Manjiri Pande

Design, development, and acceleration trials of radio-frequency quadrupole

A deuteron radio frequency quadrupole (RFQ) accelerator has been designed, fabricated, and tested at BARC, which will be used for neutron generation. The RFQ operates at a frequency of 350 MHz and needs an inter-vane voltage of 44 kV to accelerate the deuteron beam to 400 keV within a length of 1.03 m. The error analysis shows that the offset of two opposite vanes in the same direction by 100 μm leads to a change in resonant frequency by 1.3 MHz and a significant change of fields in the quadrants (∼±40% with respect to average field). From the 3D analysis, we have observed that the unwanted dipole mode frequencies are very near to the quadrupole mode frequency which will make structure sensitive to the perturbations. In order to move the dipole modes away from the quadrupole modes, we have used the dipole stabilizer rods. The 5 wire transmission line theory was used to study the perturbative analysis of the RFQ and based on this a computer program has been written to tune the cavity to get required field distribution. Based on these studies, a 1.03 m long RFQ made of OFE copper has been fabricated and tested. Even though the RFQ was designed for deuteron (D(+)) beam, we tested it by accelerating both the proton (H(+)) and D(+) beams. The RFQ was operated in pulsed mode and accelerated both H(+) and D(+) beams to designed values of 200 and 400 keV, respectively. The measured parameters are in good agreement with the designed values validating our simulations and fabrication processes. In this paper, simulations, RF measurements, and beam commissioning results are presented.

Klystron based high power RF system for proton accelerator

As a part of ADS program a proton accelerator (20 MeV, 30 mA) and its high power RF systems (HPRF) are being developed in BARC. This paper explains design details of this klystron based HPRF system.

Design of 50 kW, 5 MHz RF plasma power supply for low and intermediate level radioactive waste management

A 50 kW RF based plasma power supply has been designed for incineration of Low and intermediate level radioactive solid waste with activity of the order of 10 mR. Power supply is class C tube based amplifier. Specification has been decided based on CFD simulation of incinerator facility at BARC and plasma sustainability. This paper describes design of tube based 50 kW power amplifier from calculations and its validation with RF circuit simulation software tool

Study of RF breakdown and multipacting in accelerator components

Radio frequency (RF) structures that are part of accelerators and energy sources, operate with sinusoidally varying electromagnetic fields under high RF energy. Here, RF breakdown and multipacting take place in RF structures and limit their performance Electron field emission processes in a RF structure are precursors for breakdown processes. RF breakdown is a major phenomena affecting and causing the irreversible damage to RF structures. Breakdown rate and the damage induced by the breakdowns are its important properties. The damage is related to power absorbed during breakdown, while the breakdown rate is determined by the amplitudes of surface electric and magnetic fields, geometry, metal surface preparation and conditioning history. It limits working power and produces irreversible surface damage. The breakdown limit depends on the RF circuit, structure geometry, RF frequency, input RF power, pulse width, materials used, surface processing technique and surface electric and magnetic fields. Multipactor (MP) is a low power, electron multiplication based resonance breakdown phenomenon in vacuum and is often observed in RF structures. A multipactor discharge is undesirable, as it can create a reactive component that detunes the resonant cavities and components, generates noise in communication system and induces gas desorption from the conductor surfaces. In RF structures, certain conditions are required to generate multipacting.

Development of solid state modulating anode power supply for 1 MW Klystron system

Bhabha Atomic Research Centre (BARC) Mumbai is developing Low Energy High Intensity Proton accelerator (LEHIPA) of energy 20 MeV, 30 mA. LEHIPA comprises of Radio Frequency Quadrupole (RFQ) accelerator (3 MeV), 10 MeV Drift Tube Linac (DTL) and 20 MeV Drift Tube Linac (DTL). As per the accelerator physics design, RFQ and DTLs require about 2.4 MW of total radio frequency (RF) power. Each accelerating cavity will be driven by a 1MW continuous wave (CW) klystron (TH2089F) amplifier at 352.21 MHz. LEHIPA will operate in both, pulsed and CW mode So, the RF system is being designed to operate in the both, CW and pulse mode.