Performance of the Main Dipole Magnet Circuits of the LHC during Commissioning

During hardware commissioning of the Large Hadron Collider (LHC), 8 main dipole circuits are tested at 1.9 K and up to their nominal current. Each dipole circuit contains 154 magnets of 15 m length, and has a total stored energy of up to 1.3 GJ. All magnets are wound from Nb-Ti superconducting Rutherford cables, and contain heaters to quickly force the transition to the normal conducting state in case of a quench, and hence reduce the hot spot temperature. In this paper the performance of the first three of these circuits is presented, focussing on quench detection, heater performance, operation of the cold bypass diodes, and magnet-to-magnet quench propagation. The results as measured on the entire circuits will be compared to the test results obtained during the reception tests of the individual magnets

Performance of the Superconducting Corrector Magnet Circuits during the Commissioning of the LHC

The LHC is a complex machine requiring more than 7400 superconducting corrector magnets distributed along a circumference of 26.7 km. These magnets are powered in 1446 different electrical circuits at currents ranging from 60 A up to 600 A. Among the corrector circuits the 600 A corrector magnets form the most diverse and differentiated group. All together, about 60000 high current connections had to be made. A fault in a circuit or one of the superconducting connections would have severe consequences for the accelerator operation. All magnets are wound from various types of Nb-Ti superconducting strands, and many contain parallel protection resistors to by-pass the current still flowing in the other magnets of the same circuit when they quench. In this paper the performance of these magnet circuits is presented, focussing on the quench behaviour of the magnets. Quench detection and the performance of the electrical interconnects will be dealt with. The results as measured on the entire circuits are compared to the test results obtained at the reception of the individual magnets

Inference on Water Content in the Mantle Transition Zone Near Subducted Slabs From Anisotropy Tomography

We examine the patterns of radial anisotropy in global tomography images of the mantle transition zone near subducted slabs in the western Pacific. Fast SV velocity anomalies are observed in this region, which are compatible with anisotropy due to lattice‐preferred orientation in wadsleyite. Using mineral physics reports of the dependency of the strength of radial anisotropy on water content in wadsleyite, we estimate the water content in the transition zone near subducted slabs from the tomography images. We find that fast SV anisotropy anomalies over ~1.5% observed beneath subduction zones in the western Pacific are compatible with a low water content (smaller than ~3,000 ppm H/SI), notably beneath the Tonga‐Kermadec trenches, the Philippines, and the Sumatra trench

Will we still see SEEs?

The actions during the first years of the R2E Mitigation Project allowed to drastically reducing the rate of Single Event Errors on radiation sensitive electronic equipment installed in the LHC underground areas. Shielding and relocation activities during LS1 will allow the resolution of the present issues concerning UJs of P1, 5 and 7 as well as the P8 cavern. The parallel development of radiation tolerant power converters will address the remaining concerns in the RRs. Radiation levels in areas where luminosity is the source are under control. The remaining open questions are related to the evolution of the beam-gas source term in the arc and in the dispersion suppressor and to the evolution of losses at the betatron and momentum insertion regions. 2012 operation will allow addressing these points, which will be used for a complete forecast of radiation levels and projected failures after the resume of operation in 2014/15

Systems overview: Power Converter and their Controls

In this paper, performance of power converters for the Run 2 of the Large Hadron Collider (LHC) is evaluated. This contribution focuses on the availability of different families of power converters, their evolution, analyses known failure modes and discusses mitigation of failures in the future. The last section describes new deployments and consolidation during the Long Shutdown 2 (LS2) and their impact on hardware commissioning for the Run 3

Radiation to Electronics: Reality or Fata Morgana?

A first year of successful LHC operation has passed reaching about 50pb-1 of integrated luminosity (1‰ of nominal, 5% of 1fb-1) and more than 1% of peak luminosity, as well as a successful ion run. It is thus time having a first look on the observed radiation levels around LHC critical areas and to compare them to available simulation results. In spite of the still very low integrated intensities and cumulative luminosities, this paper summarizes the failure rate predictions by evaluating the observed radiation levels and early electronics failures, as well as the additional results from 2010 CNRAD radiation tests. Upcoming possibly in early 2011, electron cloud and scrubbing issues and their impact on radiation levels are also briefly discussed. Based on this, updated predictions for 2011 operation and beyond will be deduced, on the base of the envisaged LHC intensity, energy and luminosity reach. Starting from these estimates, priorities for short-term improvements and beam tests are presented, as well as a brief overview of upcoming ‘Radiation To Electronics (R2E)’ driven mitigation actions