- 學位論文
以亞都卜勒法冷卻鉀原子與超冷磁轉移
Sub-Doppler Cooling and Magnetic Transfer of Ultracold Potassium Atoms
摘要
在本實驗中，我們把39K的原子團由Sub-Doppler cooling的技術雷射冷卻至低溫，再使用磁陷阱捕捉並轉移原子到真空度更高的區域(Science cell)，以提高原子生命週期。而我們移動原子的技術稱為磁轉移(magnetic transport)，使用線性馬達(linear motor)裝載上線圈，以產生磁位能阱，可移動原子約40cm至超空真空區域。在此實驗中，我們量測了原子團的溫度、生命週期、磁轉移的效率。 藉由Sub-Doppler cooling的雷射冷卻技術，我們先把39K原子冷卻低於200μK，我們再利用 Magnetic quadruple trap 成功的捕捉並移動原子，並以螢光法來量測並分析此原子團。我們在磁光陷阱中捕捉了約1.21×10E8個39K原子並將約10%的原子載入磁陷阱，接著使用243G/cm的磁場梯度，磁轉移原子至Science cell，轉移的效率為24%。經由量測得知，39K在真空度比較低的區域生命週期為2.55秒；在超空真空的區域(Science cell)提高到14秒。 也同時轉移87Rb與39K至Science cell，因為在磁阱中異核原子的混合與碰撞造成額外的loss，所以39K的生命週期降為4秒。
並列摘要
We used Sub-Doppler laser cooling technique to cool down the 39K atoms lower than 200μK. In order to increase the life time of the ultra-cold atoms, then we magnetic caught and magnetic transferred the atoms by a moving anti-Helmholtz coil mounted on a linear motor track to the ultra-high vacuum chamber(Science cell). The number of atoms and the lifetime of trap were measured and analyzed using the fluorescence image method. In this experiment,1.21×10E8 of cold potassium atoms was produced in the MOT, and about 10% of that was loaded into the magnetic trap. The subsequent magnetic transferring to the science cell was achieved with a linear moving track and an efficiency of 24%. In the first chamber(MOT chamber), the life time of 39K was 2.55 sec. After transporting to Science cell, the life time increased to 14 sec due to less background collision. Meanwhile, we also trapped and transferred 87Rb and 39K simultaneously to the science cell. Because of the additional loss caused by the inter-species collision, the life time of 39K was reduced to 4sec.