Sealed Yb Ion Clock With Octupole Trap for Low-SWaP Timing
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Solution Overview
Problem
Conventional ion clocks, such as those using mercury (Hg) ions, are large, heavy, and require significant electrical power, limiting their application in smaller devices like nano satellites and UAVs, and they necessitate ion shuttling and UV radiation for optical pumping.
Innovation Solution
A microfabricated ion frequency standard utilizing ytterbium (Yb) ions in a permanently-sealed vacuum package with an octupole ion trap, employing acoustic oscillators for microwave generation and integrated optical sources for reduced size, weight, and power consumption, without the need for ion shuttling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Hg ion clock is used, then frequency stability and accuracy are achieved, but size, weight and electrical power consumption are excessive
Solution Approach 1:
The patent changes the ion species from Hg to Yb, exploiting different atomic properties of Yb ions that allow for compact trap design and efficient microwave coupling, thereby achieving high frequency stability with reduced mass
Solution Approach 2:
The patent replaces the mechanical ion shuttling system with a stationary octupole trap configuration where Yb ions are confined and interrogated in place, eliminating the need for complex ion transport mechanisms and reducing overall system weight
2Measurement precision
If conventional Hg ion clock is used, then frequency stability and accuracy are achieved, but size, weight and electrical power consumption are excessive
Solution Approach 1:
The patent integrates multiple functional components (octupole trap electrodes, microwave cavity, photodetector, heating element) within a nested hierarchical structure where smaller components are positioned within or on the surfaces of larger components, maximizing space utilization and minimizing overall clock size
Solution Approach 2:
The patent employs a three-dimensional octupole trap configuration that confines ions in all spatial dimensions, allowing for compact volume while maintaining sufficient ion storage time and interrogation efficiency for high-precision frequency measurements
3Measurement precision
If ion shuttling is implemented, then frequency measurement is enabled, but device complexity increases
Solution Approach 1:
The patent extracts the ion shuttling function from the system entirely, using a stationary octupole trap to confine and interrogate Yb ions in place, thereby simplifying the device architecture while maintaining frequency measurement capability through continuous ion confinement and microwave interrogation
4Measurement precision
If 202Hg discharge lamp is used for optical pumping, then ion preparation is achieved, but size, weight and power consumption increase
Solution Approach 1:
The patent changes the optical pumping wavelength from 194 nm (for Hg) to 399 nm (for Yb), allowing the use of more efficient and lower-power UV LEDs or laser diodes at the longer wavelength, thereby reducing electrical power consumption while maintaining effective ion preparation
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
The Yb ion frequency standard achieves significant size, weight, and power reductions, enabling compact and efficient operation suitable for small-scale applications like nano satellites and UAVs, with improved stability and accuracy.
Implementation Method 1
Microwave radiation for the ion frequency standard of the present invention can be generated using an acoustic oscillator which can comprise a film bulk acoustic wave (FBAR) oscillator, a microresonator oscillator or an acoustic bandgap (ABG) oscillator.
Implementation Method 2
A frequency-doubled vertical-external-cavity surface-emitting laser (VECSEL) can then be used to irradiate the Yb ions in the ground-state upper hyperfine level, thereby exciting the Yb ions from the ground-state upper hyperfine level into an excited-state level.
Implementation Method 3
The Yb ions in the excited-state level decay with the emission of fluorescent light which can be detected by a photodetector to generate an electrical output signal
Implementation Method 4
The electrodes, when activated with radio-frequency (rf) and direct-current (dc) electrical signals, provide electric fields which confine the Yb ions within a trap volume of the octupole ion trap.
Implementation Method 5
An electrical heater is located on the suspended membrane with a layer of ytterbium (Yb) being in thermal communication with the electrical heater. When the electrical heater is activated with an electrical current, Yb atoms are released in a cloud from the Yb layer.
Implementation Method 6
The ionization source can comprise an ultraviolet (UV) light-emitting diode (LED) which photoionizes the Yb atoms.
Data Source
AI summary
A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.