Chinese team runs cold atomic clock in space for 15 months

Chinese team runs cold atomic clock in space for 15 months
In-orbit operation of an atomic clock based on laser-cooled 87Rb atoms. Principle and structure of the space cold atom clock (CAC). The capture zone is a magneto-optical trap (MOT) with a folded beam design. The ring interrogation cavity is used for the microwave field to interrogate the cold atoms. In the detection zone, cold atoms in both hyperfine states are detected. The clock signal is obtained by feeding the error signal to the frequency of microwave source. Credit: Nature Communications (2018). DOI: 10.1038/s41467-018-05219-z

A team of researchers at the Chinese Academy of Sciences has successfully operated a cold atomic clock in space for a period of 15 months. In their paper published in the journal Nature Communications, the group describes how they succeeded in achieving the difficult task.

Cold atomic clocks keep time by measuring atomic oscillations in (so no interference occurs). They are chilled, as their name implies, to near using lasers, which makes them more precise. It would be convenient for researchers to have a cold atomic run in —that would allow for measuring time more precisely for such things as GPS applications. But space presents challenges that are not present on Earth, including the size and weight of the apparatus—both are at a premium on spacecraft. There is also the matter of shielding the clock from . Such roadblocks have prevented the use of these clocks in space, until now.

In this new effort, the researchers report that they have successfully run a cold atomic clock on board an Earth-orbiting vehicle—the Tiangong-2 Chinse space station. They report further that they ran the clock for 15 months, and during that time, they achieved a frequency stability of 3.0 x 10−13τ−1/2.

The clock used by the team was encased in three layers of mu-metal and was held at a pressure of 10-12 atmospheres. The servo-motors used to stabilize the pressure were also shielded to prevent interference from their magnetic fields. Inside of the device was a trap isolating 50 million rubidium-87 atoms held steady by microwaves and laser pulses. Measuring was done using interferometry.

The researchers suggest similar space-based clocks could be used for metrology as well as for testing principles of General Relativity and other fundamental physics constants.


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More information: Liang Liu et al. In-orbit operation of an atomic clock based on laser-cooled 87Rb atoms, Nature Communications (2018). DOI: 10.1038/s41467-018-05219-z

Abstract
Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth's radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10−13τ−1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.

Journal information: Nature Communications

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Jul 27, 2018
Design of a stable object and 'ping' response. The near field of charge has priority; therefore, removal of thermal is what? So ya trying to hold the atom still? That's what we use to call absolute zero. Try also polaring all rotations by placing the whole thing in a DC Field?

Jul 27, 2018
Anyway, time is absolute. Our physics is the Method of Measurement and the only Theory is The Existence of charge. Charge exists from its center to infinity. Charge is unique. Charge, a set of charge, defined motion, using sets with parity and those without shall define the entire Universe. Al other particles or forces are derivative. Therefore if q = +/-1 and r = {x1,x2,x3,x4} & Xi is an element of Lambda of Lambda*Time.Period = c = 1; Then build your measurements based on a complete mathematical isomorphism. The would be a Theory. Physics! Notice, time and space are now linked. Anyway you can try to keep track of nothing; but you gotta know the stability of these sets. Shielding. jeez!

Jul 27, 2018
Face it, all you can see is now! It's like Einstein riding the crest of a wave and imagining stuff; His world is the same, unless he moves into a media. So count the past anyway you wish, falling sand, ... , or is there a way to know the passage of time without absolute control? But, moving at c relative only to the center of the field, or ...

Jul 27, 2018
So any well controlled and definable oscillator.

Jul 27, 2018
This is seeking precision from non causality or whatever it turns out to be, our best guess. No disrespect intended; a state of the era of nonsense, i.e. last 4000 years.

Jul 27, 2018
hyped, whatever you call that rant you do spew your woo. I gotta say it's just meaningless noise.

Old fashion DR/SR/QM = nuclear bomb.

hypes whatever that is = squib

DR/SR/QM = nuclear bomb.

hypes = squib

DR/SR/QM = nuclear bomb.

hypes = squib

DR/SR/QM = KABOOMSIDAY!!

"Impresses me! Where did I leave my dosimeter?"

hypes = psssst..."

"Nope not impressed."

Aug 01, 2018
hyped, whatever you call that rant you do spew your woo. I gotta say it's just meaningless noise.

Old fashion DR/SR/QM = nuclear bomb.

hypes whatever that is = squib

DR/SR/QM = nuclear bomb.

hypes = squib

DR/SR/QM = nuclear bomb.

hypes = squib

DR/SR/QM = KABOOMSIDAY!!

"Impresses me! Where did I leave my dosimeter?"

hypes = psssst..."

"Nope not impressed."

Irrelevant multiple things; some nonsensical, some dangerous, none logical!

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