Films and getters · Workhorse
Bulk getters: St707 class, ZAO
ZrVFevalues describe: St 707
Why it wins
Cartridge and strip getters are the life-of-device vacuum system of sealed tubes and the silent partner of ion pumps in XHV: sealed devices have no pump port, the getter is the pump for 20 years.
Why not the alternative
Nothing else pumps for decades with zero power and zero moving parts.
Watch out
Activation temperature versus package thermal budget.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: SAES Getters datasheets and NEG literature; CERN Accelerator School, vacuum and materials proceedings.
Wet cleaning
| Recipe | never wet-clean an activated getter; handle the cartridge as delivered, gloves and dry N₂ |
|---|---|
| Forbidden | any solvent or moisture: it consumes capacity irreversibly |
| Limit | capacity, which cleaning can only spend |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | pumps |
|---|---|
| Outgassing, baked | pumps |
| Vapour pressure | none |
Temperature
| Bake, assembled | 500 °C |
|---|---|
| Vacuum degas | 500 °C |
| Metallurgical limit | activation 450–500 °C; ZAO activates lower and tolerates air |
Thermal
| Emissivity | 0.6 |
|---|
Mechanical
| Strength | sintered |
|---|---|
| Elongation | nil |
| Density | 6.5 g/cm3 |
Electrical and magnetic
| Relative permeability | ~1.0 |
|---|
Engineering
| Corrosion | pyrophoric as fine powder after activation |
|---|---|
| Joining | sintered on a strip or bolted as a module |
| Process notes | capacity for CO and CO₂ is finite and non-renewable |
| Availability and cost | SAES |
Outgassing
0 sourced measurements for this card, 2 declared absences. A rate means nothing without the pumping time it was read at, so each one states it or declares it missing. The whole base, filters included, is at /tools/outgassing/.
- St 101 NEG strip, Zr84-Al16 powder on constantan, 30 mm wide, 100 micron coating both sides (SAES Getters). Getter strip used as a linear pump, activated by resistive heating to 750 C for about half an hour.Section 1 of the source, LEP vacuum system, about 23 of the 27 km. Pumping speed for H2 about 2000 L/s per linear metre. Ultimate pressure about 2e-12 Torr in a LEP dipole chamber after 24 h baking at 150 C, set by the outgassing of CH4 and Ar divided by the pumping speed of a sputter-ion pump of about 50 L/s nominal for a 12 m chamber, with six such pumps on the same chamber, about 5e-13 Torr. Porosity raised from 7 to 13 percent for the LEP delivery. These are pumping speeds and system pressures, not specific outgassing rates. Card assignment to be checked at integration: this strip may belong to a card other than st707-zao.
- St 707 NEG strip (SAES Getters). Getter strip activated passively during a stainless steel bakeout, around 400 C, no electrical feedthrough required.Section 1 of the source: pumping curves very similar to those of St 101 are obtained after heating at 350 to 400 C. Covering the inner surface of a chamber entirely with St 707 strip, a total NEG pump, gives pumping speeds above 1e4 L/s per linear metre after a 350 C bakeout and pressures below 1e-13 Torr, measured in a 3 m stainless steel tube and stated by the source to be extrapolable to any length because the pump is modular.
Sources: S-BENVENUTI-EPAC1998. Full citations and conditions at the base and in /data/outgassing.json.
Grades
| St101 (Zr84-Al16) | strip getter heritage (LEP), activation 700 C class |
|---|---|
| St707 (Zr70-V24.6-Fe5.4) | the cartridge workhorse, activation 450 C class |
| St172 | sintered porous body pills for sealed devices |
| ZAO | sintered ZrVTiAl, high capacity, low particulation: NEXTorr class pumps |