UCL DEPARTMENT OF SPACE & CLIMATE PHYSICS

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.

Specification

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, +180^o -180^o , 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.

Status

Nominal, currently being commissioned for Solar Orbiter EAS calibration

The MSSL Optical calibration facility is a newly commissioned system to accomodate larger instruments and payloads.  The vacuum chamber consists of an outer stainless steel chamber with a thermal shroud mounted inside the chamber. A heating and cooling platen (or cold bench) is mounted within the thermal shroud which extends the thermal range capabilities of the facility.The facility has an extensive array of ports to allow the attachment of calibrated black bodies and optical beam inputs. The chamber specification is listed below.

Specification

Chamber dimensions: 2m diameter by 2.1m long

Cold bench dimensions: 1.2m wide by 2.0m long
Base vacuum pressure: 5 x 10^-6 mBar
Temperature range (shroud): -80^o C to +100^o C

Temperature range (cold bench): -180^o C to +100^o C.

Temperature control: Closed loop PID control, +0.5^o C -0.5^o C.

Temperature measurement: 3 wire 1/10 DIN PT100 sensors, 16 sensors available with the ability to add up to a maximum of 32 additional sensors.

Temperature and pressure logging: 16 channel plus pressure logging, user set logging interval.

Electrical feedthroughs: Various D-Sub connectos and high voltage connectors.

Facility Status

Nominal, currently undergoing blank testing for EarthCare MSI radiometric test campaign

The MSSL thermal vacuum test facility can also be configured as a low energy electron calibration chamber. The latter configuration is for sole use by MSSL projects. When configured for thermal vacuum tests the facility is available to other research groups and commercial establishments.

The system is housed in a cylindrical stainless steel vacuum chamber which is 1.1m long and 1.0m in diameter manufactured by Leybold. The chamber is pumped to pressures below 5x10^-7 mBar by a combination of a rotary pump, a turbopump and a helium cryopump. The electron calibration facility is housed inside a grounded mu-metal shroud inside the chamber, enclosed at both ends. This ensures that the residual magnetic field inside the chamber is less than one tenth of the Earth’s magnetic field, which results in an electron beam divergence of less than 1^o at 1keV. The mu-metal shroud is 0.7m long, 0.6m wide and ~0.6m in height.

Specifications

Dimensions: 1m diameter by 1.1m long.

Electron beam diameter: 110 mm

Electron beam energies: 30 eV to 20 KeV

Base vacuum pressure: 5 x 10^-6 mBar.
Temperature range (shroud): -40^o C to +80^o C.

Temperature range (platen): -140^o C to +100^o C.

Temperature control: Closed loop PID control, +0.5^o C -0.5^o C.

Temperature measurement: 4 wire 1/10 DIN PT100 sensors, 8 sensors total.

Temperature and pressure logging: 8 channel plus pressure logging, user set logging interval.

Electrical feedthroughs: Various D-Sub connectors and high voltage connectors (contact us for more detail)

Status

Nominal, in use by ChaPS for TechDemoSat.