= The LhARA radiobiology programme; status and plans =
**Abstract** submitted to [https://spie.org/EOO27/conferencedetails/applying-laser-driven-particle-acceleration Applying Laser-driven Particle Acceleration (ALPA)] at [https://spie.org/conferences-and-exhibitions/optics-and-optoelectronics SPIE Optics and Optoelectronics 2027]

 //Josie McGarrigle: // for the collaboration 

== Technical == 
The Laser-hybrid Accelerator for Radiobiological Applications (LhARA) is a proposed facility designed to deliver laser-driven proton and ion beams for radiobiological research and, ultimately, radiotherapy. LhARA’s scientific programme requires systematic comparison of biological responses across laser-driven ions, cyclotron ions, and X-rays. As a proof-of-principle step toward this goal, the PoPLaR (Proof-of-Principle LhARA Radiobiology) initiative has implemented a laser-driven proton beamline at the SCAPA facility, University of Strathclyde.

The PoPLaR beamline, designed, simulated, and optimised using linear optics, transports protons produced via Target Normal Sheath Acceleration (TNSA) through a permanent magnet quadrupole doublet operating at 150 T/m. A copper scatterer selected through Bayesian optimisation delivers a uniform dose field across a bespoke 2.7 cm² cell dish. In Phase 1, beam characterisation was performed using radiochromic film, with proton energies up to 11-12 MeV measured at the target. In Phase 2, the first in-vitro irradiations of biological samples using laser-driven protons were carried out in November 2025. A mean dose of 0.57 Gy per shot was delivered, with a beam uniformity coefficient of variation of 13.9%, reducible to 8.4% through scatterer repositioning. Cells were irradiated at three dose levels targeting 1, 2, and 4 Gy.

These irradiations represent an important milestone, demonstrating the feasibility of delivering controlled doses to biological samples using a laser-driven proton source. Key technical challenges identified include shot-to-shot dose variation of approximately 70% and the absence of an on-shot diagnostic, which motivate the next phase of beamline development. We will present the current beamline design and our plans for improvement.

== Programme Summary ==

== Biographical information ==

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