Electron beam weapons, or e-beamers, emit brief, very intense pulses of very high energy electrons moving at high relativistic speeds. This heats the matter to a plasma in the usual fashion for fast charged particles, but the energy to do so comes from the beam itself, whose electrons will slow down and eventually come to a stop in a relatively short distance for penetrating radiation. To overcome this, an e-beamer will emit a pulse that heats a short column of matter - be it armor or flesh or air - to a hot plasma before the electrons are absorbed. This hot plasma rapidly expands until it is highly diffuse, so the next pulse can go through with only minimal losses until it hits the fresh matter in front of the heated column. The sequence of pulses is very rapid, lasting less than a millisecond for one shot.
Electrons all repell each other because of their negative electric charge. In addition, electrons are much lighter than atoms, so in collisions with atomic nuclei the electrons tend to bounce off at large angles, causing the beam to rapidly spread into more of a spray than a beam. Fortunately, there is a way to counter this. The free electrons in the plasma the beam creates move to "screen" the beam, flowing with the electric field to partially neutralize the beam's electric field (in essense the beam will be going through a slightly electron deficient plasma because the plasma electrons were pushed out. The extra positive charges on the plasma partially counter the negative charge of the beam). This prevents the beam from exploding due to its electrical self-repulsion. Instead, the magnetic field generated by the beam acts to pinch the beam together so that it is self-focusing in matter. This self pinching allows the beam to counter this collisional spreading enough that the beam can propagate for some distance. Electron beams are not focused beams - they rely on self-pinching to maintain a tight beam rather than focusing optics, and thus they ignore the rules for beam focusing. While they do suffer from cover DR due to the atmosphere between the gunner and the target, the main factor limiting their range is the build-up of beam instabilities (see below) that cause the beam to break up and dump its energy into the air.
Unfortunately, the magnetic field of the beam tends to get trapped in the plasma the beam creates. The interaction of the beam, the field, and the plasma leads to various instabilities in the beam, causing it to break up and veer from its original path. Once the beam starts to break up, it rapidly loses all its energy to the air and comes to a stop. This always happens before the beam can diffuse enough to not cause flash-vaporization of the matter it passes through; ignore the rules for long ranges of radiation beams for electron beamers, they always cause a material explosion and have the usual ½D and Max ranges of GURPS weapons. This can be partially countered by emitting pulses so short that they outrun the trapping of their field by the plasma. Even so, electron beams are hard to aim and are short ranged. At TL 11, they have low Acc compared to other beam weapons, and effective skill before penalties for speed, range, and size is capped at 14 + 2×Acc (this replaces the Minute of Angle optional rules from GURPS Tactical Shooting pg. 32, if they are used).
If using GURPS Tactical Shooting, there are differences between bullets and electron beams that are reflected in how they are handled in-game:
Although electron beams produce the usual beam path of air flash-heated to a blue-white-hot incandescence like a lightning bolt, this beam path is not straight, particularly at distances approaching the ½D range and beyond. The beam instabilities cause it to veer and wiggle and corkscrew with ever increasing amplitude and the buildup of finer harmonics until the beam disintegrates in a flash of heated air.
When an electric charge changes speed or direction, it shakes off part of its electric field which then goes flying off on its own as electromagnetic radiation. Collisions between beam electrons and atoms are hard and fast, resulting in high energy high frequency radiation - x-rays and gamma rays. Most of this radiation is soft x-rays, and absorbed too rapidly by matter to be a radiation hazard, but the heavier the atom, the more radiation and the more energetic the radiation. Higher TLs allow controlable beams with lower electron energies, resulting in lower radiation dose. At TL 11, beams incident on materials composed of light elements with only small amounts of heavy elements, such as air, water, wood, plastic, or living organisms, will produce radiation with a radiation damage multiplier of 0.5. Damage absorbed by rock or aluminum increase the radiation mutliplier to 1, for common metals the radiation multiple is 2, and heavy metals and other very heavy elements have a radiation multiple of 4. A target will take the full dose produced from basic damage absorbed by armor or equipment he is wearing or carrying. Assume any armor or other gear that provides radiation PF contains heavy metals, which ironically lead to increased radiation exposure - although the PF protects against the radiation produced in the equipment that provides the PF. Otherwise, non-powered armors from TL 7+ can be assumed to be made of light elements only.
In vacuum or trace atmospheres, electron beams lose the interaction with the plasma they create in the air which keeps them focused but also makes them unstable. Double Acc in these conditions and ignore the cap on effective skill. The ½D range is halved, but there is no maximum range. Instead, like weapons that emit focused beams, damage is divided by the number of ½D multiples of range and becomes burning after 2× the ½D range.
The low Acc, short range, erratic beams, and radiation hazard of e-beams means that they are not commonly used. Collectors may buy them for their novelty, and they are occasionally used when expecting to encounter heavily armored opponents at close ranges. In games with supernatural elements, they may have extra effects against insubstantial targets, making them attractive for monster hunter teams (see GURPS Monster Hunters). Against these foes, the beam causes a stunning Affliction, with a penalty equal to the HT roll equal to the Size modifier from the Speed/Range table (pg. B550) reading the Damage as the Linear Measurement.
| TL | Weapon | Type | Damage | Acc | Range | Mass (kg) | ROF | Shots | Min ST | Bulk | Rcl | Cost | LC |
| 11 | Palm E-Beamer | beam-2.5 | 7 (∞) | 1 | 25/30 | 0.08/0.008 | 3 | 100 | 2 | 0 | 1 | 90 | 3 |
| 11 | Pocket E-Beamer Pistol | beam-1 | 10 (∞) | 2 | 35/40 | 0.25/0.025 | 3 | 100 | 3 | -1 | 1 | 300 | 3 |
| 11 | E-Beamer Pistol | beam0 | 16 (∞) | 2 | 60/70 | 1/0.1 | 3 | 100 | 6 | -2 | 1 | 1.2 k | 3 |
| 11 | Magnum E-Beamer Pistol | beam0 | 18 (∞) | 2 | 60/70 | 1.2/0.12 | 3 | 100 | 6 | -2 | 1 | 1.5 k | 3 |
| 11 | Auto E-Beamer Pistol | beam-0.5 | 14 (∞) | 2 | 50/60 | 1.2/0.25 | 6 | 400 | 6 | -2 | 1 | 1.5 k | 2 |
| 11 | Auto E-Beamer Carbine | beam0 | 18 (∞) | 4 | 60/70 | 2/0.5 | 5 | 400 | 5† | -3 | 1 | 2.5 k | 2 |
| 11 | Assault E-Beamer | beam+0.5 | 20 (∞) | 4 | 70/80 | 3/0.9 | 4 | 400 | 6† | -4 | 1 | 4 k | 2 |
| 11 | E-Beamer Battle Gun | beam+1 | 25 (∞) | 4 | 80/100 | 5/1.5 | 4 | 400 | 8† | -5 | 1 | 6 k | 2 |
| 11 | Portable Anti-tank E-Beamer | beam+2.5 | 40 (∞) | 4 | 150/180 | 9/0.18 | 1 | 10 | 10† | -6 | 1 | 11 k | 3 |
| 11 | Light Support E-Beamer | beam+1 | 25 (∞) | 6 | 80/100 | 11/3.5 | 10 | 1000 | 12M | -7 | 1 | 12 k | 1 |
| 11 | Heavy Support E-Beamer | beam+3 | 50 (∞) | 6 | 180/200 | 90/25 | 10 | 1000 | 34M | -10 | 1 | 100 k | 1 |
| 11 | Auto E-Beamer Cannon | beam+3.5 | 65 (∞) | 6 | 200/250 | 180/60 | 10 | 1000 | 50M | -10 | 1 | 200 k | 1 |
| 11 | E-Beamer Cannon | beam+6.5 | 200 (∞) | 6 | 700/800 | 3000/900 | 4 | 400 | 203M | -10 | 1 | 4 M | 1 |
Descriptions
Palm E-Beamer: A small, easily concealable ray gun without a grip or sights. Skill: Beam Weapons (Pistol). Aperture 0.04 cm. Beam energy 0.06 kJ. Energy used per shot 0.08 kJ. Extra power cell 0.008 kg, $0.4.
Pocket E-Beamer Pistol: A small ray pistol for concealed carry. Skill: Beam Weapons (Pistol). Aperture 0.06 cm. Beam energy 0.2 kJ. Energy used per shot 0.25 kJ. Extra power cell 0.025 kg, $1.2.
E-Beamer Pistol: A typical ray gun sidearm used by law enforcement and civilians. Skill: Beam Weapons (Pistol). Aperture 0.09 cm. Beam energy 0.8 kJ. Energy used per shot 1 kJ. Extra power cell 0.1 kg, $5.
Magnum E-Beamer Pistol: A large and bulky sidearm. Skill: Beam Weapons (Pistol). Aperture 0.09 cm. Beam energy 0.9 kJ. Energy used per shot 1.2 kJ. Extra power cell 0.12 kg, $6.
Auto E-Beamer Pistol: An auto-firing ray gun sidearm. Skill: Beam Weapons (Pistol). Aperture 0.08 cm. Beam energy 0.5 kJ. Energy used per shot 0.6 kJ. Extra power cell 0.25 kg, $12.
Auto E-Beamer Carbine: A rapid-fire longarm for vehicle crews or close-quarters combat. Skill: Beam Weapons (Rifle). Aperture 0.09 cm. Beam energy 0.9 kJ. Energy used per shot 1.2 kJ. Extra power cell 0.5 kg, $25.
Assault E-Beamer: A typical infantry longarm. Skill: Beam Weapons (Rifle). Aperture 0.11 cm. Beam energy 1.5 kJ. Energy used per shot 2 kJ. Extra power cell 0.9 kg, $40.
E-Beamer Battle Gun: A heavy-hitting military longarm. Because of the radiation danger, it is typically only used by rad-hardened combat robots. Skill: Beam Weapons (Rifle). Aperture 0.12 cm. Beam energy 2.5 kJ. Energy used per shot 3.5 kJ. Extra power cell 1.5 kg, $70.
Portable Anti-tank E-Beamer: A beamer used to against heavy armor including vehicles and battlesuits. Skill: Beam Weapons (Rifle). Aperture 0.25 cm. Beam energy 12 kJ. Energy used per shot 18 kJ. Extra power cell 0.18 kg, $9.
Light Support E-Beamer: A rapid-fire beamer used in a squad support role. Skill: Gunner (Beams). Aperture 0.12 cm. Beam energy 2.5 kJ. Energy used per shot 3.5 kJ. Extra power cell 3.5 kg, $180.
Heavy Support E-Beamer: A beamer cannon used against light vehicles. Skill: Gunner (Beams). Aperture 0.25 cm. Beam energy 20 kJ. Energy used per shot 25 kJ. Extra power cell 25 kg, $1500.
Auto E-Beamer Cannon: A rapid-fire vehicular beamer cannon. Skill: Gunner (Beams). Aperture 0.35 cm. Beam energy 40 kJ. Energy used per shot 60 kJ. Extra power cell 60 kg, $3000.
E-Beamer Cannon: A large vehicle mounted beamer cannon. Skill: Gunner (Beams). Aperture 1.1 cm. Beam energy 1500 kJ. Energy used per shot 2000 kJ. Extra power cell 900 kg, $40000.