The CH-or Crossbar H-structure is a new H-mode drift-tube structure operating in the TE 210 mode. Due to its mechanical rigidity room temperature as well as superconducting cavities can be realized [1]. A superconducting version of the CH-structure has been development at the IAP in Frankfurt, Germany. To prove the promising results optained by simulations a 19-cell, 352 MHz (β = 0.1) prototype cavity has been designed and built. This CH prototype is the first superconducting low energy multi-cell cavity for the acceleration of protons and ions. The cavity has been tested at room temperature with an rf power of up to 300 W cw and 2 kW pulsed. We present the first tests of the cavity as well as mechanical simulations.

Within the IFMIF project (International Fusion Materi- als Irradiation Facility) a high current D + -linac operated in cw mode has to be developed. The parallel acceleration of two 125 mA D + -beams from 0.1 MeV up to 40 MeV must be performed at an extremely low loss rate (0.1 - 0.2 µA/m) to avoid an activation the linac structures and guarantee hands-on maintenance. One optional layout of the acceleration facility consists of a high current ion source, low energy beam transport (LEBT), room tem- perature Radio-Frequency-Quadrupol (RFQ) followed by a superconducting H-type DTL. A first 352 MHz proto- type s.c. cavity is under construction at the ACCEL com- pany, Germany. Actual beam dynamics simulations for such a linac design including parameter errors of compo- nents are reported. Consequences for the LEBT- and RFQ-section are discussed.

Within the IFMIF project (International Fusion Materi- als Irradiation Facility) a high current D + -linac operated in cw mode has to be developed. The parallel acceleration of two 125 mA D + -beams from 0.1 MeV up to 40 MeV must be performed at an extremely low loss rate (0.1 - 0.2 µA/m) to avoid an activation the linac structures and guarantee hands-on maintenance. One optional layout of the acceleration facility consists of a high current ion source, low energy beam transport (LEBT), room tem- perature Radio-Frequency-Quadrupol (RFQ) followed by a superconducting H-type DTL. A first 352 MHz proto- type s.c. cavity is under construction at the ACCEL com- pany, Germany. Actual beam dynamics simulations for such a linac design including parameter errors of compo- nents are reported. Consequences for the LEBT- and RFQ-section are discussed.

The IFMIF project (International Fusion Materials Irradiation Facility) requests two cw linacs operated in parallel. Each of them is designed to provide a 5 MW 125 mA deuteron beam at 40 MeV for the production of an intense neutron flux with an energy around 14 MeV. This paper presents an alternative linac design for this project. The acceleration is completely based on H-type cavities. The room temperature (rt) 4-Vane-RFQ and a short IH-DTL (Interdigital-H-DTL) are followed by 4 superconducting (sc) CH-DTL (Crossbar-H) cavities. The operating frequency is 175 MHz, the designed section lengths are 13 m for the RFQ (Radio-Frequency-Quadrupole) (5 MeV), 1 m for a compact MEBT (Middle Energy Beam Transport), 2 m for the IH-cavity (10 MeV) and 9 m for the sc CH-DTL (40 MeV). The structure parameters and end-to-end multiparticle beam dynamics calculations with and without DTL errors of the whole linac will be presented and the results will be discussed.

Two Integral Split Ring (ISR) RFQs with high duty factor of 16.7% have been designed for the application of heavy ion implantation and built in the past several years at Institute of Heavy Ion Physics (IHIP) in Peking University. Two kinds of PIG ion sources with permanent magnets and LEBT were installed and optimized for the injection into these two RFQs. The positive O+ and negative O− ions were extracted and accelerated separately as well as simultaneously. The output macro pulse O− beam current reached 660μA at a transmission efficiency of more than 82%. The N+ beam was also accelerated with similar transmission efficiency, but the output current intensity for positive ions were lower than the negative ions because of the extracted current limitation of ion sources. The improvements, especially for high duty factor and experimental results with the 1MeV ISR RFQ will be presented in this paper.

H-Mode cavities (IH-DTL, IH-RFQ, 4-Vane-RFQ) have been developed successfully during the last decades for a large variety of applications in the field of ion acceleration. The CH- or Crossbar H-structure is a new H-Mode drift tube structure operating in the TE/sub 210/ mode. This structure is currently under development at the IAP in Frankfurt, Germany. This type of cavity is an excellent candidate for the use in future high current applications like IFMIF or XADS with beam currents of up to 125 mA. For these applications superconducting operation is very attractive. The overall plug power consumption is lower and the use of larger apertures can reduce the risk of activation significantly. Due to the possible superconducting operation it is important to investigate the higher order modes (HOM) in such a cavity. In this paper, we present the first results of the HOM analysis and give a status of the development of the superconducting CH cavity prototype.

H-Mode cavities (IH-DTL, IH-RFQ, 4-Vane-RFQ) have been developed sucessfully during the last decades for a large variety of applications in the field of ion accelera- tion (1). The CH- or Crossbar H-structure is a new H- Mode drift tube structure operating in the TE210 mode (2). This structure is currently under development at the IAP in Frankfurt. Due to its mechanical rigidity the CH-structure can be realized for room temperature as well as for super- conducting operation. In this paper we present the status of the development of the first superconducting CH-cavity prototype.

The work for the project study of an International Fusion Material Irradiation Facility (IFMIF) has been continued. The linac part of the facility has to provide a 40 MeV, 125 mA D+ beam for the homogenous irradiation of a Li target to produce very high neutron fluxes for fusion chamber wall material tests. The linac consists of a Radio Frequency Quadrupole (RFQ) accelerator followed by a Drift Tube Linac (DTL). To different rf structures have been investigated for the DTL: the well known Alvarez type and the IH-type, both operating successfully at several large laboratories. Moderate rf power losses in the structure has been one main aspect in the design with respect to the required cw operation. Results of multiparticle beam dynamics simulations demonstrate the capability of each structure to handle the very high currents without particle losses and at moderate emittance growth. While the Alvarez DTL design shows less emittance growth with and without errors, the IH-DTL is attractive with respect to its compactness and mechanical robustness [1].

H-type cavities have been successfully developed dur- ing the last 30 years for a large variety of applications in the field of ion acceleration. Radio Frequency Quadrupole (RFQ) and Drift Tube Linac (DTL) versions were de- signed in the H11(0)- and in the H21(0)-mode. The Inter- digital H-type (IH) drift tube structure is efficient for an energy range from 0.1 to 20 MeV/u, especially in combi- nation with the KONUS beam dynamics layout. At higher beam velocities higher frequencies must be applied for efficient operation, which can be achieved with the CH- structure (H21(1)-mode). Frequencies range from 150-800 MHz at beam energies from about 2 to 150 MeV/u. The CH-structure has small transverse dimensions and is me- chanically robust using crossed stems. This opens the possibility to build superconducting (sc) cavities, which is advantageous for cw operation. In this paper we present two beam dynamics layouts for light ion accelerators with intense beams, using the KONUS beam dynamics design: a) For an International Fusion Material Irradiation Facility (IFMIF) the acceleration of a 125 mA Deuterium beam from 2.5-20 MeV/u is required in cw operation. A combi- nation of one rt IH-tank followed by a 175 MHz sc CH- DTL has been considered. b) Several proposals deal with the acceleration of proton beams with currents ranging from a few mA up to 100 mA. Here the sc CH-DTL could cover the medium energy part of the linac from several MeV/u input energies up to about 150 MeV/u. For a 350/700 MHz frequency combination a layout is pre- sented, which is oriented on the requirements to the linac of an Accelerator Driven System (ADS) for waste trans- mutation or/and energy production. Beam simulations show in all cases that the required intensities could be accelerated with good emittance preservation, high trans- mission and high efficiency.

The work for the project study of an International Fu- sion Material Irradiation Facility (IFMIF) has been con- tinued. The linac part of the facility has to provide a 40 MeV, 125 mA D+ beam for the homogenous irradiation of a Li target to produce very high neutron fluxes for fu- sion chamber wall material tests. The linac consists of a Radio Frequency Quadrupole (RFQ) accelerator followed by a Drift Tube Linac (DTL). To different rf structures have been investigated for the DTL: the well known Al- varez type and the IH-type, both operating successfully at several large laboratories. Moderate rf power losses in the structure has been one main aspect in the design with re- spect to the required cw operation. Results of multiparti- cle beam dynamics simulations demonstrate the capability of each structure to handle the very high currents without particle losses and at moderate emittance growth. While the Alvarez DTL design shows less emittance growth with and without errors, the IH-DTL is attractive with respect to its compactness and mechanical robustness (1).

In the IFMIF (International Fusion Material Irradia- tion Facility) project the generation of a 125 mA, 40 MeV D+ beam is required to produce very high neutron fluxes from a liquid Li target to test appropriate wall materials for fusion reactor chambers. The linac design consists of a RFQ accelerator as first part (0.1 - 5 MeV) followed by a drift tube linac from 5 to 40 MeV. The required cw opera- tion favours a superconducting approach with shorter length, high efficiency and larger aperture, which gives a higher safety margin against possible particle losses and resulting structure activation. One well suited candidate may be the CH-structure, which combines high accelera- tion efficiency with comparatively small geometrical di- mensions. In a first attempt a beam dynamics design has been studied: a combination of a normal-conducting IH- cavity followed by a superconducting 175 MHz CH- section, which fulfils the IFMIF requirements. The DTL length is about 11 m only. Results of multiparticle simula- tions shows smooth beam behaviour and will be discussed together with the main structure parameters.

In the IFMIF (International Fusion Material Irradiation Facility) project the generation of a 125 mA, 40 MeV D + beam is required to produce very high neutron fluxes from a liquid Li target to test appropriate wall materials for fusion reactor chambers. The linac design consists of a RFQ accelerator as first part (0.1 - 5 MeV) followed by a drift tube linac from 5 to 40 MeV. The required cw operation favours a superconducting approach with shorter length, high efficiency and larger aperture, which gives a higher safety margin against possible particle losses and resulting structure activation. One well suited candidate may be the CH-structure, which combines high acceleration efficiency with comparatively small geometrical dimensions. In a first attempt a beam dynamics design has been studied: a combination of a normal-conducting IHcavity followed by a superconducting 175 MHz CHsection, which fulfils the IFMIF requirements. The DTL length is about 11 m only. Results of multiparticle simulations shows smooth beam behaviour and will be discussed together with the main structure parameters.

H-type cavities have been successfully developed during the last 30 years for a large variety of applications in the field of ion acceleration. Radio Frequency Quadrupole (RFQ) and Drift Tube Linac (DTL) versions were designed in the H11(0)- and in the H21(0)-mode. The Interdigital H-type (IH) drift tube structure is efficient for an energy range from 0.1 to 20 MeV/u, especially in combination with the KONUS beam dynamics layout. At higher beam velocities higher frequencies must be applied for efficient operation, which can be achieved with the CHstructure (H21(1)-mode). Frequencies range from 150-800 MHz at beam energies from about 2 to 150 MeV/u. The CH-structure has small transverse dimensions and is mechanically robust using crossed stems. This opens the possibility to build superconducting (sc) cavities, which is advantageous for cw operation. In this paper we present two beam dynamics layouts for light ion accelerators with intense beams, using the KONUS beam dynamics design: a) For an International Fusion Material Irradiation Facility (IFMIF) the acceleration of a 125 mA Deuterium beam from 2.5-20 MeV/u is required in cw operation. A combination of one rt IH-tank followed by a 175 MHz sc CHDTL has been considered. b) Several proposals deal with the acceleration of proton beams with currents ranging from a few mA up to 100 mA. Here the sc CH-DTL could cover the medium energy part of the linac from several MeV/u input energies up to about 150 MeV/u. For a 350/700 MHz frequency combination a layout is presented, which is oriented on the requirements to the linac of an Accelerator Driven System (ADS) for waste transmutation or/and energy production. Beam simulations show in all cases that the required intensities could be accelerated with good emittance preservation, high transmission and high efficiency.

In the framework of the IFMIF (International Fusion Material Irradiation Facility) project study particle dynamics calculations have been performed for a 175 MHz, 125 mA deuteron linac. The linac has to provide a 40 MeV beam with low losses and small emittance growth for the homogenous irradiation of a Li target. The linac consists of an RFQ injector followed by a drift tube linac. The complete facility would need in parallel operation two 125 mA linac. In a first attempt the particle dynamics layout of an Alvarez type DTL has been studied aiming for low RF voltages and moderate power losses in the structure due to the required CW operation. In addition first investigations have been started for an H-type DTL to further evaluate the capability of this structure for the acceleration of high intensity beams. Results will be presented and discussed including matching requirements to the DTL.

With the new concept of indirectly driven targets for heavy ion inertial fusion, the driver scenarios had to be reconsidered. A European study group (HIDIF collaboration) investigated the feasibility of a driver facility based on a linac and storage ring approach (Hofmann and Plass (Eds.), GSI-98-06 GEP, Darmstadt, 1998). In a preinjector consisting of an array of ion sources, rf-linacs and funnel devices a 400 mA Bi+ beam is formed, which is further accelerated in a main linac from about 2 GeV to its final energy of 10 GeV and then injected into the rings for storage and pulse compression. The most important requirements for the beam dynamics layout of this high intensity heavy ion linac are transmission rates of nearly 100% and very low emittance growth to avoid particle losses along the linac and at ring injection which may cause radioactivation of the structures. A particle dynamics design of an Alvarez type drift tube linac (DTL) has been successfully carried out with respect to high stability of the beam against errors and mismatch, which was checked by multiparticle simulations. Statistical errors of rf field amplitude and phase and quadrupole gradients were taken into account as well as current fluctuations, initial mismatch modes and changes of particle input distributions and combinations of different errors. Results of Monte Carlo simulations with up to 20,000 particles show a smooth behaviour of the beam and small halo development only. In addition the “telescoping” option, where three different ion species are accelerated, and the necessary modifications for the linac, have been investigated.

* Work supported by NSFC On the basis of the successful running of a 26 MHz Integral Split Ring RFQ as an Ion Implanting machine at Peking University, and the simultaneous acceleration of 300 keV O and O ions, a 1 MeV RFQ for implanting N and O ions has been completed. The RFQ tank is 2.6 m in length and 75 cm in diameter. The mini-vane electrodes are of two-dimensional cutting with cooling water channels. The ion beam reached 1 MeV at a peak RF power of 25 kW with a duty factor of 1/6. The beam transport efficiency for both O and O ions reached more than 83%. The performance and parameters of the RFQ are presented in the paper. The simultaneous implantation of both positive and negative ions at deliberate ratios is to be further studied.

Recent ion source developments resulted in the generation of high brilliance, high current beams of protons and light ions. After extraction and transport the beams with large internal space charge forces have to be captured, bunched and preaccelerated for the injection into the following driver part of a new generation of high intensity beam facilities for neutron sources, energy production, transmutation e.g. A combination of RFQ and DTL is considered to be a good solution for such a high current ion injector. Some preliminary beam dynamics layouts have been investigated by multiparticle simulations. Basic parameters like frequency, ion energy and sparking have been varied for the International Fusion Material Irradiation Facility (IFMIF) scenario as an example. The main interest was directed to high transmission, low losses and emittance conservation. The beam matching to the RFQ is shortly discussed as well as the matching between RFQ and DTL.

Multi-particle beam dynamics calculations in presence of large beam currents have been carried out for a heavy ion Drift Tube Linac (DTL), in the framework of a European study group on Heavy Ion Driven Inertial Fusion (HIDIF). Linac design parameters were determined for high transmission and low emittance growth; then statistical errors as well as on-asis mismatch were added. The influence of field errors and different mismatch combinations on beam halo formation and emittance increase has been studied numerically, e.g. phase and amplitude jitters of the rf field, small changes of quadrupole gradients, mismatch of beam bunches at linac input. For proper ring injection, a transfer line and a bunch rotation cavity have to be inserted between linac and storage rings. The energy spread reduction after bunch rotation has been investigated both numerically and analytically, comparing an ideal case with a more realistic one which includes rf errors and mismatch.