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3BG - pdf


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Extreme High Vacuum


3BG XHV Gauge

3BG EXV gauge


  • Measure to 10^-12 Pa
  • Reduction of soft X-ray & ESD
  • Low outgassing hot-cathode gauge



Manufactured by VacLab


3BG is a commercially available extreme-high vacuum hot-cathode ionization gauge head that can measure pressures as low as 5.4 × 10^–12 Pa, by reducing the limits imposed by soft x-rays, electron-stimulated desorption (ESD), and outgassing. The gauge construction consists of a cylindrical grid, which is closed at both ends. Ions are drawn from the grid through a long, axial slit made in the cylindrical surface. Thus, the ion beam that emerges forms a "belt". This belt-like ion beam is guided on a curved path by a cylindrical sector deflector and terminates on a plate collector arranged after a beam trajectory rotation of 240°. These elements are embedded in a solid cylinder of 0.2% BeCu alloy, which has a low emissivity (radiation factor) and high thermal conductivity. As a result, the effects of heat radiation and outgassing (caused by the hot-cathode filament) and soft x-ray photoemission (the grid is the soft xray source) are reduced in the deflector/collector region.


Electron energy:

120 eV, standard

Filament potential

100 V, standard

Filament power:

2 V x 1.5 A at 1.6 mA

Deflector bias:

155 V (between1-4mA)


Electron Bambardment (450 V x 10-45mA)

Bakeout temperature:

280°C max.


70 mm dia. x 58 mm


1.1 kg


BNC and 8 pin Burndy-J

Sensitivity factor:

5 ~8 x 10^-2 Pa^-1 (at 1 ~4 mA)

X-ray limit:

<5 x 10^-12 Pa

3BG operates with Oerlikon Leybold IM540.