Temperature evolution of dense gold and diamond heated by energetic laser-driven aluminum ions

At a Glance

Metadata	Details
Publication Date	2022-09-07
Journal	Scientific Reports
Authors	Changhui Song, Soohyung Lee, Woo‐Suk Bang
Institutions	Institute for Basic Science, Gwangju Institute of Science and Technology
Citations	7
Analysis	Full AI Review Included

Executive Summary

This study investigates the temporal evolution of temperature uniformity in solid-density gold and diamond samples heated by energetic laser-driven aluminum (Al) ion beams.

Core Achievement: Demonstrated that a laser-driven ion beam with a specific energy spread can achieve highly uniform heating (2-5% nonuniformity) in Warm Dense Matter (WDM) samples on a nanosecond timescale.
Heating Mechanism: Uniformity is achieved through a balance: low-energy ions heat the front surface, while high-energy ions deposit energy near the rear surface.
Temporal Dynamics: The heating process is not uniformly smooth. Nonuniformity is initially low, but significantly worsens during the peak energy deposition phase (45-87 ps), reaching up to 11.3% in diamond.
Final State Uniformity: The temperature uniformity gradually improves after the peak heating phase, resulting in a final state nonuniformity of 2-3% for gold and ~5% for diamond at 125 ps.
Simulation Tools: The analysis relies on Monte Carlo simulations (SRIM) for ion stopping power and SESAME Equation-of-State (EOS) tables for calculating time-dependent temperatures.
Material State: The samples remain at near-solid density throughout the heating process, reaching temperatures above 10,000 K (e.g., 5.13 eV for gold).

Technical Specifications

Parameter	Value	Unit	Context
Target Material 1	Gold (Au)	N/A	10 µm thickness, solid density
Target Material 2	Diamond (C)	N/A	15 µm thickness, solid density
Ion Beam Type	Aluminum (Al)	N/A	Laser-driven, quasi-monoenergetic
Average Ion Energy	140 (±33)	MeV	Input energy spectrum
Ion Incidence Angle	45	°	Angle relative to sample surface normal
Laser Intensity (Source)	~2 x 10²⁰	W/cm²	Used to generate Al ion beam
Total Heating Duration	0-125	ps	Time frame studied
Peak Heating Power (Au)	14.9	MeV/ion/ps	Occurs at 69.2 ps
Final Temperature (Au)	5.13 (±0.12)	eV	At 125 ps (using SESAME 2705)
Final Temperature (Diamond)	1.91 (±0.10)	eV	At 125 ps (using SESAME 7834)
Peak Heating Nonuniformity (Diamond)	11.3	%	Maximum observed at 87 ps
Final Temperature Nonuniformity (Au)	2-3	%	Achieved at the end of the 125 ps heating process
Volume Expansion	<3	%	Estimated volume increase during heating
Global Thermal Equilibrium Time (Au)	~1	µs	Time required after heating completes

Key Methodologies

The temporal temperature evolution was calculated using a combination of simulation and tabulated material properties:

Ion Beam Generation and Filtering:
- An intense ultrashort laser pulse (2 x 10²⁰ W/cm²) irradiated a 110 nm thick aluminum foil to generate the energetic Al ion beam.
- A 5 µm thick Al filter was placed 2.0 mm before the samples to block low-energy contaminants (protons <0.5 MeV and Al ions <10 MeV).
Stopping Power Calculation:
- The energy deposited on the samples over time was calculated using the Monte Carlo simulation code SRIM (Stopping and Range of Ions in Matter).
- The input data for SRIM was the measured energy spectrum of 10,000 incident Al ions (average 140 ± 33 MeV).
- Calculations used cold stopping power data, acknowledging potential errors (up to 4% for Au) if warm dense plasma effects were included.
Temperature Determination:
- The calculated deposited energy was converted into temperature using the SESAME Equation-of-State (EOS) tables.
- Specific tables used were No. 2700/2705 for gold and No. 7830/7834 for diamond.
Uniformity Quantification:
- Heating nonuniformity was defined as the ratio of the standard deviation of the stopping power to the average stopping power, multiplied by 100%.
- The temperature nonuniformity was similarly defined using the standard deviation of temperature divided by the average temperature.
Thermal Equilibrium Assessment:
- Local thermal equilibrium (electron-ion coupling) was expected to be reached within several picoseconds.
- Global thermal equilibrium (uniformity across the sample depth) was calculated to require much longer timescales (~1 µs for Au, ~20 µs for diamond), confirming the necessity of studying temporal uniformity during the rapid heating phase.

Commercial Applications

This research is critical for engineering applications requiring precise, rapid, and uniform energy deposition into materials under extreme conditions, particularly in the field of High-Energy Density Physics (HEDP).

Warm Dense Matter (WDM) Research: Enables highly accurate measurements of material properties (e.g., thermal conductivity, EOS) by minimizing temperature gradients, which are necessary for validating theoretical models.
Inertial Confinement Fusion (ICF) / Fast Ignition: Uniform heating by ion beams is a key requirement for pre-heating fusion fuel capsules (like diamond ablators) to the WDM state, improving ignition efficiency and stability.
Advanced Material Testing: Provides a controlled method for studying ultrafast phase transitions (e.g., melting) and material response to intense, rapid energy deposition while maintaining solid density, relevant for materials used in high-radiation environments.
High-Power Laser System Design: The findings inform the design and optimization of laser-driven ion sources, specifying the required ion energy spread to achieve desired heating profiles in target materials.
EOS Model Validation: The experimental framework supports the validation and refinement of complex EOS tables (like SESAME) by providing time-resolved temperature data under controlled, uniform heating conditions.

Tech Support

Original Source

DOI: https://doi.org/10.1038/s41598-022-18758-9