scholarly journals Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

2002 ◽  
Author(s):  
Tong Wang
Keyword(s):  
Radio Frequency ◽  
Field Emission ◽  
High Field ◽  
Superconducting Radio Frequency ◽  
Emission Studies

scholarly journals The effect of the enhanced field emission on the characteristics of the superconducting radio frequency cavities

2018 ◽  
Vol 33 (4) ◽  
pp. 341-346
Author(s):  
Marija Radmilovic-Radjenovic ◽  
Petar Belicev ◽  
Branislav Radjenovic
Keyword(s):  
Radio Frequency ◽  
Field Emission ◽  
Enhancement Factor ◽  
Effective Area ◽  
Cavity Surface ◽  
Superconducting Radio Frequency ◽  
Superconducting Cavities ◽  
Electron Field ◽  
Modal Field ◽  
And Control

Electron field emission limiting the accelerating gradient in superconducting cavities remains the dominant setback in cavity production. The need to understand and control the field emission has become increasingly important because of the prospect of using high-gradient structures in linear colliders. Since building an accelerator structure is a complicated and costly process, elimination of unnecessary steps has priority. In this paper an analysis of the influence of the enhanced field emission in superconducting radio frequency cavity together with modal field calculations by using COMSOL finite elements package has been presented. The obtained results reveal that the electric field required for the field emission is generated in the cavity irises. The imperfection of the cavity surface leading to very high fields is modelled by a simple cone. The estimated value of the enhancement factor for the cone tip of around 4 is in a good agreement with the data found in the literature. In addition, from the slopes and the intercepts of the Fowler-Nordheim plots, a dependence of the enhancement factor and the effective area on the work function has been estimated.

scholarly journals Studies of enhanced field emission relevant to high field superconducting radio frequency devices

2021 ◽  
pp. 7-7
Author(s):  
Marija Radmilovic-Radjenovic ◽  
Zeljka Nikitovic ◽  
Ranislav Radjenovic
Keyword(s):  
Electric Field ◽  
Radio Frequency ◽  
Field Emission ◽  
Enhancement Factor ◽  
Field Enhancement ◽  
Field Enhancement Factor ◽  
Accurate Estimation ◽  
Cavity Surface ◽  
Planar Surfaces ◽  
Superconducting Radio Frequency

Surface roughness represents the measure of the irregularities on the surface contributing to the local field enhancement. The traditional Fowler-Nordheim equation established for perfectly planar surfaces is not suitable for describing emission from rough surfaces. Instead, it is more appropriate to use the equation that accounts for the field enhancement factor describing the effect of the surface morphology. In superconducting radio frequency cavities field emission may occur in the irises and the tips on the cavity surface may act as an emitter leading to the high electric field. For this study, calculations for hemispherical, cylindrical, and conical tips have been performed by using a multiphysics software package COMSOL. The focus was put on the dependence of the field enhancement factor on the shape and the radius of the protrusions. The electric field strength and the current density increase with increasing the root mean square average of the profile heights due to field enhancement at the cavity irises. The lowest value of the electric field has been achieved for the hemisphere. The calculated values for the field enhancement factors are consistent with the data from the literature, in which case the protrusion may represent a small local bump on the surface of a superconducting cavity. Based on the fit of the results, presented here, the relation between the enhancement factor and the radius has been suggested. The accurate estimation of the field emission may play a crucial role in the design of accelerators and other technological applications with requirements of very high precision.

Field - and Photoassisted Field Emission Studies of Calcium Fluoride Coated Silicon Tips

1996 ◽  
Vol 06 (C5) ◽  
pp. C5-129-C5-134
Author(s):  
V. N. Konopsky ◽  
V. V. Zhirnov ◽  
N. S. Sokolov ◽  
J. C. Alvarez ◽  
E. I. Givargizov ◽  
...  
Keyword(s):  
Field Emission ◽  
Calcium Fluoride ◽  
Emission Studies

Development of a 1497-MHz, 13.5-kW Continuous-Wave Magnetron for Superconducting Radio Frequency Accelerator

2021 ◽  
pp. 1-9
Author(s):  
Wenliang Li ◽  
Pengjiao Zhang ◽  
Bowen Zhou ◽  
Hong Zhang ◽  
Youchun Liu ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Continuous Wave ◽  
Superconducting Radio Frequency

Multipod ZnO Nanoforms: Low Temperature Synthesis and Characterization

2007 ◽  
Vol 7 (2) ◽  
pp. 689-695 ◽  
Author(s):  
Tandra Ghoshal ◽  
Soumitra Kar ◽  
Subhajit Biswas ◽  
Gautam Majumdar ◽  
Subhadra Chaudhuri
Keyword(s):  
Low Temperature ◽  
Field Emission ◽  
Cross Section ◽  
Thermal Evaporation ◽  
Synthesis And Characterization ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Optical Absorbance ◽  
Higher Temperature ◽  
Emission Studies

ZnO nanotetrapods were synthesized by a simple thermal evaporation of Zn powder at a relatively low temperature ∼600 °C. The tetrapods have four legs with hexagonal cross-section. Interpenetrating growth was observed in some of these nanotetrapods. Multipod ZnO nanoforms were produced at higher temperature. The optical characterizations such as optical absorbance, photoluminescence and Raman spectroscopy reveal excellent crystal qualities of these nanoforms. The field emission studies indicated that these nanoforms could be utilized in field emission based devices.

scholarly journals Long lifetime of bialkali photocathodes operating in high gradient superconducting radio frequency gun

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
E. Wang ◽  
V. N. Litvinenko ◽  
I. Pinayev ◽  
M. Gaowei ◽  
J. Skaritka ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Electron Beams ◽  
Spot Size ◽  
Laser Spot ◽  
Laser Spot Size ◽  
High Quantum Efficiency ◽  
High Brightness ◽  
High Charge ◽  
Superconducting Radio Frequency ◽  
Long Lifetime

AbstractHigh brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance of the electron beam, which is determined by the mean transverse energy (MTE) and laser spot size, is one of the most important parameters determining the beam quality. The bialkali photocathodes illuminated by a visible laser have the advantages of high quantum efficiency (QE) and low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in the continuous wave (CW) mode at high accelerating gradients, e.g. with significant reduction of the laser spot size at the photocathode. Combining the bialkali photocathode with the SRF gun enables generation of high charge, high brightness, and possibly high average current electron beams. However, integrating the high QE semiconductor photocathode into the SRF guns has been challenging. In this article, we report on the development of bialkali photocathodes for successful operation in the SRF gun with months-long lifetime while delivering CW beams with nano-coulomb charge per bunch. This achievement opens a new era for high charge, high brightness CW electron beams.

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