Glimpses of Solar light
Ramallah sunset : A minaret is silhouetted as the sun sets over the West Bank city of Ramallah. (AFP/Abbas Momani)
Northern lights dance across the sky near Palmer, Alaska, Wednesday, Nov. 22, 2006. (AP Photo/Bob Martinson)
See More spectacular pictures of
Into the LIGHT
Rehearsal in Seville : Mares perform during a rehearsal of Sicab 2006, the International Horse Show of Spain, in Seville. (AFP/Cristina Quicler)
Where visible light cannot travel thru
Six years after its construction began, the CNGS facility at CERN has sent its first batch of neutrinos 732 km to Gran Sasso in Italy in a highly successful commissioning run.
The CERN Neutrinos to Gran Sasso (CNGS) facility was built to create a neutrino beam to search for oscillations between muon-neutrinos and tau-neutrinos. An intense, almost 100% pure beam of muon-neutrinos is produced at CERN in the direction of the Laboratorio Nazionale del Gran Sasso (LNGS), almost 732 km away in Italy . There, the OPERA experiment (see CERN Courier November 2006 p24) is being constructed to find interactions of tau-neutrinos among those of other neutrinos.
The production of the CNGS beam of muon-neutrinos follows the "classic" scheme that was first used in the 1960s at Brookhaven and CERN, and has been refined ever since. An intense proton beam from CERN's Super Proton Synchrotron (SPS) is sent to strike a target, in this case graphite. Protons that interact with nuclei in the target produce many particles, mostly unwanted, but including positively charged pions and kaons – mesons that decay naturally into pairs of muons and muon-neutrinos.
Two magnetic lenses – the horn and the reflector – collect these mesons within a selected momentum range and focus them into a parallel beam towards LNGS. After a decay tube nearly 1 km long, all the hadrons – i.e. protons that have not interacted in the target, pions and kaons that have not yet decayed, and so on – are absorbed in a hadron stopper; only neutrinos and muons can traverse this solid block of graphite and iron.
The muons, which are ultimately absorbed downstream in around 500 m of rock, are measured first in two detector stations. Only the neutrinos are left to travel onwards through the top layer of the Earth's crust towards LNGS.
Konrad Elsener, Edda Gschwendtner and Malika Meddahi @ CERN courier
The neutrino is of scientific interest because it can make an exceptional probe for environments that are typically concealed from the standpoint of other observation techniques, such as optical and radio observation.
[+/-] Click here to expand
Neutrinos for beginners & Icecream by Sabine Hossenfelder
Tunnelling in Faster than Light by Plato @ Dialogues of Eide