DEVELOPMENT AND MANUFACTURE OF COLLIMATORS FOR GAMMA-RAY IMAGING

We report the development of very fine collimator slit patterns for ga mma ray imaging. Astronomical objects emitting gamma rays cannot be im aged in a classical way. However, it is possible to measure Fourier co mponents of the images by observing gamma ray sources through pairs of patterns of fine slits placed at a mutual distance of several meters. The finest pattern should have slits 50 mum wide at a pitch of 100 mu m. To achieve high contrast images, the slit geometry must meet high p recision goals. The absolute slit position accuracy must be on the ord er of a few micrometers within an area of 130 mm x 130 mm. The slit pa tterns have been realized by stacking long thin blades separated by sm all spacers. The application of flexible spacers and precision referen ce frames results in a high pitch accuracy. The spacer design was opti mized using finite-element analysis. The spacers were made via a multi step precision etching technique. Measurements on the full-size slit p atterns show low slit position errors.