Stephen Sekula steve@hub.polari.us

Dallas, TX, USA

Husband; Associate Professor of Physics; I teach at SMU in Dallas, TX; I study the Higgs Particle with the ATLAS Experiment at the Large Hadron Collider at CERN; writer and blogger; drummer; programmer; teacher; scientist; traveler; runner; gardener; open-source aficionado.

  • Lock the Planck: the kilogram has a new definition

    ParticleNews at 2019-05-20T12:27:55Z

    "Lock the Planck: the kilogram has a new definition"

    Lock the Planck: the kilogram has a new definition

    achintya Mon, 05/20/2019 - 14:01
    METAS Kibble balance (BWM II)
    The Kibble balance (a.k.a. watt balance) built by the Swiss Federal Institute of Metrology (METAS) to measure the Planck constant with ultra-high precision (Image: CERN)

    Until today, a kilogram was defined as the mass of the International Prototype Kilogram (IPK), a platinum–iridium cylinder located in Paris, France. While all the other base units of the International System of Units (SI) had been redefined over the years based on fundamental constants of nature or atomic properties, the kilogram had remained since the late 19th century the only one to rely on a human-made artefact.

    This changes today, and metrologists – those who study measurement – are excited. On the occasion of World Metrology Day, which commemorates the signing of the Metre Convention back in 1875, the kilogram has been given a new definition. From now on, it will be defined based on the most precise measurement ever made of the Planck constant, which can be expressed in terms of the SI units kilogram, metre and second. Since the latter two units are already defined by constants of nature, the value of a kilogram can be obtained without relying on comparing it with a physical reference block.

    But measuring the Planck constant to a suitably high precision of ten parts per billion required decades of work by international teams across continents, and CERN played a small part in the endeavour.

    In 1975, British physicist Bryan Kibble proposed a device, then known as a watt balance and now called the Kibble balance in his honour, which would allow the Planck constant to be measured precisely based on the IPK. Once the precision was achieved, the Planck constant’s value could be fixed and the definitions inverted, removing the kilogram’s dependence on the IPK. Several Kibble balances around the world were constructed to compare measurements, including one in Switzerland. METAS, the Swiss Federal Institute of Metrology, has been working on their Kibble balance project for almost two decades, the activity being led by Ali Eichenberger and Henri Baumann. Knowing CERN’s expertise in magnet systems, Eichenberger and Baumann reached out to the Laboratory to help prepare the required magnets.

    “I am extremely proud to have participated in this adventure,” says Davide Tommasini from CERN’s Magnets, Superconductors and Cryostats group, who was directly involved in the project. “I do not know if the redefinition of the kilogram has a direct impact on the experiments at CERN, but the past teaches us that there are many new advancements which, at their initial moment, may not appear in their whole potential.”

    In 2018, the Kibble balance in Canada measured the Planck constant with necessary ultrahigh precision, allowing a combination of measurements from around the world to help fix its value. But does it affect the value of the kilogram itself? Not really. “The Plank constant has been fixed at 6.626070150 × 10−34 kg⋅m2/s using the IPK as standard,” explains Eichenberger. “So from today, one kilogram will stay the same. If the IPK drifts further with time then its value will change, but any mass calibration will have an uncertainty of the order of 20 parts per billion.”

    So while it is a momentous occasion worthy of celebration, you won’t have to recalibrate your bathroom scales just yet.

    https://home.cern/news/news/engineering/lock-planck-kilogram-has-new-definition

    ( Feed URL: http://home.web.cern.ch/about/updates/feed )

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    Ah, so I still weight the same? 😌

    JanKusanagi at 2019-05-20T14:08:33Z

  • LS2 report: The Proton Synchrotron’s magnets prepare for higher energies

    ParticleNews at 2019-02-13T11:27:36Z

    "LS2 report: The Proton Synchrotron’s magnets prepare for higher energies"

    LS2 report: The Proton Synchrotron’s magnets prepare for higher energies

    achintya Wed, 02/13/2019 - 09:35
    PS Magnets consolidation during LS2
    PS Magnets consolidation during LS2 (Image: CERN)

    The Proton Synchrotron (PS), which was CERN’s first synchrotron and which turns 60 this year, once held the record for the particle accelerator with the highest energy. Today, it forms a key link in CERN’s accelerator complex, mainly accelerating protons to 26 GeV before sending them to the Super Proton Synchrotron (SPS), but also delivering particles to several experimental areas such as the Antiproton Decelerator (AD). Over the course of Long Shutdown 2 (LS2), the PS will undergo a major overhaul to prepare it for the higher injection and beam intensities of the LHC’s Run 3 as well as for the High-Luminosity LHC.

    One major component of the PS that will be consolidated is the magnet system. The synchrotron has a total of 100 main magnets within it (plus one reference magnet unit outside the ring), which bend and focus the particle beams as they whizz around it gaining energy. “During the last long shutdown (LS1) and at the beginning of LS2, the TE-MSC team performed various tests to identify weak points in the magnets,” explains Fernando Pedrosa, who is coordinating the LS2 work on the PS. The team identified 50 magnets needing refurbishment, of which seven were repaired during LS1 itself. “The remaining 43 magnets that need attention will be refurbished this year.”

    Specifically, one of the elements, known as the pole-face windings, which is located between the beam pipe and the magnet yoke, needs replacing. In order to reach into the magnet innards to replace these elements, the magnet units have to be transferred to a workshop in building 151. Once disconnected, each magnet is placed onto a small locomotive system that drives them to the workshops. The locomotives themselves are over 50 years old, and their movement must be delicately managed. It takes ten hours to extract one magnet. So far, six magnets have been taken to the workshop and this work will last until 18 October 2019.

    The workshop where the magnets are being treated is divided into two sections. In the first room, the vacuum chamber of the magnets is cut so as to access the pole-face windings. The magnet units are then taken to the second room, where prefabricated replacements are installed.

    As mentioned in the previous LS2 Report, the PS Booster will see an increase in the energy it imparts to accelerating protons, from 1.4 GeV to 2 GeV. A new set of quadrupole magnets will be installed along the Booster-to-PS injection line, to increase the focusing strength required for the higher-energy beams. Higher-energy beams require higher-energy injection elements; therefore some elements will be replaced in the PS injection region as part of the LHC Injectors Upgrade (LIU) project, namely septum 42, kicker 45 and five bumper magnets.

    Other improvements as part of the LIU project include the new cooling systems being installed to increase the cooling capacity of the PS. A new cooling station is being built at building 355, while one cooling tower in building 255 is being upgraded. The TT2 line, which is involved in the transfer from the PS to the SPS, will have its cooling system decoupled from the Booster’s, to allow the PS to operate independent of the Booster schedule. “The internal dumps of the PS, which are used in case the beam needs to be stopped, are also being changed, as are some other intercepting devices,” explains Pedrosa.

    The LS2 operations are on a tight schedule,” notes Pedrosa, pointing out that works being performed on several interconnected systems create constraints for what can be done concurrently. As LS2 proceeds, we will bring you more news about the PS, including the installation of new instrumentation in wire scanners that help with beam-size measurement, an upgraded transverse-feedback system to stabilise the beam and more.


    More pictures of the PS magnets are available on CDS:

    https://home.cern/news/news/accelerators/ls2-report-proton-synchrotrons-magnets-prepare-higher-energies

    ( Feed URL: http://home.web.cern.ch/about/updates/feed )

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  • Build The Peach!

    Jason Self at 2019-02-01T14:37:58Z

    Build the peach! Build the peach!

    https://invidio.us/watch?v=W2yAAGQLE1o

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  • Astronomy Picture of the Day for 2019-01-26 12:30:01.764936

    Astronomy Picture of the Day (Unofficial) at 2019-01-26T18:30:03Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 January 26
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    The Umbra of Earth
    Image Credit & Copyright: Antonio Finazzi

    Explanation: The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. For example, on January 21 the Full Moon slid across the northern half of Earth's umbral shadow, entertaining moonwatchers around much of the planet. In the total phase of the eclipse, the Moon was completely within the umbra for 63 minutes. Recorded under clear, dark skies from the hills near Chiuduno, Italy this composite eclipse image uses successive pictures from totality (center) and partial phases to trace out a large part of the umbra's curved edge. Reflecting sunlight scattered by the atmosphere into Earth's shadow, the lunar surface appears reddened during totality. But close to the umbra's edge, the limb of the eclipsed Moon shows a distinct blue hue. The blue eclipsed moonlight originates as rays of sunlight pass through layers high in the upper stratosphere, colored by ozone that scatters red light and transmits blue.

    Tomorrow's picture: crossing the sky

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  • Astronomy Picture of the Day for 2019-01-23 12:30:02.300728

    Astronomy Picture of the Day (Unofficial) at 2019-01-23T18:30:03Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 January 23
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Orion over the Austrian Alps
    Image Credit & Copyright: Luk Vesel

    Explanation: Do you recognize this constellation? Through the icicles and past the mountains is Orion, one of the most identifiable star groupings on the sky and an icon familiar to humanity for over 30,000 years. Orion has looked pretty much the same during the past 50,000 years and should continue to look the same for many thousands of years into the future. Orion is quite prominent in the sky this time of year, a recurring sign of (modern) winter in Earth's northern hemisphere and summer in the south. Pictured, Orion was captured recently above the Austrian Alps in a composite of seven images taken by the same camera in the same location during the same night. Below and slightly to the right of Orion's three-star belt is the Orion Nebula, while the four bright stars surrounding the belt are, clockwise from the upper left, Betelgeuse, Bellatrix, Rigel, and Saiph.

    New: Instagram page features cool images recently submitted to APOD
    Tomorrow's picture: the cold eclipse

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  • Doug Whitfield at 2019-01-22T20:55:35Z

    Who should I be following? No one has posted anything in 3 hours. Last comment appears to have been 2 hours ago...

    Stephen Sekula likes this.

    I got nothing. :-)


    My feed has been fairly quiet of late as well. That said, debian@identi.ca and kfogel@identi.ca have been chatty of late.

    Stephen Sekula at 2019-01-23T00:32:14Z

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  • The @Debian 10 'buster' release freeze has begun --

    Debian Project at 2019-01-21T00:15:07Z

    The @Debian 10 'buster' release freeze has begun -- https://lists.debian.org/debian-devel-announce/2019/01/msg00008.html

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    Stephen Michael Kellat, Stephen Sekula, clacke@libranet.de ❌ shared this.

  • JanKusanagi at 2019-01-17T19:03:10Z

    I feel relaxed already! 😌

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  • Astronomy Picture of the Day for 2019-01-14 12:30:02.260530

    Astronomy Picture of the Day (Unofficial) at 2019-01-14T18:30:03Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 January 14
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Meteor and Milky Way over the Alps
    Image Credit & Copyright: Nicholas Roemmelt (Venture Photography)

    Explanation: Now this was a view with a thrill. From Mount Tschirgant in the Alps, you can see not only nearby towns and distant Tyrolean peaks, but also, weather permitting, stars, nebulas, and the band of the Milky Way Galaxy. What made the arduous climb worthwhile this night, though, was another peak -- the peak of the 2018 Perseids Meteor Shower. As hoped, dispersing clouds allowed a picturesque sky-gazing session that included many faint meteors, all while a carefully positioned camera took a series of exposures. Suddenly, a thrilling meteor -- bright and colorful -- slashed down right next the nearly vertical band of the Milky Way. As luck would have it, the camera caught it too. Therefore, a new image in the series was quickly taken with one of the sky-gazers posing on the nearby peak. Later, all of the images were digitally combined.

    Tomorrow's picture: heart & soul

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  • Jason Self at 2019-01-14T02:05:49Z

    I removed 15 of the 16 RAM modules and the computer boots into the Trisquel installer just fine. It would appear the problems can be explained away with bad memory. Time to break out Memtest86+...

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  • TARDIS

    at 2019-01-15T00:05:23Z

    What? You don't know what a TARDIS is?

    Don't you have a plain old dictionary? https://en.oxforddictionaries.com/definition/tardis 😆

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  • This weekend we have a Debian Bugsquashing Party in Venlo #Debian #BSP #Party

    Debian Project at 2019-01-11T22:15:05Z

    This weekend we have a Debian Bugsquashing Party in Venlo https://wiki.debian.org/BSP/2019/01/nl/Venlo #Debian #BSP #Party

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  • JanKusanagi at 2019-01-11T19:18:58Z

    Some giant took a bite out of the Sun!!!!! 😱

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  • JanKusanagi at 2019-01-08T04:48:14Z

    Gifted. But the thing about the Navier-Stokes problem was just a background thing. It was just funny to see it mentioned 😆

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  • JanKusanagi at 2019-01-08T02:10:51Z

    Weird, I was under the impression that it was day 7... 🤔

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  • New blog post: "Debian is back in the Mastodon/GNU Social fediverse, follow fosstodon.org/@debian"

    Laura Arjona Reina at 2018-12-21T12:36:07Z

    New blog post: "Debian is back in the Mastodon/GNU Social fediverse, follow fosstodon.org/@debian" https://larjona.wordpress.com/2018/12/21/debian-is-back-in-the-mastodon-gnu-social-fediverse-follow-fosstodon-org-debian/

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    Cool, but I already follow @Debian Project right here 😎

    JanKusanagi at 2018-12-21T13:28:48Z

  • Stephen Michael Kellat at 2019-01-06T18:07:41Z

    I had to move off quitter.se to mastodon.sdf.org.

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  • JanKusanagi at 2019-01-06T17:54:40Z

    I think at least the first one is. IIRC @Laura Arjona Reina was on it and had to move.


    She might have commented on it on her feed 😄

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  • Astronomy Picture of the Day for 2019-01-04 12:30:02.139948

    Astronomy Picture of the Day (Unofficial) at 2019-01-04T18:30:02Z

    Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

    2019 January 4
    See Explanation.  Clicking on the picture will download
the highest resolution version available.

    Ultima Thule Rotation Gif
    Image Credit: NASA, Johns Hopkins University APL, Southwest Research Institute

    Explanation: Ultima Thule is the most distant world explored by a spacecraft from Earth. In the dim light 6.5 billion kilometers from the Sun, the New Horizons spacecraft captured these two frames 38 minutes apart as it sped toward the Kuiper belt world on January 1 at 51,000 kilometers per hour. A contact binary, the two lobes of Ultima Thule rotate together once every 15 hours or so. Shown as a blinking gif, the rotation between the frames produces a tantalizing 3D perspective of the most primitive world ever seen. Dubbed separately by the science team Ultima and Thule, the larger lobe Ultima, is about 19 kilometers in diameter. Smaller Thule is 14 kilometers across.

    Tomorrow's picture: on the Far Side

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  • I have three words for you...

    JanKusanagi at 2019-01-04T19:46:36Z

    Race

    Conditions

    Suck 😠

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