GENERAL DIVISION

X-Ray Laboratory
S e p p o M a n n i n e n

The compulsory financial cut in the budget of the Faculty of Science also affected the X-ray laboratory in 1997. More than half of the laboratory personnel received salaries from external funding. Altogether MFIM 1.67, about MFIM 0.5 more than in 1996, was obtained from various sources, mainly from the Academy of Finland, TEKES and the European Synchrotron Radiation Facility (ESRF). Two members of the laboratory, Veijo Honkimäki and Pekka Suortti spent the whole of 1997 at ESRF. This trend is likely to be continued which means ever increasing efforts to cover the annual budget with external financial support.

The main development in the laboratory equipment was the purchase of a surface diffractometer from Huber at the end of 1997. This was made possible by common financing from the Department of Inorganic Chemistry and Department of Physics. After the installation of the necessary electronics and controlling devices the diffractometer can be used to study surfaces and thin films, area in common for many research groups in the departments of Physics and Chemistry.

Synchrotron radiation has been used for many experiments. Altogether 14 scientific visits were accomplished in 1997; to ESRF, to the National Synchrotron Light Source (NSLS) and to the Hamburg Synchrotron Radiation Laboratory (HASYLAB). The main topics of the experiments were (i) high resolution inelastic scattering and fluorescence spectroscopy (ESRF, NSLS), (ii) surface physics (HASYLAB) and (iii) small angle scattering (HASYLAB). A co-operative project with the Finnish Space Research Centre was also accomplished at NSLS; the properties of a semiconductor detector were studied for use in an instrument in an X-ray telescope to be used by a satellite to be launched in 1998.

Experimental work in our home laboratory largely concentrated on the applications of wide angle (WAXS) and small angle (SAXS) X-ray scattering. There were research partners from the Helsinki University of Technology (tailored polymers), Department of Chemistry (PVF and PVDF films and membranes, ion-implanted SrS:Ce thin films, potato tubers) and the Finnish Forest Research Institute (structure of wood cells) included in several research projects.

The international exchange schemes, including those with the Russian Academy of Sciences and Charles University (The Czech Republic), were continued. The four-circle diffractometer was involved in these projects to study, for example, structure studies of some non-linear optical materials, high-temperature superconductors and uranium intermetallic compounds.

Industrial collaboration with the Finnish Science Center Heureka and Quantronics Oy aimed at production of an Expo-Flu Fluorescence Analyser. The prototype was constructed at Quantronics Oy and has been installed at Heureka. It was also introduced to the European Science Centre community in November in Brussels.

Aerosol and Environmental Physics Laboratory
M a r k k u K u l m a l a

In 1997 the research activity of the Laboratory of Aerosol and Environmental Physics has focused on basic and applied aerosol science and cloud microphysics. Studies on heat and mass transfer, nucleation, condensation, aerosol dynamics, aerosol measurement technique, atmospheric aerosols, deposition of atmospheric gases, and formation and growth of cloud droplets were performed. The main aim of the studies is to develop practical applications, based on mastering fundamental physical and chemical phenomena, to solve different aerosol and environment-related problems.

Formation and growth of aerosol particles and cloud droplets have been studied using computer models developed in the laboratory. Other topics of theoretical and numerical investigations were heat and mass transfer as well as nucleation processes. Based on our theoretical investigations we have shown the existence of clouds without supersaturation (see highlights of research).

The field station SMEAR II (in Hyytiälä) has been constructed during 1995. Continuous measurement activity started in 1996. The main finding so far has been numerous observations of atmospheric nucleation bursts. The field measurements were also performed during different field campaigns. Participation in ACE-2, the North Atlantic Regional Aerosol Characterization Experiments, has been one of the main activities, and took place in June-July, 1997.

The main output of our experimental laboratory work has been the development of tools for investigating nucleation phenomena and cloud condensation nucleus activation. We have also carried out measurements of aerosol particle size distributions in a variety of laboratory systems as well as in atmospheric conditions. Our special interest has been targeted on the nanometer size range using recently developed aerosol instrumentation such as electrical mobility spectrometry and the diffusion battery technique, whereas for micron-sized particles optical counting of particles is typically used.

International co-operation has had a significant role in both the theoretical and the experimental activities of the group. During 1997 various projects (including four EU projects) continued in co-operation with research groups from Austria, Canada, The Czech Republic, Italy, Japan, The Netherlands, Russia, Sweden, The United Kingdom and The United States. On the national level we have had close collaboration especially with the department of Forest Ecology in the University of Helsinki, and with the Air Quality Department of the Finnish Meteorological Institute.

The international postgraduate training programme for aerosol and environmental physics (started at the beginning of the autumn semester 1994) was continued during1997.

Financial support from the Academy of Finland and the Nessling Foundation is gratefully acknowledged.

Electronics and Industrial Physics Research Laboratory
M a u r i L u u k k a l a

The main research projects in our Laboratory have involved combined development in electronics, optics, thermal waves and ultrasonics.

An EU project concerning microbiological growth in "premade" food packages has been completed. It uses ultrasonics by monitoring the ultrasonic absorption and second harmonic generation in food stuffs. The results have been particularly encouraging in the case of packaged milk.

A BRITE-Euram EU project is to be commenced next year and concerns thermal waves in the measurement of surface hardening of steel without damaging the sample. A large European consortium has been set up for the initial feasibility study.

We are also developing a rather simple non-contact acoustic device to measure the thickness or surface density of papersheets or other similar foils. The resolution has been about one micrometer which is good for simple equipment. We have also co-operated with Savcor Inc. to study the air content of pulp mass using ultrasonics.

The optical confocal measurement principle has been utilized to measure the crystallization of certain polymers.

Thermal image obtained with the photothermal line-scanning microscope of the Electronics Research Laboratory showing finer structure of a carbon fiber-glass fiber aerospace composite

Laboratory of Medical Physics
S a u l i S a v o l a i n e n

The research interests of the Laboratory of Medical Physics have been focused on four main areas: boron neutron capture therapy (BNCT), patient dosimetry in diagnostics and treatment, medical imaging applications and modelling of physiological and biological systems for clinical studies. Research has been done in co-operation with Helsinki University Central Hospital (HUCH), the Technical Research Center of Finland (VTT) and Finnish Centre for Radiation and Nuclear Safety (STUK).

The Finnish research reactor (FiR 1) operated by the Technical Research Center of Finland (250 kW TRIGA II pool reactor) will be used as a neutron source in BNCT. In the spring of 1997 the reactor hall has been rebuilt for treatment purposes. In the autumn season the characterisation of the beam as well the dosimetry measurements have been carried out. The facility is ready for in vivo experiments.

A method for measuring absorbed doses at the patient skin in order to approximate doses to the critical organs has been studied in collaboration with HUCH and STUK. New calculation methods have also been developed to obtain more accurate dose distributions in the patient. A computer program for calculating patient specific organ doses in diagnostic radiology has been further developed. Methods for cellular level dosimetry have been investigated.

New MRI techniques (magnetization transfer and spin lock) for increasing tissue contrast and characterization have been studied. The study was performed in vitro and in vivo in normal and in brain tumor patients.

Interest has been focused on boronophenylalanine (BPA) and bleomycin kinetics. The models are to be used in BNCT research.

The Laboratory of Medical Physics has been financed by the Academy of Finland, University of Helsinki, the State Subsidy for University Hospitals, research grant of the Departments of Radiology and Neurology (Helsinki University Central Hospital), TEKES, the Instrumentarium Science Foundation, the Finnish Society of Nuclear Medicine and the Trust of Aarne Koskelo which are gratefully acknowledged.

Theoretical Nuclear Physics
D a n O l o f R i s k a

The research efforts of the theoretical nuclear and hadron physics group during 1997 concentrated in the following topics: (1) application of the chiral quark model for the baryons previously developed by the group to the baryon current observables and the role of meson exchange currents. (2) Construction of a phenomenological Poincaré invariant constituent quark model, which fits the baryon spectra in all flavour sectors and which can be applied to the calculation of nucleon resonance form factors in point or instant form kinematics. The development of an ab initio quantized version of Skyrme's topological soliton model for the baryons along with a constructive realization of Skyrme's conjecture of the nonzero pion mass as a self consistent quantal effect. The prediction by the group of a strange pentaquark at 2860 MeV appears to have been empirically confirmed.

Experimental Nuclear Physics
K a r i E s k o l a

Collaboration with Matti Leino's group at the gas-filled recoil separator facility (RITU) at the Accelerator Laboratory of the University of Jyväskylä has been continued. For a major part of the year RITU was run in connection with the JUROSPHERE array of large germanium detectors. This unique combination of a gas-filled mass separator and "crystal ball" detector setup allowed a very selective means to study prompt gamma ray emission tagged by subsequent recoil-alpha decay event pairs. The technique was very successfully applied to a wide range of highly neutron-deficient nuclides centered in the lead region. Our collaborative studies dealt with Po and Ra isotopes.

In addition well-established, stand-alone RITU experiments were continued. The work on the new isotope 206Ac and the accompanying isomer was completed. Analysis of seemingly unorthodox alpha decay data in the 195At region has been continued. New detailed information on alpha decay characteristicss of 190Po, 189mBi and 186Pb has been obtained.

High spin spectroscopy studies were carried out in co-operation with groups at the Accelerator Laboratory in Jyväskylä and Department of Physics at Åbo Academy and Royal Institute of Technology in Stockholm. The main interest has been focused on studies of shell structure and shape co-existence in nuclei in the lead region.

Didactical Physics
K a a r l e K u r k i - S u o n i o

The group has continued its "Project of Perceptional Approach", i.e. search for constructive principles of teaching based on the conceptual and processual structure of physics (i.e. conseptualization of the separate but inter-related structures of physics) and on development of different kinds of applications for all levels of physics instruction. Among other things this includes planning of didactically relevant courses for both primary and secondary school teacher education, development of the "teachers' laboratory of perceptional experimentality", development or adaption of demonstrations, the writing of two textbook series with extensive "Teachers' Guides" for secondary school physics, and participation in the Idea-Bridge (Ideasilta) project on science for talented secondary school pupils.

The extensive complementary-education programme DFCL in Didactical Physics, started in July 1996, was completed succesfully before the end of 1997 by 145 physics teachers. The responses by the participants indicates that the programme has been effective. The new practices of modern processual teaching and perceptional experimentality have become everyday practice in many of the schools of the participants. Several of the study groups continue their activity as local centres of development and about 60 participants have decided to continue their studies and research in didactical physics for a higher degree.

The experiences from and results of the project are still to be investigated and confirmed by research. A project for this aim has been started, although in a greatly reduced extent because of the completely negative attitude by the University central administration and the Academy of Finland towards this activity.

The work of the group is closely connected with the Graduate School for Mathematics, Physics and Chemistry Education. During the second full year of operation two more university departments joined the school which now has 23 member institutes in 8 universities and more than 100 graduate students.