3/3/20111Insulation--FermiLab Failure at CERNOn Tuesday, March 27,2007 there was a serious failure in a high-pressure test at CERN of a Fermilab-built “inner-triplet” series of three quadrupole magnets in the tunnel of the Large Hadron Collider. The magnets focus the particle beams prior to collision at each of four interaction points around the accelerator. Preliminary indications are that structures supporting the inner “cold mass” of one of the three magnets within its enclosing cryostat broke at a pressure of 20 atmospheres, in response to asymmetric forces. Failure to account for the asymmetric loads in the engineering design of the magnet appears to be a likely cause. The test configuration corresponds to conditions that occur during a magnet quench, when a superconducting magnet suddenly “goes normal,” releasing large amounts of energy. Inner-Triplet Quadrupole MagnetInner Support StructureCross Section at One Support PointFermi-Lab/CERN Follow-upFrom The Sunday Times April 8, 2007Big Bang at the atomic lab after scientists get their maths wrongJonathan Leake, Science EditorA £2 billion project to answer some of the biggest mysteries of the universe has been delayed by months after scientists building it made basic errors in their mathematical calculations. The mistakes led to an explosion deep in the tunnel at the Cern particle accelerator complex near Geneva in Switzerland. It lifted a 20-ton magnet off its mountings, filling a tunnel with helium gas and forcing an evacuation. It means that 24 magnets located all around the 17-mile circular accelerator must now be stripped down and repaired or upgraded. The failure is a huge embarrassment for Fermilab, the American national physics laboratory that built the magnets and the anchor system that secured them to the machine. It appears Fermilab made elementary mistakes in the design of the magnets and their anchors that made them insecure once the system was operational. Dr Lyn Evans, who leads the accelerator construction project at CERN, the European organization for nuclear research, said the explosion had been potentially very dangerous.“There was a hell of a bang, the tunnel housing the machine filled with helium and dust and we had to call in the fire brigade to evacuate the place,” he said. “The people working on the test were frightened to death but they were all in a safe place so no-one was hurt.” An investigation by CERN researchers found “fundamental” flaws that caused the explosion, close to the CMS detector, one of the LHC’s most important experiments. Coincidentally, Fermilab stands to gain most from delays at CERN. Its researchers also operate a rival but less powerful particle accelerator, the Tevatron.3/3/20112Name the main source of heat input to the cold end of a cryostat:A. Conduction through structural supportsB. Gas conduction and convectionC. Radiant heat transferD. All of the aboveE. Depends on the design and situationThere are many sources of heat to the cold end of any cryostat.Here we ask for the main source without giving any details.Often most of the heat comes thru supports, because the cold end is massive (a magnet), but if, for example, the dewar is not designed properly, the main source can easily be radiation. In space applications, it is often convection. So the answer does depend on the particular case being considered.Thermal Insulation-Chapter 7read it!Minimize heat leaks•Structural Supports•Gas conduction and convection•Radiant heat transferInsulating SupportsConduction dominates heat leak-usually 1-d between 2 reservoirsUse integrated thermal conductivityConductivity IntegralsT0=4 KT0=6 KPower Law Conductivitiesn=1 for metals andn=3 for insulators~nTQ dominated by Thot--most of support is warmConductivity IntegralsConduction dominates heat leak-usually 1-d between 2 reservoirsUse integrated thermal conductivity3/3/20113•Bulk Fill•Foams•Layered •Basic Design Factors•Definitions: k-value and CVPInsulating MaterialsBulk FillNew materials•Cabot, aerogel beads (Nanogel®)•Aspen Aerogels, aerogel blankets (Pyrogel®and Spaceloft®)•Sordal, polyimide foams (SOLREX®)•InspecFoams, polyimide foams (SOLIMIDE®)•TAI, pipe insulation panels•NASA, Layered Composite Insulation (LCI)Thermal ConductivityMaterial thermal conductivity•milliWatt per meter-Kelvin [mW/m-K]•R-value per inch [hr-ft2-degF/Btu-in]1 mW/m-K = R144Thermal Insulating Quality of Various MaterialsRepresentative k-Values3/3/20114K-Value vs. Nitrogen Gas PressureBetween 293 K and 77 KThe conductivity of a gas is strongly temperature dependent atA. Atmospheric pressureB. Very high pressureC. Below 1 torr (mm Hg)AerogelWorld’s lightest solid•Lighter is not always better•Special class of open-pore structure nano-materials•Extremely low density (as low as several mg/cm3)•High porosity (up to 99%)•High surface area (over 1000 m2/g)•Ultrafinepore size (as small as 2-nm radius)•Derived from the supercritical drying of highly cross-linked inorganic or organic gels•Sol-Gel processing methodsSol-Gel ProcessSol-Gel ProcessAuto-Clave SystemTesting Apparatus I4421()QeATT3/3/20115Testing ApparatusIITest on Multi-Layer Insulation-Number and VacuumTest on Multi-Layer Insulation-Blanket ThicknessGas ConductionThermal couple pressure gaugeThis image cannot currently be displayed.LThermocouple-blue wiresHeater-red wiresMean free path of gas particle8.6TlPmLl Ll independent of Pdependent on PHelium at 1 mBar and 4.2 K l=1 mmGas Heat Transfer v. PressureThe conductivity of a gas is strongly temperature dependent atA. Atmospheric pressureB. Very high pressureC. Below 1 torr (mm Hg)D. Between 1 atm and 0.001 atmE. At all pressures3/3/20116Gas ConductionAND ATMOSPHERIC PRESSUREGas ConductionGas momentum transfer at a wall: Accommodation CoefficientieiwTTTTSo if full Accommodation occurs when 1ewTTTirepresents T of atom incident on wallTeis reflected atom temperatureTwis wall temperatureEmissivity of Surfaces depends on wavelength of radiation and temperature of body=1 for black body—complete absorber of radiationFor insulation want low :High electrically conducting, polished surfaceWhy heat shields are so important:Multi-layer insulation4transferQTSuper-insulated DewarHeat Transfer & Emissivity Formulae4transferQT3/3/20117Emissivity of Surfaces Emissivity of SurfacesEmissivity of