The x-ray source

 

(57) Abstract:

The invention relates to x-ray techniques and can be applied in radiation technologies, preferably those that require high pulse dose bremsstrahlung radiation with quantum energy up to 10 MeV in excess of 106times the average dose source that will find wide application in food, chemical and medical industries. The invention is: to increase the working life of the source, containing powerful pulse frequency generator 1 of the electron beam 2, the target is made in the form of carbon substrate 4 coated by electron beam generator layer 3 of metal or carbide. The metal layer may be applied in powder form mixed with carbon, taken in equal amounts. The metal layer can be protected from the generator beam carbon coating 5. In such a target function of the Converter energy beam bremsstrahlung performs a layer of metal, the mechanical load is carbon substrate having a high resistance to heat shock, carbon coating 5 protects the metal layer from sputtering, the admixture of carbon in the metal layer from slavleniyachrist for x-ray radiation. 1 C. p. F.-ly, 2 Il.

The invention relates to x-ray techniques and can be applied in radiation technologies, preferably those that require high pulse dose bremsstrahlung radiation with quantum energy up to 10 MeV in excess of 106times the average dose source that will find wide application in food, chemical and medical industries.

The known x-ray source containing electron accelerator high energy, a device for release of electrons into the atmosphere and the target is cooled by air flow [1]

The disadvantages of this source are small resource targets and the complexity of the design due to the use of the discharge device.

The known x-ray source that contains a powerful pulse frequency generator of the electron beam and a target made of metal with a large nucleus charge Zmthe thickness of the lmnot exceeding the length of the path of the electron beam in the target material [2] the Target is located in the vacuum chamber of the accelerator and is cooled due to heat radiation.

The disadvantages of this source are small size allowable density allocated to the target average power of the beam, higher than average in 106and more times. At such high pulse power tantalum target "floats", tungsten crumble.

The technical result of the invention is to increase the allowable density allocated to the target average power of the beam, and resource its work.

The technical result is achieved in that in the x-ray source that contains a powerful pulse frequency generator of the electron beam and a target made of metal with a large nucleus charge Zmthe thickness of the lmnot exceeding the length of the path of the electron beam in the target material, the target is made in the form of carbon substrate coated by electron beam generator is working layer of the same metal, and the thickness of the substrate lpselected from the condition lp< lmm/pwherem,pthe density of the metal target and the substrate (carbon), respectively. In addition, the working layer is made of a carbide of the same metal or of a mixture of the same metal with carbon and/or work on the metal layer from the generator e-beam deposited carbon coating, whose thickness lpokselected from the conditions lpok< lm.

In this con is nenovski radiation, and the graphite substrate, which has a higher resistance pulse thermal conditions, carries the mechanical load. Mixing metal with graphite prevents the "fluidity" of metal as a whole. The presence of carbon coating prevents metal sputtering. High transparency of carbon for electron and x-ray radiation allows to get almost the same output x-ray radiation, as in the case of a pure metal target. Thus, the use of carbon components in the target allows to significantly increase the allowable density of emitted energies and its resources due to the high resistance carbon components to pulse effects, and due to its higher degree of thermal radiation.

In Fig.1 and 2 presents the x-ray source, options.

The source has a pulse frequency generator 1, an accelerating electron beam 2 and the target, consisting of a working layer 3 of metal, carbon substrate 4 and the carbon cover 5 (Fig.2). The source of the electron beam 2 and the target are located in a vacuum chamber. The target is the anode of the electron beam generator. The metal layer 3, performs the function of the Converter is raised from the condition of maximum x-ray output. Usually applied tungsten or tantalum, with a large Zmand high melting temperature, the thickness of the layer lm0.5 1 run length of electrons, which is determined by the energy of the electrons. The thickness of the carbon substrate lpmade from the most durable grades of graphite or carbon tissue is selected from the conditions of ensuring the mechanical strength with minimum absorption of x-rays:

lp< lmm/pin the case of tantalum (= 16.6 g/cm3) or tungsten ( = 19.3 g/cm3) lp< 17 lm.

There are currently a number of technologies deposition of metals on the surface of graphite, for example, impregnation of graphite, as is done in the manufacture of brushes of electric motors or by using a torch and so on, the Metal may be deposited on a substrate in the form of a powder mixed with carbon, taken at approximately the same volumes. When the carbon prevents fusion of metal and change the shape of the working layer of metal, as is the case of pure tantalum plate. The graphite component of the mixture has virtually no effect on the magnitude of the output x-ray radiation. Work the metal layer can be protected outside the metal lpok< lmeth. Carbon coating inhibits erosion of the metal and at such thickness is almost transparent to the electron beam.

The source operates as follows.

When enabled, a pulse generator 1 electron beam 2, bombarding the target is absorbed by the working layer 3 of metal, which is a source of hard bremsstrahlung. At high electron energy (greater than 1 MeV) bremsstrahlung x-rays are directed mainly towards the spread of the electron beam and almost passes through a carbon substrate 4. The vacuum chamber has an exhaust port located opposite substrate 4. Depending on the scheme of the electron beam generator, the target can have zero or high positive potential.

Consider a specific example of the operation of the x-ray source, which uses a pulse frequency generator of the electron beam on the basis of the plasma current interrupter with the following parameters: pulse frequency of 2 Hz, the energy of the electron beam of 3 MeV, beam current of 20 kA, duration 100 NS, pulse beam power 6 1010Watts, average 12 103W. The path length of electrons for tungsten or tantasy 0.8 mm (1.3 g/cm2).

As the substrate 4 was used three layers of graphite cloth with a total thickness of 1.5 mm, which provides the necessary mechanical strength and with a large margin satises the bandwidth of x-ray radiation. As a working layer of metal is applied carbide powder tantalum thickness of 1.5 g/cm2or "sponge" from a tungsten wire with a diameter of 0.04 mm with a mass thickness of 1.3 g/cm2(used defective spiral bulbs). As carbon coatings using carbon cloth with a thickness of 0.5 mm (0.3 g/cm2). The dose rate of x-ray radiation at a distance of 0.5 m from the target was the same value of 0.25 kGy/h as in the case of the prototype (tantalum or tungsten plate 0.8 mm), and in the case of the above options target for the circuit of Fig.2. Resource targets of the pure metal at an average power density of 20 W/cm2approximately 1 h: tantalum plate "fused", tungsten crumble. The proposed target has worked 200 hours at an average power density of 50 W/cm2no visible signs of destruction.

Thus, the proposed scheme targets allows to double the average density allocated to n is containing a powerful pulse frequency generator of the electron beam and the target material with high atomic number zmand high melting temperature of a thickness of lmnot exceeding the length of the path of the electron beam in the target material, wherein the target is made in the form of a working layer, placed on a carbon substrate, the thickness of which is selected from the condition

lp< lmm/p,

wherem,pthe density of the material of the active layer of the target and the carbon substrate, respectively,

as a material of the active layer of the target used metal or carbide of a metal or a powder mixture of metal with carbon in equal volumes.

2. Source under item 1, characterized in that on a work target layer from the incidence of the electron beam deposited carbon coating, the thickness of the lpabouttowhich is selected from the condition lpaboutto< lm.

 

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