James K. Walker

Pilot study of new radiation-resistant plastic scintillators doped with 3-hydroxyflavone

Abstract A set of plastic scintillators using polyvinyltoluene or polystyrene as the base material, doped with p-terphenyl and/or 3-hydroxyflavone, and heated in an argon atmosphere to accelerate recovery, have displayed a significant resistance to radiation damage induced by a 250 Ci 60 Co gamma source.

Ultrahigh-resolution plastic graded-index fused image plates

Fiber-optic imaging systems such as the medical endoscope, the boroscope, the fused-image faceplate, and the image conduit are now made from glass step-index (SI) fibers, and the image resolution of the SI fiber-optic imaging systems is limited to ~5 microm. Ultrahigh-resolution fiber-optic fused-image plates with fiber diameter sizes of 5 and 2.8 microm were fabricated with plastic graded-index (GRIN) fibers. The measured image resolutions of the 5-microm SI and GRIN-based guides were comparable, and the resolution of the plastic GRIN image guides improved as the fiber diameter was reduced from 5 to 2.8 microm.

A new radiation-resistant plastic scintillator

A radiation-resistant plastic scintillator has been developed to withstand the high radiation dose regions that will be present in the proposed SSC and LHC accelerators. The base is a highly transparent and radiation resistant polysiloxane plastic. This has been doped with a variety of radiation resistant fluors. The resultant scintillators have been shown to be highly resistant to /sup 60/Co gamma radiation for doses of 10 megarad. >

Polysiloxane-based scintillators doped with oligophenylenes: Effect of color centers on radiation stability

Radiation hardness of polysiloxane-based scintillators doped with oligophenylene fluors has been investigated. Radiation damage to the chromophores themselves is negligible. The main component of light output loss under irradiation is due to production of color centers by substituents introduced into the fluors to increase solubility. When these oligophenylenes are used as primary fluors they are stable to exposures in excess of 107 rad.

Polysiloxane-based scintillators: 1,1,44-tetraphenylbutadiene

Abstract A new polysiloxane-based plastic scintillator with substituted oligophenylene and tetraphenylbutadiene as a primary and secondary fluor, respectively, has been suggested. These dyes show excellent spectral properties and fluorescence decay time, and overall radiation stability of the scintillator is very good. The final scintillator appears suitable for use at the Superconducting Super Collider.

A new polyvinyltoluene-based, radiation-resistant plastic scintillator

Abstract A plastic scintillator, doped with p-terphenyl and 3-hydroxyflavone fluors in a polyvinyltoluene base, and heated in an argon atmosphere to accelerate recovery, has significant radiation resistance.

A new radiation-hard plastic scintillator

Abstract Using commercially available products, a new plastic scintillator has been developed which is highly radiation-resistant at doses at 10 Mrad.

A pilot study of the radiation resistance of selected plastic scintillators

A study of selected plastic scintillators has been carried out with the purpose of finding at least one technique of significantly enhancing the radiation resistance of the scintillator. The authors present a status report of their current results. In summary, three basic methods can be used: (1) immerse the scintillator in argon gas, (2) an elevated ambient temperature (50 degrees C) can increase the recovery rate of the scintillator, and (3) the use of a secondary fluor which emits above 500 nm can greatly enhance the radiation resistance of a scintillator. >

Linear polydiorganosiloxanes as plastic bases for radiation hard scintillators

Abstract Melt-processible (spinnable) polydiorganosiloxanes have been tested. The polymers offer advantages over previously explored thermosetting siloxane systems. Radiation damage to the optical properties of this polymer have been measured and are smaller than other known optical polymers. Most importantly, intramolecular proton transfer dyes (e.g. 3-Hydroxyflavone) exhibit large Stokes shifted fluorescence in the thermoplastic, unlike that in comparable thermosetting systems. A plastic scintillator based on this system should find application in the harsh radiation environment of the Superconducting Super Collider.

Imaging characteristics of plastic scintillating fiber screens for mammography

A scanning slot digital mammography system using a plastic scintillating fiber screen (SFS) is currently being developed. To improve the x-ray interaction efficiency and absorption efficiency of an SFS, high Z elements can be added into the scintillating fiber core. In this paper, we investigate theoretically the zero spatial frequency detective quantum efficiency, DQE(0), and modulation transfer function, MTF(f), of three 2 cm thick SFSs made of polystyrene, polystyrene loaded with 5% by weight of lead, and polystyrene loaded with 10% by weight of tin scintillating fibers. X-ray interaction efficiency, scintillating light intensity distributions and line spread functions were generated using Monte Carlo simulation. DQE(0) and MTF(f) were computed for x-ray energies ranging from 15 to 50 keg. Loading high Z elements into the SFS markedly increased the DQE(0). For x-ray energies used for mammography, DQE(0) values of both high Z element loaded SFSs are about a factor of three higher than the DQE(0) of an Min-R screen. At mammographic x-ray energies, MTF(f) values of all three SFSs are greater than 50% at 25 lp/mm spatial frequency, and were found to be dominated by the 20 micrometer individual scintillating fiber diameter used. The results show that both high DQE(0) and spatial resolution can be achieved with the high Z element loaded SFSs, which make these SFS attractive for use in a scanning slot detector for digital mammography.