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Alignment of the nozzle to the skimmer

For the creation of cold molecular ions, it is essential that the nozzle and skimmer are aligned axially. To achieve such an alignment, two techniques were used: a coarse alignment procedure was undertaken with the source and flight region chambers at atmospheric pressure and separated from each other and fine alignment achieved with the apparatus under vacuum.
A helium-neon laser was mounted on a 30 x 30 cm optical bench consisting of two steering mirrors facing in perpendicular directions. The optics were adjusted to steer laser radiation through the gas line and exit from the nozzle. With the two chambers separated, the nozzle was aligned to the skimmer using the nozzle translational controls. When the laser spot could be observed passing cleanly through the skimmer, the nozzle and skimmer were aligned. The chambers were then reconnected and pumped down to vacuum.

Gas was then passed through the nozzle and fine adjustments made using the translational screws. Flight region pressure was then monitored, if the nozzle/skimmer alignment improved, the flight region pressure increased. If the alignment was poorer, the pressure fell. In this manner, the nozzle was correctly aligned to the skimmer, until a maximum was reached for all translations of the nozzle.


next up previous contents
Next: Mixtures of Gases Up: Experimental Previous: Skimmer and ion optics   Contents
Tim Gibbon
1999-09-06