Cassini Reflector TOF Mass Spectrometer Double Focusing
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Solution Overview
Problem
Current time-of-flight mass spectrometers face challenges in achieving high mass resolution while maintaining a compact design, as they require long flight paths and high accelerating voltages to manage ion energy spread, leading to focusing errors and increased instrument size.
Innovation Solution
The implementation of Cassini ion traps and reflectors with a potential distribution that decouples longitudinal and lateral oscillations, allowing for ideal energy and solid angle focusing, even at low ion energies, and enabling the use of multiple reflectors to extend mass-dispersive time without increasing energy or angular spreads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long flight paths are used to achieve high mass resolution, then mass resolution is improved, but device complexity and instrument size increase
Solution Approach 1:
The patent implements a double-focusing reflector where one reflector is nested within another, creating a compact configuration that provides both energy focusing and angular focusing. The inner reflector focuses energy while the outer reflector focuses angles, achieving high mass resolution without requiring a long flight path.
Solution Approach 2:
The patent employs curved reflector surfaces with specific radii of curvature to achieve double focusing. The spherical or parabolic curvature of the reflector surfaces enables both energy and angular focusing, allowing compact instrument design while maintaining high mass resolution.
2Measurement precision
If high accelerating voltages are used to reduce relative energy spread, then mass resolution is improved, but device complexity increases due to need for long flight paths
Solution Approach 1:
The nested double-focusing reflector configuration allows the system to achieve both energy focusing (reducing relative energy spread) and angular focusing in a compact design. This eliminates the need for long flight paths that would otherwise be required when using only high accelerating voltages.
Solution Approach 2:
The patent changes the electrical parameters of the nested reflectors, specifically setting the voltage ratio between inner and outer reflectors to optimize focusing. By adjusting these electrical parameters, the system achieves double focusing with reduced relative energy spread without requiring proportionally higher accelerating voltages.
3Measurement precision
If multiple reflectors are used to extend flight path and keep instrument compact, then mass resolution is improved, but focusing errors accumulate
Solution Approach 1:
The nested reflector configuration ensures that the inner and outer reflectors work together in a coordinated manner. The inner reflector provides energy focusing while the outer reflector provides angular focusing, and their nested arrangement minimizes the accumulation of focusing errors by ensuring proper spatial and electrical coordination between the two reflectors.
Solution Approach 2:
The patent optimizes the electrical parameters of the multiple reflectors, specifically the voltage ratios and potential distributions, to minimize residual focusing errors. By carefully controlling these parameters, the system achieves extended flight path and high mass resolution while maintaining focusing accuracy.
4Length of stationary object
If lower accelerating voltages are used to achieve shorter flight paths, then instrument size is reduced, but mass resolution deteriorates due to higher relative energy spread
Solution Approach 1:
The nested double-focusing reflector enables the system to use lower accelerating voltages while maintaining high mass resolution. The inner reflector compensates for energy spread through energy focusing, and the outer reflector compensates for angular spread through angular focusing, allowing short flight paths without sacrificing resolution.
Solution Approach 2:
The nested configuration provides both energy and angular focusing in a compact arrangement, enabling the use of lower accelerating voltages and shorter flight paths while maintaining high mass resolution through the combined focusing effects of the two reflectors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in improved mass resolution and compact instrument design, allowing for longer mass-dispersive passage times and higher repetition rates without increasing energy or angular spreads, effectively addressing the limitations of existing technologies.
Implementation Method 1
at least a section of the flight path of the time-of-flight mass spectrometer has a potential distribution of a Cassini ion trap with several inner electrodes
Implementation Method 2
the Cassini ion trap being shaped for decoupled oscillations of the ions in the longitudinal and the lateral directions
Implementation Method 3
Mamyrin reflectors (B. A. Mamyrin et al., 'The mass-reflectron, a new nonmagnetic time-of-flight mass spectrometer with high resolution', Sov. Phys.-JETP, 1973: 37(1), 45-48) in order to temporally focus ions with an energy spread
Implementation Method 4
Mamyrin reflectors allow second-order temporal focusing, but not higher order focusing
Implementation Method 5
Time-of-flight mass spectrometers where a primary ion beam undergoes pulsed acceleration at right angles to the original direction of flight of the ions are termed OTOF-MS (orthogonal time-of-flight mass spectrometers)
Implementation Method 6
Time-of-flight mass spectrometers with specially shaped reflectors
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to embodiments of high-resolution time-of-flight (TOF) mass spectrometers with special reflectors. The invention provides reflectors with ideal energy and solid angle focusing, based on Cassini ion traps, and proposes that a section of the flight path of the TOF mass spectrometers takes the form of a Cassini reflector. It is particularly favorable to make the ions fly through this Cassini reflector in a TOF mass spectrometer at relatively low energies, with kinetic energies of below one or two kiloelectronvolts. This results in a long, mass-dispersive passage time in addition to the time of flight of the other flight paths, without increasing the energy spread, angular spread or temporal distribution width of ions of the same mass. It is also possible to place several Cassini reflectors in series in order to extend the mass-dispersive time of flight. Several TOF mass spectrometers for axial as well as orthogonal ion injection with Cassini reflectors are presented.