Abstract
We have designed an ``ultimate'' storage ring for a future light source that would be resided in the positron-electron-project (PEP) tunnel and achieves the diffraction-limited emittances (at 1.5 \AA{}) of 12 pm-rad in both horizontal and vertical planes with a 4.5-GeV electron beam. These emittances include the contribution of intrabeam scattering at a nominal current of 200 mA in 3300 bunches. This quality beam in conjunction with a conventional 4-m undulator in a straight section can generate synchrotron radiation having a spectral brightness above ${10}^{22}\text{ }\text{ }[\mathrm{photons}/\mathrm{s}/{\mathrm{mm}}^{2}/{\mathrm{mrad}}^{2}/0.1%\mathrm{BW}]$ at a 10 keV photon energy. The high coherence at the diffraction limit makes this design competitive with 4th generation light sources based on an energy recovery linac. In addition, the beam lifetime is several hours and the dynamic aperture is large enough to allow off-axis injection. The alignment and stability tolerances, though challenging, are achievable. A ring with all these properties is only possible because of several major advances in mitigating the effects of nonlinear resonances.
Highlights
An ultimate storage ring (USR) [1], defined as an electron ring-based light source having an emittance in both transverse planes at the diffraction limit for the range of x-ray wavelengths of interest for a scientific community, would provide very high brightness photons having high transverse coherence that would extend the capabilities of x-ray imaging and probe techniques beyond today’s performance
Double bend achromat [22] (DBA) cells, widely used in light source rings, provide the insertion devices (IDs) dispersion-free straights, but their minimal natural emittance is a factor of 3 higher relative to a theoretical minimum emittance [21] (TME) cell with the same bending angle
Because the emittance of PEP-X will increase by a factor of 2 from the zero-current natural value of 29 pmrad achieved with the 7BA lattice due to intrabeam scattering with 200-mA stored beam current
Summary
An ultimate storage ring (USR) [1], defined as an electron ring-based light source having an emittance in both transverse planes at the diffraction limit for the range of x-ray wavelengths of interest for a scientific community, would provide very high brightness photons having high transverse coherence that would extend the capabilities of x-ray imaging and probe techniques beyond today’s performance. It would be a cost-effective, high-coherence 4th generation light source [2], competitive with one based on energy recovery linac (ERL) technology [3], serving a large number of users studying material, chemical, and biological sciences. VI and will discuss aspects of our design in the conclusion
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