Hysteresis and degaussing of H1 dipole magnets
- Univ. of Oxford (United Kingdom); Cornell Univ., Ithaca, NY (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
Hysteresis was observed in the H1 dipole magnets in CBETA SX line. This study is the first step in order to understand and mitigate the effects this has on field reproducibility. Ansys Maxwell 19.2 was used to model the MS1DIP05 magnet with a hysteretic core. The parameter space for a degaussing procedure using the trim coils was explored. It was found that significant degaussing can be obtained with a decaying ringing waveform of magnitudes above 10 A, so long as the frequency ƒ and decay constant w were chosen such that ƒ >> w. The circuit properties of the magnet were simulated and explored using a sinusoidal voltage input. It was found that for low frequencies ƒ << 1 Hz, the magnet behaves as a series LR circuit with R = (28.3 ± 0.5) mΩ and L = (5.7 ± 0.1) mH. At higher frequencies, hysteretic effects become significant, and resistance becomes proportional to the frequency due to hysteretic losses. A drop and saturation in inductance for higher frequencies was observed in the simulation data. Numerical instabilities were found for excitations below small voltages V < 50 mV. Experimental results on degaussing and current corrections were collected with Hall probe measurements. Good qualitative agreement with simulation results was found, but due to B-H curve details quantitative comparisons were inaccurate. Two procedures, MaxOp and MaxNull, were designed to produce repeatable operating field values to within 0.1 G.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Nuclear Physics (NP); New York State Energy Research and Development Authority (NYSERDA)
- DOE Contract Number:
- SC0012704
- OSTI ID:
- 1556890
- Report Number(s):
- BNL-211964-2019-TECH; CBETA/045
- Country of Publication:
- United States
- Language:
- English
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