Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 work-package-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development.Presented at: ASC 2014, 10-15 August, Charlotte, USA Geneva, Switzerland February 2015 Abstract -Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 workpackage-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet.The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development. IndexTerms-Accelerator magnet, EuCARD-2, Superconducting Magnets, HTS magnet design, quench protection, YBCO Roebel cable, ReBCO.

We have performed Electron Spin Resonance measurements on single crystals of the doped spinPeierls compounds CuGe1−ySiyO3 and Cu1−xMxGeO3 with M = Zn, Mg, Ni (x, y ≤ 0.1). The first part of our experiments was performed in the paramagnetic and spin-Peierls phases at 9.5, 95 and 190 GHz. All non-magnetic impurities (Si, Zn and Mg) were found to hardly affect the position and linewidth of the single line resonance, in spite of the moment formation due to the broken chains. In contrast to Si, Zn and Mg-doping, the presence of Ni (S = 1) at low concentration induces a spectacular shift towards high fields of the ESR line (up to 40% for x=0.002), together with a large broadening. This shift is strictly proportional to the ratio of Ni to Cu susceptibilities: Hence it is strongly enhanced below the spin-Peierls transition. We interpret this shift and the broadening as due to the exchange field induced by the Ni ions onto the strongly exchange coupled Cu spins. Second, the antiferromagnetic resonance was investigated in Ni-doped samples. The frequency vs magnetic field relation of the resonance is well explained by the classical theory with orthorhombic anisotropy, with g values remarkably reduced, in accordance with the study of the spin-Peierls and paramagnetic phases. The easy, second-easy, and hard axes are found to be a, c, and b axes, respectively. These results, which are dominated by the single ion anisotropy of Ni 2+ , are discussed in comparison with those in the Zn-and Si-doped CuGeO3.

We present electron-spin-resonance data obtained on finite magnetic chains of CH3NMniCd Cl, (TMMC-Cd) for x =0. 02, 0.09, and 0.2. The measurements were developed with the microwave field either parallel or perpendicular to the magnetic field. The longitudinal relaxation time was also measured in the x =0.02 and 0.09 samples. All our experimental results show a noticeable inAuence of the impurities on both the line shape and linewidth, contrary to previously published data. New nuclear magnetic resonance data dealing with high-frequency proton relaxation rates are also presented. A full treatment using the memory-function formalism has been carried out to account for the significant difference observed between pure and doped samples. Our experimental data are satisfactorily described by this theory and the model of correlation functions for finite chains.

We have measured by the modulation technique at the X band the spin-lattice relaxation rate in the one-dimensional (CH3)4NMnC13, in the temperature range 20 -300 K. The experimental data are well described by the Bloembergen and Wang model. Below 4S K, an exchange-lattice relaxation process has been evidenced.The spin dynamics in one-dimensional (1D) materials has been extensively studied by magnetic resonance" and neutron diffusion techniques. ' In these materials, the exchange-narrowed electron-spin resonance shows marked properties; they concern the angular and frequency dependences of the linewidth, the line shape, and other effects such as line shifts and half-field transitions. They are consequences of the long-time diffusive decay of spin correlations in Heisenberg 1D systems. ' In this paper, we present the first study of the electron-spin-lattice relaxation time T~in a quasiperfect 1D system. We have measured T~at X band as a function of crystal orientation and temperature (Figs. 1 and 2) in tetramethylammonium trichloromanganate (CH3)4NMnC13 (TMMC). This compound consists of MnC13 chains well separated from each other. The Heisenberg exchange coupling is very strong within the chai'ns (J = -6.7 K) but about 104 smaller between the chains. 4 We took great care to operate on perfect crystals to avoid the presence of a 3D species which was described in another publication. 'In concentrated magnetic materials, the relaxation time T~is usually very short. Its measurement by conventional techniques is rather difficult and very few experimental data are available. However, precise measurements can be obtained by the "modulation method" which was originally devised by Herve and Pescia. In a "modulation spectrometer, " the amplitude of the microwave field is modulated at a frequency A. A coil placed in the cavity, around the sample and coaxial to the magnetic field, picks up a signal S proportional to the time derivative of the longitudinal magnetization dM, /dr For 0 T~(( 1,. the magnetization follows the modulation and S~0; I O I-10 50 8 (deg) 1 90 FIG. 1. Angular variation of the spin-lattice relaxation rate in TMMC at 300 K and 9 0Hz. The solid curve is obtained from Eq. (3) without adjustable parameters. 8 is the angle between the Zeeman field and the chain axis.on the other hand, for 0 T& ))1, the relaxation is effective and S tends towards a value Sp. In the general case, two data, the low-0 slope and the asymptotic value Sp are sufficient to the determination of T~. The upper values of 0 are limited by technical difficulties and Sp cannot be obtained directly in samples where T~( 10 s. Meanwhile, it can be shown' that there is a constant ratio between Sp and the ESR signal delivered by the apparatus used just like a con-23 1339