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Publisert Legg igjen en kommentar til I f****d up…
...or maybe not that bad - but I admit that I didn´t manage to see the advent calendar through :/ I blame christmas, though 😉
And, I guess, the fact that the last month probably has been the busiest one in a while - and in addition to rest of the christmas present wrapping that has to be done, there´s also the travel bill from the trip to Berkeley and a backlog of about 100 e-mails (that I should do today). Next year I´ll be more prepared for the advent calendar, so hopefully it will be even better than this year 😛
Anyway, here are some snaps from my livingroom in Rose-slottet (Rose castle <3) last night and now - in ten minutes, or so, Alexandra will come, and we will fix the rest of the presents together, and suddenly my dad will be here, and then we´re driving home for christmas 😀

Publisert Legg igjen en kommentar til Number 18
So, in the calendar today there are gammas (gamma radiation) - I´m giving you an ALFNA matrix 😀 xD <3
The ALFNA matrix/plot is a sort of 3 dimensional plot where there is the excitation energy of some nucleus (we don´t know which one - and this is what we/I try to figure out) on the y-axis, and on the x-axis is the energy of the gamma(s) the nucleus sends out. The thing is that when a nucleus is hit by a particle, the nucleus is excited, or sort of heated - it gets some extra energy, and to get rid of that extra energy it sends out  gamma radiation. 
From earlier experiments that have been done (the bible is here) we know quite a lot about what kind of gammas (which energies) the different nuclei will emit when they are excited to this and that energy. In this particular ALFNA matrix we believe that we have oxygen-17 (there is always some oxygen 🙂 ) and beryllium-10 (the backing of the uranium foil/target is made from beryllium). The oxygen-17 peak for example, is supposed to emit a gamma ray with an energy of 870 kilo electron volts (keV), and here it is at around 1300 keV - which means that we are quite off, and everything needs to be calibrated (which is exactly what I´m working on now 😉 ).
So this is the plot I´ve been staring at today (together with my supervisor, Sunniva <3). 
...and I´m staring even more now (pretending to have a really huge brain) - looking like this 😛

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Publisert 2 kommentarer til Number 16&17…
Again I didn´t manage to make the calendar blogpost yesterday - and again I´m very sorry :/ Again I give you two for the price of one - to make it up 😉

Again there are cross-section graphs in the calendar - cross-sections are really important <3 (Later, maybe I should do a blogpost about these nuclear cross-sections;  what they really mean...)
Today there are two different cross-sections, for two different uranium isotopes (different "versions" of uranium). Both pictures show the cross-section/probability that the nucleus will fission (in blue) or capture (in red), when hit by a neutron.
Both graphs show the cross-section on the y-axis, and the energy of the neutron hitting the nucleus on the x-axis.

Uranium-238 is not a fissile nucleus; the probability that it will a capture a neutron is much bigger than the probability (cross-section) that it will fission...:(
Luckily the situation is different for the uranium-235 nucleus; the probability that this nucleus will fission when hit by a neutron is bigger than the probability that it will capture (and "eat") the neutron <3 *smiling*

Publisert Legg igjen en kommentar til Number 15
Only 8ish days ´til Christmas now...and in todays calendar is another cross-section graph - this time it´s the cross-section/probability of neutron capture on uranium-233:

On the y-axis is the value of the cross-section (the higher the number, the higher the probability of a neutron being captured by the nucleus when hitting it), and on the x-axis is the energy of the neutron.
But there are several graphs here...and they all show different values for this cross-section - the truth is that we don´t exactly know what it is (my research is into this...) :/ The blue, turqoise and red lines are the "official numbers" (evaluated nuclear data), the different dots are actual measurements (some with HUGE error bars), and the green line is calculated with the default input parameters about the nucleus.
It´s quite an important cross-section for the thorium fuel cycle, since it tells us about the probability of a neutron being captured by uranium-233 instead of making it fission (which is what we want it to do) - so it would be nice to know it better 😉

Publisert Legg igjen en kommentar til 13 + 14
So, yesterday I didn´t get the chance to share a graph, so today you´ll get a double dose 😀
Also, I got a complaint that the last graphs didnt´have any christmas decorations on them - so I´ve tried to do better this time...;)
Today you get two versions of ALPHA! 
ALPHA is the "capture to fission ratio" - it tells us how often a neutron is captured/absorbed, rather than causing a nucleus to fission. We want ALPHA to be as low as possible - since a low ALPHA means that little waste is produced 😀
First there is ALPHA for neutrons with low energy:
The red line is for uranium-233, and the blue is for plutonium-239. For low-energy neutrons, ALPHA is lower for uranium-233 than plutonium-239, and this means that there is a smaller waste production from thorium-fuels than uranium...IF the neutrons have a low energy/are thermal (this can´t be said often enough 😉 )!
Then there is ALPHA for neutrons with high energy - and here it changes (as it also did with ETA):
For neutrons with high energy the waste production is smaller for uranium-fuels than with thorium...

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Publisert 2 kommentarer til The 12th of December
Today is December the 12th, and in the calendar is the rest of what I gave you yesterday - it´s ETA again, but this time it´s ETA for neutrons with high energy (fast neutrons). The graph is very important for the neutron economy of a nuclear reactor...
ETA tells us about how many neutrons you get out for each neutron going in (to a nucleus) on average ("neutrons emitted/neutrons absorbed"). As you can see you get, on average, more neutrons from fission of plutonium-239 (blue line) than you get from uranium-233 (red line) - if the neutron going in has high energy/is a fast neutron. In other words: it´s exact opposite of what was in the calendar yesterday...!
So, since plutonium-239 is a better fissile material than uranium-233 (when hit by high-energy neutrons), you can produce more new fissile material from uranium, than you can from thorium 😀 Or, to sort of conclude: for thermal neutrons, thorium seems to be the way to do it, bur for fast neutrons, uranium/plutonium seems to be the way to do it <3<3<3

Publisert Legg igjen en kommentar til Number 11
In the calendar today is a graph that is very important for the thorium fuel cycle... 
Today I give you ETA!
ETA tells us about how many neutrons you get out for each neutron going in (to a nucleus) on average ("neutrons emitted/neutrons absorbed"). As you can see you get, on average, more neutrons from fission of uranium-233 (red line) than you get from plutonium-239 (blue line) - if the neutron going in has low energy/is a thermal neutron.
So, since uranium-233 is a better fissile material than plutonium-239 (when hit by low-energy neutrons), you can produce more new fissile material from thorium, than you can from uranium 😀 We like that <3<3<3

Publisert Legg igjen en kommentar til Number 10
In Berkeley it´s 3 PM December 10th, so it´s not too late with todays calendar graph 😉
In the calendar today is a very important and very preliminary plot - of the gamma ray strength function of uranium-234. Inside the heart is a little "bump" that is actually really important, and you will get a much better plot of this later (when the analysis is finished) - and also an explanation of what it is...but be patient, and remember that the advent season is about waiting 😉

Publisert Legg igjen en kommentar til December 9th
In the calendar today there´s a super nice graph I didn´t make myself, but I have of course made it even prettier than it already was 😉
Todays graph is a so called "cross section graph" for uranium-235.
The cross section sort of tells us about the probability that something will happen to a nucleus; in this case it´s about the cross section/probability that uranium-235 will fission <3 
On the x-axis is the energy of the neutrons hitting the uranium-235 nucleus, and on the y-axis is the cross-section. As you can see the cross-section is much bigger for low energy neutrons than for high energy neutrons - this means that there is a much much bigger probability for a nucleus to fission when it is hit by a neutron with really low energy.