The prototype IFMIF cryomodule encloses eight superconducting 175 MHz beta 0.09 Half-Wave Resonators (HWR). They are designed together with the power coupler to accelerate a high intensity deuteron beam (125 mA) from to 5 to 9 MeV. One prototype HWR and the 8 cavities to be hosted in the cryomodule have been manufactured, prepared and tested. The paper describes the phases of the cavities development, including fabrication, processing and RF frequency management. We focus on the results of the RF tests which have been performed for all bare and jacketed HWRs in a vertical cryostat.

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.

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.

A  = 0.5 5-cell 704 MHz cavity was developed in the framework of European R&D programs on high intensity pulsed proton injectors. Medium beta elliptical cavities are known to be sensitive to Lorentz detuning, which can become difficult to deal with in pulsed operation. The cavity was optimized to reduce the Lorentz detuning by means of two series of rings welded around the irises, and equipped with a piezo tuning system. In order to test the cavity in pulsed mode, a power coupler with 1 MW capability was connected to the cavity. We report here on the fully equipped cavity tests at 1.8 K carried out in the horizontal cryostat Cryholab at Saclay to study its RF and mechanical behavior in pulsed mode, mostly with 2 ms pulses at a 50 Hz repetition rate. The compensation of Lorentz force detuning has been achieved at an accelerating gradient of 13 MV/m (44 MV/m peak surface electric field).

In the framework of the European CARE-HIPPI program we develop components for superconducting high pulsed power proton linacs at 704 MHz. We have designed, fabricated and tested a beta 0.47 5-cell elliptical cavity with an optimized stiffening to reduce its sensitivity to Lorentz forces. A fast piezo tuner has been developed in order to be able to operate the cavity in pulsed mode in our horizontal test cryostat CryHoLab. We also have carried out the development of a fundamental power coupler. It is designed to transmit a power up to 1 MW at a 10 % duty cycle. A high power test area has been setup consisting of a 1 MW klystron, a pulsed high voltage power supply and a coupler test stand.

Coaxial 704 MHz power couplers have been developed for high intensity superconducting proton linacs. Projects like the Superconducting Proton Linac (SPL)[1] at CERN or the European Spallation Source ESS require up to 1 MW pulsed power with a high duty cycle in the high energy section of superconducting elliptical cavities. One pair of couplers has been successfully conditioned on the 704 MHz test stand at Saclay at room temperature at a maximum power of 1.2 MW, with 2 ms pulses and 50 Hz repetition rate, equivalent to 10% duty cycle. In order to test the coupler in realistic conditions with its cryogenic environment, we prepare a cold test with a cavity in the horizontal cryostat Cryholab.

In the frame of the CARE/HIPPI programme, superconducting accelerating cavities for pulsed proton injectors are developed. Qualification of these 704 MHz RF structures fully equipped (housed in a helium tank, with tuning system and power coupler), requires to perform high power tests in the existing horizontal cryostat CryHoLab. Before the CARE programme started, not any of European test sites was equipped with a 704 MHz high power RF source in the MW range. During the last two years, CEA-Saclay built and ordered the necessary RF equipments to make such a platform for high power RF tests in a cryogenic environment available to the partners in HIPPI and later on to any other interested European teams.

The beam-based alignment and feedback systems, essential for the future colliders, need high resolution Beam Position Monitors (BPM). In the framework of the European CARE/SRF program, the task of CEA/DSM/DAPNIA covers the design, the fabrication and the beam test of these BPMs in collaboration with DESY. The objective of this program is the production of a BPM that has a resolution five times better than the existing device while maintaining a high time resolution and which can be used in a clean environment at cryogenic temperature. Two prototypes of this monitor, based on a radio-frequency cavity with a beam pipe diameter of 78 mm, are installed on the Free Electron LASer in Hamburg (FLASH).

The power coupler needed for beta = 0.65 SRF elliptical cavities dedicated to the driver of XADS (eXperimental Accelerator Driven System) should transmit a CW RF power of 150 kW to a 10 mA proton beam. The estimated average values of the RF losses in the coupler are 130 W (respectively 46 W) for the inner (respectively outer) conductor in SW mode. Due to such high values of the RF losses, it is necessary to very carefully design and optimize the cooling circuits of the coupler in order to efficiently remove the generated heat and to reduce the thermal load to the cavity operating at T = 2 K.An experiment simulating the thermal interaction between the power coupler and a 704 MHz SRF five cells cavity was performed in the CRYHOLAB test facility in order to determine the critical heat load that can be sustained by the cavity without degradation of its RF performance. Experimental data are compared to numerical simulation results obtained with the Finite Element Method code COS-MOS/M. These data allow us also to perform in situ measurements of the thermal parameters needed in the thermal model of the coupler (thermal conductivity, thermal contact resistance). These data are used to validate numerical simulations. (c) 2006 Elsevier B.V. All rights reserved.

A high resolution Beam Position Monitor (BPM) is necessary for the beam‐based alignment systems of high energy and low emittance electron linacs. Such a monitor is developed in the framework of the European CARE/SRF programme, in a close collaboration between DESY and CEA/DSM/DAPNIA. This monitor is a radiofrequency re‐entrant cavity, which can be used either at room or cryogenic temperature, in an environment where dust particle contamination has to be avoided, such as superconducting cavities in a cryomodule. A first prototype of a re‐entrant BPM has already delivered measurements at 2K. inside the first cryomodule (ACC1) on the TESLA Test Facility 2 (TTF2). The performances of this BPM are analyzed both experimentally and theoretically, and the limitations of this existing system clearly identified. A new cavity and new electronics have been designed in order to improve the position resolution down to 1 μm and the damping time down to 10 ns.

In the framework of super conducting RF cavity R&D for high intensity proton LINAC (XADS, EURISOL ...) the IPN Orsay CEA-Saclay collaboration is developing five-cell (700 MHz, β = 0.65) cavity for the high energy section of the LINAC. A first prototype, previously tested in vertical cryostat, has been equipped with a stainless steel 316 L helium vessel and tested in the horizontal facility « CRYHOLAB » at 2K. The cryogenic installation of « CRYHOLAB » is now fully integrated and the cryostat is directly feed from a 120 l/h helium liquefier. After a short overview of the cavity horizontal tests results the cryogenic installation developments and performances will be presented .

The first five-cell niobium superconducting cavity (700 MHz, /spl beta/=0.65) has been successfully tested in the horizontal cryostat CryHoLab. Technological choices like equipment with stainless steel helium vessel and flanges appeared to be viable for the future. Preceding this test, several operations have been performed: field flatness adjustment, chemical etching, heat treatment and RF measurements in a vertical cryostat. Good performances for a multicell cavity were obtained. However, field emission and not yet elucidated phenomenon limit the accelerating field around 16 MV/m.