Micrometer-sized nozzles and skimmers for the production of supersonic He atom beams

Abstract

A modification of the laser detonation-type hyperthermal oxygen atom beam source for a long-term operation Rev. Sci. Instrum. 79, 073109 (2008); A triply differentially pumped supersonic beam target for high-resolution collision studies Rev.Micrometer-sized nozzles and skimmers made from drawn glass tubes are described and tested for the production of highly monoenergetic He atom beams. Glass nozzles with diameters between 1 m and 4 m when operated at He source stagnation pressures of up to 1000 atm provide intense beams with measured speed ratios of Sϭ50-100, in good agreement with the predicted behavior scaled from nozzles with larger openings. Miniature glass skimmers with diameters as small as 3 m were also successfully tested with conventional 10 m diameter nozzles. These miniature nozzle-beam sources can be used to greatly reduce the size of present-day He-atom surface-scattering time-of-flight spectrometers and to reduce the number of vacuum stages and the size of vacuum pumps. They also open up new experimental possibilities as illustrated by measurements of the spatial profiles of seeded nozzle beams.

Pulsed Supersonic Beams from High Pressure Source: Simulation Results and Experimental Measurements

“…Since the early days of low intensity continuous beams, skimmers have been recognized as more than a simple bystander that extracts the central portion of the beam. The effects of molecules scattering from the finite skimmer edges have long been recognized [22,24,31,[46][47][48], and the reduced transmission of the beam through the skimmer was termed "skimmer interference. " At times the term "skimmer clogging" was used to describe the dramatic reduction in skimmer transmission.…”

“…Simulations of gas flow [21] as well as measurements of actual beam parameters are presented. Previous designs of molecular beam skimmers [5,20,[22][23][24] as originally developed for the earlier low-intensity continuous beams cannot be copied for high intensity beams because skimmer interference (also known as skimmer clogging) is simply too severe with the more intense pulsed beams that are now available. In this paper, we describe recent results on nozzle design (Section 2), pulsed valve design (Section 3), molecular beam properties (Section 4), skimmer design (Section 5), and conclusions (Section 6).…”

“The Even-Lavie valve as a source for high intensity supersonic beam”

“…It was soon realized that shaping the nozzle can shape the expanding gas jet [3,[26][27][28][29] and change the number of collisions before the beam density drops to low value and the expansion and cooling practically "Freezes" [8,9,30]. Most nozzles have small length dimensions (several mm in size due to pumping limitations) and making a complicated and smooth shape is difficult [31]. We chose to study a series of simple conical shaped nozzles that are relatively easy to make [28].…”

“…Since the early days of low intensity continuous beams, skimmers have been recognized as more than a simple bystander that extracts the central portion of the beam. The effects of molecules scattering from the finite skimmer edges have long been recognized [1,5,31,[42][43][44], and the reduced transmission of the beam through the skimmer was termed "skimmer interference". At times the term "skimmer clogging" was used to describe the dramatic reduction in skimmer transmission.…”

Focusing a helium atom beam using a quantum-reflection mirror

“…Metastable helium atoms were focused by a commercial Fresnel zone plate in 1991 [1]. This method has been optimized for ground-state helium atoms by using custom-made zone plates and micro-skimmers [7]. With a 1-µm-diameter skimmer a focused spot diameter of 2 µm was achieved [3].…”