Precise pulsed magnetic field mapping using a compact pick-up probe for a pulsed sextupole magnet

Area of Science:

• Accelerator Physics
• Electromagnetism

Background:

• Pulsed sextupole magnets are crucial for beam injection at KEK-Photon Factory (KEK-PF).
• Observed oscillations in the stored beam during top-up injection required investigation.

Purpose of the Study:

• To develop a method for measuring peak magnetic fields in the zero-magnetic-field region.
• To identify the cause of stored beam oscillations during top-up injection.

Main Methods:

• Developed a compact pick-up probe with main and background coils (3.2 x 5.8 mm main coil).
• Utilized signal subtraction (background from main coil) to isolate effective magnetic field signals.
• Measured peak fields and longitudinal field structures.

Main Results:

• Successfully measured peak magnetic fields with high accuracy for magnetic field mapping.
• Detected a magnetic field signal of 2.2 × 10⁻⁴ T.
• Observed longitudinal field structure, including eddy-current effects, explaining beam oscillations.

Conclusions:

• The developed probe enables accurate measurement of pulsed magnet fields.
• Eddy-current effects in the pulsed magnet are identified as the cause of stored beam oscillations.
• This finding is crucial for improving beam stability in particle accelerators.