F. Le PimpecF. Le Pimpec 11

How DID they make light bulb How DID they make light bulb work ? work ?

Bulb Installed in 1901 at the Livermore’s (CA) Fire station. C filament - 4 W

♦ ♦ Since 1800 the electric arc Since 1800 the electric arc light was known. However, light was known. However, the life time of a filament the life time of a filament made of carbon was poor.made of carbon was poor.

♦ ♦ The problem was in The problem was in obtaining a high enough obtaining a high enough vacuum in the bulb and vacuum in the bulb and getting rid of the oxygen in getting rid of the oxygen in the residual gasthe residual gas

Use of the first Use of the first Evaporable Evaporable

GettersGetters

Phosphorus pumped lamp tend to have a red cast

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Choice of Getter – Vapor Choice of Getter – Vapor PressurePressure

After Honig and Kramer (1969)

When choosing a material to be used for a vacuum application.

One question which need to be asked is :

At Which temperature my At Which temperature my system is going to be running ?system is going to be running ?

The elements of your vacuum system must not limit the pressure you are aiming at. Their vapor pressure must be taken into account in the design. That is also true for your getter pump

AlMg

200 70010-7

1

Zn

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Ti vs Other Getters in AcceleratorTi vs Other Getters in Accelerator

A) Pumping Speed calculated at RTB) Wide variations due to film roughnessC) For H2, competition between desorption

and diffusion inside the deposited layers

Ref. “Sorption of Nitrogen by Titanium Films,” Harra andHayward, Proc. Int. Symp. On Residual Gases in Electron Tubes, 1967

1cm2

Ref. “Le Normand CERN vacuum note”

Ba - Ca - Mg : High vapor pressure. Trouble if bake out is requestedZr - Nb - Ta : Evaporation temperature too high

Typical sublimation rate 0.1 to 0.5 g/hr

0.5 g/hr ; MTi =48g/mol0.5/(48*3600) = 2.9 10-6 mol.s-1

1ML~1015 atom.cm-2

2.9 10-6 mol.s-1. Avogadro = 1.74 1018 atom.s-1

1 ms is necessary to evaporate 1 ML3 minutes = 180E3 ms hence ML for 1cm2

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Also True for Thin Films TiZr and Also True for Thin Films TiZr and TiZrVTiZrV

V. Baglin et al.

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Ionodesorption by heavy energetic Ionodesorption by heavy energetic ions on technical surfacesions on technical surfaces

E. Mahner et al.

1.5 109 Pb53+ ions (per shot) under 89.2° grazing incidence and 4.2 MeV/u

F. Le PimpecF. Le Pimpec 66

SEY & Electron CloudSEY & Electron Cloud

0.5

1

1.5

2

2.5

3

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Electron Beam Energy (eV)

Sec

ond

ary

Ele

ctro

n y

ield

Aluminium

Beryllium

Titane

Copper OFHC

Stainless Steel

NEG St 707 (activated)

NEG TiZrV (activated 200°C- 2h)

SEY of technical surfaces baked at 350°C for 24hrs

Electron cloud can exist in p+ / e+ beam accelerator and arise from a resonant condition (multipacting) between secondary electrons coming from the wall and the kick from the beam, (PEP II - KEK B - ISR - LHC).

fast head-tail instabilityfast head-tail instability

F. Le PimpecF. Le Pimpec 77

SEY & Electron CloudSEY & Electron Cloud

Hilleret et al.

TiZrV coating

2 h at 300C, CO injected at NEG T=60C

TiZrV coating

Low SEY : Choice of the activating temperature and time of the NEG - or conditioning (e- photons ions)

Contamination by gas exposure or by the vacuum residual gas increases the SEY

Results vary from sample to

sample

Angles of incidence, of the PE, yield

the shape of the curve toward higher values

Roughness is an issue