Indian Journal of Pure and Applied Physics

Indian Journal of Pure and Applied Physics

Total visitors: 1,621 since 06-06-06

ISSN: 0019-5596		CODEN: IJOPAU 44 (6) 419-490
VOLUME 44	NUMBER 6	JUNE 2006

CONTENTS

Nuclear Physics
Alpha radioactive air pollutants in different types of dwellings using solid-state nuclear track detectors	423
Mahabir Nain, R P Chauhan & S K Chakarvarti*
Extension and diffuseness parameters of semi-phenomenological nucleon density distribution	426
I Ahmad*, Jamal H Madani , Bahaa Al-Duin & M N Raffah
Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics
Improve energy distribution and beam quality of CO₂ waveguide laser array by phase-matched plate	431
Chien-Wa Ho, Ruey-Shyan Chang, Chern-Sheng Lin*& Sen-Yen Shaw
Condensed Matter: Structure, Mechanical and Thermal Properties
Correlation between EPR, dielectric spectroscopic and conductivity studies of lithium substituted Na₂Ti₃O₇ ceramic	435
D Pal, R P Tandon٭ & Shripal
Melting point variation with pressure and material synthesis with a laser heated diamond anvil cell	440
S Meenakshi, V Vijayakumar & B K Godwal*
Physical properties of PbO-Al₂O₃-B₂O₃ glasses doped with Cr₂O₃	446
M Rami Reddy, M Srinivasa Reddy & N Veeraiah*
Crystal growth and characterization of thiourea mixed ammonium dihydrogen phosphate	455
A Jayarama & S M Dharmaprakash*
Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Synthesis of MgB₂ from magnesium rich powders	461
Suchitra Rajput, Sujeet Chaudhary & Subhash C Kashyap*
Study of optical absorption and optical band gap determination of thin amorphous TeO₂-V₂O₅-MoO₃ blown films	468
Mohammad Elahi & Dariush Souri*
Interdisciplinary Physics and Related Areas of Science and Technology
Novel technique of pulse width modulator design using a ring oscillator	473
B C Sarkar & M K Mandal*
Traceability of 100 kV dc high voltage measurements at NPL, India	478
S K Mahajan, K B Ravat* & P C Kothari
Variation of width of the hysteresis loop with temperature in an emitter-coupled Schmitt trigger	482
A Gohain Barua* & Banty Tiru

__________

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 423-425

Alpha radioactive air pollutants in different types of dwellings using
solid-state nuclear track detectors

Mahabir Nain, R P Chauhan^a & S K Chakarvarti^b

Department of Physics, Government College, Karnal 132 001

^aIndira Gandhi National College, Ladwa, Kurukshetra 136 132

^bDepartment of Applied Physics NIT, Kurukshetra 136 119

Received 22 August 2005; revised 5 April 2006; accepted 13 April 2006

The alpha radioactive air pollutants like radon and its progeny are the major contributors in the radiation dose received by general population of the world. It has been estimated that the radon and its progeny constitute more than 50% of the dose equivalent received by general population from all sources of radiation, both naturally occurring and man-made. Radon (²²²Rn), a progeny of ²³⁸U, is a colourless, odourless noble gas, which is radioactive, and causes health hazards not only to uranium miners but also people living in normal houses and buildings. In the present work, measurements of alpha radioactive radon and its progeny concentration in different types of dwellings of some villages in Haryana have been carried out. In cemented dwellings, the equilibrium equivalent concentration (EEC) of radon varied from 64-80 Bq m^-3 with an average of 72 ± 3 Bq m^-3 and the annual effective dose varied from 2.7-3.4 mSv with an average of 3.1 ± 0.13 mSv. In brick dwellings, the equilibrium equivalent concentration (EEC) of radon varied from 81-106 Bq m^-3 with an average of 93 ± 4 Bq m^-3 and the annual effective dose varied from 3.5 to 4.6 mSv with an average of 4.0 ± 0.0.2 mSv. In mud dwellings, the equilibrium equivalent concentration (EEC) of radon varied from 102-148 Bq m^-3 with an average of 125 ± 9 Bq m^-3 and the annual effective dose varied from 4.4 to 6.4 mSv with an average of 5.4 ± 0.4 mSv.

Keywords: Solid-state nuclear track detector, Alpha radioactive, Air pollutants, Radon

IPC Code: G01T, H01L

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 426-430

Extension and diffuseness parameters of semi-phenomenological nucleon
density distribution

I Ahmad, Jamal H Madani, Bahaa Al-Duin & M N Raffah

Department of Physics, Faculty of Science, King Abdulaziz University, P O Box 80203, Jeddah, Saudi Arabia

Received 26 April 2005; accepted 4 April 2006

Extension and surface diffuseness parameters of Gambhir-Patil (GP) semi-phenomenological proton, neutron and their weighted average densities have been calculated for a large number of nuclei in the mass number range 12£A£238 following the method proposed by Friedrich and Voegler [Nucl Phys A, 373 (1982) 192] who used it to study the salient features of nuclear charge density distribution. It is found that the extension parameter (diffraction radius) values of the GP proton density are in good agreement with those extracted from the experimental charge form factors. The corresponding surface diffuseness parameter values are also in reasonably good agreement with the experimental values with some exceptions. The mass number dependence of the diffraction radii and diffuseness parameters of the GP proton, neutron densities, and their average have been studied.

Keywords: Nucleon density distribution, Nuclear extension parameter, Nuclear surface diffuseness, Semi-phenomenological model

IPC Code: G01R33/48

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 431-434

Improve energy distribution and beam quality of CO₂ waveguide laser array by phase-matched plate

Chien-Wa Ho₁, Ruey-Shyan Chang₁, Chern-Sheng Lin₂& Sen-Yen Shaw₃

¹Department of Electro-Optical Engineering, National United University, Miauli, Taiwan

²Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan

³ Department of Electrical Engineering, National Tsing Hua University, Hsinchu, Taiwan

Received 7 February 2005; accepted 27 February 2006

According to the theorem proposed herein, if we put a phase-matched plate at the near-field of CO₂ laser array, it can restrain the far-field off-axis lobes output energy of laser beam. In addition, we use the parameter to evaluate the laser beam quality. In this paper, when a phase-matched plate is used to near-field, energy can centralize to 92.92%, and the beam qualityof far-field is 5.63. The phase-matched plate not only can centralize energy more efficiently but also can improve the beam quality quite substantially.

Keywords: Beam quality, Centralized energy, Phase-matched plate, Waveguide laser array

IPC Code: H01P, H01S

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 435-439

Correlation between EPR, dielectric spectroscopic and conductivity studies of lithium substituted Na₂Ti₃O₇ ceramic

D Pal, R P Tandon٭ & Shripal

Department of Physics, P P N P G College, Kanpur 208 001

٭Department of Physics and Astrophysics, Delhi University, Delhi 110 007

Received 31 January 2006; revised 28 March 2006; accepted 17 April 2006

The lithium substituted Na₂Ti₃O₇ ceramics with a general formula (Na_2-xLi_xTi₃O₇) with (x = 0.1) have been synthesized by high temperature solid-state reaction technique. Preliminary EPR analysis and detailed temperature and variable frequency dielectric, conductivity measurements were carried out on the prepared sample. The lithium ions are accommodated with the sodium ions in the interlayer space. The EPR spectrum of Na_1.9Li_0.1Ti₃O₇confirms the partial reduction of Ti⁴⁺ ions to Ti³⁺. The observed dispersion in the dielectric constant-temperature relation can be explained on the basis of Maxwell-Wagner model. The conductivity plots between ln (σT) versus 1000/T have been divided into four regions. The various conduction mechanisms in the different regions have been stressed in this paper. The interlayer ionic conduction seems to play major role in conduction towards higher temperature.

Keywords: Sintering, Dielectric properties, Ionic conductivity, TiO₂

IPC Code: G01R27/26

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 440-445

Melting point variation with pressure and material synthesis by a laser heated diamond anvil cell

S Meenakshi, V Vijayakumar & B K Godwal*

High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085

Received 30 August 2005; accepted 10 April 2006

The details of a high temperature-high pressure (HT-HP) facility based on the coupling of the laser heating by diamond anvil cell are described. The measured melting curve of platinum up to 12 GPa pressures is compared with existing piston-cylinder data and with theoretical calculations. The reasonable agreement reveals the utility of this technique for the reliable measurements of high temperature-high pressure phase diagrams and melting curves for materials. The suitability of hexamethylenetetramine (HMT) as a precursor for the synthesis of C₃N₄ at HT-HP, has been investigated. It is conjectured that CN_x (C₃N₄) or C:H is formed at HT-HP, but is not quenchable.

Keywords:Diamond anvil cell, Melting point, Material synthesis, High pressure, High temperature

IPC Code: G01N 25/04, B01J 3/06

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 446-454

Physical properties of PbO-Al₂O₃-B₂O₃ glasses doped with Cr₂O₃

M Rami Reddy^†, M Srinivasa Reddy & N Veeraiah

Department of Physics, Acharya Nagarjuna University PG Centre, Nuzvid 521 201, Andhra Pradesh

^†Department of Physics, QIS College of Engineering, Ongole, Andhra Pradesh

Received 18 September 2005; revised 3 January 2006; accepted 6 March 2006

PbO-Al₂O₃-B₂O₃ glasses containing different concentrations of Cr₂O₃ ranging from 0 to 0.4 mol % were prepared. The dielectric properties (constant e, loss tand, ac conductivity s_ac over a range of frequency and temperature and breakdown strength) of these glasses have been studied. The results of these studies were analyzed with the aid of data on optical absorption, IR spectra and thermoluminescence studies on these glasses. The analysis suggests that the chromium ions exist in Cr³⁺ state which act as modifiers. When Cr₂O₃ is present in higher concentrations in the glass matrix, these ions seem to exist in Cr⁶⁺ state and take part in network forming positions with structural units.

Keywords: PbO-Al₂O₃-B₂O₃, Chromium ions, Optical absorption, Thermoluminescence, Dielectric properties

IPC Code: G01R 27/26, F21K 2/04

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 455-460

Crystal growth and characterization of thiourea mixed
ammonium dihydrogen phosphate

A Jayarama & S M Dharmaprakash

Department of Physics, Mangalore University, Mangalagangotri 574 199

Email: smdharma@yahoo.com

Received 10 August 2005; accepted 28 February 2006

Single crystals of thiourea mixed ammonium dihydrogen phosphate (TADP) have been grown in solution by slow evaporation technique at ambient temperature (30°C). TADP crystallises in body centered tetragonal system with unit cell parameters a= 7.4652Å, b=7.4970Å, c=7.5415Å. The powder X-ray diffraction pattern has been recorded and indexed. The UV-Vis-NIR transmittance and FT-IR spectrum have been recorded in the range 200-1500 nm and 400-4000 cm^-1, respectively. The lower cut-off wavelength is 230 nm in the UV region, which is higher than that of ADP crystal. The presence of functional groups has been confirmed by FTIR analysis. The microhardness of TADP was evaluated using Vicker’s indentation method. TADP crystals are thermally stable up to 200°C and shows optical non-linearity for Nd:YAG laser at 1.064 mm wavelength. The preliminary data indicate that the harmonic generation efficiency of TADP is three times that of pure ADP.

Keywords: Crystal growth, Ammonium dihydrogen phosphate, FTIR, Microhardness

IPC Code: C30B

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 461-467

Synthesis of MgB₂ from magnesium rich powders

Suchitra Rajput, Sujeet Chaudhary & Subhash C Kashyap

Department of Physics, Indian Institute of Technology Delhi, New Delhi 110 016

Received 27 January 2006; accepted 7 April 2006

Superconducting bulk MgB₂ samples have been synthesized by employing a modified heat treatment without using any additional process steps generally undertaken in view of the substantial loss of Mg during sintering owing to its high vapour pressure at the processing temperature. Starting with Mg rich powder mixtures having different atomic ratios of Mg:B (as against the nominally required 1:2 ratio), we have obtained superconducting MgB₂ samples showing a transition temperature (T_c) in the range 40.4-40.7K when synthesized at sintering temperatures in the range 720-900°C. Typically, a MgB₂ sample (T_c= 40.5K) obtained from heat treating Mg and B in the ratio of 2:2 at 870°C for 1h duration exhibited critical current density in excess of 1´10⁷ A/m² at »38K. Our results further show that MgO is not detrimental to superconductivity.

Keywords: MgB₂, Transition Temperature, Susceptibility, Superconductivity

IPC Code: H01L 39/00

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 468-472

Study of optical absorption and optical band gap determination of thin amorphous TeO₂-V₂O₅-MoO₃ blown films

Mohammad Elahi¹ & Dariush Souri²

Department of Physics, Faculty of Science, Razi University, Kermanshah, Iran

Received 16 February 2005; revised 8 March 2006; accepted 31 March 2006

The optical absorption coefficient of amorphous 40TeO₂-(60-x) V₂O₅-xMoO₃ thin films was determined in a spectral range 190-1100 nm at room temperature. The fundamental optical absorption edge was sharp. The optical gap generally increases as the proportion of MoO₃ in the mixed films increases. The width of the tail of the localized states in the band gap was determined for different compositions, which is because of the lack of long range order. The results of the usual density-of-state models of amorphous materials are presented in this paper.

Keywords: Optical absorption, Thin amorphous blown films, Optical band gap

IPC Code:G01J3/28

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 473-477

Novel technique of pulse width modulator design using a ring oscillator

B C Sarkar & M K Mandal*

Department of Physics, Burdwan University, Burdwan 713 104, West Bengal

*Department of Physics, National Institute of Technology, Durgapur, Mahatma Gandhi Avenue
Durgapur 713 209, West Bengal

E-mail: nitmkm@yahoo.co.in

Received 8 September 2005; accepted 2 March 2006

A novel technique of pulse width modulation using a multiphase ring oscillator and a multiplexer-based digitally controlled phase shifter (DCPS) has been presented. The proposed circuit can produce 0 to 100 % variation of the width of the pulse train, depending on the control word applied to DCPS. Experimental results obtained in a prototype circuit confirm the design algorithm proposed in this work.

Keywords: Ring oscillator, Phase shifter, Pulse width modulator

IPC Code: H03B

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 478-481

Traceability of 100 kV dc high voltage measurements at NPL, India

S K Mahajan, K B Ravat & P C Kothari

National Physical Laboratory, Dr K S Krishnan Marg, New Delhi 110 012

Received 20 September 2005; revised 3 March 2006; accepted 17 April 2006

Recently, dc high voltage laboratory has been established at National Physical Laboratory, India (NPLI) for calibration of high voltage (HV) equipment. High Voltage resistive divider is the heart of dc high voltage measurements. The traceability of HV measurements is directly related to divider’s traceability to Josphson voltage standard, which is the primary standard of dc voltage. In-house calibration of HV divider using traceable dc calibrator and 10 V reference standard has been discussed in the present paper. The overall uncertainty of measurement has also been calculated and is about
10 ppm.

Keywords: Calibration, High voltage measurement, Traceability

IPC Code:G12B13/00

Indian Journal of Pure & Applied Physics

Vol. 44, June 2006, pp. 482-485

Variation of width of the hysteresis loop with temperature in an
emitter-coupled Schmitt trigger

A Gohain Barua* & Banty Tiru

Department of Physics, Gauhati University, Guwahati 781 014

*E-mail: agohainbarua@yahoo.com

Received 29 September 2005; revised 13 March 2006; accepted 12 April 2006

Schmitt trigger circuits are designed with pnp transistors: the first circuit with two 2SB324 germanium transistors, and the second one with two U188 silicon transistors. At certain collector resistances in the second stage- or the driven- transistor, the variations of the hysteresis loop width in temperature range –95-75°C for the first circuit, and -100-150°C for the second one have been observed. The increase in the loop width with temperature is shown.

Keywords: Hysteresis loop, Schmitt trigger, Transistor cut-off, Transistor saturation

IPC Code: H01L 27/00

A Jayarama & S M Dharmaprakash*