Accelerator Design: the nuts and bolts…and gaskets and resistors Elvin Harms Beams Division/Fermilab [email protected]@fnal.govcosmo.fnal.gov.

Accelerator Design:the nuts and bolts…and gaskets and resistors

Elvin HarmsBeams Division/[email protected] cosmo.fnal.gov

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Introduction

“Scratch the surface’ overviewWhat goes into making an accelerator workPerspective of ‘big’ machinesPrinciples applicable to all types of acceleratorsInteractive

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What makes up a synchrotron?

Two primary components– Radiofrequency system

• Impart energy to the particle beamAccelerationMaintain beam’s energy (synchrotron light)Maintain structure (Colliding beams)

– Magnet system• Keep the beam focused• Keep the beam on course

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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• Coil placement critical to field

– Permanent

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Magnets

Gradient– “Combined” function

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Magnets

Separated function– Focusing and bending are done by separate

magnets

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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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Radiofrequency systems

Low level– Frequency– Amplitude (voltage)– feedback

High level– Accelerating cavities– Amplification

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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 large distances through a machine– 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– 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– 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 coolant hole through middle of conductor

– Water must be low conductivity (deionized) since water current flow together

– Minimze particulates – small orifices

– Remove the free oxygen– Regulate the temperature

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Piecing the machine together

Cryogenic Cooling– Superconducting coils

bathed in liquid helium at 4.6K

– 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

Controls system– Monitor and Control– Timing– Fast response– Beam removal– Coordination– Human interface

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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 – Arden’s talk tomorrow

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Where does the beam go?

Experiments / End Users– Internal to machine

• Interaction regions• Beam quality/size

– External• Rate, energy, size, and

location to deliver beam– Single-turn– Resonant extraction

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Resources

People are the most important componentOther resources– Books– Schools, Workshops, conferences– Web