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Abstract: Sex steroids are considered major regulators of sex change processes in fish. Estrogen depletion is shown to be crucial for female–male sex change initiation; however, its role in male–female sex change is largely unknown. In the present study, we examined the effects of estradiol-17β (E2) treatments on testes of initial-phase (IP) males of the three-spot wrasse (Halichoeres trimaculatus), which naturally do not undergo male–female sex change. Sexually mature IP males were fed a diet containing E2 (low, 20μg/g feed; high, 200μg/g feed) for 6 or 12 weeks, and changes in gonadal structures were examined. Percentage of sex change varied with the dosage of E2 and the duration of treatment. All individuals treated with high-dose E2 for 6 weeks had ovaries with many immature oocytes; whereas 75% of individuals treated with low-dose of E2 for 6 weeks and sampled on the 12th week had ovaries with yolky oocytes and an ovarian cavity indicating a typical mature ovary. No testicular tissue was observed in sex-reversed gonads in both treatment groups. Contrary to the previous assumptions, present results suggest that IP male wrasses have the potential to undergo male–female sex change in response to exogenous estrogen. How the presence or absence of estrogen creates sexual plasticity in gonadal germ and somatic cells remains to be clarified. [Copyright &y& Elsevier]

In order to accelerate a variety of ions in a cyclotron, it is necessary to shape the magnetic field radially according to ion species and energy. In a superconducting cyclotron this is done by using various combinations of currents in two sets of coils along with a number of trim coils. The room temperature trim coils generate large power in the vicinity of low temperature. We have shown that by optimizing the coil geometries one can avoid using trim coils for correction of field and phase. Random search method and linear programming has been used for optimizing the coil geometries. [Copyright &y& Elsevier]

Abstract: A compact inductively coupled plasma ion source (ICPIS) is developed for producing high current micron size beams for high speed micromachining applications. Angular current density (J Ω) of the beam extracted from ICPIS is measured and found to be three orders higher than that of the conventional liquid metal ion sources. An improvement in J Ω by >30% is achieved through the increase of RF power density in the plasma by reducing the plasma volume instead of operating ion source at high RF power. Studies on J Ω show that heavier ions have maximum J Ω at lower power and vice versa for the lighter ions. Ion beams of Neon, Argon, Krypton and Xenon extracted at 5 kV, have J Ω of 57, 51, 37 and 30 mA/Sr respectively at RF power in the range of 75 W–200 W. Measurements on proton beam which is very important for imaging applications show J Ω of 45 mA/Sr at 200 W. [Copyright &y& Elsevier]

Abstract: In electron cyclotron resonance (ECR) ion sources, confinement of ions and electrons is achieved with the help of an axial field in combination with a multipolar field. Generally sextupoles are used for this purpose. In a few sources, quadrupoles and octupoles also have been used. But sextupoles have been found to be most useful. We have investigated whether a combination of different multipoles can improve the performance of an ECR trap. A mixture of a sextupolar field and a dipole field has been found to enhance the electron heating to a large extent. [Copyright &y& Elsevier]

Abstract: An experimental station to monitor variations in radon and radon progeny concentrations in the gases from the thermal springs at Bakreswar, West Bengal, India has been installed. This is essentially a part of a continuous, automated, multi-parametric geochemical monitoring system (GMS) installed with a view to detect probable earthquake-related precursory changes in the spring gas emanations. The entire data acquisition system is computer driven and fully automated. Instrument readings acquired over a 24-h interval are transmitted through a tele-link facility from the field laboratory located at the thermal spring site situated about 250km away, once a day, to a workstation at our Centre in Kolkata for analysis and storage. After the system was installed during mid-December, 2004, concurrent anomalous changes in concentration profiles of 222Rn, 218Po and 214Bi occurred beyond 2 level four times during the period of present observation duration up to February 04, 2005. The monitored anomalies may be attributed to precursory dilatation responses arising due to earthquakes that had occurred subsequently in Indonesia and the Andaman and Nicobar Islands. The observed variations reveal evidence of pre-seismic radioactive heterogeneities in escaping subsurface fluids from the monitored thermal spring gases. [Copyright &y& Elsevier]

Describes a method of designing pole profiles in combined function magnets. Field due to a combined function magnet; Dipole-quadrupole magnet.

Presents a method of determining the pole profile in quadrupole magnets. Process of reducing field errors in the magnets; Factors to be considered in designing the pole profile of a magnet; Advantage of choosing error harmonics before finding the profile.

Abstract A compact accelerator based super-radiant THz source is under development at Inter University Accelerator Centre (IUAC), New Delhi. The facility is based on the principle of pre-bunched Free Electron Laser (FEL) which will produce THz radiation in the range of ∼ 0.18 to 3 THz from a modulated electron beam. A photocathode electron gun will generate a short train of micro-bunches (a "comb" beam) driven by a fibre laser system capable of producing multi micro-pulse laser beam with variable separation ("comb" laser pulse). Upon acceleration, the electron beam will be injected in to a compact undulator magnet tuned to the same frequency as the separation of the electron micro-bunches. The paper discusses the process of enhancement of super-radiant emission of radiation due to modulation in the comb beam and the conditions required to achieve maximum enhancement of the radiation power. The feasibility study of generating a comb beam at the photocathode and its transport through the beamline while preserving its temporal structure has been reported. To evaluate the characteristics of the radiation emitted from the comb beam, a C + + based particle tracker and Liẽnard–Wiechert field solver has been developed. The conceptual understanding of the emission of radiation from comb beam is shown to conform with the numerical results. The code has been used to calculate the radiation pulse energy emitted into the central cone of undulator for various comb beam configurations. [ABSTRACT FROM AUTHOR]

Presents a design of sextupole magnets with optimized circular pole faces. Importance of optimizing the circular face to minimize the field error; Application of sextupole magnets to synchrotron rings and energy beam lines in accelerators; Utilization of computer code to calculate the harmonic coefficients of sextupole magnets.

Abstract: The quadrupole magnets for FAIR Super FRS energy buncher have large usable aperture, high magnetic pole-tip field and high gradient field quality. The iron-dominated magnets with superconducting coils have to be used in this application. The NbTi coil, laminated iron, and support structure of about 22tons is immersed in liquid helium. The 4.5K helium chamber is completely covered with a thermal shield cooled by helium at 50–80K on its outer and inner surface. The helium chamber and thermal shield is enclosed in a vacuum shell. The paper presents design details of the long quadrupole. Coupled thermal, magnetic and structural analysis was carried out to design the magnet iron, magnet coil, helium vessel and support links and ensure the required gradient field quality is achieved. The paper also presents the design of support links and outer vacuum chamber. [Copyright &y& Elsevier]

Abstract: Our centre has taken up a project of development of superconducting magnetic energy storage (SMES) technology to have better power quality for its accelerator program. In the first phase, a prototype cryostable coil has been designed, fabricated and commissioned in a standard bath cryostat. The various parameters of the magnet coil have been determined in order to maximize stored energy taking into consideration the constraints like geometry, maximum current limit etc. Winding tension (Pre-stress) of 13.6MPa is maintained to keep radial stress compressive in all possible scenarios (i.e. during cool-down, excitation, etc.). Mylar is used for turn to turn insulation while 1mm thick glass epoxy based picket fences (G-10) are placed symmetrically azimuthally for layer to layer insulation as well as to ensure passage of liquid helium inside the winding. Cryostability of the conductor implies more copper to superconductor ratio and is desired as far as stability of the coil is concerned. Cryostability, however may degrade when helium vapor is trapped in between two layers. Therefore, quench behavior of the magnet along with protection system has also been studied and implemented. This paper describes issues related to design study, fabrication and also cryogenic test results of the coil. [Copyright &y& Elsevier]

Abstract: A helium evaporator for obtaining 1K temperature has been built and tested in laboratory. This will function primarily as the precooling stage for the circulating helium isotopic gas mixture. This works on evaporative cooling by way of pumping out the vapour from the top of the pot. A precision needle valve is used initially to fill up the pot and subsequently a permanent flow impedance maintains the helium flow from the bath into the pot to replenish the evaporative loss of helium. Considering the cooling power of 10mW @1.0K, a 99.0cm3 helium evaporator was designed, fabricated from OFE copper and tested in the laboratory. A pumping station comprising of a roots pump backed by a dry pump was used for evacuation. The calibrated RuO thermometer and kapton film heater were used for measuring the temperature and cooling power of the system respectively. The continuously filled 1K bath is tested in the laboratory and found to offer a temperature less than 1.0K by withdrawing vapour from the evaporator. In order to minimize the heat load and to prevent film creep across the pumping tube, size optimization of the pumping line and pump-out port has been performed. The results of test run along with relevant analysis, mechanical fabrication of flow impedance are presented here. [Copyright &y& Elsevier]

Abstract: A compact, high brightness 13.56MHz inductively coupled plasma ion source without any axial or radial multicusp magnetic fields is designed for the production of a focused ion beam. Argon ion current of density more than 30mA/cm2 at 4kV potential is extracted from this ion source and is characterized by measuring the ion energy spread and brightness. Ion energy spread is measured by a variable-focusing retarding field energy analyzer that minimizes the errors due to divergence of ion beam inside the analyzer. Brightness of the ion beam is determined from the emittance measured by a fully automated and locally developed electrostatic sweep scanner. By optimizing various ion source parameters such as RF power, gas pressure and Faraday shield, ion beams with energy spread of less than 5eV and brightness of 7100Am−2sr−1eV−1 have been produced. Here, we briefly report the details of the ion source, measurement and optimization of energy spread and brightness of the ion beam. [ABSTRACT FROM AUTHOR]

Abstract: The ion energy distribution of inductively coupled plasma ion source for focused ion beam application is measured using a four grid retarding field energy analyzer. Without using any Faraday shield, ion energy spread is found to be 50 eV or more. Moreover, the ion energy distribution is found to have double peaks showing that the power coupling to the plasma is not purely inductive, but a strong parasitic capacitive coupling is also present. By optimizing the various source parameters and Faraday shield, ion energy distribution having a single peak, well separated from zero energy and with ion energy spread of 4 eV is achieved. A novel plasma chamber, with proper Faraday shield is designed to ignite the plasma at low RF powers which otherwise would require 300–400 W of RF power. Optimization of various parameters of the ion source to achieve ions with very low energy spread and the experimental results are presented in this article. [ABSTRACT FROM AUTHOR]

Phase transition from anatase to rutile for the 70nm TiO2 crystallite has been investigated by the time differential perturbed angular correlation (TDPAC) technique. The study involved the annealing of the TiO2 nanocrystals, adsorbed with the nuclear probe (181Hf/181Ta) at trace level, at different temperatures for different durations. The TDPAC measurement was also supported by XRD measurement where the width of the peaks increases with the increase in annealing temperature indicating a crystal growth. The samples annealed up to 823K for 4h showed no phase transition, except for the growth of the crystallites. However, it showed phase transition at the same temperature (823K), when annealed for longer duration, indicating the slower kinetics of the phase transition process. Further the sample, when annealed at 1123K for 4h, showed phase transition. It has also been observed that the 181Hf tracer, adsorbed on 70nm anatase TiO2, diffuses from surface to bulk during the phase transition process and the extent of diffusion in anatase differs from that in rutile phase. However, surface to bulk mass-transfer is found to play a significant role in the phase transition process. [Copyright &y& Elsevier]

Abstract: K-500 superconducting cyclotron is in the advanced stage of commissioning at VECC, Kolkata. Superconducting magnet is one of the major and critical component of the cyclotron. It has been successfully fabricated, installed, cooled down to 4.2K by interfacing with LHe plant and energized to its rated current on 30th April, 2005 producing magnetic field of 4.8T at median plane of cyclotron. The superconducting magnet (stored energy of 22MJ) consists of two coils (α and β), which were wound on a sophisticated coil winding machine set-up at VECC. The superconducting cable used for winding the coils is multi filamentary composite superconducting wire (1.29mm diameter) having 500 filaments of 40μm diameter Nb–Ti in copper matrix which is embedded in OFHC grade copper channel (2.794mm×4.978mm) for cryogenic stability. The basic structure of coil consists of layer type helical winding on a SS bobbin of 1475mm ID×1930mm OD×1170mm height. The bobbin was afterwards closed by SS sheet to form the LHe chamber. The total weight of the coil with bobbin was about 6tonne and the total length of the superconducting cable wound was about 35km. Winding was done at very high tension (2000PSI) and close tolerance to restrict the movement of conductor and coil during energization. After coil winding, all four coils (two each on upper and lower half of median plane of cyclotron) were banded by aluminium strip (2.7mm×5mm) at higher tension (20,000PSI) to give more compressive force after cool down to 4.2K for restricting the movement of coil while energizing and thereby eliminating the chances of quench during ramping of current. After completion of coil winding by October, 2003, cryostat assembly was taken up in house. The assembly of cryostat (13tonne) with support links (9 Nos.) refrigeration port, instrumentation port, helium vapour cooled current loads, etc. was completed by June, 2004. Meanwhile assembly of magnet frame was taken up and the cryostat was positioned in the magnet frame with proper alignment by August, 2004. After installation of cryostat on magnet, the cryostat was connected to the helium refrigerator/liquefier, having refrigeration capacity of 200W and 100l/h in liquefier mode with LN2 pre-cooling. The cryogenic delivery system supplying the liquid helium and liquid nitrogen to the superconducting magnet was successfully commissioned in November, 2004. The cool down of the cryostat to 10K took around 8 days following which the LHe was filled in the cryostat (300l) on 15th January, 2005. Subsequently the superconducting coils (α and β) were energized by two DC current regulated power supplies (20V, 1000A, 10ppm stability) with slow and fast dump resistors connected externally across the superconducting coils for protection of coils at the time of power failure and quench. The paper describes the intricacies involved in coil winding, winding set-up, assembly of cryostat, cooling down the superconducting coils, filling by LHe and energization to rated current. The paper also highlights the operating experience of superconducting magnet and related test results. [Copyright &y& Elsevier]