China Jinping Underground Laboratory

China Jinping Underground Laboratory
中国锦屏地下实验室
Established December 12, 2010 (2010-12-12)
Field of research
 Dark matter physics
Director Cheng Jianping[1]
Faculty Zeng Zhi
Ma Hao
Li Jianming
Wu Qifan[1]
Location Mianning County[2]:3, Sichuan, China
28°09′12″N 101°42′41″E / 28.15323°N 101.7114°E / 28.15323; 101.7114[3]Coordinates: 28°09′12″N 101°42′41″E / 28.15323°N 101.7114°E / 28.15323; 101.7114[3]
Owner
 Yalong River Hydropower Development Company[4]
Operating agency
 Tsinghua University
Website hep.tsinghua.edu.cn/CJPLNE/
"CJPL" redirects here. For the community radio station, see CJPL-FM.

The China Jinping Underground Laboratory (Chinese: 中国锦屏地下实验室; pinyin: Zhōngguó jǐn píng dìxià shíyàn shì) is a deep underground laboratory in Sichuan, China. The cosmic ray rate in the laboratory is under 0.2 muons/m²/day,[5] placing the lab at a depth of 6720 m.w.e.[6]:2 and making it the best-shielded underground laboratory in the world.[7]:17 The actual depth of the laboratory is 2,400 m (7,900 ft), yet there is horizontal access so equipment may be brought in by truck.

Although the marble through which the tunnels are dug is considered "hard rock", at the great depth it presents greater geotechnical engineering challenges[8][9]:16–27[10]:16–19 than the even harder igneous rocks in which other deep laboratories are constructed.[11]:13–14 The 10 MPa (1500 psi; 99 atm) water pressure in the rock is also inconvenient. But marble has the advantage for radiation shielding of being low in radionuclides,[12][13] such as 40K, 226Ra, 232Th,[7]:17 and 238U.[14]:16

The laboratory is in western China, near Tibet, about 500 km (310 mi) southeast of Chengdu.[7]:3 The closest major airport is Xichang Qingshan Airport, 120 km (75 mi) away by road.[9]:5

History

The Jinping-II Dam hydroelectric power project involved excavating a number of large tunnels under Jinping mountain: four large 16.7 km (10.4 mi) headrace tunnels carrying water southeast,[8]:30 two 17.5 km (10.9 mi) vehicular access tunnels,[9]:1 and one water drainage tunnel. Hearing of the excavation in August 2008,[15][16] physicists at Tsinghua University determined that it would be an excellent location for a deep underground laboratory,[17] and negotiated with the hydropower company to excavate laboratory space in the middle of the tunnels.

A formal agreement was signed on 8 May 2009,[15] and excavation was promptly started.[9]:29 The first phase CJPL-I, consisting of a 6.5×6.5×42 m (21×21×138 ft) main hall,[18]:8 plus 55 m (180 ft) of access tunnel (4,000 m³ total excavation)[9]:15 was excavated by May 2010,[19]:7 and construction completed 12 June 2010.[19]:7 A formal laboratory inauguration was held 12 December 2010.[9]:37

The laboratory is to the southwest of the southwesternmost of the seven parallel tunnels, traffic tunnel A.

CJPL-II expansion

The laboratory is current undergoing a major (50-fold) expansion, which is expected to be complete at the end of 2015.[20]:17 This will make it the world's largest underground laboratory, larger by many measures than the current record-holder the Laboratori Nazionali del Gran Sasso.

Slightly northwest of CJPL-I, two bypass tunnels are left over from constructing the seven tunnels of the hydropower project. They are sloped criss-crossing tunnels which connect the five water tunnels (four headrace and one drainage) to the road tunnels beside and slightly above them. Totalling 210,000 m3 (7.4×10^6 cu ft),[20]:4 they have been donated to the laboratory and will be used for support facilities.[21]:5

The expansion is adding 131,000 m3 (4.6×10^6 cu ft),[22][20]:4 of additional excavation: a short connection between the bypass tunnels, and four large experimental halls, each 14×14×130 m (46×46×427 ft).[20]:6[10]:12 Although greater depth and weaker rock force the halls to be narrower than the 20 m (66 ft) wide main halls of LNGS, their combined length of 520 m (1,710 ft) will provide almost as much volume (93,300[6][lower-alpha 1] vs. 95,100 m3[lower-alpha 2]) as, and more floor space (7,280 vs. 6,000 m2) than, LNGS's three halls totalling 300 metres (980 ft).

Comparing CJPL's total volume of 341,000 m3 with LNGS's 180,000 m3 would suggest that CJPL is twice the size, but that would be misleading; all of LNGS's excavation was designed to be a laboratory, and thus can be used more efficiently than CJPL's repurposed tunnels.

CJPL facility resources[18][21][20]
CJPL-I CJPL-II
Overall volume[20]:4 4,000 m3
140,000 cu ft 		210,000 + 131,000 m3
7.4×10^6 + 4.6×10^6 cu ft
Laboratory area 273 m2
2,940 sq ft 		7,280 m2
78,400 sq ft
Laboratory volume 1,800 m3
64,000 cu ft 		93,300 m3
3.29×10^6 cu ft
Electrical power 70 kVA[20]:4 1250 kVA[20]:15
Fresh air 2,400 m3/h
85,000 cu ft/h[20]:4 		30,000 m3/h
1.1×10^6 cu ft/h[20]:10

Due to the laboratory's location within a major hydroelectric facility, additional electrical power is readily available. CJPL-II is supplied by two redundant 10 kV, 10 MVA power cables;[20]:15 the temporary limit is the 5×250 kVA step-down transformers in the laboratory (one per experiment hall, and a fifth for facilities).[20]:15 There is likewise no shortage of water[20]:14 for cooling high-powered equipment.

The muon flux (and thus water equivalent depth) in CJPL-II has not yet meed measured, and may differ slightly from CJPL-I, but it will certainly remain lower than SNOLAB in Canada and thus retain the record for the world's deepest laboratory as well.

Experiments

Experiments currently operating in CJPL are:

Also operating in the laboratory is a low background facility using a high purity germanium detector, for measuring very low levels of radioactivity.[1][18]:7 This is not a physics experiment itself, but tests materials intended for use in the experiments. It also tests materials used to construct CJPL-II.[20]:27–32

Both CDEX[10]:23 and PandaX[10]:25 have plans for larger (tonne-scale) versions in the CJPL-II space.

Notes

  1. ↑ The cross-section drawings of CJPL's halls are inconsistent.[18]:13 A vaulted roof 14 m wide with 4.08 m sagitta spans an angle of 121°; the smaller 114° angle shown would imply a larger radius and smaller sagitta of 3.8 m. These lead to cross-sectional areas of 179.434 and 180.275 m2, respectively, and lab volumes of 93,306 and 93,743 m2, respectively.
  2. ↑ LNGS's main halls are assumed to be 20 m wide, with a hemispherical roof peaking at 18 m. Thus, the cross-sectional area is 20×(8+10×π/4) = 317.08 m2.

References

  1. 1 2 3 Zeng, Zhi (2011-03-26). Low Background Facility Setup in CJPL: A Brief Introduction (PDF). Symposium on Future Applications of Germanium Detectors in Fundamental Research. Beijing. Retrieved 2014-11-19.
  2. ↑ Neutrino opportunities at Jinping (PDF). May 28, 2015. Retrieved 2015-12-24.
  3. 1 2 "Data Acquisition Project for CJPL". 21 August 2010. Retrieved 2015-09-16. CJPL position in Google Maps – http://goo.gl/xwcA (You may use the coordinates directly in google maps: 28.153227,101.711369)
  4. ↑ Lin, S.T.; YuJainmin, Q. (12 September 2013). Status and prospects of CJPL and the CDEX experiment. 13th International Conference on Topics in Astroparticle and Underground Physics. Physics Procedia 61. pp. 201–204. doi:10.1016/j.phpro.2014.12.032. The laboratory is owned by the YaLong River Hydropower Development Company, and managed by Tsinghua University, China.
  5. ↑ Wu, Yu-Cheng; Hao, Xi-Qing; Yue, Qian; Li, Yuan-Jing; Cheng, Jian-Ping; Kang, Ke-Jun; Chen, Yun-Hua; Li, Jin; Li, Jian-Min; Li, Yu-Lan; Liu, Shu-Kui; Ma, Hao; Ren, Jin-Bao; Shen, Man-Bin; Wang, Ji-Min; Wu, Shi-Yong; Xue, Tao; Yi, Nan; Zeng, Xiong-Hui; Zeng, Zhi; Zhu, Zhong-Hua (August 2013). "Measurement of cosmic ray flux in the China JinPing underground laboratory" (PDF). Chinese Physics C 37 (8): 086001. arXiv:1305.0899. Bibcode:2013ChPhC..37h6001W. doi:10.1088/1674-1137/37/8/086001.
  6. 1 2 Li, Jainmin; Ji, Xiangdong; Haxton, Wick; Wang, Joseph S.Y. (9 April 2014). "The second-phase development of the China JinPing underground Laboratory". Physics Procedia 61: 576–585. arXiv:1404.2651 [physics.ins-det]. Bibcode:2015PhPro..61..576L. doi:10.1016/j.phpro.2014.12.055.
  7. 1 2 3 4 PandaX Collaboration (August 2014). "PandaX: A Liquid Xenon Dark Matter Experiment at CJPL". Science China Physics, Mechanics & Astronomy 57 (8): 1476–1494. arXiv:1405.2882. Bibcode:2014SCPMA..57.1476C. doi:10.1007/s11433-014-5521-2.
  8. 1 2 Zhang, Chunsheng; Chu, Weijiang; Liu, Ning; Zhu, Yongsheng; Hou, Jing (2011), "Laboratory tests and numerical simulations of brittle marble and squeezing schist at Jinping II hydropower station, China" (PDF), Journal of Rock Mechanics and Geotechnical Engineering 3 (1): 30–38, doi:10.3724/SP.J.1235.2011.00030
  9. 1 2 3 4 5 6 Li, Jianmin (6 September 2013). The Status and Plan of China JinPing underground Laboratory (CJPL) (PDF). 13th International Conference on Topics in Astroparticle and Underground Physics: A Town Meeting for the 2nd-phase Development of the China Jinping Underground Laboratory. Asilomar, California. Retrieved 2014-11-19.
  10. 1 2 3 4 Li, Jianmin (9 September 2015). The recent status and prospect of CJPL (PDF). XIV International Conference on Topics in Astroparticle and Underground Physics (TAUP2015). Retrieved 2015-11-28.
  11. ↑ Zhao, Zhihong (2015-06-05). Geological conditions and geotechnical feasibility. 2015 Workshop of Jinping Neutrino Program. Tsinghua University. Retrieved 2015-08-15.
  12. ↑ Chui, Glennda (February 2010), "World's deepest lab proposed in China", Symmetry 7 (1): 5, ISSN 1931-8367
  13. ↑ Strickland, Eliza (January 29, 2014), "Deepest Underground Dark-Matter Detector to Start Up in China", IEEE Spectrum 51 (2): 20, doi:10.1109/mspec.2014.6729364, China’s new underground lab is the deepest in the world, meaning it’s well protected from cosmic radiation; in addition, the rock around it is marble, which is particularly devoid of radioactive materials that could produce false signals. “The big advantage is that PandaX is much cheaper and doesn’t need as much shielding material,” Lorenzon says.
  14. ↑ Pocar, Andrea (8 September 2014). Searching for neutrino-less double beta decay with EXO-200 and nEXO (PDF). Neutrino Oscillation Workshop. Otranto. Retrieved 2015-01-10.
  15. 1 2 Normile, Dennis (5 June 2009), "Chinese Scientists Hope to Make Deepest, Darkest Dreams Come True", Science 324 (5932): 1246–1247, doi:10.1126/science.324_1246
  16. ↑ Feder, Toni (September 2010), China, others dig more and deeper underground labs 63 (9), pp. 25–27, Bibcode:2010PhT....63i..25F, doi:10.1063/1.3490493
  17. ↑ Kang, K.J.; Cheng, J.P.; Chen, Y. H.; Li, Y.J.; Shen, M. B.; Wu, S. Y.; Yue, Q. (1 July 2009). Status and Prospects of a Deep Underground Laboratory in China (PDF). Topics in Astroparticle and Underground Physics (TAUP 2009). Journal of Physics: Conference Series 203 (012028) (Rome). doi:10.1088/1742-6596/203/1/012028.
  18. 1 2 3 4 Yue, Qian (Feb 28, 2014). The status and prospect of CJPL (PDF). Dark Matter 2014. Westwood, California. Retrieved 2014-11-19. The figure on p. 13 shows the shape of the halls, although the dimensions have evolved.
  19. 1 2 Wong, Henry (2011-09-06). Construction and commissioning of the China Jinping underground laboratory and the CDEX-TEXONO experiment. 12th International Conference on Topics in Astroparticle and Underground Physics. Munich. Retrieved 2014-11-19.
  20. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Li, Jianmin (2015-06-05). Introduction of Jinping underground laboratory II. 2015 Workshop of Jinping Neutrino Program. Tsinghua University. Retrieved 2015-08-15. A description of CJPL-II construction progress through the beginning of May 2015. Note that some pages in this presentation say the halls are 12×12 m; those appear to be figures copied from older presentations, and 14×14 is the new decision.
  21. 1 2 Li, Jainmin; Ji, Xiangdong; Haxton, Wick; Wang, Joseph S.Y. (12 September 2013). The Second-Phase Development of the China JinPing Underground Laboratory for Physics Rare Event Detectors and Multi-Disciplinary Sensors. 13th International Conference on Topics in Astroparticle and Underground Physics. Asilomar, California. Retrieved 2014-11-21.
  22. ↑ "China expands world's deepest "dark matter" lab". Xinhua. 2014-08-02. Retrieved 2014-11-19.
  23. ↑ Qian Yue (March 24, 2011). China JinPing underground Laboratory (CJPL) and China Darkmatter Experiment (CDEX) (PDF). Symposium on Future Applications of Germanium Detectors in Fundamental Research. Beijing. Retrieved 2014-11-19.

External links

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