等离子是什么_等离子是什么技术

1.等离子，什么是等离子

2.什么是等离子

3.什么是等离子体？火焰是等离子体吗？

4.什么是等离子？

5.什么是等离子体？离子体的特征分类及主要参数是什么？

等离子：

等离子态是一种普遍存在的状态。宇宙中大部分发光的星球内部温度和压力都很高，这些星球内部的物质差不多都处于等离子态。只有那些昏暗的行星和分散的星际物质里才可以找到固态、液态和气态的物质。等离子体的用途非常广泛．从我们的日常生活到工业、农业、环保、军事、宇航、能源、天体等方面，它都有非常重要的应用价值。等离子态下的物质具有类似于气态的性质，比如良好的流动性和扩散性。但是，由于等离子体的基本组成粒子是离子和电子，因此它也具有许多区别于气态的性质，比如良好的导电性、导热性。特别的，根据科学计算，等离子体的比热容与温度成正比，高温下等离子体的比热容往往是气体的数百倍。

等离子性质：

等离子是一种自发光显示技术，不需要背景光源，因此没有LCD显示器的视角和亮度均匀性问题，而且实现了较高的亮度和对比度。而三基色共用同一个等离子管的设计也使其避免了聚焦和汇聚问题，可以实现非常清晰的图像。与CRT和LCD显示技术相比，等离子的屏幕越大，图像的色深和保真度越高。除了亮度、对比度和可视角度优势外，等离子技术也避免了LCD技术中的响应时间问题，而这些特点正是动态显示中至关重要的因素。因此从目前的技术水平看，等离子显示技术在动态显示领域的优势更加明显，更加适合作为家庭和大屏幕显示终端使用。等离子显示器无扫描线扫描，因此图像清晰稳定无闪烁，不会导致眼睛疲劳。等离子也无X射线辐射。由于这些突出特点，等离子堪称真正意义上的绿色环保显示产品，是替代传统CRT彩电的理想产品。

等离子体：

“等离子体”技术，是以特定超低频率100Khz电能激发介质（Nacl）产生等离子体，等离子体中的高速带电粒子直接打断分子键，使蛋白质等组织裂解汽化成H2,O2,CO2,N2和甲烷等低分子量气体。

普通高频500-4000KHz可改变电场下，粒子一方面无法获得足够的加速时间，处于往复的震荡状态；另一方面高频下加剧的分子摩擦会产生较强的热效应，且频率越高产热越多。

但100KHz低频稳定电场下，粒子则会获得更长的加速时间，最终形成带有更大动能的高速带电粒子，直接打断分子键。此外因频率低，较之高频大大降低了分子间的摩擦产热，使切割、消融和止血等过程都在40℃~70℃内完成，从而实现微创效应。

电外科设备经历了“电刀”—“普通射频”—“等离子体射频”，由低向高的发展阶段。

等离子体用处：

1、“等离子体”技术用直接的“汽化”工作方式彻底改变了传统“射频”的“热能”工作方式，40℃~70℃的组织汽化替代了传统“切割”、“止血”等过程中上百度高温对组织的灼伤破坏作用，大大降低了手术过程中的创伤。

2、还可用等离子体脱掉烟尘中的硫、用等离子体照射来提高农作物的产量、研制大屏幕的等离子体电视机、研制等离子体火箭发动机到火星等遥远的宇宙去旅行……等离子体的应用举不胜举。

等离子体的性质：

1 等离子体是由大量带电粒子组成的非凝聚系统。例如，当气体被加热到足够高的温度，或受到高能带电粒子轰击时，中性气体原子将被电离，空间中形成大量的自由电子和阳离子，但总体上又保持电中性。

2 实际使用的等离子体则是由大量自由电子、阳离子、阴离子、原子和分子组成的、整体上近似电中性的物质状态。

3 等离子体状态是物质存在的基本形态之一，与固态，液态和气态并列，称为物质第四态。

4 等离子体的主要特征是：粒子间存在长城库仑相互作用，等离子体的运动与电磁场的运动紧密耦合，存在极其丰富的集体效应和集体运动模式。和物质的另外三态相比，等离子体可以存在的参数范围异常宽广（其密度，温度以及磁场强度都可以跨越十几个数量级）；等离子体的形态和性质受外加电磁场的强烈影响，并存在极其丰富的集体运动模式（如各种电磁波，漂移波，静电波以及非线性的相干结构和湍动）；

5 此外，等离子体对外界条件还十分敏感。所以，等离子体性质的研究强烈的依赖于具体的研究对象。?

等离子态常被称为“超气态”，它和气体有很多相似之处，比如：没有确定形状和体积，具有流动性，但等离子也有很多独特的性质。

等离子，什么是等离子

概念：当电离过程频繁发生，使电子和阳离子的浓度达到一定的数值时，物质的状态也就起了根本的变化，它的性质也变得与气体完全不同。为区别于固体、液体和气体这三种状态，我们称物质的这种状态为物质的第四态，又起名叫等离子态。

等离子体的用途非常广泛。从我们的日常生活到工业、农业、环保、军事、医学、宇航、能源、天体等方面，它都有非常重要的应用价值。

扩展资料

等离子体科研创新

在等离子体理论领域，吴博士研究发现，当粒子的费米温度大于热温度时，量子效应将起到重要作用，等离子体中的电子性质趋近于费米气，其统计行为由费米-狄拉克分布描述而不是经典的玻尔兹曼分布描述。

在量子等离子体体系方面吴博士也做过广泛的研究。他告诉笔者，在Winger-Poisson体系下，他用量子动力学方程组与磁场耦合计算得到了均匀冷量子等离子体中的线性波色散关系。

这一关系表明朗谬尔波在量子效应的影响下变得类似哨声波，也就是说朗谬尔波可以在冷等离子体中传播。同时，量子效应不会对左旋波、右旋波和寻常波产生作用。

利用量子动力学模型研究了非均匀磁化等离子体中静电漂移波的问题。电子在这里被视为低温的费米气体。得到了量子静电漂移波的解析表达式。量子效应对静电漂移波有显著的影响。磁场和空间不均匀性的作用与经典情况下的类似。此结果对二维电子气、固体物理和高密度天体等方向有借鉴意义。

“利用量子动力学对非均匀磁化电子－正电子－离子等离子体系统中的电磁波进行了研究，用Wigner-Maxwell模型得到了一个新的色散方程。从该结果可以看出正电子和电子的密度对色散有很大影响。”吴征威博士解释道。

在等离子体技术研发领域，吴征威博士主持开发的“便携式等离子体杀菌装置”和“台式等离子体消杀装置”已经形成原理样机。

其灭菌效果经中国科学院理化技术研究所认证60秒内对大肠杆菌、白色葡萄球菌、金色葡萄球菌、绿脓杆菌、白色念珠菌、克氏肺炎、黑曲霉菌等七种微生物杀灭率达到99.99%，正在进行工业样机的试制，预计完成设备选型、定型及小试后，有望形成产品。

百度百科-等离子

什么是等离子

等离子体又叫做电浆，是由部分电子被剥夺后的原子及原子被电离后产生的正负电子组成的离子化气体状物质，它广泛存在于宇宙中，常被视为是除去固、液、气外，物质存在的第四态。等离子体是一种很好的导电体，利用经过巧妙设计的磁场可以捕捉、移动和加速等离子体。等离子体物理的发展为材料、能源、信息、环境空间，空间物理，地球物理等科学的进一步发展提新的技术和工艺。

看似“神秘”的等离子体，其实是宇宙中一种常见的物质，在太阳、恒星、闪电中都存在等离子体，它占了整个宇宙的99％。现在人们已经掌握利用电场和磁场产生来控制等离子体。例如焊工们用高温等离子体焊接金属。

等离子体可分为两种：高温和低温等离子体。现在低温等离子体广泛运用于多种生产领域。例如：等离子电视，婴儿尿布表面防水涂层，增加啤酒瓶阻隔性。更重要的是在电脑芯片中的蚀刻运用，让网络时代成为现实。

高温等离子体只有在温度足够高时发生的。太阳和恒星不断地发出这种等离子体，组成了宇宙的99％。低温等离子体是在 常温下发生的等离子体（虽然电子的温度很高）。低温等离子体体可以被用于氧化、变性等表面处理或者在有机物和无机物上进行沉淀涂层处理。

等离子体是物质的第四态，即电离了的“气体”，它呈现出高度激发的不稳定态，其中包括离子(具有不同符号和电荷)、电子、原子和分子。其实，人们对等离子体现象并不生疏。在自然界里，炽热烁烁的火焰、光辉夺目的闪电、以及绚烂壮丽的极光等都是等离子体作用的结果。对于整个宇宙来讲，几乎99．9％以上的物质都是以等离子体态存在的，如恒星和行星际空间等都是由等离子体组成的。用人工方法，如核聚变、核裂变、辉光放电及各种放电都可产生等离子体。 分子或原子的内部结构主要由电子和原子核组成。在通常情况下，即上述物质前三种形态，电子与核之间的关系比较固定，即电子以不同的能级存在于核场的周围，其势能或动能不大。

由离子、电子以及未电离的中性粒子的集合组成，整体呈中性的物质状态．

普通气体温度升高时，气体粒子的热运动加剧，使粒子之间发生强烈碰撞，大量原子或分子中的电子被撞掉，当温度高达百万开到1亿开，所有气体原子全部电离．电离出的自由电子总的负电量与正离子总的正电量相等．这种高度电离的、宏观上呈中性的气体叫等离子体．希望这个回答对你有帮助

什么是等离子体？火焰是等离子体吗？

等离子体

维基百科，自由的百科全书

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等离子灯

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等离子灯

等离子体（等离子态，电浆，英文：Plasma）是一种电离的气体，由于存在电离出来的自由电子和带电离子，等离子体具有很高的电导率，与电磁场存在极强的耦合作用。等离子态在宇宙中广泛存在，常被看作物质的第四态（有人也称之为“超气态”）。等离子体由克鲁克斯在1879年发现，“Plasma”这个词，由朗廖尔在1928年最早用。

目录

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*

*

o 2.1 电离

o

o 2.3 速率分布

* 3 参见

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常见的等离子体

等离子体是存在最广泛的一种物态，目前观测到的宇宙物质中，99%都是等离子体。

* 人造的等离子体

o 荧光灯，霓虹灯灯管中的电离气体

o 核聚变实验中的高温电离气体

o 电焊时产生的高温电弧

* 地球上的等离子体

o 火焰（上部的高温部分）

o 闪电

o 大气层中的电离层

o 极光

* 宇宙空间中的等离子体

o 恒星

o 太阳风

o 行星际物质

o 恒星际物质

o 星云

* 其它等离子体

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等离子体的性质

等离子态常被称为“超气态”，它和气体有很多相似之处，比如：没有确定形状和体积，具有流动性，但等离子也有很多独特的性质。

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电离

等离子体和普通气体的最大区别是它是一种电离气体。由于存在带负电的自由电子和带正电的离子，有很高的电导率，和电磁场的耦合作用也极强：带电粒子可以同电场耦合，带电粒子流可以和磁场耦合。描述等离子体要用到电动力学，并因此发展起来一门叫做磁流体动力学的理论。

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组成粒子

和一般气体不同的是，等离子体包含两到三种不同组成粒子：自由电子，带正电的离子和未电离的原子。这使得我们针对不同的组分定义不同的温度：电子温度和离子温度。轻度电离的等离子体，离子温度一般远低于电子温度，称之为“低温等离子体”。高度电离的等离子体，离子温度和电子温度都很高，称为“高温等离子体”。

相比于一般气体，等离子体组成粒子间的相互作用也大很多。

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速率分布

一般气体的速率分布满足麦克斯韦分布，但等离子体由于与电场的耦合，可能偏离麦克斯韦分布。

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参见

* 等离子体物理学

取自"://zh.wikipedia.org/wiki/%E7%AD%89%E7%A6%BB%E5%AD%90%E4%BD%93"

Category: 等离子体物理学

Plasma (physics)

From Wikipedia, the free encyclopedia.

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This article is about plasma in the sense of an ionized gas. For other uses of the term, such as blood plasma, see plasma (disambiguation).

A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation

Enlarge

A Plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation

In physics and chemistry, a plasma is an ionized gas, and is usually considered to be a distinct phase of matter. "Ionized" in this case means that at least one electron has been removed from a significant fraction of the molecules. The free electric charges make the plasma electrically conductive so that it couples strongly to electromagnetic fields. This fourth state of matter was first identified by Sir William Crookes in 1879 and dubbed "plasma" by Irving Langmuir in 1928, because it reminded him of a blood plasma Ref.

Contents

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* 1 Common plasmas

* 2 Characteristics

o 2.1 Plasma scaling

o 2.2 Temperatures

o 2.3 Densities

o 2.4 Potentials

* 3 In contrast to the gas phase

* 4 Complex plasma phenomena

* 5 Ultracold Plasmas

* 6 Mathematical descriptions

o 6.1 Fluid

o 6.2 Kinetic

o 6.3 Particle-in-cell

* 7 Fundamental plasma parameters

o 7.1 Frequencies

o 7.2 Lengths

o 7.3 Velocities

o 7.4 Dimensionless

o 7.5 Miscellaneous

* 8 Fields of active research

* 9 See also

* 10 External links

[edit]

Common plasmas

A solar coronal mass ejection blasts plasma throughout the Solar System. ://antwrp.gsfc.nasa.gov/apod/ap020516.html Ref & Credit

Enlarge

A solar coronal mass ejection blasts plasma throughout the Solar System. ://antwrp.gsfc.nasa.gov/apod/ap020516.html Ref & Credit

Plasmas are the most common phase of matter. The entire visible universe outside the Solar System is plasma, since all we can see are stars. Since the space between the stars is filled with a plasma, although a very sparse one (see interstellar- and intergalactic medium), essentially the entire volume of the universe is plasma. In the Solar System, the planet Jupiter accounts for most of the non-plasma, only about 0.1% of the mass and 10-15 of the volume within the orbit of Pluto. Alfvén also noted that due to their electric charge, very small grains also behe as ions and form part of a plasma (see dusty plasmas).

Commonly encountered forms of plasma include:

* Artificially produced

o Inside fluorescent lamps (low energy lighting), neon signs

o Rocket exhaust

o The area in front of a spacecraft's heat shield during reentry into the atmosphere

o Fusion energy research

o The electric arc in an arc lamp or an arc welder

o Plasma ball (sometimes called a plasma sphere or plasma globe)

* Earth plasmas

o Flames (ie. fire)

o Lightning

o The ionosphere

o The polar aurorae

* Space and astrophysical

o The Sun and other stars (which are plasmas heated by nuclear fusion)

o The solar wind

o The Interplanetary medium (the space between the planets)

o The Interstellar medium (the space between star systems)

o The Intergalactic medium (the space between galaxies)

o The Io-Jupiter flux-tube

o Accretion disks

o Interstellar nebulae

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Characteristics

The term plasma is generally reserved for a system of charged particles large enough to behe as one. Even a partially ionized gas in which as little as 1% of the particles are ionized can he the characteristics of a plasma (i.e. respond to magnetic fields and be highly electrically conductive).

In technical terms, the typical characteristics of a plasma are:

1. Debye screening lengths that are short compared to the physical size of the plasma.

2. Large number of particles within a sphere with a radius of the Debye length.

3. Mean time between collisions usually is long when compared to the period of plasma oscillations.

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Plasma scaling

Plasmas and their characteristics exist over a wide range of scales (ie. they are scaleable over many orders of magnitude). The following chart deals only with conventional atomic plasmas and not other exotic phenomena, such as, quark gluon plasmas:

Typical plasma scaling ranges: orders of magnitude (OOM)

Characteristic Terrestrial plasmas Cosmic plasmas

Size

in metres (m) 10-6 m (lab plasmas) to:

102 m (lightning) (~8 OOM) 10-6 m (spacecraft sheath) to

1025 m (intergalactic nebula) (~31 OOM)

Lifetime

in seconds (s) 10-12 s (laser-produced plasma) to:

107 s (fluorescent lights) (~19 OOM) 101 s (solar flares) to:

1017 s (intergalactic plasma) (~17 OOM)

Density

in particles per

cubic metre 107 to:

1021 (inertial confinement plasma) 1030 (stellar core) to:

100 (i.e., 1) (intergalactic medium)

Temperature

in kelvins (K) ~0 K (Crystalline non-neutral plasma[2]) to:

108 K (magnetic fusion plasma) 102 K (aurora) to:

107 K (Solar core)

Magnetic fields

in teslas (T) 10-4 T (Lab plasma) to:

103 T (pulsed-power plasma) 10-12 T (intergalactic medium) to:

107 T (Solar core)

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Temperatures

The central electrode of a plasma lamp, showing a glowing blue plasma streaming upwards. The colors are a result of the radiative recombination of electrons and ions and the relaxation of electrons in excited states back to lower energy states. These processes emit light in a spectrum characteristic of the gas being excited.

Enlarge

The central electrode of a plasma lamp, showing a glowing blue plasma streaming upwards. The colors are a result of the radiative recombination of electrons and ions and the relaxation of electrons in excited states back to lower energy states. These processes emit light in a spectrum characteristic of the gas being excited.

The defining characteristic of a plasma is ionization. Although ionization can be caused by UV radiation, energetic particles, or strong electric fields, (processes that tend to result in a non-Maxwellian electron distribution function), it is more commonly caused by heating the electrons in such a way that they are close to thermal equilibrium so the electron temperature is relatively well-defined. Because the large mass of the ions relative to the electrons hinders energy transfer, it is possible for the ion temperature to be very different from (usually lower than) the electron temperature.

The degree of ionization is determined by the electron temperature relative to the ionization energy (and more weakly by the density) in accordance with the Saha equation. If only a small fraction of the gas molecules are ionized (for example 1%), then the plasma is said to be a cold plasma, even though the electron temperature is typically several thousand degrees. The ion temperature in a cold plasma is often near the ambient temperature. Because the plasmas utilized in plasma technology are typically cold, they are sometimes called technological plasmas. They are often created by using a very high electric field to accelerate electrons, which then ionize the atoms. The electric field is either capacitively or inductively coupled into the gas by means of a plasma source, e.g. microwes. Common lications of cold plasmas include plasma-enhanced chemical vapor deposition, plasma ion doping, and reactive ion etching.

A hot plasma, on the other hand, is nearly fully ionized. This is what would commonly be known as the "fourth-state of matter". The Sun is an example of a hot plasma. The electrons and ions are more likely to he equal temperatures in a hot plasma, but there can still be significant differences.

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Densities

Next to the temperature, which is of fundamental importance for the very existence of a plasma, the most important property is the density. The word "plasma density" by itself usually refers to the electron density, that is, the number of free electrons per unit volume. The ion density is related to this by the erage charge state \langle Z\rangle of the ions through n_e=\langle Z\rangle n_i. (See quasineutrality below.) The third important quantity is the density of neutrals n0. In a hot plasma this is small, but may still determine important physics. The degree of ionization is ni / (n0 + ni).

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Potentials

Lightning is an example of plasma present at Earth's surface. Typically, lightning discharges 30 thousand amps, at up to 100 million volts, and emits light, radio wes, x-rays and even gamma rays [1]. Plasma temperatures in lightning can roach 28,000 kelvins and electron densities may exceed /m3.

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Lightning is an example of plasma present at Earth's surface. Typically, lightning discharges 30 thousand amps, at up to 100 million volts, and emits light, radio wes, x-rays and even gamma rays [1]. Plasma temperatures in lightning can roach 28,000 kelvins and electron densities may exceed /m3.

Since plasmas are very good conductors, electric potentials play an important role. The potential as it exists on erage in the space between charged particles, independent of the question of how it can be measured, is called the plasma potential or the space potential. If an electrode is inserted into a plasma, its potential will generally lie considerably below the plasma potential due to the development of a Debye sheath. Due to the good electrical conductivity, the electric fields in plasmas tend to be very small, although where double layers are formed, the potential drop can be large enough to accelerate ions to relativistic velocities and produce synchrotron radiation such as x-rays and gamma rays. This results in the important concept of quasineutrality, which says that, on the one hand, it is a very good roximation to assume that the density of negative charges is equal to the density of positive charges (n_e=\langle Z\rangle n_i), but that, on the other hand, electric fields can be assumed to exist as needed for the physics at hand.

The magnitude of the potentials and electric fields must be determined by means other than simply finding the net charge density. A common example is to assume that the electrons satisfy the Boltzmann relation, n_e \propto e^{e\Phi/k_BT_e}. Differentiating this relation provides a means to calculate the electric field from the density: \vec{E} = (k_BT_e/e)(\nabla n_e/n_e).

It is, of course, possible to produce a plasma that is not quasineutral. An electron beam, for example, has only negative charges. The density of a non-neutral plasma must generally be very low, or it must be very small, otherwise it will be dissipated by the repulsive electrostatic force.

In astrophysical plasmas, Debye screening prevents electric fields from directly affecting the plasma over large distances (ie. greater than the Debye length). But the existence of charged particles causes the plasma to generate and be affected by magnetic fields. This can and does cause extremely complex behior, such as the generation of plasma double layers, an object that separates charge over a few tens of Debye lengths. The dynamics of plasmas interacting with external and self-generated magnetic fields are studied in the academic discipline of magnetohydrodynamics.

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In contrast to the gas phase

Plasma is often called the fourth state of matter. It is distinct from the three lower-energy phases of matter; solid, liquid, and gas, although it is closely related to the gas phase in that it also has no definite form or volume. There is still some disagreement as to whether a plasma is a distinct state of matter or simply a type of gas. Most physicists consider a plasma to be more than a gas because of a number of distinct properties including the following:

Property Gas Plasma

Electrical Conductivity Very low

Very high

1. For many purposes the electric field in a plasma may be treated as zero, although when current flows the voltage drop, though small, is finite, and density gradients are usually associated with an electric field according to the Boltzmann relation.

2. The possibility of currents couples the plasma strongly to magnetic fields, which are responsible for a large variety of structures such as filaments, sheets, and jets.

3. Collective phenomena are common because the electric and magnetic forces are both long-range and potentially many orders of magnitude stronger than gritational forces.

Independently acting species One Two or three

Electrons, ions, and neutrals can be distinguished by the sign of their charge so that they behe independently in many circumstances, hing different velocities or even different temperatures, leading to new types of wes and instabilities, among other things

Velocity distribution Maxwellian May be non-Maxwellian

Whereas collisional interactions always lead to a Maxwellian velocity distribution, electric fields influence the particle velocities differently. The velocity dependence of the Coulomb collision cross section can amplify these differences, resulting in phenomena like two-temperature distributions and run-away electrons.

Interactions Binary

Two-particle collisions are the rule, three-body collisions extremely rare. Collective

Each particle interacts simultaneously with many others. These collective interactions are about ten times more important than binary collisions.

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Complex plasma phenomena

Tycho's Supernova remnant, a huge ball of expanding plasma. Langmuir coined the name plasma because of its similarity to blood plasma, and Hannes Alfvén noted its cellular nature. Note also the filamentary blue outer shell of X-ray emitting high-speed electrons

Enlarge

Tycho's Supernova remnant, a huge ball of expanding plasma. Langmuir coined the name plasma because of its similarity to blood plasma, and Hannes Alfvén noted its cellular nature. Note also the filamentary blue outer shell of X-ray emitting high-speed electrons

Plasma may exhibit complex behiour. And just as plasma properties scale over many orders of magnitude (see table above), so do these complex features. Many of these features were first studied in the laboratory, and in more recent years, he been lied to, and recognised throughout the universe. Some of these features include:

* Filamentation, the striations or "stringy things" seen in a "plasma ball", the aurora, lightning, and nebulae. They are caused by larger current densities, and are also called magnetic ropes or plasma cables.

* Double layers, localised charge separation regions that he a large potential difference across the layer, and a vanishing electric field on either side. Double layers are found between adjacent plasmas regions with different physical characteristics, and can accelerate ions and produce synchrotron radiation (such as x-rays and gamma rays).

* Birkeland currents, a magnetic-field-aligned electric current, first observed in the Earth's aurora, and also found in plasma filaments.

* Circuits. Birkeland currents imply electric circuits, that follow Kirchhoff's circuit laws. Circuits he a resistance and inductance, and the behiour of the plasma depends on the entire circuit. Such circuits also store inductive energy, and should the circuit be disrupted, for example, by a plasma instability, the inductive energy will be released in the plasma.

* Cellular structure. Plasma double layers may separate regions with different properties such as magnetization, density, and temperature, resulting in cell-like regions. Examples include the magnetosphere, heliosphere, and heliospheric current sheet.

* Critical ionization velocity in which the relative velocity between an ionized plasma and a neutral gas, may cause further ionization of the gas, resulting in a greater influence of electomagnetic forces.

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Ultracold Plasmas

It is also possible to create ultracold plasmas, by using lasers to trap and cool neutral atoms to temperatures of 1 mK or lower. Another laser then ionizes the atoms by giving each of the outermost electrons just enough energy to escape the electrical attraction of its parent ion.

The key point about ultracold plasmas is that by manipulating the atoms with lasers, the kinetic energy of the liberated electrons can be controlled. Using standard pulsed lasers, the electron energy can be made to correspond to a temperature of as low as 0.1 K ? a limit set by the frequency bandwidth of the laser pulse. The ions, however, retain the millikelvin temperatures of the neutral atoms. This type of non-equilibrium ultracold plasma evolves rapidly, and many fundamental questions about its behiour remain unanswered. Experiments conducted so far he revealed surprising dynamics and recombination behiour that are pushing the limits of our knowledge of plasma physics.

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Mathematical descriptions

Plasmas may be usefully described with various levels of detail. However the plasma itself is described, if electric or magnetic fields are present, then Maxwell's equations will be needed to describe them. The coupling of the description of a conductive fluid to electromagnetic fields is known generally as magnetohydrodynamics, or simply MHD.

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Fluid

The simplest possibility is to treat the plasma as a single fluid governed by the Nier Stokes Equations. A more general description is the two-fluid picture, where the ions and electrons are considered to be distinct.

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Kinetic

For some cases the fluid description is not sufficient. Kinetic models inc

什么是等离子？

火焰一般可以看作等离子体，不过构成火焰的粒子的电离程度并不高。这将在后面进行详细讨论。那什么是等离子体呢？下面就来先为大家介绍它。

什么是等离子体？

等离子体又叫做电浆，被视为物质的第4种形态，或者称为“超气态”。简单来说就是电离了的“气体”，由离子、电子以及未电离的中性粒子组成，整体呈电中性。等离子体并不需要完全由离子构成。

等离子体属于非凝聚态，构成等离子体的粒子之间游离程度较高，粒子间的相互作用不强。至于凝聚态，就是由大量处于聚集状态的粒子构成的物态，液体和固体就是最常见的凝聚态。

等离子体并不神秘。气体通常都是由分子或原子构成的，而等离子体就是被电离（电离就是原子得到或者失去核外电子形成离子的一种过程，离子都带电）的气体。几乎所有气体都存在一定程度的电离，只是电离程度极低，因此并不能算作等离子体。并且物体要称之为等离子体，还需要具备等离子体所具备的特性，比如存在等离子体振荡、会受电磁场影响等。等离子体振荡是等离子体中的电子在惯性和离子的静电力作用下发生的简谐振动。

等离子体是宇宙中最常见的物态。宇宙中最常见的天体就是恒星，星系也是由恒星构成的，像太阳等恒星就是一个巨大的等离子体，它占了整个宇宙中物质形态的99%。自然界中的闪电就是等离子体。用人工方法，如核聚变、核裂变，也可产生等离子体。

不同等离子体在温度和密度方面差异巨大。以温度划分，等离子体可分为高温等离子体和低温等离子体。等离子体的温度分别用电子温度和离子温度表示，两者相等（或者说相差不多）则称为高温等离子体，不相等则称为低温等离子体。

最常见的等离子体是高温等离子体。处于核聚变状态的物质、电弧、闪电、极光等都是高温等离子体。高温等离子体在切割、冶炼、焊接等领域都有广泛的应用。

低温等离子体又叫做非平衡态等离子，可以存在于常温状态。辉光放电、电晕放电等现象都可以产生低温等离子体。日光灯（又叫做荧光灯）就是通过低压状态的汞蒸气通电后会发生辉光放电，并发射出紫外线，激发荧光粉发光的。在日常生活中大家耳熟能详的等离子电视，就是利用低温等离子体制成的显示器。除此之外还有等离子体涂层。

（上图为电晕放电现象）

为什么火焰属于等离子体？

火焰也是物质，是燃烧时的产物，能够发光发热。在太空中，没有重力作用，火焰会呈现为球形。

火焰的温度有高有低，不同材质燃烧时所形成的火焰，具有不同的温度。打火机火焰的温度大约在400度左右，酒精灯火焰的温度在600~700度，普通炉火的温度大约在800度左右，一般的纸张燃烧时产生的火焰温度仅为200多度。

此外，火焰又分为焰心、中焰和外焰，其中外焰由于与氧气或者氧化剂接触更充分，燃烧反应也更充分，因此温度更高。当可燃物与氧化剂接触时，温度达到着火点就会产生火焰。

一些材质燃烧时还会产生一些固体小颗粒，在热气上升的带动下夹杂在火焰中。不同的材质在燃烧时，火焰的颜色也各不相同。

一般来说温度越高，火焰中粒子的电离程度也就越高，火焰的温度一般都很高，属于高温等离子体。一些温度较低的火焰，由于电离程度太低，因此并不能完全算作等离子体，只能算是处于激发态（原子或者分子吸收能量后，被激发到高能级，尚未电离的状态）的高温气体。

上面已经说过，磁场能够影响等离子体。如果高温火焰是等离子体的话，必然会受到强磁场的影响。实验证明，火焰会受到磁场影响。

（如上图实验所示，磁场的变化能够对蜡烛火焰产生影响）

通过对等离子体有了一定的了解，相信大家也明白为什么火焰属于等离子体了。

感谢阅读，热爱科学的朋友，欢迎关注我。

什么是等离子体？离子体的特征分类及主要参数是什么？

等离子概述

冰升温至0℃会变成水，如果继续使温度上升至100%，那么水就会沸腾成为水蒸气。我们知道，随着温度的上升，物质的存在状态一般会呈现出固态→液态→气态三种物态的转化过程，我们把这三种基本形态称为物质的三态。那么对于气态物质，温度升至几千度时，将会有什么新变化呢? 由于物质分子热运动加剧，相互间的碰撞就会使气体分子产生电离，这样物质就变成由自由运动并相互作用的正离子和电子组成的混合物(蜡烛的火焰就处于这种状态)。我们把物质的这种存在状态称为物质的第四态，即等离子体(plasma)。因为电离过程中正离子和电子总是成对出现，所以等离子体中正离子和电子的总数大致相等，总体来看为准电中性。反过来，我们可以把等离子体定义为：正离子和电子的密度大致相等的电离气体。

从刚才提到的微弱的蜡烛火焰，我们可以看到等离子体的存在，而夜空中的满天星斗又都是高温的完全电离等离子体。据印度天体物理学家沙哈(M·Saha，1893-1956)的计算，宇宙中的99.9%的物质处于等离子体状态。而我们居住的地球倒是例外的温度较低的星球。此外，对于自然界中的等离子体，我们还可以列举太阳、电离层、极光、雷电等。在人工生成等离子体的方法中，气体放电法比加热的办法更加简便高效，诸如荧光灯、霓虹灯、电弧焊等等。给出了主要类型的等离子体的密度和温度的数值。从密度为106(单位：个／m3)的稀薄星际等离子体到密度为1025的电弧放电等离子体，跨越近20个数量级。其温度分布范围则从100 K的低温到超高温核聚变等离子体的108-109K(1-10亿度)。温度轴的单位eV(electron volt)是等离子体领域中常用的温度单位，1 eV=11 600 K。

通常，等离子体中存在电子、正离子和中性粒子(包括不带电荷的粒子如原子或分子以及原子团)等三种粒子。设它们的密度分别为ne ,ni ,nn ，由于 (准电中性)，所以电离前气体分子密度为ne ≈ nn。于是，我们定义电离度β = ne / (ne + nn)，以此来衡量等离子体的电离程度。日冕、核聚变中的高温等离子体的电离度都是100%，像这样β =1的等离子体称为完全电离等离子体。电离度大于1% (β≥10-2 )的称为强电离等离子体，像火焰中的等离子体大部分是中性粒子(β <10-3 )，称之为弱电离等离子体。

若放电是在接近于大气压的高气压条件下进行，那么电子、离子、中性粒子会通过激烈碰撞而充分交换动能，从而使等离子体达到热平衡状态。若电子、离子、中性粒子的温度分别为了Te，Ti，Tn，我们把这三种粒子的温度近似相等(Te ≈ Ti ≈ Tn)的热平衡等离子体称为热等离子体(thermal plasma)，在实际的热等离子体发生装置中，阴极和阳极间的电弧放电作用使得流入的工作气体发生电离，输出的等离子体呈喷射状，可用作等离子体射流(plasma jet)、等离子体喷焰(plasma torch)等。

另一方面，数百帕以下的低气压等离子体常常处于非热平衡状态。此时，电子在与离子或中性粒子的碰撞过程中几乎不损失能量，所以有Te>>Ti , Te>>Tn。我们把这样的等离子体称为低温等离子体(cold plasma)。当然，即使是在高气压下，低温等离子体还可以通过不产生热效应的短脉冲放电模式来生成。

1、等离子体被称为物质的”第四态“，是一种具有电子，原子，离子或基团的满足准中性条件的电离气体。它是区别与常规的固态，液态，气态的另一种存在。等离子体中的主要参数包括密度，电子温度，离子温度，德拜半径，电离度。这几个是最重要的参数。诊断这些参数的方法有，电探针，磁探针，发射光谱，吸收光谱，激光诱导荧光，质谱发等。

2、在地球两极上，因为太阳风暴（高能粒子分）在经过地球两极磁极时，高能粒子轰击空气中的氧气，氮气等气体，使其电离和激发，后沿地磁线运动，并产生多彩的极光，也属于等离子体。等离子体可以由气体放电产生，也可以使气体不断加热而产生。按照等离子体的温度不同可分为高温等离子体和低温等离子体。

3、比如在受控核聚变当中使用托卡马克磁约束产生的高温等离子体，其原理就是利用磁场束缚等离子体并使其不断加热，最终发生氢核聚变反应，并收集起来发电。这其实是模拟太阳上时时刻刻的聚变反应，之所以称为高温，是因为其芯部温度可以达到上亿度。

4、低温等离子体，比如弧光灯，辉光放电灯，射频放电等离子体刻蚀机等，这些气体放电产生的等离子体温度在几百K到上千K，远低于高温等离子体。高温和低温虽然是根据温度划分，但是要区别与我们常见事物的温度，不是说低温就是跟室温差不多。

5、低温等离子体中又可以分为热等离子体和冷等离子体，这是根据等离子体中离子和电子温度是否处于热平衡状态来讨论的。热等离子体说的是电子和离子处于热平衡态，它们各自的温度差不多。比如电弧等离子体焊机所产生的热等离子体，电子温度和离子温度都可达到几千度。