Solid State Laser News

The article at the above link is behind a pay wall. Here is a link to a similar article that is free to view: https://defensescoop.com/2024/01/09/navy-swo-boss-frustrated-by-shortage-of-directed-energy-weapons/
 
Wonder if particle beams would be more effective?
For what application/mission?

If your question is in response to the article Still Unhappy With Progress On Directed Energy Weapons..., the answer is No, particle beams would not be more effective than lasers or microwaves for the shipborne or land based air defense since particle beams cannot propagate very far in the atmosphere because of scattering. A possible way around the particle beam scattering in the atmosphere problem is to use a very high peak power pulsed laser to form a plasma channel that confines a charged particle beam to the plasma channel. This has been demonstrated with propagating electron beams in the atmosphere. However, the technology readiness level of such particle beam weapons is much lower than that of solid state laser and microwave weapons, so they would not solve the issue discussed in the article of the transition of laser weapons from R&D to operational fielding being too slow to meet the present need for air defense.

If your question is about the use of particle beams instead of lasers for clearing orbital debris by slowing down the debris so that it re-enters and burns up, my guess is perhaps if the particle beam system is deployed in orbit, but it would not work from ground to space as proposed for the laser system, unless the laser induced plasma channel technique discussed above is used to prevent the particle beam from being scattered by the atmosphere.
 
Has that technique ever been tried?
See
https://www.sciencedirect.com/science/article/abs/pii/S0094576522004921#:~:text=Contactless space debris removal from the geostationary orbit protected region&text=To verify the possibility of,geostationary orbit to disposal orbits.

https://phys.org/news/2018-09-plasma-thruster-space-debris-technology.html#google_vignette

https://www.sciencedirect.com/science/article/abs/pii/S0094576523000553#:~:text=One of the promising ways,to as the ion force.


https://en.wikipedia.org/wiki/Electrolaser (And reference links therein)

https://www.nature.com/articles/s41566-022-01139-z

https://www.nature.com/articles/srep40063


https://apps.dtic.mil/sti/pdfs/ADA446847.pdf

https://enviroinfo.llnl.gov/sites/e...01/B865AHistoricAmericanEngineeringReport.pdf Excerpt: "The Advanced Test Accelerator (ATA) facility (Building 865A) was built in 1983 to investigate the feasibility of propagating intense electron beams through the atmosphere. Experiments were conducted in the ATA to test electron beams in the open air to determine how beams propagate in natural environments. This was done to consider the potential for military application of electron-beam propagation, in addition to considering the interaction of electron beams with lasers and plasmas. Completed in the fall of 1983, the ATA facility was expanded in 1986 to conduct experiments using Paladin Free Electron Lasers (FELs) for the Strategic Defense Initiative Office (SDIO)." [Note: In 1987, I was briefed on the research at LLNL's ATA during a tour of the facility when I was working on technical assessments of SDI projects. That was when I first heard of the technique of propagating electron beams along laser induced plasma channels in the atmosphere.]
 
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I'm skeptical of the claim since the article says "The new Chinese cooling system, according to the report, would use gas that blows through the weapon to remove excess heat" because the specific heat capacities of gases are much lower than those of liquids, which is why liquid cooling is used in most high energy lasers.

A hybrid gas-liquid spray cooling system might be workable such as air-atomized spray cooling, which involves nothing more than blowing air with tiny droplets against a hot plate to decrease the temperature of the hot plate.

Certainly a flowing air cooled laser that could maintain the temperature during continuous operation indefinitely would be desirable since it would likely have lower size, weight and power draw than a liquid cooled laser. So, if the Chinese have made even a small advance in that direction, that would be significant even if they haven't really solved the problem yet.

None of the articles I've seen so far online provide a link to the research article in Acta Optica Sinica, which I would like to read to see what the researchers have actually reported about their research.
 
In the Tempest In a Teacup article, the authors seem to have never heard of wake turbulence from aircraft which produces wake vortices in air far from any boundaries and these wake vortices last several minutes before decaying. Wake turbulence and the resulting wake vortices have been studied in flight tests and in wind tunnel tests for many decades.

In the experiments discussed in that article, the ball of turbulence was produced in water, not in a plasma. The molecules of water are neutral, whereas the constituents of plasma are charged. Thus, the configurations used to produce the water turbulence ball may not be applicable to forming a plasma turbulence ball.

Although the article "Pair plasmas found in deep space can now be generated in the lab" says near the beginning "An international team of scientists has developed a novel way to experimentally produce plasma 'fireballs' on Earth," if you read further into the article, you find that they have created beams of electron-positron pairs with densities similar to those found in the deep space plasma "fireballs," but they have not yet created such plasma "fireballs."

The article specifically states "Now, for the first time, an international team of scientists, including researchers from the University of Rochester's Laboratory for Laser Energetics (LLE), has experimentally generated high-density relativistic electron-positron pair-plasma beams by producing two to three orders of magnitude more pairs than previously reported...In other words, the beam they generated in the lab had enough particles to start behaving like a true astrophysical plasma." The MARAUDER concept needs a confined volume of plasma, which is then launched at the target with the plasma remaining confined during launch and transit to the target. That's very different from a beam of plasma.

An electron-positron plasma beam might make a formidable directed energy weapon for use in space if it could be made to work in a compact, low enough mass configuration to be put in space, but the electron-positron beam would not propagate through the atmosphere.

For a kind of "plasma beam" weapon operating in the atmosphere, perhaps a better choice may be the electrolaser: https://en.wikipedia.org/wiki/Electrolaser "An electrolaser is a type of electroshock weapon that is also a directed-energy weapon. It uses lasers to form an electrically conductive laser-induced plasma channel (LIPC). A fraction of a second later, a powerful electric current is sent down this plasma channel and delivered to the target, thus functioning overall as a large-scale, high energy, long-distance version of the Taser electroshock gun...Because a laser-induced plasma channel relies on ionization, gas must exist between the electrolaser weapon and its target. If a laser-beam is intense enough, its electromagnetic field is strong enough to rip electrons off of air molecules, or whatever gas happens to be in between, creating plasma." See also https://www.army.mil/article/82262/ and https://www.bbc.com/news/technology-18630622
 
This an interesting advancement on research on triggering and guiding lightning using lasers that has been ongoing for a few decades, as indicated in the earlier 2021 paper by the same group of researchers, available at this link https://www.epjap.org/articles/epjap/pdf/2021/01/ap200243.pdf :

A continuously operating technique to trigger lightning would therefore be highly desirable. Lasers were identified very early as candidates for this purpose. The first tests performed in the 1970s using “long” laser pulses of several nanoseconds or more demonstrated the guiding of megavolts discharges with lengths of up to 2 m [9,10]. An attempt to trigger and guide natural lightning was made by Uchida et al. in 1999 using a combination of three lasers with a kJ-level energy to form a 2 m long plasma spark at the tip of an experimental tower [11]. The researchers reported two successful events, but this low number of events did not lead to conclusive proof of the effectiveness of the lightning triggering technique. This approach was progressively abandoned because of the discontinuous profile of the plasma generated with such “long” IR or mid-IR pulses through avalanche ionization and the huge laser energy required to extend the laser-generated plasma column beyond a few meters.

In contrast, sub-100 fs laser pulses are short enough to prevent electron avalanche. The generated plasma remains therefore transparent to the laser pulse. As a consequence, ionizing self-guided filaments can exceed 100 m in length. Filamentation is a self-guided, non-linear propagation mode that relies on the dynamic balance between the optical Kerr effect that tends to focus the laser beam and self-defocusing, mainly due to the plasma generated when the pulse intensity becomes sufficiently high [12–16]. It results in the long range propagation of a pulse with multi-GW peak intensity. A plasma track and a low air density channel are left in the wake of the pulse. These ionized light filaments can be generated at a distance of several kilometers [17], and can cover a length of more than a hundred meters [18] by an adequate choice of the laser parameters. They can be directed to any position in the atmosphere by sweeping the beam using a steering mirror.

In the 2000s, several groups demonstrated their capability to trigger high-voltage discharges over several meters with laser pulses of only 100 mJ [19–21]. By electrically connecting two electrodes that were several meters apart, the laser filaments reduce the breakdown voltage by 30% [21], triggering the discharge in conditions that would not have allowed them to without the laser. These triggered discharges are guided along the laser filaments rather than following the erratic path typical of a classical electric discharge. Furthermore, filaments are able to divert a discharge from its preferential path [22].

Based on these successful results on a laboratory scale, a mobile, femtosecond-terawatt laser, “Teramobile”, was developed [23,24]. In a field campaign at the Langmuir Laboratory of the New Mexico Tech on the South Baldy Peak, micro-discharges synchronized with the laser pulses were detected, showing that laser filaments initiated corona discharges in thunderclouds [25]. However, the short lifetime of plasma filaments (typically a few ns) prevented the initiation of upward leaders similar to the mechanism of rocket triggering. Increasing the plasma lifetime by heating the filament plasma with an additional, high-energy nanosecond laser was proposed by several groups [19,26–29]. However, this requires an additional laser of high energy, typically in the joule range. Coupling such a beam into the filament proved to be unpractical over distances exceeding a few meters.

On the other hand, filamentation initiates a low-density(air-depleted) channel [30–33]. For a low-repetition rate multi-TW laser, the air density is initially reduced by a factor of 5 over a typical length of a few meters. The density depletion still amounts to typically 10% of the ambient pressure after 1 ms. These straight, low-density channels favor the triggering and guiding of electric discharges in the atmosphere at a 60% reduced voltage [22,34]. At repetition rates in the kHz range, the depletion of the air density due to filamentation is amplified by a cumulative effect [32]. As a result, increasing the repetition rate of 100 mJ, 1030 nm laser pulses from 10 Hz to 1 kHz reduces the laser-induced breakdown voltage by a factor of 3 [35]. Therefore, a terawatt laser at a kilohertz repetition rate would allow the formation of a permanent low-density channel likely capable of guiding discharges over long distances. Based on these results, we decided to investigate the impact of laser filamentation at a kHz repetition rate on lightning strikes, in real scale. More specifically, within the Laser Lightning Rod (LLR) project [36] we focus on developing a kHz-terawatt laser system and assessing its ability to stimulate upward lightning flashes from the grounded,123 m tall telecom tower at Santis, Switzerland, in order to initiate and guide the lightning strikes.
 

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