From the Search for Quark Matter to Cancer Therapy
Heavy ion research touches upon an exceptionally wide range of subjects, reaching out beyond nuclear and atomic physics to related application- oriented fields such as plasma physics, materials science, and radiation medicine. The research program undertaken by GSI is correspondingly broad. The Darmstadt center is one of 16 major research facilities in Germany and is internationally renowned.For nearly half a century now, progress made in understanding the structure of matter - and therefore of the laws that determine the course of events in the universe - has been essentially determined by experiments conducted with particle accelerators. Within huge vacuum rings, atomic nuclei and electrons are "pumped up" with energy to the very limits of what is physically and technically attainable. Guided by magnetic fields, they are then hurled against each other or at obstacles interposed in their path. An analysis of the "debris" - newly formed particles - produced in such collisions, provides new insights into the structure of the systems under investigation and the forces that hold them together.
Whereas protons and electrons are the "tools" of elementary particle physics, the situation is different in heavy ion physics. In this discipline, which now has an impressive track record extending back over about 30 years, physicists rely on accelerated heavy ions to give them their results. Heavy ions are heavy atoms which have been stripped of some of their outer electrons and are therefore positively charged. Work in this area has led to a significant expansion in the scope of research, not only in nuclear and atomic physics, but also in other disciplines such as solid-state and materials research, biophysics, and radiation medicine. At GSI, the spectrum of basic and applied research ranges from the search for quark matter to cancer therapy.
Although GSI was founded in December 1969, preparatory work had already begun in the early 1960s. Construction commenced in November, 1971 on the site of the new research center on the northern edge of Darmstadt. The first experiments were able to start when UNILAC (the Universal Linear Accelerator) became operational in May, 1975. Regular experimentation started in January, 1976.
After ten years of successful research, it was time to expand again. In 1985, Germany's Minister for Research gave the go-ahead for the construction of the heavy ion synchrotron (German acronym SIS) and the experimental storage ring (ESR) plus related experimental setups and detection instruments - called simply "experiments" in the vernacular. With the commissioning of this new wing in 1990, a source of relativistic heavy ions - i.e., ionized atoms moving at speeds approaching that of light - became available to researchers.
Aerial view of the GSI research center upon completion of the second phase of expansion. The large buildings on the right house the heavy ion synchrotron, the experimental storage ring, and the related detectors and other experimental equipment.
Spanning 13 orders of magnitude without a gap
With about 80% of all investigation dedicated to fundamental research, the central focus of the GSI program is upon studies in the areas of nuclear and atomic physics. Nonetheless, applied research has developed in parallel and continues to gain in importance. Today, the areas of materials research, plasma physics, and biophysics each make up about 5% of the total research activities. Another 5% is devoted to accelerator development. A fact worth noting is that the scope of the research extends with barely a break across thirteen orders of magnitude. At the top end is the cell, measuring 10-5 m. Down the line are the molecule (10-9m), the atom (10-10m), the atomic nucleus (10-14m) and nucleons (10-15m). Finally, at the bottom end are the quarks (<10-18m) in the quark-gluon plasma.
In the area of nuclear physics research, it is investigations into the structure of the nucleus that are especially prized. The synthesis and discovery at GSI of the five heaviest elements of the periodic system up to the element 111 - the latter accomplished to worldwide acclaim at the beginning of 1995 - typifies the systematic pursuit of a research objective through continuous improvements in detection systems and accelerator technology. With the commissioning of the heavy ion synchrotron and the experimental storage ring, research potential has expanded to provide entirely new insights into the properties of exotic nuclei beyond the normal range of stable isotopes. The study of these exotic nuclei is of significance well beyond pure nuclear physics: it is also important for astrophysical issues such as the synthesis of elements in stars.
The second important area in basic nuclear research at GSI is the investigation of hot, dense nuclear matter. Across the entire SIS energy range (and, beyond that, to the highest energies at CERN in Geneva), heavy ion beams are providing physicists with the opportunity of studying the multiple manifestations of nuclear matter, from its normal "liquid" state to a gas composed of free nucleons, and on to the dissolution of nucleons in a quark-gluon plasma. This domain of investigation has likewise strong astrophysical implications, since scientists believe that a few fractions of a second after the big bang all the matter in the universe existed as a quark-gluon plasma. What’s more, the dramatic course of supernova explosions and the properties of the neutron stars to which they give rise are determined to a large extent by the behavior of compressed nuclear matter.
Finally, the availability of the SIS and the ESR also led to a breakthrough in atomic physics: it is now possible to completely strip the electron shell from even the heaviest of atoms. As a result, quantum electrodynamics - the most precise of all theories in physics - can now be put to the test even at the level of the highest nuclear charges.
Research in plasma physics is another major facet of work at GSI. Because of their highly efficient deposition of energy in matter, heavy ion beams allow the creation of very dense plasmas. Physicists are already carrying out important preliminary work as they strive towards the long-term goal of large-scale energy production through thermonuclear fusion reactions based on the principle of inertial confinement fusion. To support this work, a program to further increase the intensity and quality of heavy ion beams is planned for the next few years.
In a solid-state object, the high energy deposition of a heavy ion beam can also be used to alter the properties of the bombarded material at a macroscopic level. This phenomenon gives rise to the possibility of innovative technological applications in the area of materials. Particularly advantageous here is the availability of a broad spectrum of ion types and energies so that potential exists for an extremely wide range of materials modification.
The radiobiological effects of heavy ions - especially the inactivation of cells induced through radiation - have been investigated ever since the start-up of the UNILAC. With heavy ion beams, it is possible to deposit energy deep within tissues, and so to precisely localize the zone of tissue destruction, and adjust it at will by varying the beam parameters. Compared to conventional radiation medicine, this process opens up entirely new perspectives in areas such as cancer treatment. Following years of systematic research into the radiobiological effects of heavy ions, and the development of new and improved accelerator and irradiation techniques, a pilot research-project into cancer therapy with heavy ions is due to start in 1996. Such work is a perfect example of how knowledge-oriented basic research into fundamental issues and the technological developments that arise out of such research can contribute directly to the common good.
GSI and the scientific community
GSI is the kind of large-scale scientific research establishment known in Germany as a "Großforschungseinrichtung" - in many countries it would be called a National Laboratory. It currently has about 700 employees, including 300 scientists and engineers. A total budget of almost DM 130 million is provided by its two shareholders, with 90% coming from the German federal government, and the rest from the German federal state of Hesse. But what was it that led to the creation of GSI, and what role does such a large laboratory play in relation to the scientific community in the rest of Germany and the world at large?
The construction and operation of accelerator systems such as the UNILAC, SIS, and ESR, plus the complex experimental systems they require, would overtax both the human and financial resources of individual universities. Such costly installations can only be built at central sites where they are accessible to the largest possible number of users. This consideration was paramount not only in the establishment of GSI as a major research center for fundamental research, but also, for example, DESY in Hamburg. Both of these centers, together with those institutions whose research is more application-oriented, subsequently joined together to form an association of major research centers called the "Arbeitsgemeinschaft der Großforschungseinrichtungen" (AGF).
GSI's mission is not only to construct and operate large systems, but also to provide all interested scientists with access to its research facilities. In this respect, the center has become a focal point where teams of scientists from both domestic and foreign universities and other institutions can collaborate in their research. In conjunction with the center, these users develop research programs in which clearly defined objectives are established. GSI plays an important coordinating role in all of these activities. But it can only succeed in this mission if, in addition to building and operating the system, it also engages in active research.
In research too, everyone has to pull together-sometimes quite literally. This is especially true for the labor and cost-intensive projects typical of modern physics. This photo was taken during the construction of the LAND detector.
Above and beyond the obvious practical considerations, such collaboration among internal and external research teams also has an important effect upon policies in research and education. The availability of the major research center to outside scientists, most of them from German universities, allows these institutions to participate in research at the highest level. In this way, students can be offered a genuinely modern learning program that takes account of the latest technological developments. That research and teaching must go hand in hand remains as true today as it ever was, and hands-on participation in a modern research environment is a fundamental part of the education of any scientist. In this respect, the major research centers possess the advantage that their work attracts a constant stream of young talent and new ideas, thereby ensuring that their research programs are continually revitalized.
The FOPI team poses in front of the FOPI detector. No less than 68 scientists from 12 universities and research institutes, including 7 foreign research centers, collaborate on this team.
From the very beginning, GSI has striven to promote and develop close contacts to the German universities. It spends some DM 7 million annually to fund a university program known as the GSI model, in which development projects relevant to GSI research are given over to university teams. In 1994, about 200 PhD students and over 100 young scientists participated in GSI research projects.
GSI also collaborates closely with the individual institutes gathered together in the Max- Planck-Gesellschaft (Max Planck Society), especially with the Max-Planck-Institut für Kernphysik (Max Planck Institute for Nuclear Physics) in Heidelberg. On an international level, close liaison is maintained with CERN in Geneva and other leading heavy ion laboratories in Europe, the US, the CIS (Commonwealth of Independent States, i.e. the former Soviet Union), and Japan. All told, there are more than 1000 scientists from over 100 institutes in 25 countries sharing in GSI research and development work conducted within the gates of Darmstadt.