Full Characterization at Low Temperature of Piezoelectric Actuators Used for SRF Cavities Active Tuning

In the frame of the CARE project activities, supported by EU, IPN Orsay participate to the development of a fast cold tuning system for SRF cavities operating at a temperature T=2 K. The study is aimed at full characterization of piezoelectric actuators at low temperature. A new experimental facility was developed for testing various prototypes piezoelectric actuators and successfully operated for T in the range 1.8 K-300 K. Different parameters were investigated as function of T: piezoelectric actuator displacement vs. applied voltage V, capacitance vs. T, dielectric and thermal properties vs. T and finally heating DT due to dielectric losses vs. modulating voltage Vmod and frequency. We observed a decrease of the Full Range Displacement (FRD or DX) of the actuator from ~40μm @ 300K down to 1.8μm-3μm @ 1.8K, depending on both material and fabrication process of the piezostacks. Besides, both material and fabrication process have a strong influence on the shape of the characteristics DX vs. T dependence. Moreover, the variations of losses tangent with T show a maximum at T in the range 30 K-120 K. Finally a dedicated facility located at CERI (Orléans, France) for radiation hardness tests of actuators with fast neutrons at T=4.2 K was developed and the first beam tests results are summarized

An Approach for Component-Level Analysis of Cryogenic Process in Superconducting LINAC Cryomodules

International audiencePowerful superconducting linear accelerators feature accelerating sections consisting in a series of cryomod-ules (CM), each hosting superconducting radiofrequency (SRF) cavities cooled by a cryogenic process. Despite the extensive instrumentation used for the tests and valida-tion of the prototype cryomodules, it is usually very complex to link the measured global thermodynamic efficiency to the individual component performance. Previous works showed methods for assessing the global efficiency and even for allocating performances to sets of components, but few went down to a component level. For that purpose, we developed a set of techniques based on customized instrumentation, on dedicated test proto-cols, and on model-based analysis tools. In practice, we exposed the components to various operating conditions and we compared the measured data to the results from a detailed dynamic component model at the same condi-tions. This method was applied to the cryogenic debug-ging phase of the tests of the MINERVA prototype cry-omodule, which, despite the liquid helium shortage, led to an extensively detailed characterisation, for its valida-tion towards the serial construction

Accelerated Lifetime Test of Spoke Cavity Cold Tuning Systems for Myrrha

International audienceWithin the framework of MINERVA, the first Phase of MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) project, IN2P3 labs are in charge of the developments of several accelerator elements. Among those, a fully equipped Spoke cryomodule prototype was constructed, it integrates two superconducting single spoke cavities operating at 2K, the RF power couplers and the associated cold tuning systems. The extreme reliability specified for this project motivated to conduct ALT (Accelerated Lifetime Test) on two extra cold tuning systems in cryomodule like environment. Thus, by gathering information from experimental data, many aspects can be enhanced like maintenance plan consolidation, determination of aging indicators and design optimization of the whole system and its sub components. This paper describes the complete ALT process from the studying elements and the test environment design, to the experimental results and findings

Design of a New Horizontal Test Cryostat for Scrfcavities at the Uppsala University

At Uppsala University, the FREIA facility for researchand development of new accelerators and associatedinstrumentation, is presently in construction. Associatedto a new Helium Liquefier, a Horizontal Test Cryostat willbe used for high power RF tests of completely equippedSC cavities. This paper presents the main characteristicsof the cryostat. Two types of cavities have beenconsidered for test purpose: SC elliptical cavities forfuture free electron lasers and SC cavities for highintensity proton accelerators. A special valve boxincluding a subcooling stage and power coupler coolingwith supercritical Helium supply have been designed, fortemperature operation ranging from 2 K to 4.2 K. Thisfacility will play an essential role in the development andtest of cavities, couplers and cryomodules for the ESSproject. High power RF sources will be installed in orderto allow unique and complete tests of spoke cavities andcryomodules at high nominal peak power

Performances of the Two First Single Spoke Prototypes for the MYRRHA Project

International audienceThe MYRRHA project aims at the construction of an accelerator driven system (ADS) at MOL (Belgium) for irradiation and transmutation experiment purposes. The facility will feature a superconducting LINAC able to produce a proton flux of 2.4 MW (600 MeV - 4 mA). The first section of the superconducting LINAC will be composed of 352 MHz (β = 0.37) Single Spoke Resonators (SSR) housed in short cryomodules operating at 2K. After a brief presentation of the cryomodule design, this paper will aim at presenting the RF performances of the SSR tested in vertical cryostat in the framework of European MYRTE project (MYRRHA Research and Transmutation Endeavour) and at comparing experimental results (Lorentz forces, pressure sensitivity, multipacting barriers…) to simulated values

Design of a New Horizontal Test Cryostat for Scrfcavities at the Uppsala University

At Uppsala University, the FREIA facility for researchand development of new accelerators and associatedinstrumentation, is presently in construction. Associatedto a new Helium Liquefier, a Horizontal Test Cryostat willbe used for high power RF tests of completely equippedSC cavities. This paper presents the main characteristicsof the cryostat. Two types of cavities have beenconsidered for test purpose: SC elliptical cavities forfuture free electron lasers and SC cavities for highintensity proton accelerators. A special valve boxincluding a subcooling stage and power coupler coolingwith supercritical Helium supply have been designed, fortemperature operation ranging from 2 K to 4.2 K. Thisfacility will play an essential role in the development andtest of cavities, couplers and cryomodules for the ESSproject. High power RF sources will be installed in orderto allow unique and complete tests of spoke cavities andcryomodules at high nominal peak power

MYRRHA 80 kW CW RF Coupler Design

International audienceMYRRHA [1] (Multi Purpose Hybrid Reactor for High Tech Applications) is an Accelerator Driven System (ADS) project. Its superconducting linac will provide a 600 MeV - 4 mA proton beam. The first project phase based on a 100 MeV linac is launched. The Radio-Frequency (RF) couplers have been designed to handle 80 kW CW at 352.2 MHz. This paper describes the thermal, mechanical and RF studies leading to the final design of the RF coupler

Integrated Prototyping in View of the 100 MeV Linac for Myrrha Phase 1

International audienceThe MYRRHA project borne by SCK•CEN, the Belgian Nuclear Research Centre, aims at realizing a pre-industrial Accelerator Driven System (ADS) for exploring the transmutation of long lived nuclear waste. The linac for this ADS will be a High Power Proton Accelerator delivering 2.4 MW CW beam at 600 MeV. It has to satisfy stringent requirements for reliability and availability: a beam-MTBF of 250h is targeted. The reliability goal is pursued through a phased approach. During Phase 1, expected till 2024, the MYRRHA linac up to 100 MeV will be constructed. It will allow to evaluate the reliability potential of the 600 MeV linac. It will also feed a Proton Target Facility in which radioisotopes of interest will be collected through an ISOL system. This contribution will focus on the transition to integrated prototyping, which will emphasize (i) a test platform consisting of the initial section of the normal conducting injector (5.9 MeV), (ii) the realization of a complete cryomodule for the superconducting linac and of its cryogenic valve box. The cryomodule will house two 352 MHz single spoke cavities operated at 2K