High-energy Proton Irradiation Research Articles

Research on proton displacement damage effects in charge-domain accumulation type TDI CMOS image sensors

TDI CMOS image sensors are the most widely used photodetectors in space earth observation and multispectral imaging. The displacement damage caused by high-energy proton irradiation in the space environment leads to the continuous degradation of TDI CMOS image sensor parameters, seriously affecting its performance, reliability, and service life. This paper focuses on a space-based TDI CMOS image sensor chip and carries out 3 MeV proton irradiation tests and post-irradiation annealing tests to obtain the change rules of optical and electrical parameters. The degradation mechanism of sensitive parameters of TDI CMOS image sensors caused by proton irradiation is analyzed, and the sensitive region of proton displacement damage are discussed. The study demonstrates that after proton irradiation, the parameters especially full well capacity and temporal dark noise of the device degrade less, with small sensitivity to proton irradiation. However, the dark current, CTE, and pixel column FPN significantly degrade, and the degree of degradation is linearly related to the proton irradiation dose. In addition, the test also obtained the short-term and long-term annealing changes of sensitive parameters after proton irradiation of TDI CMOS image sensors, providing scientific advice for TDI CMOS image sensors space proton radiation effect tests and evaluations. The research results of this paper provide important references for the evaluation of radiation effects, on-orbit performance estimation, and radiation resistance reinforcement of space-based TDI CMOS image sensors.

Study of High-Energy Proton Irradiation Effects in Top-Gate Graphene Field-Effect Transistors

In this article, the effects of high-energy proton irradiation on top-gate graphene field-effect transistors (GFETs) were investigated by using 20 MeV protons. The basic electrical parameters of the top-gate GFETs were measured before and after proton irradiation with a fluence of 1 × 1011 p/cm2 and 5 × 1011 p/cm2, respectively. Decreased saturation current, increased Dirac sheet resistance, and negative drift in the Dirac voltage in response to proton irradiation were observed. According to the transfer characteristic curves, it was found that the carrier mobility was reduced after proton irradiation. The analysis suggests that proton irradiation generates a large net positive charge in the gate oxide layer, which induces a negative drift in the Dirac voltage. Introducing defects and increased impurities at the gate oxide/graphene interface after proton irradiation resulted in enhanced Coulomb scattering and reduced mobility of the carriers, which in turn affects the Dirac sheet resistance and saturation current. After annealing at room temperature, the electrical characteristics of the devices were partially restored. The results of the technical computer-aided design (TCAD) simulation indicate that the reduction in carrier mobility is the main reason for the degradation of the electrical performance of the device. Monte Carlo simulations were conducted to determine the ionization and nonionization energy losses induced by proton incidence in top-gate GFET devices. The simulation data show that the ionization energy loss is the primary cause of the degradation of the electrical performance.

Radiation Therapy for Ocular Melanoma – a Narrative Review with Insides from TRIUMF, Canada’s Only Proton Beam Therapy Center

"Ocular melanoma (OM) originates from melanocytes in the eye, predominantly in the uvea, particularly the choroid. The yearly incidence is around six cases per million. OM is not primarily driven by ultraviolet exposure like skin melanoma, but is usually caused by mutations in GNAQ or GNA11. Symptoms like blurry vision and visual field defects appear late. Diagnosis is often made via eye exams, specialized ultrasound, and rarely biopsy. This narrative review describes the radiation treatment modalities of OM and highlights the landscape of proton beam irradiation in Canada. Historically, enucleation was the standard of care for OM. However, current strategies consider tumor size, location, patient age, visual potential, and metastatic presence. Primary treatments include radiation therapy and surgery. Radiation therapy includes plaque brachytherapy (PB), proton beam irradiation (PBI), stereotactic radiosurgery (SRS), and stereotactic radiotherapy (SRT). Surgery includes endoresection, exoresection, and enucleation. Tebentafusp-tebn has been FDA-approved for metastatic cases. PB, the most common radiation therapy for OM, involves radioisotopes delivering radiation into the tumor. Comparable survival rates between PB and enucleation for medium choroidal melanoma have made PB the standard of care. PB has certain limitations, mainly surgical complications. PBI uses a particle accelerator for focused, high-energy proton radiation, yielding high tumor control and survival rates, though the availability of proton facilities is a significant limitation. Vancouver is the only center in Canada for PBI, administered not in a healthcare facility but at TRIUMF (Tri-University Meson Facility). TRIUMF, the world's largest cyclotron particle accelerator, in partnership with BC Cancer and UBC Department of Ophthalmology and Eye Care Center, has treated over 200 ocular melanoma patients between 1995 and 2017, achieving a 91% tumor control rate and 82% five-year survival rate. Emerging combination therapies like Ataxia Telangiectasia Mutated (ATM) protein kinase inhibition before PBI show potential, possibly reducing radiation dose and resistance."

High-Energy Proton and Atmospheric-Neutron Irradiations of SiC Power MOSFETs: SEB Study and Impact on Channel and Drift Resistances

Accelerated single event burnout (SEB) tests with 200 MeV protons and atmospheric-neutrons were performed for commercial SiC power MOSFETs with different architectures ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e</i> ., planar gate, asymmetric trench and symmetric trench). The average electric fields over the depletion layer width and the electric field distributions are reported for the tested conditions and compared for the three architectures, confirming the necessity of a lower de-rating for the trench design to protect from SEB, compared to planar ones. In addition to the epitaxial layer design, the influence of other design parameters on the SEB threshold is discussed. Finally, to investigate the presence of precursor damage in the pre-SEB region, a methodology is presented and used to study the radiation-induced degradation of the channel and drift resistances of devices which survived the SEB tests.

Effects of 5 MeV proton irradiation on 4H-SiC lateral pMOSFETs on-state characteristics

Silicon carbide (SiC) MOSFETs are often used in harsh environments where they are exposed to ionizing radiation. This paper investigates the effects of high-energy proton irradiation on SiC MOSFETs, with a particular emphasis on the on-state characteristics of lateral pMOSFETs. By comparing with the lateral 4H-SiC nMOSFET after irradiation in our prior work, we observed the deviations of important electrical parameters. As the irradiation dose increases, the threshold voltage (VTH) of pMOSFETs is negatively shifted and has more negative offsets than that of nMOSFETs. This is due to two factors which affect VTH after irradiation: the near interface oxide traps (NIOTs) and the interface traps (Nit). These two factors compensate each other for nMOSFETs, but strengthen each other for pMOSFETs. It is found that an increase in the density of interface traps (Dit) in both types of MOSFETs after irradiation. However, unlike the nMOSFET, the pMOSFET has a decreasing field effect mobility (μFE) with the increase of irradiation dose. We believed that besides the effect of Dit on μFE, NIOTs have a more profound influence on μFE, resulting in different changes between nMOSFETs and pMOSFETs’ μFE.

Annealing effects on Cu(In,Ga)Se2 solar cells irradiated by high-fluence proton beam

Radiation tolerance of Cu(In,Ga)Se2 (CIGS) solar cells has been investigated using high-fluence proton beam irradiation for application to devices in extremely-high-radiation environments. CIGS solar cells deteriorated after high-energy proton irradiation with non-ionizing energy loss of 1 × 1016 MeVneq cm−2, however, the CIGS solar cells could generate power after high-fluence irradiation. The ideality factors increased from 1.3 to 2.0, and series resistance increased, indicating that the concentration of recombination centers increased in CIGS layers. After heat-light annealing, the conversion efficiencies gradually recovered, and the recombination centers were confirmed to be partly passivated by annealing at 90 °C. The short-circuit currents for 10 μm thick CIGS solar cells were recovered by dark annealing in the same manner as for 2 μm thick CIGS solar cells. Dark annealing on irradiated CIGS solar cells has beneficial effects on passivate the recombination centers, even using thicker CIGS layers.

Assessing high-energy x-ray and proton irradiation effects on electrical properties of P-GaN and N-GaN thin films

The effects of ionizing and displacement irradiation of high-energy x-ray and 2-MeV proton on GaN thin films were investigated and compared in this study. The electrical properties of both P-GaN and N-GaN, separated from power devices, were gauged for fundamental analysis. It was found that the electrical properties of P-GaN were improved as a consequence of the disruption of the Mg–H bond induced by high-dose x-ray irradiation, as indicated by the Hall and circular transmission line model. Specifically, under a 100-Mrad(Si) x-ray dose, the specific contact resistance ρ c of P-GaN decreased by 30%, and the hole carrier concentration increased significantly. Additionally, the atom displacement damage effect of a 2-MeV proton of 1 × 1013 p/cm2 led to a significant degradation of the electrical properties of P-GaN, while those of N-GaN remained unchanged. P-GaN was found to be more sensitive to irradiation than N-GaN thin film. The effectiveness of x-ray irradiation in enhancing the electrical properties of P-GaN thin films was demonstrated in this study.

Electronic Excitation Response of DNA to High-Energy Proton Radiation in Water.

The lack of molecular-level understanding for the electronic excitation response of DNA to charged particle radiation, such as high-energy protons, remains a fundamental scientific bottleneck in advancing proton and other ion beam cancer therapies. In particular, the dependence of different types of DNA damage on high-energy protons represents a significant knowledge void. Here we employ first-principles real-time time-dependent density functional theory simulation, using a massively parallel supercomputer, to unravel the quantum-mechanical details of the energy transfer from high-energy protons to DNA in water. The calculations reveal that protons deposit significantly more energy onto the DNA sugar-phosphate side chains than onto the nucleobases, and greater energy transfer is expected onto the DNA side chains than onto water. As a result of this electronic stopping process, highly energetic holes are generated on the DNA side chains as a source of oxidative damage.

Effect of Double Insulators on the Performance Improvement of 3 MeV Proton-Irradiated AlGaN/GaN MIS-HEMTs

To improve the performance of AlGaN/GaN high electron mobility transistors (HEMTs) after exposure to high energy proton irradiation, a MIS-HEMT with Al2O3/SiNx (SiNx next to semiconductor) double insulators is proposed and fabricated. Besides, the common Schottky gate HEMT and MISHEMTs with single SiNx layer and single Al2O3 layer are also fabricated as a control for comparison. After exposed to 3 MeV proton irradiation with a fluence of 1 × 1014cm−2, the MIS-HEMT with Al2O3/SiNx double insulators shows the smallest drain saturation current and breakdown voltage degradation, the smallest voltage drift and interface charge change through IV and CV tests. The smallest degradation of the carrier density and mobility contributes to its better saturation current degradation performance. Besides, experimental results of voltage drift are in accordance with simulation results. What’s more, the MIS-HEMT with Al2O3/SiNx double insulators exhibits the lowest drain current degradation and the quickest response during hard switching tests. A relatively large displacement threshold energy of Al2O3 and better passivation effect of SiNx contribute to the reliability improvement of AlGaN/GaN HEMTs after the proton-irradiation.

High-energy proton detector based on semiconductor telescope

Abstract Space radiation particles will cause a variety of radiation effects on orbiting satellites, such as single event effects, total ionizing dose, displacement damage, etc. In response to these space radiation effects, BeiDou Navigation satellites M15/M16 operating in medium earth orbit (MEO) developed the first integrated monitor for high-energy proton and particle radiation effects, based on space particle radiation detection technology. This payload realizes the joint observation of the high-energy proton environment, particle radiation linear energy transfer spectrum, and total radiation dose in the MEO. According to the detection data, research on the characteristics and laws of the space particle radiation effects can be carried out, and the problem of spacecraft reliability verification in orbit can be solved from the causal chain. In this article, we have introduced the high-energy proton detector (energy range 3–300 MeV), including technical indicators, working principles, instrument design, and ground calibration.

The impacts of localized backside etching on proton radiation response in SOI passive devices

In this work, the effect of high-energy proton irradiation on the radiofrequency (RF) properties of silicon-on-insulator (SOI) substrates is investigated. The localized backside etching (LBE) structure is introduced for RF properties improvement and proton irradiation hardening. It is observed that after the 50 MeV proton irradiation with a fluence of 1 × 1012 p cm−2, the attenuation, crosstalk, and relative permittivity significantly decrease for conventional SOI substrates. In contrast, LBE substrates are less sensitive to proton irradiation and simultaneously exhibit better RF performance. The enhancement of the LBE structure on irradiation tolerance is qualitatively characterized by the equivalent circuit model parameter extraction.

Ultra-Rapid, Physics-Based Development Pathway for Reactor-Relevant RF Antenna Materials

This article presents a rapid, atomistically informed, experimental development pathway for fusion reactor-relevant radio-frequency (RF) antenna materials in the Cu-Cr-(Nb,Al,Zr) composition system, with the goal of improving upon GRCop-84. RF antennas in a tokamak fusion reactor will face a unique set of challenges as both structural and functional materials. The desired material must simultaneously achieve and maintain high electrical conductivity, high strength, high thermal conductivity, resist high temperatures, possess low nuclear activation, and incur low damage due to neutron bombardment. The GRCop-84 alloy serves as a starting point for iterative improvement, with the desire to reduce or eliminate Nb from the material to minimize nuclear activation. The rapid development pathway makes use of a multi-target combinatorial thick-film sputtering process to produce full ternary phase diagrams on a Si wafer substrate. Transient grating spectroscopy (TGS), a laser-ultrasonic method, will determine spatially varying thermoelastic properties, while four terminal electrical conductivity measurements will map out the best performing regions of the sample for in-depth study at larger length scales. High-energy proton and self-ion irradiation emulates the effects of neutron damage on the thermal/electric properties. With rapid turnaround time (~days) in terms of mapping radiation damage-induced material property changes in the full ternary system, these techniques allow rapid iteration toward an optimal material, testing hundreds of nearby compositions in the time it took to test one. Focused testing of larger, single composition samples (produced in an arc furnace or by laser sintering) provides data on structural and high-power RF properties and validates our thick-film-based workflow.

Impact of 100 MeV high-energy proton irradiation on β-Ga2O3 solar-blind photodetector: Oxygen vacancies formation and resistance switching effect

β-Ga2O3 based solar-blind photodetectors have strong radiation hardness and great potential applications in Earth's space environment due to the large bandgap and high bond energy. In this work, we investigated the photoelectric properties influence of β-Ga2O3 photodetector irradiated by 100 MeV high-energy protons which are the primary components in the inner belt of the Van Allen radiation belts where solar-blind photodetectors mainly worked. After proton irradiation, due to the formation of more oxygen vacancies and their migration driven by bias at the metal/semiconductor interface, transportation of carriers transforms with electron tunneling conduction for low-resistance state and thermionic emission for high resistance state. As a result, the current–voltage curves of β-Ga2O3 solar-blind photodetectors exhibit apparent hysteresis loops. The photoresponsivity of β-Ga2O3 photodetectors slightly increases from 1.2 × 103 to 1.4 × 103 A/W after irradiation, and the photoresponse speed becomes faster at a negative voltage while slower at positive voltage. The results reveal the effects of high-energy proton irradiation on β-Ga2O3 solar-blind photodetectors and provide a basis for the study of their use in a radiation harsh environment.

Effect of High-Energy Proton and Gamma Irradiation on the Structure of DNA in Solutions

Effect of High-Energy Proton and Gamma Irradiation on the Structure of DNA in Solutions

The microstructural in-sight to the mechanical behavior of alumina after high energy proton irradiation

• Mechanical behaviour of specimens extracted from alumina tubes manufactured by slip casting. • Influence of high-energy proton irradiation on the mechanical properties of alumina ceramics. • Compression and micro-indentation tests. • Microstructural changes induced by high-energy proton irradiation. The mechanical behaviour of prismatic bars extracted from a high purity alumina tube was studied comparatively in the as-received condition and after being irradiated with high-energy protons. For this study, ten samples were irradiated with 8 MeV H + ion beams up to a fluence of 1.63 × 10 16 ions/cm 2 . Values of compressive strength, elastic modulus, hardness, and fracture toughness were determined from compression and micro-indentation tests. After the mechanical tests, the relationship of the mechanical behaviour shown with the microstructure was considered by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A clear trend was observed, compressive strength and elastic modulus were considerably reduced, while hardness and fracture toughness increased. This change is attributed to radiation-induced cavities and dislocation loops after high-energy ion-irradiation.

Evaluation of the resistance of halide perovskite solar cells to high energy proton irradiation for space applications

Hybrid perovskite solar cells have been under the radar of research efforts worldwide in the recent years. In particular, halide perovskite solar cells are of great interest for space applications due to their high efficiencies, low cost and extremely low weight. A few reports have shown good tolerance of the perovskite solar cells to high energy proton irradiation that adds interest for their space use. In this work, we explore the endurance of typical mesoscopic n-i-p MAPbI 3 solar cells in LEO (low earth orbit) conditions. We observe no measurable damage to the J-V performance for 10 MeV protons by in-situ measurements for the cells containing Spiro-OMeTAD as the hole transporting material (HTL). However, when P3HT is employed as the HTL, we observe a healing effect and the efficiency improves after irradiation. For the Spiro-OMeTAD case, we do observe degradation of the performance by lowering the proton energies to 5 and 1 MeV as expected due to the increased number of collisions. Numerical simulation by wxAMPS software allows to understand the origin of the damage for the studied architecture solar cells under 5 and 1 MeV. • High energy proton irradiation produces no damage to solar cells containing Spiro-OMeTAD as the HTM while P3HT cells improves performance. • In-situ characterization of Spiro-OMeTAD cells confirms that there is no permanent damage by high energy protons. • Damage is only observed for lower energy irradiation with 5 and 1 MeV. Simulation of JV curves identifies induced defects in the perovskite layer.

High-energy proton radiation effect of Gallium nitride power device with enhanced Cascode structure

To ascertain the damage mechanism caused by high-energy proton irradiation to AlGaN/GaN power devices of enhanced Cascode structures, we study the radiation effect of enhanced Cascode structure and depletion AlGaN/GaN power devices by using 60 MeV energy protons in this work. In the case of proton injection reaching 1×10&lt;sup&gt;12&lt;/sup&gt; p/cm&lt;sup&gt;2&lt;/sup&gt;, the experimental results show that the threshold voltage of the Cascode type device is negatively drifted, the transconductance decreases, and the peak leakage current increases. The threshold voltage decreases from 4.2 V to 3.0 V, with a decrement of 1.2 V, and the peak transconductance value decreases from 0.324 S/mm to 0.260 S/mm, with a decrement of about 19.75%. There is no significant change after the conventional depleted AlGaN/GaN device has been irradiated. The Cascode-type AlGaN/GaN power device is more sensitive to proton irradiation than the depletion-type AlGaN/GaN device. The Cascode-type device is sensitive to proton irradiation because of its structure connected to a silicon-based MOS tube. Proton irradiation causes the silicon-based MOS gate oxide layer to generate a large amount of net positive charge, induces an ionization damage effect, and causes threshold voltage to negatively drift and the gate leakage current to increase. The equivalent 60 MeV energy protons and cumulative injection of 1×10&lt;sup&gt;12&lt;/sup&gt; p/cm&lt;sup&gt;2&lt;/sup&gt; dose of the &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ {}_{}{}^{60}\rm{C}\rm{o}~\rm{\gamma } $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; radiation device is used to obtain the ionization damage effect. It is found that after being irradiated by the equivalent dose &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}${}_{}{}^{60}\rm{C}\rm{o}~\rm{\gamma }$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; ray , the device has the threshold voltage decreasing from 4.15 V to 2.15 V, with a negative drift of 2 V; transconductance peak decreases from 0.335 S/mm to 0.300 S/mm, with an approximate decrement of 10.45%. The degradation of the electrical properties of the device after being irradiated by &lt;inline-formula&gt;&lt;tex-math id="M4"&gt;\begin{document}${}_{}{}^{60}\rm{C}\rm{o}~\rm{\gamma }$\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M4.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="1-20221617_M4.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; ray is consistent with the degradation law after being irradiated by high-energy protons. In order to further verify the experimental accuracy and conclusions, the ionization energy loss and non-ionization energy loss induced by radiation in the device are obtained by Monte Carlo simulation. The simulation results show that the ionization energy loss induces silicon-based MOS to generate oxide trap charge and interfacial state trap charge, which is mainly responsible for the performance degradation of AlGaN/GaN HEMT power devices with enhanced Cascode structure.

MeV proton irradiation damage in Ta: Measurements, characterization and comparison to W

The effects of high-energy proton irradiation on tantalum and its properties, were studied at the Soreq Applied Research Accelerator Facility (SARAF) using a high-flux 2.2 MeV proton beam. Samples were characterized by optical interferometry, nano-indentation and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), to study the effect of radiation damage. The experimental data on the penetration depth of 2.2 MeV protons in tantalum was found to be in good agreement with simulations and an increase of the irradiated sample’s hardness was measured. The volume expansion was found to be correlated to the total proton fluence. With the aid of density functional theory estimates of the point defect formation volumes, we suggest that hydrogen occupies mainly interstitial sites in the Ta lattice. We observed extensive diffusion of the hydrogen into the material. Thus, no blistering was observed up to a total fluence of 1.9•10 20 P/cm 2 , extending the lower bound for blister formation in tantalum to one to three orders of magnitude above the critical fluence for blistering in tungsten. A reaction-diffusion model was employed to analyze the spatial distribution of the point defects, to assist in the interpretation of the results in comparison with tungsten, and to identify the role of the hydrogen diffusion. We conclude that tantalum is a promising structural material in proton radiation environments.

Effect of Irradiation on Corrosion Behavior of 316L Steel in Lead-Bismuth Eutectic with Different Oxygen Concentrations

In an accelerator-driven system (ADS), the beam window material of the spallation neutron target is heavily irradiated under severe conditions, in which the radiation damage and corrosion co-occur because of high-energy neutron and/or proton irradiation in the lead–bismuth flow. The materials used in ADSs must be compatible with the liquid metal (lead–bismuth eutectic (LBE)) to prevent issues such as liquid metal embrittlement (LME) and liquid metal corrosion (LMC). This study considers the LMC behavior after ion irradiation of 316L austenitic steel for self-ion irradiations followed by the corrosion tests in LBE with critical oxygen concentration. The 316L samples were irradiated by 10.5 MeV-Fe3+ ions at a temperature of 450 °C, up to 50 displacements per atom (dpa). After the corrosion test performed at 450 °C in LBE with low oxygen concentration, a surface of the nonirradiated area was not oxidized but appeared with locally corrosive morphology, Ni depletion, whereas an iron/chromium oxide layer fully covered the irradiated area. In the case of the corrosion surface with high oxygen concentration in LBE, the surface of the nonirradiated area was covered by an iron oxide layer only, whereas the irradiated area was covered by the duplex layers comprising iron and iron/chromium oxides. It is suggested that irradiation can enhance the oxide layer formation because of the enhancement of Fe and/or oxygen diffusion induced by the radiation defects in 316L steel.

Evaluating Ocular Response in the Retina and Optic Nerve Head after Single and Fractionated High-Energy Protons.

There are serious concerns about possible late radiation damage to ocular tissue from prolonged space radiation exposure, and occupational and medical procedures. This study aimed to investigate the effects of whole-body high-energy proton exposure at a single dose on apoptosis, oxidative stress, and blood-retina barrier (BRB) integrity in the retina and optic nerve head (ONH) region and to compare these radiation-induced effects with those produced by fractionated dose. Six-month-old C57BL/6 male mice were either sham irradiated or received whole-body high energy proton irradiation at an acute single dose of 0.5 Gy or 12 equal dose fractions for a total dose of 0.5 Gy over twenty-five days. At four months following irradiation, mice were euthanized and ocular tissues were collected for histochemical analysis. Significant increases in the number of apoptotic cells were documented in the mouse retinas and ONHs that received proton radiation with a single or fractionated dose (p < 0.05). Immunochemical analysis revealed enhanced immunoreactivity for oxidative biomarker, 4-hydroxynonenal (4-HNE) in the retina and ONH following single or fractionated protons with more pronounced changes observed with a single dose of 0.5 Gy. BRB integrity was also evaluated with biomarkers of aquaporin-4 (AQP-4), a water channel protein, a tight junction (TJ) protein, Zonula occludens-1 (ZO-1), and an adhesion molecule, the platelet endothelial cell adhesion molecule-1 (PECAM-1). A significantly increased expression of AQP-4 was observed in the retina following a single dose exposure compared to controls. There was also a significant increase in the expression of PECAM-1 and a decrease in the expression of ZO-1 in the retina. These changes give a strong indication of disturbance to BRB integrity in the retina. Interestingly, there was very limited immunoreactivity of AQP-4 and ZO-1 seen in the ONH region, pointing to possible lack of BRB properties as previously reported. Our data demonstrated that exposure to proton radiation of 0.5 Gy induced oxidative stress-associated apoptosis in the retina and ONH, and changes in BRB integrity in the retina. Our study also revealed the differences in BRB biomarker distribution between these two regions. In response to radiation insults, the cellular response in the retina and ONH may be differentially regulated in acute or hyperfractionated dose schedules.