🔬 physics

From Simulation to Experiment: Multi-Code Modelling and Validation of Carbon-11 Production Using Natural Boron Targets

This study validates the 11B(p,n)11C reaction for producing high-purity Carbon-11 using natural boron targets by integrating TALYS simulations with TR-19 cyclotron experiments, demonstrating that boron nitride yields the highest activity (12.37 GBq) and confirming the method's suitability for future laser-driven production at ELI-NP.

Original authors: Andrei Necsoiu, Diana Cocioabă, Radu Leonte, Liviu Crăciun, Nicoleta Florea, Andreea Radu, Alexandru Jipa, Dimiter Loukanov Balabanski, Călin Alexandru Ur, Dana Niculae

Published 2026-06-25

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Andrei Necsoiu, Diana Cocioabă, Radu Leonte, Liviu Crăciun, Nicoleta Florea, Andreea Radu, Alexandru Jipa, Dimiter Loukanov Balabanski, Călin Alexandru Ur, Dana Niculae

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The Big Picture: Making a "Flashy" Medicine Ingredient

Imagine you need to bake a very specific, high-tech cake (a medicine for PET scans) that requires a special, short-lived ingredient called Carbon-11. This ingredient is like a "flashlight" that only stays lit for about 20 minutes before it fades away. Because it disappears so fast, you have to make it right next to the hospital that needs it.

Usually, doctors make this "flashlight" by shooting tiny particles (protons) at a tank of nitrogen gas. But the scientists in this paper wanted to try a different recipe: shooting those same particles at solid blocks of Boron (a metal-like element). They wanted to see if this solid method could work just as well, or maybe even better, especially for a future project involving powerful lasers.

The Experiment: The "Target Practice"

To test this, the team went to a particle accelerator (a machine called the TR-19 cyclotron) which acts like a giant slingshot. They fired protons at three different types of "targets" (blocks of material):

Amorphous Metallic Boron: A 95% pure, somewhat messy-looking metal block.
Crystalline Metallic Boron: A 98% pure, highly organized metal block.
Boron Nitride: A 98% pure block made of Boron mixed with Nitrogen (like a sandwich of two ingredients).

The Setup:
Before the protons hit the Boron, they had to pass through a few obstacles, like a thin aluminum window and a layer of cooling helium gas. Think of this like a runner trying to hit a target while running through a wind tunnel and a thin curtain. The scientists used computer simulations (like a video game physics engine) to calculate exactly how much speed the protons lost before they actually hit the Boron.

The Result: They started with protons moving at 15 "speed units" (MeV). By the time they hit the Boron, they had slowed down to 14 "speed units." The scientists checked their math and confirmed that 14 units was the "sweet spot" speed to get the most Carbon-11 out of the reaction.

The Race: Which Target Won?

After firing the protons for 30 minutes, they measured how much "flashlight" (Carbon-11) they created. Here is how the three targets performed:

The 95% Pure Metal: Produced the least amount (about 7.8 GBq).
The 98% Pure Metal: Produced a medium amount (about 10.9 GBq).
The Boron Nitride (BN): Produced the most (about 12.4 GBq).

Why did Boron Nitride win?
It's like a double-team attack. The Boron Nitride block had two ingredients: Boron and Nitrogen.

The protons hit the Boron to make Carbon-11.
Bonus: The protons also hit the Nitrogen inside the block, which created even more Carbon-11.
Plus, the BN block was denser (packed tighter), meaning there were more atoms for the protons to hit in the same amount of space.

Theory vs. Reality: The "Perfect World" vs. "Real World"

The scientists had a computer model that predicted exactly how much Carbon-11 they should get.

The Prediction: The computer said, "You will get X amount."
The Reality: They actually got about 12% to 15% less than the computer predicted.

Why the difference?
The paper explains that computers assume a perfect, smooth beam of protons hitting a perfect, smooth block. In reality, the beam might be slightly wobbly, the metal block might have tiny gaps between its particles, or the protons might lose a tiny bit of extra energy in the air. It's the difference between a video game character hitting a target perfectly and a real human throwing a dart that misses the bullseye by a few millimeters. Despite this, the real results matched the computer's pattern very closely, proving the model works.

The Safety Check: Is it Pure?

Making Carbon-11 is great, but you don't want it mixed with other radioactive "trash" that could be harmful. The team used a special camera (a gamma spectrometer) to look at their product.

The Verdict: The product was 99.9% pure.
The "Trash": The only other radioactive thing they found was a tiny, tiny amount of Beryllium-7, which is so small it doesn't matter. The rest was just the Carbon-11 they wanted. This purity meets the strict rules for making medicines.

The Conclusion

The paper concludes that:

Solid Boron works: You can successfully make Carbon-11 using solid blocks instead of gas.
Boron Nitride is the "Heavy Hitter": It produces the highest total amount of the ingredient because it gets a "double bonus" from its nitrogen content.
Crystalline Boron is the "Efficiency King": While Boron Nitride made the most total stuff, the pure crystalline metal was very efficient at what it did.
The Math Holds Up: Even though the real-world numbers were slightly lower than the computer predictions, the relationship was strong enough to trust the models for future experiments.

Why does this matter for the paper?
The authors are preparing for a future project called "Dr. Laser" at the ELI-NP facility. They are testing these solid targets now with a standard machine (the cyclotron) to prove the concept works, so they can eventually use high-power lasers to do the same job in the future. They confirmed that the solid targets are safe, pure, and effective.

Technical Summary: From Simulation to Experiment: Multi-Code Modelling and Validation of Carbon-11 Production Using Natural Boron Targets

Problem Statement
Carbon-11 ( $^{11}$ C), a critical radioisotope for Positron Emission Tomography (PET) in neurology, oncology, and cardiology, is currently produced primarily via the $^{14}$ N(p, $\alpha$ ) $^{11}$ C reaction using gaseous targets. However, the "Dr. Laser" project at the Extreme Light Infrastructure–Nuclear Physics (ELI-NP) facility seeks to establish alternative production routes using high-power lasers to accelerate protons onto solid targets. To prepare for laser-driven experiments, it is necessary to validate the $^{11}$ B(p,n) $^{11}$ C reaction using solid natural boron targets under conventional cyclotron conditions. The study aims to identify the optimal target material (amorphous metallic boron, crystalline metallic boron, or boron nitride) and investigate the dependence of produced activity on incident proton energy, while bridging the gap between theoretical nuclear reaction modelling and experimental reality.

Methodology
The research employed a multi-code modelling approach integrated with experimental validation at the TR-19 cyclotron (Horia Hulubei National Institute for Physics and Nuclear Engineering, IFIN-HH).

Theoretical Modelling:
- TALYS: Used to simulate excitation functions for the $^{11}$ B(p,n) $^{11}$ C reaction and competing channels ( $^{11}$ B(p,d) $^{10}$ B, $^{11}$ B(p,np $\alpha$ ) $^{6}$ Li, $^{11}$ B(p,n $\alpha$ ) $^{7}$ Be) over a 0–20 MeV proton energy range. This identified the optimal energy window for production and assessed radionuclidic purity.
- SRIM/TRIM: Used to model proton transport and energy loss through the experimental setup, including the cyclotron's aluminium exit window, a helium cooling layer, and a sealing foil, to determine the effective incident energy on the target surface.
- Analytical Calculations: Theoretical production rates, End-of-Bombardment (EOB) activities, and yields were calculated using nuclear reaction theory, accounting for target mass, purity, isotopic abundance, and beam flux.
Experimental Validation:
- Irradiation: Three target types were irradiated at the TR-19 cyclotron: amorphous metallic boron (95% purity), crystalline metallic boron (98% purity), and boron nitride (BN, 98% purity).
- Parameters: Protons were extracted at 15 MeV. Targets were irradiated at 5 $\mu$ A for 30 minutes.
- Measurement: Post-irradiation, targets were analyzed using high-purity germanium (HPGe) gamma spectrometry to determine radionuclidic purity and half-life. Activities were corrected to EOB.

Key Results

Energy Optimization: SRIM simulations determined that a 15 MeV extracted beam results in an effective incident energy of 14 MeV on the target surface. This energy aligns with the optimal region of the $^{11}$ B(p,n) $^{11}$ C excitation function, maximizing reaction yield.
Production Yields:
- Amorphous Metallic Boron (95%): 7.77 GBq activity (3.11 GBq/ $\mu$ Ah).
- Crystalline Metallic Boron (98%): 10.87 GBq activity (4.35 GBq/ $\mu$ Ah).
- Boron Nitride (BN, 98%): 12.37 GBq activity (4.95 GBq/ $\mu$ Ah).
Model vs. Experiment: Experimental activities were consistently lower than theoretical predictions by 11.90% to 14.54%. Despite this systematic deviation, a strong correlation was observed between the experimental data and the mathematical model.
Purity and Half-life: Gamma spectrometry confirmed a radionuclidic purity exceeding 99.9% for all targets. The measured half-life (approx. 19.8–20.4 min) matched the known $^{11}$ C half-life (20.361 min). Competing reactions, specifically the production of $^{7}$ Be, were found to have negligible impact on purity at 14 MeV.

Significance and Claims
The paper claims that the $^{11}$ B(p,n) $^{11}$ C reaction at a target energy of 14 MeV is optimal for producing $^{11}$ C using solid natural boron targets. The study validates the efficiency of using solid targets for high-purity radiopharmaceutical synthesis, demonstrating that experimental results align closely with theoretical models when practical factors (beam degradation, target geometry) are considered.

Key findings regarding target materials include:

Boron Nitride (BN) provided the highest total activity and yield, attributed to its higher apparent density and the additional contribution of the $^{14}$ N(p, $\alpha$ ) $^{11}$ C reaction channel.
Crystalline Metallic Boron (98%) is identified as the most efficient material for maximizing specific activity (activity per unit mass), whereas BN's higher total yield is partly due to its greater mass.
The study confirms that the ACSI solid target system at IFIN-HH produces $^{11}$ C with radionuclidic purity compliant with the European Pharmacopoeia (Ph. Eur.) 11th Edition.

These results serve as a foundational validation for the upcoming "Dr. Laser" project at ELI-NP, confirming that laser-driven proton acceleration on boron-based targets is a viable route for generating high-purity $^{11}$ C for medical applications.