D. Dell'Orco

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.

Development of a high gradient quadrupole for the LHC interaction regions

A collaboration of Fermilab, Lawrence Berkeley National Laboratory and Brookhaven National Laboratory is engaged in the design of a high gradient quadrupole suitable for use in the LHC interaction regions. The cold iron design incorporates a two-layer, cos(2/spl theta/) coil geometry with a 70 mm aperture operating in superfluid helium. This paper summarizes the progress on a magnetic, mechanical and thermal design that meets the requirements of maximum gradient above 250 T/m, high field quality and provision for adequate cooling in a high radiation environment.

A 50 mm bore superconducting dipole with a unique iron yoke structure

A 50-mm-bore superconducting dipole with a thin stainless steel collar and a close-in elliptical iron yoke was designed to obtain a high transfer function and low saturation effects on the multipoles. A 1-m model was built and tested. The training behavior of the first 1-m model is presented at 4.3 K and 1.8 K. At 1.8 K it reached the record field of 10.06 T. The two layer cos theta winding uses 30 and 36 strand cables identical to the cables of the 50-mm-bore Superconducting Super Collider (SSC) dipole, and it has an operating field of 6.6 T at 4.35 K with a current of 5800 A. To evaluate behavior at high fields, the mechanical structure for the model was designed for 10 T. The thin collar itself provides only a minimum prestress of 10 MPa, and the full prestress of 70 MPa is given by the iron yoke. An aluminum spacer is used to control the gap size in the vertically split iron yoke. The tapered gap in the yoke is determined by the size of the Al spacer so that during cooldown there is no loss of coil prestress and the gap remains closed when the magnet is energized.<<ETX>>

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>>

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.

Quadrupole magnets for the SSC

The authors have designed, constructed, and tested four short (1-m) models and six full-size (5-m) models of the Superconducting Super Collider (SSC) main-ring 5-m focusing quadrupole magnet (211 T/m). The results of this program are summarized. The magnet construction, test procedures, and test results are discussed. Except for modest training above the SSC operating point, the magnets performed very well and proved to be self-protecting. Some design flaws, e.g., inadequate end-clamping and pole shimming, were identified and corrected sufficiently so that the later magnets exceeded specifications.<<ETX>>

Design and construction of a hybrid-Nb/sub 3/Sn, NbTi-dipole magnet

A two layer superconducting dipole magnet-D19H, with a Nb/sub 3/Sn inner layer and a NbTi outer layer was designed, constructed and tested. The 50 mm bore inner layer of an existing NbTi dipole magnet (D19A), has been removed and replaced with a Nb/sub 3/Sn coil. The outer NbTi coil, collars, iron yoke, ring, collets and outer skin from the disassembled D19A magnet have all been reused. Employing glass insulated cable with aluminum-bronze poles and end spacers the Nb/sub 3/Sn coil was reacted at 660/spl deg/C for 240 hours and fully epoxy impregnated. The design and construction of the magnet are described and test results reported elsewhere in these proceedings.

Test results for a Nb/sub 3/Sn dipole magnet

A cosine theta type dipole magnet using Nb/sub 3/Sn conductor have been designed, built and tested. D19H is a two-layer dipole magnet with a Nb/sub 3/Sn inner layer and a recycled NbTi outer layer. Coil-pairs are connected with two of the four Nb/sub 3/Sn splices in a high field region, and compressed by a ring and collet system. The ramp-rate sensitivity and the splice resistances were pleasingly low; and the 4.4 K training was rapid. At 1.8 K, however, the unusually high frequency of outer-coil fast-motion events increased with current, effectively creating a training-ceiling at 90% of the expected outer-layer limit (10.2 T). A low end-load applied to a relatively fluffy outer layer is believed to have caused this training limit. The end-load was increased; but a retest was aborted after the magnet failed a precautionary hipot test.

Fabrication and component testing results for a Nb/sub 3/Sn dipole magnet

At present, the maximum field achieved in accelerator R&D dipoles is slightly over 10 T, with NbTi conductor at 1.8 K. Although Nb/sub 3/Sn has the potential to achieve much higher fields, none of the previous dipoles constructed from Nb/sub 3/Sn have broken the 10 T barrier. We report here on the construction of a dipole with high current density Nb/sub 3/Sn with a predicted short sample limit of 13 T. A wind and react technique, followed by epoxy impregnation of the fiberglass insulated coils, was used. The problems identified with the use of Nb/sub 3/Sn in earlier dipole magnets were investigated in a series of supplemental tests. This includes measurement of the degradation of Jc with transverse strain, cabling degradation, joint resistance measurements, and epoxy strength tests. In addition, coil assembly techniques were developed to ensure that adequate prestress could be applied without damaging the reacted Nb/sub 3/Sn cable. We report here the results of these tests and the construction status of this 50 mm bore dipole.<<ETX>>