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35

Neutrons (and protons) being spin 1/2 fermions, must fit antisymmetric wavefunctions. This "wavefunction" doesn't always involve waves, though. For nucleons - the generic term for neutron or proton - this wavefunction for the pair is a produce of (1) a spatial part, (2) a spin part, and (3) an isospin part. The isospin part is a clever way to describe ...


29

Basically, the answer is no, it's not possible. When we produce neutrons for research purposes, we have to produce them using nuclear reactions. They come out of the nuclear reactions with energies that are determined by the reaction, are not otherwise under our control, and that are on the MeV energy scale of nuclear physics. Examples of a neutron source ...


22

A neutron is not a proton and an electron lumped together (as your question seems to suggest you think) A hydrogen atom is a bound state of an electron and a proton (bound by the electromagnetic force) whereas a neutron is a bound state of three quarks (bound by the strong force). You might be tempted to think that a neutron is also a bound state of an ...


22

It's boron-10 that is the good neutron absorber. Boron-11 has a low cross section for neutron absorption. The size of the nucleus isn't terribly relevant because neutrons are quantum objects and don't have a precise position. The incident neutron will be delocalised and some part of it will almost always overlap the nucleus. What matters is the energy of ...


20

Neutrons have spin 1/2 and therefore obey the pauli exclusion principle, meaning two neutrons cannot occupy the same space at the same time. When two neutrons' wavefunctions overlap, they feel a strong repulsive force. See http://en.wikipedia.org/wiki/Exchange_interaction .


20

The neutron is in no way "composed" of a proton and an electron. It can decay to a proton, electron, and an antineutrino. But that doesn't mean that these three particles literally co-exist inside the neutron at the beginning. Instead, the decay involves some real transmutation of elementary particles. The only thing that one can say because of the decay is ...


19

Spontaneous processes such as neutron decay require that the final state is lower in energy than the initial state. In (stable) nuclei, this is not the case, because the energy you gain from the neutron decay is lower than the energy it costs you to have an additional proton in the core. For neutron decay in the nuclei to be energetically favorable, the ...


15

Isotones are nuclides having the same number of neutrons. Magic proton or neutron numbers give the nucleus greater stability. Magic 82-isotone nuclides for instance: Isobars are nuclides having the same mass number (i.e. sum of protons plus neutrons). The number of protons in beta-plus (beta-minus) decay decreases (increases) by a unit and the number of ...


15

Although a neutron is electrically neutral, it has a non-zero magnetic dipole moment. It interacts with a magnetic field to give a potential $$ U = \vec{\mu} \cdot \vec{B} $$ A gradient of magnetic field strength will give a force $$ \vec{F} = \nabla|\vec{\mu} \cdot \vec{B} | $$ It's not possible to produce large, sustained field gradients, nor is it ...


14

Conservation of energy and the electron-degenerate pressure. For the neutron to decay you must have $$ n \to p + e^- + \bar{\nu}$$ or $$ n + \nu \to p + e^- \quad. $$ In either case that electron is going to stay around, but in addition to the neutrons being in a degenerate gas, the few remaining electrons are also degenerate, which means that adding a ...


13

It would violate the law of conservation of baryons. Baryons (half-integer-spin particles, i.e. s=1/2, 3/2, 5/2,... interacting through the strong force) cannot be created at will, but must conserve the total baryonic number: protons and neutrons both have $+1$ baryon number, while their antiparticles, antiproton and antineutron, have baryon number $-1$ ...


13

It is a misnomer (at best) to characterize a neutron star as all neutrons. There are protons and electrons too. Imagine compressing a bunch of regular matter at some point it requires less energy for a proton and electron to combine to form another neutron rather than for the electron to try to fill a very high energy state. That means there are so many ...


11

The anti-particle corresponding to a neutron is an anti neutron! The neutron is made up of one up quark and two down quarks. The anti-neutron is made up of an anti-up quark and two anti-down quarks. Both have zero charge because the charges of the quarks within them balance out. You are correct that elementary particles with no charge are often their own ...


11

Masses and coupling between quarks are free parameters in the standard model, so there is not real explanation to that fact. About the measurment: you can have a look at this wikipedia article about Penning traps which are devices used for precision measurements for nucleus. Through the cyclotron frequency (Larmor factor) we can obtain the mass of the ...


10

Detectors at particle colliders are layered like onions around the collision vertex. The CMS detector at CERN First there are charged particle sensitive detectors where charged particles leave tracks because of ionisation, but mass density is low so strong interactions do not happen often; their momentum can be measured by the curvature in the ...


9

A neutron is a fermion, a hydrogen atom is a boson. This is related to the fact that a neutron decays into three fermions rather than two which is what you seem to think. A neutron is composed of three valence quarks, $u,d,d$, while a hydrogen atom is made out of $u,u,d,e^-$. The internal size of a neutron is about $10^{-14}$ meters while the internal size ...


9

Neutron decay is not a electromagnetic phenomena at all. It is governed by the weak nuclear force. This is well supported by fact that the lifetime of the neutron fits neatly into weak universality. Secondly the neutron is not it's own antiparticle. The anti-neutron is a distnct particle.


9

You didn't understand any of these questions right. Antiquarks and their bound states, including the antineutrons, are produced and observed as easily as bread and butter. Lots of details experiments with e.g. antineutrons have been performed, e.g. Scattering of antineutrons with hydrogen ...


8

The Pauli Exclusion Principle states that no two identical fermions (neutrons and protons are fermions - they have half-integer spins and obey Fermi-Dirac statistics) can occupy the same quantum state at the same time. If the neutron were to $\beta$-decay as: \begin{equation} n \longrightarrow p + e^- + \bar{\nu_e} \end{equation} then this freshly minted ...


8

A proton is made of two up quarks and a down quark, whereas a neutron is made of two down quarks and an up quark. The quark masses contribute very little of the actual mass of the proton and neutron, which mostly arises from energy associated with the strong interactions among the quarks. Still, they do contribute a small fraction, and the down quark is ...


8

Thermal neutrons capture on hydrogen and carbon with reasonable (i.e. not large, but significant) cross-sections (this is the delayed event detection methods of most organic liquid scintillator anti-neutrino detectors--i.e the one that don't dope their scintillator with Gadolinium). So though a "cloud"--meaning a localized diffuse gas--of neutrons can ...


8

The neutron is made of two down quarks and an up quark; the proton of two up quarks and a down quark. This leads to two effects that differentiate their masses. One is that the up and down quark themselves have different masses. The other is that the proton is charged, and so quantum corrections involving virtual photons affect its mass. The details are ...


8

Neutron sources You can buy a commercial off-the shelf "neutron generator", or you can use a radioactive source. Neutron generators are accelerator-based fusion reactors1 and have the advantage of being able to simply turn the neutron supply on and off. The most common source is AmBe (Americium-241/Beryllium), though Californium-252 and tritium both have ...


8

A neutron contains (on average) 1 up quark and 2 down quarks. The decay to a proton occurs when a down quark emits a W$^-$ particle and changes to an up quark. This gives a proton with two up quarks and 1 down quark. The W$^-$ particle decays to an electron and anti-neutrino. However an antiproton contains 2 up antiquarks and 1 down antiquark, which is ...


8

It can't be solo neutrons, because they are unstable and decay into protons. So far as we know, there's not a stable configuration of mostly-neutrons that occurs in nature intermediate between heavy nuclei (uranium is roughly 3-to-2 parts neutrons) and neutron stars of 1-3 solar masses (which are about 90% neutrons). What you're describing would be the kind ...


8

The mass of a free neutron is 939.566 MeV/c$^2$ (almost 1 GeV/c$^2$, so that's probably where your instructor got the "1" value), and the mass of a free proton is 938.272 MeV/c$^2$. A free neutron will decay into a free proton, free electron ($\beta^-$), and an anti-neutrino, $\bar{\nu}$. The mass of the electron is 0.511 MeV/c$^2$, and of the ...


7

OK, here is something concrete and quantitative, "Guidelines for predicting single-event upsets in neutron environments": Neutrons in the atmosphere result from cosmic-ray spallation interactions with nitrogen and oxygen nuclei. A typical reaction is a 1 GeV proton fragmenting a nitrogen necleus into lighter charged particles and simultaneoously emitting ...


7

In spite of the name, neutron stars also contain protons and electrons. This is required for equilibrium with respect to weak-interaction processes which can convert neutrons into protons and electrons. Since neutron stars also contain protons and electrons, they can contain electric currents which generate magnetic fields. It is thought that the protons ...


7

Neutron decays into a proton, electron and electron anti-neutrino. Not only electric charge but also (electronic) lepton number has to be conserved (I'm not very sure in this statement). In short: you start and have to finish with 1 matter particle (anti-matter counts as -1). Mean time $\neq$ half-life. More on wikipedia. Physically there is no difference ...



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