GLOSSARY OF SELECTED TERMS IN NUCLEAR SCIENCE 443 



tumor : A swelling. The term is usually synonymous with neoplasm but may be 



more vague. 



unstable: Capable of undergoing spontaneous change. Of a nu(;lide, radioactive; 



of a state of a system, excited. 



Van de Graaff generator : An electrostatic generator that employs a system of con- 

 \(>yer Ix'lt and spray points to charge an insulated electrode to a high potential. 



vibrating condenser, vibrating-reed dynamic condenser : A condenser whose capac- 

 itance is varied in a cyclic fashion so that an alternating electromotive force is devel- 

 oped proportional to the charge on the insulated electrode. This device forms the 

 basis for a type of electrometer. 



vibrating-reed electrometer : An instrument using a vibrating condenser to measure 

 a small charge. This term is often applied to denote the combination of an ionization 

 chamber and a vibrating-reed electrometer. 

 volume dose : Integral dose. 



volume ionization : Average ionization density in a given volume irrespective of the 

 specific ionization of the ionizing particles. 



water monitor : Any device for detecting and measuring water-borne radioactivity 

 for warning and control purposes. 



X rays: Penetrating electromagnetic radiations having wavelengths very much 

 shorter than those of visible light. They are usually produced by bombarding a 

 metallic target with fast electrons in a high vacuum. In nuclear reactions it is cus- 

 tomary to refer to photons originating in the nucleus as gamma rays and to those 

 originating in the extranuclear part of the atom as X rays. These rays were called 

 A' rays by their discoverer, Roentgen. Many medical radiologists prefer to call them 

 by his name; nonmedical usage is generally X rays. 



