Development of the Readout Electronics for the Beam Loss Monitors of the LHC

The Large Hadron Collider (LHC) of the European Laboratory for Particle Physics will be the largest particle accelerator in the world. It requires a large number of installations for its operation. One of these installations are the beam loss monitors which measure the particle losses. If these losses exceed a certain level, the beam must be extracted, otherwise the superconducting magnets could be damaged. For this reason, ionization chambers are installed outside the cryostat to transform the losses into an electric current. A wide dynamic range front end was developed to measure this current. The circuit consists of a current-to-frequency converter that works on the principle of balanced charge. Its output frequency is evaluated by counters and the data is serially transmitted from the tunnel to the surface, where the final data processing is performed. The data transmission suffers from the long cabling distance of up to 2 km. Using Manchester Code and line equalizers enables a data rate of 2 Mbit/s over a common twisted pair cable. This transmission problems lead to a detailed analysis of transmission lines in the frequency and time domain

Elongational viscosity of rubber compounds and improving corresponding models

A B S T R A C T A R T I C L E I N F O As good as the topic of elongational viscosity is covered by scientific work on thermoplastics, as little research has been done on rubber compounds. This paper focuses on the elongational properties of an SBR rubber compound using different measurement methods. First measurements were made on a Sentmanat Extensional Rheometer (SER). This method is limited to elongation rates up to 20 s -1 . Higher elongation rates (up to 300 s -1 ) can be covered with a High Pressure Capillary Rheometer (HPCR), where Cogswell´s and Binding´s models were used. The simplifications of these methods were precisely depicted and their influence on the results was evaluated. For further improvement of Cogswell´s method a previously unreleased method by Obendrauf was applied using two different laws for the approximation of shear viscosity which is essential for the calculation of elongational viscosity. The calculated elongational viscosities could be ascertained using an orifice die for the refinement of the inlet pressure measurements. Finally, the elongational viscosity curves from the HPCR were compared with the SER-viscosity data and a good correlation could be found. This suggests that elongational viscosity ascertained from converging flow measurements is comparable to SER measurements, which would be of great practical use hence HPCRs are available at many laboratories

The Beam Loss Detection System of the LHC Ring

At the Large Hadron Collider (LHC) a beam loss system will be installed in the arc, dispersion suppressor and the straight regions for a continuous surveillance of particle losses. These beam particles deposit their energy partially in the super-conducting coils leading to temperature increase, possible magnet quenches and damages. The primary and secondary halo of the beam is absorbed by the collimation system. The tertiary halo will be lost at aperture limits in the ring. Its loss distribution along the magnets has been studies. At the positions, where most of the beam losses are expected, simulations of the particle fluences outside the cryostat and induced by lost protons at the aperture have been performed with the Monte Carlo Code Geant 3.2.1. This allows determining the most suitable positions of the detectors, the needed number of monitors and the impact on the dynamic range of the detectors. The design of the beam loss monitor system is presented that meet the required sensitivity, dynamic range and time resolution

LHC beam loss monitor system design

At the LHC a beam loss system will be installed for continuous surveillance of particle losses. The system is designed to prevent hardware destructions, to avoid magnet coil quenches and to provide quantitative loss values. Over 3000 ionization chambers will be used to initiate the beam abort if the loss rates exceed the quench levels. The time and beam energy dependent quench levels require the acquisition of chamber currents in the range from 50 pA to 0.5 mA and an update of the values every 89 mu s. The acquisition and control electronics will consist of a front end electronics near (< 400 m) to the ionization chambers and a threshold controller in the surface buildings. The front end will include a charge balance converter, a counter and multiplexer part. The charge balance converter is most suitable to cover the large dynamic range. The introduced error is smaller than few % in the required dynamic range. Six channels will be transmitted over one cable of up to 3 km length. The threshold controller will issue warnings and dump signals depending on the beam energy and the loss durations. (7 refs)

Das Limb Preservation System: Evaluierung des Implantatüberlebens in Hüfte und Knie im onkologischen und nicht-onkologischen Setting

J. Appleton's Upright Paratrooper photographed Daventry Fair 3 May 1986. UP4