Use Of High Energy Electrons Research Articles

Antiferromagnetic imaging via ptychographic phase retrieval

Antiferromagnetic imaging is critical for understanding and optimizing the properties of antiferromagnetic materials and devices. Despite the widespread use of high-energy electrons for atomic-scale imaging, they have low sensitivity to spin textures. Typically, the magnetic contribution to the phase of a high-energy electron wave is weaker than one percent of the electrostatic potential. Here, we demonstrate direct imaging of antiferromagnetic lattice through precise phase retrieval via electron ptychography, paving the way for magnetic lattice imaging of antiferromagnetic materials and devices.

Single Atom Detection from Low Contrast-to-Noise Ratio Electron Microscopy Images.

Single atom detection is of key importance to solving a wide range of scientific and technological problems. The strong interaction of electrons with matter makes transmission electron microscopy one of the most promising techniques. In particular, aberration correction using scanning transmission electron microscopy has made a significant step forward toward detecting single atoms. However, to overcome radiation damage, related to the use of high-energy electrons, the incoming electron dose should be kept low enough. This results in images exhibiting a low signal-to-noise ratio and extremely weak contrast, especially for light-element nanomaterials. To overcome this problem, a combination of physics-based model fitting and the use of a model-order selection method is proposed, enabling one to detect single atoms with high reliability.

Electron-induced dissociation (EID) for structure characterization of glycerophosphatidylcholine: determination of double-bond positions and localization of acyl chains.

Glycerophospholipids are a highly abundant and diverse collection of biologically relevant lipids, and distinction between isomeric and isobaric species is a fundamental aspect for confident identification. The ability to confidently assign a unique structure to a glycerophospholipid of interest is dependent on determining the number and location of the points of unsaturation and assignment of acyl chain position. The use of high-energy electrons (>20 eV) to induce gas-phase dissociation of intact precursor ions results in diagnostic product ions for localizing double-bond positions and determining acyl chain assignment. We describe a high-resolution, tandem mass spectrometry method for structure characterization of glycerophospholipids using electron-induced dissociation (EID). Furthermore, the inclusion of nomenclature to systematically assign bond cleavage sites with acyl chain position and double-bond location enables a uniform platform for lipid identification. The EID methodology detailed here combines novel application of an electron-based dissociation technique with high-resolution mass spectrometry that facilitates a new experimental approach for lipid biomarker discovery and validation.

Additive free thermoplastic vulcanizates based on natural rubber

Electron induced reactive processing (EIReP) is an eco-friendly and sustainable reactive processing method based on the use of high energy electrons. It was used to cross-link the elastomeric domain phase during melt mixing in order to prepare natural rubber (NR) and polypropylene (PP) based thermoplastic vulcanizates (TPVs). The electron treatment with various values of absorbed dose showed a prominent effect on mechanical, rheological, and morphological characteristics of the PP/NR TPVs. SEM and TEM studies confirmed that these TPVs can exists across the co-continuous or discrete phase morphology. The maximum set of mechanical properties (tensile strength of 15 MPa and elongation at break of more than 500%) were obtained at an absorbed dose of 100 kGy for a 50/50 blend ratio of NR and PP without addition of any compatibilizer or chemicals. At higher values of absorbed dose the degradation of polypropylene showed a negative impact on the properties of the TPVs. Depending on the morphology and the evaluation of mechanical properties a structure–property co-relationship is drawn on the basis of common phenomenological understanding of the TPVs.

Does a Three-Field Electron/Minitangent Photon Technique Offer Dosimetric Advantages to a Multifield, Photon-Only Technique for Accelerated Partial Breast Irradiation?

To determine whether 3-field electron/minitangent photons (mixed-modality) technique improved dosimetry compared with a multifield, photon-only technique for accelerated partial breast irradiation (APBI). Subjects were 20 breast cancer patients previously treated with photon-only APBI as part of a clinical trial to a dose of 38.5Gy/10 fractions in 5 days. Mixed-modality replans were compared with the photon-only plans with regards to planning target volume (PTV) coverage, conformity, homogeneity, and doses to normal tissues. The mixed-modality plans had similar PTV coverage, with more conformality, and reduced the volume of the ipsilateral breast receiving > or =95% and > or =50% doses, but had the pitfalls of less homogeneity and increased exposure of the ipsilateral lung and heart receiving low-dose radiation because of the exit dose of the electron beam. Factors associated with this increase were medial/deep-seated tumor beds, large tumor beds with PTV/Ipsilateral Breast ratio >20%, and use of high energy electrons. The three-field electron/minitangent photon APBI technique was more conformal and reduced the dose to the ipsilateral breast but had the disadvantage of exposing increased volumes of heart and ipsilateral lung to low-dose radiation compared with the photon-only technique.

Discrimination between rough and smooth interfaces of multilayers inside a multilayer stack using high-energy electron scattering

The interface quality of multilayer thin-film systems is of great interest for both the understanding of the physical properties which result from the loss of symmetry at the interfaces and for application purposes. We describe a technique which uses high-energy electron radiation (300 keV) from a conventional transmission electron microscope to characterize in a scattering experiment the interface quality of such multilayer systems. The technique is based on the use of high-energy electrons, with a correspondingly large k-vector k, which leads to a Ewald sphere with radius . This Ewald sphere can for many practical purposes be approximated by a plane. Therefore, the information obtained in a scattering experiment is restricted to a plane perpendicular to the primary beam, i.e. parallel to the multilayer structure, when the electrons pass through the multilayer system along its normal vector. When pair distribution functions (pdfs) are calculated from the scattered intensities, information can be gained about the coordination of pairs of atoms of different kinds within a plane parallel to the multilayer structure only. This information can then be used to determine whether the atoms at the interfaces between layers of different types of atom inside the multilayer stack are intermixed or not intermixed on an atomic scale. The technique is described, and its use is demonstrated on an multilayer system which has been prepared in order to create both sharp interfaces and interfaces which are intermixed. A comparison with an amorphous alloy of the same nominal composition is also given.

Dosimetry of high energy electron therapy to the parotid region

Well-known inadequacies in currently available electron planning systems, and two cases of temporal lobe necrosis following electron therapy of the parotid stimulated a comprehensive head and neck phantom dosimetric study of the use of high energy electrons for parotid treatments. A typical electron field employed for the treatment of parotid malignancy was examined in an anthropomorphic head phantom from which air cavities had been excavated. Thermoluminescent dosimeter measurements were compared with predicted point doses obtained from a Theraplan Treatment planning system (V05). Data was examined for three different electron energies: 12, 16 and 20 MeV and with the addition of contoured bolus for 20 MeV. A number of significant discrepancies between the measured and predicted dose were observed. Measured doses were seen to exceed predicted doses by up to 23% in the temporal lobe. Further under-predictions of dose were found behind the mandible and in the nasal cavity. Over-predictions of dose by the planning algorithm of up to 22% were observed beside the oropharynx. Some of these discrepancies were found to relate to Theraplan under-estimation of the dose in the fall-off region. Other errors are attributable to the difficulties in predicting dose at density interfaces. Localised over- and under-predictions of this magnitude must be accounted for by the clinician prescribing treatment in terms of possible late effects on the temporal lobe and, in particular, the nominated dose specification point.

Irradiation of power semiconductor devices by high energy electrons: The Italian experience

Starting from 1982, research in the field of electron irradiation of power semiconductor devices has been conducted in Italy on experimental basis. The use of high energy electrons for carrier lifetime control in these devices has been widely investigated. In collaboration with the three major Italian power semiconductor firms, Ansaldo, IRCI and SGS-Thomson Microeletronics, series of irradiation tests have been performed on fast diodes and thyristors, GTO thyristors, power MOS transistors and insulated gate bipolar transistors in order to achieve modelling of the electrical parameters and specific adjustment of carrier lifetime. The radiation-induced defects in silicon have been studied and characterized by the DLTS technique. The optimum conditions for radiation processing of different types of fast switching power devices with medium and high blocking capabilities have been determined. Diodes and thyristors, in all power categories, which did not have the required switching and release times after diffusion, were properly adjusted by irradiation thus saving them from rejection. The results obtained have led the above mentioned firms to use this technology for series production in place of the conventional high-temperature heavy metal diffusion for lifetime control. Equipment and methods for series production have been developed, tested and put into operation.

Conjecture on the use of high energy electrons for conformal radiotherapy

Conjecture on the use of high energy electrons for conformal radiotherapy

High energy electron beam irradiation: An innovative process for the treatment of aqueous based organic hazardous wastes

Abstract The use of high energy electrons for the treatment of aqueous solutions appears to be a promising approach in solving the numerous problems associated with contaminated water. Irradiation of aqueous solutions results in the formation of reactive transient species, e– aq, H•, and HO•. In aqueous solutions of toxic and hazardous chemicals, the transient species react with the contaminants resulting in their removal from solution. The study reported in this paper utilizes a pilot plant capable of treating 120 gpm. The accelerating voltage of the electron accelerator is 1.5 MeV with variable current of up to 50 mA. Influent streams of potable water, and raw and secondary wastewater have been used for this study. The compounds studied include halogenated methanes, ethanes, ethenes, benzene and substituted benzenes. Removal efficiencies range from 85 to greater than 99%.

The use of high‐energy electrons to depilate the breech of sheep

The use of high-energy electrons for permanently depilating areas of sheep skin was evaluated. The most effective dose of electrons for depilation was 17.5Gy. Histological changes in skin treated at this dose were examined in one sheep over 18 months and in 5 sheep over 89 d. Effects of treatment on bodyweight gains and fleece growth were examined by comparing the productivity of a further 5 sheep treated on the breech with high-energy electrons, with that of conventionally mulesed sheep (n = 5) and untreated controls (n = 5). Electron treatment resulted in immediate death of cells in the germinative region of the wool follicle bulbs. Within 10 d of treatment the treated areas were completely depilated. Wool follicle shafts in the treated areas regressed rapidly towards the epidermis and remained quiescent for the whole trial (89 d). A sheep treated 18 months previously has remained largely depilated, although a few sparse fibres are present. Epidermal acanthosis and orthokeratosis were present at 26 d after treatment. The thickened stratum corneum then sloughed off, but the epidermis remained acanthotic for the entire trial. Sweat glands and most sebaceous glands were destroyed by the treatment and were replaced by fibrotic, avascular tissue in the dermis. In all other respects the external appearance of the electron-treated breech was similar to that of mulesed sheep. There were no apparent side-effects of treatment. Neither mulesing nor electron treatment altered weight gains or fleece growth rates.

The use of high-energy electrons in the treatment of malignant orbital tumors

At the third symposium on orbital tumors we presented a special betatron eye tube for radiotherapy of peribulbarly growing tumors which offers sufficient protection of the eye from the radiation. Since then we have adjusted this collimator to the 42 MeV betatron. The diameter of this tube is 6 cm. In the center a plexiglass stick of 18 or 9 cm in length is fixed coaxially. The isodose curves can be adapted within limits to the different degrees of tumor growth by variation in the length or position of the plexiglass stick or by using electrons of higher or lower energy (Figs. 1 and 2). The most sensitive parts of the eye can be brought into the area of the 10% isodose curve so that no severe radiation-induced damage occurs in spite of high doses of 3000 rad (30 Gy) in the vicinity of the eye.

The Application of High Energy X Rays and Electron Beams in Radiotherapy

It has been more than 25 years since very high energy x rays generated by a betatron were first used in the treatment of cancer. The development of these machines along with linear accelerators quickly led to the use of high energy electrons as an additional modality in cancer management. In the intervening years, the physical and biological aspects of very high energy photon and electron beam therapy have been widely discussed in the literature,-but documentation on the clinical efficacy of such modalities has been largely anecodotal. Thus the necessity for such costly equipment remains somewhat controversial. Radiotherapists are by no means in agreement as to what is the optimum energy for accelerator use in radiation therapy. This overview will review the physical characteristics of high energy x-ray beams and the factors effecting the dose distribution emphasizing both the advantages and the limitations-of such beams. Specific examples of dose distributions appropriate for a given tumor distribution using both low energy x-ray beams (4 MV), high energy x-ray beams (25 MV), and x-ray beams in combination with electron beams of various energies will be presented.

High energy electron radiotherapy in a magnetic field.

We propose the use of high energy electrons in a strong local magnetic field as the ionizing beam in radiation therapy. A high kinetic energy insures that the electrons will penetrate to deep-seated tumor masses. A high magnetic field of several tesla in the region encompassing the tumor will confine the high energy electrons to the tumor volume before the scattering of the beam becomes excessive, thus producing an enhanced electron "Bragg peak" and highly localized strong radiation dose. The conclusions are based on a detailed Monte Carlo model which includes Landau straggling, multiple scattering, and the space dependence of the magnetic field.

Dose conversion factors for use with ionisation dosemeters for 6 to 35 MeV electron beams

Abstract The use of high-energy electrons in cancer therapy has created a need for sensitive and accurate dosimetric techniques which are applicable to the measurement of electron beams. The most logical first step is to extend the use of ionisation chambers in order to measure high-energy photon and particulate beams. This article deals with a comparative study of chemical and ionisation systems. The method and results of an investigation to determine conversion factors for use with commercial ionisation instruments are reported. Some incidental findings in the use of ionisation chambers in electron dosimetry are also presented. Using a variable volume, parallel-electrode chamber, experimental evidence was obtained to substantiate the Bragg-Gray cavity nature of the thimble chambers used in routine clinical dosimetry. The conversion factors obtained for a Baldwin-Farmer and Victoreen instrument show good agreement with the theoretically calculated values. The electron dose conversion factors reported by ...

Eye Lens Protection in the Treatment of Retinoblastoma with High-Energy Electrons

Irradiation of retinoblastoma and other intra- and retro-orbital tumors presents a problem with regard to protection of the lens of the eye. Merriam and Focht (4) and a number of other workers (3, 6, 7) have shown that small doses of ionizing radiation delivered to the equator of the lens will produce an opacity in its posterior portion. With a well collimated x-ray beam, the posterior portion of the globe may be irradiated without difficulty. In using this technic, however, we have seen recurrence of tumor growth anterior to the equator of the eye. The use of high-energy electrons is attractive because they may be readily attenuated in metals. There is also scattering of electrons as they pass into the tissue. Recently Garsou and his co-workers (2) of Liège, Belgium, designed a protective device to shield the lens and allow the treatment of retro-orbital tumors. This device is a complex shield made of brass, lead, and cadmium and was used with high-energy electrons of 20 MeV and an anterior field. The device is attached to the machine and must be precisely aligned with the globe. We have been working with 10 MeV electrons and a protective shield attached to a scleral contact lens to shield the equator of the lens of the eye and allow for adequate treatment of the retina. Use of a copper shield and 10 MeV electrons permits us to stay below the threshold of neutron production in the copper (5). The threshold for neutron production in the two stable copper isotopes together with the half-lives of the resultant activities is given in TABLE I. To test the system, a cylinder of copper was irradiated to 1.2 million rads at 10 MeV and counted in a well-type scintillation counter to detect any isotope production due to a gamma-neutron reaction. No detectable counts above background were found. When the energy of the electrons was raised to 11.8 MeV and the copper was irradiated to 1.2 million rads, the copper yielded 34,424 counts per minute with a background of 152 counts per minute. Use of a 7-mm-thick copper shield made it possible to reduce the dose to the lens to less than 10 per cent of the incident dose. The range of 10 MeV electrons in copper is 6.7 mm (1). Since no electrons can penetrate the copper shield and no neutrons or induced activity is produced, the dose to the lens is due to bremsstrahlung produced by electrons in the copper and electrons scattered from the surrounding field. The isodose curves shown in Figure 1 were obtained with a single anterior field. Behind the shielding there is adequate reduction of dose in the region of the lens, with a 50 to 60 per cent isodose line in the region of the retina posteriorly. With use of a large scleral contact lens with the protective copper attached to the center, the shielding can be aligned properly with the lens of the eye.

An improved scanning electron microscope for opaque specimens

A brief survey is given of the methods of examining opaque specimens in the electron microscope. The principle of the scanning electron microscope is described and mention is made of previous instruments. The design of such microscopes is discussed and the theoretical limit on performance is determined. The optimum scanning-beam voltage, beam current and scanning speeds are given. A recently built electrostatically focused scanning electron microscope for opaque specimens is described. This microscope has several new features, including: (a) The use of high-energy electrons to reduce the effects of surface contamination of the specimen. (b) Oblique scanning of the specimen, so that the image contrasts are formed by the topography of the etched surface of the specimen. (c) Direct amplification of the electron beam with an electron multiplier having beryllium-oxide-coated dynodes. (d) Direct viewing at low magnifications on a cathode-ray tube with a long-persistence screen, and photographic; ecording from the screen at high magnifications. Examples of micrographs of aluminium taken with the instrument are included and these show a resolution of about 500 A. It is concluded that higher resolutions could be obtained with this instrument if improved magnetic shielding and astigmatism correction were to be incorporated. Some measurements on the reflection of high-energy electrons are described in an Appendix.