Compact variable-gap undulator with Hydraulic-Assist Driver

摘要

Following successful proof-of-concept experiments, we constructed compact varying-gap undulator with Hydraulic-Assist Driver. The 1.5m long undulator features a pure permanent magnet structure, period of 28.4mm and a minimum gap of 6.75mm. The bench test of the device indicated excellent mechanical and magnetic performances. It demonstrated ≤ 3° RMS optical phase errors in a wide range of gap variation; ～ 1.0 × 10~(-4) (or better) repeatability in normalized K_(und) (ΔK/K) from one gap variation to another. In special mode, when the gap was varied in correlation with undulator temperature, undulator demonstrated ～ 6.6 ×10~(-5) RMS of ΔK/K long-term (～24hrs) stability while the undulator temperature change was ～ 1.3°C. In this paper, we discuss the critical design components and criteria required for undulator mechanical stability and magnetic performance. We also describe our Lab-View-based control system governing the Hydraulic-Assist Driver. Finally, we present the test setup and results.