An ultrafast hard x-ray source generation and industrial inspection device

Abstract

This invention provides an ultrafast hard X-ray source generation and industrial inspection device, relating to the field of ultrafast laser technology. It includes: a high-contrast Yb ultrafast laser unit, a laser transmission and focusing unit, and a liquid metal jet target unit. In the high-contrast Yb ultrafast laser unit, an ultrafast laser pulse is generated by a seed source module. The ultrafast laser pulse is purified by temporal background suppression using a cross-polarization contrast purification module. The purified pulse is broadened by a stretcher, amplified by a Yb disk amplifier, and compressed by a pulse compressor. The compressed pulse is focused by the laser transmission and focusing unit. A liquid metal jet is formed by the liquid metal jet target unit. The interaction between the pulse focusing point and the liquid metal jet generates ultrafast hard X-rays. This invention provides a hard X-ray source generation and industrial inspection device that balances high average power, high temporal contrast, micro-focus source size, and long-term stable operation.

Description

Technical Field

[0001] This invention relates to the fields of ultrafast lasers, laser plasma radiation sources, X-ray imaging, and industrial non-destructive testing technologies. Background Technology

[0002] Microfocus X-ray sources are widely used in in-situ or quasi-in-situ imaging of lithium batteries, semiconductor packaging inspection, non-destructive testing of precision components, phase contrast imaging, and research-grade structural characterization. For these applications, the X-ray source needs to have high brightness and average output power while maintaining the smallest possible source size to simultaneously meet the requirements of penetration capability, spatial resolution, and imaging efficiency.

[0003] The focal size of traditional electron beam bombardment microfocus X-ray tubes is typically limited by the electron optics system, anode heat load, and power density. Increasing the electron beam power to increase X-ray flux leads to increased localized anode heat load and can cause focal enlargement; conversely, reducing the focal size to improve resolution limits the power that can be handled. Therefore, traditional microfocus sources face the bottleneck of simultaneously optimizing brightness and source size.

[0004] The interaction between ultrashort pulse lasers and metal targets can generate hard X-ray continuum and characteristic line radiation within a compact scale, and micrometer-scale source sizes can be obtained by controlling the laser focus and the target interaction volume. Among existing laser-driven X-ray schemes, Ti:sapphire femtosecond lasers have the advantages of good pulse contrast and short pulse width, but their average power is usually low, limiting the average X-ray flux. Ordinary industrial ultrafast lasers can achieve higher average power, but the pre-pulse and amplified spontaneous emission background before the main pulse may cause the target surface to pre-ionize and expand before the arrival of the main pulse, thus forming a longer density gradient, resulting in an increase in effective emission volume and a decrease in laser-to-X-ray conversion efficiency.

[0005] Furthermore, high-repetition-rate laser ablation requires the target material to be rapidly updated between adjacent pulses. Fixed targets, rotary targets, or targets with straps are prone to problems such as heat accumulation, debris contamination, target surface damage, and frequent maintenance during long-term operation. Liquid metal jet targets can provide continuously updated target surfaces, but when coupled with high-average-power laser systems, engineering challenges such as target flow stability, focus alignment, debris protection, target liquid circulation and purification, and online closed-loop control still need to be addressed.

[0006] Therefore, there is an urgent need for a hard X-ray source generation and industrial inspection device that combines high average power, high time contrast, micro-focus source size, and long-term stable operation capability. Summary of the Invention

[0007] In view of this, the present invention proposes an ultrafast hard X-ray source generation and industrial inspection device, particularly relating to a device that uses a high-contrast Yb ultrafast laser to drive a liquid metal jet target to generate high-brightness micro-focus hard X-rays for industrial inspection, in order to solve the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention proposes an ultrafast hard X-ray source generating device, comprising: High-contrast Yb ultrafast laser unit, laser transmission and focusing unit, and liquid metal jet target unit; The high-contrast Yb ultrafast laser unit is provided with a seed source module, a cross-polarization wave contrast purification module, a stretcher, a Yb disk amplifier and a pulse compressor in sequence. In the high-contrast Yb ultrafast laser unit, ultrafast laser pulses are generated by a seed source module, and the ultrafast laser pulses are purified by temporal background suppression through a cross-polarization contrast purification module; the purified pulses are broadened by a stretcher, the broadened pulses are amplified by a Yb disk amplifier, and the amplified pulses are compressed by a pulse compressor. The compressed pulse is focused using a laser transmission focusing unit; A liquid metal jet is formed through a liquid metal jet target unit; ultrafast hard X-rays are generated by the interaction between the pulse focusing focal point and the liquid metal jet.

[0009] Optionally, the cross-polarization contrast purification module includes a first polarization selection element, an XPW crystal, and a second polarization selection element arranged sequentially; wherein the first polarization selection element performs polarization selection on the ultrafast laser pulse to form the original polarized light, the XPW crystal generates a cross-polarized wave through a third-order nonlinear effect, and the second polarization selection element selects the cross-polarized wave and suppresses the original polarization background to improve the time contrast of the main pulse relative to the preceding pulse and the amplified spontaneous emission background in the ultrafast laser pulse.

[0010] Optionally, the gain medium of the Yb disk amplifier may be Yb:YAG, Yb:KGW, Yb:CALGO, Yb:CaF2 or other media, where other media are equivalent Yb-doped crystals or ceramics.

[0011] Optionally, a front-end pulse selection or front-end shaping module is provided between the seed source module and the cross-polarization wave contrast purification module, wherein the ultrafast laser pulse is selected or shaped through the front-end pulse selection or front-end shaping module.

[0012] Optionally, an MPC nonlinear compressor is provided between the pulse compressor and the laser transmission and focusing unit.

[0013] Optionally, the liquid metal jet target unit is provided with a liquid metal storage tank, a high-pressure metering pump, a liquid supply pipeline, a micron nozzle, a collection pool, and a return pipeline to form a circulating target supply channel; the micron nozzle and the collection pool are located inside the vacuum target chamber.

[0014] Optionally, in the liquid metal jet target unit, the liquid metal jet includes one or more of gallium, indium, tin, and bismuth.

[0015] On the other hand, the present invention provides an industrial inspection device for an ultrafast hard X-ray source, comprising: The generating device, X-ray modulation output unit, and industrial detection imaging unit as described in any one of claims 1-7 are arranged sequentially. Hard X-rays are extracted and modulated by an X-ray modulation output unit, and the modulated hard X-rays are used to irradiate the sample under test by an industrial inspection imaging unit to form an industrial inspection image.

[0016] Optionally, the industrial inspection imaging unit includes a sample stage for holding the sample under test and a detector for receiving industrial inspection images, wherein the detector is used to perform absorption imaging, phase contrast imaging, tomography, or time-resolved imaging.

[0017] Optionally, the generating device also includes a control unit, wherein the control unit is connected to a high-contrast Yb ultrafast laser unit, a laser transmission and focusing unit, a liquid metal jet target unit, and an industrial detection and imaging unit; the control unit synchronously controls the laser output, target flow state, the relative position of the focus and the target flow, and detector acquisition.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention utilizes XPW purification to suppress the time domain background before the main pulse, reduce the pre-ionization and pre-expansion of the target surface, and enable the main pulse to interact with the metal target with a steeper density gradient, which is beneficial to reduce the effective X-ray emission volume.

[0019] (2) The present invention adopts a Yb disk power amplification structure to improve the average power carrying capacity and long-term stable operation capability of the driving laser, which is beneficial to improving the average output flux of hard X-rays.

[0020] (3) The present invention uses a liquid metal jet target, so that different pulses act on the continuously updated fresh target surface, thereby reducing the impact of heat accumulation and target surface damage on X-ray stability.

[0021] (4) The present invention forms a closed-loop control through coaxial microscopy, target flow position, laser energy direction, contrast and X-ray output diagnosis, which is beneficial to improving shot-to-shot repeatability and consistency of industrial inspection images.

[0022] (5) The present invention can improve the brightness of hard X-rays while maintaining the size of the microfocal source, and is suitable for high-resolution non-destructive testing, phase contrast imaging and tomography. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. In the drawings: Figure 1 This is an overall structural diagram in an embodiment of the present invention; Figure 2 This is a schematic diagram of the high-contrast Yb ultrafast laser unit in an embodiment of the present invention; Figure 3 This is a schematic diagram of the cross-polarization wave contrast purification module in an embodiment of the present invention; Figure 4 This is a schematic diagram of the liquid metal jet target unit in an embodiment of the present invention. Detailed Implementation

[0024] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] This invention discloses an ultrafast hard X-ray source generation and industrial inspection device, comprising a high-contrast Yb ultrafast laser unit, a laser transmission and focusing unit, a liquid metal jet target unit, an X-ray modulation output unit, an industrial inspection imaging unit, and a control unit. The high-contrast Yb ultrafast laser unit places XPW contrast-purified lasers before the disk power amplification. The purified pulses are broadened by CPA, amplified and compressed by the Yb disk, and then focused onto a continuously updated liquid metal jet target, forming a micron-scale plasma luminescent region and outputting high-brightness hard X-rays. The control unit performs synchronous closed-loop control of laser energy, pointing, pulse contrast, target flow position, and imaging acquisition. This invention balances high average power, high temporal resolution, and micro-focal source size, and can be used for high-resolution non-destructive testing of lithium batteries, semiconductor packaging, and precision components.

[0026] This invention aims to solve the following problems existing in the prior art: 1) Microfocus X-ray sources are prone to sacrificing source size when increasing brightness and have insufficient average flux when maintaining microfocus.

[0027] 2) When high average power ultrafast laser drives a metal target, the pre-plasma expansion of the target surface caused by the pre-pulse background in the time domain leads to problems such as increased X-ray source size, decreased conversion efficiency and poor inter-pulse repeatability.

[0028] 3) Problems related to target surface renewal, target flow stabilization, precise coupling of laser focus and target flow, and closed-loop control of X-ray industrial imaging during high repetition rate target firing.

[0029] To address the aforementioned technical problems, this invention provides an ultrafast hard X-ray source generation and industrial inspection device, comprising a high-contrast Yb ultrafast laser unit, a laser transmission and focusing unit, a liquid metal jet target unit, an X-ray modulation output unit, an industrial inspection imaging unit, and a control unit.

[0030] The high-contrast Yb ultrafast laser unit includes a seed source module, an XPW contrast purification module, a chirped pulse amplifier (CPA) stretcher, a Yb disk power amplifier, and a pulse compressor arranged along the optical path.

[0031] In the high-contrast Yb ultrafast laser unit, the cross-polarization wave contrast purification module is set in front of the Yb disk power amplifier to suppress the temporal background before the main pulse before the main power amplification.

[0032] The laser transmission and focusing unit is used to focus the compressed ultrafast laser pulse onto the liquid metal jet formed by the liquid metal jet target unit, so as to generate hard X-rays in the interaction region between the laser focus and the liquid metal jet. The liquid metal jet target unit is used to continuously supply and recover liquid metal jets, so that different laser pulses act on the updated target surface area. The X-ray modulation output unit is used to extract the generated hard X-rays and perform beam limiting, filtering, or collimation. The industrial inspection imaging unit includes a sample stage for holding the sample under test and a detector for receiving transmission or phase contrast images. The control unit is used to synchronously control the laser output, target flow state, the relative position of the focal point and the target flow, and detector acquisition.

[0033] Specifically, the high-contrast Yb ultrafast laser unit also includes one or more of the following: a front-end pulse selection or front-end shaping module, an output isolation and diagnostic module, an energy pointing stabilization control module, a beam quality monitoring module, and a time contrast diagnostic module.

[0034] The front-end pulse selection or front-end shaping module is located between the seed source module and the cross-polarization contrast purification module; the output isolation and diagnostic module is located at the output end of the high-contrast Yb ultrafast laser unit; the time contrast diagnostic module is connected to the front-end pulse selection or front-end shaping module and the cross-polarization contrast purification module; the energy pointing stabilization control module is connected to the chirped pulse amplifier and Yb disk amplifier; and the beam quality detection and pulse compressor is connected to the output isolation and diagnostic module.

[0035] Specifically, the cross-polarization contrast purification module includes a first polarization selection element, an XPW crystal, and a second polarization selection element. After the incident pulse is converted into original polarized light by the first polarization selection element, it enters the XPW crystal. The XPW crystal generates a cross-polarized wave with a different polarization direction based on a third-order nonlinear effect. The second polarization selection element selects the cross-polarized wave and suppresses the unconverted original polarization background, thereby improving the temporal contrast of the main pulse relative to the preceding pulse and the amplified spontaneous emission background.

[0036] Specifically, the cross-polarization contrast purification module also includes an extinction trap for absorbing unconverted light, an adjustment mechanism for adjusting the incident angle or temperature of the XPW crystal, or a multi-stage series-connected XPW crystal structure.

[0037] The extinction light trap is configured in correspondence with the second polarization selection element.

[0038] Specifically, the cross-polarization contrast purification module is positioned where the pulse is in a compressed or nearly compressed femtosecond to picosecond range. The purified pulse is then broadened by the chirped pulse amplifier and enters the Yb disk power amplifier.

[0039] Specifically, the chirped pulse amplifier broadener employs one or more combinations of a grating broadener, an Offner broadener, a Martinez broadener, or a chirped volume Bragg grating compressor.

[0040] The pulse compressor employs one or more combinations of a reflective grating compressor, a dielectric grating compressor, a chirped volume Bragg grating compressor, or a multi-pass unit nonlinear compressor.

[0041] Specifically, the Yb disk power amplifier includes a Yb-doped gain disk, a pump-coupled optical path, a heat sink or cooling structure, and an amplification optical path. The amplification optical path adopts at least one of a multi-pass amplification optical path and a regenerative amplification optical path. The gain medium of the Yb-doped gain disk is selected from Yb:YAG, Yb:KGW, Yb:CALGO, Yb:CaF2 or their equivalent Yb-doped crystals or ceramics.

[0042] The Yb-doped gain disk is resonantly excited by the pump light of the pump-coupled optical path. A heat sink or cooling structure is set on the gain disk for temperature control. The broadened pulse is incident on the Yb-doped gain disk for gain, and then amplified by the amplification optical path.

[0043] Specifically, the laser transmission and focusing unit includes a transmission optical path protected by a vacuum or inert gas, a reflector group, a beam expander or shrinker assembly, and an off-axis parabolic mirror or a high numerical aperture lens group arranged sequentially along the optical path. The laser transmission and focusing unit is configured to adjust the laser focal spot size, focal spot position, and incident angle.

[0044] Specifically, the liquid metal jet target unit includes a vacuum target chamber, a liquid metal storage tank, a temperature-controlled heating structure, a high-pressure metering pump, a filter purifier, a liquid supply pipeline, a micron nozzle, a collection pool, and a return pipeline; The liquid metal storage tank, the high-pressure metering pump, the liquid supply pipeline, the micron nozzle, the collection pool, and the return pipeline form a circulating target supply channel.

[0045] The filter purifier is installed on the liquid supply line between the high-pressure metering pump and the micron nozzle. The micron nozzle and the collection pool are installed inside the vacuum target chamber. The temperature control heating structure is installed on the liquid metal storage tank for temperature control. Specifically, the liquid metal jet contains one or more of gallium, indium, tin, and bismuth, or contains a metal or alloy capable of forming a continuous jet and generating target characteristic radiation at a set temperature; the diameter and flow rate of the liquid metal jet are set according to the laser repetition frequency, focal size, and X-ray energy band.

[0046] Specifically, the liquid metal jet target unit or the laser transmission and focusing unit is equipped with a coaxial microscopic monitoring module, a lateral imaging module, a target flow position sensor or a plasma emission monitoring module, which are used to perform coaxial microscopic observation of the irradiated X-rays, perform lateral imaging of the X-rays, collect the target flow position and detect plasma emission, respectively; the above modules are set in corresponding positions, and the control unit adjusts the target flow pressure, target flow temperature, nozzle position, focusing optical element position or reflector attitude according to its output signal.

[0047] Specifically, the X-ray modulation output unit includes one or more of the following: X-ray exit window, filter, collimator, aperture, pinhole, slit, monochromator, debris protection window, sacrificial plate, airflow curtain, magnetic deflection structure, or electrostatic deflection structure; The industrial inspection imaging unit is configured to perform absorption imaging, phase contrast imaging, tomography, or time-resolved imaging.

[0048] The specific functions and workflow of the above-mentioned device are described below: This invention provides an ultrafast hard X-ray source generation and industrial inspection device, including a high-contrast Yb ultrafast laser unit, a laser transmission and focusing unit, a liquid metal jet target unit, an X-ray modulation output unit, an industrial inspection imaging unit, and a control unit.

[0049] The high-contrast Yb ultrafast laser unit includes a seed source module, a cross-polarization contrast purification module, a chirped pulse amplifier and stretcher, a Yb disk power amplifier, and a pulse compressor arranged along the optical path.

[0050] The cross-polarization contrast purification module is set in the front stage of the Yb disk power amplifier, so that the seed pulse or the pulse after front-end amplification is suppressed in the time domain before the main power amplification; the purified pulse is broadened and then enters the Yb disk power amplifier, and is then compressed before being output.

[0051] The cross-polarization contrast purification module preferably includes a first polarization selection element, an XPW crystal, a second polarization selection element, and an extinction trap for absorbing unconverted light. The incident pulse, after passing through the first polarization selection element, forms the original polarized light, which then generates a cross-polarized wave in the XPW crystal through a third-order nonlinear effect. The second polarization selection element selects the cross-polarized wave and suppresses the original polarization background, thereby improving the temporal contrast of the main pulse relative to the preceding pulse and the amplified spontaneous emission background.

[0052] The Yb disk power amplifier can employ multi-pass amplification, regenerative amplification, or a combination thereof. The gain medium can be Yb:YAG, Yb:KGW, Yb:CALGO, Yb:CaF2, or equivalent Yb-doped crystals or ceramics. The disk structure reduces the thermal lensing effect through a shorter heat conduction path and a larger heat dissipation area, enabling the laser unit to maintain good beam quality at high average power.

[0053] The laser transmission and focusing unit transmits compressed ultrafast laser pulses to the target chamber and focuses them onto the liquid metal jet target through an off-axis parabolic mirror or a high numerical aperture lens group.

[0054] The liquid metal jet target unit forms a circulating target supply channel through liquid storage, pressurization, temperature control, filtration, micron nozzle injection, collection, and reflux, so that the liquid metal jet is continuously renewed.

[0055] The interaction between the laser focus and the liquid metal jet forms a micron-scale plasma luminescent region and generates hard X-rays. The hard X-rays are modulated by an X-ray exit window, filter, collimator, aperture, pinhole, slit or monochromatic element and then irradiate the sample under test. The image is then received by an imaging detector to form an industrial inspection image.

[0056] The control unit is connected to the laser energy and pointing stabilization module, the time contrast diagnostic module, the target flow position monitoring module, the coaxial microscopic monitoring module, the X-ray flux or spectral shape monitoring module, and the imaging detector, and is used to synchronously control the laser output, the target flow state, the relative position of the focal point and the target flow, and the detector acquisition.

[0057] III. Core Innovations and Distinguishing Features This invention combines cross-polarized wave contrast purification with Yb disk power amplification, and positions the XPW purification at the intermediate energy, short pulse position before the main power amplification. This arrangement reduces the thermal load and damage risk to the XPW crystal compared to full-power output purification methods, while enabling the subsequent disk amplifier to improve average power and single-pulse energy while maintaining a high-contrast seed pulse.

[0058] This invention integrates a high-contrast, high-average-power Yb ultrafast laser with a liquid metal jet target into a hard X-ray microfocus source. The high-contrast pulse reduces the pre-plasma scale of the target surface, while the liquid metal jet provides a continuously updated fresh target surface. Together, they achieve a small source size and high average flux.

[0059] This invention integrates laser diagnostics, target flow diagnostics, focus-target flow coupling, X-ray modulation output, and industrial imaging into a closed-loop device, enabling the device to not only generate hard X-rays but also obtain repeatable, adjustable, and maintainable imaging results for industrial inspection.

[0060] Compared to traditional electron beam bombardment microfocus X-ray tubes, the X-ray emission region of this invention is determined by the interaction between ultrafast laser focusing and liquid metal jet, and is no longer mainly limited by the expansion of the anode hot spot; compared to the low average power Ti:sapphire laser ablation scheme, this invention improves the average power through Yb disk amplification; compared to the scheme that only uses high-power industrial ultrafast laser ablation, this invention suppresses pre-plasma and improves source size and conversion efficiency through XPW contrast purification.

[0061] The present invention will be further described below with reference to the accompanying drawings.

[0062] Example 1: Overall Structure of the Device like Figure 1 As shown, the ultrafast hard X-ray source generation and industrial testing apparatus of this embodiment includes a seed source, an XPW module, a stretcher, a regenerative amplifier, a compressor, and an MPC nonlinear compressor arranged sequentially along the laser optical path. The ultrafast laser output from the above laser link enters the laser transmission and focusing unit and is focused onto the liquid metal target. The hard X-rays generated by the liquid metal target irradiate the sample under test on the sample stage along the emission direction, and the transmission or phase contrast image is received by an imaging CCD or other X-ray detector.

[0063] In other embodiments, the regenerative amplifier can be replaced by a multi-pass disk amplifier or used in combination with a multi-pass amplifier; the MPC nonlinear compressor is an optional module that can be set or omitted according to the target pulse width, pulse energy and target power density requirements; the imaging CCD can also be replaced by a flat panel detector, a scintillator coupled CMOS detector, an energy spectrum detector or a linear array detector.

[0064] The laser output of this embodiment can be a Yb ultrafast laser with a center wavelength of approximately 1030 nm. Exemplarily, the repetition frequency is in the range of kilohertz to hundreds of kilohertz, the single pulse energy is in the millijoule to tens of millijoules, the average power is in the tens of watts to kilowatts, and the compressed pulse width is in the femtosecond to picosecond range. The above parameters are merely examples of implementation methods and do not constitute a limitation on the scope of protection.

[0065] Example 2: High-contrast Yb ultrafast laser unit like Figure 2 As shown, the high-contrast Yb ultrafast laser unit includes a seed source module, a front-end pulse selection module, an XPW contrast purification module, a CPA stretcher, a Yb disk amplifier (Yb disk power amplifier), a pulse compressor, an MPC nonlinear compressor, and an output isolation and diagnostic module. This laser unit may also include an energy pointing stabilization control module, a beam quality monitoring module, and a time contrast diagnostic module.

[0066] The seed source module outputs low-noise ultrashort pulses. The front-end pulse selection module can employ an acousto-optic modulator, an electro-optic modulator, a Pockels box, a pulse pickup, or a combination thereof to adjust the repetition frequency, pre-amplified energy, or time-domain gating.

[0067] The pulse processed by the front end enters the XPW contrast purification module to reduce the background before the main pulse before subsequent high-gain amplification.

[0068] The purified pulse enters the CPA stretcher and is stretched to a pulse width suitable for amplification, thereby reducing peak power and nonlinear phase accumulation in the amplification path. The Yb disk amplifier includes a Yb gain disk, a pump optical path, a Pockels cell or optical isolation element, and pump and cooling structures to achieve high average power amplification. The Pockels cell is positioned before the Yb gain disk, the pump provides pump light to the Yb gain disk, and the cooling structure is located on the Yb gain disk.

[0069] The amplified pulse is compressed by a pulse compressor; when it is necessary to further shorten the pulse width or increase the peak power density, the spectral broadening and recompression can be performed by an MPC nonlinear compressor.

[0070] The energy pointing stabilization control module can be implemented based on a sampling energy meter, a position-sensitive detector, a piezoelectric reflector, a fast reflector, an acousto-optic modulator, an electro-optic modulator, or pump current adjustment; the beam quality monitoring module can monitor the beam spot size, M... 2 Factors, wavefront error, and focal spot drift are monitored; the time contrast diagnostic module can periodically or online sample and measure the pulse contrast within a picosecond to nanosecond window.

[0071] Example 3: XPW Contrast Purification Module like Figure 3 As shown, the XPW contrast purification module includes a first polarization selection element, an XPW crystal, and a second polarization selection element. The incident pulse from the front-end pulse selection module is the original polarized light. First, the polarization direction is defined and the polarization purity is improved by the first polarization selection element, and then it is incident on the XPW crystal.

[0072] In XPW crystals, the main peak of the incident pulse generates a cross-polarized wave due to its high instantaneous intensity via a third-order nonlinear effect. The conversion efficiency of the low-intensity time-domain background is significantly lower than that of the main peak. The second polarization selection element selects the cross-polarized wave and blocks or attenuates the original polarization background. The unconverted light is absorbed by the extinction trap, thereby achieving time contrast purification.

[0073] XPW crystals can be nonlinear crystals or transparent media suitable for the corresponding wavelength and pulse width; the first and second polarization selection elements can be Glan prisms, thin-film polarizers, polarization beam splitters, Brewster windows, or combinations thereof. To improve long-term stability, temperature control, angle fine-tuning, spot position adjustment, or heat dissipation structures can be incorporated into the XPW crystal.

[0074] In this embodiment, the XPW contrast purification module is placed before the main power amplification, ensuring that the pulses entering the Yb disk amplifier already have high time contrast. Compared to placing the purification module at the full power output, this arrangement helps reduce the heat load and damage risk of the XPW crystal, while retaining the ability of the subsequent disk amplification to improve average power and single-pulse energy.

[0075] Example 4: Liquid Metal Jet Target Unit like Figure 4 As shown, the liquid metal jet target unit includes a vacuum target chamber, a liquid metal storage tank, a temperature-controlled heating jacket, a high-pressure metering pump, a filter purifier, a liquid supply pipeline, a micron nozzle, a liquid metal jet, a laser incident window, a focusing optical element, a laser focus / plasma, an X-ray exit window, a collection cell, a return pipeline, a CCD microscopic monitoring / coaxial microscopic observation module, a temperature / pressure / position feedback controller, and a vacuum interface / vacuum pump.

[0076] Liquid metal reservoirs are used to store liquid metal or low-melting-point alloys, while temperature-controlled heating jackets maintain the target material at a suitable temperature for spraying and circulation. High-pressure metering pumps deliver liquid metal via supply lines to the micron nozzle, and filters remove solid particles, oxides, or impurities to reduce the risk of nozzle clogging. The micron nozzle forms a continuous jet of liquid metal within the vacuum target chamber.

[0077] The focusing optics can be located within the target chamber or focus the laser onto the liquid metal jet through a laser entrance window. The laser focus interacts with the jet to form a laser focus / plasma, generating hard X-rays in this micrometer-scale region. The hard X-rays exit through the X-ray exit window, while the liquid metal that did not participate in the interaction is collected in a collection pool and returned to the liquid metal storage tank via a return pipeline.

[0078] The liquid metal jet can be made of one or more of Ga, In, Sn, and Bi, or a metal or alloy that can form a continuous jet at a set temperature. For example, the jet diameter can be set to several micrometers to tens of micrometers, and the jet velocity can be set according to the laser repetition frequency and single pulse energy to ensure that adjacent laser pulses act on the updated target surface position.

[0079] The CCD microscopy monitoring / coaxial microscopy observation module is used to observe liquid metal jets, laser focal points, or plasma emission positions. The temperature / pressure / position feedback controller adjusts the high-pressure metering pump, temperature-controlled heating jacket, micron nozzle, or focusing optics based on the microscopic image, target flow pressure, target flow temperature, and position sensor signals to ensure the laser focal point is stably applied to the target flow position.

[0080] Example 5: X-ray Modulation Output and Industrial Inspection The X-ray modulation output unit may include an X-ray exit window, filters, illumination control devices, and monochromatic elements arranged along the optical path. The X-ray spectral bands can be adjusted by selecting different filters or monochromatic elements. The illumination control device may employ a pinhole, aperture, slit, or collimator, which allows control of the illumination area and scattered background. To reduce the impact of debris, charged particles, or deposits on the optical elements and exit window, protective windows, sacrificial plates, replaceable thin films, airflow curtains, magnetic deflection structures, or electrostatic deflection structures may be incorporated.

[0081] The industrial inspection imaging unit includes a sample stage and a detector. The sample stage can be a three-dimensional translation stage, a rotary stage, a tilting stage, or a combination of motion platforms, used to achieve absorption imaging, phase contrast imaging, or computed tomography imaging at different projection angles. The detector can be selected according to the X-ray energy range and the object being detected, including a flat panel detector, X-ray CCD, scintillator-coupled CMOS detector, linear array detector, or energy dispersive spectroscopy detector.

[0082] This device can be used for non-destructive testing of lithium battery electrodes, wound cores, packaging structures, semiconductor packaging, chip interconnects, precision castings, composite materials, additively manufactured components, and minute defects. Since the size of the X-ray source is determined by the interaction region between the laser focus and the liquid metal jet, high spatial resolution can be maintained while increasing the average output flux.

[0083] Example 6: Operation and Closed-Loop Control Method: During operation, the ultrafast pulses output from the seed source are selected at the front end and then enter the XPW contrast purification module. The purified pulses are broadened by the CPA stretcher and amplified by the Yb disk amplifier, before being output through the pulse compressor and the optional MPC nonlinear compressor. The control unit adjusts the front end pulse selection, pump power, compressor spacing, mirror attitude, or nonlinear compression conditions based on energy, pointing, pulse width, beam quality, and time contrast diagnostic signals.

[0084] The liquid metal jet target unit forms a continuous jet within the target chamber. The control unit adjusts the positions of the metering pump, temperature-controlled heating jacket, and nozzle based on the target flow position, velocity, diameter, and temperature and pressure signals, and aligns the laser focus with the jet center or a preset offset position based on a coaxial microscopic image.

[0085] During the target firing process, the control unit can further adjust the laser incident angle, focal position, target flow velocity, sample stage position, and detector exposure parameters based on X-ray flux, X-ray spectrum, source size estimation, sample image signal-to-noise ratio, or image sharpness. As a result, the device can maintain stable hard X-ray output and industrial inspection image quality during long-term operation.

[0086] In one alternative implementation, the XPW contrast purification module can be used in a two-stage or multi-stage series structure to further improve the temporal background suppression capability; it can also be used in combination with Pockels box pulse selector, acousto-optic gating or optical isolator.

[0087] In one alternative implementation, the Yb disc power amplifier module may be composed of multiple disc amplification stages connected in series, or a combination of a regenerative amplification stage and a multi-pass amplification stage, to adapt to different repetition frequencies, single pulse energy, and average power requirements.

[0088] In one alternative implementation, the liquid metal jet target can be replaced with a metal strip target, a rotating disk target, or a liquid metal film target; when using a different target type, a small source size and high conversion efficiency can still be achieved using a high-contrast Yb ultrafast laser link.

[0089] In one alternative implementation, the industrial inspection imaging unit can be connected to an image reconstruction algorithm, a defect recognition algorithm, and an automatic loading and unloading mechanism for the production line to form an online inspection system.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An ultrafast hard X-ray source generating device, characterized in that, include: High-contrast Yb ultrafast laser unit, laser transmission and focusing unit, and liquid metal jet target unit; The high-contrast Yb ultrafast laser unit is provided with a seed source module, a cross-polarization wave contrast purification module, a stretcher, a Yb disk amplifier and a pulse compressor in sequence. In the high-contrast Yb ultrafast laser unit, ultrafast laser pulses are generated by a seed source module, and the ultrafast laser pulses are purified by temporal background suppression through a cross-polarization contrast purification module; the purified pulses are broadened by a stretcher, the broadened pulses are amplified by a Yb disk amplifier, and the amplified pulses are compressed by a pulse compressor. The compressed pulse is focused using a laser transmission focusing unit; A liquid metal jet is formed through a liquid metal jet target unit; ultrafast hard X-rays are generated by the interaction between the pulse focusing focal point and the liquid metal jet.

2. The generating apparatus according to claim 1, characterized in that, The cross-polarization contrast purification module includes a first polarization selection element, an XPW crystal, and a second polarization selection element arranged sequentially. The first polarization selection element performs polarization selection on the ultrafast laser pulse to form the original polarized light. The XPW crystal generates a cross-polarized wave through a third-order nonlinear effect. The second polarization selection element selects the cross-polarized wave and suppresses the original polarization background to improve the time contrast of the main pulse relative to the preceding pulse and the amplified spontaneous emission background in the ultrafast laser pulse.

3. The generating apparatus according to claim 1, characterized in that, The gain medium of the Yb disk amplifier is Yb:YAG, Yb:KGW, Yb:CALGO, Yb:CaF2 or other media, and other media are equivalent Yb-doped crystals or ceramics.

4. The generating apparatus according to claim 1, characterized in that, A front-end pulse selection or front-end shaping module is provided between the seed source module and the cross-polarization wave contrast purification module, wherein the ultrafast laser pulse is selected or shaped through the front-end pulse selection or front-end shaping module.

5. The generating apparatus according to claim 1, characterized in that, An MPC nonlinear compressor is provided between the pulse compressor and the laser transmission and focusing unit.

6. The generating apparatus according to claim 1, characterized in that, The liquid metal jet target unit is equipped with a liquid metal storage tank, a high-pressure metering pump, a liquid supply pipeline, a micron nozzle, a collection pool, and a return pipeline to form a circulating target supply channel; the micron nozzle and the collection pool are located inside the vacuum target chamber.

7. The generating apparatus according to claim 1, characterized in that, In the liquid metal jet target unit, the liquid metal jet contains one or more of gallium, indium, tin, and bismuth.

8. An industrial testing device for an ultrafast hard X-ray source, characterized in that, include: The generating device, X-ray modulation output unit, and industrial detection imaging unit as described in any one of claims 1-7 are arranged sequentially. Hard X-rays are extracted and modulated by an X-ray modulation output unit, and the modulated hard X-rays are used to irradiate the sample under test by an industrial inspection imaging unit to form an industrial inspection image.

9. The generating apparatus according to claim 8, characterized in that, The industrial inspection imaging unit includes a sample stage for holding the sample under test and a detector for receiving industrial inspection images, wherein the detector is used to perform absorption imaging, phase contrast imaging, tomography, or time-resolved imaging.

10. The generating apparatus according to claim 8, characterized in that, It also includes a control unit, which is connected to a high-contrast Yb ultrafast laser unit, a laser transmission and focusing unit, a liquid metal jet target unit, and an industrial detection and imaging unit; the control unit synchronously controls the laser output, target flow state, the relative position of the focus and the target flow, and detector acquisition.

Images