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Cao Jun | Institute of High Energy Physics | P.R. China

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核学会2009年会随想——I:千人大会

Sunday, November 22nd, 2009

11月18-20日是核学会的2009年会。我只参加了20日下午的核电子学与核探测技术分会,做了一个关于大亚湾中微子实验的报告。

核学会的年会每两年开一次,这一次规模最大,参加者上千,收了一千多篇论文,十一个分会场,口头报告三四百。回来的路上与李卫国、张闯两位老师同车,闲谈了一下会议的组织。一般来说,这种大会不容易开好,很容易流于形式,有显示度,实际交流作用不理想,成为领导们的政绩工程。会议规模大,组织成本也大。不过就这次会议而言,虽然也有不少任务指派的成份,但感觉还不坏。在晚宴时我随便找了一桌,碰巧坐在一个刚听过我报告的人旁边,而他是中石油一个做油气勘探的,公司在西安。当打了一口油井或勘探洞后,我们需要了解地质的构造。有很多种方法能够测量油井从上至下的构造,例如核方法,用几个居里的中子源,激发途经的地层,探测激发出的X射线谱来判断物质的成份。这跟王焕玉老师刚报告的月球车X射线谱仪几乎一样。也有声、电等方法,但没有一个很好的,所以他来听一听,看有没有新的思路。也谈了一些仪器研制。他们做的一种仪器,已生产200套,每套用两个日本滨松的高温光电倍增管,能耐受175度的高温,仅200套高温光电倍增管的钱就花了几千万。跟他聊过后,感觉就好多了,说明这个会议还是有用的。

另外一个规模更大的会议是物理学会的秋季会议。我参加了2006年的,感觉像走过场,没有太大意思。但对有的学科据说很有用,干脆把学科的年会与这个会合并了。美国物理学会(APS)每年也召开规模庞大的年会,坚持了这么多年,说明还是有生命力、有价值的,关键看怎么组织。APS年会的分会基本上都是小年青去报告,是一个很好的煅炼机会。而我们的年会都是找大腕小腕做不同层次的综述,全面有余,关键细节不足。应当安排相当数量的Highlights讲技术细节,各分会的组织也应当放权,更灵活一点。如果能够坚持下去,也许会变得越来越重要。

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India-based Neutrino Observatory

Thursday, October 29th, 2009

News about India-based Neutrino Observatory

Several days ago I occasionally glanced at a rolling news on CCTV News Channel “…… will build the largest neutrino observatory”. I was shocked by my ignorance. Then I stood there for almost 10 minutes to wait it showing up again. Actually it is “India plans to build the largest fundamental scientific project —— neutrino observatory”. Many Chinese media reported this news. Generally it reads: “Indian scientist Mondal told media on Oct. 10 that India plans to start the construction of the Neutrino Observatory in 2012. The location is in Tamil Nadu in south India. He said, Indian scientists hope to collaborate with western countries, make neutrino beam with the accelerator in US or Europe and aim at the planned neutrino observatory in India.”

There was a workshop on neutrino factory on Oct. 12 in India. Prof. Mondal said above to media right before this workshop. The India-based Neutrino Observatory (INO) was proposed around 2000. The laboratory will be built 1300 meters underground. It uses 50 kton iron as target, interlaced with glass resistance plate chamber (RPC) as active detectors. It can be used to study atmospheric neutrinos as Super-K does, and can also serve as the far detector of a long baseline accelerator neutrino experiment.

There are many proposals and R&D on the next generation long baseline neutrino beam, such as beta beam and muon accelerator. It is generally believed that we need wait reactor neutrino experiment, such as Daya Bay, to give a clue on the mixing angle theta13, before determining which way we should go.

 

前几天偶然从CCTV新闻频道看到一行滚动新闻“… … 将建造最大的中微子观测站”。我被自己的孤陋寡闻吓了一跳,硬是站在电视前等了十分钟,等它再次滚出来,原来是“印度计划建造全国最大的基础科学工程——中微子观测站”。网上各大媒体也纷纷转载,原文大致是:

印度科学家蒙达尔教授10日对媒体说,印度计划于2012年开始建造中微子观测站,地址初步定在南部泰米尔纳德邦。他说,印度科学家希望与西方国家展开合作,使美国或欧洲有关国家的粒子加速器产生的中微子束穿透地球、抵达印度计划建造的中微子观测站,以便观测。

印度大约在2000年的时候提出了这个实验计划(INO),在地下1300米建立一个地下实验室,采用5万吨铁做介质,用玻璃阻性板探测器(RPC)与铁板一层一层交错叠起来,并加磁场,用以探测中微子反应产生的带电粒子。其探测器类似于美国正在进行的MINOS实验。MINOS实验的探测器是塑料闪烁体,将塑料闪烁体换成RPC,造价可便宜不少,同样的经费可以做得比较大,但是RPC需要通气体,维护比塑料闪烁体难,噪声也比较大。这样的观测站可以研究大气中微子,也可以做为加速器中微子实验的远端探测器。如果用来测量大气中微子,MINOS已经比较大地提高了日本超级神岗实验的精度,Nova和T2K也可以做,INO的精度跟它们差不多。如果做加速器中微子实验,则需要有人愿意把束流对准它,探测器的朝向也不同。出现这个报道的起因是10月12日要在印度开一个关于中微子工厂的国际研讨会。印度希望在CERN建中微子工厂,然后把束流送过来。

2005年我在意大利开会时碰到这个蒙达尔,盛情地邀请中国参加INO。我说我们首先要做大亚湾实验,大亚湾实验做好以前不会谈任何其它中微子计划。实际上,等MINOS,Nova,T2K做完,INO探测大气中微子已经没有太大的意义,探测长基线中微子则是没谱的事。beta beam和muon加速器(中微子工厂)不仅造价昂贵,远远高于INO的造价,关键技术也还没有解决,值不值得修建还要看theta13的大小,要等大亚湾实验的物理结果出来以后才知道。

趁此机会到维基百科上查了一下INO的介绍,很有意思的是大部分篇幅都在讲环保问题。INO选的点在动物保护区内,环评仍在争论中。

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The beauty of data

Wednesday, September 2nd, 2009

One figure means ten thousands words.

Data is abstract. Especially, huge volume data can hardly be analyzed by our brain to have an impression. However, data could be surprisingly beautiful in another sense. Many tools are designed to visualize data. They show us the beauty of data in an unbelievable manner. Fig. 1-3 are taken from Webdesignerdepot.com, where more examples are shown.

Visualization of data is widely used in high energy physics. The first thing learned by many graduate students is how to make plots using ROOT (or PAW in the past). Although rigorous statistical methods are used in physical analysis, scanning events by eyes is always necessary for suspicious ones. Fig. 4 shows an event in Super Kamiokande detector. It looks very beautiful, and actually very interesting, because it looks like a long-sought proton decay event.

Presenting the physical results with an elaborate figure, complex relation of data could be shown intuitively. There are countless examples in particle physics. Sudbury Neutrino Observatory presented their solar neutrino study as Fig. 5. Perhaps this result is not difficult to express in numbers. But this figure is much more impressive than numbers and text. It concentrates 10 years efforts of a hundred scientists. Whenever we see this figure, we know it is SNO.

No matter the results are relatively simple, or somewhat disorder, it is always worthy to spend a lot of time to compose a figure, which should be beautiful, intuitive, and rich in content and data relation.

Fig.1, Narratives 2.0 visualizes music. Different music tracks are segmented into single channels that are then shown in a fan-like structure.

Fig.1, Narratives 2.0 visualizes music. Different music tracks are segmented into single channels that are then shown in a fan-like structure.

Fig.2, Schemaball visualizes SQL database schema. Relationships are shown based on foreign keys within tables. It’s capable of showing schemas with hundreds of different tables and relationships.

Fig.2, Schemaball visualizes SQL database schema. Relationships are shown based on foreign keys within tables. It’s capable of showing schemas with hundreds of different tables and relationships.

Fig.3, The Hierarchical Structure of the Internet was a study that looks at how the Internet is organized, both in terms of structure and connectivity. It shows how the central core of the Internet is made up of about 80 core nodes, but that even if those nodes failed, 70% of the other nodes would still function via peer-to-peer connections.

Fig.3, The Hierarchical Structure of the Internet was a study that looks at how the Internet is organized, both in terms of structure and connectivity. It shows how the central core of the Internet is made up of about 80 core nodes, but that even if those nodes failed, 70% of the other nodes would still function via peer-to-peer connections.

Fig.5, Super Kamiokande event display. It looks like a proton decay event. The Cherenkov ring at the bottom is probably a positron. In the upper half, there may be two rings formed by pion decay to two gammas.

Fig.4, Super Kamiokande event display. It looks like a proton decay event. The Cherenkov ring at the bottom is probably a positron. In the upper half, there may be two rings formed by pion decay to two gammas.

Fig.6, Flux of B-8 solar neutrinos which are muon or tau neutrinos vs flux of electron neutrinos, by SNO.

Fig.5, Flux of B-8 solar neutrinos which are muon or tau neutrinos vs flux of electron neutrinos, by SNO.

数据之美

一张图抵一万句话。

数据是抽象的,尤其是海量数据,人的大脑很难直接对大量数据进行分析并获得印象,然而从另一个角度看,数据也可以异常美丽,人们设计了很多工具,让枯燥的数据图形化,它们以令人难以置信的方式让我们看到了数据美丽的一面。图1-3摘自Webdesignerdepot,更多的例子请见原文。

数据的图形化在高能物理里广泛使用,以至于我们把它当成最自然的选择。许多研究生学的第一件事就是如何用ROOT(以前是PAW)来画图。在数据分析中尽管总是采用严格的统计方法,对可疑事例进行肉眼扫描仍然是必不可少的。图4是一个超级神岗事例,看上去非常漂亮,而且非常有趣,因为它像一个我们一直在寻找的质子衰变事例。

用一张精心构思的图来表达物理分析结果,复杂的数据关系可以得到直观的体现。这种例子在高能物理中不可胜数。例如Sudbury Neutrino Observatory (SNO)太阳中微子实验的结果见图5。也许这个结果用数据来表达并不困难,但远远没有这张图令人印象深刻。它浓缩了上百名科学家10年的努力。每当我们看到这张图时,只要一眼,我们就知道这是SNO。

无论结果是相对简单,还是显得杂乱无章,总是值得你花很多的时间去构思一张图,它应当漂亮、直观、包括尽可能多的内容和数据关系。

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Household Clean Power

Wednesday, August 12th, 2009

Last month I had a tour to Wuyuan and Sanqing Mountain of Jiangxi province. In the hotel, I watched the news of Steven Chu, Minister of US DOE, visiting China. He was prompting his white roof plan on TV. Paint white the roof, and paint light color on the road and cars, large amount of solar radiation can be reflected back, thus the greenhouse effect can be reduced, power consuming of air conditioner can be saved. California has started to carry out this plan since 2005. His another promotion, carbon tariff, is strongly against by Chinese government, as well as India, Brazil, and most European countries. It is accused as trade protectionism in the name of environment protection as it destroys the consensus of Kyoto Protocol. But I think the white roof plan should be easily accepted worldwide, although the lawmaking may take time. For example, the traditional villages I visited in Wuyuan, all have black roof tiles and white wall. It is a local architectural style and looks amazingly comfortable. I don’t hope these tiles are also painted white.

dsc048091
In north China, e.g. Beijing, the air is very dry. Dust will soon turn the white roof to gray roof. In Daya Bay Experiment, we paint the inner wall of the antineutrino detector with black fluor-carbon paint, to reduce the stray light, and have studied to paint the outer wall with white fluor-carbon paint to collect more light in the water Cherenkov detector. Fluor-carbon paint is a cheap wall paint. It has excellent Weather Resistance and, as most fluor material, can be self-cleaned by rain.

 
In Xiaoqi village, there are several water mills in the brook. At Rainbow Bridge, there is a huge one, which drives machines of a grain handling workshop. Of course they are ornaments now. People like to use more convenient electricity. However, if we install electricity generator on these mills, the cost is quite low. In general, a small diesel generator of several to 30 kW costs 1000 Yuan/kW. Save the diesel engine, the cost is only several hundreds Yuan/kW. The investment can be got back in less than 3 months. China plans to invest 4.5 trillion Yuan on clean power in the next 10 years, such as wind power, nuclear power, and solar power, etc. And the allowance to solar electricity is 1 Yuan/kWh. Comparing to the large scale investment, small ones could be more economic and more environment-friendly. 4.5 trillion is 3500 Yuan/person in average. If every Chinese invest 1000 Yuan to generate 1 kW, the total capacity will be twice of current total capacity. Household clean power looks very encouraging. 

wm

前一阵去江西婺源和三清山旅游,在旅馆中看新闻,美国能源部长朱棣文访华,再次推销他的刷白屋顶计划:将屋顶漆成白色,路面和汽车使用浅色涂装,可以大量反射太阳辐射能量,降低温室效应。同时,也可以减少空调的能源消耗。美国加州已从2005年开始逐步实施该计划。他的另一项推销——碳关税,受到中国政府,以及印度、巴西和大部分欧洲国家的强烈反对,被指为借环保之名,行贸易保护之实,颠覆了京都议定书的基础。但我想刷白屋顶计划应该是比较容易在世界范围内达成一致的,不过立法可能需要时间。我们去的婺源的传统小村庄,一律都是青瓦白墙,赏心悦目,我可不希望把徽派建筑的青瓦也统统刷成白色。

 
在中国的北方,例如北京,空气干燥,灰尘很快会将白屋顶变成灰屋顶。在大亚湾实验中,我们在中微子探测器内壁喷涂了黑色的氟碳漆以降低杂散光,并曾考虑在外壁喷涂白色的氟碳漆以提高宇宙线探测器的光探测效率。氟碳漆是一种廉价的外墙涂料,具有很好的化学耐候性,也具有氟材料的普遍特点:表面不粘。在自然雨水的冲洗下就能自洁。

 
在婺源晓起村,有几架水车在溪流里转着,看上去古色古香。在彩虹桥,有一个大型的水车,用来驱动一个谷物加工作坊。当然,现在它们都是摆设。人们当然倾向于使用更方便的电。如果给这些水车装上小的发电机,成本其实非常低。一般几千瓦到30千瓦的小型柴油发电机价格为1000元/千瓦,去掉柴油机,成本只有几百元,不到3个月就能收回投资。中国计划在10年内投资4.5万亿元发展清洁能源,如风电、核电、太阳能。目前对太阳能发电的补贴是每度1元。除了规模投资,从小的方面着手更经济,更符合环保的理念。4.5万亿相当于人均3500元。可是如果全中国每人花1000元发电1kw,已经是现在全国装机容量的两倍。化整为零,大有可为。

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Dome A

Saturday, July 18th, 2009

Today I took a workshop “Frontier cosmology at Dome A, Antarctica” held at IHEP. Dome A is the highest point in Antarctica. Although often “spammed” by news about Antarctica, I found I knew little about it. Anyway it is a bit far from us.

“Antarctic is larger than China”, the first speaker, Nobel Prize laureate George Smoot said. I know that the largest neutrino telescope icecube locates at the South Pole. Several of our Daya Bay collaborators come from icecube. “Icecube is the most impor, er, the most expensive experiment in Antarctica”, said by Smoot. “The largest advantage doing experiments in Antarctica is probably the cost. Sending 1 kg equipment to space cost 15,000$ by rocket, 60,000$ by shuttle, but only several dollars to Antarctica.” In some wave bands, Dome A is even better than in space.

Actually it is not easy to do experiments at Dome A. Starting from Zhong Shan station, it takes 20 days, 1,250 km trek under -50 degree C to reach Dome A, above 4,000 m altitude. It is probably as difficult as climbing the Everest. Nevertheless, several small programs, including an international collaborative PLATO observatory, have been started in 2008. The data will provide the parameters needed to establish a future observatory. The next programs, such as the THz telescope, may greatly contribute to the studies of the dark matter, dark energy, and the origin of the universe, etc.

topo_antactica

冰穹A

今天在高能所听了一个关于南极冰穹A的宇宙学前沿研讨会。冰穹A是南极的最高点。虽然时常听到关于南极的消息,但是我发现对南极实际上一无所知,毕竟离我们有点远。

南极大陆“比中国还大”,第一个做报告的诺贝尔奖获得者George Smoot说。我们知道最大的中微子望远镜Icecube在南极点附近。我们大亚湾合作组有几位合作者就来自Icecube实验。“Icecube是南极最重要,呃,最昂贵的实验”,Smoot说。“到南极进行天文观测最大的好处也许是成本。用火箭运送1kg的装备到太空需要1万5千美元,用航天飞机需要6万,运到南极只需要10美元,而在某些波段,冰穹A的观测条件甚至比天上还好。”

实际上,到冰穹A做实验并不容易。从中山站出发,需要在零下50度经过20天1250公里的跋涉,才能到达4000米高的冰穹A,其难度大概不亚于攀登珠穆朗玛峰。不过在2008年,几个小的研究项目,包括国际合作的PLATO自动观测站,已经在Dome A建立起来,为下一步的天文台址提供测量参数。计划中Schmidt望远镜阵、大视场成像望远镜和太赫兹波望远镜,可能对暗物质、暗能量、宇宙起源等研究做出重要贡献。

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Deep Underground Laboratory in China, chicken or the egg?

Monday, July 6th, 2009

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

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。

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龙芯签约MIPS

Saturday, June 20th, 2009

龙芯签约MIPS,引来骂声一片。某些伪专家强忍兴奋,兴灾乐祸地声称“这标志着自主产权的CPU核战略失败”。此语一出,网民留言前十条都是谩骂,没有一条支持的,三分之二的人投票不看好龙芯的未来。着实让人寒心。

自主创新不等于推倒重来,关键看是否有足够的研发力量,是否永远受制于人。能够“拿来”的东西,没有必要从零开始,重复开发。AMD采用了跟Intel一样的x86架构,得到的是市场。如果龙芯不采用MIPS架构,自搞一套,那才是愚蠢。开发完一个CPU,还得配100个“自主”的外设公司,1000个“自主”的软件公司,再强制1亿人学习“自主”的操作系统,“自主”的办公软件。该批判的不是龙芯的“不够自主”,反而是某些为了显得“自主”,不顾国际上已广泛采用的标准,自己重复开发另搞一套的项目。就像阎锡山的窄轨铁路,这样只会把自己锁起来,离开了政府支持,马上就自生自灭了。这样的项目在中国不在少数。不期望龙芯能搞成Intel,能搞成乐凯、奇瑞,就算是大获成功了。

说到奇瑞,在法国,大街上跑的车基本上都是法国的三大品牌:标致,雪铁龙,雷诺。德国人基本上开德国车,韩国人全开韩国车,美国开放一点,主要是美国车和日本车。中国人开的是万国车,全世界的汽车品牌在中国都有引进的生产线。一汽、二汽、上汽,这么多财大气粗的公司,引进了这么多品牌,也没搞出自己的东西,想生产新车型,还得继续买。引进没有错,引进100个品牌的生产线就有点可笑,引进了20年,想换个壳还得引进就有点可悲。好像也没有多少人骂。

天变不足畏,祖宗不足法,人言不足恤。自主创新之路需要面对的困难,不仅在技术。

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Clean containers never exist

Friday, June 19th, 2009

Very transparent liquid scintillator (LS) is chosen as the antineutrino target of the Daya Bay Reactor Neutrino Experiment. The antineutrino detectors are immersed in 2,000 tons of ultra-pure water. To avoid contamination of the LS or water by the detector materials, hundreds of tests have been done at Institute of High Energy Physics in Beijing and Brookheaven in U.S. since February 2007 to select the materials.

In the industry of pure water, it is well known that stainless steel will pollute water, although at low levels. The leaching rate is about 30 ng/cm2/h. The leaching rate of polypropene (PP) and polyethene (PE) is 0.14 and 0.29 times that of stainless steel. Teflon and quartz are much better, about 0.07 of stainless steel. In our compatibility tests, materials are immersed in liquid scintillator. The UV-vis absorption spectrum of the liquid is monitored over time to know if there is any impurity leaching out from materials. We found that most plastics pollute the liquid scintillator apparently. Only a small portion of fluoro-plastics has invisible leaching. It is specially interesting that high density polyethene (HDPE) is found to have only a little pollution to linear alkylbenzene (LAB), while linear low-density polyethene (LLDPE) has a lot. Probably due to different polymerization techniques, the LLDPE has more unpolymerized monomers inside, which will leach out when soaked in solvent.

Disposable plastics items are widely used in biological and pharmacological laboratories. Andrew Holt, an assistant professor of pharmacology at the University of Alberta, found that their plastic tubes can leach out two additives, the disinfectant (DiHEMDA) into water and the lubricant oleamide into methanol and DMSO, which make their results unintelligible. He reported on Science magazine in Nov. 2008 that chemicals leaching from plastic lab equipment could be compromising the accuracy of biological studies.

We conclude that 1) chemicals leaching from plastics could compromise the accuracy of particle physics experiments, but it is not a big deal worth an announcement. If it is compromising the accuracy of biological studies, that’s worth a Science article. 2) A study, maybe not original, or even a common sense, could be very valuable if it does help a lot of people.

P.S.  I asked my colleage Zhiyong Zhang if they encountered similar cases in their biology-related researches. He said yes! Several years ago, Shanghai Institute of Applied Physics surveyed the lab equipments in the market and measured the leaching impurity with ICP-MS. They identified a product with the least leaching. To avoid contaimination in their experiments, Zhiyong bought 10,000 of those tubes!

 

不存在干净的容器

大亚湾反应堆中微子实验的中微子探测器使用极为透明的液体闪烁体,中微子探测器则浸泡在纯净水中。为了防止探测器材料污染纯净水和液体闪烁体,自2007年2月起,数百个材料与纯水或液体闪烁体的化学兼容性试验在北京的高能物理所和美国的布鲁克海汶实验室进行。

在纯净水工业中,不锈钢会析出杂质污染水是常识性的,尽管不大。析出量大约是30ng/cm2/h。聚丙烯与聚乙烯的析出量约为不锈钢的0.14和0.29倍。聚四氟乙烯和石英好得多,析出量为不锈钢的0.07倍。在我们的兼容性实验中,材料被泡在液体闪烁体中,通过监测液体闪烁体的紫外可见吸光度随时间的变化来判断是否有杂质析出到液体中。我们发现除了少数氟塑料对液体闪烁体的污染难以察觉外,大部分的塑料对液体闪烁体的污染是明显的。特别有意思的是,高密度聚乙烯对烷基苯的污染很小,可是线性低密度聚乙烯则非常明显。因此我们估计,由于聚合方法不同,线性低密聚乙烯存在较多的未聚合单体,浸泡在溶剂中时易于析出。

廉价的一次性塑料器皿在全世界的生物实验室中被广泛使用。加拿大阿尔伯特大学的药理学副教授安德鲁•霍尔特发现,所用的塑料试管会析出两种生产塑料所用的添加剂:消毒剂DiHEMDA和润滑剂油酸酰胺,这些析出物使他的实验结果莫明其妙。2008年11月他在《科学》杂志上发表文章,称“从塑料实验容器中溶出的化学物质可能会使生物、医学研究的精确性大打折扣”。

我们可以得到如下结论:1)从塑料容器中析出的化学物质可能会使粒子物理实验的精确性大打折扣,不过不值得发表;如果使生物、医学研究的精确性大打折扣,那就值得发表在《科学》上。2)一项成果,也许不是原创性的,甚至是常识性的,如果能够帮助很多人,那也是很重要的成果。

后记:我问我的同事张智勇是否碰到过这种情况。他说多年前就注意到了,上海应用物理所检测了多个国内厂家的产品,最后选择了一个杂质含量最低的厂家,通过他们买了这个厂家的1万个瓶子。

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A scientist memorized at the Dragon Boat Day

Sunday, June 14th, 2009

Qu YuanMay 28 is the Dragon Boat Day of this year. I was on mission to Xia Men and returned to Beijing late at night.

The Dragon Boat Day is to memorize Qu Yuan, a pioneer of Chinese poem lived in 2300 years ago. My hometown is on the route of his exile. The traditions are rich. Qu Yuan compared himself with vanilla and beautiful woman. In “Nine Chaunts, Xiang Lady”, he wrote, “Vanilla lives on the Yuan river and orchid lives on the Li river, I miss the noble man but could not speak out.” Later on the Li river has an alias the orchid river, and the Yuan river the vanilla river. My hometown has a lot places named after the orchid river, such as Orchid River Bridge, Orchid River Park, Orchid River Mall, and Orchid River Theatre. The Vanilla River Airport was the second largest airport of the Allied Force in the Far East during the World War II.

The traditions at the Dragon Boat Day include Dragon Boat competition, Eating Zongzi (glutinous rice dumpling), hanging orris, bathing with mugwort water, drinking arsenic sulphide spirit, etc. Probably due to local limitation, I haven’t seen the most famous tradition Dragon Boat competition. I drinked the arsenic sulphide spirit when I was young, and smeared it on the forehead. Later on we knew it is poisonous and nobody do that now. Mugwort is “heaven grass”. My mother brought some recently for my daughter, and made tea to alleviate the indigestion.

The great poet has been memorized by Chinese for 2300 years. This tradition is extended to many countries in East Asia and Southeast Asia. However, it is not so well known that he is not only a poet and a politician, but also a scientist with deep thoughts as Aristotle, who was born 40 years earlier. Probably natural philosopher is a better title for him. Anyway natural philosophy is an alias of physics. In one of his poem, Heaven Questions, he asked many questions about the cosmos.

Positivistic judgment, rational analysis, and peer review are several characteristics of modern science. In Heaven Questions, he asked “it is said that the heaven is nine-tiered, but who measured it?” That’s typical positivistic judgment. “There are so many corners (at the intersection of the heaven and the earth), who knows the number?” That’s quantitative analysis. It is very different from the later popular reasoning in China such as “Confucius said” or “Chairman Mao said”.

Due to the highly simplified ancient Chinese and its age old, there are many different explanation to the verses in Heaven Questions. Prof. T.D. Lee pointed out in “Physics and Astronomy in Ancient China” that the verse “Who live in the intersection of the nine-tiered heaven (and the earth)? There are so many corners (at the intersection of the heaven and the earth), who knows the number?” actually inquires the contradiction of the theory “the heaven is round and the earth is a square”. If the theory is true, then the heaven and the earth must have intersections. Who live there and see it? There must be many corners thus not natural. Therefore, the heaven is round, and the earth must be round. The first two verses in the poem also point out a contradiction. “Who knows and circulates the state of the beginning of the universe? The heaven and the earth has not been formed yet, how to testify it?” These are typical rational analyses. Of course Qu Yuan didn’t know the light speed is limited. By observing the galaxies ten billions light-years far away from us, we could know the universe ten billion years ago, even approach the beginning of the universe.

As a poet, Qu Yuan got tons of peer reviews. Every educated Chinese know some of his verses. As a natural scientist, he got very few comments from his “peers”. TD Lee says a lot in his article mentioned above. At Xiang Shan Science Conferences in 2005, Prof. Bing-Lin Young cited his verse “that’s such a large project (to measure the tiers of the heaven), who’s the pioneer to complete it?” to encourage the Daya Bay reactor neutrino experiments. Anyway, scientists versed in ancient Chinese are few.

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端午节纪念的科学家

Sunday, May 31st, 2009

5月28日是端午节,我在厦门出差,深夜才返回北京。

端午节是纪念屈原的节日,也捎带上伍子胥。我的家乡是屈子行吟之地,历来纪念风俗较浓。屈原以香草美人自喻,在《九歌,湘夫人》中有“沅有芷兮澧有兰,思公子兮未敢言”。因此澧水别名兰江,沅江别名芷江。我的家乡澧县很多场所以兰江为名,如兰江桥、兰江公园、兰江商场、兰江剧院等。芷江机场则是抗日战争时盟军远东的第二大军用机场。

端午节的风俗有赛龙舟、吃粽子、挂艾叶菖蒲、用艾蒿水洗澡、喝雄黄酒等。也许是条件限制,最出名的风俗赛龙舟我反而没见过。小时候喝过雄黄酒,用雄黄酒点眉心,后来知道雄黄是有毒的,就不喝了。艾蒿仿佛是包治百病的仙草,我母亲前不久还带来给我女儿泡水喝,治消化不良。

一个诗人,被整个民族几千年来隆重纪念,而且还扩展到了东亚、东南亚许多国家,实在是很了不起的。但是少为人知的是,屈原不仅是伟大的诗人、政治家,也是一名伟大的科学家,其思想深度不亚于比他大40岁的亚里士多德。当然,叫自然哲学家可能更合适一点,反正自然哲学也是物理的别名。他的《天问》前几句是:
曰遂古之初,谁传道之?(译文)请问远古开始之时,谁将此态流传导引?
上下未形,何由考之?    天地尚未成形之前,又从哪里得以产生?
冥昭瞢闇,谁能极之?   明暗不分浑沌一片,谁能探究根本原因?
冯翼惟像,何以识之?   迷迷蒙蒙这种现象,怎么识别将它认清?
明明闇闇,惟时何为?   白天光明夜晚黑暗,究竟它是为何而然?
阴阳三合,何本何化?   阴阳参合而生宇宙,哪是本体哪是演变?
圜则九重,孰营度之?   天的体制传为九重。有谁曾去环绕量度?
惟兹何功,孰初作之?   这是多么大的工程。是谁开始把它建筑?
斡维焉系,天极焉加?   天体轴绳系在哪里?天极不动设在哪里?
八柱何当,东南何亏?   八柱撑天对着何方?东南为何缺损不齐?
九天之际,安放安属?   平面上的九天边际,抵达何处联属何方?
隅隈多有,谁知其数?   边边相交隅角很多,又有谁能知其数量?

现代科学的特征包括实证、理性、同行评议等要素。屈原问“圜则九重,孰营度之?”这是典型的实证主义。“隅隈多有,谁知其数?”还有量化的想法。这与后来的“子曰”或“毛主席教导我们”式的证明就完全不同。由于古文的高度精炼,时间久远,对天问的理解也各不相同。李政道先生在《中国古代的物理与天文》里指出, “九天之际,安放安属?隅隈多有,谁知其数?”是指出了古人“天圆地方”理论的矛盾。如果天是圆的、地是平的,就会相交,成“九天之际”。这相交的边沿是“安放安属”,谁愿意在哪个交界的地方?“隅隈多有,谁知其数?”,边边角角太多,相交显然不合理。因此,天是圆的,地一定也是圆的。我觉得“上下未形,何由考之?”把考翻成产生不太合理,不如直接翻成考证。天地都还未成形,那时候的情形谁看见了,并把它“传道”下来?这是典型的理性思维。当然他不知道光速是有限的,观察离我们百亿光年远的星系,就可以了解百亿年前的宇宙,甚至逼近宇宙诞生之初。

作为伟大的诗人,2300年来同行评议自然汗牛充栋,毋须细说。另类的考证也不少。有人说他不是投泊罗江自杀的,是楚王派船追上他,包粽子扔到江里的。老百姓不敢说,只好用赛龙舟、包粽子等隐喻来揭示事件真相。孙次舟、朱自清、闻一多等人考证屈原是同性恋,是楚王的男宠。还有人考证屈原的家乡不是湖北秭归,是湖南汉寿。作为科学家,似乎没有太多同行来评议。李政道先生评了一回。衣阿华大学的杨炳麟教授在香山科学会议的报告上用“惟兹何功,孰初作之?”来勉励大亚湾实验。大概精研古代典籍的科学家太少了。

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