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Mass Spectrometer at Arizona State University (ASU) |
Secondary
Ion Mass Spectrometry (SIMS)
SIMS is a technique for the characterization of solid
surfaces and thin films. It uses the process of ion formation
by bombarding the surface to be tested with a highly collimated
beam of primary ions. The surface then emits material
through a sputtering process - only a fraction of these
emitted particles is ionized. These secondary ions are
measured with a mass spectrometer to determine the quantitative
elemental, isotopic or molecular composition of the surface.
SIMS is the most sensitive surface analysis technique,
but it is more difficult to obtain quantitative results
compared to other techniques.
Take a 360-degree tour of the MegaSIMS Laboratory: High Res QT, 4.1 MB - click, hold, and drag your mouse slowly left, right, up, or down over the image.
Gas
Source Mass Spectrometry
Gas source mass spectrometers are used for measuring isotopic
ratios of light elements, which includes hydrogen, carbon,
nitrogen, and oxygen. Samples are prepared in gaseous
form, often hydrogen, nitrogen, or carbon dioxide, and
inlet into the mass spectrometer for analysis.
Resonance
Ionization Mass Spectrometry (RIMS)
RIMS is designed to determine the relative weights of
an atomic nuclei.
Total
Reflection X-Ray Florescence
In-Situ analysis used the Genesis Science team members,
which is unique in the fact that it does not require extraction
allowing the solar wind regimes to remain intact during
analysis and non-destructive to particle.
Plasma
Mass Spectrometry
A non-invasive method of extraction, allows the science
team members to study particles by using differential
chemical etching.
Accelerator
Mass Spectrometry
Accelerator mass spectrometry (AMS) differs from other
forms of mass spectrometry in that it accelerates ions
to extraordinarily high kinetic energies before mass
analysis. AMS is exceptional in its ability to sensitively
and accurately analyze elemental and isotopic compositions
How it all works
Generally negative ions are created (atoms are ionized)
in an ion source. It is preferable, but not necessary
that the charges be the same for each atom. These ions
are introduced to the gas phase and they enter an electrostatic
accelerator that accelerates them to very high kinetic
energy by presenting ever more positive electrical potentials.
Half-way through the accelerator they impact a sheet
of carbon. The impact strips off many of the ion's electrons,
converting it into a positively charged ion. In the
second half of the accelerator the now positively charged
ion is accelerated away from the highly positive center
of the electrostatic accelerator, which previously attracted
the negative ion. When the ions leave the accelerator
they are positively charged and are moving very fast.
Next, the exact ion velocities must be filtered such
that only a narrow selection of ion velocities is allowed
to pass to allow for proper mass analysis. A device
called a velocity selector, which utilizes both electric
fields and magnetic fields to allow only ions of a specific
charge and kinetic energy to pass, most frequently accomplishes
this. The ions then pass through at least one mass analyzer,
most often a magnetic or electric sector. For example
with a magnetic sector, the atom, at its known velocity
(relative to mass) and charge is released into a magnetic
field perpendicular to it velocity. This field causes
the particle's path to curve in a circular arc. The
radius of this circular arc is related to the mass-to-charge
ratio of the particle. Dedicated detectors for each
isotope or element then detect the ions. |
