A retrofit/upgrade of the Stony Brook linac

doi:10.1016/0168-9002(90)91801-H

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

Volume 287, Issues 1–2, 1 February 1990, Pages 240-246

https://doi.org/10.1016/0168-9002(90)91801-H Get rights and content

Abstract

We describe a project to replace the initial 16 split-loop resonators in the Stony Brook superconducting booster linac with β₀=0.068 quarter wave resonators (QWRs). When completed, this retrofit will assure phase stable linac operation at output energies from 20% to as much as (for the heaviest ions) 80% higher than before. The resonator performance goal of δ_a=3 MV/m at 6 W dissipation has been achieved by plating a thin lead-tin layer after tumbling the copper surface, and most of the engineering and fabrication work has been completed. Although until now multipactoring during the test runs has been intense and frequently intractable, recent experiments have demonstrated that this can be routinely eliminated by room-temperature rf “pre-processing” with careful control of the vaccum quality.

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Proposal for a Retrofit/Upgrade of the Stony Brook Linac

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Cited by (6)

Progress in lead-copper resonator technology
1993, Nuclear Inst. and Methods in Physics Research, A
A simple and effective method for the direct fabrication of lead alloy superconducting films on copper resonators is described. A set of four β_opt = 0.068 quarter-wave resonators (QWRs) for the Stony Brook linac retrofit project prepared with these techniques can produce continuous accelerating fields of 3.0–4.0 MV/m (22–28 MV/m peak surface field) in both tests and routine on-line linac operation.
Fabrication and test of a superconducting RFQ
1993, Nuclear Inst. and Methods in Physics Research, A
The fabrication and first performance tests of a prototype superconducting radio-frequency quadrupole resonator (SRFQ) are described. The SRFQ operates at 57 MHz and is optimized for a particle velocity of β = 0.033. It is constructed of copper electroplated with a lead-tin alloy. An accelerating field gradient of 1.25 MV/m was achieved with about 7 W of helium dissipation. This corresponds to an energy gain of 700 keV per unit charge over the 56 cm overall diameter of the resonator.
Freon plasma surface treatment for multipactoring
1993, Nuclear Inst. and Methods in Physics Research, A
Review of superconducting booster linacs
1993, Nuclear Inst. and Methods in Physics Research, A
Several superconducting boosters have been built and more are planned or under construction. These all use a number of independently phased resonators to permit acceleration of a wide variety of ion masses. For heavy ions, vhf frequencies are involved, and operation of the superconductors at 4.3 K, the normal boiling point of He, is practical. (Because fundamental losses in superconductors depend on frequency, some electron accelerators using much higher frequencies require colder resonators.) For boosters the resonator technology has evolved toward the use of quarter wave resonators with straight loading arms. The superconducting material is either niobium or lead. The latter is deposited as a film on copper, while the former may be sheet metal, may be bonded to copper, or may be (in principle) applied as a film on copper. The trade-offs involved and the successes of the various techniques are discussed. The rf must be controlled accurately both with regard to amplitude and phase. Because of the high unloaded Q of the resonators, additional loading is provided at some temperature well above that of the superconductor, in order to increase the bandwidth to a manageable point. Most boosters provide active control of phase by shifting the driving phase, although at least one system uses a frequency switching technique. Cross talk between independent resonator control systems must be avoided. The cryogenic systems have evolved toward a system based on a large helium refrigerator using turbine expansion and providing gas cooling to heat shields. Conservative design provides excess capacity beyond the expected requirements of the accelerator. Cryogenic distribution must be done carefully to avoid losses, and the system should be designed with capacity to match that of anticipated upgrades of the refrigerator. Most boosters use an approximately periodic focusing system with radial phase advance near 90° per unit cell. At Legnaro, however, waist to waist focusing is planned between diagnostic boxes placed between each cryostat. The pertinent operating parameters of boosters that are presently operating, are under construction, and are planned are presented.
Determining the radiofrequency dipole and quadrupole effects in quarter wave resonators
1992, Nuclear Inst. and Methods in Physics Research, A
The asymmetry of a quarter wave resonator (QWR) around the beam axis z causes deflection and additional (de)focusing of the beam: these effects are immediately related to the first terms, the dipole and the quadrupole, in a Fourier-Bessel multipole expansion of the quasistatic potential φ; the non-relativistic impulse approximation for heavy ion acceleration is given. General features of multipole dependencies from beam phase and velocities are shown.
Since the electric field square modules |E|² is measurable with the bead technique, an iterative determination of E_x and E_y from E_z and the potential φ is proposed here; the noise contribution is not amplified at the shortest wavelength Fourier components, and it can be filtered. Field errors are reduced by imposing the fit to the correct analytic form inside the drift tubes, where the fields exponentially decrease. The preliminary set of data relative to a QWR with an ogiva central rod is treated as an example, showing that dipole effects have a zero near the beam velocities optimal for acceleration.
Review of low beta structures
1999, IEEE Transactions on Applied Superconductivity

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A retrofit/upgrade of the Stony Brook linac

Abstract

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

Nucl. Instr. and Meth.

Rev. Sci. Instr.

Stony Brook Internal Report

IEEE Trans. Nucl. Sci.

IEEE Trans. Nucl. Sci.

Rev. Sci. Instr.

IEEE Trans. Nucl. Sci.

Proposal for a Retrofit/Upgrade of the Stony Brook Linac