A System for Series Magnetic Measurements of the LHC Main Quadrupoles

More than 400 twin aperture lattice quadrupoles are needed for the Large Hadron Collider (LHC) which is under construction at CERN. The main quadrupole is assembled with correction magnets in a common cryostat called the Short Straight Section (SSS). We plan to measure all SSS's in cold conditions with an unprecedented accuracy: integrated gradient of the field within 150 ppm, harmonics in a range of 1 to 5 ppm, magnetic axis of all elements within 0.1 mm and their field direction within 0.2 mrad. In this paper we describe the automatic measurement system that we have designed, built and calibrated. Based on the results obtained on the two first prototypes of the SSS's (SSS3 and SSS4) we show that this system meets all above requirements

A Machian Model of Dark Energy

Einstein believed that Mach's principle should play a major role in finding a meaningful spacetime geometry, though it was discovered later that his field equations gave some solutions which were not Machian. It is shown, in this essay, that the kinematical $\Lambda$ models, which are invoked to solve the cosmological constant problem, are in fact consistent with Mach's ideas. One particular model in this category is described which results from the microstructure of spacetime and seems to explain the current observations successfully and also has some benefits over the conventional models. This forces one to think whether the Mach's ideas and the cosmological constant are interrelated in some way.Comment: Received an Honorable mention in the Essay Contest-2002 sponsored by the Gravity Research Foundation; A paragraph added on how the model can explain the CMB anisotropy observations; To appear in the Classical and Quantum Gravit

A positron source using an axially oriented crystal associated to a granular amorphous converter

Submitted to Chinese Physics CA non conventional positron source using the intense γ radiation from an axially oriented monocrystal which materialize into e+e- pairs in a granular amorphous converter is described. The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its axis is reported. The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream, is also reported. Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density. Substituting a granular target made of small spheres to the usual compact one, makes easier the energy dissipation. The deposited energy and corresponding heating are analyzed and solutions for cooling are proposed. The configurations studied here for this kind of positron source allow its consideration for unpolarized positrons for the ILC

Towards the conversion of carbohydrate biomass feedstocks to biofuels via hydroxylmethylfurfural

This review appraises the chemical conversion processes recently reported for the production of hydroxylmethylfurfural (HMF), a key biorefining intermediate, from carbohydrate biomass feedstocks. Catalytic sites or groups required for the efficient and selective conversion of hexose substrates to HMF are examined. The principle of concerted catalysis was used to rationalise the dehydration of fructose and glucose to HMF in non-aqueous media. A survey of reported reaction routes to diesel-range biofuel intermediates from HMF or furfural is presented and self-condensation reaction routes for linking two or more HMF and furfural units together toward obtaining kerosene and diesel-range biofuel intermediates are highlighted. The reaction routes include: benzoin condensation, condensation of furfuryl alcohols, hetero Diels–Alder reaction and ketonisation reaction. These reaction routes are yet to be exploited despite their potential for obtaining kerosene and diesel-range biofuel intermediates exclusively from furfural or hydroxylmethylfurfural

Twin Rotating Coils for Cold Magnetic Measurements of 15 m Long LHC Dipoles

We describe here a new harmonic coil system for the field measurement of the superconducting, twin aperture LHC dipoles and the associated corrector magnets. Besides field measurements the system can be used as an antenna to localize the quench origin. The main component is a 16 m long rotating shaft, made up of 13 ceramic segments, each carrying two tangential coils plus a central radial coil, all working in parallel. The segments are connected with flexible Ti-alloy bellows, allowing the piecewise straight shaft to follow the curvature of the dipole while maintaining high torsional rigidity. At each interconnection the structure is supported by rollers and ball bearings, necessary for the axial movement for installation and for the rotation of the coil during measurement. Two such shafts are simultaneously driven by a twin-rotating unit, thus measuring both apertures of a dipole at the same time. This arrangement allows very short measurement times (typically 10 s) and is essential to perform cold magnetic measurements of all dipoles. The coil surface and direction are calibrated using a reference dipole. In this paper we describe the twin rotating coil system and its calibration facility, and we give the typical resolution and accuracy achieved with the first commissioned unit

Stepwise quantum decay of self-localized solitons

The two-phonon decay of self-localized soliton in a one-dimensional monatomic anharmonic lattice caused by cubic anharmonicity is considered. It is shown that the decay takes place with emission of phonon bursts. The average rate of emission of phonons is of the order of vibrational quantum per vibrational period. Characteristic time of the relaxation is determined by the quantum anharmonicity parameter; this time may vary from a few (quantum lattices, large anharmonicity) to thousands (ordinary lattices, small anharmonicity) of vibrational periods.Comment: 6 pages, 3 figure

Broad-band properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

We report about recent updates of broad-band properties of radio-loud narrow-line Seyfert 1 galaxies.Comment: 5 pages, no figures. Proceedings 28th Texas Symposium on Relativistic Astrophysics, Geneva (Switzerland), 13-18 December 201

Effects of dark sectors' mutual interaction on the growth of structures

We present a general formalism to study the growth of dark matter perturbations when dark energy perturbations and interactions between dark sectors are present. We show that dynamical stability of the growth of structure depends on the type of coupling between dark sectors. By taking the appropriate coupling to ensure the stable growth of structure, we observe that the effect of the dark sectors' interaction overwhelms that of dark energy perturbation on the growth function of dark matter perturbation. Due to the influence of the interaction, the growth index can differ from the value without interaction by an amount within the observational sensibility, which provides a possibility to disclose the interaction between dark sectors through future observations on the growth of large structure.Comment: 15 pages, 4 figures, revised version, to appear in JCA