CN104394642A - Laser plasma resonance X-ray source - Google Patents

Abstract

The invention discloses a laser plasma resonance X light source, which comprises a bracket, an accelerator capillary, a wiggler capillary, gas, a high-voltage discharge system, a laser, a seed electron beam, the accelerator capillary and the wiggler capillary are connected in series in the bracket, the accelerator capillary and the wiggler The central axes of the through holes of the capillary are parallel to each other but not coincident. The accelerator capillary and the wiggler capillary are pre-filled with gas through the gas-filled channel. The high-voltage discharge system is loaded on both ends of the accelerator capillary and the wiggler capillary through the positive and negative electrodes. The ionized gas generates a plasma channel, and the laser pulse output by the laser is guided in the plasma channel in the accelerator capillary and the wiggler capillary successively to generate a cavity, and the seed electron beam following the laser pulse enters the cavity to be accelerated and resonated X-rays are produced. The invention has the characteristics of simple structure, convenient operation and high X-ray radiation efficiency.

Description

Laser Plasma Resonance X Source

technical field

The invention relates to the field of laser wake field acceleration and synchrotron radiation light sources, in particular to a laser plasma resonance X light source.

Background technique

Since the plasma itself is an ionized quasi-neutral medium, it can carry an accelerating electric field several orders of magnitude larger than the solid medium of a traditional radio frequency accelerator. For example, when the plasma electron density is 10 ¹⁸ cm ^-3 , the electric field is about It is 1GV/cm, and increases with the increase of electron density. Therefore, a new generation of compact and relatively inexpensive miniaturized electron accelerators can be built by using the interaction of ultra-intense and ultra-short laser pulses with plasma waves, and high-quality electron beams with energy up to several GeV have been realized in experiments. One of the important applications of such electron beams is the generation of X-ray sources by synchrotron radiation.

In addition to accelerators, undulators or wigglers are needed to generate X-rays, which make the electrons oscillate transversely in the direction perpendicular to the original propagation direction of the electron beam. Traditional magnetic undulators are large in size and weight, which is inconsistent with miniaturization; the cavitation bubbles generated in the laser wake field acceleration can be used as plasma wigglers for electronic oscillations at the same time, but the electronic oscillation amplitude is generally small, and the oscillation The period increases significantly with increasing electron energy or decreasing plasma density, making it difficult to use for higher energy electron beams, and the radiation photon number efficiency is low.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a laser plasma resonance X light source. The invention should have the characteristics of simple structure, clear principle, convenient operation and high X-ray radiation efficiency.

Technical solution of the present invention is as follows:

A laser plasma resonance X light source, including a bracket, an accelerator capillary, a wiggler capillary, gas, a high-voltage discharge system, a laser and a seed electron beam, the accelerator capillary and the wiggler capillary are arranged in the bracket, and the cylinder of the accelerator capillary and the wiggler capillary The central axes of the through-holes are parallel to each other but not coincident. The No. 1 gas-filling hole and No. 2 gas-filling hole arranged laterally in the bracket communicate with the gas-filling holes in the accelerator capillary and the wiggler capillary respectively, and the two ends of the bracket are respectively provided with negative electrodes. and positive electrode. The high-voltage discharge system consists of a high-voltage power supply, a discharge resistor, a current-limiting resistor, a capacitor, a grounding device, and an inductance. The capillary of the accelerator and the capillary of the wiggler are filled with gas through the No. 1 gas-filled hole and No. 2 gas-filled hole, and the high-voltage discharge system passes through the negative electrode. And the positive electrode is loaded on both ends of the accelerator capillary and the wiggler capillary, and the plasma channel is generated by discharging the ionized gas, and the laser pulse output by the laser is guided in the plasma channel in the accelerator capillary and the wiggler capillary successively to generate cavitation, The seed electron beam following the laser pulse enters the cavity and is accelerated in the second section of the accelerator capillary, then resonantly oscillates in the third section of the wiggler capillary to generate X-rays.

In order to realize the further optimization of the present invention, a further measure is: the accelerator capillary and the wiggler capillary are made of ceramic or ruby or polyethylene material, the shape of the accelerator capillary and the wiggler capillary is a cylinder or a cuboid, and the accelerator capillary The aperture size is the same as that of the wiggler capillary, the aperture size is 50 μm-500 μm, and the distance between the through-hole central axis of the accelerator capillary and the wiggler capillary is 0.1-1 times the beam width of the laser pulse; the bracket is made of acrylic glass The shape of the stent is a hollow cylinder; the output voltage of the high-voltage discharge system is 0.3kV-5kV; the laser is a CPA laser system, and the pulse width of the output laser pulse is 10fs-200fs, and the corresponding beam width is 10μm-100μm, the normalized vector potential amplitude is 1-10; the gas in the accelerator capillary and wiggler capillary is hydrogen or helium; the electric quantity of the seed electron beam is 0.1pC-1000pC, and the energy is 1MeV -100MeV.

Principle of the present invention is as follows:

Ultra-short and ultra-intense laser pulses can expel electrons in the plasma, leaving structures with only background ions, that is, voids. The cavity moves forward with the laser pulse, and the electrostatic field formed by the charge separation in the cavity points to the center of the cavity from the surroundings, and the electrostatic field force in the cavity along the laser propagation direction (longitudinal) can accelerate the electrons, that is, the laser wake wave field acceleration. When the laser is effectively guided by the plasma channel, it will propagate with a constant beam width, which is far greater than the divergence distance of vacuum diffraction. However, if the central axis of the beam does not coincide with the central axis of the channel at the beginning, the center of the beam will no longer move forward in a straight line along the central axis of the channel, but will oscillate forward relative to the central axis of the channel; correspondingly, the formed cavitation There will also be a lateral oscillatory forward motion relative to the central axis of the channel. Due to the effect of the transverse electrostatic field force, electrons can also have transverse oscillations in the cavity similar to spring oscillators. If the electrons are accelerated to close to the speed of light (relativistic electrons), due to the transverse oscillation electrons will produce electromagnetic radiation, such as X-rays , that is, the cavity can also act as a wiggler for synchrotron radiation. But at this time, the intensity coefficient representing the characteristics of the wiggler is proportional to the transverse amplitude of electrons, but generally, the transverse oscillation amplitude of electrons in the cavity is small, and the radiation efficiency is low. If there is a transverse periodic oscillation in the center of the cavity, the period of the transverse oscillation in the center of the cavity is determined by the parameters of the plasma channel, which can be regulated by the gas density and discharge voltage; relatively, the period of the electron transverse oscillation is related to the plasma density and related to the speed of electrons. Therefore, appropriate parameters can be selected so that the transverse oscillation period of the electron is the same as the transverse off-vibration period of the cavity center, which will be similar to a resonant spring oscillator, and the electron transverse oscillation will resonate, which will significantly increase its amplitude; correspondingly, increase the wiggler The intensity coefficient, the radiated photon energy, and the number of photons radiated by each electron per oscillation cycle will increase significantly, enabling high-efficiency generation of X-rays.

Advantages of the present invention:

1. The size of the wiggler is on the order of centimeters, which significantly reduces the size and weight of the wiggler.

2. The wiggler is directly cascaded on the accelerator, without using an additional vacuum target chamber and magnetic field regulation, which is conducive to miniaturization and flexible use.

3. The wiggler is directly cascaded on the accelerator, and the same laser pulse is used, no additional laser is needed, which saves the cost of the laser. the

4. The present invention has the characteristics of simple structure, clear principle, convenient operation and high X-ray radiation efficiency.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Description of drawings

Fig. 1 is a schematic structural diagram of the laser plasmon resonance X light source of the present invention.

In the figure: 1. bracket, 2. accelerator capillary, 3. wiggler capillary, 4. gas, 5. high-voltage discharge system, 6. laser, 7. seed electron beam, 101, No. 1 inflatable channel, 102, No. 2 inflatable Channel, 103, negative electrode, 104, positive electrode, 501, high voltage power supply, 502, discharge resistor, 503, current limiting resistor, 504, capacitor, 505, grounding device, 506, inductor, 601, laser pulse, 602, cavitation .

Detailed ways

See accompanying drawing 1: a kind of laser plasma resonance X light source, comprises support 1, accelerator capillary tube 2, wiggler capillary tube 3, gas 4, high voltage discharge system 5, laser 6 and seed electron beam 7, accelerator capillary tube 2 and wiggler capillary tube 3 Arranged in the support 1, the central axes of the cylindrical through holes of the accelerator capillary 2 and the wiggler capillary 3 are parallel to each other but not coincident, and the No. Capillary 2 communicates with the gas filling hole in the wiggler capillary 2, and the two ends of support 1 are respectively provided with negative electrode 103 and positive electrode 104, and negative electrode 103 and positive electrode 104 are preferably made of copper material, and high-voltage discharge system 5 is composed of high-voltage power supply 501, Composed of discharge resistor 502, current limiting resistor 503, capacitor 504, grounding device 505 and inductor 506, accelerator capillary 2 and wiggler capillary 3 are filled with gas 4 through No. 5 is loaded on both ends of the accelerator capillary 2 and the wiggler capillary 3 through the negative electrode 103 and the positive electrode 104, and the plasma channel is generated by the discharge ionized gas 4, and the laser pulse 601 output by the laser 6 is successively in the accelerator capillary 2 and the wiggler capillary 3 The plasma channel is guided to generate a cavity 602, and the seed electron beam 7 following the laser pulse 601 enters the cavity 602 and is accelerated to generate X-rays. The accelerator capillary 2 and the wiggler capillary 3 are made of ceramic or ruby or polyethylene material, and the shape of the accelerator capillary 2 and the wiggler capillary 3 is a cylinder or a cuboid. The accelerator capillary 2 and the wiggler capillary 3 have the same pore size, and the pore size is 50 μm-500 μm. The distance between the through-hole central axes of the accelerator capillary 2 and the wiggler capillary 3 is 0.1-1 times the beam width of the laser pulse 601 . The bracket 1 is made of acrylic glass, and the shape of the bracket 1 is a hollow cylinder. The output voltage of the high voltage discharge system 5 is 0.3kV-5kV. The laser 6 is a CPA laser system, the pulse width of the output laser pulse 601 is 10 fs-200 fs, the corresponding beam width is 10 μm-100 μm, and the normalized vector potential amplitude is 1-10. The gas 4 in the accelerator capillary 2 and the wiggler capillary 3 is hydrogen or helium. The electric quantity of the seed electron beam 7 is 0.1pC-1000pC, and the energy is 1MeV-100MeV.

Embodiment: The accelerator capillary 2 and the wiggler capillary 3 with the same aperture size are filled with the same kind of gas 4 with the same density, and are discharged through the high-voltage discharge system 5, and the ionized gas 4 forms the same gas in the accelerator capillary 2 and the wiggler capillary 3. The axisymmetric plasma channel, the laser pulse 601 is guided and propagated in the plasma channel, and the beam width remains basically unchanged. The laser pulse 601 is first vertically incident into the plasma channel in the accelerator capillary 2, and propagates coaxially along the center of the channel, and the cavity 602 also moves forward linearly along the central axis of the channel; at this time, the seed electron beam 7 enters the plasma channel along the center of the channel. In the cavity 602, being accelerated, the electron beam transversely oscillates very little, mainly moving forward with acceleration, and the efficiency of radiating X-rays is low. After passing through the accelerator capillary 2, the laser pulse 601 will deviate from the center of the channel and enter the plasma channel in the wiggler capillary 3, and the center of the formed cavity 602 will continuously oscillate and change laterally. When the transverse oscillation period of electrons is the same as that of the center of the cavity 602, it will be similar to the case of a resonant spring oscillator, and the electron transverse oscillation will resonate, which will significantly increase its amplitude; correspondingly, increasing the strength coefficient of the wiggler, the radiation The photon energy and the number of photons radiated by each electron in each oscillation cycle will be significantly increased, enhancing the X-ray radiation efficiency.

In this embodiment, the gas 4 in the discharge ionization accelerator capillary 2 and the wiggler capillary 3 produces a plasma channel, which can be used repeatedly for a long time. When , the inner wall of the capillary is ablated by high-voltage discharge to form a plasma channel. The invention has the advantages of simple structure, convenient operation and high X-ray radiation efficiency, and can be used for miniaturized X-ray sources.

Claims (9)

1. a laser plasma resonance body X source, it is characterized in that, described laser plasma resonance body X source comprises support (1), accelerator capillary (2), Torsional pendulum apparatus capillary (3), gas (4), electrion system (5), laser (6) and seed electrons bundle (7), accelerator capillary (2) and Torsional pendulum apparatus capillary (3) are arranged in support (1), the central shaft of the cylindric through hole of accelerator capillary (2) and Torsional pendulum apparatus capillary (3) is parallel to each other but does not overlap, No. 1 inflation duct (101) transversely arranged in support (1) is communicated with the air-filled pore in Torsional pendulum apparatus capillary (2) with accelerator capillary (2) respectively with No. 2 inflations duct (102), the two ends of support (1) are respectively arranged with negative electrode (103) and positive electrode (104), electrion system (5) is by high voltage source (501), discharge resistance (502), current-limiting resistance (503), electric capacity (504), earthing device (505) and inductance (506) composition, gas (4) is filled with respectively by No. 1 inflation duct (101) and No. 2 inflations duct (102) in accelerator capillary (2) and Torsional pendulum apparatus capillary (3), electrion system (5) is carried in the two ends of accelerator capillary (2) and Torsional pendulum apparatus capillary (3) by negative electrode (103) and positive electrode (104), plasma channel is produced by electric discharge ionized gas (4), guided in the plasma channel of the laser pulse (601) that laser (6) exports in succession in accelerator capillary (2) and Torsional pendulum apparatus capillary (3) and produced cavity (602), the seed electrons bundle (7) of following laser pulse (601) enter into cavity (602) inherent accelerator capillary (2) section accelerated after, X-ray is produced in Torsional pendulum apparatus capillary (3) section resonance oscillations.

2. laser plasma resonance body X source according to claim 1, it is characterized in that, described accelerator capillary (2) and Torsional pendulum apparatus capillary (3) are made up of pottery or ruby or polythene material, and the shape of accelerator capillary (2) and Torsional pendulum apparatus capillary (3) is cylinder or cuboid.

3. laser plasma resonance body X source according to claim 1, it is characterized in that, described accelerator capillary (2) is identical with the pore size of Torsional pendulum apparatus capillary (3), and the aperture of accelerator capillary (2) and Torsional pendulum apparatus capillary (3) is 50 μm-500 μm.

4. laser plasma resonance body X source according to claim 1, is characterized in that, the spacing between described accelerator capillary (2) and the through hole central shaft of Torsional pendulum apparatus capillary (3) is the beamwidth of 0.1-1 times of laser pulse (601).

5. laser plasma resonance body X source according to claim 1, is characterized in that, described support (1) is made up of acrylic glass, and the shape of support (1) is hollow cylindrical.

6. laser plasma resonance body X source according to claim 1, is characterized in that, the output voltage of described electrion system (5) is 0.3kV-5kV.

7. laser plasma resonance body X source according to claim 1, it is characterized in that, described laser (6) is CPA laser system, and the pulsewidth of the laser pulse (601) of output is 10fs-200fs, corresponding beamwidth is 10 μm-100 μm, and normalization vector potential amplitude size is 1-10.

8. laser plasma resonance body X source according to claim 1, is characterized in that, the gas (4) in described accelerator capillary (2) and Torsional pendulum apparatus capillary (3) is hydrogen or helium.

9. laser plasma resonance body X source according to claim 1, is characterized in that, the electricity of described seed electrons bundle (7) is 0.1pC-1000pC, and energy is 1MeV-100MeV.