Electron Beam Extraction Research Articles

Experimental Research on the Neutralizer of Micro ECR Ion Thruster

As the key component of micro electron cyclotron resonance (ECR) ion thruster, the initial gas discharge and electron beam extraction performance of ECR neutralizer plays an important role in the whole performance of ECR ion thruster. The experiment on the neutralizer is completed to study the influence of the antenna structure, cavity length and electronic extraction board on the performance. The experimental results show that, within a certain range, as the length of the cavity is longer, the annular segment of antenna is slightly higher than ECR zone and the width of annular segment is smaller, the performance of the neutralizer is better. There is a reasonable structure for the electronic extraction board to make the performance of the neutralizer better. According to the experimental results, the optimal structure of the neutralizer is determined. For Xe gas, when the microwave power is 2.0W and the gas flow rate is 0.2sccm, the best performances of the optimal neutralizer are that extracted electron beam and coupling voltage is 4mA and 31.5V respectively.

Generation, transport, and efficient extraction of a large cross-section electron beam into an air in an accelerator with a mesh plasma cathode

AbstractThe paper presents experimental and theoretical research data on the generation, transport, and extraction of a large cross-section (750 × 150 mm2) electron beam into the air through a thin metal foil in an accelerator with a mesh plasma cathode on the bases of a low-pressure arc and with a multi-aperture two-electrode electron-optical system. When the burning conditions of the arc discharge, responsible for the generation of the emission plasma, is changed, the characteristics of this plasma were investigated, including under the conditions of the selection of electrons from it. Our experiments show that at an accelerating voltage of 200 kV, current in the accelerating gap of up to 30 A, and full width at half maximum of up to 100 µm, the average extracted power is ≈4 kW and the extracted beam current is ≈85% from the common current into the accelerating gap. Our numerical estimates give a good correlation between the arc and emission plasma parameters depending on the electrode configuration in the discharge system and on the mechanism of electron beam generation. Analysis of the emission plasma parameters under different arc conditions and of the mechanisms responsible for the beam energy loss suggests that most of the energy in the accelerator is lost at the support grid and at the output foil due to defocusing of the beam and partial electron reflection from the foil. Other mechanisms that decrease the extracted beam energy are discussed.

High resolution micro-pattern gas detectors for particle physics

Micro-pattern gaseous detectors (MPGDs) allow operation at very high background particle flux with high efficiency and spatial resolution. This combination of parameters determines the main application of these detectors in particle physics experiments: precise tracking in the areas close to the beam and in the end-cap regions of general-purpose detectors. MPGDs of different configurations have been developed and are under development for several experiments in the Budker INP. The system of eight two-coordinate detectors based on a cascade of Gas Electron Multipliers (GEM) is working in the KEDR experiment at the VEPP-4M collider in the tagging system that detects electrons and positrons that lost their energy in two-photon interactions and left the equilibrium orbit due to a dedicated magnetic system. Another set of cascaded GEM detectors is developed for the almost-real Photon Tagging System (PTS) of the DEUTRON facility at the VEPP-3 storage ring. The PTS contains three very light detectors with very high spatial resolution (below 50 μm). Dedicated detectors based on cascaded GEMs are developed for the extracted electron beam facility at the VEPP-4M collider. These devices will allow precise particle tracking with minimal multiple scattering due to very low material content. An upgrade of the coordinate system of the CMD-3 detector at the VEPP-2000 collider is proposed on the basis of the resistive micro-WELL (μ-rWELL). A research activity on this subject has just started.

The output window of a large-area accelerator with an increased electron-beam current density

The results of theoretical and experimental investigations of a large-area accelerator with a new type of output window are presented. With this window, it is possible to increase the current density of the extracted electron beam, reduce the operating temperature of the foil, and extend its service life. A two-level support structure with cooling of each level is used for this purpose. The heat load of the foil mounted on the second level of the support structure that carries the main mechanical load is reduced by partial interception of the thermal power due to direct loss of the electron beam, which is released on the first level experiencing no mechanical load. The current loss at the structural elements of the output window is estimated, and the hydraulic characteristics and foil temperature in the output device are calculated. A higher current density of the beam extracted over the foil is attained in comparison with the conventional design of the support structure.

Development of high-resolution GEM-based detector for the extracted electron beam facility at the VEPP-4M collider

The goal of the extracted beam facility at the VEPP-4M collider is to test prototypes of new detectors for particle physics. Measurements taken at this installation require high-resolution low-mass tracking detectors to precisely determine particle trajectories. The high-resolution GEM-based tracking detector developed for this facility is described in this paper.

Status and prospects of the injection complex of the Budker Institute of Nuclear Physics

This article presents the basic systems of the VEPP-5 injection complex of Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. The system of injection–extraction of electron and positron beams is described. The results of measurements of the bunch length made in the electron linear accelerator and the storage–cooler ring by a streak camera are provided. The development of assemblies of a prospective positron conversion system based on a liquid-lead target is also described.

Application of aluminum and titanium foils in low-energy wide-aperture electron accelerators

We have reported on the results of theoretical and experimental investigations of characteristics of aluminum and titanium foils used in devices to extract electron beams from wide-aperture low-energy accelerators with a high current density. The mechanical properties of foils at different temperatures and the electron beam transmission and absorption coefficients have been compared. The results of analyzing the dependences of the efficiency of the electron beam extraction from accelerators on the type of the electron–optical system, material, and thickness of the foil for various sizes of extraction windows and the same type of the slot support grids have been presented. We have proposed an analytic model for calculating the temperature of the foil in the unit cell of the support grid. The electron transmittance and absorbance, as well as the temperature regimes of the foils, have been calculated using different methods.

Betatron with variable energy for IORT

Introduction Since 2014 years in Tomsk Polytechnic University a new generation of betatrons for intraoperative radiation therapy (IORT) has been developing which has typical diameter approx. 70 cm at 6 MeV energy. The main advantages of the betatrons are that they operate at large frequency (400 Hz) at rather low pulse current, they have low energy spread and the relatively low cost of a device (typically $200,000). Purpose The purpose of the project is to develop and test the compact betatron with adjustable energy of the extracted electron beam. Materials and methods The depth dose distribution was measured along axis using plane-parallel Marcus ionization chamber and Gafchromic EBT-3 polymer film. Dosimetry was carried out following TG-51 and TRS-398 international protocols. The polymer films were calibrated using 10 MeV electron beam of Electa Axcess accelerator and 6 MeV electron beam of previous generation IORT betatron with constant energy. All measurements were performed in tissue-equivalent phantom with zero air gap. Results The investigation of 3D dose distributions generated by new type of IORT source based on betatron was carried out in the energy range 2–6 MeV with 500 keV steps. In addition the radiation background distribution near the betatron was measured and it would be used for design of biological protection. Conclusion According to the measured data it was proved that the extracted electron beam has designed energy that could be changed. The dose distributions allow assume that the compact IORT source based on betatron could be developed in the nearest future.

System for transporting an electron beam to the atmosphere for a gun with a plasma emitter

We report on the results of simulation of the gas flow in a gun with a plasma emitter and in the system for extracting the electron beam to the atmosphere, constructed on the basis of standard gasdynamic windows (GDWs). The design of the gun and GDWs is described. Calculations are performed for a pressure of about 10–3 Torr in the electron beam generation range. It is shown that the pressure drop to the atmospheric pressure in the system of electron beam extraction to the atmosphere can be ensured by two GDW stages evacuated by pumps with optimal performance.

Double-Gated, Spindt-Type Field Emitter With Improved Electron Beam Extraction

We have developed a highly sensitive, compact image sensor that comprises a field emitter array (FEA) and a high-gain avalanche-rushing amorphous photoconductor target, with the ultimate aim of developing an ultrahighly sensitive, compact, high-definition television camera. Double-gated FEs have an advantage of having a compact electron beam focusing system; however, image intensities reproduced by the sensor were nonuniform due to low electron beam current. Furthermore, the simulated electron beam current disagreed with the measured current. The electron beam current characteristics of two types of double-gated, Spindt-type FEs (both with improved electron beam current extraction) are discussed for possible use within the sensor: convex-structured and volcano-structured. A highly accurate simulation model of the image sensor using a double-gated, Spindt-type FE has been examined; the simulated electron beam currents extracted from the double-gated, Spindt-type FE are in agreement with the measured electron beam currents when the initial electron velocity is assumed, thus suggesting that the simulated anode current–anode voltage characteristic conforms to the measured one. For example, the electron beam currents extracted from the convex-structured and volcano-structured FEs when the focusing electrode is placed 0.2 $\mu \text{m}$ below the gate electrode opening at a focusing electrode voltage of 15 V are, respectively, 1.8 and 1.9 times larger than that extracted from the previously used FEs when the focusing electrode is stacked 1.5 $\mu \text{m}$ above the gate electrode. The results show potential for reducing the degradation of the uniformity of the reproduced image’s intensity, and show that the highly accurate simulation model of the sensor is valid to design the double-gated FEAs for the sensor.

Performance of the TPS Pulsed Magnets

Pulsed magnets were characterized for use for injection in the top-up mode for Taiwan Photon Source (TPS). Two kicker magnets in vacuum were implemented to inject and to extract electron beams for the booster ring. Five septum and four kicker magnets of in-air type were provided for injection into a 3-GeV storage ring. All pulsed magnets are of home design, manufactured and assembled in National Synchrotron Radiation Research Center. To verify the quality of a magnetic field and its distribution, measurement systems including long-coil and search-coil systems were installed. The pulsed power supply was improved to gain exact stability. We report that through our shielding design, the maximum leakage field of the septum along the beam trajectory is less than 0.02% of the main field.

Application of Traditional and Nanostructure Materials for Medical Electron Beams Collimation: Numerical Simulation

Nowadays, the commercial application of the electron accelerators grows in the industry, in the research investigations, in the medical diagnosis and treatment. In this regard, the electron beam profile modification in accordance with specific purposes is an actual task. In this paper the model of the TPU microtron extracted electron beam developed in the program “Computer Laboratory (PCLab)” is described. The internal beam divergence influence for the electron beam profile and depth dose distribution in the air is considered. The possibility of using the nanostructure materials for the electron beam formation was analyzed. The simulation data of the electron beam shape collimated by different materials (lead, corund- zirconia nanoceramic, gypsum) are shown. The collimator material influence for the electron beam profile and shape are analyzed.

Comparison of the calculated and experimental data of the extracted electron beam profile

The current commercial use of electron accelerators grows in research, industry, medical diagnosis and treatment. Due to this fact, the creation of a model describing the electron beam profile and shape is an actual task. The model of the TPU microtron extracted electron beam created in the program “Computer Laboratory (PCLab)” is described and compared with experimental results in this article. The value of the internal electron beam divergence determination is illustrated. The experimental data of the electron beam profiles at the selected distances from the output window are analysed and compared with the simulation data. The simulation data of the electron beam profiles are shown.

Magnetic field extraction of trap-based electron beams using a high-permeability grid

A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magnetic field by passing them through a high magnetic permeability grid with radial tines (a so-called “magnetic spider”). An Einzel lens is used to focus and analyze the beam properties. Numerical simulations are used to model non-adiabatic effects due to the spider, and the predictions are compared with the experimental results. Improvements in beam quality are discussed relative to the use of a hole in a high permeability shield (i.e., in lieu of the spider), and areas for further improvement are described.

9-2 電界集束型FEA-HARPの電子ビーム取り出し効率の改善(第9部門 センシング1)

9-2 電界集束型FEA-HARPの電子ビーム取り出し効率の改善(第9部門 センシング1)

Extracted electron and gamma beams in BINP

Facility of the extracted beams of electrons and gammas based on the e+e− VEPP-4M collider is described.This installation is designed to test prototype of detectors for HEPprojects. Design parameters of the extracted electron beam are thefollowing: intensity is not less than 50 Hz, energy range is from0.1 GeV to 3.0 GeV and energy resolution is about 2–3%. The gammaenergy range is from 0.05 GeV to 4.0 GeV with an accuracy of 0.5% ofenergy. The designed intensity of the gamma beam is about 1000 Hz.

Design and fabrication of the vacuum systems for TPS pulsed septum magnets

Three in-air pulsed septum magnets were developed to inject and extract electron beams for the 3GeV synchrotron facility, the Taiwan Photon Source (TPS). The vacuum chamber is a novel combined aluminium-stainless steel design, using a bimetallic flange to connect the two material types. To evaluate the vacuum performances of these vacuum chambers, we set up a test bench at which we simultaneously measure the rates of thermal outgassing of the aluminium chamber and the septum tube with a throughput method. The test result indicates that the rate q72 of thermal outgassing measured after 1 day from baking at 150°C was 1×10−13mbarLs−1cm−2. The magnetic leakage measurements show the combination of conductor slitting, magnetic shielding and the aluminium vacuum chamber reduce the peak value of the leakage field integral to ~10Gcm along the trajectory of the stored beam.

EBIS charge breeder for CARIBU

A high-efficiency charge breeder based on an Electron Beam Ion Source (EBIS) is being developed by the ANL Physics Division to increase the intensity and improve the purity of accelerated radioactive ion beams. A wide variety of low-energy neutron-rich ion beams are produced by the Californium Rare Isotope Breeder Upgrade (CARIBU) for the Argonne Tandem Linac Accelerator System (ATLAS). These beams will be charge-bred by an EBIS charge breeder to a charge-to-mass ratio (q/A) ≥ 1/7 and accelerated by ATLAS to energies of about 10 MeV/u. The assembly of the CARIBU EBIS charge breeder except the injection/extraction beam lines has been completed. This summer we started electron beam commissioning of the EBIS. The first results on electron beam extraction, transport from the electron gun to a high power electron collector are presented and discussed.

A large-area continuous accelerator with the extraction of a high-density electron beam

The design features of the electron accelerator with a large-area 200-keV beam and results of its investigation are described. The accelerator is based on a set of discrete longitudinal filament cathodes and operates in the continuous mode. The cross section of the beam extracted into the atmosphere is 40 × 50 cm2, and the maximal current density of the extracted electron beam is up to 100 μA/cm2. The nonuniformity of the current density distribution over the electron beam cross section is 10% or less.

High-Power Terahertz-Range Planar Gyrotrons with Transverse Energy Extraction

To increase the output power of terahertz gyrotrons to several hundred kilowatts, we suggest using a planar geometry of interaction space with a sheet electron beam and transverse energy extraction. An advantage of this scheme in comparison with conventional cylindrical geometry is the possibility to ensure effective mode selection over the open transverse coordinate in combination with radiation outcoupling that leads to a substantial reduction of Ohmic losses. Similar to unstable resonators in optics for further growth of the radiation power it is beneficial to introduce waveguide tapering.