D. P. Mitchell

A graphite crystal polarimeter for stellar X-ray astronomy.

The first crystal x‐ray polarimeter to be used for x‐ray astronomy is described. Polarization is measured by modulation of the x rays diffracted at an average 45° glancing angle from large, curved graphite crystal panels as these rotate about an axis parallel to the incident x‐ray flux. Arrangement of the crystal panels, the design of the detector, and the signal‐processing circuitry were optimized to minimize systematic effects produced by off‐axis pointing of the rocket and cosmic ray induced events. The in‐flight performance of the instrument in relation to the observed background signal is discussed.

Regulator Systems for Electromagnets

A regulator for maintaining constant, to better than 0.1 percent over long periods, the magnetic field of large (100 kw) electromagnets is described. This consists of two basic components: (1) A vacuum tube voltage regulator which compensates for rapid changes in voltage and thus anticipates the change in current which would result. (2) A current actuated element arranged so as to alter the operating point of the voltage regulator in order to compensate for slow changes in current due to changes in the temperature of the windings. Very rapid regulator action is secured with no drift or hunting to the limit specified.

One‐dimensional focusing x‐ray telescope for stellar x‐ray astronomy

A one‐dimensional x‐ray telescope of the Kirkpatrick–Baez design is described. The instrument consists of a grazing‐incidence x‐ray telescope and a multiwire proportional counter. The optics were provided with a gold reflecting surface to yield an energy response from below 0.25 to above 4.0 keV. The angular resolution of the system is 6′×9.5° over a 1.1°×9.5° field of view.