LBNL, Berkeley, California, USA
UCLA, Los Angeles, California, USA
POSTECH, Pohang, Kyungbuk, Republic of Korea
We report on the possibility of constructing an infrared FEL by combining a novel design super-conducting undulator developed at LBNL with the high brightness beam from the APEX injector facility at the Lawrence Berkeley National Laboratory. Calculations show that the resulting FEL is expected to deliver a saturated power of about a MW within a 4 m undulator length when operating in Self-Amplified-Spontaneus-Emission mode, with a single-spike of coherent radiation at 2 μm wavelength. The sub-cm undulator periods, associated with the relatively low energy of the APEX beam (20-25 MeV), forces the FEL to operate in a regime with unusual and interesting characteristics. The alternative option of laser seeding the FEL is also examined, showing the potential to reduce the saturation length even further.
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
An analysis is performed on various possible errors that may occur throughout a hybrid undulator. Of particular significance is the scaling of the various errors with variations in the gap of the device. Tuning strategies are considered for the mitigation of these errors for the entire range of usable gap. Sorting strategies for the reduction of the initial errors in the undulator are also considered. Specifically, the effectiveness of the sorting algorithm is evaluated with respect to the number of permanent magnet blocks used per pole as well as the size and distribution of the block population. The results of this analysis are applied to the LCLS-II undulators to determine the required machining and positioning tolerances and viable tuning strategies in order to meet the design requirements.
THOAI2
LBNL, Berkeley, California, USA
Undulator technology plays a critical role in FEL performance. The desire to provide a specific range of photon wavelengths for science applications constrains the design space of electron beam energy and undulator tuning capabilities. In particular, the coupling between photon wavelength, beam energy, and undulator period and strength indicates that undulator technology is a major cost driver in the design of FEL facilities. Superconducting undulators have the potential to significantly improve upon performance of current state-of-the-art undulator technologies being implemented in the first FEL facilities. Here we review the status of superconducting undulator technology, including developments in the areas of helical, planar, and variable polarizing superconducting undulator concepts at a variety of laboratories around the world. Implications of superconducting undulator performance for FEL applications are described. Finally, the major technological hurdles that remain to be addressed prior to implementation in FEL facilities are outlined, together with a summary of current R&D efforts.
LBNL, Berkeley, California, USA
LLNL, Livermore, California, USA
UCLA, Los Angeles, California, USA
POSTECH, Pohang, Kyungbuk, Republic of Korea
The APEX project at the Lawrence Berkeley National Laboratory is devoted to the development of a high repetition rate (MHz-class) electron injector for X-ray FEL applications. The injector is based on a new concept photo-gun, utilizing a normal conducting 187 MHz RF cavity operating in CW mode in conjunction with high quantum efficiency photocathodes able to deliver the required repetition rates with available laser technology. The APEX activities are staged in two phases. In Phase I, the electron photo-gun is constructed, tested and several different photo-cathodes, such as alkali antimonides, Cs2Te [1], diamond amplifiers [2], and metals, are tested at full repetition rate. In Phase II, a pulsed linac is added for accelerating the beam at several tens of MeV to prove the high brightness performance of the gun when integrated in an injector scheme. Based on funding availability, after Phase II, the program could also include testing of new undulator technologies and FEL studies. The status of Phase I, in its initial experimental phase, is described together with plans and activities for Phase II and beyond.
[1] In collaboration with INFN-LASA, Milano, Italy.
[2] In collaboration with Brookhaven National Laboratory, Upton NY, USA