Are Atomic Clocks Radioactive?
Atomic clocks keep time better than any other clock. They even keep time better than the rotation of the Earth and the movement of the stars. Without atomic clocks, GPS navigation would be impossible, the Internet would not synchronize, and the position of the planets would not be known with enough accuracy for space probes and landers to be launched and monitored.
Atomic clocks are not radioactive. They do not rely on atomic decay. Rather, they have an oscillating mass and a spring, just like ordinary clocks.
The big difference between a standard clock in your home and an atomic clock is that the oscillation in an atomic clock is between the nucleus of an atom and the surrounding electrons. This oscillation is not exactly a parallel to the balance wheel and hairspring of a clockwork watch, but the fact is that both use oscillations to keep track of passing time. The oscillation frequencies within the atom are determined by the mass of the nucleus and the gravity and electrostatic "spring" between the positive charge on the nucleus and the electron cloud surrounding it.
Monday, August 1, 2011
Now You Can Buy the Smallest Atomic Clock Ever Made
Now You Can Buy the Smallest Atomic Clock Ever Made
The new clock, precise to a millionth of a second, is 100 times smaller than its predecessor
By Julie Beck
World's Smallest Atomic Clock Symmetricom
If you have a spare $1500 burning a hole in your pocket, perhaps you’d like to spend it on an ultra-precise, ultra-small atomic clock, now available for purchase from Symmetricom Inc. Draper Laboratory and Sandia National Laboratories.
The Chip Scale Atomic Clock (CSAC), originally developed for DARPA, is 100 times smaller than its predecessors and uses 100 times less power as well. It requires only 100 milliwatts of power, measures about 1.5 inches per side and is less than half an inch deep.
The clock measures the passage of time in millionths of a second by counting the frequency of electromagnetic waves. These waves are emitted by cesium atoms are stored in a tiny container, no bigger than a grain of rice, when they are shot by a vertical-cavity surface-emitting laser (VCSEL). Replacing the previously used rubidium-based atomic vapor lamp with the VCSEL is what reduced the clock’s power consumption.
Measuring The Wavelength of CSAC's Laser: Randy Montoya/Sandia National Laboratories
A CSAC clock continues to function when GPS signals are blocked, making it incredibly useful deep underground or underwater. It could also prove handy when experts are blocking telephone signals from detonating explosive devices with electromagnetic interference, as the CSAC would continue to function.
After 10 years of development, CSAC went on the market in January. DARPA projects rarely become commercialized, so this product page, available for anyone to peruse on the web (and purchase for their deep-sea explorations), is a pretty big deal.
Atomic clock accuracy and low power make the SA.45s ideal for portable applications requiring precise synchronization and time keeping, especially in GPS-denied environments.
Breakthrough Leadership The CSAC’s unmatched portability derives from specs that include:
115mW power consumption
16cm3 volume
35g weight
±5.0E-11 accuracy at shipment
σy < 5 x 10-12 at τ = 1 hour short-term stability (Allan Deviation)
<3.0E-10/month aging rate
A New Class of Applications At two orders of magnitude better accuracy than oven-controlled crystal oscillators (OCXOs) — and up to four orders of magnitude better accuracy than temperature-controlled oscillators (TCXOs) — the CSAC’s unmatched portability opens the door to new classes of applications, such as:
Underwater sensors for seismic research or gas and oil exploration
Military systems including dismounted IED jammers, dismounted radios, GPS receivers, and unmanned aerial vehicles (UAVs)
Device Connectivity The SA.45s CSAC produces two outputs, a 10MHz square wave and 1PPS, both in a CMOS 0 – 3.3V format. It also accepts a 1PPS input for synchronization and provides an RS-232 interface for monitoring and control.
The SA.45s Chip Scale Atomic Clock (CSAC) is available in two versions:
Option 001, which operates from -10° C to +70°C for commercial applications
Option 002, which operates from -40°C to +85° C for military applications
A CSAC Developer's Kit is also available.
View entire article ►
The new clock, precise to a millionth of a second, is 100 times smaller than its predecessor
By Julie Beck
World's Smallest Atomic Clock Symmetricom
If you have a spare $1500 burning a hole in your pocket, perhaps you’d like to spend it on an ultra-precise, ultra-small atomic clock, now available for purchase from Symmetricom Inc. Draper Laboratory and Sandia National Laboratories.
The Chip Scale Atomic Clock (CSAC), originally developed for DARPA, is 100 times smaller than its predecessors and uses 100 times less power as well. It requires only 100 milliwatts of power, measures about 1.5 inches per side and is less than half an inch deep.
The clock measures the passage of time in millionths of a second by counting the frequency of electromagnetic waves. These waves are emitted by cesium atoms are stored in a tiny container, no bigger than a grain of rice, when they are shot by a vertical-cavity surface-emitting laser (VCSEL). Replacing the previously used rubidium-based atomic vapor lamp with the VCSEL is what reduced the clock’s power consumption.
Measuring The Wavelength of CSAC's Laser: Randy Montoya/Sandia National Laboratories
A CSAC clock continues to function when GPS signals are blocked, making it incredibly useful deep underground or underwater. It could also prove handy when experts are blocking telephone signals from detonating explosive devices with electromagnetic interference, as the CSAC would continue to function.
After 10 years of development, CSAC went on the market in January. DARPA projects rarely become commercialized, so this product page, available for anyone to peruse on the web (and purchase for their deep-sea explorations), is a pretty big deal.
Atomic clock accuracy and low power make the SA.45s ideal for portable applications requiring precise synchronization and time keeping, especially in GPS-denied environments.
Breakthrough Leadership The CSAC’s unmatched portability derives from specs that include:
115mW power consumption
16cm3 volume
35g weight
±5.0E-11 accuracy at shipment
σy < 5 x 10-12 at τ = 1 hour short-term stability (Allan Deviation)
<3.0E-10/month aging rate
A New Class of Applications At two orders of magnitude better accuracy than oven-controlled crystal oscillators (OCXOs) — and up to four orders of magnitude better accuracy than temperature-controlled oscillators (TCXOs) — the CSAC’s unmatched portability opens the door to new classes of applications, such as:
Underwater sensors for seismic research or gas and oil exploration
Military systems including dismounted IED jammers, dismounted radios, GPS receivers, and unmanned aerial vehicles (UAVs)
Device Connectivity The SA.45s CSAC produces two outputs, a 10MHz square wave and 1PPS, both in a CMOS 0 – 3.3V format. It also accepts a 1PPS input for synchronization and provides an RS-232 interface for monitoring and control.
The SA.45s Chip Scale Atomic Clock (CSAC) is available in two versions:
Option 001, which operates from -10° C to +70°C for commercial applications
Option 002, which operates from -40°C to +85° C for military applications
A CSAC Developer's Kit is also available.
View entire article ►
Obama and Netanyahu Run Out the Atomic Clock
Obama and Netanyahu Run Out the Atomic Clock
There is some anecdotal evidence making the rounds that supports the idea that Obama is bored by his duties as president. Don't you buy it for a minute. Obama loves the job. It's just that certain parts of it excite him more than others. For instance, take the Middle East, the Arab-Muslim world, "Palestine," and Israel. No lack of enthusiasm there. The juices are flowing, and it's obvious that President Barack Hussein Obama remains psyched about the mission.
Most presidents hold off until their second terms, when there is little left to lose, before they step in the deep doo-doo of "peace." But Obama couldn't wait. Before completing two years in office, he has already wasted thousands of man-hours and billions in borrowed political capital on the region and its problems -- mostly by beating down Israel and sucking up to her Muslim enemies.
The Israel-bashing changed (superficially) when Rahm and Axelrod whispered in Obama's ear that beneath Netanyahu's "hawkish" exterior lay a submissive pussycat. They're Chicago Jews, and they would know. For once, Obama did the smart thing. He listened to reason and good political advice. It worked, too. As soon as Obama stopped kicking the kitty and started stroking it instead, "Bibi" came out from under the bed, reborn a grateful, compliant cats-paw.
From that point on, getting Obama's other pet, Abbas, to the table with Netanyahu to say "cheese" was just an underhand toss. Yet virtually every advocate for the "peace process" -- old hands on both the left and right -- says neither side can possibly give the other what it needs and that these talks will fail along with the rest. If that collapse occurs now, what does Obama plan for an encore? Even more important, if it's all a waste of time, and destined to be another item on Obama's impressive list of failures to boot, then really, what gives?
Glad you asked. It's Iran.
In Obama's exotic world, the "peace process" is useful, but not for anything approaching peace. He's already won the Nobel Prize by just showing up at the office. Rather, it's all a dramatic sleight-of-hand, a magician's diversion. While the flashy show is in progress, the important stuff you're not supposed to notice is going on unseen -- right before your eyes. Iran is building atomic weapons and may have already passed the point where the monster can be put back into the cage, auguring nothing less than a sea change that will uproot the world order we've built our lives around for the past 65 years. Yet in the media and official circles, the suspense builds around a few Jews pouring cement while virtually no attention is paid (not even by the Tea Party) to the danger and flux that is threatening to overtake us -- except to dismiss it.
Alright, to recap part one: Obama's ersatz "peace process" keeps America spellbound and distracted while the Iranians prepare their nuclear suicide bombs.
But wait, there's more! It also ties the one pair of hands other than America's with the means and the motive to preempt the Iranian threat. After being brought to heel and publicly degraded without a struggle, will enough of the Jew remain within Netanyahu to summon up the requisite chutzpah to defy Obama and disturb the tidy status quo? While "peace" is waiting just around the next corner, Israel's freedom of action is held in suspended animation.
All of the above increases the likelihood that before the Age of Obama ends, we will share our world with a hegemonic Islamist nuclear power. Only after Ahmadinejad makes the official announcement will we first see the president appear uninterested and his eyes glaze over.
It is only natural to wonder whether all this is Obama's intent or an unforced error of Chamberlain-like proportions. In truth, it matters little because we can never know for sure, though we will find an answer of sorts every day living with the consequences. More than deficits, economic dysfunction, a defunct health care system, or a big, oppressive government, it will be messianic mullahs controlling H-bombs that Obama, and the Israelis, will be remembered for.
By Dan Friedman
There is some anecdotal evidence making the rounds that supports the idea that Obama is bored by his duties as president. Don't you buy it for a minute. Obama loves the job. It's just that certain parts of it excite him more than others. For instance, take the Middle East, the Arab-Muslim world, "Palestine," and Israel. No lack of enthusiasm there. The juices are flowing, and it's obvious that President Barack Hussein Obama remains psyched about the mission.
Most presidents hold off until their second terms, when there is little left to lose, before they step in the deep doo-doo of "peace." But Obama couldn't wait. Before completing two years in office, he has already wasted thousands of man-hours and billions in borrowed political capital on the region and its problems -- mostly by beating down Israel and sucking up to her Muslim enemies.
The Israel-bashing changed (superficially) when Rahm and Axelrod whispered in Obama's ear that beneath Netanyahu's "hawkish" exterior lay a submissive pussycat. They're Chicago Jews, and they would know. For once, Obama did the smart thing. He listened to reason and good political advice. It worked, too. As soon as Obama stopped kicking the kitty and started stroking it instead, "Bibi" came out from under the bed, reborn a grateful, compliant cats-paw.
From that point on, getting Obama's other pet, Abbas, to the table with Netanyahu to say "cheese" was just an underhand toss. Yet virtually every advocate for the "peace process" -- old hands on both the left and right -- says neither side can possibly give the other what it needs and that these talks will fail along with the rest. If that collapse occurs now, what does Obama plan for an encore? Even more important, if it's all a waste of time, and destined to be another item on Obama's impressive list of failures to boot, then really, what gives?
Glad you asked. It's Iran.
In Obama's exotic world, the "peace process" is useful, but not for anything approaching peace. He's already won the Nobel Prize by just showing up at the office. Rather, it's all a dramatic sleight-of-hand, a magician's diversion. While the flashy show is in progress, the important stuff you're not supposed to notice is going on unseen -- right before your eyes. Iran is building atomic weapons and may have already passed the point where the monster can be put back into the cage, auguring nothing less than a sea change that will uproot the world order we've built our lives around for the past 65 years. Yet in the media and official circles, the suspense builds around a few Jews pouring cement while virtually no attention is paid (not even by the Tea Party) to the danger and flux that is threatening to overtake us -- except to dismiss it.
Alright, to recap part one: Obama's ersatz "peace process" keeps America spellbound and distracted while the Iranians prepare their nuclear suicide bombs.
But wait, there's more! It also ties the one pair of hands other than America's with the means and the motive to preempt the Iranian threat. After being brought to heel and publicly degraded without a struggle, will enough of the Jew remain within Netanyahu to summon up the requisite chutzpah to defy Obama and disturb the tidy status quo? While "peace" is waiting just around the next corner, Israel's freedom of action is held in suspended animation.
All of the above increases the likelihood that before the Age of Obama ends, we will share our world with a hegemonic Islamist nuclear power. Only after Ahmadinejad makes the official announcement will we first see the president appear uninterested and his eyes glaze over.
It is only natural to wonder whether all this is Obama's intent or an unforced error of Chamberlain-like proportions. In truth, it matters little because we can never know for sure, though we will find an answer of sorts every day living with the consequences. More than deficits, economic dysfunction, a defunct health care system, or a big, oppressive government, it will be messianic mullahs controlling H-bombs that Obama, and the Israelis, will be remembered for.
By Dan Friedman
How Does a Practical Cesium Atomic Clock Work?
Atoms have characteristic oscillation frequencies. Perhaps the most familiar frequency is the orange glow from the sodium in table salt if it is sprinkled on a flame. An atom will have many frequencies, some at radio wavelength, some in the visible spectrum, and some in between the two. Cesium 133 is the element most commonly chosen for atomic clocks.
Some Definitions
Atomic Clock - A precision clock that depends for its operation on an electrical oscillator regulated by the natural vibration frequencies of an atomic system (as a beam of cesium atoms)
Atom - The smallest particle of an element that can exist either alone or in combination; the atom is considered to be a source of vast potential energy
Cesium 133 - An isotope of cesium used especially in atomic clocks and one of whose atomic transitions is used as a scientific time standard
SI Second (atomic second) - The interval of time taken to complete 9,192,631,770 oscillations of the cesium 133 atom exposed to a suitable excitation
Source: Merriam-Webster Online
To turn the cesium atomic resonance into an atomic clock, it is necessary to measure one of its transition or resonant frequencies accurately. This is normally done by locking a crystal oscillator to the principal microwave resonance of the cesium atom. This signal is in the microwave range of the radio spectrum, and just happens to be at the same sort of frequency as direct broadcast satellite signals. Engineers understand how to build equipment in this area of the spectrum in great detail.
To create a clock, cesium is first heated so that atoms boil off and pass down a tube maintained at a high vacuum. First they pass through a magnetic field that selects atoms of the right energy state; then they pass through an intense microwave field. The frequency of the microwave energy sweeps backward and forward within a narrow range of frequencies, so that at some point in each cycle it crosses the frequency of exactly 9,192,631,770 Hertz (Hz, or cycles per second). The range of the microwave generator is already close to this exact frequency, as it comes from an accurate crystal oscillator. When a cesium atom receives microwave energy at exactly the right frequency, it changes its energy state.
At the far end of the tube, another magnetic field separates out the atoms that have changed their energy state if the microwave field was at exactly the correct frequency. A detector at the end of the tube gives an output proportional to the number of cesium atoms striking it, and therefore peaks in output when the microwave frequency is exactly correct. This peak is then used to make the slight correction necessary to bring the crystal oscillator and hence the microwave field exactly on frequency. This locked frequency is then divided by 9,192,631,770 to give the familiar one pulse per second required by the real world.
View entire article ►
Some Definitions
Atomic Clock - A precision clock that depends for its operation on an electrical oscillator regulated by the natural vibration frequencies of an atomic system (as a beam of cesium atoms)
Atom - The smallest particle of an element that can exist either alone or in combination; the atom is considered to be a source of vast potential energy
Cesium 133 - An isotope of cesium used especially in atomic clocks and one of whose atomic transitions is used as a scientific time standard
SI Second (atomic second) - The interval of time taken to complete 9,192,631,770 oscillations of the cesium 133 atom exposed to a suitable excitation
Source: Merriam-Webster Online
To turn the cesium atomic resonance into an atomic clock, it is necessary to measure one of its transition or resonant frequencies accurately. This is normally done by locking a crystal oscillator to the principal microwave resonance of the cesium atom. This signal is in the microwave range of the radio spectrum, and just happens to be at the same sort of frequency as direct broadcast satellite signals. Engineers understand how to build equipment in this area of the spectrum in great detail.
To create a clock, cesium is first heated so that atoms boil off and pass down a tube maintained at a high vacuum. First they pass through a magnetic field that selects atoms of the right energy state; then they pass through an intense microwave field. The frequency of the microwave energy sweeps backward and forward within a narrow range of frequencies, so that at some point in each cycle it crosses the frequency of exactly 9,192,631,770 Hertz (Hz, or cycles per second). The range of the microwave generator is already close to this exact frequency, as it comes from an accurate crystal oscillator. When a cesium atom receives microwave energy at exactly the right frequency, it changes its energy state.
At the far end of the tube, another magnetic field separates out the atoms that have changed their energy state if the microwave field was at exactly the correct frequency. A detector at the end of the tube gives an output proportional to the number of cesium atoms striking it, and therefore peaks in output when the microwave frequency is exactly correct. This peak is then used to make the slight correction necessary to bring the crystal oscillator and hence the microwave field exactly on frequency. This locked frequency is then divided by 9,192,631,770 to give the familiar one pulse per second required by the real world.
View entire article ►
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