Chapter 358 This chapter actually reveals a truth (Part 1)
Cold atom research.
It is not difficult to see from the literal meaning that this refers to the study of atoms under ultra-low temperature conditions.
Students who did not fail high school chemistry should know this.
The most direct reflection of the temperature of an atom is the speed of the atom.
That is to say, there is a positive correlation between the two.
Room temperature.
The atoms move very fast, sliding around like Yasuo, and the question marks can't keep up with them.
To study the physical properties of atoms, we need a stable single atom or atomic group that will not wander around.
so what.
When studying atoms, you need to cool them down, that is, "freeze them."
Normally, research requires the temperature of atoms to be near u.
However, due to cost issues, in many cases it is not necessary for the entire experimental device to be at a temperature of u.
Therefore, normal research groups working on cold atoms will use lasers to cool atoms.
That is, a small area is cooled.
In later generations, some Japanese restaurants also liked to do this kind of work, but instead of cooling it, they heated it - the middle part of a piece of fresh beef was grilled, and the other parts were raw. It was euphemistically called "Sizzling Heart Beef Sashimi".
Xu Yun doesn't have much prejudice against this way of eating, but for more than 50 yuan per piece, it challenges the bottom line of people's IQ.
The topic returns to its original place.
At present, most of the principles for cooling lasers are Doppler cooling, and the principles are relatively complicated, so I won’t go into details here.
In short, this thing can reduce the temperature of atoms to very low.
But the final result of cooling is just to slow down the atoms. Although the atoms slow down, they are still scattered disorderly throughout the cooling area.
It's like you have demarcated a long highway and made all the cars in it lose power and stop in place. But if you want to study these cars, you still need to gather them together.
So at this time, another technical method is needed.
That is the magneto-optical trap.
The magneto-optical trap is referred to as the magneto-optical trap, codenamed t.
Among the top 100 microscopic experiments selected by Nature magazine in 2019, the magneto-optical trap ranked 58th. It is a very, very exquisite experimental design.
It uses magnetic fields and light fields to slowly make particles controllable and aggregated.
The specific method is to install a pair of anti-Helmholtz coils in the z direction, so that the magnetic field is distributed along the radial direction in the xy plane.
The magnetic field in the positive center is 0. Where the magnetic field is not 0, Zeeman splitting will occur.
The energy level of filling splitting is ae=gubbz/h, and the size of energy level splitting is related to the size of the magnetic field, and the size of the magnetic field is related to the spatial position.
So in the presence of t, the two-level atom will experience a force of ft.
At this time, two opposing beams of circularly polarized light are applied. When the magnetic field is forward, compared with the light of - , the light of - has less detuning and is closer to resonating with the atoms.
Therefore, the atoms will move along the direction of light propagation to a position where the magnetic field is close to 0.
The opposite is true where the magnetic field is negative, and the atoms will eventually be pushed to a place where the magnetic field is close to 0.
finally.
The atom will be trapped at the point where the magnetic field is 0.
This principle is very simple and easy to understand.
t can gather a lot of atoms, about tens of millions or more at a time, and the atomic density will be relatively high, about 10^93.
It's like a forklift pushing all the cars parked on the highway together.
Of course.
The experimental objects of traditional t are atoms. During the experiment, all atomic gases are added - yes, they are all gases. (I don't know if the concept of gaseous metal atoms is mentioned in current textbooks, but I think it is there)
Unlike atoms, Xu Yun and the others need to consider isolated point particles this time.
The two cannot be compared in terms of volume or difficulty, but the solitary point particles are also electrically neutral, so the solitary point particles are one of the very few particles that can be condensed using the t principle.
It’s just a matter of words (this chapter is not finished yet!)
Chapter 358 This chapter actually reveals a truth
Well, after all, this is only theoretically feasible.
Whether the isolated point particle can be successfully brought to the ground state still depends on the final practical operation.
"Professor Lu."
Beside the operating table, Xu Yun was introducing his experimental ideas to Lu Chaoyang.
"My idea is this. First, we use evanescent waves to construct a light field with uneven light intensity inside the beam channel."
"Then, based on the light field distribution, we lay out the electric field with the same trend."
"In this way, the difference in the dipole force generated by the evanescent wave at each point will cause the particles to keep jumping.
"Every time we jump, we slightly lower the trapping electric field, and the electrostatic repulsion between atoms will cause the charged particles to spread out, and the outer particles will escape.
"As for the isolated point particles, since they have no static mass and no charge, they will be permanently stored in the channel."
In layman's terms, Xu Yun's plan is comparable to shaking a dustpan in reality.
The particles after the collision of lead ions are equivalent to a mixture mixed with soil, seeds, bugs, and weeds.
If you want to classify them, the best way is to shake the dustpan.
As long as you design the appropriate hole size, you will always be able to shake out what you need in the end - nothing more than the specific strength and hole diameter.
Of course.
This explanation is just for the convenience of understanding. For industry insiders like Lu Chaoyang, there is much more to consider than just jitter.
He was silent for a moment, then looked up at Xu Yun
"The idea is generally feasible, but Xiao Xu, I have a question."
Lu Chaoyang said that he stretched out an index finger on each of his left and right hands and touched the fingertips.
"You see, the contact between fingertips is like two beams colliding with each other. There is no debate in this link, but
Then Lu Chaoyang straightened the originally curled thumb of his left hand, forming an equals sign with the extended index finger, and then the surfaces of the two fingers touched each other.
"But Xiao Xu, have you ever considered that lead ions in the same beam, that is, moving in the same direction, may collide or be excited due to the electric field?"
"If internal heavy ions collide, the subsequent direction will be uncontrollable."
A boy who was doing the work next to him heard this and nodded in agreement.
Lu Chaoyang's question is also not difficult to understand.
Just like on a frontal battlefield, two armies are launching missiles at each other, and the trajectories of each other's missiles are directed at each other.
But if during the flight of the missile, there is suddenly an additional force from the non-moving direction between the sky and the earth, and this force is large enough to affect the trajectory of the missile.
In this case, a situation is likely to arise
Before hitting the enemy's missile, our own missile's route was changed first, causing an internal collision.
Although the consequences of this collision are also explosions, they are obviously of no value - the purpose of launching missiles is to kill the enemy, not simply to watch fireworks.
Therefore this situation
It really has to be taken into account.
Otherwise, the entire experiment will become a joke, and Xu Yun's WeChat will also be greatly affected.
However, Xu Yun was obviously prepared for this situation. He picked up a pen and quickly wrote a formula on the paper.
exp(-|x|/x0).
Then he drew a horizontal line under the expression and stopped talking.
Looking at this gesture, a hint of astonishment appeared in Lu Chaoyang's eyes.
"This is"
A few seconds passed.
He suddenly let out an ouch and slapped his forehead hard
"Oh, look, why did I forget the deta potential well? Xiao Xu, then I have no problem."
The expression on Xu Yun's face did not change, but the slightly raised corners of his mouth still vaguely revealed his inner pride.
That's right.
Smart classmates must have figured it out.
The formula above is correct (this chapter is not finished yet!)
Chapter 358 This chapter actually reveals a truth
is the wave function of the bound state of a single atom in 1-dimensional space.
Based on this wave function, a situation can be clearly judged
When the distance between two atoms is less than twice the atomic radius, the energy of the antisymmetric state e>0, and the energy of the symmetric state =0.
The energy of free electrons is also 0.
This means that in this case, the symmetry state is already unstable and the electron can fly to infinity.
Therefore, when two lead ions are close to each other, they will naturally decompose rather than collide.
That is, at this time, they cannot be regarded as bosons.
The energy of decomposition and the energy of collision are two completely different magnitudes.
But then again.
Lu Chaoyang's misjudgment has little to do with his ability, but with the direction of the experiment.
In fact, particle physics experiments do not include Bose-Einstein condensates. In a sense, the two can even be said to be two extremes.
If it weren't for the special characteristics of solitary point particles, Lu Chaoyang would never have been exposed to this aspect at all.
So it is normal for him to make some mistakes in thinking.
The more you differentiate, the clearer it becomes.
Xu Yun then discussed some process issues with Lu Chaoyang, and after making no mistakes, they began to set up the experiment.
The production of cold atoms requires a high level of vacuum, generally around 1x10^-10ar.
Fortunately, this is not 1850, so it is not difficult to create such a vacuum environment.
"Dr. Tang Fei."
Xu Yun looked at the roster in his hand and read out a name
"It's up to you to arrange the anti-Helmholtz coil.
The Tang Fei in Xu Yun's mouth is a man in his early thirties, wearing a pair of gold-rimmed glasses, with short hair, and looks very capable.
Tang Fei is the youngest member of the entire project team after Lu Chaoyang. He is also a doctoral student trained by the University of Science and Technology. He is now a cutting-edge backbone of a research institute at the University of Science and Technology.
In fact, with Xu Yun's current status, he cannot hire seniors like Tang Fei who have already graduated and are working and have high abilities.
It just so happens that Tang Fei is currently in the critical period of being promoted as an associate researcher and needs some exposure and achievements to enrich his resume.
So I successfully joined Xu Yun's group through the introduction of Academician Pan, and Xu Yun missed the opportunity.
And even if they are divided into groups in the future, he will follow Xu Yun to work on projects.
Now that he received Xu Yun's instructions, Tang Fei immediately straightened his expression.
"No problem, leave it to me." (It's a fun thing to say. If I hadn't corrected the typo during verification, you would have seen "Marry me")
After Tang Fei leaves.
Xu Yun continued to give instructions
"Li Ruo'an, you are responsible for debugging the radio frequency field."
"receive!"
"Dr. Yang Kun, you take charge of the evanescent wave.
"clear!"
"Senior Zhang Han, you are responsible for observing wave packets - remember to set the parameters to odd multiples of 132."
"okay!"
"Senior Ye Zhi, you go and order takeout. You decide the taste. You don't want celery or coriander."
"!"
After allocating tasks.
Xu Yun and Lu Chaoyang waited at the console together.
In order to ensure that the project team can obtain efficient positive feedback after refining the division of labor these days, many project teams have gradually begun to equip spreaders.
This thing is about the size of two one-dollar coins, with a button and an anti-accidental touch switch on it.
After completing the task, release the anti-accidental touch switch and press the button again. A green dot will appear under the corresponding item on the main display, prompting the person in charge that the task of block xx has been completed.
It is said that the project team of a certain university in Yanjing also used the voice package of pangolin, which is so magical.
Xu Yun’s research team this time was equipped with a spread system.
over time.
The seven light spots in front of Xu Yun gradually changed from red to green.
About twenty minutes passed.
All the light spots turned green, one (this chapter is not over yet!)
Chapter 358 This chapter actually reveals a truth
Next to him, Lu Chaoyang snapped his fingers.
"Xiao Xu, you can summon the Dragon Balls."
Xu Yun
Ignoring the funny guy next to him, Xu Yun took a deep breath and said through the main microphone
"Attention all members, the ground state experiment of the lone point particle is about to begin. The countdown is three days.
"start!"
The moment I finished speaking and started.
This chapter is not finished yet, please click on the next page to continue reading the exciting content! Xu Yun pressed the switch on the main console.
Buzz buzz-
A beam with an order of magnitude smaller density than the first time rushes out of the beam tube.
And it's different from the first time.
Within 10^-12 seconds, a preset evanescent wave field enveloped them.
Phew~
A radiation pressure invisible to the naked eye appears.
at the same time.
The first wave of lead ions begins to collide.
Bang -
The two lead ions exploded instantly like Kennedy's head, and all kinds of things flew out.
Then another 10^-12 seconds passed.
When the anti-Helmholtz coil is energized, a magnetic field with the same intensity as the evanescent wave comes.
A large number of particles began to detune and flew out of orbit one after another.
The flying particles are guided to the target, and finally end up as electrons or photons.
Except for a few electrically neutral elementary particles
Neutrino, gluon, photon, Higgs particle, z boson.
These five types of particles are either impossible to capture, or are very difficult to capture, and will leave the channel on their own initiative.
In addition to basic particles.
There are only a few other electrically neutral composite particles left, and there are very few types.
For example, a neutron is composed of an up quark with a charge of 2/3 and two down quarks with a charge of -1/3.
Another example is x-ray particles.
The essence of x-ray particles is actually photons, so you can ignore them.
Neutrons can be absorbed by boron-containing polyethylene - this is a low-level radiation capture and will not cause nuclear fission.
When a series of operations are completed.
There is another uncharged composite particle left in the channel.
it's called
Bachaozi.
code name
4685.
To be continued
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