1. Cavendish Laboratory JJ Thomson Avenue Cambridge CB3 0HE UK
2. Faculty of Fundamental Problems of TechnologyWroclaw University of Science and Technology Wybrzeże Wyspiażskiego 27 50‐370 Wrocław Poland
3. Laboratoire National des Champs Magnetiques IntensesCNRS‐UJF‐UPS‐INSA 143 avenue de Rangueil 31400 Toulouse France
4. Institute of PhysicsFaculty of PhysicsAstronomy and InformaticsNicolaus Copernicus University 5th Grudziadzka St. 87‐100 Torun Poland