MBE Components, Beam flux monitor BFM


Beam Flux Monitor


BFM 40-150
BFM 40-150 beam flux monitor on DN40 CF (O.D. 2.75") with edge-welded bellows and linear travel 150mm (gauge head shielding parts removed)
  • Bayard-Alpert type ionization gauge

  • Compatible with AML gauge controllers

  • Mounting flange DN40 CF (O.D. 2.75")

  • Linear gauge head positioning

  • Standard linear travel 150 mm

  • Bakeable up to 250°C

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In many MBE applications the beam equivalent pressure (BEP) of the atomic or molecular beams from effusion cells can be used to determine flux ratios and growth rates near or at the sample position. Our Beam Flux Monitor BFM has been designed and optimized for this purpose.

The basic component of the BFM is the Bayard-Alpert type ionisation gauge, that is mounted on a linear motion feedthrough with edge-welded bellows. By means of this feedthrough, the gauge can be shifted linearly between a measurement- and a standby-position.

The design of the BFM includes the shielding of the gauge head, inhibiting contamination of a substrate behind the gauge head during flux-monitoring. The shielding parts can be seen on the right hand figure.

Complete assembly with gauge head shielding

View onto gauge head of BFM 40-150, complete assembly with gauge head shielding



Typical applications for the BFM beam flux monitor are:
-   flux calibration of effusion cells vs. source temperature
-   fast check of flux ratios from different sources before growth (e.g. As/Ga in III-V MBE)

The BFM series has been designed to be pin-compatible with ion gauge controllers of the PGC-series from AML. The electrical 12-pin feedthrough of the BFM mates with a standard AML gauge head connection cable. If other ion gauge controllers shall be used, adaptability to the pin-out shown on the left and match with the characteristics of the ion gauge head (see below) is required.


Ion Gauge Head Specifications (when used with AML controller):

  • Bayard-Alpert type ionization gauge measurement principle

  • 10-3 mbar to 4x10-11 mbar pressure range

  • sensitivity 17 mbar-1 (for N2)

  • X-ray limit 4x10-11 mbar

  • ceramic/metal isolator base

  • filaments: 1x tungsten, 1x thoriated iridium

  • filament voltage 6 to 20 V

  • emission current max. 10 mA (100mA tungsten, 60 mA, thoriated iridium)

  • filament bias +50 V (+0 V during e-bombardment degas)

  • collector voltage +0 V

  • grid voltage + 200 V (+500 V during e-bombardment degas)

BFM 40-150 air side view

BFM 40-150 air side view


Technical data

Mounting flange DN40 CF (O.D. 2.75") [mm / inch]; port I.D. >= 38 mm
Dimensions ( L x W x H ) 380 x 94 x 105 mm (BFM 40-150)
In-vacuum length 123 mm retracted / 273 mm extended (BFM 40-150)
Linear travel 150 mm standard, other on request
Bakeout temperature up to 250 °C
Controller AML PGC-series or compatible; other (e.g. Granville-Phillips) on request
Electrical connectors pin-compatible with AML controller cables
Measurement range 10-3 mbar to 4x10-11 mbar total pressure or BEP
Degas principle electron bombardment



Schematic drawing BFM Schematic drawing of the Beamfluxmonitor BFM