State-of-the-art devices for compact light sources Finn OShea RadiaBeam Technologies October 15, 2015 Cryogenic Short Period Undulators Why short periods? Why cryogenics? A brief update of CPMUs being produced today. RadiaBeams CPMU Design philosophy Project goals Textured Dysprosium (or not) Why FACET? F. O'Shea - FACET-II Science Opportunities Workshop - Oct 14, Outline The obvious answer: The wavelength of the radiation produced gets shorter with period length. Either: Shorter accelerator to reach given wavelength, Longer wavelength reach of existing accelerator. Opens up option for doing beam gymnastics at lower energy. But K is going to get smaller as the period length shrinks Direct reduction in K Indirect loss of field strength from the smaller magnets dB r /dT ~ -0.1%/C Cooling allows you to get back 10+% of the field strength. Why short periods? Why Cryo? F. O'Shea - FACET-II Science Opportunities Workshop - Oct 14, The not so obvious answer Aggressive designs have working point deep in the 2 nd quadrant, increasing the risk of demagnetization Demagnetization happens when the working point goes below the knee: Cryogenics moves the knee left. dH cj /dT ~ -0.5%/C H cj can get 4-6x larger with typical designs This leads to reduced risk of demagnetization Local energy deposition raises the temperature of the grain. Makes shorter periods even possible. Why short periods? Why Cryo? F. O'Shea - FACET-II Science Opportunities Workshop - Oct 14, Vacuumschmeltze has made its PrFeB material a standard product. Neomax has made a PrFeB version that can be baked (lower Br, though). ESRF has built several NdFeB undulators and is now planning on PrFeB devices. HZB is building two PrFeB undulators; one for Hamburg, one for their ring. NSLS-II has built a few prototypes. Spring-8 has built an NdFeB undulator SOLEIL has built and installed a PrFeB undulator, building one more Danfysik built an NdFeB undulator for Diamond. Most of these undulators are u >= 14 mm RadiaBeam is working on building a 7 mm period undulator F. O'Shea - FACET-II Science Opportunities Workshop - Oct 14, Current Work on CPMU The original goal was to make an undulator to take advantage of textured dysprosium (TxDy). When you get to short periods (