UCL Department of Space and Climate Physics


Low Energy Plasma Instrument Calibration

The calibration facilities provide: Low Energy Plasma (electron and ion) & Optical (wide ranging capability for low temperature optical/radiometric calibration).

The Low Energy Plasma Instrument Calibration facility is a three vacuum chamber system consisting of:

  • Electron source chamber
  • Calibration chamber
  • Ion source chamber

Electron source chamber

The electron source chamber houses the electron gun assembly; essentially a UV lamp irradiates a gold layer on a quartz disk, ejecting photoelectrons which are then accelerated to the desired energy. A gate valve allows isolation between the chambers to ensure that the electron source assembly exposure to air (for example, when the calibration chamber is vented for instrument removal) is minimised to prevent deterioration of the electron gun gold surface, which can lead to reduced performance.

Calibration chamber

Prior to a calibration campaign, the electron/ion beam is characterised via a raster scan of a channeltron/Faraday cage mounted on X-Y linear drives. The flight hardware is then mounted on a three-axis rotary table, allowing complete 3D manipulation of the instrument within the beam to provide a comprehensive calibration dataset.

Ion source chamber

The ion source chamber consists of:

  • A Peabody Scientific Duoplasmatron Ion Source
  • An Extraction gap
  • An Einzel lens
  • A Power supply package

This system can produce either positive or negative ions in a well focused beam. The ion beam energy can be varied over a wide dynamic range from 1 keV to 30 keV, with energy spreads typically less than 20 eV.

Ions produced in the arc discharge Duoplasmatron ion source are extracted from the source anode aperture by the Extraction Gap and then focused to the desired position by the Einzel Lens. The variable focus lens provides a wide range of beam options. By varying the extraction voltage, the final beam energy can be adjusted over a range of 1 to 30 keV.


Chamber dimensions: 1m diameter by 1.2m long

Base vacuum pressure: 5 x 10-6 mBar

Linear drives: Two drives, vacuum compatible, 250mm travel x and y axis

Rotary drives: Three drives, vacuum compatible, +180o -180o , x,y and z axis

Electron beam diameter: 150mm max.

Ion beam diameter: 100mm max.

Electron beam energy: 10eV to 20KeV

Ion beam energy: 1KeV to 30KeV

LV electrical feedthroughs: 9, 25 and 37 way D-Sub connectors

HV electrical feedthroughs: 10 x 10KV rated connectors (Kurt J Lesker HV10 connectors)

Number of electrical conductors: 3 x 100 conductors Douglas Electrical vacuum faceseal feedthroughs.

Vacuum pumps: Leybold Turbovac 361 turbomolecular pumps backed by oil free scroll and piston pumps. Leybold 3000L/sec cryo pump as the main vacuum pump.


Nominal, currently being commissioned for Solar Orbiter EAS calibration