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NBI Colliderscope - The artwork

The NBI Colliderscope is a light-artwork placed on the facade of the Niels Bohr Institute in Copenhagen. The work of art is connected directly to the world's largest physics experiment that right now is taking place at CERN just outside Geneva, Switzerland.

The experiment is conducted in the Large Hadron Collider (LHC), a 27 km long subterranean magnetic track where subatomic particles are smashed together with extreme energy. Hereby are created states like those that existed in our universe a few moments after it came into being. Every particle collision is registered by sensors that
generate enormous amounts of data. These data are the background for the Colliderscope. The idea of the artwork is to create a direct sensuous and intuitive translation of the data stream that ATLAS captures in the LHC collisions. By using most of the parameters in the data stream, and combining them with the random rhythm of the collisions, the work attempts to reproduce the signal from ATLAS in it's full tonality, as if the accelerator was a gigantic musical instrument. Maybe one can view the work as a visual interpretation of the music that sounded at the birth of the universe.

Technically the work is built with 96 light emitting diodes placed in a hexagonal net over the architecture of the facade of the Niels Bohr Institute. This mirrors the structure of the TRT detector in the ATLAS experiment. Every diode is borne by an aluminum arm from which it shine at a distance of 40 cm with an intensity of 5 Watt onto the grey plaster of the wall. The system of diodes is controlled by a computer that translates the original data from the TRT detector in the Atlas experiment into light signals. These signals are sent to an online server that addresses each diode with intensity, duration, frequency etc. The Colliderscope shows the latest data from the detector, which can be just minutes old, but sometimes older because the LHC does not run continuously.

The work of art has been created by physicists Clive Ellegaard and Troels Petersen in collaboration with artists Christian Skeel and Morten Skriver.

The programming of the online software is done by physicist Anders Holm.

 

The LHC Accelerator

The Large Hadron Collider is the world's largest particle accelerator. It is placed in a subterranean circular tunnel with a circumference of 27 km at a depth of between 50 and 175 metres underground at the French-Swiss border near Geneva.

The accelerator tunnel contains two separate beam tubes that cross each other at four places. The two tubes contain proton beams moving in opposite directions in the large ring. 1600 large electromagnets keep the beams in their circular tracks and focus them in order to enhance the chance of collision in the four crossing points. Most of the magnets weigh about 27 tons. The magnets are cooled by means of 96 tons of liquid helium to keep the superconducting magnets at their working temperature of -271.25 degrees Centigrade.

Before they are sent into the main accelerator the energy of the particles is gradually increased through a series of connected smaller accelerators. This system consists of most of the predecessors of the LHC accelerator at CERN, of which the oldest is from 1956. The LHC is equipped with six detectors placed around the four crossing points of the double beam tube. Two of them, the ATLAS experiment and the Compact Muon Solenoid (CMS), are created to study the broadest possible spectrum of phenomena. The two socalled ion collider experiments, ALICE and LHCb, are designed respectively to reproduce the nuclear states just after Big Bang and to look for the difference between matter and antimatter. Finally the TOTEM and the LHCf are much smaller detectors for more specialised research.


Diagram over the CERN accelerator complex. At the top the LHC with indications of the four large experiments. View image in high resolution >>


  View image in high resolution >> 

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The Atlas experiment

The ATLAS experiment is the largest of the LHC experiments. It is a densely packed high-tech construction that is 44 m long and 25 m in diameter, and weighs about 7000 tons. The experiment has been designed for the observation of very massive particles that have been impossible to observe with earlier, lower energy accelerators. The detector consists of a series of ever greater cylinders around the point where the two beams of the LHC cross.

The ATLAS detector is subdivided into three parts: the inner detector, the calorimeter and the muon spectrometer. These parts, that are further subdivided into many layers, function in a complementary fashion. Thus the ATLAS detector is able to recognise all types of particles originating from the collisions, most often with some overlap.

An important part of the ATLAS design is that the innermost layers are the most precise, and at the same time built from very little material, so as not to shadow the subsequent detectors. The inner detector consists of three parts. The first (the Pixel-Detector)
determines the origin of the particles. The next (Semi-Conductor- Tracker - SCT) determines the direction of the particles, and the last (Transition Radiation Tracker - TRT) determines, together with the previous two, the energy of the particles, and whether they are electrons or not.

It is from the TRT detector the NBI Colliderscope gets its data.

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The TRT detector

The TRT detector consists of about 500.000 straws that give a signal when a particle passes through. Each straw is four mm in diameter and up to 144 cm long. Each straw is filled with a gas that becomes ionised when a particle passes through it.

When the detector shows a number of signals in a row it means that a particle has passed through, and from the positions of the signals its origin and track are determined. The particles move in a magnetic field and, because of their charge, their track is curved. Particles with high energy curve slightly while those with lower energy curve more. Depending on the charge of the particles they bend one way or the other. This way one can determine the original energy and charge of the particle. From these data one can then reconstruct what happened in the collision. In addition the TRT detector can as a special feature recognise electrons.

The Niels Bohr Institute has participated in designing, testing, calibrating and optimising the TRT detector.


  Diagram with an indication of a track in the TRT detector.

The Particles

The LHC accelerator and the experiments around it are like a gigantic microscope that makes it possible to examine structures at the smallest physical scale (1/1,000,000,000 of an atom). The accelerator experiments will make it possible to see what the world is
made of and the laws of nature that govern it. With the LHC begins the hunt for the Higgs particle, which is the last missing piece of our present model of the world, but the accelerator experiments also search for other things such as so-called dark matter and
possible extra dimensions.

When particles are smashed together in the LHC beam tubes, conditions emerge like those that existed just after the universe came into being. Enormous forces are liberated within a very small volume. Microscopic black holes emerge and showers of extremely
small building blocks are torn apart in a nanosecond. By observing these objects' movements individually and relative to each other, the physicists hope to get a better understanding of the forces that govern our universe.

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Visualisation

The data produced by the detectors of the LHC can be visualised in many ways. The visualisations are practical aids for the physicists for communication of complex correlations instead of tables and equations. For the non-scientific person the visualisations can give a impression of the abstract matters physicists talk about. They can also often be aesthetically fascinating. Maybe because they originate in fundamental natural phenomena. The NBI Colliderscope stands out from the usual methods of visualisation of physical data by being formed by what one mght call artistic visual feelings. With its combination of many of the parameters in the measurements of the
TRT detector, the work is nonetheless just as realistic a reproduction of the events within the LHC as any other visual representation. It is actually possible to read the picture as the physical phenomenon. A possible electron appears with a strong light and remains on the facade for several seconds. Since there are no electrons in the colliding protons, the presence of an electron tells the physicist that "something interesting" has happened that is worth a closer look. Other "interesting" tracks are those that do not come directly from the proton collisions. They are reproduced as slowly moving, with dim light (i.e. they look like caterpillars).

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Behind the work

The background for the NBI Colliderscope was a wish for creating a public artistic manifestation to mark the start of the gigantic physics experiment in the LHC at CERN. By creating a direct connection between the LHC and the Niels Bohr Institute we wanted to show the deep involvement of the Institute in this project, both in its development and later in the analysis of the incoming data.

Our aim was to make the events in the LHC as immediate and concretely visual as possible, so as to spontaneously capture the interest of any casual passerby. We therefore chose to avoid the usual presentation such as screens and video projectors. This type of media would simply veil and trivialise the message through their familiarity. Instead we decided to integrate the work in the architecture of the main building of the Institute as an object in itself. This way we created a picture never seen before, and we hoped hereby, to stimulate general curiosity.

Placing the work on the facade of the Institute's main building was primarily to allow the greatest number of passersby to see it, but it also has the symbolic meaning, that it was here CERN had its first centre.

The main idea in our translation of the signals from the TRT detector was to pass on the special absence of patterns and repetition that exists at the quantum level. We did not want to explain the physics, but create a feeling of the kind you might get when on a bright
night you look at the starry sky without quite understanding what caught your attention.

The development of the NBI Colliderscope was from beginning to end a close collaboration between art and science. The final work is in all ways the result of the collective efforts of all involved, and could not have come about in any other way.

An example of the character of this collaboration is the very important part played by Bjarne Bundsøe and Henrik Bundgaard with their special technical knowledge, in getting the artistic idea to function practically.

 

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