* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: Atomic clock is 50


L

Posts: 131433
Date:
National Physical Laboratory Atomic clock
Permalink  
 


UK's atomic clock 'is world's most accurate'

An atomic clock at the UK's National Physical Laboratory (NPL) has the best long-term accuracy of any in the world, research has found.
Studies of the clock's performance, to be published in the journal Metrologia, show it is nearly twice as accurate as previously thought.
The clock would lose or gain less than a second in some 138 million years.

Read more



__________________


L

Posts: 131433
Date:
RE: Atomic clock is 50
Permalink  
 


Title: Optical transition of the 229Th nucleus in a solid-state environment
Authors: WADE RELLERGERT, SCOTT SULLIVAN,. RADOYEH SHOJAEI, UCLA, DAVID DEMILLE, Yale, RICHARD. GRECO, MARKUS HEHLEN, JUSTIN TORGERSON, LANL, ERIC. HUDSON, UCLA, THE THOR COLLABORATION

We describe a novel approach to directly measure the energy of the narrow, low-lying isomeric state in 229Th. Since nuclear transitions are far less sensitive to environmental conditions than atomic transitions, we argue that the 229Th optical nuclear transition may be driven inside a host crystal with a high transition Q. This technique might also allow for the construction of a solid-state optical frequency reference that surpasses the precision of current optical clocks, as well as improved limits on the variability of fundamental constants. Based on analysis of the crystal lattice environment, we argue that a precision of 3 x 10^-17 < delta f/f < 1 x 10^-15 after 1 s of photon collection may be achieved with a systematic-limited accuracy of deltaf/f ~ 2 * 10^-16. Improvement by a factor of 10² to 10³ of the constraints on the variability of several important fundamental constants also appears possible. We report on progress towards evaluation of candidate host crystals.

Read more (40kb, PDF)

__________________


L

Posts: 131433
Date:
Quantum Logic Clock
Permalink  
 


NIST's Second 'Quantum Logic Clock' Based on Aluminium Ion is Now World's Most Precise Clock

Physicists at the National Institute of Standards and Technology (NIST) have built an enhanced version of an experimental atomic clock based on a single aluminium atom that is now the world's most precise clock, more than twice as precise as the previous pacesetter based on a mercury atom.
The new aluminium clock would neither gain nor lose one second in about 3.7 billion years, according to measurements to be reported in Physical Review Letters.
The new clock is the second version of NIST's "quantum logic clock," so called because it borrows the logical processing used for atoms storing data in experimental quantum computing, another major focus of the same NIST research group. The second version of the logic clock offers more than twice the precision of the original.

Read more

__________________


L

Posts: 131433
Date:
RE: Atomic clock is 50
Permalink  
 


Ytterbium Gains Ground in Quest for Next-Generation Atomic Clocks
An experimental atomic clock based on ytterbium atoms is about four times more accurate than it was several years ago, giving it a precision comparable to that of the NIST-F1 caesium fountain clock, the nation's civilian time standard, scientists at the National Institute of Standards and Technology (NIST) report in Physical Review Letters.
NIST scientists evaluated the clock by measuring the natural frequency of ytterbium, carefully accounting for all possible deviations such as those caused by collisions between the atoms, and by using NIST-F1 as a "ruler" for comparison. The results were good enough to indicate that the ytterbium clock is competitive in some respects with NIST-F1, which has been improving steadily and now keeps time to within 1 second in about 100 million years.

Read more

__________________


L

Posts: 131433
Date:
Collisional effects in a clock
Permalink  
 


Physicists have measured and controlled seemingly forbidden collisions between neutral strontium atoms - a class of antisocial atoms known as fermions, which are not supposed to collide when in identical energy states. The advance makes possible a significant boost in the accuracy of atomic clocks based on hundreds or thousands of neutral atoms.
Described in the April 17 issue of the journal Science, the research was performed at JILA, a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado (CU) at Boulder.

"This is one of the most precise measurements of collisional effects in a clock" -  NIST/JILA Fellow Jun Ye.

Read more 


__________________


L

Posts: 131433
Date:
RE: Atomic clock is 50
Permalink  
 


U.S. physicists have made a new atomic clock so accurate that it will neither gain nor lose even a second in more than 200 million years, media reported Monday. The strontium atomic clock outperforms the official atomic clock used by the U.S. Commerce Department's National Institute of Standards and Technology (NIST), which promises to keep accurate time down to the second for 80 million years.

Source Reuters

__________________


L

Posts: 131433
Date:
Permalink  
 

Scientists at the UKs National Physical Laboratory (NPL) have proposed a new way to determine accurate time faster.

Very precise time keeps the Internet and e-mail functioning, ensures television broadcasts arrive at our TVs and is integral to a network of global navigation satellites (such as the Global Positioning System) used for precision mapping and surveying, environmental monitoring and personal location-based services. But time can only be useful if it is the same for everyone. And that requires a single source against which we can all check our clocks. The caesium fountain that NPL operates is one of only a handful of highly precise measurement devices around the world that inform the global primary time standard the definition of accurate time. NPLs atomic fountain measures the accuracy of existing time standards and feedback readings to inform any adjustments to Coordinated Universal Time the basis for the worldwide system of timekeeping.
NPLs instruments do not simply measure time. They measure the absorption of electromagnetic waves by caesium atoms and detect the resultant changes in the internal state of those atoms. The absorption peaks at a specific electromagnetic frequency. They can then lock this frequency and use the number of oscillations of that frequency, during a given period of time, to define a second, like the ticks of a conventional clock. One second, for example, corresponds to just over nine billion oscillations of an electromagnetic signal locked to the peak change in caesium atoms.
But an atomic clock is never perfect. One of the challenges when identifying the accurate frequency reference is that it tends to fluctuate very slightly and its average value is only known within a certain error range. In atomic fountains, these tiny errors are largely due to atoms colliding with each other inside the fountain. This is known as a collisional frequency shift. There have been several theories about what affects the collision shift and how to compensate for it but existing methods can take days or even weeks. The team at NPL has discovered a potential new approach, reducing the time it takes to confirm the accuracy of a frequency reading to a matter of hours ten times faster than it can currently be done. It is based around the state of the atoms during their flight in the fountain. They can be in one of two states upper or lower, or in a combination of the two. The NPL team in collaboration with NIST (USA) and PTB (Germany) discovered that the effect the collisions have on the frequency signal depends on which state the atoms are most in. Upper results in a negative shift, lower in a positive shift. This suggests the existence of a split between upper and lower state atoms that cancels the shift out and results in no affect to the frequency signal. Operating a caesium fountain at this zero-shift point is an attractive proposition as it removes the need to compensate for collision shifts and accelerates the process of confirming the accuracy of frequency standards. This means laboratories providing the primary time standard can feed back more readings in any given period of time, increasing the accuracy of recommended adjustments to UTC, potentially improving the overall accuracy of the worlds time.

Source (old news)

__________________


L

Posts: 131433
Date:
Caesium atom fountain clock
Permalink  
 


The Chinese Ministry of Science and Technology announced that in collaboration with many countries, China has successfully developed a caesium atom fountain clock. China's new caesium atomic frequency standard will lose less than 1 second every 6 million years. Previously the standard was set to lose 1 second every 300 thousand years.
The caesium atom fountain clock is extremely precise and the structure is very complicated. Only a small number of countries including France, the US and Germany have built such clocks, which help to define Coordinated Universal Time (UTC).

Source People's Daily Online

__________________


L

Posts: 131433
Date:
Physicists make atomic clock breakthrough
Permalink  
 


Andrei Derevianko, Kyle Beloy, and Ulyana Safronova sat down six months ago and began work on a calculation that will help the world keep better time. In competition with scientists at the University of New South Wales, the University team led by associate professor Derevianko conducted research that increased the accuracy of atomic clocks, and they did it without running a single experiment.
The team’s findings were submitted to one of the most prestigious physics journals, the “Physical Review Letters,” and they were published immediately on July 18.

Read more

__________________


L

Posts: 131433
Date:
The Pips
Permalink  
 


The radio time signal used to set UK's clocks is to move from Rugby where it has been transmitted since 1927, to Anthorn on the west coast of Cumbria.

The National Physical Laboratory (NPL), which has been responsible for the the "pips" heard on BBC radio services since the 1950, says the new transmitters at Anthorn will not require as much maintenance.
The switchover will take place following a three-month test period at the beginning of 2007 with the final transfer from Rugby to Anthorn occurring at the end of March, 2007.

__________________
1 2  >  Last»  | Page of 2  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard