The neutron is a subatomic particle, symbol n or n0, which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one atomic mass unit, they are both referred to as nucleons. Their properties and interactions are described by nuclear physics.
The chemical properties of an atom are mostly determined by the configuration of electrons that orbit the atom's heavy nucleus. The electron configuration is determined by the charge of the nucleus, which is determined by the number of protons, or atomic number. The number of neutrons is the neutron number. Neutrons do not affect the electron configuration, but the sum of atomic and neutron numbers is the mass of the nucleus.
Atoms of a chemical element that differ only in neutron number are called isotopes. For example, carbon, with atomic number 6, has an abundant isotope carbon-12 with 6 neutrons and a rare isotope carbon-13 with 7 neutrons. Some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes.
The properties of an atomic nucleus depend on both atomic and neutron numbers. With their positive charge, the protons within the nucleus are repelled by the long-range electromagnetic force, but the much stronger, but short-range, nuclear force binds the nucleons closely together. Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen nucleus. Neutrons are produced copiously in nuclear fission and fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes.
The neutron is essential to the production of nuclear power. In the decade after the neutron was discovered by James Chadwick in 1932, neutrons were used to induce many different types of nuclear transmutations. With the discovery of nuclear fission in 1938, it was quickly realized that, if a fission event produced neutrons, each of these neutrons might cause further fission events, in a cascade known as a nuclear chain reaction. These events and findings led to the first self-sustaining nuclear reactor (Chicago Pile-1, 1942) and the first nuclear weapon (Trinity, 1945).
Free neutrons, while not directly ionizing atoms, cause ionizing radiation. So they can be a biological hazard, depending on dose. A small natural "neutron background" flux of free neutrons exists on Earth, caused by cosmic ray showers, and by the natural radioactivity of spontaneously fissionable elements in the Earth's crust. Dedicated neutron sources like neutron generators, research reactors and spallation sources produce free neutrons for use in irradiation and in neutron scattering experiments.
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...
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...
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...
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...
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...
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?
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...
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 =...
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...
Homework Statement
Calculate the energy released in the alpha neutron reaction for beryllium. The mass of beryllium is 9.012183u.
^{4}_{2}He + ^{9}_{4}Be \rightarrow ^{1}_{0}n + ^{12}_{6}C
Homework Equations
The Attempt at a Solution
Tried finding the total binding energy for both...
"neutron collides elastically with a helium nucleus"
Homework Statement
A neutron collides elastically with a helium nucleus (at rest initially) whose mass is four times that of the neutron. The helium nucleus is observed to rebound at an angle θ'2 = 40° from the neutron's initial...
Hi all. I am going to be doing an experiment involving neutron scatter. I am going to be firing fast neutrons into water and then detecting the thermal neutrons scattered. I am also going to look into thermal neutron capture where the hydrogen atom captures the thermal neutron and gives off a...
Despite sharing similar physical properties(neutron and proton having little variation in masses, protons and neutron being made up of quarks, both elementary particles are held together by the strong force) why is the decay time for like a neutron 10 minutes and the decay time for like a...
Hi, I did some calculations and I worked out the density of 1 neutron to be about 3.19887549*10^57 kg/m^3. However, I want to know if the method I used is correct.
Density = mass/volume, correct?
If this is true, then
Density = [mass of neutron]/[volume of neutron]
I found the volume of a...