DE1010655B - Geiger counter filled with halogens and process for its manufacture - Google Patents

Description

NOTICE DEK REGISTRATION AND ISSUE OF EDITORIAL: JUNE 19, 1957

Geiger counter filled with halogens

The invention relates to halogens (in particular
Chlorine, bromine or iodine) filled Geiger meters. and its method of manufacture

It is known that adsorption phenomena play in electron tubes filled with at least one vapor and / or gas on the metal surfaces in them often play a detrimental role, as they affect the properties of the tubes. In particular, in meters of the above type, in which one great chemical activity of the vapors used and an even greater activity of those formed in the discharge Atoms and Ions detects these atoms and ions from the electrodes or other metal surfaces absorbed, so that with the small amount of these gases or vapors present in the tubes, this adsorption a change in the parameters of the tubes during their storage or their service life has the consequence.

The invention aims in particular to overcome this disadvantage in the production of halogens filled Geiger counters can be remedied by more effective and simpler means than before and thus an impeccable reproduction work to ensure in mass production. According to the invention, at least certain Metal surfaces of the counter tubes subjected to an electrolytic polishing treatment, which in particular any noticeable adsorption of the halogens is prevented by favoring the passivation. The invention is hereinafter referred to

explained on the drawing by way of example.

Fig. 1 and 2 show two types of inventive 30 »

according to trained Geiger counters filled with halogens; adsorbed on the electrodes or other metal surfaces. Fig. 3 shows a vessel for the present invention as the amount of these halogens in each tube very treatment of certain surfaces of the meters; 4 and 5 are graphs which show the response voltage of halosilver over time, a tenth to a few tenths of a millimeter Geiger counters show, which have an extra- lent expansion (in the order of magnitude of soft stainless steel or of one or more square decimeters of stainless steel), this cathode adsorption, which consists of molybdenum and titanium, is considerable and causes a considerable amount of time to undergo the treatment according to the invention 40 borrowed changes in the parameters of the tubes, which have and are partly untreated; closely to the quantities of gases and vapors present. Fig. 6 is a diagram showing the temporal connections. As an example in Fig. 6 the curve C _{1 is} shown running the response voltage of a with halogens, which shows for halogen tubes with iron-filled Geiger counters for several cases which chromium electrodes, which do not use special known treatment methods and 45 to prevent them Adsorption provided the treatment according to the invention correspond, where are, the drop in the response voltage with time in this course directly from the adsorption
of halogen.

It should first be addressed in the manufacture of this

Applicant:

Commissariat a l'Energie Atomique,
Paris

Representative: Dipl.-Ing. EF Eitner, patent attorney,
Munich 5, Erhardtstr. 8th

Claimed priority:
France, June 1, 1954

Andre Barthaire, Chatenay-Malabry, Seine,

Andre Benoit, Paris,

and Pierre Jacquet, Saint-Mande, Seine (France), have been named as inventors

shows. This curve shows a significant drop during the first ten days, which is almost complete Adsorption of the halogen, d. H. the Un

The difficulties encountered with the counter and the 50 which have become usable up to now.

to overcome the same proposed measures.

As already stated above, the chemically very active halogen molecules, atoms and ions of

To reduce the adsorption of the halogens it has already been proposed that the metal surfaces of a chemical cleaning with subsequent passivation treatment with nitric acid. There

709 549/338

3 4

However, if this measure was inadequate, one can manufacture counters which have numerous advantages led to it being completed while being compared to those produced by the usual procedures Meters are located at the pumping station, namely th, in particular the following, by treating the electrodes beforehand by avoiding bromine vapor treatment the vapor of the halogen used, e.g. in bromine-5, a considerable loss of time is avoided. The pump steam, the purpose of this treatment in this station can be used for a long time, since the one involved due to the electrodes a certain amount of halogen-guided bromine vapor are small and only to adsorb the amount in order to allow the later adsorption to remain in it for a short time. In addition, the bromination The very small amount of the in the finished tube is precisely dosed and controlled in the meter to prevent the presence of halogen. be io.

This bromine vapor treatment, the effectiveness of which. Practice shows that the tubes manufactured in this way depend in particular on the history of the metal since "from the beginning and throughout their entire life cycle. However, they can be relatively stable B. about 10 hours, and it often turns out to be uneven in the first few days to a final stable value _{, which makes it difficult to produce the masses (curve C 6} ) so that the tubes can be used immediately They come from the pumping station. The pumping station during a relatively long period of time. The above statements remain occupied regardless of time and are exposed to the long, highly corrosive nature or the surface condition of the used effect of the bromine. Furthermore, the bromine metal is valid. that in all cases with this treatment only weakly an iron alloy with at least 15% C is attached to the metal Chromium surfaces bound, which can be used to explain the instability of the response, regardless of their tension, which origin and their metallurgical history are produced in this way. These tubes are determined in which the partial .Fortfall of special precautionary measures has changed the pressure of the halogen. visibly of the metal to be used reduces the

In any case, it has been shown that with such a cost price.

The response voltage still tubes for a long time. The counters according to the invention, which are equipped with a

changes after manufacture. strong current (e.g. 50 μΑ) or with a parallel

For comparison with the curve C ₁ (Fig. 6) show the switched interference capacitance are used (what the

Curves C ₂ and C ₃ correspond to the drop in response voltage in the most unfavorable conditions), keep themselves

of two counters of the same series during the 30 with the lowest necessary for their work

first 30 days after the electrodes of these two bromine quantities at their parameters.

Meter made passive, but not with bromine vapor Thanks to the means according to the invention, it is further

treated while curve C _{4 made} a tube possible without difficulty to manufacture small counters,

with passivated and treated with bromine vapor where the risk of adsorption is greatest.

Electrodes concerns. The response voltage drops for a long time. It has also been found that the characteristics of the

sam during use (often size counter due to the above treatment from the beginning

properly by 50 or 60 V per year). can be improved because the horizontal course is longer

It has now been shown that one is according to the invention and the waste is smaller, what probably of it stable tubes with very little drop-off resulting from the electrolytic polishing of the metal Response voltage can be obtained by removing surface roughness, inclusions or verman the electrodes, which z. B. freed from iron and impurities, which disturbances when working Chromium exist, however, as can be evoked further below (e.g. through slow release of gas given, also other metals or alloys during use).

can be applied, an electrolytic polishing Finally, the inventively treated have

subject to treatment, in particular by giving the 45th counter a better temperature coefficient for

Metal as anode switches and a well-known process sets the response threshold (0.1 V per ° C between -60

used for anodic polishing. and + 120 ° C), and the permissible temperature range

For this, the ones known in this technology can be larger (-70 to + 100 ° C or more). The Ar baths can be used, although it is, of course, a tough current worker is that at least with certain polishers one remains stable in the above temperature range, bath can be content with polishing, as the following are some more precise details about Practice shows that this treatment alone suffices for the various possible ways of executing the being can be made to any subsequent adsorption of the halogen.

to prevent during the life of the tube, In Fig. 1 and 2 are two Ausoder according to the invention one after the other anodic polishing and then 55 guiding forms of violin instruments filled with halogens can carry out chemical passivation treatment. counters shown.

The first case in which the polishing alone The first embodiment (Fig. 1) is made of glass

seems to be sufficient, especially when using with an internal cathode. The shell 1 of such a

Polishing baths with phosphoric acid and sulfuric acid counter is expediently made of Pyrex glass

or phosphoric acid, sulfuric acid and chromic acid 60 anode wire 2 made of tungsten and its cathode 3 made of

to be present. a thin sheet of iron-chromium alloy

The second case is particularly given with 25% chromium, which is rolled up and after

if a bath is treated with perchloric acid and the above-mentioned polishing processes for polishing.

Acetic acid is used. The later passivation The second type (Fig. 2) is metallic. the

can then by a different anodic treatment 65 cathode is here a tube 4, in particular from a

or by any other method obtained iron-chromium alloy with 25% chromium, which is an

especially with the help of nitric acid. its ends by fusions 5 from the usual

Is closed by the treatment of the electrodes or other lichem glass. The anode wire 6 of a

Metal surfaces of the tubes in the above manner for such a meter, which at its inside the

Avoid later adsorption of the halogens 70 tube at the end of a glass bead 7 to reduce

tion of the peak effect, can also consist of an iron-chromium alloy with 25% chromium. An advantage of this design is that polishing only needs to be done on the inside of the cathode. As an example, it should be stated that such counters have worked satisfactorily with a cathode with a length of only 40 mm and an inner diameter of only 5.4 mm, the gas mixture of neon, argon and bromine with corresponding pressures of 250 to 400 mm Hg, of 0.1 to 1 / consisted »of the total pressure and of ⁴ / ^_10-8 / ₁₀ mm Hg °.

3 shows a vessel for the polishing treatment according to the invention of at least certain metal surfaces in Geiger counters filled with halogens.

Before this polishing treatment is carried out, the surfaces concerned, if they are heavily oxidized, initially appropriately stripped, in particular by means of an aqueous solution of nitric acid (10%) and sodium fluoride (2 to 3%). Such a bath has the property of detaching the oxide from the metal, without attacking this.

After leaving this bath, the stained surfaces are brushed and rinsed, whereupon they are used for the polishing are ready.

Two cases of polishing treatment were considered above, namely one in one automatic passivating bath and the other with subsequent additional passivation.

In the former case, in which the polishing alone is sufficient, there is e.g. B. the polishing electrolyte 8 (Fig. 3) from a bath of phosphoric acid and chromic acid (250 g 1 each).

One immersed in this bath the surface to be polished, in particular a cathode 9 (Fig. 3), which with the positive pole of a DC voltage source of about 12 V is connected. The negative pole of this voltage source is connected to the polishing cathode, which is either through a simple inside the To be polished cathode 9 is formed concentrically to this arranged conductor rod 10, if the Polishing the inner surface of the cathode is sufficient (case of Fig. 2) or by the rod 10 and one outside arranged concentrically to the cathode 9 to be polished conductive cylinder 11, if the cathode to be polished on both sides (case of Fig. 1).

The cathode to be polished is expediently supported by an insulating piece attached to the central rod 10 12 worn.

The vessel 13 containing the polishing electrolyte 8 is accommodated in a larger vessel 14, which Contains water at the desired temperature to bring the temperature of the electrolytic bath to a suitable one Set the temperature. This temperature is e.g. B. in the case under consideration between 70 and 95 ° C.

For .Kathoden 9 with a diameter of 16 mm and a length of 125 mm z. B. the duration this polishing treatment takes about 1 to 2 minutes.

After leaving the bath, the polished surfaces are hosed down and then in distilled Water and finally in an organic solvent (e.g. a mixture of ether and alcohol or methylal). They are then dried with warm air and ready for use stored protected against dust.

The second type of polishing treatment, which is followed by an additional passivation treatment must, is used as the electrolyte 8 z. B. the so-called "jacquet bath" used, which 95% acetic acid and Contains 5% perchloric acid and has the advantage that all iron-chromium alloys with any Chromium content are polished and consequently low currents can be used.

The same apparatus is used as that described for the first type of polishing treatment.

The DC electrolysis voltage here is 25 to 30 V, which is determined by the temperature of the water in the Container 14 set temperature of the electrolysis bath at most 25 ° C and the immersion time for the the above-mentioned cathodes on the order of 2 to 3 minutes.

The polished cathodes are rinsed and dried in the manner described above, whereupon them in a bath of fuming nitric acid for a few hours to achieve their passivation be dived. The polishing treatment which is the subject of the invention is also common to others Metals have been tried as ferrochromes.

It has been found that remarkable results are obtained particularly with stainless steel.

This is a very interesting advantage of the invention, since so far only iron-chromium alloys were used in the counters considered, as they are the lowest according to the known treatments Own adsorption. However, they are more difficult to manufacture and work, etc. than the stainless ones Steels.

The results of tests used to determine the Adsorption properties of various metals for halogens with and without the subject of the invention forming polishing treatment were used.

All these experiments were carried out with meters with a glass envelope and an inner cathode with a diameter of 20 mm and a length of 125 mm, the inner atmosphere of the meters consisting of a gas mixture of neon, argon and bromine with corresponding pressures of 400 mm Hg, of 1% of the total pressure and of ⁴ / io to ⁵ mm Hg was Ao.

In each of the examples below, the decrease corresponds to the response threshold in the first cases (in which the metal was chemically cleaned, but not passivated) the almost complete disappearance of bromine by adsorption.

The initial response thresholds are not the same, but vary depending on the metal in question and the treatment carried out with it between 390 and 460 V, the values for the metal polished according to the invention generally being around 30 V above the values in these "first cases".

Fig. 4 is a graph showing the changes in response threshold in volts as a function of time in days for a Geiger counter with halogens, the cathode of which was made of extra soft stainless steel (carbon content less than 0.07) and chemically cleaned but not passivated (curve A ₁ ) or chemically cleaned and passivated with nitric acid (curve A ^) or, according to the invention, polished in an automatically passivating electrolytic bath of phosphoric acid and chromic acid (curve A ₃ ) .

It can be seen that the drop in the response voltage after 6 days is about 95 or 35 or 12 V and that this decline continues in the first two cases, while in the third case it practically ends is.

Similar changes are shown in FIG. 5, the cathode used being made of a stainless steel with molybdenum and titanium (17 to 20% chromium, 8 to 10% nickel, 2 to 4% molybdenum, 0.3 to 0.4% titanium , less than 0.1% carbon, remainder iron) and chemically cleaned, but not passivated (curve .S ₁ ) or polished according to the invention in an automatically passivating electrolyte bath with phosphoric acid and chromic acid (curve B ₂ ) .

It can be seen that the drop in the response voltage after 50 days is of the order of magnitude in the first case Is 140 V and in the second case is practically zero.

Made with other stainless steels under the same conditions as those shown in FIG Tests have given the following results:

Extra-soft stainless steel with molybdenum: In the first case, a waste is made after 6 days of 80 V, which then continues, while in the second case the drop is of the order of magnitude 5 to 10 V, followed by stabilization.

Stainless steel with titanium: after 6 days a drop of 100 V is observed in the first case, which is followed by stabilization, while in the second case the drop is about 20 V and continues, so that it reaches about 40 V after 250 days.

Stainless steel (20% chromium, 2.5% nickel, 1.5% copper, less than 0.1% carbon, remainder iron): In the first case, a drop of 100 V is observed after 6 days, which is then followed rather little drop follows, while in the second case the drop is practically proportional to the time and after 150 days it reaches 70 V, whereupon stabilization practically occurs.

This example shows that the presence of copper is generally inadvisable appears.

With a cathode made of ferronickel (50% nickel and 50% iron), i. H. one with ordinary glass fusible metal, and always under the same test conditions as those on the basis of FIG. 5 one obtains a drop in the response voltage of the order of 100 V in the illustrated first case after 25 days and of 60 V in the second case after the same time (with the response voltage in this case was exceptionally lowered for 350 V).

The measurements for the last example as well as for the following were only over a period of 60 days, while the other examples were examined for 250 days.

The following experiments carried out on nickel and molybdenum can also be cited:

In the case of the chemically cleaned but not passivated nickel, the response threshold appears to be increasing 30 days after a drop of 50 V to stabilize, while with dry-cleaned and then with fuming nitric acid passivated nickel the waste, which already after 60 days is of the order of magnitude 40 V does not seem to have ended yet, whereas the same is electrolytic Metal re-polished the response threshold in a bath with phosphoric acid and chromic acid Seems to stabilize 40 days after a drop of only 10V.

In the case of the chemically purified but not passivated molybdenum, the waste is on the order of magnitude 105 V after 20 days, while it is 85 V after days for electrolytic treatment in a sulfuric acid bath polished but not passivated molybdenum was, and for the same, in the same way polished and then passivated metal with fuming nitric acid only about 20 V.

Claims (17)

Patent claims: 1. Geiger counter filled with halogens, characterized in that at least certain its metal surfaces are electrolytically polished. 2. A method for producing a counter according to claim 1, characterized in that the electrolytic polishing of metal surfaces if they are very oxidized, especially pickling by means of an aqueous solution of nitric acid (10%) and sodium fluoride (2 to 3%). 3. A method for producing a counter according to claim 1, characterized in that as Polishing electrolyte a bath with phosphoric acid and sulfuric acid or with phosphoric acid, sulfuric acid and chromic acid is used, especially a bath with phosphoric acid and chromic acid with 250 g per liter. 4. A method for producing a counter according to claim 1, characterized in that on the electrolytic polishing an additional passivation treatment follows. 5. The method according to claim 4, characterized in that a bath is used as the polishing electrolyte Acetic acid and perchloric acid is used, the proportions of which are in particular 95 and 5% (jacquet bath). 6. The method according to claim 4, characterized in that the electrolytic polishing subsequent passivation takes place by means of a different anodic treatment. 7. The method according to claim 4, characterized in that the electrolytic polishing the following passivation is carried out with the aid of nitric acid. 8. Counter according to claim 1, characterized in that it consists of glass and one on its contains electrolytically polished inner cathode on both surfaces (Fig. 1). 9. Vessel for electrolytic polishing of a cathode according to claim 8, characterized in that that the polishing cathode is formed by a rod (10) and a concentric cylinder (11), which are inside or outside the cathode (9) to be polished. 10. Counter according to claim 1, characterized in that it consists of metal and that the Cathode (4, Fig. 2) is only electrolytically polished on its inner surface. 11. Counter according to claim 1, characterized in that its electrolytically polished metal surfaces consist of an iron-chromium alloy with 25% chromium. 12. Counter according to claim 1, characterized in that its electrolytically polished metal surfaces are made of stainless steel. 13. Counter according to claim 12, characterized in that the stainless steel is extra-soft steel (carbon content less than 0.07). 14. Counter according to claim 12, characterized in that the stainless steel and molybdenum Titanium contains (17 to 20% chromium, 8 to 10% nickel, 2 to 4% molybdenum, 0.3 to 0.4% titanium, less than 0.1% carbon, remainder iron). 15. Counter according to claim 12, characterized in that the stainless steel is extra soft Steel with added molybdenum is. 10 16. Counter according to claim 1, characterized in that its electrolytically polished metal surfaces consist of nickel. 17. Counter according to A ^ns P ^rucn 1 »characterized in that its electrolytically polished. Metal surfaces are made of molybdenum. 1 sheet of drawings