Chapter 63 Coda Field Acceleration Without Losing Phase
Wei Feng grabbed his hair and thought about how to solve the phase loss problem in the laser wake field acceleration.
At present, low-energy particle colliders have nothing to study in high-energy physics, because most of the results have been understood clearly.
If you want high-energy physics to go a step further, the collider needs to have at least an electron energy of the order Te∨.
Since the laser wakefield acceleration capability is 100GeV/m, wouldn't it be enough to accelerate it by 10m? A very important constraint is - phase loss.
The phase is the phase of the phase. The plasma wave of this tail wave can be regarded as an approximate sinusoidal function. Then in a y cycle, the first half of the cycle is positive electric field strength, decelerating towards the center, and the second half cycle is negative.
, to accelerate electrons.
Therefore, the electrons must be restricted to the acceleration phase in the second half of the cycle.
But the problem is that the speed of laser propagation in plasma cannot reach the speed of light due to dispersion, so the speed of the wake wave cannot reach the speed of light.
However, electrons at the GeV energy level are very close to the speed of light (the relativistic factor gamma is about 2000), so there is a relative speed between the electron and the wake wave. When the electron moves forward, it slowly escapes the acceleration phase and enters the deceleration phase. The energy
No more can be added.
The phase loss length is also on the order of mm to cm, which is why it can only be accelerated to the GeV level at present. Therefore, the phase loss limits the maximum electron energy.
Huang Mingzhe suddenly said: "To reach the electron energy of TeV, we can only find another way at present."
"You have ideas for finding another way"
"One acceleration is not enough, then increase it a few more times."
Wei Feng thought about it, and suddenly his eyes lit up, but then he shook his head: "No, if we do this, what is the difference between tailfield acceleration and traditional accelerator?"
"..."
Huang Mingzhe immediately understood what Wei Feng meant. The multi-level joint acceleration plan he proposed could achieve 10GeV even with a single-level acceleration.
To achieve the target TeV-level collider, the equipment will be very huge and the cost will be greatly increased. The advantages compared to traditional accelerators will basically not be reflected.
And let alone level 100, currently it can only reach two levels at most. The energy of acceleration is at the 100MeV energy level, which is pitifully small compared to the target of 1TeV.
The reason is that it is too difficult. Multiple laser wakefield acceleration levels need to be accurately matched on the time and space scales of femtoseconds and microns.
The speed of high-energy electrons is basically very close to the speed of light. To avoid losing phase, the propagation speed of the laser in the plasma must be the speed of light.
Plasma is a dispersive medium, so how can it achieve the speed of light? Huang Mingzhe bit his pen in distress.
However, Wei Feng was inspired by Huang Mingzhe's idea, and he wrote and drew on the draft paper.
The drawings on the draft paper looked like ghostly drawings, but Wei Feng himself knew what they were.
"Mingzhe has some ideas, and I need you to calculate them."
"no problem."
Wei Feng expressed his thoughts, and Huang Mingzhe quickly calculated in his mind. He kept calculating the data, while Wei Feng kept revising the plan.
A week later.
"Done!"
The two of them looked at the model simulated on the computer.
The one on the right is a step mirror. In three dimensions, it is composed of many rings. Each ring has a different depth and is not on the same plane.
In this way, after the incident light is reflected, a series of halo rings will be formed, with different ∨ delays between the rings.
Then many such rings are incident on the parabolic focusing mirror on the left, and this focusing mirror is specially designed. Generally, when focusing the laser beam, it will not change the pulse width of the laser beam.
But the magic of this focusing mirror is that it can focus light from different radial positions to different longitudinal positions.
In this way, combined with the step mirror, the light from different rings (corresponding to different time delays) can be focused to different focus positions, greatly extending the length of the focus.
The purpose of this is to make the effective speed of the focus equal to the speed of light.
To put it simply, it is to focus a ring of light on a location to generate a wake field that accelerates electrons to very close to the speed of light.
When the electron reaches dephase in this wake field, the light of the next ring is focused to the place where the electron just propagates, and the time delay can be achieved by accurately adjusting the depth of the ring on the step mirror, so that the electron
Entered the second wake field generated by the second halo.
By analogy, assuming that each laser ring accelerates electrons to 10GeV, only 100 rings are needed to accelerate electrons to 1TeV.
The two people’s calculations show that it only takes 45 meters to achieve 10 TeV electron acceleration, and an acceleration distance of 4.5 meters can increase the energy level to 1TeV.
The Xizhou Alliance's large particle collider is designed to have a maximum energy level of 7TeV in one direction and 14TeV in two directions.
In other words, if Huang Mingzhe and Wei Feng follow the plan, to achieve a total energy level of 14 TeV, only an acceleration field of 63 meters in length is needed.
The total length of the Xizhou Alliance's large particle collider is 27 kilometers.
The difference between 27 kilometers and 63 meters is nearly 428 times greater, so there is no need to think about the cost.
The Xizhou Alliance machine cost a total of more than 8 billion U.S. dollars, and the annual use and maintenance fees are about 1 billion U.S. dollars. This number is scary when you think about it.
There are really not many forces in this world that can afford such a big toy. Except for the Western Continent Alliance, only China, the United States, and Japan can afford it.
As for the 100-kilometer-long super-large particle collider planned by the Institute of High Energy Physics of the Chinese Academy of Sciences, he could only say that it would be better to think about it.
"Mingzhe, how are you doing over there with the laser?"
"I asked about it yesterday. Now it has only achieved an energy level of 670J, which is still a long way from the target of 3000J."
"We have already achieved 670J. Our Materials Research Institute is really awesome." Wei Feng didn't feel it was slow, but felt it was very fast.
"Is it fast? I think it's just average." Huang Mingzhe said with a smile.
"If your words are heard by other people who are researching the materials, they may die for you." Wei Feng said with a bitter smile.
"Let's prepare and build a small test model while completing the paper."
"OK."
Huang Mingzhe does not want to hide this kind of theoretical physics. After all, no matter how beautiful the castle in the air is, it is just a decoration without materials.
Thinking Society only needs to master the core of materials, others can only stare at it.
With the help of more than twenty researchers, the Institute of Physics spent more than two million to complete a small experimental laser wakefield accelerator, although the energy level is very small.
But it is more than enough to verify their plan. Currently, there are no high-energy ultra-short pulses, so building a large-scale laser tailfield accelerator is just a decoration.
"Start the device."
All the researchers were excited. None of the high-energy physics researchers present knew about it. They did not expect that they could actually see it in private companies.
"Laser input is stable."
"The automatic laser correction system starts."
"Calculating the output energy level at the end of the tail field."
"The energy level is 4GeV."
Bang bang bang... all the researchers were clapping and howling like ghosts.
Wei Feng and Huang Mingzhe looked at each other and smiled, obviously everything was as they expected.
"Everyone, please be quiet and experiment a few more times." Huang Mingzhe ordered.
"good."
As the experiment progressed, the predicted data and experimental data of the paper were basically consistent, and the paper was revised slightly.
This paper, titled "Coke Field Acceleration without Loss of Phase," was sent to the editorial office of Acta Physica Sinica.