A MINIATURE MASS SPECTROMETER AS A MELTING PROBE PAYLOAD INSTRUMENT

1. A MINIATURE MASS SPECTROMETER AS A MELTING PROBE PAYLOAD INSTRUMENT • S. Sheridan • Planetary and Space Sciences Research Institute, Open University, Milton Keynes, • MK7 6AA, U.K. s.sheridan@open.ac.uk

2. Talk overview • Context: PSSRI research and instrumentation • Previous missions • Mass spectrometry background • Proposed payload for a melting probe • Results • Future work and conclusions

3. PSSRI instrument heritage • From sample analysis • Lunar samples • Meteorites • Stardust, Genesis… • …to in-situ instruments • Cassini-Huygens • SSP, HASI, CDA • Beagle 2 • ESS, GAP • Rosetta • Ptolemy, MUPUS, GIADA • And also enabling research: • Medical/life sciences • Next generation instruments • MEMS

4. The Gap instrument • GAP on Beagle2 (6 kg) • High precision (<<1%) • Solid sample inlet (carousel, MPAe) • Chemical sample processing • Chemical / getter pumps • Onboard reference material • Magnetic sector mass spectrometer (2kg, 5W) • VERY complex sample preparation

5. The Ptolemy instrument • Ptolemy on Rosetta lander (<5 kg) • Medium precision (1 to 5 %) • Solid sample inlet (carousel, MPAe) • Chemical sample processing • 3-4 channel gas chromatograph • Ion trap mass spectrometer (500 g, 1 W) • MEMS field emission electron source (CCLRC RAL) • Digital ion counting (no noise) • m/z 10-200 • C, H, N, O, (S?) • VERY complex sample preparation

6. The Ion trap Mass Spectrometer • Simple device: • Low mass, low power & rugged • 3 electrodes • 3D trapping field • r.f. (approximately 1 MHz) • Electron multiplier detector • Ion source • Fast scanning (m/z 10-250 in 100 ms) • Operates under poor vacuum (1x10-3 mbar) • Software control of one parameter (r.f.) • Limitations: • Requires sophisticated drive electronics

7. PSSRI Ion trap interests • Melting probe instrument • terrestrial (Lake vostock) • Europa, Mars poles • EVITA for an Instrumented mole • Active EDLS – measuring atmospheric properties (pressure, density, composition during descent e.g. to Mars) • Monitoring breathing air • Venus Entry Probe, balloon, • 100 gram microprobes • A batch of MEMS traps (due in next few weeks) • PhD student (1 Oct 2006-) sub-1 kg MS for planetary missions • Ongoing work in support of the Rosetta mission • Wellcome trust project - Breath analyser

8. The EVITA instrument • EVITA Evolved Volatiles Ion Trap Analyser • Initially developed for instrumented mole deployment • Modular system • Mission specific sampling method • Airless bodies: • Bepicolombo • NEO missions • Luna missions • Mars missions • Miniature Turbo pump (130 grams)

9. Ion trap on a Melting Probe • Instrument proposal: • Miniature ion trap (EVITA type) mass spectrometer • m/z of 10-200 amu • measurement of • either gaseous volatile compounds (if sampling in a non-aqueous environment) • or dissolved organic compounds (if sampling in an aqueous environment) • the above measurements to PPM levels • Use technology derived from previous projects • Low mass (<500 g) and low power (<1 W)

10. Sample inlet / preparation (1) (1) Thermally actuated proportional valve • Direct sampling of the environment • Feedback enables constant pressure (flow) • > 1x10-10 to 1x10-4 mbar l sec-1 • Very simple - a variable capillary leak • Pressure tested to 150 bar (Helium) • > Used on the Ptolemy instrument • Will allow evacuation during cruse phase • Limitations: • no selective control of sample species • > Lets everything into the mass spectrometer • problem with aqueous environment • > large gas load - Pumping requirement

11. Sample inlet / preparation (2) 2) Membrane inlet • Membrane is the interface between the liquid and the vacuum of the mass spectrometer • very low gas load in aqueous environments • >minimal pumping required • Rugged / simple devices • Negate extensive sample preparation • Continuous monitoring possible • Limitations: • Sensitivity depends on hydrophobicity and volatility of the analyte.

12. Ion trap for a Melting Probe

13. The prototype ion trap Prototype electronics Prototype hardware

14. Future work • More representative system • A vacuum vessel has been designed and is under construction to allow testing of the Ion trap with a MIMS and a direct inlet system • Sampling from liquids • investigation of pressure effects / length of operation with the mini chemical getter pump • Replace the Filament used in the prototype ion trap: • A batch of MEMS nanotip electron sources is being manufactured by RAL • testing and characterisation of these devices with the ion trap system • A alternative batch of miniature, rugged and low power electron sources has been procured. • A testing programme is currently underway to evaluate these devices with the Ion trap • Development of new electron multiplier devices • Further development of the Ion trap drive electronics is now required: • Funds required to enable a study to evaluate / design and manufacture an ASIC.

15. Conclusions • PSSRI has an active, ongoing programme of missions and technology development involving small ion trap mass spectrometers and the associated inlet systems • A prototype Ion trap instrument has been developed which is low mass, small, flexible in operation and could be carried by the proposed melting probe • Two sampling methods have been discussed which are compatible with the envisaged environment in which the melting probe will operate • Ongoing characterisation / development of the system is currently underway • Further development of the electronics, with the aim of designing and the eventual manufacture of an ASIC solution (maybe part of a common electronics solution???) • Looking for funding opportunities to achieve this

16. Acknowledgements • The PSSRI space instrumentation mass spectrometry group: • A.D. Morse • G.H.Morgan • S.J.Barber • I.P.Wright • M.Javis