Asymmetrical field emitter

Science.gov (United States)

Fleming, J.G.; Smith, B.K.

1995-10-10

A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

Effect of increased crystallinity of single-walled carbon nanotubes used as field emitters on their electrical properties

Energy Technology Data Exchange (ETDEWEB)

Shimoi, Norihiro, E-mail: shimoi@mail.kankyo.tohoku.ac.jp [Graduate School of Environmental Studies, Tohoku University, 6-6-20 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

2015-12-07

Single-walled carbon nanotubes (SWCNTs) synthesized by arc discharge are expected to exhibit good field emission (FE) properties at a low driving voltage. We used a coating containing homogeneously dispersed highly crystalline SWCNTs produced by a high-temperature annealing process to fabricate an FE device by a wet-coating process at a low cost. Using the coating, we succeeded in reducing the power consumption of field emitters for planar lighting devices. SWCNTs synthesized by arc discharge have crystal defects in the carbon network, which are considered to induce inelastic electron tunneling that deteriorates the electrical conductivity of the SWCNTs. In this study, the blocking of the transport of electrons in SWCNTs with crystal defects is simulated using an inelastic electron tunneling model. We succeeded in clarifying the mechanism underlying the electrical conductivity of SWCNTs by controlling their crystallinity. In addition, it was confirmed that field emitters using highly crystalline SWCNTs can lead to new applications operating with low power consumption and new devices that may change our daily lives in the future.

Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging

Directory of Open Access Journals (Sweden)

Amar Prasad Gupta

2017-07-01

Full Text Available We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm2 through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42–70 kV voltage by digital switching control between emitter and ground electrode.

Direct Synthesis of Carbon Nanotube Field Emitters on Metal Substrate for Open-Type X-ray Source in Medical Imaging.

Science.gov (United States)

Gupta, Amar Prasad; Park, Sangjun; Yeo, Seung Jun; Jung, Jaeik; Cho, Chonggil; Paik, Sang Hyun; Park, Hunkuk; Cho, Young Chul; Kim, Seung Hoon; Shin, Ji Hoon; Ahn, Jeung Sun; Ryu, Jehwang

2017-07-29

We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm² through a plasma enhanced chemical vapor deposition system. The stable field emission properties with triode electrodes after electrical aging treatment showed an anode emission current of 0.63 mA at a gate field of 7.51 V/μm. The 4.5-inch cubic shape open type X-ray system was developed consisting of an X-ray aperture, a vacuum part, an anode high voltage part, and a field emission electron gun including three electrodes with focusing, gate and cathode electrodes. Using this system, we obtained high-resolution X-ray images accelerated at 42-70 kV voltage by digital switching control between emitter and ground electrode.

High-Performance Field Emission from a Carbonized Cork.

Science.gov (United States)

Lee, Jeong Seok; Lee, Hak Jun; Yoo, Jae Man; Kim, Taewoo; Kim, Yong Hyup

2017-12-20

To broaden the range of application of electron beams, low-power field emitters are needed that are miniature and light. Here, we introduce carbonized cork as a material for field emitters. The light natural cork becomes a graphitic honeycomb upon carbonization, with the honeycomb cell walls 100-200 nm thick and the aspect ratio larger than 100, providing an ideal structure for the field electron emission. Compared to nanocarbon field emitters, the cork emitter produces a high current density and long-term stability with a low turn-on field. The nature of the cork material makes it quite simple to fabricate the emitter. Furthermore, any desired shape of the emitter tailored for the final application can easily be prepared for point, line, or planar emission.

Miniature X-ray Tube for Electric Brachytherapy using Carbon Nanotube Field Emitter

International Nuclear Information System (INIS)

Heo, Sung Hwan; Kim, Hyun Jin; Ha, Jun Mok; Cho, Sung Oh

2011-01-01

An electric brachytherapy using a miniature x-ray tube has a major advantage to reduce the x-ray exposure of human body during the cancer radiation therapy by optimal positioning of x-ray radiation source and treatment objectives. In the view of a smaller electronic x-ray source, the CNT field emitter based xray tube can be more minimized than thermionic filament emitter based one because of a simple power supplier connection of cold field emission in diode type as well as a higher electron emission brightness of CNT. This abstract is for introducing the design of a prototype CNT field emitter based miniature x-ray tube. We have vacuum sealed CNT miniature x-ray tube with 7∼10 mm diameter, and characteristics of electron emission and x-ray transportation using MCNP5 code are surveyed

Highly flexible and robust N-doped SiC nanoneedle field emitters

KAUST Repository

Chen, Shanliang

2015-01-23

Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

Highly flexible and robust N-doped SiC nanoneedle field emitters

KAUST Repository

Chen, Shanliang; Ying, Pengzhan; Wang, Lin; Wei, Guodong; Gao, Fengmei; Zheng, Jinju; Shang, Minhui; Yang, Zuobao; Yang, Weiyou; Wu, Tao

2015-01-01

Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

Study of Thermal-Field Emission Properties and Investigation of Temperature dependent Noise in the Emission Current form vertical Carbon nanotube emitters

KAUST Repository

Kolekar, Sadhu

2017-05-05

We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD), in order to understand the effect of temperature on electron emission spots in image morphology (as indicated by ring like structures) and electron emission spot intensity of the emitters. Moreover, the field electron emission images can be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 is 4.5x107 and, the actual number emitters per cm2 present for electron emission calculated from Atomic Force Microscopy (AFM) data is 1.2x1012. The measured Current-Voltage (I-V) characteristics obey the Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current are recorded at different temperatures and, temperature dependence of power spectral density obeys power law relation s(f)=I2/f2 with that of emission current and frequency.

Shielding in ungated field emitter arrays

Energy Technology Data Exchange (ETDEWEB)

Harris, J. R. [U.S. Navy Reserve, Navy Operational Support Center New Orleans, New Orleans, Louisiana 70143 (United States); Jensen, K. L. [Code 6854, Naval Research Laboratory, Washington, D.C. 20375 (United States); Shiffler, D. A. [Directed Energy Directorate, Air Force Research Laboratory, Albuquerque, New Mexico 87117 (United States); Petillo, J. J. [Leidos, Billerica, Massachusetts 01821 (United States)

2015-05-18

Cathodes consisting of arrays of high aspect ratio field emitters are of great interest as sources of electron beams for vacuum electronic devices. The desire for high currents and current densities drives the cathode designer towards a denser array, but for ungated emitters, denser arrays also lead to increased shielding, in which the field enhancement factor β of each emitter is reduced due to the presence of the other emitters in the array. To facilitate the study of these arrays, we have developed a method for modeling high aspect ratio emitters using tapered dipole line charges. This method can be used to investigate proximity effects from similar emitters an arbitrary distance away and is much less computationally demanding than competing simulation approaches. Here, we introduce this method and use it to study shielding as a function of array geometry. Emitters with aspect ratios of 10{sup 2}–10{sup 4} are modeled, and the shielding-induced reduction in β is considered as a function of tip-to-tip spacing for emitter pairs and for large arrays with triangular and square unit cells. Shielding is found to be negligible when the emitter spacing is greater than the emitter height for the two-emitter array, or about 2.5 times the emitter height in the large arrays, in agreement with previously published results. Because the onset of shielding occurs at virtually the same emitter spacing in the square and triangular arrays, the triangular array is preferred for its higher emitter density at a given emitter spacing. The primary contribution to shielding in large arrays is found to come from emitters within a distance of three times the unit cell spacing for both square and triangular arrays.

Special features of electron sources with CNT field emitter and micro grid

International Nuclear Information System (INIS)

Knapp, Wolfram; Schleussner, Detlef

2005-01-01

A micro-sized electron source plays an important role for new vacuum triode applications. For these applications, an electron source with CNT field emitter and micro grid for 1 mA was developed and investigated. The miniaturisation of the electron source was achieved by the use of a carbon nanotube (CNT) field emitter and a micro grid, with a distance of only a few micrometers. Because of the threshold field strength for field emission of CNTs being in the range 1-5 V/μm, the grid voltage can be lower than 100 V. In our contribution, we discuss the influence of the micro grid on electron source properties, especially anode-current hysteresis, anode-field penetration through the micro grid and micro-lensing effect

Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

Energy Technology Data Exchange (ETDEWEB)

Shih, Yi-Ting [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Li, Kuan-Wei [Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Honda, Shin-ichi [Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Lin, Pao-Hung; Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China)

2017-06-01

Graphical abstract: The pattern design provides a new structure of surface-conduction electron-emitter display (SED). Delta-star shaped vertically aligned CNT (VACNT) arrays with 20o tips can simultaneously provide three emitters to bombard the sides of equilateral triangles pattern of VACNT, which produces numerous secondary electrons and enhance the SED efficiency. - Highlights: • The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. • The vertically aligned CNT (VACNT) arrays with 20° tips of the delta-star arrangement are used as cathodes that easily emit electrons. The cathode pattern simultaneously provides three emitters to bombard the sides of equilateral triangles pattern of VACNT. • The VACNT arrays were covered with magnesium oxide (MgO) nanostructures to promote the surface-conduction electron-emitter display (SED) efficiency (η). • The η was stably maintained in the 75–85% range. The proposed design provides a facile new method for developing SED applications. - Abstract: The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75–85% range. The proposed design provides a facile new method for

Deduction of work function of carbon nanotube field emitter by use of curved-surface theory

International Nuclear Information System (INIS)

Edgcombe, C J; Jonge, N de

2007-01-01

The theory given earlier for field emission from a curved surface has been extended to use the parameter d characterizing the energy distribution. Measurement of the curvature of the Fowler-Nordheim plot together with d for the same emitter enables the work function of the surface to be deduced, together with emitter radius, notional surface field, effective solid angle of emission and supply factor. For this calculation an assumed form of potential distribution was used, but it is desirable to repeat the calculation with a potential obtained from atomic-scale simulation

Light radiation through a transparent cathode plate with single-walled carbon nanotube field emitters

International Nuclear Information System (INIS)

Jang, E.S.; Goak, J.C.; Lee, H.S.; Lee, S.H.; Han, J.H.; Lee, C.S.; Sok, J.H.; Seo, Y.H.; Park, K.S.; Lee, N.S.

2010-01-01

In the conventional carbon nanotube backlight units (CNT-BLUs), light passes through the phosphor-coated anode glass plate, which thus faces closely the thin film transistor (TFT) backplate of a liquid crystal display panel. This configuration makes heat dissipation structurally difficult because light emission and heat generation occur simultaneously at the anode. We propose a novel configuration of a CNT-BLU where the cathode rather than the anode faces the TFT backplate by turning it upside down. In this design, light passes through the transparent cathode glass plate while heating occurs at the anode. We demonstrated a novel design of CNT-BLU by fabricating transparent single-walled CNT field emitters on the cathode and by coating a reflecting metal layer on the anode. This study hopefully provides a clue to solve the anode-heating problem which would be inevitably confronted for high-luminance and large-area CNT-BLUs.

Source brightness and useful beam current of carbon nanotubes and other very small emitters

International Nuclear Information System (INIS)

Kruit, P.; Bezuijen, M.; Barth, J.E.

2006-01-01

The potential application of carbon nanotubes as electron sources in electron microscopes is analyzed. The resolution and probe current that can be obtained from a carbon nanotube emitter in a low-voltage scanning electron microscope are calculated and compared to the state of the art using Schottky electron sources. Many analytical equations for probe-size versus probe-current relations in different parameter regimes are obtained. It is shown that for most carbon nanotube emitters, the gun lens aberrations are larger than the emitters' virtual source size and thus restrict the microscope's performance. The result is that the advantages of the higher brightness of nanotube emitters are limited unless the angular emission current is increased over present day values or the gun lens aberrations are decreased. For some nanotubes with a closed cap, it is known that the emitted electron beam is coherent over the full emission cone. We argue that for such emitters the parameter ''brightness'' becomes meaningless. The influence of phase variations in the electron wave front emitted from such a nanotube emitter on the focusing of the electron beam is analyzed

Characteristics of Transmission-type Microfocus X-ray Tube based-on Carbon Nanotube Field Emitter

International Nuclear Information System (INIS)

Heo, Sung Hwan; Ihsan, Aamir; Cho, Sung Oh

2007-01-01

A high resolution microfocus x-ray source is widely applied to noninvasive detection for industrial demands, material science and engineering, and to diagnostic study of microbiology and micro-tomography. Carbon nanotube (CNT) is regarded as an excellent electron emitter, which outperforms conventional electron sources in point of brightness. It has been suggested that CNT is used as an electron source of a high resolution x-ray tube according to their low threshold field with atomically sharp geometry, chemically robust structure, and electric conductivity. Several researchers have reported miniaturized x-ray tube based on diode structure and micro x-ray radiography and computed tomography systems using triode types with precise emission control and electrostatic focusing. Especially, a microfocus x-ray source of 30 μm resolution has been demonstrated recently using an elliptical CNT cathode and asymmetrical Eingel lens. However, to increase the spatial resolution of x-ray source, a smaller CNT emitter is desired. Electron focusing optics must be corrected to reduce aberrations. A thin wire tip end can provide a micro-area of CNT substrate, and a magnetic lens and transmission x-ray target are proper to reduce the lens aberration and a focal length. Until now, CNT based microfocus x-ray source with less than 10 um resolution has not been shown. Here we report a microfocus x-ray source with 4.7 μm x-ray focal spot consisted of a conical CNT tip, a single solenoid lens, and a transmission type x-ray target. A magnified x-ray image larger than 230 times was resolved with advantage of microfocused focal spot and transmission x-ray target

Graphene field emitters: A review of fabrication, characterization and properties

Energy Technology Data Exchange (ETDEWEB)

Chen, Leifeng, E-mail: chlf@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027 (China); Yu, Hu; Zhong, Jiasong; Song, Lihui [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Wu, Jun, E-mail: wujun@hdu.edu.cn [Institute of Electron Device & Application, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018 (China); Su, Weitao [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China)

2017-06-15

Highlights: • The preparation, characterization and field emission properties for Gs are reviewed. • The review provides an updated progress on design and construction of Gs field emitters. • The review offers fundamental insights into understanding and design of Gs emitters. • The review can broach the subject and inspire readers in field of Gs based emitters. - Abstract: Graphenes are beneficial to electrons field emission due to its high aspect ratio, high carrier density, the larger carrier mobility, excellent electrical and thermal conductivity, excellent mechanical strength and chemical stability. In recent years, graphene or reduced oxide graphene field emitters have been successfully constructed by various methods such as chemical vapor deposition, chemical exfoliation, electrophoretic deposition, screen-printing and chemical synthesis methods. Graphene emitters are tried to construct in distribution with some angles or vertical orientation with respect to the substrate surface. The vertical alignment of graphene sheets or edges arrays can facilitate efficient electron emission from the atomically thick sheets. Therefore they have even more a low turn-on and threshold-field electronic field, high field enhancement factor, high current stability and high luminance. In this review, we shortly survey and discuss recent research progress in graphene field emission properties with particular an emphasis on their preparing method, characterization and applications in devices especially for vertical graphene and single layer graphene, also including their challenges and future prospects.

Current-voltage characteristics of carbon nanostructured field emitters in different power supply modes

Science.gov (United States)

Popov, E. O.; Kolosko, A. G.; Filippov, S. V.; Romanov, P. A.; Terukov, E. I.; Shchegolkov, A. V.; Tkachev, A. G.

2017-12-01

We received and compared the current-voltage characteristics of large-area field emitters based on nanocomposites with graphene and nanotubes. The characteristics were measured in two high voltage scanning modes: the "slow" and the "fast". Correlation between two types of hysteresis observed in these regimes was determined. Conditions for transition from "reverse" hysteresis to the "direct" one were experimentally defined. Analysis of the eight-shaped hysteresis was provided with calculation of the effective emission parameters. The phenomenological model of adsorption-desorption processes in the field emission system was proposed.

Schottky’s conjecture, field emitters, and the point charge model

Directory of Open Access Journals (Sweden)

Kevin L. Jensen

2016-06-01

Full Text Available A Point Charge Model of conical field emitters, in which the emitter is defined by an equipotential surface of judiciously placed charges over a planar conductor, is used to confirm Schottky’s conjecture that field enhancement factors are multiplicative for a small protrusion placed on top of a larger base structure. Importantly, it is shown that Schottky’s conjecture for conical / ellipsoidal field emitters remains unexpectedly valid even when the dimensions of the protrusion begin to approach the dimensions of the base structure. The model is analytic and therefore the methodology is extensible to other configurations.

Use of tapered Pyrex capillary tubes to increase the mechanical stability of multiwall carbon nanotubes field emitters

Science.gov (United States)

Mousa, M. S.; Bani Ali, E. S.; Hagmann, M. J.

2018-02-01

In this study, NanocylTM NC 7000 Thin Multiwall Carbon Nanotubes (MWCNTs) were used with a high aspect ratio (>150) made by the process of catalytic chemical vapor deposition (CCVD). The field emitter tips were prepared by inserting these MWCT into fine glass capillary tubes that were pulled at high temperatures and then cut. Measurements were carried out under ultra-high vacuum (UHV) conditions with a base pressure of 10-9 mbar. The data show the effects of initial conditioning of MWCNT and hysteresis. Compression of the MWCNT by the capillary tubes appears to provide adequate mechanical support without requiring the use of a low-melting point electrically-conductive binder as has been used previously. Emission currents in excess of 1 μA were obtained so this technique shows promise as a reliable, stable, powerful electron source.

Chemically doped three-dimensional porous graphene monoliths for high-performance flexible field emitters.

Science.gov (United States)

Kim, Ho Young; Jeong, Sooyeon; Jeong, Seung Yol; Baeg, Kang-Jun; Han, Joong Tark; Jeong, Mun Seok; Lee, Geon-Woong; Jeong, Hee Jin

2015-03-12

Despite the recent progress in the fabrication of field emitters based on graphene nanosheets, their morphological and electrical properties, which affect their degree of field enhancement as well as the electron tunnelling barrier height, should be controlled to allow for better field-emission properties. Here we report a method that allows the synthesis of graphene-based emitters with a high field-enhancement factor and a low work function. The method involves forming monolithic three-dimensional (3D) graphene structures by freeze-drying of a highly concentrated graphene paste and subsequent work-function engineering by chemical doping. Graphene structures with vertically aligned edges were successfully fabricated by the freeze-drying process. Furthermore, their number density could be controlled by varying the composition of the graphene paste. Al- and Au-doped 3D graphene emitters were fabricated by introducing the corresponding dopant solutions into the graphene sheets. The resulting field-emission characteristics of the resulting emitters are discussed. The synthesized 3D graphene emitters were highly flexible, maintaining their field-emission properties even when bent at large angles. This is attributed to the high crystallinity and emitter density and good chemical stability of the 3D graphene emitters, as well as to the strong interactions between the 3D graphene emitters and the substrate.

Relation between field energy and RMS emittance in intense particle beams

International Nuclear Information System (INIS)

Wangler, T.P.; Crandall, K.R.; Mills, R.S.; Reiser, M.

1985-01-01

An equation is presented for continuous beams with azimuthal symmetry and continuous linear focusing, which expresses a relationship between the rate of change for squared rms emittance and the rate of change for a quantity we call the nonlinear field energy. The nonlinear field energy depends on the shape of the charge distribution and corresponds to the residual field energy possessed by beams with nonuniform charge distributions. The equation can be integrated for the case of an rms matched beam to yield a formula for space-charge-induced emittance growth that we have tested numerically for a variety of initial distributions. The results provide a framework for discussing the scaling of rms emittance growth and an explanation for the well-established lower limit on output emittance. 15 refs., 4 figs

Simple-to-prepare multipoint field emitter

Science.gov (United States)

Sominskii, G. G.; Taradaev, E. P.; Tumareva, T. A.; Mishin, M. V.; Kornishin, S. Yu.

2015-07-01

We investigate multitip field emitters prepared by electroerosion treatment of the surface of molybdenum samples. Their characteristics are determined for operation with a protecting activated fullerene coating. Our experiments indicate that such cathodes are promising for high-voltage electron devices operating in technical vacuum.

Low Emittance Gun Project based on Field Emission

CERN Document Server

Ganter, Romain; Dehler, M; Gobrecht, Jens; Gough, Chris; Ingold, Gerhard; Leemann, Simon C; Shing-Bruce-Li, Kevin; Paraliev, Martin; Pedrozzi, Marco; Raguin, Jean Yves; Rivkin, Leonid; Schlott, Volker; Sehr, Harald; Streun, Andreas; Wrulich, Albin F; Zelenika, Sasa

2004-01-01

The design of an electron gun capable of producing beam emittance one order of magnitude lower than current technology would reduce considerably the cost and size of a free electron laser emitting at 0.1nm. Field emitter arrays (FEAs) including a gate and a focusing layer are an attractive technology for such high brightness sources. Electrons are extracted from micrometric tips thanks to voltage pulses between gate and tips. The focusing layer should then reduce the initial divergence of each emitted beamlets. This FEA will be inserted in a high gradient diode configuration coupled with a radiofrequency structure. In the diode part very high electric field pulses (several hundreds of MV/m) will limit the degradation of emittance due to space charge effect. This first acceleration will be obtained with high voltage pulses (typically a megavolt in a few hundred of nanoseconds) synchronized with the low voltage pulses applied to the FEA (typically one hundred of volts in one nanosecond at frequency below kilohe...

Extremely environment-hard and low work function transfer-mold field emitter arrays

Energy Technology Data Exchange (ETDEWEB)

Nakamoto, Masayuki, E-mail: m-nakamoto@rie.shizuoka.ac.jp [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan); Moon, Jonghyun [Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8011 (Japan)

2013-06-15

Extremely environment-hard and low work function field-emitter arrays (FEAs) were fabricated by a transfer-mold emitter fabrication method to produce highly reliable vacuum nanoelectronic devices able to operate stably at low voltage in highly oxidizing atmospheres. Amorphous carbon (a-C) having a work function of 3.6 eV and sp{sup 3} fraction of 85.6% prepared by plasma-enhanced chemical vapor deposition was used as the emitter material. The field-emission characteristics of the obtained transfer-mold FEAs strongly depended on their work function and morphology. The environment-hard characteristics of the transfer-mold a-C FEAs were compared with those of the transfer-mold titanium nitride FEAs and nickel FEAs. X-ray photoelectron spectroscopy was used to confirm the stable chemical states of the FEAs after oxygen radical treatment. The small amount of material oxidized (6.3%) at the surface of the a-C FEAs compared with 11.8% for the TiN-FEAs and 39.0% for Ni FEAs after oxygen radical treatment explained their almost constant work function in oxidizing atmospheres. The emission fluctuation rates of transfer-mold a-C FEAs without resistive layers under in situ radical treatment were as low as ±5.0%, compared with 5–100% for conventional FEAs with resistive layers not under highly oxidizing atmospheres. Therefore, the present environment-hard and low work function transfer-mold a-C FEAs are expected to be useful for reliable vacuum nanoelectronic devices.

Tellurium adsorption on tungsten and molybdenum field emitters

International Nuclear Information System (INIS)

Collins, R.A.; Kiwanga, C.A.

1977-01-01

Studies of the adsorption of tellurium onto tungsten and molybdenum field emitters are described and the results obtained are compared with those obtained in previous work on the adsorption of silicon and selenium. The adsorption of Te onto W was found to be much more uniform than in the case of Se. Although Te is metallic in many of its properties its adsorptive behavior on field emitters is found to be similar to that of selenium and these adsorptive properties are basically common to all semiconductors. The most evident property of these adsorbates is that the work function and emission current decrease simultaneously at coverages of less than half a monolayer and the work function subsequently increases. (B.D.)

Highly stable carbon nanotube field emitters on small metal tips against electrical arcing for miniature X-ray tubes

International Nuclear Information System (INIS)

Ha, Jun Mok; Kim, Hyun Jin; Kim, Hyun Nam; Raza, Hamid Saeed; Cho, Sung Oh

2015-01-01

If CNT emitters are operated at a high voltage or at a high electric field, electrical arcing (or vacuum breakdown) can occur. Arcing can be initiated by the removed CNTs, impurities on the CNTs or substrates, protrusion of CNTs, low operating vacuum, and a very high electric field. Since arcing is accompanied with a very high current flow and it can produce plasma channel near the emitter, CNTs are seriously damaged or sometimes CNTs are almost completely removed from the substrate by the arcing events. Detachment of CNTs from a substrate is an irreversible catastrophic phenomenon for a device operation. In addition to the detachment of CNTs, arcing induces a sudden voltage drop and thus device operation is stopped. The metal mixture strongly attached CNTs to the tip substrate. Due to the strong adhesion, CNT emitters could be pre-treated with electrical conditioning process without seriously damaging the CNTs even though many intense arcing events were induced at the small and sharp geometry of the tip substrate. Impurities that were loosely bound to the substrates were almost removed and CNTs heights became uniform after the electrical conditioning process

Vertically aligned carbon nanotube emitter on metal foil for medical X-ray imaging.

Science.gov (United States)

Ryu, Je Hwang; Kim, Wan Sun; Lee, Seung Ho; Eom, Young Ju; Park, Hun Kuk; Park, Kyu Chang

2013-10-01

A simple method is proposed for growing vertically aligned carbon nanotubes on metal foil using the triode direct current plasma-enhanced chemical vapor deposition (PECVD). The carbon nanotube (CNT) electron emitter was fabricated using fewer process steps with an acid treated metal substrate. The CNT emitter was used for X-ray generation, and the X-ray image of mouse's joint was obtained with an anode current of 0.5 mA at an anode bias of 60 kV. The simple fabrication of a well-aligned CNT with a protection layer on metal foil, and its X-ray application, were studied.

Field emission from individual multiwalled carbon nanotubes prepared in an electron microscope

NARCIS (Netherlands)

de Jonge, N.; van Druten, N.J.

2003-01-01

Individual multiwalled carbon nanotube field emitters were prepared in a scanning electron microscope. The angular current density, energy spectra, and the emission stability of the field-emitted electrons were measured. An estimate of the electron source brightness was extracted from the

Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

Science.gov (United States)

Luo, Ma; Li, Zhibing

2016-11-01

The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

Modeling of Diamond Field-Emitter-Arrays for high brightness photocathode applications

Science.gov (United States)

Kwan, Thomas; Huang, Chengkun; Piryatinski, Andrei; Lewellen, John; Nichols, Kimberly; Choi, Bo; Pavlenko, Vitaly; Shchegolkov, Dmitry; Nguyen, Dinh; Andrews, Heather; Simakov, Evgenya

2017-10-01

We propose to employ Diamond Field-Emitter-Arrays (DFEAs) as high-current-density ultra-low-emittance photocathodes for compact laser-driven dielectric accelerators capable of generating ultra-high brightness electron beams for advanced applications. We develop a semi-classical Monte-Carlo photoemission model for DFEAs that includes carriers' transport to the emitter surface and tunneling through the surface under external fields. The model accounts for the electronic structure size quantization affecting the transport and tunneling process within the sharp diamond tips. We compare this first principle model with other field emission models, such as the Child-Langmuir and Murphy-Good models. By further including effects of carrier photoexcitation, we perform simulations of the DFEAs' photoemission quantum yield and the emitted electron beam. Details of the theoretical model and validation against preliminary experimental data will be presented. Work ssupported by LDRD program at LANL.

Characterization of NiSi nanowires as field emitters and limitations of Fowler-Nordheim model at the nanoscale

Science.gov (United States)

Belkadi, Amina B.; Gale, E.; Isakovic, A. F.

2015-03-01

Nanoscale field emitters are of technological interest because of the anticipated faster turn-on time, better sustainability and compactness. This report focuses on NiSi nanowires as field emitters for two reasons: (a) possible enhancement of field emission in nanoscale field emitters over bulk, and (b) achieving the same field emission properties as in bulk, but at a lower energy cost. To this end, we have grown, fabricated and characterized NiSi nanowires as field emitters. Depending on the geometry of the NiSi nanowires (aspect ratio, shape etc.), the relevant major field emission parameters, such as (1) the turn-on field, (2) the work function, and (3) the field enhancement factor, can be comparable or even superior to other recently explored nanoscale field emitters, such as CdS and ZnO. We also report on a comparative performance of various nanoscale field emitters and on the difficulties in the performance comparison in the light of relatively poor applicability of the standard Folwer-Nordheim model for field emission analysis for the case of the nanoscale field emitters. Proposed modifications are discussed. This work is supported through SRC-ATIC Grant 2011-KJ-2190. We also acknoweldge BNL-CFN and Cornell CNF facilities and staff.

Laser-assisted electron emission from gated field-emitters

CERN Document Server

Ishizuka, H; Yokoo, K; Mimura, H; Shimawaki, H; Hosono, A

2002-01-01

Enhancement of electron emission by illumination of gated field-emitters was studied using a 100 mW cw YAG laser at a wavelength of 532 nm, intensities up to 10 sup 7 W/m sup 2 and mechanically chopped with a rise time of 4 mu s. When shining an array of 640 silicon emitters, the emission current responded quickly to on-off of the laser. The increase of the emission current was proportional to the basic emission current at low gate voltages, but it was saturated at approx 3 mu A as the basic current approached 100 mu A with the increase of gate voltage. The emission increase was proportional to the square root of laser power at low gate voltages and to the laser power at elevated gate voltages. For 1- and 3-tip silicon emitters, the rise and fall of the current due to on-off of the laser showed a significant time lag. The magnitude of emission increase was independent of the position of laser spot on the emitter base and reached 2 mu A at a basic current of 5 mu A without showing signs of saturation. The mech...

Controlling the diameters and field emission properties of vertically aligned carbon nanotubes synthesized by thermal chemical vapor deposition

International Nuclear Information System (INIS)

Choi, Sung Yool; Kang, Young Il; Cho, Kyoung Ik; Choi, Kyu Seok; Kim, Do Jin

2001-01-01

We report here the synthesis of vertically well-aligned carbon nanotubes and the effect of catalytic metal layer on the diameter of grown carbon nanotubes and the field emission characteristics of them, The carbon nanotubes were grown by thermal chemical vapor deposition at temperatures below 900 .deg. C on Fe metal catalytic layer, deposited by sputtering process on a Si substrate and pretreated by heat and NH 3 gas. We found that the thickness of metal layers could be an important parameter in controlling the diameters of carbon nanotubes. With varying the thickness of the metal layers the grain sizes of them also vary so that the diameters of the nanotubes could be controlled. Field emission measurement has been made on the carbon nanotube field emitters at room temperature in a vacuum chamber below 10 -6 Torr. Our vertically aligned carbon nanotube field emitter of the smallest diameter emits a current density about 10 mA/cm 2 at 7.2 V/μm. The field emission property of the carbon nanotubes shows strong dependence on the nanotube diameters as expected

Spectrum of classes of point emitters of electromagnetic wave fields.

Science.gov (United States)

Castañeda, Román

2016-09-01

The spectrum of classes of point emitters has been introduced as a numerical tool suitable for the design, analysis, and synthesis of non-paraxial optical fields in arbitrary states of spatial coherence. In this paper, the polarization state of planar electromagnetic wave fields is included in the spectrum of classes, thus increasing its modeling capabilities. In this context, optical processing is realized as a filtering on the spectrum of classes of point emitters, performed by the complex degree of spatial coherence and the two-point correlation of polarization, which could be implemented dynamically by using programmable optical devices.

Analytical and numerical study of New field emitter processing for superconducting cavities

Science.gov (United States)

Volkov, Vladimir; Petrov, Victor

2018-02-01

In this article a scientific prove for a new technology to maximize the accelerating gradient in superconducting cavities by processing on higher order mode frequencies is presented. As dominant energy source the heating of field emitters by an induced rf current (rf-heating) is considered. The field emitter structure is assumed to be a chain of conductive particles, which are formed by attractive forces.

Design and fabrication of carbon nanotube field-emission cathode with coaxial gate and ballast resistor.

Science.gov (United States)

Sun, Yonghai; Yeow, John T W; Jaffray, David A

2013-10-25

A low density vertically aligned carbon nanotube-based field-emission cathode with a ballast resistor and coaxial gate is designed and fabricated. The ballast resistor can overcome the non-uniformity of the local field-enhancement factor at the emitter apex. The self-aligned fabrication process of the coaxial gate can avoid the effects of emitter tip misalignment and height non-uniformity. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microelectrode for energy and current control of nanotip field electron emitters

International Nuclear Information System (INIS)

Lüneburg, S.; Müller, M.; Paarmann, A.; Ernstorfer, R.

2013-01-01

Emerging experiments and applications in electron microscopy, holography, and diffraction benefit from miniaturized electron guns for compact experimental setups. We present a highly compact microelectrode integrated field emitter that consists of a tungsten nanotip coated with a few micrometers thick polyimide film followed by a several nanometers thick gold film, both positioned behind the exposed emitter apex by approximately 10–30 μm. The control of the electric field strength at the nanometer scale tip apex allows suppression, extraction, and energy tuning of field-emitted electrons. The performance of the microelectrode is demonstrated experimentally and supported by numerical simulations

Determining the field emitter temperature during laser irradiation in the pulsed laser atom probe

International Nuclear Information System (INIS)

Kellogg, G.L.

1981-01-01

Three methods are discussed for determining the field emitter temperature during laser irradiation in the recently developed Pulsed Laser Atom Probe. A procedure based on the reduction of the lattice evaporation field with increasing emitter temperature is found to be the most convenient and reliable method between 60 and 500 K. Calibration curves (plots of the evaporation field versus temperature) are presented for dc and pulsed field evaporation of W, Mo, and Rh. These results show directly the important influence of the evaporation rate on the temperature dependence of the evaporation field. The possibility of a temperature calibration based on the ionic charge state distribution of field evaporated lattice atoms is also discussed. The shift in the charge state distributions which occurs when the emitter temperature is increased and the applied field strength is decreased at a constant rate of evaporation is shown to be due to the changing field and not the changing temperature. Nevertheless, the emitter temperature can be deduced from the charge state distribution for a specified evaporation rate. Charge state distributions as a function of field strength and temperature are presented for the same three materials. Finally, a preliminary experiment is reported which shows that the emitter temperature can be determined from field ion microscope observations of single atom surface diffusion over low index crystal planes. This last calibration procedure is shown to be very useful at higher temperatures (>600 K) where the other two methods become unreliable

Simulation and fabrication of carbon nanotubes field emission pressure sensors

International Nuclear Information System (INIS)

Qian Kaiyou; Chen Ting; Yan Bingyong; Lin Yangkui; Xu Dong; Sun Zhuo; Cai Bingchu

2006-01-01

A novel field emission pressure sensor has been achieved utilizing carbon nanotubes (CNTs) as the electron source. The sensor consists of the anode sensing film fabricated by wet etching process and multi-wall carbon nanotubes (MWNTs) cathode in the micro-vacuum chamber. MWNTs on the silicon substrate were grown by thermal CVD. The prototype pressure sensor has a measured sensitivity of about 0.17-0.77 nA/Pa (101-550 KPa). The work shows the potential use of CNTs-based field-emitter in microsensors, such as accelerometers and tactile sensors

The effects of emitter-tied field plates on lateral PNP ionizing radiation response

International Nuclear Information System (INIS)

Barnaby, H.J.; Schrimpf, R.D.; Cirba, C.R.; Pease, R.L.; Fleetwood, D.M.; Kosier, S.L.

1998-03-01

Radiation response comparisons of lateral PNP bipolar technologies reveal that device hardening may be achieved by extending the emitter contact over the active base. The emitter-tied field plate suppresses recombination of carriers with interface traps

An Investigation of Emitters Clogging Under Magnetic Field and Water Quality

Directory of Open Access Journals (Sweden)

A. Kiani

2016-02-01

Full Text Available Introduction: Water scarcity is one of the major problems for crop production. Using drip irrigation as an effective method in the efficient use of water is expanding in arid and semi-arid regions. One of the problems in under pressure irrigation during use of saline, unconventional and waste is emitters clogging. There are several ways to prevent particle deposits in pipes and clogging of emitters. Generally, conventional methods are divided into two categories: physical and chemical methods. In physical method, suspended solids and inorganic materials are removed using particles sediment sand and disc filters. In the chemical method the pH drops by adding acid to water resulting in the dissolution of carbonate sediments. With chlorine handling, organisms (i.e. algae, fungi and bacteria that are the main causes of biological clogging are destroyed. However, the application of these methods is not successful in all cases. It has been observed that the emitters have gradually become obstructed. Magnetic water is obtained by passing water through permanent magnets or through the electromagnets installed in or on a feed pipeline. When a fluid passes through the magnetized field, its structure and some physical characteristic such as density, salt solution capacity, and deposition ratio of solid particles will be changed. An experimental study showed that a relatively weak magnetic influence increases the viscosity of water and consequently causes stronger hydrogen bonds under the magnetic field.There exist very few documented research projects related to the magnetization of water technology and its application to agricultural issues in general and emitter clogging in drip irrigation method, in particular. This technology is already used in some countries, especially in the Persian Gulf states. This research was designed and implemented aimed at increasing knowledge about the application of magnetic technology and its effects on emitters clogging

Stationary scanning x-ray source based on carbon nanotube field emitters

International Nuclear Information System (INIS)

Zhang, J.; Yang, G.; Cheng, Y.; Gao, B.; Qiu, Q.; Lee, Y.Z.; Lu, J.P.; Zhou, O.

2005-01-01

We report a field emission x-ray source that can generate a scanning x-ray beam to image an object from multiple projection angles without mechanical motion. The key component of the device is a gated carbon nanotube field emission cathode with an array of electron emitting pixels that are individually addressable via a metal-oxide-semiconductor field effect transistor-based electronic circuit. The characteristics of this x-ray source are measured and its imaging capability is demonstrated. The device can potentially lead to a fast data acquisition rate for laminography and tomosynthesis with a simplified experimental setup

A compact electron gun using field emitter array

International Nuclear Information System (INIS)

Asakawa, M.R.; Ikeda, A.; Miyabe, N.; Yamaguchi, S.; Kusaba, M.; Tsunawaki, Y.

2008-01-01

A compact electron gun using field emitter array has been developed. With a simple triode configuration consisting of FEA, mid-electrode and anode electrode, the electron gun produces a parallel beam with a diameter of 0.5 mm. This electron gun is applicable for compact radiation sources such as Cherenkov free-electron lasers

Root Causes of Field Emitters in SRF Cavities Placed in CEBAF Tunnel

Energy Technology Data Exchange (ETDEWEB)

Geng, Rongli

2016-05-01

It has been suspected that appearance of new field emitters can occur in SRF cavities after their placement in accelerator tunnel for long term beam operation. This apparently has been the case for CEBAF. However, no physical evidence has been shown in the past. In this contribution, we will report on the recent results concerning the root cause of field emitters in SRF cavities placed in CEBAF tunnel. We will discuss these results in the context of high-reliability and low-cryogenic-loss operation of CEBAF.

Field emission of carbon nanotubes grown on nickel substrate

International Nuclear Information System (INIS)

Hu Yemin; Huo Kaifu; Chen Hong; Lu Yinong; Xu Li; Hu Zheng; Chen Yi

2006-01-01

Carbon nanotubes (CNTs) have been synthesized directly on the electrically conducting nickel substrate without additional catalyst. Field emission properties of the as-prepared sample were characterized using parallel plate diode configurations. It was observed that the field emission qualitatively follows the conventional Fowler-Nordheim (F-N) theory from the straight line of ln(I/V 2 ) versus 1/V plot at the high applied field region. The uniformity and stability of the electron emission have also been examined. The low electron turn-on field (E to ) and high emission current density indicates the potential applications of this new CNT-based emitter

Tellurium adsorption on single crystal faces of molybdenum and tungsten field emitters

International Nuclear Information System (INIS)

Collins, R.A.; Kiwanga, C.A.

1978-01-01

The purpose of this letter is to report the extension of previous studies of Te adsorption on Mo and W field emitters to measurements on single crystal planes. The adsorption of semiconductors on metallic emitters has been found to be characterized by simultaneous decreases in emission current and the Fowler-Nordheim work function for adsorbate coverages of less than a monolayer. (Auth.)

High resolution structuring of emitter tips for the gaseous field ionization source

International Nuclear Information System (INIS)

Kubby, J.A.; Siegel, B.M.

1986-01-01

Extraction of a stable, high brightness ion beam from an apertured field ion emitter surface requires microfabrication procedures to sculpture the surface topography on both microscopic (100 --1000 nm) and near atomic (10 --100 nm) length scales. Structuring on a near atomic scale is required to confine and stabilize the ion beam by local enhancement of the surface electrostatic field and to orient that emission on the optical axis. Control of the emitter contour on a microscopic scale is required for manipulating the supply of neutral molecules to the ionization site and also affects beam stability. We have developed a method using ion milling for configuring surface contour on microscopic and near atomic length scales which utilizes the morphological changes occurring at ion bombarded surfaces as a result of erosion by sputtering. A SEM study of the microscopic emitter topographical development is compared to computer simulations of the kinematical wave equation which depicts the erosion process. In this way, prediction of configuration on a length scale large compared to the ion penetration depth has been established. TEM observations show the surface development on the length scale of ion penetration depth. Preliminary results using this microfabricated emitter in a gaseous field ion source to produce a hydrogen ion beam with high angular beam confinement are given. Requirements for surface topography that are essential to obtain stable high brightness ion beams are discussed

Discrete space charge affected field emission: Flat and hemisphere emitters

Energy Technology Data Exchange (ETDEWEB)

Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil [Code 6854, Naval Research Laboratory, Washington, DC 20375 (United States); Shiffler, Donald A.; Tang, Wilkin [Air Force Research Laboratory, Kirtland AFB, New Mexico 87117 (United States); Rittersdorf, Ian M. [Code 6770, Naval Research Laboratory, Washington, DC 20375 (United States); Lebowitz, Joel L. [Department of Mathematics and Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States); Harris, John R. [U.S. Navy Reserve, New Orleans, Louisiana 70143 (United States); Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Petillo, John J. [Leidos, Billerica, Massachusetts 01821 (United States); Luginsland, John W. [Physics and Electronics Directorate, AFOSR, Arlington, Virginia 22203 (United States)

2015-05-21

Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.

Infrared Organic Light-Emitting Diodes with Carbon Nanotube Emitters.

Science.gov (United States)

Graf, Arko; Murawski, Caroline; Zakharko, Yuriy; Zaumseil, Jana; Gather, Malte C

2018-03-01

While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum are widespread, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter is demonstrated. By using a multilayer stacked architecture with matching charge blocking and charge-transport layers, narrow-band electroluminescence at wavelengths between 1000 and 1200 nm is achieved, with spectral features characteristic of excitonic and trionic emission of the employed (6,5) SWCNTs. Here, the OLED performance is investigated in detail and it is found that local conduction hot-spots lead to pronounced trion emission. Analysis of the emissive dipole orientation shows a strong horizontal alignment of the SWCNTs with an average inclination angle of 12.9° with respect to the plane, leading to an exceptionally high outcoupling efficiency of 49%. The SWCNT-based OLEDs represent a highly attractive platform for emission across the entire nIR. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

Science.gov (United States)

Mousa, Marwan S.; Alnawasreh, Shadi; Madanat, Mazen A.; Al-Rabadi, Anas N.

2015-10-01

Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10-9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type _I-V_plots for carbon fibers and tungsten tips.

Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

International Nuclear Information System (INIS)

Mousa, Marwan S; Alnawasreh, Shadi; Al-Rabadi, Anas N; Madanat, Mazen A

2015-01-01

Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10 -9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type -I-V-plots for carbon fibers and tungsten tips. (paper)

Multi-gated field emitters for a micro-column

International Nuclear Information System (INIS)

Mimura, Hidenori; Kioke, Akifumi; Aoki, Toru; Neo, Yoichiro; Yoshida, Tomoya; Nagao, Masayoshi

2011-01-01

We have developed a multi-gated field emitter (FE) such as a quadruple-gated FE with a three-stacked electrode lens and a quintuple-gated FE with a four-stacked electrode lens. Both the FEs can focus the electron beam. However, the quintuple-gated FE has a stronger electron convergence than the quadruple-gated FE, and a beam crossover is clearly observed for the quintuple-gated FE.

Electron emission from nano-structured carbon composite materials and fabrication of high-quality electron emitters by using plasma technology

International Nuclear Information System (INIS)

Hiraki, H.; Hiraki, A.; Jiang, N.; Wang, H. X.

2006-01-01

Many trials have been done to fabricate high-quality electron-emitters from nano-composite carbon materials (such as nano-diamond, carbon nano tubes and others) by means of a variety of plasma chemical-vapor-deposition (CVD) techniques. Based upon the mechanism of electron emission, we have proposed several strategic guide lines for the fabrication of good emitters. Then, following these lines, several types of emitters were tried. One of the emitters has shown a worldclass, top ranking for fabricating very bright lamps: namely, a low turn-on voltage (0.5 ∼ 1 V/μm to induce 10 μA/cm 2 emission current) to emit a 1 mA/cm 2 current at 3 V/μm and 100 mA/cm 2 current at a slightly higher applied voltage. The bright lamps are Mercury-free fluorescence lamps to exhibit brightness of ∼10 5 cd/m 2 with high efficiency of ∼100 lm/w.

Properties of multiple field ion emitters of tungsten and a simple method for improving their ionization efficiency

International Nuclear Information System (INIS)

Okuyama, F.; Beckey, H.D.

1978-01-01

The ion emission properties of the multiple tungsten emitters developed recently for field ionization mass spectrometry were investigated with the aid of a sector type mass spectrometer at emitter-cathode voltages of 10-15 kV using acetone, n-heptane and benzene as test substances. The emitters, which comprised a 10-μm tungsten filament bearing thickly arrayed microneedles of tungsten, produced very weak and unstable signals at voltages of about 10 kV, but increasing the voltage to 14 kV led to intensifying ion currents high enough to yield mass spectra of satisfactory quality. During the course of the experiments, it was observed that nucleating tungsten carbide particles on the emitter surface by means of a high-field chemical reaction with benzene vapours can significanlty promote the field ionization of gas molecules, presumably as a result of the field enhancement resulting from roughening of the surface. (Auth.)

Hafnium carbide nanocrystal chains for field emitters

International Nuclear Information System (INIS)

Tian, Song; Li, Hejun; Zhang, Yulei; Ren, Jincui; Qiang, Xinfa; Zhang, Shouyang

2014-01-01

A hafnium carbide (HfC) nanostructure, i.e., HfC nanocrystal chain, was synthesized by a chemical vapor deposition (CVD) method. X-ray diffractometer, field-emission scanning electron microscope, transmission electron microscope, and energy-dispersive X-ray spectrometer were employed to characterize the product. The synthesized one-dimensional (1D) nanostructures with many faceted octahedral nanocrystals possess diameters of tens of nanometers to 500 nm and lengths of a few microns. The chain-like structures possess a single crystalline structure and preferential growth direction along the [1 0 0] crystal orientation. The growth of the chains occurred through the vapor–liquid–solid process along with a negative-feedback mechanism. The field emission (FE) properties of the HfC nanocrystal chains as the cold cathode emitters were examined. The HfC nanocrystal chains display good FE properties with a low turn-on field of about 3.9 V μm −1 and a high field enhancement factor of 2157, implying potential applications in vacuum microelectronics.

Fabrication of multi-emitter array of CNT for enhancement of current density

Energy Technology Data Exchange (ETDEWEB)

Chouhan, Vijay, E-mail: vchouhan@post.kek.jp [Department of Accelerator Science, Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki (Japan); Noguchi, Tsuneyuki [High Energy Accelerator Research Organization-KEK, 1-1 Oho, Tsukuba, Ibaraki (Japan); Kato, Shigeki [Department of Accelerator Science, Graduate University for Advanced Studies, 1-1 Oho, Tsukuba, Ibaraki (Japan); High Energy Accelerator Research Organization-KEK, 1-1 Oho, Tsukuba, Ibaraki (Japan)

2011-11-11

We studied and compared field emission properties of two kinds of emitters of randomly oriented multi-wall carbon nanotubes (MWNTs), viz. continuous film emitter (CFE) and multi-emitter array (MEA). The CFE has a continuous film of MWNTs while the MEA consists of many equidistant small circular emitters. Both types of emitters were prepared by dispersing MWNTs over a titanium (Ti) film (for CFEs) or Ti circular islands (for MEAs) deposited on tantalum (Ta) followed by rooting of MWNTs into the Ti film or the Ti islands at high temperature. Emission properties of both types of emitters were analyzed with changing their emission areas. In case of the CFEs, current density decreased with an increase in emission area whereas consistent current densities were achieved from MEAs with different emission areas. In other words, the total emission current was achieved in proportion to the emission area in the case of MEAs. Additionally a high current density of 22 A/cm{sup 2} was achieved at an electric field of 8 V/{mu}m from MEAs, which was far better than that obtained from CFEs. The high current density in MEAs was attributed to edge effect, in which higher emission current is achieved from the edge of film emitter. The results indicate that the field emission characteristics can be greatly improved if a cathode contains many small equidistant circular emitters instead of a continuous film. The outstanding stability of the CFE and the MEA has been demonstrated for 2100 and 1007 h, respectively.

Ion production from LiF-coated field emitter tips

International Nuclear Information System (INIS)

Pregenzer, A.L.; Bieg, K.W.; Olson, R.E.; Panitz, J.A.

1990-01-01

Ion emission has been obtained from a LiF-coated tungsten field-emitter tip. Ion formation is thought to be caused by the high electric field experienced by the LiF. At the time of emission the electric field at the surface of the LiF is calculated to be on the order of 100 MV/cm. Inside the LiF the field is on the order of 10 MV/cm. These fields exceed the value needed to produce bulk dielectric breakdown in LiF. The surface field is of sufficient magnitude to produce ion emission by field evaporation from the crystal surface. Even prior to dielectric breakdown, precursor processes can lead to ion formation. Electric-field-stress fragmentation of the LiF layer is thought to occur, followed by ionization of the fragments

High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

International Nuclear Information System (INIS)

Hojati-Talemi, Pejman; Gibson, Mark A.; East, Daniel; Simon, George P.

2011-01-01

We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

Energy Technology Data Exchange (ETDEWEB)

Hojati-Talemi, Pejman [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia); Mawson Institute, University of South Australia, Mawson Lakes, SA 5095 (Australia); Gibson, Mark A. [Process Science and Engineering, Commonwealth Scientific and Industrial Research Organisation, Clayton, Vic 3168 (Australia); East, Daniel; Simon, George P. [Department of Materials Engineering, Monash University, Clayton, Vic 3800 (Australia)

2011-11-07

We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

Field emission from a composite structure consisting of vertically aligned single-walled carbon nanotubes and carbon nanocones

International Nuclear Information System (INIS)

Yeh, C M; Chen, M Y; Hwang, J; Gan, J-Y; Kou, C S

2006-01-01

Vertically aligned single-walled carbon nanotubes (VA-SWCNTs) have been fabricated on carbon nanocones (CNCs) in a gravity-assisted chemical vapour deposition (CVD) process. The CNCs with nanoscale Co particles at the top were first grown on the Co/Si(100) substrate biased at 350 V in a plasma enhanced chemical vapour deposition process. The CNCs typically are ∼200 nm in height, and their diameters are ∼100 nm near the bottom and ∼10 nm at the top. The nanoscale Co particles ∼10 nm in diameter act as catalysts which favour the growth of VA-SWCNTs out of CNCs at 850 0 C in the gravity-assisted CVD process. The average length and the growth time of VA-SWCNTs are ∼150 nm and 1.5 min, equivalent to a growth rate of ∼6 μm h -1 . The diameters of VA-SWCNTs are estimated to be 1.2-2.1 nm. When VA-SWCNTs are fabricated on CNCs, the turn-on voltage is reduced from 3.9 to 0.7 V μm -1 and the emission current density at the electric field of 5 V μm -1 is enhanced by a factor of more than 200. The composite VA-SWCNT/CNC structure is potentially an excellent field emitter. The emission stability of the VA-SWCNT/CNC field emitter is discussed

Viability of Using Diamond Field Emitter Array Cathodes in Free Electron Lasers

Science.gov (United States)

2010-06-01

essential component of a field emitter array is the shape of the electric field lines and equipotential lines at the surface of the array. The...BARRIER AND QUANTUM TUNNELING ...........25 B. FIELD ENHANCEMENT AND SURFACE PROTRUSIONS .........26 C. ELECTRIC FIELDS AND ELECTRON TRAVEL...26 Figure 4. Diagram of a protrusion (triangular in shape) from the surface of a cathode. The protrusion is of height h, with a

Density functional theory for field emission from carbon nano-structures.

Science.gov (United States)

Li, Zhibing

2015-12-01

Electron field emission is understood as a quantum mechanical many-body problem in which an electronic quasi-particle of the emitter is converted into an electron in vacuum. Fundamental concepts of field emission, such as the field enhancement factor, work-function, edge barrier and emission current density, will be investigated, using carbon nanotubes and graphene as examples. A multi-scale algorithm basing on density functional theory is introduced. We will argue that such a first principle approach is necessary and appropriate for field emission of nano-structures, not only for a more accurate quantitative description, but, more importantly, for deeper insight into field emission. Copyright © 2015 The Author. Published by Elsevier B.V. All rights reserved.

Study of the time and space distribution of β+ emitters from 80MeV/u carbon ion beam irradiation on PMMA

International Nuclear Information System (INIS)

Agodi, C.; Bellini, F.; Cirrone, G.A.P.; Collamati, F.; Cuttone, G.; De Lucia, E.; De Napoli, M.; Di Domenico, A.; Faccini, R.; Ferroni, F.; Fiore, S.; Gauzzi, P.; Iarocci, E.; Marafini, M.; Mattei, I.; Paoloni, A.

2012-01-01

Proton and carbon ion therapy is an emerging technique used for the treatment of solid cancers. The monitoring of the dose delivered during such treatments and the on-line knowledge of the Bragg peak position is still a matter of research. A possible technique exploits the collinear 511keV photons produced by positrons annihilation from β + emitters created by the beam. This paper reports rate measurements of the 511keV photons emitted after the interactions of a 80MeV/u fully stripped carbon ion beam at the Laboratori Nazionali del Sud (LNS) of INFN, with a poly-methyl methacrylate target. The time evolution of the β + rate was parametrized and the dominance of 11 C emitters over the other species ( 13 N, 15 O, 14 O) was observed, measuring the fraction of carbon ions activating β + emitters to be (10.3±0.7)×10 -3 . The average depth in the PMMA of the positron annihilation from β + emitters was also measured, D β + =5.3±1.1mm, to be compared to the expected Bragg peak depth D Bragg =11.0±0.5mm obtained from simulations.

Pulsed laser-deposited nanocrystalline GdB{sub 6} thin films on W and Re as field emitters

Energy Technology Data Exchange (ETDEWEB)

Suryawanshi, Sachin R.; More, Mahendra A. [Savitribai Phule Pune University, Department of Physics, Centre for Advanced Studies in Materials Science and Condensed Matter Physics, Pune (India); Singh, Anil K.; Sinha, Sucharita [Bhabha Atomic Research Centre, Laser and Plasma Technology Division, Trombay, Mumbai (India); Phase, Deodatta M. [UGC-DAE Consortium for Scientific Research Indore Centre, Indore (India); Late, Dattatray J. [CSIR-National Chemical Laboratory, Physical and Materials Chemistry Division, Pune (India)

2016-10-15

Gadolinium hexaboride (GdB{sub 6}) nanocrystalline thin films were grown on tungsten (W), rhenium (Re) tips and foil substrates using optimized pulsed laser deposition (PLD) technique. The X-ray diffraction analysis reveals formation of pure, crystalline cubic phase of GdB{sub 6} on W and Re substrates, under the prevailing PLD conditions. The field emission (FE) studies of GdB{sub 6}/W and GdB{sub 6}/Re emitters were performed in a planar diode configuration at the base pressure ∝10{sup -8} mbar. The GdB{sub 6}/W and GdB{sub 6}/Re tip emitters deliver high emission current densities of ∝1.4 and 0.811 mA/cm{sup 2} at an applied field of ∝6.0 and 7.0 V/μm, respectively. The Fowler-Nordheim (F-N) plots were found to be nearly linear showing metallic nature of the emitters. The noticeably high values of field enhancement factor (β) estimated using the slopes of the F-N plots indicate that the PLD GdB{sub 6} coating on W and Re substrates comprises of high-aspect-ratio nanostructures. Interestingly, the GdB{sub 6}/W and GdB{sub 6}/Re planar emitters exhibit excellent current stability at the preset values over a long-term operation, as compared to the tip emitters. Furthermore, the values of workfunction of the GdB{sub 6}/W and GdB6/Re emitters, experimentally measured using ultraviolet photoelectron spectroscopy, are found to be same, ∝1.6 ± 0.1 eV. Despite possessing same workfunction value, the FE characteristics of the GdB{sub 6}/W emitter are markedly different from that of GdB{sub 6}/Re emitter, which can be attributed to the growth of GdB{sub 6} films on W and Re substrates. (orig.)

Field emission response from multi-walled carbon nanotubes grown on electrochemically engineered copper foil

Energy Technology Data Exchange (ETDEWEB)

Tripathi, Amit Kumar; Jain, Vaibhav [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Saini, Krishna [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Centre of Excellence: Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Lahiri, Indranil, E-mail: indrafmt@iitr.ac.in [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Centre of Excellence: Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India)

2017-02-01

Exciting properties of carbon nanotube has proven it to be a promising candidate for field emission applications, if its processing cost can be reduced effectively. In this research, a new electrochemical technique is proposed for growing carbon nanotubes in selective areas by thermal chemical vapour deposition. In this process, electrochemical processing is used to create localized pits and deposition of catalysts, which act as roots to support growth and alignment of the CNTs on copper substrate. CNTs grown thus were characterized and studied using scanning electron microscope, transmission electron microscope and Raman spectroscopy, elucidating presence of multiwall carbon nanotubes (MWCNT). These CNT emitters have comparatively lower turn-on field and higher field enhancement factor. - Highlights: • Electrochemical pitting for localized carbon nanotube growth is proposed. • Electrochemical pitting method shows patterning effect on the substrate. • Size and density of pits depend on voltage, pH and temperature. • CNTs thus grown shows good field emission response.

Field emission of carbon quantum dots synthesized from a single organic solvent.

Science.gov (United States)

Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao

2016-11-04

In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm(-2) at 7.0 V μm(-1) and exhibits good long-term emission stability, suggesting promising application in field emission devices.

Carbon nanotubes growing on rapid thermal annealed Ni and their application to a triode-type field emission device

International Nuclear Information System (INIS)

Uh, Hyung Soo; Park, Sang Sik

2006-01-01

In this paper, we demonstrate a new triode-type field emitter arrays using carbon nanotubes (CNTs) as an electron emitter source. In the proposed structure, the gate electrode is located underneath the cathode electrode and the extractor electrode is surrounded by CNT emitters. CNTs were selectively grown on the patterned Ni catalyst layer by using plasma-enhanced chemical vapor deposition (PECVD). Vertically aligned CNTs were grown with gas mixture of acetylene and ammonia under external DC bias. Compared with a conventional under-gate structure, the proposed structure reduced the turn-on voltage by about 30%. In addition, with a view to controlling the density of CNTs, Ni catalyst thickness was varied and rapid thermal annealing (RTA) treatment was optionally adopted before CNT growth. With controlled Ni thickness and RTA condition, field emission efficiency was greatly improved by reducing the density of CNTs, which is due to the reduction of the electric field screening effect caused by dense CNTs

Arc-textured metal surfaces for high thermal emittance space radiators

International Nuclear Information System (INIS)

Banks, B.A.; Rutledge, S.K.; Mirtich, M.J.; Behrend, T.; Hotes, D.; Kussmaul, M.; Barry, J.; Stidham, C.; Stueber, T.; DiFilippo, F.

1994-01-01

Carbon arc electrical discharges struck across the surfaces of metals such as Nb-1% Zr, alter the morphology to produce a high thermal emittance surface. Metal from the surface and carbon from the arc electrode vaporize during arcing, and then condense on the metal surface to produce a microscopically rough surface having a high thermal emittance. Quantitative spectral reflectance measurements from 0.33 to 15 μm were made on metal surfaces which were carbon arc treated in an inert gas environment. The resulting spectral reflectance data were then used to calculate thermal emittance as a function of temperature for various methods of arc treatment. The results of arc treatment on various metals are presented for both ac and dc arcs. Surface characterization data, including thermal emittance as a function of temperature, scanning electron microscopy, and atomic oxygen durability, are also presented. Ac arc texturing was found to increase the thermal emittance at 800 K from 0.05. to 0.70

Control of the electromagnetic environment of a quantum emitter by shaping the vacuum field in a coupled-cavity system

NARCIS (Netherlands)

Johne, R.; Schutjens, H.A.W.; Fattahpoor, S.; Jin, C.; Fiore, A.

2015-01-01

We propose a scheme for the ultrafast control of the emitter-field coupling rate in cavity quantum electrodynamics. This is achieved by the control of the vacuum field seen by the emitter through a modulation of the optical modes in a coupled-cavity structure. The scheme allows the on-off switching

Analysis of Field Emission of Fabricated Nanogap in Pd Strips for Surface Conduction Electron-Emitter Displays

Science.gov (United States)

Lo, Hsiang-Yu; Li, Yiming; Tsai, Chih-Hao; Pan, Fu-Ming

2008-04-01

We study the field emission (FE) property of a nanometer-scale gap structure in a palladium strip, which was fabricated by hydrogen absorption under high-pressure treatment. A vigorous cracking process could be accompanied by extensive atomic migration during the hydrogen treatment. A three-dimensional finite-difference time-domain particle-in-cell method is adopted to simulate the electron emission in a surface-conduction electron-emitter display (SED) device. Examinations of conducting characteristics, FE efficiency, the local field around the emitter, and the current density on the anode plate with one FE emitter are conducted. The image of a light spot is successfully produced on a phosphor plate, which implies that the explored electrode with nanometer separation possesses a potential SED application. Experimental observation and numerical simulation show that the proposed structure can be used as a surface conduction electron emitter and has a high FE efficiency with low turn-on voltage and a different electron emission mechanism. This study benefits the advanced SED design for a new type of electron source.

Characterization of electron bunches from field emitter array cathodes for use in next-generation x-ray free electron lasers

International Nuclear Information System (INIS)

Leemann, S. C.

2007-01-01

PSI is interested in developing an x-ray free electron laser (X-FEL) as a companion radiation source to the existing Swiss Light Source. In order to achieve radiation wavelengths as low as 1 Α, the X-FEL requires excellent electron beam quality and high beam energy. The energy requirements and thus the size and cost of the project can be reduced considerably if an ultra-low emittance electron source is developed. Therefore PSI has started the Low Emittance Gun Project with the aim to design a novel type of electron source that will deliver an electron beam with unprecedented emittance at high peak currents to the linear accelerator of the proposed X-FEL. A source candidate for such a gun is field emission from cold cathodes. In order to gain first experience with field emission guns, investigate the dynamics of space charge dominated electron beams and to develop diagnostics capable of resolving ultra-low emittances, it was decided to build a 100 keV DC gun test stand. In the scope of this thesis, the test stand has been designed, assembled and commissioned. For the first time, transverse phase space measurements of bunches emitted by field emitter arrays in pulsed DC accelerating fields have been performed. (author)

Study of the time and space distribution of {beta}{sup +} emitters from 80MeV/u carbon ion beam irradiation on PMMA

Energy Technology Data Exchange (ETDEWEB)

Agodi, C. [Laboratori Nazionali del Sud dell' INFN, Catania (Italy); Bellini, F. [Dipartimento di Fisica, Sapienza Universita di Roma, Roma (Italy); INFN Sezione di Roma, Roma (Italy); Cirrone, G.A.P. [Laboratori Nazionali del Sud dell' INFN, Catania (Italy); Collamati, F. [Dipartimento di Fisica, Sapienza Universita di Roma, Roma (Italy); INFN Sezione di Roma, Roma (Italy); Cuttone, G. [Laboratori Nazionali del Sud dell' INFN, Catania (Italy); De Lucia, E. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); De Napoli, M. [Laboratori Nazionali del Sud dell' INFN, Catania (Italy); Di Domenico, A.; Faccini, R.; Ferroni, F. [Dipartimento di Fisica, Sapienza Universita di Roma, Roma (Italy); INFN Sezione di Roma, Roma (Italy); Fiore, S. [Dipartimento di Fisica, Sapienza Universita di Roma, Roma (Italy); Gauzzi, P. [Dipartimento di Fisica, Sapienza Universita di Roma, Roma (Italy); INFN Sezione di Roma, Roma (Italy); Iarocci, E. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Dipartimento di Scienze di Base e Applicate per l' Ingegneria, Sapienza Universita di Roma, Roma (Italy); Marafini, M., E-mail: michela.marafini@roma1.infn.it [Museo Storico della Fisica e Centro Studi e Ricerche ' E. Fermi' , Roma (Italy); Mattei, I. [Dipartimento di Fisica, Roma Tre Universita di Roma, Roma (Italy); Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Paoloni, A. [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); and others

2012-07-15

Proton and carbon ion therapy is an emerging technique used for the treatment of solid cancers. The monitoring of the dose delivered during such treatments and the on-line knowledge of the Bragg peak position is still a matter of research. A possible technique exploits the collinear 511keV photons produced by positrons annihilation from {beta}{sup +} emitters created by the beam. This paper reports rate measurements of the 511keV photons emitted after the interactions of a 80MeV/u fully stripped carbon ion beam at the Laboratori Nazionali del Sud (LNS) of INFN, with a poly-methyl methacrylate target. The time evolution of the {beta}{sup +} rate was parametrized and the dominance of {sup 11}C emitters over the other species ({sup 13}N, {sup 15}O, {sup 14}O) was observed, measuring the fraction of carbon ions activating {beta}{sup +} emitters to be (10.3{+-}0.7) Multiplication-Sign 10{sup -3}. The average depth in the PMMA of the positron annihilation from {beta}{sup +} emitters was also measured, D{sub {beta}{sup +}}=5.3{+-}1.1mm, to be compared to the expected Bragg peak depth D{sub Bragg}=11.0{+-}0.5mm obtained from simulations.

Ultrafast transmission electron microscopy using a laser-driven field emitter: Femtosecond resolution with a high coherence electron beam

Energy Technology Data Exchange (ETDEWEB)

Feist, Armin; Bach, Nora; Rubiano da Silva, Nara; Danz, Thomas; Möller, Marcel; Priebe, Katharina E.; Domröse, Till; Gatzmann, J. Gregor; Rost, Stefan; Schauss, Jakob; Strauch, Stefanie; Bormann, Reiner; Sivis, Murat; Schäfer, Sascha, E-mail: sascha.schaefer@phys.uni-goettingen.de; Ropers, Claus, E-mail: claus.ropers@uni-goettingen.de

2017-05-15

We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the Göttingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9 Å focused beam diameter, 200 fs pulse duration and 0.6 eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free-electron beams. - Highlights: • First implementation of an ultrafast TEM employing a nanoscale photocathode. • Localized single photon-photoemission from nanoscopic field emitter yields low emittance ultrashort electron pulses. • Electron pulses focused down to ~9 Å, with a duration of 200 fs and an energy width of 0.6 eV are demonstrated. • Quantitative characterization of ultrafast electron gun emittance and brightness. • A range of applications of high coherence ultrashort electron pulses is shown.

Field Emitter Arrays for a Free Electron Laser Application

CERN Document Server

Shing-Bruce-Li, Kevin; Ganter, Romain; Gobrecht, Jens; Raguin, Jean Yves; Rivkin, Leonid; Wrulich, Albin F

2004-01-01

The development of a new electron gun with the lowest possible emittance would help reducing the total length and cost of a free electron laser. Field emitter arrays (FEAs) are an attractive technology for electron sources of ultra high brightness. Indeed, several thousands of microscopic tips can be deposited on a 1 mm diameter area. Electrons are then extracted by applying voltage to a first grid layer close to the tip apexes, the so called gate layer, and focused by a second grid layer one micrometer above the tips. The typical aperture diameter of the gate and the focusing layer is in the range of one micrometer. One challenge for such cathodes is to produce peak currents in the ampere range since the usual applications of FEAs require less than milliampere. Encouraging peak current performances have been obtained by applying voltage pulses at low frequency between gate and tips. In this paper we report on different tip materials available on the market: diamond FEAs from Extreme Devices Inc., ZrC single ...

Nanodiamond composite as a material for cold electron emitters

International Nuclear Information System (INIS)

Arkhipov, A V; Sominski, G G; Uvarov, A A; Gordeev, S K; Korchagina, S B

2008-01-01

Characteristics of field-induced electron emission were investigated for one of newly designed all-carbon materials - nanodiamond composite (NDC). The composite is comprised by 4-6 nm diamond grains covered with 0.2-1 nm-thick graphite-like shells that merge at grain junctions and determine such properties as mechanical strength and high electric conductivity. Large number of uniformly distributed sp 3 -sp 2 interfaces allowed to expect enhanced electron emission in electric field. Combination of these features makes NDC a promising material for cold electron emitters in various applications. Experimental testing confirmed high efficiency of electron emission from NDC. In comparison with previousely tested forms of nanocarbon, NDC emitters demonstrated better stabily and tolerance to performance conditions. Unusual activation scenarios and thermal dependencies of emission characteristics observed in experiments with NDC can add new background for explanation of facilitated electron emission from nanocarbons with relatively 'smooth' surface morphology

Patterned growth of carbon nanotubes over vertically aligned silicon nanowire bundles for achieving uniform field emission.

Science.gov (United States)

Hung, Yung-Jr; Huang, Yung-Jui; Chang, Hsuan-Chen; Lee, Kuei-Yi; Lee, San-Liang

2014-01-01

A fabrication strategy is proposed to enable precise coverage of as-grown carbon nanotube (CNT) mats atop vertically aligned silicon nanowire (VA-SiNW) bundles in order to realize a uniform bundle array of CNT-SiNW heterojunctions over a large sample area. No obvious electrical degradation of as-fabricated SiNWs is observed according to the measured current-voltage characteristic of a two-terminal single-nanowire device. Bundle arrangement of CNT-SiNW heterojunctions is optimized to relax the electrostatic screening effect and to maximize the field enhancement factor. As a result, superior field emission performance and relatively stable emission current over 12 h is obtained. A bright and uniform fluorescent radiation is observed from CNT-SiNW-based field emitters regardless of its bundle periodicity, verifying the existence of high-density and efficient field emitters on the proposed CNT-SiNW bundle arrays.

Improvements in emittance wake field optimization for the SLAC Linear Collider

CERN Document Server

Decker, Franz Josef

2003-01-01

The transverse emittances in the SLAC Linear Collider can be severely diluted by collective wakefield effects and dispersion. For the 1997/98 SLC/SLD run important changes were implemented in the way the emittance is optimized. Early in the linac, where the energy spread is large due to BNS damping, the emittance growth is dominated by dispersion. In this regime emittance tuning bumps may introduce additional wakefield tails and their use is now avoided. At the end of the linac the energy spread is minimal and the emittance measurement is most sensitive to wakefield emittance dilution. In previous years, the emittances were tuned on wire scanners located near but not at the end of the linac (after about 90% of its length). Simulations show that emittance growth of up to 100% can occur in the remaining 10%. In this run wire scanners at the entrance of the Final Focus, the last place where the emittances can be measured, were used for the optimization. Screens at the end of the linac allow additional real time ...

Effect of very high magnetic field on the optical properties of firefly light emitter oxyluciferin

Energy Technology Data Exchange (ETDEWEB)

Zhou, Weihang; Nakamura, Daisuke [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Wang, Yu [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (China); Mochizuki, Toshimitsu [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, 2-2-9 Machiike-dai, Koriyama, Fukushima 963-0215 (Japan); Akiyama, Hidefumi [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Takeyama, Shojiro, E-mail: takeyama@issp.u-tokyo.ac.jp [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

2015-09-15

Magnetic field effect on enzymatic reactions is under intensive study in the past decades. Recently, it was reported that firefly bioluminescence was suppressed and red-shifted significantly when exposed to external magnetic field. However in this work, by means of selective excitation, we confirmed that emission properties of firefly light emitter “oxyluciferin” are completely immune to external magnetic field of up to 53 T. These findings pose strong contrast to existing relevant results. Potential reasons for the discrepancies found and the underlying physics towards the understanding of firefly bioluminescence were discussed. - Highlights: • Effect of ultra-high magnetic field on the optical properties of firefly light emitter oxyluciferin was reported. • Emission properties of oxyluciferin were confirmed to be immune to external high magnetic fields up to 53 T. • .Potential reasons for the discrepancies between our results and previous reports and the underlying physics were discussed.

Field Emission Property of Double-walled Carbon Nanotubes Related to Purification and Transmittance

International Nuclear Information System (INIS)

Ahn, KiTae; Jang, HyunChul; Hong, Wanshick; Park, Kyoungwan; Sok, Junghyun; Lyu, SeungChul; Lee, Hansung; Lee, Naesung; Han, Moonsup; Park, Yunsun

2011-01-01

Double-walled carbon nanotubes (DWCNTs) with high purity were produced by the catalytic decomposition of tetrahydrofuran (THF) using a Fe-Mo/MgO catalyst at 800°C. The as-synthesized DWCNTs typically have catalytic impurities and amorphous carbon, which were removed by a two-step purification process consisting of acid treatment and oxidation. In the acid treatment, metallic catalysts were removed in HCl at room temperature for 5 hr with magnetic stirring. Subsequently, the oxidation, using air at 380°C for 5 hr in the a vertical-type furnace, was used to remove the amorphous carbon particles. The DWCNT suspension was prepared by dispersing the purified DWCNTs in the aqueous sodium dodecyl sulfate solution with horn-type sonication. This was then air-sprayed on ITO glass to fabricate DWCNT field emitters. The field emission properties of DWCNT films related to transmittance were studied. This study provides the possibility of the application of large-area transparent CNT field emission cathodes.

Electron field emission characteristics of carbon nanotube on tungsten tip

International Nuclear Information System (INIS)

Phan Ngoc Hong; Bui Hung Thang; Nguyen Tuan Hong; Phan Ngoc Minh; Lee, Soonil

2009-01-01

Electron field emission characteristic of carbon nanotubes on tungsten tip was investigated in 2x10 -6 Torr vacuum. The measurement results showed that the CNTs/W tip could emit electron at 0.7 V/μm (nearly 10 times lower than that of the W tip itself) and reach up to 26 μA at the electric field of 1 V/μm. The emission characteristic follows the Fowler-Nordheim mechanism. Analysis of the emission characteristic showed that the CNTs/W tip has a very high value of field enhancement factor (β = 4.1 x 10 4 cm -1 ) that is much higher than that of the tungsten tip itself. The results confirmed the excellent field emission behavior of the CNTs materials and the CNTs/W tip is a prospective candidate for advanced electron field emitter.

A comparative study of field-emission from different one dimensional carbon nanostructures synthesized via thermal CVD system

International Nuclear Information System (INIS)

Jha, A.; Banerjee, D.; Chattopadhyay, K.K.

2011-01-01

Different one dimensional (1D) carbon nanostructures, such as carbon nanonoodles (CNNs), carbon nanospikes (CNSs) and carbon nanotubes (CNTs) have been synthesized via thermal chemical vapour deposition (TCVD) technique. The different 1D morphologies were synthesized by varying the substrate material and the deposition conditions. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). FESEM and TEM images showed that the diameters of the CNNs and CNTs were ∼40 nm while the diameters of the CNSs were around 100 nm. Field emission studies of the as-prepared samples showed that CNSs to be a better field emitter than CNNs, whereas CNTs are the best among the three producing large emission current. The variation of field emission properties with inter-electrode distance has been studied in detail. Also the time dependent field emission studies of all the nanostructures have been carried out.

Nanodiamond composite as a material for cold electron emitters

Energy Technology Data Exchange (ETDEWEB)

Arkhipov, A V; Sominski, G G; Uvarov, A A [St.Petersburg State Polytechnic University, 29 Politchnicheskaya, St.Petersburg, 195251 (Russian Federation); Gordeev, S K; Korchagina, S B [FSUE ' Central Research Institute for Materials' , 8 Paradnaya Street, St.Petersburg, 191014 (Russian Federation)], E-mail: arkhipov@rphf.spbstu.ru

2008-03-15

Characteristics of field-induced electron emission were investigated for one of newly designed all-carbon materials - nanodiamond composite (NDC). The composite is comprised by 4-6 nm diamond grains covered with 0.2-1 nm-thick graphite-like shells that merge at grain junctions and determine such properties as mechanical strength and high electric conductivity. Large number of uniformly distributed sp{sup 3}-sp{sup 2} interfaces allowed to expect enhanced electron emission in electric field. Combination of these features makes NDC a promising material for cold electron emitters in various applications. Experimental testing confirmed high efficiency of electron emission from NDC. In comparison with previousely tested forms of nanocarbon, NDC emitters demonstrated better stabily and tolerance to performance conditions. Unusual activation scenarios and thermal dependencies of emission characteristics observed in experiments with NDC can add new background for explanation of facilitated electron emission from nanocarbons with relatively 'smooth' surface morphology.

Gated field-emitter cathodes for high-power microwave applications

International Nuclear Information System (INIS)

Barasch, E.F.; Demroff, H.P.; Elliott, T.S.; Kasprowicz, T.B.; Lee, B.; Mazumdar, T.; McIntyre, P.M.; Pang, Y.; Smith, D.D.; Trost, H.J.

1992-01-01

Gated field-emitter cathodes have been fabricated on silicon wafers. Two fabrication approaches have been employed: a knife-edge array and a porous silicon structure. The knife-edge array consists of a pattern of knife-edges, sharpened to ∼200 A radius, configured with an insulated metal gate structure at a gap of ∼500 A. The porous silicon cathode consists of an insulating porous layer, containing pores of ∼50 A diameter, densely spaced in the native silicon, biased for field emission by a thin gate metallization on the surface. Emission current density of 20 A/cm 2 has been obtained with only 10 V bias. Fabrication processes and test results are presented. (Author) 4 figs., tab., 12 refs

A study of junction effect transistors and their roles in carbon nanotube field emission cathodes in compact pulsed power applications

Science.gov (United States)

Shui, Qiong

This thesis is focusing on a study of junction effect transistors (JFETs) in compact pulsed power applications. Pulsed power usually requires switches with high hold-off voltage, high current, low forward voltage drop, and fast switching speed. 4H-SiC, with a bandgap of 3.26 eV (The bandgap of Si is 1.12eV) and other physical and electrical superior properties, has gained much attention in high power, high temperature and high frequency applications. One topic of this thesis is to evaluate if 4H-SiC JFETs have a potential to replace gas phase switches to make pulsed power system compact and portable. Some other pulsed power applications require cathodes of providing stable, uniform, high electron-beam current. So the other topic of this research is to evaluate if Si JFET-controlled carbon nanotube field emitter cold cathode will provide the necessary e-beam source. In the topic of "4H-SiC JFETs", it focuses on the design and simulation of a novel 4H-SiC normally-off VJFET with high breakdown voltage using the 2-D simulator ATLAS. To ensure realistic simulations, we utilized reasonable physical models and the established parameters as the input into these models. The influence of key design parameters were investigated which would extend pulsed power limitations. After optimizing the key design parameters, with a 50-mum drift region, the predicted breakdown voltage for the VJFET is above 8kV at a leakage current of 1x10-5A/cm2 . The specific on-state resistance is 35 mO·cm 2 at VGS = 2.7 V, and the switching speed is several ns. The simulation results suggest that the 4H-SiC VJFET is a potential candidate for improving switching performance in repetitive pulsed power applications. To evaluate the 4H-SiC VJFETs in pulsed power circuits, we extracted some circuit model parameters from the simulated I-V curves. Those parameters are necessary for circuit simulation program such as SPICE. This method could be used as a test bench without fabricating the devices to

Marshmallowing of nanopillar arrays by field emission

International Nuclear Information System (INIS)

Qin Hua; Kim, Hyun-Seok; Blick, Robert H.

2010-01-01

We fabricated nanoscale field electron emitters formed by highly-doped silicon nanopillars on a silicon membrane. Electron-beam induced deposition of carbon-based contaminants is employed as a probe of the spatial activity of electron emission from the nanopillars. In stark contrast to the general assumption that field emission only occurs at the tips of nanoscale emitters, we found strong emission from the sidewalls of the nanopillars. This is revealed by the deposition of carbon contaminants on these sidewalls, so that the nanopillars finally resemble marshmallows. We conclude that field emission from nanostructured surfaces is more intricate than previously expected.

Highly stable field emission from ZnO nanowire field emitters controlled by an amorphous indium–gallium–zinc-oxide thin film transistor

Science.gov (United States)

Li, Xiaojie; Wang, Ying; Zhang, Zhipeng; Ou, Hai; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

2018-04-01

Lowering the driving voltage and improving the stability of nanowire field emitters are essential for them to be applied in devices. In this study the characteristics of zinc oxide (ZnO) nanowire field emitter arrays (FEAs) controlled by an amorphous indium–gallium–zinc-oxide thin film transistor (a-IGZO TFT) were studied. A low driving voltage along with stabilization of the field emission current were achieved. Modulation of field emission currents up to three orders of magnitude was achieved at a gate voltage of 0–32 V for a constant anode voltage. Additionally, a-IGZO TFT control can dramatically reduce the emission current fluctuation (i.e., from 46.11 to 1.79% at an emission current of ∼3.7 µA). Both the a-IGZO TFT and ZnO nanowire FEAs were prepared on glass substrates in our research, demonstrating the feasibility of realizing large area a-IGZO TFT-controlled ZnO nanowire FEAs.

Negative ion emission at field electron emission from amorphous (alpha-C:H) carbon

CERN Document Server

Bernatskij, D P; Ivanov-Omskij, V I; Pavlov, V G; Zvonareva, T K

2001-01-01

The study on the electrons field emission from the plane cathode surface on the basis of the amorphous carbon film (alpha-C:H) is carried out. The methodology, making it possible to accomplish simultaneously the registration of the emission currents and visually observe the distribution of the emission centers on the plane emitter surface is developed. The analysis of the oscillograms indicated that apart from the proper electron constituent the negative ions of hydrogen (H sup - and H sub 2 sup -), carbon (C sup -) and hydrocarbon (CH sub n sup -) are observed. The ions emission is connected with the processes of formation and degradation of the local emission centers

Emittance measurements of the CLIO electron beam

Science.gov (United States)

Chaput, R.; Devanz, G.; Joly, P.; Kergosien, B.; Lesrel, J.

1997-02-01

We have designed a setup to measure the transverse emittance at the CLIO accelerator exit, based on the "3 gradients" method. The beam transverse size is measured simply by scanning it with a steering coil across a fixed jaw and recording the transmitted current, at various quadrupole strengths. A code then performs a complete calculation of the emittance using the transfer matrix of the quadrupole instead of the usual classical lens approximation. We have studied the influence of various parameters on the emittance: Magnetic field on the e-gun and the peak current. We have also improved a little the emittance by replacing a mismatched pipe between the buncher and accelerating section to avoid wake-field effects; The resulting improvements of the emittance have led to an increase in the FEL emitted power.

Solid-state single-photon emitters

Science.gov (United States)

Aharonovich, Igor; Englund, Dirk; Toth, Milos

2016-10-01

Single-photon emitters play an important role in many leading quantum technologies. There is still no 'ideal' on-demand single-photon emitter, but a plethora of promising material systems have been developed, and several have transitioned from proof-of-concept to engineering efforts with steadily improving performance. Here, we review recent progress in the race towards true single-photon emitters required for a range of quantum information processing applications. We focus on solid-state systems including quantum dots, defects in solids, two-dimensional hosts and carbon nanotubes, as these are well positioned to benefit from recent breakthroughs in nanofabrication and materials growth techniques. We consider the main challenges and key advantages of each platform, with a focus on scalable on-chip integration and fabrication of identical sources on photonic circuits.

Density functional theory for field emission from carbon nano-structures

Energy Technology Data Exchange (ETDEWEB)

Li, Zhibing, E-mail: stslzb@mail.sysu.edu.cn

2015-12-15

Electron field emission is understood as a quantum mechanical many-body problem in which an electronic quasi-particle of the emitter is converted into an electron in vacuum. Fundamental concepts of field emission, such as the field enhancement factor, work-function, edge barrier and emission current density, will be investigated, using carbon nanotubes and graphene as examples. A multi-scale algorithm basing on density functional theory is introduced. We will argue that such a first principle approach is necessary and appropriate for field emission of nano-structures, not only for a more accurate quantitative description, but, more importantly, for deeper insight into field emission. - Highlights: • Applications of DFT to electron field emission of nano-structures are reviewed. • Fundamental concepts of field emission are re-visited with emphasis on the many-body effects. • New insights to field emission of nano-structures are obtained by multi-scale DFT calculations. • It is shown that the exchange–correlation effect on the emission barrier is significant. • Spontaneous symmetry breaking in field emission of CNT has been predicted.

Analysis of transverse RMS emittance growth of a beam induced by spherical and chromatic aberration in a solenoidal field

Energy Technology Data Exchange (ETDEWEB)

Dash, Radhakanta, E-mail: radhakanta.physics@gmail.com [Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094 (India); Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Nayak, Biswaranjan [Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094 (India); Sharma, Archana; Mittal, Kailash C. [Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400094 (India); Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2016-01-21

In a medium energy beam transport line transverse rms emittance growth associated with spherical aberration is analysed. An analytical expression is derived for beam optics in a solenoid field considering terms up to the third order in the radial displacement. Two important phenomena: effect of spherical aberrations in axial-symmetric focusing lens and influence of nonlinear space charge forces on beam emittance growth are discussed for different beam distributions. In the second part nonlinear effect associated with chromatic aberration that describes the growth of emittance and distortion of phase space area is discussed.

Beam emittance growth caused by transverse deflecting fields in a linear accelerator

Energy Technology Data Exchange (ETDEWEB)

Chao, A W; Richter, B; Yao, C Y [Stanford Linear Accelerator Center, CA (USA)

1980-12-01

The effect of the beam-generated transverse deflecting fields on the emittance of an intense bunch of particles in a high-energy linear accelerator is analyzed in this paper. The equation of motion is solved by a perturbation method for cases of a coasting beam and a uniformly accelerated beam. The results are applied to obtain some design tolerance specifications for the recently proposed SLAC Single Pass Collider.

Active packaged lamb with oxygen scavenger/carbon dioxide emitter sachet: physical-chemical and microbiological stability during refrigerated storage

Directory of Open Access Journals (Sweden)

Marco Antonio Trindade

2013-09-01

Full Text Available Lamb meat has been commercialized in Brazil almost exclusively as a frozen product due to the longer shelf life provided by freezing when compared to refrigeration. However, as a result of the current trend of increased demand for convenience products, a need has emerged for further studies to facilitate the marketing of refrigerated lamb cuts. The aim of the present study was to evaluate the contribution of active packaging technology in extending the shelf life of lamb loins (Longissimus lumborum stored under refrigeration (1±1 ° C when compared to the traditional vacuum packaging. For this purpose, two kinds of sachets were employed: oxygen scavenger sachet and oxygen scavenger/carbon dioxide emitter sachet. Experiments were conducted in three treatments: 1 Vacuum (Control, 2 Vacuum + oxygen scavenger sachet and 3 Vacuum + oxygen scavenger/carbon dioxide emitter sachet. Microbiological (counts of anaerobic psychrotrophs, coliform at 45 ° C, coagulase-positive staphylococci, Salmonella and lactic acid bacteria and physical-chemical (thiobarbituric acid reactive substances, objective color, pH value, water loss from cooking and shear force analyses were carried out weekly for a total storage period of 28 days. The experiment was performed three times for all treatments. Results showed that the lamb meat remained stable with respect to the majority of the evaluated physical and chemical indexes and remained within the standards established by Brazilian legislation for pathogenic microorganisms throughout the storage period in all three packaging systems. However, all treatments presented elevated counts of anaerobic psychrotrophic microorganisms and lactic acid bacteria, reaching values above 10(7 CFU/g at 28 days of storage. Thus, under the conditions tested, neither the oxygen scavenger sachet nor the dual function sachet (oxygen scavenger/carbon dioxide emitter were able to extend the shelf life of refrigerated lamb loin when added to this

Jamming of Quantum Emitters by Active Coated Nanoparticles

DEFF Research Database (Denmark)

Arslanagic, Samel; Ziolkowski, Richard W.

2013-01-01

to effectively cloak the emitters to a far-field observer is reported and explained through thorough near- and far-field investigations. This property offers an interesting route toward the jamming of quantum emitters/nanoantennas that might be of potential use, for instance, in biological fluorescence assays...

Macroscopic electrical field distribution and field-induced surface stresses of needle-shaped field emitters

Energy Technology Data Exchange (ETDEWEB)

Moy, Charles K.S., E-mail: charles.moy@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia); School of Civil Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Ranzi, Gianluca [ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia); School of Civil Engineering, The University of Sydney, Sydney, NSW 2006 (Australia); Petersen, Timothy C. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); Ringer, Simon P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006 (Australia); ARC Centre of Excellence for Design in Light Metals, The University of Sydney, Sydney, NSW 2006 (Australia)

2011-05-15

One major concern since the development of the field ion microscope is the mechanical strength of the specimens. The macroscopic shape of the imaging tip greatly influences field-induced stresses and there is merit in further study of this phenomenon from a classical perspective. Understanding the geometrical, as opposed to localized electronic, factors that affect the stress might improve the quality and success rate of atom probe experiments. This study uses macroscopic electrostatic principles and finite element modelling to investigate field-induced stresses in relation to the shape of the tip. Three two-dimensional idealized models are considered, namely hyperbolic, parabolic and sphere-on-orthogonal-cone; the shapes of which are compared to experimental tips prepared by electro-polishing. Three dimensional morphologies of both a nano-porous and single-crystal aluminium tip are measured using electron tomography to quantitatively test the assumption of cylindrical symmetry for electro-polished tips. The porous tip was prepared and studied to demonstrate a fragile specimen for which such finite element studies could determine potential mechanical failure, prior to any exhaustive atom probe investigation. -- Research highlights: {yields} We use electrostatic principles and finite element to model field-induced stresses. {yields} We study two-dimensional idealized needle-shaped field emitters. {yields} Stress distribution of hyperbolic, parabolic and sphere-on-orthogonal-cone tips mapped. {yields} Electron tomography to obtain the morphology of three-dimensional aluminium tips. {yields} Studies of the morphology of the porous tip demonstrate a fragile specimen.

Nitrogen incorporated ultrananocrystalline diamond based field emitter array for a flat-panel x-ray source

International Nuclear Information System (INIS)

Posada, Chrystian M.; Grant, Edwin J.; Lee, Hyoung K.; Castaño, Carlos H.; Divan, Ralu; Sumant, Anirudha V.; Rosenmann, Daniel; Stan, Liliana

2014-01-01

A field emission based flat-panel transmission x-ray source is being developed as an alternative for medical and industrial imaging. A field emitter array (FEA) prototype based on nitrogen incorporated ultrananocrystalline diamond film has been fabricated to be used as the electron source of this flat panel x-ray source. The FEA prototype was developed using conventional microfabrication techniques. The field emission characteristics of the FEA prototype were evaluated. Results indicated that emission current densities of the order of 6 mA/cm 2 could be obtained at electric fields as low as 10 V/μm to 20 V/μm. During the prototype microfabrication process, issues such as delamination of the extraction gate and poor etching of the SiO 2 insulating layer located between the emitters and the extraction layer were encountered. Consequently, alternative FEA designs were investigated. Experimental and simulation data from the first FEA prototype were compared and the results were used to evaluate the performance of alternative single and double gate designs that would yield better field emission characteristics compared to the first FEA prototype. The best simulation results are obtained for the double gate FEA design, when the diameter of the collimator gate is around 2.6 times the diameter of the extraction gate

Recent progress in nanostructured next-generation field emission devices

International Nuclear Information System (INIS)

Mittal, Gaurav; Lahiri, Indranil

2014-01-01

Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40–50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices. (topical review)

Recent progress in nanostructured next-generation field emission devices

Science.gov (United States)

Mittal, Gaurav; Lahiri, Indranil

2014-08-01

Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40-50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices.

Emittance Growth in the NLCTA First Chicane

International Nuclear Information System (INIS)

Sun, Yipeng

2011-01-01

In this paper, the emittance growth in the NLCTA (Next Linear Collider Test Accelerator) first chicane region is evaluated by simulation studies. It is demonstrated that the higher order fields of the chicane dipole magnet and the dipole corrector magnet (which is attached on the quadrupoles) are the main contributions for the emittance growth, especially for the case with a large initial emittance (γε 0 = 5 (micro)m for instance). These simulation results agree with the experimental observations.

Marshmallowing of nanopillar arrays by field emission

International Nuclear Information System (INIS)

Park, J; Qin, H; Kim, H-S; Blick, R H

2009-01-01

We have fabricated mechanically flexible field electron emitters formed by highly-doped silicon nanopillars on a silicon membrane. Electron beam induced deposition of carbon-based contaminants is employed to probe the spatial activity of electron emission from the nanopillars. The experimental configuration provides a powerful tool to investigate the physics of the field electron emission (FEE). In contrast to the general assumption that field emission only occurs at the tips of nanoscale emitters, we found that the emission from the nanopillars' sidewalls is as strong as from their tips.

Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

International Nuclear Information System (INIS)

Li Xin; Zhou Wei-Man; Liu Wei-Hua; Wang Xiao-Li

2015-01-01

Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn–Plummer method. The ZnO NPs reconstruct the ZnO–CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. (paper)

Beam emittance and the effects of the rf, space charge and wake fields: Application to the ATF photoelectron beam

International Nuclear Information System (INIS)

Parsa, Z.

1991-01-01

Laser driven photoelectron guns are of interest for use in new methods of accelerations, future development of Linear Colliders and new experiments such as Free Electron laser (IFEL). Such guns are potential source of low emittance-high current and short bunch length electron beams, where the emitted electrons are accelerated quickly to a relativistic energy by a strong rf, electric field in the cavity. We present a brief overview of the beam dynamic studies, e.g. emittance for the Brookhaven National Laboratory (BNL) ATF high brightness photocathode radio frequency gun (now in operation), and show the effects of the rf, Space Charge, and Wake fields on the photoelectrons. 4 refs., 7 figs

Diamondoid monolayers as electron emitters

Science.gov (United States)

Yang, Wanli [El Cerrito, CA; Fabbri, Jason D [San Francisco, CA; Melosh, Nicholas A [Menlo Park, CA; Hussain, Zahid [Orinda, CA; Shen, Zhi-Xun [Stanford, CA

2012-04-10

Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

The fabrication and evaluation of diamond cold cathodes for field emitter display applications

International Nuclear Information System (INIS)

Fox, N.A.

1998-08-01

Semiconducting diamond is a candidate wide-band gap material for applications in vacuum microelectronic devices. Its potential use in components that are operated at high frequencies, handle high powers or are subjected to extremes of temperature and radiation have yet to be commercially realised. The work presented below sets out to determine whether semiconducting diamond is a suitable material for such active electronic devices by examining the most efficient means of initiating electron emission from Chemical Vapour Deposited (CVD), semiconducting diamond. Novel methods are reported for the incorporation of impurity atoms of Nitrogen and Phosphorus into CVD diamond that employ ion-implantation techniques. Demonstration of the efficient incorporation of these impurities to form donor states with low activation energies into polycrystalline diamond would facilitate efficient room temperature operation of pn junctions devices. The effectiveness of boron as a p-type dopant in CVD diamond films has enabled the investigation of potential field emitter structures using different boron concentrations in order to identify their respective conduction mechanisms and to make a comparison of their relative electron emission performance. It has been concluded that efficient electron emission is observed to originate from the interface of n + -p, silicon/diamond heterojunctions that employ thin p-type regions which are less than 5μm thick. The emission current may be controlled by the application of a low voltage forward bias of less than 1 volt. Only the np junction containing 400 ppm of boron in the p-diamond layer demonstrated forward biased electron emission. It is proposed that carrier conduction across the junction interface involves recombination and tunnelling steps between interface trap states. Furthermore it is believed that due to the junction interface being in direct contact with vacuum, within this region of the emitter structure, a surface conduction emission

Design, Fabrication, and Characterization of Carbon Nanotube Field Emission Devices for Advanced Applications

Science.gov (United States)

Radauscher, Erich Justin

Carbon nanotubes (CNTs) have recently emerged as promising candidates for electron field emission (FE) cathodes in integrated FE devices. These nanostructured carbon materials possess exceptional properties and their synthesis can be thoroughly controlled. Their integration into advanced electronic devices, including not only FE cathodes, but sensors, energy storage devices, and circuit components, has seen rapid growth in recent years. The results of the studies presented here demonstrate that the CNT field emitter is an excellent candidate for next generation vacuum microelectronics and related electron emission devices in several advanced applications. The work presented in this study addresses determining factors that currently confine the performance and application of CNT-FE devices. Characterization studies and improvements to the FE properties of CNTs, along with Micro-Electro-Mechanical Systems (MEMS) design and fabrication, were utilized in achieving these goals. Important performance limiting parameters, including emitter lifetime and failure from poor substrate adhesion, are examined. The compatibility and integration of CNT emitters with the governing MEMS substrate (i.e., polycrystalline silicon), and its impact on these performance limiting parameters, are reported. CNT growth mechanisms and kinetics were investigated and compared to silicon (100) to improve the design of CNT emitter integrated MEMS based electronic devices, specifically in vacuum microelectronic device (VMD) applications. Improved growth allowed for design and development of novel cold-cathode FE devices utilizing CNT field emitters. A chemical ionization (CI) source based on a CNT-FE electron source was developed and evaluated in a commercial desktop mass spectrometer for explosives trace detection. This work demonstrated the first reported use of a CNT-based ion source capable of collecting CI mass spectra. The CNT-FE source demonstrated low power requirements, pulsing

Ampère-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator

Energy Technology Data Exchange (ETDEWEB)

Mihalcea, D. [Northern Illinois U.; Faillace, L. [RadiaBeam Tech.; Hartzell, J. [RadiaBeam Tech.; Panuganti, H. [Northern Illinois U.; Boucher, S. M. [RadiaBeam Tech.; Murokh, A. [RadiaBeam Tech.; Piot, P. [Fermilab; Thangaraj, J. C.T. [Fermilab

2014-12-01

Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional $1+\\frac{1}{2}$-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.

Few emitters in a cavity: from cooperative emission to individualization

International Nuclear Information System (INIS)

Auffeves, A; Portolan, S; Gerace, D; Drezet, A; Franca Santos, M

2011-01-01

We study the temporal correlations of the field emitted by an electromagnetic resonator coupled to a mesoscopic number of two-level emitters that are incoherently pumped by a weak external drive. We solve the master equation of the system for increasing number of emitters and as a function of the cavity quality factor, and we identify three main regimes characterized by well-distinguished statistical properties of the emitted radiation. For small cavity decay rates, the emission events are uncorrelated and the number of photons in the emitted field becomes larger than one, resembling the build-up of a laser field inside the cavity. At intermediate decay rates (as compared with the emitter-cavity coupling) and for a few emitters, the statistics of the emitted radiation is bunched and strikingly dependent on the parity of the number of emitters. The latter property is related to the cooperativity of the emitters mediated by their coupling to the cavity mode, and its connection with steady-state subradiance is discussed. Finally, in the bad cavity regime the typical situation of emission from a collection of individual emitters is recovered. We also analyze how the cooperative behavior evolves as a function of pure dephasing, which allows us to recover the case of a classical source made of an ensemble of independent emitters, similar to what is obtained for a very leaky cavity. State-of-the-art techniques of Q-switch of resonant cavities, allied with the recent capability of tuning single emitters in and out of resonance, suggest this system to be a versatile source of different quantum states of light.

Few emitters in a cavity: from cooperative emission to individualization

Energy Technology Data Exchange (ETDEWEB)

Auffeves, A; Portolan, S [CEA/CNRS/UJF Joint Team ' Nanophysics and Semiconductors' , Institut Neel-CNRS, BP 166, 25 Rue des Martyrs, 38042 Grenoble Cedex 9 (France); Gerace, D [Dipartimento di Fisica ' Alessandro Volta' and UdR CNISM, Universita di Pavia, via Bassi 6, 27100 Pavia (Italy); Drezet, A [Institut Neel-CNRS, BP 166, 25 Rue des Martyrs, 38042 Grenoble Cedex 9 (France); Franca Santos, M, E-mail: msantos@fisica.ufmg.br [Departamento de Fisica, Universidade Federal de Minas Gerais, Belo Horizonte, CP 702, 30123-970 (Brazil)

2011-09-15

We study the temporal correlations of the field emitted by an electromagnetic resonator coupled to a mesoscopic number of two-level emitters that are incoherently pumped by a weak external drive. We solve the master equation of the system for increasing number of emitters and as a function of the cavity quality factor, and we identify three main regimes characterized by well-distinguished statistical properties of the emitted radiation. For small cavity decay rates, the emission events are uncorrelated and the number of photons in the emitted field becomes larger than one, resembling the build-up of a laser field inside the cavity. At intermediate decay rates (as compared with the emitter-cavity coupling) and for a few emitters, the statistics of the emitted radiation is bunched and strikingly dependent on the parity of the number of emitters. The latter property is related to the cooperativity of the emitters mediated by their coupling to the cavity mode, and its connection with steady-state subradiance is discussed. Finally, in the bad cavity regime the typical situation of emission from a collection of individual emitters is recovered. We also analyze how the cooperative behavior evolves as a function of pure dephasing, which allows us to recover the case of a classical source made of an ensemble of independent emitters, similar to what is obtained for a very leaky cavity. State-of-the-art techniques of Q-switch of resonant cavities, allied with the recent capability of tuning single emitters in and out of resonance, suggest this system to be a versatile source of different quantum states of light.

Emittance preservation

Energy Technology Data Exchange (ETDEWEB)

Kain, V; Arduini, G; Goddard, B; Holzer, B J; Jowett, J M; Meddahi, M; Mertens, T; Roncarolo, F; Schaumann, M; Versteegen, R; Wenninger, J [European Organization for Nuclear Research, Geneva (Switzerland)

2012-07-01

Emittance measurements during the LHC proton run 2011 indicated a blow-up of 20 % to 30 % from LHC injection to collisions. This presentation will show the emittance preservation throughout the different parts of the LHC cycle and discuss the current limitations on emittance determination. An overview of emittance preservation through the injector complex as function of bunch intensity will also be given. Possible sources for the observed blow-up and required tests in 2012 will be presented. Possible improvements of emittance diagnostics and analysis tools for 2012 will be shown.

Generation of low-emittance electron beams in electrostatic accelerators for FEL applications

Science.gov (United States)

Teng, Chen; Elias, Luis R.

1995-02-01

This paper reports results of transverse emittance studies and beam propagation in electrostatic accelerators for free electron laser applications. In particular, we discuss emittance growth analysis of a low current electron beam system consisting of a miniature thermoionic electron gun and a National Electrostatics Accelerator (NEC) tube. The emittance growth phenomenon is discussed in terms of thermal effects in the electron gun cathode and aberrations produced by field gradient changes occurring inside the electron gun and throughout the accelerator tube. A method of reducing aberrations using a magnetic solenoidal field is described. Analysis of electron beam emittance was done with the EGUN code. Beam propagation along the accelerator tube was studied using a cylindrically symmetric beam envelope equation that included beam self-fields and the external accelerator fields which were derived from POISSON simulations.

Generation of low-emittance electron beams in electrostatic accelerators for FEL applications

International Nuclear Information System (INIS)

Chen Teng; Central Florida Univ., Orlando, FL; Elias, L.R. R.; Central Florida Univ., Orlando, FL

1995-01-01

This paper reports results of transverse emittance studies and beam propagation in electrostatic accelerators for free electron laser applications. In particular, we discuss emittance growth analysis of a low current electron beam system consisting of a miniature thermoionic electron gun and a National Electrostatics Accelerator (NEC) tube. The emittance growth phenomenon is discussed in terms of thermal effects in the electron gun cathode and aberrations produced by field gradient changes occurring inside the electron gun and throughout the accelerator tube. A method of reducing aberrations using a magnetic solenoidal field is described. Analysis of electron beam emittance was done with the EGUN code. Beam propagation along the accelerator tube was studied using a cylindrically symmetric beam envelope equation that included beam self-fields and the external accelerator fields which were derived from POISSON simulations. ((orig.))

Generation of low-emittance electron beams in electrostatic accelerators for FEL applications

Energy Technology Data Exchange (ETDEWEB)

Chen Teng [University of Central Florida, Orlando, FL (United States). Center for Research in Electro-Optics and Lasers (CREOL)]|[Central Florida Univ., Orlando, FL (United States). Dept. of Physics; Elias, L.R. R. [University of Central Florida, Orlando, FL (United States). Center for Research in Electro-Optics and Lasers (CREOL)]|[Central Florida Univ., Orlando, FL (United States). Dept. of Physics

1995-01-30

This paper reports results of transverse emittance studies and beam propagation in electrostatic accelerators for free electron laser applications. In particular, we discuss emittance growth analysis of a low current electron beam system consisting of a miniature thermoionic electron gun and a National Electrostatics Accelerator (NEC) tube. The emittance growth phenomenon is discussed in terms of thermal effects in the electron gun cathode and aberrations produced by field gradient changes occurring inside the electron gun and throughout the accelerator tube. A method of reducing aberrations using a magnetic solenoidal field is described. Analysis of electron beam emittance was done with the EGUN code. Beam propagation along the accelerator tube was studied using a cylindrically symmetric beam envelope equation that included beam self-fields and the external accelerator fields which were derived from POISSON simulations. ((orig.))

Generalized superradiant assembly for nanophotonic thermal emitters

Science.gov (United States)

Mallawaarachchi, Sudaraka; Gunapala, Sarath D.; Stockman, Mark I.; Premaratne, Malin

2018-03-01

Superradiance explains the collective enhancement of emission, observed when nanophotonic emitters are arranged within subwavelength proximity and perfect symmetry. Thermal superradiant emitter assemblies with variable photon far-field coupling rates are known to be capable of outperforming their conventional, nonsuperradiant counterparts. However, due to the inability to account for assemblies comprising emitters with various materials and dimensional configurations, existing thermal superradiant models are inadequate and incongruent. In this paper, a generalized thermal superradiant assembly for nanophotonic emitters is developed from first principles. Spectral analysis shows that not only does the proposed model outperform existing models in power delivery, but also portrays unforeseen and startling characteristics during emission. These electromagnetically induced transparency like (EIT-like) and superscattering-like characteristics are reported here for a superradiant assembly, and the effects escalate as the emitters become increasingly disparate. The fact that the EIT-like characteristics are in close agreement with a recent experimental observation involving the superradiant decay of qubits strongly bolsters the validity of the proposed model.

Experimental investigation of thermal emittance components of copper photocathode

Directory of Open Access Journals (Sweden)

H. J. Qian

2012-04-01

Full Text Available With progress of photoinjector technology, thermal emittance has become the primary limitation of electron beam brightness. Extensive efforts have been devoted to study thermal emittance, but experiment results differ between research groups and few can be well interpreted. Besides the ambiguity of photoemission mechanism, variations of cathode surface conditions during cathode preparation, such as work function, field enhancement factor, and surface roughness, will cause thermal emittance differences. In this paper, we report an experimental study of electric field dependence of copper cathode quantum efficiency (QE and thermal emittance in a radio frequency (rf gun, through which in situ cathode surface parameters and thermal emittance contributions from photon energy, Schottky effect, and surface roughness are extracted. It is found the QE of a copper cathode illuminated by a 266 nm UV laser increased substantially to 1.5×10^{-4} after cathode cleaning during rf conditioning, and a copper work function of 4.16 eV, which is much lower than nominal value (4.65 eV, was measured. Experimental results also show a thermal emittance growth as much as 0.92  mm mrad/mm at 50  MV/m due to the cathode surface roughness effect, which is consistent with cathode surface morphology measurements.

Superconducting wiggler magnets for beam-emittance damping rings

CERN Document Server

Schoerling, Daniel

2012-01-01

Ultra-low emittance beams with a high bunch charge are necessary for the luminosity performance of linear electron-positron colliders, such as the Compact Linear Collider (CLIC). An effective way to create ultra-low emittance beams with a high bunch charge is to use damping rings, or storage rings equipped with strong damping wiggler magnets. The remanent field of the permanent magnet materials and the ohmic losses in normal conductors limit the economically achievable pole field in accelerator magnets operated at around room temperature to below the magnetic saturation induction, which is 2.15 T for iron. In wiggler magnets, the pole field in the center of the gap is reduced further like the hyperbolic cosine of the ratio of the gap size and the period length multiplied by pi. Moreover, damping wiggler magnets require relatively large gaps because they have to accept the un-damped beam and to generate, at a small period length, a large magnetic flux density amplitude to effectively damp the beam emittance....

Beam emittance measurements on multicusp ion sources

Energy Technology Data Exchange (ETDEWEB)

Sarstedt, M.; Lee, Y.; Leung, K.N. [and others

1995-08-01

Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 {mu}m patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf-pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of an rf-generated plasma.

Beam emittance measurements on multicusp ion sources

International Nuclear Information System (INIS)

Sarstedt, M.; Lee, Y.; Leung, K.N.

1995-08-01

Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 μm patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf-pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of an rf-generated plasma

Positioning with stationary emitters in a two-dimensional space-time

International Nuclear Information System (INIS)

Coll, Bartolome; Ferrando, Joan Josep; Morales, Juan Antonio

2006-01-01

The basic elements of the relativistic positioning systems in a two-dimensional space-time have been introduced in a previous work [Phys. Rev. D 73, 084017 (2006)] where geodesic positioning systems, constituted by two geodesic emitters, have been considered in a flat space-time. Here, we want to show in what precise senses positioning systems allow to make relativistic gravimetry. For this purpose, we consider stationary positioning systems, constituted by two uniformly accelerated emitters separated by a constant distance, in two different situations: absence of gravitational field (Minkowski plane) and presence of a gravitational mass (Schwarzschild plane). The physical coordinate system constituted by the electromagnetic signals broadcasting the proper time of the emitters are the so called emission coordinates, and we show that, in such emission coordinates, the trajectories of the emitters in both situations, the absence and presence of a gravitational field, are identical. The interesting point is that, in spite of this fact, particular additional information on the system or on the user allows us not only to distinguish both space-times, but also to complete the dynamical description of emitters and user and even to measure the mass of the gravitational field. The precise information under which these dynamical and gravimetric results may be obtained is carefully pointed out

Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

Energy Technology Data Exchange (ETDEWEB)

Suriani, A.B., E-mail: absuriani@yahoo.com [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Dalila, A.R. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Mohamed, A.; Isa, I.M.; Kamari, A.; Hashim, N. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Soga, T.; Tanemura, M. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

2015-10-15

Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe{sub 3}C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe{sub 3}C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm{sup −1} at current density of 1 and 10 μA cm{sup −2}, respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters.

Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

International Nuclear Information System (INIS)

Suriani, A.B.; Dalila, A.R.; Mohamed, A.; Isa, I.M.; Kamari, A.; Hashim, N.; Soga, T.; Tanemura, M.

2015-01-01

Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe 3 C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe 3 C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm −1 at current density of 1 and 10 μA cm −2 , respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters

Emittance and beam size distortion due to linear coupling

International Nuclear Information System (INIS)

Parzen, G.

1993-01-01

At injection, the presence of linear coupling may result in an increased beam emittance and in increased beam dimensions. Results for the emittance in the presence of linear coupling will be found. These results for the emittance distortion show that the harmonics of the skew quadrupole field close to ν x + ν y are the important harmonics. Results will be found for the important driving terms for the emittance distortion. It will be shown that if these driving terms are corrected, then the total emittance is unchanged, var-epsilon x + var-epsilon y = var-epsilon 1 + var-epsilon 2 . Also, the increase in the beam dimensions will be limited to a factor which is less than 1.414. If the correction is good enough, see below for details, one can achieve var-epsilon 1 = var-epsilon x , var-epsilon 2 = var-epsilon where var-epsilon 1 , var-epsilon 2 are the emittances in the presence of coupling, and the beam dimensions are unchanged. Global correction of the emittance and beam size distortion appears possible

Harvesting Triplet Excitons with Exciplex Thermally Activated Delayed Fluorescence Emitters toward High Performance Heterostructured Organic Light-Emitting Field Effect Transistors.

Science.gov (United States)

Song, Li; Hu, Yongsheng; Liu, Zheqin; Lv, Ying; Guo, Xiaoyang; Liu, Xingyuan

2017-01-25

The utilization of triplet excitons plays a key role in obtaining high emission efficiency for organic electroluminescent devices. However, to date, only phosphorescent materials have been implemented to harvest the triplet excitons in the organic light-emitting field effect transistors (OLEFETs). In this work, we report the first incorporation of exciplex thermally activated delayed fluorescence (TADF) emitters in heterostructured OLEFETs to harvest the triplet excitons. By developing a new kind of exciplex TADF emitter constituted by m-MTDATA (4,4',4″-tris(N-3-methylphenyl-N-phenylamino)triphenylamine) as the donor and OXD-7 (1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene) as the acceptor, an exciton utilization efficiency of 74.3% for the devices was achieved. It is found that the injection barrier between hole transport layer and emission layer as well as the ratio between donor and acceptor would influence the external quantum efficiency (EQE) significantly. Devices with a maximum EQE of 3.76% which is far exceeding the reported results for devices with conventional fluorescent emitters were successfully demonstrated. Moreover, the EQE at high brightness even outperformed the result for organic light-emitting diode based on the same emitter. Our results demonstrate that the exciplex TADF emitters can be promising candidates to develop OLEFETs with high performance.

Field emission electronics

CERN Document Server

Egorov, Nikolay

2017-01-01

This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.

Effect of substrate material on the growth and field emission characteristics of large-area carbon nanotube forests

Energy Technology Data Exchange (ETDEWEB)

Ummethala, Raghunandan; Täschner, Christine; Leonhardt, Albrecht; Büchner, Bernd [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Wenger, Daniela; Tedde, Sandro F. [Siemens Healthcare GmbH, Technology Centre, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany); Eckert, Jürgen [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstrasse 12, A-8700 Leoben (Austria); Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben (Austria)

2016-01-28

Carbon nanotubes (CNTs) are a promising replacement for tungsten filaments as electron emitters in conventional x-ray sources, owing to their higher aspect ratio, superior mechanical stability, chemical inertness, and high electrical and thermal conductivities. Conditions for realizing the best emission behavior from CNTs have been formulated over the last few years. In this paper, we report the relatively less-investigated factor, namely, the influence of the nature of substrate material on the growth as well as field emission characteristics of large-area multiwalled CNTs for their practical application in medical x-ray sources. We compare the morphology of CNTs on a variety of substrates such as stainless steel, copper, molybdenum, graphite, few-layer graphene, and carbon nanowalls grown by thermal chemical vapor deposition following a simple drop-coating of catalyst. We find that CNTs grown on stainless steel and graphite show the best combination of emission characteristics under pulsed operation mode. These studies are helpful in selecting the optimum substrate material for field emission applications. Ex situ studies on field emission degradation of CNTs are presented towards the end.

Effect of substrate material on the growth and field emission characteristics of large-area carbon nanotube forests

Science.gov (United States)

Ummethala, Raghunandan; Wenger, Daniela; Tedde, Sandro F.; Täschner, Christine; Leonhardt, Albrecht; Büchner, Bernd; Eckert, Jürgen

2016-01-01

Carbon nanotubes (CNTs) are a promising replacement for tungsten filaments as electron emitters in conventional x-ray sources, owing to their higher aspect ratio, superior mechanical stability, chemical inertness, and high electrical and thermal conductivities. Conditions for realizing the best emission behavior from CNTs have been formulated over the last few years. In this paper, we report the relatively less-investigated factor, namely, the influence of the nature of substrate material on the growth as well as field emission characteristics of large-area multiwalled CNTs for their practical application in medical x-ray sources. We compare the morphology of CNTs on a variety of substrates such as stainless steel, copper, molybdenum, graphite, few-layer graphene, and carbon nanowalls grown by thermal chemical vapor deposition following a simple drop-coating of catalyst. We find that CNTs grown on stainless steel and graphite show the best combination of emission characteristics under pulsed operation mode. These studies are helpful in selecting the optimum substrate material for field emission applications. Ex situ studies on field emission degradation of CNTs are presented towards the end.

Thionyl chloride assisted functionalization of amorphous carbon nanotubes: A better field emitter and stable nanofluid with better thermal conductivity

Energy Technology Data Exchange (ETDEWEB)

Sarkar, S.K.; Jha, A. [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700 032 (India); Chattopadhyay, K.K., E-mail: kalyan_chattopadhyay@yahoo.com [Thin Film & Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700 032 (India); School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700 032 (India)

2015-06-15

Highlights: • Thionyl chloride assisted functionalization of amorphous carbon nanotubes (a-CNTs). • Improved dispersion enhanced thermal conductivity of engine oil. • Again f-a-CNTs showed enhanced field emission property compared to pure a-CNTs. - Abstract: Amorphous carbon nanotubes (a-CNTs) were synthesized at low temperature in open atmosphere and further functionalized by treating them in thionyl chloride added stearic acid-dichloro methane solution. The as prepared functionalized a-CNTs (f-a-CNTs) were characterized by Raman spectroscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, transmission and scanning electron microscopy. The nanofluid was prepared by dispersing f-a-CNTs in engine oil using ultrasonic treatment. The effective thermal conductivity of as prepared nanofluid was investigated at different loading (volume fraction of f-a-CNTs). Obtained experimental data of thermal conductivity were compared with the predicted values, calculated using existing theoretical models. Stability of the nanofluid was tested by means of zeta potential measurement to optimize the loading. The as prepared f-a-CNTs sample also showed improved field emission result as compared to pristine a-CNTs. Dependence of field emission behavior on inter electrode distance was investigated too.

Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

Science.gov (United States)

Li, Xin; Zhou, Wei-Man; Liu, Wei-Hua; Wang, Xiao-Li

2015-05-01

Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn-Plummer method. The ZnO NPs reconstruct the ZnO-CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).

Site-specific nucleation and controlled growth of a vertical tellurium nanowire array for high performance field emitters

International Nuclear Information System (INIS)

Safdar, Muhammad; Zhan Xueying; Mirza, Misbah; Wang Zhenxing; Sun Lianfeng; He Jun; Niu Mutong; Zhang Jinping; Zhao Qing

2013-01-01

We report the controlled growth of highly ordered and well aligned one-dimensional tellurium nanostructure arrays via a one-step catalyst-free physical vapor deposition method. The density, size and fine structures of tellurium nanowires are systematically studied and optimized. Field emission measurement was performed to display notable dependence on nanostructure morphologies. The ordered nanowire array based field emitter has a turn-on field as low as 3.27 V μm −1 and a higher field enhancement factor of 3270. Our finding offers the possibility of controlling the growth of tellurium nanowire arrays and opens up new means for their potential applications in electronic devices and displays. (paper)

Growth of vertically aligned arrays of carbon nanotubes for high field emission

International Nuclear Information System (INIS)

Kim, D.; Lim, S.H.; Guilley, A.J.; Cojocaru, C.S.; Bouree, J.E.; Vila, L.; Ryu, J.H.; Park, K.C.; Jang, J.

2008-01-01

Vertically aligned multi-walled carbon nanotubes have been grown on Ni-coated silicon substrates, by using either direct current diode or triode plasma-enhanced chemical vapor deposition at low temperature (around 620 deg. C). Acetylene gas has been used as the carbon source while ammonia and hydrogen have been used for etching. However densely packed (∼ 10 9 cm -2 ) CNTs were obtained when the pressure was ∼ 100 Pa. The alignment of nanotubes is a necessary, but not a sufficient condition in order to get an efficient electron emission: the growth of nanotubes should be controlled along regular arrays, in order to minimize the electrostatic interactions between them. So a three dimensional numerical simulation has been developed to calculate the local electric field in the vicinity of the tips for a finite square array of nanotubes and thus to calculate the maximum of the electron emission current density as a function of the spacing between nanotubes. Finally the triode plasma-enhanced process combined with pre-patterned catalyst films (using different lithography techniques) has been chosen in order to grow regular arrays of aligned CNTs with different pitches in the micrometer range. The comparison between the experimental and the simulation data permits to define the most efficient CNT-based electron field emitters

Emittance growth due to dipole ripple and sextupole

International Nuclear Information System (INIS)

Shih, H.J.; Ellison, J.A.; Syphers, M.J.; Newberger, B.S.

1993-05-01

Ripple in the power supplies for storage ring magnets can have adverse effects on the circulating beams: orbit distortion and emittance growth from dipole ripple, tune modulation and dynamic aperture reduction from quadrupole ripple, etc. In this paper, we study the effects of ripple in the horizontal bending field of the SSC in the presence of nonlinearity, in particular, the growth in beam emittance

Optimizing the e-beam profile of a single carbon nanotube field emission device for electric propulsion systems

Directory of Open Access Journals (Sweden)

Juliano Fujioka Mologni

2010-04-01

Full Text Available Preliminary studies on field emission (FE arrays comprised of carbon nanotubes (CNT as an electron source for electric propulsion system show remarkably promising results. Design parameters for a carbon nanotube (CNT field-emission device operating on triode configuration were numerically simulated and optimized in order to enhance the e-beam focusing quality. An additional focus gate (FG was integrated to the device to control the profile of the emitted e-beam. An axisymmetric finite element model was developed to calculate the electric field distribution on the vacuum region and a modified Fowler-Nordheim (FN equation was used to evaluate the current density emission and the effective emitter area. Afterward, a FE simulation was employed in order to calculate the trajectory of the emitted electrons and define the electron-optical properties of the e-beam. The integration of the FG was fully investigated via computational intelligence techniques. The best performance device according to our simulations presents a collimated e-beam profile that suits well for field emission displays, magnetic field detection and electron microscopy. The automated computational design tool presented in this study strongly benefits the robust design of integrated electron-optical systems for vacuum field emission applications, including electrodynamic tethering and electric propulsion systems.

Positron emitter labeled enzyme inhibitors

International Nuclear Information System (INIS)

Fowler, J.S.; MacGregor, R.R.; Wolf, A.P.; Langstrom, B.

1990-01-01

This invention involves a new strategy for imagining and mapping enzyme activity in the living human and animal body using positron emitter-labeled suicide enzyme inactivators or inhibitors which become covalently bound to the enzyme as a result of enzymatic catalysis. Two such suicide inactivators for monoamine oxidase have been labeled with carbon-11 and used to map the enzyme subtypes in the living human and animal body using PET. By using positron emission tomography to image the distribution of radioactivity produced by the body penetrating radiation emitted by carbon-11, a map of functionally active monoamine oxidase activity is obtained. Clorgyline and L-deprenyl are suicide enzyme inhibitors and irreversibly inhibit monoamine oxidase. When these inhibitors are labeled with carbon-11 they provide selective probes for monoamine oxidase localization and reactivity in vivo using positron emission tomography

Radial arrays of nano-electrospray ionization emitters and methods of forming electrosprays

Science.gov (United States)

Kelly, Ryan T [West Richland, WA; Tang, Keqi [Richland, WA; Smith, Richard D [Richland, WA

2010-10-19

Electrospray ionization emitter arrays, as well as methods for forming electrosprays, are described. The arrays are characterized by a radial configuration of three or more nano-electrospray ionization emitters without an extractor electrode. The methods are characterized by distributing fluid flow of the liquid sample among three or more nano-electrospray ionization emitters, forming an electrospray at outlets of the emitters without utilizing an extractor electrode, and directing the electrosprays into an entrance to a mass spectrometry device. Each of the nano-electrospray ionization emitters can have a discrete channel for fluid flow. The nano-electrospray ionization emitters are circularly arranged such that each is shielded substantially equally from an electrospray-inducing electric field.

Carbon nanotube substrates and catalyzed hot stamp for polishing and patterning the substrates

Science.gov (United States)

Wang, Yuhuang [Evanston, IL; Hauge, Robert H [Houston, TX; Schmidt, Howard K [Houston, TX; Kim, Myung Jong [Houston, TX; Kittrell, W Carter [Houston, TX

2009-09-08

The present invention is generally directed to catalyzed hot stamp methods for polishing and/or patterning carbon nanotube-containing substrates. In some embodiments, the substrate, as a carbon nanotube fiber end, is brought into contact with a hot stamp (typically at 200-800.degree. C.), and is kept in contact with the hot stamp until the morphology/patterns on the hot stamp have been transferred to the substrate. In some embodiments, the hot stamp is made of material comprising one or more transition metals (Fe, Ni, Co, Pt, Ag, Au, etc.), which can catalyze the etching reaction of carbon with H.sub.2, CO.sub.2, H.sub.2O, and/or O.sub.2. Such methods can (1) polish the carbon nanotube-containing substrate with a microscopically smooth finish, and/or (2) transfer pre-defined patterns from the hot stamp to the substrate. Such polished or patterned carbon nanotube substrates can find application as carbon nanotube electrodes, field emitters, and field emitter arrays for displays and electron sources.

Low-emittance Storage Rings

CERN Document Server

Wolski, Andrzej

2014-01-01

The effects of synchrotron radiation on particle motion in storage rings are discussed. In the absence of radiation, particle motion is symplectic, and the beam emittances are conserved. The inclusion of radiation effects in a classical approximation leads to emittance damping: expressions for the damping times are derived. Then, it is shown that quantum radiation effects lead to excitation of the beam emittances. General expressions for the equilibrium longitudinal and horizontal (natural) emittances are derived. The impact of lattice design on the natural emittance is discussed, with particular attention to the special cases of FODO-, achromat- and theoretical-minimum-emittance-style lattices. Finally, the effects of betatron coupling and vertical dispersion (generated by magnet alignment and lattice tuning errors) on the vertical emittance are considered.

Rare Earth Garnet Selective Emitter

Science.gov (United States)

Lowe, Roland A.; Chubb, Donald L.; Farmer, Serene C.; Good, Brian S.

1994-01-01

Thin film Ho-YAG and Er-YAG emitters with a platinum substrate exhibit high spectral emittance in the emission band (epsilon(sub lambda) approx. = 0.75, sup 4)|(sub 15/2) - (sup 4)|(sub 13/2),for Er-YAG and epsilon(sub lambda) approx. = 0.65, (sup 5)|(sub 7) - (sup 5)|(sub 8) for Ho-YAG) at 1500 K. In addition, low out-of-band spectral emittance, epsilon(sub lambda) less than 0.2, suggest these materials would be excellent candidates for high efficiency selective emitters in thermophotovoltaic (TPV) systems operating at moderate temperatures (1200-1500 K). Spectral emittance measurements of the thin films were made (1.2 less than lambda less than 3.0 microns) and compared to the theoretical emittances calculated using measured values of the spectral extinction coefficient. In this paper we present the results for a new class of rare earth ion selective emitters. These emitters are thin sections (less than 1 mm) of yttrium aluminum garnet (YAG) single crystal with a rare earth substitutional impurity. Selective emitters in the near IR are of special interest for thermophotovoltaic (TPV) energy conversion. The most promising solid selective emitters for use in a TPV system are rare earth oxides. Early spectral emittance work on rare earth oxides showed strong emission bands in the infrared (0.9 - 3 microns). However, the emittance outside the emission band was also significant and the efficiency of these emitters was low. Recent improvements in efficiency have been made with emitters fabricated from fine (5 - 10 microns) rare earth oxide fibers similar to the Welsbach mantle used in gas lanterns. However, the rare earth garnet emitters are more rugged than the mantle type emitters. A thin film selective emitter on a low emissivity substrate such as gold, platinum etc., is rugged and easily adapted to a wide variety of thermal sources. The garnet structure and its many subgroups have been successfully used as hosts for rare earth ions, introduced as substitutional

Emittance growth due to the wake field driven by an electron beam accelerated in an RF-gun of free electron laser 'ELSA'

CERN Document Server

Salah, W

2000-01-01

It appears that the ease of the parameter chosen for 'ELSA' photo injector, the influence of the exit aperture, in terms of beam quality, is slight concerning the transverse emittance: (DELTA epsilon sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r /epsilon sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub = = r)(z)approx 3% at maximum, and negligible concerning the axial emittance. To complete this paper, we recall the results previously obtained concerning the wake field of a closed or open cavity for a beam approaching the anode . They had quantitatively specified the expected deep asymmetry between the conducting walls regarding their contribution to the total wake field, besides the space-charge contribution. (Given that the radial walls have no time to contribute, these conducting walls are the cathode and the anode.) Thus, concerning the effects on whole-beam emittances, the correction (DELTA epsilon sub p sub e sub r sub p sub e sub n sub d sub i ...

Study of Thermal-Field Emission Properties and Investigation of Temperature dependent Noise in the Emission Current form vertical Carbon nanotube emitters

KAUST Repository

Kolekar, Sadhu; Patole, Shashikant P.; Patil, Sumati; Yoo, J.B.; Dharmadhikari, C.V.

2017-01-01

We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well defined cathode surface is given by Millikan and Lauritsen [1

Emittance studies of the BNL/SLAC/UCLA 1.6 cell photocathode rf gun

International Nuclear Information System (INIS)

Palmer, D.T.; Miller, R.H.; Wang, X.J.

1997-01-01

The symmetrized 1.6 cell S-band photocathode gun developed by the BNL/SLAC/UCLA collaboration is in operation at the Brookhaven Accelerator Test Facility (ATF). A novel emittance compensation solenoid magnet has also been designed, built and is in operation at the ATF. These two subsystems form an emittance compensated photoinjector used for beam dynamics, advanced acceleration and free electron laser experiments at the ATF. The highest acceleration field achieved on the copper cathode is 150 MV/m, and the guns normal operating field is 130 MV/m. The maximum rf pulse length is 3 micros. The transverse emittance of the photoelectron beam were measured for various injection parameters. The 1 nC emittance results are presented along with electron bunch length measurements that indicated that at above the 400 pC, space charge bunch lengthening is occurring. The thermal emittance, ε o , of the copper cathode has been measured

Carbon dots—Emerging light emitters for bioimaging, cancer therapy and optoelectronics

KAUST Repository

Hola, Katerina; Zhang, Yu; Wang, Yu; Giannelis, Emmanuel P.; Zboril, Radek; Rogach, Andrey L.

2014-01-01

© 2014 Elsevier Ltd. All rights reserved. Carbon dots represent an emerging class of fluorescent materials and provide a broad application potential in various fields of biomedicine and optoelectronics. In this review, we introduce various synthetic strategies and basic photoluminescence properties of carbon dots, and then address their advanced in vitro and in vivo bioapplications including cell imaging, photoacoustic imaging, photodynamic therapy and targeted drug delivery. We further consider the applicability of carbon dots as components of light emitting diodes, which include carbon dot based electroluminescence, optical down-conversion, and hybrid plasmonic devices. The review concludes with an outlook towards future developments of these emerging light-emitting materials.

Carbon dots—Emerging light emitters for bioimaging, cancer therapy and optoelectronics

KAUST Repository

Hola, Katerina

2014-10-01

© 2014 Elsevier Ltd. All rights reserved. Carbon dots represent an emerging class of fluorescent materials and provide a broad application potential in various fields of biomedicine and optoelectronics. In this review, we introduce various synthetic strategies and basic photoluminescence properties of carbon dots, and then address their advanced in vitro and in vivo bioapplications including cell imaging, photoacoustic imaging, photodynamic therapy and targeted drug delivery. We further consider the applicability of carbon dots as components of light emitting diodes, which include carbon dot based electroluminescence, optical down-conversion, and hybrid plasmonic devices. The review concludes with an outlook towards future developments of these emerging light-emitting materials.

Emittance control and RF bunch compression in the NSRRC photoinjector

International Nuclear Information System (INIS)

Lau, W.K.; Hung, S.B.; Lee, A.P.; Chou, C.S.; Huang, N.Y.

2011-01-01

The high-brightness photoinjector being constructed at the National Synchrotron Radiation Research Center is for testing new accelerator and light-source concepts. It is the so-called split photoinjector configuration in which a short solenoid magnet is used for emittance compensation. The UV-drive laser pulses are also shaped to produce uniform cylindrical bunches for further reduction of beam emittance. However, limited by the available power from our microwave power system, the nominal accelerating gradient in the S-band booster linac is set at 18 MV/m. A simulation study with PARMELA shows that the linac operating at this gradient fails to freeze the electron beam emittance at low value. A background solenoid magnetic field is applied for beam emittance control in the linac during acceleration. A satisfactory result that meets our preliminary goal has been achieved with the solenoid magnetic field strength at 0.1 T. RF bunch compression as a means to achieve the required beam brightness for high-gain free-electron laser experiments is also examined. The reduction of bunch length to a few hundred femtoseconds can be obtained.

The study of explosive emission from carbon nanotubes

International Nuclear Information System (INIS)

Korenev, Sergey

2002-01-01

The carbon nanotubes (CNT) found applications for high density current electron emitters. The main interest for forming of high current electron beams using CNT is high concentration of electrical field on the nanotubes and high value of yield by electrons for field emission. The experimental results for time processes of forming cathode plasma and extraction of electron beam are presented in the report

Studies of emittance growth in the ATF

International Nuclear Information System (INIS)

Zimmermann, F.

1997-03-01

Several different mechanisms of emittance growth in the Accelerator Test Facility (ATF) at KEK are investigated: the author calculates rise times of the fast beam-ion instability for the damping ring (DR), and discusses the emittance growth caused by coherent synchrotron radiation in the beam-transport line (BT), the effect of quadrupole wake fields in the injector linac, and, finally, a single-bunch head-tail ion effect that can occur in both the DR and the BT. A first attempt to measure the quadrupole wake on the real machine is also reported

Multibunch emittance growth and its corrections in S-Band linear collider

International Nuclear Information System (INIS)

Gao, J.

1994-11-01

Multibunch emittance growths caused by long range wake fields with the misalignments of accelerating structures and quadrupoles in S-Band linear collider are studied. Tolerances for the misalignment errors of accelerating structures and quadrupoles are given corresponding to different detuned+damped structures. At the end of main linac, emittance corrector (EC) is proposed to be used to reduce further the multibunch emittance. Numerical simulations show that the effect of EC is obvious (multibunch emittance can be reduced about one order of magnitude), and it is believed that this kind of EC will be necessary for future linear colliders. (author). 16 refs., 21 figs., 4 tabs

Electromagnetic compatibility of implantable neurostimulators to RFID emitters.

Science.gov (United States)

Pantchenko, Oxana S; Seidman, Seth J; Guag, Joshua W; Witters, Donald M; Sponberg, Curt L

2011-06-09

The objective of this study is to investigate electromagnetic compatibility (EMC) of implantable neurostimulators with the emissions from radio frequency identification (RFID) emitters. Six active implantable neurostimulators with lead systems were tested for susceptibility to electromagnetic fields generated by 22 RFID emitters. These medical devices have been approved for marketing in the U.S. for a number of intended uses that include: epilepsy, depression, incontinence, Parkinsonian tremor and pain relief. Each RFID emitter had one of the following carrier frequencies: 125 kHz, 134 kHz, 13.56 MHz, 433 MHz, 915 MHz and 2.45 GHz. The test results showed the output of one of the implantable neurostimulators was inhibited by 134 kHz RFID emitter at separation distances of 10 cm or less. The output of the same implantable neurostimulator was also inhibited by another 134 kHz RFID emitter at separation distances of 10 cm or less and also showed inconsistent pulsing rate at a separation distance of 15 cm. Both effects occurred during and lasted through out the duration of the exposure. The clinical significance of the effects was assessed by a clinician at the U.S. Food and Drug Administration. The effects were determined to be clinically significant only if they occurred for extended period of time. There were no observed effects from the other 5 implantable neurostimulators or during exposures from other RFID emitters.

Emittance compensation with dynamically optimized photoelectron beam profiles

Energy Technology Data Exchange (ETDEWEB)

Rosenzweig, J.B. [Department of Physics and Astronomy, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095 (United States)]. E-mail: rosen@physics.ucla.edu; Cook, A.M. [Department of Physics and Astronomy, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095 (United States); England, R.J. [Department of Physics and Astronomy, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095 (United States); Dunning, M. [Department of Physics and Astronomy, UCLA, 405 Hilgard Avenue, Los Angeles, CA 90095 (United States); Anderson, S.G. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Ferrario, Massimo [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionale di Frascati, Via E. Fermi 41, Frascati, Rome (Italy)

2006-02-01

Much of the theory and experimentation concerning creation of a high-brightness electron beam from a photocathode, and then applying emittance compensation techniques, assumes that one must strive for a uniform density electron beam, having a cylindrical shape. On the other hand, this shape has large nonlinearities in the space-charge field profiles near the beam's longitudinal extrema. These nonlinearities are known to produce both transverse and longitudinal emittance growth. On the other hand, it has recently been shown by Luiten that by illuminating the cathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped bunch is dynamically formed, which then has linear space-charge fields in all dimensions inside of the bunch. We study here this process, and its marriage to the standard emittance compensation scenario that is implemented in most recent photoinjectors. It is seen that the two processes are compatible, with simulations indicating a very high brightness beam can be obtained. The robustness of this scheme to systematic errors is examined. Prospects for experimental tests of this scheme are discussed.

Emittance compensation with dynamically optimized photoelectron beam profiles

International Nuclear Information System (INIS)

Rosenzweig, J.B.; Cook, A.M.; England, R.J.; Dunning, M.; Anderson, S.G.; Ferrario, Massimo

2006-01-01

Much of the theory and experimentation concerning creation of a high-brightness electron beam from a photocathode, and then applying emittance compensation techniques, assumes that one must strive for a uniform density electron beam, having a cylindrical shape. On the other hand, this shape has large nonlinearities in the space-charge field profiles near the beam's longitudinal extrema. These nonlinearities are known to produce both transverse and longitudinal emittance growth. On the other hand, it has recently been shown by Luiten that by illuminating the cathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped bunch is dynamically formed, which then has linear space-charge fields in all dimensions inside of the bunch. We study here this process, and its marriage to the standard emittance compensation scenario that is implemented in most recent photoinjectors. It is seen that the two processes are compatible, with simulations indicating a very high brightness beam can be obtained. The robustness of this scheme to systematic errors is examined. Prospects for experimental tests of this scheme are discussed

Comparison between arc drops in ignited thermionic converters with and without ion reflections at the emitter

International Nuclear Information System (INIS)

Lundgren, L.

1985-01-01

The output performance of two thermionic energy converters is compared. One converter has a normal emitter, working with zero field at the emitter which is close to the optimum working point, and the other has a low work function emitter and ion reflection at the emitter. A simple model of the plasma and the sheaths shows that a converter working with a low work function emitter and ion reflections gives a worse performance than a similar converter with a normal emitter

Emittance growth caused by nonuniform charge distribution of bunched beam in linac

International Nuclear Information System (INIS)

Chen Yinbao; Zhang Zhenhai

1993-09-01

The nonlinear space charge effect of bunched beam in linac is one of the important reasons that induces the emittance growth because of the conversion of the field energy to kinetic energy. The authors have worked out the internal field energies associated with some nonuniform space change distributions of a bunched beam, such as Gaussian distribution, waterbag distribution and parabolic distribution. And the emittance growths caused by these nonuniformities are obtained

Analysis of emittance compensation and simulation results to photo-cathode RF gun

CERN Document Server

LiuShengGuang

2002-01-01

The emittance compensation technology will be used on the photo-cathode RF gun for Shanghai SDUV-FEL. The space charge force and its effect on electron beam transverse emittance in RF gun is studied, the principle of emittance compensation in phase-space is discussed. The authors have designed a compensation solenoid and calculated its magnetic field distribution. Its performance has been studied by the code PARMELA. A simulation result indicates that the normalized transverse RMS emittance for electron beam of 1.5 nC is 1.612 pi mm centre dot mrad, electron energy E = 5.71 MeV

Nanometer-scale discernment of field emission from tungsten surface with single carbon monoxide molecule

Science.gov (United States)

Matsunaga, Soichiro; Suwa, Yuji; Katagiri, Souichi

2017-12-01

Unusual quantized beam fluctuations were found in the emission current from a cold-field emitter (CFE) operating in an extremely high vacuum of 10-10 Pa. To clarify the microscopic mechanism behind these fluctuations, we developed a new calculation method to evaluate the field emission from a heterogeneous surface under a strong electric field of 4 × 109 V/m by using the local potential distribution obtained by a first-principles calculation, instead of by using the work function. As a result of the first-principles calculations of a single molecule adsorbed on a tungsten surface, we found that dissociative adsorption of a carbon monoxide (CO) molecule enhances the emission current by changing the potential barrier in the area surrounding the C and O adatoms when these two atoms are placed at their most stable positions. It is also found that the migration of the O atom from the most stable position reduces the emission current. These types of enhancement and reduction of the emission current quantitatively explain the observed quantized fluctuations of the CFE emission current.

Investigations on the transverse phase space at a photo injector for minimized emittance

Energy Technology Data Exchange (ETDEWEB)

Miltchev, V.

2006-08-15

Radio frequency photoinjectors are electron sources able to generate beams of extremely high brightness, which are applicable to linac driven Free Electron Lasers (FEL). Because of the high phase space density, the dynamics of the electron beam is dominated by space charge interactions between the particles. This thesis studies the transverse phase space of space charge dominated electron beams produced by the Photo Injector Test Facility in Zeuthen (PITZ). The operation conditions for minimizing the transverse emittance are studied experimentally, theoretically and in simulations. The influence of the longitudinal profile of the driving UV laser pulse on the transverse emittance is investigated. Emphasis is placed on the experimental study of the emittance as a function of different machine parameters like the laser beam spot size, the amplitude of the focusing magnetic field, the rf phase and the electron bunch charge. First investigations on the thermal emittance for Cs{sub 2}Te photocathodes under rf operating conditions are presented. Measurements of the thermal emittance scaling with the photocathode laser spot size are analyzed. The significance of the applied rf field in the emittance formation process is discussed. (orig.)

Investigations on the transverse phase space at a photo injector for minimized emittance

International Nuclear Information System (INIS)

Miltchev, V.

2006-08-01

Radio frequency photoinjectors are electron sources able to generate beams of extremely high brightness, which are applicable to linac driven Free Electron Lasers (FEL). Because of the high phase space density, the dynamics of the electron beam is dominated by space charge interactions between the particles. This thesis studies the transverse phase space of space charge dominated electron beams produced by the Photo Injector Test Facility in Zeuthen (PITZ). The operation conditions for minimizing the transverse emittance are studied experimentally, theoretically and in simulations. The influence of the longitudinal profile of the driving UV laser pulse on the transverse emittance is investigated. Emphasis is placed on the experimental study of the emittance as a function of different machine parameters like the laser beam spot size, the amplitude of the focusing magnetic field, the rf phase and the electron bunch charge. First investigations on the thermal emittance for Cs 2 Te photocathodes under rf operating conditions are presented. Measurements of the thermal emittance scaling with the photocathode laser spot size are analyzed. The significance of the applied rf field in the emittance formation process is discussed. (orig.)

High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

Science.gov (United States)

Gupta, Bipin Kumar; Kedawat, Garima; Gangwar, Amit Kumar; Nagpal, Kanika; Kashyap, Pradeep Kumar; Srivastava, Shubhda; Singh, Satbir; Kumar, Pawan; Suryawanshi, Sachin R.; Seo, Deok Min; Tripathi, Prashant; More, Mahendra A.; Srivastava, O. N.; Hahm, Myung Gwan; Late, Dattatray J.

2018-01-01

The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm-1 and D-band at 1340 cm-1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

Directory of Open Access Journals (Sweden)

Bipin Kumar Gupta

2018-01-01

Full Text Available The vertical aligned carbon nanotubes (CNTs-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness as a barrier layer and iron (Fe, 1.5 nm thickness as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2–30 walls with an inner diameter of 3–8 nm. Raman spectrum analysis shows G-band at 1580 cm−1 and D-band at 1340 cm−1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm, low turn-on field (0.6 V/μm and field enhancement factor (6917 with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

Transverse emittance dilution due to coupler kicks in linear accelerators

Directory of Open Access Journals (Sweden)

Brandon Buckley

2007-11-01

Full Text Available One of the main concerns in the design of low emittance linear accelerators (linacs is the preservation of beam emittance. Here we discuss one possible source of emittance dilution, the coupler kick, due to transverse electromagnetic fields in the accelerating cavities of the linac caused by the power coupler geometry. In addition to emittance growth, the coupler kick also produces orbit distortions. It is common wisdom that emittance growth from coupler kicks can be strongly reduced by using two couplers per cavity mounted opposite each other or by having the couplers of successive cavities alternate from above to below the beam pipe so as to cancel each individual kick. While this is correct, including two couplers per cavity or alternating the coupler location requires large technical changes and increased cost for superconducting cryomodules where cryogenic pipes are arranged parallel to a string of several cavities. We therefore analyze consequences of alternate coupler placements. We show here that alternating the coupler location from above to below compensates the emittance growth as well as the orbit distortions. For sufficiently large Q values, alternating the coupler location from before to after the cavity leads to a cancellation of the orbit distortion but not of the emittance growth, whereas alternating the coupler location from before and above to behind and below the cavity cancels the emittance growth but not the orbit distortion. We show that cancellations hold for sufficiently large Q values. These compensations hold even when each cavity is individually detuned, e.g., by microphonics. Another effective method for reducing coupler kicks that is studied is the optimization of the phase of the coupler kick so as to minimize the effects on emittance from each coupler. This technique is independent of the coupler geometry but relies on operating on crest. A final technique studied is symmetrization of the cavity geometry in the

Emittances Studies at the Fermilab/NICADD Photoinjector Laboratory

CERN Document Server

Tikhoplav, Rodion; Melissinos, A C; Regis-Guy Piot, Philippe

2005-01-01

The Fermilab/NICADD photoinjector incorporates an L-band rf-gun capable of generating 1-10 nC bunches. The bunches are then accelerated to 16 MeV with a TESLA superconducting cavity. In the present paper we present parametric studies of transverse emittances and energy spread for a various operating points of the electron source (RF-gun E-field, laser length and spot size, and solenoid settings). We especially study the impact, on transverse emittance, of Gaussian and Plateau temporal distribution of the photocathode drive-laser.

Essays on carbon policy and enhanced oil recovery

Science.gov (United States)

Cook, Benjamin R.

The growing concerns about climate change have led policy makers to consider various regulatory schemes designed to reduce the stock and growth of atmospheric CO2 concentrations while at the same time improving energy security. The most prominent proposals are the so called "cap-and-trade" frameworks which set aggregate emission levels for a jurisdiction and then issue or sell a corresponding number of allowances to emitters. Typically, these policy measures will also encourage the deployment of carbon capture and storage (CCS) in geological formations and mature oil fields through subsidies or other incentives. The ability to store CO 2 in mature oil fields through the deployment of CO2 enhanced oil recovery (CO2--EOR) is particularly attractive as it can simultaneously improve oil recovery at those fields, and serve as a possible financial bridge to the development of CO2 transportation infrastructure. The purpose of this research is to explore the impact that a tandem subsidy-tax policy regime may have on bargaining between emitters and sequestration providers, and also to identify oil units in Wyoming that can profitably undertake CO 2--EOR as a starting point for the build-out of CO2 pipelines. In the first essay an economics lab experiment is designed to simulate private bargaining between carbon emitters (such as power plants) and carbon sequestration sites when the emitter faces carbon taxes, sequestration subsidies or both. In a tax-subsidy policy regime the carbon tax (or purchased allowances) can be avoided by sequestering the carbon, and in some cases the emitter can also earn a subsidy to help pay for the sequestration. The main policy implications of the experiment results are that the sequestration market might be inefficient, and sequestration providers seem to have bargaining power sufficient to command high prices. This may lead to the integration of CO2 sources and sequestration sites, and reduced prices for the injectable CO2 purchased by oil

Calculations of emittance and damping time effects in the SLC damping rings

International Nuclear Information System (INIS)

Limberg, T.; Moshammer, H.; Raubenheimer, T.; Spencer, J.; Siemann, R.

1992-03-01

In a recent NDR machine experiment the transverse emittance was studied as a function of store time and tune. To explain the observed transverse emittance damping time constants, the magnetic measurement data of the longitudinal field of the bending magnets had to be taken into account. The variation of the transverse emittances with tune due to misalignments and the associated anomalous dispersion is studied as well as the effect of synchrobetatron coupling due to dispersion in the RF cavities

Decreasing the emittance using a multi-period Robinson wigglers in TPS

Energy Technology Data Exchange (ETDEWEB)

Huamg, C. W., E-mail: huang.zw@nsrrc.org.tw [Department of Physics, National Tsing Hua University Hsinchu 30043, Taiwan (China); Hwang, C. S., E-mail: cshwang@nsrrc.org.tw [NSRRC, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan (China); Lee, S. Y., E-mail: shylee@indiana.edu [Department of Physics, Indiana University (United States)

2016-07-27

The Taiwan Photon Source (TPS) has been successfully commissioned. However, the minimum emittance in the TPS lattice is 1.6 nm rad. In the existing TPS storage ring lattice, it is imperative to reduce the emittance to below 1 nm rad. Therefore, a feasibility study for reducing the effective emittance of the TPS storage ring by using a Robinson wiggler was launched; the reduction is necessary to enhance the photon brilliance. In this study, a permanent-magnet multiperiod Robinson wiggler (MRW) was developed for use instead of the single-period Robinson wiggler. In general, the quadruple field of a combined function magnet in the storage ring is approximately few tesla per meter. According to beam dynamic analysis, we found that it is necessary to adopt a high gradient (40 T/m) combined-function MRW magnet to reduce the emittance effectively. Therefore, a high gradient field strength is required in the combined function MRW magnet. In this study, the quadrupole field strength of the MRW magnet was allowed to be approximately 40 T/m at a magnet gap of 20 mm. The period length of the MRW magnet was 300 mm and the period number was 16. The of MRWs is discussed in regard to the possibility of increasing the photon brilliance from IU22.

Electromagnetic compatibility of implantable neurostimulators to RFID emitters

Directory of Open Access Journals (Sweden)

Guag Joshua W

2011-06-01

Full Text Available Abstract Background The objective of this study is to investigate electromagnetic compatibility (EMC of implantable neurostimulators with the emissions from radio frequency identification (RFID emitters. Methods Six active implantable neurostimulators with lead systems were tested for susceptibility to electromagnetic fields generated by 22 RFID emitters. These medical devices have been approved for marketing in the U.S. for a number of intended uses that include: epilepsy, depression, incontinence, Parkinsonian tremor and pain relief. Each RFID emitter had one of the following carrier frequencies: 125 kHz, 134 kHz, 13.56 MHz, 433 MHz, 915 MHz and 2.45 GHz Results The test results showed the output of one of the implantable neurostimulators was inhibited by 134 kHz RFID emitter at separation distances of 10 cm or less. The output of the same implantable neurostimulator was also inhibited by another 134 kHz RFID emitter at separation distances of 10 cm or less and also showed inconsistent pulsing rate at a separation distance of 15 cm. Both effects occurred during and lasted through out the duration of the exposure. Conclusions The clinical significance of the effects was assessed by a clinician at the U.S. Food and Drug Administration. The effects were determined to be clinically significant only if they occurred for extended period of time. There were no observed effects from the other 5 implantable neurostimulators or during exposures from other RFID emitters.

Nonlinear electrostatic emittance compensation in kA, fs electron bunches

International Nuclear Information System (INIS)

Geer, S.B. van der; Loos, M.J. de; Botman, J.I.M.; Luiten, O.J.; Wiel, M.J. van der

2002-01-01

Nonlinear space-charge effects play an important role in emittance growth in the production of kA electron bunches with a bunch length much smaller than the bunch diameter. We propose a scheme employing the radial third-order component of an electrostatic acceleration field, to fully compensate the nonlinear space-charge effects. This results in minimal transverse root-mean-square emittance. The principle is demonstrated using our design simulations of a device for the production of high-quality, high-current, subpicosecond electron bunches using electrostatic acceleration in a 1 GV/m field. Simulations using the GPT code produce a bunch of 100 pC and 73 fs full width at half maximum pulse width, resulting in a peak current of about 1.2 kA at an energy of 2 MeV. The compensation scheme reduces the root-mean-square emittance by 34% to 0.4π mm mrad

Prototype of a subsurface drip irrigation emitter: Manufacturing, hydraulic evaluation and experimental analyses

Science.gov (United States)

Souza, Wanderley De Jesus; Rodrigues Sinobas, Leonor; Sánchez, Raúl; Arriel Botrel, Tarlei; Duarte Coelho, Rubens

2013-04-01

Root and soil intrusion into the conventional emitters is one of the major disadvantages to obtain a good uniformity of water application in subsurface drip irrigation (SDI). In the last years, there have been different approaches to reduce these problems such as the impregnation of emitters with herbicide, and the search for an emitter geometry impairing the intrusion of small roots. Within the last this study, has developed and evaluated an emitter model which geometry shows specific physical features to prevent emitter clogging. This work was developed at the Biosystems Engineering Department at ESALQ-USP/Brazil, and it is a part of a research in which an innovated emitteŕs model for SDI has been developed to prevent root and soil particles intrusion. An emitter with a mechanical-hydraulic mechanism (opening and closing the water outlet) for SDI was developed and manufactured using a mechanical lathe process. It was composed by a silicon elastic membrane a polyethylene tube and a Vnyl Polychloride membrane protector system. In this study the performance of the developed prototype was assessed in the laboratory and in the field conditions. In the laboratory, uniformity of water application was calculated by the water emission uniformity coefficient (CUE), and the manufacturer's coefficient of variation (CVm). In addition, variation in the membrane diameter submitted to internal pressures; head losses along the membrane, using the energy equation; and, precision and accuracy of the equation model, analyzed by Pearson's correlation coefficient (r), and by Willmott's concordance index (d) were also calculated with samples of the developed emitters. In the field, the emitters were installed in pots with and without sugar cane culture from October 2010 to January 2012. During this time, flow rate in 20 emitters were measured periodically, and the aspects of them about clogging at the end of the experiment. Emitters flow rates were measured quarterly to calculate

Enhancement of electron emission and long-term stability of tip-type carbon nanotube field emitters via lithium coating

International Nuclear Information System (INIS)

Kim, Jong-Pil; Chang, Han-Beet; Kim, Bu-Jong; Park, Jin-Seok

2013-01-01

Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium (Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92 V/μm, and the emission current, which was generated at an applied field of 1.2 V/μm was 56 μA. In the case of the 4.7 nm-thick Li-coated CNT, the turn-on field decreased to 0.65 V/μm and the emission current at the same applied field increased more than ten times to 618 μA. The analysis based on the Kelvin probe measurement and Fowler–Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36 eV to 4.90 eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs. - Highlights: ► CNTs are deposited via electrophoretic deposition (EPD). ► Thin films of Li are coated on CNTs via electroplating, without plasma damage. ► Li coating enhanced field emission properties and emission stability of CNTs. ► The effective work functions and field enhancement factors of CNTs are evaluated

Cu incorporated amorphous diamond like carbon (DLC) composites: An efficient electron field emitter over a wide range of temperature

Science.gov (United States)

Ahmed, Sk Faruque; Alam, Md Shahbaz; Mukherjee, Nillohit

2018-03-01

The effect of temperature on the electron field emission properties of copper incorporated amorphous diamond like carbon (a-Cu:DLC) thin films have been reported. The a-Cu:DLC thin films have been deposited on indium tin oxide (ITO) coated glass and silicon substrate by the radio frequency sputtering process. The chemical composition of the films was investigated using X-ray photoelectron spectroscopy and the micro structure was established using high resolution transmission electron microscopy. The sp2 and sp3 bonding ratio in the a-Cu:DLC have been analyzed by the Fourier transformed infrared spectroscopy studies. The material showed excellent electron field emission properties; which was optimized by varying the copper atomic percentage and temperature of the films. It was found that the threshold field and effective emission barrier were reduced significantly by copper incorporation as well as temperature and a detailed explanation towards emission mechanism has been provided.

An asymmetric emittance electron source for the GALAXIE dielectric-laser accelerator injector

Energy Technology Data Exchange (ETDEWEB)

Valloni, A.; Cahill, A.; Fukusawa, A.; Musumeci, P.; Spataro, B.; Yakub, A.; Rosenzweig, J. B. [Dept. of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90034 (United States); Accelerator Division, Laboratori Nazionali di Frascati (INFN-LNF), Via E. Fermi 40, Frascati (RM) 00044 (Italy); Dept. of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90034 (United States)

2012-12-21

The GALAXIE project is a program to develop an all-optical, very high field accelerator and undulator integrated SASE FEL system based on dielectric laser-excited structures that support >GV/m fields. These structures are very wide in one direction to allow adequate charge given beam loading considerations, but also having small (subwavelength) apertures in the narrow direction. Such small vertical dimensions yield strict restrictions on the emittance in this direction, while no such constraint exists in the wide transverse direction. However, the overall beam brightness is restricted by the performance requirements on the FEL. To meet these demands, we are studying a very high field gun with a magnetized cathode, yielding a beam with angular momentum content. This beam is then subject to a skew-quad triplet that splits the emittances; this process is reversed to give a round beam after acceleration. This symmetric emittance beam avoids gain-degrading multiple-transverse-mode operation of the FEL, which also demands that the effects of the angular momentum in the beam be mitigated. In this paper we discuss the RF design of an X-band gun to be operated at {approx}200 MV/m peak field giving a 1 pC magnetized beam with unprecedented brightness. We examine the design of the focusing and skew-quad systems, investigating the associated beam dynamics and efficacy of emittance splitting.

Numerical studies of emittance exchange in 2-D charged-particle beams

International Nuclear Information System (INIS)

Guy, F.W.

1986-01-01

We describe results obtained from a two-dimensional particle-following computer code that simulates a continuous, nonrelativistic, elliptical charged-particle beam with linear continuous focusing. Emittances and focusing strengths can be different in the two transverse directions. The results can be applied, for example, for a quadrupole transport system in a smooth approximation to a real beam with unequal emittances in the two planes. The code was used to study emittance changes caused by kinetic-energy exchange between transverse directions and by shifts in charge distributions. Simulation results for space-charge-dominated beams agree well with analytic formulas. From simulation results, an empirical formula was developed for a ''partition parameter'' (the ratio of kinetic energies in the two directions) as a function of initial conditions and beamline length. Quantitative emittance changes for each transverse direction can be predicted by using this parameter. Simulation results also agree with Hofmann's generalized differential equation relating emittance and field energy

Movement of Irrigation Water in Soil from a Surface Emitter

Directory of Open Access Journals (Sweden)

Ibrahim Abbas Dawood

2016-09-01

Full Text Available rickle irrigation is one of the most conservative irrigation techniques since it implies supplying water directly on the soil through emitters. Emitters dissipate energy of water at the end of the trickle irrigation system and provide water at emission points. The area wetted by an emitter depends upon the discharge of emitter, soil texture, initial soil water content, and soil permeability. The objectives of this research were to predict water distribution profiles through different soils for different conditions and quantify the distribution profiles in terms of main characteristics of soil and emitter. The wetting patterns were simulated at the end of each hour for a total time of application of 12 hrs, emitter discharges of 0.5, 0.75, 1, 2, 3, 4, and 5 lph, and five initial volumetric soil water contents. Simulation of water flow from a single surface emitter was carried out by using the numerically-based software Hydrus-2D/3D, Version 2.04. Two approaches were used in developing formulas to predict the domains of the wetted pattern. In order to verify the results obtained by implementing the software Hydrus-2D/3D a field experiment was conducted to measure the wetted diameter and compare measured values with simulated ones. The results of the research showed that the developed formulas to express the wetted diameter and depth in terms of emitter discharge, time of application, and initial soil water content are very general and can be used with very good accuracy.

Aberrations and Emittance Growth in the DARHT 2nd Axis Downstream Transport

Energy Technology Data Exchange (ETDEWEB)

Schulze, Martin E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-10-24

The emittance of the DARHT 2^nd Axis has been inferred from solenoid scans performed in the downstream transport (DST) region using a short kicked pulse. The beam spot size is measured by viewing optical transition radiation (OTR) in the near field as a function of the field (current) of a solenoid magnet (S4). The imaging station containing the OTR target is located about 100 cm downstream of the solenoid magnet. The emittance is then inferred using a beam optics code such as LAMDA or XTR by fitting the data to initial conditions upstream of the S4 solenoid magnet. The initial conditions are the beam size, beam convergence and emittance. The beam energy and current are measured. In preparation for a solenoid scan, the magnets upstream of the solenoid are adjusted to produce a round beam with no beam losses due to scraping in the beam tube. This is different from the standard tune in which the beam tune is adjusted to suppress the effects of ions and rf in the septum dump. In this standard tune, approximately 10% of the beam is lost due to scraping as the beam enters the small 3.75” ID beam tube after the septum. The normalized emittance inferred from recent solenoid scans typically ranges from 600 to 800 π(mm-mrad). This larger beam size increases the sensitivity to any non-linear fields in the Collins quadrupoles that are mounted along the small diameter beam tube. The primary magnet used to adjust the beam size in this region is the S3 solenoid magnet. Measurements made of the beam shape as the beam size was decreased showed significant structure consistent with non-linear fields. Using the measured magnetic fields in the Collins quadrupoles including higher order multipoles, the beam transport through the Collins quadrupoles is simulated and compared to the observed OTR images. The simulations are performed using the beam optics codes TRANSPORT [1] and TURTLE [2]. Estimates of the emittance growth and beam losses are made as a function of the S3

A comparative study of nitrogen plasma effect on field emission characteristics of single wall carbon nanotubes synthesized by plasma enhanced chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Zulfequar, Mohammad [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Harsh [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Husain, Mushahid, E-mail: mush_reslab@rediffmail.com [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia (A Central University), New Delhi 110025 (India)

2014-12-15

Highlights: • Vertically aligned single wall carbon nanotubes (SWCNTs) have been successfully grown on nickel (Ni) deposited silicon substrate. • The diameter distribution of the grown (SWCNTs) is in the range 1–2 nm. • A current density of 25.0 mA/cm{sup 2} at 1.9 V/μm of the grown SWCNTs is observed with a high turn-on field (E{sub to}) of 1.3 V/μm. • After N{sub 2} nitrogen plasma treatment, huge current density of 81.5 mA/cm{sup 2} at 2.0 V/μm was recorded with low E{sub to} of 1.2 V/μm. • The comparison of these two typical results indicates a drastic enhancement in the field emission properties after plasma treatments. - Abstract: Vertically aligned single wall carbon nanotubes (SWCNTs) with large scale control of diameter, length and alignment have successfully been grown by plasma enhanced chemical vapor deposition (PECVD) system. The nickel (Ni) as catalyst deposited on silicon (Si) substrate was used to grow the SWCNTs. Field emission (FE) characteristics of the as grown SWCNTs were measured using indigenously designed setup in which a diode is configured in such a way that by applying negative voltage on the copper plate (cathode) with respect to stainless steel anode plate, current density can be recorded. To measure the FE characteristics, SWCNTs film pasted on the copper plate with silver epoxy was used as electron emitter source. The effective area of anode was ∼78.5 mm{sup 2} for field emission measurements. The emission measurements were carried out under high vacuum pressure of the order of 10{sup −6} Torr to minimize the electron scattering and degradation of the emitters. The distance between anode and cathode was kept 500 μm (constant) during entire field emission studies. The grown SWCNTs are excellent field emitters, having emission current density higher than 25 mA/cm{sup 2} at turn-on field 1.3 V/μm. In order to enhance the field emission characteristics, the as grown SWCNTs have been treated under nitrogen (N{sub 2

Emittance measurements of high charge state argon beams from a pig source

International Nuclear Information System (INIS)

Bex, L.; Clark, D.J.; Ellsworth, C.E.; Estrella, R.M.; Gough, R.A.; Holley, W.R.

1975-10-01

The emittances of beams of Ar 4+ to Ar 8+ were measured in the axial and radial planes. The extraction voltage was 10 kV and the magnetic field was varied from about 0.5 to 0.6 Tesla. The anode slit was varied in distance from the arc, which was run both dc and pulsed. The emittance was nearly independent of charge state, but increased with total beam current. A small bowing of the arc column, which made evaluation of mirror field effects difficult, was discovered

Selective growth of carbon nanotube on silicon substrates

Institute of Scientific and Technical Information of China (English)

ZOU Xiao-ping; H. ABE; T. SHIMIZU; A. ANDO; H. TOKUMOT; ZHU Shen-ming; ZHOU Hao-shen

2006-01-01

The carbon nanotube (CNT) growth of iron oxide-deposited trench-patterns and the locally-ordered CNT arrays on silicon substrate were achieved by simple thermal chemical vapor deposition(STCVD) of ethanol vapor. The CNTs were uniformly synthesized with good selectivity on trench-patterned silicon substrates. This fabrication process is compatible with currently used semiconductor-processing technologies,and the carbon-nanotube fabrication process can be widely applied for the development of electronic devices using carbon-nanotube field emitters as cold cathodes and can revolutionize the area of field-emitting electronic devices. The site-selective growth of CNT from an iron oxide nanoparticle catalyst patterned were also achieved by drying-mediated self-assembly technique. The present method offers a simple and cost-effective method to grow carbon nanotubes with self-assembled patterns.

Compressive effect of the magnetic field on the positron range in commonly used positron emitters simulated using Geant4

Science.gov (United States)

Li, Chong; Cao, Xingzhong; Liu, Fuyan; Tang, Haohui; Zhang, Zhiming; Wang, Baoyi; Wei, Long

2017-11-01

The compressive effect of a magnetic field on the positron range from commonly used positron emitters in PET (Positron Emission Tomography) was simulated using the Geant4 toolkit with H2O as the environmental material. The compression of the positron range, which was different in the directions parallel and perpendicular to the magnetic field, showed finite final variation of relative change rate versus the magnetic field. The variation greatly depended on the positron-emission energy spectrum in the same medium. Furthermore, the volume of the positron annihilation point was dramatically compressed as the magnetic field was set in the range of 3-6T. It was more prominent for 82Rb , which is generally used as a positron source in PET technology.

Monolithic multinozzle emitters for nanoelectrospray mass spectrometry

Science.gov (United States)

Wang, Daojing [Daly City, CA; Yang, Peidong [Kensington, CA; Kim, Woong [Seoul, KR; Fan, Rong [Pasadena, CA

2011-09-20

Novel and significantly simplified procedures for fabrication of fully integrated nanoelectrospray emitters have been described. For nanofabricated monolithic multinozzle emitters (NM.sup.2 emitters), a bottom up approach using silicon nanowires on a silicon sliver is used. For microfabricated monolithic multinozzle emitters (M.sup.3 emitters), a top down approach using MEMS techniques on silicon wafers is used. The emitters have performance comparable to that of commercially-available silica capillary emitters for nanoelectrospray mass spectrometry.

Emittance measurements of high charge state argon beams from a PIG source

International Nuclear Information System (INIS)

Bex, L.; Clark, D.J.; Ellsworth, C.E.; Estrella, R.M.; Gough, R.A.; Holley, W.R.

1976-01-01

The emittances of beams of Ar 4+ to Ar 8+ were measured in the axial and radial planes. The extraction voltage was 10 kV and the magnetic field was varied from about 0.5 to 0.6 Tesla. The anode slit was varied in its distance from the arc which was run both dc and pulsed. The emittance was found to be nearly independent of charge state but to increase with total beam current. A small bowing of the arc column was discovered, which made evaluation of mirror field effects difficult

Synthesis and field emission properties of carbon nanotubes grown in ethanol flame based on a photoresist-assisted catalyst annealing process

International Nuclear Information System (INIS)

Yang Xiaoxia; Fang Guojia; Liu Nishuang; Wang Chong; Zheng Qiao; Zhou Hai; Zhao Dongshan; Long Hao; Liu Yuping; Zhao Xingzhong

2009-01-01

Carbon nanotubes (CNTs) have been grown directly on a Si substrate without a diffusion barrier in ethanol diffusion flame using Ni as the catalyst after a photoresist-assisted catalyst annealing process. The growth mechanism of as-synthesized CNTs is confirmed by scanning electron microscopy, high resolution transmission-electron microscopy and energy-dispersive spectroscopy. The photoresist is the key for the formation of active catalyst particles during annealing process, which then result in the growth of CNTs. The catalyst annealing temperature has been found to affect the morphologies and field electron emission properties of CNTs significantly. The field emission properties of as-grown CNTs are investigated with a diode structure and the obtained CNTs exhibit enhanced characteristics. This technique will be applicable to a low-cost fabrication process of electron-emitter arrays.

A compact neutron generator using a field ionization source.

Science.gov (United States)

Persaud, Arun; Waldmann, Ole; Kapadia, Rehan; Takei, Kuniharu; Javey, Ali; Schenkel, Thomas

2012-02-01

Field ionization as a means to create ions for compact and rugged neutron sources is pursued. Arrays of carbon nano-fibers promise the high field-enhancement factors required for efficient field ionization. We report on the fabrication of arrays of field emitters with a density up to 10(6) tips∕cm(2) and measure their performance characteristics using electron field emission. The critical issue of uniformity is discussed, as are efforts towards coating the nano-fibers to enhance their lifetime and surface properties.

Nanometer emittance ultralow charge beams from rf photoinjectors

Directory of Open Access Journals (Sweden)

R. K. Li

2012-09-01

Full Text Available In this paper we discuss the generation of a new class of high brightness relativistic electron beams, characterized by ultralow charge (0.1–1 pC and ultralow normalized emittance (<50  nm. These beams are created in rf photoinjectors when the laser is focused on the cathode to very small transverse sizes (<30  μm rms. In this regime, the charge density at the cathode approaches the limit set by the extraction electric field. By shaping the laser pulse to have a cigarlike aspect ratio (the longitudinal dimension much larger than the transverse dimension and a parabolic temporal profile, the resulting space charge dominated dynamics creates a uniformly filled ellipsoidal distribution and the emittance can be nearly preserved to its thermal value. We also present a new method, based on a variation of the pepper-pot technique, for single shot measurements of the ultralow emittances for this new class of beams.

RF emittance in a low energy electron linear accelerator

Science.gov (United States)

Sanaye Hajari, Sh.; Haghtalab, S.; Shaker, H.; Kelisani, M. Dayyani

2018-04-01

Transverse beam dynamics of an 8 MeV low current (10 mA) S-band traveling wave electron linear accelerator has been studied and optimized. The main issue is to limit the beam emittance, mainly induced by the transverse RF forces. The linac is being constructed at Institute for Research in Fundamental Science (IPM), Tehran Iran Labeled as Iran's First Linac, nearly all components of this accelerator are designed and constructed within the country. This paper discusses the RF coupler induced field asymmetry and the corresponding emittance at different focusing levels, introduces a detailed beam dynamics design of a solenoid focusing channel aiming to reduce the emittance growth and studies the solenoid misalignment tolerances. In addition it has been demonstrated that a prebuncher cavity with appropriate parameters can help improving the beam quality in the transverse plane.

Emittance preservation during bunch compression with a magnetized beam

Energy Technology Data Exchange (ETDEWEB)

Stratakis, Diktys [Brookhaven National Lab. (BNL), Upton, NY (United States)

2015-09-02

The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based on combining a finite solenoid field where the beam is generated together with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

Emittance measurement and optimization for the photocathode RF gun with laser profile shaping

International Nuclear Information System (INIS)

Liu Shengguang; Masafumi Fukuda; Sakae Araki; Nobuhiro Terunuma; Junji Urakawa

2010-01-01

The Laser Undulator Compact X-ray source (LUCX) is a test bench for a compact high brightness X-ray generator, based on inverse Compton Scattering at KEK, which requires high intensity multi-bunch trains with low transverse emittance. A photocathode RF gun with emittance compensation solenoid is used as an electron source. Much endeavor has been made to increase the beam intensity in the multi-bunch trains. The cavity of the RF gun is tuned into an unbalanced field in order to reduce space charge effects, so that the field gradient on the cathode surface is relatively higher when the forward RF power into gun cavity is not high enough. A laser profile shaper is employed to convert the driving laser profile from Gaussian into uniform. In this research we seek to find the optimized operational conditions for the decrease of the transverse emittance. With the uniform driving laser and the unbalanced RF gun, the RMS transverse emittance of a 1 nC bunch has been improved effectively from 5.46 πmm.mrad to 3.66 πmm·mrad. (authors)

Rayleigh scattering in an emitter-nanofiber-coupling system

Science.gov (United States)

Tang, Shui-Jing; Gao, Fei; Xu, Da; Li, Yan; Gong, Qihuang; Xiao, Yun-Feng

2017-04-01

Scattering is a general process in both fundamental and applied physics. In this paper, we investigate Rayleigh scattering of a solid-state-emitter coupled to a nanofiber, by S -matrix-like theory in k -space description. Under this model, both Rayleigh scattering and dipole interaction are studied between a two-level artificial atom embedded in a nanocrystal and fiber modes (guided and radiation modes). It is found that Rayleigh scattering plays a critical role in the transport properties and quantum statistics of photons. On the one hand, Rayleigh scattering produces the transparency in the optical transmitted field of the nanofiber, accompanied by the change of atomic phase, population, and frequency shift. On the other hand, the interference between two kinds of scattering fields by Rayleigh scattering and dipole transition modifies the photon statistics (second-order autocorrelation function) of output fields, showing a strong wavelength dependence. This study provides guidance for the solid-state emitter acting as a single-photon source and can be extended to explore the scattering effect in many-body physics.

Thermal Emittance Measurement of the Cs2Te Photocathode in FZD Superconducting RF

CERN Document Server

Xiang, R; Michel, P; Murcek, P; Teichert, J

2010-01-01

The thermal emittance of the photocathode is an interesting physical property for the photoinjector, because it decides the minimum emittance the photoinjector can finally achieve. In this paper we will report the latest results of the thermal emittance of the Cs2Te photocathode in FZD Superconducting RF gun. The measurement is performed with solenoid scan method with very low bunch charge and relative large laser spot on cathode, in order to reduce the space charge effect as much as possible, and meanwhile to eliminate the wake fields and the effect from beam halos.

The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

Science.gov (United States)

Mentel, Juergen

2018-01-01

A mono-layer of atoms, electropositive with respect to the substrate atoms, forms a dipole layer, reducing its work function. Such a layer is generated by diffusion of emitter material from the interior of the substrate, by vapour deposition or by deposition of emitter material onto arc electrodes by cataphoresis. This cataphoretic emitter effect is investigated within metal halide lamps with transparent YAG ceramic burners, and within model lamps. Within the YAG lamps, arcs are operated with switched-dc current between rod shaped tungsten electrodes in high pressure Hg vapour seeded with metal iodides. Within the model lamps, dc arcs are operated between rod-shaped tungsten electrodes—one doped—in atmospheric pressure Ar. Electrode temperatures are determined by 1λ -pyrometry, combined with simulation of the electrode heat balance. Plasma temperatures, atom and ion densities of emitter material are determined by emission and absorption spectroscopy. Phase resolved measurements in YAG lamps seeded with CeI3, CsI, DyI3, TmI3 and LaI3 show, within the cathodic half period, a reduction of the electrode temperature and an enhanced metal ion density in front of the electrode, and an opposite behavior after phase reversal. With increasing operating frequency, the state of the cathode overlaps onto the anodic phase—except for Cs, being low in adsorption energy. Generally, the phase averaged electrode tip temperature is reduced by seeding a lamp with emitter material; its height depends on admixtures. Measurements at tungsten electrodes doped with ThO2, La2O3 and Ce2O3 within the model lamp show that evaporated emitter material is redeposited by an emitter ion current onto the electrode surface. It reduces the work function of tungsten cathodes above the evaporation temperature of the emitter material, too; and also of cold anodes, indicating a field reversal in front of them. The formation of an emitter spot at low cathode temperature and high emitter material

Emittance growth due to noise and its suppression with the Feedback system in large hadron colliders

International Nuclear Information System (INIS)

Lebedev, V.; Parkhomchuk, V.; Shiltsev, V.; Stupakov, G.

1993-03-01

The problem of emittance growth due to random fluctuation of the magnetic field in hadron colliders is considered. Based on a simple one-dimensional linear model, a formula for an emittance growth rate as a function of the noise spectrum is derived. Different sources of the noise are analyzed and their role is estimated for the Superconducting Super Collider (SSC). A theory of feedback suppression of the emittance growth is developed which predicts the residual growth of the emittance in the accelerator with a feedback system

FACET Emittance Growth

Energy Technology Data Exchange (ETDEWEB)

Frederico, J; Hogan, M.J.; Nosochkov, Y.; Litos, M.D.; Raubenheimer, T.; /SLAC

2011-04-05

FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3.2 nC electron bunches to {approx}20 {micro}m long and {approx}10 {micro}m wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.

FACET Emittance Growth

International Nuclear Information System (INIS)

Frederico, Joel

2011-01-01

FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3.2 nC electron bunches to ∼20 (micro)m long and ∼10 (micro)m wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.

Emittance growth caused by bends in the Los Alamos free-electron laser energy recovery experiment

International Nuclear Information System (INIS)

Carlsten, B.E.

1987-01-01

Experimentally transporting the beam from the wiggler to the decelerators in the energy recovery experiment (ERX) at the Los Alamos National Laboratory free-electron laser was more difficult than expected because of the large initial emittance in the beam. This emittance was apparently caused in an early 60 0 achromatic bend. To get this beam through subsequent bends without wall interception, the quadrupole focusing had to be changed from the design amount; as a result, the emittance grew further. This paper discusses various mechanisms for this emittance growth in the 60 0 bend, including effects caused by path changes in the bend resulting from wake-field-induced energy changes of particles in the beam and examines emittance filters, ranging from a simple aperture near a beam crossover to more complicated telescope schemes designed to regain the original emittance before the 60 0 bend

Low emittance photoinjectors

International Nuclear Information System (INIS)

Ferrario, Massimo

2001-01-01

Photon colliders require high charge polarized electron beams with very low normalized emittances, possibly lower than the actual damping rings design goals. Recent analytical and numerical efforts in understanding beam dynamics in RF photoinjectors have raised again the question as to whether the performances of an RF electron gun based injector could be competitive with respect to a damping ring. As a matter of discussion we report in this paper the most recent results concerning low emittance photoinjector designs: the production of polarized electron beams by DC and/or RF guns is illustrated together with space charge compensation techniques and thermal emittance effects. New ideas concerning multi-gun injection system and generation of flat beams by RF gun are also discussed

Emittance preservation during bunch compression with a magnetized beam

Energy Technology Data Exchange (ETDEWEB)

Stratakis, Diktys

2016-03-01

The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based in combining a finite solenoid field where the beam is generated with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth from CSR can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

Emittance growth in displaced, space-charge-dominated beams with energy spread

International Nuclear Information System (INIS)

Barnard, J.J.; Miller, J.; Haber, I.

1993-01-01

Conversion of transverse energy associated with the coherent motion of displaced beams into thermal energy, and thus emittance growth, has been predicted theoretically by a number of authors. Here, they authors show, using 2-D particle-in-cell simulations, that emittance growth is inhibited for tune depressed beams, if the energy spread of the beam is not too large. Further, using a uniform density model to calculate the space charge field of the beam, they numerically determine the criteria for emittance growth as a function of tune depression, energy spread, and beam displacement over a wide range of parameters. A theoretical interpretation of the results is presented. This study is applicable to an inertial fusion reactor driven by a heavy ion accelerator

Smith-Purcell experiment utilizing a field-emitter array cathode measurements of radiation

CERN Document Server

Ishizuka, H; Yokoo, K; Shimawaki, H; Hosono, A

2001-01-01

Smith-Purcell (SP) radiation at wavelengths of 350-750 nm was produced in a tabletop experiment using a field-emitter array (FEA) cathode. The electron gun was 5 cm long, and a 25 mmx25 mm holographic replica grating was placed behind the slit provided in the anode. A regulated DC power supply accelerated electron beams in excess of 10 mu A up to 45 keV, while a small Van de Graaff generator accelerated smaller currents to higher energies. The grating had a 0.556 mu m period, 30 deg. blaze and a 0.2 mu m thick aluminum coating. Spectral characteristics of the radiation were measured both manually and automatically; in the latter case, the spectrometer was driven by a stepping motor to scan the wavelength, and AD-converted signals from a photomultiplier tube were processed by a personal computer. The measurement, made at 80 deg. relative to the electron beam, showed good agreement with theoretical wavelengths of the SP radiation. Diffraction orders were -2 and -3 for beam energies higher than 45 keV, -3 to -5 ...

On the feasibility of sub-100 nm rad emittance measurement in plasma accelerators using permanent magnetic quadrupoles

Science.gov (United States)

Li, F.; Wu, Y. P.; Nie, Z.; Guo, B.; Zhang, X. H.; Huang, S.; Zhang, J.; Cheng, Z.; Ma, Y.; Fang, Y.; Zhang, C. J.; Wan, Y.; Xu, X. L.; Hua, J. F.; Pai, C. H.; Lu, W.; Gu, Y. Q.

2018-01-01

Low emittance (sub-100 nm rad) measurement of electron beams in plasma accelerators has been a challenging issue for a while. Among various measurement schemes, measurements based on single-shot quad-scan using permanent magnetic quadrupoles (PMQs) has been recently reported with emittance as low as ˜200 nm Weingartner (2012 Phys. Rev. Spec. Top. Accel. Beams 15 111302). However, the accuracy and reliability of this method have not been systematically analyzed. Such analysis is critical for evaluating the potential of sub-100 nm rad emittance measurement using any scheme. In this paper, we analyze the effects of various nonideal physical factors on the accuracy and reliability using the PMQ method. These factors include aberration induced by a high order field, PMQ misalignment and angular fluctuation of incoming beams. Our conclusions are as follows: (i) the aberrations caused by high order fields of PMQs are relatively weak for low emittance measurement as long as the PMQs are properly constructed. A series of PMQs were manufactured and measured at Tsinghua University, and using numerical simulations their high order field effects were found to be negligible . (ii) The largest measurement error of emittance is caused by the angular misalignment between PMQs. For low emittance measurement of ˜100 MeV beams, an angular alignment accuracy of 0.1° is necessary. This requirement can be eased for beams with higher energies. (iii) The transverse position misalignment of PMQs and angular fluctuation of incoming beams only cause a translational and rotational shift of measured signals, respectively, therefore, there is no effect on the measured value of emittance. (iv) The spatial resolution and efficiency of the detection system need to be properly designed to guarantee the accuracy of sub-100 nm rad emittance measurement.

Carbon-10: Example of cyclotron production of positron emitters as an open research field

DEFF Research Database (Denmark)

Alves, F.; Lima, J.J.P.; Nickles, R.J.

2007-01-01

This paper supports the thesis that significant improvement of PET output response to clinical questions can be achieved by innovation in radionuclide production. Moreover, that development can be performed with the resources available at a clinical centre. Carbon-10 production parameters studies...

Amplification of intrinsic emittance due to rough metal cathodes: Formulation of a parameterization model

Energy Technology Data Exchange (ETDEWEB)

Charles, T.K. [School of Physics and Astronomy, Monash University, Clayton, Victoria, 3800 (Australia); Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria, 3168 (Australia); Paganin, D.M. [School of Physics and Astronomy, Monash University, Clayton, Victoria, 3800 (Australia); Dowd, R.T. [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria, 3168 (Australia)

2016-08-21

Intrinsic emittance is often the limiting factor for brightness in fourth generation light sources and as such, a good understanding of the factors affecting intrinsic emittance is essential in order to be able to decrease it. Here we present a parameterization model describing the proportional increase in emittance induced by cathode surface roughness. One major benefit behind the parameterization approach presented here is that it takes the complexity of a Monte Carlo model and reduces the results to a straight-forward empirical model. The resulting models describe the proportional increase in transverse momentum introduced by surface roughness, and are applicable to various metal types, photon wavelengths, applied electric fields, and cathode surface terrains. The analysis includes the increase in emittance due to changes in the electric field induced by roughness as well as the increase in transverse momentum resultant from the spatially varying surface normal. We also compare the results of the Parameterization Model to an Analytical Model which employs various approximations to produce a more compact expression with the cost of a reduction in accuracy.

Optical Performance of Carbon-Nanotube Electron Sources

International Nuclear Information System (INIS)

Jonge, Niels de; Allioux, Myriam; Oostveen, Jim T.; Teo, Kenneth B. K.; Milne, William I.

2005-01-01

The figure of merit for the electron optical performance of carbon-nanotube (CNT) electron sources is presented. This figure is given by the relation between the reduced brightness and the energy spread in the region of stable emission. It is shown experimentally that a CNT electron source exhibits a highly stable emission process that follows the Fowler-Nordheim theory for field emission, fixing the relationship among the energy spread, the current, and the radius. The performance of the CNT emitter under realistic operating conditions is compared with state-of-the-art electron point sources. It is demonstrated that the reduced brightness is a function of the tunneling parameter, a measure of the energy spread at low temperatures, only, independent of the geometry of the emitter

Transverse and longitudinal emittance measurements in the ELSA linac

International Nuclear Information System (INIS)

Loulergue, A.; Dowell, D.H.; Joly, S.; De Brion, J.P.; Haouat, G.; Schumann, F.

1997-01-01

The ELSA RF linac photoinjector has been designed to deliver high-brightness electron beams. The present paper deals with the transverse and longitudinal emittance measurements, at different locations along the ELSA beam line, and the analysis of their variations as a function of the photoinjector parameters : magnetic field generated by the anode focusing lens, bunch charge and pulse duration. While transverse emittance has been already studied in other similar installations, there has been little study of the electron beam longitudinal dynamics. Experimental results are presented and compared to simulation-code expectations. For 2.0 nC, 85 A electron bunches, a normalized rms emittance of 2 π mm mrad and a brightness of 4.5 x 10 13 A/(π m rad) 2 at the linac exit have been measured as well as less than 10 keV rms energy spread (or less than 0.1% at 16.5 MeV). (orig.)

Diamond field emitter array cathodes and possibilities for employing additive manufacturing for dielectric laser accelerating structures

Energy Technology Data Exchange (ETDEWEB)

Simakov, Evgenya Ivanovna [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Andrews, Heather Lynn [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Herman, Matthew Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hubbard, Kevin Mark [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Weis, Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-09-20

These are slides for a presentation at Stanford University. The outline is as follows: Motivation: customers for compact accelerators, LANL's technologies for laser acceleration, DFEA cathodes, and additive manufacturing of micron-size structures. Among the stated conclusions are the following: preliminary study identified DFEA cathodes as promising sources for DLAs--high beam current and small emittance; additive manufacturing with Nanoscribe Professional GT can produce structures with the right scale features for a DLA operating at micron wavelengths (fabrication tolerances need to be studied, DLAs require new materials). Future plans include DLA experiment with a beam produced by the DFEA cathode with field emission, demonstration of photoemission from DFEAs, and new structures to print and test.

A new concept for the modeling of the positron emitter production for the particle therapy

International Nuclear Information System (INIS)

Priegnitz, Marlen

2012-01-01

One of the three main tumour treatment forms is radiation therapy. Here, the application of ion beams, in particular protons and carbon ions, is of growing importance. This high precision therapy requires a consequent monitoring of the dose delivery since the induced dose deposition is very sensitive to density changes in the irradiated tissue. Up to now, positron emission tomography (PET) is the only in vivo method in clinical use for monitoring the dose deposition in ion beam therapy. It allows for the verification of the particle range as well as the position of the irradiation field. The distribution of activity measured by means of PET cannot be compared directly to the planned dose distribution. Thus, a calculation of the expected activity distribution is required which then can be compared to the measurement. Simulation of the expected activity distribution requires the exact knowledge of various cross sections. Only a few of them have been measured in the required energy range so far. Therefore, in Monte Carlo simulations often intrinsic nuclear models or semi-empirical parametrization are used which often exhibit insufficient accuray. Among experts the question on the optimum ion species for tumour therapy is still open. Especially lithium ions exhibit a great potential due to their favourable physical and radiobiological properties. Also for these ions a PET monitoring is highly desirable. The presented work shows the feasibility of range verification by means of PET for lithium irradiation. Furthermore, a concept for modeling positron emitter distributions without the knowledge of cross sections is developed. This prediction is based on depth-dependent positron emitter yields measured in reference materials (water, graphite and polyethylene). With these data the positron emitter distribution in any material of known stoichiometry can be calculated by means of an appropriate linear combination. The feasibility of the yield concept is shown for lithium and

High brightness fiber laser pump sources based on single emitters and multiple single emitters

Science.gov (United States)

Scheller, Torsten; Wagner, Lars; Wolf, Jürgen; Bonati, Guido; Dörfel, Falk; Gabler, Thomas

2008-02-01

Driven by the potential of the fiber laser market, the development of high brightness pump sources has been pushed during the last years. The main approaches to reach the targets of this market had been the direct coupling of single emitters (SE) on the one hand and the beam shaping of bars and stacks on the other hand, which often causes higher cost per watt. Meanwhile the power of single emitters with 100μm emitter size for direct coupling increased dramatically, which also pushed a new generation of wide stripe emitters or multi emitters (ME) of up to 1000μm emitter size respectively "minibars" with apertures of 3 to 5mm. The advantage of this emitter type compared to traditional bars is it's scalability to power levels of 40W to 60W combined with a small aperture which gives advantages when coupling into a fiber. We show concepts using this multiple single emitters for fiber coupled systems of 25W up to 40W out of a 100μm fiber NA 0.22 with a reasonable optical efficiency. Taking into account a further efficiency optimization and an increase in power of these devices in the near future, the EUR/W ratio pushed by the fiber laser manufacturer will further decrease. Results will be shown as well for higher power pump sources. Additional state of the art tapered fiber bundles for photonic crystal fibers are used to combine 7 (19) pump sources to output powers of 100W (370W) out of a 130μm (250μm) fiber NA 0.6 with nominal 20W per port. Improving those TFB's in the near future and utilizing 40W per pump leg, an output power of even 750W out of 250μm fiber NA 0.6 will be possible. Combined Counter- and Co-Propagated pumping of the fiber will then lead to the first 1kW fiber laser oscillator.

Non-stochastic effects of different energy beta emitters on pig and mouse skin

International Nuclear Information System (INIS)

Peel, D.M.; Hopewell, J.W.; Hansen, L.S.; Coggle, J.E.; Charles, M.W.; Wells, J.

1982-01-01

In this collaborative study skin areas of various sizes were irradiated with different energy beta emitters. In the post-irradiation period fields were examined for erythema, desquamation, ulceration and dermal necrosis. The aim of the study is to determine the threshold doses for the different biological reactions as a function of the energy of the radiation and the size of skin field irradiated. At St. Bartholomew's Hospital and Oxford the irradiation of mouse and pig skin was carried out using strontium-90 and thulium-170 sources. In addition, mice were irradiated with thallium-204, a slightly lower energy beta emitter than thulium. (author)

Low emittance electron storage rings

Science.gov (United States)

Levichev, E. B.

2018-01-01

Low-emittance electron (positron) beams are essential for synchrotron light sources, linear collider damping rings, and circular Crab Waist colliders. In this review, the principles and methods of emittance minimization are discussed, prospects for developing relativistic electron storage rings with small beam phase volume are assessed, and problems related to emittance minimization are examined together with their possible solutions. The special features and engineering implementation aspects of various facilities are briefly reviewed.

Common mode noise on the main Tevatron bus and associated beam emittance growth

International Nuclear Information System (INIS)

Zhang, P.; Johnson, R.P.; Kuchnir, M.; Siergiej, D.; Wolff, D.

1991-05-01

Overlap of betatron tune frequencies with the power supply noise spectrum can cause transverse beam emittance growth in a storage ring. We have studied this effect for tunes near the integer, where the betatron frequency is low. By injecting noise onto the main power supply bus, it was determined that common mode noise was the dominant source of emittance growth. A noise suppression feed-back loop was then used to reduce the noise and the emittance growth. These experiments are described as are investigations of the common mode propagation along the Tevatron bus and measurements of the fields generated by common mode excitation of isolated Tevatron magnets. 3 refs., 4 figs

Development of a Robust, High Current, Low Power Field Emission Electron Gun for a Spaceflight Reflectron Time-of-Flight Mass Spectrometer

Science.gov (United States)

Southard, Adrian E.; Getty, Stephanie A.; Feng, Steven; Glavin, Daniel P.; Auciello, Orlando; Sumant, Anirudha

2012-01-01

Carbon materials, including carbon nanotubes (CNTs) and nitrogen-incorporated ultrananocrystalline diamond (N-UNCD), have been of considerable interest for field emission applications for over a decade. In particular, robust field emission materials are compelling for space applications due to the low power consumption and potential for miniaturization. A reflectron time-of-flight mass spectrometer (TOF-MS) under development for in situ measurements on the Moon and other Solar System bodies uses a field emitter to generate ions from gaseous samples, using electron ionization. For these unusual environments, robustness, reliability, and long life are of paramount importance, and to this end, we have explored the field emission properties and lifetime of carbon nanotubes and nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) thin films, the latter developed and patented by Argonne National Laboratory. We will present recent investigations of N-UNCD as a robust field emitter, revealing that this material offers stable performance in high vacuum for up to 1000 hours with threshold voltage for emission of about 3-4 V/lJm and current densities in the range of tens of microA. Optimizing the mass resolution and sensitivity of such a mass spectrometer has also been enabled by a parallel effort to scale up a CNT emitter to an array measuring 2 mm x 40 mm. Through simulation and experiment of the new extended format emitter, we have determined that focusing the electron beam is limited due to the angular spread of the emitted electrons. This dispersion effect can be reduced through modification of the electron gun geometry, but this reduces the current reaching the ionization region. By increasing the transmission efficiency of the electron beam to the anode, we have increased the anode current by two orders of magnitude to realize a corresponding enhancement in instrument sensitivity, at a moderate cost to mass resolution. We will report recent experimental and

Bent solenoids for spectrometers and emittance exchange sections

International Nuclear Information System (INIS)

Norem, J.

1999-01-01

Bent solenoids can be used to transport low energy beams as they provide both confinement and dispersion of particle orbits. Solenoids are being considered both as emittance exchange sections and spectrometers in the muon cooling system as part of the study of the muon collider. They present the results of a study of bent solenoids which considers the design of coupling sections between bent solenoids to straight solenoids, drift compensation fields, aberrations, and factors relating to the construction, such as field ripple, stored energy, coil forces and field errors

Modified theoretical minimum emittance lattice for an electron storage ring with extreme-low emittance

Directory of Open Access Journals (Sweden)

Yi Jiao

2011-05-01

Full Text Available In the continuing efforts to reduce the beam emittance of an electron storage ring composed of theoretical minimum emittance (TME lattice, down to a level of several tens of picometers, nonlinear dynamics grows to be a great challenge to the performance of the storage ring because of the strong sextupoles needed to compensate for its large global natural chomaticities coupled with its small average dispersion function. To help in dealing with the challenge of nonlinear optimization, we propose a novel variation of theoretical minimum emittance (TME lattice, named as “modified-TME” lattice, with minimal emittance about 3 times of the exact theoretical minimum, while with more compact layout, lower phase advance per cell, smaller natural chromaticities, and more relaxed optical functions than that in a TME cell, by using horizontally defocusing quadrupole closer to the dipole or simply combined-function dipole with horizontally defocusing gradient. We present approximate scaling formulas to describe the relationships of the design parameters in a modified-TME cell. The applications of modified-TME lattice in the PEP-X storage ring design are illustrated and the proposed lattice appears a good candidate for synchrotron radiation light source with extremely low emittance.

Half-lives of proton emitters using relativistic mean field theory

International Nuclear Information System (INIS)

Sahu, Bidhubhusan; Patra, S. K.; Agarwalla, S. K.

2011-01-01

The proton radioactivity lifetimes of proton emitters from the ground and the isomeric states are calculated using the microscopic M3Y + Ex and R3Y + Ex (proposed) nucleon-nucleus interaction potentials. These interaction potentials are obtained by single folding the densities of the daughter nuclei supplemented by a zero-range pseudopotential. The quantum-mechanical-tunneling probability is calculated within the WKB approximation. The calculated results are found to be in good agreement with the experimental data for both the M3Y and R3Y interactions.

A device for electron gun emittance measurement

International Nuclear Information System (INIS)

Aune, B.; Corveller, P.; Jablonka, M.; Joly, J.M.

1985-05-01

In order to improve the final emittance of the beam delivered by the ALS electron linac a new gun is going to be installed. To measure its emittance and evaluate the contribution of different factors to emittance growth we have developed an emittance measurement device. We describe the experimental and mathematical procedure we have followed, and give some results of measurements

Improving Defect-Based Quantum Emitters in Silicon Carbide via Inorganic Passivation.

Science.gov (United States)

Polking, Mark J; Dibos, Alan M; de Leon, Nathalie P; Park, Hongkun

2018-01-01

Defect-based color centers in wide-bandgap crystalline solids are actively being explored for quantum information science, sensing, and imaging. Unfortunately, the luminescent properties of these emitters are frequently degraded by blinking and photobleaching that arise from poorly passivated host crystal surfaces. Here, a new method for stabilizing the photoluminescence and charge state of color centers based on epitaxial growth of an inorganic passivation layer is presented. Specifically, carbon antisite-vacancy pairs (CAV centers) in 4H-SiC, which serve as single-photon emitters at visible wavelengths, are used as a model system to demonstrate the power of this inorganic passivation scheme. Analysis of CAV centers with scanning confocal microscopy indicates a dramatic improvement in photostability and an enhancement in emission after growth of an epitaxial AlN passivation layer. Permanent, spatially selective control of the defect charge state can also be achieved by exploiting the mismatch in spontaneous polarization at the AlN/SiC interface. These results demonstrate that epitaxial inorganic passivation of defect-based quantum emitters provides a new method for enhancing photostability, emission, and charge state stability of these color centers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Emittance measurement and modeling for the Fermilab Booster

Directory of Open Access Journals (Sweden)

Xiaobiao Huang

2006-01-01

Full Text Available Turn-by-turn beam profile data measured at the Fermilab Booster are studied. Lattice models with experimental accelerator ramping parameters are used to obtain the lattice functions for data analysis. We studied the horizontal and vertical emittance growth behavior in different stages of a booster ramping cycle and its relation to the beam intensity. The transverse and longitudinal components in the horizontal beam width are separated by a fitting model which makes use of the different scaling rules of the beam momentum. We analyze the post-transition horizontal beam size oscillation based on a model where the longitudinal phase-space mismatch has resulted from rf voltage mismatch during the transition-energy crossing. We carried out systematic multiparticle simulation to show that the source of the vertical emittance growth is a combination of the random errors in skew-quadrupole and dipole fields, and the systematic Montague resonance. The effect of random quadrupole field is small for the Fermilab Booster because the betatron envelope tunes are reasonably far away from the half-integer stop band.

Photon scattering from a system of multilevel quantum emitters. I. Formalism

Science.gov (United States)

Das, Sumanta; Elfving, Vincent E.; Reiter, Florentin; Sørensen, Anders S.

2018-04-01

We introduce a formalism to solve the problem of photon scattering from a system of multilevel quantum emitters. Our approach provides a direct solution of the scattering dynamics. As such the formalism gives the scattered fields' amplitudes in the limit of a weak incident intensity. Our formalism is equipped to treat both multiemitter and multilevel emitter systems, and is applicable to a plethora of photon-scattering problems, including conditional state preparation by photodetection. In this paper, we develop the general formalism for an arbitrary geometry. In the following paper (part II) S. Das et al. [Phys. Rev. A 97, 043838 (2018), 10.1103/PhysRevA.97.043838], we reduce the general photon-scattering formalism to a form that is applicable to one-dimensional waveguides and show its applicability by considering explicit examples with various emitter configurations.

Vertically aligned carbon nanotube field-effect transistors

KAUST Repository

Li, Jingqi; Zhao, Chao; Wang, Qingxiao; Zhang, Qiang; Wang, Zhihong; Zhang, Xixiang; Abutaha, Anas I.; Alshareef, Husam N.

2012-01-01

Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed

Carbon and oxygen abundances of field RR Lyrae stars. I. Carbon abundances

International Nuclear Information System (INIS)

Butler, D.; Manduca, A.; Deming, D.; Bell, R.A.

1982-01-01

From an analysis of KPNO 4-m echelle plates and simultaneous uvbyβ photometry, we have determined carbon abundances and carbon-to-iron ratios for a large number of field RR Lyrae stars having [Fe/H]> or approx. =-1.2. It is found that these field RR Lyrae stars: stars which are known to be in an advanced evolutionary state: have carbon-to-iron ratios which are similar to those of unevolved stars

Diamond-based single-photon emitters

International Nuclear Information System (INIS)

Aharonovich, I; Castelletto, S; Simpson, D A; Su, C-H; Greentree, A D; Prawer, S

2011-01-01

The exploitation of emerging quantum technologies requires efficient fabrication of key building blocks. Sources of single photons are extremely important across many applications as they can serve as vectors for quantum information-thereby allowing long-range (perhaps even global-scale) quantum states to be made and manipulated for tasks such as quantum communication or distributed quantum computation. At the single-emitter level, quantum sources also afford new possibilities in terms of nanoscopy and bio-marking. Color centers in diamond are prominent candidates to generate and manipulate quantum states of light, as they are a photostable solid-state source of single photons at room temperature. In this review, we discuss the state of the art of diamond-based single-photon emitters and highlight their fabrication methodologies. We present the experimental techniques used to characterize the quantum emitters and discuss their photophysical properties. We outline a number of applications including quantum key distribution, bio-marking and sub-diffraction imaging, where diamond-based single emitters are playing a crucial role. We conclude with a discussion of the main challenges and perspectives for employing diamond emitters in quantum information processing.

Emittance compensation of CW DC-gun photoinjector

International Nuclear Information System (INIS)

Li Peng; Wu Dai; Xu Zhou; Li Ming; Yang Xingfan

2011-01-01

Emittance growth induced by space charge effect is very important, especially for CW DC-gun photoinjector. In this work, the linear space charge force and its effect on electron beam transverse emittance are studied, and the principle and properties of emittance compensation by solenoid are analyzed. The CAEP DC-gun photoinjector with a solenoid is also simulated by code Parmela. Simulated results indicate that the normalized transverse emittance of an 80 pC bunch at the 350 keV DC-gun ex-it is 5.14 mm · mrad. And after compensated by a solenoid, it becomes 1.27 mm · mrad. The emittance of beam is well compensated. (authors)

A low-emittance lattice for SPEAR

International Nuclear Information System (INIS)

Safranek, J.; Wiedemann, H.

1992-01-01

The design and implementation of a low emittance lattice for the SPEAR storage ring including measurements of the performance of the lattice are presented (J. Safranek, Ph. D. thesis, Stanford University, 1991). The low emittance lattice is designed to optimize the performance of SPEAR as a synchrotron radiation source while keeping SPEAR hardware changes at a minimum. The horizontal emittance of the electron beam in the low emittance lattice is reduced by a factor of 4 from the previous lattice. This reduces the typical horizontal source size and divergence of the photon beams by a factor of 2 each and increases the photon beam brightness. At 3 GeV the horizontal emittance is 129 π nm rad, which makes the low emittance lattice the lowest emittance, runnning synchroton radiation source in the world in the 1.5 to 4.0 GeV energy range for the emittance scaled to 3 GeV. The measured vertical emittance was reduced to half that typically seen at SPEAR in the past. The brightness of the photon beams was further incrased by reducing β y at the insertion devices to 1.1 m and reducing the energy dispersion at the insertion devices by more than a factor of 2 on average. The horizontal despersion at the rf cavities was reduced by a factor of nearly 4 which gives much less problems with synchrobetatron resonances. The dynamic and physical apertures of the lattice are large, giving long beam lifetimes and easy injection of electrons. The measurements of the linear optics and intensity dependent phenomena gave resonable agreement with the design . The overall performance of the machine was very good. Injection rates of 10 to 20 mA/min and larger were achieved routinely, and 100 mA total current was stored. Repeated ramping of stored beam from the injection energy of 2.3 GeV to the running energy of 3.0 GeV was achieved with very little beam loss. This low emittance configuration is expected to be the operating configuration for SPEAR starting in January 1992. (orig.)

Radiation emitter-detector package

International Nuclear Information System (INIS)

O'Brien, J.T.; Limm, A.C.; Nyul, P.; Tassia, V.S. Jr.

1978-01-01

Mounted on the metallic base of a radiation emitter-detector is a mounting block is a first projection, and a second projection. A radiation detector is on the first projection and a semiconductor electroluminescent device, i.e., a radiation emitter, is on the second projection such that the plane of the recombination region of the electroluminescent device is perpendicular to the radiation incident surface of the radiation detector. The electroluminescent device has a primary emission and a secondary emission in a direction different from the primary emission. A radiation emitter-detector package as described is ideally suited to those applications wherein the secondary radiation of the electroluminescent device is fed into a feedback circuit regulating the biasing current of the electroluminescent device

Emittance investigation of RF photo-injector

CERN Document Server

Yang Mao Rong; Li Zheng; Li Ming; Xu Zhou

2002-01-01

A high-power laser beam illuminates a photocathode surface placed on an end wall of an RF cavity. The emitted electrons are accelerated immediately to a relativistic energy by the strong RF find in the cavity. But space charge effect induces beam emittance growth especially near the cathode where the electrons are still nonrelativistic. The author analyzes the factors which lead the transverse emittance growth and method how to resolve this problem. After introducing solenoidal focusing near the photocathode, the beam emittance growth is suppressed dramatically. The beam emittance is given also after compensation and simulation results. The measurements show these results are coincident

Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

Energy Technology Data Exchange (ETDEWEB)

Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Harsh [Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India); Husain, Mushahid, E-mail: mush-reslab@rediffmail.com [Department of Physics, Jamia Millia Islamia (A Central University), New Delhi 110025 (India); Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi 110025 (India)

2014-02-28

Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

Optical characterization of OLED emitter properties by radiation pattern analyses

Energy Technology Data Exchange (ETDEWEB)

Flaemmich, Michael

2011-09-08

Researches in both, academia and industry are investigating optical loss channels in OLED layered systems by means of optical simulation tools in order to derive promising concepts for a further enhancement of the overall device performance. Besides other factors, the prospects of success of such optimization strategies rely severely on the credibility of the optical input data. The present thesis provides a guideline to measure the active optical properties of OLED emitter materials in situ by radiation pattern analyses. Reliable and widely applicable methods are introduced to determine the internal electroluminescence spectrum, the profile of the emission zone, the dipole emitter orientation, and the internal luminescence quantum efficiency of emissive materials from the optical far field emission of OLEDs in electrical operation. The proposed characterization procedures are applied to sets of OLEDs containing both, fluorescent polymeric materials as well as phosphorescent small-molecular emitters, respectively. On the one hand, quite expected results are obtained. On the other hand, several novel and truly surprising results are found. Most importantly, this thesis contains the first report of a non-isotropic, mainly parallel emitter orientation in a phosphorescent small-molecular guest-host system (Ir(MDQ)2(acac) in a-NPD). Due to the latter result, emitter orientation based optimization of phosphorescent OLEDs seems to be within reach. Since parallel dipoles emit preferably into air, the utilization of smart emissive materials with advantageous molecular orientation is capable to boost the efficiency of phosphorescent OLEDs by 50%. Materials design, the influence of the matrix material and the substrate, as well as film deposition conditions are just a few parameters that need to be studied further in order to exploit the huge potential of the dipole emitter orientation in phosphorescent OLEDs.

Experimental studies of emittance growth and energy spread in a photocathode RF gun

International Nuclear Information System (INIS)

Yang, J.; Sakai, F.; Okada, Y.; Yorozu, M.; Yanagida, T.; Endo, A.

2002-01-01

In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91±0.28 πmm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac

Experimental studies of emittance growth and energy spread in a photocathode RF gun

CERN Document Server

Yang, J; Okada, Y; Yorozu, M; Yanagida, T; Endo, A

2002-01-01

In this paper we report on a low emittance electron source, based on a photocathode RF gun, a solenoid magnet and a subsequent linac. The dependencies of the beam transverse emittance and relative energy spread with respect to the laser injection phase of the radio-frequency (RF) gun, the RF phase of the linac and the bunch charge were investigated experimentally. It was found that a lower beam emittance is observed when the laser injection phase in the RF gun is low. The emittance increases almost linearly with the bunch charge under a constant solenoid magnetic field. The corrected relative energy spread of the beam is not strongly dependent on the bunch charge. Finally, an optimal normalized rms transverse emittance of 1.91+-0.28 pi mm mrad at a bunch charge of 0.6 nC was obtained when the RF gun was driven by a picosecond Nd:YAG laser. A corrected relative rms energy spread of 0.2-0.25% at a bunch charge of 0.3-2 nC was obtained after the beam was accelerated to 14 MeV by the subsequent linac.

Criteria for emittance compensation in high-brightness photoinjectors

Directory of Open Access Journals (Sweden)

Chun-xi Wang

2007-10-01

Full Text Available A critical process in high-brightness photoinjectors is emittance compensation, which brings under control the correlated transverse emittance growth due to the linear space-charge force. Although emittance compensation has been used and studied for almost two decades, the exact criteria to achieve emittance compensation is not as clear as it should be. In this paper, a perturbative analysis of slice envelopes and emittance evolution close to any reference envelope is developed, via which space-charge and chromatic effects are investigated. A new criterion for emittance compensation is found, which is complementary to the well-known matching condition for the invariant envelope and agrees very well with simulations.

Small horizontal emittance in the TESLA damping ring

International Nuclear Information System (INIS)

Decking, W.

2001-01-01

The present TESLA damping ring is designed for a normalized horizontal emittance of 8x10 -6 m. γ-γ collisions at the TESLA linear collider will benefit from a further decrease of the horizontal emittance. This paper reviews the processes which limit the horizontal emittance in the damping ring. Preliminary estimates on the smallest horizontal emittance for the present TESLA damping ring design as well as an ultimate limit of the emittance reachable with the TESLA damping ring concept will be given

Beam diagnostics using an emittance measurement device

International Nuclear Information System (INIS)

Sarstedt, M.; Becker, R.; Klein, H.; Maaser, A.; Mueller, J.; Thomae, R.; Weber, M.

1995-01-01

For beam diagnostics aside from Faraday cups for current measurements and analysing magnets for the determination of beam composition and energy the most important tool is an emittance measurement device. With such a system the distribution of the beam particles in phase-space can be determined. This yields information not only on the position of the particles but also on their angle with respect to the beam axis. There are different kinds of emittance measurement devices using either circular holes or slits for separation of part of the beam. The second method (slit-slit measurement), though important for the determination of the rms-emittance, has the disadvantage of integrating over the y- and y'-coordinate (measurement in xx'-plane assumed). This leads to different emittance diagrams than point-point measurements, since in xx'-plane for each two corresponding points of rr'-plane there exists a connecting line. With regard to beam aberrations this makes xx'-emittances harder to interpret. In this paper the two kinds of emittance diagrams are discussed. Additionally the influence of the slit height on the xx'-emittance is considered. The analytical results are compared to experimental measurements in rr'-, rx'- and xx'-phase-space. (orig.)

Lower Emittance Lattice for the Advanced Photon Source Upgrade Using Reverse Bending Magnets

Energy Technology Data Exchange (ETDEWEB)

Borland, M.; Berenc, T.; Sun, Y.; Sajaev, V.

2017-06-01

The Advanced Photon Source (APS) is pursuing an upgrade to the storage ring to a hybrid seven-bend-achromat design [1]. The nominal design provides a natural emittance of 67 pm [2]. By adding reverse dipole fields to several quadrupoles [3, 4] we can reduce the natural emittance to 41 pm while simultaneously providing more optimal beta functions in the insertion devices and increasing the dispersion function at the chromaticity sextupole magnets. The improved emittance results from a combination of increased energy loss per turn and a change in the damping partition. At the same time, the nonlinear dynamics performance is very similar, thanks in part to increased dispersion in the sextupoles. This paper describes the properties, optimization, and performance of the new lattice.

Development and field-scale optimization of a honeycomb zeolite rotor concentrator/recuperative oxidizer for the abatement of volatile organic carbons from semiconductor industry.

Science.gov (United States)

Yang, Ji; Chen, Yufeng; Cao, Limei; Guo, Yuling; Jia, Jinping

2012-01-03

The combined concentrator/oxidizer system has been proposed as an effective physical-chemical option and proven to be a viable solution that enables Volatile Organic Carbons (VOCs) emitters to comply with the regulations. In this work, a field scale honeycomb zeolite rotor concentrator combined with a recuperative oxidizer was developed and applied for the treatment of the VOC waste gas. The research shows the following: (1) for the adsorption rotor, zeolite is a more appropriate material than Granular Activated Carbon (GAC). The designing and operation parameters of the concentrator were discussed in detail including the size and the optimal rotation speed of rotor. Also the developed rotor performance's was evaluated in the field; (2) Direct Fired Thermal Oxidizer (DFTO), Recuperative Oxidizer (RO), Regenerative Thermal Oxidizer (RTO) and Regenerative Catalytic oxidizer (RCO) are the available incinerators and the RO was selected as the oxidizer in this work; (3) The overall performance of the developed rotor/oxidizer was explored in a field scale under varying conditions; (4) The energy saving strategy was fulfilled by reducing heat loss from the oxidizer and recovering heat from the exhaust gas. Data shows that the developed rotor/oxidizer could remove over 95% VOCs with reasonable cost and this could be helpful for similar plants when considering VOC abatement.

Strong Coupling and Entanglement of Quantum Emitters Embedded in a Nanoantenna-Enhanced Plasmonic Cavity

Energy Technology Data Exchange (ETDEWEB)

Hensen, Matthias [Institut; Heilpern, Tal [Center; Gray, Stephen K. [Center; Pfeiffer, Walter [Fakultät

2017-10-12

Establishing strong coupling between spatially separated and thus selectively addressable quantum emitters is a key ingredient to complex quantum optical schemes in future technologies. Insofar as many plasmonic nanostructures are concerned, however, the energy transfer and mutual interaction strength between distant quantum emitters can fail to provide strong coupling. Here, based on mode hybridization, the longevity and waveguide character of an elliptical plasmon cavity are combined with intense and highly localized field modes of suitably designed nanoantennas. Based on FDTD simulations a quantum emitter-plasmon coupling strength hg = 16.7 meV is reached while simultaneously keeping a small plasmon resonance line width h gamma(s) = 33 meV. This facilitates strong coupling, and quantum dynamical simulations reveal an oscillatory exchange of excited state population arid a notable degree of entanglement between the quantum emitters spatially separated by 1.8 mu m, i.e., about twice the operating wavelength.

Nonintercepting emittance monitor

International Nuclear Information System (INIS)

Miller, R.H.; Clendenin, J.E.; James, M.B.; Sheppard, J.C.

1983-08-01

A nonintercepting emittance monitor is a helpful device for measuring and improving particle beams in accelerators and storage rings as it allows continuous monitoring of the beam's distribution in phase space, and perhaps closed loop computer control of the distributions. Stripline position monitors are being investigated for use as nonintercepting emittance monitors for a beam focused by a FODO array in the first 100 meters of our linear accelerator. The technique described here uses the signal from the four stripline probes of a single position monitor to measure the quadrupole mode of the wall current in the beam pipe. This current is a function of the quadrupole moment of the beam, sigma 2 /sub x/ - sigma 2 /sub y/. In general, six independent measurements of the quadrupole moment are necessary to determine the beam emittance. This technique is dependent on the characteristically large variations of sigma 2 /sub x/ - sigma 2 /sub y/ in a FODO array. It will not work in a focusing system where the beam is round at each focusing element

Low emittance configuration for spear

International Nuclear Information System (INIS)

Blumberg, L.N.; Harris, J.; Stege, R.; Cerino, J.; Hettel, R.; Hofmann, A.; Liu, R.Z.; Wiedemann, H.; Winick, H.

1985-01-01

The quality of synchrotron radiation beams from SPEAR, in particular the brilliance of undulator radiation, can be improved significantly by reducing the emittance of the stored electron beam. A reduction of the horizontal emittance by a factor of 3.5 to a value of 130 nanometer-radians (nm-r) at 3 GeV has been achieved by using stronger focussing, mainly in the horizontal plane. The low emittance configuration also reduces the dispersion and vertical beta functions in the straight sections, making them more suitable for wigglers. The higher betatron tunes lead to a larger phase advance between the two kickers, which has to be corrected during injection by shunting current from some quadrupoles. The configuration was optimized within SPEAR hardware limitations and tested for dynamic aperture with the tracking program PATRICIA. After implementation of this scheme, beam was successfully injected and accumulated. The measured emittance of the stored beam was in agreement with calculations. Presently the configuration is being made operational

Emittance measurements by variable quadrupole method

International Nuclear Information System (INIS)

Toprek, D.

2005-01-01

The beam emittance is a measure of both the beam size and beam divergence, we cannot directly measure its value. If the beam size is measured at different locations or under different focusing conditions such that different parts of the phase space ellipse will be probed by the beam size monitor, the beam emittance can be determined. An emittance measurement can be performed by different methods. Here we will consider the varying quadrupole setting method.

Multinozzle emitter arrays for ultrahigh-throughput nanoelectrospray mass spectrometry

Science.gov (United States)

Wang, Daojing; Mao, Pan; Wang, Hung-Ta; Yang, Peidong

2017-10-17

The present invention provides for a structure comprising a plurality of emitters, wherein a first nozzle of a first emitter and a second nozzle of a second emitter emit in two directions that are not or essentially not in the same direction; wherein the walls of the nozzles and the emitters form a monolithic whole. The present invention also provides for a structure comprising an emitter with a sharpened end from which the emitter emits; wherein the emitters forms a monolithic whole. The present invention also provides for a fully integrated separation of proteins and small molecules on a silicon chip before the electrospray mass spectrometry analysis.

Hybrid emitter all back contact solar cell

Science.gov (United States)

Loscutoff, Paul; Rim, Seung

2016-04-12

An all back contact solar cell has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. The other emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The solar cell includes contact holes that allow metal contacts to connect to corresponding emitters.

Smith-Purcell experiment utilizing a field-emitter array cathode: measurements of radiation

International Nuclear Information System (INIS)

Ishizuka, H.; Kawamura, Y.; Yokoo, K.; Shimawaki, H.; Hosono, A.

2001-01-01

Smith-Purcell (SP) radiation at wavelengths of 350-750 nm was produced in a tabletop experiment using a field-emitter array (FEA) cathode. The electron gun was 5 cm long, and a 25 mmx25 mm holographic replica grating was placed behind the slit provided in the anode. A regulated DC power supply accelerated electron beams in excess of 10 μA up to 45 keV, while a small Van de Graaff generator accelerated smaller currents to higher energies. The grating had a 0.556 μm period, 30 deg. blaze and a 0.2 μm thick aluminum coating. Spectral characteristics of the radiation were measured both manually and automatically; in the latter case, the spectrometer was driven by a stepping motor to scan the wavelength, and AD-converted signals from a photomultiplier tube were processed by a personal computer. The measurement, made at 80 deg. relative to the electron beam, showed good agreement with theoretical wavelengths of the SP radiation. Diffraction orders were -2 and -3 for beam energies higher than 45 keV, -3 to -5 at 15-25 keV, and -2 to -4 in between. The experiment has thus provided evidence for the practical applicability of FEAs to compact radiation sources

Anthropogenic Methane Emissions in California's San Joaquin Valley: Characterizing Large Point Source Emitters

Science.gov (United States)

Hopkins, F. M.; Duren, R. M.; Miller, C. E.; Aubrey, A. D.; Falk, M.; Holland, L.; Hook, S. J.; Hulley, G. C.; Johnson, W. R.; Kuai, L.; Kuwayama, T.; Lin, J. C.; Thorpe, A. K.; Worden, J. R.; Lauvaux, T.; Jeong, S.; Fischer, M. L.

2015-12-01

Methane is an important atmospheric pollutant that contributes to global warming and tropospheric ozone production. Methane mitigation could reduce near term climate change and improve air quality, but is hindered by a lack of knowledge of anthropogenic methane sources. Recent work has shown that methane emissions are not evenly distributed in space, or across emission sources, suggesting that a large fraction of anthropogenic methane comes from a few "super-emitters." We studied the distribution of super-emitters in California's southern San Joaquin Valley, where elevated levels of atmospheric CH4 have also been observed from space. Here, we define super-emitters as methane plumes that could be reliably detected (i.e., plume observed more than once in the same location) under varying wind conditions by airborne thermal infrared remote sensing. The detection limit for this technique was determined to be 4.5 kg CH4 h-1 by a controlled release experiment, corresponding to column methane enhancement at the point of emissions greater than 20% above local background levels. We surveyed a major oil production field, and an area with a high concentration of large dairies using a variety of airborne and ground-based measurements. Repeated airborne surveys (n=4) with the Hyperspectral Thermal Emission Spectrometer revealed 28 persistent methane plumes emanating from oil field infrastructure, including tanks, wells, and processing facilities. The likelihood that a given source type was a super-emitter varied from roughly 1/3 for processing facilities to 1/3000 for oil wells. 11 persistent plumes were detected in the dairy area, and all were associated with wet manure management. The majority (11/14) of manure lagoons in the study area were super-emitters. Comparing to a California methane emissions inventory for the surveyed areas, we estimate that super-emitters comprise a minimum of 9% of inventoried dairy emissions, and 13% of inventoried oil emissions in this region.

On the preservation of single- and multi-bunch emittance in linear accelerators

International Nuclear Information System (INIS)

Drevlak, M.

1995-11-01

This document is concentrated on the investigation of the dynamics of a particle beam in a linear accelerator. We numerically simulate a number of effects and evaluate the severity of their impact on the beam. Furthermore, we examine the applicability of several correction techniques aiming at the suppression or correction of the effects diluting the beam emittance. First, there is the issue of single-bunch dynamics : we see that wake field effects and dispersive errors can cause a significant emittance growth. Secondly, long range dipole wakes and dispersive effects arising from the energy spread between different bunches will cause relative offsets between the individual bunches and likewise result in emittance growth. Finally, we observe interactions between the single-bunch and multi-bunch dynamics in a bunch train, which further aggravate these effects. The corrective measures against emittance growth are first tested with respect to individual effects relating to issues of single- or multi-bunch dynamics. Later, these different correction techniques are joined to one machine tuning procedure that will be applied in order to achieve good emittance preservation for operation of the accelerator with a full beam consisting of the full number of bunches. The performance of this procedure is tested in simulations of the combined single- and multi-bunch dynamics. Finally, tolerances on the machine alignment as well as machine and beam parameters are established. (orig.)

Hydraulic performance evaluation of pressure compensating (pc) emitters and micro-tubing for drip irrigation system

International Nuclear Information System (INIS)

Mangrio, A.G.; Asif, M.; Jahangir, I.

2013-01-01

Drip irrigation system is necessary for those areas, where the water scarcity issues are present. The present study was conducted at the field station of Climate Change, Alternate Energy and Water Resources Institute (CAEWRI), National Agricultural Research Center (NARC), Islamabad, during 2013, regarding drip irrigation system. Drip irrigation system depends on uniform emitter application flow. All the emitters were tested and replicated thrice at pressure head (34 to 207Kpa) with an increment of 34 Kpa. The minimum and maximum discharges were 1.32 - 3.52, 3.36 - 5.42, and 43.22 - 100.99 Lph, with an average of 2.42, 4.63 and 73.66 Lph, for Bow Smith, RIS and Micro-tubing, respectively. It indicates that more than 90% of emission uniformity (EU) and uniformity coefficient (CU) for all Emitters, which shows excellent water application with least standard deviation, ranging 0.12 to 2.37, throughout the operating pressure heads in all emitters. An average coefficient of variation (CV) of all emitters were behaving less than 0.07, indicating an excellent class at all operating pressure heads between 34 to 207 Kpa. Moreover, the relationship of discharge and pressure of emitters indicates that discharge increased with the increase of pressure head. The Q-H curve plays key role in the selection of emitters. (author)

2-D emittance equation with acceleration and compression

International Nuclear Information System (INIS)

Hahn, K.D.; Smith, L.

1988-10-01

Since both acceleration and compression are required for an Inertial Fusion Driver, the understanding of their effect on the beam quality, emittance, is important. This report attempts to generalize the usual emittance formula for the drifting beam to include these effects. The derivation of the 2-D emittance equation is carried out and a comparison with the particle code results is given. The 2-D emittance at a given axial location is reasonable to consider for a long beam, particularly with velocity tilt; transverse emittance averaged over the entire bunch is not a useful quantity. 6 refs., 2 figs., 1 tab

Emittance growth in rf linacs

International Nuclear Information System (INIS)

Jameson, R.A.

1979-01-01

As the space-charge limit is approached, the current that can be accelerated in an rf linac and the output emittance that can be expected are discussed. The role of the envelope equations to estimate limits is outlined. The results of numerical experiments to explore general properties of emittance growth are given

Dynamical theory of single-photon transport in a one-dimensional waveguide coupled to identical and nonidentical emitters

Science.gov (United States)

Liao, Zeyang; Nha, Hyunchul; Zubairy, M. Suhail

2016-11-01

We develop a general dynamical theory for studying a single-photon transport in a one-dimensional (1D) waveguide coupled to multiple emitters which can be either identical or nonidentical. In this theory, both the effects of the waveguide and non-waveguide vacuum modes are included. This theory enables us to investigate the propagation of an emitter excitation or an arbitrary single-photon pulse along an array of emitters coupled to a 1D waveguide. The dipole-dipole interaction induced by the non-waveguide modes, which is usually neglected in the literature, can significantly modify the dynamics of the emitter system as well as the characteristics of the output field if the emitter separation is much smaller than the resonance wavelength. Nonidentical emitters can also strongly couple to each other if their energy difference is less than or of the order of the dipole-dipole energy shift. Interestingly, if their energy difference is close but nonzero, a very narrow transparency window around the resonance frequency can appear which does not occur for identical emitters. This phenomenon may find important applications in quantum waveguide devices such as optical switches and ultranarrow single-photon frequency comb generator.

Production of alpha emitters for therapy

International Nuclear Information System (INIS)

Vucina, J.; Orlic, M.; Lukic, D.

2006-01-01

The basis for the introduction of alpha emitters into nuclear medical practice are their radiobiological properties. High LET values and short ranges in biological tissues are advantageous in comparison with nowadays most often used beta emitters, primarily 90 Y and 131 I. Given are the most important criteria for the introduction of a given radionuclide in the routine use. Shown are the procedures for the production of the most important alpha emitters 211 At, 212 Bi and 213 Bi. (author)

Minimum emittance in TBA and MBA lattices

Science.gov (United States)

Xu, Gang; Peng, Yue-Mei

2015-03-01

For reaching a small emittance in a modern light source, triple bend achromats (TBA), theoretical minimum emittance (TME) and even multiple bend achromats (MBA) have been considered. This paper derived the necessary condition for achieving minimum emittance in TBA and MBA theoretically, where the bending angle of inner dipoles has a factor of 31/3 bigger than that of the outer dipoles. Here, we also calculated the conditions attaining the minimum emittance of TBA related to phase advance in some special cases with a pure mathematics method. These results may give some directions on lattice design.

Minimum emittance in TBA and MBA lattices

International Nuclear Information System (INIS)

Xu Gang; Peng Yuemei

2015-01-01

For reaching a small emittance in a modern light source, triple bend achromats (TBA), theoretical minimum emittance (TME) and even multiple bend achromats (MBA) have been considered. This paper derived the necessary condition for achieving minimum emittance in TBA and MBA theoretically, where the bending angle of inner dipoles has a factor of 3 1/3 bigger than that of the outer dipoles. Here, we also calculated the conditions attaining the minimum emittance of TBA related to phase advance in some special cases with a pure mathematics method. These results may give some directions on lattice design. (authors)

Dielectric optical antenna thermal emitters and metamaterials

Science.gov (United States)

Schuller, Jonathan Aaron

Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this thesis, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial. We further show that these particles can serve as "broadcasting" antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas.

All-optical control and super-resolution imaging of quantum emitters in layered materials.

Science.gov (United States)

Kianinia, Mehran; Bradac, Carlo; Sontheimer, Bernd; Wang, Fan; Tran, Toan Trong; Nguyen, Minh; Kim, Sejeong; Xu, Zai-Quan; Jin, Dayong; Schell, Andreas W; Lobo, Charlene J; Aharonovich, Igor; Toth, Milos

2018-02-28

Layered van der Waals materials are emerging as compelling two-dimensional platforms for nanophotonics, polaritonics, valleytronics and spintronics, and have the potential to transform applications in sensing, imaging and quantum information processing. Among these, hexagonal boron nitride (hBN) is known to host ultra-bright, room-temperature quantum emitters, whose nature is yet to be fully understood. Here we present a set of measurements that give unique insight into the photophysical properties and level structure of hBN quantum emitters. Specifically, we report the existence of a class of hBN quantum emitters with a fast-decaying intermediate and a long-lived metastable state accessible from the first excited electronic state. Furthermore, by means of a two-laser repumping scheme, we show an enhanced photoluminescence and emission intensity, which can be utilized to realize a new modality of far-field super-resolution imaging. Our findings expand current understanding of quantum emitters in hBN and show new potential ways of harnessing their nonlinear optical properties in sub-diffraction nanoscopy.

Cancer from internal emitters

International Nuclear Information System (INIS)

Boecker, B.B.; Griffith, W.C. Jr.

1995-01-01

Irradiation from internal emitters, or internally deposited radionuclides, is an important component of radiation exposures encountered in the workplace, home, or general environment. Long-term studies of human populations exposed to various internal emitters by different routes of exposure are producing critical information for the protection of workers and members of the general public. The purpose of this report is to examine recent developments and discuss their potential importance for understanding lifetime cancer risks from internal emitters. The major populations of persons being studied for lifetime health effects from internally deposited radionuclides are well known: Lung cancer in underground miners who inhaled Rn progeny, liver cancer from persons injected with the Th-containing radiographic contrast medium Thorotrast, bone cancer from occupational or medical intakes of 226 Ra or medical injections of 224 Ra, and thyroid cancer from exposures to iodine radionuclides in the environment or for medical purposes

Development of Emittance Analysis Software for Ion Beam Characterization

International Nuclear Information System (INIS)

Padilla, M.J.; Liu, Yuan

2007-01-01

Transverse beam emittance is a crucial property of charged particle beams that describes their angular and spatial spread. It is a figure of merit frequently used to determine the quality of ion beams, the compatibility of an ion beam with a given beam transport system, and the ability to suppress neighboring isotopes at on-line mass separator facilities. Generally, a high-quality beam is characterized by a small emittance. In order to determine and improve the quality of ion beams used at the Holifield Radioactive Ion Beam Facility (HRIBF) for nuclear physics and nuclear astrophysics research, the emittances of the ion beams are measured at the off-line Ion Source Test Facilities. In this project, emittance analysis software was developed to perform various data processing tasks for noise reduction, to evaluate root-mean-square emittance, Twiss parameters, and area emittance of different beam fractions. The software also provides 2D and 3D graphical views of the emittance data, beam profiles, emittance contours, and RMS. Noise exclusion is essential for accurate determination of beam emittance values. A Self-Consistent, Unbiased Elliptical Exclusion (SCUBEEx) method is employed. Numerical data analysis techniques such as interpolation and nonlinear fitting are also incorporated into the software. The software will provide a simplified, fast tool for comprehensive emittance analysis. The main functions of the software package have been completed. In preliminary tests with experimental emittance data, the analysis results using the software were shown to be accurate

DEVELOPMENT OF EMITTANCE ANALYSIS SOFTWARE FOR ION BEAM CHARACTERIZATION

Energy Technology Data Exchange (ETDEWEB)

Padilla, M. J.; Liu, Y.

2007-01-01

Transverse beam emittance is a crucial property of charged particle beams that describes their angular and spatial spread. It is a fi gure of merit frequently used to determine the quality of ion beams, the compatibility of an ion beam with a given beam transport system, and the ability to suppress neighboring isotopes at on-line mass separator facilities. Generally a high quality beam is characterized by a small emittance. In order to determine and improve the quality of ion beams used at the Holifi eld Radioactive Ion beam Facility (HRIBF) for nuclear physics and nuclear astrophysics research, the emittances of the ion beams are measured at the off-line Ion Source Test Facilities. In this project, emittance analysis software was developed to perform various data processing tasks for noise reduction, to evaluate root-mean-square emittance, Twiss parameters, and area emittance of different beam fractions. The software also provides 2D and 3D graphical views of the emittance data, beam profi les, emittance contours, and RMS. Noise exclusion is essential for accurate determination of beam emittance values. A Self-Consistent, Unbiased Elliptical Exclusion (SCUBEEx) method is employed. Numerical data analysis techniques such as interpolation and nonlinear fi tting are also incorporated into the software. The software will provide a simplifi ed, fast tool for comprehensive emittance analysis. The main functions of the software package have been completed. In preliminary tests with experimental emittance data, the analysis results using the software were shown to be accurate.

Mathematical design of a novel input/instruction device using a moving acoustic emitter

Science.gov (United States)

Wang, Xianchao; Guo, Yukun; Li, Jingzhi; Liu, Hongyu

2017-10-01

This paper is concerned with the mathematical design of a novel input/instruction device using a moving emitter. The emitter acts as a point source and can be installed on a digital pen or worn on the finger of the human being who desires to interact/communicate with the computer. The input/instruction can be recognized by identifying the moving trajectory of the emitter performed by the human being from the collected wave field data. The identification process is modelled as an inverse source problem where one intends to identify the trajectory of a moving point source. There are several salient features of our study which distinguish our result from the existing ones in the literature. First, the point source is moving in an inhomogeneous background medium, which models the human body. Second, the dynamical wave field data are collected in a limited aperture. Third, the reconstruction method is independent of the background medium, and it is totally direct without any matrix inversion. Hence, it is efficient and robust with respect to the measurement noise. Both theoretical justifications and computational experiments are presented to verify our novel findings.

Dielectric Optical Antenna Emitters and Metamaterials

Science.gov (United States)

Schuller, Jon

2009-03-01

Optical antennas are critical components in nanophotonics research due to their unparalleled ability to concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas from wavelength-size metallic structures. However, recent research has begun to exploit the scattering resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, and metamaterials. In this talk, we experimentally and theoretically characterize the resonant modes of subwavelength rod-shaped dielectric particles and demonstrate their use in negative index metamaterials and novel infrared light emitters. At mid-infrared frequencies, Silicon Carbide (SiC) is an ideal system for studying the behavior of dielectric optical antennas. At frequencies below the TO phonon resonance, SiC behaves like a dielectric with very large refractive index. Using infrared spectroscopy and analytical Mie calculations we show that individual rod-shaped SiC particles exhibit a multitude of resonant modes. Detailed investigations of these SiC optical antennas reveal a wealth of new physics and applications. We discuss the distinct electromagnetic field profile for each mode, and demonstrate that two of the dielectric-type Mie resonances can be combined in a particle array to form a negative index metamaterial [1]. We further show that these particles can serve as ``broadcasting'' antennas. Using a custom-built thermal emission microscope we collect emissivity spectra from single SiC particles at elevated temperatures, highlighting their use as subwavelength resonant light emitters. Finally, we derive and verify a variety of general analytical results applicable to all cylindrical dielectric antennas and discuss extensions of the demonstrated concepts to different materials systems and frequency regimes. [1] J.A. Schuller, et al., Phys. Rev. Lett. 99, 107401 (2007)

Quantum efficiency and thermal emittance of metal photocathodes

Directory of Open Access Journals (Sweden)

David H. Dowell

2009-07-01

Full Text Available Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths with major advances occurring since the invention of the photocathode gun and the realization of emittance compensation. These state-of-the-art electron beams are now becoming limited by the intrinsic thermal emittance of the cathode. In both dc and rf photocathode guns details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance for metal cathodes using the Fermi-Dirac model for the electron distribution. We use a consistent theory to derive the quantum efficiency and thermal emittance, and compare our results to those of others.

Spatially explicit analysis of field inventories for national forest carbon monitoring

Directory of Open Access Journals (Sweden)

David C. Marvin

2016-06-01

Full Text Available Abstract Background Tropical forests provide a crucial carbon sink for a sizable portion of annual global CO2 emissions. Policies that incentivize tropical forest conservation by monetizing forest carbon ultimately depend on accurate estimates of national carbon stocks, which are often based on field inventory sampling. As an exercise to understand the limitations of field inventory sampling, we tested whether two common field-plot sampling approaches could accurately estimate carbon stocks across approximately 76 million ha of Perúvian forests. A 1-ha resolution LiDAR-based map of carbon stocks was used as a model of the country’s carbon geography. Results Both field inventory sampling approaches worked well in estimating total national carbon stocks, almost always falling within 10 % of the model national total. However, the sampling approaches were unable to produce accurate spatially-explicit estimates of the carbon geography of Perú, with estimates falling within 10 % of the model carbon geography across no more than 44 % of the country. We did not find any associations between carbon stock errors from the field plot estimates and six different environmental variables. Conclusions Field inventory plot sampling does not provide accurate carbon geography for a tropical country with wide ranging environmental gradients such as Perú. The lack of association between estimated carbon errors and environmental variables suggests field inventory sampling results from other nations would not differ from those reported here. Tropical forest nations should understand the risks associated with primarily field-based sampling approaches, and consider alternatives leading to more effective forest conservation and climate change mitigation.

Beam phase space and emittance

International Nuclear Information System (INIS)

Buon, J.

1990-12-01

The classical and elementary results for canonical phase space, the Liouville theorem and the beam emittance are reviewed. Then, the importance of phase portraits to obtain a geometrical description of motion is emphasized, with examples in accelerator physics. Finally, a statistical point of view is used to define beam emittance, to study its law of approximate conservation and to treat two particular examples

Internal emitter research and standard setting

International Nuclear Information System (INIS)

Stannard, J.N.

1981-01-01

The history of the use of data from internal emitter research in the derivation of safety standards is reviewed. At first, observed biological effects were correlated with body burdens or exposure levels. This direct approach is illustrated by detailed accounts of the cases of uranium and plutonium. In the 1950's, when it was decided to provide standards for over 200 isotopes, the direct approach was replaced by a system of calculations. This necessitated changes in internal emitter research programs to provide metabolic data, and the development of models such as Reference Man and the Lung and Gastrointestinal Tract models. The continuing contribution of internal emitter research to standard setting can be seen in the references quoted in the metabolic data section of the new ICRP report (ICRP Publication 30). Present trends suggest a possible return to the direct use of internal emitter effects data for obtaining risk estimates. (U.K.)

A comparative study of the plasmon effect in nanoelectrode THz emitters: Pulse vs. continuous-wave radiation

Energy Technology Data Exchange (ETDEWEB)

Moon, Kiwon; Lee, Eui Su; Lee, Il-Min; Han, Sang-Pil; Kim, Hyun-Soo; Park, Kyung Hyun, E-mail: khp@etri.re.kr [Terahertz Basic Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Choi, Jeongyong [Metal-Insulator Transition Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of); Lee, Donghun [Optical Internet Components Research Section, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700 (Korea, Republic of)

2016-08-15

Plasmonic field enhancement in terahertz (THz) generation is one of the recently arisen techniques in the THz field that has attracted considerable interest. However, the reported levels of enhancement of THz output power in the literature are significantly different from each other, from less than two times to about two orders of magnitude of enhancement in power, which implies the existence of other major limiting factors yet to be revealed. In this work, the contribution of the plasmonic effect to the power enhancement of THz emitters is revisited. We show that the carrier collection efficiency in a THz emitter with plasmonic nanostructures is more critical to the device performance than the plasmonic field enhancement itself. The strong reverse fields induced by the highly localized plasmonic carriers in the vicinity of the nanoelectrodes screen the carrier collections and seriously limit the power enhancement. This is supported by our experimental observations of the significantly enhanced power in a plasmonic nanoelectrode THz emitter in continuous-wave radiation mode, while the same device has limited enhancement with pulsed radiation. We hope that our study may provide an intuitive but practical guideline in adopting plasmonic nanostructures with an aim of enhancing the efficiency of optoelectronic devices.

Cooling mechanical motion via vacuum effect of an ensemble of quantum emitters.

Science.gov (United States)

Nie, Wenjie; Chen, Aixi; Lan, Yueheng

2015-11-30

We design a hybrid optomechanical setup, in which an ensemble of quantum emitters is coupled with a movable mirror through vacuum interaction. The optical cavity is driven along with the quantum emitters and therefore the coupling between the cavity field and the ensemble determines the dynamics of the coupled system. In particular, we investigated the influence of the vacuum coupling strength on the effective frequency and the effective damping rate of the movable mirror, which shows that the vacuum interaction enhances greatly the effective damping rate. Further, the cooling characteristics of the mechanical resonator is analyzed in detail by counting the effective phonon number in the mirror's motion. It is found that the ground-state cooling of the mechanical motion can be approached in the bad cavity limit when the vacuum coupling is included. The dependence of the cooling of the mechanical motion on the parameters of the cavity and the quantum emitter is investigated in detail numerically.

Plasmon-Assisted Selective and Super-Resolving Excitation of Individual Quantum Emitters on a Metal Nanowire.

Science.gov (United States)

Li, Qiang; Pan, Deng; Wei, Hong; Xu, Hongxing

2018-03-14

Hybrid systems composed of multiple quantum emitters coupled with plasmonic waveguides are promising building blocks for future integrated quantum nanophotonic circuits. The techniques that can super-resolve and selectively excite contiguous quantum emitters in a diffraction-limited area are of great importance for studying the plasmon-mediated interaction between quantum emitters and manipulating the single plasmon generation and propagation in plasmonic circuits. Here we show that multiple quantum dots coupled with a silver nanowire can be controllably excited by tuning the interference field of surface plasmons on the nanowire. Because of the period of the interference pattern is much smaller than the diffraction limit, we demonstrate the selective excitation of two quantum dots separated by a distance as short as 100 nm. We also numerically demonstrate a new kind of super-resolution imaging method that combines the tunable surface plasmon interference pattern on the NW with the structured illumination microscopy technique. Our work provides a novel high-resolution optical excitation and imaging method for the coupled systems of multiple quantum emitters and plasmonic waveguides, which adds a new tool for studying and manipulating single quantum emitters and single plasmons for quantum plasmonic circuitry applications.

Electrophoretic deposition and field emission properties of patterned carbon nanotubes

International Nuclear Information System (INIS)

Zhao Haifeng; Song Hang; Li Zhiming; Yuan Guang; Jin Yixin

2005-01-01

Patterned carbon nanotubes on silicon substrates were obtained using electrophoretic method. The carbon nanotubes migrated towards the patterned silicon electrode in the electrophoresis suspension under the applied voltage. The carbon nanotubes arrays adhered well on the silicon substrates. The surface images of carbon nanotubes were observed by scanning electron microscopy. The field emission properties of the patterned carbon nanotubes were tested in a diode structure under a vacuum pressure below 5 x 10 -4 Pa. The measured emission area was about 1.0 mm 2 . The emission current density up to 30 mA/cm 2 at an electric field of 8 V/μm has been obtained. The deposition of patterned carbon nanotubes by electrophoresis is an alternative method to prepare field emission arrays

Operating single quantum emitters with a compact Stirling cryocooler.

Science.gov (United States)

Schlehahn, A; Krüger, L; Gschrey, M; Schulze, J-H; Rodt, S; Strittmatter, A; Heindel, T; Reitzenstein, S

2015-01-01

The development of an easy-to-operate light source emitting single photons has become a major driving force in the emerging field of quantum information technology. Here, we report on the application of a compact and user-friendly Stirling cryocooler in the field of nanophotonics. The Stirling cryocooler is used to operate a single quantum emitter constituted of a semiconductor quantum dot (QD) at a base temperature below 30 K. Proper vibration decoupling of the cryocooler and its surrounding enables free-space micro-photoluminescence spectroscopy to identify and analyze different charge-carrier states within a single quantum dot. As an exemplary application in quantum optics, we perform a Hanbury-Brown and Twiss experiment demonstrating a strong suppression of multi-photon emission events with g((2))(0) Stirling-cooled single quantum emitter under continuous wave excitation. Comparative experiments performed on the same quantum dot in a liquid helium (LHe)-flow cryostat show almost identical values of g((2))(0) for both configurations at a given temperature. The results of this proof of principle experiment demonstrate that low-vibration Stirling cryocoolers that have so far been considered exotic to the field of nanophotonics are an attractive alternative to expensive closed-cycle cryostats or LHe-flow cryostats, which could pave the way for the development of high-quality table-top non-classical light sources.

Operating single quantum emitters with a compact Stirling cryocooler

Energy Technology Data Exchange (ETDEWEB)

Schlehahn, A.; Krüger, L.; Gschrey, M.; Schulze, J.-H.; Rodt, S.; Strittmatter, A.; Heindel, T., E-mail: tobias.heindel@tu-berlin.de; Reitzenstein, S. [Institute of Solid State Physics, Technische Universität Berlin, 10623 Berlin (Germany)

2015-01-15

The development of an easy-to-operate light source emitting single photons has become a major driving force in the emerging field of quantum information technology. Here, we report on the application of a compact and user-friendly Stirling cryocooler in the field of nanophotonics. The Stirling cryocooler is used to operate a single quantum emitter constituted of a semiconductor quantum dot (QD) at a base temperature below 30 K. Proper vibration decoupling of the cryocooler and its surrounding enables free-space micro-photoluminescence spectroscopy to identify and analyze different charge-carrier states within a single quantum dot. As an exemplary application in quantum optics, we perform a Hanbury-Brown and Twiss experiment demonstrating a strong suppression of multi-photon emission events with g{sup (2)}(0) < 0.04 from this Stirling-cooled single quantum emitter under continuous wave excitation. Comparative experiments performed on the same quantum dot in a liquid helium (LHe)-flow cryostat show almost identical values of g{sup (2)}(0) for both configurations at a given temperature. The results of this proof of principle experiment demonstrate that low-vibration Stirling cryocoolers that have so far been considered exotic to the field of nanophotonics are an attractive alternative to expensive closed-cycle cryostats or LHe-flow cryostats, which could pave the way for the development of high-quality table-top non-classical light sources.

A low emittance configuration for spear

International Nuclear Information System (INIS)

Blumberg, L.N.; Cerino, J.; Harris, J.; Hettel, R.; Hofmann, A.; Liu, R.Z.; Stego, R.; Wiedemann, H.; Winick, H.

1985-01-01

The quality of synchrotron radiation beams from SPEAR, in particular the brilliance of undulator radiation, can be improved significantly by reducing the emittance of the stored electron beam. A reduction of the horizontal emittance by a factor of 3.5 to a value of 130 nanometer-radians (nm-r) at 3 GeV has been achieved by using stronger focussing, mainly in the horizontal plane. The low emittance configuration also reduces the dispersion and vertical beta functions in the straight sections, making them more suitable for wigglers. The higher betatron tunes lead to a larger phase advance between the two kickers, which has to be corrected during injection by shunting current from some quadrupoles. The configuration was optimized within SPEAR hardware limitations and tested for dynamic aperture with the tracking program PATRICIA. After implementation of this scheme, beam was successfully injected and accumulated. The measured emittance of the stored beam was in agreement with calculations. Presently the configuration is being made operational

Emittance growth rates for displaced beams

International Nuclear Information System (INIS)

Anderson, O.A.

1993-05-01

Emittance growth rates have been previously analyzed for nonuniform beams in linear channels and for initially uniform mismatched beams in nonlinear channels. These studies were for centered beams. Additional emittance growth can arise in cases where the beam is initially displaced. The purpose of this study is to obtain growth rates for displaced beams. This work differs from studies involving random displacement of electrodes. Our analysis assumes instead that the focusing system is perfectly aligned but that the beam is initially displaced with respect to the equilibrium axis. If the focusing force is slightly nonlinear, we find a gradual transfer of the potential energy of beam displacement into kinetic energy associated with emittance growth. We present explicit results for the emittance growth distance as a function of the nonlinearity of the channel. These results will have practical importance for designers of accelerators and transport systems when setting realistic tolerances for initial beam alignment. These tolerances will depend on the nonlinearity and the length of the system

Emittance variations in current-amplifying ion induction linacs

International Nuclear Information System (INIS)

Fessenden, T.J.

1991-01-01

Since 1985 the Heavy Ion Fusion Accelerator Research program at the Lawrence Berkeley Laboratory has been studying current amplification and emittance variations in MBE-4, a four-cesium-beam induction linac. This experiment models much of the accelerator physics of the electrostatically focused section of a fusion driver. Four space-charge dominated Cs + beams, initially about one meter in length at currents of 5-10 mA, are focused by electrostatic quadrupoles and accelerated in parallel from approximately 200 keV up to one MeV by 24 accelerating gaps. Final currents of 20-40 mA per beam are typical. Recent experiments with extremely low emittance beams (var-epsilon n =0.03 mm-mRad) have investigated variations of transverse and longitudinal normalized emittance for drifting and accelerating beams. These very strongly tune-depressed beams (σ 0 =72 degree, σ∼6 degree) are difficult to match to the accelerator so as to avoid emittance growth during acceleration. During transport strong emittance fluctuations are observed in good qualitative agreement with simulations. Warmer beams with less tune depression exhibit little to no emittance growth, show smaller emittance fluctuations, and are much easier to match. A summary of findings from the MBE-4 studies is presented

Emittance variations in current-amplifying ion induction linacs

International Nuclear Information System (INIS)

Fessenden, T.J.

1991-04-01

Since 1985 the Heavy Ion Fusion Accelerator Research program at the Lawrence Berkeley Laboratory has been studying current amplification and emittance variations in MBE-4, a four-cesium-beam induction linac. This experiment models much of the accelerator physics of the electrostatically focused section of a fusion driver. Four space-charge dominated Cs + beams, initially about one meter in length at currents of 5--10 mA, are focused by electrostatic quadrupoles and accelerated in parallel from approximately 200 keV up to one MeV by 24 accelerating gaps. Final currents of 20--40 mA per beam are typical. Recent experiments with extremely low emittance beams (ε n = 0.03 mm-mRad) have investigated variations of transverse and longitudinal normalized emittance for drifting and accelerating beams. These very strongly tune-depressed beams (σ o = 72 degrees, σ∼6 degree) are difficult to match the accelerator so as to avoid emittance growth during acceleration. During transport strong emittance fluctuations are observed in good qualitative agreement with simulations. Warmer beams with less tune depression exhibit little to no emittance growth, show smaller emittance fluctuations, and are much easier to match. A summary of findings from the MBE-4 studies is presented. 12 refs., 8 figs

Gamma flux responsive self-powered detector with a tubular emitter

International Nuclear Information System (INIS)

Goldstein, N.P.; Todt, W.H.

1982-01-01

A gamma-sensitive flux detector comprises tubular emitter, an insulating core within the emitter and an insulating layer about the emitter, and a tubular conductive collector electrode about the insulating layer. The emitter material may be platinum, lead, bismuth, tantalum, tungsten; platinum preferred

Computer simulation of the emittance growth due to noise in large hadron colliders

International Nuclear Information System (INIS)

Lebedev, V.

1993-03-01

The problem of emittance growth due to random fluctuations of the magnetic field in a hadron collider is considered. The results of computer simulations are compared with the analytical theory developed earlier. A good agreement was found between the analytical theory predictions and the computer simulations for the collider tunes located far enough from high order betatron resonances. The dependencies of the emittance growth rate on noise spectral density, beam separation at the Interaction Point (IP) and value of beam separation at long range collisions are studied. The results are applicable to the Superconducting Super Collider (SSC)

Realisation of a ultra-high vacuum system and technique development of microscopical emitters preparation in silicium. First measurements of field emission current and field photoemission

International Nuclear Information System (INIS)

El Manouni, A.

1990-12-01

The development of research in the domain of photocathode (electron sources) illuminated by laser light to produce intense multiple bunches of electrons in short time is needed by many applications as linear collider e + e - , free electron laser, lasertron, etc... In this way, after a study of field emission, of photoemission and of photofield emission, we prepared microscopical emitters in silicium heavy and weakly doped a boron using a technique of microlithography. Then, we realized a system of ultra-high vacuum of studying property of emission from photocathodes realized. The experiment results obtained in field emission and photofield emission have shown that a behaviour unexpected for P-silicium tips array compared to P + -silicon tips array. With P-type silicon, a quantum yield of 21 percent has been measured for laser power of 140 mW and for applied field of 1.125 x 10 7 V/m and an instantaneous response to laser light beam has been observed. It has been noted that presence of oxyde at the surface of photocathode limits extensively the emission current. The fluctuations of emission current are due to quality of vacuum [fr

A combined emitter threat assessment method based on ICW-RCM

Science.gov (United States)

Zhang, Ying; Wang, Hongwei; Guo, Xiaotao; Wang, Yubing

2017-08-01

Considering that the tradition al emitter threat assessment methods are difficult to intuitively reflect the degree of target threaten and the deficiency of real-time and complexity, on the basis of radar chart method(RCM), an algorithm of emitter combined threat assessment based on ICW-RCM (improved combination weighting method, ICW) is proposed. The coarse sorting is integrated with fine sorting in emitter combined threat assessment, sequencing the emitter threat level roughly accordance to radar operation mode, and reducing task priority of the low-threat emitter; On the basis of ICW-RCM, sequencing the same radar operation mode emitter roughly, finally, obtain the results of emitter threat assessment through coarse and fine sorting. Simulation analyses show the correctness and effectiveness of this algorithm. Comparing with classical method of emitter threat assessment based on CW-RCM, the algorithm is visual in image and can work quickly with lower complexity.

Measurements of Thermal Emittance for Cesium Telluride Photocathodes at PITZ

CERN Document Server

Miltchev, V; Grabosch, H J; Han, J H; Krasilnikov, M; Oppelt, A; Petrosian, B; Staykov, L; Stephan, F

2005-01-01

The thermal emittance determines the lower emittance limit and its measurement is of high importance to understand the ultimate injector performance. In this contribution we present results of thermal emittance measurements under rf operation conditions for various Cs2Te cathodes and different accelerating gradients. Measurements of thermal emittance scaling with the cathode laser spot size are presented and analysed. The significance of the Schottky effect in the emittance formation process is discussed.

Electron emitter pulsed-type cylindrical IEC

International Nuclear Information System (INIS)

Miley, G.H.; Gu, Y.; Stubbers, R.; Zich, R.; Anderl, R.; Hartwell, J.

1997-01-01

A cylindrical version of the single grid Inertial Electrostatic Confinement (IEC) device (termed the C-device) has been developed for use as a 2.5-MeV D-D fusion neutron source for neutron activation analysis. The C-device employs a hollow-tube type cathode with similar anodes backed up by ''reflector'' dishes. The resulting discharge differs from a conventional hollow cathode discharge, by creating an explicit ion beam which is ''pinched'' in the cathode region. Resulting fusion reactions generate ∼10 6 neutron/s. A pulsed version is under development for applications requiring higher fluxes. Several pulsing techniques are under study, including an electron emitter (e-emitter) assisted discharge in a thorated tungsten wire emitter located behind a slotted area in the reflector dishes. Pulsing is initiated after establishing a low power steady-state discharge by pulsing the e-emitter current using a capacitor switch type circuit. The resulting electron jet, coupled with the discharge by the biased slot array, creates a strong pulse in the pinched ion beam. The pulse length/repetition rate are controlled by the e-emitter pulse circuit. Typical parameters in present studies are ∼30micros, 10Hz and 1-amp ion current. Corresponding neutron measurements are an In-foil type activation counter for time averaged rates. Results for a wide variety of operating conditions are presented

The Quantum Efficiency and Thermal Emittance of Metal Photocathodes

International Nuclear Information System (INIS)

Dowell, D.

2009-01-01

Modern electron beams have demonstrated the brilliance needed to drive free electron lasers at x-ray wavelengths, with the principle improvements occurring since the invention of the photocathode gun. The state-of-the-art normalized emittance electron beams are now becoming limited by the thermal emittance of the cathode. In both DC and RF photocathode guns, details of the cathode emission physics strongly influence the quantum efficiency and the thermal emittance. Therefore improving cathode performance is essential to increasing the brightness of beams. It is especially important to understand the fundamentals of cathode quantum efficiency and thermal emittance. This paper investigates the relationship between the quantum efficiency and the thermal emittance of metal cathodes using the Fermi-Dirac model for the electron distribution. We derive the thermal emittance and its relationship to the quantum efficiency, and compare our results to those of others

Field emission characteristics of vertically aligned carbon nanotubes with honeycomb configuration grown onto glass substrate with titanium coating

Energy Technology Data Exchange (ETDEWEB)

Huang, Yung-Jui [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chang, Hsin-Yueh; Chang, Hsuan-Chen [Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Shih, Yi-Ting; Su, Wei-Jhih [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Ciou, Chen-Hong [Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chen, Yi-Ling [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Honda, Shin-ichi [Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280 (Japan); Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

2014-03-15

Highlights: • We have successfully designed the honeycomb patterns on glass substrate by photolithography technique. • Honeycomb-VACNTs were synthesized successfully onto glass substrate by using thermal CVD and covered different Ti films on VACNTs by e-beam evaporation. • After coating the Ti films, the current density reached 7 mA/cm{sup 2} when the electric field was 2.5 V/μm. • The fluorescence of VACNTs with Ti 15 nm films exhibits the high brightness screen and emission uniformity. -- Abstract: Carbon nanotubes (CNTs) were grown successfully onto a glass substrate using thermal chemical vapor deposition (TCVD) with C{sub 2}H{sub 2} gas at 700 °C. The synthesized CNTs exhibited good crystallinity and a vertically aligned morphology. The vertically aligned CNTs (VACNTs) were patterned with a honeycomb configuration using photolithography and characterized using field emission (FE) applications. Owing to the electric field concentration, the FE current density of VACNTs with honeycomb configuration was higher than that of the un-patterned VACNTs. Ti was coated onto the VACNT surface utilizing the relatively lower work function property to enhance the FE current density. The FE current density reached up to 7.0 mA/cm{sup 2} at an applied electric field of 2.5 V/μm. A fluorescent screen was monitored to demonstrate uniform FE VACNTs with a honeycomb configuration. The designed field emitter provided an admirable example for FE applications.

Recent advances in carbon nanotube-based electronics

International Nuclear Information System (INIS)

Sharma, Prithu; Ahuja, Prerit

2008-01-01

CNT-electronics is a field involving synthesis of carbon nanotubes-based novel electronic circuits, comparable to the size of molecules, the practically fundamental size possible. It has brought a new paradigm in science as it has enabled scientists to increase the device integration density tremendously, hence achieving better efficiency and speed. Here we review the state-of-art current research on the applications of CNTs in electronics and present recent results outlining their potential along with illustrating some current concerns in the research field. Unconventional projects such as CNT-based biological sensors, transistors, field emitters, integrated circuits, etc. are taking CNT-based electronics to its extremes. The field holds a promise for mass production of high speed and efficient electronic devices. However, the chemical complexity, reproducibility and other factors make the field a challenging one, which need to be addressed before the field realizes its true potential

Cooperative spontaneous emission of nano-emitters with inter-emitter coupling in a leaky microcavity

International Nuclear Information System (INIS)

Hong, Suc-Kyoung; Nam, Seog Woo; Yang, Hyung Jin

2015-01-01

We study the spontaneous emission from a few two-level nano-emitters placed in a leaky microcavity with Lorentzian spectral density near a critically damped regime. Collective features of the spontaneous emission are investigated by numerical analysis of the excitation dynamics when initially one nano-emitter is totally excited but we do not know which one. The results show that there are three decay rates in the excitation dynamics, two for simple exponential decays and one for damped oscillatory decay. The excitation dynamics is found to critically depend on the regime of the system. It is shown that the spontaneous emission is enhanced or suppressed depending on whether the system is in the underdamped or overdamped regime, respectively. On the other hand, the cooperative spontaneous emission is suppressed in the underdamped while it is enhanced in the overdamped regime. Furthermore, the effect of the direct inter-emitter coupling on the breaking of the cooperativeness of the spontaneous emission is shown as well. (paper)

Nanodiamond Emitters of Single Photons

Directory of Open Access Journals (Sweden)

Vlasov I.I.

2015-01-01

Full Text Available Luminescence properties of single color centers were studied in nanodiamonds of different origin. It was found that single photon emitters could be realized even in molecularsized diamond (less than 2 nm capable of housing stable luminescent center “silicon-vacancy.” First results on incorporation of single-photon emitters based on luminescent nanodiamonds in plasmonic nanoantennas to enhance the photon count rate and directionality, diminish the fluorescence decay time, and provide polarization selectivity are presented.

Tolerances for the vertical emittance in damping rings

International Nuclear Information System (INIS)

Raubenheimer, T.O.

1991-11-01

Future damping rings for linear colliders will need to have very small vertical emittances. In the limit of low beam current, the vertical emittance is primarily determined by the vertical dispersion and the betatron coupling. In this paper, the contributions to these effects from random misalignments are calculated and tolerances are derived to limit the vertical emittance with a 95% confidence level. 10 refs., 5 figs

Emittance growth of bunched beams in bends

International Nuclear Information System (INIS)

Carlsten, B.E.; Raubenheimer, T.O.

1995-01-01

Talman [Phys. Rev. Lett. 56, 1429 (1986)] has proposed a novel relativistic effect that occurs when a charged particle beam is bent in the magnetic field from an external dipole. The consequence of this effect is that the space-charge forces from the particles do not exhibit the usual inverse-square energy dependence and some part of them are, in fact, independent of energy. This led to speculation that this effect could introduce significant emittance growth for a bending electron beam. Subsequently, it was shown that this effect's influence on the beam's transverse motion is canceled for a dc beam by a potential depression within the beam (to first order in the beam radius divided by the bend radius). In this paper, we extend the analysis to include short bunch lengths (as compared to the beam pipe dimensions) and find that there is no longer the cancellation for forces both transverse to and in the direction of motion. We provide an estimate for the emittance growth as a function of bend angle, beam radius, and current, and for magnetic compression of an electron bunch

Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

NARCIS (Netherlands)

Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

2016-01-01

Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

Test results on two thermionic converters with cermet emitters

International Nuclear Information System (INIS)

Saunders, M.; Danielson, L.; Huffman, F.

1983-01-01

An emitter made of a directionally solidified Mo-Al 2 O 3 , Cr 2 O 3 eutectic was provided by Eindhoven University of Technology in Eindhoven, The Netherlands. Although the high temperature braze cycle used in bonding this electrode to the emitter substrate destroyed its characteristic needle microstructure, the converter gave good performance. Apparently, chemical species evaporated from the emitter onto the collector provided a low collector work function. The resulting low barrier indices suggest that this surface is a promising emitter

Increasing emitter efficiency in 3.3-kV enhanced trench IGBTs for higher short-circuit capability

DEFF Research Database (Denmark)

Reigosa, Paula Diaz; Iannuzzo, Francesco; Rahimo, Munaf

2018-01-01

In this paper, a 3.3-kV Enhanced Trench IGBT has been designed with a high emitter efficiency, for improving its short-circuit robustness. The carrier distribution profile has been shaped in a way that it is possible to increase the electric field at the surface of the IGBT, and thereby, counteract...... the Kirk Effect onset. This design approach is beneficial for mitigating high-frequency oscillations, typically observed in IGBTs under short-circuit conditions. The effectiveness of the proposed design rule is validated by means of mixed-mode device simulations. Then, two IGBTs have been fabricated...... with different emitter efficiencies and tested under short circuit, validating that the high-frequency oscillations can be mitigated, with higher emitter efficiency IGBT designs....

Reducing emissions from deforestation and degradation: What contribution from carbon markets?

OpenAIRE

Bellassen , Valentin; Crassous , R.; Dietzsch , L.; Schwartzman , S.

2008-01-01

Tropical deforestation is responsible for 15-20% of total man-made emissions of greenhouse gases. In December 2007, at the international conference of Bali, the United Nations acknowledged that a viable solution to climate change must include a mechanism to limit deforestation and forest degradation. Today, the most widely used economic tool to reduce emissions is carbon markets: caps on emitters, and trade allowed between emitters and reducers, drive a price signal on carbon and provide ince...

Transverse emittance growth in staged laser-wakefield acceleration

Directory of Open Access Journals (Sweden)

T. Mehrling

2012-11-01

Full Text Available We present a study on the emittance evolution of electron bunches, externally injected into laser-driven plasma waves using the three-dimensional particle-in-cell (PIC code OSIRIS. Results show order-of-magnitude transverse emittance growth during the injection process, if the electron bunch is not matched to its intrinsic betatron motion inside the wakefield. This behavior is supported by analytic theory reproducing the simulation data to a percent level. The length over which the full emittance growth develops is found to be less than or comparable to the typical dimension of a single plasma module in current multistage designs. In addition, the analytic theory enables the quantitative prediction of emittance degradation in two consecutive accelerators coupled by free-drift sections, excluding this as a scheme for effective emittance-growth suppression, and thus suggests the necessity of beam-matching sections between acceleration stages with fundamental implications on the overall design of staged laser-wakefield accelerators.

Emittance measurements in Grumman 1 MeV beamline

International Nuclear Information System (INIS)

Debiak, T.; Gammel, G.; Melnychuk, S.

1992-01-01

The emittance of a 30 keV H - beam has been measured with an Allison type electrostatic analyser at two positions separated by 85 cm along the Grumman 1 MeV beamline LEBT at low currents (about 4 mA, no Cs 2 O additive in the source) and at higher currents (10-15 mA, with Cs 2 O additive in the source). No emittance growth was observed between the two positions, but, at the higher current level, the emittance was about 60% higher than at the low current level (Σ n ,rms = .0045 π cm-mrad vs. 0070 π cm-mrad). Argon was then introduced up to a partial pressure of 4x10 -5 torr, and the emittance decreased back to a range corresponding to that found at the lower currents. However, beam noise was observed at the downstream position, and there is evidence for a small amount of emittance growth (<20%) between the two positions

Transfer mechanisms between emitter molecules for OLED applications

Energy Technology Data Exchange (ETDEWEB)

Steinbacher, Frank [Department of Materials Science VI, University of Erlangen-Nuernberg (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Chiu, Chien-Shu [Department of Electrical Engineering and Information Technology, Technical University of Braunschweig (Germany); Siemens AG, CT MM 1, Erlangen (Germany); Krause, Ralf; Hunze, Arvid [Siemens AG, CT MM 1, Erlangen (Germany); Winnacker, Albrecht [Department of Materials Science VI, University of Erlangen-Nuernberg (Germany)

2009-07-01

Within the last few years white organic light emitting diodes based on small molecules have shown the potential to have a promising future in the field of lighting technology. Nevertheless there is still room for improvement of the overall efficiency and lifetime of white OLEDs. A deeper understanding of the energy transfer mechanisms between different matrix and emitter molecules used in the OLED stack concept can help to optimize the layout and reduce driving voltage thus increasing the power efficiency and color stability of the device. To simplify the complex interactions within a complete white OLED we start out with a basic model system only containing the molecules of interest. This enables us to predict the fundamental concepts causing the behavior of more intricate systems. Using photoluminescence, excitation spectra and time-resolved photoluminescence we investigated the exciton transfer between different dyes for a variety of emitter systems. Our results indicate a dependence of exciton transfer probability on the total concentrations and therefore the distance between the molecules involved.

Emittance Growth during Bunch Compression in the CTF-II

Energy Technology Data Exchange (ETDEWEB)

Raubenheimer, Tor O

1999-02-26

Measurements of the beam emittance during bunch compression in the CLIC Test Facility (CTF-II) are described. The measurements were made with different beam charges and different energy correlations versus the bunch compressor settings which were varied from no compression through the point of full compression and to over-compression. Significant increases in the beam emittance were observed with the maximum emittance occurring near the point of full (maximal) compression. Finally, evaluation of possible emittance dilution mechanisms indicate that coherent synchrotron radiation was the most likely cause.

Electrohydrodynamic emitters of ion beams

International Nuclear Information System (INIS)

Dudnikov, V.G.; Shabalin, A.L.

1990-01-01

Physical processes determining generation of ion beams with high emission current density in electrohydrodynamic emitters are considered. Electrohydrodynamic effects developing in ion emission features and kinetics of ion interaction in beams with high density are discussed. Factors determining the size of the emission zone, emission stability at high and low currents, cluster generation, increase of energy spread and decrease of brightness are analyzed. Problems on practical provision of stable EHD emitter functioning are considered. 94 refs.; 8 figs.; 1 tab

Emittance measurements in low energy ion storage rings

Science.gov (United States)

Hunt, J. R.; Carli, C.; Resta-López, J.; Welsch, C. P.

2018-07-01

The development of the next generation of ultra-low energy antiproton and ion facilities requires precise information about the beam emittance to guarantee optimum performance. In the Extra-Low ENergy Antiproton storage ring (ELENA) the transverse emittances will be measured by scraping. However, this diagnostic measurement faces several challenges: non-zero dispersion, non-Gaussian beam distributions due to effects of the electron cooler and various systematic errors such as closed orbit offsets and inaccurate rms momentum spread estimation. In addition, diffusion processes, such as intra-beam scattering might lead to emittance overestimates. Here, we present algorithms to efficiently address the emittance reconstruction in presence of the above effects, and present simulation results for the case of ELENA.

A universal formula for the field enhancement factor

Science.gov (United States)

Biswas, Debabrata

2018-04-01

The field enhancement factor (FEF) is an important quantity in field emission calculations since the tunneling electron current depends very sensitively on its magnitude. The exact dependence of FEF on the emitter height h, the radius of curvature at the apex Ra, as well as the shape of the emitter base are still largely unknown. In this work, a universal formula for the field enhancement factor is derived for a single emitter. It depends on the ratio h/Ra and has the form γ a = ( 2 h / R a ) / [ α 1 ln ( 4 h / R a ) - α 2 ] , where α1 and α2 depend on the charge distribution on the emitter. Numerical results show that a simpler form γ a = ( 2 h / R a ) / [ ln ( 4 h / R a ) - α ] is equally valid with α depending on the emitter-base. Thus, for the hyperboloid, conical, and ellipsoid emitters, the value of α is 0, 0.88, and 2, while for the cylindrical base, α ≃ 2.6.

High current plasma electron emitter

International Nuclear Information System (INIS)

Fiksel, G.; Almagri, A.F.; Craig, D.

1995-07-01

A high current plasma electron emitter based on a miniature plasma source has been developed. The emitting plasma is created by a pulsed high current gas discharge. The electron emission current is 1 kA at 300 V at the pulse duration of 10 ms. The prototype injector described in this paper will be used for a 20 kA electrostatic current injection experiment in the Madison Symmetric Torus (MST) reversed-field pinch. The source will be replicated in order to attain this total current requirement. The source has a simple design and has proven very reliable in operation. A high emission current, small size (3.7 cm in diameter), and low impurity generation make the source suitable for a variety of fusion and technological applications

Transverse emittance measurement and preservation at the LHC

Energy Technology Data Exchange (ETDEWEB)

Kuhn, Maria

2016-06-20

The Large Hadron Collider (LHC) at CERN is a high energy storage ring that provides proton and heavy ion collisions to study fundamental particle physics. The luminosity production is closely linked to emittance preservation in the accelerator. The transverse emittance is the phase space density of the beam and should be conserved when the particle beam is transformed through the accelerator. Perturbing effects, however, can lead to emittance increase and hence luminosity degradation. Measuring the emittance growth is a complex task with high intensity beams and changing energies. The machine optics and the transverse beam size have to be measured as accurately as possible. Beta function measurements with k-modulation are discussed. With this method the quadrupole focussing strength is varied and the resulting tune change is traced to determine the beta function at the quadrupole. A new k-modulation measurement tool was developed for the LHC. The fully automatic and online measurement system takes constraints of various systems such as tune measurement precision and powering limitations of the LHC superconducting circuits into account. With sinusoidal k-modulation record low beta function measurement uncertainties in the LHC have been reached. 2015 LHC beta function and β*, which is the beta function at the collision point, measurements with k-modulation will be presented. Wire scanners and synchrotron light monitors are presently used in the LHC to measure the transverse beam size. Accuracy and limitations of the LHC transverse profile monitors are discussed. During the 2012 LHC proton run it was found that wire scanner photomultiplier saturation added significant uncertainty on all measurements. A large discrepancy between emittances from wire scanners and luminosity was discovered but not solved. During Long Shutdown 1 the wire scanner system was upgraded with new photomultipliers. A thorough study of LHC wire scanner measurement precision in 2015 is presented

Emittance calculations for the Stanford Linear Collider injector

International Nuclear Information System (INIS)

Sheppard, J.C.; Clendenin, J.E.; Helm, R.H.; Lee, M.J.; Miller, R.H.; Blocker, C.A.

1983-03-01

A series of measurements have been performed to determine the emittance of the high intensity, single bunch beam that is to be injected into the Stanford Linear Collider. On-line computer programs were used to control the Linac for the purpose of data acquisition and to fit the data to a model in order to deduce the beam emittance. This paper will describe the method of emittance calculation and present some of the measurement results

Beam emittance measurement from CERN thermionic guns

International Nuclear Information System (INIS)

Kester, O.; Rao, R.; Rinolfi, L.

1992-01-01

In the LEP Injector Linacs (LIL) a thermionic gun provides electron beams with different peak intensities at an energy of 80 keV. The beam emittances were estimated from the EGUN programme. Since the gun is of triode type, the main contribution to the emittance comes from the grid. The simulation programme does not model the real geometry by assuming a cylindrical symmetry, while the grid does not have such symmetry. A Gun Test Facility (GTF), allowing emittance measurements, based on the 3-gradients-method was installed. The experimental results are presented. (author) 6 refs.; 6 figs

Multi-dimensional beam emittance and β-functions

International Nuclear Information System (INIS)

Buon, J.

1993-05-01

The concept of r.m.s. emittance is extended to the case of several degrees of freedom that are coupled. That multi-dimensional emittance is lower than the product of the emittances attached to each degree of freedom, but is conserved in a linear motion. An envelope-hyperellipsoid is introduced to define the β-functions of the beam envelope. On the contrary of an one-degree of freedom motion, it is emphasized that these envelope functions differ from the amplitude functions of the normal modes of motion as a result of the difference between the Liouville and Lagrange invariants. (author) 4 refs

Beam phase space and emittance

International Nuclear Information System (INIS)

Buon, J.

1992-02-01

The classical and elementary results for canonical phase space, the Liouville theorem and the beam emittance are reviewed. Then, the importance of phase portraits to obtain a geometrical description of motion is emphasized, with examples in accelerator physics. Finally, a statistical point of view is used to define beam emittance, to study its law of approximate conservation, with three particular examples, and to introduce a beam envelope-ellipse and the β-function, emphasing the statistical features of its properties. (author) 14 refs.; 11 figs

Combustion powered thermophotovoltaic emitter system

Energy Technology Data Exchange (ETDEWEB)

McHenry, R.S. [Naval Academy, Annapolis, MD (United States). Naval Architecture, Ocean and Marine Engineering

1995-07-01

The US Naval Academy (USNA) has recently completed an engineering design project for a high temperature thermophotovoltaic (TPV) photon emitter. The final apparatus was to be portable, completely self contained, and was to incorporate cycle efficiency optimization such as exhaust stream recuperation. Through computer modeling and prototype experimentation, a methane fueled emitter system was designed from structural ceramic materials to fulfill the high temperature requirements necessary for high system efficiency. This paper outlines the engineering design process, discusses obstacles and solutions encountered, and presents the final design.

Coupling single emitters to quantum plasmonic circuits

DEFF Research Database (Denmark)

Huck, Alexander; Andersen, Ulrik Lund

2016-01-01

In recent years, the controlled coupling of single-photon emitters to propagating surface plasmons has been intensely studied, which is fueled by the prospect of a giant photonic nonlinearity on a nanoscaled platform. In this article, we will review the recent progress on coupling single emitters...

Theory and measurements of emittance preservation in plasma wakefield acceleration

Energy Technology Data Exchange (ETDEWEB)

Frederico, Joel

2016-12-01

In this dissertation, we examine the preservation and measurement of emittance in the plasma wakefield acceleration blowout regime. Plasma wakefield acceleration (PWFA) is a revolutionary approach to accelerating charged particles that has been demonstrated to have the potential for gradients orders of magnitude greater than traditional approaches. The application of PWFA to the design of a linear collider will make new high energy physics research possible, but the design parameters must first be shown to be competitive with traditional methods. Emittance preservation is necessary in the design of a linear collider in order to maximize luminosity. We examine the conditions necessary for circular symmetry in the PWFA blowout regime, and demonstrate that current proposals meet these bounds. We also present an application of beam lamentation which describes the process of beam parameter and emittance matching. We show that the emittance growth saturates as a consequence of energy spread in the beam. The initial beam parameters determine the amount of emittance growth, while the contribution of energy spread is negligible. We also present a model for ion motion in the presence of a beam that is much more dense than the plasma. By combining the model of ion motion and emittance growth, we find the emittance growth due to ion motion is minimal in the case of marginal ion motion. In addition, we present a simulation that validates the ion motion model, which is under further development to examine emittance growth of both marginal and pronounced ion motion. Finally, we present a proof-of-concept of an emittance measurement which may enable the analysis of emittance preservation in future PWFA experiments.

Measurement of transverse emittance in the Fermilab booster

Energy Technology Data Exchange (ETDEWEB)

Graves, William Sproull [Wisconsin U., Madison

1994-01-01

A new beam profile monitor has been built and installed in the Fermilab Booster synchrotron. It nondestructively measures the beam's vertical density distribution on a fast turn-by-turn basis. This enables one to measure the beam's transverse emittance and to observe emittance growth as it occurs. For high intensities (>2 times 10^{12 } protons), the normalized 95% emittance was observed to grow from 6pi mm-mrad at injection to 16pi mm-mrad at extraction. The initial (<5 msec) emittance growth and beam losses are shown to be caused by the space charge tune shift onto integer and 1/2 integer resonance lines. The growth near injection accounts for approximately 40% of the observed emittance increase throughout the acceleration cycle. The remaining 60% is due to two factors: slow linear growth due to betatron-motion driven by noise in the rf system; and faster growth after the transition energy that is caused by coupling of the longitudinal beam motion into the transverse planes.

From classical to quantum plasmonics: Classical emitter and SPASER

Science.gov (United States)

Balykin, V. I.

2018-02-01

The key advantage of plasmonics is in pushing our control of light down to the nanoscale. It is possible to envision lithographically fabricated plasmonic devices for future quantum information processing or cryptography at the nanoscale in two dimensions. A first step in this direction is a demonstration of a highly efficient nanoscale light source. Here we demonstrate two types of nanoscale sources of optical fields: 1) the classical metallic nanostructure emitter and 2) the plasmonic nanolaser - SPASER.

Formation of short-lived positron emitters in reactions of protons of energies up to 200 MeV with the target elements carbon, nitrogen and oxygen

CERN Document Server

Kettern, K; Qaim, S M; Shubin, Yu N; Steyn, G F; Van der Walt, T N; 10.1016/j.apradiso.2004.02.007

2004-01-01

Excitation functions were measured by the stacked-foil technique for proton induced reactions on carbon, nitrogen and oxygen leading to the formation of the short-lived positron emitters /sup 11/C (T/sub 1 /2/=20.38 min) and /sup 13/N (T/sub 1/2/=9.96 min). The energy region covered extended up to 200 MeV. The product activity was measured non-destructively via gamma -ray spectrometry. A careful decay curve analysis of the positron annihilation radiation was invariably performed. The experimental results were compared with theoretical data obtained using the modified hybrid nuclear model code ALICE-IPPE for intermediate energies. The agreement was found to be generally satisfactory. The data are of importance in proton therapy.

Spherical proton emitters

International Nuclear Information System (INIS)

Berg, S.; Semmes, P.B.; Nazarewicz, W.

1997-01-01

Various theoretical approaches to proton emission from spherical nuclei are investigated, and it is found that all the methods employed give very similar results. The calculated decay widths are found to be qualitatively insensitive to the parameters of the proton-nucleus potential, i.e., changing the potential parameters over a fairly large range typically changes the decay width by no more than a factor of ∼3. Proton half-lives of observed heavy proton emitters are, in general, well reproduced by spherical calculations with the spectroscopic factors calculated in the independent quasiparticle approximation. The quantitative agreement with experimental data obtained in our study requires that the parameters of the proton-nucleus potential be chosen carefully. It also suggests that deformed proton emitters will provide invaluable spectroscopic information on the angular momentum decomposition of single-proton orbitals in deformed nuclei. copyright 1997 The American Physical Society

Self-powered detectors with thulium emitter

International Nuclear Information System (INIS)

Haller, P.; Klar, E.

1978-01-01

In addition to fission chambers, prompt-indicating self-powered (SPN) detectors are used for measuring the neutron flux density in the core of power reactors. Although current SPN detectors with a cobalt emitter give satisfactora results, detectors with other emitter materials have been analyzed and tested. The author describes the properties and decay pattern of the nuclide thulium and presents the results of measurements made while testing thulium detectors. (orig.) [de

Using hydrocarbon as a carbon source for synthesis of carbon nanotube by electric field induced needle-pulsed plasma

International Nuclear Information System (INIS)

Kazemi Kia, Kaveh; Bonabi, Fahimeh

2013-01-01

In this work different hydrocarbons are used as the carbon source, in the production of carbon nanotubes (CNTs) and nano onions. An electric field induced needle pulse arc-discharge reactor is used. The influence of starting carbon on the synthesis of CNTs is investigated. The production efficiency is compared for Acetone, Isopropanol and Naphthalene as simple hydrocarbons. The hydrocarbons are preheated and then pretreated by electric field before being exposed to plasma. The hydrocarbon vapor is injected into plasma through a graphite spout in the cathode assembly. The pulsed plasma takes place between two graphite rods while a strong electric field has been already established alongside the electrodes. The pulse width is 0.3 μs. Mechanism of precursor decomposition is discussed by describing three forms of energy that are utilized to disintegrate the precursor molecules: thermal energy, electric field and kinetic energy of plasma. Molecular polarity of a hydrocarbon is one of the reasons for choosing carbon raw material as a precursor in an electric field induced low power pulsed-plasma. The results show that in order to obtain high quality carbon nanotubes, Acetone is preferred to Isopropanol and Naphthalene. Scanning probe microscopy techniques are used to investigate the products. - Highlights: • We synthesized CNTs (carbon nano tubes) by needle pulsed plasma. • We use different hydrocarbons as carbon source in the production of CNTs. • We investigated the influence of starting carbon on the synthesis of CNTs. • Thermal energy, electric field and kinetic energy are used to break carbon bonds. • Polar hydrocarbon molecules are more efficient than nonpolar ones in production

Localization of Narrowband Single Photon Emitters in Nanodiamonds.

Science.gov (United States)

Bray, Kerem; Sandstrom, Russell; Elbadawi, Christopher; Fischer, Martin; Schreck, Matthias; Shimoni, Olga; Lobo, Charlene; Toth, Milos; Aharonovich, Igor

2016-03-23

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.

Innovative energy efficient low-voltage electron beam emitters

International Nuclear Information System (INIS)

Felis, Kenneth P.; Avnery, Tovi; Berejka, Anthony J.

2002-01-01

Advanced electron beams (AEB) has developed a modular, low voltage (80-125 keV), high beam current (up to 40 ma), electron emitter with typically 25 cm of beam width, that is housed in an evacuated, returnable chamber that is easy to plug in and connect. The latest in nanofabrication enables AEB to use an ultra-thin beam window. The power supply for AEB's emitter is based on solid-state electronics. This combination of features results in a remarkable electrical efficiency. AEB's electron emitter relies on a touch screen, computer control system. With 80 μm of unit density beam penetration, AEB's electron emitter has gained market acceptance in the curing of opaque, pigmented inks and coatings used on flexible substrates, metals and fiber composites and in the curing of adhesives in foil based laminates

Innovative energy efficient low-voltage electron beam emitters

Science.gov (United States)

Felis, Kenneth P.; Avnery, Tovi; Berejka, Anthony J.

2002-03-01

Advanced electron beams (AEB) has developed a modular, low voltage (80-125 keV), high beam current (up to 40 ma), electron emitter with typically 25 cm of beam width, that is housed in an evacuated, returnable chamber that is easy to plug in and connect. The latest in nanofabrication enables AEB to use an ultra-thin beam window. The power supply for AEB's emitter is based on solid-state electronics. This combination of features results in a remarkable electrical efficiency. AEB's electron emitter relies on a touch screen, computer control system. With 80 μm of unit density beam penetration, AEB's electron emitter has gained market acceptance in the curing of opaque, pigmented inks and coatings used on flexible substrates, metals and fiber composites and in the curing of adhesives in foil based laminates.

A high-DC-voltage GaAs photoemission gun: Transverse emittance and momentum spread measurements

International Nuclear Information System (INIS)

Engwall, D.; Bohn, C.; Cardman, L.

1997-01-01

We have built a high-DC-voltage photoemission gun and a diagnostic beamline permitting us to measure rms transverse emittance (ε x ) and rms momentum spread (δ) of short-duration electron pulses produced by illuminating the cathode with light from a mode-locked, frequency-doubled Nd:YLF laser. The electron gun is a GaAs photocathode source designed to operate at 500kV. We have measured ε x and δ for conditions ranging from emittance-dominated to space-charge-dominated. We report these measurements as functions of microbunch charge for different beam radii, pulse lengths, and voltages/field gradients at the cathode, and compare them with PARMELA calculations

Coherent single-photon absorption by single emitters coupled to one-dimensional nanophotonic waveguides

Energy Technology Data Exchange (ETDEWEB)

Chen Yuntian; Wubs, Martijn; Moerk, Jesper [DTU Fotonik, Department of Photonics Engineering, Oersteds Plads, DK-2800 Kgs Lyngby (Denmark); Koenderink, A Femius, E-mail: yche@fotonik.dtu.dk [Center for Nanophotonics, FOM Institute for Atomic and Molecular Physics (AMOLF), Science Park 104, 1098 XG Amsterdam (Netherlands)

2011-10-15

We study the dynamics of single-photon absorption by a single emitter coupled to a one-dimensional waveguide that simultaneously provides channels for spontaneous emission (SE) decay and a channel for the input photon. We have developed a time-dependent theory that allows us to specify any input single-photon wavepacket guided by the waveguide as the initial condition, and calculate the excitation probability of the emitter, as well as the time evolution of the transmitted and reflected fields. For single-photon wavepackets with a Gaussian spectrum and temporal shape, we obtain analytical solutions for the dynamics of absorption, with maximum atomic excitation {approx}40%. We furthermore propose a terminated waveguide to aid the single-photon absorption. We found that for an emitter placed at an optimal distance from the termination, the maximum atomic excitation due to an incident single-photon wavepacket can exceed 70%. This high value is a direct consequence of the high SE {beta}-factor for emission into the waveguide. Finally, we have also explored whether waveguide dispersion could aid single-photon absorption by pulse shaping. For a Gaussian input wavepacket, we found that the absorption efficiency can be improved by a further 4% by engineering the dispersion. Efficient single-photon absorption by a single emitter has potential applications in quantum communication and quantum computation. (paper)

Very bright, near-infrared single photon emitters in diamond

Directory of Open Access Journals (Sweden)

D. W. M. Lau

2013-09-01

Full Text Available We demonstrate activation of bright diamond single photon emitters in the near infrared range by thermal annealing alone, i.e., without ion implantation. The activation is crucially dependent on the annealing ambient. The activation of the single photon emitters is only observed when the sample is annealed in forming gas (4% H2 in Ar above temperatures of 1000 °C. By contrast, no emitters are activated by annealing in vacuum, oxygen, argon or deuterium. The emitters activated by annealing in forming gas exhibit very bright emission in the 730-760 nm wavelength range and have linewidths of ∼1.5-2.5 nm at room temperature.

Measurement of emittance of metal interface in molten salt

International Nuclear Information System (INIS)

Araki, N.; Makino, A.; Nakamura, Y.

1995-01-01

A new technique for measuring the total normal emittance of a metal in a semi-transparent liquid has been proposed and this technique has been applied to measure the emittance of stainless steel (SUS304), nickel, and gold in molten potassium nitrate KNO 3 . These emittance data are indispensable to analyzing the radiative heat transfer between a metal and a semitransparent liquid, such as a molten salt

Quantifying, Assessing, and Mitigating Methane Emissions from Super-emitters in the Oil and Gas Supply Chain

Science.gov (United States)

Lyon, David Richard

Methane emissions from the oil and gas (O&G) supply chain reduce potential climate benefits of natural gas as a replacement for other fossil fuels that emit more carbon dioxide per energy produced. O&G facilities have skewed emission rate distributions with a small fraction of sites contributing the majority of emissions. Knowledge of the identity and cause of these high emission facilities, referred to as super-emitters or fat-tail sources, is critical for reducing supply chain emissions. This dissertation addresses the quantification of super-emitter emissions, assessment of their prevalence and relationship to site characteristics, and mitigation with continuous leak detection systems. Chapter 1 summarizes the state of the knowledge of O&G methane emissions. Chapter 2 constructs a spatially-resolved emission inventory to estimate total and O&G methane emissions in the Barnett Shale as part of a coordinated research campaign using multiple top-down and bottom-up methods to quantify emissions. The emission inventory accounts for super-emitters with two-phase Monte Carlo simulations that combine site measurements collected with two approaches: unbiased sampling and targeted sampling of super-emitters. More comprehensive activity data and the inclusion of super-emitters, which account for 19% of O&G emissions, produces a emission inventory that is not statistically different than top-down regional emission estimates. Chapter 3 describes a helicopter-based survey of over 8,000 well pads in seven basins with infrared optical gas imaging to assess high emission sources. Four percent of sites are observed to have high emissions with over 90% of observed sources from tanks. The occurrence of high emissions is weakly correlated to site parameters and the best statistical model explains only 14% of variance, which demonstrates that the occurrence of super-emitters is primarily stochastic. Chapter 4 presents a Gaussian dispersion model for optimizing the placement of

Boundary conditions on the plasma emitter surface in the presence of a particle counter flow: I. Ion emitter

Energy Technology Data Exchange (ETDEWEB)

Astrelin, V. T., E-mail: V.T.Astrelin@inp.nsk.su; Kotelnikov, I. A. [Russian Academy of Sciences, Budker Institute of Nuclear Physics, Siberian Branch (Russian Federation)

2017-02-15

Emission of positively charged ions from a plasma emitter irradiated by a counterpropagating electron beam is studied theoretically. A bipolar diode with a plasma emitter in which the ion temperature is lower than the electron temperature and the counter electron flow is extracted from the ion collector is calculated in the one-dimensional model. An analog of Bohm’s criterion for ion emission in the presence of a counterpropagating electron beam is derived. The limiting density of the counterpropagating beam in a bipolar diode operating in the space-charge-limited-emission regime is calculated. The full set of boundary conditions on the plasma emitter surface that are required for operation of the high-current optics module in numerical codes used to simulate charged particle sources is formulated.

Measurement of the internal bremsstrahlung spectrum of a 89Sr beta emitter in the 1–100 keV photon energy regime

International Nuclear Information System (INIS)

Singh, Amrit; Dhaliwal, A.S.

2015-01-01

The internal bremsstrahlung (IB) spectrum of 89 Sr, which is a unique first forbidden beta emitter, is studied in the 1–100 keV photon energy regime. The IB spectrum is experimentally measured using a Si(Li) detector, which is efficient in this photon energy regime, and is compared with the IB distributions that are predicted by the Knipp, Uhlenbeck and Bloch (KUB), Nilsson, and Lewis and Ford theories. In the soft energy regime up to 15 keV, the measured results are in agreement with all the aforementioned theories. However, from 16–30 keV, the experimental results are in agreement with the Lewis and Ford theory, which applies to forbidden transitions, and at higher photon energies, the Nilsson theory best describes the measured results. The differences among the different theories also increase with the photon energy. The effect of the electrostatic Coulomb field on the IB process for beta emitters with different end-point energies is investigated by comparing the ratio of the IB probabilities predicted using the KUB and Nilsson theories for 35 S and 89 Sr, i.e., soft and hard beta emitters, respectively. The Coulomb effect is shown to be significant in the high photon energy regime and for beta emitters with low end-point energies. - Highlights: • Internal bremsstrahlung spectrum of 89 Sr, a unique first forbidden beta emitter, is studied. • The measurements are taken in the photon energy regions of 1–100 keV with Si(Li) detector. • The measured results are deviating from Lewis and Ford theory and are close to the Nilsson theory. • The effect of Coulomb field on the IB process for different end point energy sources is investigated. • Effect of Coulomb field is more for low energy beta emitter towards the high energy end

Rf and space-charge induced emittances in laser-driven rf guns

International Nuclear Information System (INIS)

Kim, Kwang-Je; Chen, Yu-Jiuan.

1988-10-01

Laser-driven rf electron guns are potential sources of high-current, low-emittance, short bunch-length electron beams, which are required for many advanced accelerator applications, such as free-electron lasers and injectors for high-energy machines. In such guns the design of which was pioneered at Los Alamos National Laboratory and which is currently being developed at several other laboratories, a high-power laser beam illuminates a photo-cathode surface placed on an end wall of an rf cavity. The main advantages of this type of gun are that the time structure of the electron beam is controlled by the laser, eliminating the need for bunchers, and that the electric field in rf cavities can be made very strong, so that the effects due to space-charge repulsion can be minimized. In this paper, we present an approximate but simple analysis for the transverse and longitudinal emittances in rf guns that takes into account both the time variation of the rf field and the space-charge effect. The results are compared and found to agree well with those from simulation. 7 refs., 6 figs

Investigation of slice emittance using an energy-chirped electron beam in a dispersive section for photo injector characterization at PITZ

Energy Technology Data Exchange (ETDEWEB)

Ivanisenko, Yevgeniy

2012-06-15

This work describes a transverse slice emittance diagnostics with an RMS temporal resolution down to 2 ps that was implemented at the Photo Injector Test facility in Zeuthen (PITZ). The measurements were performed for several bunch charges generated by a laser pulse that has a flat-top temporal profile of 21-22 ps FWHM duration. This diagnostics allows to study the beam projected emittance compensation with a solenoid magnetic field experimentally and therefore contributes to the beam emittance optimization for the needs of short wavelength linac-based FELs in particular. The diagnostics is based upon the usage of electron bunches which have a correlation between the longitudinal position and the momentum of the bunch particles. This property allows to convert the bunch longitudinal distribution into a transverse one in a dipole magnet. A slit with a narrow opening at the dipole exit selects a fraction of the particle ensemble, a slice, which emittance is analyzed at a screen downstream. Slit scan and quadrupole scan techniques can be used to measure the emittance of the slices. In the experiments it was found that the slice emittance values are 5-10% lower than the projected emittance values, indicating a good effectivity of the solenoid compensation. The emittance obtained using quadrupole scan technique has shown different results when compared to slit scan technique due to a beam halo. The observed beam halo in phase space contributes up to 40% of the emittance value while having only 10% of the bunch charge.

Investigation of slice emittance using an energy-chirped electron beam in a dispersive section for photo injector characterization at PITZ

International Nuclear Information System (INIS)

Ivanisenko, Yevgeniy

2012-06-01

This work describes a transverse slice emittance diagnostics with an RMS temporal resolution down to 2 ps that was implemented at the Photo Injector Test facility in Zeuthen (PITZ). The measurements were performed for several bunch charges generated by a laser pulse that has a flat-top temporal profile of 21-22 ps FWHM duration. This diagnostics allows to study the beam projected emittance compensation with a solenoid magnetic field experimentally and therefore contributes to the beam emittance optimization for the needs of short wavelength linac-based FELs in particular. The diagnostics is based upon the usage of electron bunches which have a correlation between the longitudinal position and the momentum of the bunch particles. This property allows to convert the bunch longitudinal distribution into a transverse one in a dipole magnet. A slit with a narrow opening at the dipole exit selects a fraction of the particle ensemble, a slice, which emittance is analyzed at a screen downstream. Slit scan and quadrupole scan techniques can be used to measure the emittance of the slices. In the experiments it was found that the slice emittance values are 5-10% lower than the projected emittance values, indicating a good effectivity of the solenoid compensation. The emittance obtained using quadrupole scan technique has shown different results when compared to slit scan technique due to a beam halo. The observed beam halo in phase space contributes up to 40% of the emittance value while having only 10% of the bunch charge.

Emittance growth and tune spectra at PETRA III

International Nuclear Information System (INIS)

Wanzenberg, R.

2011-08-01

At DESY the PETRA ring has been converted into a synchrotron radiation facility, called PETRA III. 20 damping wigglers have been installed to achieve an emittance of 1 nm. The commissioning with beam started in April 2009 and user runs have been started in 2010. The design current is 100 mA and the bunch to bunch distance is 8 ns for one particular filling pattern with 960 bunches. At a current of about 50 mA a strong vertical emittance increase has been observed. During machine studies it was found that the emittance increase depends strongly on the bunch filling pattern. For the user operation a filling scheme has been found which mitigates the increase of the vertical emittance. In August 2010 PETRA III has been operated without damping wigglers for one week. The vertical emittance growth was not significantly smaller without wigglers. Furthermore tune spectra at PETRA III show characteristic lines which have been observed at other storage rings in the connection with electron clouds. Measurements at PETRA III are presented for different bunch filling patterns and with and without wiggler magnets. (orig.)

Galex Lyman-alpha Emitters: Physical Properties, Luminosity Bimodality, And Morphologies.

Science.gov (United States)

Mallery, Ryan P.

2010-01-01

The Galaxy Evolution Explorer spectroscopic survey has uncovered a large statistically significant sample of Lyman-alpha emitters at z sim0.3. ACS imaging of these sources in the COSMOS and AEGIS deep fields reveals that these Lyman-alpha emitters consist of two distinct galaxy morphologies, face on spiral galaxies and compact starburst/merging systems. The morphology bimodality also results in a bimodal distribution of optical luminosity. A comparison between the UV photometry and MIPS 24 micron detections of these sources indicates that they are bluer, and have less dust extinction than similar star forming galaxies that lack Lyman-alpha detection. Our findings show how the global gas and dust distribution of star forming galaxies inhibits Lyman-alpha emission in star forming galaxies. GALEX is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the CNES of France and the Korean Ministry of Science and Technology.

A polarization-insensitive plasmonic photoconductive terahertz emitter

KAUST Repository

Li, Xurong

2017-11-16

We present a polarization-insensitive plasmonic photoconductive terahertz emitter that uses a two-dimensional array of nanoscale cross-shaped apertures as the plasmonic contact electrodes. The geometry of the cross-shaped apertures is set to maximize optical pump absorption in close proximity to the contact electrodes. The two-dimensional symmetry of the cross-shaped apertures offers a polarization-insensitive interaction between the plasmonic contact electrodes and optical pump beam. We experimentally demonstrate a polarization-insensitive terahertz radiation from the presented emitter in response to a femtosecond optical pump beam and similar terahertz radiation powers compared to previously demonstrated polarization-sensitive photoconductive emitters with plasmonic contact electrode gratings at the optimum optical pump polarization.

Emittance measurement for high-brightness electron guns

International Nuclear Information System (INIS)

Kobayashi, H.; Kurihara, T.; Sato, I.; Asami, A.; Yamazaki, Y.; Otani, S.; Ishizawa, Y.

1992-01-01

An emittance measurement system based on a high-precision pepper-pot technique has been developed for electron guns with low emittance of around πmm-mrad. Electron guns with a 1 mmφ cathode, the material of which is impregnated tungsten or single-crystal lanthanum hexaboride (La 1-x Ce x )B 6 , have been developed. The performance has been evaluated by putting stress on cathode roughness, which gives rise to an angular divergence, according to the precise emittance measurement system. A new type of cathode holder, which is a modified version of the so called Vogel type, was developed and the beam uniformity has been improved. (Author) 5 figs., tab., 9 refs

Emittance formula for slits and pepper-pot measurement

International Nuclear Information System (INIS)

Zhang, M.

1996-10-01

In this note, a rigid formula for slits and pepper-pot emittance measurement is derived. The derivation is based on the one- dimensional slit measurement setup. A mathematical generalization of the slit emittance formula to the pepper-pot measurement is discussed

MEV Energy Electrostatic Accelerator Ion Beam Emittance Measurement

OpenAIRE

I.G. Ignat’ev; M.I. Zakharets; S.V. Kolinko; D.P. Shulha

2014-01-01

The testing equipment was designed, manufactured and tried out permitting measurements of total current, current profile and emittance of an ion beam extracted from the ion beam. MeV energy electrostatic accelerator ion H + beam emittance measurement results are presented.

Alpha-emitters for medical therapy workshop

International Nuclear Information System (INIS)

Feinendegen, L.E.; McClure, J.J.

1996-01-01

A workshop on ''Alpha-Emitters for Medical Therapy'' was held May 30-31, 1996 in Denver Colorado to identify research goals and potential clinical needs for applying alpha-particle emitters and to provide DOE with sufficient information for future planning. The workshop was attended by 36 participants representing radiooncology, nuclear medicine, immunotherapy, radiobiology, molecular biology, biochemistry, radiopharmaceutical chemistry, dosimetry, and physics. This report provides a summary of the key points and recommendations arrived at during the conference

Alpha-emitters for medical therapy workshop

Energy Technology Data Exchange (ETDEWEB)

Feinendegen, L.E.; McClure, J.J.

1996-12-31

A workshop on ``Alpha-Emitters for Medical Therapy`` was held May 30-31, 1996 in Denver Colorado to identify research goals and potential clinical needs for applying alpha-particle emitters and to provide DOE with sufficient information for future planning. The workshop was attended by 36 participants representing radiooncology, nuclear medicine, immunotherapy, radiobiology, molecular biology, biochemistry, radiopharmaceutical chemistry, dosimetry, and physics. This report provides a summary of the key points and recommendations arrived at during the conference.

Design for a practical, low-emittance damping ring

International Nuclear Information System (INIS)

Krejcik, P.

1988-01-01

The luminosity requirements for future high-energy linear colliders calls for very low emittances in the two beams. These low emittances can be achieved with damping rings, but, in order to reach the design goal of a factor 10 improvement over present day machines, great care must be taken in their design. This paper emphasizes the need to address simultaneously all of the factors which limit the operational emittance in the ring. Particularly since in standard designs there is a conflict between different design parameters which makes it difficult to extrapolate such designs to very low emittances. The approach chosen here is to resolve such conflicts by separating their design solutions. Wigglers are used predominantly in zero-dispersion regions to achieve the desired damping rate, whereas in the arcs high dispersion insertions are made in regions of zero curvature to allow for easier chromaticity control

Narrowband infrared emitters for combat ID

Science.gov (United States)

Pralle, Martin U.; Puscasu, Irina; Daly, James; Fallon, Keith; Loges, Peter; Greenwald, Anton; Johnson, Edward

2007-04-01

There is a strong desire to create narrowband infrared light sources as personnel beacons for application in infrared Identify Friend or Foe (IFF) systems. This demand has augmented dramatically in recent years with the reports of friendly fire casualties in Afghanistan and Iraq. ICx Photonics' photonic crystal enhanced TM (PCE TM) infrared emitter technology affords the possibility of creating narrowband IR light sources tuned to specific IR wavebands (near 1-2 microns, mid 3-5 microns, and long 8-12 microns) making it the ideal solution for infrared IFF. This technology is based on a metal coated 2D photonic crystal of air holes in a silicon substrate. Upon thermal excitation the photonic crystal modifies the emitted yielding narrowband IR light with center wavelength commensurate with the periodicity of the lattice. We have integrated this technology with microhotplate MEMS devices to yield 15mW IR light sources in the 3-5 micron waveband with wall plug efficiencies in excess of 10%, 2 orders of magnitude more efficient that conventional IR LEDs. We have further extended this technology into the LWIR with a light source that produces 9 mW of 8-12 micron light at an efficiency of 8%. Viewing distances >500 meters were observed with fielded camera technologies, ideal for ground to ground troop identification. When grouped into an emitter panel, the viewing distances were extended to 5 miles, ideal for ground to air identification.

Field-warmed soil carbon changes imply high 21st-century modeling uncertainty

Directory of Open Access Journals (Sweden)

K. Todd-Brown

2018-06-01

Full Text Available The feedback between planetary warming and soil carbon loss has been the focus of considerable scientific attention in recent decades, due to its potential to accelerate anthropogenic climate change. The soil carbon temperature sensitivity is traditionally estimated from short-term respiration measurements – either from laboratory incubations that are artificially manipulated or from field measurements that cannot distinguish between plant and microbial respiration. To address these limitations of previous approaches, we developed a new method to estimate soil temperature sensitivity (Q10 of soil carbon directly from warming-induced changes in soil carbon stocks measured in 36 field experiments across the world. Variations in warming magnitude and control organic carbon percentage explained much of field-warmed organic carbon percentage (R2  =  0.96, revealing Q10 across sites of 2.2 [1.6, 2.7] 95 % confidence interval (CI. When these field-derived Q10 values were extrapolated over the 21st century using a post hoc correction of 20 Coupled Model Intercomparison Project Phase 5 (CMIP5 Earth system model outputs, the multi-model mean soil carbon stock changes shifted from the previous value of 88 ± 153 Pg carbon (weighted mean ± 1 SD to 19 ± 155 Pg carbon with a Q10-driven 95 % CI of 248 ± 191 to −95 ± 209 Pg carbon. On average, incorporating the field-derived Q10 values into Earth system model simulations led to reductions in the projected amount of carbon sequestered in the soil over the 21st century. However, the considerable parameter uncertainty led to extremely high variability in soil carbon stock projections within each model; intra-model uncertainty driven by the field-derived Q10 was as great as that between model variation. This study demonstrates that data integration should capture the variation of the system, as well as mean trends.

Design of a minimum emittance nBA lattice

Science.gov (United States)

Lee, S. Y.

1998-04-01

An attempt to design a minimum emittance n-bend achromat (nBA) lattice has been made. One distinct feature is that dipoles with two different lengths were used. As a multiple bend achromat, five bend achromat lattices with six superperiod were designed. The obtained emittace is three times larger than the theoretical minimum. Tunes were chosen to avoid third order resonances. In order to correct first and second order chromaticities, eight family sextupoles were placed. The obtained emittance of five bend achromat lattices is almost equal to the minimum emittance of five bend achromat lattice consisting of dipoles with equal length.

Remote detection of single emitters via optical waveguides

Science.gov (United States)

Then, Patrick; Razinskas, Gary; Feichtner, Thorsten; Haas, Philippe; Wild, Andreas; Bellini, Nicola; Osellame, Roberto; Cerullo, Giulio; Hecht, Bert

2014-05-01

The integration of lab-on-a-chip technologies with single-molecule detection techniques may enable new applications in analytical chemistry, biotechnology, and medicine. We describe a method based on the reciprocity theorem of electromagnetic theory to determine and optimize the detection efficiency of photons emitted by single quantum emitters through truncated dielectric waveguides of arbitrary shape positioned in their proximity. We demonstrate experimentally that detection of single quantum emitters via such waveguides is possible, confirming the predicted behavior of the detection efficiency. Our findings blaze the trail towards efficient lensless single-emitter detection compatible with large-scale optofluidic integration.

Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

Science.gov (United States)

Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

2009-01-01

Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

Plasma treatment for producing electron emitters

Science.gov (United States)

Coates, Don Mayo; Walter, Kevin Carl

2001-01-01

Plasma treatment for producing carbonaceous field emission electron emitters is disclosed. A plasma of ions is generated in a closed chamber and used to surround the exposed surface of a carbonaceous material. A voltage is applied to an electrode that is in contact with the carbonaceous material. This voltage has a negative potential relative to a second electrode in the chamber and serves to accelerate the ions toward the carbonaceous material and provide an ion energy sufficient to etch the exposed surface of the carbonaceous material but not sufficient to result in the implantation of the ions within the carbonaceous material. Preferably, the ions used are those of an inert gas or an inert gas with a small amount of added nitrogen.

Transverse Emittance Measurement and Preservation at the LHC

CERN Document Server

AUTHOR|(CDS)2082907

The Large Hadron Collider (LHC) at CERN is a high energy storage ring that provides proton and heavy ion collisions to study fundamental particle physics. The luminosity production is closely linked to emittance preservation in the accelerator. The transverse emittance is the phase space density of the beam and should be conserved when the particle beam is transformed through the accelerator. Perturbing effects, however, can lead to emittance increase and hence luminosity degradation. Measuring the emittance growth is a complex task with high intensity beams and changing energies. The machine optics and the transverse beam size have to be measured as accurately as possible. Beta function measurements with k-modulation will be discussed. With this method the quadrupole focussing strength is varied and the resulting tune change is traced to determine the beta function at the quadrupole. A new k-modulation measurement tool was developed for the LHC. The fully automatic and online measurement system takes constra...

Emittance increase caused by core depletion in collisions

CERN Document Server

Bruce, R

2009-01-01

A new effect is presented, which changes the emittance during colliding-beam operation in circular colliders. If the initial transverse distribution is Gaussian, the collision probability is much higher for particles in the core of the beam than in the tails. When small-amplitude particles are removed, the remaining ones therefore have a larger transverse emittance. This effect, called core depletion, may cause a decrease in luminosity. An approximate analytic model is developed to study the effect and benchmarked against a multiparticle tracking simulation. Finally, the time evolution of the intensity and emittances of a Pb bunch in the Large Hadron Collider (LHC) at CERN is calculated, taking into account also other processes than collisions. The results show that integrated luminosity drops by 3--4% if core depletion is taken into account. It is also found that core depletion causes the transverse emittance to be larger when more experiments are active. This observation could be checked against experimenta...

Selective solar absorber emittance measurement at elevated temperature

Science.gov (United States)

Giraud, Philémon; Braillon, Julien; Raccurt, Olivier

2017-06-01

Durability of solar components for CSP (Concentrated Solar Power Plant) technologies is a key point to lower cost and ensure their large deployment. These technologies concentrated the solar radiation by means of mirrors on a receiver tube where it is collected as thermal energy. The absorbers are submitted to strong environmental constraints and the degradation of their optical properties (emittance and solar absorbance) have a direct impact on performance. The characterization of a material in such condition is complicated and requires advanced apparatuses, and different measurement methods exist for the determination of the two quantities of relevance regarding an absorber, which are its emittance and its solar absorbance. The objective is to develop new optical equipment for measure the emittance of this solar absorber at elevated temperature. In this paper, we present an optical bench developed for emittance measurement on absorbers is conditions of use. Results will be shown, with a discussion of some factors of influence over this measurement and how to control them.

Strong coupling of collection of emitters on hyperbolic meta-material

Science.gov (United States)

Biehs, Svend-Age; Xu, Chenran; Agarwal, Girish S.

2018-04-01

Recently, considerable effort has been devoted to the realization of a strong coupling regime of the radiation matter interaction in the context of an emitter at a meta surface. The strong interaction is well realized in cavity quantum electrodynamics, which also show that strong coupling is much easier to realize using a collection of emitters. Keeping this in mind, we study if emitters on a hyperbolic meta materials can yield a strong coupling regime. We show that strong coupling can be realized for densities of emitters exceeding a critical value. A way to detect strong coupling between emitters and hyperbolic metamaterials is to use the Kretschman-Raether configuration. The strong coupling appears as the splitting of the reflectivity dip. In the weak coupling regime, the dip position shifts. The shift and splitting can be used to sense active molecules at surfaces.

Low emittance lattices for electron storage rings revisited

International Nuclear Information System (INIS)

Trbojevic, D.; Courant, E.

1994-01-01

Conditions for the lowest possible emittance of the lattice for electron storage rings are obtained by a simplified analytical approach. Examples of electron storage lattices with minimum emittances are presented. A simple graphical presentation in the normalized dispersion space (Floquet's transformation) is used to illustrate the conditions and results

Single-layer nano-carbon film, diamond film, and diamond/nano-carbon composite film field emission performance comparison

International Nuclear Information System (INIS)

Wang, Xiaoping; Wang, Jinye; Wang, Lijun

2016-01-01

A series of single-layer nano-carbon (SNC) films, diamond films, and diamond/nano-carbon (D/NC) composite films have been prepared on the highly doped silicon substrate by using microwave plasma chemical vapor deposition techniques. The films were characterised by scanning electron microscopy, Raman spectroscopy, and field emission I-V measurements. The experimental results indicated that the field emission maximum current density of D/NC composite films is 11.8–17.8 times that of diamond films. And the field emission current density of D/NC composite films is 2.9–5 times that of SNC films at an electric field of 3.0 V/μm. At the same time, the D/NC composite film exhibits the advantage of improved reproducibility and long term stability (both of the nano-carbon film within the D/NC composite cathode and the SNC cathode were prepared under the same experimental conditions). And for the D/NC composite sample, a high current density of 10 mA/cm"2 at an electric field of 3.0 V/μm was obtained. Diamond layer can effectively improve the field emission characteristics of nano-carbon film. The reason may be due to the diamond film acts as the electron acceleration layer.

BEAM EMITTANCE MEASUREMENT TOOL FOR CEBAF OPERATIONS

International Nuclear Information System (INIS)

Chevtsov, Pavel; Tiefenback, Michael

2008-01-01

A new software tool was created at Jefferson Lab to measure the emittance of the CEBAF electron beams. The tool consists of device control and data analysis applications. The device control application handles the work of wire scanners and writes their measurement results as well as the information about accelerator settings during these measurements into wire scanner data files. The data analysis application reads these files and calculates the beam emittance on the basis of a wire scanner data processing model. Both applications are computer platform independent but are mostly used on LINUX PCs recently installed in the accelerator control room. The new tool significantly simplifies beam emittance measurement procedures for accelerator operations and contributes to a very high availability of the CEBAF machine for the nuclear physics program at Jefferson Lab.

Space Charge Correction on Emittance Measurement of Low Energy Electron Beams

Energy Technology Data Exchange (ETDEWEB)

Treado, Colleen J.; /Massachusetts U., Amherst

2012-09-07

The goal of any particle accelerator is to optimize the transport of a charged particle beam along a set path by confining the beam to a small region close to the design trajectory and directing it accurately along the beamline. To do so in the simplest fashion, accelerators use a system of magnets that exert approximately linear electromagnetic forces on the charged beam. These electromagnets bend the beam along the desired path, in the case of bending magnets, and constrain the beam to the desired area through alternating focusing and defocusing effects, in the case of quadrupole magnets. We can model the transport of such a beam through transfer matrices representing the actions of the various beamline elements. However, space charge effects, produced from self electric fields within the beam, defocus the beam and must be accounted for in the calculation of beam emittance. We present below the preliminary results of a MATLAB code built to model the transport of a charged particle beam through an accelerator and measure the emittance under the influence of space charge effects. We demonstrate the method of correctly calculating the emittance of a beam under space charge effects using a least square fit to determine the initial properties of the beam given the beam size measured at a specific point after transport.

Achievement of ultralow emittance coupling in the Australian Synchrotron storage ring

Directory of Open Access Journals (Sweden)

R. Dowd

2011-01-01

Full Text Available Investigations into producing an electron beam with ultralow vertical emittance have been conducted using the Australian Synchrotron 3 GeV storage ring. A method of tuning the emittance coupling (ϵ_{y}/ϵ_{x} has been developed using a machine model calibrated through the linear optics from closed orbits method. Direct measurements of the beam emittance have not been possible due to diagnostic limitations, however two independent indirect measurements both indicate a vertical emittance of 1.2–1.3 pm rad (ϵ_{y}/ϵ_{x}=0.01%. Other indirect measurements support the validity of these results. This result is the smallest vertical emittance currently achieved in a storage ring.

Measurements of Transverse Emittance for RF Photocathode Gun at the PAL

CERN Document Server

Park Jang Ho; Park, Sung-Ju; Soo Ko In; Wang, Xijie; Woon Parc, Yong; Xiang, Dao

2005-01-01

A BNL GUN-IV type RF photo-cathode gun is under fabrication for use in the FIR (Far Infra-Red) facility being built at the Pohang Accelerator Laboratory (PAL). Performance test of the gun will include the measurement of transverse emittance profile along the longitudinal direction. Successful measurement of the emittance profile will provide powerful tool for the commissioning of the 4GLS (4th generation light source) injectors based on the emittance compensation principle. We are going to achieve this withthe use of pepper-pot based emittance meters that can be moved along the longitudinal direction. In this article, we present design considerations on the emittance meter with the resolution of 1 mm mrad.

Aluminum oxide film thickness and emittance

International Nuclear Information System (INIS)

Thomas, J.K.; Ondrejcin, R.S.

1991-11-01

Aluminum reactor components which are not actively cooled could be subjected to high temperatures due to gamma heating after the core coolant level dropped during the ECS phase of a hypothetical LOCA event. Radiative heat transfer is the dominant heat transfer process in this scenario and therefore the emittance of these components is of interest. Of particular interest are the safety rod thimbles and Mark 60B blanket assemblies; for the K Reactor, these components have been exposed to low temperature (< 55 degrees C) moderator for about a year. The average moderator temperature was assumed to be 30 degrees C. The Al oxide film thickness at this temperature, after one year of exposure, is predicted to be 6.4 μm ± 10%; insensitive to exposure time. Dehydration of the film during the gamma heating accident would result in a film thickness of 6.0 μm ± 11%. Total hemispherical emittance is predicted to be 0.69 at 96 degrees C, decreasing to 0.45 at 600 degrees C. Some phenomena which would tend to yield thicker oxide films in the reactor environment relative to those obtained under experimental conditions were neglected and the predicted film thickness values are therefore conservative. The emittance values predicted for a given film thickness are also conservative. The conservativisms inherent in the predicted emittance are particularly relevant for uncertainty analysis of temperatures generated using these values

Measured emittance dependence on injection method in laser plasma accelerators

Science.gov (United States)

Barber, Samuel; van Tilborg, Jeroen; Schroeder, Carl; Lehe, Remi; Tsai, Hai-En; Swanson, Kelly; Steinke, Sven; Nakamura, Kei; Geddes, Cameron; Benedetti, Carlo; Esarey, Eric; Leemans, Wim

2017-10-01

The success of many laser plasma accelerator (LPA) based applications relies on the ability to produce electron beams with excellent 6D brightness, where brightness is defined as the ratio of charge to the product of the three normalized emittances. As such, parametric studies of the emittance of LPA generated electron beams are essential. Profiting from a stable and tunable LPA setup, combined with a carefully designed single-shot transverse emittance diagnostic, we present a direct comparison of charge dependent emittance measurements of electron beams generated by two different injection mechanisms: ionization injection and shock induced density down-ramp injection. Notably, the measurements reveal that ionization injection results in significantly higher emittance. With the down-ramp injection configuration, emittances less than 1 micron at spectral charge densities up to 2 pC/MeV were measured. This work was supported by the U.S. DOE under Contract No. DE-AC02-05CH11231, by the NSF under Grant No. PHY-1415596, by the U.S. DOE NNSA, DNN R&D (NA22), and by the Gordon and Betty Moore Foundation under Grant ID GBMF4898.

Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam

Energy Technology Data Exchange (ETDEWEB)

Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J.; Sun, Y.-E; Maxwell, T.; Edwards, H.; /Fermilab

2012-05-01

Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.

Internal Auger emitters: effects on spermatogenesis and oogenesis in mice

International Nuclear Information System (INIS)

Rao, D.V.; Mylavarapu, V.B.; Sastry, K.S.R.; Howell, R.W.

1988-01-01

The in vivo biological effects of Auger emitters are investigated using [A] spermatogenesis in mouse testis, and [B] oogenesis in mouse ovary as experimental models. Spermhead survival and induction of abnormal sperm, following intratesticular administration of radiopharmaceuticals, were the end points in Model A. Of interest in Model B is primary oocyte survival after intraperitoneal injection of the radiochemicals. The effectiveness of the Auger emitter is determined relative to its beta emitting companion or external X-rays in the absence of such an analogue. Results reveal pronounced effects of Auger emitters on all end points, not dependent on mode of administration. The efficacy of the Auger emitter is related intimately to its subcellular distribution, which, is governed by the chemical form of the carrier molecule. Conventional dosimetry is inadequate and biophysically meaningful dosimetric approaches are needed to understand in vivo effects of Auger emitters. (author)

Transverse beam emittance optimization for the injection into BESSY II

Energy Technology Data Exchange (ETDEWEB)

Kramer, Felix [Helmholtz Zentrum Berlin, Institut Beschleunigerphysik (Germany); Humboldt-Universitaet zu Berlin, Institut fuer Physik (Germany)

2016-07-01

For top up injection into the storage ring BESSY II an average injection efficiency of at least 90% is required. In low alpha mode the injection efficiency does not meet the requirements. Future BESSY II features will include shorter bunches in the storage ring (VSR) and user transparent injection with a non linear kicker. These will raise the demands on the quality of the injected beam even further. This work investigates the development of transverse emittance over the acceleration cycle in the synchrotron and the possibility of transverse emittance exchange by a sequence of skew quadrupoles in the transfer line. Results of emittance measurements and emittance exchange simulations will be given.

Living with a carbon allowance: The experiences of Carbon Rationing Action Groups and implications for policy

International Nuclear Information System (INIS)

Howell, Rachel A.

2012-01-01

Carbon Rationing Action Groups (CRAGs) are grassroots voluntary groups of citizens concerned about climate change, who set themselves a carbon allowance each year and provide support to members seeking to reduce their direct carbon emissions from household energy use and personal transport. Some groups have a financial penalty for carbon emitted in excess of the ration, and systems whereby under-emitters are rewarded using the monies collected from over-emitters. CRAGs therefore operate the nearest scheme in existence to the proposed policy of Personal Carbon Trading (PCT). This paper reports the findings of a study of the opinions and experiences of individuals involved in CRAGs (‘CRAGgers’). In general, interviewees have made significant behavioural changes and emissions reductions, but many would be unwilling to sell spare carbon allowances within a national PCT system. The choices made by CRAGgers with respect to the design and operation of their ‘carbon accounting’, their experiences of reducing fossil fuel energy use, and their views on personal carbon trading at CRAG and national level are discussed. Some possible implications for PCT and other policies are considered, as well as the limitations of CRAGs in informing an understanding of the potential impacts and operation of PCT. - Highlights: ► Reports opinions and experiences of members of Carbon Rationing Action Groups (CRAGs). ► Many interviewees have made significant reductions to their carbon footprint. ► CRAGs offer insights into individuals' experiences of living with a carbon allowance. ► Most CRAGs involve highly motivated individuals and avoid trading. ► They nonetheless offer some insights into Personal Carbon Trading and other policies.

Nanosecond field emitted and photo-field emitted current pulses from ZrC tips

International Nuclear Information System (INIS)

Ganter, R.; Bakker, R.J.; Gough, C.; Paraliev, M.; Pedrozzi, M.; Le Pimpec, F.; Rivkin, L.; Wrulich, A.

2006-01-01

In order to find electron sources with low thermal emittance, cathodes based on single tip field emitter are investigated. Maximum peak current, measured from single tip in ZrC with a typical apex radius around 1 μm, are presented. Voltage pulses of 2 ns duration and up to 50 kV amplitude lead to field emission current up to 470 mA from one ZrC tip. Combination of high applied electric field with laser illumination gives the possibility to modulate the emission with laser pulses. Nanoseconds current pulses have been emitted with laser pulses at 1064 nm illuminating a ZrC tip under high-DC electric field. The dependence of photo-field emitted current with the applied voltage can be explained by the Schottky effect

Nanosecond field emitted and photo-field emitted current pulses from ZrC tips

Energy Technology Data Exchange (ETDEWEB)

Ganter, R. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland)]. E-mail: romain.ganter@psi.ch; Bakker, R.J. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Gough, C. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Paraliev, M. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Pedrozzi, M. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Le Pimpec, F. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Rivkin, L. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Wrulich, A. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland)

2006-09-15

In order to find electron sources with low thermal emittance, cathodes based on single tip field emitter are investigated. Maximum peak current, measured from single tip in ZrC with a typical apex radius around 1 {mu}m, are presented. Voltage pulses of 2 ns duration and up to 50 kV amplitude lead to field emission current up to 470 mA from one ZrC tip. Combination of high applied electric field with laser illumination gives the possibility to modulate the emission with laser pulses. Nanoseconds current pulses have been emitted with laser pulses at 1064 nm illuminating a ZrC tip under high-DC electric field. The dependence of photo-field emitted current with the applied voltage can be explained by the Schottky effect.

Field emission from a new type of electron source

International Nuclear Information System (INIS)

Mousa, M.S.

1987-01-01

A new type of field emission electron source has been developed. In this paper, the construction, characteristics and behaviour of tungsten micropoint emitters coated with a sub-micron layer of hydrocarbon using a TEM with poor ( ∼ 1 0 -3 torr) vacuum conditions are described. The hydrocarbon coating has been verified using the X-Ray energy dispersive analysis technique of a SEM. The technical capabilities and potential of the new type of electron source are compared with those of other comparable composite micropoint field emitters and other types of electron sources currently in use. The emission properties presented here include I-V characteristics, emission images and electron energy spectra of this type of composite micropoint emitters. The effect on the behaviour and characteristics of baking the coated emitters at temperatures ranging between 140 0 C and 350 0 C is also studied. The behaviour of the emitter has been interpreted in terms of a field-induced hot-electron emission mechanism associated with metal-insulator-vacuum (M-I-V) regime

Self-consistent Analysis of Three-dimensional Uniformly Charged Ellipsoid with Zero Emittance

International Nuclear Information System (INIS)

Batygin, Yuri K.

2001-01-01

A self-consistent treatment of a three-dimensional ellipsoid with negligible emittance in time-dependent external field is performed. Envelope equations describing the evolution of an ellipsoid boundary are discussed. For a complete model it is required that the initial particle momenta be a linear function of the coordinates. Numerical example and verification of the problem by a 3-dimensional particle-in-cell simulations are given

Six-dimensional muon beam cooling using a homogeneous absorber: Concepts, beam dynamics, cooling decrements, and equilibrium emittances in a helical dipole channel

Directory of Open Access Journals (Sweden)

Yaroslav Derbenev

2005-04-01

Full Text Available The fast reduction of the six-dimensional phase space of muon beams is an essential requirement for muon colliders and also of great importance for neutrino factories based on accelerated muon beams. Ionization cooling, where all momentum components are degraded by an energy absorbing material and only the longitudinal momentum is restored by rf cavities, provides a means to quickly reduce transverse beam sizes. However, the beam energy spread cannot be reduced by this method unless the longitudinal emittance can be transformed or exchanged into the transverse emittance. Emittance exchange plans until now have been accomplished by using magnets to disperse the beam along the face of a wedge-shaped absorber such that higher momentum particles pass through thicker parts of the absorber and thus suffer larger ionization energy loss. In the scheme advocated in this paper, a special magnetic channel designed such that higher momentum corresponds to a longer path length, and therefore larger ionization energy loss, provides the desired emittance exchange in a homogeneous absorber without special edge shaping. Normal-conducting rf cavities imbedded in the magnetic field regenerate the energy lost in the absorber. One very attractive example of a cooling channel based on this principle uses a series of high-gradient rf cavities filled with dense hydrogen gas, where the cavities are in a magnetic channel composed of a solenoidal field with superimposed helical transverse dipole and quadrupole fields. In this scheme, the energy loss, the rf energy regeneration, the emittance exchange, and the transverse cooling happen simultaneously. The theory of this helical channel is described in some detail to support the analytical prediction of almost a factor of 10^{6} reduction in six-dimensional phase space volume in a channel about 56 m long. Equations describing the particle beam dynamics are derived and beam stability conditions are explored. Equations

Vertically aligned carbon nanotube field-effect transistors

KAUST Repository

Li, Jingqi

2012-10-01

Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed on the sidewall of the stack to bridge the source and drain. Both the effective gate dielectric and gate electrode were normal to the substrate surface. The channel length is determined by the dielectric thickness between source and drain electrodes, making it easier to fabricate sub-micrometer transistors without using time-consuming electron beam lithography. The transistor area is much smaller than the planar CNTFET due to the vertical arrangement of source and drain and the reduced channel area. © 2012 Elsevier Ltd. All rights reserved.

Field penetration induced charge redistribution effects on the field emission properties of carbon nanotubes - a first-principle study

International Nuclear Information System (INIS)

Chen, C.-W.; Lee, M.-H.; Clark, S.J.

2004-01-01

The effect of field penetration induced charge redistribution on the field emission properties of carbon nanotubes (CNTs) have been studied by the first-principle calculations. It is found that the carbon nanotube becomes polarized under external electric field leading to a charge redistribution. The resulting band bending induced by field penetration into the nanotube tip surface can further reduce the effective workfunction of the carbon nanotubes. The magnitude of the redistributed charge ΔQ is found to be nearly linear to the applied external field strength. In addition, we found that the capped (9, 0) zigzag nanotube demonstrates better field emission properties than the capped (5, 5) armchair nanotube due to the fact that the charge redistribution of π electrons along the zigzag-like tube axis is easier than for the armchair-like tube. The density of states (DOS) of the capped region of the nanotube is found to be enhanced with a value 30% higher than that of the sidewall part for the capped (5, 5) nanotube and 40% for the capped (9, 0) nanotube under an electric field of 0.33 V/A. Such enhancements of the DOS at the carbon nanotube tip show that electrons near the Fermi level will emit more easily due to the change of the surface band structure resulting from the field penetration in a high field

Alpha particle emitters in medicine

International Nuclear Information System (INIS)

Fisher, D.R.

1989-09-01

Radiation-induced cancer of bone, liver and lung has been a prominent harmful side-effect of medical applications of alpha emitters. In recent years, however, the potential use of antibodies labeled with alpha emitting radionuclides against cancer has seemed promising because alpha particles are highly effective in cell killing. High dose rates at high LET, effectiveness under hypoxic conditions, and minimal expectancy of repair are additional advantages of alpha emitters over antibodies labeled with beta emitting radionuclides for cancer therapy. Cyclotron-produced astatine-211 ( 211 At) and natural bismuth-212 ( 212 Bi) have been proposed and are under extensive study in the United States and Europe. Radium-223 ( 223 Ra) also has favorable properties as a potential alpha emitting label, including a short-lived daughter chain with four alpha emissions. The radiation dosimetry of internal alpha emitters is complex due to nonuniformly distributed sources, short particle tracks, and high relative specific ionization. The variations in dose at the cellular level may be extreme. Alpha-particle radiation dosimetry, therefore, must involve analysis of statistical energy deposition probabilities for cellular level targets. It must also account fully for nonuniform distributions of sources in tissues, source-target geometries, and particle-track physics. 18 refs., 4 figs

A numerical study of emittance growths in RF guns

CERN Document Server

Masuda, K; Sobajima, M; Kitagaki, J; Ohnishi, M; Toku, H; Yoshikawa, K

1999-01-01

A beam with greatly reduced emittance is required for further improvements of FELs, in particular, for FELs of shorter wavelengths, and of narrower bandwidths. From this viewpoint, the BNL/SLAC/UCLA 1.6-cell S-band photocathode RF gun performance characteristics were calculated, first in order to evaluate what may contribute to the emittance growths in photocathode RF guns. We developed an RF gun to produce an electron beam with an extremely low emittance, by using a 2-D simulation code. It is found that, by optimizing the laser injection phase, the drive laser spot radius and the cavity shape around the laser spot, the beam emittance by the 1.6-cell RF gun can be greatly reduced to 2.1 pi mm mrad, from the previous 4.4 pi mm mrad of the original shape.

Simulation studies of emittance growth in RMS mismatched beams

International Nuclear Information System (INIS)

Cucchetti, A.; Wangler, T.; Reiser, M.

1991-01-01

As shown in a separate paper, a charged-particle beam, whose rms size is not matched when injected into a transport channel or accelerator, has excess energy compared with that of a matched beam. If nonlinear space-charge forces are present and the mismatched beam transforms to a matched equilibrium state, rms-emittance growth will occur. The theory yields formulas for the possible rms-emittance growth, but not for the time it takes to achieve this growth. In this paper we present the results of systematic simulation studies for a mismatched 2-D round beam in an ideal transport channel with continuous linear focusing. Emittance growth rates obtained from the simulations for different amounts of mismatch and initial charge will be presented and the emittance growth will be compared with the theory. 6 refs., 7 figs

Field emission properties of the graphenated carbon nanotube electrode

Energy Technology Data Exchange (ETDEWEB)

Zanin, H., E-mail: hudson.zanin@bristol.ac.uk [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Faculdade de Engenharia Elétrica e Computação, Departamento de Semicondutores, Instrumentos e Fotônica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N. 400, CEP 13 083-852 Campinas, São Paulo (Brazil); Ceragioli, H.J.; Peterlevitz, A.C.; Baranauskas, Vitor [Faculdade de Engenharia Elétrica e Computação, Departamento de Semicondutores, Instrumentos e Fotônica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N. 400, CEP 13 083-852 Campinas, São Paulo (Brazil); Marciano, F.R.; Lobo, A.O. [Laboratory of Biomedical Nanotechnology/Institute of Research and Development at UNIVAP, Av. Shishima Hifumi, 2911, CEP 12244-000 Sao Jose dos Campos, SP (Brazil)

2015-01-01

Graphical abstract: - Highlights: • Facile method to prepare graphenated carbon nanotubes (g-CNTs). • The electric field emission behaviour of g-CNTs was studied. • g-CNTs show better emission current stability than non-graphenated CNTs. - Abstract: Reduced graphene oxide-coated carbon nanotubes (RGO-CNT) electrodes have been prepared by hot filament chemical vapour deposition system in one-step growth process. We studied RGO-CNT electrodes behaviour as cold cathode in field emission test. Our results show that RGO-CNT retain the low threshold voltage typical of CNTs, but with greatly improved emission current stability. The field emission enhancement value is significantly higher than that expected being caused by geometric effect (height divided by the radius of nanotube). This suggested that the field emission of this hybrid structure is not only from a single tip, but eventually it is from several tips with contribution of graphene nanosheets at CNT's walls. This phenomenon explains why the graphenated carbon nanotubes do not burn out as quickly as CNT does until emission ceases completely. These preliminaries results make nanocarbon materials good candidates for applications as electron sources for several devices.

Low Emittance Tuning Studies for SuperB

Energy Technology Data Exchange (ETDEWEB)

Liuzzo, Simone; /INFN, Pisa; Biagini, Maria; /INFN, Rome; Raimondi, Pantaleo; /INFN, Rome; Donald, Martin; /SLAC

2012-07-06

SuperB[1] is an international project for an asymmetric 2 rings collider at the B mesons cm energy to be built in the Rome area in Italy. The two rings will have very small beam sizes at the Interaction Point and very small emittances, similar to the Linear Collider Damping Rings ones. In particular, the ultra low vertical emittances, 7 pm in the LER and 4 pm in the HER, need a careful study of the misalignment errors effects on the machine performances. Studies on the closed orbit, vertical dispersion and coupling corrections have been carried out in order to specify the maximum allowed errors and to provide a procedure for emittance tuning. A new tool which combines MADX and Matlab routines has been developed, allowing for both corrections and tuning. Results of these studies are presented.

Increased field-emission site density from regrown carbon nanotube films

International Nuclear Information System (INIS)

Wang, Y.Y.; Gupta, S.; Liang, M.; Nemanich, R.J.

2005-01-01

Electron field-emission properties of as-grown, etched, and regrown carbon nanotube thin films were investigated. The aligned carbon nanotube films were deposited by the microwave plasma-assisted chemical vapor deposition technique. The surface of the as-grown film contained a carbon nanotube mat of amorphous carbon and entangled nanotubes with some tubes protruding from the surface. Hydrogen plasma etching resulted in the removal of the surface layer, and regrowth on the etched surface displayed the formation of a new carbon nanotube mat. The emission site density and the current-voltage dependence of the field emission from all of the samples were analyzed. The results showed that the as-grown sample had a few strong emission spots and a relatively high emission current density (∼20 μA/cm 2 at 1 V/μm), while the regrown sample exhibited a significantly increased emission site density

A Laboratory Goniometer System for Measuring Reflectance and Emittance Anisotropy

Directory of Open Access Journals (Sweden)

Arjan de Jong

2012-12-01

Full Text Available In this paper, a laboratory goniometer system for performing multi-angular measurements under controlled illumination conditions is described. A commercially available robotic arm enables the acquisition of a large number of measurements over the full hemisphere within a short time span making it much faster than other goniometers. In addition, the presented set-up enables assessment of anisotropic reflectance and emittance behaviour of soils, leaves and small canopies. Mounting a spectrometer enables acquisition of either hemispherical measurements or measurements in the horizontal plane. Mounting a thermal camera allows directional observations of the thermal emittance. This paper also presents three showcases of these different measurement set-ups in order to illustrate its possibilities. Finally, suggestions for applying this instrument and for future research directions are given, including linking the measured reflectance anisotropy with physically-based anisotropy models on the one hand and combining them with field goniometry measurements for joint analysis with remote sensing data on the other hand. The speed and flexibility of the system offer a large added value to the existing pool of laboratory goniometers.

Impact of water temperature and structural parameters on the hydraulic labyrinth-channel emitter performance

Directory of Open Access Journals (Sweden)

Ahmed I. Al-Amoud

2014-06-01

Full Text Available The effects of water temperature and structural parameters of a labyrinth emitter on drip irrigation hydraulic performance were investigated. The inside structural parameters of the trapezoidal labyrinth emitter include path width (W and length (L, trapezoidal unit numbers (N, height (H, and spacing (S. Laboratory experiments were conducted using five different types of labyrinth-channel emitters (three non-pressure compensating and two pressure-compensating emitters commonly used for subsurface drip irrigation systems. The water temperature effect on the hydraulic characteristics at various operating pressures was recorded and a comparison was made to identify the most effective structural parameter on emitter performance. The pressure compensating emitter flow exponent (x average was 0.014, while non-pressure compensating emitter’s values average was 0.456, indicating that the sensitivity of non-pressure compensating emitters to pressure variation is an obvious characteristic (p<0.001 of this type of emitters. The effects of water temperature on emitter flow rate were insignificant (p>0.05 at various operating pressures, where the flow rate index values for emitters were around one. The effects of water temperature on manufacturer’s coefficient of variation (CV values for all emitters were insignificant (p>0.05. The CV values of the non-pressure compensating emitters were lower than those of pressure compensating emitters. This is typical for most compensating models because they are manufactured with more elements than non-compensating emitters are. The results of regression analysis indicate that N and H are the essential factors (p<0.001 to affect the hydraulic performance.

Controlled growth of well-aligned carbon nanotubes with large diameters

Science.gov (United States)

Wang, Xianbao; Liu, Yunqi; Zhu, Daoben

2001-06-01

Well-aligned carbon nanotubes (CNTs) with large diameters (25-200 nm) were synthesized by pyrolysis of iron(II) phthalocyanine. The outer diameter up to 218.5 nm and the length of the well-aligned CNTs can be systematically controlled by varying the growth time. A tube-in-tube nano-structure with large and small diameters of 176 and 16.7 nm, respectively, was found. The grain sizes of the iron catalyst play an important role in controlling the CNT diameters. These results are of great importance to design new aligned CNT-based electron field emitters in the potential application of panel displays.

Growth and field emission properties of one-dimensional carbon composite structure consisting of vertically aligned carbon nanotubes and nanocones

International Nuclear Information System (INIS)

Zhang Hongxin; Feng, Peter X; Fonseca, Luis; Morell, Gerardo; Makarov, Vladimir I; Weiner, Brad R

2009-01-01

A simple approach is demonstrated for quickly growing a large-area aligned carbon composite nanostructure consisting of vertically aligned nanotubes and nanocones by the catalyst-assisted pulsed laser deposition techniques. The pyrolytic graphite was used as carbon source. The carbon nanocones were first grown on the molybdenum substrate with Ni catalysts. The carbon nanotubes have a uniform shape and length, aligned vertically on carbon nanocones, and the average diameter is about 7 nm. The special carbon composite arrays exhibit excellent field emission behaviours. The long-term field emission current stability of the one-dimensioned carbon nanostructure has also been investigated. No obvious current density decay was observed after a 10-day continuous experiment, indicating the super stability of the sample as cathode material.

On the design guideline for the low emittance synchrotron radiation source

International Nuclear Information System (INIS)

Kamiya, Y.; Kihara, M.

1983-09-01

In this note we will describe how the emittance of the electron storage ring is determined by the orbit parameters of the storage ring and show the lowest value of emittance which is achieved theoretically. Implication of this note with regard to the design of the low emittance storage ring will be discussed. (author)

Homogeneous Gaussian Profile P+-Type Emitters: Updated Parameters and Metal-Grid Optimization

Directory of Open Access Journals (Sweden)

M. Cid

2002-10-01

Full Text Available P+-type emitters were optimized keeping the base parameters constant. Updated internal parameters were considered. The surface recombination velocity was considered variable with the surface doping level. Passivated homogeneous emitters were found to have low emitter recombination density and high collection efficiency. A complete structure p+nn+ was analyzed, taking into account optimized shadowing and metal-contacted factors for laboratory cells as function of the surface doping level and the emitter thickness. The base parameters were kept constant to make the emitter characteristics evident. The most efficient P+-type passivated homogeneous emitters, provide efficiencies around 21% for a wide range of emitter sheet resistivity (50 -- 500 omega/ with the surface doping levels Ns=1×10(19 cm-3 and 5×10(19 cm-3. The output electrical parameters were evaluated considering the recently proposed value n i=9.65×10(9 (cm-3. A non-significant increase of 0.1% in the efficiency was obtained, validating all the conclusions obtained in this work, considering n i=1×10(10 cm-3.

Improved field emission properties of thiolated multi-wall carbon nanotubes on a flexible carbon cloth substrate

International Nuclear Information System (INIS)

Chuang, F T; Chen, P Y; Cheng, T C; Chien, C H; Li, B J

2007-01-01

In this paper we report the observation of enhanced field emission properties from thiolated multi-wall carbon nanotubes (MWCNTs) produced by a simple and effective two-step chemical surface modification technique. This technique implements carboxylation and thiolation on the MWCNTs synthesized by microwave plasma chemical vapor deposition (MPCVD) on the flexible carbon cloth substrate. The resulting thiolated MWCNTs were found to have a very low threshold field value of 1.25 V μm -1 and a rather high field enhancement factor of 1.93 x 10 4 , which are crucial for applications in versatile vacuum microelectronics

A new concept for the modeling of the positron emitter production for the particle therapy; Ein neues Konzept zur Modellierung der Positronenemitter-Produktion bei der Partikeltherapie

Energy Technology Data Exchange (ETDEWEB)

Priegnitz, Marlen

2012-07-01

One of the three main tumour treatment forms is radiation therapy. Here, the application of ion beams, in particular protons and carbon ions, is of growing importance. This high precision therapy requires a consequent monitoring of the dose delivery since the induced dose deposition is very sensitive to density changes in the irradiated tissue. Up to now, positron emission tomography (PET) is the only in vivo method in clinical use for monitoring the dose deposition in ion beam therapy. It allows for the verification of the particle range as well as the position of the irradiation field. The distribution of activity measured by means of PET cannot be compared directly to the planned dose distribution. Thus, a calculation of the expected activity distribution is required which then can be compared to the measurement. Simulation of the expected activity distribution requires the exact knowledge of various cross sections. Only a few of them have been measured in the required energy range so far. Therefore, in Monte Carlo simulations often intrinsic nuclear models or semi-empirical parametrization are used which often exhibit insufficient accuray. Among experts the question on the optimum ion species for tumour therapy is still open. Especially lithium ions exhibit a great potential due to their favourable physical and radiobiological properties. Also for these ions a PET monitoring is highly desirable. The presented work shows the feasibility of range verification by means of PET for lithium irradiation. Furthermore, a concept for modeling positron emitter distributions without the knowledge of cross sections is developed. This prediction is based on depth-dependent positron emitter yields measured in reference materials (water, graphite and polyethylene). With these data the positron emitter distribution in any material of known stoichiometry can be calculated by means of an appropriate linear combination. The feasibility of the yield concept is shown for lithium and

Minimum emittance of three-bend achromats

International Nuclear Information System (INIS)

Li Xiaoyu; Xu Gang

2012-01-01

The calculation of the minimum emittance of three-bend achromats (TBAs) made by Mathematical software can ignore the actual magnets lattice in the matching condition of dispersion function in phase space. The minimum scaling factors of two kinds of widely used TBA lattices are obtained. Then the relationship between the lengths and the radii of the three dipoles in TBA is obtained and so is the minimum scaling factor, when the TBA lattice achieves its minimum emittance. The procedure of analysis and the results can be widely used in achromats lattices, because the calculation is not restricted by the actual lattice. (authors)

High emittance black nickel coating on copper substrate for space applications

Energy Technology Data Exchange (ETDEWEB)

Somasundaram, Soniya, E-mail: jrf0013@isac.gov.in; Pillai, Anju M., E-mail: anjum@isac.gov.in; Rajendra, A., E-mail: rajendra@isac.gov.in; Sharma, A.K., E-mail: aks@isac.gov.in

2015-09-15

Highlights: • High emittance black nickel coating is obtained on copper substrate. • The effect of various process parameters on IR emittance is studied systematically. • Process parameters are optimized to develop a high emittance black nickel coating. • Coating obtained using the finalized parameters exhibited an emittance of 0.83. • SEM and EDAX are used for coating characterization. - Abstract: Black nickel, an alloy coating of zinc and nickel, is obtained on copper substrate by pulse electrodeposition from a modified Fishlock bath containing nickel sulphate, nickel ammonium sulphate, zinc sulphate and ammonium thiocyanate. A nickel undercoat of 4–5 μm thickness is obtained using Watts bath to increase the corrosion resistance and adhesion of the black nickel coating. The effect of bath composition, temperature, solution pH, current density and plating time on the coating appearance and corresponding infra-red emittance of the coating is investigated systematically. Process parameters are optimized to develop a high emittance space worthy black nickel coating to improve the heat radiation characteristics. The effect of the chemistry of the plating bath on the coating composition was studied using energy dispersive X-ray analysis (EDAX) of the coatings. The 5–6 μm thick uniform jet black zinc–nickel alloy coating obtained with optimized process exhibited an emittance of 0.83 and an absorbance of 0.92. The zinc to nickel ratio of black nickel coatings showing high emittance and appealing appearance was found to be in the range 2.3–2.4.

Emittance measuring unit for 100% duty factor linac injector beams

Energy Technology Data Exchange (ETDEWEB)

Shubaly, M R; Pachner, J Jr; Ormrod, J H; Ungrin, J; Schriber, S O [ed.

1976-11-01

A description is given of a system to measure the emittance of a 750 keV 100 mA dc proton beam suitable for injection into a 100% duty factor linear accelerator. A relatively slowly pulsed 45/sup 0/ magnet switches the beam to a beam dump inside the emittance measuring unit for approx. 10 s. A fast pulsed 5/sup 0/ magnet then deflects the beam to a multiple aperture ''pepper-pot'' plate for 300 ..mu..s. Beamlets passing through the plate travel 520 mm and produce a pattern on a scintillator screen. A photograph of the pattern is analyzed to determine beam emittance. Preliminary results on low current beams show a gross increase in the emittance in the horizontal plane.

An Online Multisensor Data Fusion Framework for Radar Emitter Classification

Directory of Open Access Journals (Sweden)

Dongqing Zhou

2016-01-01

Full Text Available Radar emitter classification is a special application of data clustering for classifying unknown radar emitters in airborne electronic support system. In this paper, a novel online multisensor data fusion framework is proposed for radar emitter classification under the background of network centric warfare. The framework is composed of local processing and multisensor fusion processing, from which the rough and precise classification results are obtained, respectively. What is more, the proposed algorithm does not need prior knowledge and training process; it can dynamically update the number of the clusters and the cluster centers when new pulses arrive. At last, the experimental results show that the proposed framework is an efficacious way to solve radar emitter classification problem in networked warfare.

An ionization pressure gauge with LaB6 emitter for long-term operation in strong magnetic fields

Science.gov (United States)

Wenzel, U.; Pedersen, T. S.; Marquardt, M.; Singer, M.

2018-03-01

We report here on a potentially significant improvement in the design of neutral pressure gauges of the so-called ASDEX-type which were first used in the Axially Symmetric Divertor EXperiment (ASDEX). Such gauges are considered state-of-the-art and are in wide use in fusion experiments, but they nonetheless suffer from a relatively high failure rate when operated at high magnetic field strengths for long times. This is therefore a significant concern for long-pulse, high-field experiments such as Wendelstein 7-X (W7-X) and ITER. The new design is much more robust. The improvement is to use a LaB6 crystal instead of a tungsten wire as the thermionic emitter of electrons in the gauge. Such a LaB6 prototype gauge was successfully operated for a total of 60 h in B = 3.1 T, confirming the significantly improved robustness of the new design and qualifying it for near-term operation in W7-X. With the LaB6 crystal, an order of magnitude reduction in heating current is achieved, relative to the tungsten filament based gauges, from 15-20 A to 1-2 A. This reduces the Lorenz forces and the heating power by an order of magnitude also and is presumably the reason for the much improved robustness. The new gauge design, test environment setup at the superconducting magnet, and results from test operation are described.

Emittance and trajectory control in the main linacs of the NLC

International Nuclear Information System (INIS)

Assmann, R.; Adolphsen, C.; Bane, K.; Raubenheimer, T.O.; Thompson, K.

1996-09-01

The main linacs of the next generation of linear colliders need to accelerate the particle beams to energies of up to 750 GeV while maintaining very small emittances. This paper describes the main mechanisms of static emittance growth in the main linacs of the Next Linear Collider (NLC). The authors present detailed simulations of the trajectory and emittance control algorithms that are foreseen for the NLC. They show that the emittance growth in the main linacs can be corrected down to about 110%. That number is significantly better than required for the NLC design luminosity

Internal dynamics and emittance growth in space-charge-dominated beams

International Nuclear Information System (INIS)

Anderson, O.A.

1987-01-01

Previous analytical studies have related transverse rms emittance growth in nonuniform beams to changes in the beam density profile, but the time evolution of the process has not been analyzed. Our new approach analyzes the internal motion of the beam and from this obtains the explicit time dependence of the rms emittance. It is shown to reach its peak value explosively in about one quarter of a plasma period. The subsequent behavior depends on the uniformity of the initial density profile. We derive a uniformity criterion that determines whether or not the emittance oscillates periodically and present examples of density profiles for which the emittance returns to its initial value and then continues to oscillate. We discuss a class of continuous initial profiles that lead to discontinuous shocklike behavior (with partial irreversibility of the oscillations) and a class of segmented profiles for which the emittance jumps to its maximum value in one fourth of a plasma period and remains at that value with essentially no further change. (author)

Carbon nanotubes field-effect transistor for rapid detection of DHA

International Nuclear Information System (INIS)

Nguyen Thi Thuy; Nguyen Duc Chien; Mai Anh Tuan

2012-01-01

This paper presents the development of DNA sensor based on a network carbon nanotubes field effect transistor (CNTFETs) for Escherichia coli bacteria detection. The DNA sequences were immobilized on single-walled carbon nanotubes of transistor CNTFETs by using absorption. The hybridization of the DNA probe sequences and complementary DNA strands was detected by electrical conductance change from the electron doping by DNA hybridization directly on the carbon nanotubes leading to the change in the metal-CNTs barrier energy through the modulation of the electrode work function of carbon nanotubes field effect transistor. The results showed that the response time of DNA sensor was approximately 1 min and the sensitivity of DNA sensor was at 0.565 μA/nM; the detection limit of the sensor was about 1 pM of E. coli bacteria sample. (author)

Modular low-voltage electron emitters

International Nuclear Information System (INIS)

Berejka, Anthony J.

2005-01-01

Modular, low-voltage electron emitters simplify electron beam (EB) technology for many industrial uses and for research and development. Modular electron emitters are produced in quantity as sealed systems that are evacuated at the factory, eliminating the need for vacuum pumps at the point of use. A plug-out-plug-in method of replacement facilitates servicing. By using an ultra-thin 6-7 μm titanium foil window, solid-state power supplies, an innovative design to extract and spread the beam (enabling systems to be placed adjacent to each other to extend beam width) and touch-screen computer controls, these modular units combine ease of use and electrical transfer efficiency at voltages that can be varied between 80 kV and 150 kV with beam currents up to 40 mA per 25 cm across the beam window. These new devices have been made in three widths: 5 cm, 25 cm, and 40 cm. Details of the beam construction and illustrations of industrial uses will be presented. Traditional uses in the graphic arts and coatings areas have welcomed this modular technology as well as uses for surface sterilization. Being compact and lightweight (∼15 kg/emitter), these modular beams have been configured around complex shapes to achieve three-dimensional surface curing at high production rates

Modular low-voltage electron emitters

Science.gov (United States)

Berejka, Anthony J.

2005-12-01

Modular, low-voltage electron emitters simplify electron beam (EB) technology for many industrial uses and for research and development. Modular electron emitters are produced in quantity as sealed systems that are evacuated at the factory, eliminating the need for vacuum pumps at the point of use. A plug-out-plug-in method of replacement facilitates servicing. By using an ultra-thin 6-7 μm titanium foil window, solid-state power supplies, an innovative design to extract and spread the beam (enabling systems to be placed adjacent to each other to extend beam width) and touch-screen computer controls, these modular units combine ease of use and electrical transfer efficiency at voltages that can be varied between 80 kV and 150 kV with beam currents up to 40 mA per 25 cm across the beam window. These new devices have been made in three widths: 5 cm, 25 cm, and 40 cm. Details of the beam construction and illustrations of industrial uses will be presented. Traditional uses in the graphic arts and coatings areas have welcomed this modular technology as well as uses for surface sterilization. Being compact and lightweight (∼15 kg/emitter), these modular beams have been configured around complex shapes to achieve three-dimensional surface curing at high production rates.

Beam dynamics in rf guns and emittance correction techniques

International Nuclear Information System (INIS)

Serafini, L.

1994-01-01

In this paper we present a general review of beam dynamics in a laser-driven rf gun. The peculiarity of such an accelerating structure versus other conventional multi-cell linac structures is underlined on the basis of the Panofsky-Wenzel theorem, which is found to give a theoretical background for the well known Kim's model. A basic explanation for some proposed methods to correct rf induced emittance growth is also derived from the theorem. We also present three emittance correction techniques for the recovery of space-charge induced emittance growth, namely the optimum distributed disk-like bunch technique, the use of rf spatial harmonics to correct spherical aberration induced by space charge forces and the technique of emittance filtering by clipping the electron beam. The expected performances regarding the beam quality achievable with different techniques, as predicted by scaling laws and simulations, are analyzed, and, where available, compared to experimental results. (orig.)

Transverse emittance measurement at REGAE via a solenoid scan

Energy Technology Data Exchange (ETDEWEB)

Hachmann, Max

2012-12-15

The linear accelerator REGAE at DESY produces short and low charged electron bunches, on the one hand to resolve the excitation transitions of atoms temporally by pump probe electron diffraction experiments and on the other hand to investigate principal mechanisms of laser plasma acceleration. For both cases a high quality electron beam is required. A quantity to rate the beam quality is the beam emittance. In the course of this thesis transverse emittance measurements by a solenoid scan could be realized and beyond that an improved theoretical description of a solenoid was successful. The foundation of emittance measurements are constituted by theoretical models which describe the envelope of a beam. Two different models were derived. The first is an often used model to determine the transverse beam emittance without considering space charge effects. More interesting and challenging was the development of an envelope model taking space charge effects into account. It is introduced and cross checked with measurements and simulations.

Transport and emittance study for 18 GHz superconducting-ECR ion source at RCNP.

Science.gov (United States)

Yorita, T; Hatanaka, K; Fukuda, M; Ueda, H; Kibayashi, M; Morinobu, S; Tamii, A

2012-02-01

As the upgrade program of the azimuthally varying field (AVF) cyclotron is at the cyclotron facility of the RCNP, Osaka University for the improvement of the quality, stability, and intensity of accelerated beams, an 18 GHz superconducting (SC) ECR ion source has been installed to increase beam currents and to extend the variety of ions, especially for highly charged heavy ions which can be accelerated by RCNP AVF cyclotron. The production development of several ions such as B, O, N, Ne, Ar, Ni, Kr, and Xe has been performed by Yorita et al. [Rev. Sci. Instrum. 79, 02A311(2008); 81, 02A332 (2010)]. Further studies for the beam transport have been done in order to improve the beam current more for injection of cyclotron. The effect of field leakage of AVF main coil is not negligible and additional steering magnet has been installed and then beam transmission has been improved. The emittance monitor has also been developed for the purpose of investigating correlation between emittance of beam from ECR ion sources and injection efficiency. The monitor consists with BPM82 with rotating wire for fast measurement for efficient study.

Vertical electric field stimulated neural cell functionality on porous amorphous carbon electrodes.

Science.gov (United States)

Jain, Shilpee; Sharma, Ashutosh; Basu, Bikramjit

2013-12-01

We demonstrate the efficacy of amorphous macroporous carbon substrates as electrodes to support neuronal cell proliferation and differentiation in electric field mediated culture conditions. The electric field was applied perpendicular to carbon substrate electrode, while growing mouse neuroblastoma (N2a) cells in vitro. The placement of the second electrode outside of the cell culture medium allows the investigation of cell response to electric field without the concurrent complexities of submerged electrodes such as potentially toxic electrode reactions, electro-kinetic flows and charge transfer (electrical current) in the cell medium. The macroporous carbon electrodes are uniquely characterized by a higher specific charge storage capacity (0.2 mC/cm(2)) and low impedance (3.3 kΩ at 1 kHz). The optimal window of electric field stimulation for better cell viability and neurite outgrowth is established. When a uniform or a gradient electric field was applied perpendicular to the amorphous carbon substrate, it was found that the N2a cell viability and neurite length were higher at low electric field strengths (≤ 2.5 V/cm) compared to that measured without an applied field (0 V/cm). While the cell viability was assessed by two complementary biochemical assays (MTT and LDH), the differentiation was studied by indirect immunostaining. Overall, the results of the present study unambiguously establish the uniform/gradient vertical electric field based culture protocol to either enhance or to restrict neurite outgrowth respectively at lower or higher field strengths, when neuroblastoma cells are cultured on porous glassy carbon electrodes having a desired combination of electrochemical properties. Copyright © 2013 Elsevier Ltd. All rights reserved.

Deformation bands in porous carbonate grainstones: Field and laboratory observations

NARCIS (Netherlands)

Cilona, A.; Baud, P.; Tondi, E.; Agosta, F.; Vinciguerra, S.; Rustichelli, A.; Spiers, C.J.

2012-01-01

Recent field-based studies documented deformation bands in porous carbonates; these structures accommodate volumetric and/or shear strain by means of pore collapse, grain rotation and/or sliding. Microstructural observations of natural deformation bands in carbonates showed that, at advanced stages

Preservation of low slice emittance in bunch compressors

Directory of Open Access Journals (Sweden)

S. Bettoni

2016-03-01

Full Text Available Minimizing the dilution of the electron beam emittance is crucial for the performance of accelerators, in particular for free electron laser facilities, where the length of the machine and the efficiency of the lasing process depend on it. Measurements performed at the SwissFEL Injector Test Facility revealed an increase in slice emittance after compressing the bunch even for moderate compression factors. The phenomenon was experimentally studied by characterizing the dependence of the effect on beam and machine parameters relevant for the bunch compression. The reproduction of these measurements in simulation required the use of a 3D beam dynamics model along the bunch compressor that includes coherent synchrotron radiation. Our investigations identified transverse effects, such as coherent synchrotron radiation and transverse space charge as the sources of the observed emittance dilution, excluding other effects, such as chromatic effects on single slices or spurious dispersion. We also present studies, both experimental and simulation based, on the effect of the optics mismatch of the slices on the variation of the slice emittance along the bunch. After a corresponding reoptimization of the beam optics in the test facility we reached slice emittances below 200 nm for the central slices along the longitudinal dimension with a moderate increase up to 300 nm in the head and tail for a compression factor of 7.5 and a bunch charge of 200 pC, equivalent to a final current of 150 A, at about 230 MeV energy.

Coupling of Quantum Emitters in Nanodiamonds to Plasmonic Structures

DEFF Research Database (Denmark)

Kumar, Shailesh

This PhD thesis describes work towards the enhancement and efficient channeling of photons emitted from a single photon emitter. The emitter used is a defect center, the Nitrogen-Vacancy (NV) center, in diamond. The NV-center has many unique properties, such as long coherence time of its electron...

Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H− ion source

International Nuclear Information System (INIS)

Ueno, A.; Koizumi, I.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

2014-01-01

The prototype rf-driven H − ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H − ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (T PE ) of about 120 °C compared with the typically used T PE of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H − ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances

Discrete quantum dot like emitters in monolayer MoSe{sub 2}: Spatial mapping, magneto-optics, and charge tuning

Energy Technology Data Exchange (ETDEWEB)

Branny, Artur; Kumar, Santosh; Gerardot, Brian D., E-mail: b.d.gerardot@hw.ac.uk [Institute of Photonics and Quantum Sciences, SUPA, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Wang, Gang; Robert, Cedric; Lassagne, Benjamin; Marie, Xavier; Urbaszek, Bernhard, E-mail: urbaszek@insa-toulouse.fr [Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077 Toulouse (France)

2016-04-04

Transition metal dichalcogenide monolayers such as MoSe{sub 2}, MoS{sub 2}, and WSe{sub 2} are direct bandgap semiconductors with original optoelectronic and spin-valley properties. Here we report on spectrally sharp, spatially localized emission in monolayer MoSe{sub 2}. We find this quantum dot-like emission in samples exfoliated onto gold substrates and also suspended flakes. Spatial mapping shows a correlation between the location of emitters and the existence of wrinkles (strained regions) in the flake. We tune the emission properties in magnetic and electric fields applied perpendicular to the monolayer plane. We extract an exciton g-factor of the discrete emitters close to −4, as for 2D excitons in this material. In a charge tunable sample, we record discrete jumps on the meV scale as charges are added to the emitter when changing the applied voltage.

Emittance Measurements from a Laser Driven Electron Injector

Energy Technology Data Exchange (ETDEWEB)

Reis, David A

2003-07-28

The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 {angstrom}, the LCLS requires an electron injector that can produce an electron beam with approximately 1 {pi} mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the laser and electron beam at the GTF. A convolved measurement of the relative timing between the laser and the rf phase in the gun shows that the jitter is less than 2.5 ps rms. Emittance measurements of the electron beam at 35 MeV are reported as a function of the (Gaussian) pulse length and transverse profile of the laser as well as the charge of the electron beam at constant phase and gradient in both the gun and linac. At 1 nC the emittance was found to be {approx} 13 {pi} mm-mrad for 5 ps and 8 ps long laser pulses. At 0.5 nC the measured emittance decreased approximately 20% in the 5 ps case and 40% in the 8 ps case. These measurements are between 40-80% higher than simulations for similar experimental conditions. In addition, the thermal emittance of the electron beam was measured to be 0.5 {pi} mm-mrad.

Quadrupole Transfer Function for Emittance Measurement

CERN Document Server

Cameron, Peter; Jansson, Andreas; Tan, Cheng-Yang

2008-01-01

Historically the use of the quadrupole moment measurement has been impeded by the requirement for large dynamic range, as well as measurement sensitivity to beam position. We investigate the use of the transfer function technique [1-3] in combination with the sensitivity and 160dB revolution line rejection of the direct diode detection analog front end [4] to open the possibility of an emittance diagnostic that may be implemented without operational complication, quasi- parasitic to the operation of existing tune measurement systems. Such a diagnostic would be particularly useful as an emittance monitor during acceleration ramp development in machines like RHIC and the LHC.

Emitter/absorber interface of CdTe solar cells

Energy Technology Data Exchange (ETDEWEB)

Song, Tao, E-mail: tsong241@gmail.com; Sites, James R. [Physics Department, Colorado State University, Fort Collins, Colorado 80523 (United States); Kanevce, Ana [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

2016-06-21

The performance of CdTe solar cells can be very sensitive to the emitter/absorber interface, especially for high-efficiency cells with high bulk lifetime. Performance losses from acceptor-type interface defects can be significant when interface defect states are located near mid-gap energies. Numerical simulations show that the emitter/absorber band alignment, the emitter doping and thickness, and the defect properties of the interface (i.e., defect density, defect type, and defect energy) can all play significant roles in the interface recombination. In particular, a type I heterojunction with small conduction-band offset (0.1 eV ≤ ΔE{sub C} ≤ 0.3 eV) can help maintain good cell efficiency in spite of high interface defect density, much like with Cu(In,Ga)Se{sub 2} (CIGS) cells. The basic principle is that positive ΔE{sub C}, often referred to as a “spike,” creates an absorber inversion and hence a large hole barrier adjacent to the interface. As a result, the electron-hole recombination is suppressed due to an insufficient hole supply at the interface. A large spike (ΔE{sub C} ≥ 0.4 eV), however, can impede electron transport and lead to a reduction of photocurrent and fill-factor. In contrast to the spike, a “cliff” (ΔE{sub C} < 0 eV) allows high hole concentration in the vicinity of the interface, which will assist interface recombination and result in a reduced open-circuit voltage. Another way to mitigate performance losses due to interface defects is to use a thin and highly doped emitter, which can invert the absorber and form a large hole barrier at the interface. CdS is the most common emitter material used in CdTe solar cells, but the CdS/CdTe interface is in the cliff category and is not favorable from the band-offset perspective. The ΔE{sub C} of other n-type emitter choices, such as (Mg,Zn)O, Cd(S,O), or (Cd,Mg)Te, can be tuned by varying the elemental ratio for an optimal positive value of ΔE{sub C}. These

Ion concentration in micro and nanoscale electrospray emitters.

Science.gov (United States)

Yuill, Elizabeth M; Baker, Lane A

2018-06-01

Solution-phase ion transport during electrospray has been characterized for nanopipettes, or glass capillaries pulled to nanoscale tip dimensions, and micron-sized electrospray ionization emitters. Direct visualization of charged fluorophores during the electrospray process is used to evaluate impacts of emitter size, ionic strength, analyte size, and pressure-driven flow on heterogeneous ion transport during electrospray. Mass spectrometric measurements of positively- and negatively-charged proteins were taken for micron-sized and nanopipette emitters under low ionic strength conditions to further illustrate a discrepancy in solution-driven transport of charged analytes. A fundamental understanding of analyte electromigration during electrospray, which is not always considered, is expected to provide control over selective analyte depletion and enrichment, and can be harnessed for sample cleanup. Graphical abstract Fluorescence micrographs of ion migration in nanoscale pipettes while solution is electrosprayed.

Emittance of a finite scattering medium with refractive index greater than unity

International Nuclear Information System (INIS)

Crosbie, A.L.

1980-01-01

Refractive index and scattering can significantly influence the transfer of radiation in a semitransparent medium such as water, glass, plastics, or ceramics. In a recent article (1979), the author presented exact numerical results for the emittance of a semiinfinite scattering medium with a refractive index greater than unity. The present investigation extends the analysis to a finite medium. The physical situation consists of a finite planar layer. The isothermal layer emits, absorbs, and isotropically scatters thermal radiation. It is characterized by single scattering albedo, optical thickness, refractive index, and temperature. A formula for the directional emittance is derived, the directional emittance being the emittance of the medium multiplied by the interface transmittance. The ratio of hemispherical to normal emittance is tabulated and discussed

MD2065: Emittance exchange with linear coupling

CERN Document Server

Carver, Lee Robert; Persson, Tobias Hakan Bjorn; Amorim, David; Levens, Tom; Pesah, Arthur Chalom; CERN. Geneva. ATS Department

2018-01-01

In order to better understand the luminosity imbalance between ATLAS and CMS that was observed in 2016, it was proposed to perform a test whereby the horizontal and vertical emittances are exchanged by crossing the tunes in the presence of linear coupling. The luminosity before and after the exchange could be compared to see if the imbalance stems purely from the uneven emittances or if there is an additional mechanism in play. However, due to limited machine availability only tests at injection were able to performed.

Cancellation of RF Coupler-Induced Emittance Due to Astigmatism

Energy Technology Data Exchange (ETDEWEB)

Dowell, David H.; /SLAC

2016-12-11

It is well-known that the electron beam quality required for applications such as FEL’s and ultra-fast electron diffraction can be degraded by the asymmetric fields introduced by the RF couplers of superconducting linacs. This effect is especially troublesome in the injector where the low energy beam from the gun is captured into the first high gradient accelerator section. Unfortunately modifying the established cavity design is expensive and time consuming, especially considering that only one or two sections are needed for an injector. Instead, it is important to analyze the coupler fields to understand their characteristics and help find less costly solutions for their cancellation and mitigation. This paper finds the RF coupler-induced emittance for short bunches is mostly due to the transverse spatial sloping or tilt of the field, rather than the field’s time-dependence. It is shown that the distorting effects of the coupler can be canceled with a static (DC) quadrupole lens rotated about the z-axis.

Growth rate of non-thermodynamic emittance of intense electron beams

International Nuclear Information System (INIS)

Carlsten, B.E.

1998-01-01

The nonlinear free-energy concept has been particularly useful in estimating the emittance growth resulting from any excess energy of electron beams in periodic and uniform channels. However, additional emittance growth, that is geometrical rather than thermodynamic in origin, is induced if the particles have different kinetic energies and axial velocities, which is common for mildly relativistic, very intense electron beams. This effect is especially strong if particles lose or gain significant kinetic energy due to the beam's potential depression, as the beam converges and diverges. In this paper we analyze these geometric emittance growth mechanisms for a uniform, continuous, intense electron beam in a focusing transport channel consisting of discrete solenoidal magnets, over distances short enough that the beam does not reach equilibrium. These emittance growth mechanisms are based on the effects of (1) energy variations leading to nonlinearities in the space-charge force even if the current density is uniform, (2) an axial velocity shear radially along the beam due to the beam's azimuthal motion in the solenoids, and (3) an energy redistribution of the beam as the beam compresses or expands. The geometric emittance growth is compared in magnitude with that resulting from the nonlinear free energy, for the case of a mismatched beam in a uniform channel, and is shown to dominate for certain experimental conditions. Rules for minimizing the emittance along a beamline are outlined. copyright 1998 The American Physical Society

Measurement of the transverse emittance for the NSC Pelletron

International Nuclear Information System (INIS)

Rodriques, G.; Mandal, A.; Chopra, S.; Joshi, R.; Datta, S.K.; Roy, A.

1998-01-01

The knowledge of the emittance (transverse and longitudinal) of the NSC pelletron is essential for matching the acceptance of the LINAC which is to be installed to augment the pelletron beam energies. The transverse emittance of NSC pelletron has been measured by employing a focussing element and a down-stream beam profile monitor

Low Cost Constant – Head Drip Irrigation Emitter for Climate ...

African Journals Online (AJOL)

Low Cost Constant – Head Drip Irrigation Emitter for Climate Change Adaptation in Nigeria: Engineering Design and Calibration. ... The drip system comprises of abarrel, sub-main line, lateral lines, tubes and emitters, it can irrigate140 crop ...

Experimental studies on coherent synchrotron radiation at an emittance exchange beam line

Science.gov (United States)

Thangaraj, J. C. T.; Thurman-Keup, R.; Ruan, J.; Johnson, A. S.; Lumpkin, A. H.; Santucci, J.

2012-11-01

One of the goals of the Fermilab A0 photoinjector is to investigate experimentally the transverse to longitudinal emittance exchange (EEX) principle. Coherent synchrotron radiation in the emittance exchange line could limit the performance of the emittance exchanger at short bunch lengths. In this paper, we present experimental and simulation studies of the coherent synchrotron radiation (CSR) in the emittance exchange line at the A0 photoinjector. We report on time-resolved CSR studies using a skew-quadrupole technique. We also demonstrate the advantages of running the EEX with an energy-chirped beam.

Outstanding field emission properties of wet-processed titanium dioxide coated carbon nanotube based field emission devices

Energy Technology Data Exchange (ETDEWEB)

Xu, Jinzhuo; Ou-Yang, Wei, E-mail: ouyangwei@phy.ecnu.edu.cn; Chen, Xiaohong; Guo, Pingsheng; Piao, Xianqing; Sun, Zhuo [Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China); Xu, Peng; Wang, Miao [Department of Physics, Zhejiang University, 38 ZheDa Road, Hangzhou 310027 (China); Li, Jun [Department of Electronic Science and Technology, Tongji University, 4800 Caoan Road, Shanghai 201804 (China)

2015-02-16

Field emission devices using a wet-processed composite cathode of carbon nanotube films coated with titanium dioxide exhibit outstanding field emission characteristics, including ultralow turn on field of 0.383 V μm{sup −1} and threshold field of 0.657 V μm{sup −1} corresponding with a very high field enhancement factor of 20 000, exceptional current stability, and excellent emission uniformity. The improved field emission properties are attributed to the enhanced edge effect simultaneously with the reduced screening effect, and the lowered work function of the composite cathode. In addition, the highly stable electron emission is found due to the presence of titanium dioxide nanoparticles on the carbon nanotubes, which prohibits the cathode from the influence of ions and free radical created in the emission process as well as residual oxygen gas in the device. The high-performance solution-processed composite cathode demonstrates great potential application in vacuum electronic devices.

Double-step annealing and ambient effects on phosphorus implanted emitters in silicon

International Nuclear Information System (INIS)

Koji, T.; Tseng, W.F.; Mayer, J.W.; Suganuma, T.

1979-01-01

Emitters of npn silicon bipolar transistors have been made by a phosphorus implantation at 50 keV P + to a dose of 1 x 10 16 cm -2 . This was followed by high temperature processes to reduce lattice disorder, to drive-in the phosphorus atoms, and to form oxide layers. The first process step was carried out by using single- and double-step anneals in various ambients (dry N 2 , dry 0 2 and steam) while the drive-in and oxidation steps were common for all structures. Electrical measurements on emitter/base leakage current, low frequency (popcorn) noise and current gain showed that the annealing ambient had a major influence. The transistors with implanted emitters annealed in a dry N 2 ambient are comparable to commercial ones with thermally-diffused emitters. Transmission electron microscopy observations on samples annealed in steam ambients revealed dislocations extending into the sidewall of the emitter/base junction. This sidewell penetration of dislocations is the main origin of the degradation of the emitter/base junction characteristics. (author)

Emittance growth in the DARHT Axis-II Downstream Transport

Energy Technology Data Exchange (ETDEWEB)

Ekdahl, Jr., Carl August [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Schulze, Martin E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-04-14

Using a particle-in-cell (PIC) code, we investigated the possibilities for emittance growth through the quadrupole magnets of the system used to transport the high-current electron beam from an induction accelerator to the bremsstrahlung converter target used for flash radiography. We found that even highly mismatched beams exhibited little emittance growth (< 6%), which we attribute to softening of their initial hard edge current distributions. We also used this PIC code to evaluate the accuracy of emittance measurements using a solenoid focal scan following the quadrupole magnets. If the beam is round after the solenoids, the simulations indicate that the measurement is highly accurate, but it is substantially inaccurate for elliptical beams

Extraction of emission parameters for large-area field emitters, using a technically complete Fowler–Nordheim-type equation

International Nuclear Information System (INIS)

Forbes, Richard G

2012-01-01

In papers on cold field electron emission from large-area field emitters (LAFEs), it has become widespread practice to publish a misleading Fowler–Nordheim-type (FN-type) equation. This equation over-predicts the LAFE-average current density by a large highly variable factor thought to usually lie between 10 3 and 10 9 . This equation, although often referenced to FN’s 1928 paper, is a simplified equation used in undergraduate teaching, does not apply unmodified to LAFEs and does not appear in the 1928 paper. Technological LAFE papers often do not cite any theoretical work more recent than 1928, and often do not comment on the discrepancy between theory and experiment. This usage has occurred widely, in several high-profile American and UK applied-science journals (including Nanotechnology), and in various other places. It does not inhibit practical LAFE development, but can give a misleading impression of potential LAFE performance to non-experts. This paper shows how the misleading equation can be replaced by a conceptually complete FN-type equation that uses three high-level correction factors. One of these, or a combination of two of them, may be useful as an additional measure of LAFE quality; this paper describes a method for estimating factor values using experimental data and discusses when it can be used. Suggestions are made for improved engineering practice in reporting LAFE results. Some of these should help to prevent situations arising whereby an equation appearing in high-profile applied-science journals is used to support statements that an engineering regulatory body might deem to involve professional negligence. (paper)

Calculating emittance for Gaussian and Non-Gaussian distributions by the method of correlations for slits

International Nuclear Information System (INIS)

Tan, Cheng-Yang; Fermilab

2006-01-01

One common way for measuring the emittance of an electron beam is with the slits method. The usual approach for analyzing the data is to calculate an emittance that is a subset of the parent emittance. This paper shows an alternative way by using the method of correlations which ties the parameters derived from the beamlets to the actual parameters of the parent emittance. For parent distributions that are Gaussian, this method yields exact results. For non-Gaussian beam distributions, this method yields an effective emittance that can serve as a yardstick for emittance comparisons

Emittance growth due to negative-mass instability above transition

International Nuclear Information System (INIS)

Ng, King-Yuen.

1994-08-01

Due to space-charge effect, there is a growth of bunch emittance across transition as a result of negative-mass instability. The models of growth at cutoff frequency and growth from high-frequency Schottky noise are reviewed. The difficulties of performing reliable simulations are discussed. An intuitive self-bunching model for estimating emittance growth is presented

Silicon microelectronic field-emissive devices for advanced display technology

Science.gov (United States)

Morse, J. D.

1993-03-01

Field-emission displays (FED's) offer the potential advantages of high luminous efficiency, low power consumption, and low cost compared to AMLCD or CRT technologies. An LLNL team has developed silicon-point field emitters for vacuum triode structures and has also used thin-film processing techniques to demonstrate planar edge-emitter configurations. LLNL is interested in contributing its experience in this and other FED-related technologies to collaborations for commercial FED development. At LLNL, FED development is supported by computational capabilities in charge transport and surface/interface modeling in order to develop smaller, low-work-function field emitters using a variety of materials and coatings. Thin-film processing, microfabrication, and diagnostic/test labs permit experimental exploration of emitter and resistor structures. High field standoff technology is an area of long-standing expertise that guides development of low-cost spacers for FEDS. Vacuum sealing facilities are available to complete the FED production engineering process. Drivers constitute a significant fraction of the cost of any flat-panel display. LLNL has an advanced packaging group that can provide chip-on-glass technologies and three-dimensional interconnect generation permitting driver placement on either the front or the back of the display substrate.

Experimental studies on coherent synchrotron radiation at an emittance exchange beam line

Directory of Open Access Journals (Sweden)

J. C. T. Thangaraj

2012-11-01

Full Text Available One of the goals of the Fermilab A0 photoinjector is to investigate experimentally the transverse to longitudinal emittance exchange (EEX principle. Coherent synchrotron radiation in the emittance exchange line could limit the performance of the emittance exchanger at short bunch lengths. In this paper, we present experimental and simulation studies of the coherent synchrotron radiation (CSR in the emittance exchange line at the A0 photoinjector. We report on time-resolved CSR studies using a skew-quadrupole technique. We also demonstrate the advantages of running the EEX with an energy-chirped beam.

Very low recombination phosphorus emitters for high efficiency crystalline silicon solar cells

International Nuclear Information System (INIS)

Ortega, P; Vetter, M; Bermejo, S; Alcubilla, R

2008-01-01

This work studies low recombination phosphorus emitters on c-Si. The emitters are fabricated by diffusion from solid sources and then passivated by thermal oxide yielding sheet resistances between 15 and 280 Ω/sq. Emitter saturation current densities lie in the 2.5–110 fA cm −2 range, leading to implicit open-circuit voltages between 674 and 725 mV. Bulk lifetime is limited by intrinsic recombination mechanisms. Surface recombination velocities between 80 and 300 cm s −1 have been obtained, appearing among the lowest reported in this range of emitter sheet resistances

Transport and acceleration of low-emittance electron beams

International Nuclear Information System (INIS)

Henke, H.

1989-01-01

Linear accelerators for colliders and for free-electron lasers require beams with both high brightness and low emittance. Their transport and acceleration is limited by single-particle effects originating from injection jitter, from the unavoidable position jitter of components, and from chromaticity. Collective phenomena, essentially due to wake fields acting within the bunch, are most severe in the case of high-frequency structures, i.e. a small aperture. Whilst, in the past, the transverse wake-field effects were believed to be most serious, we know that they can even be beneficial when inducing a corresponding spread in betatron oscillation either by an energy spread along the bunch or by an RF focusing system acting on the bunch scale. This paper evaluates the different effects by simple analytical means after making use of the smooth focusing approximation and the two-particle model. Numerical simulation results are used for verification. 14 refs., 6 figs., 2 tabs

Origins of transverse emittance blow-up during the LHC energy tramp

CERN Document Server

Kuhn, M; Arduini, G; Kain, V; Schaumann, M; Tomas, R

2014-01-01

During LHC Run 1 about 30 % of the potential peak performance was lost due to transverse emittance blow-up through the LHC cycle. Measurements indicated that the majority of the blow-up occurred during the energy ramp. Until the end of LHC Run 1 this emittance blow-up could not be eliminated. In this paper the measurements and observations of emittance growth through the ramp are summarized. Simulation results for growth due to Intra Beam Scattering will be shown and compared to measurements. A summary of investigations of other possible sources will be given and backed up with simulations where possible. Requirements for commissioning the LHC with beam in 2015 after Long Shutdown 1 to understand and control emittance blow-up will be listed.

Field electron emission from pencil-drawn cold cathodes

Energy Technology Data Exchange (ETDEWEB)

Chen, Jiangtao; Yang, Bingjun; Liu, Xiahui; Yang, Juan; Yan, Xingbin, E-mail: xbyan@licp.cas.cn [Laboratory of Clean Energy Chemistry and Materials, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)

2016-05-09

Field electron emitters with flat, curved, and linear profiles are fabricated on flexible copy papers by direct pencil-drawing method. This one-step method is free of many restricted conditions such as high-temperature, high vacuum, organic solvents, and multistep. The cold cathodes display good field emission performance and achieve high emission current density of 78 mA/cm{sup 2} at an electric field of 3.73 V/μm. The approach proposed here would bring a rapid, low-cost, and eco-friendly route to fabricate but not limited to flexible field emitter devices.

Cancer therapy with alpha-emitters labeled peptides.

Science.gov (United States)

Dadachova, Ekaterina

2010-05-01

Actively targeted alpha-particles offer specific tumor cell killing action with less collateral damage to surrounding normal tissues than beta-emitters. During the last decade, radiolabeled peptides that bind to different receptors on the tumors have been investigated as potential therapeutic agents both in the preclinical and clinical settings. Advantages of radiolabeled peptides over antibodies include relatively straightforward chemical synthesis, versatility, easier radiolabeling, rapid clearance from the circulation, faster penetration and more uniform distribution into tissues, and less immunogenicity. Rapid internalization of the radiolabeled peptides with equally rapid re-expression of the cell surface target is a highly desirable property that enhances the total delivery of these radionuclides into malignant sites. Peptides, such as octreotide, alpha-melanocyte-stimulating hormone analogues, arginine-glycine-aspartic acid-containing peptides, bombesin derivatives, and others may all be feasible for use with alpha-emitters. The on-going preclinical work has primarily concentrated on octreotide and octreotate analogues labeled with Bismuth-213 and Astatine-211. In addition, alpha-melanocyte-stimulating hormone analogue has been labeled with Lead-212/Bismuth-212 in vivo generator and demonstrated the encouraging therapeutic efficacy in treatment of experimental melanoma. Obstacles that continue to obstruct widespread acceptance of alpha-emitter-labeled peptides are primarily the supply of these radionuclides and concerns about potential kidney toxicity. New sources and methods for production of these medically valuable radionuclides and better understanding of mechanisms related to the peptide renal uptake and clearance should speed up the introduction of alpha-emitter-labeled peptides into the clinic. Copyright 2010 Elsevier Inc. All rights reserved.

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

International Nuclear Information System (INIS)

Ikeda, Shunsuke; Sekine, Megumi; Romanelli, Mark; Cinquegrani, David; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-01-01

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface

Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

Science.gov (United States)

Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

2014-02-01

A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.