pre zaujimavost :-)
Marek Pavlu
pavlu@HWserver.cz
Neděle Březen 12 21:16:05 CET 2006
Zdravim,
Hezke, ale vždy me uchvati, když se někdo pocita se stupni Celsia, kdyz
Kelvin je proste jednodussi a kdyz reknu chaldim na 4K, tak 90% lidi vyskoci
a rekne: "No jasne, tekuty helium!" :)...
Ale to jen tak, tak me nesezerte:))))...
S pozdravem,
Marek Pavlu
// -----Original Message-----
// From: hw-list-bounces@list.hw.cz [mailto:hw-list-bounces@list.hw.cz] On
// Behalf Of Daniel Valuch
// Sent: Sunday, March 12, 2006 7:12 PM
// To: HWnews
// Subject: OT: pre zaujimavost :-)
//
// Po 3 tyzdnoch chladenia dosiahol 223 tonovy supravodivy magnet
// experimentu CMS teplotu 4K. Vnutorne pole by maloo byt pri nominalnom
// prude 20kA ca. 4 Tesla, vid clanok nizsie...
//
// obrazok:
// http://doc.cern.ch//archive/electronic/cern/others/PHO/photo-
// cms/magnet/magnet-2006-002.jpg
//
//
// The CMS solenoid is cold - and that's an understatement. At -269° C, the
// gigantic coil is chilling out at its operating temperature and is
// superconducting, an important milestone for the AT/ECR cryogenics group,
// the CMS coil collaboration (which includes CERN, ETH Zürich, Fermilab,
// INFN Genova, ITEP Moscow and Saclay) and the CMS collaboration at large.
//
// The coil consists of 14.5 tonnes of superconducting cables, which are
// embedded into 74 tonnes of pure aluminum and reinforced with 126 tonnes
// of high mechanical-strength aluminum alloy and 9 tonnes of insulation.
// Added together, that's a 223.5-tonne magnet. Cooling a component of such
// massive proportions is anything but easy.
//
// 'Superconductivity so far, despite it's great potential, has not yet
// made a mark in the commercial world because there is the complication of
// cooling down to liquid helium temperature, which is sophisticated,
// complicated and expensive,'said CMS Magnet and Integration Group Leader
// Domenico Campi. 'Nevertheless, for such a huge experiment like CMS, we
// cannot avoid the use of superconductors and thus of cryogenics. It is
// simply inconceivable to make a magnet of such power with a resistive
// conductor within acceptable parameters.'
//
// After completion, the coil was suspended from the vacuum tank using
// large titanium tie-bars, under the supervision of Bruno Levesy from
// Saclay. The coil's vacuum vessel was then welded closed by the firm DWE
// under the supervision of Hubert Gerwig, Andrea Gaddi and collaborators.
// The cool-down process began in early February. Cryogenics engineers had
// to carefully cool the magnet evenly and slowly to protect it from
// deformation and damage.
//
// The cool-down is achieved by circulating helium gas through a series of
// pipes surrounding the coil. In the first phase, the helium is steadily
// refrigerated to ever lower temperatures by the means of -196° C liquid
// nitrogen. Then, to achieve the lowest temperatures, the helium is
// injected into small turbines, cooled to liquefaction temperature and
// sent to fill up the coil circuits.
//
// After the three-week cooling campaign, the superconducting magnet is now
// resting at its operating temperature.
//
// The service and operation of the helium refrigeration plant is led by a
// team of two: project leader Goran Perinic and technical engineer Thierry
// Dupont. They are supported by a team of operators and their colleagues
// from the technical support sections led by Marco Pezzetti and Olivier
// Pirotte of the AT-ECR cryogenics group.
//
// The cool-down system is fully automated, but Perinic and Dupont have
// spent the last three weeks close to the plant, in the control room or in
// front of a computer at home, closely watching the slow refrigeration
// process and ready to intervene at the smallest sign of trouble. They've
// both worked on the project for six years.
//
// 'It is nice to add a tiny milestone to a technology whose roots are in
// Geneva,' Perinic said. 'It is just more than 128 years ago that Raoul
// Pictet managed to refrigerate a gas to a cryogenic temperature and to
// liquefy it for the first time at the University of Geneva. I doubt that
// he had imagined an application like this.'
//
// For the nominal current of 20,000 Amps, the solenoid is designed to
// reach a magnetic field of 4 Tesla, almost 100 000 times the Earth's
// magnetic field. It will have enough stored energy (2.7 GigaJoule) to
// melt 18 tonnes of gold. The superconducting coil will be kept at
// operating temperature for magnetic testing starting in May. It will be
// lowered into the CMS cavern, 90 metres underground, before the end of
// the year.
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