Neutron Definition and 746 Threads

Can simple mass accretion turn a neutron star into a Black Hole, or does a BH require temperatures and pressures from the collapsed massive star?

Is my understanding correct that the short term stability of fast neutron liquid metal cooled reactors is based primarily on the thermal expansion of the core, while the Doppler coefficient is far less significant factor, as the Doppler coefficient primarily affects the low energy neutrons? (The...

Hi, before I start this is not coursework or any work attached to my degree but part of an internship at a neutron research facility at a level appropriate for Masters students and higer, so I felt it necessary to post it here rather than the homework section (sorry if I'm mistaken). I've been...

Homework Statement What is the Q value in units of MeV in each of the following processes? i) The spontaneous fission of 232U92 to 145La57 and 87Br35 ii) The neutron induced fission of 232U92 to 146La57 and 87Br35 Explain why heavy nuclei such as 232U92 do not usually undergo fission...

I was wondering, does anyone know of a lower limit on the mass of a neutron star from fundamental physics? That is, the smallest it could be before its pressure would make it explode. I don't mean the Chandrasekhar limit, as that's the upper limit for a white dwarf. Neutron stars occurring...

Oh hello. I'm quite uncertain about one of the reasons for the discovery of the neutron. Apparently, the neutron is supposed to be the radiation released by alpha particles hitting Beryllium. When the radiation hits Paraffin wax, the paraffin wax releases protons. At first, people thought that...

I refer to the last paragraph of http://physicsworld.com/cws/article/news/46592 quote: A few hundred milliseconds later, the neutron is captured by a proton to form a deuteron Can someone please explain how a proton captures a neutron or provide links to articles describing this

Yeah it's true, I heard him talking all about it tonight. He said he came up with the theory for it a while ago and he heard of it recently then he knew he was right. Among other things, he briefly said he connected quantum mechanics and consciousness. Then to top it off he said physicists...

Most common isotopes of He has 2 neutrons, Li has 3 neutrons and so on right, until Z increases to higher numbers and we get to elements like iron, where the nucleus doesn't have equal numbers of protons and neutrons anymore. But why isn't the number of protons and neutrons equal in the most...

So I have been reading about the cross section of neutron capture and have been reading about how the cross section for neutrons in a given material depends on neutron energy, the most important factor obviously. But I have not seen as much information on how, for a neutron of a given thermal...

Homework Statement Deep in space, two neutron stars are separated (center-to-center) by a distance of 18 X 106 km apart. Neutron star A has a mass of 153 X 1028 kg and radius 52000 m while the neutron star B has a mass of 159 X 1028 kg and radius 72000 m. They are initially at rest with...

Like the question says, would a neutrino be stopped by the very high density matter in a neutron star? IH

If a super-duper-hyper-energetic particle like the OMG particle (refer http://en.wikipedia.org/wiki/Oh-My-God_particle) were to impact the surface of a neutron star, could the tremendous impact density it creates lead to the beginnings of an embryonic black hole that would (slowly/quickly?)...

does neutrons have electromagnetic force? I mean it is the electromagnetic force which allows particles to feel each other in the first place during detection process, but neutron is neutral with no charge so does it possesses it?

Problem statement How fast must a neutron be traveling relative to a detector in order to have a measured kinetic energy that is equal to its rest energy? An "attempt" I know Ek = mc^2 - m0c^2 But if Ek = m0c^2, wouldn't the two terms cancel out from this equation? I am having trouble...

If you add up the g-factor for the electron, the proton and the neutron it is not exactly zero. Doesn't this calculate to a magnetic moment for every atom in the universe proportional to it's mass.

Does the absorption cross section to scattering cross section ratio of an isotope vary with neutron energy or stay constant? I have heard that cross sections in general are inversely proportional to velocity (eg the fission cross section of U235 is about 1000 times higher for thermal neutrons...

I keep reading that when a U-238 atom absorbs a neutron it turns into Pu-239. How does that happen? If I'm not mistaken Pu-239 is U-238 plus 2 protons and 2 electrons and minus 2 neutrons. When U-238 absorbs the neutron and becomes U-239 I can see that it can turn into Pu-239 if 2 neutrons decay...

Talking to the point, I need to know how a free neutron interacts with light (or a photon). Or, if they do not interact, the reason behind it. The reason why I am asking this question: Assume that a free neutron is being hit by light. If I assume that light is an EM wave, I can conclude...

I'm thinking about the thermodynamics of electron capture: p + e --- n + v(e) + energy (That is, proton absorbs electron to give neutron, electron neutrino and energetic photons.) This is thermodynamically disfavored given the substantial energy barrier to fusion to a neutron...

I am working on some neutron experiments and have to calculate the heat released in the boron neutron capture 10B + 1n - > Li + Alpha particle The reaction has a Q value of 2.31 MeV. Is this entire energy converted to heat? Also, in the two types of reactions of neutron with Boron...

http://arxiv.org/abs/1101.4298 The missing link: Merging neutron stars naturally produce jet-like structures and can power short Gamma-Ray Bursts Luciano Rezzolla, Bruno Giacomazzo, Luca Baiotti, Jonathan Granot, Chryssa Kouveliotou, Miguel A. Aloy (Submitted on 22 Jan 2011) "Short Gamma-Ray...

I have been reading up on radioactivity (Wikipedia). I keep coming across articles which talk about emission of Neutrons (during Plutonium decay, for example). Now I know alpha radiation is basically Helium-4 nuclei, but that consists of both Protons and Neutrons combined in a nucleus. What...

Ok so my problem is I have absolutely no idea where to start. I have been able to figure out other problems but this I can't get my head around. I am unsure as to the equations I need to use for collisions and how to obtain the correct answer. Homework Statement A nuclear reactor (see...

Neutrons have no charge, and in neutron stars we have matter that is only made of tightly packed neutrons. The mass is very great due to density. If I were to go fetch a baseball sized ball of neutron star matter from a neutron star and lay it on hard concrete ground... Other than making a...

A very simple question, but needs to know proper explanation. Why the neutron scattering from hydrogen is negative while deuterium and almost all other atom has positive scattering?

Homework Statement I have a (numerically calculated) cross section for a neutron scattering from a nucleus which looks like: 1) Am I correct in saying that there are three resonant peaks and these correspond to three different resonant particles? 2) If so, are the lifetimes of the...

Can someone explain what are the implications for the 13 neutron beams that have been observed at Fukushima? How are they created? What will cause more to be created?

Homework Statement How many collisions will be necessary to slow a neutron down from 14.1 MeV to thermal energy (0.0253 eV)? A=24 Homework Equations E'=[(A-1)/(A+1)]^2 x E The Attempt at a Solution The calculation is not an issue- I understand how to use the equation and what...

Basically as the title says, what type of fusion would give the highest number of neutrons for a given amount of power. Also am I correct in assuming that most fusion methods will always produce more neutrons than other neutron sources such as americium-beryllium? (There are probably some...

Hello all. I'm am a first time poster but a long time visitor. I am having a little trouble that I was hoping someone far wiser and more knowledgeable than myself might be able to help with. I've been using MCNP to investigate criticality in a simple geometry consisting of a central natural...

Will black dwarfs eventually quantum tunnel into neutron stars if proton decay doesn't occur?

I'm wondering about the visual appearance of neutron stars up close. Do they continue to emit light like a white dwarf? Can cooled ones be gray or black? The xray emissions from pulsars will not be visible to us. Due to their high mass, they will bend light in a similar manner to a black hole...

In the early universe electrons and protons would combine to form neutrons and few, if any, protons would remain. If the mass difference were greater than the binding energies of nuclei, neutrons inside nuclei would decay leaving no nuclei behind. Does anyone know why the above...

I thought others might be interested in this: http://arxiv.org/abs/1011.6142 As a nuclear physicist, I don't find it surprising to hear that neutron stars are superfluid. Nuclei are superfluid. I'm not clear on the relationship between superfluidity and cooling. Can anyone explain this using...

I know that nuclear fusion is the source of energy for our sun and most of the other stars. Neutron stars and white dwarfs have very high surface temperatures. What is the source of their energy?

Hi, I have been wondering about a neutron dipole moment, though hypothetical what symmetries would it be violating, wouldn't it be Parity and Time reversal? If this were to be true, would it therefore make the statement below false and the word "inverted" would imply parity? "T is the law of...

I believe the neutron decays with a half life around 12 minutes via the weak mechanism. I'm wondering what causes a particular neutron to decay. At the moment the neutron decays, has it encountered (run into) a stray weak field? Or ... does the neutron decay just because of internal forces...

Homework Statement A helium-4 nucleus (rest mass 4.00151 u) is formed when a helium-3 nucleus (rest mass 3.01493 u), stationary in the laboratory frame, captures a slow neutron (rest mass 1.00867 u), in the following reaction. 3He+n→4 He+γ Determine the energy (in MeV) of the γ-ray in the...

First of all, I know that that very large stars tend to form black holes, and smaller stars, but still massive in comparison to our sun, tend to form neutron stars. My question is, if matter is lost when a star collapses into a black hole, but can still form one, why is it that it is a star...

What are White Dwarfs & Black Dwarfs? And what are Chandrasekhar's limits? Also I want to know about Neutron Star.

Homework Statement A neutron moving with a speed v makes a head-on collision with a hydrogen atom in ground state kept at rest. Find the minimum kinetic energy of the neutron, for which inelastic collision may take place. Mass of neutron = Mass of Hydrogen = 1.67 x 10-27kgThe Attempt at a...

Just want to see if I got this. When a neutron comes into contact with a nucleus of an atom, two things (that I know of) can happen. One is that the nucleus can absorb the neutron, this typically happens in lighter atoms due to the stronger force over the smaller nucleus being able to withstand...

How do we calculate the decay width or the mean lifetime of neutron/

Good day All, A quick question: (My knowledge / assumption): A neutron moves very fast and can go through almost anything, right? What will happen if said neutron enters a very cold (as close to zero kelvin as possible) environment? (Will it slow down, etc?) TX

Homework Statement The problem is attached Homework Equations Absorption rate=flux*absorbtion absorption=cross section*neutron density neutron density=Avegadro number *density/atomic mass The Attempt at a Solution the problem is just simple but the problem i faced is just...

Could anybody advise me, where i can read about how to calculate radiation dose from neutron source for human body. Excuse me for a second similar topic.

Hi All. Could you help me with following: Homework Statement We have: Neutron source Cf-252 Activity of Neutron source Cf-252 = 200 kBq The thickness of the protection of water-based = 30 cm Weight of the man = 80 kg Distance to a source = 1 m Questions How to calculate the absorbed...

Hi I'm looking for a good description (high-school to 1st year level) why the ratio of protons to neutrons matters for stability. Single neutrons are unstable, but in a nucleus they are stable and the more nucleons you have the greater the strong force. So why can't you have stable isotopes...

The proton activation data file/s contain the target and product data plus the cross sections at a range of energies, so the reaction rates can be calclated. The only neutron cross section data files I have found have just the overall cross sections. Are there any files available that give the...