The design of a coded aperture mask for Prometheus I
Wooten, James Gregory
Haymes, Robert C.
Master of Science
A coded aperture mask has been designed for Prometheus I, a Rice University gamma-ray telescope sensitive to energies ranging from 0.03 MeV to 6.5 MeV. The mask will allow Prometheus I to record images at those energies. If it is successful, these will be the first astronomical MeV gamma ray images ever recorded. To create the mask, first a basic 9 x 7 uniformly redundant array was generated using the m-sequences method described by E. C. Fenimore (1983). A two by two mosaic of that pattern produced the final 18 x 14 array. The mask is passive rather than active; the opaque sections are two inches thick and made of tungsten. The distance from the center of one square to the center of an adjacent one is 5/8 inch, which is equal to the distance from the center of one detector element to a neighboring one. With 128 of the 252 mask elements transparent, the mask will have an open fraction of 50.7%. When it is installed on Prometheus I, the mask will be located 60 inches from the detector, giving the instrument an angular resolution of 28.6 arc minutes. Its fully coded field of view will be 5.4$\sp\circ$ and its partially coded field of view will be 16$\sp\circ$. The first flight of Prometheus I is scheduled for summer 1994.