Neutron Definition and 746 Threads

I am a graduate student and I am thinking of doing a project on "Inelastic neutron scattering and density functional theory". Can you please inform me what are the exact background knowledge(courses) I should have to.

Ok so the equation for the probability that a fast neutron will not leek out of a non infinite mass is Pfnl= exp(-(Bg)^2 Tth) so Bg is the geometric buckling and for a sphere that value is (pie/r)^2. My question is what is exp? And what is Tth / how do I get the value of it?

I was curious as to the difference in free neutron decay and the lack of decay when bound in a nucleus. I found the following statement here http://en.m.wikipedia.org/wiki/Neutron#Free_neutron_decay I don't understand that. Is the wave function of the neutron different when free or bound...

Ok so I recently read this article (http://www.extremetech.com/extreme/184280-focus-fusion-has-cheap-clean-earth-saving-fusion-power-been-right-under-our-noses-all-along). This gave me a few ideas and a few questions. I would like to create a smaller version of this setup to fuse deuterium into...

The question is attached. I'm not sure how to approach to part (b). The energy released could be in 3 forms, the rest mass energy for those matter ejected during supernova explosion, the binding energy released as the atomic structure changed, the ejected matter carries off some kinetic...

Here is my understanding, please correct me if I am wrong, thanks At the end of the giant stage of a star, it experiences a supernova explosion, and turns into a neutron star (could be pulsar) or black hole, the explosion releases a lot of its matter. Here is what I don't understand: 1...

Hi thanks for reading. Is it possible to derive an explicit formula for the neutron scattering cross section as a function of energy and angle of incident and scattered neutrons respectively? This is for a (n,p) elastic collision with H-1 as the target.

p + n -> p + n + ∏^- check charge conservation: + 1 + 0 = +1 + 0 -1 it doesn't equal so it wouldn't be possible? please could someone suggest why this is, or if I'm doing something wrong? thanks in advance. edit is it because the pion is the force carrier therefore should not be...

If a neutron is unstable outside the nucleus, then what makes it stable within the nucleus? Does the binding of particles together somehow make them stable? Neutrons decay via the weak force, but are bound in the nucleus by the strong force. Does the strong force inhibit the weak force...

Consider an atom having multiple protons and neutrons in its nucleus, which of the two nucleons will have higher magnitude of potential energy?

So, I was disappointed to find out that the surface of a neutron star is at 1 million kelvin, not 100 billion kelvin. I did some calculations a while back using the 100 billion K as a temperature (the core temperature of a neutron star), and found that it would be emitting more radiation than...

This is related to a homework problem but I want to understand it as well. How can a proton break up into a positron and neutron when a neutron clearly has a greater mass than a proton?

The most probable velocity of thermal neutrons can than be approximated by the Boltzmann constant and is given by the following: v = sqrt (2kT/m) where k is the Boltzmann constant T is the temperature m is the mass of the neutrons My question is why is the above equation not the...

Homework Statement Estimate the neutron energy needed to produce fission of 208Pb. Is it likely that such neutrons woould be released in the resulting fission? Homework Equations Eexcitation=Qexcitation+Tn Qexcitation=[m(208Pb)+mn-m(209Pb)]c2 V=(e2/4πεo)(Z1Z2/r)...

I'm in year 10 and I have been studying physics and chemistry. When I learned isotopes, I notice that for isotopes, the number of neutron is always higher than that of proton. Is it possible that there are isotopes that the number of neutron is lower than that of proton? If no, is that because...

Hi all Can someone please describe how the form factor used in Rutherford scattering is applicable to neutron probing of nuclei? Also, is the kinetic energy required to probe a given radius simply given by the de Broglie wavelength where momentum, p >= h-bar / Radius ? (Relativity...

Hi everyone! First of all, I'm a brand new member and am looking forward to spending time on this forum, learning a bit more about science, and getting to know some of you. Anyway, here's what's been on my mind lately: I've heard that a thimbleful of neutron star material weighs as much as a...

Stimulated virtual W+, W- when supernova core--> neutron star? Weak interactions allow supernova core electrons and protons to convert to neutrons and neutrinos allowing (under the right conditions) the formation of a neutron star? Large numbers virtual W+ and W-bosons are produced in a short...

I have to figure out how to prove that the neutron flux for a point source is given by ø=\frac{S}{4πr^2}. I can get this type of solution, but I have an e^(-r/L) in the numerator. I'm assuming I'm missing some theory somewhere as apparently this is the solution for a point source in an...

Hello All I'm doing my theses in BNCT(Boron neutron capture therapy).I did it with 2.5 Mev imaginary accelerator. there are many reactors to compare my data with theirs.but Unfortunately I couldn't find some Real accelerators based on BNCT to compare my MCNP-X output data with theirs. could u...

Homework Statement U → Th + α The speed of α = 6 x 105 m/s. Find the speed of neutron of Thorium! Homework Equations E = mc2 momentum The Attempt at a Solution I am pretty sure there is missing information, maybe the mass of α and Th. I just want to ask the way to solve it...

Hi All, I am preparing for PhD quals and have been looking at problems from other universities. I came across this one and am stumped on how to tackle it. " Assume that the neutron density in a neutron star is 30.1/fm (that is 0.1 neutron per cubic Fermi). Assuming T=0 and ignoring any...

Yesterday, I read about Hawking's new proposal regarding the firewall paradox. A more general thought about standard black holes occurred to me. Black holes including stellar black holes are of course always presented as if the event horizon is an invisible barrier, which the unfortunate...

I've been reading about fast reactor designs lately (not necessarily ones that have actually been built). A few articles I've come across < https://drive.google.com/folderview?id=0B-MNeRy61MgpTVExcUQ3T3ZWWG8&usp=sharing > discuss the possibility of building fast reactors, fueled with molten U...

Hello everyone. I need a hint of how to do the following question. I spent long time trying to solve and I could not do it. An ionization chamber that will be used to measure fast neutron absorbed dose rate consists of ethylene (C2H4) gas at a density of (1.2×10^-4 g/cm^3) enclosed by...

So how much denser than is a neutron star than an atom? Is it called a neutron star because electron's orbital effect no longer exists/acts the same, so as to no longer cause 99.99% of everything to be space?

Homework Statement Suppose that an earth-mas object collides with a neutron star with radius 10 km and mass 1.4 $M_{sun}$. The material of the earth-like object would wrap around the neutron star and form a thin layer on top of the original neutron star surface. Assume the material gets...

1. 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 '2 = 41° from the neutron's initial direction. The neutron's initial speed is 5.6 105 m/s. Determine the angle at...

Hello People I need help with the following assignment: It states: Consider an ideal moderator with zero absorption cross section, Ʃa = 0, and a diffusion coefficient, D, which has a spherical shape with an extrapolated radius, R. If neutron sources emitting S neutrons/cm3sec are distributed...

How many neutrons are in a neutron star with a diameter of 42.0 km? I was under the impression it was just (42.0e3/1e-15)^3 = 7.0048e58 but that's wrong??

Homework Statement The Crab Nebula is a cloud of glowing gas about 10 light-years across, located about 6500 light years from the Earth (the figure (Figure 1) ). It is the remnant of a star that underwent a supernova explosion, seen on Earth in 1054 a.d. Energy is released by the Crab Nebula...

Simply put, either by chance or a suicidal type-III Civilization, 2 neutron stars, or a neutron star an a large-ish main sequence star are thrown at each other and fall STRAIGHT into each other. What happens? Does the ~1.4 C Newtonian impact speed result in them getting blown up and releasing...

Assumptions 1) a=absorption 2) f=fission 3) ∅=neutron flux 4) time independent 5) group 1, fast neutrons 6) group 2, thermal neutrons 7) All fission neutron are boring in fast group 8) All neutrons created by thermal group, thus vƩf2 exists vƩf2 does not 9) Down scattering occurs but up...

If a fast moving thermal neutron can be slowed down to increase absorption chances, is there a way it can be brought a halt? If yes, what will be the behavior of such neutron?(Apart from a simple fact that reaction comes to a halt)

What is the force that makes a neutron eject an electron, and how strong is it?

I have make many threads about this topic because I am really interested. I reading that from an pdf,but I have some "idiot" questions too. 1)A guy told me that If you run in other speed from an other you see his clock slower. I have hear about paradox of twins,that this with biggest speed...

I thought readers would be interested in this interesting article today on black hole and neutron star mergers and the very small possibility of instantaneous sterilization and extinction of all life on earth:http://www.space.com/22231-gamma-ray-bursts-neutron-stars.html...

Homework Statement A parallel beam of neutrons with speed 200m/s is incident on an absorbing sheet with a slit of width 0.01mm. Calculate the width of the beam 10m behind the slit. Hint The slit localizes the neutrons transversely (y) to their propagation direction x. The resulting ΔPy gives...

I have a book on nuclear reactions which details the mean free paths for thermal neutron scattering as: 0.37cm for water and 2.2cm for heavy water The transport cross sections are listed as 0.45cm for water and 2.6cm for heavy water. Does anyone know how to calculate these from the thermal...

Hi all, this is my first post here and i apologize if some rules aren't followed. I have to complete the Project 13.1 (studies of neutron stars: p 346-350) http://www.cec.uchile.cl/cinetica/pcordero/MC_libros/Hjorth-Jensen2008.pdf When browsing using pdf pages 346 to 350, assignments 1...

Can anyone help me with an approximate answer to this or point me in the direction of avenues to get an answer to this? This has practical applications and is potentially worrying. Roughly how much (or how many atoms) of cobalt-59 exposed to the average neutron radiation at in-flight...

Hey Everyone, I'm working on a question and can't quite get the answer out. QUESTION: Part (a) "\left|\alpha\right\rangle and \left|\beta\right\rangle are the eigenfunctions for neutrons polarized respectively along positive and negative z directions. If the neutron, initially in...

I want to know the reason why the thermal neutrons with energy of 0.0253eV is so important. As far as I know, a neutron with an energy of 0.0253 eV is used as reference to measure nuclear cross sections such as absorption, fission, scattering, etc. And I want to know the details and more...

Homework Statement Solve for the flux distribution using the 1D neutron diffusion equation in a finite sphere for a uniformly distributed source emitting S0 neutrons/cc-sec. My problem right now is that I can't figure out the boundary conditions for this problem. We usually work with...

Problem: A flux of 10^12 neutrons/m^2 emerges each second from a port in a nuclear reactor. If these neutrons have a Maxwell-Boltzmann energy distribution corresponding to T=300 K, calculate the density of neutrons in the beam. Solution: The average velocity of neutrons coming from the...

Homework Statement The equation for the "average" velocity of a gas molecule in a closed container is: Vrms = ( 3 x k x T / m )^ 1/2 where k = 1.38 x 10 ^ 23 Joules/K T is temp in Kelvin m = mass per ion in kg = Atomic Mass M / Avagadro's Number Na so for N2, I...

When paraffin wax (or borated paraffin) is bombarded with neutrons, what does the paraffin emit? (If memory serves me correctly I think it emits protons...?) Also what are typical energies that the emitted particles have?

Simple question, please help. I think it belongs in this forum, though I apologize if there's a nuclear physics forum or somewhere else I should put this. I came across this thread when trying to figure out why electrons don't rest at zero distance away from the nucleus of an atom. So as I...

Dear all, I'm starting to study neutron star accretion and a lot of physical phoenomena coming from different scales come along and a consistent picture is frankly hard to grasp. But for now, a real mind boggling question can't exit my mind. Are Neutron stars, as a whole Quantum, or...

Consider a fissile element whose magnitude is at the order of a neutron. In this situation, how can we derive the point kinetic equations? Thanks everyone.