|  | G |
SECTION G — PHYSICS

|  | G |
Note(s) In this section, the following term is used with the meaning indicated: "variable" (as a noun) means a feature or property (e.g., a dimension, a physical condition such as temperature, a quality such as density or colour) which, in respect of a particular entity (e.g., an object, a quantity of a substance, a beam of light) and at a particular instant, is capable of being measured; the variable may change, so that its numerical expression may assume different values at different times, in different conditions or in individual cases, but may be constant in respect of a particular entity in certain conditions or for practical purposes (e.g., the length of a bar may be regarded as constant for many purposes). Attention is drawn to the definitions of terms or expressions used, appearing in the notes of several of the classes in this section, in particular those of "measuring" in class Fulltext... Hierarchy... Expanded...G01 and "control" and "regulation" in class Fulltext... Hierarchy... Expanded...G05. Classification in this section may present more difficulty than in other sections, because the distinction between different fields of use rests to a considerable extent on differences in the intention of the user rather than on any constructional differences or differences in the manner of use, and because the subjects dealt with are often in effect systems or combinations, which have features or parts in common, rather than "things", which are readily distinguishable as a whole. For example, information (e.g., a set of figures) may be displayed for the purpose of education or advertising (Fulltext... Hierarchy... Expanded...G09), for enabling the result of a measurement to be known (Fulltext... Hierarchy... Expanded...G01), for signalling the information to a distant point or for giving information which has been signalled from a distant point (Fulltext... Hierarchy... Expanded...G08). The words used to describe the purpose depend on features that may be irrelevant to the form of the apparatus concerned, for example, such features as the desired effect on the person who sees the display, or whether the display is controlled from a remote point. Again, a device which responds to some change in a condition, e.g., in the pressure of a fluid, may be used, without modification of the device itself, to give information about the pressure (Fulltext... Hierarchy... Expanded...G01L) or about some other condition linked to the pressure (another subclass of class Fulltext... Hierarchy... Expanded...G01, e.g., Fulltext... Hierarchy... Expanded...G01K for temperature), to make a record of the pressure or of its occurrence (Fulltext... Hierarchy... Expanded...G07C), to give an alarm (Fulltext... Hierarchy... Expanded...G08B), or to control another apparatus (Fulltext... Hierarchy... Expanded...G05). The classification scheme is intended to enable things of a similar nature (as indicated above) to be classified together. It is therefore particularly necessary for the real nature of any technical subject to be decided before it can be properly classified.

NUCLEONICS

|  | G21 |
NUCLEAR PHYSICS; NUCLEAR ENGINEERING

|  | G21K |
TECHNIQUES FOR HANDLING PARTICLES OR ELECTROMAGNETIC RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA- OR X-RAY MICROSCOPES (X-ray technique Fulltext... Hierarchy... Expanded...H05G; plasma technique Fulltext... Hierarchy... Expanded...H05H) [2]

|  | G21K 1/00 |
Arrangements for handling radiation or particles, e.g. focusing, moderating (radiation filters Fulltext... Hierarchy... Expanded...G21K 3/00) [2]

|  | G21K 1/02 |
· | using diaphragms, collimators [2]

|  | G21K 1/04 |
· · | using variable diaphragms, shutters, choppers [2]

|  | G21K 1/06 |
· | using diffraction, refraction, or reflection, e.g. monochromators (Fulltext... Hierarchy... Expanded...G21K 1/10, Fulltext... Hierarchy... Expanded...G21K 7/00 take precedence) [2]

|  | G21K 1/08 |
· | Deviation, concentration, or focusing of the beam by electric or magnetic means (electron-optical arrangements in electric discharge tubes Fulltext... Hierarchy... Expanded...H01J 29/46) [2]

|  | G21K 1/087 |
· · | by electrical means [4]

|  | G21K 1/093 |
· · | by magnetic means [4]

|  | G21K 1/10 |
· | Scattering devices; Absorbing devices [2]

|  | G21K 1/12 |
· · | Resonant absorbers or driving arrangements therefor, e.g. for Mössbauer-effect devices [3]

|  | G21K 1/14 |
· | using charge exchange devices, e.g. for neutralising or changing the sign of the electrical charges of beams (producing or accelerating neutral particle beams Fulltext... Hierarchy... Expanded...H05H 3/00) [3]

|  | G21K 1/16 |
· | using polarising devices, e.g. for obtaining a polarised ion beam [3]

|  | G21K 3/00 |
Radiation filters, e.g. X-ray filters [2]

|  | G21K 4/00 |
Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens (photographic processes using X-ray intensifiers Fulltext... Hierarchy... Expanded...G03C 5/17; discharge tubes comprising luminescent screens Fulltext... Hierarchy... Expanded...H01J 1/62; cathode ray tubes for X-ray conversion with optical output Fulltext... Hierarchy... Expanded...H01J 31/50) [3]

|  | G21K 5/00 |
Irradiation devices (adaptations of reactors to facilitate irradiation Fulltext... Hierarchy... Expanded...G21C 23/00; discharge tubes for irradiating Fulltext... Hierarchy... Expanded...H01J 33/00, Fulltext... Hierarchy... Expanded...H01J 37/00) [2]

|  | G21K 5/02 |
· | having no beam-forming means [2]

|  | G21K 5/04 |
· | with beam-forming means [2]

|  | G21K 5/08 |
· | Holders for targets or for objects to be irradiated [2]

|  | G21K 5/10 |
· | with provision for relative movement of beam source and object to be irradiated [3]

|  | G21K 7/00 |
Gamma- or X-ray microscopes [2]