ICFA Beam Dynamics Newsletter

Abstract

The Collider-Accelerator Department at Brookhaven National Laboratory is building a high-brightness 500 mA capable Energy Recovery Linac (ERL) as one of its main R&D thrusts towards eRHIC, the polarized electron -hadron collider as an upgrade of the operating RHIC facility. The ERL is in final assembly stages, with injection commisioning starting in October 2012. The objective of this ERL is to serve as a platform for R&D into high current ERL, in particular issues of halo generation and control, Higher-Order Mode (HOM) issues, coherent emissions for the beam and highbrightness, high-power beam generation and preservation. The R&D ERL features a superconducting laser-photocathode RF gun with a high quantum efficiency photoccathode served with a load-lock cathode delivery system, a highly damped 5-cell accelerating cavity, a highly flexible single-pass loop and a comprehensive system of beam instrumentation. In this ICFA Beam Dynamics Newsletter article we will describe the ERL in a degree of detail that is not usually found in regular publications. We will discuss the various systems of the ERL, following the electrons from the photocathode to the beam dump, cover the control system, machine protection etc and summarize with the status of the ERL systems. Elements of the BNL ERL PhotocathodeIt is natural to start the description of the ERL from the photocathode, where the electron beam is born, and where its initial emittance is constrained.The design of photocathodes for ERLs is one of the key challenges for these machines. In particular, various applications, like X-ray sources and hadron cooling require very low transverse emittance electron beams from the cathode as well as high Quantum Efficiency (QE) at visible wavelengths. This latter requirement is driven by the need to have efficient transverse and longitudinal pulse shaping and by the desirability of using compact and efficient laser sources, such as fiber lasers as the BNL-98271-2012-NE