Speaker
Dmitry Ilyin
(St. Petersburg Nucl. Phys. Inst., Gatchina)
Description
Some time ago it was demonstrated that the method of Nuclear Reaction
Analysis (NRA) is very effective for investigation of the aging effects in the
gas-filled detectors operated under high accumulated dose. The most
important plasmachemical reactions for the gas mixtures (Ar/CO2/CF4 and
Xe/CO2/CF4) produce many different active species including oxygen and
fluorine. For the detection and quantitative evaluation of the oxygen and
carbon content as a function of depth in the gold, the following nuclear
reactions with deuterons and protons in the energy range of 0.7-1.1MeV
have been applied: 12C(d,p)13C and 16O(d,p)17O. Application of the NRA in
our aging investigations gave us a reliable confirmation of the oxygen key
role in the wire-swelling mechanism and demonstrated the kinetics of
oxygen transport into the depth of the gold coating. Special interest for our
gas mixtures are two chemical agents which determine possible gold
etching: fluorine and xenon-fluorine XeFn(n=2,4,6) compounds. These
agents are strong oxidizers and may interact with the gold, causing etching.
So, in order to understand one of more important stages of the wire aging
mechanism development, it was principally important to develop the NRA
method for investigation of fluorine distribution in the anode wires. To
investigate the fluorine content and depth profile in wire the nuclear
reaction 19F(p, α) 16O has been used. The energy spectrum of the α-
particles produced by the (p,α)-reaction has been measured. It was shown
that sensitivity of proposed method is about 1×10 16 at/cm3. The fluorine
concentration and their depth distributions have been measured for different
gas mixtures under the total accumulated dose up to 1.8C/cm for each.
Author
Dmitry Ilyin
(St. Petersburg Nucl. Phys. Inst., Gatchina)
