[en] Control system for RF source of 30 MeV, 3 kW RF Linac for neutron generation is being developed. The system consists of two 15 MeV linac structures, each powered independently with klystron rated for 7.5 MW(pk)/7.5 kW(avg). Two klystron modulators of 160kV, 110A, 7μs and 250Hz feed pulsed power into the klystron, which produces RF power at 2856 MHz. The klystrons will be driven by low power RF driver amplifiers programmed for matching phase, frequency and power into the linac. Both the driver amplifiers are controlled through RS-232 Protocol. The HV pulsing and RF drive for the klystron has been interlocked with water flow, arc detector, SF6 gas pressure etc. The control system is designed using Real time embedded controller, where pulses for synchronization are being generated in FPGA. Most of the power supplies like electromagnet, HVDC, etc. are on RS-232 protocol. These power supplies are controlled via suitable RS-232 to Ethernet converter. State machine topology is being used to design the logic. The database for logging data is developed in SQL. This paper describes the details of the software implementation and hardware used to realize the control of the RF power source. (author)

[en] The electron guns for the DC accelerators and RF Linacs are designed and developed at EBC/APPD/BARC, Kharghar. These electron guns need to be characterized for its design and performance. Two test benches were developed for characterizing the electron guns. Various beam diagnostic devices for measuring beam currents and beam sizes were developed. Conical faraday cup, segmented faraday cup, slit scanning bellows movement arrangement, multi-plate beam size measurement setup, multi- wire beam size measurement setup, Aluminum foil puncture assembly etc. were developed and used. The paper presents the in-house development of various beam diagnostics for characterizing electron guns and their use. (author)

[en] A 5 kV electron gun was designed and developed using planar configuration for the focusing electrode and anode. The gun uses a LaB₆ pellet as cathode, which is indirectly heated using a tungsten filament. The gun was used as injector in the 3 MeV DC electron accelerator at EBC, Kharghar. A Titanium window puncture resulted in the cathode poisoning and reduction in beam current. This paper describes the higher power filament heating of the cathode to restore the cathode emission performance, its consequent filament failure, modifications in the gun, and beam characterization on test bench. (author)

[en] A 40 kV electron gun is designed and developed using the Pierce configuration for the focusing electrode. Simulations were carried out using CST Particle Studio. The Gun is a thermionic type electron gun with indirect heating of the LaB₆ cathode. The gun is capable of delivering a beam current of more than 1.0 A at 40 kV with a beam size of less than 4 mm. The cathode assembly housing the LaB₆ cathode pellet consists of cups and heat shields made out of Tantalum and Rhenium sheets. The cathode assembly and the electron gun was fabricated, assembled and tested on test bench. This paper presents the gun design, cathode conditioning, HV cold conditioning, beam characterization and grid biasing experiments on test bench. (author)

[en] Pulsed klystrons are used as the power source in industrial electron linacs. These klystrons need to be tested on matched water load before connecting it to the RF structure of the linac. For this purpose, a klystron test facility has been set up at Electron Beam Centre, Navi Mumbai. This facility is provided with a line-type modulator (150 kV, 110 A, 8-10 us, 250 Hz), driver amplifier, electromagnet power supplies, Low Conductivity Water (LCW) circulation system for cooling, oil recirculation system, material handling system and X-ray shielding. A WR284-based waveguide plumbline, including circulator, directional coupler and matched water load, is provided at the output end of the klystron. Real-time control and interlock system has been designed and developed for this facility. This paper describes the details involved in the development of the test facility and the testing of the 7.5 MW pulsed klystron on water load. (author)

[en] Fast Current Transformers are used in RF Linacs to measure beam current and it is an expensive import item. Passive, in-flange FCTs have been designed and developed in-house to measure pulsed beam currents. A soft ferrite (MnZn) core has been used around an Alumina ceramic break and conflate flanges have been welded at both ends. An outer cover has been provided for return path to the image current. The FCT’s are of two different sizes having ferrite cores of ID: 38 mm (FCT I) and ID: 104 mm (FCT II) with CF35 and CF100 end flanges. The optimized number of secondary turns for FCT I and II are 11 and 8 respectively. The calibration of FCT has been done by passing a known pulsed current of duration ∼4.2 μs through the center of the toroid core. The output voltage was measured across a 50μ resistor connected at the secondary. The measured sensitivity of FCT I and FCT II is 2.0 V/A and 2.6 V/A. The beam current from an Electron Gun has been measured at different extraction voltages using indigenous FCT. The results are found to be in good agreement with imported FCT of Bergoz make. At an extraction voltage of 30 kV, beam current measured by indigenous FCT is 496 mA while that by the imported one is 488 mA. (author)

[en] The electron gun for the compact linac was designed using the CST Particle Studio Software. It is a triode gun Pierce focusing electrode of ID 23 mm and angle ∼ 67.5 degrees, to give ∼ 1 A of beam current at 85 kV and having a diameter of less than 3.0 mm at a distance of 100 mm from the cathode. The cathode-focusing electrode distance is 8 mm. The electron gun was fabricated, assembled and tested on test bench. It was then connected to the compact linac and beam commissioning was done. By knowing the change in rf reflected power from no beam condition to full beam load condition, the beam current was estimated. Also, injection voltage was varied to get different output radiation dose from the target. The paper presents the compact gun design and development, gun testing on test bench and its performance with compact linac. (author)

[en] The field emission properties of nano-structured materials have been the subject of extensive research for applications in field emission related device. Their low turn-on voltage and high emission current density make nano-structure based cold cathode an attractive method of generating an energetically clean, low power beam for electron gun. Accelerator and Pulse Power Division has taken initiative to study the feasibility of constructing field emission based electron gun for 3 MeV DC accelerator. The DC gun is required to generate 10 mA current, 5 KV DC electron beam. As a first step, a new set up has been designed and fabricated to study the field emission property of different samples. Three different samples of carbon nanotube directly grown on inconel substrate by plasma CVD under different conditions are studied for field emission property. The base pressure during the field emission measurement was kept at 2e-6 mbar and cathode anode distance was 1 mm. Maximum emission current density up to 19 mA/cm² is obtained at 1.6 KV DC Voltage for one of the sample. The same sample also exhibit low turn-on field i.e. 0.6 V/μm for another sample where CNTs were grown on unoxidised cathode, turn on field is 3.5 V/μm. Field emission current up to 64 micro-Ampere is obtained at 5 KV DC voltage. In this paper, we describe in details the experimental results obtained from different samples. (author)