R.W. Hanft

Bio: R.W. Hanft is an academic researcher from Fermilab. The author has contributed to research in topics: Superconducting magnet & Magnet. The author has an hindex of 11, co-authored 59 publications receiving 486 citations.

Time variations of fields in superconducting magnets and their effects on accelerators

Abstract: The time dependence of magnetic fields in the superconducting magnets of the Fermilab Tevatron is discussed. A field variation of order 1 G at the aperture radius is observed. Studies on both full-sized Tevatron dipoles and prototype magnets have been used to elucidate these effects. Explanations based on eddy currents in the coil matrix or on flux creep in the superconducting filaments are explored with these tests. Measurement results and techniques for controlling the effect based on novel laboratory tests and the latest accelerator operation are presented. It is shown that small but important changes in the fields occur with (ln t) time dependencies. For accelerator operation, in both laboratory and accelerator measurements, some events which might be associated with nonsmooth behavior (sudden changes on the relevant time scale) and with deviations at long times from observed (ln t) behavior have been seen. >

About the mechanics of SSC dipole magnet prototypes

Abstract: During the last two years, nine 4‐cm aperture, 17‐m‐long dipole magnet prototypes were produced by Brookhaven National Laboratory (BNL) under contact with the Superconducting Super Collider (SSC) Laboratory These prototypes are the last phase of a half‐decade‐long R&D program, carried out in collaboration with Fermi National Accelerator Laboratory and Lawrence Berkeley Laboratory, and aimed at demonstrating the feasibility of the SSC main‐ring dipole magnets They also lay the groundwork for the 5‐cm‐aperture dipole magnet program now underway After reviewing the design features of the BNL 4‐cm‐aperture, 17‐m‐long dipole magnets, we describe in detail the various steps of their fabrication For each step, we discuss the paramaters that need to be mastered, and we compare the values that were achieved for the nine most recent prototypes The data appear coherent and reproducible, demonstrating that the assembly process is under control We then analyze the mechanical behavior of these magnets during cooldown and excitation, and we attempt to relate this behavior to the magnet features The data reveal that the mechanical behavior is sensitive to the collar‐yoke interference and that the magnets exhibit somewhat erratic changes in coil end‐loading during cooldown

Studies of time dependence of fields in Tevatron superconducting dipole magnets

Abstract: The time variation in the magnetic field of a model Tevatron dipole magnet at constant excitation current has been studied. Variations in symmetry allowed harmonic components over long time ranges show a log t behavior indicative of 'flux creep'. Both short-time-range and long-time-range behavior depend on the excitation history. Similar effects are seen in the remnant fields present in full-scale Tevatron dipoles following current ramping. Both magnitudes and time dependences are observed to depend on details such as ramp rate, flattop duration, and number of ramps. In a few magnets, variations are also seen in symmetry-disallowed harmonics. >

Magnetic Field Properties of Fermilab Energy Saver Dipoles

Abstract: At Fermilab we have operated a production line for the fabrication of 901 21 foot long superconducting dipoles for use in the Energy Saver/Doubler. At any one time 772 of these dipoles are installed in the accelerator and 62 in beamlines; the remainder are spares. Magnetic field data are now available for most of these dipoles; in this paper we present some of these data which show that we have been able to maintain the necessary consistency in field quality throughout the production process. Specifically we report harmonic field coefficients, showing that the mechanical design permits substantial reduction of the magnitudes of the normal and skew quadrupole harmonic coefficients; field shape profiles; integral field data; and field angle data. Details of the measurement apparatus and procedures are described elsewhere.

A buffer-gas cooled Bose-Einstein condensate

Abstract: We report the creation of a Bose-Einstein condensate using buffer-gas cooling, the first realization of Bose-Einstein condensation using a broadly general method which relies neither on laser cooling nor unique atom-surface properties. Metastable helium ((4)He*) is buffer-gas cooled, magnetically trapped, and evaporatively cooled to quantum degeneracy. 10(11) atoms are initially trapped, leading to Bose-Einstein condensation at a critical temperature of 5 microK and threshold atom number of 1.1 x 10(6). This method is applicable to a wide array of paramagnetic atoms and molecules, many of which are impractical to laser cool and impossible to surface cool.

Superconducting Magnets for Particle Accelerators

Abstract: Superconductivity has been the most influential technology in the field of accelerators in the last 30 years. Since the commissioning of the Tevatron, which demonstrated the use and operability of superconductivity on a large scale, superconducting magnets and rf cavities have been at the heart of all new large accelerators. Superconducting magnets have been the invariable choice for large colliders, as well as cyclotrons and large synchrotrons. In spite of the long history of success, superconductivity remains a difficult technology, requires adequate RD it highlights the main characteristics and main achievements, and gives a perspective on the development of superconducting magnets for the future generation of very high energy colliders.

Correction of the persistent current effect in Nb/sub 3/Sn dipole magnets

Abstract: The paper describes a method and results of simulation of persistent current effect in high field Nb/sub 3/Sn dipole magnets being developed for the future hadron colliders Simple and effective techniques of passive correction of the persistent current effect in superconducting accelerator magnets are proposed Using of these techniques allows a significant reduction of sextupole and decapole field components induced by persistent currents in a coil

Fields and First Order Perturbation Effects in Two-Dimensional Conductor Dominated Magnets - eScholarship

Abstract: General expressions are given for the field and its expansion coefficients produced by a two dimensional conductor structure surrounded by iron with a circular inside boundary. Saturation effects are described in terms of the tangential field at that boundary. The effects of the following types of perturbations are discussed: displacement, rotation and error excitation of a conductor, change of conductor shape, and modification of the inside contour of the iron. A design criterion is given to minimize the error fields associated with a displacement of the iron shell relative to the conductor structure. Expressions for the force and torque acting on a conductor are derived both for the unperturbed and perturbed magnet. Formulae are presented that allow convenient and fast evaluation of pertinent quantities with a computer when the structure is too complicated for hand computations.