NonEvaporable Getters NEGs in the ILC BDS 111006
Non-Evaporable Getters (NEGs) in the ILC BDS 11/10/06 Meeting with SAES Getters John Amann – ILC Mechanical Engineering 11/13/06
Meeting with SAES Getters: Michael Ferris (US Applications Engineer) Paolo Manini (Business Area Manager) Mauro Pivi (SLAC) John Amann (SLAC)
NEGs at CERN • NEG used for pumping since 1950’s, sintered or strips. • At CERN deposited micron NEG film (Ti 30 V 40 Zr 30) directly on chamber. • Reduces gas pressure. • Acts like conductance free distributed pump. • Barrier for gases, reduces thermal out-gassing. • Other interesting features – low secondary electron yield, low gas de-sorption rates from charged particle, photon bombardment. • Ideal for very narrow, conductance limited chambers.
The Coating Process • Magnetron sputtering process. • Can be applied to Al, Cu, SS. • Uses krypton gas plasma = less entrapment in film than argon. • Chamber must fit inside 45 cm diameter magnet coil. • Maximum chamber lengths of ~6. 5 m, limited by facility. • Longer sections can be coated and welded together (Al, SS). • 1 micron on 2 m section takes 1 day to coat. • Thickness of coating can vary over irregular surfaces, profiles. • Areas to be uncoated can be masked. Difficult to achieve sharp edge boundary. • Electrically conductive, not as good as Al however.
Operation and Performance of NEGs • To activate the NEG material it must be heated at ~200°C for up to a day. • Chambers which need to be activated would require wrapping with heat tape. • After initial activation, the material should not need activation again for life, barring a vent/leak. • An alternative to coating whole chambers, the CF mounted NEG pump.
Uncertainties/Concerns • Durability of NEG material under high SR power of ILC beam. • Overall long term durability of coating, will it flake off resulting in reduced pumping efficiency of chamber? • They (SAES) seem interested in investigating the SR durability. • PEPII experience, works well until heated by SR. Must be careful with placement for ILC. • SAES production capacity and logistics, if at Fermi possible US facility.
Recommendations Consider replacing some ion pumps with CF mounted NEG pumps. • 400 l/s NEG pump ~$3000 vs. 400 l/s diode ion pump ~$6000. • PS should be about same order. • Very compact and lightweight, can mount in any orientation. • Pump cartridge can be replaced quickly if damaged. • Activation heater is integrated with TC on CF, chambers would need heat tapes, etc. • Does not pump noble gases, so can not eliminate all ion pumps.
Recommendations Investigate use of NEG films at ILC BDS. • Test durability/performance in ILC-like environment (SR, etc. ). • Obtain cost estimate for coating typical chamber sections (BNL chamber ~$10 k for. 25 m x 5 m section). • Develop pumping model for coated chambers. Need to understand what we are getting for the $$. • Think about where it might be used (near IP to reduce backgrounds). • Is it cost effective? Will it last the life of the ILC?
- Slides: 8