K. M. Varier

K. M. Varier
University of Kerala · Department of Physics

About

82
Publications
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849
Citations
Citations since 2017
12 Research Items
263 Citations
201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050

Publications

Publications (82)
Article
The effects of irradiation of cast speculum metal mirrors using high-energy electrons (6 MeV and 9 MeV) and X-rays (6 MeV and 10 MeV) from a medical linear accelerator setup are studied in detail for the first time. Analyses using the techniques of X-ray diffraction, atomic force microscopy and Ultraviolet–Visible spectroscopy reveal that the irrad...
Article
The angle integrated total scattering cross sections of some rare earth oxides were determined experimentally for 59.54 keV gamma rays in the angular ranges of 0–4o, 0–6o, 0–8o and 0–10o. From the experimental total scattering cross sections, the corresponding angle integrated incoherent scattering cross sections obtained from ENDF library (based o...
Conference Paper
Gamma ray attenuation studies play an important role in industry, agriculture, medicine, radiation dosimetry etc. In the present study, we have made an attempt to determine the linear attenuation coefficient for 662 keV gamma rays in pure coconut oil, in paraffin oil and in a mixture of both. From the experimentally obtained linear attenuation coef...
Article
The effective atomic numbers and effective electron densities of some polymers having medical applications are determined for total as well as partial gamma ray interaction processes in the wide range of energies 1 keV to 100 GeV. Mass energy-absorption coefficient and effective atomic number corresponding to gamma ray energy absorption in these me...
Article
Full-text available
Background: The onset of a noncompound nuclear fission (NCNF) process such as quasifission was already predicted for heavy symmetric systems with the charge product greater than 1400. However, quasifission is observed indeed in very asymmetric reactions forming Ra216 with much lower charge product(≈700). A comprehensive idea about the dependence of...
Preprint
Recent advances in grazing incidence X-ray optics using synchrotron radiation sources have stimulated the need for basic research in high quality mirror materials for novel applications. In this paper we communicate the results of the first measurements of glazing angle X-ray reflectivity (XRR) of speculum metal mirrors using synchrotron radiation...
Article
A light-weight multichannel analyser (MCA)-based γ-ray spectrometer, developed earlier at the Inter University Accelerator Centre, New Delhi, has been used as part of the PG curriculum, to determine the effective atomic numbers for γ attenuation of ¹³⁷Cs γ-ray in different types of samples. The samples used are mixtures of graphite, aluminum and se...
Article
Full-text available
A \(\gamma \)-ray spectroscopy system based on a 1\(^{\prime \prime }\times 1^{\prime \prime }\) NaI(Tl) detector and 1.5\(^{\prime \prime }\) photomultiplier tube has been developed at IUAC for teaching laboratory applications involving radioactive sources. Following along the lines of the Phoenix and Expeyes hardware developed in the laboratory e...
Article
A java code incorporating a user friendly GUI has been developed to calculate the parameters of chemically etched track profiles of ion-irradiated solid state nuclear track detectors. Huygen’s construction of wavefronts based on secondary wavelets has been used to numerically calculate the etched track profile as a function of the etching time. Pro...
Article
Solid-state nuclear track detectors (SSNTDs) find applications in many fields of science and technology. Polycarbonates like CR-39 or Lexan are most widely used for such applications. Pokalon is a relatively new member of the polycarbonate family of SSNTDs. It has the same monomer as that of Makrofol. In the present work we have studied the bulk et...
Article
Evaporation residue (ER) and fission cross sections were measured for the reaction &${}^{18}$;O+&${}^{194}\mathrm{Pt}$; forming the compound nucleus 212Rn. Fission fragment angular distributions and anisotropies are consistent with the saddle point model predictions. Measured ER cross sections were fitted with statistical model calculations assumin...
Article
Fission fragment mass-angle and mass ratio distributions have been measured for the 30Si+180Hf reaction in the beam energy range 128-148 MeV. Quasifission signature is observed in this reaction, forming the compound system 210Rn. The results are compared with a very asymmetric reaction 16O+194Pt, forming the same compound nucleus. Calculations assu...
Article
Full-text available
Evaporation residue (ER) cross sections for the O16,18+Pt198 reactions are measured in order to investigate fission hindrance. Compound nuclei (Rn214,216) are formed in the above fusion reactions at excitation energies in the range of 40-68 MeV. The experimental ER cross sections are compared with predictions from the statistical model calculations...
Article
Full-text available
Atomic scattering factor is in general a complex number represented by the sum of normal scattering factor (f(0)) and anomalous scattering factors [real (f ') and imaginary (f '')]. Anomalous scattering factors in Ag, In, Cd and Sn were determined experimentally from attenuation data measured using PIXE and compared with theoretical values. The dat...
Article
Fission fragment mass-ratio distributions have been studied for the reactions 16O+194Pt, 24Mg+186W and 30Si+180Hf all forming the same compound nucleus (CN) 210Rn at near barrier energies. The measured fission fragment massratio variances for the three reactions were compared with statistical model calculations assuming CN formation. The mass varia...
Article
Effective atomic numbers of various combinations of elements with 13≤Z≤5013≤Z≤50 which in effect form heterogeneous layers have been deduced using the mass attenuation values determined experimentally using 59.54 keV gamma rays. The results are compared with the theoretical values obtained using XCOM and the values calculated with an empirical form...
Article
Fission fragment angular distributions have been measured for 16O + 194Pt reaction forming the compound system 210Rn, in the laboratory energy range from 79 to 90 MeV. The measured fission fragment anisotropies as a function of Ec.m./VBEc.m./VB are compared with the predictions of standard saddle point statistical model (sspm). Anisotropies calcula...
Article
Full-text available
Coherent and incoherent scattering cross sections have been measured using a high purity germanium detector on elements in the range of Z = 13–50 using 241Am gamma rays. The cross sections have been derived by comparing the net count rate obtained from the Compton peak of aluminum with the elastic/Compton peak of the target element. The measured cr...
Article
Full-text available
Evaporation residue cross sections for the reaction 16O+194Pt were measured at beam energies in the range 75.4–103.1 MeV using the gas-filled separator Hybrid Recoil Mass Analyzer at the Inter University Accelerator Centre, New Delhi. The transmission efficiency of the separator was obtained using the calibration system 16O+184W and a Monte Carlo s...
Article
Full-text available
Evaporation residue (ER) excitation function in the complete fusion of 16O with 194Pt is measured around the Coulomb barrier using gas-filled mode of the HYbrid Recoil mass Analyser (HYRA) at the Inter University Accelerator Centre (IUAC), New Delhi. Measured ER excitation function is compared with statistical model calculation. Nuclear dissipation...
Article
Coherent and incoherent scattering cross section measurements have been carried out using a HPGe detector on elements in the range of Z = 13 - 50 using 241 Am gamma rays. The cross sections have been derived by comparing the net count rate obtained from the Compton peak of aluminium with the corresponding peak of the target. The measured cross sect...
Article
Hybrid recoil mass analyzer (HYRA) is a unique, dual-mode spectrometer designed to carry out nuclear reaction and structure studies in heavy and medium-mass nuclei using gas-filled and vacuum modes, respectively and has the potential to address newer domains in nuclear physics accessible using high energy, heavy-ion beams from superconducting LINAC...
Article
Full-text available
Mass attenuation coefficients (µ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd, Cd and Sn foils. The measurements were carried out at the K α and K β energy values of the target elements by two techniques: (1) Proton-induced X...
Article
Full-text available
Fission fragment mass ratio distributions have been measured for the reactions 16O+194Pt and 24Mg+186W, both leading to the same compound nucleus, 210Rn, at near-barrier energies. The measured fission fragment mass ratio variances for 16O+194Pt and 24Mg+186W are compared with the calculations assuming compound nucleus formation. Mass variances of f...
Article
Fission fragment mass angle correlation and mass ratio distributions have been measured for 16O + 194Pt reaction forming the composite system 210Rn in the energy range 75 MeV to 102 MeV in laboratory frame. No mass angle correlation was observed and the mass ratio distributions were compared with theoretical calculations assuming compound nucleus f...
Article
The fusion excitation functions and barrier distributions for the fusion of 12C, 16O, 28Si and 35Cl on 92Zr have been calculated using one-dimensional barrier penetration model, taking scattering potential as the sum of Coulomb and proximity potential. Calculated results are compared with experimental data and CC calculations using code CCFULL. At...
Article
Full-text available
We have carried out photon attenuation measurements at several energies in the range from 49.38 keV to 57.96 keV around the K-absorption edges of the rare earth elements Sm, Eu, Gd, Tb, Dy and Er using 59.54 keV gamma rays from 241Am source after Compton scattering from an aluminium target. Pellets of oxides of the rare earth elements were chosen a...
Article
The fission fragment angular distribution measurements for the 13C+235U system have been carried out to study the entrance channel dependence and spin dependent effects in the fission fragment anisotropies. This particular combination of target and projectile leads to 248Cf compound nucleus that has been studied earlier using three other entrance c...
Article
Evaporation residue cross sections and spin distributions have been measured for 200Pb compound nucleus formed in 16O+184W reaction at the laboratory beam energies of 84, 92, 100, 108, 116, and 120 MeV. The evaporation residues have been selected using the recoil mass spectrometer, HIRA and detected using a 2D position sensitive silicon detector. T...
Article
Full-text available
We have carried out some photon interaction measurements using 59.54 keV γ-rays from a 241Am source. These include γ attenuation studies as well as photoelectric absorption studies in various samples. The attenuation studies have been made using leaf and wood samples, samples like sand, sugar etc., which contain particles of varying sizes as well a...
Article
Full-text available
The total γ-ray interaction cross-sections on mixed absorbers were determined at 662 keV with a view to study the effective atomic numbers for γ-ray absorption under narrow beam good geometry set-up. The measurements were taken for the combination of metallic absorbers like aluminium, copper, lead and mercury and also for the simulated absorbers by...
Article
Fission fragment anisotropies and fusion cross sections were measured for 13C+232Th in the energy range 0.9
Article
L-subshell ionisation cross-sections for Ta, W and Pt by proton impact in the energy range of 2–5.2 MeV have been determined from the experimental data on X-ray production cross-section and the currently available radiative transition probabilities, fluorescence and Coster–Kronig factors of Krause, Werner and Jitschin and Xu. The measured ionisatio...
Article
Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2+ and 3- states failed to explain these enhancements completely. A possibility of transfer channels contributing to the residual enhancements had been suggested. In order...
Article
Proton induced X-ray Emission (PIXE) has been used to measure the trace metals especially heavy metals in Chaliyar river water samples to assess the impact of pollutants from the industrial wastes. Water samples were collected in summer and rainy seasons from three different depths along the course of the river. Measurements were carried out with 2...
Article
Full-text available
Large enhancements have been observed in the sub-barrier fusion cross sections for Ti + Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2+ and 3- states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements had been suggested. In order...
Article
The Chaliyar river, located in Kerala, India has shown preoccupying pollution levels, that constitute a threat to public health and the ecological system. PIXE and PIGE techniques have been employed to measure the elemental concentrations in the river sediment samples. Thick targets were prepared out of the sediment samples collected from various s...
Article
Backscattering peak is one of the main features of the pulse height spectrum from a gamma ray detector. This arises mainly from materials outside the detector like source backing, photo multiplier tube housing, shielding etc. We have studied the effect of source backing on the relative importance of the back scattered peak for a NaI(I) scintillatio...
Article
Analysis of trace elemental concentration in the Chaliyar river water has been carried out using the Proton Induced X-ray Emission (PIXE) spectroscopic technique. Water samples were collected from different locations along the course of the river during summer and rainy seasons. Samples were prepared by a preconcentration method. The PIXE analysis...
Article
L X-ray production cross sections and their ratios in Ta, W and Pt have been measured for the bombardment of protons in the energy range 2–5.2 MeV in steps of 0.4 MeV. The data in the energy range 3.8–5.2 MeV have not been reported so far. The X-ray production cross sections compare well (within 10%) with theoretical values obtained using the decay...
Article
Trace elements present in bottled mineral water have been studied by PIXE and ICP-MS. Samples from ten different brands of bottled mineral water were prepared by preconcentration techniques. Measurements were carried out using the 2 MeV proton beam obtained from 3 MV Tandem pelletron accelerator at the Institute of Physics, Bhubaneswar. Our results...
Article
Full-text available
Measurements of sub-barrier transfer reactions are reported for the systems 28Si C 64Ni, 32Si C 64Ni and 28Si C 144Nd using the recoil mass spectrometer HIRA in kinematic coincidence mode. The problem related to M=Q-ambiguity in measurements with mass separators has been resolved. Excellent mass resultion with a large solid angle is obtained by cor...
Article
Excitation functions for one- and two-nucleon transfer in 28Si + 68Zn system have been measured at energies below the Coulomb barrier. The experiment was carried out by detecting the forward recoiling targetlike nuclei using the recoil mass separator, HIRA. With a pulsed beam, the time-of-flight of the recoils was measured and used to resolve the M...
Article
Fusion cross sections and mean angular momenta have been measured for the four systems 28Si+94,100Mo and 58,64Ni+64Ni and can be explained in the framework of the coupled-channels (CC) approach. In particular the influence of 2n-transfer channels with positive Q-values shows up. The direct relation between excitation function and angular momenta ha...
Article
Full-text available
Fusion process in the near and sub-barrier region has been investigated for the systems 48Ti+58,60,64Ni using the heavy-ion reaction analyzer (HIRA). Fusion excitation functions and the mean angular momenta are obtained from the measured evaporation residue cross sections. Significant enhancements both in the cross section and mean angular momentum...
Article
The fusion excitation functions for the 46Ti+64Ni, 5°Ti+~Ni and 19F+93Nb systems have been measured from ~ 10% below to 15% above the nominal Coulomb barrier, utilizing the recoil mass separator, HIRA at the Nuclear Science Centre, New Delhi. Mean spins have been deduced from the fusion cross sections by two different methods, one using the statist...
Article
The fusion excitation functions for the 46Ti+64Ni, 5°Ti+~Ni and 19F+93Nb systems have been measured from ~ 10% below to 15% above the nominal Coulomb barrier, utilizing the recoil mass separator, HIRA at the Nuclear Science Centre, New Delhi. Mean spins have been deduced from the fusion cross sections by two different methods, one using the statist...
Article
Full-text available
According to Stelson’s neutron flow model the threshold barrier is correlated to the onset of neutron flow. A systematic study of a large set of systems indicates that there exists a very good correlation between the threshold barrier and the intersurface distance after including the zero point motion of collective surface vibrations of the collidi...
Article
A detector system has been developed for the focal plane of the HIRA. It consists of two independent detectors, a low-pressure multiwire proportional counter (LP-MWPC) followed by a split-anode ionization detector. Details of the design and test results are presented. Using slow pre-amplifiers, the position resolution is 21 mm and the time resoluti...
Article
Gas amplification factors have been measured for isobutane and P10 gases in single wire proportional counter and parallel plate avalanche counter geometries for reduced field strength value ranging from 140 to 1000 V cm−1Torr−1. Data using the SWPC were found to satisfy the Aoyama formula for gas amplification with m = 0 and also the Diethorn formu...
Article
A numerical method has been developed for determining the etched track profile and its parameters like diameter and track length for CR-39 track detector for low energy alpha particles. The track etch rate is assumed to vary along the track and etching is assumed to take place normal to the etched surface at any time. The results agree well with th...
Article
The results of the measurement of fusion cross sections σfus and mean angular momenta <l for the five systems 16O+112Cd, 28Si+94,100Mo and 58,64Ni+64Ni are reported. The direct comparison between the fusion excitation function and <l (E) confirms consistency of the two independent observables. By analyzing the data in the framework of the coupled c...
Article
Cross sections for the elastic scattering of 59.54 keV gamma rays through 141° by Al, Cu, Mo, Yb, Ta, Au and Pb have been accurately determined using a Si(Li) detector. The values of the cross sections have been obtained by a normalization technique based on a comparison with the Compton scattering from the essentially free electrons from an Al sca...
Article
Cross sections for the elastic scattering of 88.03-keV γ rays through 125° by aluminum, gold, lead, and bismuth have been measured with a semiconductor detector. Simultaneously, information has been obtained regarding resonance Raman scattering and Compton scattering in the case of bismuth, and K-shell photoeffect cross sections in the case of gold...
Article
Using 137Cs gamma rays, the effect of finite absorber dimensions on attenuation measurements has been studied. Copper and mercury targets were used. Absorber dimensions up to five mean free paths were used. A correlated effect was observed in the measurements due to absorber thickness and its dimensions in the transverse directions. The values of t...
Article
Attenuation coefficients have been measured for aluminum for x rays in the energy region 7–15 keV. The x rays were obtained by proton excitation of copper, tantalum, and lead targets. A new method has been used to extract the attenuation coefficients of the individual components of the copper K x rays and the L x rays of tantalum and lead without n...
Article
The bremsstrahlung background in the PIXE spectra of thick non-conducting targets has been studied in detail using proton and alpha particle beams. Using targets of mica, ceramic and quartz, spectra were taken for various positions of bombardment along the length of the target. The variation of the endpoint energy Emax was studied under various con...
Article
PIXE analysis of human hair samples was carried out with 2 MeV protons. The trace elemental contents in hair samples collected from different parts of the same person had standard deviations ranging from 17 % to 28% whereas those from hair samples of different persons had standard deviations ranging from 26 % to 69 % . Significant differences in th...
Article
The proton-induced X-ray emission (PIXE) technique was applied to the identification and analysis of gunshot residues. Studies were made of the type of bullet and bullet hole identification, firearm discharge element profiles, the effect of various target backings, and hand swabbings. The discussion of the results reviews the sensitivity of the PIX...
Article
Elemental composition of water is of great importance as it is the prime source of the trace elements essential for the growth of living organisms. It has been known from early times that water from hot springs and other natural sources has beneficial effects on human health. There are also regional mythical beliefs that water from these sources ha...
Article
The PIXE technique has been successfully applied to study crime related problems in forensic science. The experimental arrangements and various practical problems involved are discussed. Consistency and reproducibility checks are presented. The results from the gun-shot residue profiles of the associated elements about the bullet hole obtained for...
Article
Elastic scattering cross-sections of lead, tantalum and molybdenum were determined with the help of a Ge (Li) detector for 1.17 and 1.33 MeV rays between 30° and 115°. Theoretical evaluations of the cross-sections are based on a coherent addition of the well-known nuclear Thomson scattering amplitudes, the Rayleigh amplitudes calculated by Kissel a...
Article
The good resolution of a Ge(Li) detector was used to measure gamma ray attenuation coefficients in narrow beam geometry. The effect of multiple scattering on the pulse height distribution of the transmitted gamma rays and on the measured attenuation coefficients was studied and shown to be small up to three mean free paths. Values of attenuation co...
Article
Cited References Count:50|ELSEVIER SCIENCE BV|PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS|Ackermann, D|Bednarczyk, P|Corradi, L|Napoli, DR|Petrache, CM|Spolaore, P|Stefanini, AM|Varier, KM|Zhang, H|Scarlassara, F|Beghini, S|Montagnoli, G|Muller, L|Segato, GF|Soramel, F|Signorini, C|ISI Document Delivery No.:VQ784
Article
Full-text available
Cross sections for the elastic scattering of 88.03 keV gamma rays through 125 degrees by aluminium, gold, lead and bismuth have been measured with a semiconductor detector. Simultaneously information has been obtained regarding resonance Raman scattering and Compton scattering in the case of bismuth, and K shell photoeffect cross sections in the ca...

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