Saurabh Saha

Simple analog correlator

An analog correlator has been constructed using a delay unit which is realized by simulation of the sixth-order Pade approximated result of exp(-jomegatau) where j= radical-1, omega the angular frequency of the signals of concern, and tau the delay in seconds. Several sinusoidal signals and a noise spectrum have been autocorrelated with this correlator; also, it has been applied to determine the impulse response of an RC low-pass filter. Results are in good agreement with theoretical predictions. This correlator has been used to study low- frequency signals in the region 1-50 kHz.

Direct display of electron temperature oscillation in a plasma

A simple differential technique using a floating Langmuir probe and a hot probe has been used to obtain direct oscillographic display of electron temperature oscillation in a plasma. The reliability of the method has been tested in artificially generated moving striations in the positive column of a cold cathode argon discharge (Id=8 mA; p=0.1 torr; 2r=5 cms).

Measurement of plasma diamagnetism in the SINP tokamak by a flux loop system inside the vacuum vessel

Plasma diamagnetism has been measured in the SINP tokamak by a toroidal flux loop placed inside the vacuum vessel. The flux due to the strong toroidal field has been compensated for by a coplaner annular loop which encircles but does not contain the plasma column. The influence of the eddy currents in the vacuum vessel and the conducting shell in these loops has been calculated analytically by a circuit model using the theory of linear networks and compensated accordingly. This method has been shown to yield an almost exact compensation for toroidal flux (∼0.01%) as well as pickups from other fields. Typical results with plasma shots have been presented.

Real time measurement of plasma position in the SINP tokamak

An electronic hardware has been developed for the real time determination of the position of the plasma column in the SINP tokamak. The method is based on the Fourier integration of the poloidal magnetic field using cos θ and sin θ coils. The spurious pickups in these coils due to time varying magnetic fields have been explained by a model as being due to eddy currents in the vacuum vessel and the conducting shell. These pickups have been compensated in the hardware by simulating the effects of the eddy currents by linear networks. This diagnostic provides outputs proportional to the horizontal and vertical displacements of the plasma column at three toroidal locations simultaneously. An output proportional to the plasma current is also available. Performance evaluation shows that for both plasma current and displacements, the hardware outputs are in good agreement with the values computed by software.

Excitation of pure ion Bernstein waves by the interaction of an energetic ion beam with the beam-created plasma

The results of the interaction of a high energy ion beam with its self-created plasma in an axial magnetic field is presented. The authors observed unstable waves propagating in the azimuthal direction and identified it as the pure ion Bernstein waves from a study of its propagation characteristics. The experimental results are compared with the linear theory of electrostatic instabilities in a plasma whose ion energy distribution function is a mixture of a Maxwellian background and a delta -function component. Propagation of the unstable waves in a direction opposite to the direction of ion Larmor rotation is observed which corroborates the theoretical result in presence of a radial density gradient.

To Study Seasonal Variation in Serum Total Testosterone Levels in Adult Males

Levels of serum total testosterone vary with season. The levels of serum total testosterone have profound effect on metabolism of the body and affects weight and waist circumference. The present study was conducted to assess the seasonal changes in serum total testosterone levels. The study was conducted in 55 healthy male medical students of first professional M.B.B.S. and employees of 18 to 50 years age group at G.S.V.M. Medical College, Kanpur. The serum total testosterone levels were estimated by ELISA kit with the help of ELISA reader in the months of December & January and May & June. The change in mean weight, mean height, BMI, and Waist to Hip ratio of the subjects were found stastistically insignificant(p>0.05). Waist circumference in Dec-Jan was 81.3±7.9 cm and in May-June was 80.6±8.0 cm. This decrease in waist circumference was significant (p<0.05). The serum total testosterone in Dec-Jan was 4.43±0.99 ng/ml and in May-June was 3.05±0.85. This decrease in serum total testosterone was significant (p<0.05).

To Study Seasonal Variation in Autonomic Parameters in Adult Males

The present study was conducted to assess the seasonal changes in autonomic parameters. The study was conducted in 55 healthy male medical students of first professional M.B.B.S. and employees of 18 to 50 years age group at G.S.V.M. Medical College, Kanpur. The change in mean weight, mean height, body mass index(BMI), and Waist to Hip ratio of the subjects were found stastistically insignificant (p>0.05). Waist circumference in Dec-Jan was 81.3±7.9 cm and in May-June was 80.6±8.0 cm. This decrease in waist circumference was significant (p 0.05).

Hard x-ray correlation analysis as a diagnostic tool for the measurement of magnetic turbulence in tokamaks

A diagnostic has been developed for the measurement and characterization of the magnetic turbulence occurring in the core region of a tokamak. A specially shielded detector looking in the tangential direction has been employed to measure the thin target bremsstrahlung from the core plasma. The thick target bremsstrahlung from the limiter is also recorded at the same time. Auto- and cross-correlation analyses have been shown to yield, respectively, the stochasticity of the magnetic fluctuations in the core region and the consequent diffusion coefficient of the nonthermal electrons. The measured stochasticity bears a relationship with the diffusion coefficient. Data obtained from internal magnetic probes corroborate the above trend but the hard x-ray measurement data are shown to be more reliable than those obtained from magnetic probes.