Relativistic Plasma Beamer Weapons

Relativistic plasma weapons, or p-beams, use a particle accelerator to produce pulses of high energy, relativistic protons. To keep these from rapidly defocusing due to their mutual electric repulsion, a pulse of electrons is injected with the protons going the same speed and direction to produce a diffuse hydrogen plasma moving at relativistic speeds. The protons have 2000 times the mass of the electrons, so they are responsible for most of the energy of the beam. For this reason, p-beams are sometimes called proton beams.

In air, the electrons will be stripped from the plasma beam, leaving a beam of relativistic protons. These will self-focus in the same way as an electron beam. Protons are more stable than lighter electrons, but Acc is still only 3/5 normal. If using the Minute of Angle optional rules from GURPS Tactical Shooting pg. 32, effective skill is capped at 22 + 2×Acc.

When high energy protons encounter matter, they suffer continuous energy loss like all charged particles. However, most of the energy dumped into the matter comes when a proton smacks directly into a nucleus. These protons carry enough energy to shatter a nucleus and create a shower of mesons in the process. The nuclear fragments and charged particles rapidly dump their energy into the surrounding matter. In addition, the lighter or uncharged nuclear fragments produce a spray of radiation - neutrons, pions, muons, and gamma rays - that will cause radiation damage to anything nearby. These nuclear collisions are discrete processes that remove the protons from the beam, and and so p-beams are treated as radiation beams with both discrete and continuous energy deposition. They cause four damage increments of 30 basic damage before continuous ionization slows the beam to a stop. The radiation damage multiple is 100.

When using the advanced rules from GURPS Tactical Shooting, the following changes to the rules are used to reflect how plasma beams travel differently from bullets:

In vacuum or trace atmospheres, ignore rules on Minute of Angle (pg. 32). Accelerator beams are more predictable than bullets - the pointing accuracy is generally better than the beam spread - and with no air around they do not suffer random deflection that could lead to inaccuracies.
The rules for Bullet Travel (pg. 32) are only relevant in spacecraft to spacecraft combat at high tech levels. Plasma beams move close to light speed - 250,000,000 to 300,000,000 meters per second - as to make no difference.
When using Precision Aiming (pg. 26), a compass replaces a wind gauge. Wind and gravity make next to no difference in the path of the beam, but plasma does interact with magnetic fields.
Rangefinding (pg. 27) alone is not enough to give a bonus, but knowing not only the range but also the strength and direction of the magnetic field and its trapped plasma density and how these quantities change between the gunner and the target will give a +1 bonus to Acc.

TL Weapon Type Damage Acc Range Mass (kg) ROF Shots Min ST Bulk Rcl Cost LC
11 Light P-Beam Cannon Beam+1 30⊗4 (∞) 15+4 80 km/300 km/5000 km/- 70/20 10 1000 30M -10 1 80 k 1
11 Medium P-Beam Cannon Beam+2 30⊗4 (∞) 15+4 180 km/700 km/11000 km/- 150/40 10 1000 46M -10 1 200 k 1
11 Heavy P-Beam Cannon Beam+10 30⊗4 (∞) 15+4 6000 km/25000 km/350000 km/- 30000/8000 4 400 607M -10 1 35 M 1

Descriptions
     Light P-Beam Cannon: A beamer cannon used against light vehicles. Skill: Gunner (Beams). Aperture 12 cm. Depth of focus multiplier 0.4. Beam energy 15 kJ. Energy used per shot 20 kJ. Extra power cell 20 kg, $1000.
     Medium P-Beam Cannon: A rapid-fire vehicular beamer cannon. Skill: Gunner (Beams). Aperture 20 cm. Depth of focus multiplier 0.35. Beam energy 30 kJ. Energy used per shot 40 kJ. Extra power cell 40 kg, $2000.
     Heavy P-Beam Cannon: A large vehicle mounted beamer cannon. Skill: Gunner (Beams). Aperture 30 cm. Depth of focus multiplier 5. Beam energy 15000 kJ. Energy used per shot 20000 kJ. Extra power cell 8000 kg, $400000.

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