Ion Detector Electron Lens Segmentation for MCP Area Expansion
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Solution Overview
Problem
Ion detectors with microchannel plates (MCPs) face challenges in expanding the effective region for capturing ions, particularly in quadrupole time-of-flight mass spectrometry, due to limitations in the electron lens structure, which results in insufficient focusing of electrons with varying energy and angles.
Innovation Solution
An ion detector design incorporating an MCP unit, a signal output device, and a reset unit with focus electrodes and a reset element, allowing for an electron lens structure with independent control of two adjacent electron lenses to reset variations in electron angle and velocity, thereby expanding the effective region of the MCP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single electron lens is used to focus electrons from the MCP output surface, then the electron beam can be focused to a small region, but the effective region of the MCP for capturing ions is limited to about 25 mm in diameter
Solution Approach 1:
The single electron lens is divided into two separate electron lenses (first electron lens and second electron lens) arranged in sequence. The first electron lens performs initial focusing of electrons from the MCP, while the second electron lens performs final focusing onto the detector. This segmentation allows each lens to operate within its optimal focusing range, enabling the MCP effective region to be expanded to 40 mm or more while maintaining precise electron focusing on the detector surface.
2Area of stationary object
If the effective region of the MCP is expanded to 40 mm or more for Q-TOF mass spectrometry, then more ions can be captured, but the single electron lens structure cannot sufficiently focus electrons from such a large area
Solution Approach 1:
The electron optical path is extended by introducing a second electron lens, effectively adding a dimensional element to the focusing system. This two-stage focusing approach allows electrons from a larger MCP area (40 mm or more) to be progressively focused: the first lens collects electrons from the expanded MCP region, and the second lens concentrates them onto the detector, overcoming the limitation of single-lens focusing capability.
3Measurement precision
If the distance between the MCP output surface and the detector is reduced to improve electron focusing, then electron lens performance is enhanced, but the physical space required for the detector assembly is reduced
Solution Approach 1:
The electron focusing function is segmented into two stages performed by separate electron lenses. This allows the detector assembly to be compact (reduced length) while maintaining high detection precision, as the two-lens system achieves effective focusing within a shorter overall distance compared to a single lens requiring larger working distance.
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 configuration enables focused electrons to be directed to a minute region, enhancing the ion detection capability and overcoming the limitations of conventional electron lens structures by effectively expanding the MCP's effective region.
Implementation Method 1
the MCP outputs an electron from the first output surface in response to an incident ion (charged particle) on the first input surface
Implementation Method 2
a first focus electrode serving as an electron lens... a second focus electrode serving as an electron lens
Data Source
AI summary
To provide an ion detector having an electron lens structure that enables expansion of an effective region of an MCP for capturing ions.The ion detector comprises an MCP unit including an MCP and a first focus electrode, a signal output device including an electron detector surface, and a reset unit disposed between the MCP unit and the signal output device. The reset unit includes a reset element and a second focus electrode. The reset element includes a second input surface and a second output surface opposing each other. On the second output surface, the reset element resets variations in incident angle and velocity of electrons on the second input surface.