Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
JLab, Newport News, Virginia, USA
The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport arcs, may result in phase space degradation. On one hand, the CSR can perturb electron transverse motion in dispersive regions along the beamline, causing emittance growth. On the other hand, the CSR effect on the longitudinal beam dynamics could result in microbunching gain enhancement. For transport arcs, several schemes have been proposed* to suppress the CSR-induced emittance growth. Similarly, several scenarios have been introduced** to suppress CSR-induced microbunching gain, which however mostly aim for linac-based machines. In this paper we try to provide sufficient conditions for suppression of CSR-induced microbunching gain along a transport arc, analogous to*. Several example lattices are presented, with the relevant microbunching analyses carried out by our semi-analytical Vlasov solver***. The simulation results show that lattices satisfying the proposed conditions indeed have microbunching gain suppressed. We expect this analysis can shed light on lattice design approach that could suppress the CSR-induced microbunching gain.
*D.Douglas et al, JLAB-ACP-14-1751, S.DiMitri et al, PRL (2013), R.Hajima, NIMA (2004), Y.Jiao et al, PRSTAB (2014)
**Z.Huang et al, PRSTAB (2004), Saldin et al, NIMA (2004)
***C.Tsai et al, FEL'15
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
JLab, Newport News, Virginia, USA
Microbunching instability (MBI) has been one of the most challenging issues in the transport of high-brightness electron beams for modern recirculating or energy recovery linac machines. Recently we have developed and implemented a Vlasov solver* to calculate microbunching gain for an arbitrary beamline lattice design, based on the extension of early theoretical formulation** for the microbunching amplification from an initial density perturbation to the final density modulation. For more thorough analyses, in addition to the case of (initial) density to (final) density amplification, we in this paper extend the previous formulation to more general cases, including energy-to-density, density-to-energy and energy-to-energy amplifications for a recirculation machine. Such semi-analytical formulae are then incorporated into our Vlasov solver, and reasonable agreement is obtained when the semi-analytical results are benchmarked with particle tracking simulation using ELEGANT***.
* C.Y. Tsai et al, FEL'15
** S. Heifets et al, PRSTAB 5, 064401 (2002), Z. Huang and K. Kim, PRSTAB 5, 074401 (2002), M. Vneturini, PRSTAB 10, 104401 (2007)
*** M. Borland, APS LS-287, 2000
JLab, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during collision at the collider ring. A new electron cooling process simulation program has been developed to fulfill the requirements of the JLEIC electron cooler design. The new program allows the users to calculate the electron cooling rate and simulate the cooling process with either DC or bunched electron beam to cool either coasting or bunched ion beam. It has been benchmarked with BETACOOL in aspect of accuracy and efficiency. In typical electron cooling process of JLEIC, the two programs agree very well and we have seen a significant improvement of computational speed using the new one. Being adaptive to the modern multicore hardware makes it possible to further enhance the efficiency for computationally intensive problems. The new program is being actively used in the electron cooling study and cooler design for JLEIC. We will present our models and some simulation results in this paper.