Neutron Definition and 772 Threads

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?

I have been wondering recently about the neutron dipole moment, after looking it up with the limited things available on the internet (to my knowledge anyway :) ) I have a few questions hopefully someone could answer for me. Firstly of the three symmetries, as I understand it, Parity, Charge...

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...

Homework Statement I'm taking an independent study course at my college in which my professor and I have decided to make a neutron spin flipper. To do this, I've got to solve Laplace's Equation for a cylindrical shell of (obviously) finite length and thickness. Can I assume azimuthal symmetry...

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...

If proton decay does not occur, are neutron stars immortal? I was hearing that that was the case.

Homework Statement Calculate the energy of a neutron wavelength 0.1nm Homework Equations The Attempt at a Solution let L = lambda So i just use E = hv/L L = hv/E But how do i write v in terms of E? isn't E the total energy rather than just kinetic...

Does anyone know where I can find good tables for low energy nuclear processes? For example collisions to products like: - proton into a material yields neutrons - neutron into a material is captured to give different element - electron into a proton yields a neutron etc. Here's an example type...

I don't know much about quarks but if a proton is uud and a neutron is udd, is the (mass of a neutron)-(mass of proton)=mass of a down quark?

Can we calculate the difference in mass between a Proton and Neutron? If so, how? [ Moderator: why did you move this from QM to general physics? ]

Hi, I'm having some trouble interpreting an equation. In Lamarsh's Introduction to Nuclear Engineering. The formulae for neutron attenuation is: I(x) = I_{0} exp(-\Sigma_{t} x I am given the formulae \frac{-dI}{I(x)} = \Sigma_{t} dx This formulae has been described as "the probability of a...

http://www.physorg.com/news/2010-11-laser-neutron-yield-energy.html DT produces 17 MeV per fusion, so that's an output of about 800 joules; a factor of about 150X short of break even for energy applied to the target, and perhaps ~1000X short of the gain required for a practical fusion power...

How much energy does a neutron need to be able to split an atom and start nuclear fission?

A letter in the current issue of Nature: ==quote== A two-solar-mass neutron star measured using Shapiro delay P. B. Demorest1, T. Pennucci2, S. M. Ransom1, M. S. E. Roberts3 & J. W. T. Hessels4,5 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22093, USA...

When a neutron star flucuates into a black hole does the gravity increase tenfold? Or does the neutron star gravity (while turning into a black hole) increase as expected with the addition of more mass?

Homework Statement Verify the following equation \frac{E^{1}}{E}=(\frac{A-1}{A+1})^{2} Where A is the atomic mass of the target nucleus hit by an incoming neutron, E is the energy of the neutron before collision, and E^{1} is the energy of the neutron after collision. Please note that the...

Homework Statement Suppose you want to observe neutron diffraction in a crystal with 0.27nm spacing between lattice planes. Part A asks for the momentum of neutrons with a wavelength equal to the spacing. I used p = h/lambda to get the correct answer 2.5×10−24kgms-1 Question1: Find the...

Dears I know that the neutron diffusion coefficient D= (The transport mean free path/3), but in some documents i read that:( D=The transport mean free path*v/3) where v=The neutron number. How is that?

Is there any direct evidence that black holes are smaller in size than (less massive) neutron stars?

Hello, I am looking at scattering cross sections for neutrons. From basic scattering theory and the partial wave expansion I have understood that the reaction and scattering cross sections are dependant of each other. There can be scattering without reactions but only 1:1 the other way around...

Firstly, I would like to say hello to everyone as this is my first post. I am an artist working a personal project that will be a visual investigation into the effects of a collision between a Neutron Star and Earth. The star would have a fully collapsed core at 1.5 solar masses (maybe...

Hi all I have been searching the internet but not with much luck. What can be expected to happen when a tritium is bombarded with a neutron of suitable energy? Will a neutron be knocked off or not? Regards bmeagle

Homework Statement The energy that binds an orbiting electron to the hydrogen nucleus is 13.4 eV. Calculate the ratio of the binding energy per nucleon to the binding per electron in deuterium. Which particle is held more tightly, the electron or the neutron? Homework Equations using...

If black holes are not real, just wondering? By the way they may or may not exist. But since some people don't believe they exist and some do, then if you DO NOT , how do you explain what happens to neutron stars that are 20 -25 the size of the sun? typo in the title, it should read: " what...

Hi guys. I have a small question and i would appreciate your help. I want to find how many neutrons per second (in 4π) are produced from a neutron generator. The generator works with T(d,n) reaction.. We have 0.5 mA d at 100keV energy that hits a target of titanium-tritium that has 2*10^20...

I always here about neutron stars and black holes sucking the gs from their companions. However, a star loses mass before it becomes a neutron star so I don't understand why it afects its neighbor more when it is a neutron star than when it was a regular star.

Homework Statement If a neutron star were bright enough to see its surface with a telescope, we'd be able to see not just the hemisphere facing toward us but also part of the far hemisphere. Explain why and estimate the latitude above which the far side could be seen. Homework Equations...

Dear all I have done some studies trying to understand the relation between the QCD theta angle and neutron electric dipole moment. General, the QCD vacuum produces the term L_{\theta} = \theta g_s^2\: G_a^{\mu\nu} \, G^a_{\mu\nu} this I can derive! I have studied Srednicki ch 93, Ramond...

Homework Statement Moderating a Neutron In a nuclear reactor, neutrons released by nuclear fission must be slowed down before they can trigger additional reactions in other nuclei. To see what sort of material is most effective in slowing (or moderating) a neutron, calculate the ratio of a...

What causes the neutron to have a magnetic moment , and is it paramagnetic or diamagnetic.

How can you measure the mean density of a neutron star if your only told its mass is three times that of the Sun?

Homework Statement What is the de Broglie wavelength of a neutron whose kinetic energy is equal to the average kinetic energy of a gas of neutrons at temperature T = 17 K? Homework Equations lambda = h/p = h/mv. The Attempt at a Solution Well first I tried taking the h =...

Does a moving neutron have an electric field ?

Homework Statement I have an assignment question that asks the me to look up the partial mass attenuation coefficients for Beryllium for Rayleigh Scattering, Compton Scattering, the Photoelectric Effect, and Pair Production in both the nuclear and electron fields on the NIST database for...

Hi guys, I am trying to calculate the macroscopic cross section (scattering and absorption) for high energy neutrons between 1 MeV and 10^7 MeV in Silicon. I am using the macroscopic cross section to determine the mean free path. To calculate the macroscopic cross section, i need to know the...

Neutrinos can pass through solid objects like the Earth easily, and a light-year of lead would only stop half of them from passing through. What about something very dense like a white drawf or neutron star? How readily can neutrinos penetrate that? What % flux reduction would be achievable...