diffraction-limited storage rings Journal of
Synchrotron Radiation
Generation of picosecond electron bunches in storage rings
ISSN 1600-5775
Xiaobiao Huang,* Thomas Rabedeau and James Safranek Received 26 February 2014 Accepted 8 May 2014
SSRL, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA. *E-mail: [email protected]
Approaches to generating short X-ray pulses in synchrotron light sources are discussed. In particular, the method of using a superconducting harmonic cavity to generate simultaneously long and short bunches in storage rings and the approach of injecting short bunches from a linac injector into a storage ring for multi-turn circulation are emphasized. If multi-cell superconducting RF (SRF) cavities with frequencies of 1.5 GHz can be employed in storage rings, it would be possible to generate stable, high-flux, short-pulse X-ray beams with pulse lengths of 1–10 ps (FWHM) in present or future storage rings. However, substantial challenges exist in adapting today’s high-gradient SRF cavities for high-current storage ring operation. Another approach to generating short X-ray pulses in a storage ring is injecting short-pulse electron bunches from a high-repetition-rate linac injector for circulation. Its performance is limited by the microbunching instability due to coherent synchrotron radiation. Tracking studies are carried out to evaluate its performance. Challenges and operational considerations for this mode are considered. # 2014 International Union of Crystallography
Keywords: short pulse; picosecond; storage ring.
1. Introduction Synchrotron radiation light sources have been a major source of high-flux high-brightness X-rays that are used in scientific research in condensed matter physics, material science, chemistry, environmental science, biology and medical sciences in the last few decades. One trend of synchrotron radiation light source development is to increase the photon beam brightness by reducing the electron beam emittance in the storage rings. New machines under construction will have horizontal emittances near or well below 1 nm (NSLS II, 2006; MAX IV, 2010) for 3 GeV electron beams. With the multibend achromat lattice design approach, upgrade lattices for existing facilities with emittances around 100 pm for 6 GeV beams have been proposed (SLAC, 2013). There are also lattice designs that have reached diffraction-limited emittances at lower beam energies (SLAC, 2013). Future machines that implement these lattices would deliver photon beams with 100–1000-fold higher average brightness than presently achieved in storage rings. There is another direction in the development of synchrotron radiation light sources which is aimed at providing short X-ray pulses to meet the increasing demand for such capability by the user community for time-resolved experiments. X-ray pulses with lengths
Synchrotron Radiation
Generation of picosecond electron bunches in storage rings
ISSN 1600-5775
Xiaobiao Huang,* Thomas Rabedeau and James Safranek Received 26 February 2014 Accepted 8 May 2014
SSRL, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA. *E-mail: [email protected]
Approaches to generating short X-ray pulses in synchrotron light sources are discussed. In particular, the method of using a superconducting harmonic cavity to generate simultaneously long and short bunches in storage rings and the approach of injecting short bunches from a linac injector into a storage ring for multi-turn circulation are emphasized. If multi-cell superconducting RF (SRF) cavities with frequencies of 1.5 GHz can be employed in storage rings, it would be possible to generate stable, high-flux, short-pulse X-ray beams with pulse lengths of 1–10 ps (FWHM) in present or future storage rings. However, substantial challenges exist in adapting today’s high-gradient SRF cavities for high-current storage ring operation. Another approach to generating short X-ray pulses in a storage ring is injecting short-pulse electron bunches from a high-repetition-rate linac injector for circulation. Its performance is limited by the microbunching instability due to coherent synchrotron radiation. Tracking studies are carried out to evaluate its performance. Challenges and operational considerations for this mode are considered. # 2014 International Union of Crystallography
Keywords: short pulse; picosecond; storage ring.
1. Introduction Synchrotron radiation light sources have been a major source of high-flux high-brightness X-rays that are used in scientific research in condensed matter physics, material science, chemistry, environmental science, biology and medical sciences in the last few decades. One trend of synchrotron radiation light source development is to increase the photon beam brightness by reducing the electron beam emittance in the storage rings. New machines under construction will have horizontal emittances near or well below 1 nm (NSLS II, 2006; MAX IV, 2010) for 3 GeV electron beams. With the multibend achromat lattice design approach, upgrade lattices for existing facilities with emittances around 100 pm for 6 GeV beams have been proposed (SLAC, 2013). There are also lattice designs that have reached diffraction-limited emittances at lower beam energies (SLAC, 2013). Future machines that implement these lattices would deliver photon beams with 100–1000-fold higher average brightness than presently achieved in storage rings. There is another direction in the development of synchrotron radiation light sources which is aimed at providing short X-ray pulses to meet the increasing demand for such capability by the user community for time-resolved experiments. X-ray pulses with lengths
