Vane Coupling Rings: A Simple Technique for Stabilizing a Four-Vane Radiofrequency Quadrupole Structure

Abstract

The benefits of stabilized accelerating struc tures, with regard to the manufacture and operation, have been well documented. The four-vane radiofrequency quadrupoles (RFQ) presently being designed and constructed in many laboratories are not stabil ized because of the weak electromagnetic coupling between the quadrant resonators. This paper presents a simple technique developed at the Lawrence Rerkeley Laboratory using vane coupling rings (VCR's) which azimuthally stabilize the RFQ structure and greatly enhar.i its use as a practical accelerator, in particular the VCR's: o Completely eliminate the dipole modes in the frequency range of interest; o Provide adequate quadrant balance with an initial precision mechanical alignment of the vanes; o Enhance axial balance and simplify end tuners. Experimental verification tests on a scale model will be discussed.

RFQ's: An introduction

“…• e " • hown in Fig-. vane tips togeth._r witll va,lie COul)ling rings [17]. This t:.chnl(tuc, s ' ure 12, greatly reduces the sensitivity to assembly errors and reduces tile RFQ tuning procedure to one of only establishing the proper longitlMinal voltage dis-' tribution, usually by moving the e11dwalls.…”

Investigation of Electromagnetic Field Perturbation With Respect to Mechanical Imperfections in Radio-Frequency Quadrupole (RFQ) Structure

“…1 have different field distribution from fields in Q3-4 by vane perturbation. Field discrepancy between Q1-2 and Q3-4 depends on the transverse field stabilizing method of RFQs [13], [26]. Therefore, another RFQ model without PISL, is created and simulated with a same perturbation size.…”

“…The SNS RFQ operating at 402.5 MHz was modeled using CST Microwave Studio (MWS) [21] for a short structure by Lawrence Berkeley National Laboratory (LBNL) [10]. The LBNL model which has one section length (0.93 m) is composed of -mode stabilizer loops (PISL) [11]- [13], slug tuners, as shown in the left side of Fig. 1(a), and end plates in addition to the RFQ body.…”