22138

تزريق، گير اندازي و شتاب دهي الكترونها در موج دنباله توليدي از اندركنش تپ ليزري چيرپ شده با پلاسما

دكتري

فيزيك

1393

1398/11/26

دكتر محمد حسين مهديه - دكتر اسماعيل اسلامي

فيزيك

اين پايان نامه به اندركنش نوع خاصي از تپهاي ليزري با پلاسما به منظور تقويت موج دنباله اختصاص يافته است. تزريق و شتابدهي دسته الكترون در موقعيتهاي متفاوت موج دنباله مورد بررسي قرار گرفته است. نتايج محاسبات نشان داد كه در تزريق الكترون در موج دنباله توليدي از تپ ليزري چيرپ شده، الكترونها انرژي بيشتري را كسب كرده و زودتر گير اندازي ميشوند. با دور شدن محل تزريق از تپ ليزري، كيفيت الكترونهاي شتابدهي شده كاسته شد. با تزريق دسته الكترون در بيشينه موج دنباله توليدي، الكترونها داراي انرژي بيشتر و كيفيت بهتر بودند. طبق نتايج ارائه شده، تزريق خارج محوري منجر به افزايش ده برابري گسيلندگي دسته الكترون ميگردد. در ادامه پژوهش، به ادغام دو روش كانال پلاسمايي و انعكاس از سطح لوله مويين به منظور تقويت هدايت تپ ليزري و افزايش انرژي ذرات باردار اختصاص يافته است. كد WAKE-EP، براي شبيه سازي به كار گرفته شده است. نتايج نشان داد كه به كارگيري تپ ليزري ايري و كانال پلاسمايي، منجر به بهبود كيفيت دسته الكترونها ميگردد.

1399/04/07

Injection and acceleration of electron bunch in a plasma wakefield generated in a chirped laser pulse

2/14/2021 12:00:00 AM

A comparative study of different injection configurations in the wakefield generated by a chirped laser pulse is studied. The preferable electron injection region is considered for different injection schemes. For injection in the chirped laser pulse, the energy spread has approximately the same final value independently of its injection position while energy spread changes strongly for injection in the wakefield. It is demonstrated that an externally injected electron bunch with an initial energy of can achieve an energy gain of by using periodical chirped laser pulses. In particular, strong bunch decoherence is observed for off-axis injection in a plasma-channel-guided-laser wakefield. This strong bunch decoherence leads to a considerable increase in the bunch emittance growth. It is indicated that periodical chirped laser pulse can trap electrons earlier than other pulses. It is shown that periodical chirped laser pulses lead to decrease the minimum momentum necessary to trap the electrons. This is due to the fact that periodical chirped laser pulses are globally much efficient than nonchirped pulses in the wakefield generation. It is found that chirped laser pulses could lead to much larger electron energy than that of nonchirped pulses. Relative energy spread has a lower value in the case of periodical chirped laser pulses. We analyzed the influence of laser guiding at intensity of inside a capillary tube on the performance of an one GeV accelerator stage of a Laser Plasma Accelerator. The guiding of the laser is achieved by a combined action of a radial density profile of the plasma and the reection on the capillary walls. The main objective is to get an optimized capillary radius of reduced dimensions in order to reduce the energy required for generating the plasma inside the capillary. For the best-matched capillary radius of minimal value, we analyze the influence of diffraction at the capillary entrance by comparing a Gaussian and an Airy radial profile. We show that, with an Airy profile, adding a plasma channel improves significantly the acceleration stage performances, when using a laser duration shorter than in resonant conditions. Furthermore, by changing the ratio of the capillary radius with the laser waist we determine the minimum radius of a capillary with channel guiding for which a Gaussian beam can yield an effcient acceleration at GeV energies.