Sheng Jingwei, Wan Shuangai, Sun Yifan, Dou Rongshe, Guo Yuhao, Wei Kequan, He Kaiyan, Qin Jie, Gao Jia-Hong
Beijing City Key Lab for Medical Physics and Engineering, Institution of Heavy Ion Physics, School of Physics, Peking University, Beijing, China.
Beijing Automation Control Equipment Institute, Beijing, China.
Rev Sci Instrum. 2017 Sep;88(9):094304. doi: 10.1063/1.5001730.
In recent years, substantial progress has been made in developing a new generation of magnetoencephalography (MEG) with a spin-exchange relaxation free (SERF)-based atomic magnetometer (AM). An AM employs alkali atoms to detect weak magnetic fields. A compact AM array with high sensitivity is crucial to the design; however, most proposed compact AMs are potassium (K)- or rubidium (Rb)-based with single beam configurations. In the present study, a pump-probe two beam configuration with a Cesium (Cs)-based AM (Cs-AM) is introduced to detect human neuronal magnetic fields. The length of the vapor cell is 4 mm, which can fully satisfy the need of designing a compact sensor array. Compared with state-of-the-art compact AMs, our new Cs-AM has two advantages. First, it can be operated in a SERF regime, requiring much lower heating temperature, which benefits the sensor with a closer distance to scalp due to ease of thermal insulation and less electric heating noise interference. Second, the two-beam configuration in the design can achieve higher sensitivity. It is free of magnetic modulation, which is necessary in one-beam AMs; however, such modulation may cause other interference in multi-channel circumstances. In the frequency band between 10 Hz and 30 Hz, the noise level of the proposed Cs-AM is approximately 10 f T/Hz, which is comparable with state-of-the-art K- or Rb-based compact AMs. The performance of the Cs-AM was verified by measuring human auditory evoked fields (AEFs) in reference to commercial superconducting quantum interference device (SQUID) channels. By using a Cs-AM, we observed a clear peak in AEFs around 100 ms (M100) with a much larger amplitude compared with that of a SQUID, and the temporal profiles of the two devices were in good agreement. The results indicate the possibility of using the compact Cs-AM for MEG recordings, and the current Cs-AM has the potential to be designed for multi-sensor arrays and gradiometers for future neuroscience studies.
近年来，在开发基于无自旋交换弛豫（SERF）的原子磁力计（AM）的新一代脑磁图（MEG）方面取得了重大进展。原子磁力计利用碱金属原子来检测微弱磁场。一个具有高灵敏度的紧凑型原子磁力计阵列对该设计至关重要；然而，大多数提议的紧凑型原子磁力计是基于钾（K）或铷（Rb）的单光束配置。在本研究中，引入了一种基于铯（Cs）的原子磁力计（Cs-AM）的泵浦-探测双光束配置来检测人体神经元磁场。蒸汽室的长度为4毫米，这完全可以满足设计紧凑型传感器阵列的需求。与最先进的紧凑型原子磁力计相比，我们新的Cs-AM有两个优点。首先，它可以在SERF模式下运行，所需的加热温度低得多，这有利于传感器更靠近头皮，因为易于隔热且电加热噪声干扰较小。其次，设计中的双光束配置可以实现更高的灵敏度。它无需磁调制，而单光束原子磁力计需要磁调制；然而，这种调制可能在多通道情况下引起其他干扰。在10赫兹至30赫兹的频带内，所提议的Cs-AM的噪声水平约为10 fT/Hz，与最先进的基于K或Rb的紧凑型原子磁力计相当。通过参考商用超导量子干涉器件（SQUID）通道测量人体听觉诱发电场（AEF），验证了Cs-AM的性能。通过使用Cs-AM，我们观察到AEF在100毫秒左右（M100）出现明显峰值，其幅度比SQUID的大得多，并且两种设备的时间分布吻合良好。结果表明使用紧凑型Cs-AM进行脑磁图记录的可能性，并且当前的Cs-AM有潜力设计用于未来神经科学研究的多传感器阵列和梯度计。
