The cover image is a picture of the new 60Co spherically symmetric source (before final welding of the outer hemispheres) designed by NIST for testing radiation detection instruments. The inner sphere is designed to mimic 60Co gamma-ray beam irradiators inside their closed shielding while the outer sphere allows the source to float in water. See the article in this issue of the Journal by Lucas and Pibida for more information about this subject. Cover arranged by C. Carey