Patent Publication Number: US-8976932-B2

Title: X-ray generating device

Description:
TECHNICAL FIELD 
     The present invention relates to an electron beam emitting device. 
     BACKGROUND 
     In technological development, an X-ray generator has been downsized to improve transportability, reduce occupied space and consumed energy and realize the minimum exposure to an X-ray. 
     In general, an X-ray generator has the structure for emitting an electron beam from an electron source, accelerating the electron by high electric field generated by a high potential source, irradiating the electron accelerated with high energy on a metal piece and emitting an X-ray from the metal piece. 
     For example, in an X-ray generator disclosed in the non-patent document 1, a downsized X-ray tube provided with a field emission type carbon nanotube cathode as an electron source, a high potential generator for applying the X-ray tube with high voltage ultra short pulses and a high frequency coaxial cable are used. 
     In addition, an X-ray generator for heating a pyroelectric member by a Peltier device, irradiating an electron emitted from the pyroelectric member on a copper piece and emitting an X-ray from the copper piece is proposed as referred to the non-patent document 1. 
     The technology related to the present invention is also referred to the non-patent documents 2-4. 
     RELATED PATENT DOCUMENT 
     Patent Document 
     Patent document 1: JP-B-3090910 
     Non-Patent Document 
     Non-patent document 1: Published online 31 Jan. 2005 in Wiley InterScience. DOI: 10.1002/xrs.800 
     Non-patent document 2: Develop of X-ray generator by pyroelectric crystal and laser light, 44th X-ray analysis synoisium, Oct. 18, 2008, P21 
     Non-patent document 3: Electron emission from LiNbO3 crystal excited by Nd:YAG laser, Extended abstracts of the 57 th  meeting 2010, The Japan Society of Applied Physics and the Related Societies. 
     Non-patent document 4: Electron emission from LiNbO3 crystal excited by ultraviolet laser, J.Vac.Sci.Technolo.B28(2),March/April 2010 
     SUMMARY OF THE INVENTION 
     Problems to be solved by the Invention 
     All the X-ray generators described above realize the downsizing. However, Inventors of the present invention suggest the following problems through their investigation. 
     A small X-ray generator is used for a cancer treatment. In the cancer treatment, the small X-ray generator is inserted into a human body to irradiate an X-ray directly on a cancer cell. If the small X-ray generator provided with a field emission type carbon nanotube cathode is used from such a view point, it becomes necessary to apply high voltage to the cathode. Even if an insulated coaxial cable is used, the small X-ray generator makes the people concerned reluctant to the treatment. 
     Further, in the X-ray generator using a pyroelectric member, the pyroelectric member is provided on a Peltier device to emit an electron from the pyroelectric member heated by the Peltier device. So, in the X-ray generator provided using the pyroelectric member, it is not necessary to apply high voltage to the Peltier device. However, while the pyroelectric member is cooled, electrons are continuously emitted from the pyroelectric member still at high temperature. So, it is difficult to control on and off of the X-ray generation. It takes time to completely shut off the electron emission from the pyroelectric member by cooling the whole of the pyroelectric member. 
     In each of the methods disclosed in the non-patent documents 3 and 4, it is difficult to emit an X-ray with an intensity strong enough for the cancer treatment. 
     Inventors of the present invention propose a new X-ray generator for emitting an X-ray from an pyroelectric member by irradiating an ultraviolet laser beam on the pyroelectric member in a prior patent application PCT/JP2010/002489. 
     The Inventors have studied the X-ray generator to stabilize the generation of the X-ray. 
     Means for Solving the Problem 
     The one of the objects of the present invention is to stabilize the generation of an X-ray in an X-ray generator which utilizes an ultraviolet laser beam. 
     The inventors turned their attention on the fact that the ultraviolet laser beam receiving surface of the pyroelectric member changed in color when the ultraviolet laser beam was irradiated on the pyroelectric member. As a reason for the change in color, the denaturalization or the desorption of the substance of the pyroelectric member itself, or the denaturalization or the absorption of the gas particles around the pyroelectric member is considered. In any case, in the ultraviolet laser beam receiving surface of the pyroelectric member, the substance which is denaturalized by absorbing the energy of the ultraviolet laser beam is easily ionized to make the potential unstable on the ultraviolet laser beam receiving surface. As a result, it is considered that the potential becomes unstable on the surface opposite to the ultraviolet laser beam receiving surface, namely the electron beam emitting surface of the pyroelectric member. 
     Accordingly, the Inventors stabilize the potential on the ultraviolet laser beam receiving surface (the first surface) by preventing the ultraviolet laser beam receiving surface from being denaturalized, so that the electron beam is stably emitted. As a result, it was observed that the stable X-ray with a strong intensity is generated. 
     Namely, the first aspect of the present invention is defined in the following. 
     An X-ray generator comprising: 
     an ultraviolet laser beam generator; 
     an electron beam emitting device having an ultraviolet laser beam receiving surface for receiving an ultraviolet laser beam generated by the ultraviolet laser generator and an electron beam emitting surface distinguished from the ultraviolet laser beam receiving surface for emitting an electron beam; 
     a metal piece for receiving the electron beam emitted from the electron beam emitting surface to emit an X-ray; and 
     denaturalization prevention means for preventing a substance forming the ultraviolet laser beam receiving surface from being denaturalized by the ultraviolet laser beam. 
     According to the X-ray generator as defined in the first aspect of the present invention, for example, even if the ultraviolet laser beam is irradiated on the electron beam emitting device like the pyroelectric member, the substance on the ultraviolet laser beam receiving surface is not changed. The electron beam emitting device is also referred to the device hereinafter. Since the substance is not ionized, the potential on the ultraviolet laser beam surface is stabilized in the device. Here, the potential is not necessarily zero. Accordingly, the electron beam is emitted stably from the electron beam emitting surface. Such the electron beam is irradiated on the metal piece to emit the X-ray from the metal piece. 
     The second aspect of the present invention is defined in the following. 
     Namely, in the X-ray generator defined in the first aspect of the present invention, the denaturalization prevention means includes a controller for controlling the ultraviolet laser beam generator to make an intensity of an unitary pulse constituting the ultraviolet laser beam less than 1000 μJ or equal to 1000 μJ and a width of the unitary pulse less than 100 ns or equal to 100 ns. 
     According to the study of the Inventors, the comparatively low intensity of the unitary pulse of the ultraviolet laser beam prevents the substance on the ultraviolet laser beam receiving surface of the device from being denaturalized or ionized. On the other hand, the width of the unitary pulse of the ultraviolet laser beam less than 100 ns or equal to 100 ns makes the total energy amount of the ultraviolet laser beam per time large enough by simultaneously keeping the intensity of the unitary pulse low. 
     In other words, the intensity of the unitary pulse is determined not to denaturalize the substance possibly existing on the ultraviolet laser beam receiving surface, namely the substance constituting the device and the gaseous substance surrounding the receiving surface. The total energy amount of the ultraviolet laser beam per time is determined to emit the electron beam from the electron beam emitting surface of the device. 
     The intensity of the unitary pulse of the ultraviolet laser beam and the total applied energy of the ultraviolet laser beam per time can be determined correspondingly to the material constituting the device and the atmosphere surrounding the device. For example, it is preferred that the intensity of the unitary pulse constituting the ultraviolet laser beam is less than 1000 μJ or equal to 1000 μJ and the width of the unitary pulse is less than 100 ns or equal to 100 ns. The respective minimum values are restricted by the wavelength, the frequency and the total energy per time. 
     In the device of the present invention, LiNbO 3  single crystal, LiTaO 3  single crystal or the like may be used as the pyroelectric member. Further, ferroelectric substance including PLZT (Lead-lanthanum zirconate-titanate) or the like may be used as the pyroelectric member. According to the Inventor&#39;s study, even if the controlled ultraviolet laser beam is irradiated on the device, the temperature of the device does not change practically in principle. Incidentally, the temperature of the device sometimes rose by the shift of the irradiated position or the like to reduce the emission amount of the X-ray. 
     In the case described above, the emission amount of the X-ray recovered when the irradiation of the ultraviolet laser beam was shut off or the irradiation energy per time was reduced ( 1 ) and/or when the device was cooled. Incidentally, for cooling the device ( 2 ), the method for disposing the electron beam emitting device in contact with or near to low temperature substance including a peltier device or the like, or circulating coolant around the electron beam emitting device may be adopted. 
     It is preferred that a thermometer for measuring the temperature of the device is provided to control the temperature of the device. 
     Further, in the Inventor&#39;s study, it is found that the atmosphere surrounding the ultraviolet laser beam receiving surface is not particularly restricted in the device by controlling the ultraviolet laser beam. Namely, the ultraviolet laser beam receiving surface may be exposed to air. Even in the case described hereinbefore, it is necessary to dispose the electron beam emitting surface and the metal piece faced with the electron beam emitting surface of the device within vacuum. 
     In case that substance denaturalized remarkably on the ultraviolet laser beam receiving surface is applied to the device, it is preferred that the ultraviolet laser beam receiving surface is hermetically covered with a protection film which is stable and transparent to the ultraviolet laser beam. It is important to form the protection film of material which absorbs the ultraviolet laser beam of the applied wave length as less as possible, which prevents the temperature rise of the device caused by the absorption of the ultraviolet laser beam. For example, when an ultraviolet ray of wavelength 266 nm which is a quadruple wave of YAG laser is applied, it is preferred to use inorganic material including composite quartz glass, magnesium fluoride or the like which transmits the ultraviolet ray more than 90%. When such the protection film which absorbs the ultraviolet ray although minutely is used, it is preferred to provide the cooling system. It is preferred that the protection film is conductive or dielectrically polarized as a dielectric although an insulator. In addition, if the thickness of the protection film is less than the nanometer order, it becomes necessary to contact the conductive material even minutely. In this case, it is preferred to avoid the arrangement for contacting the conductive material itself with another conductor. Although the necessity for avoiding such the arrangement depends on the resistivity of the conductor, it is most preferable to avoid such the arrangement. Namely, it is necessary to form the condition electrically insulated from the ground. In other words, for compensating the charge necessary for the spontaneous polarization from outside, it is necessary to promote the rapid movement of the charge easily. In addition, the sudden temperature rise caused through the conductor of the earth line by the external disturbance is also prevented. 
     As an ultraviolet laser beam generator, a YAG laser generator may be used, for example. The ultraviolet laser beam generated from the ultraviolet laser beam generator is introduced to the one edge of an optical fiber which is faced with the ultraviolet laser beam receiving surface of the device at the other edge of the optical fiber. A laser diode or a light emitting diode constituted by III group nitride family chemical compound semiconductor may be used. An exicimer laser is preferably used for outputting high power. 
     It is preferred to apply an ultraviolet laser beam with wavelength less than or equal to 300 nm. Most of the ultra-violet ray with such short wavelength is absorbed on the uppermost surface of the pyroelectric substance to attain the high energy conversion efficiency. The wavelength of the ultraviolet laser beam is determined to have larger energy than the band gap energy of the applied electron beam emitting device. For preventing the denaturalization of the substance caused by the energy concentration, it is preferred that the ultraviolet laser beam is irradiated with uniform intensity on all over the ultraviolet laser beam receiving surface of the electron beam emitting device. 
     It is preferred that the ultraviolet laser beam is irradiated on the opposite surface to the surface faced with the metal piece in the electron beam emitting device. 
     So, the metal piece, the electron beam emitting device and the ultraviolet laser beam generator are arranged on a line. As a result, the whole apparatus can be assembled easily. 
     When a stick like pyroelectric substance is used as the electron beam emitting device, the one edge of the stick like pyroelectric substance is faced with the metal piece and the other edge is irradiated by the ultraviolet laser beam. 
     In the electron beam emitting device, a protrusion may be formed on the electron beam emitting surface faced with the metal piece by a fine fabrication process to promote the emission of the electron. 
     For the metal piece, a thin plate formed of copper or copper alloy may be used. As a matter of course, if the X-ray is emitted in accordance with the irradiation of the electron, metal except copper, namely, aluminum or aluminum alloy may be used, for example. 
     A member for supporting the electron beam emitting device may be selected arbitrarily in condition for making no effect on the emission of the electron. For example, the side face of the electron beam emitting device except the ultraviolet laser beam receiving surface and the electron beam emitting surface may be supported by an insulator. In addition, the ultraviolet laser beam receiving surface may be fixed to a conductive supporting member by a cantilever. In this case, it is preferred to make the conductive supporting member electrically floating, namely not connected to the ground. By adopting the constitution described above, the configuration of the apparatus can be simplified in correspondence to the requirements for downsizing and saving weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing the structure of an X-ray generator of an embodiment. 
         FIG. 2  is a block diagram showing the structure of an X-ray generator of another embodiment. 
         FIG. 3  is a block diagram showing an energy conversion system of an embodiment. 
         FIG. 4  is a schematic diagram for showing the constitution of an X-ray generator of an example. 
         FIG. 5  is an output chart of an X-ray generator of an example. 
         FIG. 6  is an output chart of an X-ray generator of another example. 
         FIG. 7  is an output chart in cased that a distinct pyroelectric member is used. 
         FIG. 8  is an output chart in cased that another distinct pyroelectric member is used. 
         FIG. 9  is a sectional view showing a detail within a chamber. 
         FIGS. 10A-10C  are charts showing an output of an X-ray in respective configurations of a SUS plate. 
         FIGS. 11A-11C  are diagrams showing a configuration of a pyroelectric member to a SUS plate, an output chart of an X-ray and a temperature change. 
         FIGS. 12A-12C  are diagrams showing a configuration of a pyroelectric member to a SUS plate, an output chart of an X-ray and a temperature change. 
         FIGS. 13A-13C  are diagrams showing another configuration of a pyroelectric member to a SUS plate, an output chart of an X-ray and a temperature change. 
         FIGS. 14A-14C  are diagrams showing another configuration of a pyroelectric member to a SUS plate, an output chart of an X-ray and a temperature change. 
         FIG. 15  shows an equipment for measuring a temperature and a surface potential of a pyroelectric member when an ultraviolet laser beam with an unitary pulse of mJ order intensity is irradiated on the ptroelectric member. 
         FIG. 16  shows an equipment for measuring a temperature and a surface potential of a pyroelectric member when an ultraviolet laser beam with an unitary pulse of μJ order intensity is irradiated on the ptroelectric member. 
         FIGS. 17A and 17B  show a surface potential of a pyroelectric member heated and cooled. 
         FIGS. 18A and 18B  show a surface potential on an ultraviolet laser beam receiving surface of a pyroelectric member when an mJ order ultraviolet laser beam is irradiated on the pyroelectric member heated and cooled. 
         FIGS. 19A and 19B  show a surface potential on an electron beam emitting surface of a pyroelectric member when an mJ order ultraviolet laser beam is irradiated on the pyroelectric member heated and cooled. 
         FIGS. 20A and 20B  show a surface potential on an ultraviolet laser beam receiving surface of a pyroelectric member when an μJ order ultraviolet laser beam is irradiated on the pyroelectric member heated and cooled. 
         FIGS. 21A and 21B  show a surface potential on an electron beam emitting surface of a pyroelectric member when an μJ order ultraviolet laser beam is irradiated on the pyroelectric member heated and cooled. 
         FIG. 22  is a block diagram showing another embodiment. 
         FIG. 23  is a block diagram showing another embodiment. 
         FIG. 24  is a block diagram showing another embodiment. 
         FIG. 25  is a block diagram showing another embodiment. 
         FIG. 26  is a graph showing a recovery of an X-ray generator. 
     
    
    
     EMBODIMENTS 
     Embodiments of the present invention are described in the following. 
       FIG. 1  is a schematic diagram showing the structure of an X-ray generator  1  of an embodiment. The X-ray generator  1  is suitably configured to be inserted to the digestive organ or the like of a human body. 
     The X-ray generator  1  has a head unit  10 , a fiber unit  40  and a control unit  50 . 
     The head unit  10  is provided with a cylindrical chassis  11  which has a concave configuration  14 . At the central position of the forefront surface of the chassis  11 , an X-ray transmission window  13  formed of beryllium is provided. At the central position of the bottom surface of the concave configuration  14 , an ultraviolet ray transmission window  16  formed of quartz glass is provided to transmit an ultraviolet laser beam. Inside of the chassis  11 , a vacuum condition is held approximately between 10 −3  and 10 −4  Torr. 
     Inside of the chassis  11 , a pyroelectric member  20  and a copper piece  25  are provided. The pyroelectric member  20  is formed cylindrically of LiNbO 3  single crystal and used for the electron beam emitting device. The ultraviolet ray transmission window  16 , the pyroelectric member  20 , the copper piece  25  and the X-ray transmission window  13  are disposed on the same axis. 
     In  FIG. 1 , a thermocouple thermometer  31 , a Peltier device  33 , an X-ray detector  35  and an optical device  37  are connected through respective lines  32 ,  34 ,  36  and  38  to the connector  39 . Each line includes a power source line and a signal line as the need arises. The optical device  37  is provided with a light source and a camera to protrude from the chassis  11 . An LED light source may be used for the light source and a CCD may be used for the camera. When the head unit  10  is inserted into the digestive organ of a human body, the appearance around the inserted area can be observed visually by the optical device  37 . 
     The connector  39  is disposed in the concave configuration  14  of the chassis  11  so that the connector  39  is connected with the connector  45  of the fiber unit  40 . 
     The fiber unit  40  has a structure that an optical fiber  43  and a line  46  are inserted to a fiber main body  41  which is generally used for a fiber unit of a gastric endoscope or the like. For the optical fiber  43 , an optical fiber used for ultraviolet rays may be applied. For example, for the core unit of the optical fiber  43 , quartz glass may be used. The line  46  includes a power source line and a signal line. 
     The forefront of the fiber unit  40  is inserted to the concave configuration  14  of the head unit  10  to seal both the forefront and the concave configuration  14  by a gasket  48 . 
     The control unit  50  has an ultraviolet laser beam generator  51 , a driver  52  for the ultraviolet laser beam generator  51 , and a controller  53  for controlling electric devices  31 ,  33 ,  35 ,  37  and  39  within the head unit  10 . The numeral  55  indicates another controller for controlling the driver  52  and the controller  53 . 
     The light emitting unit of the ultraviolet laser beam generator  51  is faced with the optical fiber  43  which is provided on the base end section of the fiber unit  40 . On such the optical fiber  43 , the ultraviolet laser beam is irradiated. 
     For the ultraviolet laser beam generator  51 , a YAG pulse laser oscillator may be used. The output power of the YAG pulse laser oscillator is restricted by the driver  52 . The wavelength of the ultraviolet laser beam is not particularly restricted if the electron beam emitting device  20  can be activated to work, namely to emit an electron beam from the device  20 . Even so, it is preferred that the wavelength of the ultraviolet laser beam is shorter than the transmission wavelength of the electron beam emitting device  20 . 
     The temperature of the electron beam emitting device  20  is sometimes increased by the irradiation of the ultraviolet laser beam. So, in this example, the Peltier device  33  is provided near the electron beam emitting device  20  to cool the electron beam emitting device  20  by the cooled Peltier device  33 . For increasing the cooling efficiency, the Peltier device  33  may contact the electron beam emitting device  20  with insulating material. 
     When the temperature of the electron beam emitting device  20  rises above the predetermined temperature, the controller  53  may apply current to the Peltier device  33  according to the predetermined program, for cooling the electron beam emitting device  20  through the cooled Peltier device  33 . When the electron beam emitting device  20  is cooled below the predetermined temperature, the controller  53  suspends the current to the Peltier device  33 . 
     If a heat-exchanger is provided inside of the chassis  11  for applying coolant, the control for cooling the electron beam emitting device works out by circulating the coolant through the fiber unit  40  similarly to the control described above. 
     An X-ray detector is provided between the copper piece  25  and the ultraviolet ray window  13 . The output power of the X-ray detector  35  is monitored by the controller  53 . If the amount of X-ray radiation exceeds the predicted threshold value, the controller  53  transmits a signal to the controller  55  so that the controller  55  can transmits a control signal to the driver  52 . Then, the driver  52  moves the shutter of the ultraviolet laser beam generator  51  to suspend the emission of the ultraviolet laser beam or decrease the output power of the ultraviolet laser beam. 
     The status that the amount of X-ray radiation exceeds the predicted threshold value also includes the status that the radiation of the X-ray is observed even if small when the X-ray should not be radiated, in addition to the status itself that the amount of X-ray radiation exceeds the predicted threshold value. 
       FIG. 2  shows an X-ray generator of another embodiment. The same element as that of  FIG. 1  is referred to the same numeral as that of  FIG. 1  and the explanation thereof is eliminated. 
     As shown in the embodiment of  FIG. 2 , in the head unit  61 , the ultraviolet laser beam receiving surface  21  of the electron beam emitting device  20  protrudes outwardly from the chassis  11 . Even if the ultraviolet laser beam receiving surface  21  of the electron beam emitting device  20  is exposed to the atmosphere as described above, the generation of an X-ray can be detected similarly to that of the embodiment of  FIG. 1 . 
     Since the ultraviolet laser beam receiving surface  21  protrudes outwardly from the chassis  11  in the embodiment described above, the receiving surface  21  can be cleaned up easily when used repeatedly to extend the lifetime of the head  61 . 
     In each embodiment described above, the configuration for irradiating the controlled ultraviolet laser beam on the pyroelectric member  20  to emit the electron beam from the pyroelectric member  20  constitutes a new electron beam emitting device. 
     Inventors are now study a principle for emitting the electron beam from the pyroelectric member by irradiating the controlled ultraviolet laser beam on the pyroelectric member. Inventors found at least a fact that the ultraviolet laser beam receiving surface does not change in color at all by controlling the irradiation of the ultraviolet laser beam. Namely, the material of the ultraviolet laser beam receiving surface is not denaturalized at all, or the quantity of the denaturalized material is very small even if the ultraviolet laser beam receiving surface is denaturalized. So, the potential of the ultraviolet laser beam receiving surface becomes stable to stabilize the potential of the electron beam emitting surface. The stable X-ray is emitted from the copper piece which has received the stable electron beam. 
     For preventing the material of the ultraviolet beam receiving surface from being denaturalized, it may be taken into consideration to cover the ultraviolet laser beam receiving surface with a protection film. The protection film is stable and transparent to the ultraviolet laser beam. In addition, the protection film is airtight and adhered to the ultraviolet laser beam receiving surface to prevent easily denaturalized material from being put between the protection film and the receiving surface. 
     Such the protection film is formed of inorganic material including magnesium fluoride or the like. In addition, it is preferred in the pyroelectric member that the wall around and near the receiving surface is also covered with the protection film. 
     The controlled ultraviolet laser beam is irradiated on the electron beam emitting device  20 . When the electron beam is emitted stably from the electron beam emitting device, a high potential arises on the electron beam emitting surface of the electron beam emitting device. In other words, the electron beam emitting device is not only an electron gun but also a high potential generating device. The high potential arising in the electron beam emitting device can be converted into other kinds of thermal energy, light energy or the like or signal. 
       FIG. 3  shows the constitution of a system therefore. 
     In  FIG. 3 , the same element as that of  FIG. 1  is referred to the same numeral as that of  FIG. 1  and the explanation thereof is eliminated. In  FIG. 3 , the numeral  70  indicates a converter for converting voltage to another kind of energy, and the numeral  71  indicates another converter for converting voltage to signal. These converters  70  and  71  are coupled to the electron beam emitting surface  23  of the electron beam emitting device  20 . It is preferred that the electron beam emitting surface  23  is covered with a conductive film  76 . 
     On the other hand, it is preferred in the electron beam emitting device that the ultraviolet laser beam receiving surface  21  is covered with a protection film  75  for preventing the ultraviolet laser beam receiving surface  21  from being denaturalized. 
     EXAMPLES 
     Next, one example of the present invention is described in the following. 
       FIG. 4  is a schematic diagram for showing the constitution of an X-ray generator  100  of the example. 
     Namely, inside of a chamber  101  of the X-ray generator  100 , pyroelectric member  103  formed of LiNbO 3  as the electron beam emitting device and copper foil  104  are provided. The pressure of the chamber  101  is reduced to 5×10 −4  Torr by a rotary vacuum pump  105 . The chamber  101  is provided with a quartz window  107  for guiding the ultraviolet laser beam and a beryllium window  108  for emitting the X-ray. 
     A YAG laser generator  110  is used for the ultraviolet laser beam generator. The laser beam emitted from the YAG laser beam generator  110  is diffused by a lens  113  to form a circular cross section of diameter 5 mm at the edge face of the pyroelectric member  103 . 
     The intensity of the X-ray passing through the beryllium window  108  is detected by a GM counter  115 . 
     When the YAG laser beam was irradiated by the 30 kHz rectangular pulse with the intensity of 1600 mW, the generated X-ray was observed as shown in  FIG. 5 . In  FIG. 5 , the vertical scale indicates the count number of the GM counter. 
     The YAG laser beam is irradiated continuously in the experiment shown in  FIG. 5 . On the other hand, when the YAG laser beam is irradiated intermittently, the result is shown in  FIG. 6 . As shown in  FIG. 6 , it is recognized that the generation and shutoff of the X-ray are synchronized with the on and off of the ultraviolet ray. 
       FIGS. 7 and 8  show the output result of the X-ray when LiTaO 3  is used for the electron beam emitting device in the apparatus shown in  FIG. 4 . 
     The larger the pyroelectric coefficient becomes, the larger the generated voltage becomes. So, even if the power irradiation on LiTaO 3  is lower than that on LiNbO 3 , the power irradiation on LiTaO 3  is likely more effective than that on LiNbO 3 . 
     Incidentally, the pyroelectric coefficient becomes maximum rightly below Curie temperature. 
     In addition, Curie temperatures of LiTaO 3  and LiNbO 3  are respectively 690 degrees C. and 1200 degrees C. 
       FIG. 9  is a diagram showing the constitution of the chamber  101  inside of the X-ray generator  1  of an example in detail. The same element as that of  FIG. 4  is referred to the same numeral as that of  FIG. 4  and the explanation thereof is eliminated. 
     In a pair of SUS plates of the example, the through-holes  201  and  202  are formed. In the periphery of the through-hole  201  of the SUS plate  200  disposed at the ultraviolet ray irradiation side, ultraviolet laser beam receiving surface of the pyroelectric member  103  is fixed through conductive material. The copper foil  104  is fixed in the periphery of the through-hole  202  of the SUS plate  200  disposed at the X-ray emission side. The pair of SUS plates  200  and  200  are fixed by a insulation screw formed of polycarbonate. 
     In case ( 1 ), when the SUS plate  200  disposed at the ultraviolet ray irradiation side is connected to ground, X-ray is not generated. 
     Incase ( 2 ), also when the SUS plate  200  disposed at the ultraviolet ray irradiation side is contacted with the chamber  101  and connected to ground through the chamber  101 , X-ray is not generated. 
     In case ( 3 ), on the other hand, when the SUS plate  200  disposed at the ultraviolet ray irradiation side is not connected to ground, X-ray is generated. 
     In the state that the SUS plate  200  disposed at the ultraviolet ray irradiation side is not connected to ground as described in case ( 3 ) above, the configuration for mounting the electron beam emitting device  103  on the SUS plate  200  and the effect for generating the X-ray are shown in  FIGS. 11-14 . In  FIGS. 11-14 , the same element as that of  FIG. 9  is referred to the same numeral as that of  FIG. 9  and the explanation thereof is eliminated. 
     In the example of  FIGS. 11A-11C , the electron beam emitting device  103  is mounted on the SUS plate  200  through synthetic quartz glass  300  and double-sided conductive tapes  301  as shown in  FIG. 11A . In such the example, it is observed that the X-ray is generated as shown in  FIG. 11B . The temperature change in the device  103  is shown in  FIG. 11C . 
     Incidentally, there is a time lag of about 240 seconds (S 0 =300 seconds) between the irradiation of ultraviolet laser beam and the generation of X-ray. The irradiation of ultraviolet laser beam is terminated at time S 1  (=1000 seconds) as shown in  FIGS. 11B and 11C . 
     In the example of  FIGS. 12A-12C , insulating material constituted by a double-sided insulating tape  303  is provided between the synthetic quarts glass  300  and the device  103  as shown in  FIG. 12A . Also in such the example, although the temperature rise is observed, the generation of the X-ray is not observed as shown in  FIGS. 12B and 12C . 
     In the example of  FIGS. 13A-13C , insulating material constituted by a double-sided insulating tape  301  is provided between the SUS plate  200  and the synthetic quarts glass  300  as shown in  FIG. 13A . Also in such the example, although the temperature rise is observed, the generation of the X-ray is not observed as shown in  FIGS. 13B and 13C . 
     In the example of  FIGS. 14A-14C , the device  103  is mounted through the double-sided conductive tape  301  directly on the SUS plate  200 . In the example, the generation of X-ray is observed as shown in  FIG. 14B . Incidentally, there is a time lag of about 240 seconds (S 3 =300 seconds) between the irradiation of ultraviolet laser beam and the generation of X-ray. The irradiation of ultraviolet laser beam is terminated at time S 4  (=720 seconds) as shown in  FIGS. 14B and 14C . 
     Considering the configuration for supporting the pyroelectric member  103  from the result shown in  FIGS. 11A-14C , it is recognized preferably that the ultraviolet ray receiving surface should be fixed to the conductor by keeping electric conductivity. 
     Considering the result shown in  FIGS. 11A-14C , the electron beam emission from the pyroelectric member  103 , namely the generation of X-ray is not produced by the temperature rise of the pyroelectric member. In the examples shown in  FIGS. 12A-12C  and  13 A- 13 C, although the temperature rise is observed, the generation of X-ray is not detected. 
     Next, study on the intensity of ultraviolet laser is shown in  FIGS. 15-21A . 
       FIG. 15  shows an apparatus for measuring the potential and the temperature of the surface of the pyroelectric member  103  when ultraviolet laser beam (mJ laser beam) with the comparatively strong intensity of unitary pulses is irradiated on the pyroelectric member  103 . In  FIG. 15 , the numeral  315  indicates a thermocouple thermometer and the numeral  318  indicates a surface potential meter. The peripheral surface of the pyroelectric member  103  is supported by a retainer  319  formed of ceramic to reduce the temperature rise of the pyroelectric member  103  caused by the ultraviolet laser beam as low as possible. 
       FIG. 16  shows a configuration when ultraviolet laser beam (μJ laser beam) with the comparatively weak intensity of unitary pulses is irradiated on the pyroelectric member  103 . In  FIG. 16 , the same element as that of  FIG. 15  is referred to the same numeral as that of  FIG. 15  and the explanation thereof is eliminated. 
     In each example shown in  FIG. 15  or  16 , the power of the ultraviolet laser beam per unit time is the same each other (as referred to 400 mW, for example). 
     In the pyroelectric member  103  irradiated by the ultraviolet laser beam shown in  FIG. 15 , the ultraviolet laser beam receiving surface is changed to black color. On the other hand, in the pyroelectric member  103  irradiated by the ultraviolet laser beam shown in  FIG. 16 , the ultraviolet laser beam receiving surface does not change in color. 
       FIGS. 17A and 17B  show the relation between the temperature of the pyroelectric member  103  and the surface potential of the ultraviolet laser beam receiving surface shown in  FIGS. 15 and 16 . As shown in  FIGS. 17A and 17B , if the pyroelectric member  103  is heated, the surface potential of the pyroelectric member is also changed to make electrons on the surface emittable. Here, the pyroelectric member  103  is heated by hot air generated by a dryer commercially available. 
     As shown in  FIGS. 18A and 18B , when the ultraviolet laser beam with the comparatively strong intensity of unitary pulses shown in  FIG. 15  is irradiated on the pyroelectric member  103  which is heated in the same condition as that of  FIGS. 17A and 17B , the surface potential on the ultraviolet laser beam receiving surface of the pyroelectric member  103  becomes zero. Similarly, as shown in  FIGS. 19A and 19B , the surface potential of the electron beam emitting surface also becomes zero. 
     In the state described above, the electron beam is not emitted. 
     In other words, although the surface of the pyroelectric member  103  is charged in the same heating condition as that of  FIGS. 17A and 17B  to complete the function of the pyroelectric member itself, if the ultraviolet laser beam is irradiated in the same condition as that of  FIGS. 18A and 18B , the surface of the pyroelectric member  103  becomes 0V to cease the emission of electron beam, eventually generating no X-ray. 
     On the other hand, as shown in  FIGS. 20A ,  20 B,  21 A and  21 B, when the ultraviolet laser beam with the comparatively weak intensity of unitary pulses shown in  FIG. 16  is irradiated on the pyroelectric member  103  which is heated in the same condition as that of  FIGS. 17A and 17B , the ultraviolet laser beam receiving surface of the pyroelectric member  103  is charged. 
     From the results shown in  FIGS. 15-21B , it is recognized that the energy of the ultraviolet laser beam makes an effect on the emission of the electron beam from the pyroelectric member, eventually the generation of X-ray. 
     The energy of the ultraviolet laser beam is chosen appropriately to hold the charged state on the surface of the pyroelectric member, namely the electron beam emitting device. 
     It is preferred according to the study of the Inventors that the intensity of an unitary pulse is less than 1000 μJ or equal to 1000 μJ and the width of the unitary pulse is less than 100 ns or equal to 100 ns. 
     In addition, even if the intensity of the unitary pulse is 1-100 mJ, if the width of the unitary pulse is chosen by psec or fsec order or the cooling effect is thoroughly exerted, the denaturalization on the surface of the pyroelctric body can be prevented to keep the charged state on the surface. By the way, mJ pulse energy is not practical since it is difficult to transmit mJ pulse energy through an optical fiber at present. 
       FIG. 22  shows an apparatus of another embodiment. 
     The apparatus  100  has an ultraviolet laser beam generator  110 , an electron beam emitting device  120 , optical fibers  131 - 133 , a detector  140  and a switching device  141 . 
     The ultraviolet laser beam generator  100  generates an ultraviolet laser beam with the intensity of an unitary pulse less than 1000 μJ or equal to 1000 μJ and the width of the unitary pulse less than 100 ns or equal to 100 ns, namely the ultraviolet laser beam transmittable through the optical fibers  131 - 133  for an ultraviolet ray. The numeral  111  indicates a controller for the ultraviolet laser beam generator. 
     For the optical fibers  131 - 133 , an optical fiber network used for an optical communication network is available. 
     For example, when a specific pulse signal is included in an ultraviolet laser ray transmitted through the optical fiber  132 , the detector  140  activates a switching device  141  to irradiate the ultraviolet laser beam from the ultraviolet laser beam generator  100  through the optical fiber  133  on the electron beam emitting device  120 . Accordingly, electrons are emitted from the electron beam emitting device  120 . 
     The constitution described above includes a configuration that a light ordinarily transmitted through an optical fiber network is used for an optical communication and if the specific signal is detected by the detector  140 , the optical fiber network connects the ultraviolet laser beam generator  100  and the electron beam emitting device  120 . The specific signal described above is also transmitted to the controller  111  to drive the ultraviolet laser beam generator  100 . 
       FIG. 23  shows an apparatus  200  of another embodiment. 
     In  FIG. 23 , the same element as that of  FIG. 22  is referred to the same numeral as that of  FIG. 22  and the explanation thereof is eliminated. 
     In the embodiment, a metal piece  125  including copper foil or the like is provided on the electron beam emitting surface side of the electron beam emitting device  120  to emit an X-ray from the metal piece  125 . 
     The operations of other elements are similar to those of  FIG. 22 . 
       FIG. 24  shows the present invention of another embodiment. 
     In  FIG. 24 , the same element as that of  FIG. 1  is referred to the same numeral as that of  FIG. 1  and the explanation thereof is eliminated. 
     In the embodiment of  FIG. 24 , the head unit  10  is provided with an infrared ray emitting unit  1147 . An infrared laser beam IR from the infrared ray emitting unit  1147  is emitted on an X-ray irradiation region. Accordingly, the X-ray irradiation region can be heated. A detecting unit indicated by the numeral  1137  is provided with a radiation type thermometer to measure the temperature of the region irradiated by the infrared laser beam IR. 
     The infrared laser beam is generated from an infrared laser beam generator  1151 . Then, the infrared laser beam is introduced through an infrared ray fiber  1143  built in the fiber unit  41  into an infrared ray path  1145  of the head unit  10 . The infrared ray path  1145  is also constituted by an infrared ray fiber. Although the infrared ray path  1145  is penetrated through the inside of the head unit  10  in  FIG. 24 , the infrared ray path  1145  is not necessarily provided within the head unit  10  which is deaerated for the electron beam emitting device  20 . Namely, the infrared ray path  1145  may be disposed at a space separated from the electron beam emitting device  20  by providing a partition wall between the electron beam emitting device  20  and the infrared ray path  1145 . Also a thermometer  1137  and the control system  38  and  39  for controlling the thermometer  1137  may be disposed similarly. 
     The numeral  1152  indicates a controller for controlling the infrared laser generator  1151 . 
     It is preferred that a plurality of infrared ray emitting units  1147  are disposed at equal distances around the X-ray emitting window provided at the center. As a result, the efficiency for rising the temperature on the X-ray irradiation region is improved. Instead of the infrared ray emitting unit  1147  used for a heating unit, a heater may be provided in contact with the X-ray irradiation region or near to the X-ray irradiation region. 
     A detecting unit  1137  may be provided with a CCD for detecting an infrared ray to form an image of the X-ray irradiation region. 
     The apparatus shown in  FIG. 24  is used effectively for a hyperthermia treatment, for example. 
       FIG. 25  shows the present invention of another embodiment. Incidentally, the same element as that of  FIG. 24  is referred to the same numeral as that of  FIG. 24  and the explanation thereof is eliminated. 
     In the embodiment of  FIG. 25 , the head  10  is provided with a gas/liquid supply apparatus  1247 . The gas/liquid supply apparatus  1247  is configured to form a nozzle-like figure for ejecting gas or liquid on the X-ray irradiation region. Accordingly, the X-ray irradiation region can be cleaned up around the X-ray irradiation, namely before, during and after the X-ray irradiation. 
     In addition to the cleaning of the X-ray irradiation region, antisepsis, treatment or dyeing of the X-ray irradiation region can be performed by selecting a gas or a liquid. 
     The gas or the liquid is ejected from a pump  21  to a tube  1243  built in the fiber unit  41 . The numeral  1244  indicates a connector at the side of the fiber unit  41 , and the numeral  1246  indicates a connector at the side of the head. The head unit  10  is also provided with a tube  1245  to supply the gas or the liquid for the nozzle  1247 . In the head unit  10 , the tube  1245  may be separated from the electron beam emitting device  20 . 
     A detecting unit  1247  is provided with at least one photo detector for detecting various kinds of wavelengths of the lights emitted from the X-ray irradiation region. The light emitted from the X-ray irradiation region includes a visible light, an infrared ray, an ultraviolet ray and an X-ray in the wavelength of the light. 
     The following effects are obtained by using the detector  1247 . 
     Distinguished from the irradiation from the outside of a living body, it is very important to be able to observe “chemical radiation” itself directly by irradiating rightly on the object before the “chemical radiation” passes through other parts.
     1. It becomes possible to observe biochemical and physiological information on a cell and a tissue by utilizing various spectroscopic features of a living tissue without the effect caused by the scattering of other tissues.   2. In the prior art, the scattering of other tissues or the like causes fluctuation phenomena in a spectrum. So, it is necessary to obtain the exact information by calculating correlation between an exact spectrum and an observed spectrum through various kinds of “correlation spectroscopy”. In the embodiment of the present invention, the exact information can be obtained without calculating the correlation.   

     A living body examination by endoscopic X-ray irradiation realizes optical diagnostics. In the optical diagnostics, it becomes possible to observe various kinds of fluorescent phenomena reflecting the energy state of a cell and the density of a specific ion including a metal ion of Ca2+ or the like by using a fluorescent reagent called as a contrast agent in general. For example, in the optical diagnostics, it becomes possible to observe a specific cancer cell. As a result, in the optical diagnostics, a region ranging from a cell level to the whole tissue can be observed. These observations cannot be realized by the optically transmitting image examination of the prior art. 
     The embodiments of  FIGS. 24 and 25  may be applied to the embodiment of  FIG. 2 . 
     A way studied by the Inventors for stably outputting an X-ray long time is described in the following. 
     Isopropyl alcohol is introduced as reducing gas into a vacuum vessel which holds a pyroelectric member. The pressure within the vessel is always held 2−3×10 −2  Torr by a vacuum pump. 
     Although the region within the vessel supplied with the reducing gas is not particularly restricted, it is preferred that the reducing gas is effectively supplied on the electron beam emitting surface. 
       FIG. 26  shows a result when isopropyl alcohol is introduced to the vessel  101  of the apparatus shown in  FIG. 4 . From the result shown in  FIG. 26 , it is understood that when isopropyl alcohol is introduced with the laser off, the emission of X-ray recovers. 
     Isopropyl alcohol is introduced by a quantity to keep the pressure about 1 Torr within the vessel  101 . However, the quantity is not limited as described above. 
     Incidentally, when the laser is on, even if isopropyl alcohol is introduced, the emission of X-ray does not recover. 
     For making a condition for emitting the X-ray, the electron is emitted from the pyroelectric member to the copper foil. So, it becomes important to provide the electron on the electron emitting surface of the pyroelectric member. If described in another aspect, it becomes important to provide a hydrogen bond on the electron emitting surface. Accordingly, reducible isopropyl alcohol is used for an electron source. Other reducible alcohol or hydrogen gas may be used as a reducible substance. 
     For providing the hydrogen bond on the electron beam emitting surface, when the reducible gas is supplied, the laser is suspended to deactivate the electron beam emitting surface. 
     Namely, for revitalizing the electron emitting device including the pyroelectric member or the like, while the reducible gas is supplied at least on the electron beam emitting surface, the laser is switched off to deactivate the electron beam emitting surface. 
     As described above, the revitalization is described as to the emission of X-ray, which suggests the revitalization of the electron beam emitting function of the electron beam emitting device. 
     The present invention is not limited to the illustrated embodiments or examples alone, but may be changed or modified within the scope easily devised by those skilled in the art without departing from the spirit of the present invention. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
       1 ,  60 ,  100 ,  110  X-ray generator 
       10  Head unit 
       11  Chassis 
       13  X-ray transmission window 
       16  Ultraviolet laser beam transmission window 
       20 ,  103  Electron beam emitting device 
       21  Ultraviolet laser beam receiving surface 
       23  Electron beam emitting surface 
       25 ,  104  Metal piece 
       41  Fiber unit 
       43  Optical fiber 
       51  Ultraviolet laser beam generator