The Accelerated Procedure for Electrical Work (TPA)

The accelerated procedure for electrical work [in French: Travaux électriques selon Procédure Accélérée (TPA)] was introduced in October 1996. It allows the contractor to carry out minor electrical installation jobs (about 350 a year) independently. The special features of the TPA are that the number of hours to be worked is limited to 16 and the cost to less than 1000 CHF. This procedure has substantial advantages for both the requesters and ST division. Firstly, the requester benefits from direct contact with the contractor, prompt action and simplified invoicing. In addition, ST division, relieved of ordinary minor work, can concentrate on larger-scale projects and can take advantage of a simplified system of administration. The author sets out the course of the procedure, its advantages and drawbacks, the statistics and the results of a satisfaction questionnaire. This procedure could be adapted and extended to other operations linked to future contracts

Cooling process of the LHC energy extraction resistors

The energy stored in all the LHC dipoles, about 11 GJ, can potentially cause severe damage to the magnets, bus bars and current leads. In order to protect the superconducting elements after a resistive transition, the energy is dissipated into dump resistors switched in series with the magnet chains. This paper describes the cooling process of the resistors and explains the choice process for the main components of the cooling equipment

Results from Commissioning of the Energy Extraction Facilities of the LHC Machine

The risk of damage to the superconducting magnets, bus bars and current leads of the LHC machine in case of a resistive transition (quench) is being minimized by adequate protection. The protection is based on early quench detection, bypassing the quenching magnets by cold diodes, energy density dilution in the quenching magnets using heaters and, eventually, energy extraction. For two hundred and twenty-six LHC circuits (600 A and 13 kA) extraction of the stored magnetic energy to external dump resistors was required. All these systems are now installed in the machine and the final hardware commissioning has been undertaken. After a short description of the topology and definitive features, layouts and parameters of these systems the paper will focus on the results from their successful commissioning and an analysis of the system performance

Design and operational aspects of a bi-polar semi-conductor switch as possible candidate for replacement of electro-mechanical switchgear in energy extraction systems for the LHC corrector magnet circuits

More than 600 DC opening switches assure the role of energy extraction in the powering circuits of the bipolar, superconducting beam corrector magnet chains in the LHC collider at CERN. Although the operational experience from several years of extensive use has proven the high reliability of the electro-mechanical breakers, their relatively high need for regular, preventive maintenance and subtle adjustments as well as their limited lifetime has stimulated the interest in considering alternative solutions. The paper presents the development and operational performance details of a prototype, 1 kA, bipolar extraction switch based on back-to-back IGCT's with blocking diodes. The specific features related to the zero-current passing are described and quantified. The associated difficulties for the controls of a powering system to assure the necessary current stability at the transitory points are analyzed, considering the requirements from the beam dynamics. Parameters of various solutions are described in details

Arc detector system for extraction switches in LHC CERN

The opening switches, which will be used in case of quenches or other failures in CERN’s future LHC collider to extract the large amounts of energy stored in the magnetic field of the superconducting chains of main dipoles (8 chains with 1350 MJ each) and main quadrupoles (16 chains with about 24 MJ each) consist of an array of series/parallel connected, electro-mechanical D.C. breakers, specifically designed for this particular application. During the opening process the magnet excitation current is transferred from the cluster of breakers to extraction resistors for rapid de-excitation of the magnet chain. An arc detector has been developed in order to facilitate the determination of the need for maintenance interventions on the switches. The paper describes the arc detector and highlight results from operation of the detector with a LHC pilot extraction facility

Posttranslational processing of endogenous and of baculovirus-expressed human gastrin-releasing peptide precursor.

The 27-amino-acid gastrin-releasing peptide (GRP1-27) is a neuropeptide and growth factor that is synthesized by various neural and neuroendocrine cells. The major pro-GRP hormone (isoform I) contains both GRP1-27 and a novel C-terminal extension peptide termed pro-GRP31-125. In order to define potentially active neuropeptides that could be generated from this novel protein domain, we analyzed the posttranslational processing of endogenous human pro-GRP1-125 in a small-cell lung cancer cell line. Because such studies are much easier in an overexpression system, we investigated at the same time the posttranslational processing of baculovirus-expressed human pro-GRP1-125 in an insect ovary cell line. In the small-cell lung cancer cell line, GRP1-27 was cleaved as expected from the endogenous prohormone at a pair of basic amino acids (29 and 30) and alpha-amidated at its C-terminal methionine; however, a number of novel peptides were generated by additional cleavages in the pro-GRP31-125 domain. In the insect ovary cell line, GRP1-27 was cleaved from the expressed prohormone by a different mechanism, as were a number of other peptides that appeared to be similar in size to those produced by the human neuroendocrine tumor cell line. These data show for the first time that an insect ovary cell line that is widely used to overexpress proteins can process a human neuropeptide precursor. They also reveal the existence of novel pro-GRP-derived peptides that are candidates for biologically active ligands

A high-current, IGBT-based static switch for energy extraction in superconducting power circuits: Concept, design and production of a 30 kA monopolar and a 1 kA bipolar fast opening switches

The steadily increasing demand from the particle physics community for higher beam energies and higher integrated beam luminosity has reinforced the necessity for new accelerator equipment, frequently breaking with conventional technologies. One of the fields where new and innovative engineering is required and where interesting developments are ongoing, is the domain of fast switching of high DC currents, such as it is required for rapid and safe extraction of large quantities of energy stored in superconducting magnet circuits. The 30 kA opening switch, developed at CERN within the International High-Luminosity Large Hadron Collider project (HL-LHC), is an example of the innovative engineering required to satisfy the demands related to circuit protection. The paper presents the integration into an IGBT-based static DC switch of a variety of different inspired design principles, such as a triple-busbar layout for optimized circuit symmetry, the extensive use of laminated, water-cooled busbars and an optimized capacitive compensation of the parasitic inductances as well as a complete analysis of the thermal budget management of the individual IGBT modules. The paper will also briefly present the design of a compact modular, bipolar and redundant 1 kA IGBT-based switch assembly which features an all-laminated busbar concept