Discrete bipolar operational amplifiers were irradiated with neutrons in order to study the evolution of the short circuit currents. Also, this paper explores the effect of the reduction of this current in devices based on operational amplifiers.

The insertion regions located around the four interaction points of the Large Hadron Collider (LHC) are mainly composed of the low-triplets, the separation dipoles and their respective electrical feed-boxes (DFBX). The low-triplets are Nb-Ti superconductor quadrupole magnets, which operate at 215 T/m in superfluid helium at a temperature of 1.9 K. The commissioning and the first operation of these components have been performed. The thermo-mechanical behavior of the low-triplets and DFBX were studied. Cooling and control systems were tuned to optimize the cryogenic operation of the insertion regions. Hardware commissioning also permitted to test the system response. This paper summarizes the performance results and the lessons learned.

specific R&D programme in these domains.engineering challenge in applied superconductivity and cryogenicsf and has thus required a unprecedented luminosity of 1034 cm·2.s·l. Therefore, the LHC also represents a major it will provide proton-proton collisions with a center-of-mass energy of 14 TeV and at an below 2 K,3 to be installed in the 26.7 km circumference tunnel of the present LEP collider, ring of high-field, twin-aperture superconducting magnets2 operating in superfluid helium December 1994, will be the next major research facility in high-energy physics} Based on a operation, including response of the system to transients such as current ramp and discharge, industrial PLCs connected to an industrial supervision system. We report on performance in cooldown of the 109 kg cold mass. The system is fully instrumented, controlled by dedicated and auxiliary magnet circuits, as well as a 120 kW liquid nitrogen vaporizer for controlled also includes 15 kA, 1.6 kA, 500 A, 250 A and 50 A current lead pairs for powering of main installed capacities of 120 W @ 1.8 K and 10 g/s supercritical helium at 4.5 K. The system built and are operating a dedicated cryogenic system feeding the LHC Test String, with cryomagnets. Based on existing large-capacity cryogenic infrastructure, we have designed, providing refrigeration at the 1.9 K, 4.5-to-20 K, and 50·to-75 K levels to the LHC of the machine lattice. This also corresponds to the length of the elementary cooling loops testing and operation of a 50-m long superconducting magnet string, representing a half-cell A maj or milestone in the preparation of the Large Hadron Collider (LHC) proj ect is the ABSTRACT

The cryogenic system [1] for the Large Hadron Collider accelerator is presently in its final phase of commissioning at nominal operating conditions. The refrigeration capacity for the LHC is produced using eight large cryogenic plants and eight 1.8 K refrigeration units installed on five cryogenic islands. Machine cryogenic equipment is installed in a 26.7-km circumference ring deep underground tunnel and are maintained at their nominal operating conditions via a distribution system consisting of transfer lines, cold interconnection boxes at each cryogenic island and a cryogenic distribution line.The functional analysis of the whole system during all operating conditions was established and validated during the first sector commissioning in order to maximize the system availability. Analysis, operating modes, main failure scenarios, results and performance of the cryogenic system are presented. ABSTRACTThe cryogenic system [1] for the Large Hadron Collider accelerator is presently in its final phase of commissioning at nominal operating conditions. The refrigeration capacity for the LHC is produced using eight large cryogenic plants and eight 1.8 K refrigeration units installed on five cryogenic islands. Machine cryogenic equipment is installed in a 26.7-km circumference ring deep underground tunnel and are maintained at their nominal operating conditions via a distribution system consisting of transfer lines, cold interconnection boxes at each cryogenic island and a cryogenic distribution line.The functional analysis of the whole system during all operating conditions was established and validated during the first sector commissioning in order to maximize the system availability. Analysis, operating modes, main failure scenarios, results and performance of the cryogenic system are presented.

String 2 [1,2] is a full-size model of an LHC cell of the regular part of the arc. It is composed of six dipole magnets with their correctors, two short straight sections with their orbit and lattice corrector magnets, and a cryogenic distribution line running alongside the magnets. The commissioning of String 2 Phase 1, with one half-cell and the following quadrupole, has started in April 2001. As for String 1 [3], the facility was built to individually validate the LHC systems and to investigate their collective behaviour during normal operation (pumpdown, cool-down and powering) as well as during exceptional conditions such as quenches.String 2 is a stepping stone towards the commissioning of the first sector (one eight of LHC) planned for 2004. It is expected to yield precious information on the infrastructures, the installation, the tooling and the procedures for the assembly, the testing and the commissioning of the individual systems, as well as the global commissioning of the technical systems. This paper describes the procedures followed for the commissioning and details the preparation for the first cool-down and for the powering.