The fabrication and initial testing of the SNS RFQ

Abstract

The Lawrence Berkeley National Laboratory (LBNL) is designing and building the 2.5 MeV front end injector for the Spallation Neutron Source (SNS) [1,2]. This injector comprises an H -ion source, a low energy beam transport line (LEBT), a radio-frequency quadrupole (RFQ) and a beam transport line designed to provide fast chopping of the beam. The RFQ is designed to accelerate the H -beam from the energy of 65 keV to 2.5 MeV, while bunching it at 402.5 MHz. This high duty factor (6%) structure is made of a combination of Glidcop® and OFE copper and is fully brazed. The RFQ is built in 4 modules, each approximately one meter long. This paper covers the mechanical fabrication details of the modules, three of which have been completed. While the modules are coming out of production, they are conditioned and tested to full power. This paper will also describe the results of the beam tests on the first module, including capture efficiency and transmission.

Design of a 200-MHz Continuous-Wave Radio Frequency Quadrupole Accelerator for Boron Neutron Capture Therapy

“…Currently, the main cavity types of RFQ are four-vane RFQ [17][18][19] and four-rod RFQ [20][21][22]. The four-vane RFQ is suitable for accelerating light particles, such as protons and deuterons, and can operate under continuous-wave (CW) conditions.…”

High dimensional characterization of the longitudinal phase space formed in a radio frequency quadrupole

“…Additionally, the design is constrained to produce ≤ 95 keV-deg at maximum current output. This goal was met with normalized input emittance 0.2 mm-mrad and simulation transmission > 90% [15][16][17]. In this paper, the PARMTEQ simulation is repeated with an input beam based on LEBT measurements.…”

Application of a new procedure for design of 325 MHz RFQ

“…Similar to many other linear accelerators, the PD [1] requires an RFQ for initial acceleration and formation of the bunched beam structure. The required parameters of the FNAL RFQ are very similar to the SNS [2] and J-PARC [3]. The RFQ design includes two main tasks: a) the beam dynamics design resulting in a vane tip modulation table for machining and b) the resonator electromagnetic design resulting in the final dimensions of the resonator.…”

“…-2 -rf wavelength, it is difficult to stabilize the operating field and damp field errors. To address this problem, the SNS and J-PARC RFQ designs included π-mode stabilizing loops (PISLs) [3]. PISLs complicate the resonator design and increase its cost, therefore we propose to minimize the length of the RFQ resonator to allow for the use of field stabilizers simpler than PISLs.…”