Although the high-temperature superconducting (HTS) REBa 2 Cu 3 O x (REBCO, RE = rare earth elements) material has a strong potential to enable dipole magnetic fields above 20 T in future circular particle colliders, the magnet and conductor technology needs to be developed. As part of an ongoing development to address this need, here we report on our CORC ® canted cos θ magnet called C2 with a target dipole field of 3 T in a 65 mm aperture. The magnet was wound with 70 m of 3.8 mm diameter CORC ® wire on machined metal mandrels. The wire had 30 commercial REBCO tapes from SuperPower Inc., each 2 mm wide with a 30 µm thick substrate. The magnet generated a peak dipole field of 2.91 T at 6.290 kA, 4.2 K. The magnet could be consistently driven into the flux-flow regime with reproducible voltage rise at an engineering current density between 400 -550 A mm −2 , allowing reliable quench detection and magnet protection. The C2 magnet represents another successful step towards the development of high-field accelerator magnet and CORC ® conductor technologies. The test results highlighted two development needs: continue improving the performance and flexibility of CORC ® wires and develop the capability to identify locations of first onset of flux-flow voltage.

REBa 2 Cu 3 O x (REBCO, RE = rare earth elements) coated conductors can carry high current in high background fields, in principle enabling dipole magnetic fields beyond 20 T. Although model accelerator magnets wound with single REBCO tapes have been successfully demonstrated, magnet technology based on high-current REBCO cables for high-field accelerator magnet applications has yet to be established. We developed a two-layer canted cos θ dipole magnet with an aperture of 70 mm using 30 m long commercial Conductor on Round Core (CORC R) wires. The 3.1 mm diameter CORC R wire contained 16 commercial REBCO tapes with a 30-µm thick substrate. The magnet was tested at 77 and 4.2 K. It generated a peak dipole field of 1.2 T with 4.8 kA at 4.2 K with neither thermal runaway nor training. Reasonable geometric field quality and strong magnetization-current effects with multipole decay were observed. Our work demonstrated a feasible high-temperature superconducting magnet technology as a first step toward a new accelerator magnet paradigm that will enable high-field inserts for next-generation circular colliders and stand-alone magnets that can operate over a wide temperature range for a broad range of applications.

Abstrflct -High-gradient snpcrconducting quadiupole magnets me hcjng devcloped by thc US LIIC Accclcrsior Projca for thc Interaclion Rcgions of the Largc Hadron Collider. Dctcrininntion of the magnetic iixis lor alignmcnt of thcsc magnets will hc performed using n singlc stretcticd wire systcm. These incnsuremcnts will be dnne both a1 mom and cryogenic temperatures with very IOJI~ wire lenglhs, up to 20111. This paper repork on thc stretchcd wire alignmeiit tncthodology to be employed and thc resiilts of rccerit rontn-fciiipcraliire mc:isuretnents on n 2 m modcl magnci wiili long wirc lengths. INTROUUCTKIN'l'lic low-p insertion qnadrupoks currently under tlevelopmcnt at PNAL and KBK will have their alignment parameters metisurcd after being installed in cryostats at PNAL. As these magnets providc the final focus before collision for thc LHC beam, thclr alignment tnust be accurately determined. Such dignincnt measurements are required at both room and cryogenic temperatures because only thc FNAL magnets will undergo testing at cryogenic temperatures; thc remaining tnagncts will rcly on warm alignnicnt measu.cmcnts and measnreincnt of the correlation betwecn warm and cold alignment parameters. Purthermorc, although the length of thc MQX magnet assemblies rangc from 5.5 to 6.5 m, the Q2 has two such lnilgnets and a corrector package housed wiihin R singlc cryostat approximatcly 15 m in length. When mountcd on B tcst stand, with cryogcnic etid cans, aligiiment measurements inust be performed within ii beam tube o f length -20 m.The alignment device chosen for these tneasurcments is i\ SiIiglc Stretched Wire (SSW) systcm of the type used nt IlIiSY for thc HERA qiiadrripules [ I ] and for the Main Injector quadrupoles at PNAL [ 2 ] . Thc goals for rhe systcm arc tneasurcinent in the transvcrse planc of the average quadrupole axis (vertical and horizontal) to 50 ptn and roll to 100 p a d (including transfcr to magnct l'irlucials) under thc mcnsurement conditions cited abovc, hi additinn, in order to place the Q2AiQ2B device SO as to minimize thc eFFects of relative misalignments of the scparnte elcments (which cannot be adjusted after installation i o the cryostat), the true axcs of the individual Q2AlQZB magnets innst also be determined (ratlicr than just their average centers). This papcr outlines the syslem and techniqucs that will be used to achieve these measurement rcquiretnents and prcacnts the rcsults of recent tcsts o f thc methods involved.Manascripl rcccivcd Scptcinbcr 27. 1999. Work supportcd hy tlic U S . Dclurtnicnr uf Ewrgy.A single wirc is stretchcd between two sets r)f precision motion stages ils shown sclicmarically in Fig. 1. Thc return wire of the loop lics fixed on the bottom of the beam pipe or outside the magncr. Fig. I . Cnordinntc definitions fur SSW and inognel systcniThe vcctor potential at the ccnter of thc quadrupolc field of gradient ,p can bc expressed as where 11, b,,, a, arc thc multipole order, and normnl and skew coefficients, R is the rcference radius, x.y arc the huriiontal and verti...

The upgrade of the Large Hadron Collider (LHC) collimation system foresees additional collimators in the LHC dispersion suppressor areas. The longitudinal space for the collimators could be provided by replacing some NbTi LHC main dipoles with shorter 11 T Nb 3 Sn dipoles. To demonstrate this possibility, Fermilab and CERN have started a joint program to develop a Nb 3 Sn dipole prototype suitable for installation in the LHC. The first step of this program is the development of a 2-mlong, 60-mm-bore, single-aperture demonstrator dipole with the nominal field of 11 T at the LHC operational current of 11.85 kA. This paper presents the results of magnetic measurements of the single-aperture Nb 3 Sn demonstrator dipole including geometrical harmonics, coil magnetization, and iron saturation effects. The experimental data are compared with the magnetic calculations.Index Terms-Field quality, magnetic measurement, superconducting accelerator magnets.

Abstract-In order to study dynamic effects in accelerator magnets, such as the decay of the magnetic field during the dwell at injection and the rapid so-called "snapback" during the first few seconds of the resumption of the energy ramp, a fast continuous harmonics measurement system was required. A new magnetic field measurement system, based on the use of digital signal processors (DSP) and Analog to Digital (A/D) converters, was developed and prototyped at Fermilab. This system uses Pentek 6102 16 bit A/D converters and the Pentek 4288 DSP board with the SHARC ADSP-2106 family digital signal processor. It was designed to acquire multiple channels of data with a wide dynamic range of input signals, which are typically generated by a rotating coil probe. Data acquisition is performed under a RTOS, whereas processing and visualization are performed under a host computer.Firmware code was developed for the DSP to perform fast continuous readout of the A/D FIFO memory and integration over specified intervals, synchronized to the probe's rotation in the magnetic field. C, C++ and Java code was written to control the data acquisition devices and to process a continuous stream of data. The paper summarizes the characteristics of the system and presents the results of initial tests and measurements.