Development and operation of a Pr2Fe14B based cryogenic permanent magnet undulator for a high spatial resolution x-ray beam line

Abstract

Short period, high field undulators are used to produce hard X-rays on synchrotron radiation based storage ring facilities of intermediate energy and enable short wavelength Free Electron Laser. Cryogenic permanent magnet undulators take benefit from improved magnetic properties of RE2F e14B (Rare Earth based magnets) at low temperatures for achieving short period, high magnetic field and high coercivity. Using P r2F e14B instead of N d2F e14B, which is generally employed for undulators, avoids the limitation caused by the Spin Reorientation Transition phenomenon, and simplifies the cooling system by allowing the working temperature of the undulator to be directly at the liquid nitrogen one (77 K). We describe here the development of a full scale (2 m), 18 mm period P r2F e14B cryogenic permanent magnet undulator (U18). The design, construction and optimization, as well as magnetic measurements and shimming at low temperature are presented. The commissioning and operation of the undulator with the electron beam and spectrum measurement using the Nanoscopmium beamline at SOLEIL are also reported.

Interferometry for full temporal reconstruction of laser-plasma accelerator-based seeded free electron lasers

“…We choose a set of parameters (see table 1) compatible with the most recent achievements of the groups targeting both quality and reliability, mandatory for an FEL application [21,42,[44][45][46]. With a short period undulator [47], these typical 200 MeV beams can be used to target the vacuum ultra-violet range. We therefore consider a seed at 160 nm (see table 1) generated in gas [48,49] using a branch of the main laser [49].…”

Comparison of Achievable Magnetic Fields with Superconducting and Cryogenic Permanent Magnet Undulators – A Comprehensive Study of Computed and Measured Values

“…As will be discussed in the section "Comparison of Generic CPMU Model Calculations to Real Undulators" the magnet heights chosen for the CPMUs that have been built (and for which magnet dimensions were published) are indeed shorter. The pole is assumed to be 0.8 cm shorter than the magnet; this is close to the values found in thoroughly optimized APS models with taller magnets, and it is also the value chosen for the CPMU at SOLEIL [9]. The difference in B eff between a magnet height of 3 cm and 5 cm is about 1% (see Fig.…”

“…(The spin reorientation reduces the on-axis undulator field if magnets are cooled below the transition temperature.) As a result, many recent undulators are constructed with PrFeB magnets [9]. This study presents results for both magnet materials.…”

Challenges of in-vacuum and cryogenic permanent magnet undulator technologies

“…The magnetic characteristics of several magnet materials were explored at SPring-8 [22], SOLEIL [25] and HZB [26,27] to characterize the magnetic performance of CPMUs. At ESRF in 2008, a 2-m long CPMU with a period length of 18 mm was built based on NdFeB magnets [28] becoming the first full-scale CPMU operating in a storage ring [29,30] followed by other CPMUs operating in storage rings such as SOLEIL [31], DLS [32], SLS [33] and ESRF [34]. A CPMU at ESRF demonstrated that a nonbaked device can operate smoothly in a storage ring [34].…”

“…A CPMU at ESRF demonstrated that a nonbaked device can operate smoothly in a storage ring [34]. The first full-scale PrFeB-CPMU with a period length of 18 mm has been designed and operated in the storage ring at SOLEIL [31]. From then on, PrFeB-CPMUs have become the preferred choice for the development of CPMUs because of the higher magnetic field compared to NdFeB-CPMUs.…”