pre zaujimavost :-)

[Marek Pavlu]

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. 
//  _______________________________________________ 
//  HW-list mailing list  -  sponsored by www.HW.cz 
//  Hw-list@list.hw.cz 
//  http://list.hw.cz/mailman/listinfo/hw-list 



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