Studies on carbon nanotubes and fullerenes under extreme conditions.

Ion beam irradiation of materials can cause defect creation as well as defect annealing depending on the ion beam parameters such as ion fluence and the energy loss of ions in materials. In present review, we report the behaviour of carbon nanotubes under exteme conditions such as laser irradiation and ion irradiation. The reorientation of the crystalline planes in confined single crystal nickel nanorods inside carbon nano tube, induced by heavy ion irradiation, is reported.

Studies of emittance of multiply charged ions extracted from high temperature superconducting electron cyclotron resonance ion source, PKDELIS.

For the high current injector project at Inter University Accelerator Centre, a high temperature superconducting electron cyclotron resonance (ECR) ion source, PKDELIS, would provide the high charge state ions. The emittance of the ECR ion source is an important parameter to design further beam transport system and to match the acceptances of the downstream radio frequency quadrupole and drift tube linac accelerators of the high current injector. The emittance of the analyzed beam of PKDELIS ECR source has been measured utilizing the three beam size technique.

The effect of the dc bias voltage on the x-ray bremsstrahlung and beam intensities of medium and highly charged ions of argon.

X-ray bremsstrahlung measurements from the 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Pantechnik-Delhi Ion Source were measured as a function of negative dc bias voltage, keeping all other source operating parameters fixed and the extraction voltage in the off condition. The optimization of medium and highly charged ions of argon with similar source operating parameters is described. It is observed that the high temperature component of the electron is altered significantly with the help of bias voltage, and the electron population has to be maximized for obtaining higher current.

Compact multiwire proportional counters for the detection of fission fragments.

Two large area multistep position sensitive (two dimensional) multiwire proportional counters have been developed for experiments involving study of fission dynamics using general purpose scattering chamber facility at IUAC. Both detectors have an active area of 20x10 cm(2) and provide position signals in horizontal (X) and vertical (Y) planes, timing signal for time of flight measurements and energy signal giving the differential energy loss in the active volume. The design features are optimized for the detection of low energy heavy ions at very low gas pressures.

NEXAFS and XMCD studies of single-phase Co doped ZnO thin films.

A study of the electronic structure and magnetic properties of Co doped ZnO thin films synthesized by ion implantation followed by swift heavy ion irradiation is presented using near-edge x-ray absorption fine structure (NEXAFS) and x-ray magnetic circular dichroism (XMCD) measurements. The spectral features of NEXAFS at the Co L(3,2)-edge show entirely different features than that of metallic Co clusters and other Co oxide phases. The atomic multiplet calculations are performed to determine the valence state, symmetry and the crystal field splitting, which show that in the present system Co is in the 2+ state and substituted at the Zn site in tetrahedral symmetry with 10Dq = -0.

Surface plasmon resonance of Ag nanoparticles embedded in partially oxidized amorphous Si matrix.

Nanocomposite films containing Ag nanoparticles embedded in partially oxidized amorphous Si matrix were deposited on silica glass substrates by co-sputtering of Ag and Si with 1.5 keV neutral Ar atoms. The Ag content and thickness of the nanocomposite films was determined by Rutherford backscattering spectrometry.

KeV ion-induced effective surface modifications on InP.

In the present study, we have analyzed the changes in surface morphology leading to formation of periodic structures known as ripples which arise due to an interplay between sputtering and surface diffusion. The 1.5 keV Ar atoms with a flux of 14.

Development of Ge nanoparticles embedded in GeO2 matrix.

Germanium (Ge) nanoparticles have attracted a lot of attention due to their excellent optical properties. In this paper, we report on the formation of Ge nanoparticles embedded in GeO2 matrix prepared by electron beam evaporation and subsequent annealing. Transmission electron microscopy (TEM) studies clearly indicate the formation of Ge nanocrystals in the films annealed at 500 degrees C.

High precision (14 bit), high density (octal) analog to digital converter for spectroscopy applications.

Nuclear and particle physics experiments with large number of detectors require signal processing and data collection strategies that call for the ability to collect large amount of data while not sacrificing the precision and accuracy of the data being collected. This paper deals with the development of a high precision pulse peak detection, analog to digital converter (ADC) module with eight independent channels in plug-in daughter card motherboard model, best suited for spectroscopy experiments. This module provides multiple channels without cross-talk and of 14 bit resolution, while maintaining high density (each daughter card has an area of just 4.

Setup for in situ deep level transient spectroscopy of semiconductors during swift heavy ion irradiation.

A computerized system for in situ deep level characterization during irradiation in semiconductors has been set up and tested in the beam line for materials science studies of the 15 MV Pelletron accelerator at the Inter-University Accelerator Centre, New Delhi. This is a new facility for in situ irradiation-induced deep level studies, available in the beam line of an accelerator laboratory. It is based on the well-known deep level transient spectroscopy (DLTS) technique.

Effect of swift heavy ions in Ni-Al nanocrystalline films studied by X-ray absorption spectroscopy.

X-ray absorption spectroscopic measurements have been used to compare the electronic structures of swift heavy ions (100 MeV Si ions) irradiated and pristine Ni-Al nanocrystalline films. Results from X-ray diffraction (XRD), X-ray absorption near-edge structure (XANES) spectra at Al K-, and Ni L(2,3)-edges and extended X-ray absorption fine structure (EXAFS) at Ni K-edges are discussed. The observed XRD peaks indicate the improvement of crystalline nature and Al(111) clustering after the swift heavy ion interactions.

Setup for in situ x-ray diffraction study of swift heavy ion irradiated materials.

An in situ x-ray diffraction (XRD) setup is designed and installed in the materials science beam line of the Pelletron accelerator at the Inter-University Accelerator Centre for in situ studies of phase change in swift heavy ion irradiated materials. A high vacuum chamber with suitable windows for incident and diffracted X-rays is integrated with the goniometer and the beamline. Indigenously made liquid nitrogen (LN2) temperature sample cooling unit is installed.

Butterfly structure: signature of vibrational flopping in dissociative acetylene.

We report experimental evidence for molecular deformation due to a vibrationally active transition state of multiply charged acetylene molecules under the impact of low energy Ar8+ projectiles. "Butterflylike" structures are observed in the experimental coincidence spectra between hydrogen and carbon ionic fragments. Such structures can be generated by numerical simulations and are found to originate from the bending motion of the dissociating molecule.

Magnetic force microscopy of nano-size magnetic domain ordering in heavy ion irradiated fullerene films.

In the present work, magnetic force microscopy is employed to investigate the magnetic ordering in ion irradiated fullerene films. It is observed that magnetic domain size is approximately 100-200 nm and magnetic signal is stronger at the domain boundaries. Magnetic signal arise in irradiated films is confirmed by magnetic measurements using a superconducting quantum interference device which increases with the ion fluence.

Synthesis and characterization of gold nanorings.

In the present work, we report the formation of Au nanorings on quartz substrate by thermal evaporation of Au on quartz and subsequent annealing in certain conditions as a function of metal volume fraction and annealing temperature. Optical extinction cross-sections measurements and atomic force microscopy (AFM) studies have been performed on the as-deposited and annealed samples. No signature of nanoparticles formation is found in case of as-deposited samples, while spectra of annealed samples show a clear signature of surface plasmon resonance absorption (SPR) peaks around 580 nm, which reveals the formation of Au nanostructure.

Synthesis of nanocrystalline tin oxide thin film by swift heavy ion irradiation.

Nanocrystals of tin oxide were formed in e-beam evaporated films by swift heavy ion (SHI) irradiation. The nucleation of nanocrystals occurred due to electronic excitation by swift heavy ion. Nanophase thin films are characterized systematically by HRTEM, GAXRD, EDX, and UV/NIS absorption techniques.