Design optimization of an electron-to-photon conversion target for ultra-high dose rate x-ray (FLASH) experiments at TRIUMF.
Phys Med Biol
; 67(10)2022 05 12.
Article
en En
| MEDLINE
| ID: mdl-35299167
ABSTRACT
OBJECTIVE:
To develop a bremsstrahlung target and megavoltage (MV) x-ray irradiation platform for ultrahigh dose-rate (UHDR) irradiation of small-animals on the Advanced Rare Isotope Laboratory (ARIEL) electron linac (e-linac) at TRIUMF.APPROACH:
An electron-to-photon converter design for UHDR radiotherapy (RT) was centered around optimization of a tantalum-aluminum (Ta-Al) explosion-bonded target. Energy deposition within a homogeneous water-phantom and the target itself were evaluated using EGSnrc and FLUKA MC codes, respectively, for various target thicknesses (0.5-1.5 mm), beam energies (Ee-= 8, 10 MeV) and electron (Gaussian) beam sizes (2σ= 2-10 mm). Depth dose-rates in a 3D-printed mouse phantom were also calculated to infer the compatibility of the 10 MV dose distributions for FLASH-RT in small-animal models. Coupled thermo-mechanical FEA simulations in ANSYS were subsequently used to inform the stress-strain conditions and fatigue life of the target assembly. MAINRESULTS:
Dose-rates of up to 128 Gy s-1at the phantom surface, or 85 Gy s-1at 1 cm depth, were obtained for a 1 × 1 cm2field size, 1 mm thick Ta target and 7.5 cm source-to-surface distance using the FLASH-mode beam (Ee-= 10 MeV, 2σ= 5 mm,P = 1 kW); furthermore, removal of the collimation assembly and using a shorter (3.5 cm) SSD afforded dose-rates >600 Gy s-1, albeit at the expense of field conformality. Target temperatures were maintained below the tantalum, aluminum and cooling-water thresholds of 2000 °C, 300 °C and 100 °C, respectively, while the aluminum strain behavior remained everywhere elastic and helped ensure the converter survives its prescribed 5 yr operational lifetime.SIGNIFICANCE:
Effective design iteration, target cooling and failure mitigation have culminated in a robust target compatible with intensive transient (FLASH) and steady-state (diagnostic) applications. The ARIEL UHDR photon source will facilitate FLASH-RT experiments concerned with sub-second, pulsed or continuous beam irradiations at dose rates in excess of 40 Gy s-1.Palabras clave
Texto completo:
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Electrones
/
Aluminio
Tipo de estudio:
Health_economic_evaluation
Límite:
Animals
Idioma:
En
Revista:
Phys Med Biol
Año:
2022
Tipo del documento:
Article
País de afiliación:
Canadá