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Project List » Nonperturbative processes in strong-field QED

Nonperturbative processes in strong-field QED
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Acronym: ProQED
Contracting Authority: Institutul de Fizica Atomica (IFA)
Number / Date of the contract: ELI-06 / 2020-10-16
PN-III-P5/Subprogramul 5.1
Project Manager: Dr. Mircea Pentia
Partners:
Starting date / finishing date: 2020-10-16 / 2023-10-15
Project value: 752321 RON
Abstract: The project aims to study the nonlinear phenomena produced in the quantum vacuum, using 10 PW high power lasers from the ELI-NP infrastructure. We will study the possibilities to achieve conditions for γ photons production, which afterwards by interacting with the virtual pairs e+e- from the vacuum quantum fluctuations can provide enough energy to transform them into real pairs, possible to be detected and measured.
According to the Quantum Electrodynamics (QED), matter can be created from physical vacuum with the very strong electric and magnetic fields. The effect was theoretically described by J. Schwinger in 1951 [1]. But the production of e+e- pairs requires a very strong stationary electric field, of the value ES = 1.3 1016 V/cm. For an EM field this implies a huge intensity (I ~ E2) IS = 2.3 1029 W/cm2. Unfortunately, these values are significantly higher than the possible values achieved under current experimental conditions.
However, there are a number of proposed mechanisms that allow the catalysis of the production of e+e- pairs with laser pulses of lower intensities, such as ELI-NP (I ~ 1022 W/cm2) [2-4]. We also must consider the relativistic increase of the transverse component of the electric field for a charged particle moving at relativistic speed. As such, we will be able to study, in order to propose some experimental works at ELI-NP, various mechanisms of Schwinger pair production in interactions with the physical vacuum.
We will consider various experimental methods:
  1. Time-varying electric fields (E component of EM wave) of a high intensity laser pulses [4-6].
  2. Tunneling effect, considering the exponential decrease in the pair production rate with the inverse of the electric field value: ~ exp (-ES / E) [7,8]
  3. Possibility to combine the action of a low frequency laser (in the optical field) of high intensity, with that of a fast high frequency laser of low intensity. The fast pulse will transfer energy to the electron, extracted from a solid or gaseous target, which by tunnel effect, will be able to pass through the barrier produced by the slow, longer pulse (long wavelength) of the other laser [9-12]
  4. Pair production in the presence of a Coulomb field
  5. The Breit-Wheeler pair production in multiphoton interactions
  6. Finally, a "Letter of Intent" will be issued to implement an experimental setup, mounted and put into operation in the E6 area of ELI-NP, for experimental testing of some nonperturbative QED processes


Objectives:
  • The first major objective of the project is to prepare and train a strong team in the theoretical and experimental physics for study some QED nonperturbative effects with PW lasers of high intensity
  • The second major objective of the project is to establish an experimental setup given some possible schemes:
    1. The first scheme uses two laser pulses of opposite direction, focused on a gaseous target. In this interaction are produced high-intensity gamma photons and electron-positron pairs
    2. The second scheme uses two elliptically polarized 10 PW laser pulses, incident on a thin carbon target. The electrons produced are accelerated by the wakefield pressure of the laser pulse and interact with the other high-intensity laser pulse. This configuration allows Compton back-scattering production of intense gamma photons
    3. The third possible scheme will replace the second 10 PW laser pulse with the reflected pulse of the first pulse. This first laser pulse passes through the plasma and is reflected by a mirror and then interacts with the high-energy electron group and generates gamma photons and positrons
    4. The fourth scheme involves two linearly polarized laser pulses, incident on a thin Al foil, on both sides. It is estimated that approximately 20% of the laser energy will be converted into a gamma photon burst with a flux > 1014 s-1. The gamma conversion efficiency in the case of irradiation on both sides would be three times higher than in the case of one side irradiation with a single laser pulse. The electron-positron plasma generated with such laser pulses would be eight times denser compared to irradiation by a single laser pulse
    5. The fifth possible scheme uses the two 10 PW lasers with an oblique incidence on a solid target. An over-dense positron bunch production (~ 1022 cm-3) is expected, with a high yield (3 x 1010). Such a positron yield is 50 times higher than that produced with a single laser of the same power.


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