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Title: High Resolution Mass Spectrometry In Space Exploration: Past Triumphs, Present Goals, Future Progress


1
High Resolution Mass Spectrometry In Space
ExplorationPast Triumphs, Present Goals, Future
Progress
  • Rob Sheldon
  • NSSTC
  • July 30, 2004

2
Outline
  • What is Mass Spectroscopy?
  • Weighing atoms, molecules, viruses
  • The Art of Weighing
  • A Short History with Nobel Prizes
  • An Even Shorter History of Space Mass
    Spectrometers
  • HELIX

3
What is Mass Spectroscopy?
4
The Art of Weighing
5
Why Weigh? or How Weigh?
  • Why?
  • Quantity Economics is established on this.
  • Quality e.g. Identity. (Archimedes eureka story)
  • How?
  • Gravitational force (static)
  • Directly spring balance (susceptible to
    external noise)
  • Comparatively pan balance (common mode
    rejection)
  • Inertial forces (dynamic, e.g. space station
    scales)
  • Resonant frequency (copper pennies, ripe
    watermelons)
  • Hefting (selecting hammers)
  • Galileo showed they were the same mass, so
    physics students are taught to never say weight

6
English Units of Weight
  • 1 block 5 lbs
  • 1 head 6 3/4 lbs
  • 1 clove or brick 7 lbs
  • 1 quartern 4 lbs
  • 1 gallon 10 lbs
  • 1 score 20 lbs
  • 1 truss (straw) 36 lbs
  • 1 frail 50 lbs
  • 1 firkin 56 lbs or 2 quarters
  • 1 bushel 63 lbs
  • 1 tub 84 lbs
  • 1 box 90 lbs
  • 1 fagot or seam 120 lbs
  • 1 sack 168 lbs
  • 1 wey 182 lbs
  • 1 grain ( 64.79891 mg) with 7000 1 pound
  • 16 grains 1 gram 1.03678256 g
  • 27.34375 grains 1 dram ( 1.771 g)
  • 16 dram 1 ounce ( 28.35 g)
  • 16 ounces 1 pound ( 453.59 g )
  • 14 pounds 1 stone ( 6.3503 kg)
  • 2 stones 1 British quarter ( 12.701 kg)
  • But US quarter 25 pounds ( 11.34 kg)
  • hundredweight or cwt.
  • 4 British quarters 112 pounds ( 50.80 kg)
  • 4 US quarters 100 pounds ( 45.35 kg)
  • 20 hundredweights 1 ton,
  • British long ton ( 2240 lb or 1016.04 kg)
  • US short ton ( 2000 lb or 907.18 kg)

7
Lagrange vs. Hamilton
  • Newton is overemphasized in physics instruction.
    Goldsteins 1950 Classical Mechanics introduced
    physicists to the importance of energy measures
    and their equivalence to forces. Feynman
    attempted a lecture series starting with energy
    conservation. Some HR problems are insoluble
    with forces, but simple with energy.
  • Hamiltonian methods (vs Lagrangian integration of
    forces) are used by accelerator magnet designers
    because they work faster and are more accurate.
    (Lie algebra convergence etc)
  • All our techniques of weighing used forces. Is
    there another way to weigh using energy ?

8
Illustrated w/Heisenbergs Uncertainty Principle
  • ?x ?(mv) ? h/2?
  • Now, multiply divide by v, e.g. v/v 1
  • ?x/v ?(mv)v ? ?t ?E ? h/2?
  • A force is described as a change in momentum,
    ?(mv). So weighing objects with known force
    requires measuring a displacement, ?x.
  • Therefore given a known energy, E, we can weigh
    by measuring elapsed time (time-of-flight), ?t .

9
Some Corollaries
  • A known force need not be measured, (e.g.,
    gravity) it need only remain the same during the
    measurement. Relative masses (ratios) are usually
    good enough.
  • Displacement must always be measured. Resolution
    then depends on measurement of displacement.
    (mirrors, lasers etc.)
  • Likewise a known energy need not be measured, but
    elapsed time must be, and resolution goes with
    time.
  • Therefore R ?x/x or ?t/t. Which is better?

10
Balance vs. Atwoods Machine
  • 2 ?x/g ?t² (M-m)/(Mm)

Errors in timing from pendulum clock, 0.1s/10s
1
West Point1900
11
Accuracy of Methods
  1. Spring balance, direct force measurement, rarely
    used in last 3000 years. Precision depended
    directly on ?x/x 1. Very noisy, accuracy
    affected by everything.
  2. Pan balance, direct force measurement,
    null-configuration (common mode rejection)
    enabled precision to the level of the
    differential noise (air currents) Accuracy
    dominated by calibration error. E.g. Biblical
    injunctions against separate selling and
    buying weights. Guesstimate ?m/m lt 1
  3. Timing methods never used. Error ?t/t gt 1 with
    pendulum clocks, probably gt10 with ancient
    timers.
  4. Dynamic balance, eg., frequency of pendulum
    never used. Frequency standards unknown.
    Multiplies the errors of timing (3) with the
    errors in length (1). Error gt10

12
Weighing atoms
  • Weighing atoms is hard. Pan balances can achieve
    micrograms, but molecules are
    micro-micro-micro-micrograms!
  • It turned out that the accuracy of measurement is
    exactly opposite for atoms than for apples.
  • Dynamic (FTMS) has the highest accuracy, Rgt106
  • Timing (TOFMS), R106,
  • Static (spatial) measurement (Mattauch-Herzog),
    R105.

13
The Weight of Glory
  • Avogadros number (actually due to Austrian Josef
  • Loschmidt in 1865, but renamed for a frenchman by
    1926
  • Nobel laureate J. Perrin) predicted the weight of
    atoms.
  • Ernst Mach, pre-eminent mathematician,
    physicist, and philosopher of the 19th century,
    did not believe in atoms because he couldnt see
    them. In 1905 Albert Einstein derived Avogadros
    number from Brownian motion. All these indirect
    methods, however, required macroscopic
    quantities, and incurred large errors. But in
    1897, though we couldnt see them, we could weigh
    them individually.
  • J.J. Thomson "At first there were very few who
    believed in the existence of these bodies smaller
    than atoms. I was even told long afterwards by a
    distinguished physicist who had been present at
    my 1897 lecture at the Royal Institution that
    he thought I had been 'pulling their legs.'"

14
A Short History of Mass Spectrometer Nobel Prizes
15
Joseph John Thomson (Physics 1906)
  • in recognition of the great merits of his
    theoretical and experimental investigations on
    the conduction of electricity by gases"
  • Cambridge University, 1856-1940

Thomson Parabola E // B, R10
16
Francis Aston (Chemistry 1922)
  • Cambridge University 1877 - 1945
  • for his discovery, by means of his mass
    spectrograph, of isotopes, in a large number of
    non-radioactive elements, and for his enunciation
    of the whole-number rule.

Crossed E and B R1
17
Static Force Measurement (?x)
  • Thomson Demonstration, physics

Aston Application, chemistry
18
Double Focussing Magnetic Sector
  • Astons contribution was to use the
    deflection by B to balance E. Careful
    considerations led to the double focussing
    magnetic sector MS attributed to both
    Nier-Johnson and Mattauch-Herzog.

19
Hans Dehmelt Wolfgang Paul (Physics 1989)
  • for the development of the ion trap technique

University of Washington, Seattle b. 1922(in
Görlitz, Germany)
  • University of Bonn
  • Federal Republic of Germany
  • 1913--1993

20
Dynamic Force Measurement (??)
Static electric field produces a quadratic
restoring force along z-axis. Hookes Law. But
since ?²?0, (Laplaces eq), d²?/dz ² -d ²?/dr ²
0, positive curvature in one coordinate
negative curvature in the other. Convergence in
z Divergence in r. ADD coaxial B-field to
stabilize.
Penning Trap (FT-ICR MS)
Resonant frequency ? ?mass
21
The Paul Trap
  • RF instead of B-field. Two possibilities 2-D
    (QuadMS) and 3-D (Ion Trap MS)

22
How can RF replace B?
  • Just as the ball starts to roll left or right,
    the hyperbolic saddle is rotated 90 degrees, so
    the ball is pushed back to the center in x.
    DUST!

23
John Fenn Koichi Tanaka (Chemistry 2002)
  • for the development of methods for identification
    and structure analyses of biological
    macromolecules
  • for their development of soft desorption
    ionisation methods for mass spectrometric
    analyses of biological macromolecules

Shimadzu Corp. Kyoto, Japan 1959--
Virginia Commonwealth University Richmond,
VA (Yale Emeritus) 1917--
24
Ionization Methods
  • Weve completely ignored the necessity of using
    ions (rather than neutral atoms) ionization.
  • Electron impact ionization E1ev is fine for
    atoms and inorganic molecules, but breaks most
    organic bonds, fragmenting them. Gentler
    ionization methods must be used for biomolecules.
  • Electron, plasma, ion, atom, laser impact are
    rough
  • Thermal, field-emission, chemical reaction better
  • Protonation Matrix assisted are easy gentle.

25
Time MeasurementThe Reflectron TOF MS
  • A narrow pulse of nearly mono-energetic ions
    streams through a drift region, where
    velocity-dispersion separates masses. Timing the
    arrival shows mass peaks. But Peakwidth
    pulse width dE/E.
  • The solution is a mirror, that makes the more
    energetic ions take a longer path, and to first
    order, correct dE/E

26
W.Stephens, W.Wiley I.McLaren B.Mamyrin
(Physics, 20??)
  • for the invention of time-of-flight reflectron
    MS.
  • Why am I so sure?
  • 1) Physics demonstration, Chemistry applied³
  • 2) Biochemistry applications using TOF are
    becoming very compelling, and there has to be a
    physics demonstration first.
  • 3) TOF is getting better and smaller but
    magnets, quads are maxed out.
  • 4) It is the next logical way to weigh.

27
An Even Shorter History of Space MS
28
(Plasma vs Radiation)
Property Plasma Radiation
Discoverer Langmuir 1910 Becquerel 1897
Energy eV keV MeV
Mass Measurement Deflection E B-fields Ionization dE/dx, emulsion
Detection Photomultiplier, Faraday cup Direct ionization, scintillation
29
The Challenge of Space MS
Property Space Lab
Weight kg 10-100kg
Power 5-10W 100-1000 W
Size lt50cm 1-10 m
Robust 1g 10g _at_100Hz
MTBF Years hours
UV 100Mcts/s 1ct/s
Source Temp 1-100 keV 0.001 keV
Energy width 100 .01-1
Radiation 10-100kRad/y lt1 kRad/y
30
SW/Plasma MS Timeline
Mass Spectrometer Year, Mission Resolution
Ion Traps 1959 Luna 1 lt 2
Faraday Cup 1961 Explorer 10 2
Electrostatic E/Q 1962 Mariner 2 3
Wien Filter 1983 ISEE-3 5
Magnetic Sector 71 Apollo, 86 Giotto gt40, gt10
Linear TOF 1984 Ampte 15
Isochronous TOF 1996 Wind 100
Reflectron TOF 2004 Rosetta gt3000
Helical TOF 20?? gt1000
31
Why Bother with Composition?
  • Minor effects of minor ions said a colleague
  • The Plasma Ecosystem
  • Origins tracers
  • Fast/slow solar wind ionosphere/SW mspheric
  • Acceleration both as tracer and trigger
  • O changes reconnection rate
  • Transport both tracer and differentiator
  • SEP composition reveals E/q acceleration
  • Death ENA visualizations (IMAGE)
  • He from SW, O from Earth

32
Sun-Earth Connection
  • AMPTE magnetospheric data, model and ratio, for
    He, showing inability of standard models to
    account for SW input into the magnetosphere.

33
SW Elemental Composition
  • Mass can separate degenerate M/Q species
  • Charge states give coronal temperatures at
    different altitudes.
  • Differentiate Fast/Slow SW
  • Ascertain SW origins

34
SW Isotopic Composition
  • Isotopes can reveal unique acceleration in SW.
    3He, 15N.
  • Triple Mg isotopes permit studies of mass
    fractionation of Solar interior.
  • Origins of proto-solar nebulae, age of the sun.

35
Origins of Solar System
36
Origins of Life
  • 1974-Viking lander on Mars

K. Biemann b. Austria 1926
37
Origins of Universe
  • 6Li is a crucial element formed in the big bang
  • 10Be believed to be a tracer for cosmic ray
    lifetime
  • Ne22 gives information on SW processes in
    Wolf-Rayet stars
  • Pickup ions are interstellar neutrals that have
    drifted into the heliosphere and become charged.
    We learn about ISM from them.

38
What Does the Future Hold?
  • Increase in mass resolution and sensitivity are
    needed for measuring isotopes in the highly
    rarified interstellar medium (ISM).
  • High mass range is needed for looking for
    biomarkers on Mars, Europa, Titan, comets.
  • Faster data acquisition needed to see finer
    details of solar wind, shocks and flybys.
  • More robust, compact instruments will enable more
    science on limited future opportunities.

39
TOF and Gating
  • As the timeline shows, TOF has the most growth
    potential of all the techniques so far. The major
    hurdle in improving TOF Resolution (and
    sensitivity, which gives better dynamic
    resolution) is the width of start pulse, e.g.
    gating.
  • Carbon foils give ns widths, but at a steep
    price. No one has found a way around it, everyone
    has tried.
  • Therefore faster electronic gates are needed AND
    longer TOF. But longer TOF means bigger!?
  • We solve all these problems with a helical TOF.

40
NSSTC TOF lab
41
Schematic TOF MS concept
42
Prototype HELIX with gate
SIMION Ion Trajectories
43
First Data
44
Predictions
  • NASA origins theme will not succeed w/o MS.
  • Mass spectrometry will continue to produce Nobel
    prizes in the 21st century.
  • The trends show that MS will get smaller, more
    robust, and more capable. TOF seem to be gaining
    on Quads for size and portability. They also have
    the edge in power consumption and sensitivity.
  • HELIX is one of many solutions to making TOF more
    compact. We are within a factor of 10x of having
    it in a cell-phone. Now you can be smarter than
    your dog.
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