1. Choi Ilwoo1,3 , Nam Changhee1,2
Spectral Change of Backscattered Laser Pulse During Laser-Driven Proton Acceleration
Lee SUnggeun1,2 , Kim Ijong1,3 ,
Choi Ilwoo1,3 , Nam Changhee1,2
1Center for Relativistic Laser Science, Institute for Basic Science, Gwangju , Korea
2Department of Physics and Photon Science, Gwangju Institute of Science and Technology, Gwangju , Korea
3Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju , Korea

2. Contents Theoretical background of Ion Acceleration
Spectral change during acceleration
Experimental setting
Result
Summary

3. Laser Proton/Ion Acceleration

4. RPA
Electron is push by enough high intensity laser pulse contemporally
Charge separation occurs, and coulomb force is generated between electron layer and ions
Ions accelerates

5. Spectral change during acceleration
Electron layer can reflect incident laser pulse
Moving layer with relativistic speed occurs relative Doppler effect
Reflected light experienced redshift

6. Experimental Setup

7. Comparison of before/after beam hitting the target
Input spectrum range
( nm) 1 1 2
Red shift range
(850nm~) 2

8. Typical spectrum with various maximum proton energy

9. Proton Energy vs Redshift
Polymer target (1g/cm2 -> 200nc)
CP laser
X axis : maximum proton energy obtained by TPS
Y axis : Spectrum Integration over 900nm

10. Amount of redshift Changes in Various Condition
Polymer target (1g/cm2 -> 200nc)
CP laser
Diamond-Like Carbon target (2.7g/cm2 -> 500nc)
CP laser

11. Amount of redshift Changes in Various Condition
Diamond-Like Carbon target (2.7g/cm2 -> 500nc)
CP laser
Diamond-Like Carbon target (2.7g/cm2 -> 500nc)
LP laser

12. Summary
We have investigated the spectral structure of backscattered laser pulses during the laser proton acceleration performed with a PW laser.
We have confirmed that backscattered light experience more Doppler effect compare to the transmitted light.
The relation between the spectral structure of reflected laser pulses and proton energy spectra will be clarified with respect to experimental conditions, such as laser and target parameters