f. le pimpec 1 how did they make light bulb work ? bulb installed in 1901 at the livermore’s (ca)...
TRANSCRIPT
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
F. Le PimpecF. Le Pimpec 22
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
F. Le PimpecF. Le Pimpec 33
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
F. Le PimpecF. Le Pimpec 44
Also True for Thin Films TiZr and Also True for Thin Films TiZr and TiZrVTiZrV
V. Baglin et al.
F. Le PimpecF. Le Pimpec 55
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