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Radiation hardness tests of piezoelectric actuators with fast neutrons at liquid helium temperature
M. Fouaidy1, G. Martinet1, N. Hammoudi1, F. Chatelet1, A. Olivier1, S. Blivet1, F. Galet1

Piezoelectric actuators, which are integrated into the cold tuning system and used to compensate the small mechanical deformations of the cavity wall induced by Lorentz forces due to the high electromagnetic surface field, may be located in the radiation environment during particle accelerator operation. In order to provide for a reliable operation of the accelerator, the performance and life time of piezoelectric actuators (~24.000 units for ILC) should not show any significant degradation for long periods (i.e. machine life duration: ~20 years), even when subjected to intense radiation (i.e. gamma rays and fast neutrons). An experimental program, aimed at investigating the effect of fast neutrons radiation on the characteristics of piezoelectric actuators at liquid helium temperature (i.e. T~4.2 K), was proposed for the working package WP#8 devoted to tuners development in the frame of CARE project. A neutrons irradiation facility, already installed at the CERI cyclotron located at Orléans (France), was upgraded and adapted for actuators irradiations tests purpose. A deuterons beam (maximum energy and beam current: 25 MeV and 35µA) collides with a thin (thickness: 3 mm) beryllium target producing a high neutrons flux with low gamma dose (~20%): a neutrons fluence of more than 1014 n/cm2 is achieved in ~20 hours of exposure. A dedicated cryostat was developed at IPN Orsay and used previously for radiation hardness test of calibrated cryogenic thermometers and pressure transducers used in LHC superconducting magnets. This cryostat could be operated either with liquid helium or liquid argon. This irradiation facility was upgraded for allowing fast turn-over of experiments and a dedicated experimental set-up was designed, fabricated, installed at CERI and successfully operated for radiation hardness tests of several piezoelectric actuators at T~4.2 K. This new apparatus allows on-line automatic measurements of actuators characteristics and the cryogenic parameters. Further, the test-cell and actuators are equipped with high purity Ni foils for measuring the total neutrons dose by an activation method. In this report, the details of the irradiation test facility will be described then the experimental data will be analyzed and discussed.
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
Physique/Physique/Instrumentations et Détecteurs
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