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光钟物理系统的小型化是制约可搬运光钟及空间冷原子光钟发展的重要因素.主要介绍了小型化锶原子光钟物理系统的研制实验.采用真空腔内置反亥姆霍兹线圈，构建一个小电流、低功耗及小体积的磁光阱.实验中测得真空线圈通电电流仅为2 A时，磁光阱中心区域轴向磁场梯度可达到43 Gs/cm，完全满足锶原子多普勒冷却与俘获对磁场梯度的要求.目前已经成功将锶原子光钟物理系统体积缩小至60 cm×20 cm×15 cm，约为实验室原锶光钟物理系统体积的1/10，并且实现了锶原子的一级冷却，测得俘获区冷原子团的直径为1.5 mm，温度约为10.6 mK.锶同位素88Sr和87Sr的冷原子数目分别为1.6×106和1.5×105.重抽运激光707和679 nm的加入，消除了冷原子在3P2和3P0两能态上的堆积，最终可将冷原子数目提高5倍以上.The compactness and robustness of the vacuum setup are the major limitations to develop transportable and space-borne optical clocks. The first step in the engineering challenge is to reduce volume and weight with respect to a stationary system. In this paper, we present the realization of a miniaturized vacuum system by building two anti-Helmholtz coils inside the vacuum magneto-optical-trap (MOT) chamber. The built-in coils are specially designed to minimize the distance between the coils, and in this way it is possible to reduce the current needed to realize a typical magnetic gradient of 40 Gs/cm required for blue MOT. When the MOT coil current is 2 A, an axial magnetic field gradient of 43 Gs/cm is obtained in the center of the MOT, which is enough for the first stage Doppler cooling. This novel design allows us to reduce size, weight and power consumption with respect to a traditional laser cooling apparatus, and simultaneously avoid complicating the water cooling equipment. Our vacuum system has a size of 60 cm×20 cm×15 cm, about 1/10 of the original system in the laboratory. In addition, the circularly polarized Zeeman slowing laser is sent to counter propagating atomic beam, and atoms at a few hundred meters per second are now routinely slowed down to velocities of tens of meters per second. As a result, about 16.4% of the atoms are actually trapped into the blue MOT. The final temperature of the blue MOT is approximately 10.6 mK, and the internal diameter is 1.5 mm by observing the expansion of the atoms from the MOT. The populations of cold atoms finally trapped in the MOT are 1.6×106 of 88Sr and 1.5×105 of 87Sr. The 1S0 → 1P1 transition used for the blue MOT is not perfectly closed due to the decay channel of the 5p1P1 → 4d1D2, and a part of atoms are stored in the 3P2 and 3P0 states. To prevent the atoms from losing, 707 and 679 nm repumping lasers are employed to recycle these atoms in the 3P1 state, and then the atoms decay to the ground state 1S0. Now the typical number of loaded atoms dramatically increases by 5 times compared with before. The slowing efficiency of Zeeman slower is also optimized for the operation with deceleration related to the parameter of magnet length, which uses more effectively available magnetic field distribution, in contrast to the usual constant deceleration mode. Our future work will focus on constructing a Zeeman slower combined with permanent magnets or an electric magnet for better tuning of the magnetic field.
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Keywords:
- compact Sr optical clock /
- built-in anti-Helmholtz coil /
- space-borne cold atom optical clock
[1] Campbell S L, Hutson R B, Marti G E, Goban A, Darkwah Oppong N, McNally R L, Sonderhouse L, Robinson J M, Zhang W, Bloom B J, Ye J 2017 Science 358 90
[2] Le Targat R, Lorini L, Le Coq Y, Zawada M, Guéna J, Abgrall M, Gurov M, Rosenbusch P, Rovera D G, Nagórny B, Gartman R, Westergaard P G, Tobar M E, Lours M, Santarelli G, Clairon A, Bize S, Laurent P, Lemonde P, Lodewyck J 2013 Nat. Commun. 4 2109
[3] Takano T, Takamoto M, Ushijima I, Ohmae N, Akatsuka T, Yamaguchi A, Kuroishi Y, Munekane H, Miyahara B, Katori H 2016 Nat. Photon. 10 662
[4] Falke S, Lemke N, Grebing C, Lipphardt B, Weyers S, Gerginov V, Huntemann N, Hagemann C, Al-Masoudi A, Häfner S, Vogt S, Sterr U, Lisdat C 2014 New J. Phys. 16 073023
[5] Ushijima I, Takamoto M, Das M, Ohkubo T, Katori H 2015 Nat. Photon. 9 185
[6] Lin Y G, Wang Q, Li Y, Meng F, Lin B K, Zang E J, Sun Z, Fang F, Li T C, Fang Z J 2015 Chin. Phys. Lett. 32 090601
[7] Hachisu H, Ido T 2015 Jpn. J. Appl. Phys. 54 112401
[8] Akamatsu D, Inaba H, Hosaka K, Yasuda M, Onae A, Suzuyama T, Amemiya M, Hong F L 2014 Appl. Phys. Express 7 012401
[9] Schiller S, Görlitz A, Nevsky A, Koelemeij J C J, Wicht A, Gill P, Klein H A, Margolis H S, Mileti G, Sterr U, Riehle F, Peik E, Tamm C, Ertmer W, Rasel E, Klein V, Salomon C, Tino G M, Lemonde P, Holzwarth R, Hänsch T W 2007 Nucl. Phys. B 166 300
[10] Salomon Ch, Dimarcq N, Abgrall M, Clairon A, Laurent P, Lemonde P, Santarelli G, Uhrich P, Bernier L G, Busca G, Jornod A, Thomann P, Samain E, Wolf P, Gonzalez F, Guillemot Ph, Leon S, Nouel F, Sirmain Ch, Feltham S 2001 C. R. Phys. 2 1313
[11] Cacciapuoti L, Salomon C 2009 Eur. Phys. J. Special Topics 172 57
[12] Godun R M, Nisbet-Jones P B R, Jones J M, King S A, Johnson L A M, Margolis H S, Szymaniec K, Lea S N, Bongs K, Gill P 2014 Phys. Rev. Lett. 113 210801
[13] Fortier T M, Ashby N, Bergquist J C, Delaney M J, Diddams S A, Heavner T P, Hollberg L, Itano W M, Jefferts S R, Kim K, Levi F, Lorini L, Oskay W H, Parker T E, Shirley J, Stalnaker J E 2007 Phys. Rev. Lett. 98 070801
[14] Sullivan D B, Ashby N, Donley E A, Heavner T P, Hollberg L W, Jefferts S R, Klipstein W M, Phillips W D, Seidel D J 2005 Adv. Space Res. 36 107
[15] Schiller S, Görlitz A, Nevsky A, Alighanbari S, Vasilyev S, Abou-Jaoudeh C, Mura G, Franzen T, Sterr U, Falke S, Lisdat C, Rasel E, Kulosa A, Bize S, Lodewyck J, Tino G M, Poli N, Schioppo M, Bongs K, Singh Y, Gill P, Barwood G, Ovchinnikov Y, Stuhler J, Kaenders W, Braxmaier C, Holzwarth R, Donati A, Lecomte S, Calonico D, Levi F 2012 Let's Embrace Space (Vol. Ⅱ) (Luxembourg: Publications Office of the European Union) p452
[16] Świerad D, Häfner S, Vogt S, Venon B, Holleville D, Bize S, Kulosa A, Bode S, Singh Y, Bongs K, Rasel E M, Lodewyck J, Le Targat R, Lisdat C, Sterr U 2016 Nat. Sci. Rep. 6 33973
[17] Li L, Qu Q Z, Wang B, Li T, Zhao J B, Ji J W, Ren W, Zhao X, Ye M F, Yao Y Y, L D S, Liu L 2016 Chin. Phys. Lett. 33 063201
[18] Origlia S, Schiller S, Pramod M S, Smith L, Singh Y, He W, Viswam S, Świerad D, Hughes J, Bongs K, Sterr U, Lisdat C, Vogt S, Bize S, Lodewyck J, Le Targa R, Holleville D, Venon B, Gill P, Barwood G, Hill I R, Ovchinnikov Y, Kulosa A, Ertmer W, Rasel E M, Stuhler J, Kaenders W, the SOC2 consortium contributors 2016 Quantum Opt. 9900 990003
[19] Poli N, Schioppo M, Vogt S, Falke St, Sterr U, Lisdat Ch, Tino G M 2014 Appl. Phys. B 117 1107
[20] Koller S B, Grotti J, Vogt S, Al-Masoudi A, Dörscher S, Häfner S, Sterr U, Lisdat C 2017 Phys. Rev. Lett. 118 073601
[21] Cao J, Zhang P, Shang J J, Cui K F, Yuan J B, Chao S J, Wang S M, Shu H L, Huang X R 2017 Appl. Phys. B 123 112
[22] Vogt S, Lisdat C, Legero T, Sterr U, Ernsting I, Nevsky A, Schiller S 2011 Appl. Phys. B 104 741
[23] Xu Q F, Liu H, Lu B Q, Wang Y B, Yin M J, Kong D H, Ren J, Tian X, Chang H 2015 Chin. Opt. Lett. 13 100201
[24] Geng T, Yan S B, Wang Y H, Yang H J, Zhang T C, Wang J M 2005 Acta Phys. Sin. 54 5104 (in Chinese) [耿涛, 闫树斌, 王彦华, 杨海菁, 张天才, 王军民 2005 54 5104]
[25] Fu J X, Li Y M, Chen X Z, Yang D H, Wang Y Q 2001 Acta Opt. Sin. 21 414 (in Chinese) [付军贤, 李义民, 陈徐宗, 杨东海, 王义遒 2001 光学学报 21 414]
[26] Brzozowski T M, Maczynska M, Zawada M, Zachorowski J, Gawlik W 2002 J. Opt. B 4 62
[27] Tian X 2010 M.S. Thesis (Xi'an: National Time Service Center, University of Chinese Academy of Sciences) (in Chinese) [田晓 2010硕士学位论文 (西安: 中国科学院大学国家授时中心)]
[28] Wang Y Q 2007 Laser Cooling and Trapping of Atoms (Beijing: Peking University Press) p294 (in Chinese) [王义遒 2007 原子的激光冷却与陷俘 (北京: 北京大学出版社) 第294页]
[29] Lett P D, Watts R N, Westbrook C I, Phillips W D 1988 Phys. Rev. Lett. 61 169
[30] Savard T A 1998 Ph.D. Dissertation (Durham: Duke University)
[31] Ovchinnikov Y B 2008 Eur. Phys. J. Special Topics 163 95
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[1] Campbell S L, Hutson R B, Marti G E, Goban A, Darkwah Oppong N, McNally R L, Sonderhouse L, Robinson J M, Zhang W, Bloom B J, Ye J 2017 Science 358 90
[2] Le Targat R, Lorini L, Le Coq Y, Zawada M, Guéna J, Abgrall M, Gurov M, Rosenbusch P, Rovera D G, Nagórny B, Gartman R, Westergaard P G, Tobar M E, Lours M, Santarelli G, Clairon A, Bize S, Laurent P, Lemonde P, Lodewyck J 2013 Nat. Commun. 4 2109
[3] Takano T, Takamoto M, Ushijima I, Ohmae N, Akatsuka T, Yamaguchi A, Kuroishi Y, Munekane H, Miyahara B, Katori H 2016 Nat. Photon. 10 662
[4] Falke S, Lemke N, Grebing C, Lipphardt B, Weyers S, Gerginov V, Huntemann N, Hagemann C, Al-Masoudi A, Häfner S, Vogt S, Sterr U, Lisdat C 2014 New J. Phys. 16 073023
[5] Ushijima I, Takamoto M, Das M, Ohkubo T, Katori H 2015 Nat. Photon. 9 185
[6] Lin Y G, Wang Q, Li Y, Meng F, Lin B K, Zang E J, Sun Z, Fang F, Li T C, Fang Z J 2015 Chin. Phys. Lett. 32 090601
[7] Hachisu H, Ido T 2015 Jpn. J. Appl. Phys. 54 112401
[8] Akamatsu D, Inaba H, Hosaka K, Yasuda M, Onae A, Suzuyama T, Amemiya M, Hong F L 2014 Appl. Phys. Express 7 012401
[9] Schiller S, Görlitz A, Nevsky A, Koelemeij J C J, Wicht A, Gill P, Klein H A, Margolis H S, Mileti G, Sterr U, Riehle F, Peik E, Tamm C, Ertmer W, Rasel E, Klein V, Salomon C, Tino G M, Lemonde P, Holzwarth R, Hänsch T W 2007 Nucl. Phys. B 166 300
[10] Salomon Ch, Dimarcq N, Abgrall M, Clairon A, Laurent P, Lemonde P, Santarelli G, Uhrich P, Bernier L G, Busca G, Jornod A, Thomann P, Samain E, Wolf P, Gonzalez F, Guillemot Ph, Leon S, Nouel F, Sirmain Ch, Feltham S 2001 C. R. Phys. 2 1313
[11] Cacciapuoti L, Salomon C 2009 Eur. Phys. J. Special Topics 172 57
[12] Godun R M, Nisbet-Jones P B R, Jones J M, King S A, Johnson L A M, Margolis H S, Szymaniec K, Lea S N, Bongs K, Gill P 2014 Phys. Rev. Lett. 113 210801
[13] Fortier T M, Ashby N, Bergquist J C, Delaney M J, Diddams S A, Heavner T P, Hollberg L, Itano W M, Jefferts S R, Kim K, Levi F, Lorini L, Oskay W H, Parker T E, Shirley J, Stalnaker J E 2007 Phys. Rev. Lett. 98 070801
[14] Sullivan D B, Ashby N, Donley E A, Heavner T P, Hollberg L W, Jefferts S R, Klipstein W M, Phillips W D, Seidel D J 2005 Adv. Space Res. 36 107
[15] Schiller S, Görlitz A, Nevsky A, Alighanbari S, Vasilyev S, Abou-Jaoudeh C, Mura G, Franzen T, Sterr U, Falke S, Lisdat C, Rasel E, Kulosa A, Bize S, Lodewyck J, Tino G M, Poli N, Schioppo M, Bongs K, Singh Y, Gill P, Barwood G, Ovchinnikov Y, Stuhler J, Kaenders W, Braxmaier C, Holzwarth R, Donati A, Lecomte S, Calonico D, Levi F 2012 Let's Embrace Space (Vol. Ⅱ) (Luxembourg: Publications Office of the European Union) p452
[16] Świerad D, Häfner S, Vogt S, Venon B, Holleville D, Bize S, Kulosa A, Bode S, Singh Y, Bongs K, Rasel E M, Lodewyck J, Le Targat R, Lisdat C, Sterr U 2016 Nat. Sci. Rep. 6 33973
[17] Li L, Qu Q Z, Wang B, Li T, Zhao J B, Ji J W, Ren W, Zhao X, Ye M F, Yao Y Y, L D S, Liu L 2016 Chin. Phys. Lett. 33 063201
[18] Origlia S, Schiller S, Pramod M S, Smith L, Singh Y, He W, Viswam S, Świerad D, Hughes J, Bongs K, Sterr U, Lisdat C, Vogt S, Bize S, Lodewyck J, Le Targa R, Holleville D, Venon B, Gill P, Barwood G, Hill I R, Ovchinnikov Y, Kulosa A, Ertmer W, Rasel E M, Stuhler J, Kaenders W, the SOC2 consortium contributors 2016 Quantum Opt. 9900 990003
[19] Poli N, Schioppo M, Vogt S, Falke St, Sterr U, Lisdat Ch, Tino G M 2014 Appl. Phys. B 117 1107
[20] Koller S B, Grotti J, Vogt S, Al-Masoudi A, Dörscher S, Häfner S, Sterr U, Lisdat C 2017 Phys. Rev. Lett. 118 073601
[21] Cao J, Zhang P, Shang J J, Cui K F, Yuan J B, Chao S J, Wang S M, Shu H L, Huang X R 2017 Appl. Phys. B 123 112
[22] Vogt S, Lisdat C, Legero T, Sterr U, Ernsting I, Nevsky A, Schiller S 2011 Appl. Phys. B 104 741
[23] Xu Q F, Liu H, Lu B Q, Wang Y B, Yin M J, Kong D H, Ren J, Tian X, Chang H 2015 Chin. Opt. Lett. 13 100201
[24] Geng T, Yan S B, Wang Y H, Yang H J, Zhang T C, Wang J M 2005 Acta Phys. Sin. 54 5104 (in Chinese) [耿涛, 闫树斌, 王彦华, 杨海菁, 张天才, 王军民 2005 54 5104]
[25] Fu J X, Li Y M, Chen X Z, Yang D H, Wang Y Q 2001 Acta Opt. Sin. 21 414 (in Chinese) [付军贤, 李义民, 陈徐宗, 杨东海, 王义遒 2001 光学学报 21 414]
[26] Brzozowski T M, Maczynska M, Zawada M, Zachorowski J, Gawlik W 2002 J. Opt. B 4 62
[27] Tian X 2010 M.S. Thesis (Xi'an: National Time Service Center, University of Chinese Academy of Sciences) (in Chinese) [田晓 2010硕士学位论文 (西安: 中国科学院大学国家授时中心)]
[28] Wang Y Q 2007 Laser Cooling and Trapping of Atoms (Beijing: Peking University Press) p294 (in Chinese) [王义遒 2007 原子的激光冷却与陷俘 (北京: 北京大学出版社) 第294页]
[29] Lett P D, Watts R N, Westbrook C I, Phillips W D 1988 Phys. Rev. Lett. 61 169
[30] Savard T A 1998 Ph.D. Dissertation (Durham: Duke University)
[31] Ovchinnikov Y B 2008 Eur. Phys. J. Special Topics 163 95
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