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Cassini Calibration

A controlled access laboratory for post launch calibration, characterization, and diagnostics of the Cassini Plasma Spectrometer (CAPS) and the Cassini Ion & Neutral Mass Spectrometer (INMS).


Cassini Plasma Spectrometer (CAPS) Chamber

CAPS Chamber Features:

  • Chamber door opens greater than 90 degrees.
  • Interior tray drawer permits supported extraction of CAPS instrument & insertion of instruments up to approximately 16” x 16” x 16” cube
  • Up to three lab benches available for conversion to ESD operations if necessary.
  • Main chamber dimensions: 24” diameter x 24” deep cylinder
  • System pumping: 450l/s Seiko Seiki magnetically-levitated turbomolecular pump backed by an scroll pump (no oil containing pumps used in the lab)
  • Additional bottom flange port for second turbopump or cryopump
  • 8” CF viewport
  • 10” CF multi-pin instrument electrical feedthrough flange
  • Numerous available flanges at an assortment of chamber positions for electrical or vacuum feedthroughs
  • High purity nitrogen available for instrument purging
  • Chamber vented with high purity nitrogen
  • Chamber pressure, temperature, and CAPS instrument conditions monitored remotely
  • Routine base pressures of 1 x 10-7 Torr
  • Reaches high vacuum (turbo starts) in 10 minutes
  • No thermal control
  • No TQCM, No RGA


INMS Chamber Features:

  • 16” x 16” stainless steel cylindrical chamber
  • Three (3) 8” CF ports, two (2) 10” CF port, one (1) 13.25” CF port, and ten (14) 2.75” CF ports
  • Axis of target flange (13.25” CF), all three (3) 8” CF flanges and two (2) 2.75” CF flanges occupy same horizontal plane
  • Axis of target flange (13.25” CF), two (2) 10” CF flanges and one (1) 8” CF flanges occupy same vertical plane
  • All metal sealed flanges and fittings
  • Ceramic insulators and isolation
  • Nominal base vacuum level 3 x 10-10 Torr after 200C bakeout
  • INMS instrument bakeable to 250C
  • Chamber bakeable to 400C, but limited to program, mission, science instrument, ion gun and turbopump temperature considerations

Cassini Ion & Neutral Mass Spectrometer Calibration Chamber

INMS Schematics

INMS Chamber Features (cont):

  • INMS gimbal motion control (+/- 10 degrees in any plane)
  • Scriptable movement, ion gun and instrument control
  • Instruments or detectors up to 13.25” CF size
  • Automated chamber parameter control, monitoring and recording
  • Hardware and software overpressure failsafe protection mechanisms for system and mission critical flight hardware
  • PC-controlled HV power supplies for up to 30 ion lens elements
  • Four (4) automated filament emission regulator power supplies for operating up to four (4) ionization sources
  • Flight-qualified RF power supply for quadrupole rod operation
  • Two (2) Granville-Phillips Stabil-Ion® gauges for pressure measurement and vacuum interlock operation from 1×10-4 to 1×10-10 Torr range
  • MKS spinning rotor gauge transfer standard for precise NIST-traceable pressure measurements from 1×10-2 to 1×10-7 Torr operation
  • Two (2) Granville-Phillips Convectron® gauge for turbopump foreline monitoring and main chamber during venting and initial evacuation
  • Pfeiffer PrismaPlus quadrupole mass spectrometer (QMS) residual gas analyzer (RGS)
  • No TQCM
  • No clean room or tent
  • < 1 hour to reach 1×10-6 Torr, 3×10-10 Torr typical after bakeout


Ion Source

  • Nominally supplies 5 ion species H+, Ar+, Ne+, He+, N+ and ion species relevant to Cassini mission, but other species possible
  • Ion energies from 1 keV down to < 10 eV
  • MCP imaging detection system
  • Faraday cup detection and beam monitoring system
  • Ion optics for beam spreading at target
  • Internal ion apertures for beam diagnostics and focusing
  • SwRI-developed custom ion source
  • Drift tubes for conducting ions to target at low eV
  • Ion source-to-target distance: ~30”

Cassin INMS Calibration System Ion Gun

Sample INMS mass scan

Graphical User Interface (GUI) for ion gun operation

Materials prohibited in both ion gun and main chamber: nylon, silicone, PVC, low molecular weight hydrocarbons, zinc, cadmium, brass, particulate contaminated or producing items/mechanisms (blacklight inspection prior to chamber entry preferred).

Image Gallery

Contact Information


Dr. Hunter Waite


Greg Fletcher

Lab Access

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