JPH03159043A - Manufacture of x-ray target containing small amount of gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an X-ray target for an X-ray generator and its structure.

[Conventional technology]

Conventional X-ray targets are made of metal, such as molybdenum and tungsten, sintered using powder metallurgy, or are made lighter by brazing a metal substrate with light graphite. A combined sales structure is common.

Recently, there has been a strong demand in the market for longer life of single-rotation bearings, and in order to meet this demand by making the target lighter, targets are made by coating graphite with a thin film of metal such as tungsten using the CVD method (hereinafter referred to as CVD).
The development of targets (hereinafter referred to as targets) is progressing.

Conventional CVD targets mainly involve inventions related to the structure of the film and the shape of the target, as in Patent No. 60996.

[Problem to be solved by the invention]

Since the CVD target is made of graphite containing many pores, the CVD gas gets trapped in these pores. This phenomenon is particularly noticeable on the CVD surface of graphite which is directly hit by the gas ejected from the nozzle, and the gas existing in the pores is sealed by the metal film formed by the CVD reaction. CV
After the D target is installed in the vacuum tube, this gas is released little by little and the degree of vacuum decreases accordingly, resulting in a problem that the life of the vacuum tube is shortened.

An object of the present invention is to provide an X-ray target with a long tube life by reducing the internal gas released from the CVD target.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention releases gas in graphite pores by vacuum heat treatment and hydrogen heat treatment as a method for removing internal gas. Although this method is effective even if it is carried out once the metal layer has been coated, it is more effective and more desirable to carry it out before the metal intermediate layer is coated and the metal layer is coated. Furthermore, by forming the metal intermediate layer into columnar crystals grown in a direction perpendicular to the coating surface, the gas within the graphite can easily pass through the metal intermediate layer, which is effective in degassing.

[Effect]

As shown in Fig. 1, the intermediate layer 2 is generally thinner than the metal layer 3, so by performing vacuum heat treatment after coating the intermediate layer 2, the gas in the graphite is released through the intermediate layer 2. .

Thereafter, the metal layer 3 is coated, but at this time, the gas that coats the metal layer 3 does not enter into the graphite due to the presence of the intermediate layer 2, and an X-ray target with less gas contained in the graphite is obtained. Similar effects can be obtained by performing hydrogen heat treatment instead of vacuum heat treatment. However, the mechanism is different.

In other words, in vacuum heat treatment, the gas diffuses within the graphite and is released to the outside, whereas in hydrogen treatment, hydrogen gas enters the graphite and causes a reduction reaction with the CVD gas, solidifying the CVD gas, thereby reducing the amount of gas in the graphite. The amount of internal gas is reduced. In either method, the key point is to perform vacuum treatment or hydrogen treatment at the point when the thin intermediate layer 2 is formed, i.e., when the gas contained in the graphite is easily released or when hydrogen gas is easily penetrated. 6 [Example] to be carried out An example of the present invention will be described below with reference to Table 1.

Table 1 Treatment method and amount of residual fluorine ions The graphite substrate has a size of φ100m, t25m+a, and a density of 1
．． 8 g/a7 was used. The structure of the CVD film was such that the intermediate layer 2 was made of Re (rhenium) to ensure film adhesion, and the metal layer 3 was made of an alloy film of W (tungsten) and Re. This manufacturing method is described next. The graphite substrate was ultrasonically cleaned in pure water, and then heated at 1500°C for 1 hour at 1×10-”T.
Vacuum degassing treatment was performed at a pressure of orr or less. CV
The source gas of D is ReFe.

WFe gas is used, and hydrogen gas for reduction reaction is used as carrier gas. Intermediate layer 2, Re, is a graphite substrate of 3
The pressure at which ReFs gas was heated to 00° C. and ReFs gas was sprayed at 100 cc/min and hydrogen gas was sprayed at 5 Q/min onto the CVD surface of the graphite through a nozzle to deposit Re onto the graphite was set to normal pressure. The deposition time was 10 minutes, and a film of Re5108m was obtained. After forming Re, vacuum heat treatment and hydrogen heat treatment were performed on different samples. The vacuum heat treatment was maintained at a temperature in the range of 700 to 800'C and a pressure of I x 10-' orr for 1 hour. Hydrogen heat treatment at 700'C to 800°C with a hydrogen flow rate of 5
Processed at ρ/min. After each heat treatment, metal layer 3
The conditions for forming are: normal pressure, graphite temperature of 600° C., and WFe gas of 1000 cc/min.

A 500 μm alloy layer of W and Re was formed by flowing ReFs gas at 3 cc/min and hydrogen gas at 5 Q/min for 30 minutes. Table 1 summarizes the results of analysis of the CVD gas contained in the target in which the metal layer 3 was formed without any treatment after forming the intermediate layer 2, and the target in which the vacuum heat treatment and hydrogen heat treatment were performed. be. Since the CVD raw material gas is fluoride-based, F (fluorine) ions were analyzed. In order to analyze the raw material gas in the target graphite, graphite was cut into small pieces using a dry method with a diameter of less than 5 I, poured into a fixed amount of 100 μm of pure water, boiled for 30 minutes, and then F ions were poured out. Water was determined by ion chromatography as the amount of residual fluorine ions. As a result, the amount of residual fluorine ions in untreated target h1 is 80-1200PP! 1, whereas those subjected to vacuum heat treatment Nα and hydrogen treatment Nα are below the detection limit of 1 pp+s, and it is known that CVD gas inherent in graphite is reduced by vacuum heat treatment and hydrogen heat treatment. . For comparison, an analysis result (Na3) of a sample that was not treated before the formation of the metal layer 3, but was vacuum treated under the same conditions as 1llQ1 after the formation of the metal layer 3, was 80~
At 1000 ppm, there is no significant effect in reducing fluorine ions, and from this it can be said that it is desirable to perform vacuum heat treatment or hydrogen heat treatment before forming the metal layer 3.

〔Effect of the invention〕

According to the present invention, by performing vacuum heat treatment or hydrogen heat treatment before forming the metal layer, CV in graphite is reduced.
Since the D gas can be removed efficiently, an X-ray target containing less gas can be obtained, and the vacuum level of the X-ray tube using this target was conventionally 5 × 10-'Torr.
I
Improved scanning.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an X-ray tube target showing one embodiment of the present invention. 1... Graphite substrate, 2... Metal intermediate layer, 4... X-ray generating metal layer.

Claims (1)

[Scope of Claims] 1.
In the wire target, after coating the metal intermediate layer and performing vacuum heat treatment,
An X-ray target characterized by coating the metal layer. 2. The X-ray target according to claim 1, wherein after coating the intermediate layer, hydrogen heat treatment is performed instead of vacuum heat treatment, and then the metal layer is coated. 3. The X-ray target according to claim 1, wherein the vacuum heat treatment is performed at 700°C. 4. The X-ray target according to claim 2, wherein the hydrogen heat treatment is performed at 700°C.