[Show abstract][Hide abstract] ABSTRACT: This paper reports the development of 350 MHz superconducting
cavities of a spoke-loaded geometry, intended for the velocity range
0.2<v/c<0.6. Two prototype single-cell cavities have been
designed, one optimised for velocity v/c=0.4, and the other for
v/c=0.29. Construction of the prototype niobium cavities is nearly
complete. Details of the design and construction are discussed, along
with the results of cold tests
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
[Show abstract][Hide abstract] ABSTRACT: A system has been developed at Jefferson Lab for measuring
transverse position of very low current beams delivered to the
Experimental Hall B of the Continuous Electron Beam Accelerator Facility
(CEBAF). At the heart of the system is a position sensitive cavity
operating at 1497 MHz. The cavity utilizes a unique design which
achieves a high sensitivity to beam position at relatively low cavity Q.
The cavity output RF signal is processed using a down-converter and a
commercial lock-in amplifier operating at 100 kHz. The system interfaces
with a VME based EPICS control system using the IEEE 488 bus. The main
features of the system are simple and robust design, and wide dynamic
range capable of handling beam currents from 1 nA to 1000 nA with an
expected resolution better than 100 μm. This paper outlines the
design of the system
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
[Show abstract][Hide abstract] ABSTRACT: An ion linac formed of superconducting rf cavities can provide a multi-beam driver accelerator for the production of nuclei far from stability. A multi-beam driver supports a wide variety of production reactions and methods. This paper outlines a concept for a 1.3 GV linac capable of delivering several hundred kilowatts of uranium beam at an energy of 400 MeV per nucleon. The linac would accelerate the full mass range of ions, and provide higher velocities for the lighter ions, for example 730 MeV for protons. The accelerator will consist of an ECR ion source injecting a normally conducting RFQ and four short IH structures, then feeding an array of more than 400 superconducting cavities of six different types, which range in frequency from 58 to 700 MHz. A novel feature of the linac is the acceleration of beams containing more than one charge state through portions of the linac, in order to maximize beam current for the heavier ions. Such operation is made feasible by the large transverse and longitudinal acceptance provided by the large aperture and high gradient which are characteristic of superconducting rf cavities.
[Show abstract][Hide abstract] ABSTRACT: The 4 GeV CEBAF accelerator at Thomas Jefferson National Accelerator Facility (Jefferson Lab) is arranged in a five-pass racetrack configuration, with two superconducting radio-frequency (SRF) linacs joined by independent magnetic transport arcs. The 1497 MHz continuous electron beam is composed of 3 interlaced variable-intensity 499 MHz beams that can be independently directed from any of the five passes to any of the three experimental halls. Beam extraction is made possible by a system of nine warm sub-harmonic separator cavities capable of delivering a 100 microrad kick to any pass at a maximum machine energy of 6 GeV. Each separator cavity is a half-wavelength, two cell design with a high transverse shunt impedance and a small transverse dimension. The cavities are powered by 1kW solid state amplifiers operating at 499 MHz. Cavity phase and gradient control are provided through a modified version of the same control module used for the CEBAF SRF cavity controls. The system has recently been tested while delivering beam to Hall C. In this paper the authors present a description of the RF separator system and recent test results with beam.
[Show abstract][Hide abstract] ABSTRACT: The Spallation Neutron Source (SNS) * linear accelerator low-level RF control system has been developed within a collaboration of Lawrence Berkeley, Los Alamos, and Oak Ridge national laboratories. Three distinct generations of the system, previously described, have been used to support beam commissioning at Oak Ridge. The third generation system went into production in early 2004, with installation in the coupled-cavity and superconducting linacs to span the remainder of the year. The final design of this system will be presented along with results of performance measurements.
[Show abstract][Hide abstract] ABSTRACT: Jefferson Lab's CEBAF electron accelerator has recently begun delivering spin-polarized electrons for nuclear experiments. Spin-polarized electrons are emitted from a GaAs photocathode that is illuminated with pulsed laser light from a diode laser synchronized to the 3 rd subharmonic (499 MHz) of the accelerating cavity frequency (1497 MHz). Up to three experimental halls (A, B and C) are served by the photoinjector each with their own beam requirements. To accomplish this, three independent diode lasers are synchronized and combined to illuminate the GaAs photocathode emitting a 1497 MHz pulse train of electrons. In addition an RF bunching cavity approximately 2 m down stream from the photocathode is used to compensate for space charge effects at the higher beam currents. The RF system that controls these elements is a modified VME based system. Custom RF VME modules control phase and amplitude for each laser diode and the bunching cavity. Power requirements were satisfied with commercial RF amplifiers, 5 W for the diode lasers and 10 W for the bunching cavity. Simple software algorithms using the EPICS control system correct phase and amplitude drifts. The RF system is compact, simple and allows for easy hardware or software modifications.