Real Accelerators: a facility overview the nuts and bolts…and gaskets and resistors United States...
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Transcript of Real Accelerators: a facility overview the nuts and bolts…and gaskets and resistors United States...
Real Accelerators: a facility overviewthe nuts and bolts…and gaskets and resistors
United States Particle Accelerator School – Accelerator FundamentalsIndiana University/Baton Rouge6 – 17 January 2003Elvin HarmsBeams Division/[email protected]
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Introduction
‘Scratch the surface’ overviewWhat goes into making a real working acceleratorPerspective of ‘big’ machinesPrinciples applicable to all types of acceleratorsInteractive
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Scale
Table topE. O. Lawrence
early cyclotron ‘dees’
Berkley, California USA
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Scale
Big machine
LHC – 27 kilometers
(under construction)
CERNGeneva,
Switzerland
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What makes up an Accelerator?
Two primary components– Magnet system
• Keep the beam focused• Keep the beam on course
– Radiofrequency system• Impart energy to the particle beam
AccelerationMaintain beam’s energy
(synchrotron light)Maintain structure (colliding beams)
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Magnets
Electromagnets– Conventional
• Water or air-cooled• Copper or aluminum coils• Iron shapes and contains the field
– Superconducting• Liquid helium cooled• Higher fields > higher energies• Ramp slowly• Coil placement critical to field
Permanent
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Magnets
Gradient or ‘Combined function’– Steering and focusing by a single element
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Magnets
Separated function– Focusing and bending are done by separate
magnets• Quadrupole for focusing• Dipole for bending
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Magnets
Flavors– Dipoles– Quadrupoles– Correctors
• ‘trim’ dipoles• (skew) quadrupoles• sextupoles• even higher order• Special purpose
– Injection/Extraction– Light sources
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Magnets
Flavors
Quadrupole Sextupole
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Magnets
Flavors– Undulator/Wiggler
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Magnets
Superconducting
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Radiofrequency systems
Low level– Frequency– Amplitude (voltage)– feedback
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Radiofrequency systems
High level– Amplification– Accelerating cavities
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Piecing the machine together
A true complex, not just a machine
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Piecing the machine together
Cascade of accelerators– Different technologies are more efficient in different
energy regimes• Ion sources• Injectors• Collectors• Transfer lines• End accelerator
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Piecing the machine together
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Piecing the machine together
Power– Accelerators require
lots of it!– Stable and reliable
source
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Piecing the machine together
Power– Magnets connected in series
• Distribution• Regulation/feedback loops• Current changes through a component leads to changes
in beam behavior (never better…)
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Piecing the machine together
Contain the beam in a pipeVacuum– Particles travel a long way while being accelerated/in
storage– Scattering by air can lead to reduced beam quality
• emittance growth• energy loss
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Piecing the machine together
Vacuum– Quality: 10-7 mbar and lower for
circular machines– Distributed pumping– Ion pumps, TSP’s, cryo
pumping– Pick the correct materials and
seals– Meticulous cleaning beforehand– UHV: bake the chamber in
place
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Piecing the machine together
Cooling– Virtually every component requires some sort of
external cooling, electronics, too– Water is most common medium– Superconducting components require cryogens– Coolant should be in as direct contact with heat load
as possible (best thermal transfer)
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Piecing the machine together
Water Cooling– Conventional magnet coils
typically have a coolant hole through middle of conductor
– Control the chemistry• Water must be low conductivity
(deionized) since water & current flow together
• Remove the dissolved oxygen• Minimize particulates – small
orifices– Regulate the temperature
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Piecing the machine together
Cryogenic Cooling– Superconducting
coils bathed in liquid helium at 4.6K or less
– Lots of refrigeration (significant power use)
– Low heat loss– Magnets are super
“thermos” bottles
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Piecing the machine together
Enclosure– Electrical and Radiation
hazards when operating– Personnel protection
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Piecing the machine together
Equipment housing– Want power supplies and other interface equipment
as close as possible, but accessible
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Keeping it all together / Making it work
Alignment– Keep it in line!
– Tevatron 150 to 800 GeV in 30 seconds
– 0 = 21s– C ~4 miles– > 1.4 million miles traveled
during acceleration alone
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Keeping it all together / Making it work
Alignment– Where is it?
• Position of components with respect to each other
• Macro-positioning
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Keeping it all together / Making it work
Alignment– Move it
• Reference system• Fixturing• Component stands• Remote positioning
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Keeping it all together / Making it work
Diagnostics– Where’s the beam, what does it look like, how many
particles?• Beam Position Monitor• Beam Loss Monitor• Profile Monitor/Wire scanner• Schottky detector• Toroid• Resistive Wall Monitor• Damper• …
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Keeping it all together / Making it work
Diagnostics
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Keeping it all together / Making it work
Diagnostics
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Keeping it all together / Making it work
Controls system– Monitor and Control– Timing– Fast response– Beam removal– Coordination– Human interface
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Where does the beam go?
Experiments / End Users– Internal to machine
• Interaction regions• Beam quality/size
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Where does the beam go?
Experiments / End Users– External
• Rate, energy, size, and location to deliver beam
– Single-turn– Resonant extraction– Synchrotron light
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Resources
People are the most important componentOther resources– Books– Schools, Workshops, conferences– Web