Randolph Wojcik

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.

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. >

The aging of wire chambers filled with dimethyl ether: wire and construction materials and freon impurities

Abstract This is a complete summary of our study of the aging of different types of wire chambers, with a variety of construction materials and wires, filled with dimethyl ether (DME) of varying degrees of purity. The resistive Nicotin and Stablohm wires were corroded by DME, producing fast aging. The moderately resistive stainless steel wires were able to withstand extended irradiation (up to 1 C/cm) in high-purity DME without any apparent damage; and gold-plated tungsten and molybdenum wires exhibited a comparable behavior. Many construction materials were tested and recommendations are thus reached as to what kinds of materials are safe in building DME-operated wire chambers. Among many different Freon and hydrocarbon impurities detected in DME by means of gas chromatography (GC), Freon-11 was found to be mostly responsible for the aging, even with noncorrosive stainless steel or gold-plated wires. The availability and feasibility of obtaining Freon-free DME is reported as well.

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.

Some results on the ageing of wire chambers with dimethyl ether

Abstract Ageing results of three test wire detectors when filled with dimethyl ether (DME) are presented. DME gas was analyzed before and during the tests for the presence of electronegative impurities, such as Freons. A strong dependence of the rate of ageing on the wire composition was observed. The resistive wires, such as Stablohm and Nicotin, produced fast ageing. Also, even the best available purified DME, as of today, used with gold-plated wires, produced some slow ageing. The rate of amplitude decrease depended on the Freon impurity level.

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. >

An aging study of wire chambers with dimethyl ether: effects of wire material and freon content

The authors report results on the aging of different types of resistive and non-resistive wires in wire chambers filled with dimethyl ether (DME) of varying degrees of purity. Among the Freon impurities detected in our DME batches, only Freon-11 was found to contribute to the aging process. Of the resistive wires, Nicotin and Stablohm produced fast aging, whereas stainless steel withstood extended irradiation in purified DME (up to 1 C/cm) without any apparent damage. Gold-plated tungsten and molybdenum wires produced results comparable to those of the stainless steel.

Preliminary study of radiation damage in liquid scintillators

An initial examination of radiation-damage phenomenology in selected liquid scintillators was made. Standard liquid scintillators exhibited substantial radiation damage after dosage levels of several megarads. Unlike the case with plastic scintillators, no significant changes in transmission were detected, implying that no strong absorption of the secondary fluor should occur in long samples. The observed substantial drop in scintillation pulse height after exposures of several megarad from a /sup 60/Co gamma source is attributed to radiation-induced absorption of the primary fluors emission by the damaged solvent. Some new formulations have shown significantly greater radiation resistance. >

Development of Improved, Radiation-Resistant Plastic and Liquid Scintillators for the SSC

Plastic scintillators available on the market suffer from radiation damage at doses much lower than the ones expected at the SSC. The two major effects are induced transmission losses and damage to the scintillating fluors. The dominant radiation-induced absorption effects in the blue part of the transmission spectrum can be remedied by the use of large Stokes shift fluors emitting in the green region above 500 nm. With these fluors, the newly produced scintillators based on polyvinyltoluene and polystyrene have greatly enhanced radiation resistance. In cases when even the improved plastic scintillators will fail, liquid scintillators can be used. When damaged, the active material can be replaced without dismounting detector modules. Contrary to expectations, our tests showed that standard liquid formulations are damaged at rather low radiation doses of 1–5 Mrad. Newly developed formulations are significantly more radiation resistant.