21235

۲۱۲۳۵

طراحي شبكه الكترومغناطيس با گسيلندگي بسيار كم براي حلقه انبارش چشمه نور ايران

دكتري

فيزيك اتمي مولكولي

۱۳۹۲

۱۳۹۸/۰۶/۳۱

دكتر مسعود جزايري

دكتر محمود ملاباشي

فيزيك

چكيده در اين پايان¬نامه با طراحي اپتيك (شبكه الكترومغناطيس) حلقه انبارش چشمه نور ايران، عملكرد آن در حضور انواع خطاها و اختلال¬ها بررسي شده است. براي رسيدن به گسيلندگي افقي بسيار كم، اپتيك حلقه انبارش بر اساس شبكه الكترومغناطيس تك فام دوقطبي چندگانه با تعداد مغناطيس دوقطبي 5 تايي طراحي شده است. با انتخاب چنين شبكه¬¬اي، حلقه انبارش چشمه نور ايران داراي محيط 528 متر و گسيلندگي افقي 270 پيكومتر راديان است كه قادر خواهد بود فوتونهايي را با درخشندگي 1×10^21 [((photons/s)/〖mm〗^2 )/〖mrad〗^2 /0.1BW%] براي طيف وسيعي از پژوهشگران و محققان فراهم كند. براي كاهش بيشتر گسيلندگي از مغناطيس¬هاي دوقطبي گراديان دار كه همزمان مولفه ميدان مغناطيسي دوقطبي و چهار قطبي را دارند استفاده شده است. به علت آنكه گسيلندگي شبكه بيشتر با گسيلندگي شبكه سلول واحد معين مي¬شود، مقدار گراديان مغناطيس-هاي چهار قطبي و دو قطبي با توجه به فرايند بهينه سازي براي رسيدن به كمترين گسيلندگي ممكن شبكه مشخص شدند. براي بهينه سازي حركت غيرخطي الكترونها، از حل هاميلتوني حركت الكترونها در حضور ميدانهاي غير خطي استفاده شد. با استفاده از روش اختلال، يك توزيع بهينه براي شدت و مكان قرارگيري شش قطبي¬هاي مختلف طوري به دست آمد كه حركت باريكه الكتروني حداقل تا دامنه تزريق الكترونها به داخل حلقه انبارش آشوبناك نباشد. براي انجام اين كار از روش ردگيري ذرات و تحليل نگاشت فركانس حركت الكترونها استفاده شد. با استفاده از الگوريتم SVD، اختلال مسير بسته الكترونهاي كه در اثر ميدان دوقطبي حاصل از خطاهاي همراستايي و خطاي ميدان به وجود مي¬آيند اصلاح و به مقادير قابل قبول كاهش داده شد. همچنين با توجه به اينكه خطاهاي همراستايي و ميدان تاثير چشمگيري روي اپتيك غيرخطي باريكه و در نتيجه كاهش ناحيه پايداري الكترونها دارند از روش محاسبه مستقيم ناحيه پايداري و تحليل نگاشت فركانسي براي شناسايي تشديد¬هاي تحريك شده و بررسي اثر خطاهاي مختلف روي ميزان تحريك پذيري آنها استفاده شد. براي مطالعه و محاسبه تاثيرات اثرات جمعي الكترونها روي پايداري باريكه در داخل¬ حلقه انبارش از ردگيري 6 بعدي ذرات استفاده شد. به منظور بررسي عملكرد شبكه طراحي شده، پاره¬اي از ناپايداريها كه ناشي از اندركنش الكترون با محيط هستند مورد مطالعه قرار گرفتند. تابش سنكروتروني همدوس و مدهاي جفت شده عرضي دو ناپايداري بودند كه به صورت تحليلي مورد بررسي قرار گرفته¬ و آستانه ناپايداري براي هر كدام ار آنها به دست آمد. تزريق باريكه به داخل حلقه انبارش چشمه نور ايران با استفاده از دو روش مطالعه و شبيه سازي شد. روش اول كه روش متداول براي تزريق باريكه است از چهار ضربه زن دوقطبي براي تزريق به داخل حلقه انبارش استفاده شد. روش دوم كه اخيرا در چشمه¬هاي نور مختلف به كار گرفته مي¬شود استفاده از ضربه زن چند قطبي غير خطي است. با مطالعه ديناميك باريكه فرايند تزريق، تلورانس¬هاي لازم براي ميدان و شكل پالس ضربه¬زنها (دقت منابع تغذيه)، عملكرد مغناطيس سپتوم، ميزان تقدم و تاخر زماني و عدم تطابق انرژي باريكه تزريق شده به دست آمد.

1398/07/29

Design and performance of an ultra low emittance lattice for Iranian light source facility storage ring

9/22/2019 12:00:00 AM

Iranian Light Source Facility (ILSF) is a fourth-generation light source under design and construction in Qazvin city. The circumference of the ILSF storage ring is 528 m and its horizontal emittance is 270 pm-rad which will be enable to produce photons with the brilliance of 1×10^21 [((photons/s)/〖mm〗^2 )/〖mrad〗^2 /0.1BW%] for the wide range of the researchers and scientists. In this thesis, the optics design and performance of the ILSF storage ring has been investigated in the presence of various types of errors and disruptions. In order to achieve a very small horizontal emittance, the optics of storage ring is based on multi-bend achromat lattice. By choosing such a lattice, the ILSF storage ring will consists of 20 super-periods. Of this number of straight sections, 17 straights will be allocated for installation of insertion devices. In addition, the radio frequency cavities will be installed in the 2 straight sections. The injection equipment will be installed in another straight section. To further reduce the emittance, the dipole magnets have simultaneously the dipole and quadrupole magnetic field component. Since the emittance of the lattice is determined mainly by the emittance of unit cell, the gradient of the dipole and quadrupole magnets was determined according to the optimization process to reach the lowest possible emittance. In the design of new generation storage rings, the use of strong quadrupole magnets is inevitably needed to achieve very small emittance. In order to correct the chromatic aberration caused by quadrupoles, as well as avoiding head-tail instability, it is necessary to use strong sextupole magnets. Sextupole magnets, due to the presence of non-linear fields in certain amplitudes, cause chaotic electron motion and unstable beam. One of the main challenges in the design of the new generation storage rings is chaotic motion of the electrons in smaller amplitudes due to the strong field of sextupole magnets. In this thesis, in order to solve this challenge, by calculating the Hamiltonian of electrons motion inside storage ring and solving it using perturbation method, an optimal distribution for the strength and location of the sextupole magnets is obtained such that the electron motion to be regular at least in the range of electrons injected amplitude into the ring. To do this, particle tracking and electron motion frequency mapping analysis were used. Due to the limited tolerances in the construction and alignment of different magnets and girders within the storage ring and the presence of insertion devices with essential nonlinear fields, in the real machine, various disturbances will affect the rotating beam within the storage ring. Employing the SVD algorithm, the distortion of the electron paths generated by the dipolar field due to alignment errors and field error is corrected and reduced to the acceptable values. Since the alignment and field errors affect the electrons closed orbit and produce coupling in transverce plan, it will have significant effect on the nonlinear beam dynamics. The direct computation of the dynamic aperture and frequency map analysis are used to identify the excited resonances and their effect on the lattice dynamic aperture. Due to the very small emittance of ILSF storage ring and, therefore, the small horizontal dispersion function, the lattice has small momentum compaction factor. Because of this, the length of the electron bunches is short and, as a result, the interaction of the electron with the electron and the electron with the environment (vacuum chamber) are strong. In other words, the collective effects, is much stronger than that of the other storage rings. Two scattering phenomena so-called Touscheck and intra-beam scattering are two type of electron-electron scattering that have a detrimental effect on the lifetime and emittance of the electrons inside the storage ring. Six-dimensional particle tracking is used to study and calculate their effects on the storage ring parameters. To investigate the performance of the designed lattice, a series of instabilities that are caused by the interaction of the electron with the environment were studied. Coherent synchrotron radiation and transverse mode coupling instability are investigated analytically, and the instabilities threshold are obtained for each of them. Beam injection into storage ring has been investigated by using two methods. As a first method, I have studied the beam injection using four dipolar kickers. It is common method for injecting beam into storage ring. In the second method, the beam injecting using nonlinear multipole kicker has been investigated. By studying the beam dynamics of the injection process, the required field tolerance, pulse shaping (power supply accuracy), septum performance, time jitter, and energy mismatch of the injected beam are obtained.