C. Taylor

Magnet system for an ECR ion source

A superconducting magnet assembly has been built for an ECR (Electron Cyclotron Resonance) ion source at the 88-inch cyclotron at LBL. Three 34-cm ID solenoids provide axial plasma confinement and a sextupole assembly in the solenoid bore provides radial stability. Two large solenoids are spaced 50 cm. Apart with a smaller opposing solenoid between. The sextupole assembly is 92 cm long with winding inner diameter of 20 cm. And outer diameter of 27.2 cm. The design goal is to achieve a field on axis of 4 T and 3 T at the mirrors with 0.4 T between and a sextupole field of 2.0 T at 15-cm diameter in the confinement volume. Each solenoid uses rectangular conductor wish copper/SC ratio of 4; the three coils are wet-wound on a one-piece aluminum bobbin with aluminum banding for radial support. The sextupole uses rectangular conductor with copper/SC ratio of 3. Each of the 6 coils is wet-wound with filled epoxy on a metal pole; the ends of the pole are aluminum and the central 34-cm is iron to augment the sextupole field. The six coils are assembled on a 20-cm-OD stainless steel tube with a 1.4-cm thick 30.0-cm OD aluminum tube over the assembly for structural support. Thin metal bladders are expanded azimuthally between each coil and axially at tire ends to pre-load the assembly. The sextupole assembly fits inside the solenoid bobbin, which provides support for the magnetic forces. The magnet exceeds design requirements with minimum training.

Test results for a high field (13 T) Nb/sub 3/Sn dipole

A Nb/sub 3/Sn dipole magnet (D20) has been designed, constructed, and tested at LBNL. Previously, we had reported test results from a hybrid design dipole which contained a similar inner Nb/sub 3/Sn and outer NbTi winding. This paper presents the final assembly characteristics and parameters which will be compared with those of the original magnet design. The actual winding size was determined and a secondary calibration of the assembly pre-load was done by pressure sensitive film. The actual azimuthal and radial D20 pre-loading was accomplished by a very controllable novel stretched wire technique. D20 reached 12.8 T (4.4 K) and 13.5 T (1.8 K) the highest dipole magnetic fields obtained to date in the world.

The third generation superconducting 28 GHz electron cyclotron resonance ion source VENUS (invited).

VENUS is a third generation electron cyclotron resonance (ECR) ion source, which incorporates a high field superconducting NbTi magnet structure, a 28 GHz gryotron microwave source and a state of the art closed cycle cryosystem. During the decade from initial concept to regular operation, it has demonstrated both the feasibility and the performance levels of this new generation of ECR ion sources and required innovation on magnet construction, plasma chamber design, and beam transport. In this paper, the development, performance, and major innovations are described as well as a look to the potential to construct a fourth generation ECR ion source.

Results with the superconducting electron cyclotron resonance ion source VENUS (invited)

During the last year, the VENUS electron cyclotron resonance (ECR) ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR ion source project as the RIA research and development injector is the production of 240 eμA of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 eμA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W rf power and the performance is very promising. For example, 1100 eμA of O6+, 180 eμA of Ar12+, 150 eμA of Xe20+, and 100 eμA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner...

Test of a high-field bend magnet for the ALS

It is possible to replace several of the existing 36 conventional 1.5 T, 1 m long bend magnets in the ALS (Advanced Light Source) at LBNL with short, higher field superconducting magnets to produce synchrotron radiation with higher energy. The authors have built and tested four prototype magnets using different conductors, coil shapes, structural support and fabrication methods. All reached the required field for bending 1.9 GeV electrons 10 degrees; however, the first three had excessive training. The final design, Superbend 4, reached short-sample current with no training. Construction details, stress analysis and test results are presented for Superbend 4.

Design of the Nb/sub 3/Sn dipole D20

The design of a 55-mm bore superconducting Nb/sub 3/Sn dipole with a short sample field of 13 T at 4.3 K and a current of 5500 A/turn is presented. The superconducting dipole has two layers of Nb/sub 3/Sn coils, each wound in a double pancake. The inner cable has 37 strands with a strand diameter of 0.75 mm and a Cu/Sc ratio of 0.4; the outer cable has 47 strands with a diameter of 0.48 mm and a Cu/Sc ratio of 1.15. To obtain a high transfer function and low saturation effects on the multipoles, the stainless steel collar is elliptical and the iron yoke is close in. The thin collar itself provides only a minimum prestress and the full prestress of 100 MPa is given by a 25-mm welded stainless steel shell or by winding a wire around the yoke. Aluminium spacers are used as assembly tools and as a means to control the gap size in the vertically split iron yoke. The authors present the magnetic design and the calculated stress and strain distribution in structure and coils. A 1-m model called D20 is to be built and tested at LBL.<<ETX>>

Development of a 40 mm bore magnet cross section with high field uniformity for the 6.6T SSC dipole

LBL-21297 Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Accelerator & Fusion Research Division Presented at the 1986 Applied Superconductivity Conference, Baltimore, MD, September 29-0ctober 3, 1986 DEVELOPMENT OF A 40 mm BORE MAGNET CROSS SECTION WITH HIGH FIELD UNIFORMITY FOR THE 6.6T SSC DIPOLE S, Caspi , W, Gilbert, M, Helm, L.J, Laslett, and C, Taylor September 1986 Prepared for the U.S, Department of Energy under Contract DE-AC03-76SF00098

A 6.3 T bend magnet for the Advanced Light Source

The Advanced Light Source (ALS) is a 1.5 to 1.9 GeV high-brightness electron storage ring operating at LBL that provides synchrotron radiation for a large variety of users. It is proposed to replace three of the thirty six 1.5 T, one meter long bend magnets with very short high-field superconducting (SC) dipoles. These magnets would provide bend-magnet synchrotron radiation to six beamlines with a critical energy of at least 6 keV that is much better suited for protein crystallography and other small-sample X-ray diffraction and adsorption studies, than is currently available at the ALS. The magnet design is described, including coil, yoke, magnetic field analysis, and cyrostat. A prototype magnet is under construction at LBL.

Design and fabrication of a high aspect ratio cable for a high gradient quadrupole magnet

The Large Hadron Collider interaction regions require quadrupoles with a 70 mm diameter bore, a gradient of 250 T/m, and good cooling so that the magnets can operate in a high radiation background without quenching. In order to meet these stringent requirements, a two-layer magnet with a high aspect ratio cable has been designed. This cable utilizes the SSC inner and outer layer strands, which have been optimized and are available in large quantities. The initial design parameters for both cables are 15.2 mm width; the inner cable has 38 strands of 0.8 mm diam wire and a keystone angle of 0.99 deg. The outer cable has 46 strands of 0.65 mm diam wire and a keystone angle of 0.69 deg. These cables have been fabricated and then subjected to a number of tests to insure their performance in the quadrupole. These test results, including model coil winding studies, electrical property measurements, and mechanical property measurements will be presented.

LARGE SCALE SUPERFLUID PRACTICE

Since 1979 Lawrence Berkeley Laboratory has been testing superconducting magnets in He II. The 1 atm pressure, 1.8 K, He II, test facility, is an integral part of the LBL Research and Development program on high field superconducting dipole magnets for particle accelerators. Some of the experience gained in this facility and the details of its operation are reported.