Closed Orbit Correction For The Synchrotrons Of HIMM And HIAF

The closed orbit is the reference orbit of betatron oscillation.In synchrotrons,the ideal reference orbit will be distorted by the field imperfections and misalignments of the magnets.The closed orbit distortions?COD?will reduce the efficient physics aperture and the beam quality.In this thesis,the theoretical analyses of closed orbit distortion and correction are introduced.The design of correction systems for different synchrotrons in HIMM and HIAF facilities is accomplished.The singular value decomposition?SVD?algorithm is adopted in the simulations and commissioning of global closed orbit cor-rection.In the simulations,the field imperfections and misalignments of magnets as well as the errors of BPMs and correctors are considered.HIMM is a miniaturized medical machine dedicated to cancer treatment with a compact structure.The large deflection angle of dipole magnets results in large errors,which impacts the closed orbit obviously.The longitudinal misalignments of dipole magnets induce uncorrectable closed orbit growth.Limited by the longitudinal space,the distribution of correction elements is imperfect,which influences the correction re-sults.In this thesis,detailed simulations of closed orbit distortion and correction have been analyzed.For the first time,detailed analyses of longitudinal misalignments for dipole magnets and a solution have been given.The response matrices and the dis-persion functions have been measured,and the test of closed orbit correction has been accomplished.Consequently,the performance of closed orbit correction agrees well with the simulation results.The High Intensity heavy-ion Accelerator Facility?HIAF?comprises two main synchrotrons:the Booster Ring?BRing?and the Spectrometer Ring?SRing?.In this thesis the closed orbit distortions and corrections of BRing and SRing have been simu-lated and analyzed.The distributions of correction elements have been optimized.The requirements for the alignments of magnets and other elements have been determined.The optics of BRing is similar to a FODO lattice.The closed orbit correction based on SVD has obvious characteristic of harmonic correction.The eigenvectors of response matrices should be analyzed in frequency domain.Limited by the requirements of injection and extraction systems,the correction elements in the straight sections are aligned with poor periodicity.The closed orbits after correction are larger than that in the arc sections.The last 3 eigenvectors represent 3 straight sections respectively.The reduced singular values will result in closed orbit deterioration in these areas.In this thesis a new correction method based on adjustment of singular values and the DC harmonic correction is presented.The non-periodic impact is effectively reduced and the correction results are obviously optimized.Due to the fast magnetic field ramping rate of 12T/s,the high requirement of the or-bit feedback system during the acceleration process has been proposed.Considering the physics requirements and elements'parameters,the feedback frequency is determined to be 100Hz.Arter removing the noises through SVD,the orbit oscillation frequen-cies are calculated in real time.The differential control is applied to optimize the orbit feedback process.In addition,the relative field errors caused by eddy current is about5.85×10^-2,which is much larger than the demand of dipole field errors.Therefore,special methods of closed orbit correction and orbit variation analysis are applied to calculate the relative field errors up to the accuracy of 1.2×10^-4.The effect of eddy current can be removed by changing the ramping curve of dipole field.The multiple operation modes and optics should be considered in the design of correction system for SRing.The correction in the isochronous mode(=1.43)is particularly important since the maximumfunction is very large.In the thesis the disturbance of linear optics in this mode is analyzed through adjusting different local bump orbits.The main reason of optical disturbance is the change of the incidence angle in dipole magnets.After several times measurements of response matrices and correction calculation,the closed orbit with maximum value of 1.6mm in all modes can meet the physics requirements.