Heavy Ion RFQ Research Articles

Longitudinal emittance measurement for an external-bunching-based heavy-ion RFQ

Longitudinal emittance at the RFQ output is a very important parameter to determine the particle loss in the subsequent linac. To understand the quality of beams delivered by an external-bunching-based heavy-ion RFQ and to provide key information for High Intensity heavy ion Accelerator Facility (HIAF) superconducting linac, longitudinal emittance was measured at the protype of HIAF front-end at Institute of Modern Physics (IMP). An 81.25 MHz quarter wave resonator (QWR) re-buncher was developed and installed behind the RFQ. A voltage scan of the re-buncher and the corresponding bunch length measurement determine the longitudinal emittance. The measurements were implemented for different operation conditions of the pre-buncher which is installed upstream of the RFQ and is a Multi-Harmonic-Buncher (MHB) operating with two frequencies. Measured longitudinal emittance trends for different pre-bunching variants follow those expected from simulation but are systematically lower than estimated. Both simulation and measurement predict a relatively lower emittance while the MHB operating with the RFQ fundamental frequency. The reason has been discussed in this study.

Design of a Continuous Wave Heavy Ion RFQ for BISOL

Design of a Continuous Wave Heavy Ion RFQ for BISOL

Fast-bunching design of compact heavy ion RFQ linac

We propose the construction of a compact linac as the injector of a cancer therapy facility at the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS). Based on a traditional setup, a new compact fast-bunching design is first introduced to optimize the 600 keV/u RFQ with a 0.05 pmA $$^{12}\hbox {C}^{4+}$$ beam. This shortens the RFQ structure length from the standard design value of 272–230 cm while effectively regulating the particle loss and emittance growth. In addition, a detailed error analysis was performed after the optimization process. The error sources cover input beam parameters errors, machining errors and alignment errors. The simulation results show that the beam loss and emittance growth of the RFQ are acceptable and within typical ranges of error.

The beam commissioning of a CW high charge state heavy ion RFQ

The SSC-LINAC project is launched at Institute of Modern Physics in China to develop one new linear accelerator (LINAC) injector for separated sector cyclotron (SSC). It includes a high charge state ion source, a CW RFQ and a DTL section, and is designed to accelerate ions up to 580keV/u. Now the ion source and the RFQ cavity have been installed in the main hall and the beam commissioning has been carried out. Two kinds of ions have been tested, 16O5+ and 40Ar8+. The experiment result of 16O5+ is: the measured beam current is 180μA at entrance of RFQ and 150μA at exit of RFQ. The output energy of 16O5+ is 141.89keV/u. The measured beam current is 210μA at entrance of RFQ and 198μA at exit of RFQ for 40Ar8+. The output energy of 40Ar8+ is 142.78keV/u. The experiment results agree with the design parameters of RFQ very well. This paper presents: the design consideration of beam dynamics, RF and cooling structure design; measurement of the cold model; high power test of RFQ and beam commissioning result.

RF and field measurements of the SSC-LINAC RFQ

The 53.667 MHz continuous-wave heavy ion RFQ has been designed and manufactured for the SSC-LINAC project. This four-rod RFQ accelerates ions with maximum mass to charge ratio of 7 from 3.728 keV/u to 143 keV/u. Measurements have been carried out to check the RF performance of the cavity and the quality of the electric field. The S11 of the power coupler is adjusted to better than -44 dB, and the Q 0 of the cavity is 6440. The quality of the electric field is evaluated by the perturbation method. The measurement procedure and data analysis will be discussed in detail. The error due to gravity of the perturbation bead has been corrected by averaging the fields in different quadrants. As a result, the unflatness of the electric field is ±2.5%, and the dipole field component distributes from 0% to 20% in different longitudinal positions, which indicates the asymmetry of the quadrupole field. The unflatness of the quadrupole field distribution represents a good agreement with the simulation results. High power RF test and beam commissioning of the RFQ are on schedule in early 2014.

Conceptual Design of 50MHz Heavy Ion RFQ

Conceptual Design of 50MHz Heavy Ion RFQ

ITEP MEVVA ion beam for reactor material investigation

Since 2008 the ion beam irradiation modeling experiments for the testing of reactor materials radiation hardness are under development at the ITEP heavy ion RFQ injector with MEVVA ion source. Ion beam irradiation method has certain advantages for such tests. One of them is high speed of defect formation. Moreover, the irradiated samples can be investigated by traditional investigation methodic because they have not radioactivity induced. The special sample support with electrostatic deflector was constructed and installed at the injector output. The result of ion beam dynamics simulation throughout the deflector as well as the detailed description of the test facility is presented. The first experimental results are presented as well. They have been demonstrated promising results.

Essay of Accelerator R&D in a Small Laboratory of a University <Study of three POP accelerators using heavy ion RFQ linac of Tokyo Institute of Technology ―1992–2008―>

Essay of Accelerator R&D in a Small Laboratory of a University <Study of three POP accelerators using heavy ion RFQ linac of Tokyo Institute of Technology ―1992–2008―>

Enhancement of ion beam charge states by adding a second anode to the metal-vapor vacuum-arc ion source

We report detailed investigations of ion charge state enhancement in an alternative metal-vapor-vacuum arc ion source configuration, consisting of two anodes with staggered (but partially overlapping) high current discharges in axial high magnetic field gradients. The experiments demonstrated that driving an additional current in a vacuum arc in a magnetic mirror configuration resulted in substantial ion charge state enhancement. Maximum ion charge states of Pb 6+ and U 8+ were extracted. Results are presented for high charge state uranium beam generation and acceleration in the 27 MHz heavy-ion RFQ LINAC TIPr-1.

Acceleration test of heavy ion RFQ linac at TIT

An 80 MHz heavy ion RFQ linac at Tokyo Institute of Technology (TIT) has been constructed for research on inertial fusion and plasma experiments. Equipment for beam acceleration has been fabricated and assembled to confirm the performance with low currents of the RFQ. The linac successfully accelerated He + and C 2+ ion beams to their final energies of 219 keV/u. The obtained beam transmission was more than 89% with currents of a few tens μA.

Design and construction of heavy ion RFQ linac with effective acceleration structure

At the Tokyo Institute of Technology, generating a plasma with a heavy ion beam has been studied for basic research on inertial fusion and a heavy-ion pumped laser. These experiments require a high intensity and high brightness beam. An 80 MHz heavy-ion RFQ linac is being constructed to meet the requirements. This linac accelerates particles with a charge to mass ratio ( q A ) greater than 1 16 from 5 keV/amu up to 214 keV/amu. Two-dimensional (2D) machining is applied for cutting of the RFQ vane-tips. We simulated the beam optics including effects of higher order harmonies in the intervane potential (H. Deitinghoff, A. Schempp, H. Klein and O. Pan, Particle Acc. 37–38 (1992) 47; Chen Chia-Erh, Fang Jia-Xun, Li Weigo, Pan Oujia, Lu Yuanrong, Li Deshan, Wang Lishan, Yu Maolin, H. Deitinghoff, A. Schempp and H. Klein, Proc. European Particle Acc. Conf. (1992) p. 1328) for optimization of the vane parameters. In order to increase the acceleration efficiency, synchronous phase was gradually raised from −30° to −20° in the accelerator section of the cavity. The expected beam transmission is 91.8% for a beam current of 0 mA and 68.4% for 10 mA.

Beam dynamics calculations for a prototype of a high-current heavy-ion RFQ

A 27 MHz heavy-ion RFQ for high currents at low ion energies has been designed and built for RF and beam tests. The accelerating structure is a 4-rod RFQ with spiral stems, developed in the institute. This RFQ will serve as a prototype for the first part of a large RFQ, which may be installed in the new high-current injector of GSI. Particle dynamics calculations were carried out to check the RFQ design with respect to beam quality and transmission in the bunch-forming process. Results of calculations are discussed including some requirements of HIIF injection. A description of the experimental set-up and first results from beam measurements will be given by Kipperet al. in this volume.

Optimization of RFQ vane parameters using a non-linear beam dynamics code

For optimization of the vane parameters of a heavy-ion RFQ, we used a beam dynamics code including effects of higher-order harmonics in the intervane potential. By using a three-module cavity structure, we obtained not only precise and easy assembling but also stable RF characters during operation.

Transport and acceleration of high current uranium ion beams

Measurements have been made of the transport of beams produced by the high current ion source, MEVVA, and of the injection of these beams into the GSI heavy ion RFQ linac. This configuration has provided initial tests of the MEVVA ion source in an injector environment, and of the RFQ with uranium as the accelerated species. Beam currents of 78 mA of titanium and 19 mA of uranium, at an extraction voltage of 40 kV, have been transported through a 4.7 m long beam transport channel, and up to 40 mA of uranium has been transported through a single-gap accelerating column at a voltage of about 150 kV. A current of up to 5 mA of U 3+ has been measured at the exit detector of the RFQ.

Mechanical Design of a Heavy Ion RFQ

The mechanical design and construction of a 199.3 MHz heavy ion RFQ for charge states q/A as low as 0.14 is described. The vane supports and positioning adjustments are signifcant features of this design. They provide the capability of achieving the precision vane alignment required. The maximum difference between calculated and measured apertures between the vanes is 0.0035 inches, and the average difference is 0.0010 inches. Various important aspects of the design and construction including material selection and plating, RF joints, thermal loading and vacuum system are described. Assembly techniques, methods of mechanical measurement, alignment and structure stability are discussed in detail.

Design Considerations on Peak Electrical Fields and Maximum Beam Currents for Heavy Ion RFQ Linacs

Aperture and frequency determine voltage limits with respect to sparking. For a corresponding application of Kilpatrick's criterion exact knowledge of peak electrical fields in the RFQ is required. Results of calculations for Bi2+ fusion injectors considered in our institute are presented. As a general result maximum beam current turns out approximately proportional to electrode voltage. Some notes on the influence of space charge models shall be reported.

Beam Dynamics and Vane Geometry in the LBL Heavy Ion RFQ

The LBL Heavy Ion RFQ accelerator, presently undergoing acceptance tests, extends the application of the RFQ principle to charge-to-mass ratios considerably less than one. In this design the aperture is very small compared to the operating wavelength, causing a large capacitive loading of the structure and also in a high sensitivity of the field configuration of the structure to vane alignment. A structure has been derived that eases the vane alignment procedure and reduces the sensitivity to vane misalignment. The selection of the vane cross section facilitates machining and eventual frequency trimming.