Volume 45, Number 34, 2000
Proceedings of the International Symposium
ADVANCES IN NUCLEAR PHYSICS
(Fifty Years of Institutional Physics Research in Romania)
910 December 1999, Bucharest, Romania
Organized by "Horia Hulubei" National Institute of Nuclear Physics and Engineering (IFINHH)
Sponsored by
 UNESCO Venice Ofﬁce (UVOROSTE)
 JINR Dubna
 National Agency for Science, Technology and Innovation, Bucharest
 Romanian Commercial Bank, via ProFIZICA NGO
EDITORS:
Dorin Poenaru and Sabin Stoica
"Horia Hulubei" National Institute of Nuclear Physics and Engineering, Bucharest, Romania
PREFACE Dorin N. Poenaru Romanian Journal of Physics 45, 167170 (2000)
Fission Modes
Preformation Probabilities for Light Ternary Clusters in the Cold Fragmentation of $^{252}$Cf A. Florescu, A. Sandulescu, D. S. Delion, J. H. Hamilton, A. V. Ramayya, W. Greiner Romanian Journal of Physics 45,
171176 (2000)
The preformation probabilities for $\alpha$ and $^{11}$Be clusters in the cold ternary fragmentation of $^{252}$Cf are estimated within a microscopic model starting from single particle WoodsSaxon wave functions and with a large space BCStype configuration mixing. The resulting position of the maximum of cluster preformation probability is situated in the region between the two heavier fragments near the scission point and it approaches the ﬁssion axis as the distance between the fragments increases.
Alpha HalfLives of Superheavy Nuclei with Z = 104118 and N = 163175 Produced in the Reaction of $^{86}$Kr with $^{208}$Pb I. Silisteanu, W. Scheid, A. Sandulescu Romanian Journal of Physics 45,
177184 (2000)
The groundstate $\alpha$decay properties of some evenodd isotopes of superheavy elements with Z = 106118 are investigated in the framework of an integral approach treating the decaying states as proper resonance states. Theoretical results on decay rates are presented and compared to the recent data (V . Ninov et al., Phys. Rev. Lett. C83, 1104 (1999)) and phenomenological predictions (R. Smolanczuk, Phys. Rev. C59, 2634 (1999)). Some conclusions are drawn on the possibilities of identiﬁcation of new elements and study their nuclear properties on the basis of calculated rates.
Rotations and Vibrations of Trinuclear Molecules S. Misicu, P. O. Hess, W. Greiner Romanian Journal of Physics 45,
185189 (2000)
A model describing the rotations and vibrations of trinuclear molecules is presented. The treatment is made in the spirit of the BohrMotelson's collective model of the nucleus. The twobody interactions between the composing clusters are calculated assuming density independent M3Y forces, supplemented by a phenomenological repulsive component. Under simplifying assumptions, such as the linear chain quasiequilibrium configuration and freezing of the contact point between the light cluster and the heavy clusters, analytical solutions are available.
SingleParticle Effects in the ﬁne Structure of Superasymmetric ﬁssion M. Mirea Romanian Journal of Physics 45,
191194 (2000)
In this contribution, Coriolis and radial couplings intend to explain the fine structure of alpha and cluster radioactivities, regarded as superasymmetric fission processes.
Nuclear Shape Parameterization for Multicluster Fission B. Dobrescu Romanian Journal of Physics 45,
195200 (2000)
A realistic parameterisation able to characterise, at least from a qualitative point of view, the evolution of nuclear shape for a multicluster fission process was developed. It is developed using seven smoothly joined portions of quadratic surfaces of revolution and it can fairly reproduce the initial, middle and final stages for binary, ternary and beyond ternary symmetrical and asymmetrical fission processes.
Nuclear Structure
Simultaneous Projection of ParticleNumber and Angular Momentum BCS WaveFunctions in the RareEarth Nuclei M. R. Oudih Romanian Journal of Physics 45,
201204 (2000)
A method of simultaneous particlenumber and angularmomentum projection of the BCS wavefunction is presented. The particlenumber projection method is of FBCS type. In the framework of the adiabatic approximation, the rotational energies of the axially symmetric eveneven nuclei are established and numerically calculated for the rareearth region.
The YRAST Superdeformed Band in $^{59}$Cu Corina Andreoiu, D. Rudolph, C. E. Svensson, C. Baktash, J. Eberth, C. Fahlander, D. S. Haslip. D. R. Lafosse, S. D. Paul, D. G. Sarantites, H. G. Thomas, J. C. Waddington, W. Weintraub, J. N. Wilson Romanian Journal of Physics 45,
205209 (2000)
On the Structure of Deuterons under Their Collision V. Romanov, G. Filipov Romanian Journal of Physics 45,
211214 (2000)
The phase shift of deuterondeuteron scattering is calculated in the energy domain from zero up to the decay threshold of one of the deuterons. Behaviour of the wave functions of the approaching deuterons is investigated. The data about the wave functions is contained in the coefficients of Fourierexpansion of the wave function of the system. The approach for extracting such data is developed. The variation of the deuteron wave function is studied.
Reactions
A New Approach of a Global AlphaOptical Model Potential at Low Energies Cornelia Grama Romanian Journal of Physics 45,
215218 (2000)
New Class Resonant States Corresponding to Attractors in the $k$Plane. DiNuclear Quasimolecular States N. Grama Romanian Journal of Physics 45,
219222 (2000)
One shows that the parent quasimolecular shape resonant states are a particular case of a new class of resonant states (NCRS) recently identified by the present authors. The properties of the quasimolecular states (energies, widths, rotational character, deviation from the linear dependence of the energy on $l(l + 1)$, doorway character, criteria for observability) result in a natural way from the general properties of this newclass of resonant states.
Riemann Surface Approach to Bound and Resonant States. Exotic Resonant States for a Central Rectangular Potential N. Grama Romanian Journal of Physics 45,
223225 (2000)
A novel approach to bound and resonant states in the scattering by a central potential $gV(r)$, $g \in \mathbb{C}$, followed by a real barrier, based on a global analysis of the $S$matrix poles is presented.
About Classical Motion of Nucleon Wave Packets Arina M. Sytcheva, G. F. Filipov, S. V. Korennov Romanian Journal of Physics 45,
227230 (2000)
The comparison of nucleon wave packet motion with exact quantum solution obtained in FockBargmann representation has been done. Also has been clarified the physical meaning of nucleon wave packet classical description. Thus the energy band of validity of antisymmetrized molecular dynamics has been determined.
Various Aspects Concerning the Nuclear Caloric Curve Al. H. Răduţă, Ad. R. Răduţă Romanian Journal of Physics 45,
231235 (2000)
The sharp microcanonical model from [Al. H. Răduţă and Ad. R. Răduţă, Phys. Rev. C 55, 1344 (1997); 56, 2059 (1997)] is used to make evaluations of the nuclear caloric curve for sources chosen from a wide range of mass. A wide plateau of the caloric curve situated at approximately 5 MeV temperature resembling the 1995 ALADIN caloric curve is evidenced in all considered cases. Coulomb repulsive and excitation degrees of freedom are shown to be responsible for the formation of the wide plateau of the caloric curve. In a second stage, the model is refined and improved by considering the experimental energy levels for the fragments with $A \le 6$ and by including the stage of secondary particle emission. The new version of the model is used for deducing the sequence of equilibrated nuclear sources by fitting simultaneously the calculated multiplicity of the intermediate mass fragments and the charge asymmetry on the corresponding experimental data. This allows for a direct comparison between the model predicted HeLi isotopic caloric curve and the experimental data.
Soft Dipole Mode of $^6$He in Asymptotic Potential Approximation G. F. Filippov, Yu. A. Lashko, L. P. Shvedov Romanian Journal of Physics 45,
237240 (2000)
Completely antisymmetrized $1^$ continuum wave functions as well as the ground state wave function for $^6$He have been constructed in asymptotic potential approximation. The behaviour of twochannel $S$matrix elements shows on the existence of $1^$ resonant state just above the threebody decay threshold of $^6$He.
Importance of the Wave Function Tail in Computing the PreEmission Probability for the Halo Neutron from $^{11}$Be Fusion with Light and Heavy Targets Cristina Bordeanu Romanian Journal of Physics 45,
241243 (2000)
The preemission probability for the halo neutron from $^{11}$Be fusion with light and heavy targets at different beam energies was estimated. The halo neutron density distribution was taken into consideration. In this way, the geometrical method for evaluation of the neutron preemission was improved.
Astrophysics and Cosmic Rays
ChargedParticle Induced Thermonuclear Reaction Rates: A Compilation for Astrophysics Cornelia Grama Romanian Journal of Physics 45,
245247 (2000)
Muons as Messengers from the Cosmos Ileana Magdalena Brâncuş Romanian Journal of Physics 45,
249253 (2000)
The observation of muonic component arising from Extensive Air Showers (EAS) provides information on the energy, the mass and the hadronic interactions of the primary cosmic particle penetrating from the outer space in the atmosphere. This information is inferred from the observations of EAS with a large groundbased extended detector array KASCADE in Forschungzentrum Karlsruhe, Germany. Interesting complimentary information is obtained from the inclusive ﬂuxes of positive and negative muons, related to neutrino ﬂuxes of different flavours in the atmosphere, measured in IFINHH (Bucharest, Romania) by use of a smallsized sophisticated detector setup.
The Role of Muons for the Atmospheric Neutrino Anomaly J. Wentz Romanian Journal of Physics 45,
255258 (2000)
The importance of muons in the analyses of the atmospheric neutrino anomaly is studied. Especially the muon charge ratio proves to be a relevant check for the simulations of atmospheric neutrino ﬂuxes. A compilation of data on the muon charge ratio shows the necessity of new experimental investigations.
Measurements of the Charge Ratio of Atmospheric Muons in the Range 0.2  1.0 Gev/C by Observing the Decay Electrons from Muonic Atoms B. Vulpescu, J. Wentz, I. M. Brâncuş, H. Rebel, A. F. Badea, H. Bozdog, M. Duma, A. Haungs, H. J. Mathes, M. Petcu, M. Roth Romanian Journal of Physics 45,
259261 (2000)
The method of measuring precisely the different life times of negative and positive muons when stopped in matter, realised with the compact scintillator detector setup WILLI in the NIPNEHH Bucharest, has been used to study the charge ratio of atmospheric muons.
What Do We Learn about the Longitudinal Development of Extensive Air Showers in the Atmosphere by Observing the Arrival Time of the Muon Component? A. F. Badea Romanian Journal of Physics 45,
263265 (2000)
The muon arrival time distributions map the longitudinal development of Extensive Air Showers (EAS) via the timeofflight of muons produced in large atmospheric heights offering the possibility of an indirect determination (Linsley’s method [1, 2]) of the elongation rate and showing effects for mass discrimination of the EAS primaries.
[1] J. Linsley, 15th ICRC (Plodiv, Bulgaria), vol. 12, 89 (1977). [2] J. Linsley and A. A. Watson, Phys, Rev. Lett. 46, 459 (1981).
Atomic Physics
The Main Achievements in the Atomic and Nuclear Physics Research Using the Track Detection Ana Daniş, Mariana Ciubotariu, Al. Enulescu, C. Ciortea Romanian Journal of Physics 45,
267277 (2000)
Some main achievements obtained by the authors in the atomic and nuclear experimental physics research using the fission and/or alpha track micromapping technique are described. An experimental checking out of natural radioactive decay by emission of heavy ions, the U biodistribution, retention and elimination in the internal contamination of animals, investigations on the fissionable element dispersion systems, including the stabilization/changes of the dispersion states of these systems as well as the sorption of the dispersed phase on the different "insoluble beds", fissionable element atom distributions and their content measurements in any liquid and solid samples, references material remedying and preparation procedures and several applications of the fission track method in reactor physics, geochronology and industry are briefly presented and exemplified by photos.
Study and Development of the 14 Ghz ECR Ion Source Recris for Atomic Physics and Material Researches Ş. Dobrescu, L. Schachter, Al. BădescuSingureanu, K. E. Stiebing, S. Runkel Romanian Journal of Physics 45,
279283 (2000)
The electron cyclotron resonance (ECR) ion sources (ECRIS) are now and in the predictable future the ideal sources of highly charged heavy ions. After a short presentation of the working principle of an ECRIS, the recently completed Romanian ECR ion source RECRIS is described. Its main characteristics and first tests are presented. In order to enhance the production of the ions in the highest charge states special metaldielectric structures (Al$$Al$_2$O$_3$) have been developed in IFINHH and tested in the IKF 14 GHz ECR ion source. Very important enhancement factors, up to 50, of the highest charge states of argon beams were obtained.
Mathematical Physics
Boson Expansion for Kähler Orbits Ş. Berceanu, A. Gheorghe Romanian Journal of Physics 45,
285288 (2000)
Explicit boson expansions for collective models on Kähler orbits of coherent states are constructed. The infinitesimal generators for the unitary irreducible representations of nilpotent and semisimple Lie dynamical groups are written down as the sum of polynomials in creation operators times the annihilation operators and the unit operator. These polynomials for Dysontype boson expansions are explicitly characterised by the Bernoulli numbers and the Cartan matrices for the complex simple Lie groups.
On the Quantiﬁcation of Free Fields of Spin 1 and 2 D. R. Grigore Romanian Journal of Physics 45,
289295 (2000)
The second quantization of an "elementary" particle, that is a projective unitary irreducible representation of the Poincaré group (H, $U$) (here the first entry is the Hilbert space where the representation $U$ acts) is a prescription of constructing an associated Hilbert space (called Fock space) $\mathcal{H}_{phys} \equiv \mathcal{F}^{\pm}(\mathrm{H})$, where the sign indicates the statistics [1, 7].
For particles of higher spin, appearing in electromagnetism, YangMills theories of gravitation, it is convenient to extend the Fock space by adding fictious particles (called ghosts). If the extended Hilbert space $\mathcal{H}^{gh}$ then one tries to determine an operator $Q$, called supercharge which verifies $Q^2 = 0$ and such that the physical Hilbert space is $\mathcal{H}_{phys} \equiv \mathrm{Ker}(Q)\mathrm{Im}(Q)$.
The rigorous proof of this equivalence seems to be missing from the literature. Although, no general theorem of this type seems to be available, this is a proof for the case of the massless particle of helicity 1 (photon), the massive particle of spin 1 (heavy Bosons) and massless spin 2 particle (the graviton).
As a consequence, we argue that the condition of gauge invariance which is generally postulated in these theories, is in fact not an independent axiom but the rather natural condition that the $S$matrix factorizes to the physical Hilbert space.
[1] J. M. Cook, Trans. Amer. Math. Soc. 74, 222 (1953). [2] M. Dütsch, T. Hurth, F. Krahe, G. Scharf, Il Nuovo Cimento A107, 375 (1994). [3] H. Epstein, V. Glaser, Ann. Inst. H. Poincaré 19A, 211 (1973). [4] D. R. Grigore, On the Uniqueness of the NonAbelian Gauge Theories in the EpsteinGlaser Approach to Renormalization Theory, hepth/9806244, Romanian Journ. Phys. 44, 853 (1999). [5] D. R. Grigore, The Standard Model and its Generalizations in the EpsteinGlaser Approach to Renormalization Theory, hepth/9810078, Journ. Phys. A 33, 8443 (2000). [6] D. R. Grigore, hepth/9905190, Class. Quant. Gravity 17, 319 (2000). [7] D. Kastler, Electrodynamique Quantique (Dunod, 1972).
HamiltonJacobi Formulation of Constrained Systems Y. Güler Romanian Journal of Physics 45,
297300 (2000)
The aim of this paper is to obtain a valid and consistent HamiltonJacobi theory of singular systems.The Caratheodory's equivalent Lagrangians method is used to reach this aim. This formulation leads us to a set of HamiltonJacobi partial differential equations, with more than one Hamiltonian. Classical fields are treated as singular system in $(n+4)$dimensional space formed by fields $\varphi_i$, $i=1,2, \ldots, n$ and $x_\mu$. Integrability conditions of canonical equations are determined and planewave solution of real scalar field is obtained.
Multiple Scales and Bilinear Approach for 1D Nonlocal Nonlinear Lattices A. S. Cârstea, Dan Grecu, Anca Vişinescu Romanian Journal of Physics 45,
301307 (2000)
The multiple scales method was used to discuss nonlinear 1D lattice systems with harmonic long range interactions (LRI). Two types of LRI were discussed, one decreasing as a power law, and the other exponentially. In the first case a mixed KdV + mKdV + BenjaminOno equation was found in the continuum limit. Nonsingular rational solutions were obtained using the bilinear formalism, In the second case, in the small amplitude limit, the NLS equation was found to describe the evolution of the leading amplitude. In order to avoid secular terms this has to satisfy also the next equations in the NLS hierarchy.
Weakly Localized and Supersymmetric Structures in Nonlinear Evolution Equations A. S. Cârstea Romanian Journal of Physics 45,
309313 (2000)
Extending the gaugeinvariance principle for $\tau$ functions of the standard bilinear formalism in the supersymmetric case, we deﬁne $\mathcal{N} =1$ supersymmetric Hirota operators. Using them, we bilinearize SUSY KdV equation. The solution for multiple collisions of supersolitons is given.
Purity and Decoherence in the Theory of Open Quantum Systems Aurelian Isar Romanian Journal of Physics 45,
315318 (2000)
The condition for purity of states of a damped harmonic oscillator is considered in the Lindblad theory for open quantum systems. For a special choice of the environment coefﬁcients, the correlated coherent states with constant variances are the only states which remain pure during the evolution of the system. The states which reserve their purity in time are also the states which minimize the entropy production and therefore, they are the most stable under evolution in the presence of the environment and play an important role in the description of decoherence phenomenon.
Dissipative Tunneling through a Potential Barrier in the Lindblad Theory of Open Quantum Systems Aurelian Isar Romanian Journal of Physics 45,
319321 (2000)
In the Lindblad theory for open quantum systems, an analytical expression of the tunneling probability through an inverted parabola is obtained. This probability depends on the environment coefficients and increases with the dissipation and the temperature of the thermal bath.
Lax Tensors and Separable Coordinates D. Băleanu Romanian Journal of Physics 45,
323326 (2000)
The Lax tensors of the threedimensional separable coordinates are investigated. The Lax tensors on the dual manifold are analysed.
National Facilities, Applications and Nuclear Instruments
National Facilities for the Management of Institutional Radioactive Waste in Romania Gheorghe Rotărescu Romanian Journal of Physics 45,
327330 (2000)
Time Behavior Evaluation of Wwrs IfinHh Reactor Spent Fuel Characteristics Using the Scale 4.3 Computational System Daniela Ene, Gheorghe Rotărescu Romanian Journal of Physics 45,
331335 (2000)
The time evolution of the radioactive inventory, gamma and neutron sources, and thermal power of the WWRS IFINHH reactor spent fuel is calculated in this work via SCALE 4.3 computational system. The evaluation of these spent fuel characteristics needed for the storage variant analysis is based on a method previously established in IFINHH Bucharest [1] consisting in burnup calculations by means of ORIGENS code [2] which apply specific problem dependent libraries defined for classes of fuel elements and processed with SAS2H, SCALE calculation module [3]. The reliability of the calculations performed was tested by comparison against similar calculation, for the same representative fuel elements, performed by ORIGENJR and HELIOS codes in VKTA Rossendorf [4]. Five reference times of 5, 10, 25, 50 and 100 years after December 31, 1999 were taken into account. Results for all 222 fuel assemblies of both types i.e. EK10 and S36, irradiated in the reactor are presented and discussed into the paper.
[1] D. Ene et al., in: Proc. of Sixth Conference on Critically Safety ICNC'99, Paris, p. 1725 (1999). [2] O. W. Hermann, and R. M. Westfall, NUREG/CR0200, Revision 5, Vol. 2, Section F7, ORNL (1997). [3] O. W. Hermann, and C. V. Parks, NUREG/CR0200, Revision 5, Vol. 2, Section S2, ORNL (1997). [4] E. Franke, VKTA Rossendorf, personal communication (1999).
Project of Positron Source at the U120 Cyclotron Bucharest. Status Report P. M. Racolţa, N. Miron, L. Popa Simil, Dana Voiculescu Romanian Journal of Physics 45,
337339 (2000)
To extend the applications with our U120 Cyclotron we started a project of offline and online positron sources produced at the cyclotron. This machine may be successfully used for producing positron sources with few days halflife for offline positron studies (e.g. $^{48}$V), or a cyclotron online intense positron beam (e.g. $^{27}$Si) with a variable energy for various material study experiments, enough to cover a depth range from few micrometers down to tens of nanometers. Until now, using a V48 positron we performed experiments for determination of the Doppler broadening of the 511 keV peak for different materials (copper, lead, indium). This research is carried out on a cooperation agreement between lFINHH Bucharest and LISESChisinau. The positron source project is now in its initial stage. This stage consists of the experiments on the offline version using positron sources produced in the cyclotron (e.g. $^{48}$V, $^{22}$Na), to develop experience with detection chains, (Doppler broadening and positron annihilation lifetime spectroscopy), to choose proper experiments in order to select moderator materials (W, Mo, Pt, etc.) and to study and design the different versions for the online production of positrons with the cyclotron. Slow positron are valuable tools in atomic physics, material science and solid state physics research. The controlled energy beam facility can be used to probe defects in metals, to study Fermi surfaces and material surfaces and interfaces and to obtain detailed information about the electronic structure of materials. The aim of this project is to perform applications in the semiconductor industry, for coating materials. polymers. biomaterials, etc. .
Low Resistivity Substrates for the Silicon Microstrips Sensors Optimisation M. Angarano, G.M. Bilei, A. Mihul, Otilia Militaru Romanian Journal of Physics 45,
341344 (2000)
High energy physics search for increasingly rare events continue to be directed to the ever higher luminosity. For this reason, the radiation damage becomes more important for all detection elements. Silicon microstrip sensors are required to operate in the high particles flux in order to provide good resolution of particles tracks. Relativelylow resistivity substrates were proposed as an effective mean to improve the longterm performance of microstrip detectors. Radiation effects on two different bulk resistivity domains ($\sim 1.8$ k$\Omega \cdot$cm and $68$ k$\Omega\cdot$cm) of $n$type silicon detectors were studied.
HighEnergy HeavyIon Irradiation Effect on Boron Redistribution in Silicon Nicoleta Dinu, I.V. Antonova, V.A. Skuratov, V.I. Obodnikov, A. Yu. Didyk, L. N. Safronov Romanian Journal of Physics 45,
345348 (2000)
The effect of 710 MeV Bi ion irradiation on boron profiles in silicon crystals has been investigated. It has been found a boron redistribution during annealing as a result of this irradiation and a reduction of the number of electrically active boron in the straggling zone of boron implant. The observed effect could be attributed to the formation of the defect clusters introduced by highenergy ion irradiation in ion track range.
A Method for Elemental Analysis of Bones by Recoiling Atoms in Heavy Ion Beams Livia Brazdes Romanian Journal of Physics 45,
349351 (2000)
A quantitative method for elemental analysis of bones, based on detection and identification of recoiling atoms, in a 100 MeV Iodine beam, accelerated at the Bucharest Tandem, has been worked out. In the developed method it was possible to resolve each element between Z = 3 (Lithium ) and Z = 38 (Strontium). It was found that in osteoporotic bones the ratio of Magnesium to Calcium is about two times less than for normal bones. A high concentration of Lithium in a trabecular bone, more than ten times higher than in cortical and in normal bones has been found.
HTS Zimmerman SQUIDs, Associated Electronics and Some Anomalies Al. Rusu, G. Aldica, Al. Niculescu, Alina Radu, S. Popa Romanian Journal of Physics 45,
353359 (2000)
The Josephson effect is described. Macroscopic quantum interference phenomenon is demonstrated. The interest for RF SQUIDs is justified. The existence of anomalous SQUIDs is put in evidence. A $3n V_{eff}/\sqrt{Hz}$ input equivalent noise voltage of the electronics is a good value as long as the inductor coupled to the SQUID is not superconducting.
Multiple Sampling Ionization Chamber (MUSIC) for Fusion Induced by Halo Nuclei Investigation Horia Petraşcu Romanian Journal of Physics 45,
361363 (2000)
A high resolution MUSIC, for low and medium energy ions, has been developed. The high pulse height resolution was obtained by coupling the preamplifiers directly to the anode pads. The pulse height measurements were performed by using a $^{241}$Am $\alpha$source. The energy loss distribution widths measured in P10 gas at pressures between 200 and 300 torr are in agreement with the theory of Badhwar. The achieved resolution of the chamber is close to the statistical limit. MUSIC was used for fusion investigations by using $^{11}$Li radioactive beam and Si and C targets. It was found to be very useful in eliminating the energy degraded and parasitic beam admixtures. It is expected that this type of chamber could be used also for isotopes of light elements identification, in Accelerator Mass Spectrometry (AMS) applications.
Array Detector for Neutron ProEmission Investigations Marius Petraşcu Romanian Journal of Physics 45,
365367 (2000)
An array detector consisting of 81 elements $4 \times 4 \times 12$ cm$^3$ has been built. This detector will be used for $nn$ coincidence measurements on neutrons preemitted in fusion induced by $^{11}$Li halo nuclei. A detection efficiency equal to 34% for 13 MeV neutrons was estimated by Monte Carlo calculations. The crosstalk equal to about 6% was estimated for two adjacent detectors and equal to about 1% for two detectors separated by one detector.
Surveillance System at IFINHH Using Gamma Probe SI01 A. Cîmpean Romanian Journal of Physics 45,
369370 (2000)
It is necessary to have online radiation measurements over Măgurele zone because of the nuclear reactor. These measurements are done with a gamma probe designed at IFINHH.
Statistical Discrimination Based Monitor for Radioactive Gases and Vapors L. Purghel, N. Vâlcov Romanian Journal of Physics 45,
371374 (2000)
The statistical discrimination method is based on the dependence of the resulting $k$factor on the relative values of the ionization current components in a mixed nuclear radiation field. Although the functionality of the schemes using the statistical discrimination method for measuring different radioactive gases and vapors is different, the basic structures are quite similar. They all contain a gas flowing ionization chamber (with a sampling pump), a preamplifier, a data acquisition system and a personal computer. As a consequence, a multifunctional monitor for radioactive gases and vapors has been taken into consideration. A special designed software allows for tuning te monitor on different gases (vapors) and on the associated radiation field (i.e. natural radiation background or gammaray field). Some performances of the monitor concerning the Radon and Tritium volume activity measurements in relatively strong gammaray fields are presented.
A Radon Monitor with Statistical Discrimination. Functional Model N. Vâlcov, L. Purghel, A. Vasilescu Romanian Journal of Physics 45,
375379 (2000)
The main condition to be fulfilled by the components of a nuclear radiation field in order to be measured by the statistical discrimination method is to have essentially differing statistical factors. This could be the case for the Radon volume activity measurements in the presence of a gammaray or a natural background radiation field, because alphaparticles emitted by Radon isotopes and by their progeny are losing in the sensitive volume of an ionization chamber much larger quantities of energy than the gammaray induced Compton electrons or even the cosmicray components of the natural radiation background.
