Local Electron Beam Research Articles

Energy absorption during pulsed electron beam spot melting of 304 stainless steel: Monte-Carlo simulations and in-situ temperature measurements

The absorption coefficient during pulsed, conduction-mode electron beam spot melting of 304 stainless steel was measured at different combinations of accelerating voltage [60,80] kV, beam current [10,15,20] mA, pulse length [0.6–12] mS and beam inclination angle [0, 15, 35, 55, 65]°. Ignoring evaporative and radiative heat loss, the absorption coefficient was determined directly by fitting in-situ thermocouple measurements to an analytical function, with an average adjusted R-square fit parameter of 0.9996 over the 103 measurements. The absorption coefficient was found to be insensitive to both beam current and accelerating voltage, but decreased with increasing inclination angle. Measurements are compared to estimates generated from Monte-Carlo electron trajectory simulations using the CASINO software, with good agreement for all process parameter combinations, experimentally demonstrating the capability of Monte-Carlo methods to estimate local electron beam heat transfer.

Atomic structure and formation mechanism of sub-nanometer pores in 2D monolayer MoS2.

We use electron-beam nanofabrication to create sub-nanometer (sub-nm) pores in 2D monolayer MoS2 with fine control over the pore size down to 0.6 nm, corresponding to the loss of a single Mo atom and surrounding S atoms. The sub-nm pores are created in situ with 1 nm spatial precision in the MoS2 lattice by control of the angstrom sized probe in an aberration corrected scanning transmission electron microscope with real time tracking of the pore creation. Dynamics of the sub-nm pore creation are captured at the atomic scale and reveal the mechanism of nanopore formation at accelerating voltages of 60 and 80 kV to be due to displacing a Mo atom from the lattice site onto the surface of the MoS2. This process is enabled by the destabilization of the Mo bonding from localized electron beam induced S atom loss. DFT calculations confirm the energetic advantage of having the ejected Mo atom attach on the sheet surface rather than being expelled into vacuum, and indicate sensitivity of the nanopore potential as a function of the adsorption position of the ejected Mo atom. These results provide detailed atomic level insights into the initial process of single Mo loss that underpins the nucleation of a nanopore and explains the formation mechanism of sub-nm pores in MoS2.

Potential application of carbon nanotube core as nanocontainer and nanoreactor for the encapsulated nanomaterial

Fe3C nanorod filled inside carbon nanotube has been irradiated inside transmission electron microscope at both room and high temperature. In-situ response of Fe3C nanorod as well as CNT walls has been studied. It has been found that when electron irradiation is performed at room temperature (RT), nanorod first bends and then tip makes at the end whereas at high temperature (∼490°C) nanorod slides along the tube axis and then transforms into a faceting particle. Extrusion of solid particle filled in the core of CNT has also been demonstrated. It is suggested that these morphological changes in nanorod may have happened due to the compression which was generated either by shrinkage of tube or by local electron beam heating. Presented results demonstrate that CNT core could be used as nano-container or reactor.

Localization of Narrowband Single Photon Emitters in Nanodiamonds

Diamond nanocrystals that host room temperature narrowband single photon emitters are highly sought after for applications in nanophotonics and bioimaging. However, current understanding of the origin of these emitters is extremely limited. In this work, we demonstrate that the narrowband emitters are point defects localized at extended morphological defects in individual nanodiamonds. In particular, we show that nanocrystals with defects such as twin boundaries and secondary nucleation sites exhibit narrowband emission that is absent from pristine individual nanocrystals grown under the same conditions. Critically, we prove that the narrowband emission lines vanish when extended defects are removed deterministically using highly localized electron beam induced etching. Our results enhance the current understanding of single photon emitters in diamond and are directly relevant to fabrication of novel quantum optics devices and sensors.

Folliculotropic Mycosis Fungoides in an Adolescent: A Rare Case.

Folliculotropic mycosis fungoides (FMF) is an uncommon and aggressive form of mycoses fungoides with preferential involvement of head and neck region. Lesions of FMF present as erythematous plaques or papules with follicular prominences, acneiform lesions, cysts, nodules, patches of scarring alopecia, and prurigo-like lesions. The mean age of diagnosis is at 60 years and it is extremely rare in childhood and adolescence. We report a case of a 16-year-old male patient who presented with a 2-month history of an asymptomatic erythematous infiltrated plaque over the forehead. Histological examination was consistent with diagnosis of FMF. He was successfully treated with local electron beam therapy.

Mycosis Fungoides of the Oral Cavity: Fungating Tumor Successfully Treated with Electron Beam Radiation and Maintenance Bexarotene.

Oral involvement in mycosis fungoides is unusual and portends a poor prognosis. The clinical findings of three new cases are described along with a differential diagnosis and review of the literature. For brevity, only one patient is discussed in detail below whereas the other two cases are solely described in table form. The patient had a four-year history of mycosis fungoides before developing an exophytic tongue tumor. He was treated with local electron beam radiation and is disease-free to date while being on maintenance therapy with oral bexarotene. Analysis of the data collected from our review of the literature and the present cases reveal key insights.

Diagnostics of Local Electron Beam Losses in Microtron-recuperator on Novosibirsk Free Electron Laser Beamline via Detection of Induced X-rays

The Novosibirsk Free Electron Laser (NovoFEL) is based on a four-turn microtron-recuperator. To ensure its stable operation and radiation generation, it is necessary to provide a stable mode of electron beam recirculation and minimize beam losses on the vacuum chamber wall on all the beam way in the accelerator beamline. To this end it is necessary to know the longitudinal distribution of these losses along the beamline.A system for registration of beam losses was created. The system applies optical fibers placed along the vacuum chamber and nearby it. If local electron beam losses occur somewhere in the vacuum chamber, electrons falling to the vacuum chamber wall cause generation of X- and gamma rays. This radiation in turn originates optical emission in an optical fiber nearby the region of electron “precipitation” on the chamber wall. Then, executing some transformation and processing of the time dependencies of signals from these optical fibers, one can obtain the longitudinal distribution of electron beam losses along the accelerator line in all its four turns.

Local vacuum electron beam welding for pressure vessel applications

Welding of thick section components such as pressure vessels used in the nuclear industry is traditionally performed using arc welding techniques, requiring multiple weld passes, with interstage non-destructive examination (NDE) and preheating of the component to reduce the risk of hydrogen cracking. Electron beam (EB) welding offers the opportunity to weld thick section components in a single pass and negates the need for interstage NDE, resulting in saving significant time and cost in the fabrication of nuclear vessels. Furthermore, elimination of the preheat step may be possible since the EB process is carried out in a vacuum environment. However, due to the physical size and geometry of nuclear vessels, traditional vacuum chambers would be prohibitively expensive when considering the low volume of output in the nuclear industry. Rolls-Royce and TWI are working on a local vacuum, or ‘out of chamber’, EB welding system, which eliminates the need of such a vacuum chamber and brings the vacuum to the component, thus making EB welding of nuclear vessels more practical and financially viable.

Leonine facies (LF) and mycosis fungoides (MF): A single-center study and systematic review of the literature

Leonine facies (LF) is defined as displaying facial features similar to that of a lion with prominent convexities and furrowed creases. LF develops in a very small population of patients with cutaneous T-cell lymphoma. We aimed to study the clinicopathologic features and overall prognosis associated with LF in patients with mycosis fungoides and Sézary syndrome. We conducted a single-center retrospective study, reviewing 1338 patients with mycosis fungoides seen from 1987 to 2015 at a tertiary referral center for cutaneous T-cell lymphoma, and a systematic review of 14 patients in the literature. We identified 10 patients with mycosis fungoides who developed LF. Folliculotropism was seen in all patients with LF who had facial biopsy specimens. Radiation was a beneficial therapy. Complete remission was achieved in 1 patient and overall 5-year survival was 26%. Systematic review of 10 additional patients showed that all patients with LF, including ours, had stage-IV disease and some degree of blood involvement, but not all met criteria for Sézary syndrome. This was a retrospective study with a small sample size. LF is associated with stage-IV cutaneous T-cell lymphoma, is often accompanied by folliculotropism and blood involvement, and can be treated with local electron beam therapy.

Unilesional folliculotropic mycosis fungoides: a unique variant of cutaneous lymphoma

Unilesional folliculotropic mycosis fungoides (UFMF) has been rarely reported. The aim of this study was to describe our experience with UFMF. Data were collected on all patients with clinicopathological UFMF who attended the Department of Dermatology of a tertiary university-affiliated medical centre in 1996-2013 and were followed prospectively. The sample included seven patients (five male, two female) of mean age 38 years at diagnosis; two were aged <18 years. The lesion presented as a solitary patch/plaque with follicular accentuation in five patients, an infiltrated plaque devoid of hair in one and with follicular nodules in one. Four patients had alopecia, and one, secondary anetoderma. The lesion was located on a limb in four patients, the trunk in two, and the face in one. In all cases, the atypical folliculotropic lymphocytes expressed mainly surface CD4(+). Monoclonality was detected in three of the six patients analysed. Treatment consisted of localized electron beam in five patients, all of whom had a complete response (CR), and excision in one patient. The remaining patient, a 9-year-old boy, was treated with topical psoralen and UVA with CR. The duration of follow-up was 0.5-10 years (mean 4). There were no recurrences in six patients and local recurrence in one. UFMF presents at a young age, usually with early disease clinical morphology. The treatment goal should be cure. Our experience indicates an excellent prognosis of early UFMF with no multifocal/internal spread.

Optical properties of single plasmonic holes probed with local electron beam excitation.

Similar to nanoparticles, nanoscale holes form a basic building block in a wide array of nanophotonic devices. Here we study the spectral and angular cathodoluminescence response of individual nanoholes with diameters ranging from 50 to 180 nm. Taking advantage of the deep-subwavelength excitation resolution, we find that the holes can be excited efficiently at the edge of the hole and that the response becomes stronger in the near-infrared part of the spectrum for larger holes. Using finite-difference time-domain simulations, we characterize the resonant modes inside the holes. We measure the angle-resolved cathodoluminescence response and observe strong beaming toward the side of electron beam excitation, complementary to what was shown for nanoparticles. The angular response can be explained by assuming a coherent superposition of radiating dipole moments, where the contribution of in-plane magnetic and electric dipole components increases for larger diameters.

Zeolites are no longer a challenge: Atomic resolution data by Aberration-corrected STEM

Transmission electron microscopy is undoubtedly an indispensable tool for materials characterization, which can currently reach sub-angstrom resolution down to the elemental building blocks of matter, isolated single atoms of most elements. In addition to the phenomenal image resolution, if the material is strong enough, it can be accompanied with chemical information, converting electron microscopy into a unique method for the analysis of a great variety of materials. Unfortunately, extracting all this valuable information is not simple as most materials in one way or another are affected by the strong and localized electron beam. Radiolysis is one kind of reaction between electrons and matter than can cause irreversible structural transformations in our materials. This effect is the predominant factor in zeolites, zeotypes and the majority of molecular sieves. In the present work some results, taken at high voltage (300kV) and minimizing the exposure to the beam, are presented proving the feasibility of the technique to obtain unprecedented atomic resolution information of different zeolites and microporous solids.

Local electron beam excitation and substrate effect on the plasmonic response of single gold nanostars

We performed cathodoluminescence (CL) spectroscopy and imaging in a high-resolution scanning electron microscope to locally and selectively excite and investigate the plasmonic properties of a multi-branched gold nanostar on a silicon substrate. This method allows us to map the local density of optical states from the nanostar with a spatial resolution down to a few nanometers. We resolve, both in the spatial and spectral domain, different plasmon modes associated with the nanostar. Finite-difference time-domain (FDTD) numerical simulations are performed to support the experimental observations. We investigate the effect of the substrate on the plasmonic properties of these complex-shaped nanostars. The powerful CL-FDTD combination helps us to understand the effect of the substrate on the plasmonic response of branched nanoparticles.

Preparation of infertile male rabbits by local electron beam irradiation for intratesticular transplantation of autologous bone marrow stem cells

To explore an efficient and safe protocol for the preparation of infertile male rabbits from which bone marrow stem cells (BMSCs) could be isolated and cultured. Autologous BMSCs could be used for intratesticular transplantation and male infertility research. For this model, various doses (e.g., 6, 8, 10, or 12 Gy) of electron beam irradiation from a linear accelerator were locally applied to the scrotum of 5-month-old male New Zealand white rabbits. The effects of irradiation were compared between treatment groups, and with age-matched normal controls. Both morphology and hollow ratios of seminiferous tubules (HRST) were examined two, four, six, eight and 12-weeks post-irradiation. The seminiferous epithelium showed varying degrees of damage in all treatment groups compared with unirradiated controls, yet Sertoli and Leydig cells appeared unaffected. A dose-dependent response in spermatogenesis was also observed. BMSCs that were isolated and cultured from rabbits of the normal control group and the 12 Gy treatment group were compared with respect to morphology and growth. Starting at 6 weeks, HRST of the 12 Gy-treatment group were stable, and were the highest among all the groups. BMSCs from rabbits treated with 12 Gy also exhibited similar growth as the control group. Local dose of 12 Gy to the testes of 5-month-old male New Zealand rabbits is a protocol with which to obtain autologous bone marrow stem cells.

Central nervous system involvement of primary cutaneous diffuse large B cell lymphoma-leg type diagnosed according to the WHO 2008 classification

Dear Editor,Primary cutaneous large B cell lymphoma-leg type(PCLBCL-LT) is a unique subtype of diffuse large B celllymphoma, which predominantly affects the skin [1, 2].Unlike other types of cutaneous B cell lymphoma,PCLBCL-LT frequently disseminates to extracutaneoussites [1, 2]; however, invasion of the central nervous system(CNS) is quite rare.A 75-year-old Japanese female developed two tumors inher chest wall and was diagnosed with PCLBCL-LT. Shereceived three cycles of R-CHOP (50 % dose) [3] followedby local electron beam radiotherapy and subsequentlyachieved complete remission. However, the lymphoma hassince recurred twice (on the left forehead and in the leftmalar region), and the patient received local electron beamradiotherapy on each occasion. Four years after the initialdiagnosis, she experienced nausea and difficulty in swallow-ing. Upon examination, a left-sided facial paresis and a newcutaneous tumor on the left side of the forehead (with adiameter of 10 mm) were noted. CT scanning of the trunkand a bone marrow aspirate showed no evidence of recurrentlymphoma. Contrast-enhanced T1-weighted MRI images ofthe brain revealed homogeneously enhancing periventricularlesionscrossingthecorpuscallosum(Fig.1a)andsurroundinghyperintensity on fluid-attenuated inversion recovery images(Fig.1b).Theenhancedlesionsshowedrestricteddiffusionondiffusion-weighted images. Lymphoma-like cells were ob-served (13 cells/μl) in the cerebrospinal fluid (CSF) as eval-uated by cytospin preparation. Histologic examination of thecutaneous tumor showed diffuse proliferation of both centro-blasts and immunoblasts, which expressed CD20 and BCL2.PCR analysis of cells from the cutaneous tumor and the CSFshowed monoclonal rearrangement of the immunoglobulinheavy chain gene, with the same-sized PCR products. Fromthese findings, the patient was diagnosed with a CNS relapseof PCLBCL-LT. She received four cycles of high-dose meth-otrexate (2.5 g/m2) plus rituximab (375 mg/m2) and twocycles of R-ESHAP chemotherapy (50 % dose) [4]. Aftertwo cycles of high-dose methotrexate-based treatment, herconsciousness disturbances and neurologic abnormalitiesshowed a marked improvement. After the completion of allscheduledchemotherapies,sheachievedacompleteremissionand was able to eat and walk by herself.At present, four cases of CNS involvement of recur-rent PCLBCL-LT have been reported [5–7]. However, allcases were diagnosed according to the EORTC classifi-cation [5–7]. This article is the first case report describ-ing CNS relapse in a patient with PCLBCL-LTdiagnosed according to the WHO 2008 classification[2]. Furthermore, PCR analysis showed that the skintumor at diagnosis and the abnormal cells in the CSFwere of the same clonal origin.We experienced a rare case of CNS-relapsed PCLBCL-LT. Further investigations are needed to clarify the exactincidence of CNS recurrence in PCLBCL-LT according tothe WHO 2008 classification.

A Case of ALK+ Anaplastic Large T Cell Lymphoma (ALCL) with Lymphomatous Meningitis

Abstract 5226 Background:Anaplastic large T cell lymphoma may present with indolent cutaneous T cell infiltration, progressing to more aggressive skin disease and systemic involvement. In adults lymphomatous meningitis is very rare complication. Case Report:A 62 year old Jamaican woman had been diagnosed with biopsy proven psoriasis when 42 years of age. Ustekinumab had been initiated without effect two months prior to her presentation to us. A new cutaneous nodule on her left neck was then found, shave biopsy of which revealed psoriasiform dermatitis with epidermotropism, suspicious for early patch stage mycosis fungoides. The lesion was CD30+, suggestive of ALCL and was positive for ALK. Positron emission tomography revealed an SUV of 6.0 in the neck mass, but lymph nodes in all regions had an SUV of <2.3. Axillary lymph node biopsy, bone marrow biopsy and flow cytometry were negative. Local electron beam radiation was administered to the left supraclavicular space with complete resolution of the cutaneous nodule. About 2 months following completion of radiation therapy she noted anorexia, 30 lb weight loss, night sweats and left hip pain. Physical examination revealed a sick woman, with whole body scaling red-brown macules and plaques. CBC was normal except for Hb of 10 g/dl, platelets 453,000/dl. Hepatic and renal function studies were normal. ESR was 84 mm/hr, lactic dehydrogenase 670 IU (reference range 300–600 IU) and calcium 15.1 mg/dl. HTLV1, HIV, hepatitis panel and anti-nuclear antibody serologies were negative. Computer automated tomography of the pelvis demonstrated 6×2×8 cm soft tissue mass on the sacrum invading left sacro-iliac joint and ilium. Biopsy revealed ALCL, positive for CD43, CD2dim, CD7dim, CD30, and nuclear and cytoplasmic ALK1, while negative for CD43, 3, 4, 5, 8, 19,20, 34, 138, PAX5, AE1/AE3, Cam5, S100 and TdT. The mass was irradiated with alleviation of pain, but cutaneous nodules progressively appeared and continuous fever developed with negative blood cultures. There was increasing confusion, blurred vision and bilateral abducens paralysis. Magnetic resonance imaging of the head and spine revealed dural enhancement and multiple extra- and intercranial interosseous masses, one of which involved the posterior sella turcica. Cyclophosphamide, doxorubicin, vincristine and prednisone were initiated; lumbar puncture was refused. Within 2 days after treatment initiation the cutaneous nodules disappeared, fever subsided, the left abducens palsy resolved completely while the right improved. Conclusion:Our patient's long standing indolent skin disease abruptly progressed to cutaneous and systemic ALCL, with evidence of lymphomatous meningitis. The response of her abducens palsies and other CNS findings to systemic chemotherapy alone suggests that her meningeal involvement may have arisen from that of adjacent bones. Involvement of CNS in ALK positive systemic anaplastic large cell lymphoma is rare and reported in mainly pediatric cases. Disclosures:No relevant conflicts of interest to declare.

An X-ray fluorescence depth distribution function for electron beam microanalysis

A new method for calculating the function ϕ(ρz) for local electron beam microanalysis is proposed. The method is based on a description of the spatial distribution of the electron beam energy loss at normal incidence on a sample.

Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiOx

Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiO_<i>x</i>

Cover Picture: Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiOx (Angew. Chem. Int. Ed. 27/2010)

Electrons as Invisible Ink A SiOx surface can be locally activated with a focused electron beam (1) such that subsequently dosed [Fe(CO)5] decomposes (2) and autocatalytically grows to pure Fe nanocrystals (3) at predefined positions until the precursor supply is stopped. In their Communication on page 4669 ff., H. Marbach et al. describe how the two-step process might be the starting point of a novel way to generate nanostructures (see the 3D representation of the SEM data in the background).

On direct-writing methods for electrically contacting GaAs and Ge nanowire devices

The electronic transport and gating characteristics in GaAs and Ge nanowires (NWs) are altered significantly following either indirect or direct exposure to a focused Ga+ ion beam (FIB), such as that used to produce Pt electrical contacts to NWs. While these results challenge the assumptions made in some previously reported work relating to the electronic properties of semiconductor NWs using FIB-assisted production of contacts and/or their leads, local electron beam induced deposition is shown to be a reliable and facile route for producing robust electrical contacts to individual vapor phase-grown NWs in a manner that enables study of their actual carrier transport properties.