AMS-02 is een state-of-the-art deeltjesfysica-experiment dat ontworpen is om te opereren als een externe module aan het International Space Station (ISS). Het zal gebruik maken van de unieke mogelijkheden van een experiment in de ruimte om het universum en haar ontstaan te bestuderen door te zoeken naar antimaterie en donkere materie. Daarnaast doet het precisiemetingen aan de samenstelling van kosmische straling en flux.
Elf jaar geleden ontwierp Nikhef een nieuw koelconcept voor de AMS-02 detector; CO2-koeling. Deze nieuwe methode van koelen zorgt voor aanzienlijk minder materiaal in de detector dan eerdere methoden. Het door Nikhef ontworpen AMS-02 koelconcept werd door het Nationaal Lucht- en Ruimtevaartlaboratorium (NLR) verder ontwikkeld en gerealiseerd.
Bart Verlaat, ingenieur op de afdeling Mechanische Technologie van Nikhef is nog steeds bij het project betrokken en hielp in 2010 met het testen van het systeem in de Space Simulator bij de European Space Agency (ESA) en in 2011 met de testen in de ruimte van het koelsysteem vanuit het Mission Control Center van NASA in Houston.
"Ik ben blij te horen dat AMS positive wetenschappelijke resultaten laat zien. Hopelijk heeft de goede werking van ons koelsyteem daar aan bijgedragen. Het koelsysteem doet het bovenverwachting goed. Sinds het begin van de missie is temperatuur van de detector stabiel op 0oC, en hebben we hem niet meer hoeven bij te stellen, iets wat we wel verwacht hadden door de veranderende thermische omgeving in de ruimte"
Original CERN press release
Geneva 3 April 2013. The international team running the Alpha Magnetic Spectrometer (AMS1) today announces the first results in its search for dark matter. The AMS paper, to be published in the journal Physical Review Letters, reports the observation of an excess of positrons in the cosmic ray flux. AMS spokesperson, Professor Samuel Ting, will present the AMS findings in a webcast seminar at CERN2 at 17:00 CEST today.
The AMS results are based on some 25 billion recorded events, including 400,000 positrons with energies between 0.5 GeV and 350 GeV, recorded over a year and a half. This represents the largest collection of antimatter particles recorded in space. The positron fraction increases from 10 GeV to 250 GeV, with the data showing the slope of the increase reducing by an order of magnitude over the range 20-250 GeV. The data also show no significant variation over time, or any preferred incoming direction. These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations.
“As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector,” said AMS spokesperson, Samuel Ting. “Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”
Cosmic rays are charged high-energy particles that permeate space. The AMS experiment, installed on the International Space Station, is designed to study them before they have a chance to interact with the Earth’s atmosphere. An excess of antimatter within the cosmic ray flux was first observed around two decades ago. The origin of the excess, however, remains unexplained. One possibility, predicted by a theory known as supersymmetry, is that positrons could be produced when two particles of dark matter collide and annihilate. Assuming an isotropic distribution of dark matter particles, these theories predict the observations made by AMS. However, the AMS measurement can not yet rule out the alternative explanation that the positrons originate from pulsars distributed around the galactic plane. Supersymmetry theories also predict a cut-off at higher energies above the mass range of dark matter particles, and this has not yet been observed. Over the coming years, AMS will further refine the measurement’s precision, and clarify the behaviour of the positron fraction at energies above 250 GeV.
“When you take a new precision instrument into a new regime, you tend to see many new results, and we hope this this will be the first of many,” said Ting. “AMS is the first experiment to measure to 1% accuracy in space. It is this level of precision that will allow us to tell whether our current positron observation has a Dark Matter or pulsar origin.”
Dark matter is one of the most important mysteries of physics today. Accounting for over a quarter of the universe’s mass-energy balance, it can be observed indirectly through its interaction with visible matter but has yet to be directly detected. Searches for dark matter are carried out in space-borne experiments such as AMS, as well as on the Earth at the Large Hadron Collider and a range of experiments installed in deep underground laboratories.
“The AMS result is a great example of the complementarity of experiments on Earth and in space,” said CERN Director General Rolf Heuer. “Working in tandem, I think we can be confident of a resolution to the dark matter enigma sometime in the next few years.”
Background information:
"First result from the AMS experiment"
Video press conference:
http://www.nasa.gov/home/hqnews/2013/apr/HQ_M13-054_AMS_Findings_Briefing.html
AMS Paper on Physical Review Letters:
http://physics.aps.org/articles/v6/40
2. CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its member states are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a candidate for accession. Cyprus, Israel and Serbia are associate members in the pre-stage to membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have observer status.