A novel, elegant method for passive compensation of magnetization-current-induced field errors in the CERN LHC 10 T superconducting dipole magnets by permanent multipole magnets
A novel, elegant method for passive compensation of magnetization-current-induced field errors in the CERN LHC 10 T superconducting dipole magnets by permanent multipole magnets
复制标题
一种新颖、优雅的方法，用于通过永磁体对 CERN LHC 10 T 超导偶极磁体中的磁化电流感应场误差进行无源补偿
DOI：
10.1109/tmag.1987.1064890
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
A. Asner
中科院分区：
文献类型：
--
作者：
A. Asner
欧洲核子研究中心目前正在研究一台大型强子对撞机--LHC，它有大约1‘600到12米长的10 T双口径高场超导偶极子，最终将安装在正在建造的e+e对撞机LEP机器27公里的隧道中。在这些偶极子中，最大的磁场误差是由直径为10µm的NbTi1.8K或Nb3Sn4.5K细丝中的磁化电流引起的，在0.5T注入到LHC的磁场中扰动粒子的闭合轨道。为了补偿直径为3 cm的负1.9 O/00的六极子相对误差，提出了一种新颖、简洁、廉价的方法：在每个12m长的SC偶极子内放置一个连续的、薄的、同心的永久六极子层，或在其末端插入两个短集总校正器。为了确定补偿效率，考虑了由于几何、磁场和温度影响以及与主偶极子磁场的相互作用而引起的SC绕组磁化电流效应的系统误差和随机误差以及永久六极校正器的误差源，特别考虑到校正器必须在液氦温度下工作。对SmCo永磁体和NdBFe永磁体样品的低温测量表明，剩余磁场Br值提高了约7%，重复性好到了LN2时的10-4at，LHe温度和非常好的机械性能。在1.9T以下的外场和对偶极场中的低温样品测量结果表明，剩余磁场减小了-ABr/Br=-5.7%。将相反的偶极场减小到零，仍然有-2.5%的永久退磁效应。根据计算、力学性能和低温永磁体样品测量，提出的超导磁体绕组磁化电流误差补偿是完全可行的，误差减小系数可达3..5。一个修正的永久六极原型磁体已经订购，并将进行全面测试。
CERN is at present studying a Large Hadron Collider --LHC- with some 1'600 up to 12 m long 10 T-, twin bore, high field uperconducting dipoles to be eventually installed in the 27 km tunnel of the e+-e-collider, the LEP machine, actually under construction. In these dipoles the largest magnetic field error perturbing the particle closed orbit at 0.5 T injection field into the LHC, is caused by magnetization currents in the NbTi 1.8K or Nb 3 sn 4.5K filaments of expected 10 µm diameter. To compensate this negative 1.9 O/oo relative sextupole error at 3 cm bore diameter, a novel, elegant and inexpensive method is proposed ; one could either place a continuous, thin and concentric permanent sextupole layer within each 12 m long S.C. dipole or referably insert two short lumped correctors at its ends. To determine the compensation efficiency, systematic and random errors of the magnetization current effect in the S.C. windings and error sources in the permanent sextupole correctors due to geometrical, magnetic and temperature inlluences as well as to the interplay with the main dipole field are considered, taking notably into account that the correctors will have to operate at liquid helium temperature. Low temperature measurements on samples of permanent SmCo and NdBFe magnets indicate consistant and interesting improvement in the remanent field B r of about 7 %, excellent reproducibility of B r to a few 10-4at LN 2 , and LHe temperatures as well as very good mechanical behaviour. Low temperature sample measurements in external and opposed dipole fields up to 1.9 T resulted in a remanent field reduction of -AB r /B r = - 5.7 %. Reducing the opposed dipole field to zero, a permanent demagnetization effect of - 2.5 % remained. Based on computations, mechanical properties and low temperature permanent magnet sample measurements, the proposed compensation of magnetization current induced error in windings of superconducting magnets is entirely feasible ; an error reduction factor of3..5 can be expected. A correcting permanent sextupole prototype magnet has been ordered and will be completely tested.