IKP

 ZEL

 ZAT

In charge: Prof. R. Maier, IKP, r.maier@fz-juelich.de

Aims and Objectives

The synchrotron COSY is a cooler and storage ring for the acceleration of polarized and non-polarized protons and deuterons with momenta up to 3.65 GeV/c. lt is the combination of features that makes this accelerator unique. Experiments in Hadron Physics use highly brilliant beams with very good energy resolution in a wide energy range. Two methods for beam cooling are available: Electron cooling at low energies preferably used for accelerator development and beam-halo suppression for external experiments, stochastic cooling in the upper energy range as a routine tool for experiments.

Scientists from national and international laboratories and universities use the COSY beam at internal and external target stations.

Significant Results in 2003

The experimental studies at the Cooler Synchrotron COSY are dedicated to the investigation of proton-proton as well as proton-nucleon reactions to gain information on the sub-nuclear structure of baryons and mesons as well as their modifications in nuclear matter. The general objective of these studies is the better understanding of the hadron structure in the medium energy domain.

According to the experimental demands the COSY accelerator system is improved continuously with special priority on high intensity polarised proton and deuteron beams. Measures taken for physical and technical improvements are requested to have a minimum impact only on the beam time for experiments. In 2003 the accelerator was operational for 7300 h; 5560 h could be delivered to the various internal and external target stations and 1740 h were dedicated to machine development.

Comprehensive studies were carried out to preserve a high degree of polarisation in a proton beam up to the maximum momentum. In the year 2003 for the first time a polarised proton beam was electron cooled after injection, then accelerated and made available for an experiment. The small emittance of the cooled proton beam reduces the strength of the depolarising resonances, so that after acceleration a beam polarisation as high as 90% was achieved.

Different extraction modes have been routinely established or enhanced. An ultra-fast extraction is applied to kick out an electron-cooled beam in about 200 ns. This mode is used at the experiment JESSICA for studies of the high power target station for ESS. In contrast, a stochastic slow extraction method is established to provide external beams ranging from 20s up to several minutes.

COSY experiments like GEM and TOF significantly gain in resolution from a beam with best possible brilliance at the target place. These experiments are equipped with veto counters which limit the acceptance of beam in presence of halo particles. As the small emittance of an electron cooled beam keeps preserved during the acceleration process it can be extracted using the general (stochastic) extraction procedure at any specified energy. As an example a cooled beam of 1.2•10¹⁰ protons was extracted at 1.57 GeV/c with a rate of 5•10⁸ protons/s. With an excellent beam spot achieved at the target the primary beam intensity could be increased by a factor of 60 for the same veto counting rate compared with a uncooled beam. This will enable the investigation

As a reaction of the increasing demand for deuterons the acceleration (up to 3.3 GeV), e-cooling and extraction of deuteron beams could be demonstrated at COSY. Up to 1.3•10¹¹ uncooled deuterons and cooled deuteron beams of 5•10¹⁰ ions could be achieved. For the first time polarised deuterons were injected into COSY, accelerated and delivered to internal and external experiments. During the acceleration of polarised deuterons in COSY no depolarising resonances have to be crossed. So, the experiments could make use of a deuteron beam with an intensity of up to 6•10⁹ and a high degree of polarisation.

As the intensity of polarised beams is limited by lower ion source currents compared to unpolarized beams, experiments were carried out with multiple injections in combination with electron cooling. With 900 injections over 15 minutes and continuous electron cooling it was possible to accelerate up to 2•10¹⁰ polarised protons. Due to the long injection time this procedure is only interesting for internal target experiments with long beam lifetimes.

During the machine development periods detailed studies were carried out about beam loss mechanisms during injection and acceleration. The analysis and careful matching made it possible to increase the intensity of unpolarized proton beams by a factor of 3 to 1.5•10¹¹ accelerated protons.

In close collaboration with the Central Technology Division (ZAT) significant projects have been realized. Besides others a new target chamber was built for ANKE. The COSY-ring obtained a new injection chamber. Far-reaching investigations have been conducted with respect to super conducting acceleration structures and their corresponding cryostats.

The Central Institute for Electronics (ZEL) supported the IKP in its tasks through the development of a new CCD-camera system. This camera has at present worldwide the highest resolution for position and energy of low energy gamma rays. In addition complex systems for the data acquisition with MWPSs and Vertex-detectors at ANKE and straw detectors at TOF have been developed. In preparation for future demands developments have been initiated for high-rate data reduction in front end systems.