• J.-L. Biarrotte
  IPN, Orsay
• P. Bertrand
  GANIL, Caen
• C. Peaucelle
  IN2P3 IPNL, Villeurbanne
• T. Thuillier
  LPSC, Grenoble
• O. Tuske, D. Uriot
  CEA, Gif-sur-Yvette

The SPIRAL-2 superconducting linac driver, which aims at delivering 5 mA, 40 MeV deuterons and up to 1 mA, 14.5 A.MeV q/A=1/3 heavy ions, has now entered its construction phase in GANIL (Caen, France). The linac is composed of two injectors feeding one single RFQ, followed by a superconducting section based on 88 MHz independently-phased quarter-wave cavities with room-temperature focusing elements. The first stages of the injectors have been fully built and are now operational. They have been partly commissioned with beam in Grenoble and Saclay in 2010. This paper describes the results obtained so far in this context.

• F.B. Bouly, J.-L. Biarrotte, C. Joly
  IPN, Orsay

An Accelerator Driven System (ADS) for transmutation of nuclear waste requires a high power proton beam (several MWs) to reach the necessary spallation efficiency. Due to the induced thermal stress to the subcritical core, the high-power proton linac will have to fulfil stringent reliability requirements to minimise the number of unwanted beam trips (> 1 sec.) per operation cycle. In view of the construction of the MYRRHA ADS demonstrator, in Mol (Belgium), beam dynamic analyses were carried out to evaluate the fault tolerant capability of the superconducting linac, in the particular case of a radiofrequency (RF) cavity failure. This analysis was coupled with simulations on the RF behaviour of 700 MHz superconducting cavitiy as well as its tuning and feedback loop systems. Such considerations led to the development of a prototypical digital Low Level RF (LLRF) system to control the cavity phase and accelerating field, especially in the case of fast cavity retuning for failure compensation. In this paper we summarize the work which has been performed so far toward the development of such a fault-tolerant RF linac.

• J.-L. Biarrotte
  IPN, Orsay
• H. Klein
  IAP, Frankfurt am Main
• A.C. Mueller
  IN2P3, Paris
• P. Pierini
  INFN/LASA, Segrate (MI)
• D. Vandeplassche
  SCK-CEN, Mol

The goal of the MYRRHA project is to demonstrate the technical feasibility of transmutation in an Accelerator Driven System (ADS) by building a new flexible irradiation complex in Mol (Belgium). The MYRRHA facility requires a 600 MeV accelerator delivering a maximum proton flux of 4 mA CW operation. Such a machine belongs to the category of the high-power proton accelerators, with an additional requirement for exceptional reliability: because of the induced thermal stress to the subcritical core, the number of unwanted beam interruptions should be minimized down to the level of about 10 per 3-month operation cycle, a specification that is far above usual proton accelerators performance. This paper describes the reference solution adopted for such a machine, based on a so-called 'fault-tolerant' linear superconducting accelerator, and presents the status of the associated R&D.

• F.B. Bouly, J.-L. Biarrotte, S. Bousson, C. Commeaux, C. Joly, J. Lesrel
  IPN, Orsay
• A. Bosotti, P.M. Michelato, R. Paparella, P. Pierini, D. Sertore
  INFN/LASA, Segrate (MI)

Accelerator Driven systems (ADS) are being considered for their potential use in the transmutation of nuclear waste. Because of the induced thermal stress to the subcritical core, the high-power proton LINAC will have to fulfill stringent reliability requirements and to minimize the number of unwanted beam trips per operation cycle. It is forseen to build an ADS demonstrator (MYRRHA) in Mol (Belgium). Such a device will be piloted by a 600 MeV / 4mA superconducting linac. IPN Orsay and INFN Milano are in charge of the realisation and tests of a prototypical cryomodule for the high energy section of the accelerator, equipped with a 5-cell superconducting cavity. Developed at INFN, this RF cryogenic accelerating device is tested for the first time at IPN. We will describe the status of the R&D activities on this device. The first low power tests of the 5-cell superconducting cavity in its prototypical cryomodule will be reviewed. Those tests aim to evaluate the cavity performances after installation in the module (16MV/m in vertical test) but also to measure the tuning systems behaviors in view of reliability considerations for 'fast fault-recovery scenarios'.

• E. Rampnoux, S. Berthelot, J.-L. Biarrotte, P. Blache, C. Commeaux, F. Doizon, D. Grolet, P. Szott, J.-F. Yaniche
  IPN, Orsay

MYRRHA project consists of the construction of an experimental facility in order to demonstrate the technical feasibility of Transmutation of high-level nuclear waste in an Accelerator Driver System. Thus the sub-critical core must be fed by a neutron beam resulting from a great quality spallation of a high-intensity proton beam on a target. Because of the induced thermal stress to the subcritical core, the high-power proton LINAC must have a great reliability to minimize the number of unwanted beam trips. The MYRRHA ADS demonstrator requires a high power proton superconductive linac (600MeV/4mA) operating in CW mode with the characteristic that each components of it must have the greatest reliability. In this framework IPN Orsay is in charge of the development of a power coupler for the 5-cells superconducting cavities present in the high energy section of the linac. We will describe all the stages about power coupler developments, from the conception to the conditioning. We will present the design, the commissioning of the test stand and the results of the couplers conditioning. A last part will show the reliability tests carried out with a 50 kW RF power during a long time.