Neutron Beamer Weapons
Modern science can create neutron beams that are a narrow spray of particles. We cannot create focused neutron beams nor does anyone have any idea how this could be done. However, one may imagine that the science of advanced civilizations may figure this out, especially if superscience is available to use gravity or force shield focusing.
Neutrons are uncharged.
They drift through matter as if it were not there until they hit an atomic nucleus.
This interaction makes neutron beams radiation beams with only discrete process energy transfer.
The rate at which neutrons smack into nuclei depends on the neutron energy.
Here, we consider three different energies - epithermal, fast, and relativistic.
The radiation damage multiple is 100.
- Epithermal neutrons deposit their energy the fastest, so they have less penetration but cause more heating.
When they encounter a nucleus, epithermal neutrons either bounce off, imparting part of their energy to the nucleus while the neutron scatters away; or they get captured by the nucleus and spit out some other particle to conserve energy, usually a gamma ray but sometimes an alpha particle.
Epithermal neutrons are best at transfering their energy to the target when the target contains lots of hydrogen. Since neutrons have the same mass as hydrogen nuclei, a neutron smacking into hydrogen is like a billiard ball smacking another billiard ball - much of the energy of one ball can be transferred to the other. On the other hand, a neutron impacting a heavy nucleus is like a billiard ball hitting a bowling ball - the billiard ball is likely to bounce off with most of its original speed while the bowling ball barely moves. In this case, the billiard ball keeps most of its original energy from before the collision while the bowling ball gets very little. A consequence of this is that when an epithermal neutron beam goes through hydrogen rich material (such as water, biological tissue, wax, plastic, oils, gasoline) it does full damage. Anything else takes at most 1/3 damage, common metals and other intermediate weight elements take 1/10 damage, and heavy metals and other heavy elements take 1/30 damage from the neutron beam. This damage reduction in no way reduces the radiation exposure.
In settings with advanced medicine that allows rapid and effective treatment of radiation exposure, epithermal neutron beamers may be the preferred weapon aboard spacecraft or other vehicles or installations with pressure hulls or with sensitive equipment or containers that could pose serious dangers if breached. The lower damage of epithermal beams to non-biological targets produces less danger of a dangerous release of hazardous materials, puncture of a pressure hull, or damage to vital equipment. In this case, security forces may set their weapons as a matter of course to be defocused to the point that the thermal effects cook meat but will not harm equipment. If medical treatment of radiation exposure reaches this level, the LC of radiation beams will be higher - 3 for pistols or rifles with ROF 3 or less, 2 for pistols or rifles with ROF 4 or more.
- Fast neutrons interact less often than epithermal neutrons, but more often than relativistic neutrons, giving them an intermediate penetration and heating along the beam path.
When a fast neutron smacks a nucleus, it may bounce off or get captured like epithermal neutrons, but very often it hits hard enough to knock pieces off the nucleus - generally additional neutrons, protons, or alpha particles - or to leave the nucleus in an excited state which decays via the emission of a gamma ray.
- Relativistic neutrons deposit their energy the slowest leading to greater penetration but less heating.
When a relativistic neutron hits a nucleus, the nucleus shatters into pieces while pions and other heavier mesons boil out of the quantum vacuum and gamma rays are shaken off from the rapidly changing distribution of the nuclear electromagnetic field.
The nuclear fragments and pions go flying out at high velocities.
Charged nuclear fragments rapidly dump their energy into the surrounding matter, leading to localized heating, while uncharged nuclear fragments (additional neutrons), gamma rays, pions, and the pion decay products (muons) penetrate some distance leading to radiation exposure.
When using the advanced rules from GURPS Tactical Shooting, the following changes to the rules are used to reflect how neutron beams travel differently from bullets:
- Ignore rules on Minute of Angle (pg. 32).
Neutron beams are more predictable than bullets - the pointing accuracy is generally better than the beam spread, while air does not deflect them and they are moving too fast to be appreciably deflected by gravity.
- The rules for Bullet Travel (pg. 32) are usually not important. Epithermal neutrons move at about 4000 km/s, fast neutrons at about 40,000 km/s, and relativistic neutrons about 250,000 km/s.
- When using Precision Aiming (pg. 26), ballistic tables and a wind gauge are unneccessary because wind does not affect the beam's path and gravity has negligible effect on particles moving this fast.
- Rangefinding (pg. 27) gives no bonus because the beam essentially travels in a straight line so that range has no effect on the beam path.
TL 11^, Epithermal neutronsChange neutron energy