Multiturn injection of EBIS ions in booster

Gardner, C.J.

Brookhaven National Laboratory (BNL) Electron Beam Ion Source

关键词: Acceleration;    Nucleons;    Electron Beam Ion Source;    Velocity Electron Beam Ion Source;    Electrostatics;   

DOI  :  10.2172/990713
RP-ID  :  BNL--94068-2010-IR
RP-ID  :  DE-AC02-98CH10886
RP-ID  :  990713

美国|英语

来源: UNT Digital Library

【 摘 要 】

Ions from EBIS are injected into Booster after acceleration by an RFQ and a Linac. The velocity of the ions at Booster injection is c{beta} where c is the velocity of light and (1) {beta} = 0.0655. The kinetic energy is (2) W = mc{sup 2}({gamma}-1) where m is the ion mass and (3) {gamma} = (1-{beta}{sup 2}){sup -1/2}. Putting in numbers one gets a kinetic energy of approximately 2 MeV per nucleon for each ion. The revolution period at injection is 10.276 {micro}s. The ions in the EBIS trap are delivered in a beam pulse that ranges from 10 to 40 {micro}s in length. This amounts to 1 to 4 turns around the machine. The transverse emittance (un-normalized) of EBIS beams just prior to injection into Booster is 11{pi} mm milliradians in both planes. This is an order of magnitude larger than the nominal 1{pi} mm milliradians for Tandem beams. Injection proceeds by means of an electrostatic inflector in the C3 straight section and four programmable injection dipoles in the C1, C3, C7, and D1 straights. These devices have been in use for many years for the injection of ions from Tandem as described in [1] and [2]. The inflector brings the incoming beam to the edge of the Booster acceptance and the dipoles produce a closed orbit bump that initially places the closed orbit near the septum at the in ector exit. During injection the orbit bump must be collapsed at a rate that keeps the injected beam from hitting the septum while continuing to allow beam to be injected into the machine acceptance. The process is discussed in [2] and [3]. There it is assumed that the injected beam moves with the closed orbit as the bump collapses. In the present report this is shown to be a valid approximation if the bump collapses sufficiently slowly. It is also shown that by judiciously choosing the horizontal tune and the initial distance of the closed orbit from the septum one can inject up to 4 turns of EBIS beams without loss on the septum. The reason for wanting to inject over a period of 4 rather than fewer turns is that this allows the beam to be distributed over a larger area of the Booster acceptance, thereby reducing the space charge force on the beam particles.