高效雙腔體架構之玻色愛因斯坦凝聚態的製備

Efficient production of Bose-Einstein condensates in double chamber vacuum system

葉宇皓(Yu-Hao Yeh)

指導教授 ： 陳永芳

共同指導教授 ： 張銘顯(Ming-Shien Chang)

國立臺灣大學/理學院/物理學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202002235

摘要

本實驗致力於實現高效雙腔體架構之銣原子玻色愛因斯坦凝聚。本實驗以腔體間的差動幫浦維持兩真空腔體間大於1000倍之壓力差，其中科學真空腔的真空度為1.3 × 10^−11 mbar，銣原子源側的真空腔真空度為5×10^8 mbar。經分析與優化，超高真空腔之磁光阱(Magneto-optical trap)的原子捕捉率約1 × 10^8 1/s，經灰色糖蜜冷卻(Gray molasses cooling)，我們在三維磁光阱內捕捉到約1×10^9 顆原子，並降溫至18 μK。目前已將2.9×10^6 顆原子載入光偶極阱(Optical dipoletrap)，進行強迫蒸發冷卻後，相空間密度(Phase space density) 達到1.1×10^−4，阱內剩餘原子為4.6×10^4 顆原子。

關鍵字

87銣原子 ； 二維磁光阱 ； 灰色糖蜜冷卻 ； 光偶極阱 ； 玻色愛因斯坦凝聚

並列摘要

The goal of this experiment is to realize efficient production of rubidium Bose-Einstein condensates. We built a dual-chamber ultra-high vacuum system with a pressure difference of more than three orders of magnitude, where 1.3 × 10^−11 mbar is achieved in the science chamber, while 5 × 10^−8 mbar is detected in the vapor chamber. We transferred laser-cooled atoms from the 2D+ magneto-optical trap (MOT) in the vapor chamber to the 3D MOT in the science chamber with a loading rate of 1×10^8 1/s. We further implemented the gray molasses cooling (GMC) and compared the performance of GMC with temporal dark MOT. The optimized atom number after GMC is 1×10^9 with a temperature of 18 μK. We loaded 2.9×10^6 atoms into an optical dipole trap (ODT), and performed the evaporative cooling. We achieved a final phase space density of 1.1×10^−4, with 4.6×10^4 atoms remained in the trap.

並列關鍵字

87Rubidium ； 2D+ magneto-optical trap ； Gray molasses cooling ； Optical dipole trap ； Bose-Einstein condensation

參考文獻

[1] W. Ketterle, D. S. Durfee, and D. M. Stamper-Kurn. Making, probing and understanding bose-einstein condensates, 1999.

[2] Satyendra Nath Bose. Plancks gesetz und lichtquantenhypothese. Zeitschrift für Physik, 1924.

[3] Mike H Anderson, Jason R Ensher, Michael R Matthews, Carl E Wieman, and Eric A Cornell. Observation of bose-einstein condensation in a dilute atomic vapor. science, pages 198–201, 1995.

[4] Kendall B Davis, M-O Mewes, Michael R Andrews, Nicolaas J van Druten, Dallin S Durfee, DM Kurn, and Wolfgang Ketterle. Bose-einstein condensation in a gas of sodium atoms. Physical review letters, 75(22):3969, 1995.

[5] Dale G Fried, Thomas C Killian, Lorenz Willmann, David Landhuis, Stephen C Moss, Daniel Kleppner, and Thomas J Greytak. Bose-einstein condensation of atomic hydrogen. Physical Review Letters, 81(18):3811, 1998.