R.K. Bhowmik

Bio: R.K. Bhowmik is an academic researcher from Variable Energy Cyclotron Centre. The author has contributed to research in topics: Coulomb barrier & Quasiparticle. The author has an hindex of 3, co-authored 5 publications receiving 21 citations.

An axial ionization chamber for heavy ion identification

Abstract: The design and performance of an axial ionization chamber is described. The contribution of straggling to the energy resolution of this detector is inv

Heavy fragment emission in alpha-induced reactions on aluminum at 60 MeV.

Abstract: The production of intermediate-mass fragments ranging from Z=3 to 8 emitted in the reaction of 60 MeV alpha on an aluminum target has been experimentally studied. The energy spectra of the emitted fragments in the angular range of 20\ifmmode^\circ\else\textdegree\fi{}\char21{}130\ifmmode^\circ\else\textdegree\fi{} have been measured and the total production cross sections of each fragment have been estimated from the data. The double-differential cross-section data have been compared with the predictions made using (a) a phenomenological moving source model and (b) a binary fragmentation model. The absolute total emission cross sections for various fragments have been calculated assuming the statistical decay of a fully equilibrated compound nucleus and have been compared with the corresponding experimental estimates. It is found that the exit-channel deformation plays a significant role in the estimation of the Coulomb barrier of the separating nuclei. A theoretical procedure for the estimation of the exit-channel Coulomb barrier for the deformed system has been incorporated in the present calculation.

High Spin States in the Odd–Odd 150Eu Nucleus

Abstract: High spin rotational bands in the odd–odd 150Eu nucleus, produced in the 148Nd(7Li,5n) reaction, were investigated by in-beam γ spectroscopy. Seven bands above the 588.8 keV (45 ns) isomeric level were observed. Probable single- and double-octupole-phonon coupling states were identified. Two positive parity bands are interpreted in terms of two quasiparticles (a proton and a neutron) coupled to an axially symmetric rotor core. Otherwise, the rest of the high spin levels are described by multiparticle–hole excitations.

A gas-jet coupled ISOL system at VECC

Abstract: A gas-jet recoil transport (GJRT) system at VECC is being extensively used for the study of short-lived nuclei. A transport efficiency of ∼70–90% has been obtained for a large number of elements at a distance of ∼40 ft using a 1.27 mm tygon capillary. For the same distance, a transit time of ∼900 ms has been obtained using a pressure differential of 1 atmosphere. To extend the capability of the present system, a mass separator coupled to the GJRT has been designed. The integrated system will consist of a GJRT system, a skimmer, an ion-source, a beam transport system and a tape-transport type detection assembly. The beam optics of a 90° analyser magnet have been computed using the code ODESSA developed at VECC. A mass resolving power of ∼600 and a dispersion of ∼2.36 m have been estimated including second order aberrations. With reduced capillary length, the facility should allow the study of nuclides with half-lives ∼100 ms.

The experimental set-up of the RIB in-flight facility EXOTIC

Abstract: We describe the experimental set-up of the Radioactive Ion Beam (RIB) in-flight facility EXOTIC consisting of: (a) two position-sensitive Parallel Plate Avalanche Counters (PPACs), dedicated to the event-by-event tracking of the produced RIBs and to time of flight measurements and (b) the new high-granularity compact telescope array EXPADES (EXotic PArticle DEtection System), designed for nuclear physics and nuclear astrophysics experiments employing low-energy light RIBs. EXPADES consists of eight Δ E – E res telescopes arranged in a cylindrical configuration around the target. Each telescope is made up of two Double Sided Silicon Strip Detectors (DSSSDs) with a thickness of 40/60 μm and 300 μm for the Δ E and Eres layer, respectively. Additionally, eight ionization chambers were constructed to be used as an alternative Δ E stage or, in conjunction with the entire DSSSD array, to build up more complex triple telescopes. New low-noise multi-channel charge-sensitive preamplifiers and spectroscopy amplifiers, associated with constant fraction discriminators, peak-and-hold and Time to Amplitude Converter circuits were developed for the electronic readout of the Δ E stage. Application Specific Integrated Circuit-based electronics was employed for the treatment of the Eres signals. An 8-channel, 12-bit multi-sampling 50 MHz Analog to Digital Converter, a Trigger Supervisor Board for handling the trigger signals of the whole experimental set-up and an ad hoc data acquisition system were also developed. The performance of the PPACs, EXPADES and of the associated electronics was obtained offline with standard α calibration sources and in-beam by measuring the scattering process for the systems 17O+58Ni and 17O+208Pb at incident energies around their respective Coulomb barriers and, successively, during the first experimental runs with the RIBs of the EXOTIC facility.

Review of Nuclear Physics Experiments for Space Radiation

Abstract: Human space flight requires protecting astronauts from the harmful effects of space radiation. The availability of measured nuclear cross section data needed for these studies is reviewed in the present paper. The energy range of interest for radiation protection is approximately 100 MeV/n to 10 GeV/n. The majority of data are for projectile fragmentation partial and total cross sections, including both charge changing and isotopic cross sections. The cross section data are organized into categories which include charge changing, elemental, isotopic for total, single and double differential with respect to momentum, energy and angle. Gaps in the data relevant to space radiation protection are discussed and recommendations for future experiments are made.

Candidate chiral doublet bands in Pm 138

Abstract: High-spin states of $^{138}\mathrm{Pm}$ have been populated using the $^{124}\mathrm{Te}(^{19}\mathrm{F},\phantom{\rule{0.28em}{0ex}}5\mathrm{n})^{138}\mathrm{Pm}$ reaction at a beam energy of 105 MeV. A new positive-parity side band with the same $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{ u}{h}_{11/2}$ configuration as that of the yrast band is observed in $^{138}\mathrm{Pm}$. The properties of the two positive-parity bands show general agreement with the fingerprints of chiral rotation and thus these two bands are suggested to be candidates for near degenerate chiral doublet bands. Besides, odd-even spin staggering of the $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{ u}{h}_{11/2}$ bands is studied systematically in odd-odd Cs, La, Pr, and Pm isotopes. As a result of this study we suggest that the spin value of lowest observed state of the yrast band be reassigned as 9 in $^{138}\mathrm{Pm}$. This new spin assignment is also supported by the argument of alignment additivity.