Modeling and Computer Simulation of the Pulsed Powering of Mechanical D.C. Circuit Breakers for the CERN/LHC Superconducting Magnet Energy Extraction System

This article presents the results of modeling and computer simulation of non-linear devices such as the Electromagnetic Driver of a D.C. Circuit Breaker. The mechanical and electromagnetic parts of the Driver are represented as equivalent electrical circuits and all basic processes of the Driver's magnetic circuit are calculated

Energy Extraction in the CERN Large Hadron Collider: a Project Overview

In case of a resistive transition (quench), fast and reliable extraction of the magnetic energy, stored in the superconducting coils of the electromagnets of a particle collider, represents an important part of its magnet protection system. In general, the quench detectors, the quench heaters and the cold by-pass diodes across each magnet, together with the energy extraction facilities provide the required protection of the quenching superconductors against damage due to local energy dissipation. In CERN's LHC machine the energy stored in each of its eight superconducting dipole chains exceeds 1300 MJ. Following an opening of the extraction switches this energy will be absorbed in large extraction resistors located in the underground collider tunnel or adjacent galleries, during the exponential current decay. Also the sixteen, 13 kA quadrupole chains (QF, QD) and more than one hundred and fifty, 600 A circuits of the corrector magnets will be equipped with extraction systems. The extraction switch-gear is based on specially designed, mechanical high-speed DC breakers, in certain cases combined with capacitive snubber circuits for arc suppression. This paper is an overview of the complete project with emphasis on the arguments and motivation for the choice of equipment and methods. It presents the basic properties of the principal components, the operational aspects and the present state of advancement. Finally, it highlights the implications of the extraction process on other systems of the LHC collider

Measurement of J/ψ→γηcJ/\psi\to\gamma\eta_{\rm c} decay rate and ηc\eta_{\rm c} parameters at KEDR

Using the inclusive photon spectrum based on a data sample collected at the $J/\psi$ peak with the KEDR detector at the VEPP-4M $e^+e^-$ collider, we measured the rate of the radiative decay $J/\psi\to\gamma\eta_{\rm c}$ as well as $\eta_{\rm c}$ mass and width. Taking into account an asymmetric photon lineshape we obtained $\Gamma^0_{\gamma\eta_{\rm c}}=2.98\pm0.18 \phantom{|}^{+0.15}_{-0.33}$ keV, $M_{\eta_{\rm c}} = 2983.5 \pm 1.4 \phantom{|}^{+1.6}_{-3.6}$ MeV/$c^2$, $\Gamma_{\eta_{\rm c}} = 27.2 \pm 3.1 \phantom{|}^{+5.4}_{-2.6}$ MeV.Comment: 6 pages, 3 figure

Measurement of B(J/psi->eta_c gamma) at KEDR

We present a study of the inclusive photon spectrum from 6.3 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of the radiative decay J/psi -> eta_c gamma, eta_c width and mass. Taking into account an asymmetric photon line shape we obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4 +- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.Comment: 6 pages, 1 figure. To be published in the proceedings of the 4th International Workshop on Charm Physics (Charm2010), October 21-24, 2010, IHEP, Beijin

Measurement of J/psi to eta_c gamma at KEDR

We present a study of the inclusive photon spectra from 5.9 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV, G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009, Beijing, Chin

Measurement of Γee(J/ψ)\Gamma_{ee}(J/\psi) with KEDR detector

The product of the electronic width of the $J/\psi$ meson and the branching fractions of its decay to hadrons and electrons has been measured using the KEDR detector at the VEPP-4M $e^+e^-$ collider. The obtained values are: $\Gamma_{ee}(J/\psi) = 5.550 \pm 0.056 \pm 0.089 \, \text{keV},$ $\Gamma_{ee}(J/\psi) \cdot \mathcal{B}_\text{hadrons}(J/\psi) = 4.884 \pm 0.048 \pm 0.078 \, \text{keV},$ $\Gamma_{ee}(J/\psi) \cdot \mathcal{B}_{ee}(J/\psi) = 0.3331 \pm 0.0066 \pm 0.0040 \, \text{keV}.$ The uncertainties shown are statistical and systematic, respectively. Using the result presented and the world-average value of the electronic branching fraction, one obtains the total width of the $J/\psi$ meson: $\Gamma = 92.94 \pm 1.83 \, \text{keV}.$ These results are consistent with the previous experiments.Comment: 19 pages, 13 figure

Status of “ZELENOGRAD” storage ring

In 2000, after a long break, works on creation of a technological storage ring complex (TSC) have been renewed in ZELENOGRAD. TSC was developed at Budker INP of Siberian Branch of Russian Academy of Science. It consists of a linear accelerator on the electron energy up to 80 MeV, a small storage ring on the energy 450 MeV, a main storage ring on the energy 2 GeV and two electron transfer lines (TL-1 and TL-2). The Main Ring (MR) with energy of electrons 2 GeV is the dedicated synchrotron radiation source intended for the decision of problem of submicron technologies and realization of various researches in a range of wavelengths of 0.2…2000 Å. Linac was mounted and put into operation during 2000-2002. The circulating electron current was received in small storage ring in 2005. Currently, the assembling of TL-2 is being completed. The inspection of the main storage ring equipment made before is carried out. Besides, a modification of all control and power supply system MR is done and a modern electronic element base will be introduced. The status and the nearest planes concerning TSC main storage ring are described.У 2000 р. після довгої перерви відновилися роботи по створенню технологічного накопичувального комплексу - ТНК, у м. Зеленограді. ТНК був розроблений в ІЯФ СВ РАН. Він складається з лінійного прискорювача (ЛП) на енергію до 80 МеВ, малого накопичувача (МН) на енергію 450 МеВ, основного великого накопичувача (ВН) на енергію 2,2 ГеВ і двох каналів перепуску (ЕОК-1 й ЕОК-2). Накопичувач електронів з енергією електронів Е = 2,2 ГеВ є спеціалізованим джерелом СВ, призначеним для вирішення проблем субмікронних технологій, а також для проведення досліджень у проміжку довжин хвиль 0.2…2000 Å. Лінійний прискорювач був змонтований і запущений протягом 2000-2002 р. У 2005 р. був отриманий циркулюючий струм електронів у Малому накопичувачі. У цей час закінчується монтаж ЕОК-2. Проводиться ревізія устаткування ВН. Крім того, проводиться модернізація всіх систем керування і живлення і перехід на сучасну елементну базу. Описується статус ТНК і найближчі плани по монтажу і запуску ВН.В 2000 г. после долгого перерыва возобновились работы по созданию технологического накопительного комплекса – ТНК, в г. Зеленограде. ТНК был разработан в ИЯФ СО РАН. Он состоит из линейного ускорителя (ЛУ) на энергию до 80 МэВ, Малого накопителя (МН) на энергию 450 МэВ, основного большого накопителя (БН) на энергию 2.2 ГэВ и двух каналов перепуска (ЭОК-1 и ЭОК-2). Накопитель электронов с энергией электронов Е = 2.2 ГэВ является специализированным источником СИ, предназначенным для решения проблем субмикронных технологий, а также для проведения исследований в области длин волн 0.2…2000 ангстрем. Линейный ускоритель был смонтирован и запущен в течение 2000-2002 г. В 2005 г. был получен циркулирующий ток электронов в Малом накопителе. В настоящее время заканчивается монтаж ЭОК-2. Проводится ревизия оборудования БН. Кроме того, проводится модернизация всех систем управления и питания и переход на современную элементную базу. Описывается статус ТНК и ближайшие планы по монтажу и запуску БН

The CERN/LHC energy extraction switches and their arc detector system

To extract the large amount of energy stored in the magnetic field of the LHC superconducting dipoles (8 chains with 1350 MJ each) and quadrupoles (16 chains with about 24 MJ each), opening switches will be used. The switches consist of an array of electromechanical D.C. breakers, specifically designed for this particular application. The opening process transfers the magnet excitation current from the array of eight breakers to the extraction resistors, rapidly deexciting the magnet chain. The arcing behavior in breakers of the array has been studied. In order to facilitate the maintenance of the switches an arc detector has been developed. This paper describes the design of the extraction switches and presents the test results, obtained at the LHC pilot extraction facility