Hefei Light Source High Brightness Mode Of Operation

Hefei light source (HLS) runs on the general purpose light source (GPLS) mode . The emittance of GPLS is 166 nm-rad. The high brilliance light source (HBLS) mode, which reduces the emittance to 27 nm-rad, is one of the items in the National Synchrotron Radiation Lab (NSRL) phase II project. But in the commissioning, we find HBLS lattice has some shortcomings. Two groups of quadrupoles have too strong magnetic fields, resulting in high currents and high temperatures. The machine can not continuously work in this condition. The horizontal tune is close to super-periodic structural resonance, which increases the sensitivity to the magentic field errors and misalign errors of the focusing quadrupoles. The straight sections have high vertical beta functions, which are unsuitable to the operation of insertion devices, especially the operation of the superconducting wiggler. In order to solve these problems, new high brilliance lattices are proposed.The new lattices satisfy the following requirements. Firstly all the quadrupole coefficients are less than 4.3 m^-2. Secondly their tunes have fine positions. Thirdly all the straight sections have low vertical beta functions to fit the operation of insertion devices. Fourthly low emittances are achieved. The new two-folded high brilliance lattice (L2) decreases the emittance to 55.94 nm-rad. The tunes are (4.45, 2.43). The vertical beta functions in straight sections are 0.35 m and 3.56 m. A series of four-folded high brilliance lattices (L4-1, L4-2 and L4-3) are also proposed. The emittances of them are 42.33 nm-rad, 25.71 nm-rad and 16.14 nm-rad. The tunes are (5.20, 2.53), (5.21, 2.55) and (5.21, 2.54). They have similar tunes and beta functions, so we can reduce the emittance to 16.14 nm-rad step by step in the commissioning. The vertical beta functions in straight sections of L4-3 are 1.14 m. The computating results show that the brilliances of the synchrotron radiation lights with the critical wavelength in the middle point of the bend magnets have already reached or exceeded the level of HBLS. The linear and nonlinear optics of new lattices, the process of close orbit distortion correction, and the lifetime of L4-3 are also discussed.It is one of the design purposes that the insertion devices can operate on the new lattices. So the effects of undulators and wigglers on L4-3 mode are studied. We present an analytic magnetic field model of the permanent magnet undulator in HLS, and build up the symplectic map of undulator by- symplectic integration and generating function. Then we evaluate the effects of undulator by tracking study. The result shows that it is not necessary to compensate the effects of undulator according to the small changes of the linear optics. We only build the hard edge magnetic model of the superconducting wiggler in HLS because of the lack of magnetic field data. The wiggler makes the tunes and beta functions change a lot, so its effects have to be compensated. Two compensating plans, local compensation and global compensation,...