1. B. I. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin Ave., 61103 Kharkov, Ukraine
2. National Technical University “Kharkov Polytechnic Institute”, 21 Frunze str., 61002 Kharkov, Ukraine
3. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, UK, OX110QX
4. P. J. Šafárik University in Košice, Faculty of Science, Park Angelinum 9, 04154 Košice, Slovakia