Solid State Laser News

260MV/cm looks like they are talking about particle acceleration. Might be useful for proton therapy. But for weapons, doubtful.
V/m is a usually a measure of electric field strength. It also gives an equivalent W/cm^2 in the first article.
 
https://optics.org/news/15/6/6

Xcimer lands $100M to build fusion energy prototype​


"...the startup’s plan is to leverage laser technology originally conceived as part of the US Strategic Defense Initiative (aka “Star Wars” program) of the 1980s, using 248 nm-emitting KrF sources that have since played a key role in semiconductor manufacturing as the light source in deep-ultraviolet lithography systems.

“Xcimer’s laser architecture will produce up to ten times higher laser energy at ten times higher efficiency and over 30 times lower cost per joule than the NIF laser system that achieved fusion scientific breakeven in December 2022,” it claims, with CEO Conner Galloway..."
 
https://optics.org/news/15/6/6

Xcimer lands $100M to build fusion energy prototype​


"...the startup’s plan is to leverage laser technology originally conceived as part of the US Strategic Defense Initiative (aka “Star Wars” program) of the 1980s, using 248 nm-emitting KrF sources that have since played a key role in semiconductor manufacturing as the light source in deep-ultraviolet lithography systems.

“Xcimer’s laser architecture will produce up to ten times higher laser energy at ten times higher efficiency and over 30 times lower cost per joule than the NIF laser system that achieved fusion scientific breakeven in December 2022,” it claims, with CEO Conner Galloway..."
Yah, but the NIF laser is only like 0.8% efficient from memory, 10x that is still only 8% so unless the Q-plasma is >25:1 (i.e. about >12x higher than the best achieved by NIF), you ain't getting a net electrical output (you still have to convert that heat output back to electricity).

But okay:
Burn propagation
Like NIF, Xcimer’s fuel capsules are based on deuterium-tritium, but Xcimer plans to use a much larger size and mass, yielding higher performance, easier manufacturing, and more robust operation.

“The higher performance means a power plant can operate at lower repetition rates (below 1 Hz) than conventional IFE concepts,” it explains. “Fusion takes place in about a cubic centimeter in the center of the target chamber and is far removed from the ‘plasma-facing first wall’ of the chamber with no physical connection.

“This also enables the use of molten salt coolant flow to protect the chamber[’s] first structural wall from the fusion output.”

Xcimer also claims that the short confinement time and high density in the target means it will undergo “burn propagation”, where ignition of only a small amount of fusion fuel can release enough energy to ignite the rest of the fuel - akin to using a match to light a fire.

“This leads to high facility ‘wall-plug’ gains, even with a 5-10 per cent efficient laser,” it says.

However still, why not use a more efficient laser? I mean a fibre laser or metastable rare gas laser would have a far higher efficiency even if you had to frequency multiply them twice over to get the correct wavelength.
 
Yah, but the NIF laser is only like 0.8% efficient from memory, 10x that is still only 8% so unless the Q-plasma is >25:1 (i.e. about >12x higher than the best achieved by NIF), you ain't getting a net electrical output (you still have to convert that heat output back to electricity).

But okay:


However still, why not use a more efficient laser? I mean a fibre laser or metastable rare gas laser would have a far higher efficiency even if you had to frequency multiply them twice over to get the correct wavelength.
They want to scale to 10 MegaJoules (1E7 J) in nanosecond pulses. Nanosecond pulsed fiber lasers/amplifiers are limited to less than several milliJoules (~1E-3 J) per pulse per fiber for singlemode fibers and a few tens of milliJoules (~1E-2 J) per pulse per fiber for large core multimode fibers. In order to get near diffraction-limited focusing, one would need to use singlemode fibers and coherently combine their outputs. If you could get, for example, 5 mJ per nanosecond pulse from each singlemode fiber, you would need to coherently combine the outputs of 2 Billion fibers to get 10 MJ in a nanosecond pulse. Even if you could get 50 mJ per pulse from each multimode fiber and somehow clean up the beam quality to near diffraction-limited, you would still need to combine the outputs from 200 Million fibers. That's why fiber lasers/amplifiers would not be a good fit for laser fusion.

I don't know what limitations, if any, there would be for metastable rare gas lasers for use in laser fusion.
 
I also thought that 351nm (as per NIF) was optimal for laser fusion, so wouldn't XeF be a better excimer laser? What about alkali vapour lasers?
 
I also thought that 351nm (as per NIF) was optimal for laser fusion, so wouldn't XeF be a better excimer laser? What about alkali vapour lasers?
The article at this link discusses the importance of laser wavelength in laser fusion: https://pubs.aip.org/aip/pop/articl...he-importance-of-laser-wavelength-for-driving

Essentially, the shorter the wavelength the better.

The article states, "ArF is the shortest wavelength laser (⁠0.193 vs 0.351 um on the NIF) that can reach the energy and powers required for high-gain laser fusion.8 As shown in this paper, the short wavelength improves the laser–target coupling efficiency, thereby reducing the laser energy needed to obtain conditions for a high-gain ICF implosion. It also has a large native bandwidth that can enable laser bandwidths of order 10 THz on target.8 This combination of short wavelength and multi-THz bandwidth can also suppress undesired laser-plasma instabilities (LPI). ArF shares these and other desired capabilities with the krypton fluoride (KrF) laser demonstrated at the NRL Nike facility.9 This includes the flexible induced spatial incoherence (ISI) beam smoothing scheme, where the desired focal distribution is imaged from an aperture in the laser front-end to the target. This beam smoothing approach enables straightforward implementation of zooming (shrinking) the focal diameter to follow an imploding pellet.10,11 For laser direct drive, zooming substantially increases the coupling efficiency to an imploding target and can mitigate the cross-beam energy transfer (CBET) instability.12 ...

The ArF laser was recognized as having attractive properties as a driver for inertial fusion more than 40 years ago. Researchers in the United States and Japan constructed two 100 J class systems in the late 1970s and mid-1980s, respectively.13,14 Work on ArF was abandoned for many years in belief that frequency multiplied glass laser drivers would suffice. Modest size efforts continued with the 0.248 um KrF laser (similar to ArF in architecture).15–17 Recently, NRL researchers decided to explore the feasibility of using the deeper UV ArF option for ICF. The high-energy ArF amplifiers employ electron-beam pumping similar to that developed for KrF. NRL's Electra facility, which was developed to demonstrate the rep-rate and energy-related capabilities of KrF lasers,18 has been modified for ArF operation and has recently demonstrated a world record ArF energy (200 J). It is now being utilized to advance the basic science and technologies of electron-beam-pumped ArF operation.19 ...

Shorter wavelength drivers have an inherent advantage because they deposit their laser energy deeper into the target at higher densities (the plasma critical surface where the laser reflects is higher by the inverse square of λ, the laser wavelength). This results in a cooler, more collisional plasma corona that is more absorptive. It also produces a higher pressure per unit power deposited, which results in a higher hydrodynamic efficiency. The drive efficiency increases because the resulting smaller ablation (rocket) velocity at the higher density more closely matches the needed implosion speed.20 In addition, the higher frequency light decreases the electron oscillation velocity in the laser electric field (⁠osc∼⁠), reducing the ponderomotive force effects that drive laser-plasma instabilities (LPI). These expectations were borne out by early studies,21–23 both experimentally and theoretically, that confirmed that shorter laser wavelengths increased absorption, pressure, and mass ablation rates while also decreasing the hot electrons generated by LPI."

I take from this that although the shorter wavelength of ArF would be advantageous, the KrF laser has had more development for reaching higher pulse energies.

I am not very knowledgeable about alkali vapor lasers. This article https://lasers.llnl.gov/science/photon-science/directed-energy from LLNL discusses their use for directed energy weapons, but does not give specifics. It does not mention their possible use for laser fusion, which is telling since the article is from LLNL. Perhaps they are more suitable for continuous wave (cw) operation than pulsed operation, but I don't know. The paper at this link https://www.researchgate.net/public...iode-pumped_alkali_lasers_DPALs_Plenary_Paper discusses high power cw alkali vapor lasers.
 
Great information, but based on this it seems laser ICF is long way off yet. If ~8% is the best laser efficiency they have to work with the Q-plasma will have to be more than an order of magnitude better better than anything currently achieved to get positive net electriccal generation from it.
 
Great information, but based on this it seems laser ICF is long way off yet. If ~8% is the best laser efficiency they have to work with the Q-plasma will have to be more than an order of magnitude better better than anything currently achieved to get positive net electriccal generation from it.
Controlled nuclear fusion of any type for commercial electrical power generation is a long way off (at least two decades and probably longer) in my opinion. I think there is a good possibility that laser-based ICF may never be commercially viable.

Perhaps the projectile-based approach to ICF that First Light Fusion is researching may become commercially viable some day, but it is far too soon to tell.

In their approach, after triggering a sort of railgun, a copper disk-shaped projectile will fly at about 7 km/s towards a target that’s encapsulating the fuel (ideally deuterium + tritium). It’s about 1-3 millimeters in size and is uniquely designed to amplify and direct the effects of the impact, which gives rise to a pressure wave that collapses the fuel. This then turns into plasma, sparking fusion.

First Light Fusion successfully demonstrated deuterium-deuterium (DD) projectile induced fusion in November of 2021. Experiments were performed on First Light Fusion’s 38 mm bore, two-stage light gas gun. This facility can launch a 100 g solid projectile at 6.5 km s−1. Neutron diagnostics included scintillators and moderated helium-3 proportional counters. The UK Atomic Energy Authority (UKAEA) verified the experimental setup, modelled the detector responses and witnessed two experiments. They also reviewed the full campaign dataset, analysis and interpretation of the results.

In January 2023, it was announced that First Light Fusion had entered an agreement with the UKAEA to develop First Light's "Machine 4" (M4) at the UKAEA's Culham Campus. M4 will attempt to demonstrate the capacity of projectile fusion to reach net energy gain. Belgium-based engineering company Tractebel announced the signing of a framework agreement in July 2023 to jointly develop the M4 facility with First Light.
 
Controlled nuclear fusion of any type for commercial electrical power generation is a long way off (at least two decades and probably longer) in my opinion. I think there is a good possibility that laser-based ICF may never be commercially viable.

Perhaps the projectile-based approach to ICF that First Light Fusion is researching may become commercially viable some day, but it is far too soon to tell.

In their approach, after triggering a sort of railgun, a copper disk-shaped projectile will fly at about 7 km/s towards a target that’s encapsulating the fuel (ideally deuterium + tritium). It’s about 1-3 millimeters in size and is uniquely designed to amplify and direct the effects of the impact, which gives rise to a pressure wave that collapses the fuel. This then turns into plasma, sparking fusion.

First Light Fusion successfully demonstrated deuterium-deuterium (DD) projectile induced fusion in November of 2021. Experiments were performed on First Light Fusion’s 38 mm bore, two-stage light gas gun. This facility can launch a 100 g solid projectile at 6.5 km s−1. Neutron diagnostics included scintillators and moderated helium-3 proportional counters. The UK Atomic Energy Authority (UKAEA) verified the experimental setup, modelled the detector responses and witnessed two experiments. They also reviewed the full campaign dataset, analysis and interpretation of the results.

In January 2023, it was announced that First Light Fusion had entered an agreement with the UKAEA to develop First Light's "Machine 4" (M4) at the UKAEA's Culham Campus. M4 will attempt to demonstrate the capacity of projectile fusion to reach net energy gain. Belgium-based engineering company Tractebel announced the signing of a framework agreement in July 2023 to jointly develop the M4 facility with First Light.
ITER is supposed to get close(ish) to break even though - circa 240MWe out for 440MWe in.

FLF's technique is very interesting. Theoretically the speed required is 50km/s (conical-shaped DT pellet), M3 achieves 20km/s, so some way off.


The projectile mass is 100g, so theoretically that's 20MJ KE, which at 50% (guessed) efficiency for the gun is 40MJe input. Theoretically with 100% efficienct fusion, 1kg of DT pellet gives 330TJ, so 33 TJ for 100g. Assuming it's a 1-1 mass target.


Indeed M4 is going for 60km/s.


Machine 4 will have a stored electrical energy of about 100 megajoules with the capability of launching projectiles at 60 kms per second. This speed on impact inside the target will accelerate to about 200kms per second as a result of First Light’s exclusive amplifier technology.
First Light is aiming for net energy gain with Machine 4 with fuel gain of 100 or more. This machine is the building block for the pilot power plant, validating First Light’s simulation codes, while de-risking the design of high-gain targets for power production.

It would be amazing if the UK can pull this off.
 
ITER is supposed to get close(ish) to break even though - circa 240MWe out for 440MWe in.

FLF's technique is very interesting. Theoretically the speed required is 50km/s (conical-shaped DT pellet), M3 achieves 20km/s, so some way off.


The projectile mass is 100g, so theoretically that's 20MJ KE, which at 50% (guessed) efficiency for the gun is 40MJe input. Theoretically with 100% efficienct fusion, 1kg of DT pellet gives 330TJ, so 33 TJ for 100g. Assuming it's a 1-1 mass target.


Indeed M4 is going for 60km/s.





It would be amazing if the UK can pull this off.
The 2017 article at https://sites.nationalacademies.org/cs/groups/bpasite/documents/webpage/bpa_184787.pdf entitled "Worldwide Timelines for Fusion Energy" states:

"Even though numerous worldwide roadmaps and plans have been developed in recent decades [1-9], the schedule for placing a fusion power plant on the grid is still uncertain. The main reasons are the recent delay in ITER schedule, the unreadiness of structural materials along with many fusion technologies, and/or the lack of funding for necessary R&D programs. At the present time, all countries are revising their roadmaps primarily because the delay in ITER...

There is a wide agreement between international fusion communities that a demonstration plant (DEMO) is the last step necessary to reduce the technical and programmatic risk associated with the first commercial power plant. Beyond ITER, multiple small-scale facilities and significant fusion technologies remain to be developed to bridge the large gap between existing fusion experiments and DEMO operation.

As Figure 2 illustrates, all countries projected operating DEMOs in 30-40 years, targeting power production from DEMO in the 2045-2055 timeframe" That figure also shows the first power plant starting operation in the late 2050s to early 2060s.

These roadmaps and timelines, however, were developed prior to the issues ITER has had since 2017.

ITER will be submitting it's latest baseline schedule revision this month, June 2024. It is expected that the new schedule will show a delay compared to the previous schedule due to Covid-19 related delays, problems with the vacuum vessel sector's welding joint region and corrosion-induced cracks in thermal shield piping, and because of modifications to ITER's configuration, phased installation and new research schedule. See https://world-nuclear-news.org/Articles/ITER-s-proposed-new-timeline-to-be-submitted-in-Ju .

Yes, it will be amazing if FLF and the UKAEA achieve net energy gain from projectile-based ICF at the M4 facility, but it will be only one small step of the many subsequent steps necessary to develop such an approach for commercial electrical power production.
 
Perhaps MARAUDER can have another chance:


Scans and such

Cool footage

The rest is silence
 
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Perhaps MARAUDER can have another chance:

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
 
Thanks for the interesting article.

In the article, Mark Lewis states: “The thing that has changed is we’ve actually realized that solid-state lasers are the way to go, and not chemical lasers...That’s number one. Number two is we’ve gotten power levels of those solid-state lasers up to the point where they can actually do some real harm...We’re at the power levels now where we can actually blast a hole in something. We can blind something, we can take something out. And we can do it in a package that’s practical.”

Yes, the solid state laser power levels of a few tens to a few hundred kilowatts can do "some real harm" to some rather soft targets (e.g., drones, small aircraft, guided bombs) at rather short ranges (a few to a few tens of kilometers), but they have not yet reached the multi-megawatt levels required for hardened targets (like ICBM re-entry vehicles (RVs)) at a few hundred kilometer to a few megameter ranges for strategic missile defense. That is why the article says that MDA is looking at applying the solid state lasers for long range target tracking first, while waiting for further R&D to scale up the solid state lasers to the power levels needed for strategic missile defense.

This is not new, and certainly not a "sea change" as Mark Lewis states in the article. It's just the latest spin to get more funding to ramp up the effort on work that has already been going on for a long time. My guess is that it's probably an effort to get money needed to finally push airborne long range laser tracking technology across the "Valley of Death" and into the field. I worked on applying solid state lasers (and gas lasers) for long range target tracking for SDI back in the mid- to late 1980s, and I was still working on applying solid state lasers (particularly fiber lasers) for similar applications a few years before I retired in 2021. What changed over that time was improvements in laser, power system, beam director, sensor, tracking algorithm, and processor technologies.
 
That's good news! Space-to-space high speed data cross links are a great application for free space optical communications, and developing a standardized waveform to insure compatibility and interoperability from the start is smart. A question not addressed in the article is will they be able to get other companies, like SpaceX with its Starlink satellite network for example, to adopt their standard for cross links?
 

Military and intelligence leaders watched as coast guard officers showed photos of what the agency said was a military-grade laser that China had pointed at a Philippines ship in disputed waters days earlier.
 
The part you extracted from the article is the only mention of the laser in the article.

I found it frustrating that the article does not provide any further information on the laser. They don't give any description of what the photos showed - were they of the laser device itself or of the laser spot on some part of the ship? Was the laser device operational when pointing at the ship or just pointing at the ship without emitting a laser beam?

The article states: "'The public deserves to know,' the retired general told the officials. 'Publish the photographs.'

The previously undisclosed meeting marked a pivotal moment, as Manila began a publicity blitz to highlight the intensifying territorial dispute in the South China Sea..."

However, the article does not show any of the photos of the military-grade laser nor provide any links to the photos that were released in the aforementioned "publicity blitz." Instead, the article has only two fairly generic photos at the top of the article: 1. FILE PHOTO: Philippine Coast Guard flyby over the South China Sea, and 2. FILE PHOTO: Philippines and U.S. troops participate in joint live fire exercises.
 
I found the following Youtube video about this from last year:
View: https://www.youtube.com/watch?v=UGkluDAKL80


The video shows a green beam of light coming from a ship. The way that the beam is pointing around sporadically makes me think that it is probably one of those extremely bright Chinese handheld laser pointers that someone is pointing around by hand.
 
The Pentagon California based DIU, Defense Innovation Unit, with its budget of almost $1 billion this year is attempting to partially solve the problem the Navy has with the Houthi in the Red Sea and expending its stock of $4 million SM-2s at the cheap Houthi drones, is seeking industry’s help for a kinetic defeat solution for medium-sized (~330 lbs) UAVs. "Requiring the assets be available for testing within 90 days of a prototype award and for the company to be capable of delivering five “production representative prototypes within 12 months” of an award. // “The solution must minimize the cost per defeat to reduce the asymmetry of the current cost of traditional air defense defeat solutions compared to the threat // High-powered microwave and directed energy solutions will not be considered kinetic defeat solutions for this solicitation", presuming too short in range (required 15 km), immature, costly, power intensive etc?

PS No information has been released to date by the Navy on the prototype Lockheed Helios 60-150 kW laser fitted to the Burke USS Preble Aug' 2023 and if the trials were successful.


 
IMOHO, HPMW or Laser are better suited fired from the ship.
Think power source, the cost and mass of it to be efficient when there is mostly no limitations for that to be employed at sea from a ship (no masking obstacles justifying the shooter to be at close range).

See also that GPS jammer are not suited as a solution (for the main reasons I would assume)
 
The Pentagon California based DIU, Defense Innovation Unit, with its budget of almost $1 billion this year is attempting to partially solve the problem the Navy has with the Houthi in the Red Sea and expending its stock of $4 million SM-2s at the cheap Houthi drones, is seeking industry’s help for a kinetic defeat solution for medium-sized (~330 lbs) UAVs. "Requiring the assets be available for testing within 90 days of a prototype award and for the company to be capable of delivering five “production representative prototypes within 12 months” of an award. // “The solution must minimize the cost per defeat to reduce the asymmetry of the current cost of traditional air defense defeat solutions compared to the threat // High-powered microwave and directed energy solutions will not be considered kinetic defeat solutions for this solicitation", presuming too short in range (required 15 km), immature, costly, power intensive etc?

PS No information has been released to date by the Navy on the prototype Lockheed Helios 60-150 kW laser fitted to the Burke USS Preble Aug' 2023 and if the trials were successful.


Looking at the mission of the DIU (see below) and the short development schedule, either they already know about some capabilities already under development by some companies, or the solicitation is a "fishing expedition" to see if such capabilities are already under development.

About the DIU: The Defense Innovation Unit (DIU) strengthens national security by accelerating the adoption of commercial technology throughout the military and bolstering our allied and national security innovation bases. DIU partners with organizations across the Department of Defense (DoD)to rapidly prototype and field dual-use capabilities that solve operational challenges at speed and scale...Our expert team, working in seven critical technology sectors, engages directly within the venture capital and commercial technology innovation ecosystem, many of which are working with the DoD for the first time. Our streamlined process delivers prototypes to our DoD partners, along with scalable revenue opportunities for our commercial vendors, within 12 to 24 months.

About HELIOS, in a January 2024 article https://breakingdefense.com/2024/01...e-realistic-about-laser-weapons-admiral-says/ , Rear Adm. Fred Pyle said that HELIOS and the Preble (DDG-88) are expected to conduct testing over the course of this year.

From the May 1, 2024 article "House Armed Forces Committee Holds Hearing on the Fiscal Year 2025 Navy and Marine Corps Budget Request" https://www.navy.mil/Press-Office/T...hearing-on-the-fiscal-year-2025-navy-and-mar/ , "CARLOS DEL TORO: Thank you, Congressman. You're absolutely right that we need to make even greater investments in the future. We should have been making them for a long, long time, but nevertheless we are continuing to make investments in order to get Helios deployable. She will hopefully be deployable here sometime in the next several months, but certainly by the end of the year, hopefully on USS Preble."

I think this indicates that the HELIOS trials are still ongoing, but should be completed before the end of 2024. Since the Navy plans to deploy HELIOS by the end of the year, it is not clear if or when they will release the sea trial results of the system. The Navy may just announce that HELIOS successfully completed sea trials and is being deployed if and when that happens.

Also, the 60 kW HELIOS operational range is up to 8 km (5 miles) according to https://www.nationaldefensemagazine...9/navy-destroyer-adds-helios-laser-to-arsenal : "The system [HELIOS] — which can blast more than 60 kilowatts of directed energy at targets up to five miles away — is currently being installed on a Flight IIA Arleigh Burke-class destroyer that is undergoing upgrades, a company spokesperson told National Defense in an email."

I think that the 300+ kW lasers coming out of the High Energy Laser Scaling Initiative (HELSI) might get to 15 km operational range against some targets based on the square law and some atmospheric extinction loss scaling with range.

According to the 3 April 2024 article at https://www.navalnews.com/event-new...0-kw-helcap-laser-system-for-intercept-tests/ :

"The US Navy's High Energy Laser Counter Anti-Ship Cruise Missile (ASCM) Project (HELCAP) is set to conclude next year with a major demonstration...

The main goal of HELCAP is to serve as a building block for future programs by tackling technical challenges that have plagued laser weapons, such as advanced laser beam control, effects of atmospheric turbulence, precision tracking in high clutter environments, and automatic target identification and aimpoint selection.

The efforts of HELCAP and years of technology maturation under separate programs meant to tackle specific technological issues will culminate as these program elements come together to form the Laser Weapon Testbed (LWT) that is central to the HELCAP.

At the core of the Laser Weapon Testbed will be a 300+ kW class sourced from the Office Secretary of Defense’s High Energy Laser Scaling Initiative (HELSI), which has funded industry teams to deliver several 300+ kW class lasers.

This laser source will be combined with a prototype beam control testbed developed by the Navy and alongside a prototype control system, will all be integrated into an auxiliary prime power and cooling system.

This Laser Weapon Testbed will be moved to the White Sands Missile Range (WSMR), where it will be conducting system verification testing this year. At White Sands, the LWT will begin its round of testing by assessing the system’s beam control, tracking, and adaptive optics subsystems performance.

After completing major component and subsystems testing, the Navy will start testing the system against targets of increasing complexity. At the low-end, the system will be tested against static ground targets, followed by dynamic (moving) ground targets, before eventually transitioning to interception of low-cost unmanned aerial targets and cruise missile surrogates.

Once the program comes to a close, it will serve as the basis for improving the Navy’s follow-on systems to the Surface Navy Laser Weapon System (SNLWS) Increment I (HELIOS). As of currently writing, there are no plans for the program to have leave-behind assets or prototypes for integration into ships."
 
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https://www.navalnews.com/event-new...0-kw-helcap-laser-system-for-intercept-tests/
Reading the Naval News article it states the HELCAP is a 300+ kW laser design is meant to defeat Anti-Ship Cruise Missiles in a specific “crossing” scenario and can only defend against missiles that are “crossing” them while headed for nearby friendly ships and implying that its unable to defend against direct head-on attacks.

Speculating this implies a 300+ kW laser is not considered powerful enough to burn through a hardened Mach 2+ sea skimming ASCM nosecone e.g. BrahMos or a hypersonic Kinzhal/Dagger in the limited time laser on target whereas it could burn through the much softer body material e.g. aluminium of the ASCM in the longer crossing time available?
 
https://www.navalnews.com/event-new...0-kw-helcap-laser-system-for-intercept-tests/
Reading the Naval News article it states the HELCAP is a 300+ kW laser design is meant to defeat Anti-Ship Cruise Missiles in a specific “crossing” scenario and can only defend against missiles that are “crossing” them while headed for nearby friendly ships and implying that its unable to defend against direct head-on attacks.

Speculating this implies a 300+ kW laser is not considered powerful enough to burn through a hardened Mach 2+ sea skimming ASCM nosecone e.g. BrahMos or a hypersonic Kinzhal/Dagger in the limited time laser on target whereas it could burn through the much softer body material e.g. aluminium of the ASCM in the longer crossing time available?
I'd say that's a reasonable speculation.

In the head-on scenario, it may be better for the target ship to use electronic countermeasures (ECM), infrared countermeasures (IRCM), and/or electro-optic countermeasures (EOCM) to spoof, jam or blind the missile's radar, GPS, IR and/or EO targeting/tracking systems, as well as using kinetic interceptors.

The laser pointing and tracking system will have to operate at a very high angular rate for the "crossing" scenario to keep the laser spot steady on the target, especially for a hypersonic missile. The atmospheric compensation system will have to have a high temporal bandwidth because of the high speed pseudowind due to the high slew rate of the laser beam as it tracks the high-speed crossing target. These aspects of the "crossing" scenario will be much more challenging than for the "head-on" scenario.
 
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I'd say that's a reasonable speculation.

In the head-on scenario, it may be better for the target ship to use electronic countermeasures (ECM), infrared countermeasures (IRCM), and/or electro-optic countermeasures (EOCM) to spoof, jam or blind the missile's radar, GPS, IR and/or EO targeting/tracking systems, as well as using kinetic interceptors.

The laser pointing and tracking system will have to operate at a very high angular rate for the "crossing" scenario to keep the laser spot steady on the target, especially for a hypersonic missile. The atmospheric compensation system will have to have a high temporal bandwidth because of the high speed pseudowind due to the high slew rate of the laser beam as it tracks the high-speed crossing target. These aspects of the "crossing" scenario will be much more challenging than for the "head-on" scenario.
Would a short pulse of slightly less energy (say 200kJ), lasting maybe 0.001s be more effective or less effective? Or maybe a pulse stream of the same 200kJ over a second but in 0.001s bursts every 0.01s?
 
Would a short pulse of slightly less energy (say 200kJ), lasting maybe 0.001s be more effective or less effective? Or maybe a pulse stream of the same 200kJ over a second but in 0.001s bursts every 0.01s?
Pulsed vs. CW lasers effectiveness is a complicated question to answer.

Here are some references for what I write below:

https://www.rp-photonics.com/pulsed_lasers.html

https://www.rp-photonics.com/chirped_pulse_amplification.html

https://www.rp-photonics.com/divided_pulse_amplification.html

https://breakingdefense.com/2021/10/rapid-pulse-laser-weapons-could-be-the-pentagons-future-edge/

The use of millisecond pulsed illumination vs cw illumination that you hypothesize probably won't make much difference other than to the type of laser that can produce such illumination since the time scales of micro-thermal processes are on the order of milliseconds, and since the peak powers of a few MW will not be high enough to produce a high enough intensity for a reasonable spot size on the target for the laser to vaporize the surface.

Millisecond pulses are considered to be in the quasi-cw regime, and can be achieved by chopping a cw laser output, or using pulsed pumping of the laser.

Most pulsed lasers use Q-switching, and typically have ~ one to a few hundred nanosecond pulses.

Picosecond to nanosecond pulses can be produced by gain switching.

Femtosecond to picosecond pulses can be produced by cavity-dumping and trains of such pulses at lower energies can be produced by mode-locking. Such ultrashort pulses at very high energies can be generated by starting with longer pulses that are compressed to much shorter pulses and amplified either by chirped pulse amplification or divided pulse amplification.

Free Electron Lasers (FELs) can also generate high power pulses from ultrashort pulses to long pulses (>~ms) at high pulse repetition rates.

It has been known since the 1960s that high intensity pulsed laser illumination of materials vaporizes the surface of the material in a process called ablation. The ablation causes a shock wave that enters the material and causes further damage to the material, and if strong enough, to structures in contact with the material, thereby enhancing the destructiveness of the laser compared to just thermal damage caused by laser heating by cw and long pulse lasers.

However, the high intensity electromagnetic fields of the laser illumination ionizes the ablation produced vapor creating a plasma. This plasma forms in less than nanoseconds. At a certain plasma electron density, which depends on the laser wavelength, the plasma becomes highly reflective to the laser light and will reflect away most of the remaining energy in the laser pulse for pulses longer than about nanoseconds. Thus, pulses substantially shorter than the nanosecond scale are preferred to efficiently use most of the laser pulse energy in damaging the target.

However, it becomes more difficult and technologically more complicated, to pack as much energy into lasers pulses shorter than the nanosecond scale.

One way to try to get the best of both high peak power pulsed laser ablation shock induced damage and high cw power thermal damage is to have an ultrashort pulse laser with high pulse peak power in pulses short enough to get most of the energy in the pulse into the target material before the plasma forms with a density high enough to reflect the laser light, and then repeat those pulses with the time between pulses being long enough that the plasma expands and dissipates before the next pulse arrives, but short compared to the thermal time scale so that the material does not cool down significantly between pulses. These constraints favor extremely short ~fs to ~ps duration pulses with pulse repetition frequencies roughly on the order of hundreds of Hz to tens of MHz.

Another approach would be to use a train of extremely short pulses (<~ps) with very high pulse repetition frequencies (>~GHz) in a short burst duration (<~ns) to get multiple pulses on target before the plasma reaches high enough electron density to reflect subsequent pulses, then repeat the bursts at hundreds of Hz to tens of MHz burst rates.

Also, just because a laser produces ultrashort pulses at a high pulse repetition rate, does not mean that it will be suitable for producing pulse induced ablation damage to the target. If the pulse peak power is too low and the pulse repetition rate is too high, it will act like a cw laser at the same wavelength with the same average power. For example, an FEL weapon design given in a Naval Postgraduate School thesis uses 2 ps duration pulses at a pulse repetition frequency of 500 MHz with an average electron beam power of 50 MW, for an optical output average power of 1 MW in the 1.0 - 1.1 um wavelength regime: https://apps.dtic.mil/sti/tr/pdf/AD1009175.pdf . Because of the high repetition rate of 500 MHz, low per pulse energy of 2 mJ and moderately high peak power of 1 GW, this laser weapon will probably not ablate the surface of the target and will have about the same effects on the target as a 1 MW cw laser at the same wavelength. The thesis discusses the time required to melt the target, which is the cw thermal effect, but does not mention vaporizing, ablating, nor inducing a shock wave which would be the result of pulse damage as discussed above. In addition, for a reasonable initial beam size to produce a reasonable spot size on the target at range, the peak pulse power is too low to form a plasma channel in the atmosphere to keep the beam from spreading as it propagates through the atmosphere (see the breakingdefense.com link given in the references above). The pulse characteristics of this FEL design were chosen to optimize the operation of the FEL, not for their effects on atmospheric propagation nor on the lethality to the target.

It is too early in the R&D of such high power ultrashort pulse lasers to tell which candidate technologies, if any, will be weaponizable, and if they will provide a sufficient advantage over more mature high power cw laser technologies to justify the cost of replacing the more mature cw laser weapons that will have been fielded by the time that the ultrashort pulse lasers might be ready for transition to fielding.
 
On lasers and optics
 
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Is that laser system the Compact Laser Weapons System (CLaWs)? https://www.marines.mil/News/News-D...rps-at-the-forefront-for-ground-based-lasers/

If not, what laser system is it?

According to https://www.afcea.org/signal-media/contracting/marine-corps-extends-use-compact-laser "Boeing first manufactured the modular, high-energy weapon system for the Marines under an initial production contract signed in 2017. At the time, Boeing offered the CLWS in 2-kW, 5-kW and 10-kW configurations—however, the current power is unknown, as the Marine Corps declined to specify the kilowatt capability in use due to the security concerns of their current operations."
 
 
 
 

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