Cryogenic Current Comparators for Larger Beamlines
The new version of a cryogenic current comparator with eXtended dimensions (CCC-XD) for the beam monitoring of charged particles, which is currently in the optimization cycle, is presented herein. The CCC-XD is designed for a nondestructive, highly sensitive monitoring of a few nA beam intensities for 150-mm beamline diameters at the Facility for Antiproton and Ion Research at GSI (Helmholtz Center of Heavy Ion Research). The new CCC comprises a combined superconducting pickup loop, a magnetic shield, and a ferrite core with superconducting quantum interference device based readout. Compared to the previous CCC currently running at CERN, the niobium shield exhibits enlarged geometric dimensions, which results in a more effective suppression of magnetic stray fields from the beamline environment. First results of laboratory measurements as well as simulations of the electrical behavior are presented in this paper. The CCC-XD system—in combination with a newly developed cryostat—will be ready for testing in the beamline of CRYRING at GSI in 2018.
Transmission operators for the non-overlapping Schwarz method for solving Helmholtz problems in rectangular cavities
In this paper we discuss diﬀerent transmission operators for the non-overlapping Schwarz method which are suited for solving the time-harmonic Helmholtz equation in cavities ( i.e. closed domains which do not feature an outgoing wave condition). Such problems are heavily impacted by back-propagating waves which are often neglected when devising optimized transmission operators for the Schwarz method. This work explores new operators taking into account those back-propagating waves and compares them with well-established operators neglecting these contributions. Notably, this paper focuses on the case of rectangular cavities, as the optimal (non-local) transmission operator can be easily determined. Nonetheless, deviations from this ideal geometry are considered as well. In particular, computations of the acoustic noise in a three-dimensional model of the helium vessel of a beamline cryostat with optimized Schwarz schemes are discussed. Those computations show a reduction of 46% in the iteration count, when comparing an operator optimized for cavities with those optimized for unbounded problems.
Parameters for low energy operation of CESR
We present a detailed design for operation of the Cornell Electron Storage Ring, CESR, in the energy range covering the /spl psi/ resonances and the Charm and Tau thresholds, as well as reaching to the upper Y resonances near 11 GeV. The addition of 18 m of super-ferric wiggler magnets will partially restore low energy beam emittance and damping times. Installation of superconducting quadrupoles in the interaction region and the addition of high performance superconducting RF cavities will enhance performance at all energies. Studies of optics, beam dynamics, wiggler and vacuum system performance, beam stability, and beam-beam effects confirm operation with a luminosity of 3/spl times/ 10/sup 32/ CM/sup -2/ sec/sup -1/ at 1.88 GeV.