Breaking Matter Down

Mass Spectrometer and particle Accelerators

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Breaking Matter Down
Mass spectrometer
Before entering the mass spectrometer, solids and liquids are converted into gas (volatised)
by rapid heating or using a heating coil to heat samples electrically. They are carried into the
mass spectrometer by an inert gas.
The mass spectrometer consists of 4 sections;
The ion chamber
The velocity selector
The momentum selector
The ion detector
Ion Chamber
In the ion chamber particles are ionised by bombarding them with high energy electrons.
Each collision between a free high energy electron and an electron attached to a nucleus
knocks out one electron from the atom, giving it a positive net charge of 1. As most of the
ions have a net charge of +1, it can be assumed that the mass spectrometer separates ions
based on mass and not charge.

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Velocity Selector
The velocity selector selects ions moving at a certain velocity. Electric and magnetic fields
are applied in opposite directions so that they cancel each other out for particles moving at
a certain velocity that will therefore not be deflected and do travel straight through to the
momentum selector.
F E = EQ , F M = BQv
E
EQ = BQv v = B
Momentum Selector
All ions in the momentum selector have the same velocity.…read more

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Linear Accelerator
Adjacent drift tubes are oppositely charged, meaning that the particle is always accelerated
towards the next tube.
Inside the drift tube is uncharged, therefore inside the drift tube the particle travels at
constant speed. This gives the supply time to reverse the polarity before the particle exits
the drift tube and avoid deceleration of the particle.
As the particle is accelerating, the length of the drift tubes must therefore increase.…read more

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QB
T = 1
f = 2m
Therefore frequency does not depend on velocity. Similar particles with similar
charge-to-mass ratios will all orbit with the same period regardless of their speed.…read more

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Relativity applies. The theory of special relativity only applies when the particle is moving at
constant speed ­ when accelerating, Einstein's Theory of Relativity must be applied.…read more

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Therefore we should not see any muons at sea level but we do. Taking into account
t0 2.2x10-6
relativistic effects t = 2
= = 3.5x10-5s
(1- v
c2
)
3x10
x108
1-( 0.998 x 38 )
2
v = ts s = vt = 0.998 x 3x10 x 3.5x10 = 10500m therefore it is likely that muons will be
found at sea level.…read more

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Bqv = mv2/r <--- Shows that the magnetic field causes circular motion.
Creates spiralling path for particles.
Synchrotrons:
Varying magnetic fields allow the particles to have a pathway with a constant radii.
This means that they can be increased to greater speeds than in cyclotrons.
Particle detectors
In bubble chambers charged particles are deflected, making them curve in different
directions - allows the particles' charge sign to be detected.
Allows the charge/momentum/energy to be found.…read more

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