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在很多精密原子光谱实验中，杂散磁场或者磁场强度的不均匀所引入的系统误差，是影响实验不确定度的主要因素之一. 为保证测量精度，必须实现精密的磁场控制. 氦原子精细结构的精密光谱测量可用于测定精细结构常数，同时也是检验多电子原子体系量子电动力学理论的一种重要方法. 本文介绍所设计制作的磁屏蔽系统和余弦线圈产生精密可控磁场，并利用He原子光谱对所加磁场进行了精密测定. 磁屏蔽结构可将外磁场降低到小于0.8 mGs（1 Gs=10-4 T），控制磁场在20 Gs 范围内时，光谱测量区域磁场的不均匀性和控制误差均小于10 mGs. 在此实验条件下，氦原子精细结构精密光谱测量中磁场所导致的系统误差小于0.2 kHz.Systematic error caused by stray magnetic fields is often one of the major sources of the uncertainties in many precision measurements. It is necessary to accurately control the magnetic fields in these measurements. The spectrum of the fine structure of helium can be used to determine the fine structure constant, and also to test the quantum electrodynamic theory of multi-electron systems. In this work, we present a magnetic shield that can eliminate stray magnetic fields and a cosine coil that generates a uniform magnetic field. The central magnetic strength produced by the coil is measured through the spectrum of a 4He metastable atomic beam. The magnetic shield reduces the strength of the external magnetic field down to less than 0.8 mGs. The variation of the magnetic strength in the spectrum region is less than 10 mGs at a magnetic strength up to 20 Gs. In this case, the uncertainty introduced by the magnetic field will be less than in the spectrum of helium fine structure.
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Keywords:
- helium /
- fine structure /
- magnetic shield /
- magnetic measurement
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[27] Calvo E, Cerrada M, Botella I G, Palomares C, Rodriguez I, Toral F, Verdugo A 2009 Nucl. Instrum. Methods Phys. Res. A 600 560
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[30] Chen G J, Li M C, Zhou Y L 1986 Metal Soft Magnetic Materials and Heat Treatment (Beijing: China Machine Press) p47 (in Chinese) [陈国钧, 李茂昌, 周元龙 1986 金属软磁材料及其热处理 (北京: 机械工业出版社) 第47页]
[31] Shi J J, Dai Z Y, Xie L 2000 High Power Laser and Particle Beams 12 635 (in Chinese) [施将君, 戴志勇, 谢龙 2000 强激光与粒子束 12 635]
[32] Tang B, Jelicks L A 2001 Proc. Intl. Soc. Mag. Reson. Med 9 1110
[33] Lewis M L, Hughes V W 1973 Phys. Rev. A 8 2845
[34] Yan Z C, Drake G W F 1994 Phys. Rev. A 50 R1980
[35] Clairon A, Laurent P, Santarelli G, Ghezali S, Lea S N, Bahoura M 1995 IEEE Trans. Instrum. Meas. 44 128
[36] Romalis M V, Griffith W C, Jacobs J P, Fortson E N 2001 Phys. Rev. Lett. 86 2505
[37] Swallows M D, Loftus T H, Griffith W C, Heckel B R, Fortson E N, Romalis M V 2013 Phys. Rev. A 87 012102
[38] Gustavson T L, Bouyer P, Kasevich M A 1997 Phys. Rev. Lett. 78 2046
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[1] Schwartz C 1964 Phys. Rev. 134 A1181
[2] Pachucki K, Yerokhin V A 2010 Phys. Rev. Lett. 104 070403
[3] Pachucki K 2006 Phys. Rev. Lett. 97 013002
[4] Smiciklas M, Shiner D 2010 Phys. Rev. Lett. 105 123001
[5] Hanneke D, Hoogerheide S F, Gabrielse G 2011 Phys. Rev. A 83 052122
[6] Hodgman S S, Dall R G, Byron L J, Baldwin K G H, Buckman S J, Truscott A G 2009 Phys. Rev. Lett. 103 053002
[7] Lach G, Pachucki K 2001 Phys. Rev. A 64 042510
[8] Pastor P C, Giusfredi G, Natale P D, Hagel G, Mauro C D, Inguscio M 2004 Phys. Rev. Lett. 92 023001
[9] Pastor P C, Giusfredi G, Natale P D, Hagel G, Mauro C D, Inguscio M 2006 Phys. Rev. Lett. 97 139903
[10] Giusfredi G, Pastor P C, Natale P D, Mazzotti D, Mauro C D, Fallani L, Hagel G, Krachmalnicoff V, Inguscio M 2005 Can. J. Phys. 83 301
[11] George M C, Lombardi L D, Hessels E A 2001 Phys. Rev. Lett. 87 173002
[12] Borbely J S, George M C, Lombardi L D, Weel M, Fitzakerley D W, Hessels E A 2009 Phys. Rev. A 79 060503(R)
[13] Zelevinsky T, Farkas D, Gabrielse G 2005 Phys. Rev. Lett. 95 203001
[14] Castillega J, Livingston D, Sanders A, Shiner D 2000 Phys. Rev. Lett. 84 4321
[15] Keyser A R, Rice J A, Schearer L D 1961 J. Geophys. Res. 66 4163
[16] Gravrand O, Khokhlov A, Mouel J L L, Leger J M 2001 Earth Planets Space 53 949
[17] Frandsen A M A, Conner B V, Amersfoort J V, Smith E J 1978 IEEE Trans. Geosci. Electron. GE-16 195
[18] Magnes W, Michelena M D 2009 IEEE Trans. Geosci. Electron. 45 4493
[19] Kominis I K, Kornack T W, Allred J C, Romalis M V 2003 Nature 422 596
[20] Sun Y, Feng G P, Cheng C F, Tu L Y, Pan H, Yang G M, Hu S M 2012 Acta Phys. Sin. 61 170601 (in Chinese) [孙羽, 冯高平, 程存峰, 涂乐义, 潘虎, 杨国民, 胡水明 2012 61 170601]
[21] Drever R W P, Hall J L, Kowalski F V, Hough J, Ford G M, Munley A J, Ward H 1983 Appl. Phys. B 31 97
[22] Black E D 2001 Am. J. Phys. 69 79
[23] Mager A J 1970 IEEE Trans. Magnet. MAG-6 67
[24] Gubser D U, Wolf S A, Cox J E 1979 Rev. Sci. Instrum. 50 751
[25] Sumner T J, Pendlebury J M, Smith K F 1987 J. Phys. D: Appl. Phys. 20 1095
[26] Burt E A, Ekstrom C R 2002 Rev. Sci. Instrum. 73 2699
[27] Calvo E, Cerrada M, Botella I G, Palomares C, Rodriguez I, Toral F, Verdugo A 2009 Nucl. Instrum. Methods Phys. Res. A 600 560
[28] Cui Y R, Liu H, Shi Y, Li X M, Ma H Z 2005 Foundry Technol. 26 1145 (in Chinese) [崔雅茹, 刘环, 施源, 李小明, 马红周 2005 铸造技术 26 1145]
[29] Li C J 2000 Southern Iron and Steel 116 7 (in Chinese) [李晨隽 2000 南方钢铁 116 7]
[30] Chen G J, Li M C, Zhou Y L 1986 Metal Soft Magnetic Materials and Heat Treatment (Beijing: China Machine Press) p47 (in Chinese) [陈国钧, 李茂昌, 周元龙 1986 金属软磁材料及其热处理 (北京: 机械工业出版社) 第47页]
[31] Shi J J, Dai Z Y, Xie L 2000 High Power Laser and Particle Beams 12 635 (in Chinese) [施将君, 戴志勇, 谢龙 2000 强激光与粒子束 12 635]
[32] Tang B, Jelicks L A 2001 Proc. Intl. Soc. Mag. Reson. Med 9 1110
[33] Lewis M L, Hughes V W 1973 Phys. Rev. A 8 2845
[34] Yan Z C, Drake G W F 1994 Phys. Rev. A 50 R1980
[35] Clairon A, Laurent P, Santarelli G, Ghezali S, Lea S N, Bahoura M 1995 IEEE Trans. Instrum. Meas. 44 128
[36] Romalis M V, Griffith W C, Jacobs J P, Fortson E N 2001 Phys. Rev. Lett. 86 2505
[37] Swallows M D, Loftus T H, Griffith W C, Heckel B R, Fortson E N, Romalis M V 2013 Phys. Rev. A 87 012102
[38] Gustavson T L, Bouyer P, Kasevich M A 1997 Phys. Rev. Lett. 78 2046
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