Delta Undulator for Cornell Energy Recovery Linac

In anticipation of a new era of synchrotron radiation sources based on Energy Recovery Linac techniques we designed, built and tested a short undulator magnet prototype whose features make optimum use of the unique conditions expected in these facilities. The prototype has pure permanent magnet (PPM) structure with 24mm period, 5mm diameter round gap and is 30cm long. In comparison with conventional undulator magnets it has • Full X-ray polarization control. It may generate varying linear polarized as well as left and right circular polarized x-rays with photon flux much higher than existing Apple-II type devices. • 40% stronger magnetic field in linear and approximately 2 times stronger in circular polarization modes. This advantage translates into higher x-ray flux. • Compactness. The prototype can be enclosed in a ∼ 20cm diameter cylindrical vacuum vessel. These advantages were achieved through a number of non-conventional approaches. Among them is control of the magnetic field strength via longitudinal motion of the magnet arrays. The moving mechanism is also used for x-ray polarization control. The compactness is achieved using a recently developed permanent magnet soldering technique for fastening PM blocks. We call this device a ”Delta” undulator after the shape of it’s PM blocks. The presented article describes the design study, various aspects of the construction and presents some test results. PACS numbers: 85.70.-w, 41.60.-m, 07.85.Qe †Mail send to: A. Temnykh, Wilson Lab, Cornell University, NY 14850, USA E-mail [email protected] , tel. +1 607 255 4882, fax +1 607 255 8062