BNL, Upton, Long Island, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
JLab, Newport News, Virginia, USA
Cornell University, Ithaca, New York, USA
Cornell's Lab of Accelerator-based Sciences and Education (CLASSE) and the Collider Accelerator Department (BNL-CAD) are developing the first SRF multi-turn energy recovery linac with Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) racetrack. The existing injector and superconducting linac at Cornell University are installed together with a single NS-FFAG arcs and straight section at the opposite side of the the linac to form an Electron Energy Recovery (ERL) system. Electron beam from the 6 MeV injector is injected into the 36 MeV superconducting linac, and accelerated by four successive passes: from 42 MeV up to 150 MeV using the same NS-FFAG structure made of permanent magnets. After the maximum energy of 150 MeV is reached, the electron beam is brought back to the linac with opposite Radio Frequency (RF) phase. Energy is recovered and reduced to the initial value of 6 MeV with 4 additional passes. There are many novelties: a single NS-FFAG structure, made of permanent magnets, brings electrons with four different energies back to the linac. A new adiabatic NS-FFAG arc-to-straight section merges 4 separated orbits into a single orbit in the straight section.
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A major upgrade project (dubbed CHESS-U) is planned to elevate performance of Cornell High Energy Synchrotron Source (CHESS) to the state-of-art 3rd generation light sources. In the project, about 80-m of Cornell Electron Storage Ring (CESR) will be replaced with double-bend achromat (DBA) lattice to reduce electron beam emittance. In this presentation, we will describe designs of the CHESS-U vacuum system, including new beam pipe extrusions and chambers, sliding joints, and crotch absorbers. Vacuum pumping system consists of distributed pumps (in the form of NEG strips) in the dipole chambers, and compact discrete NEG/Ion pumps in the quad straight and undulator beampipes. MolFlow+ is used to evaluate pumping performances of the CHESS-U vacuum system. First, we demonstrate that the planned vacuum pumping system can achieve and sustain required ultra-high vacuum level in CHESS-U operations, after an initial beam conditioning. Second, we will explore beam commissioning processes of the new vacuum chambers, and simulate the saturation of the NEG strips during the commissioning. These simulations will aid continuing design optimization for the CHESS-U vacuum pumping system.