Abs&uct-A cosine theta type dipole magnet using Nb3Sn conductor have been designed, built and tested. D19H is a twolayer dipole magnet with a Nb$n inner layer and a recycled NbTi outer layer. Coil-pairs are connected with two of the four Nb3Sn splices in a high field region, and compressed by a ring and collet system. The ramprate sensitivity and the splice resistances were pleasingly low, and the 4.4K training was rapid. At 1.8K, 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.
A two layer superconducting dipole magnet-D19H, with a Nb3Sn inner layer and a NbTi outer layer was designed, constructed and tested. The 50" bore inner layer of an exisihg NbTi dipole magnet (D19A), hia been removed and replaced with a Nb3Sn 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& coil was reacted at 660'C for 240 hours and fully epoxy impregnated. The design and construction uf the magnet are described and test results reported elsewhere in these pmceedingsll].
AhstraciThc early design and test results llavc hccn prcviiiusly reportctl. [ 11 During thc subscqucnt operation of "1~20" the accelerator prntntypc dipolc lias provided 110th additional and iiiorc dcteilcd data as tu i t s charactcristics and pcrforinancc. D20's use as a tcsl Sxilily for high Ilcld critical current incasiircincnts 121 has ~~r o v i d c d opcriitional expcricncc end history pertaining to accelerator rctltiircd cliariictcristics.'Sherc llas hccii recently oht;iincd data related to ficld quality, operational rcprotlocibilily and rcliahility, whicli will he presented. This prototype "1>20" has ;ittaincd the higlicst magnetic Cicld OS any iiccelcliitiir protntypc dipolc coiistructcd and routinclv.
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