Source: https://knepublishing.com/index.php/KnE-Energy/article/view/2023/4580
Timestamp: 2019-04-25 16:20:18+00:00

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3Joint Stock Company "State Scientific Centre of the Russian Federation – Institute for Physics and Power Engineering named after A. I. Leypunsky"
Copyright © 2018 A.V. PODKOPAEV and A.I. MIS'KEVICH.
Excimer molecules is a wide class of the compounds that include rare gas-halide molecules . The XeBr * excimer molecule was the first excimer molecules for which laser generation was obtained . Characteristics of the XeBr * emission on 282 nm wavelength allows to use it in many of the modern equipment with a great success. For example, the XeBr * excimer molecule emission is accepted to be most effective in the excimer lamps for removing organic impurities . There is a big disadvantage that bromine and many of other compounds that used as the gas mixture compounds have a great chemical activity . Accordingly, the research of kinetic of the rare gas-halide excimer molecules and investigation for a new donor compounds is actual tasks.
The C 2 HBrClF 3 molecule was used in research as the bromine donor for the XeBr * excimer molecule. This substance (halothane) is a liquid that have molecular weight of 197,381, boiling temperature of 50.2 ∘ С and the vapor pressure of 243 Torr. The Halothane have a much less chemical activity in comparison with other materials used as donors of the Br atom. The number of experiments was occurred to investigate the ability of application of halothane and to estimate basic parameters of the halothane-based gas mixture luminescence.
Two setups were used in experiments. The first one was meant for research of gas mixture luminescence under the e-beam excitation, and the next one for the uranium 235 fission fragment bombardment. The first setup  consist of a gas loop, accelerator part and registration system. The gas mixture of essential composition was created in the gas loop from gas balloons that contain necessary rare gases. This mixture gets an additional purification from impurities by multiplied passes through the filter that contain titanium sponge heated up to 700 ∘ С. The necessary amount of halothane was added to the mixture from the halothane-containing capsule by using a gauge tube. The resultant mixture gets a continuous mixing by membrane pump. The mixture had been excited by e-beam from RADAN-220 accelerator. IMA-150E accelerating tube was placed in the chamber contained by investigated media. The e-beam with an energy by a mean of 150 keV excite the gas mixture during the pulse of the accelerator that have 5 ns wide. The start of accelerator was synchronized with the lite emission registration system. The chamber with size of 100x150 mm was made of stainless steel and had a silica windows on each side for the exit of light. The system of registration consists of Maya-2000 Pro spectrometer that have 0,5 nm/div resolution, MDR-23 monochromator, PMT-106 photomultiplier and the fast digital oscilloscope with the 2 ns/div time resolution.
The equipment that was a part of «Stand B» experimental statement for nuclear-pumped lasers researches was used for uranium fission fragment excitation od investigated gas mixtures . It consists of fast aperiodic pulse reactor BARS-6 and the system of laser elements. The laser element in which experiments take plays is a tube of 250 sm length and 2,5 sm diameter, that have uranium oxide layer on its inner wall. The sides of tube are mounted with optical windows for light emission. The light exit from the reactor room by the system of mirrors and then it is focused on measuring equipment. The Maya2000 Pro spectrometer, PMT-100 and PMT-106 photomultipliers connected with Tektronix1012 fast digital oscilloscope was used as a measuring equipment.
The gas loop has been evacuated to the pressure of 0.001 Torr before the work with RADAN-220 accelerator has begun. The gas mixture of Ar and Xe at the ratio of 760:15 Torr was made in the gas loop. Than the resultant mixture has been cleaned trough the titanium filter. Concentration of impurities was monitored by the Maya2000 Pro spectrometer from its luminescence spectrum. The pumping trough the titanium filter was over when intensity of impurity's spectral lines became lower. The halothane vaporous was added to gas mixture by the gauge tube, which was a part of gas loop. The gauge tube was calibrated by the volume and its volume have a ratio of 1:100 to the whole gas loop. Consequently, managing the pressure of vaporous in the tube with precision up to 0.01 Torr the halothane concentration was managed with precision up to 0,0001 Torr when it was added to the gas loop. Than the number of accelerator shots with variation of the halothane concentration in a range from 0.0005 to 1,6 Torr have been occurred. The data from spectrometer and oscilloscope have been recording to the PC memory as digital worksheets during these pulses. The worksheets from spectrometer contain the data about level of intensity of signal in the all channels from 200 to 1100 nm at a pitch of 0.5 nm. The worksheets from the oscilloscope contain the value of voltage on the photomultiplier output in the time range of 500 ns at a pitch of 2 ns.
For the fission fragment excitation experiments the laser element that had been previous evacuated for pressure of 0.05 Torr was filed with gas mixture of Ar-Xe-C 2 HBrClF 3 with the partial pressure ratio of 760:15:0,05. Torr. The start of measurement equipment was synchronized with the start of reactor pulse. During the luminescence pulse, the data from spectrometer was recorded by a same way that has been described before and the data from oscilloscope was recorded in a time range of 1 ms at a pitch of 2 ns.
Luminescence spectrum (а) and time resolved dependency of luminescence intensity on 282 nm (b). The Ar-Xe-C2HBrClF3 gas mixture with a partial ratio of (760:15:0,005) excited by e-beam.
The decay rate to the C2HBrClF3 partial pressure dependency of XeBr* excimer molecule. The Ar-Xe-C2HBrClF3 gas mixture with atmospheric pressure.
Luminescence spectrum (а) and time resolved dependency of luminescence intensity on 282 nm (b). The Ar-Xe-C2HBrClF3 gas mixture with a partial ratio of (760:15:0,005) excited by U235 fission fragment.
The data about XeBr * luminescence under e-beam excitation and uranium fission fragment excitation of the Ar-Xe-C 2 HBrClF 3 gas mixture was obtained. The data was classified and processed in PC by Origin 9.0 program. The background subtraction and averaging by a 5 measurements for a e-beam experiments was made during procession of data worksheets. Averaging was made by LS method and it have shown that an error of spectrometer measurement was less than 6 % and 0,2 % at the mean. The error oscilloscope measurement was less than 10 % and 2 % at the mean.
The Luminescence spectrum of Ar-Xe-C 2 HBrClF 3 gas mixture with the partial pressures ratio of 760:15:0,05 Torr under e-beam excitation is shown on the Figure 1a. The Figure 1b. demonstrate the time resolve dependency of luminescence intensity on the B-X transition (λ max =282 nm) of XeBr * excimer molecule that was generated in investigated gas mixture under e-beam excitation.
The dependency of light yield from halothane partial pressure was obtained by integrating of intensity of the XeBr * B-X emission broadband (λ max =282 nm) in gas mixtures with various halothane concentration. Optimal concentration of this type of bromine donor belong to the range from 0.04 to 0.06 Torr for the Ar-Xe-C 2 HBrClF 3 with the ratio of Ar:Xe of 760:15 Torr. Than the curve form of emission Ln(U)(t) was analyzed where U is voltage registered by oscilloscope and it was proportional to luminescence intensity on the XeBr * excimer molecule B-X transition (282 nm). The line area was detected in the field of ln(U) reduction, the contrary time of gas mixture emission have been given by the slope of this line. The calculation of decay rate constant of XeBr * excimer molecule by C 2 HBrClF 3 molecule was made by plotting of the contrary time of emission against the halothane pressure (Figure 2). The line extrapolation of contrary time of emission to halothane concentration dependency was used to calculation. The slope of extrapolation line give the value of decay rate to be equal to 6,3*10 -10± 0,6*10 -10 (sm 3 /s). The value of emission time of XeBr * in investigated mixture of 125 ± 10 ns was given by interpolation of the extrapolated line to the point of zero halothane concentration.
The luminescence spectrums of Ar-Xe-C 2 HBrClF 3 for a mixture with ratio of partial pressures of 760:15:0,05 Torr and the time resolved dependency of XeBr * B-X (λ max =282 nm) transition luminescence intensity was obtained in the experiment with uranium fission fragments and they are shown on the Figure 3 a. and b.
The XeBr * excimer molecule luminescence parameters in new gas mixture based on halothane was obtained during the experimental work. Generally, the values of obtained parameters with halothane as a donor are comparable with another donor's parameters. For example, the Br 2 decay rate is about from 1x10 -9 sm 3 /s  to 6x10 -10 sm 3 /s  according to the different estimates. It is shows that the halothane quite usable as a donor of Br in works with XeBr * excimer molecule. Moreover, it was shown by the luminescence spectrum obtained during the excitation experiments that halothane can be also used as Cl and F donor and by this way UV sources of all three B-X transition emission of XeBr * , XeCl * and XeF * respectively can be received.
The following research of halothane as a Br donor will be focused on the laser generation on 282 nm line, also with nuclear pumping. However, the number of experiment must be produced to determine optimal compound of active laser media and resonator properties.
Authors would like to thank all the personal of the IPPE who working in reactor laser statement “Stend-B” for assistant in experiments with uranium fission fragment excitation and other personal of lab for help in mounting and adjustment of measurement equipment.
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