Monolithic Photodiode Array for Ion-Trap Mass Spectrometer
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Solution Overview
Problem
Miniaturized ion-trap mass spectrometers face challenges in coupling and transmitting RF power due to parasitic losses, and achieving high frequency drive for low mass ion trapping, making it difficult to construct large arrays in chip-scale size for effective ion trapping.
Innovation Solution
A micro-scale ion-trap mass spectrometer driven by a monolithic photodiode array that generates high voltage at radio frequency, using a high-voltage photovoltaic source with serially connected photodiodes and an external light source for RF modulation, closely matching the ion trap's output impedance and reducing transmission losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional RF power coupling methods are used to drive miniaturized ion traps, then the ion trap can be operated at required frequencies, but large parasitic losses occur due to impedance mismatch and transmission line losses
Solution Approach 1:
The patent integrates the RF power source directly into the ion trap structure by fabricating a photodiode array monolithically on the same chip. This merging eliminates separate transmission lines and coupling structures, thereby removing the source of parasitic losses and impedance mismatch problems.
Solution Approach 2:
The patent introduces light as an intermediary to transfer energy to the ion trap. Instead of direct electrical coupling that causes parasitic losses, optical energy is used to generate RF voltage locally at the ion trap through the photodiode array, acting as a lossless intermediary.
2Volume of moving object
If the ion trap dimensions are decreased to achieve miniaturization, then the device size is reduced, but the drive frequency must be increased to maintain resolution for low mass ions
Solution Approach 1:
The patent replaces the traditional electrical RF drive system with an optical system. Light from an external source drives the photodiode array, which generates the required RF frequencies locally. This substitution allows precise frequency control without the limitations of external RF transmission lines.
3Productivity
If large arrays of ion traps are constructed on chip-scale substrates, then the analytical capability is enhanced, but parasitic losses increase due to distributed trapping structures
Solution Approach 1:
The patent segments the RF power generation function into multiple photodiode elements distributed across the chip. Each photodiode can be independently driven by the optical source, allowing large arrays of ion traps to be powered without requiring long transmission lines that would cause parasitic losses.
4Power
If external RF power sources are used to drive the ion trap, then the required voltage and frequency can be achieved, but the device complexity increases due to coupling structures
Solution Approach 1:
The ion trap structure serves its own power generation needs through the integrated photodiode array. The same chip that houses the ion traps also contains the power source, eliminating the need for external RF generators and complex coupling structures.
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
Enables efficient ion trapping and analysis of both large and small molecules with high sensitivity and resolution, suitable for applications like mobile gas detection and chemical analysis, by providing a compact, low-power, and high-voltage RF source in proximity to the ion trap.
Implementation Method 1
A high-voltage photovoltaic source can be located in proximity with the spectrometer structure. The high-voltage photovoltaic source is generally configured to include a large number of monolithically fabricated and serially connected photodiodes. An external light source (e.g., light emitting diode, laser diode, etc) can be utilized to illuminate the photodiodes in order to generate a high voltage across the photodiode array.
Implementation Method 2
An RF voltage modulation may be attained by modulating the light source at a desired RF frequency.
Data Source
AI summary
A chip-scale ion-trap mass spectrometer driven by a monolithic photodiode array and a method of fabricating the same. A high-voltage photovoltaic source is located in proximity to the ion-trap mass spectrometer structure. The high-voltage photovoltaic source includes monolithically fabricated and serially connected photodiodes. An external light source illuminates the photodiodes to generate a high voltage across the photodiode array. An RF voltage modulation is attained by modulating the light source at a desired RF frequency. The high-voltage photodiode array may be monolithically fabricated in association with the ion-trap mass spectrometer. The photodiode array requires a small area compared to the ion-trap mass spectrometer size as the spectrometer typically possess a very small capacitance and a low power consumption.