Magnetic characterization for cryogenic permanent-magnet undulators: a first result

Area of Science:

• Physics
• Materials Science
• Accelerator Technology

Background:

• Cryogenic permanent-magnet undulators (CPMU) offer improved magnetic performance by cooling permanent magnets (PMs) to cryogenic temperatures.
• Enhancing magnetic properties like remanence and coercivity is crucial for advanced synchrotron radiation sources.

Purpose of the Study:

• To develop and utilize a high-precision Hall probe measurement system for magnetic field mapping of CPMUs at cryogenic temperatures.
• To investigate the impact of temperature variations on the magnetic performance and field errors of CPMU prototypes.

Main Methods:

• Development of a novel measurement system with dynamic Hall probe alignment using optical laser beams within a vacuum chamber.
• Conducting magnetic field mapping of a CPMU prototype at various cryogenic temperatures.
• Analyzing field profiles to deduce magnetic properties and assess error components.

Main Results:

• The maximum remanence of the CPMU prototype closely matched values from single-magnet measurements.
• Magnetic field error components affecting electron trajectory and phase were found to be insensitive to temperature changes.
• The developed measurement system enabled high-precision characterization of magnetic fields at cryogenic conditions.

Conclusions:

• Cryogenic cooling of permanent magnets in undulators can be effectively characterized using a specialized high-precision measurement system.
• The temperature insensitivity of field errors simplifies the construction process, allowing field correction based on room-temperature measurements.
• This research facilitates the development and deployment of advanced cryogenic permanent-magnet undulators.