logging in or signing up A Short Introduction to Plasma dollfan Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 972 Category: Science & Tech.. License: All Rights Reserved Like it (0) Dislike it (0) Added: December 23, 2009 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: gaurav111160 (25 month(s) ago) nice and enough information is given in this ppt. Saving..... Post Reply Close Saving..... Edit Comment Close By: gyogesh (26 month(s) ago) this is very useful ppt thanks 4 it Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Plasma : Plasma A Short & Basic Introduction Wang fanJune.2009 What Is It? : What Is It? Plasma can be defined as a partially or wholly ionized gas with a roughly equal number of positively and negatively charged particles , It consists of a collection of free-moving electrons and ions. Plasma typically takes the form of neutral gas-like clouds, as seen, for example, in the case of stars. Like gas, plasma does not have a definite shape or a definite volume unless enclosed in a container, but, unlike gas, in the influence of a magnetic field, it may form structures such as spheres, beams and double layers. Slide 3: The Nobel prize winning American chemist Irving Langmuir first used this term to describe an ionized gas in 1927. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be the fourth state of matter. More than 99% of matters in the universe exists in plasma. Plasma - the Fourth State of Matter : Plasma - the Fourth State of Matter Plasma Categories : Plasma Categories According to the temperature of plasma: Characteristics : Characteristics Plasma Density Temperatures Debye length Plasma frequency Plasma Density : Plasma Density For plasma to exist, ionization is necessary. The term "plasma density" by itself usually refers to the "electron density", that is, the number of free electrons per unit volume. The degree of ionization of a plasma is the proportion of atoms which have lost electrons, and is controlled mostly by the temperature. The degree of ionization α is defined as α = ni/(ni + na) where ni is the number density of ions and na is the number density of neutral atoms. Temperatures : Temperatures Because of the large difference in mass, the electrons come to thermodynamic equilibrium amongst themselves much faster than they come into equilibrium with the ions or neutral atoms. For this reason the "ion temperature" may be very different from (usually lower than) the "electron temperature". This is especially common in weakly ionized plasmas, where the ions are often near the ambient temperature. Temperature controls the degree of plasma ionization. A plasma is sometimes referred to as being "hot" if it is nearly fully ionized, or "cold" if only a small fraction (for example 1%) of the gas molecules are ionized. Even in a "cold" plasma the electron temperature is still typically several thousand degrees Celsius. Debye screening : Debye screening A Debye sphere is a volume whose radius is the Debye length, in which there is a sphere of influence, and outside of which charges are screened. the Debye length λD defined by Plasma Frequency : Plasma Frequency Consider a neutral plasma, consisting of a gas of positively charged ions and negatively charged electrons. If one displaces by a tiny amount all of the electrons with respect to the ions, the Coulomb force pulls back, acting as a restoring force. the electron plasma frequency the ion plasma frequency the plasma frequency as the electrons are so much lighter than ions Examples of artificial plasma : Examples of artificial plasma Glow discharge plasmas: non-thermal plasmas generated by the application of DC or low frequency RF (<100 kHz) electric field to the gap between two metal electrodes. Probably the most common plasma; this is the type of plasma generated within fluorescent light tubes. Slide 12: Dielectric barrier discharge (DBD): this is a non-thermal discharge generated by the application of high voltages across small gaps where in a non-conducting coating prevents the transition of the plasma discharge into an arc. It is also widely used in the treatment of fabrics. Slide 13: Arc discharge: this is a high power thermal discharge of very high temperature ~10,000 K. It can be generated using various power supplies. It is commonly used in metallurgical processes. For example it is used to melt rocks containing Al2O3 to produce aluminium Plasma Application : Plasma Application PDP : PDP A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32" inches or larger). Many tiny cells between two panels of glass hold an inert mixture of noble gases. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light. A Samsung PN50B450 50"-inch Plasma HDTV, an example of a modern Plasma television. Plasma Spraying : Plasma Spraying Plasma spraying, a method of thermal spraying, is a materials processing technique for producing coatings using a plasma jet. Deposits having thickness from micrometers to several millimeters can be produced from a variety of materials, including metals, ceramics, polymers and composites. How it works : How it works The material to be deposited (feedstock) — typically as a powder, sometimes as a liquid or wire — is introduced into the plasma jet, emanating from a plasma torch. In the jet, where the temperature is on the order of 10,000K, the material is melted and propelled towards a substrate. There, the molten droplets flatten, rapidly solidify and form a deposit. Commonly, the deposits remain adherent to the substrate as coatings. Slide 18: Field of Applications ITER-First Wall : ITER-First Wall You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
A Short Introduction to Plasma dollfan Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 972 Category: Science & Tech.. License: All Rights Reserved Like it (0) Dislike it (0) Added: December 23, 2009 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: gaurav111160 (25 month(s) ago) nice and enough information is given in this ppt. Saving..... Post Reply Close Saving..... Edit Comment Close By: gyogesh (26 month(s) ago) this is very useful ppt thanks 4 it Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript Plasma : Plasma A Short & Basic Introduction Wang fanJune.2009 What Is It? : What Is It? Plasma can be defined as a partially or wholly ionized gas with a roughly equal number of positively and negatively charged particles , It consists of a collection of free-moving electrons and ions. Plasma typically takes the form of neutral gas-like clouds, as seen, for example, in the case of stars. Like gas, plasma does not have a definite shape or a definite volume unless enclosed in a container, but, unlike gas, in the influence of a magnetic field, it may form structures such as spheres, beams and double layers. Slide 3: The Nobel prize winning American chemist Irving Langmuir first used this term to describe an ionized gas in 1927. The ability of the positive and negative charges to move somewhat independently makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma therefore has properties quite unlike those of solids, liquids or gases and is considered to be the fourth state of matter. More than 99% of matters in the universe exists in plasma. Plasma - the Fourth State of Matter : Plasma - the Fourth State of Matter Plasma Categories : Plasma Categories According to the temperature of plasma: Characteristics : Characteristics Plasma Density Temperatures Debye length Plasma frequency Plasma Density : Plasma Density For plasma to exist, ionization is necessary. The term "plasma density" by itself usually refers to the "electron density", that is, the number of free electrons per unit volume. The degree of ionization of a plasma is the proportion of atoms which have lost electrons, and is controlled mostly by the temperature. The degree of ionization α is defined as α = ni/(ni + na) where ni is the number density of ions and na is the number density of neutral atoms. Temperatures : Temperatures Because of the large difference in mass, the electrons come to thermodynamic equilibrium amongst themselves much faster than they come into equilibrium with the ions or neutral atoms. For this reason the "ion temperature" may be very different from (usually lower than) the "electron temperature". This is especially common in weakly ionized plasmas, where the ions are often near the ambient temperature. Temperature controls the degree of plasma ionization. A plasma is sometimes referred to as being "hot" if it is nearly fully ionized, or "cold" if only a small fraction (for example 1%) of the gas molecules are ionized. Even in a "cold" plasma the electron temperature is still typically several thousand degrees Celsius. Debye screening : Debye screening A Debye sphere is a volume whose radius is the Debye length, in which there is a sphere of influence, and outside of which charges are screened. the Debye length λD defined by Plasma Frequency : Plasma Frequency Consider a neutral plasma, consisting of a gas of positively charged ions and negatively charged electrons. If one displaces by a tiny amount all of the electrons with respect to the ions, the Coulomb force pulls back, acting as a restoring force. the electron plasma frequency the ion plasma frequency the plasma frequency as the electrons are so much lighter than ions Examples of artificial plasma : Examples of artificial plasma Glow discharge plasmas: non-thermal plasmas generated by the application of DC or low frequency RF (<100 kHz) electric field to the gap between two metal electrodes. Probably the most common plasma; this is the type of plasma generated within fluorescent light tubes. Slide 12: Dielectric barrier discharge (DBD): this is a non-thermal discharge generated by the application of high voltages across small gaps where in a non-conducting coating prevents the transition of the plasma discharge into an arc. It is also widely used in the treatment of fabrics. Slide 13: Arc discharge: this is a high power thermal discharge of very high temperature ~10,000 K. It can be generated using various power supplies. It is commonly used in metallurgical processes. For example it is used to melt rocks containing Al2O3 to produce aluminium Plasma Application : Plasma Application PDP : PDP A plasma display panel (PDP) is a type of flat panel display common to large TV displays (32" inches or larger). Many tiny cells between two panels of glass hold an inert mixture of noble gases. The gas in the cells is electrically turned into a plasma which then excites phosphors to emit light. A Samsung PN50B450 50"-inch Plasma HDTV, an example of a modern Plasma television. Plasma Spraying : Plasma Spraying Plasma spraying, a method of thermal spraying, is a materials processing technique for producing coatings using a plasma jet. Deposits having thickness from micrometers to several millimeters can be produced from a variety of materials, including metals, ceramics, polymers and composites. How it works : How it works The material to be deposited (feedstock) — typically as a powder, sometimes as a liquid or wire — is introduced into the plasma jet, emanating from a plasma torch. In the jet, where the temperature is on the order of 10,000K, the material is melted and propelled towards a substrate. There, the molten droplets flatten, rapidly solidify and form a deposit. Commonly, the deposits remain adherent to the substrate as coatings. Slide 18: Field of Applications ITER-First Wall : ITER-First Wall