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New Portable Atomic Clock
Context:
The Indian Institute of Science Education and Research, Pune, is actively engaged in the development of a strontium optical atomic clock.
More on News
- Indian astronomers from Inter-University Centre for Astronomy and Astrophysics are developing a similar clock using ytterbium ions.
- A study published in Nature has introduced a portable optical atomic clock that can be used onboard ships despite some loss in accuracy due to size and robustness.
Atomic Clocks:
Atomic clocks are the cornerstone of the Global Positioning System (GPS), the network of satellites that facilitates daily navigation, emergency responses, military operations, and more.
- Atomic clocks are highly accurate, losing or gaining only one second over 300 million years.
- Current Limitations of Atomic Clocks: Conventional and optical atomic clocks are sophisticated but bulky, energy-intensive, fragile, and expensive, restricting their use to large research facilities.
Working of an Atomic Clock:
- Design and Definition: Uses atoms of isotope caesium-133 (Cs-133). It is highly stable and naturally abundant.
- International Committee for Weights and Measures defined one second using Cs-133 in 1967.
- India also uses a Cs-133 atomic clock for national timekeeping.
- Fundamental Property: Atoms can jump between different energy levels, absorbing energy (e.g., electromagnetic radiation).
- Mechanism: Researchers apply microwave radiation to Cs atoms in a cavity, causing a resonance when the frequency matches the transition energy of the atoms.
- Frequency and Time Measurement: Transition frequency is exactly 9,192,631,770 Hz. When Cs-133 atom completes oscillations one second has passed.
- Precision: Caesium atomic clock loses or gains a second every 1.4 million years.
Advancements with Optical Atomic Clocks:
- Accuracy: Accurate than traditional atomic clocks due to their resonance frequency in the optical range, which includes visible light, ultraviolet, and infrared radiation.
- Use of Lasers: The researchers use lasers to excite atomic transitions.
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- Resulting in highly coherent light with precise properties and great stability due to the constant frequency and wavelength relationships.
- Strontium (Sr) is the most commonly used atom due to its narrow linewidths and stable optical transitions.
Portable Optical Atomic Clocks:
- Developed using molecular iodine as the frequency standard. Less accurate than lab versions, but still only a loss/gain of one second every 9.1 million years.
- Miniaturisation: Traditional optical atomic clocks are large and hard to transport.
- Objective: To fit within standardised racks (data centres, laboratories, telecommunications facilities).
- Components Miniaturised:
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- Spectrometer: Measures transition frequencies; volume of 2.5 litres.
- Laser System: Uses optical fibres; volume of 1 litre; operates at 1,064 nm wavelength.
- Frequency Comb: Generates series of equally spaced optical frequencies; volume of 0.5 litres.
- Final Specifications:
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- Total volume: 35 litres (size of a large backpack).
- Weight: 26 kg.
- Power Consumption: 85 W (slightly more than an incandescent light bulb).
Testing and Applications at Sea
- Researchers at U.S. National Institute of Standards and Technology (NIST) conducted initial tests on two prototypes.
- PICKLES and EPIC, autonomously for 34 days in April 2022.
- Optical atomic clocks showed less fluctuation over short periods, surpassing NIST’s ST05 which is a highly accurate and stable atomic clock based on hydrogen atoms.
- VIPER, another clock with a smaller spectrometer and simplified laser design, deployed on a boat at Pearl Harbor, Hawaii.
- Stability at Sea:
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- Clocks remained stable despite ship’s motion, temperature fluctuations (2-3°C), and changes in humidity (4-5%).
- Stable for up to 1,000 s at a time, but longer operation exposed them to temperature fluctuations.
- The development of such setups is crucial for navigation, maritime communication, and scientific research, enabling precise monitoring of underwater seismic and volcanic activity.
- Instruments on board the spacecraft could help scientists test relativity theories and also reduce the cost of satellite-based navigation.
