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Basics of beam dynamics
Published in Xiaobiao Huang, Beam-based Correction and Optimization for Accelerators, 2019
Particles in a beam tend to diverge from each other as they travel along the orbit due to their slightly different directions of motion. If no intervention is taken, the transverse beam size will indefinitely grow, causing beam loss on the vacuum chamber. Quadrupole magnets provide a magnetic field that varies linearly with transverse position. Such a field bends the stray particles back toward the design orbit as particles with larger excursions receive larger correcting kicks. This is called focusing. However, a quadrupole magnet that focuses the beam in the horizontal direction necessarily defocuses it in the vertical plane and vice versa. To keep the beam focused in both transverse directions, quadrupole magnets with opposite polarities are placed alternately along the beam path. This is the alternating gradient focusing scheme, also called the strong focusing scheme. A properly designed strong focusing scheme maintains the orbit stability and keeps a compact beam size.
Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation
Published in Journal of Nuclear Science and Technology, 2022
Kazami Yamamoto, Michikazu Kinsho, Naoki Hayashi, Pranab Kumar Saha, Fumihiko Tamura, Masanobu Yamamoto, Norio Tani, Tomohiro Takayanagi, Junichiro Kamiya, Yoshihiro Shobuda, Masahiro Yoshimoto, Hiroyuki Harada, Hiroki Takahashi, Yasuhiro Watanabe, Kota Okabe, Masahiro Nomura, Taihei Shimada, Takamitsu Nakanoya, Ayato Ono, Katsuhiro Moriya, Yoshio Yamazaki, Kazuaki Suganuma, Kosuke Fujirai, Nobuhiro Kikuzawa, Shin-Ichiro Meigo, Motoki Ooi, Shuichiro Hatakeyama, Tomohito Togashi, Kaoru Wada, Hideaki Hotchi, Masahito Yoshii, Chihiro Ohmori, Takeshi Toyama, Kenichirou Satou, Yoshiro Irie, Tomoaki Ueno, Koki Horino, Toru Yanagibashi, Riuji Saeki, Atsushi Sato, Osamu Takeda, Masato Kawase, Takahiro Suzuki, Kazuhiko Watanabe, Tatsuya Ishiyama, Shinpei Fukuta, Yuki Sawabe, Yuichi Ito, Yuko Kato, Kazuo Hasegawa, Hiromitsu Suzuki, Fumiaki Noda
The area of transverse injection painting has been designed for 216 π mm mrad, which is 1.5 times smaller than the aperture of the primary collimator (Table 1). A large painting area results in a lower number of foil hits of the circulating beams and would thus be preferable. However, at the beginning of beam commissioning, beam loss had increased when the painting area extended to >100 π mm mrad [96]. Numerical simulations and experiments revealed that this beam loss increase was attributed to the modulation of the beta function due to the edge effect of the injection bump magnets [97]. Therefore, we installed an additional quadrupole magnet system. This new system comprises six defocusing quadrupole magnets and independent power supplies for these six magnets [98]. The programmable power supplies can output an arbitrary current waveform. We made an excitation pattern to compensate for the modulation using additional quadrupole magnets. Before correction, the maximum modulation of the beta function was about 30%. It was reduced to only a few % after correction. Finally, we successfully extended the painting area to 200 π mm mrad, which resulted in further mitigating beam loss [96].
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
S5. After the measurement is completed, the control system will automatically trigger the data solution module, use the measurement data of the two special matte globular reflection markers at both ends of the harmonic coil to fit the circumference respectively. Construct the axis of the harmonic coil and the magnetic measurement coordinate system of the harmonic coil; Harness the imported quadrupole magnet calibration data in the control system. By combining with the measurement data of the laser tracker reflectors conversion markers on the quadrupole magnet upper surface fiducials, the calibration coordinate system of the quadrupole magnet, as well as the deviation of 6-DOF between the harmonic coil magnetic measurement coordinate system and the quadrupole magnet calibration coordinate system of the quadrupole magnet , is calculated. The solution model of the 6-DOF relationship between the coordinate system and is shown in Equations (2), (3), (4) and (5). The rotation matrix model between the two coordinate systems is as follows (19,20):
Experimental study of the effects of quadrupole magnetic field and hydro-thermal parameters on bubble departure diameter and frequency in a vertical annulus
Published in Experimental Heat Transfer, 2022
Habil Jafari Zandabad, Leila Jahanshaloo, Habib Aminfar, Mousa Mohammadpourfard
Amirzehni et al. [23] have studied the process of BDD variation owing to heat flux and mass flux changes in water flowing through the vertical annulus. The mass fluxes and heat fluxes considered as 85 and 125 kg/m 2s and 40 kW/m 2, respectively. Then the same experiments were performed in the presence of a uniform field of the quadrupole magnet. In order to compare the obtained results of the BDD variation in the absence of magnetic field, a theoretical model was employed. The BDD grew in the existence and in the lack of the magnetic field with increasing the heat flux and decreasing the mass flux. However, the bubble diameter at the moment of detachment in the presence of the magnetic field was smaller than the diameter of the bubble in the absence of the magnetic field. On the other hand, by applying the magnetic field the BDD became smaller and its behavior was controlled.