Modeling electron beam parameters and plasma interface position in an anode plasma electron gun with hydrogen atmosphere

Laser plasma acceleration (LPA) capable of providing femtosecond and GeV electron beams in cm scale distances brings a high interest for different applications, such as free electron laser and future colliders. Nevertheless, LPA high divergence and energy spread require an initial strong focus to mitigate the chromatic effects. The reliability, in particular with the pointing fluctuations, sets a real challenge for the control of the dispersion along the electron beam transport. We examine here how the magnetic defects of the first strong quadrupoles, in particular, the skew terms, can affect the brightness of the transported electron beam, in the case of the COXINEL transport line, designed for manipulating the electron beam properties for a free electron laser application. We also show that the higher the initial beam divergence, the larger the degradation. Experimentally, after having implemented a beam pointing alignment compensation method enabling us to adjust the position and dispersion independently, we demonstrate that the presence of non-negligible skew quadrupolar components induces a transversal spread and tilt of the beam, leading to an emittance growth and brightness reduction. We are able to reproduce the measurements with beam transport simulations using the measured electron beam parameters.

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Investigation of electron beam parameters inside the drift region of plasma cathode electron gun

Journal of Physics Conference Series ◽

10.1088/1742-6596/365/1/012048 ◽

2012 ◽

Vol 365 ◽

pp. 012048

Author(s):

Deepak K Verma ◽

U N Pal ◽

N Kumar ◽

J Prajapati ◽

M Kumar ◽

...

Keyword(s):

Electron Beam ◽

Electron Gun ◽

Drift Region ◽

Plasma Cathode ◽

Beam Parameters

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New type electron gun with electrostatic and electromagnetic lenses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107459 ◽

1978 ◽

Vol 36 (1) ◽

pp. 62-63

Author(s):

T. Ichinokawa ◽

H. Maeda

Keyword(s):

Electron Microscopy ◽

Electron Beam ◽

Optimum Condition ◽

Bias Voltage ◽

Electron Gun ◽

Charge Effect ◽

Micro Fabrication ◽

Maximum Brightness ◽

New Type ◽

The Ideal

I. IntroductionThermionic electron gun with the Wehnelt grid is popularly used in the electron microscopy and electron beam micro-fabrication. It is well known that this gun could get the ideal brightness caluculated from the Lengumier and Richardson equations under the optimum condition. However, the design and ajustment to the optimum condition is not so easy. The gun has following properties with respect to the Wehnelt bias; (1) The maximum brightness is got only in the optimum bias. (2) In the larger bias than the optimum, the brightness decreases with increasing the bias voltage on account of the space charge effect. (3) In the smaller bias than the optimum, the brightness decreases with bias voltage on account of spreading of the cross over spot due to the aberrations of the electrostatic immersion lens.In the present experiment, a new type electron gun with the electrostatic and electromagnetic lens is designed, and its properties are examined experimentally.

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Energy Distribution in Electron Beams

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096096 ◽

1972 ◽

Vol 30 ◽

pp. 568-569

Author(s):

Tamotsu Ohno

Keyword(s):

Electron Beam ◽

Energy Distribution ◽

Cross Section ◽

Integral Curve ◽

Electron Beams ◽

Electron Gun ◽

Angular Divergence ◽

Apparent Increase ◽

Integral Width ◽

The Cross

The energy distribution in an electron; beam from an electron gun provided with a biased Wehnelt cylinder was measured by a retarding potential analyser. All the measurements were carried out with a beam of small angular divergence (<3xl0-4 rad) to eliminate the apparent increase of energy width as pointed out by Ichinokawa.The cross section of the beam from a gun with a tungsten hairpin cathode varies as shown in Fig.1a with the bias voltage Vg. The central part of the beam was analysed. An example of the integral curve as well as the energy spectrum is shown in Fig.2. The integral width of the spectrum ΔEi varies with Vg as shown in Fig.1b The width ΔEi is smaller than the Maxwellian width near the cut-off. As |Vg| is decreased, ΔEi increases beyond the Maxwellian width, reaches a maximum and then decreases. Note that the cross section of the beam enlarges with decreasing |Vg|.

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A New High Intensity Grid Cap for RCA-EMU-3 Electron Microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101323 ◽

1968 ◽

Vol 26 ◽

pp. 316-317

Author(s):

George Christov ◽

Bolivar J. Lloyd

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

High Voltage ◽

High Intensity ◽

Electron Gun ◽

Tungsten Filament ◽

Fluorescent Screen ◽

Electron Microscopes ◽

Pass Through ◽

Ground Potential

A new high intensity grid cap has been designed for the RCA-EMU-3 electron microscope. Various parameters of the new grid cap were investigated to determine its characteristics. The increase in illumination produced provides ease of focusing on the fluorescent screen at magnifications from 1500 to 50,000 times using an accelerating voltage of 50 KV.The EMU-3 type electron gun assembly consists of a V-shaped tungsten filament for a cathode with a thin metal threaded cathode shield and an anode with a central aperture to permit the beam to course the length of the column. The cathode shield is negatively biased at a potential of several hundred volts with respect to the filament. The electron beam is formed by electrons emitted from the tip of the filament which pass through an aperture of 0.1 inch diameter in the cap and then it is accelerated by the negative high voltage through a 0.625 inch diameter aperture in the anode which is at ground potential.

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Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179749 ◽

1990 ◽

Vol 48 (1) ◽

pp. 198-199

Author(s):

Ryo Iiyoshi ◽

Susumu Maruse ◽

Hideo Takematsu

Keyword(s):

Electron Beam ◽

Tungsten Wire ◽

Local Heating ◽

Electron Gun ◽

Original Position ◽

Beam Power ◽

Radius Of Curvature ◽

High Brightness ◽

Beam Focusing ◽

Time Operation

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.

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Application of Novel Non-Thermal Physical Technologies to Degrade Mycotoxins

Journal of Fungi ◽

10.3390/jof7050395 ◽

2021 ◽

Vol 7 (5) ◽

pp. 395

Author(s):

Mohammad Yousefi ◽

Masoud Aman Mohammadi ◽

Maryam Zabihzadeh Khajavi ◽

Ali Ehsani ◽

Vladimír Scholtz

Keyword(s):

Electron Beam ◽

Food Systems ◽

Large Scale ◽

Plasma Electron ◽

Pulsed Light ◽

Beam Radiation ◽

Practical Applications ◽

Electron Beam Radiation ◽

Non Thermal Plasma ◽

Agriculture And Food

Mycotoxins cause adverse effects on human health. Therefore, it is of the utmost importance to confront them, particularly in agriculture and food systems. Non-thermal plasma, electron beam radiation, and pulsed light are possible novel non-thermal technologies offering promising results in degrading mycotoxins with potential for practical applications. In this paper, the available publications are reviewed—some of them report efficiency of more than 90%, sometimes almost 100%. The mechanisms of action, advantages, efficacy, limitations, and undesirable effects are reviewed and discussed. The first foretastes of plasma and electron beam application in the industry are in the developing stages, while pulsed light has not been employed in large-scale application yet.

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