Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
JLab, Newport News, Virginia, USA
The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.
JLab, Newport News, Virginia, USA
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
For the analysis of the coherent synchrotron radiation (CSR) induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.
JLab, Newport News, Virginia, USA
Northern Illinois University, DeKalb, Illinois, USA
DESY, Hamburg, Germany
SLAC, Menlo Park, California, USA
ODU, Norfolk, Virginia, USA
JINR, Dubna, Russia
Texas A&M University, College Station, Texas, USA
Old Dominion University, Norfolk, Virginia, USA
Science and Technique Laboratory Zaryad, Novosibirsk, Russia
ANL, Argonne, Illinois, USA
The Medium-energy Electron Ion Collider (MEIC) at JLab is designed to provide high luminosity and high polarization needed to reach new frontiers in the exploration of nuclear structure. The luminosity, exceeding 1033 cm-2s−1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm-2s−1, is achieved by high-rate collisions of short small-emittance low-charge bunches made possible by high-energy electron cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) can be easily preserved and manipulated due to the unique figure-8 shape of the collider rings. A fully consistent set of parameters have been developed considering the balance of machine performance, required technical development and cost. This paper reports recent progress on the MEIC accelerator design including electron and ion complexes, integrated interaction region design, figure-8-ring-based electron and ion polarization schemes, RF/SRF systems and ERL-based high-energy electron cooling. Luminosity performance is also presented for the MEIC baseline design.
JLab, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Studies of beam quality preservation during recirculation * have been extended to generate a design of a compact arc providing bunch compression with positive momentum compaction ** and control of both incoherent and coherent synchrotron radiation (ISR and CSR) effects using the optics balance methods of diMitri et al.***. In addition, the arc/compressor generates very little micro-bunching gain. We detail the beam dynamical basis for the design, discuss the design process, give an example solution, and provide simulations of ISR and CSR effects. Reference will be made to a complete analysis of micro-bunching effects ****.
* D. Douglas et al., these proceedings
** S. Benson et al., these proceedings
*** S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013
**** C.Y. Tsai et al., these proceedings
JLab, Newport News, Virginia, USA
ODU, Norfolk, Virginia, USA
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Numerous proposals invoke recirculation and/or energy recovery for cost-performance optimization. These often encounter challenges with the beam-quality-degrading effects of incoherent and coherent synchrotron radiation (ISR and CSR). We describe a means of controlling of this degradation. The approach utilizes results by diMitri et al. *, and invokes behavior observed during simulations of the recirculation process. The method is based on the use of periodically isochronous 2nd-order achromats; this not only insures that the conditions for the suppression of CSR-driven emittance growth are met*, it also suppresses micro-bunching gain over a broad range of parameter space **. Details of specific designs will be presented, and a reference to an analysis of micro-bunching effects ** provided. A planned test of the CSR suppression mechanism in CEBAF will be described.
*S. diMitri et al., Phys. Rev. Lett. 110, 014801, 2 January 2013.
**C.Y. Tsai et al., these proceedings.
CSU, Fort Collins, Colorado, USA
JLab, Newport News, Virginia, USA
LANL, Los Alamos, New Mexico, USA