Setup for Studying Radio- and Thermally Stimulated Luminescence and Electrical Conductivity in Parallel with Mass Spectrometry of Decomposition Products
Abstract Generated abstract
A combined experimental setup is described for investigating radiation-induced and thermally stimulated processes in solid compounds under high vacuum. The apparatus permits measurements on a single sample of X-ray luminescence, thermoluminescence, spectral ranges from 200 to 800 nm using light filters, temperature dependences from minus 190 to plus 400 degrees Celsius, X-ray and thermally stimulated currents, and gaseous decomposition products by radio-frequency mass spectrometry. The paper details the construction of the vacuum cell, cooling and heating arrangement, optical detection system, electrical feedthroughs, and coupled vacuum and mass-spectrometric system. The authors report that the setup operated stably in different measurement regimes and was simple to maintain.
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Setup for Studying Radio- and Thermally Stimulated Luminescence and Electrical Conductivity in Parallel with Mass Spectrometry of Decomposition Products
Yu. A. Zakharov, S. I. Rukodeev
(Presented by the scientific seminar of the Department of Radiation Chemistry)
A comprehensive study of the physical and physicochemical processes occurring in irradiated compounds is necessary for establishing the mechanism of radiation transformations. At the same time, the accuracy of the experiment is increased, and the time required to obtain the corresponding amount of information is sharply reduced when setups are used that make it possible to measure several characteristics simultaneously on a single sample.
Information on the ionic and electronic processes occurring during irradiation of solid compounds is provided by the study of their luminescent and electrophysical properties in various regimes, including in a radiation field and under conditions of heating after irradiation. However, the literature contains no description of simple setups for studying these processes.
The setup constructed by us and described here makes it possible, in high vacuum, to determine by means of light filters the spectral range of X-ray and thermoluminescence in the region of 200–800 nm, and its temperature changes in the range from −190 to +400°C; to record the thermoluminescence curve under excitation both by X-radiation and by light; to analyze the evolved gaseous reaction products formed during irradiation and heating; and to measure X-ray- and thermally stimulated currents,
Fig. 1. 13—insulation, 14—light filter, 15—thermocouple.
The setup consists of a vacuum metal cell 1 (see Fig. 1), having a quartz window 2, a window 3 for irradiation with X-rays (covered with aluminum foil 0.2 mm thick), and four electrical feedthroughs 4—two for the thermocouple measuring the temperature of the specimen, and two for carrying out electrophysical measurements. The specimen, on a metal or insulating substrate, is placed in the recess of holder 5, made of copper, which can either be washed by liquid nitrogen or its vapors from Dewar vessel 6, or heated by cylindrical heater 7. The holder is thermally decoupled from the cell body in the form of a thin-walled tube 8 made of stainless steel, which has low thermal conductivity. All vacuum seals of the cell are made of fluoroplastic. The cell is evacuated through a valve to a pressure of \(5 \cdot 10^{-7}\) torr by an NVO-40 forevacuum pump with a nitrogen trap. For analysis of gaseous products [1], an RMO-4 sensor of an IPDO-1 radio-frequency mass spectrometer, additionally pumped by a titanium pump to a pressure of \(5 \cdot 10^{-8}\) mm Hg, is connected to the vacuum system through a valve with a metal seal. The luminescence of the specimen during X-ray and thermoluminescence is recorded by a photomultiplier; the signal from it is amplified by an F18 photoelectric amplifier and recorded on an EPP-09 potentiometer. To record UV luminescence, a scintillator is added to the PMT. Between the quartz window of the cell and the photocathode of the PMT there is a cassette 9 for changing color glasses without exposing the PMT and the specimen to light, and a diaphragm 10 with an aperture of variable diameter. In photoexcitation of the specimen under study, a light source is mounted instead of the PMT, and the corresponding light filters are placed in the cassette.
The supply of liquid nitrogen or its vapors from the Dewar vessel to the holder and the specimen is effected by adapter 11 and valve 12, which switches the coolant feed mode: liquid nitrogen, or its vapors. The adapter consists of two metal [[unclear: rods/tubes]], coaxially fixed in a fluoroplastic plug.
Fig. 3. 1—VN-461 forevacuum pump; 2—NVO-40 mercury-vapor pump; 3—nitrogen trap; 4—valve; 5—cell; 6—titanium pump; 7—sensor of the RMO-4 mass spectrometer; 8—LM-2 pressure sensor; 9—LT-2 pressure sensor.
Fig. 4. 1—adapter head;
2—cooling-agent overflow jacket;
3–4—tubes for feeding liquid and gaseous nitrogen;
5—opening above the nitrogen level;
6—heater.
tubes lowered to the bottom of the Dewar vessel. At the lower end of the tubes an agitator is placed, which creates excess pressure in the vessel, as a result of which the liquid nitrogen flows through the central tube into the cavity of the sample holder, unless the valve connects the opening of the outer tube, located above the level of the liquid nitrogen, with the cavity of the holder. In the opposite case, only liquid-nitrogen vapor is drawn through this opening into the holder. The design of the valve is shown in Figure 2. Figure 3 gives the schematic diagram of the vacuum system of the setup.
The setup described was operated by us in the regime of various measurements and proved to be stable in operation and simple in maintenance.
REFERENCES
- V. A. Neostruev, D. A. Sakharov, Izv. TPI, 199, 47, 1969.