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22-27 October 2018
Mahatma Mandir Conference Centre
Asia/Kolkata timezone
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Design and testing of X-mode reflectometry system for coupling studies of lower hybrid waves in ADITYA-U tokamak

24 Oct 2018, 14:00
4h 45m
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Poster P4 Posters

Speaker

Mr Jagabandhu Kumar (InIPR)

Description

A new passive active multijunction antenna (PAM) has been designed and is in advance stages of fabrication for ADITYA-U tokamak. The PAM antenna has the ability to couple lower hybrid waves (LHW’s) in to the plasmas near cut-off densities. The coupling of LHW’s depends on plasma density and its profile near the mouth of the antenna. To determine these plasma parameters, experimentally, an X-mode reflectometry system has been designed and is under fabrication. The reflectometery system is designed to operate in the frequency range from 26 GHz to 36 GHz and would cover a density range from SOL to 5x1018 m-3 with a toroidal magnetic field between 1 T and 1.5 Tesla. The total frequency band is swept in 100 microsecond to improve density profile reconstruction. The ADITYA reflectometer is built to operate in frequency modulation continuous mode (FW-CM) or at a fix frequency mode for density fluctuation study. The reflectometery consists of two parts, i.e., the transmitter and the receiver. The transmitter mainly consists of microwave source, amplifier, a single sideband modulator (SSBM), frequency multiplier and a horn antenna to launch x-mode in to the plasma. Similarly the receiver consists of horn antenna, amplifier, mixer and de-modulator. In the de-modulator section, a quadratic demodulation (IQ) is used to extract in-phase and quadrature-phase information from the reflected signal. These measurements provides the density profile information. Finally, an ADC with 12 bit resolution will convert the analog signal in to a digital signal which will be processed through a FPGA based data acquisition system. Sectorial E-plane horn antenna is designed using commercial available software for transmitting/receiving microwave signal to/from the plasma and has an input cross-section of 7.112mm x 3.556mm and output cross-section of 7.112mm x 63.64mm. The length of antenna is 120mm. The analysis of the antenna meets our design requirement of high gain (16dB), low insertion loss and low VSWR (1.1). As the sectorial E-plane antenna is placed inside the tokamak, the above mentioned gain is significant. The details of the reflectometry system focusing on the design of sectorial E plane horn antenna, microwave hardware, test result of different microwave components, along with the density profile reconstruction technique will be presented in this paper.
Country or International Organization India
Paper Number EX/P4-22

Primary author

Co-authors

Mr Amit Patel (Charotar University of Science and Technology, Changa, Anand, Gujarat,India) Mr Chetan Virani (InIPR) Mr Keyur Mahant (Charotar University of Science and Technology, Changa, Anand, Gujarat,India) Mr Kiran Ambulkar (InIPR) Dr Pramod Sharma (InIPR) Mr Yogesh Jain (InIPR)

Presentation Materials

Paper