Construction And Application Of Linear Accelerators

Construction And Application Of Linear Accelerators A linear accelerator particle is a type of particle which accelerator greatly increases the velocity of charged subatomic particles or ions by subjecting the charged particles to a series of oscillating electric potentials along a linear beam line; this method of particle acceleration was invented in 1928 by Rolf Wideroe. Linear accelerators have many applications, from the generation of X-rays for medical purposes, to being an injector for a higher-energy of accelerators, to the investigation of the properties of subatomic particles. The design of a linear accelerator depends on the type of particle that is being accelerated: electrons, protons or ions. Introduction: The first linear accelerators used only a single stage of acceleration, with a direct current potential providing the energy. This could be provided by a Van de Graaff generator or a voltage multiplier power supply. Such the accelerators are severely limited in accelerating power since at high voltage; energy is lost due to corona discharge with electrical energy dissipated into the surrounding atmosphere. Such devices are still used as ion injectors for other accelerating devices. The accelerating potential in electron volts is equal to the voltage potential between the ion source and the target. The maximum voltage potential relative to the ground potential is generally not limited by the generator but rather by the tendency of voltage potential to leak away due to corona discharge or to suddenly drop due to a spark. While various techniques may be applied to raise this maximum potential the structures required become impractically massive or expensive. The multiple-stage accelerators were limited by the lack of suitable electron tubes capable of operating at high frequency and high power while maintaining both precise frequency and phase control. Various other types of accelerators such as the cyclotron and synchrocyclotron were developed to overcome these limitations. With the development of the high power klystron tube it became practical to continue the development of the linear accelerator, first for use as a high-speed injector for the synchrotron and finally as a high-power accelerator for research use, culminating in the two-mile-long Stanford Linear Accelerator (SLAC). Construction and Working: It will be consist of following components: (1) The design of the source depends on the particle that is being moved. Electrons are generated by a cold cathode, the hot cathode and photocathode, or radio frequency ion sources. Protons are generated in an ion source, which can have many different designs. If the heavier particles are to be accelerated, e.g. uranium ions and the specialized ion source are needed. (2) A high voltage source for the initial injection of particles. (3) A hollow pipe vacuum chamber. The length will vary with the application. If the device is used for the production of X-rays for inspection or therapy the pipe may be only 0.5 to 1.5 meters long. If the device is to be an injector for a synchrotron it may be about 10 meters long. If the device is used as the primary accelerator for nuclear particle investigations, it may be several thousand meters long. (4) Within the chamber, electrically isolated cylindrical electrodes are placed, whose length varies with the distance along the pipe. The length of each electrode is determined by the frequency and power of the driving power source and the nature of the particle to be accelerated, with shorter segments near the source and longer segments near the target. The mass of the particle has a large effect on the length of the cylindrical electrodes; for e.g. An electron is considerably lighter than a proton and so will generally require a much smaller section of cylindrical electrodes as it accelerates very quickly à ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬ think about a boulder versus a ping pong ball; it is easier to accelerate the ping pong ball. Likewise, because its mass is so small, even compared to the nucleus of an atom, electrons have much less kinetic energy than protons at the same speed. Because of the possibility of electron emissions from highly charged surfaces, the voltages used in the accelerator have an upper limit, so this cannot be as simple as just increasing voltage to match increased mass. (5) One or more sources of radio frequency energy used to energize the cylindrical electrodes. The very high power accelerator will use one source for each electrode. The sources must operate at precise power, frequency and phase appropriate to the particle type to be accelerated to obtain maximum device power Quadrupole magnets surrounding the linac of the Australian Synchrotron are used to help focus the electron beam (6) An appropriate target the electrons are accelerated to produce X-rays then water cooled tungsten target is used. Various target materials are used when protons or other nuclei are accelerated, depending upon the specific investigation. For particle-to-particle collision investigations the beam may be directed to a pair of storage rings, with the particles kept within the ring by magnetic fields. The beams may then be extracted from the storage rings to create head on particle collisions.As the particle bunch passes through the tube it is unaffected while the frequency of the driving signal and the spacing of the gaps between electrodes are designed so that the maximum voltage differential appears as the particle crosses the gap. This accelerates the particle, imparting energy to it in the form of increased velocity. At speeds near the speed of light, the incremental velocity increase will be small, with the energy appearing as an increase in the mass of the particles. In portions of the accelerator where this occurs, the tubular electrode lengths will be almost constant. (7) The additional magnetic or electrostatic lens elements may be included to ensure that the beam remains in the center of the pipe and its electrodes. (8) The very long accelerators may maintain a precise alignment of their components through the use of servo systems guided by a laser beam. Fig. (1.1) 805MHz SCC LINAC Working: A linear accelerator works on the principle of electric attraction and repulsion. A charged particle such as an electron or a proton is injected into a tube with a similar charge (negative for electrons, positive for protons). Just beyond that tube is another tube with an opposite charge. The particle gets attracted by the far tube, so it moves towards the next tube. Recall that inside a conductor, the electric field is zero therefore the charge of the tube its in doesnt affect it. But when its in the space between the tubes, it experiences an electric field which drives it forward. Just as it hits the next tube, its polarity switches so now its the same as the particle. A third tube, just beyond the second one, gets charged with the opposite polarity, and the same thing happens. This continues on, tube after tube. The particle gets a kick of energy each time it sees a new field, and the electric potential gets converted into kinetic energy. As the particle gets faster, the tubes hav e to get longer; the particle spends the same amount of time in each tube. Obviously, the geometry of the tubes and the frequency with which theyre switched needs to be calculated precisely. Linear accelerators of this type can be many miles long; theyre often long enough that the curvature of the earth needs to be accounted for during their construction. But they can accelerate particles to a significant fraction of the speed of light. Fig. (1.2) 208MHz DT LINAC Fig.(1.3) Applications of LINAC: The LINAC System highly efficient accelerators are ideally suited to many applications in industry, medicine, and research. (1) LINAC Synchrotron Injector is serving as the perfect first stage to other higher energy accelerators. (2) Semiconductor Processing. (3) Boron Neutron Capture Therapy (BNCT) conventionally uses a nuclear reactor as the neutron source. Our LINAC-based neutron source provides a better controlled neutron energy spectrum, at lower cost, without the concern of radioactive waste associated with a reactor. (4) Isotope Production Our LINACs are ideally suited for isotope production, such as the PET isotopes. (5) Neutron Radiography. (6) Neutron Activation Analysis. (7) Surface Science. (8) Particle-Induced X-ray Emission (PIXE). (9) Pulsed Neutron Applications is LINAC-based neutron source allows for pulsed neutron beams for applications such as time-of-flight measurements. Uses: A linear accelerator (LINAC) is most commonly used for external beam radiation patients with cancer. It delivers a uniform dose of high-energy x-ray to the region of the patientà ¢Ãƒ ¢Ã¢â‚¬Å¡Ã‚ ¬Ãƒ ¢Ã¢â‚¬Å¾Ã‚ ¢s tumor. These x-rays can destroy the cancer cells, while sparing the surrounding normal tissue. The linear accelerator uses microwave technology to accelerate electrons in a part of the accelerator called the wave guide and then allows these electrons to collide with a heavy metal target. As a result of these collisions, high energy x-rays are scattered from the target. A portion of these x-rays is collected and then shaped to form a beam that matches the patients tumor. The beam comes out of a part of the accelerator called a gantry, which rotates around the patient. The patient lies on a moveable treatment couch and lasers are used to make sure the patient is in the proper position. Radiation can be delivered to the tumor from any angle by rotating the gantry and moving the treatment couch. Fig. (1.4) LINAC Advantages and Disadvantages of linear accelerator: Advantages: Linear accelerator of appropriate design are capable of accelerating heavy ions to energies exceeding those available in ring-type accelerators, which are limited by the strength of the magnetic fields required to maintain the ions on a curved path. The High power LINACs are also being developed for production of electrons at relativistic speeds, required since fast electrons traveling in an arc will lose energy through synchrotron radiation; this is the limits the maximum power that can be imparted to electrons in a synchrotron of given size. LINACs are also capable of prodigious output, producing a nearly continuous stream of particles, whereas a synchrotron will only periodically raise the particles to sufficient energy to merit a shot at the target. The burst can be held or stored in the ring at energy to give the experimental electronics time to work, but the average output current is still limited. The high density of the output makes the LINAC particularly attractive for use in loading storage ring facilities with particles in preparation for particle to particle collisions. The high mass output also makes the device practical for the production of antimatter particles, which are generally difficult to obtain, being only a small fraction of a targets collision products. These may then be stored and further used to study matter-antimatter annihilation. As there are no primary bending magnets, this cost of an accelerator is reduced. Medical grades LINACs accelerate electrons using a complex bending magnet arrangement and a 6-30 million electron-volt potential to treat both benign and malignant disease. The reliability, flexibility and accuracy of the radiation beam produced have largely supplanted cobalt therapy as a treatment tool. The device can simply be powered off when not in use; there is no source requiring heavy shielding. Disadvantages: (1) The device length limits the locations where one may be placed. (2) A great number of driver devices and their associated power supplies are required, increasing the construction and maintenance expense of this portion. (3) The walls of the accelerating cavities are made of normally conducting material and the accelerating fields are large, the wall resistivity converts electric energy into heat quickly. On the other hand superconductors have various limits and are too expensive for very large accelerators. Therefore, high energy accelerators such as SLAC, still the longest in the world, limiting the average current output and forcing the experimental detectors to handle data coming in short bursts. Future Scope: Any of the next generation accelerators will need high power of sources and if accelerating systems that transfer ac power to beam power efficiently. The challenges though span a wide range of technologies and wavelength. From very low frequency cavities used in Muon Colliders (70 MHz) to very high frequency cavities in Multi TeV linear colliders (30 GHz and more), many of the designs are based on experience and where experience is missing, scaling laws are used. How does Breakdown scale with electric field stength, pulse length and frequency? What limits peak power and effciency in modern power sources? The experts in this field should generally try to answer these questions and therefore give guidance to the accelerator designers. Limits on fields, peak powers and efficiencies should therefore be an outcome of the working group. Given the experience in the ongoing RD programs for normal and superconducting cavities the performance achieved today should be described, as well as the limitations and possible cures. The time scale for establishing these cures should be summarized as well. For both, the normal conducting and the superconducting case the subsystems (Modulators, Klystrons, Pulse Compression systems) and cavities should be addressed independently with a description of present status and of the progress being made over the last five years to allow some extrapolation. For the power sources itself, a very active field only partially driven by accelerator builders, future trends and new directions of improvements should be described. This group should also describe the likely spinoffs of these different technologies into other fields, coming out of the technical developments being done in the HEP research environment.

Buying A Computer :: Technology Market Analysis Informative

Buying a computer today is much more complicated then it was ten years ago. The choices we have are abundant, and the information we must gather to make those choices is much greater. The average consumer is a more educated buyer; they at least have some ideas of what they want in a computer. Yet, we must still ask ourselves these significant questions; such as: What will the primary function of my computer be? What computer components should I consider at the time of purchase? How much money do I have to spend? Where should I go to purchase my computer? For this report, I will consider the requirements of a typical family: using a mini-tower PC with the Windows 95 operating system, word processing, and entry-level publishing programs; as well as, an anti-virus package, games with high-level graphics and sound, and the internet. I will also consider the following components; those essential for the computer to work faster, and more efficient. They are as follows: Central Processing U nit (CPU) – System Memory (RAM) – Storage Device(s). The following is a detailed look at the CPU, RAM, and Storage devices; the important components that you should consider when purchasing a PC. Computer systems, particularly the higher-end models, come in several Configurations: desktop, mini tower, or tower. The configuration you chose should depend - to some extent - on the amount of expansion, (if any) you may want to plan for in the future. Most tower configurations have a greater amount of expandability than mini tower and desktop models. Also, the amount of space that you have in your home for the system should be taken into consideration. Tower configurations are usually placed on the floor; (however, not the mini tower models) whereas, desktop models are made to sit on the surface where the keyboard and monitor are located. The first consideration is the CPU. Today, the Intel Corporation is still the leading manufacturer of microprocessors. However; other chi p manufacturers, such as Cyrix and AMD, are rapidly climbing the industry ladder to compete with Intel in the CPU marketplace. Although these other microprocessors are probably just as good as an Intel, there may be some subtle differences in them that may affect their performance. The speed of the processor is very important; this is the measure of its clock rate - which indicates the number of instructions that can be processed per second.

Obesity; Root Cause Of Many Diseases.

Obesity is a medical condition in which excess of fat has accumulated in the body and may give rise to health problems. A person is obese when his body mass index is above 30 kg/m2. Body mass index is ratio of an individual’s weight and height, and can be calculated by dividing person’s weight with square of his height. The most commonly used measure of weight status is body mass index, or BMI. Years of research have shown that BMI provides good estimate of â€Å"fatness† and correlates well with important health outcomes. For adult men and women healthy BMI falls between 18 to 25 kg/m2 .Overweight is defined as a BMI between 25 and 30; and obesity a BMI of 30 or higher. So it is important tool for clinicians trying to screen to determine who may be at risk because of carrying around too much weight for their height. More or less every region of world is facing this problem. Once a problem of wealthy nations, obesity now impacts countries at all economic levels, bringing with it a wave of ill health and lost productivity. Worldwide rate of obesity doubled since 1980, with just over 200 million adult men and just under 300 million adult women obese.Of all high-income countries, the United States has the highest rate of overweight and obesity, with fully a third of population obese, a rate projected to rise around 50 percent by 2030. Obesity is also on the rise in South Asian countries including Pakistan. According to Forbes, Pakistan is ranked 165 (out of 194 countries), with 22. 2% of individuals crossing the threshold of obesity. In Pakistan the highest concentration of the obese lies in the big cities as compared to the rural countryside. At the other times in history obesity was considered as sign of wealth and prosperity, as mankind suffered scarcity of food in the past.But now obesity has been declared as a disease by American Medical Association. Whether or not it is considered a disease, it is also an important risk factor for many c hronic diseases. Obesity is associated with many chronic heart diseases such as angina, myocardial infarction (heart attack), high blood pressure, deep vein thrombosis and more. A 2002 study concluded that 21% of ischemic heart disease is due to obesity, while a 2008 European consensus puts the number at 35%. Obesity has been cited as the main cause of high blood pressure.The risk of hypertension (high blood pressure) is five times higher in the obese as compared to those of normal weight. A definitive link between obesity and hypertension has been found using animal and clinical studies, which have suggested that there are multiple mechanisms for obesity induced hypertension. People who are overweight are at much greater risk of developing type 2 diabetes mellitus than normal weight individuals . Being overweight puts extra pressure on body’s ability to control blood glucose using insulin and therefore makes it much more likely for you to develop diabetes.Almost 90% of peopl e with type 2 diabetes mellitus are overweight. Many respiratory system diseases may be outcome of obesity such as asthma, obstructive sleep apnea etc. Obesity may be associated with variety of reproductive system diseases for example polycystic ovarian syndrome, infertility, birth defects, intra-uterine fetal death etc. Gastrointestinal diseases such as gastroesophageal reflux disease, gall stone, fatty liver are predominant in the overweight. Many types of cancers occur with increased frequency in those who are overweight or obese.A study from United Kingdom showed that 5% of cancer is due to excess weight. Certain neurological conditions are also attributed to increased body weight. Apart from associated morbidity and mortality, obesity has many social and economic implications as well. The obese are often subject of ridicule as a result they suffer from depression and lose self-confidence. Obesity reduces man-power thus incurs economic loss. A combination of excessive food energ y intake, lack of exercise is thought to cause most cases of obesity.A limited number of cases are primarily due to genetics, medical reasons and psychiatric illnesses. In contrast, increasing rates of obesity at societal level are felt to be due to easily accessible and palatable diet, increased reliance on cars and mechanized manufacturing. Food energy is calculated in terms of calories, excess of calories when taken are stored in body in the form of fat. Thus energy dense foods increase body fat by supplying extra of calories and ultimately lead to obesity.Sweetened beverages and fast food meals provide more calories than required and are most important contributing factors for obesity in United States and European countries. Lack of regular physical exercise plays significant role in obesity. Worldwide there has been shift to less physically demanding work, significant portion of world’s population doesn’t get sufficient exercise. This is mainly due to invention of machines that save much of the hard work in every field. Obesity may be result of many genetic and environmental factors, as it tends persist in certain families due to inheritance of defective genes.Experts have related increased body weight in children with their time spent on watching television; more they spent their time watching television more they are prone to obesity. Obesity is sometimes clinical feature of some diseases for example Cohen syndrome, Prader Willi syndrome etc. Proper diet and physical exercise has been mainstay of long term management of the obesity. Fiber diet such as wheat, corn and certain vegetables help maintain healthy weight. Regular physical exercise burns extra calories, thus prevents excessive deposition of fat in the body tissues.Certain drugs and surgical procedures are also known to treat obesity, but are less preferred. It is clear that obesity is root cause of many diseases such as angina, myocardial infarction, hypertension, diabetes mellitu s and many more. Once it was prevalent in affluent nations, now it is problem of all nations of the world. Obesity results from high energy foods such as sweetened beverages, fast food meals. It may also result from sedentary life style and other genetic and environmental factors. Obesity can be managed by taking proper diet and regular physical exercise.

Can Evolution Ever Explain Why Men Rape Essay - 1646 Words

Can evolution ever explain why men rape? Why is it considered a societal norm for men to rape women? Rape can be an act of any sexual activity that is carried out using force or threat of injury against the will of a female. It mostly occurs when the victim is underage, incapable of valid consent (i.e. drunk, drugged), or when there is a known perpetrator (i.e. family member, friend). It is unfortunate that some women get raped even when having no affiliations with the perpetrator. Despite a decrease in the reported rape cases, the statistic is misleading because most victims are not reporting the incidence. Through research, one may suggest that evolution may explain why men rape. There has been an increase in social peer pressure, a high demand in culture expectations, and a rise in individual problems (i.e. revenge, alcoholism). Thus, the incidence of rape has increased while most victims do not report it. The number of reported rapes and sexual assaults has decreased in the Unite d States. According to the National Crime Victimization Survey, the population-adjusted rate of rape has dropped 55% from 1993, when the survey was started, to 2013 (Drum, 2014). It is difficult to know for sure if this number is accurate because many cases of sexual assault and rape are not reported to authorities. The National Sexual Violence Resource Center estimates that roughly 63% of sexual assaults are not reported to police (2015). Still at least 25% of American women haveShow MoreRelatedThe Field Of Sociology Is An Old But Ever Changing Systematic Study Of Human Behavior1579 Words   |  7 PagesThe field of sociology is an old but ever changing systematic study of human behaviour in a social context. Within the field of sociology, in order to create a contextual understanding of the influences that create society in which we live theories are employed to explain the forces that shape our social world. Such theories are essential in explaining emerging social phenomena suc h as pornification (Furze et al, 2015). Pornification of the social world has become a significant mass media issueRead MoreSex Offenders : Treatment And Prevention For The Future3425 Words   |  14 Pages475 – 001: Biology, Culture, and Evolution Dr. Christopher Dana Lynn Psychological Traits, Biological Commonalities, and Genetic Links in Repeat Sex Offenders: Treatment and Prevention for the Future Scientists and researchers have given little attention and on-going investigation with regard to the study of the motivations behind rapists and repeat sex offenders. By looking at a study by Lee, Caruso, Goins, Southerland in 2003, an attempt can be made to answer the question ofRead MoreHow Catch A Criminal : Instruments And Techniques Used For Investigations1651 Words   |  7 PagesHow to Catch a Criminal: Instruments and Techniques used for Investigations Why are Criminal Investigation and Tools for them Important? We all know of those popular television shows like CSI, Criminal Minds and Law and Order and how they depict the life of Criminal Investigators. They are young, independent, living somewhere on Paradise Island and in their spare time, when not hanging on a beach with a Pina Colada, they get a call about a case needing to be solved immediately. Which they do, byRead MoreSex Minority1961 Words   |  8 Pagesthey can be dealt with and to prevent them from becoming gays and lesbians? Without a doubt the so-called â€Å"symptoms† are superficial and reflect a mind-set dependent on pseudo-science. The word â€Å"symptoms† explain everything, it stigmatized those LGBT people. Those â€Å"symptoms† maybe not use to idendify but discriminate LGBT students. In similar situations which have occurred here in Malaysia and around the world, this has resulted in mental and physical abuse, bullying, torture and even rape. We haveRead MoreCharlotte Perkins Gilman, Ida B. Wells Barnett and the Fight for Fairness and Equality for Undocumented Immigrants2243 Words   |  9 Pageslaid the groundwork for the modern day struggles for civil rights, in particular the fight for fair treatment and equality of undocumented immigrants. Gilman and Wells-Barnett did not gain admiration for maintaining the status-quo, which is exactly why it is important to apply their methods of research and analysis to the fight for the equality of undocumented immigrants. This paper focuses on the revolutionary theories Gilman and Wells-Barnett are most known for, and discusses the potential implicationsRead MoreReligion : Uncovering A Great Fallacy1774 Words   |  8 Pagesof a god can be proven however, this is not true. The atheist argues that there are no good arguments that can be brought for the existence of God that cannot be otherwise well rebutted. I’ll argue using as few scientific facts as possible under the impression that they won’t be needed. This posit ion, while countering many thousands of belief systems, is, in a way, an attempt to tackle the very core of theocracy and its associated behaviors. The first question that must be asked is â€Å"why must religionRead MoreCity of God, by Fernando Meirelles and Pixote, by Hector Bebenco3034 Words   |  13 Pages Rocket stands on the fence balancing equally between both the gang lifestyle and his escape. In Pixote, Pixote is forced into the gang lifestyle by by societal constraints, and authoritative figures that limit the choices . In this essay I will explain how societal norms and ideas inflicted on children mold the future of the Brazilian culture typical for teens and children in the slums/ favelas. The idea that, from birth these kids will become products of the favela, which leads to youth transgressionRead More Sexual Innuendoes in the Films of Alfred Hitchcock Essay example3477 Words   |  14 PagesSexual Innuendoes in the Films of Alfred Hitchcock When watching an Alfred Hitchcock movie, have you ever found yourself sympathizing with a deceptive seductress or a soon-to-be sex offender? If so, you may have felt guilt from watching such sexual innuendoes, but don’t feel too bad. This is just one of the intents of Alfred Hitchcock as he weaves many of his tales with sensual characters. His films portray a vast array of sexuality from showing a battle of the sexes and tales of romance toRead MoreSocial Conflict Theory3263 Words   |  14 Pageseconomic interest with the property. It is this type of relationship which the conflict theorist will use to show that social relationships are about  power  and exploitation. Padgitt continues, Marx argued that through a dialetic process, social evolution was directed by the result of class conflict. Marxism argues that human history is all about this conflict, a result of the strong-rich exploiting the poor-weak. From such a perspective, money is made through the exploitation of the worker. It isRead MoreReligion Is Poison8248 Words   |  33 Pageswords, it can mean anything we want it to mean, but in a discussion, it is important that we understand how the word is used. I believe it is impossible to give a satisfactory universal definition of religion. Because it crosses so many different boundaries in human experience, religion is notoriously difficult to define partly due to two problems: they are too narrow and omit numerous belief systems which many agree are religious, or they are too broad, suggesting that everything is or can be a religion