X-ray Energy Range Research Articles

X-ray multi-scale microfabrication system and x-ray imaging evaluation system all in one beamline

We have completed a system that can achieve both deep x-ray lithography and submicron x-ray lithography with a single beamline by introducing the combination of x-ray plane and cylindrical mirrors. This x-ray lithography system can provide a large-scale microfabrication processing with 210 × 300 mm2 (A4 size). To exploit multiscale lithography, the beamline has a beam transport vacuum duct with a two-stage stacked structure and a 5-axis stage. This two-stage stacked structure allows us to fabricate both micron scale structures with high aspect ratios and submicron scale structures using the same beamline. In addition, x-ray imaging and computer tomography (CT) system are connected to the x-ray lithography system for nondestructive inspection and evaluation of the fabricated microstructures. The x-ray imaging system constructed this study has a relatively low energy range of x-ray energy in the beamline, which is in the range of 2–15 keV or less. Therefore, relatively good absorption contrast can be obtained for plastic materials, biomaterials, and the like. Since nondestructive imaging of the processed shape by x-ray lithography is possible, it is a very useful system in processing and evaluation can be performed simultaneously. This system also enables us to obtain the live images with keeping the creature alive in liquid using an indirect x-ray imaging system which converts x-ray images to visible light images through the fluorescent plate.

Assessment of the Attenuation Properties of Commercial Lead-Free Radiation-Shielding Composite Materials Against Medical X-rays

Six commercial, lead-free, radiation protective materials were tested for their attenuation across a range of X-ray energies used in medical diagnostic imaging and interventional radiology. While all the tested materials showed the specified attenuation at the X-ray energy claimed by their manufacturers, only two of the materials showed satisfactory attenuation in an extended range of medical X-ray energies (generated in X-ray tubes with voltages between 50 and 150 kV). The lead-free materials are lighter than the lead-containing materials, which is very important for those wearing the radiation protective garments for an extended time; however, the main focus in the promotion of radiation-shielding materials should still be on their attenuation efficacy against both the primary and the scattered X-rays present in medical environments. The end users should be informed on the material attenuation in an extended energy range, especially in the range where scatter radiation occurs, and not just about the peak material attenuation performance at energies where the X-rays are generated. Scatter radiation is the main reason for the occupational radiation exposure of medical personnel, who should have the whole picture about the shielding ability of the protective garments that they strongly rely on.

Ex-vivo atherosclerotic plaque characterization using spectral photon-counting CT: Comparing material quantification to histology

Background and aimsAtherosclerotic plaques are characterized as being vulnerable to rupture based on a series of histologically defined features, including a lipid-rich necrotic core, spotty calcification and ulceration. Existing imaging modalities have limitations in their ability to distinguish between different materials and structural features. We examined whether X-ray spectral photon-counting computer tomography (SPCCT) images were able to distinguish key plaque features in a surgically excised specimen from the carotid artery with comparison to histological images. MethodsAn excised carotid plaque was imaged in the diagnostic X-ray energy range of 30–120 keV using a small-bore SPCCT scanner equipped with a Medipix3RX photon-counting spectral X-ray detector with a cadmium telluride (CdTe) sensor. Material identification and quantification (MIQ) images of the carotid plaque were generated using proprietary MIQ software at 0.09 mm volumetric pixels (voxels). The plaque was sectioned, stained and photographed at high resolution for comparison. ResultsA lipid-rich core with spotty calcification was identified in the MIQ images and confirmed by histology. MIQ showed a core region containing lipid, with a mean concentration of 260 mg lipid/ml corresponding to a mean value of −22HU. MIQ showed calcified regions with mean concentration of 41 mg Ca/ml corresponded to a mean value of 123HU. An ulceration of the carotid wall at the bifurcation was identified to be lipid-lined, with a small calcification identified near the breach of the artery wall. ConclusionsSPCCT derived material identification and quantification images showed hallmarks of vulnerable plaque including a lipid-rich necrotic core, spotty calcifications and ulcerations.

Soft X-ray spectro-ptychography of boron nitride nanobamboos, carbon nanotubes and permalloy nanorods.

Spectro-ptychography offers improved spatial resolution and additional phase spectral information relative to that provided by scanning transmission X-ray microscopes. However, carrying out ptychography at the lower range of soft X-ray energies (e.g. below 200 eV to 600 eV) on samples with weakly scattering signals can be challenging. Here, results of soft X-ray spectro-ptychography at energies as low as 180 eV are presented, and its capabilities are illustrated with results from permalloy nanorods (Fe 2p), carbon nanotubes (C 1s) and boron nitride bamboo nanostructures (B 1s, N 1s). The optimization of low-energy X-ray spectro-ptychography is described and important challenges associated with measurement approaches, reconstruction algorithms and their effects on the reconstructed images are discussed. A method for evaluating the increase in radiation dose when using overlapping sampling is presented.

Printable Perovskite Diodes for Broad-Spectrum Multienergy X-Ray Detection.

Multienergy X-ray detection is critical to effectively differentiate materials in a variety of diagnostic radiology and nondestructive testing applications. Silicon and selenium X-ray detectors are the most common for multienergy detection; however, these present poor energy discrimination across the broad X-ray spectrum and exhibit limited spatial resolution due to the high thicknesses required for radiation attenuation. Here, an X-ray detector based on solution-processed thin-film metal halide perovskite that overcomes these challenges is introduced. By harnessing an optimized n-i-p diode configuration, operation is achieved across a broad range of soft and hard X-ray energies stemming from 0.1 to 10's of keV. Through detailed experimental and simulation work, it is shown that optimized Cs0.1 FA0.9 PbI3 perovskites effectively attenuate soft and hard X-rays, while also possessing excellent electrical properties to result in X-ray detectors with high sensitivity factors that exceed 5 × 103 and 6 × 104 µC Gy-1 cm-2 within soft and hard X-ray regimes, respectively. Harnessing the solution-processable nature of the perovskites, roll-to-roll printable X-ray detectors on flexible substrates are also demonstrated.

PolyX beamline at SOLARIS—Concept and first white beam commissioning results

PolyX is a compact bending magnet beamline under construction at National Synchrotron Radiation Centre SOLARIS, which will be available to users in mid-2023. The beamline is focused on X-ray microimaging and microspectroscopy in the tender/hard (4–15 keV) X-ray energy range. The name PolyX comes from polycapillary X-ray optics that will be extensively used for efficient X-ray focusing and from the possibility of using polychromatic or broadband X-rays to increase the rather low flux from the SOLARIS bending magnet in the hard X-ray energy range. Polycapillary optics will provide focal spots with sizes of 8–200 μm. Single bounce ellipsoidal capillary is expected to provide a ∼2 μm focal spot size. The main experimental techniques at PolyX will be X-ray absorption and phase-contrast imaging and microtomography, micro-X-ray fluorescence imaging and micro-X-ray absorption spectroscopy. This paper presents the concept of PolyX beamline and preliminary “white” beam commissioning results.

Energy variation of double K -shell photoionization of Ne

We report on an experimental and theoretical study of double $K$-shell photoionization of Ne over the 2.3--8.5 keV x-ray energy range. The ratio of double-to-single $K$-shell photoionization cross sections was determined experimentally by measuring the relative rates of the $KK\ensuremath{-}K{L}_{2,3}{L}_{2,3}$ ($^{2}D$) Auger hypersatellite and the $K\ensuremath{-}{L}_{2,3}{L}_{2,3}$ ($^{1}D$) diagram Auger transitions. By scaling the hypersatellite-diagram Auger-electron ratios to $KK/K$ cross-section ratios, comparison was made with theoretical cross-section ratios of He-like ${\mathrm{Ne}}^{8+}$ determined by the $R$ matrix with pseudostates method. The experimental Ne and theoretical ${\mathrm{Ne}}^{8+}$ cross-section ratios show similar variations with energy, but the experimental ratios systematically exceed the calculated ratios and also show a lower threshold energy for double $K$-shell photoionization onset compared to the computed ${\mathrm{Ne}}^{8+}$ threshold. The discrepancy is attributed to effects of $L$-shell electrons not included in the He-like ${\mathrm{Ne}}^{8+}$ calculations. Quantified scaling with nuclear charge $Z$ along the He-like isoelectronic sequence indicates that the measured 10-electron $Z=10$ double $K$-shell photoionization cross section behaves like the computed He-like $Z=8.9$ cross section, suggesting an effective nuclear screening parameter of ${s}_{L}=1.1$ by the additional eight outer $L$-shell electrons. Experimental results for the energy variations of Auger electron transitions from other multielectron hole states are also discussed.

Calibration of a PIXE system at Peking University

A method combining particle-induced X-ray emission spectrometry (PIXE) and elastic backscattering spectrometry (EBS) was used to calibrate the PIXE system at Peking University. The selected thin standard samples were typically 50 μg/cm2 and the thicknesses of two thick standard samples are 3 mm. The calibration of PIXE system was divided into the calibration curve measurement of thin standard samples and the external standard method of thick standard samples. Both thin and thick samples cover the commonly used PIXE X-ray energy range 1.4–18.0 keV. GUPIXWIN introduces an Instrument factor H to describe the calibration process. It is found that the measured H(Z) curve can be approximated as a Z-independent line with an average value of 3.30×10−4. The deviation of multiple measurements of a single element is between 0.42% and 4.75%. For thick samples, the incident particles are protons and 3He+, a H value of (4.97±0.01)×10−4 was obtained.

Micro-Computed Tomography Beamline of the Australian Synchrotron: Micron-Size Spatial Resolution X-ray Imaging

The first new beamline of the BRIGHT project—involving the construction of eight new beamlines at the Australian Synchrotron—is the Micro-Computed Tomography (MCT) beamline. MCT will extend the facility’s capability for higher spatial resolution X-ray-computed tomographic imaging allowing for commensurately smaller samples in comparison with the existing Imaging and Medical Beamline (IMBL). The source is a bending-magnet and it is operating in the X-ray energy range from 8 to 40 keV. The beamline provides important new capability for a range of biological and material-science applications. Several imaging modes will be offered such as various X-ray phase-contrast modalities (propagation-based, grating-based, and speckle-based), in addition to conventional absorption contrast. The unique properties of synchrotron radiation sources (high coherence, energy tunability, and high brightness) are predominantly well-suited for producing phase contrast data. An update on the progress of the MCT project in delivering high-spatial-resolution imaging (in the order of micron size) of mm-scale objects will be presented in detail with some imaging results from the hot-commissioning stage.

Enhanced microprobe endstation for high-throughput and versatile sample analysis at APS 2-ID

The new APS-U 2-ID Microprobe instrument will provide high-throughput and versatile sample analysis capabilities and will bridge the gap to higher resolution APS-U nanoprobes. Available techniques include XRF microscopy, tomography, µXANES, µSAXS, ptychography, and laminography. A very high flux of more than 1013 photon/s is delivered across a wide range of x-ray energies from 7-20 keV. KB mirror focusing optics enable a small 50nm spot size for detailed resolution, while also providing a long working distance of 50 mm to accommodate large samples of up to 10x10 mm. The Microprobe will accommodate samples in an inert helium environment, with controlled flow of fluids, electrical biasing, and sample heating & cooling. High throughput is enabled by fast and smooth fly-scanning stages, a high-accuracy metrology system, new detectors, and upgrades in the multi-bend achromat storage ring, insertion device, 2-ID beamline, and monochromator. All these instrument upgrades will empower advancements in biological, materials and environmental sciences.

The SXP instrument at the European XFEL

The successful implementation of the baseline instruments at the European XFEL has triggered a second phase of instrument developments aiming to extend the portfolio of available techniques. At the soft X-ray undulator (SASE 3), the Soft X-ray Port (SXP) instrument is currently under construction. Conceived as an open port, it focuses primarily on femtosecond time-resolved X-ray photoelectron spectroscopy (TR-XPES), which has proven to be a powerful tool to understand the properties of materials and the interaction between their internal degrees of freedom. The extension of this technique to the soft X-ray energy range is only possible at MHz free electron lasers (FELs) due to space-charge effects which limit the maximum photon flux per pulse on the sample. In this contribution, the SXP instrument at the European XFEL and the implementation of TR-XPES using a momentum microscope are presented. The photon energy range available at SASE 3, 0.25 keV to 3.5 keV, and the variable polarization will allow for the simultaneous characterization of the electronic, magnetic, chemical and structural properties of materials with femtosecond time resolution. To this end, a wide range of laser excitation wavelengths, ranging from the XUV to the THz region, will be available.

Ultra-compact x-ray spectrometer for high-repetition-rate laser-plasma experiments.

We present in this work the development of an ultra-compact, multi-channel x-ray spectrometer (UCXS). This diagnostic has been specially built and adapted to perform at high-repetition-rate (>1Hz) for high-intensity, short-pulse laser plasma experiments. X-ray filters of varying materials and thicknesses are chosen to provide spectral resolution up to ΔE ≈ 1keV over the x-ray energy range of 1-30keV. These filters are distributed over a total of 25 channels, where each x-ray filter is coupled to a single scintillator. The UCXS is designed to detect and resolve a large variety of laser-driven x-ray sources such as low energy bremsstrahlung emission, fluorescence, and betatron radiation (up to 30keV). Preliminary results from commissioning experiments at the ABL laser facility at Colorado State University are provided.

Development of LGAD sensors with a thin entrance window for soft X-ray detection

We show the developments carried out to improve the silicon sensor technology for the detection of soft X-rays with hybrid X-ray detectors. An optimization of the entrance window technology is required to improve the quantum efficiency. The LGAD technology can be used to amplify the signal generated by the X-rays and to increase the signal-to-noise ratio, making single photon resolution in the soft X-ray energy range possible. In this paper, we report first results obtained from an LGAD sensor production with an optimized thin entrance window. Single photon detection of soft X-rays down to 452 eV has been demonstrated from measurements, with a signal-to-noise ratio better than 20.

Simulation of X-ray Hartmann wavefront sensing with the Synchrotron Radiation Workshop.

X-ray wavefront measurement is an important beam diagnostic tool, especially for the diffraction-limited X-ray beam. These in situ diagnostics give a better understanding of beam imperfections, and they enable feedback for possible corrections and/or optical alignment improvements. Hartmann wavefront sensing is one of the promising techniques to perform in situ X-ray wavefront measurements. In this work, a simulation tool of the X-ray Hartmann Wavefront Sensor (HWS) is developed under the Synchrotron Radiation Workshop (SRW) framework. Using this new simulation capability, one can take advantage of the full SRW package to simulate Hartmann wavefront sensing with the beam traveling from the X-ray source to the sample through different X-ray optical components. This SRW HWS simulation tool can help to optimize the wavefront sensor parameters for a specific X-ray energy range. It can also simulate an in situ wavefront measurement experiment with a particular beamline optical layout and predict the expected results of the wavefront measurement under different beamline configurations.

Treatment Response Assessment Using Daily Dual-Energy CT during Pre-Operative Radiation Therapy for Early-Stage Breast Cancer

<h3>Purpose/Objective(s)</h3> We have previously reported that the low energy mono-energetic images (MEI) derived from dual-energy CT (DECT) can amplify the detection of radiation-induced changes in tissue. This work aims to investigate the use of low energy MEI derived from daily DECT to assess tumor response during radiation therapy (RT) of early-stage breast cancer. <h3>Materials/Methods</h3> Daily DECT data acquired during routine CT-guided RT delivery for 35 early-stage breast cancer patients enrolled in an institutional prospective pre-operative accelerated partial breast irradiation trial, along with tumor pathological data collected from the biopsy before RT and the excised tissue from the surgery post RT, were analyzed. All patients were treated with 30 Gy in 5 fractions in two weeks. The DECTs were acquired immediately before the fractional dose delivery using an in-room CT scanner equipped with a sequential DE protocol. MEI images across a range of x-ray energies were reconstructed using an image-based material decomposition. Fractional changes in mean CT number (mCTN) in gross tumor volume (GTV) on MEIs were extracted and the changes from the first to the last fraction were correlated to the tumor cellularity changes from the pathological data collected before and after RT using the Student's T-Test. As a control, the mCTN changes on MEIs in a region far from irradiated volumes were calculated. The results from the MEI data were compared to those obtained from the standard 120 kVp CTs of the same subjects. <h3>Results</h3> The data from 20 out of 35 patients were found to be suitable for this analysis. The greatest enhancement in GTV mCTN change was observed for MEI at 40 keV, the lowest available energy. The average change in GTV mCTN between the first and last fractions of treatments was 2.9 times larger for 40 keV MEIs than that for the standard 120 kVp CTs. For 11 out of the 20 patients, the GTV mCTN changes were greater than 15 HU on the 40 keV MEI and their average change in cellularity was 36.5 ± 10.3%. For the remaining 9 patients, the GTV mCTN changes were less than 15 HU on the 40 keV MEI and the average change in cellularity was 14.4 ± 9.8%. The correlation between change in GTV mCTN and change in cellularity was found to be significant (p=0.02). The average mCTN change in the control region was of 0.2 ± 2.0 HU on the 40 keV for all 20 patients. <h3>Conclusion</h3> Tumor pathological response for early-stage breast cancer treated with pre-operative accelerated partial breast irradiation can be predicted by the change of quantitative features, such as mean CT number, on low energy MEI derived from DECT acquired during the radiation treatment. Compared to the standard CT, the low energy MEIs substantially amplify the changes of mCTN, enhancing the viability of using quantitative CT features as a biomarker for early RT response assessment.

Chiral surface spin textures in Cu2OSeO3 unveiled by soft X-ray scattering in specular reflection geometry

ABSTRACT Resonant elastic soft X-ray magnetic scattering (XRMS) is a powerful tool to explore long-periodic spin textures in single crystals. However, due to the limited momentum transfer range imposed by long wavelengths of photons in the soft x-ray region, Bragg diffraction is restricted to crystals with the large lattice parameters. Alternatively, small-angle X-ray scattering has been involved in the soft energy X-ray range which, however, brings in difficulties with the sample preparation that involves focused ion beam milling to thin down the crystal to below a few hundred nm thickness. We show how to circumvent these restrictions using XRMS in specular reflection from a sub-nanometer smooth crystal surface. The method allows observing diffraction peaks from the helical and conical spin modulations at the surface of a Cu 2 OSeO 3 single crystal and probing their corresponding chirality as contributions to the dichroic scattered intensity. The results suggest a promising way to carry out XRMS studies on a plethora of noncentrosymmetric systems hitherto unexplored with soft X-rays due to the absence of the commensurate Bragg peaks in the available momentum transfer range.

Synthesis of Single Crystal Perovskite MAPbBr3 by Using Anti-solvent Vapor-assisted Crystallization Method for X-Ray Photodetector Application

Perovskite methylammonium lead tri-bromide (MAPbBr3) has been extensively studied for active material of X-ray photodetector, due to its suitable bandgap with the X-ray energy range and its high value of charge carrier diffusion to produce both high efficiency and sensitivity of photodetector. However, the high resistivity due to the large crystal defect density caused by its polycrystalline crystal structure will reduce the charge carrier mobility and lifetime and therefore produce less sensitive photodetector. The solution to overcome these problems is the perovskite MAPbBr3 material must be in the form of single crystal to produce low crystal defect density. Another practical problem for X-ray photodetector application is the most of the reported perovskite crystals have the size less than 1 cm2. For the practical purposes of X-ray photodetector devices, a cubic structure and large crystal dimension (larger than 1 cm2) are required to adjust into the flat-panel detector. In this research, MAPbBr3 perovskite crystals were synthesized by using Anti-solvent Vapor-assisted Crystallization (AVC) method. The precursor MAPbBr3 was prepared by dissolving MABr and PbBr2 with molar ratio of 1.25 and 1.0 in dimethylformamide (DMF). Dichloromethane (DCM) was used as anti-solvent. The diffusion of anti-solvent DCM into precursor solution was controlled by providing a small hole on the top of vial which contains the precursor. The crystal growth rate was controlled by varying the volume ratio of DCM and MAPbBr3 precursor solution. The obtained largest crystal size of 7mm × 7mm was prepared with a volume ratio of DCM and precursor of 2.67 and a volume of 3 mL precursor solution. The energy gap MAPbBr3 crystal is 2.14 eV derived from UV-Vis absorbance spectrum. The XRD pattern of the crystal showed that the perovskite MAPbBr3 had cubic crystal structure with a lattice constant of 5.99 Å. The diffraction pattern of the crystal showed a dominant peak of crystal plane (100). This result confirmed that the synthesized MAPbBr3 crystal has a single crystal oriented in x-axis direction.

X-ray emission associated with radiative recombination for Pb82+ ions at threshold energies

For decelerated bare lead ions at a low beam energy of 10 MeV/u, the x-ray emission associated with radiative recombination (RR) at threshold energies has been studied at the electron cooler of CRYRING@ESR at GSI, Darmstadt. In our experiment, we observed the full x-ray emission pattern by utilizing dedicated x-ray detection chambers installed at 0∘ and 180∘ observation geometry. Most remarkably, no line distortion effects due to delayed emission are present in the well-defined x-ray spectra, spanning a wide range of x-ray energies (from about 5 to 100 keV), which enables us to identify fine-structure resolved Lyman, Balmer, and Paschen x-ray lines along with the RR transitions into the K, L, and M shells of the ions. For comparison with theory, an elaborate theoretical model is established taking into account the initial population distribution via RR for all atomic levels up to Rydberg states with principal quantum number n=165 in combination with time-dependent feeding transitions. Within the statistical accuracy, the experimental data are in very good agreement with the results of rigorous relativistic predictions. Most notably, this comparison sheds light on the contribution of prompt and delayed x-ray emission (up to 70 ns) to the observed x-ray spectra, originating in particular from yrast transitions into inner shells.2 MoreReceived 19 January 2022Accepted 31 March 2022DOI:https://doi.org/10.1103/PhysRevA.105.052804Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAtomic & molecular collisionsAtomic spectraElectronic transitionsTechniquesEnergy-dispersive x-ray spectroscopyAtomic, Molecular & OpticalAccelerators & Beams

Are tungsten-based nuclear fusion components truly invisible to x-ray inspection?

The ability to detect undesired volumetric defects in reactor components could affect the safety and reliability of a fusion power plant and change the expected lifetime and performance of the reactor. This is even more true for critical reactor parts like plasma-facing components (PFCs) which have to withstand challenging in-vessel conditions due to a combination of plasma bombardment, radiation, and nuclear heating. The structural integrity of these components prior to their installation in a nuclear fusion reactor needs to be assessed non-destructively. Until now, industrial x-ray radiography and tomography have not been used to non-destructively inspect fusion components due to their lack of penetration power into dense material such as tungsten which is often used to manufacture PFCs. However, aiming to revert this consolidated belief, we have demonstrated for the first time the feasibility of assessing volumetric defects non-destructively on DEMO divertor mock-up by means of MeV energy range x-ray tomography. The authors believe that the application of this technology could be easily extended for inspecting large fusion components and positively impact procedures to be followed in the qualification of fusion components for current and future nuclear reactors.

Simulation model criteria for a synchrotron radiation based MBRS/MRT clinical facility

MicroBeam Radiosurgery (MBRS, also referred to as Microbeam Radiation Therapy, MRT) is a potential clinical technique for the treatment of solid tumors. MBRS utilizes a series of narrow 30 to 50μm beams of ultra-high, lethal dose synchrotron x-ray radiation (peaks) separated by relatively wide spaces of no radiation (valleys) with spacings of 200 to 400μm center-to-center. It has been observed that healthy small animal tissue, including neurologic tissue (brain and spinal cord), can recover quickly, but solid tumors take a prolonged time of many months to regrow. This vast difference in recovery period is the basis for the therapeutic effect of MBRS on tumors. The interactions of X rays and tissue cells in alignment with the microbeams cause some deposited dose to be delivered to the tissue between the peak region of the microbeams and spill into the valley regions. It is generally believed that the dose delivered between the microbeam peak regions must be maintained at a low level to maximize the efficacy of MBRS. To date the most widely used criterion for the efficacy of MBRS is known as the Peak-to-Valley Dose Ratio (PVDR). This ratio depends on the geometry of the system along with the X-ray spectra. As most of the experimental work to date has used polychromatic microbeams of X rays, the PVDR will change with the energy range and spectrum. We are reporting novel investigations and present data suggesting considerations additional to the PVDR are needed for the design of a human clinical facility. In this paper we studied X-ray interactions in simulated human biologic material (Water - H2O) using the MCNP6 radiation transport computer code. The new slit geometry dependent information includes: (1) rounding of peak shape; (2) decrease of the maximum peak height with decreasing peak slit width; (3) qualitative and quantitative changes to the “skirt” radiation dose delivered in the valley regions adjacent to the peak regions. All these effects were highly dependent on incident X-ray energy because of the transition of the dominant X-ray interaction from the photo-electric effect to atomic Compton scattering with increasing energy in the 50 to 300 keV range. Changes in the radiation dose distributions, as a function of X-ray energy, delivered to both the peak and valley regions after the X-ray interactions were investigated in detail. Insights from understanding how the dose is delivered in the valley regions have implications for the calculations of the clinical radiation dose planning. Accurate dose distribution calculations are necessary in human clinical treatment since it is anticipated that most patients will have received prior radiation therapy treatments that need to be considered in microbeam dose planning so that radiation side-effects and toxicity are accounted for and minimized.This work suggests an X-ray energy range of 130–250 keV is the most appropriate range for a human clinical facility. Using the results of this work, the authors suggest that the PVDR may not be the only criteria one should consider for determining the energy range needed for a human clinical facility; analysis of the data presented demonstrates the benefit of also using the full width at 10% maximum of the distribution.