The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV cw deutron accelerators. A superconducting option for the 5 to 40 MeV linac is based on Half-Wave Resonators (HWR) has been choosen. The first cryomudule should contain 8 HWR's with resonant frequency of 175 MHz and β=v/c=0.094. The paper describes RF design of half-wave length resonator. The requirents on high power coupler define its installation in the cavity central region. Few options of cavity tune were investigated, the capacitive tuner installed opposite to the coupler port have been accepted. The cavity structural analyses have been conducted and cavity stiffening has been worked out.

The Linear IFMIF Prototype Accelerator (LIPAc), which is presently under design and realization, aims to accelerate a 125 mA deuteron beam up to 9 MeV. Therefore, a low-beta 175 MHz Half-Wave Resonator (HWR) was initially designed and manufactured with a tuning system based on a capacitive plunger located in the electric field region. Following the results of the vertical tests at 4.2K, this tuning system was abandoned and replaced by a conservative solution based on the HWR wall deformation using an external mechanical tuner. This paper will focus on the manufacturing of the prototype cavity, the studies realized to explain the first test results and the solutions taken to overcome the difficulties, leading to the validation of the prototype. Then, we will present the new cavity design.

The Linear IFMIF Prototype Accelerator (LIPAc), which is presently under design and realization, aims to accelerate a 125 mA deuteron beam up to 9 MeV. Therefore, a low-beta 175 MHz Half-Wave Resonator (HWR) was initially designed and manufactured with a tuning system based on a capacitive plunger located in the electric field region. Following the results of the vertical tests at 4.2K, this tuning system was abandoned and replaced by a conservative solution based on the HWR wall deformation using an external mechanical tuner. This paper will focus on the manufacturing of the prototype cavity, the studies realized to explain the first test results and the solutions taken to overcome the difficulties, leading to the validation of the prototype. Then, we will present the new cavity design.

N. Bazin, P. Bosland, S. Chel, G. Devanz, N. Grouas, P. Hardy, J. Migne, F. Orsini, F. Peauger, CEA, F-91191, Gif-sur-Yvette, France Abstract In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV [1], a Linear IFMIF Prototype Accelerator (LIPAc) is presently under design for the first phase of the project. A superconducting option has been chosen for the 5 MeV RF Linac, based on a cryomodule composed of 8 low-beta Half Wave Resonators (HWR), 8 Solenoid Packages and 8 RF couplers. The initial solution for the frequency tuning system of the HWR was an innovated system based on a capacitive plunger located in the electric field region, allowing a large tuning range of ±50 kHz, while keeping the cavity rigid enough to fulfill the Japanese regulations on pressurized vessel. Following the cold test results obtained on HWR equipped with the first design of plunger in 2011 [2], the project decided to change the tuning system by a more conservative solution based on the HWR wall deformation. Nevertheless RF and thermal simulations were realized to understand the previous test results and the conceptual design of a new plunger in niobium was proposed to resolve the issue. The mechanical constraint is to sufficiently deform the plunger to tune the cavity while staying in the elastic range of the niobium material. For the thermal simulations, all the non-linear properties of the materials and the effects of the RF fields are taken into account: thermal conductivity and surface resistance are depending on the temperature, RF fields computed with dedicated software are leading to thermal dissipations in the materials and the vacuum seal.

The design phase of the IFMIF-EVEDA Power Couplers for the Superconductive HWR has been accomplished. TiN and copper coatings specifications have been validated on samples. A coupler window equipped with a truncated antenna and RF matching transition have been fabricated and tested to qualify the manufacturing processes and to demonstrate the technical feasibility of the coupler. Series of tests were successfully performed on these subassemblies. The last part of the design phase consists of the design validation by manufacturing two coupler prototypes and testing their performances at full power. Finishing processes and validation tests are on-going.

In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV [1], a Linear IFMIF Prototype Accelerator (LIPAc) is presently under design for the first phase of the project. A superconducting option has been chosen for the 5 MeV RF Linac, based on a cryomodule composed of 8 low-beta Half Wave Resonators, 8 Solenoid Packages and 8 RF couplers. This paper will mainly focus on recent tests in laboratory of the main components of this cryomodule: HWR, RF coupler mock up, and solenoid prototypes. A section is dedicated to the HWR activities: realization and preliminary vertical tests of the two HWR prototypes. One prototype was equipped with the innovating cold tuning system, located in the central region of the cavity. Another section gives results on RF coupler’mock-up and solenoids prototypes. Finally, the LIPAc cryomodule current design is also presented.

The Linear IFMIF Prototype Accelerator (LIPAc) will be a 9 MeV, 125 mA CW deuteron accelerator which aims to validate the technology that will be used in the future IFMIF accelerator. The SRF Linac design is based on superconducting Half Wave Resonators (HWR) cavities operating at 4.4 K. Due to space charge associated to the high intensity beam, a short, but strong, superconducting focusing magnet package is necessary between cavities. The selected configuration has been a superconducting NbTi solenoid acting as a magnetic lens and a concentric outer solenoid in antiparallel configuration to reduce the harmful stray field on the cavities. The selected arrangement for the steerers is a pair of parallel racetrack coils for each vertical and horizontal axis. This paper describes the manufacturing techniques of the different coils, and the tests realized in warm and cold conditions. Special attention is put to the training test of the main solenoid, since the nominal working point in the load line is very high (86.2%).

In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power CW accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV, an accelerator prototype (EVEDA) is presently under design for the first phase of the project [1]. A superconducting option has been chosen for the 9 MeV RF Linac, based on a cryomodule composed of 8 low-beta Half-Wave Resonators (HWR), 8 Solenoid Packages and 8 RF couplers. This paper will focus on the HWR sub-system: the RF, thermo mechanical design, and the realization of the first prototype of HWR will be presented. The resonator tuning frequency is controlled by an innovating tuning system, located in the central region of the cavity. The different options for tuning will be discussed and the final thermo mechanical design will be detailed. A dedicated testbench for the tuning system under development is presented.

The IFMIF-EVEDA accelerator will handle a 9 MeV, 125 mA continuous wave (CW) deuteron beam which aims to validate the technology that will be used in the future IFMIF accelerator. The Linac design is based on superconducting Half Wave Resonators (HWR) operating at 4.4 K. Due to space charge associated to the high intensity beam, a strong superconducting focusing magnet package is necessary between cavities, with nested steerers and a Beam Position Monitor (BPM). First of all, this paper describes the preliminary study to choose between two quadrupoles or one solenoid as focusing device, both using NbTi wire. The solenoid shows more advantages, mainly associated to available space and reliability. Then, electromagnetic and mechanical design of the solenoid and the steerers are reported. Special care is taken in order to fulfil the fringe field limit at the cavity flange. An active shield configuration using an antisolenoid has been adopted, avoiding remnant magnetization associated to passive shielding materials.

The IFMIF-EVEDA project aims to de feasibility of a high intensity material irrad and one of its main components is a protot intensity deuteron accelerator. This prototyp in Rokkasho in Japan. It includes a cryomod of 8 superconducting cavities (HWR) pow kW couplers to accelerate the deuteron beam to 9 MeV. The beam is focused inside the c 8 superconducting solenoids. The cryomod to respect some severe beam dynamics req particular a restricted space for the compon and an accurate alignment to be kept d down. A double cryogenic supply has been is necessary to control the cavity cooling from the solenoid one. The cryomodule also be compatible with its environment in building. This paper gives a general ove cryomodule current design and its interfac the concept chosen for the cryogenic sy summarizes the method foreseen for the alignment and describes the integration Rokkasho.

The driver of the International Fusion Material Irradiation Facility (IFMIF) consists of two 125 mA, 40 MeV cw deuteron accelerators (1-2). A superconducting option for the 5 to 40 MeV linac based on Half-Wave Resonators (HWR) has been chosen. The first cryomodule houses 8 HWR's with resonant frequency of 175 MHz and geometric β=v/c=0.094. This paper describes the RF design of half-wave length resonator together with structural analyses. Detailed simulations of resonance multipactor discharge in HWR are presented. Due to the required high coupling, the power coupler is located in mid-plane of the cavity. Several cavity tuning options were investigated: the capacitive tuner located in mid-plane and opposite to the power coupler port offers a large tuning range and will be tested first. CAVITY RF DESIGN The goal of the cavity electrodynamics design is to optimise the cavity geometry to minimize values of peak electrical and magnetic fields on the cavity surface relative to the accelerating electrical field on the cavity axes (Bpk/Eacc and Epk/Eacc). The fabrication technology and resonator structural properties also should be taken into account from the very beginning of the design. For low-beta cavity design RF parameters do not play the same important role like for elliptical cavities. An enhancement of an accelerating field by 20-30% doesn't result in the substantial reduction of an accelerator length or the number of cavities. That's why the project values for Eacc are usually easily achievable. It means, for this type of resonators the stability of the cavity structure against any external distortions is the primer design goal.

In the framework of the International Fusion Materials Irradiation Facility (IFMIF), which consists of two high power accelerator drivers, each delivering a 125 mA deuteron beam at 40 MeV in CW, a Linear IFMIF Prototype Accelerator (LIPAc), is presently under design and realization for the first phase of the project [1]. This accelerator prototype includes a Superconducting RadioFrequency Linac (SRF Linac), which is designed for the transportation and focalization of the deuteron beam up to 9 MeV. This SRF Linac is a large cryomodule of ~6 m long, working at 4.4 K and at the frequency of 175 MHz in continuous wave. It is mainly composed of 8 low-beta Half-Wave Resonators (HWR), 8 Solenoid Packages and 8 RF Power Couplers. This paper focuses on the recent developments and changes made on the SRF Linac design: following the abandon of the HWR frequency tuning system, initially based on a plunger located inside the central region of the resonator, a new external tuning system has been designed, implying a complete redesign of the resonator and consequently impacting the cryomodule lattice. The recent changes in the design are presented in this paper. In addition, cold tests were performed on a HWR prototype and cold tests results of the magnets prototypes are also presented.