Warm magnetic measurements of MCBCs: comparison between the results obtained with the Quadrupole Industrial Magnetic Measurement and the Corrector Industrial Magnetic Measurement systems

MCBCs modules are first magnetically measured at Tesla using a second-generation Corrector Industrial Magnetic Measurement (CIMM). After assembly into the SSS quadrupoles, measurements are repeated at CERN using the Quadrupole Industrial Magnetic Measurement (QIMM) system. In this note, we compare the measurements provided by the two systems. In all the 18 cases examined, the correlation found is excellent. The consistency of the results obtained indicates that both systems are effective, that modules are correctly measured by the firm personnel and that magnetic characteristics of the modules do not change during their assembly in cold masses

Hall-velocity limited magnetoconductivity in a 2D Wigner solid

The magnetoconductivity s(B) of a classical 2D electron crystal on superfluid4He is non-linear. Experimentally we find a contribution to s(B) which at constant field, gives s(B)8J x, the current density, while at constant current, s(B) 8 1/B. In this region the Hall velocity ¿H slowly approaches the ripplon velocity ¿I at the first reciprocal lattice vector, due to strong electron-ripplon interactions with the helium. The magnetoconductivity decreases sharply for ¿H>¿I. Fluctuations in s(B) are seen above the melting temperature

Hall-velocity limited magnetoconductivity in a classical two-dimensional Wigner crystal

The magnetoconductivity sxx(B) of a classical two-dimensional electron crystal on superfluid 4He is nonlinear. Experimentally, we find a contribution to sxx(B) which, at constant field B, gives sxx(B)¿Jx, the current density, while at constant current, sxx(B)¿1/B. For increasing Jx, the Hall velocity ¿H slowly approaches the ripplon velocity ¿l at the first reciprocal lattice vector, due to strong electron-ripplon interactions with the helium. The magnetoconductivity then decreases sharply for ¿H>¿1

Hall-velocity limited magnetoconductivity in a classical two-dimensional Wigner crystal

The magnetoconductivity sxx(B) of a classical two-dimensional electron crystal on superfluid 4He is nonlinear. Experimentally, we find a contribution to sxx(B) which, at constant field B, gives sxx(B)¿Jx, the current density, while at constant current, sxx(B)¿1/B. For increasing Jx, the Hall velocity ¿H slowly approaches the ripplon velocity ¿l at the first reciprocal lattice vector, due to strong electron-ripplon interactions with the helium. The magnetoconductivity then decreases sharply for ¿H>¿1

Magnetotransport of 2D electrons on liquid helium in the fluid and solid phases

The magnetoconductivity s(B) in the two-dimensional (2D) nondegenerate electron fluid and 2D solid has been analyzed theoretically and investigated experimentally, from 60 mK to 1.3 K in magnetic fieldsB up to 8 Tesla. In the fluid phase, s(B) is described by the Drude model in weak to moderately strong classical fields, including the range ßB»1. At higher fields (depending on the density s(B) is nonmonotonous and diplays a minimum. This behavior is due to many-electron effects, which can be described in terms of cyclotron orbit diffusion controlled by an internal fluctuational electric field. The squared internal field derived from experiments is in good agreement with computer simulations. In the solid phase electron transport becomes strongly non-linear even for weak driving voltagesV 0. Experimentally we determine, from the losses, the effective AC Corbino conductivity at a frequencyf. We find that s(BafV 0/B forV 0 below some threshold voltageV c . In this region the Hall velocity ¿ H approaches the ripplon phase velocityv 1=w(G 1)/G 1 at the first reciprocal lattice vectorG 1 of the electron solid. We suggest that this behaviour is due to to a resonant drag force from the Bragg-Cerenkov radiation of coherent ripplons by the moving crystal

Field Quality and Hysteresis of LHC Superconducting Corrector Magnets

The Large Hadron Collider (LHC) will use some 7600 superconducting corrector magnets. The magnetic field quality is measured at room temperature by 12 magnetic measurement benches employed by the corrector manufacturers. CERN performs magnetic measurements at 4.2 K and at 1.9 K on a small subset of corrector magnets. The paper discusses the correlation between the warm and cold field measurements. The field quality is compared to the target field quality for LHC. Many corrector circuits will be powered in a way which cannot be predicted before LHC will start operation and which even then may change between physics runs. The measured magnetic hysteresis and its influence on possible setting errors during operation is discussed, in particular for the orbit correctors and the tuning/trim quadrupole magnet circuits