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.
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.
A Capture Cryo Module (CCM) consisting of two single cell 1.3 GHz, β = 1, niobium cavities is being developed for the superconducting electron linac injector at VECC. Electron beam of 100 keV and 2 mA from a thermionic gun will be accelerated in the CCM and thereafter in an Injector Cryo Module (ICM) to 10 MeV. Single cell cavities in the CCM are independently phased and a coaxial TTF-III coupler is chosen for rf power coupling into each cavity. The presence of the coupler perturbs the field symmetry of the cavity introducing local transverse kicks to the incoming electron beam in the coupler region. Numerical analysis taking into account the changing velocity profile as well as the off-axis field seen by the electron as it moves through the cavities has been carried out for estimating the kick. The variation of the kick with longitudinal position of electrons in the beam bunch introduces transverse emittance growth. This has been calculated using the field seen by the electron. The analytical calculations are compared with results from particle tracking with simulated 3D fields. It is found that coupler induced kick does not appreciably change the emittance values at 10 MeV.
This paper reports the design, development and testing of a
3.0 kW, 37.8 MHz radio frequency (RF) amplifier system that has
been built by combining four solid-state amplifier modules of
1.0 kW each. The design philosophy and test results of individual
components such as driver amplifier, final amplifier modules, power
divider/combiner, dual directional coupler (DDC) with system control
and interlocks are discussed in detail. Compact 4-way Wilkinson
power divider and combiner have been implemented using combination
of 50 Ω coaxial cables at this lower frequency of
37.8 MHz. It provides better isolation between the ports and also
have high power handling capability. The amplifier has been tested
with existing 37.8 MHz quarter-wave resonator type re buncher in
the Radioactive Ion Beam (RIB) facility. The performance test
results of developed RF system with Re buncher cavity have been
presented in this report.
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