science

NIST-F2

NIST-F2 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand NIST-F2 rather than just read about it. In short: NIST-F2 is a caesium fountain atomic clock that, along with NIST-F1, serves as the United States' primary time and frequency standard. NIST-F2 was brought online on 3 April 2014.

Key takeaways

NIST-F2 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NIST-F2 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NIST-F2 from memory before moving on to harder problems.

Reference excerpt

NIST-F2 is a caesium fountain atomic clock that, along with NIST-F1, serves as the United States' primary time and frequency standard. NIST-F2 was brought online on 3 April 2014.

Accuracy

NIST-F1, a cesium fountain atomic clock used since 1999, has a fractional inaccuracy (δf / f) of less than 5×10−16.

Anticipated accuracy The planned performance of NIST-F2 is δf / f < 1×10−16. At this planned performance level the NIST-F2 clock will not gain or lose a second in at least 300 million years.

Evaluated accuracy The evaluated accuracy (uB) reports of various primary frequency and time standards are published online by the International Bureau of Weights and Measures (BIPM). The first in-house accuracy evaluation of NIST-F2 reported a uB of 1.1 × 10−16. In March 2014 and March 2015 the NIST-F2 cesium fountain clock reported a uB of 1.5 × 10−16 in the BIPM reports of evaluation of primary frequency standards. The last submission of NIST-F1 to BIPM TAI was February 2016.

Replicas At the request of the Italian standards organization, NIST manufactured many duplicate components for a second version of NIST-F2, known as IT-CsF2 to be operated by the Istituto Nazionale di Ricerca Metrologica (INRiM), NIST's counterpart in Turin, Italy. As of February 2016 the IT-CsF2 cesium fountain clock started reporting a uB of 1.7 × 10−16 in the BIPM reports of evaluation of primary frequency standards.

References

External links NIST Time and Frequency Div. — 2004: Strategic Focus 1 (National Institute of Standards and Technology) "NIST Launches a New U.S. Time Standard: NIST-F2 Atomic Clock" on YouTube "Time gets an upgrade". newscientist.com. New Scientist. Retrieved 27 February 2018.

Illustrations

Worked examples

Example 1 — a first encounter with NIST-F2

Start with the simplest possible case. Write down what NIST-F2 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to NIST-F2 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about NIST-F2 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of NIST-F2

In research: NIST-F2 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses NIST-F2 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: NIST-F2 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Atomic clocks, National Institute of Standards and Technology, so understanding it makes those chapters shorter.
In everyday life: Look for NIST-F2 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study NIST-F2 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NIST-F2 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain NIST-F2 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NIST-F2 in simple terms?

NIST-F2 is a caesium fountain atomic clock that, along with NIST-F1, serves as the United States' primary time and frequency standard. NIST-F2 was brought online on 3 April 2014.

Why does NIST-F2 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study NIST-F2?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on NIST-F2.