LABORATORY OF NEW SCIENTIFIC AND RESEARCH PROJECTS IN NUCLEAR PHYSICS

• Multiple neutron generation analysis
• TUE detecting by methods of laser spectroscopy
• Variations of isomeric nuclei half-life

1. Multiple neutron generation analysis

The works were started in 80-s with the purpose to determine electron yields from massive heavy targets under proton impact for the sake of creation of nuclear waste transmutation and electronuclear power production. For the first time there were measured and published accumulated neutron yields under impact of 1 GeV protons against lead, cupper, and aluminum [1]. Secondary neutron spectra and neutron fluxes in various points within and out of massive targets [2] were studied by the method of threshold activation detectors. These results allowed evaluation of opportunity to use proton accelerators in electronuclear installations and also prospective neutron fields of their target assemblies.

In 1996-1997 in Brookhaven Laboratory (USA) they obtained provisional results, which pointed out abnormally high probability to emit 100-120 neutrons in single interaction of cosmic particle with massive lead target. In 1997 we made attempt to check this information that suggested the idea to design a special installation to be arranged in underground laboratory with the purpose to decrease low-energy particle background. The installation (INM-2) was constructed and the measurements were carried out in underground laboratory of RPA KRI (depth - 70 m), and then - in underground laboratory of Oulu City University (Finland) within the frameworks of CUPP Project [5] at depths of 440 and 220 m. The results obtained proved the availability of abnormally large multiplicities of neutrons at secondary mu-meson interaction (and may be other penetrative particles too) with massive lead target (289 Kg) [4]. In the end of 2000 Nevada State University (USA) also jointed this work. By the order of this University we constructed one similar installation more (NMDS), on which in 2004 there were started measurements of neutron multiplicity distributions, induced by energetic component of cosmic rays [6].

Both in our laboratory and in USA there are being conducted simultaneous theoretical evaluations of the expected neutron yields, using MCNP, FLUKA (USA), and CONTROL, MCNP4, GEANT3 (RPA KRI) codes. The comparison of these evaluations with experimental data should give explanation to the mechanism of multiple origination of neutrons (or recognize anomalies capable of giving information about a structure and an effect from penetrative component of cosmic radiation). The works are in progress.

2. TUE detecting by methods of laser spectroscopy

These works were started in 1999 within the frameworks of ISTC Project # 616 with the purpose to find TUE detection methods to be more sensitive and expressive in comparison with ordinary analysis procedure (radiochemistry + alpha spectrometry). At the present time the sensitivity of the most sensitive laser methods (Time Resolved Laser Induced Fluorescence - TRLIF, for instance) reaches 10^-12 - 10^-13 mole in a sample and photoluminescence of TUE is used in these methods for signal registration. Unfortunately, plutonium and neptunium are not capable of giving photoluminescence in solution and cannot be used in TRLIF. We were first succeeded in detection of specific chemiluminescence in solutions containing plutonium and neptunium [7, 8, 9] that allows to development of techniques for TUE laser analysis with the use of chemiluminescence stimulation and to simultaneous determination of valent states and types of molecules, in which TUE are bound. The works are in progress.

3. Variations of isomeric nuclei half-life

These works were started in 1986 and were applied to changes in a half-life of isomeric nuclei of ^235mU, imbedded in metal silver matrix [10]. In experiments there was detected an effect of this isomer decay retardation, which overstepped the limits of the known period variations caused by chemical linkage of outer atom shells. The effect could not find any direct theoretical explanation, however, the works were continued with another isomeric nuclei, in particular, with explanation ^229mTh [11]. There were also conducted experiments on ^235mU isomeric state excitation by high-power laser roentgen radiation, which were not resulted in any sizeable yield of the isomer.

At present in relation with the fact that the possibility to induce isomeric state transitions for ^178m2Hf [12] and ^180mTa is subjected to discussion in publications, there are planned experiments aimed at accumulation and separation of these isomers (without carriers and with minimum content of ground state nuclei) with the purpose to study and check the effects under discussion. The works are in progress.

Publications

1. Bakhmoutkin S.V., Bogdanov A.I., Bogdanov V.G., et al. Neutron Energy Spectra on the Surface of Cylindrical Lead Target Irradiated by 1 GeV Protons. // Atomic Energy. - 1987. - v. 62. - No 1. - p. 59-61.
2. Bakhmoutkin S.V., Nosov A.A., Rimski-Korsakov A.A. Yield Measuring for Nuclides Generated under 1 GeV Proton Interaction with Cylindrical Lead Target. // Atomic Energy. - 1987. - v. 63. - No 2. - p. 137-140.
3. Rimski-Korsakov A.A., Daniel A.V. Thick Target Experiments in GeV Region as Benchmarks for Intermediate Energy Nuclear Data. // Advisory Group Meeting on Intermediate Energy Nuclear Data. - IAEA, Vienna. - 1990.
4. Ward T.E., Rimsky-Korsakov A.A., Triumfov N.G. et al. High Multiplicity Neutron Production on Pb Targets Caused by Cosmic Rays. // Bulletin of the American Physical Society, Proceedings of April 2001 APS Meeting. - v. 46. - No.2. - p. 51-52.
5. Peltoniemi J., Rimsky-Korsakov A., Kudryashev N. et al. CUPP Project Report CUPP-08/2003, October 2001, Oulu, Finland.
6. Rimsky-Korsakov A.A., Kudryashev N.A. Neutron Multiplicity Detector System. // V.G. Khlopin Radium Institute, Subcontract with University of Nevada, Las Vegas, Progress Reports #1-#5, Purchase Order # 2S02TM00003. - 2002-2003.
7. Gangrskiy Yu.P., Izosimov I.N., Markov B.N., et al. Use of Laser Spectroscopy Methods to StudyCharacteristics of Heavy Nuclei. // Preprint RI-212. - Moscow. - CNIIAtominform. - 1989.
8. Izosimov I.N., Gorshkov N.G., Mashirov L.G. et al. In: Proceedings of the V International Workshop Application of Lasers in Atomic Nuclei Research. (Poznan, Poland, 2001). - Ed. Joint Institute for Nuclear Research, Dubna. - 2002. - E15-2002-84. - p. 153-175.
9. Gorshkov N.G., Izosimov I.N., Kazimov A.A., et al. Luminol Chemifluorescence Induced under the Excitation of NpO₂F₄OH³- complexes by Nitrogen Laser (λ = 337,1 1 nm). // Radiochemistry. - 2003. - v. 45. - No.1. - p. 27-31.
10. Koltsov V.V., Rimskiy-Korsakov A.A. The Effect of Conductive Environment to the Decay of ^235mU. Isomer. // Proceed. of the USSR AS, Ser. Phys. - 1989. - v. 53. - No 11. - p. 2085-2088.
11. Vorykhalov O.V., Koltsov V.V. Search for Isomeric Transition with Energy Below 5 eV in the Nucleus of ²²⁹Th. // Proceed. of the RAS, Ser. Phys. - 1995. - v. 59. - No 1. - p. 24-28.
12. Collins C.B., Davanloo F., Iosif M.C. et.al. Study of the Gamma Emission from the 21-yr Isomer of ¹⁷⁸Hf Induced by x-Ray Irradiation. // сДЕТОБС ЖЙЪЙЛБ. - 2000. - Ф. 63. - ? 12. - У. 2163-2168.