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Record field in a 10 mm-period bulk high-temperature superconducting undulator

The HTS bulk undulator project recently achieved the specifications for the magnetic field strength of its 10 mm period and 4.0 mm diameter aperture hard x-ray undulator. Designed for the new microscopy tomography (I-TOMCAT) beamline of SLS2.0 based on simulations, it has been experimentally demonstrated. An example of the magnetic field profile is shown in Fig. 1. Also shown is the performance summary : magnetic field strength (B0) versus driver solenoid field (ΔBs). A record field of 2.1T was measured which exceeds the specifications by 5% and the magnetic errors do not exceed those for conventional permanent magnet undulators, whith more than 3 times weaker field. Further details are available in https://doi.org/10.1088/1361-6668/acc1a8.

Thanks to the modular design, the superconducting disks could be rearranged to test for the first time a new helical undulator design. The measurement results of the magnetic field profiles (Bx and By) are presented in Fig. 2, together with two pictures of the sample, open and closed. Such an undulator could produce hard X-ray Free Electron Laser (FEL) radiation with higher power and in a more compact beamline than in presently employed planar configurations. Our results represent a fundamental step-change in undulator technology with significant consequences for X-ray FEL designs, making these facilities significantly more compact, affordable, and efficient than today, https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.5.L032020.