The Vacuum Chamber, Attached Equipment for Vacuum Maintenance and Sample Production, and Experimental Method

All of the experiments described in this thesis took place within a vacuum chamber (figures 4.1, 4.2, 4.4.)

Figure: A Schematic Diagram of the Pumps and Pressure Measurement Apparatus Connected to the Ultra-High Vacuum (UHV) Chamber, inside Which the Experiments Were Conducted; Arrows Represent Flows of Gas, and Broken Lines Represent Pressure Measurements; Pirani Gauges Measure Total Pressure in a High-Pressure Range between $4\times{}10^{-2}\,\mathrm{mbar}$ and $5\,\mathrm{mbar}$, the Penning Gauge Measures Total Pressure in an Intermediate Range, and the Ion Gauge Measures Total Pressure in a Low-Pressure Range between $8\times{}10^{-11}\,\mathrm{mbar}$ and $10^{-5}\,\mathrm{mbar}$; the Mass Spec Measures Total Pressure, and the Partial Pressures of Individual Gas Species.

Figure 4.2: A Schematic Diagram of the Equipment for Preparing the Sample, Contained in the UHV Chamber; Each Arrow Represents a Flow of Matter or Energy, Described alongside the Arrow, from an Item of Equipment to the Sample, Designed to Alter the Sample in a Manner Described Later in This Chapter.

Figure 4.3: A Schematic Diagram of the Equipment for Measuring or Observing Characteristics of the Sample; Arrows with Hollow Heads Represent Flows of Matter or Energy into the Sample, Used To Illuminate or Excite the Sample, To Render a Measurement Possible; Arrows with Filled Heads Represent Information-Carrying Flows of Matter out of The Sample; where the Arrow Is Solid, the Experiment It Represents Has Been Successfully Undertaken in This UHV Chamber; where the Arrow Is Broken, the Experiment Is a Future Possibility; Arrows of the Same Colour All Relate to the Same Illumination or Excitation of the Sample.

Figure 4.4: A Photograph of the UHV Chamber, inside Which the Experiments Were Conducted

The technological principles of the vacuum maintenance equipment are described in detail in Ultrahigh Vacuum Practice [9], with useful additional information in ``vacuum technology'' [75]. The central portion of the vacuum chamber, in which the sample holder (figure 4.5) is situated, is [37] constructed from $\mu$-metal, in order to screen out external magnetic fields, while most of the peripheral portions are constructed from stainless steel. During the experiment described in part III, the chamber, and associated equipment, maintained the gas pressure to which the sample was exposed, at all times other than during argon ion sputtering, below $(22\pm{}0.29)\times{}10^{-9}\,\mathrm{mbar}$, with a base pressure of $(140\pm{}2.9)\times{}10^{-12}\,\mathrm{mbar}$.

There follow more detailed descriptions of the apparatus for sample preparation, attached to the vacuum chamber.