Annu Sharma

Effect of nitrogen ion implantation on the optical and structural characteristics of CR-39 polymer

The effect of nitrogen ion implantation has been examined in transparent surfaces of CR-39 polymer. Samples were implanted with 100keV N+ ions to various doses ranging from 1014to1017cm−2. The chemical and structural changes in the implanted specimens were performed using Raman spectroscopy and glancing angle x-ray diffraction. Ultraviolet-visible absorption analysis indicates a drastic decline in optical band gap from 3.50eV in virgin sample to 0.80eV at an implantation dose of 1017ionscm−2.The effect of nitrogen ion implantation has been examined in transparent surfaces of CR-39 polymer. Samples were implanted with 100keV N+ ions to various doses ranging from 1014to1017cm−2. The chemical and structural changes in the implanted specimens were performed using Raman spectroscopy and glancing angle x-ray diffraction. Ultraviolet-visible absorption analysis indicates a drastic decline in optical band gap from 3.50eV in virgin sample to 0.80eV at an implantation dose of 1017ionscm−2.

Surface disordering and its correlations with properties in argon implanted CR-39 polymer

The influence of Ar+ implantation induced disordering in the surface layers of the CR-39 polymer on its optical properties and surface hardness has been studied. The specimens were implanted at 130 keV to the doses of 5 × 1014, 1 × 1015, 1 × 1016 Ar+ cm−2. The structural behavior of the pre- and postimplanted specimens was investigated using UV-Visible, Raman, and x-ray diffraction techniques. Formation of disordered graphitelike structures in the implanted layers of polycarbonate has been observed using Raman and UV-Visible spectroscopy. A significant increase in the value of disorder content (Urbach energy) from 0.77 eV to 1.48 eV and a continuous decline in optical bandgap (from 3.43 eV to 2.32 eV) with increasing implantation dose have been observed. This decrease in optical bandgap has been found to have linear dependence on the increase in the Urbach energy, which points toward the formation of disordered structures in the implanted layers of CR-39 polymer. Further, Knoop microhardness is found to b...

Stopping power for heavy ions (3⩽Z⩽35) in solids at energies ∼0.5–2.5 MeV/n

Abstract The Hubert et al. formulation for stopping power calculations has been extended below its recommended range of validity, i.e. 2.5–500 MeV/n. It has been established that the extended formulation for projectiles with Z =3–35 provides a good agreement with the experimental data for elemental targets (6⩽ Z ⩽79) and complex materials e.g. CR-39, LR-115, Mylar, Kapton, polycarbonate and Havar in the energy range 0.5–2.5 MeV/n.

Stopping power of Mylar for heavy ions up to copper

Abstract The stopping powers of Mylar for several heavy ions covering Z =11 to 29 in the energy range ∼0.3 to 2.3 MeV/n have been measured using the elastic recoil detection technique and twin detector system. The technique provided a unique method to generate a variety of variable energy ion species utilizing a fixed energy 140 MeV Ag 13+ primary beam from the Pelletron accelerator facility at Nuclear Science Center, New Delhi, India. Most of these measurements are new. The experimentally measured stopping power values have been compared with those calculated using LSS theory, Ziegler et al. formulation and Northcliffe and Schilling tabulations. Merits and demerits of these formulations are highlighted. Stopping power calculations using the Hubert et al. formulation have been extended successfully beyond its recommended range of validity, i.e. 2.5–500 MeV/n down to energies as low as 0.5 MeV/n.

Some environmental effect studies on the response of CR-39(Dop) plastic track detector

Abstract In the present work we have studied the effect of temperature of detector material during irradiation and the effect of storage of the detector material in vacuum prior to irradiation on detector response. For this purpose, the samples of CR-39(Dop) plastic track detectors have been exposed to 5.45 MeV alpha particles in exposure unit. The temperature of the detector has been varied from -10°C to 50°C in an interval of 10°C. To study the effect of storage in vacuum, the samples have been stored in vacuum (∼ 10 -2 torr) for different time intervals (0–72 hours) prior to irradiation. These exposed samples has been etched together in 6.25 N NaOH at 70°C for different etching times. The response of the detector has been found to become better (i) with the decrease of temperature of detector during irradiation and (ii) with the decrease of storage time in vacuum prior to irradiation.

Modification of optical properties of polycarbonate by gamma irradiation

A detailed analysis of absorption, transmission, and reflection spectra of virgin and gamma-irradiated (50–800 kGy) polycarbonate polymer reveals that both indirect as well as direct band gap coexist in virgin and gamma-irradiated samples. The indirect band gap has been found to decrease from 3.00 eV (virgin sample) to 2.78 eV at a dose of 800 kGy. The emission behaviour of gamma-irradiated polycarbonate indicates a clear-cut emission peak in the visible region at –466 nm in the samples with a gamma dose of 400 kGy and above. The refractive index has a decreasing tendency as a result of the increasing gamma dose.

dE/dx measurements for heavy ions with Z = 6-29 in polycarbonate

Abstract d E /d x measurements for heavy ions with Z =6–29 in the polycarbonate (C 16 H 14 O 3 ) absorber in the energy range ∼0.3–3.0 MeV/u have been carried out utilizing the Pelletron accelerator facility at Nuclear Science Centre, New Delhi, India. The experimentally measured stopping power values have been compared with those calculated using Lindhard, Scharff and Schiott theory, Northcliffe and Schilling, Ziegler et al. (with and without bonding corrections) and extended Hubert et al. formulations. Merits and demerits of these formulations are highlighted.

Range of heavy ions in solids: A comparative study

Abstract In the present work, a stack composed of two sub-stacks of CR-39 and Lexan polycarbonate sheets separated by a few A1 sheets of total thickness ≈5 mm has been exposed at an angle of 45° (w.r.t. the detector surface) to Fe, Al and N ions with energies 199, 123, 99.5 MeV/n, respectively, from the heavy ion accelerator (BEVALAC) at Berkeley, U.S.A. After opening the stack, the detector sheets were etched under optimum etching conditions and the range of these ions in the stack was determined. Theoretical calculations of range for these ions in the stack as well as for some other heavy ions (e.g. U, Au, La, Fe, Ar, Ne, N) in different media have been made using the formulations of Benton and Henke, Mukherjee and Nayak, Ziegler et al. and Hubert et al. Finally a comparison has been made with the experimental results.

Cole-cole analysis and electrical conduction mechanism of N+ implanted polycarbonate

In this paper, we present the analysis of the dielectric (dielectric constant, dielectric loss, a.c. conductivity) and electrical properties (I–V characteristics) of pristine and nitrogen ion implanted polycarbonate. The samples of polycarbonate were implanted with 100 keV N+ ions with fluence ranging from 1 × 1015 to 1 × 1017 ions cm−2. The dielectric measurements of these samples were performed in the frequency range of 100 kHz to 100 MHz. It has been observed that dielectric constant decreases whereas dielectric loss and a.c. conductivity increases with increasing ion fluence. An analysis of real and imaginary parts of dielectric permittivity has been elucidated using Cole-Cole plot of the complex permittivity. With the help of Cole-Cole plot, we determined the values of static dielectric constant (es), optical dielectric constant (e∞), spreading factor (α), average relaxation time (τ0), and molecular relaxation time (τ). The I–V characteristics were studied using Keithley (6517) electrometer. The elec...

An experimental study of stopping power for MeV heavy ions

A 60 MeV Ag primary ion beam was used to generate secondary recoil ion beams of Cl, K, Ca, Sc, Ti, V, Mn and Cu in the energy range 0.1-0.6 MeV . The stopping power in the carbon absorber was measured and compared with Lindhard, Scharff and Schiott (LSS) theory, the Northcliffe and Schilling model and semiempirical estimates of Ziegler et al (1985). Data for heavier ions of Ag, I and Au from other sources was also considered in order to extend the scope of such a comparison. LSS theory was found to satisfy the data within a narrow mid-velocity range (-, where is Bohr velocity). Estimates made by Ziegler et al were seen to generally agree to within a few per cent except for energies below 0.2 MeV , where deviations as high as 25% were seen. Expected oscillations could not be discerned down to the lowest ion velocities so far attempted.