S.K. Sharma

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.

Stopping power of heavy ions in solids: A comparative study

Abstract A comparative study of various stopping power formulations have been made by comparing the calculated stopping power values with the corresponding experimental values for different projectiles, e.g. U, Pb, Au, Xe, Mo, Kr, Cu, Ca, Ar, P, O, N, Li etc. in different targerts, e.g. Be, C, Al, Si, Ti, Ni, Cu, Zr, Ag, Ta, Au, Bi, U, (CH) n , Mylar, Hostaphan etc. at various energies (≈ 3–400 MeV / n ). It has been observed that the Hubert et al . formulation provides results in best agreement with the experimental results for all projectile and target combinations in this energy domain.

Energy loss of MeV heavy ions in carbon

Abstract A novel technique, using secondary forward recoil ions generated in thin standard targets by energetic very heavy primany ion beam, has been employed to measure energy loss of several ion species (Z1 = 8 to 29) covering energies between 0.1 and 1.0 MeV/u. Energy variation was simp y affected by changing the detector angle between 35° to 70°, avording the dominant elastic scattering of the primary beam. A twin detector permitted simultaneous measurement of both unabsorted and absorbed spectra. The experimental data on stopping power are compared with evaluated values using LSS theory and TRIM. A better understanding of the validity of available theoretical evaluations has become possible, with a need for higher precision in experimental data in some cases.

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.

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.

Stopping power of carbon for Si, Fe, Ni and Cu ions using the ERDA technique

Abstract We have been carrying out systematic random stopping power experiments in the low velocity region ( ν 0 to 5 ν 0 , where ν 0 is the Bohr velocity) using heavy ions ( Z 1 = 8 to 29). The objective is to supplement in a significant way the currently available scanty data in this region. In order to optimise the data collection for a variety of heavy ions, we have used our recently developed technique of adopting a twin detector in conjunction with Elastic Recoil Detection Analysis (ERDA) technique. In continuation, we now report energy losses of Si, Fe, Ni and Cu ions in carbon foil in the energy range 0.1-1.1 MeV/u. Here we are reporting experimental stopping power data for Ni ions in the velocity region of 0.1-0.6 MeV/u. Most of the experimental data have an error of around 6%. Comparison of the now available data have been made with existing theoretical and semiempirical models.

Stopping power of carbon for heavy ions upto copper

Abstract Stopping powers for ions of O, Cl, Sc, Ti, Cr, Mn, Fe and Cu in the energy range 0.2–1.0 MeV/n have been measured in carbon foils using the elastic recoil ion technique and a twin detector system. Very heavy ions of Gold and Iodine of energy around 100 MeV have been employed to generate the various recoil ions using pure thin (≈ 1000A) elemental/compound targets. The data have an overall average accuracy of 6%. The stopping power for Sc, Mn and Fe ions in the energy region 0.2–1.0 MeV/n as well as those for Ti and Cu ions in the energy region below 0.45 MeV/n are perhaps the first such measurements. The limitations of LSS theory even within the range of its applicability has been demonstrated. Varelas and Biersack estimates agree well in the region of their applicability lying above the ion velocity limit set for LSS theory. Northcliffe and Schilling predictions as well as the TRIM estimates provide the best fit with data. However, one does notice variations upto 25% for some ions at lower energi...

Stopping power of mylar and carbon

Abstract The energy loss measurements for O and Ti ions were done in a 2 μ mylar foil and A ions in carbon foil (75.5 μg/cm2). The choice of the mylar was due to its wide application in ERDA (Elastic Recoil Detection Analysis) experiments and thin windows for gaseous detectors. As a new approach, recoil ions produced in heavy ion scattering (ERDA) were utilised for (dE/dx)e measurements. The energy loss thus measured for different energies of the secondary beam selected by changing the detection angle have been reported earlier by us. In the present work these experimental stopping powers are compared with values obtained using various theoretical models as well as semi emperical model and TRIM simulation code. LSS theory is used for low velocity case and Bethe formula for high velocity case. In the intermediate velocity region, suitable modifications of Bethe formula and Braggs rule for stopping power of compounds (Mylar) has been used and reasonable agreement obtained

MeV heavy ion stopping power measurements using NSC Pelletron

Abstract Surface modification and characterization are being undertaken increasingly using the MeV heavy ion beams. Interpretation of such data requires reliable and precise values of stopping powers involved. Sufficient data exists above 2.5 MeV/n but less information is available at lower energies. The present series of experiments report the results of stopping power measurements for various ion species between Z = 8 and 29, covering the energy range ∼ 0.2–1.0 MeV/n in carbon. The elastic recoil ion detection system provided a unique method to generate variety of variable energy ion species utilising a fixed energy heavy (Z = 47, 53, 79) projectile beam from the NSC Delhi 15 MV Pelletron facility. The data has been compared with available theoretical and semiempirical fitting treatments. Relative merits and demerits of these formulations have been highlighted. Future projections to our line of investigation have been indicated in the light of some recent innovative theoretical predictions.

Comparative study of various stopping power formulations for heavy ions in solids

A comparative study of different energy loss formulations viz. Benton and Henke, Mukherjee and Nayak, Zieglar et al. and Hubert et al. has been done at lower energies (0.5 to 5 MeV/n) with the aim to identify their relative validity in this energy range. Calculated results using these formulations have been compared with experimental results available in literature.