Signal enhancement strategies for angular profile measurements of gas injected in ultrahigh vacuum
(Color online) Schematic depiction of the experimental setup. The dotted arc represents the pendulum motion of the detection unit. Inset shows details of the gas flows in and out of the aperture.
(Color online) Cross section of the chamber showing the mechanism allowing for pendulum motion. The right part shows the relevant geometric parameters for a conical nozzle (not to scale).
(Color online) Injected flow-rate as a function of the pressure measured by the flux sensor and by the BAIG situated on the chamber sidewall. Straight lines represent the best linear fits of the data.
(Color online) Calculated angular flux profiles incident on the aperture inlet for molecules coming from a thin hole nozzle (signal) and from the chamber walls (background).
(Color online) Transmission probability vs first impact depth for molecules entering a straight tube and being diffusively reflected on its walls (shown for various tube’s ratios).
(Color online) Transmission probability vs incidence angle for molecules injected into a straight tube for various ratios indicating the variations of angular selectivity with ratio.
(Color online) Graphical chart indicating the filtering tube’s to be used in order to maximize according to the setup geometry and to the maximum acceptable signal loss (left). Corresponding background level reduction calculated assuming isotropic distribution (right).
(Color online) Flux profile measured out of a tubular nozzle using no filtering tube. Line is drawn as eye guide only.
(Color online) Normalized flux profiles out of a tube measured in the following conditions: (1) linear sensor motion with partial BAIG encapsulation (triangles), (2) pendulum motion with total encapsulation (circles), and (3) same as previous one with the addition of a filtering tube (squares). Lines are drawn as eye guides only.
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