Electrostatic Van de Graaff Accelerator.
Electrostatic Van de Graaff accelerator, as one of basic experimental facilities of NPI, was built in 1964 and from that time it has been continuously upgraded. Recent replacement of standard diffusion vacuum pumps with molecular ones and improvement of HV gas isolation has led to a substantial improvement of accelerator performance. The accelerator can accelerate 1-H^+ ,2-H^+ and 4-He^+ ions to energies from 1-2.5 MeV. The beam energy is stabilized to 5.E-4 and the maximum beam intensities are few microA. The particle beam is formed by standard ion-optical elements and transported through three beam lines available into target chambers for RBS, PIXE and PIGE analyses. These days, the accelerator is used exclusively for interdisciplinary research in solid state physics and physical chemistry (80 - 90% of operating time) and for routine analyses of biological, medical and enviromental samples. Average operating time of the accelerator is about 1000 hours/year.
Neutron Physics Facilities.
Reactor LWR--15 of the Nuclear Research Institute.
The reactor LWR-15 of the Nuclear Research Institute at Rez, where we hire experimental channels, serves as a main neutron source for the experiments performed by the Nuclear Physics Institute. Light water and medium power research reactor LWR-15 after the last reconstruction and upgrading finished at the end of the year 1990 achieves the parameters equivalent with other medium power reactors in the world. At present the reactor LWR-15 besides the similar KFKI reactor in Budapest is with its nominal power of 10 MW, neutron flux 1.E14 n cm^-2 s^-1 in the core and a number of horizontal beam tubes a unique neutron source in Central Europe providing attractive research possibilities in the basic and applied research with neutrons. Thermal beams of considerably high flux provided by the reactor and guided from its core to the measuring instruments, are ideal tools for study of the structure and physical properties of condensed matter and particular problems of nuclear and fundamental physics. However, the uniqueness of some information obtained may be paid by a relatively high cost of such experiments.
Experimental equipment on LWR-15.
As displayed on the schematic sketch of the instrumental arrangement at six horizontal beam holes of the reactor LWR-15, the following experimental facilities installed at channels No. 3,4,8 and 9 are in our disposal:
Equipment for Nuclear Spectroscopy.
Electrostatic spectrometer ESA 12 is a precise, multipurpose instrument for the high-resolution spectroscopy of electrons emitted in radioactive transformations. The double-pass cylindrical mirror analyser combined with the preacceleration/preretardation system enables one to cover the energy range from 0 eV to 20 keV and vary instrumental resolution from 0.8 to 200 eV. The achieved FWHM of 1.0 eV is the best one reported in conversion electron spectroscopy. The surface layer of radioactive samples can be examined by photoelectron spectroscopy using Al-X rays.
The instrument proved useful in nuclear physics (keV electromagnetic transitions), atomic physics (lifetime of vacancies) and nuclear chemistry (valence state of trace amounts of radioactive atoms). The present task is precise beta-ray spectroscopy in searches for massive neutrinos.
Experimental setup available for in-beam nuclear
High-resolution ( 1.9 keV at 1332 keV) HPGe detector with relative efficiency of 20% and moderate quality Ge(Li) detectors (volumes of about 40 cm^3) are connected with standard precise electronic equipment. The gamma-gamma coincidence apparatus with event-by-event recording is at our disposal as well.
One of the basic devices in the Department of Nuclear Spectroscopy is the anti-Compton spectrometer which has been in operation since 1978. It consists of a Ge(Li) detector and NaI(Tl) scintillation detector ( diameter 254 x 250 mm) which is split into two identical parts optically separated. This enables us to use the instrument also as a pair spectrometer. Anticoincidence (anti-Compton), double coincidence and tripple coincidence spectra can be registered simultaneously. In this spectrometer, the continuous Compton background is suppressed more than 6 times (for 60-Co) and the natural background about 300 times so that higher sensitivity can be achieved with this device than with standard gamma-spectrometers.
Semiconductor detectors at 4.2 K.
During the last years interest in the detection of nuclear radiation at liquid helium temperature highly increased in connection with the particle angular distribution experiments using the method of low temperature nuclear orientation. These experiments are performed with radioactive sources implanted into the ferromagnetic hosts which are cooled down to the milikelvin temperatures. The deterioration of the detector performance at 4.2 K temperature is commonly known problem. The HPGe planar detectors (thickness and diameter about 6~mm) were fabricated in our department and tested at liquid helium temperature. The energy resolutions of 3.1 keV for K-electrons of transition 1063 keV (207-Bi) and 21 keV for alpha particles of 5486 keV (241-Am) were achieved. These detectors will be used in low temperature nuclear orientation measurements with dilution refrigerator.
Multi-detector correlation system.
A multi-detector correlation apparatus has been built in NPI at Rez for the collaboration with the Laboratory of Nuclear Problems of JINR Dubna in the frame of the ISOL facility YASNAPP-2 (nuclear spectroscopy on proton beam), installed on proton beam of the JINR Dubna phasotron. It was designed for measuring of single gamma-ray spectra, prompt and delayed gamma-gamma spectra and directional correlations of gamma rays emitted from radioactive nuclei in off-line or on-line experiments. The detection part of the system can consist of up to seven different detectors - Ge(Li), HPGe or Si(Li) ( D. Venos, P. Tlusty: Nucl. Instr. Meth. A336(1993)567.) In on-line experiment a tape device is used, which transports the collected mass-separated short-lived isotopes to the detectors.
Experimental facilities available for R-XRF and NAA.
A 100 mCi 241-Am excitation source in conjunction with a semiconductor Si(Li) detector (active area 25 mm^2, resolution FWHM of 170 eV for 5.9 keV X-rays) is employed for R-XRF.
For NAA, long-time irradiation is carried out in vertical channels of a LWR-15 nuclear reactor of the Nuclear Research Institute Rez p.l.c. in a neutron flux density ranging from 5.E12 up to 2.E14 cm^-2 s^-1, whereas for short-time irradiation using a pneumatic facility, a vertical channel with a neutron flux density of 6-8.E13 cm^-2 s^-1 is available. Gamma-ray spectrometry measurements are carried out employing 4 coaxial HPGe detectors with relative efficiency of 11-23% and resolution FWHM of 1.75-1.90 keV for the 1332.5 keV gamma-rays of 60-Co. An automatic sample changer is also available as well as radiochemical laboratories.
Radiochemistry laboratory and isotope production.
Most of radioactive objects, needed for nuclear spectroscopy and analytical projects at the department, is made by our hot laboratory. Its scope involved a target design and processing, development of appropriate chemical separation method and source preparation. Several years the laboratory is engaged in cyclotron targets processing (including rare earth targets), developing radioactive sources for electron spectroscopy, application of INAA techniques and technetium chemistry studies.
Moreover, there exists a research-scale-production of cyclotron radionuclides for academic partners here. For example, the isotopes as 44-Ti, 48-V, 57-Co, 58-Co, 123-I, 207-Bi have been produced during last years. Both regular and parasitic beams of Institute cyclotron have been employed for these purposes. Recently, a development of some products based on 68-Ge started (calibrating sources for PET machines, 68-Ge/68-Ga generator of ``ionic'' type, positron emitting sources for material research).
The BGO detector system for PET radiodiagnostics.
The six-fold BGO detector system has been developed for the iodine distribution measurements. This apparatus has been constructed and tested at our Nuclear Spectroscopy Department for Service Hospital Frederic Joliot in Orsay. The coincidences of annihilation gamma-rays originating from the decay of positron emitters usually used in PET cameras are measured. The detector system enables us to study the distribution of radioactive nuclei in pacient's body and hence it makes possible the in-vivo measurement by PET machine.
Nuclear Reactions Facilities.
Magnetic multichannel analyser
A reinstalled magnetic multichannel analyser allows of the high-resolution measurements of angular distributions for eleven angles simultaneously. The basic parameters of the spectrograph are:
The 14 MeV polarized neutron facility.
The neutron polarized ion source (NPIS) facility is based on the polarization transfer process in the 3-H(d,n)4-He reaction initiated by polarized 200 keV deuterons. Being the main priority of the present facility, the ``adiabatic transition'' scheme used in the polarized deuteron source makes possible a direct measurement of the vector-to-tensor polarization ratio (and consequently the value of neutron polarization).
The facility could be routinely exploited as a calibrated 14 MeV neutron source with a yield up to 5.E5 neutrons/sr x sec and neutron polarization P_n=0.3 (P_n=0.8 when RF-transition scheme is used). A time-of-flight spectrometer with resolution of about 3 ns is installed in the facility.
The achromatic magneto-optical system (AMOS).
For angular distribution measurements at extremely small laboratory angles (including zero), time measurements, and for the generation of secondary radioactive beams, the special magnetic system was designed and realized. The system is designed as a symmetrical one of the Dipole-Quadrupole-Quadrupole-Dipole type, which creates, in linear approximation, a dispersionless image of the beam spot at the point where the telescope for particle registration is located. The dispersion plane passes through the centre of system where it is possible to choose the required energy interval of registered particles. The system was proposed for the cyclotron U-120M (k=40) and optimized taking into account second-order abberations.
Continuum wave laser system.
The basic device for the study of the light induced drift (LID) effect is laser system delivered by ``Inversion, ltd'' (Novosibirsk, Russia). The system contains continuum wave Ar+ laser with power up to 20 W which pumps the narrow band continuum wave dye tunable laser with power up to 300 mW. The dye laser wavelength can be automatically stabilized and scaned within spectral range of 10 GHz. The laser system alows of high resolution measurements and investigations of atomic and molecular systems in the visible spectral range.
Radiation Dosimetry Facilities.
System of instruments for measurement of
environmental radiation doses.
The Department of Radiation Dosimetry possesses a number of instruments for the measurement of environmental doses and dose rates. These are the high pressure ionization chambers RSS-111 and RSS-112 (made by Reuter Stokes, USA), the plastic scintillation detector NB 3201 or its more sophisticated version NB 3202 (made by Tesla, CR) and finally the GM counter RP 114 (made by ZMA, CR). These types of instruments are probably the most frequently used instruments for measuring air kerma rates in the environment. The instruments have been extensively used in different projects on measurement of environmental radiations especially doses to the air crew members ( F. Spurny at al.: Radiat. Prot. Dosim. 48(1993)73.). The department has its long tradition in organizing of intercomparisons of the environmental dose and dose rate meters. In 1990, the intercomparison was organized with participants from Austria, the Czech Republic, the Federal Republic of Germany and Slovakia (F. Pernicka: Intercomparison of Environmental Gamma Dose and Dose Rate Meters in the CSFR 1990. In Proc. of the 110 PTB Seminar, Braunschweig, Nov 30 - Dec 01, 1993. )
Track etch detectors and their use.
Department of Radiation Dosimetry has at disposal the experimental set-up for study of the basic properties of TEDs (track etch detectors) and theirs applications as well. It consists of the equipment both for chemical and electrochemical treatment (universal multidetector etching stand) and image analyser (Leitz-Lucia) equipped by special software making possible automatic 3-dimensional analysis of particle tracks.
Investigations of basic properties of TEDs concern mainly of the determination and optimization of response to charged particles and its energetical and angular dependence, determination of characteristic detector parameters and study of influence of various factors on the track development.