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Coupling and nonlinear dynamics correction
Published in Xiaobiao Huang, Beam-based Correction and Optimization for Accelerators, 2019
The strengths of the leading order RDTs by sextupoles are linearly proportional to the integrated gradients of the sextupoles. For example, the f3000 coefficient is related to sextupole strengths via f3000=−∑ib2,iLiβx,i32ei3Δϕx,i48(1−ei6πνx), where b2,iLi is the integrated strengths of sextupole i and Δϕx,i is the horizontal phase advance between the sextupole and the observation point. The phase of the complex RDT coefficient changes with location in the ring but its amplitude does not change except at the locations of the multipole magnets that drive the resonance. Across a multipole magnet, the RDT coefficient has a step change as the contribution from the multipole magnet changes phase. If the RDTs can be measured before and after the multipole magnet, the strength of the magnet could be determined directly.
Research on automatic positioning technology for magnetic field measurement of multipole magnet harmonic coil in heavy ion accelerator
Published in Radiation Effects and Defects in Solids, 2022
W. J. Chen, Y. Q. Yang, X. D. Zhang, Y. J. Zheng, B. Zhang, J. Yang, S. M. Wang, G. Z. Sun, J. D. Yuan, D. L. Yang
As shown in Figure 1, the traditional harmonic coil magnetic field measurement system measures and locates the harmonic coil through the laser tracker and the reflectors installed at both ends of the harmonic coil (6,7). In the process of measurement and positioning, the measurement can only be completed normally with the reflective port of the laser tracker reflectors facing the illuminator of the laser tracker, otherwise the measurement accuracy of the laser tracker will be affected and even the light will be cut off (8). Therefore, there should be a special surveyor rotating the reflective port of the laser tracker reflector in real time with the rotation of the harmonic coil, and rotating the laser tracker reflector during positioning and measuring the harmonic coil. In the process, the harmonic coil may move due to poor control. The positioning of the multipole magnet is to use the laser tracker to measure the fiducials of the magnet, and the technical staff manually adjust the support of the multipole magnet to complete the positioning. In the process of harmonic coil magnetic field measurement, it is often necessary to repeat the above positioning measurement for several times to complete the harmonic coil magnetic field measurement of a single magnet (9,10). It takes long time and high labor costs to do the positioning of the harmonic coil magnetic field measurement. With the gradual increase of the volume of the new generation heavy ion accelerator, the number of multipole magnets has also increased greatly, with higher requirements for various indicators of harmonic coil magnetic field measurement (11,12). The traditional positioning technology of the harmonic coil magnetic field measurement system can not meet the needs of mass multipole magnet harmonic coil magnetic field measurement of the new generation heavy ion accelerator (13).