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Here we have selected a few of the photos from PTB which are often requested. You can download them – in print quality and with captions.

Our images have been placed under the Opens external link in new windowCreative Commons License Opens external link in new windowCC-BY 4.0. This means you are free to share our images and also to adapt them for any purpose, even commercially. Our source information is stated for each image that you are free to use and this information must be used in the form that it was published there.

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SI Base Units

MetreMetre

  • Emission of iodine molecules in the red and green spectral range (8.1 MB) Particularly stable lasers make it possible that a wavelength once measured – and, thus, the unit of length – can be maintained in laser wavelength standards/frequency standards. PTB keeps different laser wavelength standards in the infrared, red and green spectral range at its disposal. The photo shows the emission of iodine molecules in the red and green spectral range.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Frequency combs (1.4 MB) Frequency combs connect the world of the meter with the world of the second. They quasi serve as a "gear" which allows frequencies to be "transmitted" without any loss of accuracy. In contrast to the frequency synthesis chains used in the past, they allow any laser frequency desired to be measured. They are, for example, used to compare optical frequencies with primary clocks or for the direct comparison of two optical frequencies. The image shows the spectrally expanded frequency comb spectrum of a titan-sapphire laser.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • krypton standard lamp (6.3 MB) With the krypton standard lamp it became possible for the first time to couple the unit of length to an atomic constant and to reproduce it at any place on Earth without a loss of accuracy. From 1960 to 1983, the krypton standard lamp served to realize the unit of length.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

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KilogramKilogram

  • The international prototype of the kilogram (4.4 MB) The international prototype of the kilogram, kept under three bell jars at the International Bureau of Weights and Measures (BIPM) in Sèvres near Paris. (Photo: PTB/BIPM)
  • The international prototype of the kilogram (2.7 MB) The international prototype of the kilogram, kept under three bell jars at the International Bureau of Weights and Measures (BIPM) in Sèvres near Paris. (Photo: PTB/BIPM)
  • View into a prototype balance of PT (3.6 MB) View into a prototype balance of PTB with the aid of which 1-kg mass standards can be linked up with the national prototype of the kilogram. The balance shown is a 1-kg vacuum-mass comparator, installed in a vacuum-proof chamber.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Weights (9.2 MB) Weights. At PTB, the masses of standards are derived from the national prototype of the kilogram in the large span from 1 mg up to 5 t. This is how the mass scale is realized.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's sphere interferometer (3.8 MB) PTB's sphere interferometer allows complete diameter topographies to be determined with extreme accuracy. It is one of the decisive measuring devices within the scope of PTB's Avogadro project. In 1996, it was, for the first time, installed by Gerhard Bönsch and Arnold Nicolaus as a fundamentally new optical multi-beam interferometer with spherical reference faces.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Diameter variations on a silicon sphere (1.9 MB) Diameter variations on a silicon sphere measured with the sphere interferometer within the scope of the Avogadro project. The color variation from blue to red visualizes deviations from the perfect spherical form of approx. 20 nm. The volume is calculated from a great number of diameter measurements.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Silicon single crystal (1.2 MB) From such silicon single crystals, a sphere for the Avogadro project is manufactured with great effort. This single crystal consists to more than 99 % of the isotope silicon-28.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's mass spectrometer (7.2 MB) PTB's mass spectrometer which is used to determine the ratio of the different silicon isotopes.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

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SecondSecond

  • Coding scheme of the time signals emitted by DCF77 (118 kB) Coding scheme of the time signals emitted by DCF77; M: minute mark, R: bit reserved for internal use; A1: announcement bit of an imminent change from CET to CEST or vice versa, Z1 (Z2): announcement of a leap second, S: start bit of the encoded time information (0.2 s), P1, P2, P3: parity check bits.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • The two cesium fountains CSF1 and CSF2 (6.5 MB) Prominent showpieces of PTB: the atomic clocks (here: the two fountain clocks). No other physical quantity can be measured as precisely as time.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

     

    The two cesium fountains CSF1 and CSF2 (with Dr. Stefan Weyers, Head of the "Time Standards" Working Group)

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's optical strontium clock (4.0 MB) PTB's optical atomic clock which works with stored strontium atoms.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • View of the ultra-high vacuum chamber of PTB's optical strontium clock (829 kB) View of the ultra-high vacuum chamber where strontium atoms are cooled and stored. The blue fluorescent light in the upper third of the window is a cloud of cold strontium atoms (the drop-shaped formation below the blue fluorescent atom beam in the upper part of the vacuum window).

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • primary atomic clock CS2 (1.9 MB) PTB's primary atomic clock CS2 furnishes the second intervals of legal time (CET and CEST) with the aid of which all radio-controlled clocks in Germany are controlled via a long-wave transmitter in Mainflingen near Frankfurt.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Fluorescence of a cloud of calcium atom (827 kB) Fluorescence of a cloud of calcium atoms during the first phase of laser cooling in PTB's optical calcium clock.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • The first cesium fountain CSF1 of PTB (2.4 MB) Since the year 2000, the first cesium fountain CSF1 of PTB has contributed to the realization of International Atomic Time. In this clock, cesium atoms are laser-cooled down to 2 μK and run on a ballistic trajectory to achieve the longest possible request time.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Transmission mast of DCF77 (2.7 MB) Transmission mast of DCF77 in Mainflingen, south-east of Frankfurt/Main. The time signal cannot be received with normal longwave radios – but with "radios for the time": Radio-controlled clocks deliver the official time "wireless" to everyone who wants to have it to his home or his wrist.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's cesium fountain CSF1 (2.4 MB) PTB physicist Stefan Weyers at the first cesium fountain CSF1 of PTB which was put into operation in 1999. Since 2005, it has a "colleague", CSF2.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • The propagation distance of the transmitter DCF7 (1.4 MB) The propagation distance of the transmitter DCF77 is approx. 2000 km. In some cases, signals have, however, even been received in Australia.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Optical ytterbium clock at PTB (2.0 MB) Optical atomic clock on the basis of a stored ytterbium ion: Electrode system of the ion trap developed at PTB.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

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AmpereAmpere

  • Josephson voltage standard from PTB (9.6 MB) Josephson voltage standard from PTB with approx. 70 000 series-connected tunnel elements, generating together 10 volts. (Photo: PTB) Or: Programmable 10-volt Josephson circuit from PTB.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Quantum Hall device (2.3 MB) Quantum Hall device (in a sample carrier) for the reproduction of the unit of resistance. The device consists of semiconductor hetero-structures which are manufactured by molecular beam epitaxy in PTB's Clean Room Center.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's molecular beam epitaxy machine (2.0 MB) PTB's molecular beam epitaxy machine used to manufacture semiconductor quantum standards such as quantum Hall resistors.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Graphene oven (1.1 MB) For the simplification of resistance metrology, the material graphene, which was discovered only a few years ago, offers a great potential. Graphene is a single-layer network of carbon atoms which shows the quantum Hall effect at higher temperatures and lower magnetic fields than the Ga/Al arsenide structures presently used for quantum Hall resistors. Research activities of the past few years have shown that graphene produced from SiC is suited best for metrological applications. Therefore, an apparatus for the manufacture of graphene from SiC has been established in the Clean Room Centre of PTB.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • On this silicon chip, Klaus von Klitzing discovered the quantum Hall effect (9.9 MB) It is already a museum piece: On this silicon chip, Klaus von Klitzing discovered the quantum Hall effect.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • The quantum metrology triangle (345 kB) The quantum metrology triangle shows the relations between the three electrical units volt, ohm and ampere and the involved fundamental constants. To close the triangle, only the ampere, as the last of the three units, must be placed on the basis of a fundamental constant (the charge of an electron).

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Bridge building in the nanocosmos (771 kB) Bridge building in the nanocosmos – towards a quantum standard for the ampere.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Transistor structures (377 kB) Counting of single electrons? Yes, with these transistor structures.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Semiconductor single electron (SET) pump (76 kB) Electron-microscopic image of a semiconductor single electron (SET) pump: Gate electrodes (violet, yellow) cross a small conducting track made of semiconductor material (green).

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Semiconductor structure (0.9 MB) This semiconductor structure can measure single electrons and their charge. Four pumps are integrated onto the chip; each of them has three gate electrodes (yellow) crossing a semiconductor wire (blue). The pumped electrons are detected with the aid of three single-electron detectors (gray).

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • A chip with a SET (Single-Electron-Tunneling) circuit (1.3 MB) A chip with a SET (Single-Electron-Tunneling) circuit, installed in the sample holder. The window of the printed circuit card allows the circuit to be contacted by means of the contact pad which is visible above it.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

KelvinKelvin

CandelaCandela

  • "Hefner candle" (1.7 MB) From 1896 to 1941, the "Hefner candle" was used as a state-approved standard for the unit of luminous intensity in Germany, Austria and in Scandinavia. Candela literally means "candle". The Hefner candle furnishes a flame with always the same properties and with an uncertainty of 1.5 %.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Hefner candle (1.3 MB) From 1896 to 1941, the "Hefner candle" was used as a state-approved standard for the unit of luminous intensity in Germany, Austria and in Scandinavia. Candela literally means "candle". The Hefner candle furnishes a flame with always the same properties and with an uncertainty of 1.5 %.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Cryogenic radiometer (644 kB) From the satellite-based remote sensing instrument to the exposure facility of the semi-conductor industry, from color measurements to radiation thermometry: reliable measurements of the radiant power of light sources require the determination of the spectral responsivity of radiation detectors. For this purpose, absolute measuring primary detector standards are used. The sensitivity of a radiation detector at different wavelengths is obtained by a comparison measurement (calibration) against a primary standard or a reference receiver which has already been calibrated. As primary standards, PTB uses in the spectral ranges from the long-wave infrared or terahertz radiation to short-wave X-rays so-called cryogenic radiometers. These are thermal detectors which are operated at a very low temperature (–269 °C) and whose core piece is a radiation absorber. These cryogenic radiometers allow best relative measurement uncertainties clearly below 0.01 % to be achieved in radiant power measurements.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Standard lamp (0.9 MB) In the times prior to using cryogenic radiometers, the standard lamp was indispensible. It glowed only approx. 20 minutes per year. PTB had 23 of these national standards for the unit of luminous intensity "candela" at its disposal to calibrate other lamps or photometers with it.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

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Consumer Protection

Consumer ProtectionConsumer Protection

  • Measurements for electromagnetic compatibility (1.2 MB) As a provider of metrological services, PTB performs several thousands of calibrations and tests every year. Photo: Measurements for electromagnetic compatibility.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Ignition of an air-gas mixture (537 kB) Safety engineering is a top priority at PTB (and not only in explosion protection). The photos shows the ignition of an air-gas mixture by laser radiation.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Explosion (1.1 MB) Each highly technical society is also a society at risk. Reliable metrology is needed to recognize these risks and to minimize them. In Germany, PTB provides the metrological basis for monitoring.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • "Artificial ears" (2.7 MB) Even if you can no longer hear, PTB's services are required: The regular checking of audiometers is made possible by the provision and testing of "artificial ears" through PTB.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's reverberation room (868 kB) PTB's reverberation room: The rotating screen makes sure that the sound of a noise source is distributed in the room as uniformly as possible.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's 2 MN force standard machine (1.6 MB) The fact that force measurements have something to do with safety becomes particularly evident when carrying out crash tests with dummies. The force which acts on the dummy in the case of a simulated accident is determined by force transducers everywhere on the dummy's body. These devices are checked at regular intervals by the automobile companies in their calibration laboratories. The force calibration machines used for this purpose can be traced back directly to the standards of PTB. The photo shows the largest force standard machine of PTB, which works with direct deadweight effect: the 2 MN force standard machine.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • PTB's 2-meganewton force standard machine (1.2 MB) It is the colossus among PTB's force measuring machines: The 2-meganewton force standard machine extends over three floors (the image is composited graphically here). It contains heavy-weight plates of several tons – the reason for its enormous dimensions. The exterior of its even stronger sister, which can measure loads of up to 16.5 meganewtons, is by far less impressive, because in her case, the force is transmitted hydraulically.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Air dust collector (2.6 MB) At PTB, this air dust collector is used to continuously check the air dust for possible radioactive loads. It is part of Germany's nationwide measuring and information system (IMIS) which was established after the nuclear accident in Chernobyl. With the aid of this measuring system it came to light that radioactive hospital waste had one day been burnt by mistake in a furnace in Gibraltar.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • "Water phantom" of PTB (1.9 MB) View into the "water phantom" of PTB. In this water calorimeter, three sensors – one round one and two pin-shaped ones – are located which are called "ionization chambers". They are calibrated here to calibrate, in turn – at a later date – irradiation devices in hospitals. Only on an irradiation device tested in this way can the physician in charge adjust the exact treatment dose.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

  • Wheel loader balance (1.7 MB) At PTB, measuring instruments are tested by statutory mandate – also the wheel loader balances shown in the photo.

    (Reference: Physikalisch-Technische Bundesanstalt/www.ptb.de)

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