Results 1 - 10 of 466
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[en] The status and recent results of searches in the endpoint regions of nuclear beta decay spectra for the effect of neutrino mass are reviewed. The various sources and spectrometers employed in these measurements are presented with respect to the problems of statistical accuracy and systematic uncertainties. Neutrino mass greater than about 8 eV is clearly ruled out. The experiments agree on the value of the tritium endpoint and agree with ion cyclotron resonance values for the 3H - 3He mass difference. However there are curious and possibly significant features to the data in the most recent experiments, variously interpreted as negative neutrino mass-squared, as additional shake-off probability, or even as a bump 25 eV below the endpoint. Finally, a possible future experiment in 187Re using a cryogenic calorimeter technique is presented. This experiment avoids several systematic uncertainties and has the capability to achieve adequate statistical accuracy to test for these effects with a very different decay and spectrometer
[en] The development of nuclear medicine is based on research of new radiopharmaceuticals, in particular, relying on technetium-99m, the most used radioisotope in terms of availability and low cost. A similar study on Rhenium (185/187Re) is essential for monitoring physico-chemical studies due to the high specific activity of technetium-99m. During this work, we have synthesized and labeled with technetium the N-methyl-4-hydroxy piperidinyl ferrocenyl carboxylate. The marking is done by exchange of ligands between the iron group of ferrocene and tricabonyl technetium core. We have succeeded to synthesis the N-methyl-4-hydroxy piperidinyl carboxyl cyclopentadienyl tricarbonyl rhenium (the molecular analogue of the technetium). We characterized it by MS, IR and NMR (1H, 13C) The structure of N-methyl-4-hydroxy piperidinyl carboxyl cyclopentadienyl tricarbonyl technetium is well justified.
[en] The experiment to study the β-decay of 187Re, of end point energy 2.6 keV, using a cryogenic μ-calorimeter is presented. The objective of this rhenium experiment is to provide mass limits on the ν-bare, as an alternative to the current tritium β decay experiments. A preliminary low statistics 187Re β spectrum is presented, which was obtained with a NTD-germanium thermistor coupled to a superconducting rhenium foil, where the energy resolution was measured by an external 55Fe X-ray source to be σ of 13 eV at 5.9 keV. (author)
[en] A large worldwide collaboration is growing around the project of Micro-calorimeter Arrays for a Rhenium Experiment (MARE) for a direct calorimetric measurement of the neutrino mass with a sensitivity of about 0.2 eV/c2. Many groups are joining their experience and technical expertise in a common effort towards this challenging experiment which will use the most recent and advanced developments of the thermal detection technique.
[en] Isotopic composition of various elements has found wide applications in environmental and geological application such as chronometer and isotope tracing and fingerprinting of various processes and materials. Different kind of mass spectrometers are used to determine isotope composition based on the elements to be analyzed such as thermal ionisation mass spectrometer (TIMS), isotope ratio mass spectrometer (IRMS), secondary ion mass spectrometer (SIMS), resonance ion mass spectrometer (RIMS), accelerator mass spectrometer (AMS), inductively coupled plasma mass spectrometer (ICP-MS). These mass spectrometers are used to determine the precise isotope composition depending on the type of element, its ionisation potential and application. One of the main differences in these mass spectrometers is the mode of ionisation, for example, TIMS ionises the element by thermal heating whereas in case of IRMS, it is electron bombardment and in case of SIMS it is done by ions of some other elements
[en] Measurements of Re and major ion abundances in the source waters of the Yamuna, one of the large Himalayan rivers, have been carried out to better understand the geochemical behaviour of Re during weathering and transportation. These studies shed light on the closed system behaviour of Re, an essential pre-requisite for the application of 187Re - 187Os isotope pair as chronometer to date rocks, especially organic rich sediments
[en] Preparation of thin targets for nuclear physics experiment is an important and very hectic task since it is very crucial to the success of the experiment. Usually very thin self supporting targets are required to minimize the energy loss of the reaction products. But in certain cases it is very difficult to produce self supporting thin targets. In such cases targets with very thin backing of low Z material is also preferred. In this work 187Re targets of 200 μg/cm2 thickness were prepared with a C backing of 13 μg/cm2. The targets are prepared for the studies of energy distribution of evaporation residues (ERs) produced in the nuclear reaction experiment, using HYRA facility at IUAC. The desired thickness was 150-250 μg/cm2 so that the ERs produced in the reaction will not be stopped within the targets. These targets are prepared using E gun evaporation method