Testing Getters

Info on getters

• Saes getters are an industrial solution to dispensing alkali metals.

• http://www.saesgetters.com/

Implementation

• Once in vacuum, its important to degas the source.• Operate source at a current just below threshold for

several hours (Several > 5 hours, threshold ~2.7 A).• Getter will not work up to 5 A now.• Raise current to ~8A for 2-5s several times.• Source becomes very reproducible, threshold ~2.7A.• 3 – 3.8 A gives adequate flux without overloading

vacuum.Umakant D. Rapol, Ajay Wasan, and Vasant Natarajan, ‘Loading of a Rb magneto-optic trap from a getter source’

WarningFortagh, Grossmann, Hansch and Ziemmermann, ‘Fast loading of a magneto-optical trap from a pulsed thermal source’• Warn against allowing the pressure to raise above “one order of

magnitude otherwise irreversible contamination of the reactive load of the dispenser from the residual gas”

• Other paper claims it doesn’t undergo “irreversible contamination” if the pressure does rise by several orders of magnitude during initial degassing. “Perhaps what they call irreversible contamination is similar to our observation that Rb atoms are not released even at currents of 5 A when the source is operated the first few times after bakeout. But, as mentioned earlier, this can be reversed by applying high-current pulses to evaporate any surface layer that might have formed.”

Decay of background vapour

• Ideally want to reproduce this.