Affichage de 2107 résultats

The 3.70 metre Big European Bubble Chamber (BEBC) was dismantled on 9 August 1984. One of the biggest detectors in the world, it produced direct visual recording of particle tracks. 6.3 million photos of interactions were taken with the chamber in the course of its existence.

A wire chamber used at CERN's Proton Synchrotron accelerator in the 1970s. Multi-wire detectors contain layers of positively and negatively charged wires enclosed in a chamber full of gas. A charged particle passing through the chamber knocks negatively charged electrons out of atoms in the gas, leaving behind positive ions. The electrons are pulled towards the positively charged wires. They collide with other atoms on the way, producing an avalanche of electrons and ions. The movement of these electrons and ions induces an electric pulse in the wires which is collected by fast electronics. The size of the pulse is proportional to the energy loss of the original particle.

Was used in a PS experiment. Before the days of electronic detectors, visual techniques were used to detect particles, using detectors such as spark chambers and bubble chambers. This plexiglass lens was used to focus the image of tracks so they could be photographed.

for parts

A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

A device to convert light into an electric signal (the name is often abbreviated to PM). Photomultipliers are used in all detectors based on scintillating material (i.e. based on large numbers of fibres which produce scintillation light at the passage of a charged particle). A photomultiplier consists of 3 main parts: firstly, a photocathode where photons are converted into electrons by the photoelectric effect; secondly, a multiplier chain consisting of a serie of dynodes which multiply the number of electron; finally, an anode, which collects the resulting current.

The pulse of a particle accelerator. 128 of these radio frequency cavities were positioned around CERN's 27-kilometre LEP ring to accelerate electrons and positrons. The acceleration was produced by microwave electric oscillations at 352 MHz. The electrons and positrons were grouped into bunches, like beads on a string, and the copper sphere at the top stored the microwave energy between the passage of individual bunches. This made for valuable energy savings as it reduced the heat generated in the cavity.

OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. The Silicon Tungsten Luminometer was part of OPAL's calorimeter which was used to measure the energy of particles. Most particles end their journey in calorimeters. These detectors measure the energy deposited when particles are slowed down and stopped.

One of the two "ASM/2-32EM" boxes installed in 1988, from "Cisco Systems Inc." - then an unknown 20-employee company in Menlo Park, California (USA). This is one of the first two Cisco boxes to appear in Switzerland, and possibly Europe. The 220v power supply was a special modification made for use at CERN. They supported IP address filtering, which seemed just what CERN needed to help protect the new Cray XMP-48 super computer from network hackers. The two ASM boxes were both routers and terminal servers. They protected a secure private Ethernet segment used by the Cray project, as well as providing secure terminal connections to that segment, including CERN's first dialback terminal service, which allowed Cray and CERN system analysts to work on the machine from home, using another Cisco feature called TACACS. (Kindly offered by B. Segal who discovered this company while at a Usenix Conference in Phoenix, Arizona in June 1987.)

<!--HTML-->Antiproton target used for the AA (antiproton accumulator). The first type of antiproton production target used from 1980 to 1982 comprised a rod of copper 3mm diameter and 120mm long embedded in a graphite cylinder that was itself pressed into a finned aluminium container. This assembly was air-cooled and it was used in conjunction with the Van der Meer magnetic horn. In 1983 Fermilab provided us with lithium lenses to replace the horn with a view to increasing the antiproton yield by about 30%. These lenses needed a much shorter target made of heavy metal - iridium was chosen for this purpose. The 50 mm iridium rod was housed in an extension to the original finned target container so that it could be brought very close to the entrance to the lithium lens. Picture 1 shows this target assembly and Picture 2 shows it mounted together with the lithium lens. These target containers had a short lifetime due to a combination of beam heating and radiation damage. This led to the design of the water-cooled target in a titanium alloy body <A href="http://weblib.cern.ch/format/showfull?uid=519512&base=OBJOBJ&sysnb=0000166"> (see object AC-020).</A>