G. P. Garmire

X-Ray Telescope For Sounding Rocket-Borne Observations

The X-ray astronomy group at Caltech has developed an X-ray telescope for sounding rocket-borne observations above the Earths atmosphere. The telescope consists of a pair of nested aluminum mirrors, 40.64 cm and 31.65 cm in diameter with a total geometrical collecting area of 200 cm2. The mirror surfaces have been machined at the Y-12 plant of the Oak Ridge National Laboratory using an air bearing spindle lathe and a diamond tool. Design and performance characteristics will be presented. The design of the next generation telescope of 91 cm diameter will be presented.

Experiments With Diamond-Turned Metal X-Ray Mirrors

The following report summarizes our experiences in attempting to make Wolter Type I X-ray telescope mirrors using the diamond-turning facilities at the Oak Ridge Y-12 Laboratory.

DISCUSSION PAPER: X-RAY ASTRONOMY.

The unexpected discovery of x-ray emission from an object outside of the solar system by Giacconi, Gursky, Paolini and Rossi in 1962 during a rocket flight, came as a great surprise to the scientific world. The fact that the first object discovered outshone the quiet Sun at energies greater than five kiloelectron volts (kev) was even more startling. In the ensuing five years since this discovery, a great deal has been learned about these sources. It is generally agreed that the emission of x-rays by an object signifies that either the object is being illuminated by x-rays and is fluorescing or else the object contains electrons with energies greater than the x-ray energies observed. The exact details of the emission process have been used to classify the radiation into several different types, each yielding spectra of different shapes when intensity is plotted against x-ray energy. The most promising processes currently envisaged to exist in nature are thermal bremsstrahlung from a hot plasma, blackbody radiation from a very hot star or neutron star, inverse Compton scattering of photons by high-energy electrons, and magnetic bremsstrahlung from high energy (h 1 Bev) electrons in a magnetic field. Within the last two years a number of spectral observations have been made by detectors flown on rockets and high altitude balloons by a large number of different groups. At present no spectra corresponding to blackbody radiation have been observed out of a total of about five sources studied. The most brilliant source, Sco X-1, appears to have a spectrum corresponding to a plasma with a temperature of about 60 million degrees (I, (E)deE = Ke-E/tT dE/EVT). On the other hand, the Crab Nebula, which is the remnant of a supernova explosion in A.D. 1054, appears to be radiating with a power law spectrum, (I,(E)dE = KE-YdE). Unfortunately, the emission process may be rather complex, combining regions of different bmperatures within a single object, as proposed by Morrison and Sartori (1967). 0. P. Manly (1966) has pointed out that magnetic bremsstrahlung may produce a power law spectrum or a spectrum resembling a hot plasma, depending on the form of the electron spectrum. Tucker and Gould (1966) have shown that a hot plasma composed of the typical cosmic abundance will show spectral lines in the x-ray range. These lines are weak, and have not yet been observed. The detection and measurement of the relative intensity and profiles of these lines will clearly provide unambiguous identification of the emission mechanism.