在实验室中模拟天体粒子所产生的震动波加速剂由恒星爆炸供电

When stars explode as supernovas, they produce shock waves in the plasma surrounding them. So powerful are these shock waves, they can act as particle accelerators that blast streams of particles, called cosmic rays, out into the universe at nearly the speed of light. Yet how exactly they do that has remained something of a mystery.

现在,科学家已经发明了一种新的方式通过建立在实验室震荡的缩小版来研究天体物理冲击波的内部运作。他们发现的天体物理冲击在非常小的规模开发动荡 - 不能被天文观测中可以看出vwin手机版秤 - 朝着冲击波有助于电子踢他们升压到最终,难以置信的速度前。

“These are fascinating systems, but because they are so far away it’s hard to study them,” said Frederico Fiuza, a senior staff scientist at the Department of Energy’s SLAC National Accelerator Laboratory, who led the new study. “We are not trying to make supernova remnants in the lab, but we can learn more about the physics of astrophysical shocks there and validate models.”

注射问题

Astrophysical shock waves around supernovas are not unlike the shockwaves and sonic booms that form in front of supersonic jets. The difference is that when a star blow up, it forms what physicists call a collisionless shock in the surrounding gas of ions and free electrons, or plasma. Rather than running into each other as air molecules would, individual electrons and ions are forced this way and that by intense electromagnetic fields within the plasma. In the process, researchers have worked out, supernova remnant shocks produce strong electromagnetic fields that bounce charged particles across the shock multiple times and accelerate them to extreme speeds.

astrophysical_shock_figure_sv_final.jpg

在实验室中模拟天体粒子所产生的震动波加速剂由恒星爆炸供电

要在超新星遗迹模仿的冲击波,SLAC的研究人员和他们的同事在美国国家点火设施发射了强大的激光器在两个碳排放目标,发送两个血浆流入对方。在那里会见中,等离子体形成类似于在天体冲击可见冲击波。(格雷格·斯图尔特/ SLAC国家加速器实验室)

Yet there’s a problem. The particles already have to be moving pretty fast to be able to cross the shock in first place, and no one’s sure what gets the particles up to speed. The obvious way to address that issue, known as the injection problem, would be to study supernovas and see what the plasmas surrounding them are up to. But with even the closest supernovas thousands of light years away, it’s impossible to simply point a telescope at them and get enough detail to understand what’s going on.

幸运的是,FIUZA,他的博士后研究员安娜·格拉西和他的同事有另一个想法:他们会尝试模仿在实验室超新星遗迹的冲击波条件,指出一些格拉西的计算机模型可能是可行的。

最显著,团队需要建立一个快速,弥漫冲击波,可以模拟超新星残骸的冲击。他们还需要证明等离子体的密度和温度的方式与这些冲击的车型一致的增加 - 当然,他们想了解,如果冲击波会在非常高的速度下拍摄出电子。

点燃冲击波

为了实现这样的事情,球队去了国家点火装置,在劳伦斯·利弗莫尔国家实验室能源部的用户工具。目前,研究人员拍摄了一些世界上最强大的激光器在一对碳片,创造了对等离子流的直奔相互转化。当流相遇,光学和X射线观测显示所有功能的团队正在寻找,这意味着他们已经在实验室中产生类似超新星遗迹冲击条件的冲击波。

最重要的是,他们发现,在形成冲击时,它的确能够加速电子的光接近的速度。他们观察到,用基于测量的震荡特性,他们预计加速度一致的最大电子速度。然而,这些电子是如何达到如此高速的微观细节仍不清楚。

幸运的是,模型可以帮助揭示一些细微之处的,最早的基准测试针对实验数据。“我们看不到的细节粒子如何获得能量,即使在试验,更不用说在天体物理观测,而这正是模拟真正发挥作用,”格拉西说。

实际上,计算机模型显示了可能是对电子注入问题的解决方案。震荡中的湍流电磁场波本身似乎能够提高电子加速到粒子可以再次逃脱冲击波和跨回来,以获得更高速的地步,FIUZA说。事实上,得到颗粒用的装置要足够快,以穿越冲击波似乎非常相似,当冲击波得到的颗粒达天文数字的速度,只是在小范围内会发生什么。

面向未来

Questions remain, however, and in future experiments the researchers will do detailed measurements of the X-rays emitted by the electrons the moment they are accelerated to investigate how electron energies vary with distance from the shock wave. That, Fiuza said, will further constrain their computer simulations and help them develop even better models. And perhaps most significantly, they will also look at protons, not just electrons, fired off by the shock wave, data which the team hopes will reveal more about the inner workings of these astrophysical particle accelerators.

更一般地,该发现可能有助于科学家超越天文观测或在我们的太阳系中多驯冲击基于飞船观测的局限性。“这项工作开辟了一条新途径,研究在实验室超新星遗迹冲击的物理学,” FIUZA说。

其他作者包括来自美国劳伦斯利弗莫尔国家实验室的研究人员;罗彻斯特大学;密歇根大学;普林斯顿大学;麻省理工学院;加拿大阿尔伯塔大学;弗里德里希亚历山大大学埃尔兰根 - 纽伦堡,德国;英国牛津大学;与日本大阪大学。这项研究是由科学的能源办公室的部的支持。德赢手机版

Citation: Frederico Fiuza, et al.自然物理学,2020年6月8日(DOI:10.1038 / s41567-020-0919-4

如有问题或意见,请联系沟通的SLAC办公室communications@slac.stanford.edu


本新闻稿中来自originating research organization. Content may be edited for style and length. Have a question?vwin彩票投注

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出问题了。

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