Ion Storage Aperture Contamination via DC Voltage Ramping
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Solution Overview
Problem
In ion storage devices used in mass spectrometry, the contamination of apertures by ions leads to performance degradation due to the buildup of sample material, which requires tedious cleaning and disrupts ion transport, especially for heavy ions that travel longer distances and experience higher losses, resulting in a limited mass-to-charge ratio range of 15-20 and inefficient ion trapping.
Innovation Solution
A method and apparatus for injecting ions into an ion storage device involving an RF trapping field, a gas, and a DC voltage ramp on the end electrode to create a potential barrier that prevents returning ions from striking the aperture, allowing a wider mass range to be trapped and reducing contamination by dynamically controlling the DC voltage during ion injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ions are injected into the ion trap through the aperture, then ion trapping capability is improved, but aperture contamination occurs due to ion deposition
Solution Approach 1:
The patent applies dynamics by making the DC voltage on the aperture electrode time-dependent. The voltage is dynamically adjusted: initially set to allow ion injection, then ramped up after injection to create a potential barrier that prevents ion deposition on the aperture. This temporal variation in voltage resolves the contradiction between enabling ion trapping and preventing aperture contamination.
Solution Approach 2:
The patent uses preliminary action by first establishing the ion injection process with an initial DC voltage setting that facilitates ion entry into the trap. After the ions have been successfully injected, the DC voltage is then increased to create the protective potential barrier. This sequential approach ensures ion trapping occurs first, followed by contamination prevention.
2Adaptability or versatility
If heavy ions are trapped in the ion trap, then mass range is extended, but ion losses increase due to longer braking length
Solution Approach 1:
The patent applies parameter changes by modifying the DC voltage parameter on the aperture electrode over time. By ramping the voltage after ion injection, the system creates a time-dependent potential barrier that adapts to prevent heavy ion losses. This parameter change allows the system to accommodate heavy ions with longer braking lengths while minimizing their deposition on the aperture.
3Object-generated harmful factors
If DC voltage is increased to prevent ion deposition, then aperture contamination is reduced, but ion injection efficiency decreases
Solution Approach 1:
The patent uses periodic action by implementing a two-stage voltage protocol: first, a lower DC voltage is applied during the ion injection phase to maintain high injection efficiency; second, after injection is complete, the voltage is ramped up to a higher level to prevent ion deposition. This temporal separation of voltage levels resolves the contradiction between injection efficiency and contamination prevention.
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 reduces aperture contamination, improves ion trapping efficiency for a wider mass range, and enhances ion transmission by preventing ions from depositing on the aperture, thus maintaining instrument performance and reducing the need for frequent cleaning.
Implementation Method 1
three-dimensional and two-dimensional (linear or toroidal) RF ion traps that utilise a combination of potential and pseudopotential wells in order to confine ions within the trap
Implementation Method 2
the ions lose energy in low-energy collisions with a bath gas contained in the trap until they equilibrate with the gas, thus reducing their kinetic energy from several electronvolts down to thermal energies of the order of kT
Implementation Method 3
ramping the DC voltage applied to the end electrode during at least a period from injecting the ions through the aperture to the return of the ions to the first end, such that by the time the ions return to the first end a potential barrier is provided by the DC voltage that prevents the returning ions from striking the end electrode
Implementation Method 4
When confining ions in an ion trap, Coulombic repulsion, or space charge, between the trapped ions opposes the confining forces of the applied potential and pseudopotential wells
Data Source
AI summary
A method of injecting ions into an ion storage device, comprising: providing an RF trapping field in the ion storage device that defines a trapping volume in the ion storage device by applying one or more RF voltages to one or more trapping electrodes; providing a gas in the trapping volume; injecting ions into the trapping volume through an aperture in an end electrode located at a first end of the ion storage device, the end electrode having a DC voltage applied thereto; reflecting the injected ions at a second end of the ion storage device, opposite to the first end, thereby returning the ions to the first end; and ramping the DC voltage applied to the end electrode during the period between injecting the ions through the aperture and the return of the ions to the first end, such that by the time the ions return to the first end for a first time a potential barrier is established by the ramped DC voltage that prevents returning ions from striking the end electrode. Also an apparatus for injecting ions into an ion storage device, which comprises a controller for ramping a first DC voltage applied to an end electrode of the device having an entrance aperture during a period between injection of ions through the entrance aperture and a return of the injected ions to the aperture so as to establish a potential barrier that prevents returning ions from striking the end electrode.