CPO software package for designing charged-particle optical systems
Submitting Institution
University of ManchesterUnit of Assessment
PhysicsSummary Impact Type
TechnologicalResearch Subject Area(s)
Physical Sciences: Atomic, Molecular, Nuclear, Particle and Plasma Physics, Other Physical Sciences
Summary of the impact
A software package called CPO has been developed that simulates the
motion of charged particles
in electromagnetic fields. More than 200 benchmark tests have established
CPO as the gold
standard in low-energy charged-particle optics. A spin-off company was
formed to market CPO,
[text removed for publication]
Underpinning research
The key researchers were:
Prof. F. H. Read, FRS, (Head of Research Group, 1993-2005 and Emeritus
thereafter).
Dr N. J. Bowring (Senior Experimental Officer, 1993-2002, and
collaborations thereafter).
Prof. G.C. King (Sen. Lect., 1993-5; Reader, 1995-01; Prof. of Physics,
2001-07 and
Emeritus thereafter).
Prof. A. J. Murray (Lect. 1999-01; Sen. Lect. 2001-02; Reader 2002-07;
Prof. of Physics,
2008-date).
The impact is based on research undertaken in atomic and molecular
physics during the period
1993 to the present, which in that time produced >150 peer-reviewed
publications with > 40
publications on electron optics and associated instrumentation. As part of
the research
programme, a software package called Charged Particle Optics (CPO) was
developed to simulate
the motion of charged particles in electrostatic and magnetic fields; see
[5] for a recent description.
Underpinning this research was the development of a three-dimensional
technique, which employs
the Boundary Element (BE) method for solving electromagnetic
problems rather than conventional
Finite Element (FE) or Finite Difference (FD) methods. This
BE method is one or two orders of
magnitude more accurate than FE or FD methods for the same computing time
[5]. Other
advantages of CPO software are that it can deal with electrodes of
essentially any shape and it is
particularly powerful for space-charge problems such as electron guns. In
the course of the
research, CPO was also developed to handle magnetic fields as well as
electrostatic fields.
The use of CPO led to the following key advances: (i) the design of
electrostatic lenses with very
low aberrations, which was achieved through the high accuracy in modelling
electron trajectories,
(ii) the development of high-current electron guns, which exploited the
ability of CPO to include the
effects of Coulomb interactions between charged particles [3], (iii) the
optimisation of three-dimensional
electron optical devices [2] and (iv) the invention of new electron
optical devices [1]. A
good example of this is the invention of the magnetic angle-changer.
This enabled for the first time,
electrons that are scattered from a gaseous target be detected over the
full range of scattering
angle, from 0 to 180°, [4,6]. This enabled theory to be tested in regions
that were previously
inaccessible to experiment and provided the most accurate values of
scattering cross-sections that
are of practical importance. The magnetic angle-changer was described by
an international
conference speaker [text removed for publication] as "the most important
development in low-
energy electron spectroscopy in 25 years".
References to the research
The research has been published in leading journals including; Physical
Review Letters, Journal of
Physics B: Atomic, Molecular and Optical Physics and Review of Scientific
Instruments. The
publications have been cited on numerous occasions; for example, refs. [1]
and [4] have been cited
94 and 61 times respectively, according to Web of Knowledge. The
research has also been
presented at international conferences including the: International
Conference on Photonic,
Electronic & Atomic Collisions and International conference
on Charged Particle Optics.
Key references
[1] "Production and optical properties of an unscreened but localized
magnetic field", Read F. H.
and Channing J., Rev. Sci. Instrum., 67, 1996, 2372-7, (1996). DOI: 10.1063/1.1147004
[2] "Accurate Monte-Carlo calculation of Boersch energy and angle
spreading", Read F.H. and
Bowring N.J., Rev. Sci. Instrum., 74, 2280, (2003). DOI:10.1063/1.1544422
[3] "The parallel cylindrical mirror electron energy analyser", Read
F.H., Rev. Sci. Instrum., 73,
1129, (2002). DOI: 10.1063/1.1435841
Other References
[4] "Measurements of elastic electron scattering in the backward
hemisphere", Zubek M., Gulley
N., King G.C. and Read F.H., J. Phys. B Atom. Molec. Phys, 29, L239,
(1996). DOI:
10.1088/0953-4075/29/6/011
[5] "The CPO programs and the BEM for charged particle optics", Read F.H.
and Bowring N.J.,
Nucl. Instrum. Meths. in Phys. Res., 654, 273, (2011). DOI:10.1016/j.nima.2010.12.163
[6] "Super-elastic scattering from calcium over the complete angular
scattering range using a
magnetic angle changing device." Hussey M., Murray A.J., MacGillivary
W.R., and King G.C.,
Phys. Rev. Letts. 99, 133202, (2007). DOI: 10.1103/PhysRevLett.99.133202
Details of the impact
Research in atomic and molecular physics at Manchester requires
state-of-the-art instrumentation
for the study of atoms and molecules by electron spectroscopy. This
requires accurate knowledge
of the behaviour of electrons and ions in the electrostatic and magnetic
fields of the
instrumentation. Consequently, a software package (CPO) was developed to
model this behaviour
precisely. Analytical instruments using charged-particle optics are also
widely used in industry.
These instruments also need to have the highest performance for the
increasingly demanding
requirements of customers. Consequently, a spin-off company was formed to
make CPO available
to manufacturers of scientific instruments and other users of electron
optics. This company, called
Charged Particle Optics Ltd, was started by two staff from the School of
Physics and Astronomy
(Read & Bowring).
The principle advantage of CPO for customers is that it is one or two
orders of magnitude more
accurate than conventional finite element or finite difference methods.
This has been demonstrated
by more than 200 benchmark tests that are based on problems that have well
known analytical
solutions. These benchmark tests are readily available to prospective
customers, [A] and these
tests have established CPO as the gold standard of charged particle
optics. This superior accuracy
provides, for example, enhanced mass resolution in a mass spectrometer
[text removed for
publication]. Other important advantages are that CPO can easily deal with
electrodes of any
shape and of very different sizes, such as nano-sized electrodes in
centimetre-sized systems, and
because CPO is a charge-based method, it can deal with systems that
include space charge
and/or cathodes. These are of crucial importance to manufactures of high
throughput analysis
tools, [text removed for publication] . Moreover, a manufacturer can use
CPO to develop and test
designs for new products before any metal is machined, saving them
considerable time and cost
[text removed for publication].
CPO has been sold [text removed for publication].
Illustrative Examples of Impact
(i) [text removed for publication].
(ii) [text removed for publication]
(iii) At the Jet Propulsion Laboratory (JPL), California, CPO was used to
simulate the electron
ionizer in the prototype of a gas chromatographic mass spectrometer system
that was later flown
as a flight version to the International Space Station (ISS). The purpose
of this instrument is to
monitor the concentration — at the parts-per-million to parts-per-billion
levels — of trace, toxic
chemical species in the ISS cabin atmosphere. Species include acetone,
ethanol, aldehydes,
ketones, benzene, and perfluoropropane. The unit also monitors the major
constituent species N2,
O2, CO2, and Ar. Both types of measurements are
needed to assure astronaut safety in the cabin.
All data are processed on-board by the instrument, and as well transmitted
to JPL for further
analysis and archiving. The full space-charge capability of CPO was
especially important to the
design and testing of the electron ionizer of the mass spectrometer. [text
removed for publication]
The instrument was used successfully for two years aboard the Space
Station, and was recently
returned to Earth for refurbishment [text removed for publication].
Summary of Economic Impact
[text removed for publication]
Sources to corroborate the impact
[A] Information about CPO, benchmark tests and prices from: Charged
Particle Optics programs
web site: http://www.electronoptics.com/.
[B] [text removed for publication]
[C] [text removed for publication]
[D] [text removed for publication]
[E] [text removed for publication].