1 of 30 rjralba workshop, barcelona, 12-13 th sept 2005 the evolution of vacuum system design for...

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 1 of 30

The Evolution of Vacuum System Design for

Accelerators over 30 years at Daresbury Lab

Ron ReidGroup Leader, Vacuum Science Group

ASTeCCCLRC Daresbury Laboratory

Warrington WA4 4AD, UK

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 2 of 30

Outline

• Our second accelerator (SRS)• System Design

• Pressure calculations• Materials• Pumps• Gauges• Conditioning• Our next accelerator

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 3 of 30

The SRS

• NINA• SRS (1980)

• First 2nd Generation Light Source• Medium Energy• 2GeV, 1A (350mA), 100m, 3.88Å• 10-9 Torr; 12 hours

• < 10-9 Torr, >40 hrs @300mA• Two major upgrades

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 4 of 30

The SRS

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 5 of 30

The SRS

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 6 of 30

Simple Vacuum Layout

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 7 of 30

Vacuum System Design - Then

• Highly simplified – • Analytical solution of gas flow equations

• No PCs – mainframes with turnround of days

• Simple “finite element” models• Fortran decks

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 8 of 30

Vacuum System Design - Now

• PCs ubiquitous• Realistic calculations of complex systems

• Monte Carlo simulations• Angular coefficients

• Quick optimisations of layouts

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 9 of 30

Materials

• Stainless steels as now• Aluminium less common• Absorbers

• Copper• Finite element calculations

• Glidcop

• Fabrication Techniques• EB and plasma welding now more generally

available

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 10 of 30

Pumps

Then Now

Roughing

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 11 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 12 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 13 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 14 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil sealed

Air Bearing

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 15 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil lubricated;

Air Bearing

Greased ceramic

Magnetic

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 16 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil lubricated;

Air Bearing

Greased ceramic

Magnetic

Ion Pumps

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 17 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil sealed

Air Bearing

Greased ceramic

Magnetic

Ion Pumps Diode; Triode; “Noble”

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 18 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil sealed

Air Bearing

Greased ceramic

Magnetic

Ion Pumps Diode; Triode; “Noble”

Diode; Triode; DI; Starcell

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 19 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil sealed

Air Bearing

Greased ceramic

Magnetic

Ion Pumps Diode; Triode; Noble

Diode; Triode; Noble; Starcell

UHV

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 20 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil sealed

Air Bearing

Greased ceramic

Magnetic

Ion Pumps Diode; Triode; Noble

Diode; Triode; Noble; Starcell

UHV TSP

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 21 of 30

Pumps

Then Now

Roughing Sorption; Diaphragm

Dry mechanical pumps

Turbos Oil sealed

Air Bearing

Greased ceramic

Magnetic

Ion Pumps Diode; Triode; Noble

Diode; Triode; Noble; Starcell

UHV TSP TSP; Neg

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 22 of 30

Pumping schemes

• In SRS about 50% of circumference is dipole magnets vacuum vessels

• Main radiation absorbers are linear (distibuted) in dipole vessels• Main gas load

• Most restricted pumping

• Solution: DIPs

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 23 of 30

DIPs

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 24 of 30

Pumping schemes

• In SRS the DIPs give almost half the applied pumping speed during beaming

• Losing just one DIP gives a noticeable decrease in lifetime

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 25 of 30

Pumping schemes

• Our new machine designs have much smaller apertures, dipoles occupy only a small fraction of the circumference

• DIPs no longer appropriate

• Machines use discrete photon stops

• Current preferred solution• NEG (discrete and film)

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 26 of 30

Gauges

• Little change in type of gauge• Except BAG often replaced by IMG

• Main difference is the electronics – now compact, more reliable

• Biggest difference is in control - then home brewed, now uses standard interfaces

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 27 of 30

Conditioning

• Then - beam scrubbing effect was known• But limited data and best measured values of

η were ~10-6 mol γ-1

• SRS design needed 10-7

• Cleanup rate not well characterised

• Now much greater range of systematic data and clean up rates predictable as a function of beam dose

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 28 of 30

Our next accelerator – 4GLS

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 29 of 30

4GLS

• Direct vacuum challenges are few

• Most of the machine needs to be at modest UHV, maybe HV

• But• Photocathode gun is XHV

• Superconducting linacs

• Particulate Cleanliness is a real challenge

rjr ALBA Workshop, Barcelona, 12-13th Sept 2005 30 of 30

Concluding Ramblings

Thanks for your indulgence!