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# Machine Parameters

The Table 3 below presents a summary of the characteristics of the electron beam of the storage ring:

Table 3: Main global parameters of the electron beam. |

The following Table 4 gives the main optics functions, electron beam sizes and divergences at the various source points. For insertion device source points, the beta functions, dispersion, sizes and divergences are computed in the middle of the straight section. Two representative source points of bending magnet radiation have been selected, corresponding to an angle of observation of 3 mrad (9 mrad) from the exit, which corresponds to different magnetic fields. Electron beam profiles are Gaussian and the size and divergence are presented in terms of rms quantities. The associated full width half maximum sizes and divergences are 2.35 times larger. Horizontal electron beam sizes and divergences are given for the uniform filling modes and apply to almost all filling patterns except for the single bunch, for which a slightly larger size and divergence is attained due to the increased energy spread of the electron beam. Vertical electron beam sizes and divergences apply to the Uniform, 2x1/3 and Hybrid filling modes only. In order to increase the lifetime of the stored beam, the vertical beam sizes and divergences are increased by a typical 50% in 16 and single bunch filling patterns.

Table 4: Beta functions, dispersion, rms beam sizes and divergences for the various source points of the ESRF. |

The lifetime, bunch length and energy spread depend to a large extent on the filling pattern. These are given in the following Table 5 for a few representative filling patterns. It should be noted that in both the 16 bunch and single bunch filling patterns the energy spread and bunch length decay with the current (the value indicated in the table corresponding to the maximum current). The bunch lengths are given for the usual RF accelerating voltage of 8 MV.

Table 5: Current, lifetime, bunch length and energy spread in various representative filling modes. |