A four-rod type heavy-ion radio frequency quadrupole (RFQ) linac has been designed, constructed, and tested for the rare ion beam (RIB) facility project at VECC. Designed for cw operation, this RFQ is the first postaccelerator in the RIB beam line. It will accelerate A/q < or = 14 heavy ions coming from the ion source to the energy of around 100 keV/u for subsequent acceleration in a number of Interdigital H-Linac. Operating at a resonance frequency of 37.83 MHz, maximum intervane voltage of around 54 kV will be needed to achieve the final energy over a vane length of 3.12 m for a power loss of 35 kW. In the first beam tests, transmission efficiency of about 90% was measured at the QQ focus after the RFQ for O(5+) beam. In this article the design of the RFQ including the effect of vane modulation on the rf characteristics and results of beam tests will be presented.

Abstract.A non-interceptive bunch length detector system for the measurement of bunch width of accelerated beam has been designed and developed. This detector system is based on emitted secondary electrons produced by a primary ion beam hitting a thin tungsten wire placed in the beam path.The measurement of the longitudinal beam shape for wide range of beam energy, intensity as well as ion species is possible with this detector. One of the main components of the detector system is a RF deflector cavity used to deflect electrons in correlation with rf phase of the accelerator. The detailed design, development with measurement results of the deflector cavity resonator have been reported in this paper.

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Radioactive ion beams (RIB) have been produced on-line, using a gas-jet recoil transport coupled Electron Cyclotron Resonance (ECR) ion-source at the VECC-RIB facility. Radioactive atoms∕molecules carried through the gas-jet were stopped in a catcher placed inside the ECR plasma chamber. A skimmer has been used to remove bulk of the carrier gas at the ECR entrance. The diffusion of atoms∕molecules through the catcher has been verified off-line using stable isotopes and on-line through transmission of radioactive reaction products. Beams of (14)O (71 s), (42)K (12.4 h), (43)K (22.2 h), and (41)Ar (1.8 h) have been produced by bombarding nitrogen and argon gas targets with proton and alpha particle beams from the K130 cyclotron at VECC. Typical measured intensity of RIB at the separator focal plane is found to be a few times 10(3) particles per second (pps). About 3.2 × 10(3) pps of 1.4 MeV (14)O RIB has been measured after acceleration through a radiofrequency quadrupole linac. The details of the gas-jet coupled ECR ion-source and RIB production experiments are presented along with the plans for the future.

An analytical and cold model study of a prototype extended vane rod-type RFQ (radio frequency quadrupole linac) is presented. The bead-pull measurement allowed us to experimentally determine the effect of shaping of the vane-supporting posts and, most interestingly, the size of the vacuum enclosure in the dipolar and quadrupolar field asymmetry. Disk shaped beads of BaTiO3 have been tailor made for this purpose. The special shape of the beads has allowed precise measurements of frequency shifts all along the length of the RFQ. The measured quadrupolar asymmetry and dipole component at a radial distance of 7 mm from the beam axis are within ±1% for the optimized structure. Particle tracking of a 10 mA proton beam with a simulated 3D field for the optimized full scale RFQ with modulated vanes has been carried out. Simulation shows vertical and horizontal shifts of only 0.01 mm and 0.03 mm, respectively, for the accelerated beam at the exit of RFQ. The percentage of accelerated particles lying within an energy width of ±40 keV about 800 keV is increased from 86% for the original enclosure to 88% for the reduced enclosure, whereas the transmission efficiency is 100% for both the cases.