Tapered Nozzle Division Portion for Mass Spectrometer Mach Disk Suppression
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Solution Overview
Problem
The generation of Mach disks in mass spectrometers is not sufficiently suppressed across a wide range of operating conditions, particularly when analyzing in vivo samples, due to changes in pressure ratios between the ionization and intermediate vacuum chambers, which affects detection sensitivity.
Innovation Solution
A mass spectrometer design incorporating a nozzle unit with a division portion that has a tapered projection, where the diameter decreases toward the outflow port, is used to divide the sample flow, allowing it to cross and flow into the vacuum chamber, effectively canceling expansion waves and suppressing Mach disk formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional nozzle with a fixed circular opening is used, then the Mach disk can be suppressed under specific pressure conditions, but the suppression effectiveness deteriorates when pressure ratios change
Solution Approach 1:
The nozzle member employs a tapered projection whose diameter varies along the flow direction, creating dynamic flow division that adapts to different pressure ratios. The tapered geometry allows the flow division effect to remain effective across a wide range of operating conditions, unlike fixed circular openings that only work at specific pressure ratios.
Solution Approach 2:
The invention changes the geometric parameter of the nozzle from a fixed circular opening to a tapered projection with varying diameter. This parameter variation along the flow direction enables the nozzle to maintain Mach disk suppression effectiveness under changing pressure conditions by adjusting the flow division pattern.
2Reliability
If the nozzle opening diameter is reduced to suppress Mach disk, then Mach disk generation is suppressed, but the ion transmission efficiency decreases
Solution Approach 1:
The tapered projection divides the ion flow into multiple streams, creating segmented flow paths. This segmentation suppresses Mach disk formation by preventing the coherent supersonic jet that causes shock waves, while the cumulative effect of multiple flow streams maintains adequate ion transmission to the vacuum chamber.
Solution Approach 2:
The tapered projection introduces a new geometric dimension (radial variation of diameter along the axis) to the nozzle design. This dimensional addition creates flow division in the radial direction while maintaining axial flow progression, suppressing Mach disk without significantly reducing overall transmission.
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 design consistently suppresses Mach disk generation across varying operating conditions, enhancing the sensitivity and stability of mass spectrometry by ensuring the sample flow divides and cancels expansion waves, thereby reducing interference and improving detection accuracy.
Implementation Method 1
The sample gas generates an expansion wave when moving between chambers having a large pressure difference. The Mach disk is generated when the expansion wave is reflected at the boundary of the jet and the reflected wave interferes and amplifies.
Implementation Method 2
The Mach disk is generated when the expansion wave is reflected at the boundary of the jet and the reflected wave interferes and amplifies.
Data Source
AI summary
The mass spectrometer includes an ionization unit that ionizes a sample; a nozzle unit having an inflow port that is connected to the ionization unit by a flow pipe and through which the ionized sample flows, and an outflow port from which the sample flowing in flows out; a vacuum chamber that is evacuated by vacuum evacuation means and into which the sample flows from the nozzle unit; a mass analysis unit that is located downstream of a flow of the sample relative to the vacuum chamber and that selects ions from the sample; and an ion detection unit that detects the ions selected by the mass analysis unit, wherein a division portion that divides a flow of the sample is provided inside the nozzle unit, and the division portion has a tapered projection whose diameter decreases toward the outflow port.