Generation of Soft X-Ray/VUV Photons with a Hybrid/Bias Micropole Undulator on the LLNL Linac

The recently introduced class of micropole undulators, i.e., undulators with submilli-meter periods, promises a wide variety of useful applications in x-ray science and technology. One of the most important of these could turn out to be the efficient generation of highly coherent soft x rays on economical low-energy storage rings or linacs. Over the last year and a half, an intensive experimental effort has been in progress at the Lawrence Livermore National Laboratory (LLNL) to characterize the radiation emitted on a linac by a novel hybrid/bias micropole undulator fabricated at the Stanford Synchrotron Radiation Laboratory. In this initial report, the properties of this new 706-μm-period insertion device and its generation of 66-eV soft x rays on the LLNL linac are described. Although in the present experiment power levels of a fraction of a picowatt at linac currents of several tens of picoamperes were generated, this was in agreement with theoretical predictions. Operation of our prototype device on a higher energy machine at currents of several milliamperes could consequently be expected to produce milliwatt levels of soft x-ray output, making it an x-ray source potentially competitive with bending magnets on high-energy storage rings.