SGER: Mechanism for Emission of Penetrating Radiation from Ferroelectric Crystals

SGER：铁电晶体穿透辐射的发射机制

• 批准号: 0309886
• 负责人: Seth Putterman
• 金额: $ 10万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-15 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0309886&HistoricalAwards=false
• 关键词: SGER; Mechanism; Emission; Penetrating; Radiation

This Small Grants for Exploratory Research (SGER) project will examine a spectacular property of certain ferroelectric crystals: Conversion of diffuse thermal heat energy (normally associated primarily with lattice vibrations) into spontaneous emission of electrons from the surface of the crystal. The phenomenon is somewhat analogous to "photoemission" but here a poorly understood thermal conversion process replaces the photon. The thermally emitted electrons have energies of 100Kilovolts or more. Under easily obtained laboratory conditions, and with a small crystal, the emitted electron current can exceed a nano-ampere. The energies of the emitted electrons are measured by conventional methods and show that emission can be pulsed, and that it depends on the heating cycle of the crystal. The goal of this project is to understand, optimize and control these phenomena, for which a complete theory is not yet available. Environmental conditions such as temperature, crystal size, coercive field, and vacuum pressure will be varied to increase the electron current and energy, hopefully to the Megavolt range. Students will be trained in a range of modern laboratory techniques. The basic science that results from understanding this effect could open a window to a new class of collective solid-state dynamics. For example, localization of the effect could lead to an electron source for a compact projection transmission electron microscope.%%%This Small Grants for Exploratory Research (SGER) project will examine a spectacular, property of certain crystals: Ferroelectric crystals such as lithium niobate are extraordinary materials in that internal electric fields as large as 100 million volts/cm can be produced spontaneously owing to the arrangements of positive and negative ions in the crystal lattice. These fields can be put to work: Upon smoothly increasing the temperature of a small 1 cm^3 crystal, electrons are emitted and used to create x-rays. The goal of this project is to elucidate the fundamental scientific process whereby the energy involved in a gentle and diffuse heating becomes focused on electrons and causes them to be emitted with energies characteristic of the x-rays found in medical x-ray devices. A key goal is to determine the maximum energy, power, and current achievable in this compact geometry. Broad technological consequences could be realized if one is successful in localizing the high-energy emission to a nanoscale tip. In this case the energy transduction made possible by ferroelectricity might lead to a prototype compact projection transmission electron microscope. Students will be trained in a laboratory techniques ranging from solid-state chemistry to nuclear spectroscopy to x-ray generation and detection.

这个探索性研究（SGER）项目的小赠款将检查某些铁电晶体的一个壮观的属性：从晶体表面的电子的自发发射的扩散热热能（通常主要与晶格振动）的转换。 这种现象有点类似于“光电发射”，但在这里，一个知之甚少的热转换过程取代了光子。 热发射的电子具有100千伏或更高的能量。 在容易获得的实验室条件下，并且使用小晶体，发射的电子电流可以超过纳安培。 发射的电子的能量通过常规方法测量，并显示发射可以是脉冲的，并且它取决于晶体的加热周期。 该项目的目标是理解，优化和控制这些现象，目前还没有完整的理论。 环境条件，如温度，晶体尺寸，矫顽场和真空压力将被改变，以增加电子电流和能量，希望到兆伏范围。 学生将接受一系列现代实验室技术的培训。 理解这种效应所产生的基础科学可以为一类新的集体固态动力学打开一扇窗户。 例如，这种效应的局部化可能导致一种用于紧凑型投影透射电子显微镜的电子源。%这个探索性研究（SGER）项目的小赠款将研究某些晶体的一个壮观的性质：铁电晶体，如锂酸盐是非凡的材料，由于晶格中正负离子的排列，可以自发产生高达1亿伏/厘米的内部电场。 这些场可以发挥作用：在平稳地增加一个1立方厘米的小晶体的温度时，电子被发射出来并用于产生X射线。 该项目的目标是阐明基本的科学过程，其中涉及温和和扩散加热的能量集中在电子上，并使它们以医用X射线设备中发现的X射线的能量特征发射。 一个关键的目标是确定最大的能量，功率和电流可在这种紧凑的几何形状。 如果成功地将高能辐射定位到纳米级尖端，就可以实现广泛的技术后果。 在这种情况下，铁电性使能量转换成为可能，可能导致原型紧凑的投影透射电子显微镜。 学生将接受实验室技术培训，从固态化学到核光谱学，再到X射线的产生和检测。