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 楼主| 发表于 2008-11-22 12:33:21 | 显示全部楼层
本帖最后由 qysnn 于 2014-12-9 17:16 编辑

官方网站:http://stardustathome.ssl.berkeley.edu/

Friday, November 14, 2008
Shots Fired
We have been working with our colleagues at the University of Heidelberg, Germany for the last two weeks, using their tandem van de graaf dust accelerator to fire submicron dust particles into aerogel tiles and aluminum foils.  Zack Gainsforth from Berkeley is working with Frank Postberg, Ralf Srama and Eberhard Gruen on this important project.
2008.11.14 星期五
开火
上两周我们和同事在德国海德堡大学用他们的 tandem van de graaf 尘埃加速器将亚微米尘埃颗粒射入凝胶块和铝箔片中。来自伯克利的 Zack Gainsforth 同 Frank Postberg、Ralf Srama 及 Eberhard Gruen 共同参与此项重要项目。

We are shooting particles into flight spare aerogel tiles and aluminum foils at various velocities from 5 to 25 km/sec. The projectiles are submicron latex, aluminum, and iron spheres. Our goal is to determine the dependence of track and crater size (diameter and depth) on particle type and velocity. We are optimistic that this will lead to improved laboratory analogs for the interstellar dust impacts in the Stardust collectors. They still will not be perfect -- an absolutely accurate laboratory simulation of interstellar dust impacts is probably impossible -- so we still have to keep an open mind about the appearance of the tracks that we're working so hard to find.
我们用5-25km/sec的不同速度将微粒射入飞行备件的凝胶块和铝箔中。弹丸是亚微米的乳胶、铝和铁质球。我们的目标是测定轨迹和冲击坑的大小(直径和深度)与不同类型、速度颗粒间的依赖程度。这有助于改进对星际尘埃撞击“星尘”收集器的实验室模拟,对此我们很乐观。这些依然是无法做到完美的——对星际尘埃撞击绝对精确的实验室模拟恐怕是不可能的——所以对那些我们努力寻找的轨迹外观依然要保持开放的心态。

Also, over the last 10 days or so, our colleagues Frank Brenker, Bart Vekemans, Laszlo Vincze, Sylvia Schmitz and Manfred Burghammer have been looking at new picokeystones on the x-ray microprobe beamline ID21 at  the European Synchrotron Radiation Facility  This is a beautiful instrument, and the analyses have been going well.  
同时,在过去的差不多10天里,我们的同事 Frank Brenker, Bart Vekemans, Laszlo Vincze, Sylvia Schmitz 和 Manfred Burghammer 在用欧洲同步辐射器的X射线探针ID21(x-ray microprobe beamline ID21)观察一个新的微楔块儿,这真是一个好工具,分析进行的很顺利。

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 楼主| 发表于 2008-11-28 16:21:02 | 显示全部楼层
Thursday, November 20, 2008
Update from Heidelberg:
We've had a successful time at Heidelberg so far. In the first week we shot aerogel tiles with 1/2 micron sized spheres of latex imbued with sulfur and coated with a conductive polymer. This yielded the first successful artificial tracks with known impactor size and velocities in the range of 5-30 km/s. We still have to analyze them at the synchrotron, but preliminary tracks look like:
2008.11.20 星期四
海德堡方面的进展
这是我们在海德堡最成功的一段时间。在头一周我们用浸过硫并涂上一种导电聚合物的半微米大小的橡胶球轰击了凝胶块。这首次成功产生了速度在5-30km/s 之间与已知撞击大小相仿的人工轨迹。我们还需要在同步加速器上研究它们,不过准备的轨迹就像这样:
heidelberg189.2a.006-765620.jpg

You will notice there are both tiny crater like pits, as well as darker and more conventional looking tracks. What this means is still up in the air, but we suspect the larger dark tracks consist of multiple latex spheres bunched together in blobs before impacting.
你会注意到这些既有像凹坑一样的微小弹坑,也有颜色比较深、更常规一些的轨迹。这说明了什么依然还悬在空中,不过我们猜测较大、较暗的轨迹是在撞击之前数个粘在一起的橡胶球造成的。

In addition, we have tracks that were created by head on collisions with the aerogel (as opposed to the angled shots above) which should more accurately reflect the look of interstellar tracks as seen in the Stardust@Home microscope. We haven't been able to analyze them yet, but if we have trouble finding them, we know who to ask...
此外,我们的轨迹是迎面撞击产生的(与之相反的是成角度的射到上面)能更加真实的反映出星际尘埃轨迹在Stardust@Home 显微镜中呈现出的外观。我们现在还不能分析它们,不过假如我们在寻找它们上出现困难,我们知道找谁帮忙...

While latex is a good analogue for interstellar particles, it does have a couple shortcomings. First, it's density is around 1 gram/cm^3, which is 1/2 - 1/3 of what we expect for interstellar particles. This means that the tracks may not look entirely the same. Why don't we shoot minerals such as we expect to hit? Well, for two reasons. First, what if interstellar particles don't look like we expect? Second, we can't ... until now (more in a bit).
虽然橡胶是星际尘埃颗粒很好的模拟物,它还是有一些缺点。首先,它的密度大约是1克/立方厘米,这只有我们认为的星际尘埃颗粒密度的1/2 - 1/3。为什么不用符合我们期望的矿物来射击呢?很好、有两个原因。首先,要是星际颗粒不像我们认为的那样呢?其次,我们还不能...直到现在(再过一会儿)。

The other problem with latex is that it is made almost entirely out of carbon, hydrogen and oxygen. This makes it very hard to find in aerogel which has carbon, and oxygen in it. (Hydrogen doesn't show up well, and besides, in a lab, there is lots of hydrogen about in the form of water.)
橡胶的另一个问题是它完全是碳、氢和氧制成的。含有碳和氧的东西很难在凝胶中被发现。(氢不是很显眼,除此之外,在实验室里有大量的氢以水的形式存在。)

However, these latex spheres are special. They are imbued with sulfur. This actually kills two birds with one stone. First, we can see sulfur in some of our instruments, thus making the impactor more visible. Second, if you were following the scientific results from the cometary side, you may remember that we initially thought the comet was lacking in sulfur, but then discovered that it wasn't all showing up due to the track and particle characteristics. There is even some evidence that sulfur may "evaporate" into the surrounding material during the heat of the impact. So, now we get to see how the sulfur behaves when it slams into aerogel at hypervelocities!
然而,这些是特殊的橡胶球,它们浸过硫。这真是个一箭双雕的办法。首先,我们的一些设备可以看到硫,这使得撞击更加的显眼。其次,如果你追踪彗星尘埃那方面的科学成果,就会记得当初我们认为彗星是缺乏硫元素的,但是随后发现由于轨迹和颗粒的特性它没有全部显示出来。甚至有些迹象表明在撞击的加热过程中硫可能“蒸发”进入到周围的物质中。所以,现在我们想看看当其以超高速撞进凝胶时硫有怎样的行为表现。

Nevertheless, we wanted something heavier. So we followed the next week with iron particles. These usually shoot well, but they have a downside: they are now several times heavier than what we expect to hit, and the particles themselves very in size from nanometers up to microns. So iron shot makes it much more difficult for us to analyze track morphologies. Nevertheless, because our instruments are so excellent at seeing iron, the variation in particle size shouldn't really matter -- it just requires more elbow grease (or is that forehead grease). That leaves the fact they are heavier. Well, now we have something 3x lighter, and something 3x heavier than an interstellar grain. If they're not too different, then we can assume interstellar tracks look the same. If they are, we can assume interstellar tracks look like something in between. And if a heavy or light particle happened to hit the collector, then we know what it looks like too!
然而我们还想要一些重型的。于是随后的一周里我们用了铁颗粒。它们的射击性能通常都不错,但是它们也有不好的一面:它们是我们期望射击重量的数倍,并且颗粒自身的大小从纳米到微米都有。所以铁弹使我们对轨迹形态的分析变得非常困难。不过,由于我们的设备在看到铁方面实在太优秀了,对不同大小的颗粒并不是很在意——多干些力气活罢了。那就剩下比较重这一点了。好了,现在我们有了大约1/3以及3倍于星际尘埃重量的颗粒。如果它们的差别不是很大,那我们就能假设星际尘埃轨迹看上去差不多。如果有差别,我们就能假设星际尘埃轨迹看上去会是中间的某种形态。并且假如一个重或轻的颗粒碰巧击中收集器,那我们也能知道它看上去会是什么样子!

Unfortunately, we only got half of the iron shots, because in contrast to past experience, our iron source had a bad work ethic and went on vacation towards the end of the week, giving us only slow particles at a few km/s. This was just the luck of the draw. All the same, we got at least 1 of everything we wanted, so we're happy. Two of each sample was greedy anyway. :-)
不幸的的是,我们仅得到了一半的铁弹,因为比照以往的经验,我们的铁源有一个很糟糕的职业习惯接近周末的时候要去休假,只给了我们速度仅几个km/s的低速颗粒。真是太走运了。我们还是得到了至少一件我们想要的东西,所以我们很高兴。第二点就是无论如何每一个样本都是难得的。:-)

In the third week, we started out with a special "bonus" mixture. Aluminum mixed with PMMA (polymer) beads. Aluminum is a wonderful material for us because it weighs approximately what we expect interstellar grains to weigh, and it shows up brightly in our instruments. Perfect you say! Yes, well, there is a problem. Aluminum has an awful history of sticking to itself, and then clogging the accelerator (resulting in no tracks). For this reason, we mixed it with PMMA as sometimes mixtures jog the material and avert sticking. We don't really care about the PMMA, but if we get a few shots of it, that's a bonus too. To our delight, we got very fast tracks on the first day -- over 100 particles at 50-60 km/s!!! This is practically 3x the speed we expect from interstellar particles so this is a real coup d'etat! The next morning I came in grinning ear to ear, expecting to get all the other velocities we wanted but alas, it wasn't meant to be -- the accelerator was clogged. So much for the PMMA.
在第三周,我们开始用一种额外的混合物,铝与PMMA(聚合物)混合的珠子。铝对我们来说是一种很不错的材料,因为它的重量接近我们预计的星际颗粒的重量,并且在设备中表现明亮。听起来不错嘛。是的,不过,还有个问题。铝有份很糟糕的档案它自己会粘在一起,然后阻塞加速器(结果就是没有轨迹)。因此我们用PMMA与之混合,因为混合物会不时的弹开材料避免粘连。我们并不是很在意PMMA,不过假如我们得到了几个弹孔那也是一份奖金。让我们喜悦的是,在第一天里我们得到了很高速的轨迹——超过100个速度在50-60km/s的颗粒!!!这差不多是我们预计来自星际颗粒速度的3倍,这真是场政变!第二天早上我进来的时候笑得合不拢嘴,希望得到我们想要的其他速度但是唉,看来是不可能了——加速器被阻塞了。PMMA太多了。

The downside of clogging the accelerator is it takes several days to reload -- and we're now on our last week of the trip. So, we got busy and replaced the sample. It is now loading (vacuum is pumping) and hopefully, by tomorrow afternoon we should be able to resume shooting. Wish us luck!
加速器阻塞的不利影响是需要好几天重新装载——此刻已是我们这趟旅行的最后一周了。于是我们连忙重新换了样品。现在正在启动中(真空泵在抽气),有希望在明天午后能够继续射击。祝我们好运!

What are we shooting now? More aluminum? Nope. Because Mario Trieloff at the University of Heidelberg and Frank Postberg at the Max Planck Institute have pulled a rabbit out of their hat. We can shoot orthopyroxene -- a mineral more or less identical to something we might expect in an interstellar dust grain.WOW! This wasn't possible just a few weeks ago. They have developed a new technique for preparing minerals for firing just within the last few weeks, and now, for the first time, we're going to get mineral shots into aerogel at tens of km/s. Oooh! I'm wringing my hands and licking my chops.
我们现在要射击什么呢?更多的铝?不。因为 Mario Trieloff 在汉堡大学、Frank Postberg 在马克思普朗克学会有惊人之举。我们可以射击斜方辉石——一种有点儿像我们所期望的星际尘埃中有的矿物。WOW!就在几周之前这是不可能的。他们就在前几周里开发出了一种新的技术来准备射击用的矿物,现在,我们将首次把矿物以几十km/s的速度射进凝胶。哦!我正在舔着嘴、双手在冒汗。

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发表于 2009-1-15 22:27:43 | 显示全部楼层
看来要探索宇宙的奥秘真不容易啊。。。。。
     按说当然是先找六个他们认为最有可能的轨迹啦。除非他们特别沉得住气,从最不象的开始找。虽说并不意外,也不气馁。但看来他们有点吃不准了,跑到德国去做模拟撞击了。。。。说不定以后还会更改轨迹的搜索特征,重新来一次呢!(老实说现在的特征应该是很合理的啊。。。)  还有那个怀疑撞到太阳能版上的二次轨迹。。。。不是说以20km/s以上速度运动的微米级大小的星尘撞上硬物就会汽化的吗?所以才用气凝胶作为搜集版材料啊。。。。。是否太空中的微粒并没有想象中高速呢?而这又意味着什么呢。。。。。他们用了不同的重量,不同的速度去模拟撞击。。。看来一切都有可能啊。。。
     “现实比我们想象的更不可思议”     呵呵,期待中。。。。
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 楼主| 发表于 2009-1-23 21:34:59 | 显示全部楼层
产生二次轨迹的微粒是太阳能板被撞击产生的抛射物,原始撞击体有多大是不太好确定的。如果参照彗星尘埃的例子,毫米级的颗粒在铝片上打个坑并“存活”下来是不成问题的。
这是一股流入太阳系的星际尘埃流,而捕获地点也算是在太阳系的核心区域情况复杂,这一网撒下去谁知道会捞起什么呢。
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发表于 2009-2-10 21:34:10 | 显示全部楼层
这么说,这个二次轨迹肯定不是“星尘”了?我还有个奇想,有没有考虑尘埃流的运动方向呢。。。有必要检查一下太阳能电池板、收集版的背面。。。
还有必要继续找吗?
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 楼主| 发表于 2009-3-23 22:07:16 | 显示全部楼层
继续找是肯定的,前一段官方新闻里给出了3个音频,鉴于俺可悲的听力 听力好的去试试吧
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 楼主| 发表于 2009-5-31 21:46:39 | 显示全部楼层
Tuesday, May 26, 2009
2009年5月26日 星期二

What has been happening.....
过去所发生的事......

We want to share with you some new developments in the search for interstellar dust that we are cautiously excited about. We want to say from the beginning that we don’t understand everything yet, and that this may lead to a dead end. This is a bit like detective work – we’re sorting through the clues, and there is always a stage of confusion before things become clear. It is important to follow every lead. This is often how science works. The confusing parts (we hope) become the exciting parts, because we learn from what we don’t know. We’re sharing our confusion and our excitement with you, even though the story is far from complete.
我们打算与大家分享一些搜索星际尘埃的新进展,它们令我们感到谨慎的兴奋。话说在头里,我们目前还不理解所有的事,这有可能把我们领进死胡同。这有点儿像侦探的工作——我们在线索中不断排序,在事情明朗前总会有一段混乱的阶段。追踪每一条线索都非常重要。科学工作经常是这样的。令人困扰的部分(我们希望)变成令人激动的部分,因为我们从那些不了解的事情中学到了东西。我们将与大家分享我们的困惑和兴奋,即使离故事结束还远着呢。

First, a quick status report on the project. Last year we focused on extracting candidates, so we were not able to do any additional scanning. We have good scan data on 247 cm2 of the collector – about 30% of the scannable area. 30 extractions have been done since the beginning of the Interstellar Preliminary Examination. 16 of these were interstellar candidates. The extraction process has evolved somewhat during the first year of the ISPE, but not in a substantial way. All candidates are now mounted between silicon nitride windows by default. 14 of these have been analyzed at synchrotrons all over the world. 12 do not appear to be consistent in their composition with interstellar dust. Two are sufficiently interesting that we want to do further study on them. One was lost due to a pre-existing fracture in the keystone. Unfortunate as this is, it emphasizes the need for a cautious approach to sample prep and extractions. Rather than rush, it is better to move carefully through the extraction phase in order to minimize sample loss and damage. One additional candidate is still under analysis.
首先是项目现状简报。去年我们集中在做候选物的提取,因此没能做任何进一步的扫描。我们有收集器247平方厘米扫描较好的数据——大约是可扫描面积的30%。在星际尘埃预查(ISPE)开始后完成了30个提取工作,其中有16个是星际尘埃的候选者。在ISPE的头一年里提取的过程发生了一些演化,但不是很本质的。所有的候选者通常情况下都安放在氮化硅窗体中。其中有14个已经被世界各地的同步加速器分析过了。12个在其成分上未表现出与星际尘埃相一致。2个十分的有趣,我们打算进一步的研究它们。有一个由于楔块儿中已存在的一条裂缝而丢失了。这真太不幸了,这着重表明准备样品和提取时需要非常小心的处理。与其仓促完成,还是在提取阶段小心的移动以减少样品的损失和破坏更好些。还有一个额外的候选者仍在分析中。

Based on the early estimates of the number of interstellar dust particles that we are likely to have collected, we have about ten times more candidates than we expect to have interstellar dust particles – in other words, we expect to extract and analyze about 10 candidates for every real interstellar dust particle that we find. We are refining this estimate now – so far it appears that the number of interstellar dust particles collected was likely lower than the original estimate. If this turns out to be correct, this means we will have more work to do than we initially anticipated to find the interstellar dust particles. We have done no extractions since last Fall, since the Cosmic Dust Lab (CDL) has been switched over to doing work on Interplanetary Dust Particles (IDPs). We expect to resume extractions when CDL is switched back over to interstellar dust work, nominally at the end of May. We also expect that some foils will be extracted so that the foils subteam can begin work on searching for impact craters of interstellar dust.
基于早先对我们可能收集到的星际尘埃数量的估计,候选者的数量是我们预期获得星际尘埃数量的十倍——换句话说,我们预计每找到一个星际尘埃颗粒就要大约提取和分析10个候选者。我们正在改进这一估计——到目前它似乎表明收集到的尘埃数量可能比原先预计的少。如果这一结果是正确的,那就意味着与最初预计相比要发现星际尘埃我们有更多的工作要做了。自从彗星尘埃实验室(CDL)转换到做行星际尘埃工作以及上一次提取失败以来我们没有再做提取工作。我们希望当CDL再次转换到做星际尘埃工作时继续进行提取工作,名义上是在5月末。我们还希望能取出一些衬片,以便衬片分队能寻找星际尘埃的撞击坑。

Now to the recent developments that we’re cautiously excited about. Stardust@home dusters have found 29 so-called “high-angle” tracks. These are tracks of particles that didn’t come straight into the collector, but entered at a significant angle – typically about 45 degrees. I want to emphasize that these were identified by Stardust@home dusters, not by us. The fact that these were found by our amateur colleagues is a tremendous demonstration of the value of the Stardust@home approach. Some of these high-angle tracks were discovered in the first days of the project. We had not thought of these as being likely interstellar candidates, for three reasons. First, the projectiles came in at a large zenith angle with respect to the aerogel surface. This was not expected for interstellar dust, because the interstellar dust collector was intentionally oriented during the exposures so that the interstellar dust would come more or less straight into the detector. Second, the azimuth angles were such that the tracks seemed to be coming not from space, but from the solar panels of the spacecraft. Third, the tracks did not appear to us to be high-velocity tracks, such as those seen on the cometary side of the collector, where particles were captured at 6 km/sec. High-velocity tracks, from projectiles at >>1 km/sec, make carrot-shaped tracks in aerogel. The tops are wide because the projectile produces an energetic shock wave in the aerogel that expands dramatically and blows out a relatively large cavity in the aerogel. As the projectile slows, the shock weakens and eventually disappears when the projectile drops below the speed of sound. The result is a carrot-shaped track. But the high-angle tracks were thin and smooth, which in our experience looked more like slow. (<< 1 km/sec) projectiles. Finally, we extracted five of these tracks and examined them using synchrotron x-ray fluorescence microscopy (SXRF) and by scanning transmission x-ray microscopy (STXM). We found that three of them contained significant amounts of cerium, which is a rare element and is not expected in any significant quantities in any primitive extraterrestrial material. All of these lines of evidence led us to conclude that the high-angle tracks were highly likely to be ejecta from impacts on the aft solar panels of the spacecraft.
对于最近的进展我们谨慎的兴奋。Stardust@home 的搜尘者发现了29个被称作“大角度”的轨迹。这是那些没有笔直的进入收集器的颗粒轨迹,而是以一个有意义的角度——典型的约45度进入的。我想强调,这些是 Stardust@home 搜尘者识别出来的,不是我们。实际上我们的爱好者的这些发现是 Stardust@home 这种途径价值的极佳证明。其中一些大角度轨迹是在项目的第一天被发现的。我们不认为这些像是星际尘埃候选者,有三点原因。首先,弹丸是以相对于凝胶表面大的天顶角度进入的。这不被认为是星际尘埃,因为星际尘埃收集器暴露在外期间是有意定向的因此星际尘埃差不多会是笔直的进入。第二,从方位角看这些轨迹不像是来自太空,而是来自飞船的太阳能电池板。第三,在我们看来这些好像不是那种在彗星尘埃收集器里可以看到的高速轨迹,那里捕获的颗粒速度是 6km/sec。高速轨迹来自于远大于 1km/sec 的弹丸,在凝胶中形成胡罗卜的形状。宽的顶部是由于弹丸在凝胶中产生了一个高能的冲击波,冲击波在凝胶中显著的扩展并炸出一个相对大的空腔。随着弹丸减速激波变弱,当弹丸降到音速之下最终消失。结果就是一个萝卜形的轨迹。但是大角度轨迹是细而平坦的,根据我们的经验看上去像是很慢的(<<1km/sec)弹丸。最终,我们取出了5个这样的轨迹并用同步X射线荧光显微镜和X射线扫描隧道显微镜进行了仔细检查。我们发现其中3个含有可观的铈,这是种稀有元素不被认为会以任何可观的量出现在任何原始的地外物质中。所有这些证据使我们得出结论,大角度轨迹极有可能是飞船尾部太阳能电池板上撞击溅射出来的。

But not so fast. Three developments have led us to reconsider seven of these 29 tracks.
但是别太急。三个发明引导我们重新考虑这29个中的7个。

First, we recently did some experiments with our colleagues Frank Postberg, Mario Treiloff, Ralf Srama, Sebastian Bugiel, and Eberhard Grün at the University of Heidelberg. They have cleverly adapted a particle accelerator, a van de Graaf accelerator, to accelerate small dust particles. For very small dust particles, they can achieve speeds up to 100 km/sec! This is the same accelerator that produced the calibration track in the phase I Stardust@home images. The dust accelerator works as follows. A bowl of the dust that you want to shoot is placed at the high-voltage end of a long evacuated pipe. The voltage is about 2 million volts. A sharp needle sticks up from the bowl. A high frequency voltage is applied to the bowl, which occasionally causes one of the dust particles to jump out of the bowl onto the tip of the needle, where it acquires a large charge and is accelerated down the 2 megavolt potential into the target. (Who thought of that??) However, it gets even more clever. Because this is a stochastic (random) process, the dust particles acquire wildly varying charges, so the accelerated dust comes out with a wide range of speeds. But to get unambiguous results, we need to have the particles coming out in only a narrow range of speeds, say 15-16 km/sec. So they use three detectors located at different positions along the flight path of the dust. These detectors can detect the passage of the dust particle, and by measuring the time delay between the passage of the dust grain past the three stations, they can measure the speed of the dust grain. If the speed isn’t right, the particle is rejected using a pair of electrostatic plates near the end of the pipe, to deflect the dust grain away from the target. Of course, all of this happens so fast that no person actually makes the decision – it is all done by electronics.
首先,最近我们和海登堡大学的同事 Frank Postberg, Mario Treiloff, Ralf Srama, Sebastian Bugiel, Eberhard Grün 一起做了一些实验。他们聪明的改造了一种范德格拉夫粒子加速器,来加速微小的尘埃颗粒。对于微小的尘埃颗粒,它们能获得达到 100km/sec 的速度!就是在 Stardust@home 第一阶段里用来产生校准轨迹的那台加速器。尘埃加速器是这样工作的。一碗准备射击用的尘埃放置在一条抽空的高电压管一端。电压大约是2百万伏。一个尖针从碗里伸出来。一个高频电压作用在碗上,会随机的使某个尘埃颗粒从碗里跳到针尖上,并在那里获得大量电荷并被2百万电势加速进入目标。(是谁想出来的?)真是很聪明啊。因为这是一个随机的过程,尘埃颗粒获得电荷数量范围很宽,所以被加速的尘埃获得的速度范围很宽。但是为了得到明确的结果,我们需要使颗粒在一个窄的速度范围内出来,比方说 15-16km/sec。于是他们在尘埃飞行路线的不同位置放了三个探测器。这些探测器能探测到尘埃颗粒的经过,并通过测量器通过三个探测器的时间差得出尘埃颗粒的速度。如果速度不合适,在管道末端附近一对静电板会使尘埃偏离射击目标。当然这一切发生的非常快,没人能做出决定——一切由电子设备完成。




Using the dust accelerator, Zack Gainsforth and our German colleagues shot small particles of latex, aluminum, a polymer called PMMA, orthopyroxene, and iron, into aerogel and aluminum foils at speeds from 10-20 km/sec. The latex particles produced very short tracks in the aerogel, which was not a surprise. However, the iron and the orthopyroxene particles appeared to produce very long, thin tracks, reminiscent of the high-angle tracks in the Stardust collector. The reason that we emphasize the word appeared is that there was a complication in the experiment. Sometimes the dust source in the accelerator “spits” -- that is, it produces rare bursts of particles, that can confuse the triggering system and allow slow, large particles to get through while the gate is open to allow a legitimate high-velocity particle through. We saw evidence of these in some of the shots, but not in the shots of the orthopyroxene or of the iron. In the iron shots, we saw about as many particles in the aerogel as we expected based on the number of times that the filter triggered. So there are two questions: (1) if these particles were actually slow, where are the fast ones that should also be in the target aerogels? (2) if the tracks we see are made by particles that are truly traveling fast, why do they make whisker-shaped tracks instead of carrot-shaped ones? We still don’t know the answer to either of these questions. We’re doing some additional shots in the next months with a new, improved filter that we expect to do better at rejecting “spits”.
Zack Gainsforth 和我们的德国同事用尘埃加速器把一些橡胶、铝、一种叫PMMA(聚甲基丙烯酸甲酯)的聚合体、斜方辉石、铁的小颗粒以 10-20km/sec 的速度射进凝胶和铝箔片中。橡胶颗粒在凝胶中产生了非常短的轨迹,这并不奇怪。不过,铁和斜方辉石颗粒显现出造成了非常长而细的轨迹,令人想起星尘收集器中的大角度轨迹。我们强调“显现”一词的原因是在实验中出现了一个难题。某些时候加速器的尘埃源会“吐出”,就是产生了少量粒子的喷发,这会扰乱触发系统使速度慢的大颗粒通过为合法粒子通过而开启的闸门。在一些射击中我们看到了这一现象的证据,但在斜方辉石或铁的射击中却没有。在铁的射击中,我们在凝胶中看到了同触发过滤器计数一样多的颗粒。那么就出现了两个问题:(1)这些颗粒是否确实很慢,那些应该出现在目标凝胶中的快速颗粒跑哪儿了?(2)我们看到的这些轨迹是否真是由快速颗粒制造的,为什么它们形成须状轨迹而不是萝卜形轨迹?我们还不知道这些问题的答案。我们准备在后面几个月里用改进的过滤器做更多射击,希望能更好的拒绝“呕吐”。




斜方辉石


Second, Ryan Ogliore in our group at SSL has been modeling the trajectories of interstellar dust particles in the solar system. He has found that the largest interstellar dust particles can come into the detector at a substantial angle. This is because the interstellar collector was oriented to collect dust with β = 1. What is β? β is a ratio -- it is the ratio of the outward force that sunlight exerts on dust particles to the inward gravitational force exerted by the sun. For particles much larger than 1 micron (like the Earth!) β is essentially zero. But for small particles, around the wavelength of light (a few hundred nanometers) β can be 1 or even greater, depending on its size, shape and density. Large particles from interstellar space travel along hyperbolic orbits that curve inward toward the sun as they go through the solar system. Small particles with β<1 also travel along hyperbolic orbits, but ones that curve outward from the sun. Particles with β exactly equal to one just travel in straight lines through the solar system. Because it was not known what the average value of β was for the interstellar dust, the spacecraft controllers oriented the spacecraft and the collector to track the β = 1 particles. When you do the simulation, you find that the largest particles (those with small β) would come into the collector by flying between the solar panels of the spacecraft, and so in the collector you would expect them to produce tracks that have an orientation of "north", or, if you think about the hands of a clock, about 12 o'clock. There is a complication in that the Sample Return Capsule lid, during some phases of the collections, could actually block particles with small β and keep them from reaching the collector.
第二,我们组里在SSL的成员 Ryan Ogliore 在做星际尘埃颗粒在太阳系中弹道模型。他发现最大的星际尘埃颗粒能以基本一致的角度进入探测器。这是由于星尘收集器定向的收集 β=1 的尘埃。β是什么?β是一个比值,它是作用在尘埃上的阳光产生的外部力与太阳施加的引力的比值。对于比1微米大得多的粒子(比如地球)来说β基本上是0。但是对于尺度在光波波长(几百个纳米)附近的小颗粒β能达到甚至超过1,这取决于它的大小、形状和密度。来自星际空间的大颗粒在穿越太阳系时是沿一条向着太阳内弯的双曲线轨道。β>1(注:我怀疑他手滑了- -) 的小颗粒同样是双曲线的轨道,不过是向外弯的。那些β恰好等于1的星际尘埃以直线穿越太阳系。因为不知道星际尘埃β均值是多少,所以飞船控制人员将飞船和收集器定向到β=1的粒子轨道方向。如果你做一下模拟,你会发现那些最大的粒子(小β值)将从飞船的太阳能板之间飞入收集器,于是你会期望它们在收集器中产生有特定指“北”的轨迹,或者可以当作手表的12点方向。样品返回舱(RSC)盖子方面还存在一个问题,在某些收集阶段中,它实际上有可能阻碍了小β值的颗粒接触收集器。


Third, intriguingly, among these 29 tracks, there are seven that have an azimuth between 11:00 and 12:00. We have assumed that these are ejecta from an impact or impacts on the SRC lid, based on their similarity to the others that really do appear to be secondary ejecta based on the Ce content. And in fact, they all do point back to the SRC lid, but only for some of the collection times. The point is that the collector was on a hinged “wrist” and was constantly being rotated to track the β=1 dust stream. For other collection times, these tracks appear to point over the lid and into space. We don’t know when each track was collected, so the situation is ambiguous: for some collection times these events point into the small-β interstellar dust stream, for others they point into the SRC lid. Obviously, this is a critical question, and is not one that is resolvable just by looking at the track trajectories. We have to do more. We have to extract and analyze them.
第三,有趣的是,在这29个轨迹中有7个的方位角在11:00-12:00之间。我们猜测这些来自SRC盖子上的一个或几个撞击的溅射,根据它们相似且与其他不同的铈含量,它们似乎真是二次溅射物。并且实际上,它们的确都指向SRC盖子,不过仅是在收集的某段时间里。关键是收集器是在一个铰链关节上,会经常的转动来追踪 β=1 的尘埃流。在其他的收集时间里这些轨迹的指向似乎是越过了盖子指向太空。我们不清楚每一条轨迹是何时收集到的,于是情况变得模糊了:在某些收集时间里这些事件指向小β尘埃流;其他时间它们指向了SRC盖子。明显,这是个很重要的问题,而且不是仅通过查看轨迹弹道就能解决的问题。我们还要做更多。我们不得不将其取出分析。

It turns out that we have extracted one of these “midnight” tracks. This is sample, I1004,1,2, VM number VM number 862370V1. Last year we examined it using beamline 11.0.2 at the Advanced Light Source. This is the most powerful Scanning Transmission X-ray Microscope (STXM) in the world. We have been working with the beamline scientist, Tolek Tyliszczak, to analyze interstellar candidates on 11.0.2. Unfortunately, it turns out that we had inadvertently analyzed not the track but a feature that was very similar to the track but turned out to be a machining artifact left over from the “keystone” extraction of the track from the collector. We didn’t find any detectable elements in it, which in retrospect is no surprise. So recently George Flynn and Steve Sutton reexamined this track on beamline 2-ID-D at the Advanced Photon Source at Argonne National Laboratory. They did find detectable elements. They are still analyzing the data from this track, so stay tuned. We will also re-examine this track on 11.0.2 at the end of May.
我们已经取出了这些“午夜”轨迹中的一个。这就是样本 I1004,1,2 VM 编号862370V1。去年我们用先进光源的 11.0.2 光束对其进行了检查。这是世界上最强大的扫描透射X射线显微镜(STXM)。我们曾同光束科学家 Tolek Tyliszczak 一同工作在11.0.2上分析星际尘埃候选者。遗憾的是我们分析的不是轨迹而是一个很像轨迹的构造,是从收集器中提取“楔块”过程中人为加工的遗留物。我们没有在其中发现任何可探测的元素,回想起来这也不算意外。因此最近 George Flynn 和 Steve Sutton 在阿冈国家实验室的先进光子源(Advanced Photon Source) 光束2-ID-D 上重新检查了这条轨迹。他们的确发现了可探测的元素。他们依然在分析这条轨迹的数据,我们也会在5月末重新在11.0.2上再次检查该轨迹。

Even if I1004,1,2 turns out to be secondary ejecta, there are still six more tracks that could turn out to be interstellar. When the Cosmic Dust Lab re-opens in May, the first order of business will be to very carefully re-measure the trajectories of these particles, then extract them for analysis.
即便假设 I1004,1,2 原本就是二次溅射物,还有6个可能成为星际尘埃的轨迹。一旦彗星尘埃实验室5月再次开放,第一个议程就是非常仔细的重新测量这些颗粒的弹道,然后提取出来加以分析。

It’s possible that you have collectively identified real bona-fide interstellar dust particles in the Stardust collectors, the first contemporary particles from outside the Solar System ever identified. But it’s also possible that we are following a false lead. We’re still not sure, so we’re trying to gather as much evidence about the particles as we can. I expect we’ll know more in the weeks and months ahead.
有可能你在星尘收集器中共同鉴别出货真价实的星际尘埃颗粒,这可是当代首批来自太阳系之外的粒子被鉴别出来。但同样有可能我们跟着一条错误的线索。现在还不确定,所以我们尽量收集关于颗粒尽可能多的证据。我期望在随后的数周及数月里我们能了解的更多。

I want to express again my gratitude to you. Without your tremendous efforts, we would not have found these tracks. If it turns out that any one of these is likely to be interstellar dust, after our big celebration, we will redo the calibrations for Stardust@home to include these high-angle tracks. Meanwhile, keep up the fantastic work!
我想再次表达我对大家的感谢。没有你们巨大的贡献,我们可能找不到这些轨迹。假如其中有任何一个最终可能是星际尘埃的话,在我们的重大庆祝之后,我们将为Stardust@home重新制作包括这些大角度轨迹的校准片。在此期间,继续这奇妙的工作吧!

Andrew and the Stardust@home team

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 楼主| 发表于 2009-8-4 11:41:24 | 显示全部楼层
Friday, July 31, 2009
2009年7月31日 星期五

In June, just as we were switching over from work on Interplanetary Dust to Stardust Interstellar work there was a failure of the air chiller that handles the air coming into the Cosmic Dust Lab (CDL). Although the interstellar tray was never in danger this failure could in principle have put the interstellar tray at risk. This incident has caused us to reconsider the wisdom of doing scanning and extractions on the entire tray at once. Although we had thought hard about possible failure modes we did not anticipate this one and may not anticipate the next one, which might have less happy consequences. In consultation with the Interstellar Preliminary Examination (ISPE) Science Council and the Stardust Oversight Committee of the Curation and Analysis Planning Team for Extraterrestrial, Materials (CAPTEM), we have decided to do scanning of tiles and extraction of tracks on individual tiles after they have been extracted from the tray rather than before. There is a consensus that this approach will present less overall risk to the collector.
六月,就在我们从行星际尘埃换回星际尘埃之后控制进入宇宙尘埃实验室(CDL)空气的气体冷却器坏掉了。虽然尘埃收集盘绝不会受损但这一故障理论上可能将收集盘置于风险之中。这一插曲使我们重新考虑立即对整个收集盘进行扫描和提取是否明智。虽然我们认真考虑了很多可能的失败模式,但我们没有预计到这种情况也不可能预计到下一种可能产生不愉快后果的情况。同星际尘埃预调查科学家 Council 和 星尘监督委员会、地外物质管理与分析计划小组(CAPTEM)的 Materials 磋商后,我们决定先将凝胶块从盘中取出然后再扫描以及对单独的块进行轨迹的提取。一致认为这种途径对收集器将有低的整体风险。

Although the new approach has numerous advantages – improved imaging for scanning, improved extraction speed, immediate extraction of foils, and the ability to do scanning and extractions in parallel – we did not take it before because of concern about loss of trajectory information and loss of aerogel collecting area during extraction. To address these concerns we will place artificial "witness tracks" into each aerogel tile before it is removed from the tray to permanently record the local orientation. We have also done successful extractions of three tiles so far without substantial loss of material. We will carefully monitor future extractions to minimize loss of material. Finally, we have designed and built prototypes of new tile holders that will be used to mount each tile permanently for long-term storage.
然而新的途径有着诸多优点——提高扫描成像质量;提高提取速度;能立即取出箔片;并且可以并行的进行扫描和提取——我们以前没有这样做是考虑到丢失弹道信息和提取过程中损失凝胶收集区域。为消除这些担心我们将在每一个凝胶块被从盘中取出前在其中设置人工的“说明轨迹”以永久的记录局部方向。我们已经成功的完成了三个凝胶块的取出没有出现可观的物质损失。我们会小心的监控未来的取出工作使材料损失最少。最后,我们已经设计并制造了新的凝胶块原型支架,支架将用于永久的安置每一个凝胶块以便长期存放。

The failure of the air chiller on the air handling system for CDL resulted in a substantial delay in restarting work on the IS tray, and thus of scanning and uploading new data for Stardust@home. However, we think that in the end this is good news: the new approach should give a substantial improvement in processing speed, and may provide better selectivity in finding IS dust candidates due to the improvement in imaging.
CDL 的空气调节系统气体冷却器的故障导致重新启动对IS盘的工作重大延误,以及由此造成扫描和为Stardust@home上传新数据的延误。不过,我们认为最终是个好消息:新方法将使处理速度有实质性的提升,并因提升的成像质量在寻找IS尘埃候选者时提供更好的选择性。

Thanks,
Andrew

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发表于 2009-10-17 02:16:09 | 显示全部楼层
我想再次表达我对大家的感谢。没有你们巨大的贡献,我们可能找不到这些轨迹。假如其中有任何一个最终可能是星际尘埃的话,在我们的重大庆祝之后,我们将为Stardust@home重新制作包括这些大角度轨迹的校准片。在此期间,继续这奇妙的工作吧!

  唉。。果不其然,要有新特征的校准。原来他们一早就只确定一个方向。。唉。。的确不应该定死 β=1  希望没有铸成大错。
   现在也不能怎么着了。。继续找呗。。。他们的空调系统怎么老有问题 不是第一次了。
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发表于 2009-10-25 21:30:38 | 显示全部楼层
本版有点冷啊
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发表于 2010-3-8 21:31:12 | 显示全部楼层
2010 年 3 月 8 日

【星尘号探测器首次获得宇宙尘埃样本】

北京时间3月8日消息据俄罗斯新闻网报道,美国的“星尘”号探测器在人类历史上首次获取了弥漫在星际间的宇宙尘埃的样本并将它们传回了地球。科学家们指出,这是人类首次获得这类物质。据介绍,这些尘埃是构建宇宙中各种可见天体--包括恒星和行星--的主要物质。


宇宙尘埃是构成宇宙中可见部分的基础物质

“星尘”号探测器最初的任务被设定为获取“维尔德 2”号彗星尾部的物质样本并将其送回地球进行分析。

不过,美国国家宇航局的专家们还赋予了该探测器另外一项任务--捕捉星际尘埃。

在长达七年的飞行过程中,“星尘”号探测器已飞越了48亿公里的距离。其上配备的专门容器中放置有气溶胶,能够搜集到弥漫在宇宙中的微小物质。

在2006年1月份,该探测器便曾将收集有彗星物质的容器发射回了地球。

通过对该容器中采集到的物质进行分析,科学家们惊喜地发现,其中居然还存在着两粒星际尘埃。据介绍,其中一粒星际尘埃由来自加拿大的布鲁斯·哈德森所发现。布鲁斯·哈德森目前正和其他数千名研究人员对“星尘”号探测器传回当地物质进行分析。

目前,哈德森发现的这一星际尘埃已被命名为“猎户座”。

据介绍,星际尘埃主要由恒星喷发出的气体演化而成。这种尘埃可稳定地存在于宇宙空间之中,经受住宇宙射线和引力场的作用。正是这些微小的物质最终聚集在一起并演化出了像太阳系这样的天体构造。

目前,科学家们已在新发现的两粒宇宙尘埃样本种检测出镁、铝、铁、铬、镍、锰、铜和钙等金属元素。

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发表于 2010-3-8 21:34:21 | 显示全部楼层
2010 年 3 月 8 日

项目将开始长达一周时间的离线(将在 3 月 18 日恢复在线)。

期间服务器将更新软件和硬件,并准备开始第三阶段。
更多第三阶段的信息会很快告知。

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发表于 2010-3-20 13:09:15 | 显示全部楼层
2010 年 3 月 20 日

Stardust@home 第三阶段将于 3 月 22 日开始。

请大家到时进行新的培训课程,就算你已经非常有经验。

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发表于 2010-3-23 16:46:32 | 显示全部楼层
2010 年 3 月 23 日

猎户座的星尘发现非常意外,也非常幸运,同时项目也迫切需要找到更多的星尘,如果想了解更多的信息请点击这个链接查看 ISPE #6 的更新:http://stardustathome.ssl.berkeley.edu/ispe_update/#six

第三阶段也正式启动,鼓励大家先去通过新的培训课程,即使你已经非常有经验,这无需注册。

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发表于 2019-6-22 14:27:23 | 显示全部楼层
http://stardustathome.ssl.berkel ... e-mcangus-particle/

2019年6月21日
Stardust@home的贡献者McAngus的发现被正式确认为一种珍贵的星际尘埃粒子。

June 21, 2019
It was truly a joyous moment this month, when Stardust Principal Investigator Dr. Andrew Westphal was able to convey directly to longtime duster McAngus (aka Augusto) that he was the first finder of the latest precious interstellar dust particle. Check out the actual track below that Augusto was savvy enough to click on, and then watch/hear his reaction to the news of his discovery in the video that follows. Our hats are off to you Augusto, and we’re very honored to have you on the team!
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