DE2226130A1 - X-RAY ELECTROPHOTOGRAPHIC PHOTOGRAPHIC METHOD - Google Patents

Description

Siemens Aktiengesellschaft Erlangen, May 26, 1972

-... »· Henkestrasse 127

'■ ".... · VPA 72/5073 Kn / Kof

X-ray electrophotographic recording process

The invention relates to an X-ray photographic recording method in which a sheet-like electrode that emits electrons under the influence of X-rays is exposed imagewise to X-rays and this electrode is opposed to an insulating recording material arranged on a counter-electrode at a distance, the space is filled with ionizable gas and a direct voltage is applied to the electrodes is applied and the distance, the level of the excited DC voltage and the filling gas used are chosen in mutual dependence so that the electron flow emerging due to the imagewise exposure in an imagewise distribution is accelerated in the direction of the field to such an extent that impact ionization occurs and then one Causes secondary ion multiplication and that an extinguishing gas is used in the intermediate space in a manner known per se to reduce a standing discharge

In the case of devices for carrying out such methods, visible images are obtained in a known manner, which without use

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formation of expensive photographic layers and without carrying out a photographic process running through several development baths process arise. In contrast, the insulating layer is an inexpensive recording material, which may even be can be used repeatedly (see e.g. Zentralblatt für die Complete Radiologie 49 (1956) pages II7 / II8).

The aforementioned method has been considerably improved by aligning the electron flow in the field direction in the manner mentioned in the first paragraph and accelerating it to such an extent that impact ionization occurs, which causes a further course of secondary multiplication (cf. e.g. DT-PT 1 497 093). It is true that devices of this type produce x-ray images of objects up to a size of about 200 mm in diameter. With larger formats, however, great difficulties arise. These are based on the fact that the plates of the arrangement must be very precisely parallel so that the same field strength and thus the same charge multiplication prevail everywhere. The high gain that can be achieved with the arrangement mentioned made it possible to generate charge images with almost any small dose. The resolution is limited by the number of effectively absorbed X-ray quanta. This latter number is very low (about 1%) because of the poor efficiency in converting the X-ray quanta into electrons at the cathode. τ

According to the invention, the above-mentioned disadvantages are avoided by that one of the electrodes is dissolved into narrow electrically interconnected strips that are parallel to each other lie and that the gas is under increased pressure.

In the solution according to the invention, use is made of the fact that the adjustment accuracy of the arrangement of the electrodes is significantly lower when inhomogeneous electric fields are used. Then for a concentric arrangement with the electron radii P ₁ and rg for the field strength

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A change in the radius r «, for example, only comes in logarithmically. The multi-wire proportional chamber is a useful application of this Consideration. The avalanche amplification utilized according to the invention is only possible in the immediate vicinity of the anode wires in this chamber in front of you, because only there is the necessary high field strength. In the invention, therefore, the anode is divided into a plurality of elements divided with high curvature. In addition, the image carrier is so thin that the electric field in the gas space on the one hand is still sufficiently homogeneous and, on the other hand, the image carrier can carry the charges without breakdown.

Polycarbonates, for example in in the form of foils that are 2 to 10 µm thick. In one embodiment, which makes it possible to implement the invention, a parallel grid of thin lines is used which ten lines per millimeter are applied. As conductive The material is vaporized on aluminum behind a template made of wires in the form of lines. As an insulating covering a layer of vapor-deposited polycarbonate is then applied, which is 5 µm thick.

The parallel lines of the electrode can also be used in the etching technique with photoresist lacquers and possibly high quality organic vapor deposition layers with polymerisation by ultraviolet or electrons. The electrode surfaces provided with the lacquer or polymerisation layer and freed from these layers at the desired points are then vaporized with the conductive material and freed from the polymerisation or photoresist lacquer for completion, so that the electrode lines only remain at the desired points.

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I,

It is known from the technology of proportional counter tubes that gases with a sufficiently high atomic number, such as xenon, have quite considerable absorption for X-rays under sufficiently high pressure. Xenon is too expensive for a camera that can be used in general X-ray technology. However, iodine methane (CH, J) has almost the same absorption. To bring it to a pressure of 76Ο Torr, one requires heating to 42.3 ⁰ C. In I500 Torr increased pressure is obtained at 58 ⁰ C. With iodine methane, you can achieve sufficient pressure distributions at temperatures that are easily manageable in technology.

Because of the guidance of the generated charge carriers in the field, one can Use longer distances in the gas than the resolved point distances is equivalent to. This has already been done with known arrangements in which two plates are the electrodes of the receiving arrangement form, at around atmospheric pressure and 1 mm plate spacing, resolutions of five lines per millimeter are obtained. One can therefore Use gas sections of 3 mm in CKUJ from I5OO Torr, in which about 6 # of the 50 keV radiation is absorbed. Under these circumstances, X-ray images are then usable in the case of radiation can be produced from 1 milli-x-ray. In this regard, there is thus comparability with X-ray recordings with intensifying screens; against what Xeroradiographs would require many times the dose.

Other gases that can be used in the ionization room are, for example, iodine ethane and iodine butane. At low temperatures, ie approx. 100 ^° C., they too reach a sufficiently high pressure. If one can reasonably thermally isolate the receiving chamber, and pure iodine is used in .the one must apply for the achievement of prints about 1,000 Torr heating to about 15O ⁰ C. It is only necessary to ensure that, for example in medical applications, the body of the patient to be examined remains separated from hot parts.

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Further details and advantages of the invention are provided below explained on the basis of the exemplary embodiments shown in the figures.

In Fig. 1, a receiving chamber is drawn in section, which is designed according to the invention,

In Fig. 2 a detail from the chamber, in which in particular the placed image carrier, i.e. the Plastic film that is visible

in FIG. 2a the arrangement of the electrode strips,

in Fig. 3 the dependence of the pressure on the temperature. for various gases suitable for filling the receiving devices according to the invention and

in FIG. 4 the X-ray absorption of iodine methane depending on the radiation quality.

In Fig. 1, 1 denotes the frame, which is rectangular according to the desired recording format and is inserted gas-tight into the 1 mm thick and made of hard magnesium input plate 2. It carries on its surface facing the interior of the chamber, possibly on an intermediate insulation. layer the electrode strips j5, which are 1.5 μm thick, 25 μm wide and are arranged next to one another at a distance of 75 μm. . They are made of aluminum and are electrically connected to one another and to the power source 4, which supplies a maximum of 5 kV, at both ends via the lines J3- and j5 ^tf. The frame also contains nooh on two opposite sides, one oasis inlet 5 and one oasis outlet 6 through which the. Chamber can be filled with iodomethane , which is under a pressure

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" ⁶ " 2225130

of 1500 Torr. The frame 1 is releasably connected to the lower part 8 of the chamber via the seal 7. The lower part is made of steel and at the same time serves as a counter electrode which is connected to the negative pole of the power source 4.

To produce a recording, a voltage of 3.8 kV is applied to the electrode lines 3 and to the counter electrode 8. Then ions are generated in the gas path 9, which is particularly visible in FIG. There they are collected on the film 10, particularly drawn out in FIG. 2, which is 5 Aim thick and consists of polycarbonate, removed from the lower part 8 after the frame 1 has been lifted off and fed to powder development in the manner known from xerography.

The plate becomes the transfer of the powder image in a manner known per se to an image carrier, that is to say a paper or a film 2 is cleaned and is ready for a new recording.

Before making a recording, a uniform, weak pre-charge of the foil 10, e.g. with a positive charge, can be advantageous as this achieves greater charge contrasts the.

. From the curves of Figure 3 is seen that the iodomethane CH ₇ J used in the gas path 9 as well as the other substances uranium hexafluoride UFG, iodoethane COHF - J and iodobutane CJEUJ and iodine J in the range up to 15O ⁰ C the presently useful Reach pressures in excess of 1000 Torr. The I5OO Torr in iodomethane be achieved at 58 ⁰ C. In FIG. K , the percentage absorption per cm and ata shows that the absorption edge of the iodized hydrocarbon iodomethane is between 30 and 40 keV, ie in the diagnostically important X-ray range.

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Claims (3)

Claims (l ^^ X-ray electrophotographic recording process in which a gas space which is spread out in the form of an area under the influence of X-rays and which emits electrons in an image-like manner is exposed and this gas space is parallel to the surface of an insulating layer arranged on a counter electrode is limited and a DC voltage is applied to the electrodes, the distance being the level of the applied DC voltage and the filling gas used are chosen in mutual dependence so that the; due to the imagewise exposure in image-wise distribution escaping ion current aligned in the field direction is accelerated so far that impact ionization occurs and in the further course a 'secondary ion multiplication is effected and that to avoid a standing discharge in a known manner, an extinguishing gas in the intermediate space is used because you are marked raw, that one of the electrodes is dissolved into narrow strips (3), which are parallel to each other and the gas space (9) is under increased pressure. · 2. The method according to claim 1, characterized in that the gas is heavy atomic and in particular an iodine-containing organic compound. y 3. Apparatus for performing the method according to claim 1, characterized in that the distance between the Electrodes is 0.3 to 5 mm, preferably 3 mm, and the insulating film has a thickness of 1.5 to 10 μm, in particular 5 / µm. 309849 / 108B Blank page