introduction to charged particle optics * theory and simulation

Report
CPOTS – 2nd ERASMUS Intensive Program
Introduction to Charged Particle Optics:
Theory and Simulation
http://cpots2012.physics.uoc.gr
Dept. of Physics, University of Crete
Aug 19 – Sept 2, 2012
Heraklion, Crete, GREECE
Group Project
Magnetic Bottle Electron Spectrometer
Nimet Okumuş
Socrates Anastasopoulos
David Alcocer Velarde
http://cpots2012.physics.uoc.gr
2
Abstract
The principles of magnetic bottle
mass spectrometer
Theoretical analysis
Energy resolution of magnetic
bottle spectrometer
Conclusions
3
Magnetic Bottle Electron Spectrometer
Weak uniform
B field
The use of permanent magnets
requires modifications of the
transition region (between the
high-field electron production
zone and the low-field drift tube
analyzer) to avoid axial field
reversals
associated
with
fringing fields.
Strong
B field
•
Electrons spiral in B field which reduces adiabatically
•
Electron energy measured by time of flight to detector
•
Lets use a standard spectrometer, e.g. hemispherical analyser with an
e-
entrance aperture
•
Very small solid angle, most electrons lost!
•
4 collection of electrons
Analyser
eee-
4
Investigate Spectrometer Properties
•
Measure the time of flight for electrons with
different conditions (using Record function)
•
Find the energy resolution of the spectrometer in
different situation
5
SIMION Magnetic Bottle Spectrometer
Particles Definition
SIMION Magnetic Bottle Spectrometer
Flying Particles
Three different group
with energy 40, 20, 5 eV
SIMION Modelling of Magnetic Bottle Spectrometer
From this 2 equations
we exported the
relation between
Kinetic Energy and
TOF
K is constant.
Energy Resolution of
Spectrometer
8
SIMION Magnetic Bottle
Spectrometer
Bi=2000 gauss
Bf=10 gauss
Transition Region=9 mm
Calibration
factor=KE×(TOF)2
K=0.179574 eV µsec²
Convertion TOF to KE
TOF
KE
Magnetic Bottle Spectrometer Resolution
The resolution of the Spectrometer is: 10%
Energy resolution = 19.75 eV/(20.6-18.6) eV ≈10%
Energy resolution = 9.95 eV/(10.4-9.4) eV ≈ 10%
Energy resolution doesn’t depend on KE.
ΔKE
CPOTS 2012: S9 - JBG
ΔKE
http://cpots2012.physics.uoc.gr
12/XX
Resolution
Resolution= 9.6 / (10.35-8.9)=6.6%
Resolution= 8.6/ (10.25-7.1)=2.7%
Bi= 3000 Gauss
Bi=8000 Gauss
ΔKE
ΔKE
CPOTS 2012: S9 - JBG
http://cpots2012.physics.uoc.gr
13/XX
Conclusion
Resolution of spectrometer is depent on length of
the time of flight tube.
The resolution changes with B field .
Energy resolution doesn’t depend on KE.
CPOTS 2012: S9 - JBG
http://cpots2012.physics.uoc.gr
14/XX

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