Synchrotron radiation sources have sufficient brightness to permit the construction of aberration free diffractometers with perfectly symmetric instrument resolution functions. This paper outlines the development of one such general purpose instrument. It combines X-ray optical and mechanical simplicity with versatility, high speed and adequate resolution for general purpose measurements in both angle scanning and energy scanning data collection modes of operation. These ideas were developed as part of a long term collaboration with W. Parrish of I.B.M. San Jose at the Stanford Synchrotron Radiation Facility and an instrument with identical X-ray optics has been avairable for users at Daresbury Laboratory for several years.
