CA1119231A - X-ray irradiation head for panoramic irradiation - Google Patents
X-ray irradiation head for panoramic irradiationInfo
- Publication number
- CA1119231A CA1119231A CA000381567A CA381567A CA1119231A CA 1119231 A CA1119231 A CA 1119231A CA 000381567 A CA000381567 A CA 000381567A CA 381567 A CA381567 A CA 381567A CA 1119231 A CA1119231 A CA 1119231A
- Authority
- CA
- Canada
- Prior art keywords
- target
- axis
- irradiation head
- irradiation
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
ABSTRACT OF THE DISCLOSURE:
A X-ray irradiation head for panoramic irradiation using a beam of accelerated charged particles comprises a target having a surface of revolution the axis of which is coinciding with the axis along which the beam propagates in the absence of the deflection, and a magnetic deflection device comprising a quadripolar magnetic device to deflect the beam of charged particles in its entirety and to make it converge on a target in a small impinging zone, the magnetic field of this device rotates about the axis of the irradiation head, mean deflection of the beam being variable and the impinging zone moving on the target in such a way that the particle beam successively produces photons in several directions when impinges upon the target.
A X-ray irradiation head for panoramic irradiation using a beam of accelerated charged particles comprises a target having a surface of revolution the axis of which is coinciding with the axis along which the beam propagates in the absence of the deflection, and a magnetic deflection device comprising a quadripolar magnetic device to deflect the beam of charged particles in its entirety and to make it converge on a target in a small impinging zone, the magnetic field of this device rotates about the axis of the irradiation head, mean deflection of the beam being variable and the impinging zone moving on the target in such a way that the particle beam successively produces photons in several directions when impinges upon the target.
Description
~119231 The present application is a division o~ Canadian patent application number 300,237 filed March 31, 1978.
This invention relates to a X-ray irradiation head for panoramic irradiation.
The present invention concerns a X-ray irradiation head for panoramic irradiation using a beam of charged and accelerated particles. The irradiation head has a longitudinal axis along which the particles propagate in the absence of deflections. The head comprises an electromagnetic deflection device for deflecting the charged particles and a target having a surface producing X-rays. This surface is a surace of revQlution the axis of which coincides with the axis of the irradiation head. The deflection device separates the paths of the particles fEom the axis in such a way that the particles impinge upon the target. The deflection device comprises a multipolar magnetic device, and a feed circuit, to deflect the beam of charged particles in its entirety and to make it converge on the target in a small impinging zone.
The magnetic device is fed by a feed circuit such that the magnetic field rotates about the axis of the irradiation head, the mean defl~ction of the deflected beam being variable and the impinging zone moving correlatively on the target. The multlpolar magnetic device is a quadripolar magnetic device.
The windings of pole pieces of the quadripolar magnetic device are fed in pairs and in series by two sinusoidal currents in quadrature delivered by the feed curcuit for periodic scanning of the target by the beam of particles.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the following description and the attached drawings among which:
- Fig. 1 shows the emission lobes corresponding to . ~119231 a conventional target (PRIOR ART);
- Fig. 2 shows the emission lobes corresponding to a target according to the invention;
- Fig. 3 shows a third embodiment of the irradiation head according to the invéntion, the panoramic irradiation being effected by scanning of the target by the beam of accelerated electrons.
The emission of high-energy X-rays by means of a linear accelerator is obtained in the following manner :
electrons are supplied by a thermoemissive cathode under an electrical field of from 30 to 50 Kv for example. These electrons are then accelerated in an accelerating section of the UHF type (a few thousand Mhz) by hign-power pulses (a few megawatts) lasting several microseconds and striking the target which is generally a tungsten pellet. When an electron strikes the target, it is suddenly decelerated, giving rise to the emission of an electromagnetic radiation. In addition, electrons of the beam cause the ionisation of certain atoms of the target and the migrations of the electrons on the various layers of the atoms cause photons to be emitted. The intensity of the radiation depends upon the heating voltage of the cathode and the directivity of the radiation emitted depends upon the energy of the X-rays emitted. In Fig. 1 which corresponds to the prior art, a tungsten target 1, under the impact of the beam of electrons, emits in a radiation lobe 2 with electrons having an energy of 2 MeV, in a radiation lobe 3 with electrons having an energy of 5 MeV and in a radiation lobe 4 with electrons having an energy of 10MeV ; the narrowest lobe 4 corresponds to a more directional radiation.
Fig. 2, schematically slows an embodiment in accordance with the invention. A tungsten target 5 frustoconical in shape emits a radiation lobe 6 under the impact of the lll~Z3~
deflected beam of electrons e . The deflection system for the beam of electrons is such that the impact zone describes on the target a circle centred on the axis of the non-deflected beam and the end of the radiation lobe also describes a circle of radius R in the plane orthogonal to the axis of the accel-erated beam. Another position of the radiation lobe is shown in dotted lines in the drawing.
The irradiation head according to the present invention and shown in Fig. 3 enables the entire beam of electrons to be deflected so that it strikes the target on an impact zone of small surface area. This impact zone is capable of being displaced on the target either in steps, in which case images of each of the points of the object to be analysed are obtained, or continuously, in which case the impact zone scans the target at a rhythm determined by the frequencies of the currents applied to the deflection coils:
The cover of the irradiation head 20 shown in Fig. 3 comprises a vacuum envelope 21 in which travels a beam 22 of accelerated electrons. The tungsten target 25 is frustoconical in shape. In this embodiment, the accelerated beam of electrons is deflected in its entirety relative to the axis of the incident beam of accelerated electrons and is made to rotate about that axis by means of a quadripolar magnetic ~device 40 of which the wiring diagram is shown in the part of the drawing showing a section along X through the irradiation head shown in the first part of the drawing. A cuxrent Il delivered by a current source flows through the windings of the poles 41 and 42 between the points 1 and 2 whilst a current I2 delivered by the current source flows through the windings of the poles 43 and 44 between the points 3 and 4. The currents Il and I2 are sinusoidal currents of pulsation phase-shlfted by 2 1119;~31 The poles 1 and 2 create an instan.taneous induction Bx = BOX sin ~ t along the axis X, soX being the ~aximum amplitude of the induction along the axis X.
Under the effect of this induction, the beam of accelerated electrons undergoes a deflection x alo~g the axis X : x = k Box sin ~ t.
The poles 3 and 4 create an instantaneous induction By = Boy cos ~ t along the axis Y, boy being the maximum amplitude of the induction along the axis Y. Under the effect of this induction, the beam of accelerated electrons undergoes a deflection ~ along the axis Oy of amplitude y = k ~oy cos ~t. k is a constant which depends upon the distance travelled by the beam after having left the in.teraction space of the magnetic field up to the target. The centre of the impact zone of the beam on the target in a plane orthogonal to the axis of the irradiation head describes a circle if the components of the induction along X and Y, BOX and Boy, are equal or an ellipse i these components are different~
Accordingly, alternating currents of the type in question make it possible for example for the impact zone to describe a circle on the.tungsten target, in which case the axis of the radiatlon lobe generates a frustum With the same arrangement, i~ the currents Il and I2 are adjusted to constant values, the beam of electrons is deflected from its path along the axes X and Y of constant values and remains fixed providing the currents Il and I2 do not change value.
An arrangement such as th~s enables structures in which it is possible to introduce the irradiation head to be examined point by point. By increasing the current flowing through the exciting coils, the beam of electrons is deflected through a larger angle and it is possible, by selecting the shape of the poles and the shape of the vacuum envelope in such a way that the beam of electrons is not blocked by the walls of the en~elope and does in fact strike the target, to obtain a X-radiation lobe of which the axis is perpendi-cular to the axis of the incident beam of accelerated electrons, in which case, irradiation is radial relative to the axis of revolution of the irradiation head.
A panoramic irradiation, by scanning of the target of revolution, is obtained with an arrangement such as this, the beam of electrons rotating about the axis of the irradiation head.
The invention is not limited to the embodiments of the irEadiation head described and illustrated.
In particular, the targets described above were in the form of a frustum or~spherical cap. These forms are by no means the only forms and it is possible to use a target in the form of a cylinder of revolution. However, if the radiation emitted is to be homogeneous for different azimuths, it is important to ensure that the directions of incidence of the electrons on the corresponding zones of the target are not too different. The forms illustrated in the drawings enable the target to be bombarded in quasi-normal directions, - irrespective of the azimuth.
In addition, in the description of the scanning mode, the currents passing through the two electromagnets were described as having the same pulsation. If the currents have different pulsations, it is still possible to scan the target although, in that case, the figure described is a Lissajous figure.
Finally, this deflection device described is the simplest to use for obtaining the required results (deflection of the entire beam and scanning to include a solid angle).
Deflection devices using several pairs of poles-~ay be used .
to rotate the beam of charged particles about the axis of the irradiation head. For example, to obtain periodic scanning of the target of revolution, it is possible to use three pairs of poles respectively fed by currents phase- ;
shifted by 3 or, generally, n pairs of poles fed by currents phase-shifted by -n creating a rotating magnetic field.
This irradiation head may be used in a portable accelerator for borings in petroleum exploration, for medical radiography or in metallurgy for examining plates, joints or hollow parts.
, .
This invention relates to a X-ray irradiation head for panoramic irradiation.
The present invention concerns a X-ray irradiation head for panoramic irradiation using a beam of charged and accelerated particles. The irradiation head has a longitudinal axis along which the particles propagate in the absence of deflections. The head comprises an electromagnetic deflection device for deflecting the charged particles and a target having a surface producing X-rays. This surface is a surace of revQlution the axis of which coincides with the axis of the irradiation head. The deflection device separates the paths of the particles fEom the axis in such a way that the particles impinge upon the target. The deflection device comprises a multipolar magnetic device, and a feed circuit, to deflect the beam of charged particles in its entirety and to make it converge on the target in a small impinging zone.
The magnetic device is fed by a feed circuit such that the magnetic field rotates about the axis of the irradiation head, the mean defl~ction of the deflected beam being variable and the impinging zone moving correlatively on the target. The multlpolar magnetic device is a quadripolar magnetic device.
The windings of pole pieces of the quadripolar magnetic device are fed in pairs and in series by two sinusoidal currents in quadrature delivered by the feed curcuit for periodic scanning of the target by the beam of particles.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the following description and the attached drawings among which:
- Fig. 1 shows the emission lobes corresponding to . ~119231 a conventional target (PRIOR ART);
- Fig. 2 shows the emission lobes corresponding to a target according to the invention;
- Fig. 3 shows a third embodiment of the irradiation head according to the invéntion, the panoramic irradiation being effected by scanning of the target by the beam of accelerated electrons.
The emission of high-energy X-rays by means of a linear accelerator is obtained in the following manner :
electrons are supplied by a thermoemissive cathode under an electrical field of from 30 to 50 Kv for example. These electrons are then accelerated in an accelerating section of the UHF type (a few thousand Mhz) by hign-power pulses (a few megawatts) lasting several microseconds and striking the target which is generally a tungsten pellet. When an electron strikes the target, it is suddenly decelerated, giving rise to the emission of an electromagnetic radiation. In addition, electrons of the beam cause the ionisation of certain atoms of the target and the migrations of the electrons on the various layers of the atoms cause photons to be emitted. The intensity of the radiation depends upon the heating voltage of the cathode and the directivity of the radiation emitted depends upon the energy of the X-rays emitted. In Fig. 1 which corresponds to the prior art, a tungsten target 1, under the impact of the beam of electrons, emits in a radiation lobe 2 with electrons having an energy of 2 MeV, in a radiation lobe 3 with electrons having an energy of 5 MeV and in a radiation lobe 4 with electrons having an energy of 10MeV ; the narrowest lobe 4 corresponds to a more directional radiation.
Fig. 2, schematically slows an embodiment in accordance with the invention. A tungsten target 5 frustoconical in shape emits a radiation lobe 6 under the impact of the lll~Z3~
deflected beam of electrons e . The deflection system for the beam of electrons is such that the impact zone describes on the target a circle centred on the axis of the non-deflected beam and the end of the radiation lobe also describes a circle of radius R in the plane orthogonal to the axis of the accel-erated beam. Another position of the radiation lobe is shown in dotted lines in the drawing.
The irradiation head according to the present invention and shown in Fig. 3 enables the entire beam of electrons to be deflected so that it strikes the target on an impact zone of small surface area. This impact zone is capable of being displaced on the target either in steps, in which case images of each of the points of the object to be analysed are obtained, or continuously, in which case the impact zone scans the target at a rhythm determined by the frequencies of the currents applied to the deflection coils:
The cover of the irradiation head 20 shown in Fig. 3 comprises a vacuum envelope 21 in which travels a beam 22 of accelerated electrons. The tungsten target 25 is frustoconical in shape. In this embodiment, the accelerated beam of electrons is deflected in its entirety relative to the axis of the incident beam of accelerated electrons and is made to rotate about that axis by means of a quadripolar magnetic ~device 40 of which the wiring diagram is shown in the part of the drawing showing a section along X through the irradiation head shown in the first part of the drawing. A cuxrent Il delivered by a current source flows through the windings of the poles 41 and 42 between the points 1 and 2 whilst a current I2 delivered by the current source flows through the windings of the poles 43 and 44 between the points 3 and 4. The currents Il and I2 are sinusoidal currents of pulsation phase-shlfted by 2 1119;~31 The poles 1 and 2 create an instan.taneous induction Bx = BOX sin ~ t along the axis X, soX being the ~aximum amplitude of the induction along the axis X.
Under the effect of this induction, the beam of accelerated electrons undergoes a deflection x alo~g the axis X : x = k Box sin ~ t.
The poles 3 and 4 create an instantaneous induction By = Boy cos ~ t along the axis Y, boy being the maximum amplitude of the induction along the axis Y. Under the effect of this induction, the beam of accelerated electrons undergoes a deflection ~ along the axis Oy of amplitude y = k ~oy cos ~t. k is a constant which depends upon the distance travelled by the beam after having left the in.teraction space of the magnetic field up to the target. The centre of the impact zone of the beam on the target in a plane orthogonal to the axis of the irradiation head describes a circle if the components of the induction along X and Y, BOX and Boy, are equal or an ellipse i these components are different~
Accordingly, alternating currents of the type in question make it possible for example for the impact zone to describe a circle on the.tungsten target, in which case the axis of the radiatlon lobe generates a frustum With the same arrangement, i~ the currents Il and I2 are adjusted to constant values, the beam of electrons is deflected from its path along the axes X and Y of constant values and remains fixed providing the currents Il and I2 do not change value.
An arrangement such as th~s enables structures in which it is possible to introduce the irradiation head to be examined point by point. By increasing the current flowing through the exciting coils, the beam of electrons is deflected through a larger angle and it is possible, by selecting the shape of the poles and the shape of the vacuum envelope in such a way that the beam of electrons is not blocked by the walls of the en~elope and does in fact strike the target, to obtain a X-radiation lobe of which the axis is perpendi-cular to the axis of the incident beam of accelerated electrons, in which case, irradiation is radial relative to the axis of revolution of the irradiation head.
A panoramic irradiation, by scanning of the target of revolution, is obtained with an arrangement such as this, the beam of electrons rotating about the axis of the irradiation head.
The invention is not limited to the embodiments of the irEadiation head described and illustrated.
In particular, the targets described above were in the form of a frustum or~spherical cap. These forms are by no means the only forms and it is possible to use a target in the form of a cylinder of revolution. However, if the radiation emitted is to be homogeneous for different azimuths, it is important to ensure that the directions of incidence of the electrons on the corresponding zones of the target are not too different. The forms illustrated in the drawings enable the target to be bombarded in quasi-normal directions, - irrespective of the azimuth.
In addition, in the description of the scanning mode, the currents passing through the two electromagnets were described as having the same pulsation. If the currents have different pulsations, it is still possible to scan the target although, in that case, the figure described is a Lissajous figure.
Finally, this deflection device described is the simplest to use for obtaining the required results (deflection of the entire beam and scanning to include a solid angle).
Deflection devices using several pairs of poles-~ay be used .
to rotate the beam of charged particles about the axis of the irradiation head. For example, to obtain periodic scanning of the target of revolution, it is possible to use three pairs of poles respectively fed by currents phase- ;
shifted by 3 or, generally, n pairs of poles fed by currents phase-shifted by -n creating a rotating magnetic field.
This irradiation head may be used in a portable accelerator for borings in petroleum exploration, for medical radiography or in metallurgy for examining plates, joints or hollow parts.
, .
Claims (4)
1. A-X-ray irradiation head for panoramic irradiation using a beam of charged and accelerated particles, said irradiation head having a longitudinal axis along which said particles propagate in the absence of deflections, said head comprising an electromagnetic deflection device for deflecting said charged particles and a target having a surface producing X-rays, said surface being a surface of revolution the axis of which coincides with the axis of the irradiation head, said deflection device separating the paths of the particles from said axis in such a way that the particles impinge upon the target ; said deflection device comprising a multipolar magnetic device, and a feed circuit, to deflect the beam of charged particles in its entirety and to make it converge on said target in a small impinging zone, the magnetic device being fed by a feed circuit such that the magnetic field rotates about the axis of the irradiation head, the mean deflection of the deflected beam being variable and the impinging zone moving correlatively on said target ; said multipolar magnetic device being a quadripolar magnetic device, and the windings of pole pieces of said quadripolar magnetic device being fed in pairs and in series by two sinusoidal currents in quadrature delivered by the feed circuit for periodic scanning of the target by the beam of particles.
2. A X-ray irradiation head for panoramic irradiation as claimed in claim 1, wherein said target is frustoconical shaped and has the same axis as the irradiation head, the small base surface of the cone forming the end of the irradiation head.
3. X-ray irradiation head as claimed in claim 1, wherein said target is in the form of a spherical cap centered on said axis.
4. A X-ray irradiation head for panoramic irradiation as claimed in claim 2, wherein a direct target is arranged in the axis of the irradiation head on the small base surface of the cone, the deflection device operation being stopped for direct irradiation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000381567A CA1119231A (en) | 1977-04-01 | 1981-07-10 | X-ray irradiation head for panoramic irradiation |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7709949A FR2386109A1 (en) | 1977-04-01 | 1977-04-01 | G-RAY IRRADIATION HEAD FOR PANORAMIC IRRADIATION AND G-RAY GENERATOR INCLUDING SUCH IRRADIATION HEAD |
| FR7709949 | 1977-04-01 | ||
| CA300,237A CA1115764A (en) | 1977-04-01 | 1978-03-31 | X-ray irradiation head for panoramic irradiation |
| CA000381567A CA1119231A (en) | 1977-04-01 | 1981-07-10 | X-ray irradiation head for panoramic irradiation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119231A true CA1119231A (en) | 1982-03-02 |
Family
ID=27165593
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000381567A Expired CA1119231A (en) | 1977-04-01 | 1981-07-10 | X-ray irradiation head for panoramic irradiation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1119231A (en) |
-
1981
- 1981-07-10 CA CA000381567A patent/CA1119231A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |