BEAM TRANSPORT LINE DESIGN FOR EMITTANCE ADJUSTMENT PLS XFEL

Pohang Accelerator Laboratory (PAL), which is running 3rd generation light source, is planning to construct a free electron laser (FEL) facility using the existing linear accelerator. To make the linear accelerator to satisfy the required beam energy and quality, we decided to expand the linac as well as to upgrade the existing linac. The additional linac (which is called W-FEL) will accelerate the electron up to 1.2 GeV. Along with the existing linac (which is called X-FEL) of 2.5 GeV, the final electron beam will be accelerated to 3.7 GeV. At first, two separate beamlines for W-FEL and X-FEL were considered and the beam transport lines (BTLs) were designed to bend the electron beams up to 30 and 20 degrees respectively due to the construction restriction. However, those large bending angles result in severe emittance growth from coherent synchrotron radiation (CSR) effect. So, we design the FEL BTL in the way to reduce emittance growth. This paper presents simulation results of emittance growth and another beam dynamic parameter