Liquid scintillators for optical fiber applications

#This disclosure relates to liquid scintillator systems meeting the requirements of long wavelength emission and short impulse response necessary for long path, wide bandwidth optical fiber applications. Such systems are used for radiation detection and transmission of information in the form of light pulses corresponding to the radiation. The system is characterized by a new radiation-to-light converter of the type commonly called a "fluor" or a scintillator.

#Low loss optical fibers are finding increasing application in plasma diagnostics, particularly when immunity to electromagnetic interference and wide bandwidth are required. The fibers normally serve to transmit a light pulse, generated in a radiation-to-light converter, to a remote photodetector. Under some conditions, Cerenkov light generated by relativistic electrons in the fiber itself suffices to characterize the radiation environment. An example of such a system is described in U.S. Pat. No. 3,984,332, issued Oct. 5, 1976. This disclosure is concerned with the more general case where the light is generated in a liquid or plastic scintillator.

#The detection of radiation is commonly accomplished utilizing a transducer which responds to the radiation in a manner which can be used to generate an electrical signal corresponding to some characteristic of the radiation. The electrical signal is transmitted over electric cables, commonly coaxial cables, to a location remote from the transducer for processing. However, the transmission characteristics of coaxial cables are such that significant distortion of information can occur, particularly in pulses of duration shorter than about 5 nsec.

#FIG. 1 is a schematic representation of a radiation detection system for use in conjunction with the scintillators;

#FIG. 2 illustrates the emission spectrum of Coumarin 540-A in benzyl alcohol; and

#FIG. 3 illustrates the emission spectrum of Coumarin 540-A in a ternary system.

#Referring now to FIG. 1, which schematically illustrates the system, a radiation-to-light converter 10 emits light 12 when subjected to radiation 14. A substantial portion of the emitted light 12 should be at a wavelength greater than 500 nm and have a decay time less than about 2 ns in order to provide an appropriate match with the optical transmission characteristics of fiber optic wave guide 16. Emitted light 12 is received at one end 18 of guide 16, transmitted therethrough and emitted at the other end 22. It is then detected by a suitable photodetector 23 after suitable processing, such as by lens 26 and filter 27, if desired. A filter 28 between fluor 10 and fiber receiving end 18 in place of, or in addition to, filter 27 may be preferable in some applications. The output 29 of photodetector 23, which is representative of radiation 14, is then available for display, recording, analysis, and/or other processing, such as by recording and analysis modules 31.

#The constituents of the fluors of scintillators for the radiation-to-light converter 10 utilizes Coumarin 540-A as a primary or secondary solute, together with a suitable solvent, such as benzyl alcohol or pseudo-cumene.

#The scintillators described herein were excited during experimental tests with 50-psec (FWHM) bursts of 6-MeV electrons at 360 pps from an L-band linear accelerator (LINAC). Peak electron currents used during the measurements typically ranged from 50 to 500 mA.