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Collimating a Newtonian Scientifically
In 2003 my partner Kathleen, proposed a bungalow with a great view of the night sky. December 2005 and one year into telescopes, the optics of the length halved again 8” Cape-Newise got me tasting my own medicine unwittingly and gladly. The confident advertising style mirrored mine for Bailey designed hi-fi speakers, making 100 in the 70’s, exporting 30 to Germany. My approach has been that of being Isaac Newton through the ages, and after each advancement writing down the achievements at the eyepiece. The 3rd edition of March 2014 was still only 16 pages, 6 of which were the instructions and still are. 50 pages of interest were enabled by 2 months in a recliner chair waiting for surgery...
The Effect of Collimation on the Resolution and Peak-to-total Ratio of a NaI(T1) Crystal
Restricting the incident radiation to a small area of a Na(T1) scintillation crystal improves the resolution and peak-to-total ratio of the spectrometer. This effect was studied with a series of tapered lead collimators, all with the same apex but with differing apertures, in front of a 4 in. by 4 in. diameter NaI(T1) scintillation crystal. Sources of gamma rays with energies from 0.28 to 2.76 Mev were located at the apex of the taper. Optimum resolution of about 25 percent greater than broad-beam resolution was obtained with a 0.25-in. diameter aperture. Anomalous effects were observed with a smaller opening. (Author).
Gamma-ray Collimator Penetration and Scattering Effects
Expressions are developed which give the amount of unidirectional radiation from a distant radiation source passing through a cylindrical hole in a slab of material, including the amount of radiation which penetrates the edges of the hole, as a function of angle between the radiation direction and the axis of the hole. The modifications necessary for sources at finite distances are indicated. These functions are integrated over appropriate angles for distant line sources and for extended sources. It is shown that, to a first approximation, the results are the same as the geometrical aperture for a like diameter hole in a similar slab with one mean free path of material removed from each side. The effects due to scattering from the walls of the collimator are discussed and an approximate method of calculation is presented with results for a specific collimator.
