June 11, 2025

Wei Lin (林瑋)

Development of Laser-Accelerated Ion Beams and Diagnostics Using Solid and Gaseous Targets

Advisor: Chih-Hao Pai (白植豪)

1

State-of-the-art overview

Introduction to Laser-Driven Ion Acceleration

Micrometer-scale source size

Ultrafast ion bunch duration (fs-ps)

S. S. Bulanov et al. (2016)

2

Introduction to Laser-Driven Ion Acceleration

Ultrafast Laser

Target

General concept

Blow-Off

Plasma

3

Laser-driven ion acceleration for p-B fusion

Boron-11 is the dominant isotope (80 %) in natural boron

Direct conversion of fusion energy into electricity

Introduction to Laser-Plasma Ion Acceleration

4

• Real-time control of target parameters

• Optical probing for plasma dynamics

Ion acceleration in gaseous target

ion

• Strong laser-plasma coupling

Introduction to Laser-Plasma Ion Acceleration

5

Ion diagnostics – Thomson Parabola Spectrometer

• In-situ measurement of ion spectrum
• Nonlinear fluorescent response
• Low sensitivity for low-energy proton and heavy ions

Introduction to Laser-Plasma Ion Acceleration

6

Energy filter

• Absolute ion number determination
• Post-experiment, single measurement
• Complex to analyze

Tasl image^TM

Introduction to Laser-Plasma Ion Acceleration

Ion diagnostics – CR39 detector

7

Outlines

• Development of Physics-Based Algorithm for Pit Geometry Detection on Etched CR39 Ion Detectors

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• Phosphor Response of P43 Scintillator to Multi-MeV Protons in TNSA Experiments

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• Laser-Driven Ion Acceleration Using Tailored Hydrogen Gas Jets via Machining Pulse Preconditioning

Development of Physics-Based Algorithm for Pit Geometry Detection on Etched CR39 Ion Detectors

9

Fundamentals for Pit Formation

G. Somogyi and S. A. Szalay, Track-diameter kinetics in dielectric track detectors, Nucl. Instrum. Methods, 1973

10

G. Somogyi and S. A. Szalay, Track-diameter kinetics in dielectric track detectors, Nucl. Instrum. Methods, 1973

The Identification of major and minor axis:

Fundamentals for Pit Formation

11

For proton with 1 MeV and incident angle 70°

Fundamentals for Pit Formation

Evolution of the CR39 surface

12

Literature Review

A. P. Fews (1992)

13

M. Seimetz et al., 2018

Literature Review

14

M. S. Schollmeier et al., 2023

Literature Review

15

This Work

Precisely identifying peak position and the major/minor axes

Works well even at highly dense regions

16

5 μm

Procedures for Pit Detection

Test image

17

Procedures for Pit Detection

Peak detection

Otsu global thresholding on gray level gradient

Hough transform line accumulator space

18

Procedures for Pit Detection

Oval detection

Unit radiating arrows represent the ideal pits

Oval is fitted by the dot product with the ideal pits

19

Procedures for Pit Detection

Overlapping pits separation

20

Procedures for Pit Detection

Detection results

Phosphor Response of P43 Scintillator to Multi-MeV Protons in TNSA Experiments

22

Fundamental of Scintillators

Ion

J. B. Birks, Scintillations from Organic Crystals : Specific Fluorescence and Relative Response to Different Radiations (1951)

23

Composition: Gd₂O₂S:Tb

Light emission: 360 - 680 nm (peak at 545 nm)

Aluminum layer

Phosphor layer

Fundamental of Scintillators

Introduction to P43 scintillator

24

Setup

Thomson Parabola Spectrometer

25

Thomson Parabola

Spectrometer

Main Laser Beam

20 μm C-H foil

Target-Normal-Sheath-Acceleration (TNSA) Scheme

Setup

(800 nm / 7 μm / 42 fs / 5 × 10¹⁹ W∙cm^-2)

26

Calibration Method

Fence-like CR39 and signals

Proton

Carbon

(7.25N NaOH at 70°C for 30 mins)

27

Results

Fluorescent and number surface densities related to proton energy

28

Results

Fluorescent response function

Laser-Driven Ion Acceleration Using Tailored Hydrogen Gas Jets via Machining Pulse Preconditioning

30

Simulation

Mixed gas (N:H = 2:1)

2D Particle-In-Cell (EPOCH) simulation

Numerical resolution parameters:

Laser parameters:

31

Simulation

32

Simulation

33

Ion acceleration in gaseous target

Setup

Timeline

Machining Pulse

Main Pulse

Nozzle

34

Gas jet

Nozzle

Mask

Machining beam

Machining beam preconditioning

Setup

Timeline

Machining Pulse

Main Pulse

Nozzle

35

Machining beam preconditioning

Setup

0.5 - 6 mm

M = 0.0816

Relay Imaging

Timeline

Machining Pulse

Main Pulse

Nozzle

36

Tailored structure from shadowgraph

Results

Timeline

Machining Pulse

Main Pulse

Nozzle

Probe Pulse

37

Tailored structure from scattering imaging

Results

Timeline

Machining Pulse

Main Pulse

Probe Pulse

Scattering light

Nozzle

38

150 μm

150 μm

Minimizing target structure

Results

Timeline

Machining Pulse

Main Pulse

Probe Pulse

Scattering light

Nozzle

39

Shock front broadening using mixed gas

Results

N : H = 1 : 1

Timeline

Machining Pulse

Main Pulse

Probe Pulse

Scattering light

Nozzle

15.8 ns

40

Observe electron signals only

Results

Timeline

Machining Pulse

Main Pulse

Probe Pulse

Scattering light

Nozzle

15.8 ns

Phosphor

41

5-μm Al

10-μm Al

20 μm

Proton signals from CR39

Results

450 - 900 keV

42

Prepulse of the Laser Observed from Shadowgraph

Nozzle

10 ps Prepulse

Main Pulse

Results

43

CsI(Tl) scintillators for higher sensitivity

Results

K. Renuka, et al., (2012)

44

Conclusions

• A pit detection algorithm for etched CR39 ion detectors was developed, enabling reliable analysis even in densely populated regions.

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• The response function of the P43 scintillator was experimentally measured and showed agreement with the theoretical model.

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• Simulations and experimental investigations of ion acceleration from gaseous targets were conducted. The target were tailored using shock waves generated by a machining pulse, and the resulting protons were successfully detected using CR39 detectors.

Thank you for your attention