Nucleation Processes in Liquid Helium

* 非技术摘要 * 气泡在液体中的形成是许多不同过程的结果。它们可以在含有气体的液体上的压力降低时产生，例如，当一罐苏打水被打开时。当液体被加热到沸点以上时，在船的螺旋桨周围的湍流中也会形成气泡。在某些情况下，气泡的产生具有不期望的效果。例如，随着时间的推移，在船的螺旋桨附近产生的气泡会损坏螺旋桨。另一方面，气泡的产生也可以是非常有用的，如在超声波清洁器中。这个个人研究者奖支持一个项目，研究泡沫是如何形成的，以及如何控制它们的形成，以获得技术优势。将进行实验，以研究在一些不同的条件下，在液氦气泡的产生。之所以选择液氦进行这些实验，是因为它可以以特殊的纯度生产，因此可以控制或消除液体中杂质可能产生的影响。该项目的主要目的是研究电子对气泡形成的影响。由于参与研究的不同实验技术的数量，该项目为从事该项目的研究生提供了良好的培训。技术摘要 * 在本研究项目中，将对浸没在液氦中的电子进行研究。在以前的研究中，已经表明，当电子被引入液氦时，它会迫使液体中打开一个小空腔。这个“电子泡”的半径约为2nm。将开发一种新技术，使观察电子在液体中移动时的位置成为可能。电子泡将在大约1微秒的时间内膨胀到更大的尺寸，然后用闪光灯照亮。在第二个项目中，附着在量子化涡旋线上的电子将被成像，从而提供有关涡旋线拓扑结构的信息。由于研究中涉及的不同实验技术的数量，该项目为从事该项目的研究生提供了良好的培训。

******NON-TECHNICAL ABSTRACT******Bubbles form in liquid as a result of a number of different processes. They can be produced when the pressure on a liquid that contains gas is reduced, when a can of soda is opened, for example. Bubbles also form in the turbulence around the propeller of a ship, and when a liquid is heated above its boiling point. In some situations, bubble production has undesirable effects. For example, over the course of time the bubbles produced near to the propeller of a ship damage the propeller. On the other hand, bubble generation can also be very useful, as in an ultrasonic cleaner. This individual investigator award supports a project to study how bubbles are formed and how to control their formation for technological advantage. Experiments will be performed to investigate bubble production in liquid helium under a number of different conditions. Liquid helium is chosen for these experiments because it can be produced with exceptional purity, and so effects that might arise from impurities in the liquid can be controlled or eliminated. The main aim of the project is the investigation of the effect of electrons on bubble formation. Because of the number of different experimental techniques that are involved in the research, this project provides excellent training for the graduate students working on the project.****** TECHNICAL ABSTRACT******In this research project a study will be made of electrons immersed in liquid helium. In previous research, it has been shown that when an electron is introduced into liquid helium, it forces open a small cavity in the liquid. This "electron bubble" has a radius of approximately 2nm. A new technique will be developed that will make it possible to observe the position of an electron as it moves through the liquid. The electron bubble will be expanded to a larger size for a time of around 1 microsecond and then illuminated with light from a flash lamp. In a second project, electrons that are attached to a quantized vortex line will be imaged, thus providing information about the topology of the vortex line. Because of the number of different experimental techniques that are involved in the research, this project provides excellent training for the graduate students working on the project.