The 
Laser is a Mekanism block that fires a continuous beam out of its front, which will damage mobs, set them on fire and slowly break through blocks. It uses 4,000 FE (10,000 J) every tick that it’s powered, and it can’t be switched off with redstone. The beam reaches up to 64 blocks, and it stops at the first block that it hits.
Most players will build Lasers for one reason, which is to ignite a Fusion Reactor. That needs a single pulse of at least 400 million FE, so the beams are collected in a 
Laser Amplifier first and then released all at once. There’s also the 
Laser Tractor Beam, which is used to mine with them and keep the drops.
How to Make It
A Laser takes 3 
Reinforced Alloys, 2 
Energy Tablets, a 
Steel Casing and a 
Diamond. The Laser Amplifier is 7 
Steel Ingots around a 
Basic Energy Cube and a Diamond, and you’ll get a Laser Tractor Beam by crafting an amplifier with a 
Personal Chest or 
Personal Barrel on top of it.
All three will face whichever way you were pointing when you placed them, including straight up or down. The Laser only takes power through its back, so the cable has to come in from directly behind it. It holds 800,000 FE, which is enough for 10 seconds of firing if the supply drops out.
How It Works
As soon as a Laser has energy it’ll start to fire, and it carries on for as long as it’s being supplied. There’s no screen or redstone control on it, so the only way to turn one off is to cut its power. The beam doesn’t get weaker over distance either, so a target 60 blocks away is hit just as hard.
Damage
The beam deals 1 damage for every 1,000 FE in it, which is 4 damage a tick from a single Laser, and it sets whatever it hits on fire as well. That’s 2 hearts every tick, so most mobs won’t last a second in front of one. If there’s any energy left over after a kill, it carries on to the next mob behind.
It’ll hurt you just the same as it hurts a mob, so be careful where the beams are pointing before you power them. A raised 
Shield is able to block the beam, and a MekaSuit fitted with 
Laser Dissipation Units will absorb most of it.
Breaking Blocks
When the beam is resting on a block, energy builds up in it until the block breaks, and how long that takes depends on its hardness. A single Laser gets through 
Stone in under a second and 
Deepslate in a second and a half, whereas 
Obsidian takes about 25 seconds. The drops are left on the ground, and it can’t break anything that’s unbreakable, like 
Bedrock.
Remember that a Laser will mine whatever it’s aimed at, including your own base. Make sure every beam ends on a Laser Amplifier or a 
Laser Focus Matrix, or turn off Aesthetic World Damage in the config if you don’t want blocks broken at all.
Laser Amplifier
The Laser Amplifier can only be charged by Laser beams, which it’ll accept from any side. You won’t be able to fill one from a cable. It stores up to 2 billion FE and doesn’t lose any of it over time, then fires what it’s holding out of its front as one beam.
Its screen has three settings, which are a minimum energy, a maximum energy and a delay in ticks. It’ll only fire once it’s holding at least the minimum, and it never sends more than the maximum in one shot. With everything left at the defaults, it just passes on whatever comes in every tick, which is a way to merge several Lasers into one stronger beam.
That merged beam hits with the total of everything going in, so ten Lasers through an amplifier will deal 40 damage a tick and mine ten times as fast. The amplifier can also give off a redstone signal, either while its beam is hitting an entity or to show how full it is, which is picked from the Redstone Output button.
Igniting a Fusion Reactor
To start a Fusion Reactor, a beam of at least 400 million FE has to hit its Laser Focus Matrix in a single tick. Firing a Laser straight at it won’t ever get there, as the heat leaks away faster than one beam adds it. So you’ll aim your Lasers into an amplifier, and the amplifier at the matrix.
Set the amplifier’s minimum to a little over 400 MFE, and it’ll hold everything until it has enough and then release it in one pulse. It’s best to go slightly above that figure, as a pulse that lands right on the line might still use up the 
Hohlraum without lighting anything. How long the charge takes is down to how many Lasers you’ve built.
| Lasers | Power needed | Time to 400 million FE |
|---|---|---|
| 1 | 4,000 FE/t | 83 minutes |
| 4 | 16,000 FE/t | 21 minutes |
| 10 | 40,000 FE/t | 8 minutes 20 seconds |
| 20 | 80,000 FE/t | 4 minutes 10 seconds |
A full amplifier holds enough for five ignitions, so there’s no harm in letting it charge past the minimum while you get the fuel ready. The reactor needs Deuterium and Tritium already waiting in its tanks when the pulse lands, otherwise it’ll go out again straight away and you’ll need another Hohlraum.
Laser Tractor Beam
The Laser Tractor Beam is an amplifier that keeps what it mines. It’s charged by Lasers in the same way, but it has no settings, so it fires everything that it’s holding every tick. Any block that its beam breaks goes into its own 27 slots, and items lying in the path of the beam are pulled in too.
That makes it the piece to use for a Laser-driven 
Cobblestone generator or a mob farm, where you’d want the drops collected. If it fills up, the extra will be dropped a couple of blocks in front of it. A Comparator reads how full it is, and the slots are output only, so a Logistical Transporter is able to empty it.
Upgrades and Automation
None of the three take upgrades, so a stronger beam always means more Lasers. Each Laser needs its own 4,000 FE/t, which adds up quickly, as twenty of them will draw 80,000 FE/t between them. It’s worth putting them on a separate Universal Cable line that you’re able to cut, as that’s the only off switch they’ve got.
The Laser Amplifier is the part that can be controlled. It follows a redstone signal like other Mekanism machines, so you could hold it with a 
Lever and release the pulse by hand instead of relying on the minimum. Once the Lasers are in place, the Fusion Reactor itself is the next thing to build.
FAQ
One is enough, as the Laser Amplifier saves the energy up, it just takes about 83 minutes to reach the 400 million FE that’s needed. Ten Lasers will do it in a little over 8 minutes, and twenty in about 4. The pulse has to arrive in a single tick, so the amplifier isn’t optional.
Aim the Lasers into the amplifier and point its front at the Laser Focus Matrix on the reactor. Then open the amplifier and set the minimum energy to a little over 400 MFE, which makes it hold the charge and fire it as one pulse. A redstone signal can be used to hold it back as well.
A Laser has no screen and doesn’t respond to redstone, so it fires for as long as it has energy. The only way to stop one is to cut the power going into its back, like with a separate cable that you’re able to break or switch.
They can, as a beam will break any block it rests on once enough energy has built up, with Stone taking under a second and Obsidian about 25 seconds from one Laser. A plain Laser leaves the drops on the ground, whereas a Laser Tractor Beam stores them in its own inventory.
