基于核自旋自由旋进的超灵敏磁力测量
Ultra-sensitive magnetometry based on free precession of nuclear spins
摘要：
我们讨论了一个非常灵敏的低场磁强计的设计和性能的基础上检测的自由自旋旋进的气体，核极化的3 He或129氦样品与SQUID作为磁通量探测器。该装置将被用来控制波动的磁场和梯度在一个新的实验寻找一个永久的电偶极矩的中子，以及在一个新型的3 He/129氦时钟比较实验，这应该是敏感的恒星变化的相对自旋进动频率。可测得特征自旋进动时间T_2达60小时。结合大于5000：1的信噪比，这导致在220 s的积分时间之后的灵敏度水平为deltaB= 1fT，并且在一天之后的灵敏度水平为deltaB= 10^（-4）fT。即使在该灵敏度范围内，磁力计性能在统计上也是有限的，并且磁力计固有的噪声源不是限制性的。原因是自由旋进的3 He（129 He）核自旋几乎完全与环境解耦。这使得这种类型的磁力计对于需要长期稳定性的精确磁场测量特别有吸引力。
英文摘要：
We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized 3He or 129Xe samples with a SQUID as magnetic flux detector. The device will be employed to control fluctuating magnetic fields and gradients in a new experiment searching for a permanent electric dipole moment of the neutron as well as in a new type of 3He/129Xe clock comparison experiment which should be sensitive to a sidereal variation of the relative spin precession frequency. Characteristic spin precession times T_2 of up to 60h could be measured. In combination with a signal-to-noise ratio of > 5000:1, this leads to a sensitivity level of deltaB= 1fT after an integration time of 220s and to deltaB= 10^(-4)fT after one day. Even in that sensitivity range, the magnetometer performance is statistically limited, and noise sources inherent to the magnetometer are not limiting. The reason is that free precessing 3He (129Xe) nuclear spins are almost completely decoupled from the environment. That makes this type of magnetometer in particular attractive for precision field measurements where a long-term stability is required.
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