HELIOS consisted of two fixed-target experiments at
the SPS
which studied heavy ion
collisions (NA34/2) and lepton production in hadronic interactions (NA34/1). I worked with the trigger
system and with the analysis of muon pair data.
NA34/1 used a
proton beam of transverse size of only 50 microns that impinged on a beryllium wire-target with
50 micron diameter.
High precision tracking in the vertex region was achieved by silicon strip detectors.
Charged particle momenta were measured using a dipole magnet and high resolution drift chambers.
Electrons were identified by the combination of the transition radiation detector and the
finely segmented front section of the Uranium/Liquid Argon calorimeter. Essentially the
complete centre of mass solid angle was covered by the Uranium/Scintillator and
Uranium/Liquid Argon calorimeters. Further downstream, muons were identified and
measured in a modified version of the NA3 muon spectrometer.
The Super Proton Synchrotron
The Super Proton Synchrotron (SPS) started operations in 1976 as a
400 GeV fixed target proton machine. The energy was later increased to 450 GeV.
The accelerator is situated in a 6.9 km long tunnel of diameter 4.14 m.
There are six straight sections for injection, extraction and RF acceleration.
The bending is provided by 744 dipole magnets with a peak field of 1.8 T.
The cross-section of the beam is maintained by a system of 216 quadrupole magnets.
The acceleration is achieved by the RF-system which consists of four cavities operating at 200.2 MHz:
two of 20 m length and two of 16.5 m length. They are all installed in one long straight section (LSS 3).
Initially only two cavities were installed, a third cavity was installed in 1978 and a forth one in 1979.
Designed for protons, the SPS has also accelerated electrons, positrons and heavy ions.
The fixed target experiments were carried out in two large halls called the
North area and the West area.
The SPS was converted to a proton-antiproton collider with 270 GeV beams in 1981.
The beam energy in the collider was later increased to 315 GeV and then to 450 GeV.
Responsible for the content of this page is
Vincent Hedberg
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