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

Abstract

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.

Beam acceleration through proton radio frequency quadrupole accelerator in BARC

“…For the LEHIPA RFQ the design vane voltage is 68 kV with a peak electric field of 28 MV/m. The design of the RFQ is similar to a 400 keV RFQ that was built earlier [5,9]. The optimized parameters of the RFQ are shown in table 2.…”

Experimental study of pulsed ion beam generated by different pulsing topology in 2.45 GHz ECR proton source

“…In LEHIPA, the initial beam acceleration trial requires a pulsed ion beam from an ion source with 1 ms of T on time and a repetition rate of 2 Hz with beam rise and fall time in the range of 50 μs. The quality of the pulse beam from the ion source in terms of beam current, emittance, and proton fraction should be compatible with the acceptance of the next section of accelerating structure [2]- [5]. Also, it is desirable that the extracted beam current should have a good flat top with a low beam ripple.…”