Room Temperature, Earth's Field MASER

本研究的目的是构建一种能够在室温和地球磁场中工作的微波激射器。微波激射器（Microwave amplification by the stimulated emission of radiation）实际上是激光器的前身，大约在50年前由汤斯、巴索夫和普罗霍罗夫发现，并因此获得1964年诺贝尔物理学奖。激光器可以被简单地认为是微波激射器，它工作在紫外或可见光谱中的高频光子，而微波激射器工作在微波频率。这两种系统都依赖于一种具有激发能级的化学物质，该化学物质通过光子或与其他物质的碰撞被激发到较低的能级。然后，除了进入系统的原始光子之外，原子或分子还发射光子。进入系统的光子激发相同频率的更多光子的发射，这意味着产生单色辐射的强光束。最初，激光被视为一个寻找应用的好主意。它们的生产数量很少，美国政府一度下令，出于军事和安全目的，每台激光器都应该打上一个数字--当这种设备的市场潜力变得明显时，这个想法很快就失去了吸引力。今天，激光器的产量已达数十亿，并已应用于从DVD播放器到激光眼科手术的所有行业。另一方面，脉泽只用于非常专业的应用，如原子钟和射频望远镜中的放大器。脉泽是旅行者号宇宙飞船发出的令人惊叹的太阳系图像的来源。那么，为什么脉泽没有被广泛应用呢？有两个关键原因。第一，脉泽需要低温，这就意味着要使用低温液体或特殊的冰箱。第二，它们需要高磁场，这意味着使用需要高功率的大型磁体，如果是电磁铁，通常用水冷却，如果是超导磁体，则用氦气冷却。这项研究的目的是制造一种在室温和地球磁场中工作的微波激射器。这当然是一个非常雄心勃勃的项目，但它是在项目中使用的一些材料的研究中得到证实的，这些材料是非常高Q的谐振器。高Q谐振器的研究已经进行了几年，现在看来，可以用高Q谐振器和相当低的功率制成固态脉塞。我们初步的探测实验表明，在室温和地球磁场下，脉冲模式下实现脉泽是可能的。即将进行的研究将探索新的材料，这些材料将使微波激射器更加稳定，并且需要非常低的功率来达到微波激射所需的阈值。

The work we propose in this research is to construct a MASER that can work at room temperature and in the Earth's magnetic field.The MASER (Microwave amplification by the stimulated emission of radiation) is in fact the forerunner of the LASER and was discovered around 50 years ago by Townes, Basov, and Prokhorov who shared the 1964 Nobel Prize in Physics for this work. A LASER can be thought of simply as MASER that works with higher frequency photons in the ultraviolet or visible light spectrum whereas a maser works at microwave frequencies. Both systems rely on a chemical species with an excited energy-level population being stimulated into lower energy levels, either by photons or collisions with other species. Photons are then emitted by the atom or molecule, in addition to the original photons that entered the system. The photons entering the system stimulate the emission of further photons of the same frequency, meaning that a strong beam of monochromatic radiation is produced. Originally the laser was seen as a good idea looking for an application. They were made in small numbers and at one point the US government decreed that every laser should be stamped with a number for military and security purposes - an idea that soon lost its appeal when the market potential for the quantities of the devices became apparent. Today lasers are made in their billions and have found their way into applications in all sectors of industry from DVD players to laser eye surgery. Masers on the other hand are used only in very specialised applications such as atomic clocks and as amplifiers in radiofrequency telescopes. Masers were responsible for the stunning images of the solar system sent by the Voyager spacecraft. So why have masers not been widely applied? There are two key reasons. First masers need cryogenic temperatures and this means the use of either cryogenic liquids or special fridges. Second, they need high magnetic fields and this means the use of bulky magnets that need high power and usually cooling with water, if an electromagnet, or with helium, if a superconducting magnet. This research is aimed at producing a maser that will operate at room temperature and in the earth's magnetic field. This is of course an extremely ambitious project but it is borne out of research in some of the materials that will be used in the project and these are the very high Q resonators. Work on high Q resonators has been carried out by the group for several years and now it appears that a solid state maser can be made using a high Q resonator and quite a low power. Our initial scouting experiments have shown that it is indeed possible to achieve masing at room temperature and earth's field in pulsed mode. The research that will be carried out will explore new materials that will miniaturise the maser and require very low power to achieve the threshold required for masing.