Design and prototyping of sub-millimeter-period undulators for free electron laser

Official URL: https://risc01.sabanciuniv.edu/record=b2579526_(Table of contents)

The invention of the optical microscope in the 17th century shed light on the world of microorganisms, and later on, the invention of electron microscopes in 1931 opens up the world of structures in sub-nanometer dimensions. However, another but more powerful tool, Free Electron Laser (FEL), was invented in 1971 by John Madey. FEL shed light on a world, which is at the same time ultra-small (below 100 nm) and ultra-fast (down to fs), such as the hydrogen transfer time of the molecules (~1 ns), the spin precession time (~10 ps) and computing time (~1 ns). In a typical FEL, a beam of electrons is accelerated to almost the speed of light in an electron accelerator. E-beam then passes through an undulator; an insertion device consists of two parallel arrays of magnets with alternating polarity, facing each other with an air gap in between. Due to the alternating pattern of the magnetic field, electrons follow a sinusoidal path instead of going straight, which radiates energy. A Free Electron Laser generates tunable, coherent, high-power radiation, currently spanning wavelengths from millimeter to x-ray (XFEL). One of the critical parameters of the XFEL is the undulator period which has a direct effect on the x-ray radiation. The current state of the art of XFEL'S; LCLS/SLAC uses an undulator period of 3 cm and creates an output radiation wavelength down to 1.5 A using an e-beam with the energy of ~14 GeV. However, this kind of high-energy e-beam could only be generated on gigantic accelerator facilities. Reducing the undulator period from 3 cm to 300 μm (short-period) would reduce the required e-beam energy to 1.4 GeV. Consequently, more compact e-beam sources could be used and make XFELs readily available for special applications. In a different perspective, short-period undulators would generate higher energy radiation when coupled with high-energy electron accelerators, such as gamma rays, which would pave the way to discoveries in Science. In this study, sub-millimeter-period Undulators will be designed and prototyped. Micron size magnets will be synthesized by using e-beam evaporation, triode sputtering, photo, and e-beam lithography. The produced micro magnets will be assembled into an undulator after rigorous modeling. Also, advanced synthesized micro-magnets could be used as the building blocks of the next generation of magnetic micro-tools. The project's ultimate goal would be testing the undulator in a running XFEL.