Shielded three-axis vector operation of a multichannelatomic magnetometer

• Main Authors: Tzu-Yu Wu, 吳紫瑜
• Other Authors: Ming-Feng Shih
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/43732676206006159534

碩士 === 國立臺灣大學 === 物理研究所 === 97 === Abstract One of the most potential applications of non-linear optics is a state-of-art atomicmagnetometer, which finds wide range of applications from material science, information storage to direct measurement of biological magnetic fields. The basic principle behind the magnetometer is based on the resonant nonlinear magneto-optical effect, which Larmor precession can be used to measure of spin-polarized atoms in a magnetic field.[1] This precession modifies the optical absorptive and dispersive properties of the atoms and causes the polarization of the probe beam to rotate to a small angle, which can be traced back to characterize the magnetic field. The theoretical sensitivity of atomic magnetometer is limited by the quantum shot noise, related to the transverse relaxation time of the spin polarized atoms.[2] By operating the atomic magnetometers with high atom density in an environment with a near zero magnetic field, spin exchange collision as a source of relaxation could be eliminated and the noise limit could be lowered down to 0.3 fT/ Hz.[3] To block the environmental field, the center piece of this fT atomic magnetometer is shielded by high-permeability magnetic shielding and the residual fields are compensated by three-axis Helmholtz coil.[4, 5] For the work presented here, I provide an improved version of an atomic magnetometer in [6] with noise level below 1 nT / Hz . It has a multichannel-inputs system along with its applicable two-stage Lock-In software been built up for the purpose of constructing a magnetic gradiometer, a heating system redesigned with introducing a temperature feedback controller and a magnetic shielding assembly set on the system.