D.J. Harding

A New Correction Magnet Package for the Fermilab Booster Synchrotron

Since its initial operation over 30 years ago, most correction magnets in the Fermilab Booster Synchrotron have only been able to fully correct the orbit, tunes, coupling, and chromaticity at injection (400MeV). We have designed a new correction package, including horizontal and vertical dipoles, normal and skew quadrupoles, and normal and skew sextupoles, to provide control up to the extraction energy (8GeV). In addition to tracking the 15Hz cycle of the main, combined function magnets, the quadrupoles and sextupoles must swing through their full range in 1 ms during transition crossing. The magnet is made from 12 water-cooled racetrack coils and an iron core with 12 poles, dramatically reducing the effective magnet air gap and increasing the corrector efficiency. Magnetic field analyses of different combinations of multipoles are included.

Restoring the Skew Quadrupole Moment in Tevatron Dipoles

In early 2003 it was realized that mechanical changes in the Tevatron dipoles had led to a deterioration of the magnetic field quality that was hindering operation of the accelerator. After extensive study, a remediation program was started in late 2003 that will continue through 2005. The mechanical and magnetic effects are discussed. The readjustment process and experience are reported, along with other observations on aging magnets.

A Fast-Sampling, Fixed Coil Array for Measuring the AC Field of Fermilab Booster Corrector Magnets

A system employing an array of inductive pick-up coils around the perimeter of a cylinder has been developed for measurements of the rapidly changing field in the new corrector magnets for the Fermilab Booster. The coils are fabricated on printed circuit boards and feature windings which buck dipole, quadrupole, and sextupole fields, allowing sensitive measurements of both strength and higher-order harmonics. The array of coils is simultaneously sampled at data rates of up to 100 kHz with 10 kHz bandwidth using 24-bit ADCs.

A slowly rotating coil system for AC field measurements of Fermilab Booster correctors

A method for measurement of rapidly changing magnetic fields has been developed and applied to the testing of new room temperature corrector packages designed for the Fermilab Booster Synchrotron. The method is based on fast digitization of a slowly rotating tangential coil probe, with analysis combining the measured coil voltages across a set of successive magnet current cycles. This paper presents results on the field quality measured for the normal and skew dipole, quadrupole, and sextupole elements in several of these corrector packages.

Design for Fermilab Main Injector magnet ramps which account for hysteresis

Although the dominant fields in accelerator electromagnets are proportional to the excitation current, precise control of accelerator parameters requires a detailed understanding of the fields in Main Injector magnets including contribution from eddy currents, magnet saturation, and hysteresis. Operation for decelerating beam makes such considerations particularly significant. Analysis of magnet measurements and design of control system software is presented. Field saturation and its effects on low field hysteresis are accounted for in specifying the field ramps for dipole, quadrupole and sextupole magnets. Some simplifying assumptions are made which are accepted as limitations on the required ramp sequences. Specifications are provided for relating desired field ramps to required current ramps for the momentum, tune, and chromaticity control.

New corrector system for the Fermilab Booster

We present an ambitious ongoing project to build and install a new corrector system in the Fermilab 8 GeV booster. The system consists of 48 corrector packages, each containing horizontal and vertical dipoles, normal and skew quadrupoles, and normal and skew sextupoles. Space limitations in the machine have motivated a unique design, which utilizes custom wound coils around a 12 pole laminated core. Each of the 288 discrete multipole elements in the system will have a dedicated power supply, the output current of which is controlled by an individual programmable ramp. This paper describes the physics considerations which drove the design, as well as issues in the control of the system.

Design and fabrication of a multi-element corrector magnet for the Fermilab Booster synchrotron

To better control the beam position, tune, and chromaticity in the Fermilab Booster synchrotron, a new package of six corrector elements has been designed, incorporating both normal and skew orientations of dipole, quadrupole, and sextupole magnets. The devices are under construction and installation at 48 locations is planned. The density of elements and the rapid slew rate have posed special challenges. The magnet construction is presented along with DC measurements of the magnetic field.

A wide aperture quadrupole for the Fermilab main injector synchrotron

During the design of the Fermilab Main Injector synchrotron it was recognized that the aperture was limited at the beam transfer and extraction points by the combination of the Lambertson magnets and the reused Main Ring quadrupoles located between the Lambertsons. Increased intensity demands on the Main Injector from antiproton production for the collider program, slow spill to the meson fixed target program, and high intensity beam to the high energy neutrino program have led us to replace the aperture-limiting quadrupoles with newly built magnets that have the same physical length but a larger aperture. The magnets run on the main quadrupole bus, and must therefore have the same excitation profile as the magnets they replaced. We present here the design of the magnets, their magnetic performance, and the accelerator performance.

Magnetic field strength and shape measurements of the Fermilab Main Injector quadrupoles

All of the new quadrupoles for the Fermilab Main Injector ring have been built and measured. The magnets are 2.95 m and 2.54 m in length with a 41.7 mm bore. In operation, the magnets run from 1.61 T/m at 8.9 GeV/c to 15.7 T/m at 120 GeV/c and 19.6 T/m at 150 GeV/c. These points correspond to injection, Main Injector fixed target physics and antiproton production, and extraction for transfer to the Tevatron. Good field uniformity is required to ensure a stable beam over the whole acceleration cycle. A significant octupole is included to assist in resonant extraction. The performance of these quadrupoles, in both integrated strength and field uniformity, is presented. All magnets produced meet the accelerator requirements.

Design and Fabrication of a Multi-Element Corrector Magnet for the Fermilab Booster

A new package of six corrector elements has been designed to better control the beam position, tune, and chromaticity in the Fermilab Booster synchrotron. It incorporates both normal and skew orientations of dipole, quadrupole, and sextupole magnets. These new corrector magnets will be installed in the Fermilab Booster ring in place of old style corrector elements. A severe space restriction and rapid slew rate have posed special challenges. The magnet design, construction, and performance are presented.