Patent Application
20140138359
Projections by the Energy Information Agency and current Intergovernmental Panel on Climate Change (IPCC) scenarios expect worldwide electric power demand to double from its current level of about 2 terawatts electrical power (TWe) to 4 TWe by 2030, and could reach 8-10 TWe by 2100. They also expect that for the next 30 to 50 years, the bulk of the demand of electricity production will be provided by fossil fuels, typically coal and natural gas. Coal supplies 41% of the world's electric energy today, and is expected to supply 45% by 2030. In addition, the most recent report from the IPCC has placed the likelihood that man-made sources of CO2 emissions into the atmosphere are having a significant effect on the climate of planet earth at 90%. “Business as usual” baseline scenarios show that CO2 emissions could be almost two and a half times the current level by 2050. More than ever before, new technologies and alternative sources of energy are essential to meet the increasing energy demand in both the developed and the developing worlds, while attempting to stabilize and reduce the concentration of CO2 in the atmosphere and mitigate the concomitant climate change.
Nuclear energy, a non-carbon emitting energy source, has been a key component of the world's energy production since the 1950's, and currently accounts for about 16% of the world's electricity production, a fraction that could—in principle—be increased. Several factors, however, make its long-term sustainability difficult. These concerns include the risk of proliferation of nuclear materials and technologies resulting from the nuclear fuel cycle; the generation of long-lived radioactive nuclear waste requiring burial in deep geological repositories; the current reliance on the once through, open nuclear fuel cycle; and the availability of low cost, low carbon footprint uranium ore. In the United States alone, nuclear reactors have already generated more than 55,000 metric tons (MT) of spent nuclear fuel (SNF). In the near future, we will have enough spent nuclear fuel to fill the Yucca Mountain geological waste repository to its legislated limit of 70,000 MT.
Fusion is an attractive energy option for future power generation, with two main approaches to fusion power plants now being developed. In a first approach, Inertial Confinement Fusion (ICF) uses lasers, heavy ion beams, or pulsed power to rapidly compress capsules containing a mixture of deuterium (D) and tritium (T). As the capsule radius decreases and the DT gas density and temperature increase, DT fusion reactions are initiated in a small spot in the center of the compressed capsule. These DT fusion reactions generate both alpha particles and 14.1 MeV neutrons. A fusion burn front propagates from the spot, generating significant energy gain. A second approach, magnetic fusion energy (MFE) uses powerful magnetic fields to confine a DT plasma and to generate the conditions required to sustain a burning plasma and generate energy gain.
Important technology for ICF is being developed primarily at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL), assignee of this invention, in Livermore, Calif. There, a laser-based ICF project designed to achieve thermonuclear fusion ignition and burn utilizes laser energies of 1 to 2 MJ. Fusion yields of the order of 10 to 20 MJ are expected. Fusion yields in excess of 200 MJ are expected to be required in a central hot spot fusion geometry if fusion technology, by itself, were to be used for cost effective power generation. Thus, significant technical challenges remain to achieve an economy powered by pure ICF energy.
In addition to ICF applications, there is broad interest in the area of high average power lasers for materials processing, drilling, cutting and welding, military applications, and the like. In the past a number of efforts have been made to regulate laser induced damage on SiO2 optics by pre-initiating damage and then repairing it as a final processing step before the optics are used. This method has the advantage of allowing weak locations on an optic to self identify by initiation under controlled circumstances. Because the process is done before installation, weak locations on an optic can be repaired after a single initiation pulse, rather than after being initiated and grown for some number of shots as would likely be the case if the damage were to initiate after installation.
Laser-induced damage on both surfaces, but especially the exit surface of fused silica optics is a topic of considerable interest for large aperture, high-power laser systems such as the NIF and the Laser MegaJoule (LMJ). Laser damage can be discussed in terms of two key problems: damage initiation by a single pulse and damage growth due to subsequent laser pulses. Despite the progress made in understanding damage processes, there is a need in the art for improved methods and systems for mitigating the growth of laser damage sites on optical elements.
According to the present invention, techniques related to optical systems are provided. More particularly, embodiments of the present invention provide methods and systems for mitigating the growth of damage sites on optical elements. Merely by way of example, the methods and systems described herein have been applied to the conditioning of small sites (e.g., less than 20 in μm in size) using short pulses (e.g., less than 1 ns in duration). Embodiments of the present invention are applicable to a variety of optical materials including fused silica optics.
The inventors have determined that the growth of laser damage on optical elements (e.g., fused silica optical components) depends on several parameters including laser fluence, wavelength, pulse duration, and site size. The inventors have studied the growth behavior of small damage sites on the exit surface of SiO2 optics under exposure to tightly controlled laser pulses. The results demonstrate that the onset of damage growth is not governed by a threshold, but is probabilistic in nature and depends both on the current size of a damage site and the laser fluence to which it is exposed. Additionally, it is demonstrated that laser exposure history also influences the behavior of individual sites.
According to embodiments of the present invention, the growth of damage sites on optical components (e.g., SiO2-based optics) used in high power lasers is reduced or eliminated by pre-exposure to pulses of a few hundred picoseconds in duration. Such pre-exposure causes weak locations on the optics surface to self-identify by initiating very small damage sites. In some embodiments, the sites that initiate will be only a few microns in diameter and will have a very low probability of growing even without any further treatment. It has been demonstrated that both laser mitigation and acid etching have a near perfect ability to prevent such small sites from growing.
As described herein, measurements of the probability of the formation of a damage site as a function of pre-cursor site size demonstrate that the smaller the site, the smaller the likelihood of growth on a given shot. This observation and the size dependence of initiation size on pulse duration enables the ability to initiate damage sites small enough that they will be un-likely to grow. Pulses as short as a few tens of picoseconds (or shorter) are used to produce sites as small as a micron or less in size. It should be noted that a one micron site is expected to have a probability of growth of ˜10−6.
Currently both the National Ignition Facility (NIF) and the Laser Mega Joule pre-treat large SiO2 optics used in their systems with various methods to enhance the working lifetime of the optics. As an example, NIF currently uses only an acid mitigation technique that effectively reduces damage, but degrades the surface figure of the optic. Laser Mega Joule currently uses a long pulse laser to pre-initiate their optics. Sites created by the long pulse laser (i.e., a XeF laser) produce damage sites about 50 times larger than those produced by the methods described herein. The sites produced by a XeF tend to grow if exposed to subsequent laser energy and are extremely difficult to repair by etching or laser melting or ablation while small sites are easier to repair and may not tend to grow, even without repair.
As described herein, the inventors have demonstrated that initiation with short pulses produces sites ˜50 times smaller than sites initiated by the pre-initiation method discussed above (i.e., XeF laser pre-initiation). Additionally, the inventors have determined that both acid and laser mitigation techniques are more suitable for rendering small sites inert (i.e., preventing them from growing). Consequently, using short pulse initiation prior to laser or chemical mitigation is a technique useful for making more robust optics. Moreover, etching small sites produces much less undulations in the input surface then laser or acid mitigation, which in turn produces much less downstream modulation of the beam. Moreover, because small sites have a small probability of growth, if sites are initiated at a small enough size, no further treatment may be necessary for the optical component.
The inventors have determined that the onset of damage growth is not governed by a threshold, but is probabilistic in nature and depends both on the current size of a damage site and the laser fluence to which it is exposed. Furthermore, the history of laser exposure also influences the behavior of individual sites. This taken with the shot to shot independence to the probability of growth clearly indicates that internal features of the damage sites evolve with each laser exposure even if such changes do not manifest as observable changes to the site diameter. Embodiments of the present invention are applicable to the development of predictive models on laser damage evolution from initiation to a preset size imposed by various damage repair protocols. Thus, embodiments of the present invention can be used to post-process optics in order to make them more robust.
According to an embodiment of the present invention, a method of processing an optical element is provided. The method includes providing the optical element. A surface region of the optical element includes one or more pre-cursors. The method also includes raster scanning a laser beam across the optical element. The laser beam comprises a plurality of laser pulses, each of the laser pulses being characterized by a pulse length less than 1 ns. The method further includes exposing the one or more pre-cursors to the laser beam and observing a light emission event from one of the one or more pre-cursors.
According to an embodiment of the present invention, a system for processing an optical element is provided. The system includes a stage operable to support the optical element. A surface region of the optical element includes one or more pre-cursors. The system also includes a picosecond laser operable to provide a laser beam including a plurality of laser pulses. Each of the laser pulses is characterized by a pulse length less than 1 ns. The system further comprises a control system coupled to at least one of the stage or the picosecond laser and operable to raster scan the laser beam across the optical element and an optical detector operable to observe a light emission event from one of the one or more pre-cursors.
Numerous benefits are achieved by way of the present invention over conventional techniques. For example, embodiments of the present invention provide methods and systems in which less surface area of the optical element is modified that in conventional techniques, resulting in smaller damage sites and, thereby, smaller mitigation sites. These benefits enable the optical elements to be exposed to higher fluence at which the number of initiations are no longer small. As an example, using the methods and systems described herein, ˜1000 times more sites can be accommodated on an optical element with the same global beam quality degradation as associated with conventional techniques. Additionally, small sites are faster to repair with laser techniques (e.g., requiring less manpower) and requiring less powerful lasers (e.g., requiring lower equipment cost) to affect the repair.
Moreover, for a given repair technique, the repair of smaller sites has a much higher success rate and causes less downstream modulation (i.e., less local degradation of beam quality), which reduces the constraints of where adjacent optics can be located. It should be noted that acid etching is not typically an option with XeF initiated sites since they are too large and a significant fraction will continue to grow (i.e., repair and/or mitigation will likely fail). As described herein the sites may be initiated at a small enough size so that no further mitigation is necessary. Additionally, the techniques described herein are suitable for in situ pre-initiation. With a pulse shape agile laser, such as NIF, weak spots on the optical element can be initiated after instillation. If a sufficiently short pulse is used, the pre-initiation sites will be small enough that they will not grow. Embodiments of the present invention are applicable to mirrors, both during manufacture (i.e., off-line) or after installation in a system with a pulse shape agile laser. Additionally, embodiments of the present invention are also applicable to mitigation of surface damage on crystals. These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures.
According to the present invention, techniques related to optical systems are provided. More particularly, embodiments of the present invention provide methods and systems for mitigating the growth of damage sites on optical elements. Merely by way of example, the methods and systems described herein have been applied to the conditioning of small sites (e.g., less than 20 in μm in size) using short pulses (e.g., less than 1 ns in duration). Embodiments of the present invention are applicable to a variety of optical materials including fused silica optics.
Past work has relied on XeF lasers because of their excellent beam and reliability characteristics. The disadvantage to using a XeF laser is that the pulse shape has an effective temporal duration much longer than the pulses used on fusion class laser systems requiring higher fluence and producing larger damage sites, as discussed below. As previously mentioned, the long pulse duration of the XeF system is extremely detrimental in two ways. The first way in which the use of a XeF laser for pre-initiation is detrimental is that higher fluence must be used in order to prepare an optic. As local hot spots can move from location to location, an optic often needs to be resistant to damage from fluences significantly above the beam average. The size of damage sites increases with increased fluence. XeF lasers are also detrimental because their effective pulse duration is much longer than the pulses typically used on fusion class laser systems. This feature also increases the initiation size of damage sites. The two effects combine to make sites so large that they will most probably grow under laser illumination. In addition, the smaller a site is, the higher probability that it will be successfully repaired. As a result, large sites are very difficult and more costly if not impossible to repair.
In recent years, advances in the manufacturing and post-processing steps have lead to significant improvements in the surface quality of fused silica components and thus a notable reduction in the number of initiations per optic. The size of damage initiation sites created by nanosecond (ns) pulses is strongly influenced by the pulse duration, shape, and fluence but ranges from less than 1 μm to 30 μm. The overall site morphology, including modified material, stresses and fractures, plays an important role in the future evolution of such a site under subsequent laser exposure. In general terms, the damage process is likely to re-ignite at the damage site location, causing an expansion of the damaged volume, referred to as damage growth. Specifically, small sites (with diameters less than ˜50 μm) grow, in general, in response to a higher laser fluence and their behavior is better described by a probability of growth. As described herein, the growth probability of laser induced damage sites on the exit surface of SiO2 optics are analyzed under exposure to carefully controlled and characterized laser pulses. Descriptive statistics are used to summarize the evolution of a large ensemble of sites. This method allows quantification of the effects of site size and laser fluence on the probability of growth from data sets collected at fixed pulse durations.
Damage tests with 1-cm diameter beams show that the fluence needed to produce a density of 1 site per square mm with a XeF laser is between 25 and 30 J/cm2 where, a typical pulse shape used for ignition experiments will produce the same damage density at fluences between 15 J/cm2 and 20 J/cm2.
Our experimental approach to growth studies can be summarized as follows: The advantage provided by the 3-cm diameter Optical Science Laboratory (OSL) laser beam was used to simultaneously test a large number of sites with local fluences that vary within ±2-3 J/cm2 (due to the ˜17% spatial beam contrast) around the beam average fluence. For each site, the local mean fluence was computed in a ˜0.5 mm patch with 10% uncertainty using the fluence registration method. Individual site diameters are measured after each laser shot using a robotic microscope under various illuminations (back- and oblique incidence-light resulting in bright and dark field images, respectively) with optical resolution as high as 0.86 μm. This highly parallel technique greatly enhances data collection rate while maintaining precision not typically available in-situ. The description below focuses on sites exposed on the exit surface of SiO2 samples in high-vacuum with 351-nm, 5-ns Flat-In-Time (FIT) pulses.
According to an embodiment, an unknown parameter (i.e., probability of growth) is estimated from a limited number of observations. Thus, in these embodiments, it is important to consider the limitations on accuracy imposed by the sample sizes. The percent error on a probability measurement based on the number of observations, n, can be estimated from:
where p is the expected probability value. In other words, if probability of an outcome is low, a larger number of observations are needed to maintain a given uncertainty. As a rule of thumb, a minimum of 50 samples is required to maintain uncertainty of less than 15% for events with a likelihood of ˜5% or more.
For the above reasons, embodiments of the present invention use a raster scan initiation method to prepare a large number of damage sites with sizes in the ˜10-80 μm range on a single substrate to be tested simultaneously. These sites were initiated in a regular array with nominal spacing of 1 mm with a single pulse from a 355-nm, Nd:YAG table top laser with an 8-ns near Gaussian temporal profile focused to a spatial Gaussian spot of ˜450 μm (diameter at 1/e2 of intensity) on the exit surface of a 1-cm thick silica substrate (e.g., Corning 7980 glass).
The laser fluence was tailored to a level such that the single-shot (S/1) probability to initiate damage at any given location did not exceed 30%. For a bare silica substrates prepared with high damage resistance surfaces, this lower fluence corresponds to 40-45 J/cm2 while a fluence of 60-70 J/cm2 was necessary for 100% initiation probability under similar focusing conditions (peak fluence values are quoted here). There are several benefits of using a raster approach in combination with lower initiation fluence. Not only are many more small sites generated on a given sample compared to past sample preparations, but the size distribution (and the overall damage morphology) produced by this method is very similar to that observed from large beam initiation, i.e., mostly single pit damage sites with diameters up to ˜40 μm.
However, due to inherent shot-to-shot laser fluence fluctuations and/or non-uniformities in the substrate surface, a small number of larger (up to 80 μm) and/or multi-pit sites were also initiated. We thus ensure that the sites are representative of those encountered in high power, large aperture laser systems and the results of this work are applicable to the development of predictive models on laser damage evolution within such systems. The sample was translated in a raster scan pattern and a single laser pulse was fired at each of ˜900 locations from a preset grid with 1 mm spacing, resulting in ˜300 initiated sites within the 3-cm OSL beam aperture. If a higher throughput of initiation sites is desired, while preserving the site morphologies, a sample could be scanned twice using interleaved grids, i.e., minimum site separation of 0.5 mm. The combination of a preset grid and a small focused beam used for initiation minimizes the cross talk between adjacent damage sites with diameters up to about ˜500 μm, which is not a significant limitation considering that only a small fraction of these small sites will grow at fluences up to about 12 J/cm2.
A typical damage site initiation layout as well as the size distribution of individual pits prepared by the raster-scan method (one pass) outlined above are illustrated in
Based on the OSL beam contrast, it is possible to design probability of growth experiments at fixed fluences to cover the range of 4-12 J/cm2 (in high-vacuum, 351-nm, 5-ns FIT pulses). Specifically, three samples were prepared with up to 300 small damage sites per sample using the raster scan method outlined above and exposed for 4-5 shots at 5 J/cm2, 8.5 J/cm2, and 10.5 J/cm2 nominal fluences, respectively. Furthermore, in order to study the effects of laser exposure history, the fluence on one of the samples (#1) was ramped from low to high using small fluence increments (5, 6 J/cm2, 8.5 J/cm2, and 10.5 J/cm2 with 4, 5, 2, and 2 shots at each fluence step, respectively).
Upon completion of the shot sequences and the acquisition of micrographs for individual sites on a given sample, the data was reduced as follows. The pre- and post-shot micrographs of individual sites are compared and a binary growth decision is made, either 1 or 0 if the lateral dimensions of the sites, including sub-surface fracture, did or did not change following the laser shot, respectively. In some implementations, this growth classification is made by a human, whereas in other implementations, it is based on an image thresholding routine. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. It should be noted that although human evaluation can be labor intensive, it enables the virtual elimination of experimental errors (including instrument and image processing) in the detection of growth.
The growth classification procedure after one laser exposure is illustrated in
Referring to
As described below, a preliminary, single-shot probability of growth analysis was performed by computing the fraction of growing sites in each size bin after each shot for a series of laser shots with the same average fluence (not using the local mean fluence for each site yet, i.e., all sites are grouped in one fluence bin). It should be noted that the starting size bin membership of individual sites may or may not be preserved upon subsequent shots depending on their shot-to-shot diameter change.
Herein, we adopt the hypothesis of a shot independent probability of growth for series of nearly identical laser exposures and its direct implications to data analysis. The latter is considerably simplified as we combine all shots as if it were one shot with effectively many more sites exposed at once to their local mean fluence. Indeed, instead of tracking the evolution of a limited number of sites in each size bin from shot to shot, i.e., a single-shot approach that keeps track of shot history and individual sites, we will now group together all observations of sites/shots (corresponding to a size bin) from the tabulated data set associated with an experiment/sample. Each entry (row) in our data set may contain, for example, the site ID, shot number, current site size, previous site size (determines the membership to a size bin for probability measurements), local mean fluence, growth decision (1 or 0), and possibly other attributes (derived or measured parameters) corresponding to one observation of a site on a specific laser shot. The outcome of this analysis is augmented statistics within each size bin that now includes the original sites (as-initiated) and new members (in all but the lowest size bin) as their diameter is changing upon subsequent laser shots. In other words, this cumulative single-shot approach mixes observations of sites with similar size but different laser exposure history (one or more shots at fixed fluences) and provides a first order account of the effects of site size on the probability of growth.
Data analysis was performed for the two experimental scenarios discussed above, namely small damage sites exposed to series of i) nearly constant (at 5 J/cm2, 8.5 J/cm2, and 10.5 J/cm2 from three separate, but similarly prepared samples, respectively) and ii) ramp-up fluence (at 5 J/cm2, 6 J/cm2, 8.5 J/cm2, and 10.5 J/cm2 from sample #1 only) sequence of shots. We note that only the first shots at 5 J/cm2 on sample #1 are included in the data set for constant fluence. In addition, these experiments have effectively covered a wide range of fluences from ˜2 J/cm2 up to ˜13 J/cm2 due to the OSL beam contrast and the use of multiple samples (experiments). Because each of the ˜300 sites on a part may see a different fluence on each shot, every site/exposure is treated as an independent experiment. This highly parallel technique has allowed us to amass data sets in excess of 3000 and 4000 entries for constant fluence and ramped fluence experiments, respectively. The results of the cumulative single-shot analysis approach are presented in
Due to the nature of the raster scan initiation method (with the goal of producing a large number of small sites) and the range of fluences illustrated herein (up to ˜13 J/cm2), the largest size bins were sparsely populated, while the smallest sites (up to 30 μm) rarely grew. All data points in
First, the general trends that apply to both experiments should be noted. The probability of growth is strongly dependent on site size and fluence, i.e., increasing for larger sites and higher fluences. In particular, size effects dominate the growth behavior of sites with diameters up to 50 μm, i.e., the rate at which the probability increases from 0 to 1 (slope) is very distinct for the first three size bins. To better quantify these size effects, we use a 4-parameter logistic function to fit the probability of growth data vs. fluence for each individual size bin (solid and dashed curves in
where A1,2 are initial and final values, x0 is the center value, and p is the power (shape), respectively. This model is effective in reproducing the shape of the data presented in
Additionally, is should be noted that the effects of laser exposure history can be clearly seen by comparing the shape of the probability vs. fluence curves for the same size bins from
Furthermore, in
According to embodiments of the present invention the picosecond laser is characterized by a pulse length that ranges between 5 ps and 1 ns, for example, a pulse length between 20 ps and 500 ps. In a particular embodiment, the pulse length is between 100 ns and 300 ns.
The method further includes exposing the one or more pre-cursors to the laser beam (614) and observing a light emission event from one of the one or more pre-cursors (616). Observing a light emission event can include measuring spectral information related to the light emission event. Observing a light emission event can also include imaging the optical element using at least one camera.
According to some embodiments of the present invention, the laser beam is characterized by a lasing wavelength (e.g., 351 nm) and the light emission event is characterized by a wavelength profile different than the lasing wavelength. Under some conditions, the wavelength profile of the light emission event is a harmonic of the lasing wavelength. Under other conditions, the wavelength profile of the light emission event is characterized by a blackbody radiation curve.
In some embodiments, the spectral content of the emission from the one or more pre-cursors is utilized to analyze the efficacy of the damage repair. As an example, during raster scanning of the optical element, passivation could be indicated by the emission being characterized by a blackbody radiation curve, indicating that absorption of the laser pulse by the pre-cursor resulted in generation of an absorption front in the material, which produces the blackbody flash. If no blackbody radiation is observed, then that could be an indicator that absorption in the material was not sufficient to launch the absorption front and that the pre-cursor has not been ablated or removed. Several systems for detecting the spectral content of the emission from the pre-cursor could be used, including two cameras with predetermined wavelength spectral filters, a color camera with multiple channel outputs, a spectrometer, or the like.
In some optional embodiments, the method also includes recording a location associated with the light emission event from the one of the one or more pre-cursors (618) and mitigating damage at the location of the one of the one or more pre-cursors (620). The damage at the location of the one of the one or more pre-cursors can be less than 80 μm in size.
The picosecond laser pulses are preferably characterized by “flat in time” pulse shapes with reduced tails in comparison to conventional pulses. In particular, excimer laser pulses are characterized by long pulse tails. The inventors have determined that the long pulse tail associated with excimer lasers produces fracture at the precursor site, adversely impacting mitigation efforts. Thus, top hat shaped pulses are utilized in some embodiments, treating the precursor sites and terminating the delivery of optical energy in a rapid manner. As an example, the pulse shape has a pulse length less than 1 ns FWHM and a fall time less than 80 ps. The short tails associated with embodiments of the transfer enough energy to the precursor site to treat the precursor, but do not deposit significant energy into the material surrounding the precursor site, which is a phenomenon associated with long pulse tails.
Considering the fluences associated with precursor treatment, the fluence ranges from about 1 J/cm2 to about 1 J/cm2 for a 350 ps pulse and from about 0.5 J/cm2 to about 1 J/cm2 for a 100 ps pulse.
Embodiments of the present invention utilize laser pulses with short durations in comparison to conventional laser repair pulses, producing a small amount of damage that is localized around the precursor site, enabling passivation of precursor sites, converting them into damage sites that are benign with respect to future pulses passing through the optical element. By identifying these benign damage sites, the method may be extended to passivation using a laser other than the picosecond laser. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.
It should be appreciated that the specific steps illustrated in
In the embodiment illustrated in
In an embodiment, the beam from the picosecond laser 710 is raster scanned over the optical element and the camera 730 is used to record an image of the area being raster scanned. The PC can record the location that is being imaged. The beam can be raster scanned by moving the beam (e.g., with controllable mirrors) or by moving/rotating the optical element 705 on a stage as illustrated in
It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the U.S. Department of Energy and Lawrence Livermore National Security, LLC, for the operation of Lawrence Livermore National Laboratory.
