors are hindered by the Earth's nurturing, protective atmosphere that blurs images and scatters and absorbs light. But this telescope...actually requires the atmosphere to operate. As the gamma rays impact the upper atmosphere they produce air showers of high-energy particles. Adorned with 382 separate mirrors each 60 centimeters in diameter and equipped with a fast camera, the telescope records in detail the brief flashes of optical light, called Cherenkov light, created by the air shower particles. Great pic too!" Beautiful telescope. Kudos to the engineers.
These Telescopes measure gamma rays with energies above 40 GeV, far above enegies of nuclear decay (MeV range, a factor of 1000 less). The HESS project page contains more information, about the (cosmic) origin of these gamma rays.
One could measure the change in these isotopes when gamma rays hit them, thus measuring the gamma rays. Has anyone played with this?
You are talking about the nuclear "photoelectric" effect. It is in principle possible, but very inefficient (nuclei do not capture gamma rays very well). Actually this was initially researched by W. Gentner in the 1930ies in Heidelberg, where they now build the HESS telescope (among others).