Variable-period undulators as synchrotron radiation sources

A concept for variable-period undulators for the production of synchrotron radiation from both medium- and high-energy storage rings is described. This concept is based on a staggered array of permeable poles placed in a magnetic solenoid that produces a longitudinal field. The concept permits variations in the short magnetic period of the undulator of as much as 100%. The unique capabilities of such undulators will allow them to be tuned by the variation of the period length and of the solenoid field. The device can be operated at either constant flux or constant power, independent of X-ray energy. It is expected that the new concept will have a major impact on the production and applications of X-rays because of the inherent simplicity and flexibility of the design and the absence of radiation damage. Analyses of the magnetic and mechanical design concepts are presented.