[en] For a RF ion source test facility, the driver is used to produce plasma, and the matching unit is the key for the driver to absorb RF power. The driver's impedance could be equivalent to a resistance and an inductance in series. A matching unit which consisted of an RF transformer and two variable capacitances was chosen, it was analyzed by an ideal transformer model and its electrical parameters were derived under the condition of matching. When a quartz glass driver was mounted onto the test facility at HUST, a matching unit was implemented, it transmitted RF power into the driver and then plasma was successfully produced. (authors)

[en] The paper presents the results obtained from the study of a radiofrequency (RF) oscillator developed for use in an RF ion source, for the development of a low energy charged particle accelerator. An investigation was made on the main factors attributing to the operating frequency of the oscillator. Four different RF coils are constructed using a copper tube for studying the different operating frequencies. The RF output power was measured using a modified form of the photometric method. The variation of RF power with operating frequency are discussed. (paper)

[en] Plasma column works like an RF antenna which uses plasma element instead of metal conductor. This plasma acts as a monopole transmission antenna, whose transmission wavelength corresponds to the size of plasma length by varying plasma column length and power. One can transmit/receive varied frequency signals using plasma column. Plasma column transmission/reception can be controlled and varied in real time to program the system for different frequency hopping. This paper presents automation system developed for transmission/reception of RF waves using plasma column. The power spectrum is plotted in order to check the received signal strength of the particular central frequency. It has the facility to feed the experimental data or any kind of data profiles of user choice. Labview based control system has been developed to control the plasma column length and power as per the transmitted frequency. USRP (Universal Software Radio Peripheral) is a device which receives / transmits radio frequency, in our system configuration. The USB based NI USRP has been used as a receiver as well as transmitter. The Receiver (Rx) application initially configures USRP with the known frequency to receive the new frequency, once the transmission (Tx) application sends the new frequency, the Rx application receives and tunes USRP with the new frequency to receive the data in that frequency. From the received frequency the length of the plasma column is calculated, then by using experimental data i.e. length vs plasma power data file, the power in dbm is extracted from the file according to the calculated length. The RF generator power automatically set by the control system with the extracted power information by length vs power data file. The RF generator have TCP/IP and USB interface to connect with computer. The received data is processed and the power spectrum is plotted, the peaks above the specified threshold are stored in to the file. The Tx application transmits sound files and the data files with multiple iterations. (author)

[en] High power radio frequency waves in the megahertz frequency range have a wide range of application like tokamak fusion reactor, accelerators, aerospace and defense sector. The RF waves can be transmitted via rigid coaxial transmission lines (TL) at high power. In order to radiate the desired wave spectrum from an antenna and reduce the VSWR in the unmatched TL section just after the antenna feeder, a prematching stub is often required. The prematching stub necessarily required to be variable instead of fixed, to adjust the VSWR depending on frequency of operation and plasma condition from shot to shot basis. Furthermore, it is also imperative to pressurize it to reduce the chances of high voltage node arcing in the unmatched TL sections and components. A new pressurized and mechanically variable stub is designed to cater this requirement. The pressurizing capability is checked in house and a pressurizable multipin feedthrough is also designed with the help of local vendor. Feedthrough are successfully tested up to 4.5 bar for 6 hours without any detectable leaks or reduction in holding pressure. The detailed design aspect shall be discussed in this poster. (author)

[en] Plasma-assisted methods were applied to enhance the activity of TiO₂-based photocatalysts. A radio frequency (RF)-plasma was applied to treat the bare and Ru dye-sensitised TiO₂ nanopowders (anatase) to enhance their photocatalytic activity. Plasma treatment was performed either in inert or in reactive atmosphere. In latter case, the plasma treatment resulted in covering the catalysts with a polymer layer. The photocatalytic activities of catalysts were evaluated by measuring the photodegradation of methyl orange (MO) in aqueous solution exposed to ultraviolet (UV) light. The MO concentration in solution was measured spectrophotometrically (UV-Vis spectrophotometry). The photocatalytic activity expressed in term of rate constant was 2.6 times higher for TiO₂ covered with a polymer layer than that for bare titania. A decrease in activity was observed after RF-plasma treatment of bare TiO₂. (authors)

[en] The cryogenic Penning Ion trap (PIT) facility at VECC has a specially designed cryostat where the trap along with its detection electronics will remain immersed in the liquid helium filled bore of a 5T superconducting cryomagnet dewar. Detailed descriptions of the magnet and mechanical assembly for immersing the trap assembly were described

[en] n analytical and numerical study of the coupling of strip-line antenna with small tokamak plasma is presented with the help of the ICRH antenna code SITAR (Simulation of ICRH anTennaA Resistance). The antenna is of finite poloidal and toroidal dimensions and screened from the plasma by a metal screen of anisotropic conductivity that shorts out the toroidal components of radio frequency electric field. A linear model of refractive index in plasma evanescent region has been considered to describe the propagation of wave in it. The plasma in the coupling region is described by cold plasma dielectric tensors with non-uniform density and toroidal magnetic field along the radial direction. Inclusion of finite antenna length, antenna lead currents as well as toroidal and poloidal variation of current in it (3D analysis) introduces an important difference in the antenna load resistance and inductance compared to those calculations when lead current is ignored and plasma is assumed to be invariant along the poloidal direction (2D analysis). The effect of plasma density, antenna length, wall and plasma edge distances on antenna load resistance and inductance has been studied using parameters of Aditya-U and SST-1 tokamaks. (author)

[en] Ion current in a radio frequency (RF) ion source depends on parameters such as RF power, gas pressure, magnetic field, extraction voltage, etc. RF power and gas pressure determines the degree of ionization or plasma density inside a gas discharge tube. The magnetic field makes the electron path helical which increases the probability of collisions. The extraction potential exerts a Lorentz force to aid extraction of charged particles towards the extraction region. Ions are extracted along the axis of a discharge tube due to the potential difference created by the extraction or focusing electrode. Optimal conditions for formation of useful ion beam only exist for specific values of these parameters. The present study determines the operational characteristics of the newly developed RF ion source for extraction of high ion currents. Different components of the ion source are developed & studied to obtain their optimum values. The optimum operating parameters are: RF power = 220 Watts; Magnetic field = 500 Gauss; Extraction potential = 4 kV; Pressure = 1.7 x 10^-6 mbar; Focusing potential = 1 kV; Ion current = 1.479 mA

[en] We demonstrate the trapping of cold ${}^{87}Rb$ atoms in a toroidal geometry using a radio frequency (rf) dressed quadrupole magnetic trap formed by superposing a strong rf-field on a quadrupole trap. This rf-dressed quadrupole trap has the minimum potential away from the quadrupole trap centre on a circular path which facilitates trapping in toroidal geometry. In these experiments, the laser cooled atoms were first trapped in a quadrupole trap, then cooled evaporatively using a weak rf-field, and finally trapped in an rf-dressed quadrupole trap. The radius of the toroid could be varied by varying the frequency of the dressing rf-field. It has also been demonstrated that a single rf source and an antenna can be used for the rf-evaporative cooling as well as for the rf-dressing of atoms. The atoms trapped in the toroidal trap may have applications in the realization of an atom gyroscope as well as in studying the quantum gases in low dimensions. (paper)

[en] The two projects of the ITER Neutral Beam Test Facility in Padova are MITICA, the full scale prototype of the heating Neutral Beam Injector (NBI) and SPIDER, the full-size negative ion source of the NBI. Both include a Radio Frequency (RF) Ion Source where plasma is produced by the inductive coupling with coils wound around vacuum chambers called driver cases. Each coil is fed at 1 MHz up to a power of 100 kW, which corresponds to a voltage of about 12 kV rms, with nominal plasma parameters. According to the ITER requirements, the ion source is in vacuum to avoid radiation induced conductivity; concern on the voltage hold off of the source components exists, in particular related to the contact zone between the coil and the driver case characterized by intensification of the E-field. The development of a test bed called High Voltage Radio Frequency Test Facility (HVRFTF) has been launched to study the issues related to the voltage hold off in this operational environment and to verify the electrical design of the drivers adopted in the ion sources of SPIDER and MITICA. The paper presents the studies addressed to identify the HVRFTF requirements, to conceive and design suitable driver mock-up to reproduce operative conditions relevant to the RF drivers of SPIDER and MITICA for the characterization of their dielectric strength, to work out a suitable RF circuit for the HVRFTF to generate the required voltage and to design a flexible test arrangement allowing the variation of the quantities which influence the voltage hold off, such as the pressure, geometry and materials of the devices under test, in order to perform parametric analyses.