DE1204431B - Measuring cells for generating an electrical signal to indicate the presence of an ionizable gas component - Google Patents

Description

BONDES REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

GOIn

German KL: 421-4 / 16

Number: 1204431

File number: B 63048IX b / 421

Filing date: June 27, 1961

Opening day: November 4, 1965

The invention relates to measuring cells for ionizable compounds which are contained in a gas stream. Such a measuring cell can be used, for example, to display contamination during the production of Noble gases, in the measurement of air pollution, for the detection of explosive vapors and in connection be used with a gas chromatograph. The invention relates to the design of these measuring cells.

Several modes of operation of such ionization measuring cells are known. The selective ionization in a hydrogen flame measuring chamber is in »gas chromatography«, 1958 edition, Desty, London. The use of radioactive isotopes for Generation of metastable atoms in the test gas is described by Lovelock in the "Journal of Chromatography", 1958, Vol. 1, p. 35. Another measuring cell of this type is in "Nature", December 1958, Vol. 182, Pp. 1663 and 1664. In this, the carrier gas to be examined is passed through a capillary Ionization chamber fed. In addition, the measuring cell is a purge gas, a noble gas, such as. B. argon, fed. A radioactive substance is introduced into the measuring cell, which prevents the transition of argon into creates a metastable excited state. These excited atoms collide with the molecules of the gas to be detected together and thereby ionize the same. The ionization current between a cathode and anode arranged in the measuring cell are used to display the gas content to be measured. The use of radioactive substances as in this case has the disadvantage that it is cumbersome Safety measures are required when using and radioactive emitters as well as a result considerable statistical fluctuations in the radiation output generate disturbing noise.

Accordingly, it was the goal to create a measuring cell that the dangerous handling of avoids radioactive material and also uses a radiation source that has a noise level which is considerably below that of conventional arrangements.

With the arrangement according to German Auslegeschrift 1 074 293, the gas to be measured is thereby ionized so that UV radiation enters through a window provided in the measuring cell and thereby the ionization caused by radiation. In the French patent 1 220 332 is also one radioactive substance introduced into the measuring cell. It is still suggested that the radioactive To arrange the substance at the entrance of the measuring cell in such a way that the ionization takes place before the ionization

Measuring cells for generating an electrical
Signals to indicate the presence of a
ionizable gas component

Applicant:

Beckman Instruments, Inc., Fullerton, Calif.

(V. St. A.)

Representative:

Dr. phil. G. B. Hagen, patent attorney,

Munich-Solln, Franz-Hals-Str. 21

Named as inventor:

Maurice Robert Burnell,

William Smith Gallaway, Fullerton, Calif .;

Richard Albert Foster, La Habra, Calif.

(V. St. A.)

Claimed priority:

V. St. v. America June 27, 1960 (38 907) - -

Gas jet containing the gas to be measured enters the field between the anode and cathode of the measuring cell.

According to the invention, which is characterized in the claims, are used to ionize the analyzing gas uses electrons generated by photoemission of a metal surface, preferably caused by ultraviolet radiation. These electrons have an average not enough energy to generate the carrier gas, e.g. B. argon to ionize. Your energy that still is increased by the acceleration by an anode of high potential, but is sufficient that too to ionize the substances to be analyzed. Even if you have the arrangement according to the German interpretative document 293 by introducing secondary electron-emitting metal surfaces into the beam path would change within the measuring cell, this would still have considerable disadvantages. The components of the test gas to be analyzed would flow through the space of the measuring cell by the electrons are generated. Parts of the test gas can absorb radiation, which in turn the flow of the emitted electrons, which determine the basic current and the sensitivity of the measuring cell.

509 720/361

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men, changes. In addition, components of the thermal energy of 0.038 eV at room temperature would be tested as well as the carrier gas, even at temperature this would result in effective energies up to the smallest contamination of the same, on the second 12 eV. In argon, values up to double electrons have resulted from the action of UV radiation t of this effective value,
knock down emitting metal surface. An electron-emitting metal surface formed in the inventive coating arranged separately in the interior of the gas channel on the electron generation chamber would worsen the emission inherent currents with a purge gas flow into the first ionic shaft. But it is known that at tion chamber and mix there with the test gas of the generation of secondary electrons outermost from the measuring column. In doing so, they effect is necessary as a result of their cleanliness. io now higher energy levels the ionization of the loading

Accordingly, the ionizing electrons are part of the test gas flow. As a result of elastic and, according to the invention, by photo emission in a non-elastic collision with the purge gas, the measuring cell creates space, which loses its effect on the test gas from the space in (argon) and other gases, but electrons lose part of the energy achieved , is separated, so that the carrier gas and the test gas with 15 Since the first state of excitation of argon 11.6 eV does not come into contact with the electron source. is, the argon acts as an energy drain and holds. B. Argon, the electrons are the electron energy at about this level, electrons supplied to the room in which the ionization. This causes only a small amount of ionization of the test gas. Get close to where the purge gas enters. Gases with a lower anode arranged in the ionic ionization measuring cell, such as the ionization voltage, are, however, ionized and can be accelerated by this and can thus be measured quickly and conveniently. The mode of operation of the ionization chamber, which is necessary for ionizing the test gas, is similar to the energy. However, the carrier gas is not ionized. a Geiger proportional counter; This means that the above-mentioned disadvantages are excessively charged, so that from the ionization of wounds that would arise if electrons from the 25 constituents of the test gas were collected on previous arrangements, those for ionizing the electrode. By increasing the electrons required for test gas by emitting the voltage of the ionization chamber, secondary electrons can be converted, for example, by UV multiplication of the electrons through impact ionization. The use of so that a stronger electrical signal radioactive substances for the ionization and the _DA-30 is obtained enough.

by conditional safety arrangements on an In one embodiment, one is relative

Such a device as well as the associated high large electron generating chamber are provided, the costs are eliminated. By turning off the an ultraviolet lamp it contains. The Ionisationskambeachtlichen interference level radioactive substance is the _me r is relatively small. Their minimum size is increased by the sensitivity of the device. 35 Breakdown voltage between electrodes and

The use of hydrogen flame gauges determines the chamber wall. The sensitivity of the chambers, such as those in the above- measuring cell is approximately proportional to the volume, led literature reference are described is with the The volume should also not be so large that a The disadvantage is that they broaden the pulse peaks through distribution in rooms or areas with the risk of explosion is not possible. In addition, 40 of the components of the test gas enter the carrier gas, is used for areas of application where a rapidly changing The purge gas supports a sharp formation of the Licher sample content is to be measured, how this can be assigned to the individual components of the sample, for example in gas chromatography the case of the pulse peaks or produces a smaller effekist, a measuring cell with a very low effective tive volume, since the components of the test gas with Volume required. These requirements are also flushed through the cell at a higher speed an arrangement according to the invention is sufficient. will.

Briefly summarized are the above-mentioned as material for the illuminated surface of the elec-

ten objects according to the invention solved as follows. In a conventional type of measuring cell, the test is taken into account, the electron work function of which is lower than the gas carried in a carrier gas, which is the energy brought by the optical light source. Electrons are released from the measuring cell by means of a flushing gas. It is suitable trons supplied, which are generated by photo emission in a material such as aluminum, bismuth, cadecond, connected to this measuring cell chamber mium, cobalt, copper, lead, molybdenum, silver, tan. The electrons are made up of the tal, tin and zinc. It is also possible to accelerate anode arranged in a metallic surface measuring cell. The rinses are in oxidic form. The gas stream preferably mixes with the one containing the test gas. Copper is used, since an oxidation is the tendency for the carrier gas stream. The ionization emission of photoelectrons then takes place in the test gas. The ionization current between changes. For metal with a low work function, see the anode and cathode are measured. _z . B. potassium or cesium, is not sufficient in the visible

The processes in the measuring cell according to the invention 60 baren range. X-rays can also be used currently interpreted as follows: to be turned. In addition to argon, the purging gases are used

The impact of high-energy protons on the helium, neon, krypton and xenon still in consideration, metallic surface of the housing causes one provided that they are sufficiently clean. Egress of electrons with an energy that is only further to the purge gas and to the carrier gas is little above the thermal energy. These 65 make the requirement that their ionization take place in the noble gas atmosphere as a result of the elec- tric span above the ionization voltage of the test gas tric field to an energy that is several hundred, so that it is not from the in the ionization chamber is as great as the thermal energy. With a mer entering electrons are ionized.

5 6

The measurements available since then close the 24. There is one in the electron generation chamber Possibility not from that arranged in the electron generation electron source. According to the presentation chamber metastable atoms of the purge gas, the preferred embodiment, is ultra-generated will. The metastable atoms reach violet lamp 25 in a base 26 and this again also in the ionization chamber and carry there 5 fixed in a plug 27, the lamp 25 is from A power source 28 is fed by collisions with components of the test. Gas circulated around the housing also contribute to the ionization of the same. The main one closes a metallic avenge that on impact ionization work, however, seems to be due to the electrons of the radiation from the lamp giving off photoelectrons, Because their mean translational speed can be expediently made of copper about five thousand times that of io Rohr, which contains both the mechanical GeArgon (The housing used for example as a purge gas for the measuring cell and also as is). The transition from the metastable to metallic surface is effective. Furthermore are usual board members acts in the stable state in the purge gas directions intended for measuring the ionization, atoms also as an energy outflow for the energetic - including a power source 31 and an elec- tron Electrons, so that thereby the possibility of 15 trometer amplifier 32; the wall of the metal housing Ionization of the carrier gas is also reduced and an electrode 33 will form the ionization chamber. mer, the electrode is fastened in an insulating plug 34 as an optical energy source for generating electrons. For the gas exit from the ionization In addition to ultraviolet lamps, a gas discharge line 35 is also provided. One Mercury arc, hydrogen lamps, xenon 20 gas supply 36 is used to initiate a gas lamp, Heating wires or X-ray tubes into consideration, currents into the electron generation chamber. One provided that the impingement of the further gas supply 37 sent out by them is provided in order to Radiate a metallic or metal oxide test gas from the chromatographic column into the Area causes the appearance of electrons. Introduce ionization chamber.

For further illustration, the following is an exemplary embodiment with reference to FIG. 2, the ionization chamber 24 of the drawings will be described. a copper tube with an outer diameter of 9.5 mm FIG. 1 is a block diagram and illustrates the formation of an ionization chamber using the measuring cell in conjunction with one with a volume of about 1 ml. The lamp 25 gas chromatograph; 30 was of the Pen-Ray No. 11-SC-1 type, the electron-fi g. Figure 2 shows a preferred embodiment of the generating chamber consisting of a piece of copper of the measuring cell according to the invention; tube with an outer diameter of 15.9 mm. 3 to 10 show a modified embodiment of a variable 2000 V current source used in conjunction with the measuring cell according to FIG. 2; binding with a micro-micro-ammeter (Mo-Fig. II and 12 show further, modified ^{versions 35 del} l Kiethley Mr. 410) as an amplifier. The measuring cell guide, which is equipped with an accelerator grid of the invention in chromatographic analysis in addition to the electron source. sen in the same way as usual measuring chambers

The measuring cell of the invention is used below in.

Connection with a gas chromatograph. However, it is on this application form 40 elements of the measuring cell is not critical. the not restricted and can be used in the analysis of any embodiment according to FIG. 3 is similar to that of Test gas flows with ionizable compounds in FIG. 2, but it contains an inwardly directed will. teten back 40 at the junction of the two F i g. 1 shows a typical arrangement of a gas chamber of the housing and a baffle plate 41, which Chromatograph with a pressure or flow 45 on the supply line 37 just before its end controller 15, a sample feed 16, which is chromatographically attached. Such a design enforces an intenphic Column 17, a measuring cell 18 and a sivere mixing of the two incoming gas streams Writer 19. The flow of carrier gas becomes through and virtually completely eliminates any diffusion the pressure regulator 15 is controlled; Usually argon of the test gas from the column is used in the electrons, However, other gases such as 5 ° generation chamber 23 can also be used. Embodiments correspond to helium can be used. 2 and 3 are generally referred to as At a given time, a sample of straight cells is called straight line cells. Fig. 4 shows a similar through the sample feed 16 in the carrier gas lent type, in which the flow of the gas stream through splashes, the constituent parts of the sample become rectangular at the electron generation chamber 23 Passage through the chromatic column from one to the other 55 to the gas flow through the ionization chamber 24 separated. The measuring cell delivers an output run. This design is usually powered as an L-cell, this shows the length of time that draws for each.

Component for flow through the column required. Two embodiments of Γ cells are in the that is, and also gives a quantitative figure. 5, 6 and 7 shown. In the measuring cell according to Measurement of each component. The output current 60 Fig. 5 are the axes of the two tubular The measuring cell is usually converted into some kind of structural element which forms the two chambers of the GeForm for later perusal and examination house form, in the same plane, during this recorded, but can also only for the same axes in the design according to the F i g. 6 and 7 early visual observation on a pointer device are offset from one another. In the embodiment will wear. 65 of Figures 8 and 9 is the electron generation die The measuring cell is shown in detail in Fi g. 2 shown; chamber 23 ring-shaped around the ionization chamber 24 it comprises a housing 22 with an electron placed, instead of the straight lamp 25 is a generating chamber 23 and an ionization chamber circular lamp 42 is used. In a practical

Claims (1)

7 8 See execution of this design was a lamp line 36 entering gas flow through the opening Pen-Ray No. ll-SC-5 used. 52 flushed into the ionization chamber 44. The sieve Fig. 10 shows another embodiment of the or grid 50 has opposite the wall of the measuring chamber chamber, which has a positive potential from a solid copper block 70 43 and can accordingly be made. Inside the block 70 5 anode are designated. In the application, a chamber 71 was created by suitable measures, such as drilling the anode normally at a potential of. A sleeve 72, operated about 800 V opposite the chamber wall, which serves as the wall of the ionization chamber, projects the special acceleration anode according to that from a base 73, which in turn by means of an embodiment according to FIG. 11 is for operating plate 74 against an outer surface of the block 70 ge ίο of the measuring cell is not necessary because the positive bracket is attached. An insulating disk 75 is arranged between the plate 74 and the base of the device for ionization measurement, the kel 73, and the telelectrode 33 required for increasing the energy of the electrons is fixed in the insulating disk 75 and can erect the field. The grid 50 can be used and protrudes into the sleeve 72. The conduit 37 from which, by intercepting part of the photochromatographic column, leads through a tube 15 emitted electrons, the basic current or perturbation 76 into the block 70 and ends at the open level too control or decrease.
The end of the sleeve 72. The pipeline 36 for the supply line. Another type of measuring cell with evacuation of the argon flushing gas ends in a different leveling anode is shown in FIG. A metal pipe fastener 77 and stands with the chamber 71 in lisches pipe 60 is at both ends with Isolierstop connection. The lamp 25 is closed by a sleeve 78, 20 fen 61 and 62, respectively. An inlet conduit 63 is carried which is attached by means of a pipe fastener 79 to the gas chromatic column leading through a block; The lamp lies in the chamber of the stopper, here the stopper 62, while a gas 71 is located above the pipe 37. The outlet line 64 is preferably arranged in the other stopper and the sleeve 72 is somewhat conical, which makes it better; Infeed and discharge allow a good gas flow. Gas flow properties within the measuring cell 25 through the pipe. The ultraviolet lamp 25 is to be achieved in. The exhaust pipe 35 passes through the one base 26 attached, which is supported by the plug base 73 and stands with the interior of the sleeve 72 in 62. An accelerating anode like compound. This type of construction results in a solid and extends over approximately the grid 50 between the stops visible measuring cells, which are easily produced, join together 61 and 62 and surround the lamp 25. The ionization device can be set and dismantled again and is well shielded against external influences. By placing the positive side of the current source 45 measuring cells according to FIG. 3 to 10 are in the same way with the anode 50 and the other terminal with the manner as the measuring cell according to FIG. 2 connected tube 60 is connected. At this particular and operated. Embodiment lie the electron source and Another modified design of the measuring 35 the ionization chamber within a single Rau cell, as appropriate for some applications; this results in a mechanically simpler measuring cell, is moderate is shown in FIG. The measuring cell has, however, not all the advantages of the previously described T-unit formed and has a first tubular plane has embodiments. This execution piece 43, which allows the use of an anode as an electron generation chamber serves, and a second one, serves as an ionization chamber- 40 electron acceleration right next to the electrode Pipe section 44 on. That from the chromatographetron source without the need for a special one see column outflowing gas is according to the dar- power source. provided training from left to right by the It should be noted that although all execution ionization chamber directed. The usual forms of provision are used above in connection with a device for ionization measurement, a production from metal tubes has been described finally a current source 45, an electrometer, but that this type of construction is not necessarily an amplifier 46 and a scoreboard or scribe is necessary. For example, glass tubes or 47; a lead of the amplifier is to be used with the pipe other building materials, it is only 44 connected, the positive terminal of the power source necessary that in the electron generation chamber is connected to an electrode 48, which inside 5 ° a metallic surface is present from the Elekhalb the ionization chamber can be emitted by an insulating stoptron. At a Praktifen 49 is attached. see execution a glass tube was used, Inside the electron generating chamber 43 is the inside of the tube was arranged with a metal foil from an electron source, which is placed with the elec- Correspondingly, according to the embodiment according to FIG. 55, the ionization chamber must have a positive and a negative electrode, FIG. 2 can match. The electron generator can, however, also be supplied from a glass tube. Furthermore, devices are available in which the two electrodes are attached. Establishing an electric field in the chamber. It should also be noted that the electron generator is equipped with which the energy of the electrons generated in the chamber, even a wall made of glass or mer, can be considerably increased. 60 Quartz with the metal surface inside the chamber. According to the embodiment according to and the light source outside the chamber aufwei-Fig. 11 is inside the tube 43 around the sen, the radiation from the light source, lamp 25, a metal screen or grille 50 is arranged, then through the glass wall to which the grille is attached to the insulating plug 27. Directed between metal surface,
see the metal wall and the grille is a 65 ..
Power source 51 for electron acceleration.
switches. The energy- 1. measuring cell generated in the chamber 43 for generating an electrically rich electron are controlled by the signal through the pipe to indicate the presence of a constituting ionizable gas component (test gas), which has a first chamber in which Electrodes are provided for generating an electric field, as well as inlet and outlet means for the supply and discharge of the test gas, and the ionization of the test gas in this first Chamber takes place, characterized in that in a second, connected to the first Chamber (23) by an optical radiation source (25) on the walls of the same Secondary electrons are triggered by the flow of one of the secondary electrons essentially non-ionizable purge gas and due to the acceleration by the potential the electrodes (23) in the first chamber (24) are fed to the same and there the ionization of the test gas. 2. Measuring cell according to claim 1, characterized in that the radiation source (25) is an ultraviolet emitter is. ao 3. Measuring cell according to claim 2, characterized in that the wall surface of the second chamber (24) is made of copper. 4. Measuring cell according to claim 1 to 3, characterized in that the carrier gas and the flushing gas Are noble gases. 5. Measuring arrangement according to claim 4, characterized in that the carrier gas and the flushing gas consist essentially of argon. 6. Measuring cell according to claim 4 or 5, characterized in that the main components of the Carrier and purge gas have an excitation voltage which is so high that these gases by the electrons of the highest energy, which are generated in the ionization chamber (23), not be ionized. 7. Measuring cell according to claim 1, characterized in that the path of the purge gas through the the second chamber (23) used to generate the electrons is in line with the path of the test gas through the first chamber (24) serving for ionization of the same, wherein in the connecting section between the two chambers (23, 24) devices (40, 41) for aligning the purge gas flow to the first chamber (24) are arranged towards. 8. Measuring cell according to claim 1, characterized in that the path of the purge gas through the second chamber (23) approximately at right angles to the path of the test gas through the first chamber (24) is, the first chamber (24) on that of the device for supplying the purge gas (36) distant end of the second chamber (23) is arranged, and in that the means for Feeding of the test gas (37) in the transition section between the two chambers (23, 24) attached and directed towards the first chamber (24). 9. Measuring cell according to claim 1, characterized in that the second chamber (23) is concentric is placed around the ionization chamber (24), the device for introduction and Alignment of the test gas flow (32) in the connecting section between the two chambers (23, 24) are arranged and aligned with the first chamber (24). Considered publications:
German Auslegeschrift No. 1074293;
French Patent No. 1220 332;
"Nature" (London), 182 (1958), 4, pp. 1663 and 1664. 1 sheet of drawings 509 720/361 10.65 © Bundesdruckerei Berlin