R. Maier

Cooler synchrotron COSY — Performance and perspectives

Abstract COSY is a cooler synchrotron and storage ring delivering protons with momenta between 300 MeV/c and 3300 GeV/c for experiments in medium energy physics. It contains two cooling systems to shrink the beam phase space. An electron-cooling system reaches up to a momentum of 600 MeV/c and is complemented by a stochastic cooling system that covers the upper range from 1500 to 3300 MeV/c. Beam extraction is accomplished by the conventional resonant extraction mechanism as well as with the stochastic extraction method. Proton beams are being delivered routinely to three internal and three external experimental areas.

COSY- 11, an internal experimental facility for threshold measurements

Abstract The COSY-11 installation is an internal experiment at the cooler synchrotron and storage ring COSY Julich. It has been designed for full geometrical acceptance close to threshold for meson production studies, especially in the 1 GeV/ c 2 mass range. The experimental setup makes use of a regular C-type COSY dipole magnet, following a cluster target, to separate reaction products from the beam and to analyze their momenta, thus allowing the observation of charged reaction products at small angles with beam energies close to threshold. Resonances will be identified by missing mass reconstructions from measured four-momenta of two outgoing protons in the predominantly studied pp → ppX reaction. In addition, charged mesons either produced directly or from decays of X will be detected. The different components of the experimental facility are presented.

Electron and stochastic cooling at COSY

The synchrotron and storage ring COSY delivers proton beams with momenta between 300 and 3500 MeV/c for internal and external experiments. It is operating both with electron and stochastic cooling. The electron cooling is used mainly at the injection energy with 22 keV electrons to increase the intensity of the polarised proton beam with a combined cooling stacking injection. In addition, the electron-cooled proton beam is used for diagnostic purposes of machine parameters. The stochastic cooling for COSY is working in the proton momentum range between 1.5 and 3.5 GeV/c and is up to now only used for equilibrium experiments with thin internal targets and long #at top times. The longitudinal stochastic cooling system is extended by a fast frequency variable optical notchlter to make use of a supercycle in COSY with from cycle to cycle varying #at top energies. The results of the electron cooling and stacking injection as well as the good results of the optical notchlter for the stochastic cooling will be presented. ( 2000 Elsevier Science B.V. All rights reserved.

Cooler synchrotron COSY

Abstract COSY Julich is a cooler synchrotron and storage ring delivering high precision beams with at present up to 5·10 10 protons with momenta between 600 MeV/c and 3.3 GeV/c for medium energy physics. Two cooling systems are used to accomplish this goal. An electron-cooling system that reaches up to a momentum of 645 MeV/c and a stochastic cooling system that covers the upper momentum range from 1500 to 3300 MeV/c. Since its inauguration in April 1993 substantial progress in developing beams for internal and external experiments has been achieved and the physics program is now running. At the beginning of 1996 a polarized proton beam could be successfully accelerated up to 820 MeV/c for the first time.

Acceleration of Polarized Protons and Deuterons at COSY

At the cooler synchrotron COSY, protons and deuterons are accelerated up to 3.65 GeV/c. Vertically polarized proton beams with more than 70% polarization have been delivered in recent years to internal as well as to external experiment areas at different momenta up to the maximum momentum of COSY. In a strong‐focusing synchrotron like COSY, imperfection and intrinsic resonances cause polarization losses during acceleration. The existing magnet system of COSY allows to overcome all imperfection resonances by exciting adiabatic spin flips without polarization losses. A tune‐jump system consisting of two fast quadrupoles has been developed to handle intrinsic resonances in COSY. This magnet system is being successfully utilized at all intrinsic resonances in the momentum range of COSY. For the acceleration of vertically polarized deuterons, additional correction provisions are not necessary to preserve polarization during acceleration because depolarizing resonances are not crossed in the momentum range of C...

Threshold measurements at the internal experimental facility COSY-11

Abstract The experimental setup and detection technique of the COSY-11 installation, an internal experimental facility at the cooler synchrotron and storage ring COSY Julich, are described. The detection system has been designed for meson production studies with full geometrical acceptance close to threshold. Preliminary results of first measurements are presented, emphasis is put on strangeness production in the reactions pp → ppK + K − and pp → pK + Λ .

First results from subthreshold K+-production measurements with ANKE

Abstract The new spectrometer ANKE has been put into operation at the accelerator COSY of the Forschungszentrum Julich. An initial scientific goal is to study K+-production in pA collisions at subthreshold energies below the free NN-threshold of T = 1.58 GeV. First measurements of double differential cross sections in p12C collisions at emission angles around 0° have been performed at T = 1.0, 1.2 and 2.0 GeV. The challenge is to identify the kaons in a huge background of pions and protons, since the signal to background ratio decreases to about 10−6 at T = 1.0 GeV. For background suppression detectors and a trigger system based on energy-loss and time-of-flight measurements have been developed. In the analysis the decay of kaons (τ = 12.4 ns) stopped in the detection system into μ+ and π+ is exploited as well as the track information from the wire chambers.

Investigation of production and fission decay of heavy hypernuclei at COSY Jülich

Abstract The production of very heavy hypernuclei has been investigated at COSY Julich in the interaction of protons of 1.0 GeV, 1.5 GeV and 1.9 GeV with bismuth and uranium. Identification was based on the detection of fragments from Λ delayed fission using a recoil-shadow technique which yielded cross sections for production and fission decay of hypernuclei of about 5μb (Bi target) and 20±4(stat.)−8+13(syst.)μb (U target). A lifetime of 240±45(stat.)±40(syst.) ps has been deduced for the uranium target from the position distribution of fission fragments.