Chapter 601 Qualifications for Walking on Two Feet
"Neutron bomb?"
Hearing this word coming out of Xu Yun's mouth.
Several big guys at the scene were suddenly startled, with obvious surprise on their faces.
They would never have imagined that Xu Yun would associate tandem accelerators with neutron bombs.
Qian Bingqiong stood up from his position with a crash, and his chair was overturned to the ground by his excessive movement.
But he had no intention of lifting the chair up. Instead, he swallowed his saliva and looked at Xu Yun steadily:
"Xiao Han, what are you talking about? Can those accelerators help us create a neutron bomb?"
Hearing this, Xu Yun took a deep breath, looked at Qian Bingqiong solemnly, and gave an affirmative answer:
"That's right."
Qian Bingqiong's face suddenly turned red when he saw this, and he suddenly felt a rush of heat from his heart to his mind, so that his body shook twice.
Fortunately, Lu Guangda on the side had quick eyesight and quick hands, and quickly supported Qian Bingqiong's arm, so that no personal-threatening accident occurred.
A full half minute passed.
Qian Bingqiong's expression finally returned to calm, and he slowly sat back on the stool that Lao Guo had straightened up.
At this moment.
The atmosphere of the whole scene was really subtle.
The room seemed like an extremely cold icehouse, but under the silence that seemed to freeze the air, something seemed to be surging.
neutron.
This is a microscopic particle that was discovered very early. It is uncharged and electrically neutral, so it is called a neutron.
Neutrons are everywhere. In all atoms, except for the No. 1 isotope of hydrogen, "protium", all atoms contain neutrons.
When you take a bite of rice, it contains more than 10^24 neutrons.
At first glance, there seems to be nothing special about neutrons.
But if the neutron breaks away from the atom to form a highly penetrating neutron beam, its properties will be different - it is a real murder weapon.
Classmates who are human in this life should all know.
Cells are the basic units that constitute living organisms—note, they are basic units, not the smallest units.
Any cell in the human body contains countless molecules, and molecules are composed of atoms, which means that there is a huge number of atoms in each cell.
As for atoms, they are composed of protons, electrons and neutrons.
The neutron beam passes through the human body.
It will cause the molecules and atoms in the human body to deteriorate or become charged ions, causing nuclear reactions of carbon, hydrogen, and nitrogen atoms in the human body, destroying cell tissues.
At the macro level, it can cause convulsions, intermittent coma, muscle disorders, loss of resistance, and in severe cases, death within a few hours.
The earliest recorded killing by a neutron beam can be traced back to August 21, 1945.
At that time, Daghlian, a scientist at Alamos National Laboratory, was accidentally exposed to severe neutron radiation while conducting experiments.
Although he immediately received special treatment, the destructive effects of the neutron were irreversible—at least for the time.
Ever since.
The hapless scientist died 25 days later at the age of 24.
Here comes something more interesting.
When Daggerion was alive, there was a senior who was one year older than him, and they had a good relationship. This person was named Sam Cohen.
The epitaph on Daggerion's tombstone was carved by Sam Cohen himself.
to be honest.
No one knows whether Daghlian's death had any real impact on Sam Cohen, but one fact is.
In the 1950s, Sam Cohen was the first to propose the conjecture of using neutron beams as weapons and made many theoretical designs.
Neutron bomb.
The concept of this weapon has since entered the stage, and later generations have recognized Sam Cohen as the father of the neutron bomb.
The nuclear explosion power of weapons such as neutron bombs is very small, only one-tenth that of ordinary nuclear bombs, but it can release a large number of neutron beams.
These neutron beams will penetrate armored structures and kill a large number of people without causing damage to property.
Give an example.
A neutron bomb with the equivalent of 1,000 tons of TNT exploded 90 meters above your head.
Shock waves, optical radiation and radioactive contamination, these "dirty things", only work within a range of 180 meters from the center of the explosion.
However, the neutron stream 800 meters away from the explosion center can penetrate the 30 cm thick steel plate, causing casualties to the personnel protected by the steel plate.
That is
It kills people without damaging anything, and has no serious radiation effects.
For example, there is a famous joke on the Internet in later generations, which came from the mouth of an old friend of the Yellow River:
If you explode a neutron bomb at Wudaokou Vocational and Technical College, you can leave a whole body for Peking University next door, and the Chinese Academy of Sciences next door will be able to pick it up in two days.
But on the other hand.
Neutron bombs are clean, but at this time, this thing is a fantasy weapon.
Don't talk about Rabbit, Gaul, England, these countries.
Even the two super gangsters, Mao Xiong and Hai Duan Duan, are still in the conceptual stage of conceiving the neutron bomb at this time.
As of now.
Today’s most advanced neutron bomb achievements still come from across the sea:
They will develop a neutron warhead the size of a television set next year. After Jianlou discovers that this thing is purely a fraud, the project team members will be sent to Greenland to harvest ice.
Follow the historical trajectory.
It would not be until 1977 that the country across the sea would actually develop and test-detonate the first neutron bomb in human history, and then enter the research and development track of third-generation nuclear weapons.
The Rabbits would have to figure it out in 1984, and then it wouldn't be officially announced until 1999.
And now that Xu Yun is saying that he can create a neutron bomb, how can he keep Qian Bingqiong and others from losing their composure?
After a while.
Qian Bingqiong couldn't help but twitch his nose twice, and asked Xu Yun again:
"Xiao Han, are you sure this accelerator is useful for the development of neutron bombs?"
Xu Yun still nodded heavily and explained:
"I'm pretty sure, Director Qian, that neutron bomb, neutron bomb, as the word implies, involves the properties of neutrons, which is the so-called neutron radiation."
"The generation method of high-energy neutrons can rely on reactors, but there are only two methods of attribute detection."
"The first is to intercept high-energy rays from outer space, and the second is to bombard heavy metal targets with high-speed electron beams to cause the targets to release a large number of neutrons, and then collect their scattering data."
"So if you want to develop a neutron bomb, you either have the ability to fly into outer space to intercept high-energy rays, or you can only rely on particle accelerators to assist research."
"Of course, the deuterium-tritium neutron source can be considered one of the standard solutions, but if this thing could be developed, we would already have mastered the development of hydrogen bombs and neutron bombs."
Hearing Xu Yun's words.
Qian Bingqiong was silent for a moment, and subconsciously glanced at Lu Guangda beside him.
Qian Bingqiong's original idea was to ask Lu Guangda for his opinion, but Lu Guangda didn't notice his gaze and fell into deep thought.
After a while.
Lu Guangda couldn't help but tap his fingers on the table a few times, and said after careful consideration:
"Xiao Han, bombarding heavy metal targets with particle beams to generate neutrons is indeed a feasible technology."
"But the question is, can the .80MeV energy level really allow us to master a large amount of neutron data?"
"I remember that Mr. Zhao and others calculated a model. I can't remember the specific data clearly, but the energy level needs to be at least GeV and above."
"Although the tandem accelerator at Cambridge University is the best in the world at the time, it is still more than ten times behind the GeV level."
"If the data cannot be obtained after the exchange, we will lose both my wife and our troops."
Lu Guangda's thinking was very clear. He did not consider whether the neutron bomb was worth it, but directly considered its theoretical feasibility.
Everyone present knew that the neutron bomb was not a little bit more important than the atomic bomb in this period.
First, it is a reflection of the level of national defense technology.
Being able to develop a neutron bomb before the furry bears and across the sea would be of immeasurable help to the rabbits internationally - these days are different from later generations, and today's rabbits really need international recognition.
Secondly,
Neutron bombs have little radiation risk and are generally much cleaner than atomic bombs.
If the rabbits could figure out how to miniaturize the neutron bomb, its deterrence would be completely different.
After all, rabbits these days are standard barefoot ones and are not afraid of wearing shoes. If something happens to you, even if you are across the sea, you will fight at your will - the Peninsula War has just passed and there has not yet been one round.
True.
For various reasons, rabbits would definitely not dare to use the atomic bomb.
But if it is a neutron bomb that has been miniaturized, then hey.
So after learning Xu Yun's thoughts.
Lu Guangda immediately changed his mind from "whether it's worth it" to "can it be possible".
As for Mr. Zhao in his mouth, he naturally refers to Mr. Zhao Zhongyao.
As the current general manager of the domestic accelerator industry, Zhao Zhongyao has deduced the impact energy levels required for many particles.
Four years ago, he estimated that the excitation energy level at which neutrons could be observed and recorded in large quantities was around 1.1-1.3 GeV, which was more than ten times higher than 80 MeV.
However, in the face of Lu Guangda's doubts, Xu Yun shook his head and gave an answer that surprised him:
"Director Lu, with all due respect, there are actually some errors in the value calculated by Mr. Zhao."
Lu Guangda was suddenly startled:
"Error?"
Xu Yun nodded, with a trace of emotion on his face:
"That's right, experimental-level neutron beams don't actually need such high energy levels - Director, do you have a pen here?"
Li Jue on the side was listening attentively. He didn't react for a few seconds after hearing the words, but then he nodded quickly:
"Yes, yes, I will get it for you now."
Say it.
Li Jue stood up and walked to his desk, took out a pen and a piece of paper, and handed them to Xu Yun:
"Give."
Xu Yun took the pen and paper, spread the calculation paper on the table, and wrote to Lu Guangda:
"Director Lu, according to Gudsmit's classification back then, the spin of a neutron is 1/2. You should know this, right?"
Lu Guangda hummed lightly, but the expression on his face didn't change much.
The concept of spin was proposed in 1925. Nowadays, even in China, there is a lot of relevant information. Many physics undergraduates are familiar with it, let alone big guys like him.
Then Xu Yun continued writing:
"A beam of electrons with momentum ki=2π/λ and energy E=2ki2/2mn is incident on the target, and the scattering process satisfies the conservation of momentum and energy."
"Then there is a transferred momentum Q=kfki, which means |Q|=ki2+kf22kikfcos(2θs), and ω=EiEf."
"Where θs is the angle between the initial momentum and the final momentum, and ω is the frequency of element excitation in the target material excited by neutrons."
"The scattering cross section satisfies Fermi's golden rule, which is d2σ/dΩdEf|λi→λf=(kf/ki)(mn/2π2)2||2δ."
"Then use the Born approximation to regard the incident wave as a plane wave, and then substitute the delta function to get the wave vector of the neutron, right?"
Lu Guangda thought for a long time this time, carefully going through Xu Yun's thoughts, and then nodded after confirming that there was nothing wrong.
Lao Guo, Qian Wushi and others on the side also showed expressions of approval.
Li Jue quickly scanned the scene and found that everyone except himself was reacting, so he folded his hands on his chest and nodded his head a few times as if thinking.
Then Xu Yun handed the pen to Lu Guangda and said to him:
"Director Lu, please calculate the wave vector parameters of neutrons - assuming that the energy level of neutron scattering is 20MeV."
Lu Guangda glanced at him, said nothing, took the pen and paper and started calculating.
Although he didn't have a specific map of neutron scattering, he could still deduce the dynamic structure factor if he knew the particle spin and the magnitude given by Xu Yun.
But keep it in mind.
Lu Guangda suddenly raised his eyebrows and looked at Xu Yun in astonishment:
"17.87? Xiao Han, how is this possible?"
As everyone knows.
There are many parameters that describe the movement of a particle, such as frequency, wave number, wavelength and even equivalent temperature.
Another example.
wave arrow.
The neutron wavevector scattered by 20MeV is about 2.20 to the power 1. This parameter was calculated by Lu Guangda when he was studying for his PhD across the sea.
Not to mention that in today's 596 project, due to various calculation needs, a large number of related wave vector parameters are also involved.
Not an exaggeration.
Lu Guangda could forget anything, but he could never forget this value.
However, the value of the neutron wave vector obtained based on conventional reasoning is eight times different from what he already knew. This obviously challenges the three views.
It's like asking you how long an adult cat is, including its tail. Some people might say one meter, some might say 40 centimeters, but who would say their cat is five meters long?
So it's obvious.
There must be something wrong somewhere.
Think of this.
Lu Guangda looked at Xu Yun again, turned the calculation paper to him, and asked him:
"Xiao Han, what on earth is going on?"
When Xu Yun saw this, he didn't show off, but sighed slightly and explained:
"Director Lu, to tell you the truth, this is an anomaly discovered by a senior at Cambridge University named Accelerator during an experiment.
"He is a fan of vector calculations, so he rarely wanted to use wave vectors to describe neutrons, but after the calculation, such a strange situation happened."
"So he made repeated comparisons mathematically, and finally discovered a situation, that is."
"This is the magnetic moment of the neutron causing trouble. Its abnormal magnetic moment leads to errors in the model."
Lu Guangda was stunned for two seconds, but soon his tone rose a lot:
"Magnetic moment?"
Xu Yun nodded solemnly.
In a sense.
The errors caused by the calculation of particle magnetic moments have deceived an entire generation in the physics community.
magnetic moment.
When mentioning this word, many people may subconsciously think of the magnetic moment of a magnet.
But actually.
In addition to macroscopic magnetic moment, there is another concept of microscopic magnetic moment in invisible microscopic particles.
It is an intrinsic property of particles and is related to spin.
I once explained the meaning of spin, which is the rotation of the nucleus about its central axis in a complex state of common motion.
The rotating particles induce momentum moments around them that are aligned in the direction of their rotation axis - for example, what keeps a gyroscope upright when it rotates is its momentum moment. The rotating charge will also generate a magnetic moment around itself, which is called a magnetic moment. magnetic field.
And in all particles.
Neutrons, uncharged particles, also have magnetic moments. This is an anomaly discovered by Stern (not the NBA one) in the 1930s.
At this time.
The neutron magnetic moment calculated by the physics community is approximately -3.82 unit nuclear magnetons, but the physics community only knows about it.
How the magnetic moment appears and what it means to neutrons is still unknown.
According to Xu Yun
It is precisely because of the existence of this magnetic moment that there is a problem in mathematical calculations?
Then Xu Yun paused and continued to explain:
"Director Lu, you should remember Stern's model for calculating the magnetic moment of neutrons, right?"
Lu Guangda nodded and wrote an expression on the paper:
μns=gnse/2mphbar/2=gns/2ehbar/2mp.
Xu Yun reached out and tapped the mp in it, and said:
"Look here, the mp here is the isospin mass of the free neutron, that is, the two orthogonal basis vectors of the isospin doublet. Together, they form a subspace with an isospin of 1/2." (Note: To prevent being caught, let me explain it in advance. This is actually a weak isospin that is easy to understand in calculations)
"From the perspective of quantum mechanics, symmetry will lead to degeneracy of energy levels - taking the hydrogen atom as an example, without considering perturbation theory, when n and l are the same, no matter what the m value and Sz value are, The energy is the same.”
"This is the degeneracy of energy levels caused by typical symmetry. These degenerate energy levels form an invariant subspace"
"So when the neutron is in the unexcited state inside the target, the spin magnetic moment radius of the negative charge in the outer layer needs to deduct an electric potential barrier."
"That is, the specific initial state λi of the neutron should actually undergo an additional Lorentz transformation. At the same time, the neutron does not stimulate the movement of the nucleus, so corresponding to elastic scattering, the neutron energy is conserved"
Listening to Xu Yun was like a succubus who was wrong, whispering like a devil.
Lu Guangda couldn't help but pick up the pen again and quickly started calculating on the paper.
Sure enough.
After deducting an electric potential barrier as Xu Yun said, the value he calculated this time was close to 2.20^-1.
The reason why it is close but not equal is mainly because he chose the mean parameter of the experiment in memory for the convenience of calculation. The data cannot be too precise - after all, this calculation was a bit sudden.
Immediately afterwards.
Lu Guangda realized something again and substituted this idea into Zhao Zhongyao's model.
Ten minutes later.
Lu Guangda wrote down a number with some sadness:
69.7MeV.
At this moment.
Among the big guys at the scene, even Li Jue can easily understand the meaning of this number:
It represents the energy level at which neutrons can be knocked out in the laboratory and leave enough information.
It has shrunk twenty times faster than the original figure, and is within the coverage area of Cambridge University's tandem electrostatic accelerator.
See this situation.
Qian Bingqiong couldn't help but open his mouth again and wanted to ask Lu Guangda's opinion:
"Lu"
However, before he could say a word, he was interrupted again by Lu Guangda:
"Wait! Xiao Han, according to your idea, doesn't that mean"
"Since the negative charges in the outer layer are also spinning and share their spin engine with the light protons, the spins of the positive and negative charges will produce magnetic moments, but since the equivalent radius of the negative charges in the outer layer is larger than that of the positive charges in the inner layer, Will the total magnetic moment of neutrons appear as a negative charge magnetic moment? ”
"That is, within the existing particles, are there other smaller particle models?"
When it comes to this.
The expression on Lu Guangda's face already showed a hint of horror.
Lu Guangda looked a little belatedly.
The corner of Xu Yun's mouth finally couldn't help but curl up:
"If nothing else, it should be so."
That’s right!
Except for the neutron bomb.
Xu Yun had another reason to get the tandem electrostatic accelerator no matter what. That is.
He wants to give China's theoretical physics community a break. From now on, Rabbit can be on the application and theoretical side
Walk on two feet together!
(End of chapter)