General view of the solenoid
CMS is one of the detectors of the four experiments (besides Alice, Atlas and LHCb) which will be installed at CERN on the LHC proton collider, in Geneva.
To determine the particle momentum, a magnetic field is used: the more energetic the particule, the stronger the magnetic field. In CMS, the magnetic field is produced by an electro-magnet, which is a superconducting coil of 7 m in diameter, 12.50 m in length, cooled at liquid helium temperature (-269°C). The coil is located inside a vacuum tank, which provides the thermal insulation. All this whole is located inside the iron yoke, of a total weight of 12500 t, which canalizes the magnetic flux produced by the coil and minimizes the fringing field.
Dapnia, which has been at the origin of the conception of the superconducting solenoid, the largest ever built, has also been in charge of the study and follow-up of its assembly, with the creation of a specific tooling. The rather complex assembly has been performed without major problems. This success is also due to the CERN assembly team and to the industrial companies which have delivered various parts and have been involved in the final assembly.
Localization:
The magnet is located at Point 5 of the LHC collider (at CERN, in Geneva)
Collaborations:
Main participants to the solenoid:
Countries:
- Italy
- France
- Switzerland
- USA
Laboratories:
- Cern : general coordination for the CMS collaboration, external cryogenics, electrical power circuit, instrumentation
- CEA-Dapnia (Saclay) : general study of the cold mass, assembly study and coordination, detailled study and industrial follow-up of specific components, tests of critical components, participation to the global tests
- ETH Zurich : conductors
- INFN Genova : winding
- University of Wisconsin: yoke
French collaborations to the CMS magnet :
- Air Liquide (refrigerator)
- Techmeta (reinforcement of conductor)
- SDMS (proximity cryogenics)
- Lenoir-Elec (current breakers)
- Franc-Comptoise Industrie (yoke assembly at CERN)
- Velan (magnetic valve)
Assembly of the five coil modules in February 2005
Scientific approach
Specificities:
Dapnia contribution
- Detailled study and industrial follow-up of specific components (suspension tie-rods, thermal shields, internal and proximity cryogenics, current leads)
- Tests of critical components (prototypes of electrical junctions, current leads, suspension tie-rods, proximity cryogenics)
- Coordination of cold mass assembly
- Participation to the tests in the surface hall and in the underground cavern
The Saclay team before the start of the cooldown in February 2005
Progress and perspectives
- December 1998: Coil Engineering Design Report
- Beginning 2000: Construction of the first parts of the cold mass
- From May 2000: Arrival of the first parts yoke at CERN. This marks the begining of the detector assembly in the surface hall
- Beginning 2005: arrival at CERN of the 5th and last coil module
- Summer 2005: The cold mass assembly is introduced in the yoke
- February 2006: Magnet cooldown to 4 K
- Mid-July 2006: Start of the electrical tests. The first cosmic rays are detected
Perspectives:
- During 2007: Lowering and installation in the underground cavern of all the parts of the magnet, as well as of other parts of the detector
- End 2007: Cooldown in the underground cavern, electrical tests at low current
-1st quarter 2008: Powering to the nominal field in the underground cavern
Scientific and technical assesment All the tasks under Dapnia responsability have been done in a satisfactory technical way, and in phase with the general magnet planning.
Outstanding facts
- Swivelling of the CMS vacuum tank (July 2002)
- End 2005: The cold mass assembly is inserted in the yoke
Contact
Artistic view of the solenoid
last update : 03-16 00:00:00-2010 (2261)
The ultimate constituents of matter 
Physics at the LHC
The Electronics, Detectors and Computing Division The Particle Physics Division Accelerators, Cryogenics and Magnetism Department (SACM) The Systems Engineering Division
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Since 1996 Dapnia has been responsible for the general design of the solenoid for the CMS experiment of the Large Hadron Collider (LHC) project, as part of a collaboration agreement with CERN. Within Dapnia, SACM acts as the pilot division for the project in regard to the magnetic and thermal design of the magnet, supervision of assembly and surface testing at CERN. It is helped by the SIS (Service d’ingénierie des systèmes) as regards the mechanical design and instrumentation aspects, as well as industrial production monitoring. Apart from its size, what is particular to this solenoid are the conductor reinforced by an aluminium alloy and the design of an internal ... More » |
