When I was a graduate student, my roommate Zhiguo Yao was analyzing the LVD data to search for evidence of dark matter. I thought at that time that Italian are interesting. A bunch of experiments were supported in Gran Sasso laboratory (1400m underground), but none of them seems hopeful. Later on, Super-K proved the neutrino oscillation. Neutrino study became hot. Even later, WMAP said our universe is consisted of 73% dark energy, 23% dark matter, and only 4% normal matter. The dark matter study became hot. All these studies need be done deep underground. Now look again at the experiments in Gran Sasso, each one seems very interesting.
Two weeks ago, Sanford laboratory (1500m underground) at Homestake, US, is ready. Two experiments will be hosted first. LUX will search for dark matter using liquid Xenon detector and Majorana will search for neutrinoless double beta decay. As a comprehensive research plan, Homestake will host laboratories from surface to 2500 m deep underground for engineering, geoscience, astrophysics, biology, etc.
China hopes to establish a deep underground laboratory for many years. On one side, no attractive site is identified. One the other side, which is more important, no attractive project is proposed, which could push the setup of the laboratory. An attractive project should either be initiative, or have plenty of R&D, thus could be competitive in the world. This is not easy. After all, Europe, US, and Japan have tens of years experiences on the underground experiments. For China, it is a Chicken or the egg dilemma. Without an underground lab, R&D can not be carried out. Probably a competitive project can never be proposed. If set up a lab first, then shall we do there? Probably it is just a follower after spending hundreds millions. This tuition is expensive.
Just two hours before the opening of Beijing Olympic Game, several scientists were hit by a news that a traffic tunnel for Jinping water power plant in Sichuan was completed. The maximum overburden of the tunnel is 2375 m and 3/4 of the 17.5 km tunnel has overburden more than 1500 m. Tsinghua University then signed an agreement with the owner of the power plant to set up an underground lab. HPGe detector for dark matter search is planned. Shanghai Jiao Tong University plans a liquid Xenon detector. Several institutes of Chinese Academy of Sciences also submit a R&D plan for dark matter search. Now the “chicken” could be ready. But how to make it lay eggs? One way is to start several small scale R&D first and determine which way to go later. Otherwise a competitive plan should come first and integrate the resources to complete it. But the lab and project management should be creative to make it happen.
By the way, the two-stage hydropower development of Jinping is very creative.
Jinping Mountain
国家地下实验室——先有鸡还是先有蛋
上研究生时，我的室友姚志国在分析LVD的实验数据，期望从中找出暗物质的迹象。当时觉得意大利人挺有意思，在Gran Sasso实验室（地下1400米）进行了一堆实验，似乎都不着边，没有一个有希望看到点东西。后来，Super-K证实了中微子振荡，中微子研究变得热起来。再后来，WMAP说宇宙中暗能量占73%，暗物质占23%，普通物质只占4%，暗物质研究变得热起来。现在再看Gran Sasso进行的一堆实验，似乎每一个都挺有意思。
两个星期前，美国Homestake的Sanford实验室（地下1500米）落成，将进行LUX实验（利用液氙探测暗物质）和Majorana实验（无中微子双衰变）。作为一个完整的研究计划，Homestake还将陆续从地表到地下2500米建立实验室，进行工程、地球科学、天文、生物等方面的研究。
多年以来，中国一直想建立自己的地下实验室。一个原因是没有找到合适的地方，更主要的原因是没有合适的项目，能够作为一个切入点，使地下实验室的建立成为一种迫切需要，推动它的建立。一个合适的项目，或者是有原创性的想法，或者是有充分的技术的积累，具有国际竞争力。但是目前很难提出一个具有国际竞争力的实验项目，毕竟欧美日在地下实验上已有几十年的积累。因此，这就是一个先有鸡还是先有蛋的问题。不建地下实验室，研发跟不上，也许永远切不进去；建了，不知道干什么好，也许花上亿的经费，只能跟在别人后面跑，这个学费是很高昂的。
北京奥运会开幕前两小时，四川锦屏山交通隧道竣工。隧道的最大埋深为2500米，17.5公里的隧道，埋深大于1500米的占3/4。清华大学与隧道的业主二滩水电站签订协议，准备在隧道旁建立地下实验室，利用高纯探测器进行小规模的暗物质研究。上海交大提出了液氙探测器方案。中国科学院的几个研究所也提交了一个暗物质研究的计划。现在鸡是可以造出来了，怎么让它下蛋呢？一种可能是先补课，大家都开始小规模的预研，重复国外已经做过的事，等条件成熟再上大项目。要不然，需要提出有竞争力的方案，并整合国内有限的人力物力，集中精力先做一个实验，但是管理方式需要创新。
顺便说一下，锦屏水电二级开发的主意倒是非常有创意。
