Author: Khan, D.
Paper Title Page
TUP020
Optimization of PAL-XFEL's 3 Bunch Compressor Linac  
 
  • H.-S. Kang, H. Heo, C. Kim, C.-K. Min, H. Yang
    PAL, Pohang, Kyungbuk, Republic of Korea
  • D. Khan, T.O. Raubenheimer, J. Wu
    SLAC, Menlo Park, California, USA
 
  The Pohang Accelerator Laboratory X-Ray Free Electron Laser (PAL-XFEL) consists of a 10 GeV normal-conducting linac delivering an electron bunch to two undulator beamlines and FEL radiation between 0.1 nm (Hard XRay) and 4.5 nm (Soft X-Ray). To provide high quality FEL lasing, it is paramount to optimize the linac settings under the consideration of the collective effects a beam may experience during transport to the undulator. The PAL-XFEL linac consists of four S-band linac sections, an X-band harmonic linearizer proceeding the first linac section, and a three chicane bunch compression system (the very first of its kind in operation). The addition of the third bunch compressor opens the possibility of heightened mitigation of CSR during compression and an increased flexibility of system configuration. In this paper, we outline a procedure to optimize the PAL-XFEL linac under several compression configurations using the particle tracking code Elegant and present its results.  
 
TUP027 Cancellation of Coherent Synchrotron Radiation Kicks at LCLS 1
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  In this paper, we look at the cancellation of Coherent Synchrotron Radiation (CSR) induced emittance growth using a phase-advance manipulation technique pioneered by R. Hajima, and extended in the Courant-Snyder formalism by S. Di Mitri. Bending systems in a linear accelerator are essential for beam transport and bunch compression. With the ever-growing demands of high-energy, short wavelength free electron laser (FEL) drivers, the CSR effect has emerged to be a detrimental factor in emittance stability. Under linear approximation, it is showed that the CSR driven dispersive kicks in successive bending magnet systems can, with proper balancing of the linac optics, cancel each other to nullify transverse emittance growth. This technique of optics balancing in the constant bunch length regime is the focus of this paper. We will present our findings for the emittance measurements generated in Elegant simulations for the current LCLS-I dogleg system.  
 
TUP028 Approximated Expressions for the Coherent Synchrotron Radiation Effect in Bending Magnets 1
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  In this paper, we describe the development of simplified analytic expressions for the Coherent Synchrotron Radiation's (CSR) root-mean-square induced energy spread, typically found in the bending magnets of short bunch-length charged particle accelerators. The expressions are derived for a Gaussian longitudinal bunch distribution and compared with the full-rigor CSR wakefield integral expressions while entering, traversing and exiting a bending magnet. The validity of the expressions are then tested against ELEGANT with the simulation of an unchirped beam traveling across a bending magnet into a drift section, and the second stage bunch compressor (BC2) of the proposed LCLS-II beamline.  
 
TUP030 An Emittance-Preservation Study of a Five-Bend Chicane for the LCLS-II-HE Beamline 1
 
  • D. Khan, T.O. Raubenheimer
    SLAC, Menlo Park, California, USA
 
  The Linac Coherent Light Source II (LCLS-II) is an upgrade intended to advance the great success of its predecessor, LCLS-I, to maintain its position at the forefront of X-ray science. The introduction of a niobium-metal superconducting linac for LCLS-II not only increases the repetition rate to the MHz level (from 120 Hz), but also boasts an average brightness many orders higher (~10,000) than that of LCLS-I. Though, these improvements do not come without a price: the peak brightness suffers by a factor of 10, owing its degradation to the impact of Coherent Synchrotron Radiation (CSR) diminishing the peak current of the beam in the second bunch compressor (BC2). In this paper, we discuss the impact of implementing a plug-compatible 5-bend chicane for BC2 on the beam's emittance dilution for a high-energy, low-emittance configuration of LCLS-II (LCLS-II-HE). The results are compared with that of a standard 4-bend chicane under various settings in Elegant and CSRTrack.