 Hello everyone, Homi Bawa National Institute is offering the course on Accelerator Physics. The course will be useful to graduate and postgraduate students, research scholars and faculty members. We use accelerators every day without knowing about them. The CRT based televisions and microwave ovens are very efficient accelerators. In fact, accelerators are an integral part of our life. Although accelerators were developed initially for basic research, they are now used extensively in medical science, industry, national security, environmental science, production and study of new particles and super heavy elements. Isotopes produced using accelerators are used for diagnostics and treatment. Electron accelerators are used for food irradiation and cancer therapy and also as synchroton radiation sources for material science research. Recently, it is proposed to use accelerators for nuclear energy generation through ADS, which is Accelerator Deven Subcritical Reactor System, using Thorium as a fuel, which is abundantly available in India. These thorium-based systems are expected to be inherently safe. Also it is estimated that thorium available in India can solve the nuclear fuel problem for about 500 to 600 years. Depending on how voltage is generated and acceleration is done, accelerators are categorized as DC accelerators and RF accelerators. RF accelerators could be linear or cyclic. Today, accelerators in the energy range of KV to TeV have been built. About 35 to 40,000 accelerators are in operation worldwide. In DC accelerators, the charged particles are subjected to potential difference only once and hence they are accelerated to not very high energies. However, DC accelerators are still popular as they can provide beams of high resolution, which is a requirement for nuclear reaction studies, particularly nuclear spectroscopy. In RF accelerators, a low voltage is used repeatedly to get high energy beams. In linear RF accelerators, the charged particles are accelerated in a linear path, whereas in the circular accelerators, they move in a circular path. Linear accelerators are expensive due to their large lengths. The cost is considerably reduced by making them circular accelerators. However, in circular accelerators, power loss due to emission of synchrotron radiation is very significant. There is no power loss due to synchrotron radiation in linear accelerators, as beam banding is not involved. In order to design, operate and utilize them efficiently, the physics of the accelerators should be well understood. The course gives a general understanding of how different types of accelerators work. Charged particle accelerations using different types of accelerating structures will also be discussed. The course will also give a general understanding of longitudinal and transverse beam dynamics. The course consists of three modules. I will be covering the first module on DC accelerators. Prof. Rajni Pandey will be teaching linear accelerators. Module 3 on cyclic accelerators will be given by Prof. Amlendu Sharma. Thank you and welcome to the course.