I have just finished up the Great Courses class on Nuclear Physics and I’m curious about the “stickiness ” of protons vs. neutrons. Does anyone have a graph of neutron/proton cross-sections vs. a range (sorry, a *domain* for you math purists out there) of energys? Any nucleus will do (H-1, H-4, or one of the stable leads preferred, but I’m not a stickler here).
What is a reliable source for obtaining fusion, capture and scattering cross-section data?
My hand-waving, back-of-a-napkin understanding of these things would suggest the more energetic the neutron, the higher the probability of interaction as the de Broglie wavelength of the particle gets smaller.
However that's obviously not the case. So what's going on? Are other interactions besides the neutron absorption cross section dominating? Does one need to consider the opposite reaction, whereby the de Broglie wavelength of the nucleus is actually too large to interact with the neutron? I'm just speculating here...
As I understand it, the neutron cross section of an element is the approximate surface area with which a stray neutron can collide. I can't see how this is altered by anything else than the size of the nucleus, as the bigger the nucleus, the more nucleus there is to hit, right?
However that is not true. The neutron cross sections of various elements are graphed here: http://periodictable.com/Properties/A/NeutronCrossSection.html
As can be seen, there seems to be little correlation between neutron cross section and atomic number (and therefore nucleus size)
So why do some elements, such as oxygen, have such a small neutron cross section? What forces are at work here? I don't think it can be electric charge because neutrons are neutral.
Also I've read that they use Zirconium (n=40) (b=0.184) in nuclear fuel rods because it has such a small neutron cross-section... but other solids such as Silicon (b=0.166), Lead (b=0.171), and Bismuth (B=0.034) are significantly lower, yet are not used. Is this because alloyed Zirconium is a better compromise with structural strength?
Thanks in advance!
I am aware that it is far from the magic numbers. Does this mean that it has a half filled shell, therefore making it more probable that it will capture a neutron?
I can't quite justify why that makes it more likely. Perhaps the outer shell requires a lower energy of incoming neutron to absorb it? ... Because the shell is half full?
Any clarity on the matter would be appreciated. Sorry for the confused post
Hi all, i'm learning abut Boron Neutron Capture Therapy, and i'm a little confused as to why 10-Boron has such a high thermal neutron cross-section. In looking at the values for each element on the periodic table and i see no discernible pattern between elements. Why is this?
The concept of the cross-section confuses me a lot, its given in units barns (area) but its a measure of probability.
Hi!
I'm the founder and main admin of ArdaCraft, a server which seeks to re-create J.R.R. Tolkien's Middle-earth in Minecraft. We've been running since 2014 and have garnered quite a bit of attention in the Minecraft community (and internet in general) for our scope and attention to detail. Here is our official trailer, which should give you a good overview. We were also recently featured by Nerd of the Rings on YouTube and got over 300k views.
The reason I'm posting on /r/geology is that we’d like to up our game by bringing a semi-realistic version of Middle-earth’s geology to life as part of our recreation. None of us are trained geologists however, so I’m turning to this community in the hope that someone might volunteer to help!
A paper published in 1996 theorised where plate boundaries and faults would be located in Middle-earth, as well as drawing many other conclusions based on evidence in the text. The aim would be to transform the findings of this paper into a basic map which indicates which rock type would be found where (on the surface). Several years ago a trained geologist did this for localised areas on our map - this is an example of the sort of thing he used to do. We already have a heightmap of Middle-earth which can be used as a basis.
Builders on our server have learned a decent amount about geology over time – including features like limestone pavement, calcite caves, and glaciers with medial moraines - and I'd like to continue that legacy as much as possible. If you play (or have ever played Minecraft) and like The Lord of the Rings, you'd be a perfect fit!
Many thanks for reading.
I understand that no stealth aircraft is literally invisible; they are just very hard for radar to see. But what exactly does it mean when people say that stealth aircraft have minuscule RCS's? People always say the F-35 has an RCS of a pebble. If an adversary noticed a bunch of pebbles floating at 20,000 feet, wouldn't that adversary assume these are stealth aircraft? Or is the point that it is basically impossible for radar to pick up pebbles that are floating at 20,000 feet? Does a small radar cross-section make it more difficult for an adversary to gain a weapons-grade lock, as opposed to just spotting it on radar? By this I mean, maybe an adversary might know where an F-35 is without being able to launch an AMRAAM at it? Could a small RCS make it so that the adversary has a general idea of the direction in which an F-35 is located without knowing its precise location? Does the size of the RCS have relevance when it comes to AAM or SAM threats? Is one more perceptive than the other?
I have just finished up the Great Courses class on Nuclear Physics and I’m curious about the “stickiness ” of protons vs. neutrons. Does anyone have a graph of neutron/proton cross-sections vs. a range (sorry, a *domain* for you math purists out there) of energys? Any nucleus will do (H-1, He-4, or one of the stable leads preferred, but I’m not a stickler here).
What is a reliable source for obtaining fusion, capture and scattering cross-section data?
What is a reliable source for obtaining fusion, capture and scattering cross-section data?
