Design and testing of a DC ion injector suitable for accelerator-driven transmutation

Abstract

For a number of years, Los Alamos personnel have collaborated with a team of experimentalists at Chalk River Labs (CRL) near Deep River, Ontario, Canada who were pursuing the development of the front end of a high power cw proton accelerator. At the termination of this program last year, Los Alamos acquired this equipment. With the help of internal Laboratory funding and modest defense conversion funds, we have set up and operated the accelerator at Los Alamos. Operational equipment includes a slightly modified Chalk River Injector Test Stand (CRITS) including a 50 keV proton injector and a 1.25 MeV radio‐frequency quadrupole (RFQ) with a klystrode rf power system. Substantial upgrading and modification of the ac power system was necessary to provide the required ac voltage (2400 vac) and power (2 MVA) needed for the operation of this equipment. A companion paper describes in detail the first ion source and beam‐transport measurements at Los Alamos. Many of the challenges involved in operating an rf linear accelerator to provide neutrons for an accelerator‐driven reactor are encountered at the front (low energy) end of this system. The formation of the ion beam, the control of the beam parameters, and the focusing and matching of a highly space‐charge‐dominated beam are major problems. To address the operating problems in this critical front end, the Accelerator Operations and Technology Division at the Los Alamos National Laboratory has designed the APDF (Accelerator Prototype Demonstration Facility). The front end of this facility is a 75 keV, high‐current, ion injector which has been assembled and is now being tested. This paper discusses the design modifications required in going from the 50 keV CRITS injector to the higher current, 75 keV injector. Major innovative changes were made in the design of this injector. This design eliminates all the control electronics and most of the ion source equipment at high potential. Also, a new, high‐quality, ion‐extractor system has been built. A dual‐solenoid lens will be used in the low energy beam transport (LEBT) line to provide the capability of matching the extracted beam to a high‐current ADTT linac. This new injector is the first piece of hardware in the APDF program and will be used to develop the long‐term, reliable cw beam operation required for ADTT applications.