JP2002323566A - X-ray pulse width measuring method and device using hydrated electron generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray pulse width measuring method and device capable of measuring the pulse width of an X-ray pulse in a femto-second area and performing a precise integrated measurement free from electric jitter. SOLUTION: The X-ray pulse 3 is emitted to water 4 to generate hydrated ions, and a pulse laser beam 7' successively changed in delay time is emitted to water 4 to successively measure the absorption factor by the hydrated ions. The pulse width of the X-ray pulse 3 is measured from the delay time dependency of the absorption factor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the pulse width of an X-ray pulse in the femtosecond range by using hydrated electron generation.

[0002]

2. Description of the Related Art In recent years, laser-induced plasma has been used for X-ray generation. Laser-induced plasma X-rays can generate short-pulse X-rays,
It is used for high time resolution X-ray diffraction and X-ray shadow photography. A pulse laser is used to excite the plasma,
The pulse width of the generated X-rays depends on the pulse width of the excitation laser, and it is theoretically possible to generate an X-ray pulse having a femtosecond pulse width by using a femtosecond pulse laser. For time-resolved measurement, the X-ray pulse width determines its time resolution, and it is important to determine the X-ray pulse width used for time-resolved measurement.

Conventionally, an X-ray streak camera has been used for measuring the pulse width of an X-ray pulse. In the measurement using the X-ray streak camera, since the X-ray photons are converted into electron beams by the photocathode and measured, the time resolution is limited by the response time of the photocathode, and the shortest time resolution is currently 2 picoseconds. (Gold photoelectric surface) is the limit, and the pulse width of the X-ray pulse having the pulse width in the femtosecond region cannot be measured. In addition, the streak camera has a problem that it requires a photomultiplier and therefore has a lot of noise, and it is difficult to perform an integration measurement in a high time resolution measurement due to an electrical jitter based on the noise. As described above, conventionally, the pulse width of the X-ray pulse having the pulse width in the femtosecond region cannot be measured.

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention can measure the pulse width of an X-ray pulse in a femtosecond region, and has no electrical jitter, and therefore can perform highly accurate integrated measurement. An object of the present invention is to provide a method and an apparatus for measuring a pulse width of an X-ray pulse.

[0005]

Means for Solving the Problems The inventors of the present invention irradiate water with an X-ray pulse to generate hydrated electrons, and the absorptivity of the pulsed laser light by the generated hydrated electrons depends on the pulse width. And completed the present invention.

In order to solve the above-mentioned problems, the method of measuring an X-ray pulse width using hydrated electron generation according to the present invention irradiates water with an X-ray pulse to generate hydrated ions, The water is irradiated with a pulsed laser beam having a delay time from the irradiation to measure the absorptance by the hydrated ions, and this measurement is repeated by sequentially changing the delay time. The pulse width of the line pulse is measured.

According to this method, water irradiated with X-rays generates hydrated ions in proportion to the X-ray intensity and on the order of femtoseconds.
Since it has a strong absorption band in the vicinity, the absorption rate of the hydrated ions is measured by irradiating a pulsed laser beam having a wavelength of about 800 nm, and if the measurement is performed several times with successive changes in the delay, the absorption rate depends on the delay time. The intensity distribution of the X-ray pulse on the time axis can be measured with a time resolution corresponding to the pulse width of the pulse laser beam, and therefore the pulse width can be measured with high accuracy. Further, since the intensity distribution is measured by the optical absorptance, there is no electrical jitter, and a highly accurate integrated measurement can be performed.

Further, according to the X-ray pulse width measuring method using hydrated electron generation of the present invention, the pulse laser beam is divided into a first pulse laser beam and a second pulse laser beam,
Irradiating the substance with a pulsed laser beam to generate a laser-induced plasma X-ray pulse, irradiating the X-ray pulse to water to generate hydrated ions, and having a delay time from the X-ray pulse irradiation The water is irradiated with a second pulse laser beam to measure the absorptance due to hydrated ions, and this measurement is repeated by sequentially changing the delay time. The width is measured. According to this method, the intensity distribution on the time axis of the laser-induced plasma X-ray pulse can be measured with a time resolution corresponding to the pulse width of the pulsed laser light, and therefore, the pulse width can be measured with high accuracy. Also, since the intensity distribution is measured by the optical absorptance, there is no electrical jitter,
Highly accurate integrated measurement is possible.

Furthermore, X using the hydrated electron generation of the present invention is
The line pulse width measuring device is an X-ray pulse source, water that irradiates an X-ray pulse emitted from the X-ray pulse source to generate hydrated ions, a container for holding water, a pulse laser light source,
X is the pulse laser light emitted from the pulse laser light source.
It is characterized by having a delay circuit for delaying in synchronization with a line pulse source, and a light intensity measuring device for measuring the absorption rate of the delayed pulsed laser light by hydrated ions. According to this configuration, the pulse width of the X-ray pulse in the femtosecond region emitted from all the X-ray pulse sources can be measured.

Further, the X-ray pulse width measuring apparatus using hydrated electron generation of the present invention comprises a pulse laser light source, and a pulse laser light emitted from the pulse laser light source. A beam splitter for splitting into laser light, a substance that irradiates a first pulsed laser light to generate a laser-induced plasma X-ray pulse, water that irradiates the X-ray pulse to generate hydrated ions, A second optical delay circuit that delays the pulsed laser light; and a light intensity measuring device that measures the absorptance of the second pulsed laser light by hydrated ions. According to this configuration, a laser-induced plasma X-ray pulse can be generated from a single pulse laser light source, and the pulse width of the X-ray pulse in the femtosecond region can be measured.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram showing the principle of an X-ray pulse width measuring method and a measuring apparatus using hydrated electron generation of the present invention. In FIG. 1, an X-ray pulse width measuring apparatus 1 using hydrated electron generation of the present invention includes an X-ray pulse source 2,
Water 4 for irradiating an X-ray pulse 3 emitted from an X-ray pulse source 2, a container 5 for holding the water 4, and a pulse laser light source 6
A delay circuit 8 for delaying the pulse laser light 7 emitted from the pulse laser light source 6, and a light intensity measuring device for measuring the light intensity after the delayed pulse laser light 7 has passed through the container 5 holding the water 4. 9.

The pulse laser light source 6 includes the X-ray pulse source 2
And the X-ray pulse source 2
The pulse laser beam 7 can be oscillated in synchronization with the generation of the X-ray pulse 3. Water produces hydrated ions when irradiated with X-rays in proportion to the X-ray intensity and with a femtosecond response time. The hydrated ion has a lifetime of picoseconds or more and has a strong light absorption edge near 800 nm. As the pulse laser light source 6, a pulse laser light source having an oscillation wavelength near 800 nm and a pulse width on the order of femtoseconds is used.

According to this configuration, the X-ray pulse 3 emitted from the X-ray pulse source 2 irradiates the water 4 to generate hydrated ions in the water 4. The pulse laser light 7 is given a delay time by a delay circuit 8, the delayed pulse laser light 7 ′ is irradiated on the water 4 held in the holding container 5, and the light intensity transmitted through the holding container 5 is measured with a light intensity measuring device. 9 to determine the absorptance of the pulse laser beam 7 'by hydrated ions. By repeating the irradiation of the X-ray pulse 3 and the measurement of the absorptance of the pulse laser beam 7 ′ with the changed delay time a plurality of times in this way, the pulse of the X-ray pulse 3 is determined from the delay time dependence of the absorptivity. Find the width.

Next, a method for obtaining the X-ray pulse width from the delay time dependence of the absorption rate will be described. FIG. 2 is a diagram for explaining a method of obtaining the X-ray pulse width from the absorptance of the pulsed laser light. In the figure, the horizontal axis represents time, and the vertical axes in (a), (b) and (c) of FIG.
Shows the intensity profile of the X-ray pulse 3 in the water 4 on the time axis. The vertical axis of FIG. 2D indicates the integrated absorption rate or absorption rate of the pulse laser beam 7 ′. The arrow in the figure indicates the time when the pulse laser beam 7 ′ is irradiated on the water 4.

As shown in FIG. 2A, at time t ₁ , a part of the X-ray pulse 3 has reached the water 4 and the number of hydrated ions generated in the water 4 is as shown in FIG. 2 (a) is proportional to the area of the hatched portion. Pulse laser beam 7 '
2A is proportional to the hydrated ion concentration, the absorption rate of the pulse laser beam 7 ′ delayed by the delay circuit 8 to reach the time t ₁ by the water 4 is as shown in FIG. It is proportional to the area of the shaded area. FIG. 2 (b)
As shown at time t ₂ , the peak of the X-ray pulse 3 has reached the water 4 at time t _2, and the water 4 of the pulse laser light 7 delayed by the delay circuit 8 to reach time t _2. Is proportional to the area of the hatched portion in FIG. FIG. 2C is the same. in this way,
The absorption rate at each time t is proportional to the integrated value of the profile 11 on the time axis of the X-ray pulse 3 until time t. As described above, the water 4 is irradiated with the pulse laser beam 7 ′ while the delay time is sequentially changed by the delay circuit 8, and the transmitted light intensity is measured to obtain the light absorptance, and the curve 12 in FIG.
As shown in (1), the pulse width of the X-ray pulse 3 can be obtained from the half-value width of the curve 13 by obtaining the absorption integral curve and the time derivative curve 13 of the curve 12.

According to this method, the pulse width of the X-ray pulse in the femtosecond region can be measured with the accuracy of the femtosecond order by using the pulse laser beam 7 having the pulse width of the femtosecond order. Further, since the light intensity is measured and obtained, high-precision time integration measurement can be performed without electric jitter.

Next, an embodiment of the present invention will be described. FIG. 3 is a diagram showing a configuration of an X-ray pulse width measuring apparatus using hydrated electron generation of the present invention. In the figure, an X-ray pulse width measuring device 30 using hydrated electron generation of the present invention comprises a femtosecond laser device 31 and a pulse laser beam 32 oscillated from the femtosecond laser device 31 into a first pulse laser beam 33. A beam splitter 35 for splitting the laser beam into a second pulse laser beam 34 and an X-ray generator disposed in a vacuum chamber 37 for irradiating the first pulse laser beam 33 to generate a laser-induced plasma X-ray pulse 36 Target 38
And water 40 held in a holding container 39 for irradiating an X-ray pulse 36 to generate hydrated electrons, an optical delay circuit 41 for setting a delay time to the second pulsed laser light 34, and a holding container 39. And a light intensity measuring device 42 for measuring the intensity of the transmitted second pulsed laser light 34.
The vacuum chamber 37 has a curved mirror 43 for condensing the first pulse laser beam 33 and irradiating the X-ray generation target 38 with the first pulse laser beam 33. X-ray window 44 made of beryllium.

The holding container 39 for the water 40 and the optical system in the vicinity thereof will be described in detail. FIG. 4 is a diagram showing a configuration of a water holding container and an optical system. In the figure, the holding container 39 is
A glass container 51 and an X-ray introduction window 52 made of beryllium or a polymer film provided on a side wall of the glass container 51.
have. The X-ray pulse 36 is introduced into the glass container 51 filled with water 40 through the X-ray introduction window 52, and is emitted from the side wall of the glass container 51 facing the X-ray introduction window 52. The second pulsed laser light 34 is condensed by the condenser lens 53 at one point of water 40 in the glass container 51 from a direction orthogonal to the incident direction of the X-ray pulse 36, introduced, and transmitted through one point of the water 40. The light is collimated by the condenser lens 54 and enters the light intensity measuring device 42. Optical delay circuit 41
Is composed of a fixed mirror pair and a movable mirror pair, and an arbitrary delay time can be set by moving the movable mirror pair. The delay time resolution is 1 femtosecond and 0.3
By moving μm, the delay time can be changed by one femtosecond.

According to the apparatus having the above-described configuration, the pulse laser beam 32 oscillated from the femtosecond laser device 31 is converted into the first pulse laser beam 33
And a second pulsed laser beam 34, and the first pulsed laser beam 33 is condensed by a curved mirror 43 arranged in a vacuum chamber 37 and irradiates an X-ray generation target 38 to generate an X-ray pulse 36. Let it. X-ray pulse 36 is X
The water 40 is irradiated through the X-ray introduction window 52 of the glass container 51 through the line window 44 and emitted from the glass container 51. The second pulse laser light 34 is added with a delay time by an optical delay circuit 41, condensed by a condenser lens 53 from a direction orthogonal to the incident direction of the X-ray pulse 36, introduced into a glass container 51, The transmitted light emitted from 51 is collimated by a condenser lens 54 and is incident on a light intensity measuring device 42 to measure the transmitted light intensity. Then, the delay time is sequentially changed, and the above measurement is repeated a plurality of times.
The pulse width of the X-ray pulse 36 can be obtained in the same procedure as in the above.

According to the apparatus having the above-described configuration, a laser-induced plasma X-ray pulse can be generated from a single pulse laser light source, and the pulse width of the X-ray pulse in the femtosecond region can be measured. Also, since the pulse width is determined by measuring the light intensity, there is no electrical jitter,
High-accuracy time integration measurement can be performed.

[0021]

As can be understood from the above description, according to the X-ray pulse width measuring method and apparatus using hydrated electron generation of the present invention, the pulse width of the X-ray pulse in the femtosecond region can be measured. It is possible to provide an X-ray pulse width measuring method and apparatus which can perform the integration measurement with high accuracy and without any electrical jitter, and thus can perform highly accurate integrated measurement. Therefore, according to the present invention, it is extremely useful when applied to medical, industrial, and biological fields requiring high time resolution measurement.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of an X-ray pulse width measurement method and apparatus using hydrated electron generation of the present invention.

FIG. 2 is a graph illustrating a method for obtaining an X-ray pulse width from an absorption rate of a pulse laser beam.

FIG. 3 is a diagram showing a configuration of an X-ray pulse width measuring apparatus using hydrated electron generation of the present invention.

FIG. 4 is a diagram showing a configuration of a water holding container and an optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray pulse width measuring device using hydration electron generation 2 X-ray pulse source 3 X-ray pulse 4 Water 5 Holding container 6 Pulse laser source 7 Pulse laser beam 7 'Pulse laser beam with delay time 8 Optical delay circuit Reference Signs List 9 light intensity measuring device 10 signal line 11 profile of X-ray pulse on time axis 12 absorption rate integral curve 13 time differential curve 30 X-ray pulse width measuring device using hydrated electron generation 31 pulse laser device 32 pulse laser beam 33 First pulse laser beam 34 Second pulse laser beam 35 Beam splitter 36 X-ray pulse 37 Vacuum vessel 38 Laser-induced plasma X-ray generating substance 39 Holding vessel 40 Water 41 Optical delay circuit 42 Light intensity measuring instrument 43 Curved mirror 44 X Line window 51 Glass container 52 X-ray window 53, 54 Condensing lens

Continued on the front page (72) Inventor Kazutaka Nakamura 10-1-302 Asagidai Negishi, Naka-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Yoichiro Hironaka 154-2-102, Oba-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Fumiichi Saito 4-9-16-201 F-term (reference) 2G088 FF02 GG30 KK40

Claims (4)

[Claims] 1. An X-ray pulse is applied to water to generate hydrated ions, and a pulse laser beam is applied to the water with a delay time from the X-ray pulse irradiation to produce hydrated ions. Measuring the absorptance, repeating this measurement while sequentially changing the delay time, and measuring the pulse width of the X-ray pulse from the delay time dependence of the absorptance, characterized in that X-ray pulse width measurement method used. 2. A pulse laser beam is divided into a first pulse laser beam and a second pulse laser beam, and the first pulse laser beam is irradiated on a substance to generate a laser-induced plasma X-ray pulse. The X-ray pulse is irradiated on water to generate hydrated ions, and the water is irradiated with the second pulsed laser light with a delay time from the irradiation of the X-ray pulse to generate hydrated ions. Measure the absorption rate,
The measurement is repeated while sequentially changing the delay time, and the pulse width of the plasma X-ray pulse is measured from the delay time dependency of the absorption rate, wherein the X-ray pulse using hydrated electron generation is characterized. Width measurement method. 3. An X-ray pulse source, water for irradiating an X-ray pulse emitted from the X-ray pulse source to generate hydrated ions, a container for holding the water, a pulse laser light source,
A delay circuit for delaying the pulse laser light emitted from the pulse laser light source in synchronization with the X-ray pulse source;
Having a light intensity measuring device for measuring the absorption rate of the delayed pulsed laser light by hydrated ions,
X-ray pulse width measurement device using hydration electron generation. 4. A pulse laser light source, a beam splitter for dividing a pulse laser light emitted from the pulse laser light source into a first pulse laser light and a second pulse laser light, and the first pulse laser light A substance for irradiating to generate a laser-induced plasma X-ray pulse, water for irradiating the X-ray pulse to generate hydrated ions, a container for holding the water, and a delay for the second pulsed laser light. X-ray pulse width measurement using hydrated electron generation, comprising: an optical delay circuit for providing the pulsed laser light; and a light intensity measuring device for measuring the absorption rate of the delayed second pulsed laser light by hydrated ions. apparatus.