Nuclear Bragg Diffraction of Synchrotron Radiation at the 8.41 keV Resonance of Thulium
For the first time nuclear Bragg diffraction of synchrotron radiation at the 8.41 keV resonance of 169Tm was observed. Time differential measurements were performed with the pure nuclear (424) reflection of a thulium iron garnet single crystal. The dynamical theory of Mossbauer optics is applied to evaluate the time spectra. The measurements reveal information about the hyperfine fields which has not been accessible before by conventional Mossbauer spectroscopy with polycrystalline samples.
Several studies for the LHC luminosity upgrade pointed out the need for low-beta quadrupoles with apertures larger than the present baseline (70 mm). In this paper we focus on the design issues of a 130 mm aperture quadrupole. We first consider the Nb-Ti option, presenting a magnetic design with the LHC dipole and quadrupole cables. We study the electromagnetic forces and we discuss the field quality constraints. For the Nb3Sn option, we sketch three designs, two based on the LARP 10 mm width cable, and one on a larger cable with the same strand. The issue of the stress induced by the e.m. forces, which is critical for the Nb3Sn, is discussed using both scaling laws and finite element models.