593 research outputs found
Development of LHC-IR model quadrupoles in the US
Insertion quadrupoles with large aperture and high gradient are required to achieve the luminosity upgrade goal of 1035 cm-2 s-1 at the Large Hadron Collider (LHC). In 2004, the US Department of Energy established the LHC Accelerator Research Program (LARP) to develop a technology base for the upgrade. The focus of the magnet program, which is a collaboration of three US laboratories, BNL, FNAL and LBNL, is on development of high gradient quadrupoles using NbSn in order to operate at high field and with sufficient temperature margin. Other program components address issues regarding magnet design, radiation-hard materials, long magnet scale-up, quench protection, fabrication techniques and conductor and cable R&D. This paper reports on the development od model quadrupoles and outlines the long-term goals of the program
Simulation of coupled-oscillator feedback
A new technique aiming at the stabilization of the strong head-tail effect, based on the use of feedback oscillators coupled to the TMC modes, was proposed and tested in LEP. In this report, the results obtained by simulating the collective motion of the bunch in the presence of the new feedback using the multi-particle tracking program TRISIM will be presented, in order to better understand the physics of the system and to evaluate, for some of the possible configurations, the hardware specifications which would be required to obtain a 25% increase of the maximum bunch current with respectc to the TMC threshold
Acoustic detection in superconducting magnets for performance characterization and diagnostics
Quench diagnostics in superconducting accelerator magnets is essential for
understanding performance limitations and improving magnet design.
Applicability of the conventional quench diagnostics methods such as voltage
taps or quench antennas is limited for long magnets or complex winding
geometries, and alternative approaches are desirable. Here, we discuss acoustic
sensing technique for detecting mechanical vibrations in superconducting
magnets. Using LARP high-field Nb3Sn quadrupole HQ01 [1], we show how acoustic
data is connected with voltage instabilities measured simultaneously in the
magnet windings during provoked extractions and current ramps to quench.
Instrumentation and data analysis techniques for acoustic sensing are reviewed.Comment: 5 pages, Contribution to WAMSDO 2013: Workshop on Accelerator Magnet,
Superconductor, Design and Optimization; 15 - 16 Jan 2013, CERN, Geneva,
Switzerlan
Magnetic Quench Antenna for MQXF Quadrupoles
High-field MQXF-series quadrupoles are presently under development by LARP and CERN for the upcoming LHC luminosity upgrade. Quench training and protection studies on MQXF prototypes require a capability to accurately localize quenches and measure their propagation velocity in the magnet coils. The voltage tap technique commonly used for such purposes is not a convenient option for the 4.2-m-long MQXF-A prototype, nor can it be implemented in the production model. We have developed and tested a modular inductive magnetic antenna for quench localization. The base element of our quench antenna is a round-shaped printed circuit board containing two orthogonal pairs of flat coils integrated with low-noise preamplifiers. The elements are aligned axially and spaced equidistantly in 8-element sections using a supporting rod structure. The sections are installed in the warm bore of the magnet, and can be stacked together to adapt for the magnet length. We discuss the design, operational characteristics and preliminary qualification of the antenna. Axial quench localization capability with an accuracy of better than 2 cm has been validated during training test campaign of the MQXF-S1 quadrupole
Star formation history in the SMC: the case of NGC602
Deep HST/ACS photometry of the young cluster NGC 602, located in the remote
low density "wing" of the Small Magellanic Cloud, reveals numerous pre-main
sequence stars as well as young stars on the main sequence. The resolved
stellar content thus provides a basis for studying the star formation history
into recent times and constraining several stellar population properties, such
as the present day mass function, the initial mass function and the binary
fraction. To better characterize the pre-main sequence population, we present a
new set of model stellar evolutionary tracks for this evolutionary phase with
metallicity appropriate for the Small Magellanic Cloud (Z = 0.004). We use a
stellar population synthesis code, which takes into account a full range of
stellar evolution phases to derive our best estimate for the star formation
history in the region by comparing observed and synthetic color-magnitude
diagrams. The derived present day mass function for NGC 602 is consistent with
that resulting from the synthetic diagrams. The star formation rate in the
region has increased with time on a scale of tens of Myr, reaching in the last 2.5 Myr, comparable to what is
found in Galactic OB associations. Star formation is most complete in the main
cluster but continues at moderate levels in the gas-rich periphery of the
nebula.Comment: 24 pages. Accepted for publication in A
- âŠ