Experimental Analysis and Modeling of the Electrical and Thermal Transients of the Diode-By-pass for the LHC- Magnet Protection at Cryogenic Temperatures

For the protection of the LHC superconducting lattice magnets cold bypass diodes will be installed inside the magnet cryostat, subjecting them to superfluid helium temperatures and radiation. During a magnet quench, the power generated in the diode must be dissipated in the adjacent heat sinks of copper that are part of the diode package. Results from endurance tests on the diode package are presented. A simple thermo-electric model has been developed to simulate the thermal and electrical transients in the diode package during the endurance pulse. Simulation results are in good agreement with the measured temperatures

Irradiation Tests at Cryogenic Temperatures on Diffusion Type Diodes for the LHC Superconducting Magnet Protection

Within the framework of the LHC magnet protection system, the irradiation hardness of high current by-pass diodes is subject to examination. The relocation of these diodes and recent calculations give rather low irradiation levels for the position of the diodes. This offers the possibility to replace the originally foreseen epitaxial type diodes by diffusion type diodes. Therefore, different types of 75mm diffusion diodes were submitted to an irradiation test program. One part of the experiments was performed in the Munich Research Reactor. Further irradiation tests were carried out in the northern fixed target area of the SPS accelerator at CERN

Protection of LHC superconducting corrector magnets

The protection of superconducting magnets in case of a quench has to be considered already in the design phase for the proton-proton collider LHC. The protection of main dipole and quadrupole magnets, based on cold diodes and quench heaters, is reported elsewhere [1]. In this paper the protection of other magnets is discussed. In the arcs some of the magnets are connected in series: sextupole magnets to correct the lattice chromaticity, small sextupole and decapole magnets to correct systematic field errors of the dipoles and octupole magnets. The magnets in the arcs to correct horizontal and vertical closed orbit excursions are powered individually. In the insertions other superconducting magnets will be used: quadrupole magnets for the low-beta insertions, orbit corrector magnets, etc. Some magnets will be constructed with sufficient copper stabilization to safely absorb the energy. For other magnets different methods of protection after the detection of a quench in the circuit are envisaged

Electrodynamic behaviour of the LHC superconducting magnet string during a discharge

A string of three dipole magnets and one quadrupole magnet, representing a half cell of the future LHC collider, has been assembled and tested at CERN. In order to avoid high temperatures in the magnets and high voltages between coils and ground in case of a quench, a reliable magnet protection system is necessary. The magnets are by-passed by protection diodes which are located in the cold mass. In case of a quench most of the stored magnetic energy is dissipated in the resistive parts of the magnets. Many natural and heater provoked quenches have been performed during the two experimental runs of the string at 1.9 K. This paper describes the electrodynamic behaviour during a fast discharge (i.e. after a quench) of the magnet string configuration. A simulation program was developed to evaluate parameters which cannot be directly measured, such as the current sharing between magnets and diodes, as well as the dissipated energy. The simulation program gives also the possibility for worst-case calculations, for example non-uniform magnet quench characteristics and protection heater delays

Quench propagation tests on the LHC superconducting magnet string

The installation and testing of a series connection of superconducting magnets (three 10 m long dipoles and one 3 m long quadrupole) has been a necessary step in the verification of the viability of the Large Hadron Collider at CERN. In the LHC machine, if one of the lattice dipoles or quadrupoles quenches, the current will be by-passed through cold diodes and the whole magnet chain will be de-excited by opening dump switches. In such a scenario it is very important to know whether the quench propagates from the initially quenching magnet to adjacent ones. A series of experiments have been performed with the LHC Test String powered at different current levels and at different de-excitation rates in order to understand possible mechanisms for such a propagation, and the time delays involved. Results of the tests and implications regarding the LHC machine operation are described in this paper

Long sequence of Quaternary Rocks in the Heidelberg Basin Depocentre

Die neue Forschungs-Kernbohrung aus Heidelberg wird beschrieben und gegliedert. Die Forschungs- und Bohraktivitäten im Heidelberger Becken (HDB) begannen im Jahr 2002; sie erschließen ein kontinentales Sedimentarchiv im Oberrheingraben (URG). Im HDB wird eine der längsten Sedimentabfolgen quartärer Sedimente in Europa erwartet, dank kontinuierlicher Subsidenz des Beckens in Verbindung mit kontinuierlichem Input von Sedimenten unterschiedlicher Herkunft. Das HDB befindet sich auf halber Strecke zwischen dem alpinen Einzugsgebiet des Rheins und seiner Mündung in die Nordsee. Eine kontinuierliche Sedimentation ist hier eher möglich als am Alpenrand mit seinen Schmelzwasser-Erosionsereignissen oder an der Küste mit ihren Meeresspiegelschwankungen. Dieser eher geringe Einfluss des Klimas hat zur Folge, dass die Tektonik eine umso größere Rolle bei der Steuerung der Sedimentation spielt. Die über 500 m mächtige quartäre Abfolge ist daher in erster Linie durch Tektonik kontrolliert, wobei Klimasignale ebenfalls erkannt werden können. Die hier vorgestellte Gliederung der Abfolge beruht auf Provenienz, Lithofazies und wechselnden Verhältnissen von Akkomodationsraum und Sedimentinput (a/s-ratio). Dazu kommen biostratigraphische Zeitmarken. Im skizzierten Sedimentations-Szenario dominieren fluviale Verhältnisse; dazwischen zwei lakustrine Abschnitte. Letztere sind verknüpft mit zunehmendem Akkomodationsraum, der in mindestens einer Zeitscheibe über die Grabenrandstörung hinweg sich bis in die Täler des Odenwalds erstreckt.researc

The Protection System for the Superconducting Elements of the Large Hadron Collider at CERN

The protection system for the superconducting elements of the Large Hadron Collider (LHC) [1] at the European Laboratory for Particle Physics (CERN), and its associated equipment are presented: quench detectors, cold diodes, quench heaters and related power supplies, extraction resistors and associated current breakers. Features such as radiation resistance, redundancy and required reliability are discussed

The LHC Prototype Full-Cell: Design Study

As a continuation of the experimental program carried-out with String 1, project management decided toward the end of 1995 to construct an LHC prototype Full-Cell, also known as String 2. The present document reports on the outcome of the one-year design effort by the community of specialists contributing to the LHC Prototype Full-Cell: it informs specialists on the boundary areas with other syste ms and conveys to the general public a description of the facility