Focusing a compensated proton beam with a high compression coefficient

An analysis is made of the possibility of focusing 10–30 keV charge-compensated proton beams with a current of 1 kA and an area compression coefficient >1.5×10³. To obtain a high degree of compression a combination of ballistic focusing and magnetic compression is used. The parameters of the focusing channel are determined and an estimate is made of the possible effect of the compensating electron background on the effectiveness of focusing of the proton beam. Zh. Tekh. Fiz. 67, 73–80 (May 1997)     

A dedicated small‐angle X‐ray scattering beamline with a superconducting wiggler source at the NSRRC

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small‐angle X‐ray scattering (SAXS) beamline has been installed with an in‐achromat superconducting wiggler insertion device of peak magnetic field 3.1 T. The vertical beam divergence from the X‐ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (ΔE/E? 2 × 10^?4) in the energy range 5–23 keV, or by a double Mo/B₄C multilayer monochromator for 10–30 times higher flux (～10¹¹ photons s^?1) in the 6–15 keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of ～0.9 mm × 0.3 mm (horizontal × vertical) at the focus point located 26.5 m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing‐incidence SAXS (GISAXS) from liquid surfaces. Two online beam‐position monitors separated by 8 m provide an efficient feedback control for an overall beam‐position stability in the 10 µm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray‐tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core‐shell quantum dots) and GISAXS from liquid surfaces.     

Experimental and computational study of the passage of an electron beam through the curvilinear element of the Drakon stellarator system in a tenuous plasma

Results are presented from the first stage of studies on the passage of an electron beam with energy 100–500 eV in a magnetic field of 300–700 Oe through the curvilinear solenoid of the KRéL unit, the latter being a prototype of the closing segment of the Drakon stellarator system, in the plasma-beam discharge regime. The ion density at the end of the curvilinear part of the chamber, n _i ≈8×10⁸–10¹⁰ cm⁻³, the electron temperature T _e ≈4–15 eV, and the positions at which the beam hits the target for different distances from it to the electron source are determined experimentally. The motion of the electron beam is computationally modeled with allowance for the space charge created by the beam and the secondary plasma. From a comparison of the experimentally measured trajectories and trajectories calculated for different values of the space charge, we have obtained an estimate for the unneutralized ion density of the order of 5×10⁷ cm⁻³. Zh. Tekh. Fiz. 69, 22–26 (February 1999)     

Ultra slow muon microscopy by laser resonant ionization at J-PARC, MUSE

As one of the principal muon beam line at the J-PARC muon facility (MUSE), we are now constructing a Muon beam line (U-Line), which consists of a large acceptance solenoid made of mineral insulation cables (MIC), a superconducting curved transport solenoid and superconducting axial focusing magnets. There, we can extract 2 × 10⁸/s surface muons towards a hot tungsten target. At the U-Line, we are now establishing a new type of muon microscopy; a new technique with use of the intense ultra-slow muon source generated by resonant ionization of thermal Muonium (designated as Mu; consisting of a μ ^?+? and an e^???) atoms generated from the surface of the tungsten target. In this contribution, the latest status of the Ultra Slow Muon Microscopy project, fully funded, is reported.     

A Guided Field for Raman Free Electron Laser Could Be Removed with New Beam Source

A guided field is an important part for focusing the intense beam in Raman free electron laser. A new electron beam source with high brightness of 10¹²A/(m rad)² based on a pseudospark discharge was developed [1]. Numerical simulation showed that the guided field for compact free electron lasers could be removed using the new beam source. An electron beam with 12 kA current and 300 kV voltage was obtained. Self-pinch effect of high current beam was observed, the beam propagates 75 cm with constant diameter of 1.5 mm without guided field.     

Gamma-ray solid laser: ion-optical system for fasthigh-quality focusing of powerful non-paraxial ion beams of largeformat enriched with excited nuclei

An ion-optical system (IOS) for fast high-quality focusing of powerful paraxial ion beams of large format is suggested. Such beams could be enriched in excited short-lived (10^-4-10^-6 s) laser-active nuclei (ELAN). To increase the beam power, ions are collected from the visible surface (10-10⁴ cm²) of an intermediate target (converter). The full converter surface is enhanced by a factor of 10²-10⁴ by a special micro-relief and achieves 10³-10⁷ m². The toms containing ELAN are created in the converter by a powerful radiation source using neutrons, γ quanta, charged particles, etc. Those ELAN atoms are emitted from the converter surface and selectively ionized by a dye laser just above the surface. Using a specially chosen emitter (converter) shape, a paraxial ion beam is formed. This is due to the micro-relief structure of the emitter surface, its high-quality orientation, and cylindrical (instead of spherical) ion optics. In the vicinity of an active medium (AM) for a gamma-ray laser, the ions are decelerated so that they can penetrate only into 1-3 outer layers of the host matrix, e.g., diamond. This makes heating of the AM by the ion beam negligible in comparison to self-heating due to internal conversion. Analytical and numerical estimation of the IOS aberrations have shown that the compression of the ion beam exceeds10⁵-10⁶, and that a considerable part (10%) of the ELAN reach the AM in a time as short as10^-7 s. This ensures the rapid and controllable deposition of ELAN into an AM within a gamma-laser system based on existing techniques without using nuclear explosions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Solid neon moderated electrostatic or magnetic positron beam

A high intensity variable energy positron beam has been constructed at Brookhaven National Laboratory (BNL). Positrons from a 97 mCi²²Na source are moderated by a thin layer of solid neon. A magnetic guiding system delivered up to 5×10⁶ e⁺/sec to an experiment. Currently, tests are under way to facilitate the operation with the magnetic guiding system or—for other experimental sites—with an electrostatic beam transport. The electrostatic lenses are fabricated from μ-metal. No compensation of the earth's magnetic field is required. Several experiments can utilize the beam on a time-sharing basis. In the near future, the source will be replaced by⁶⁴Cu, which has a much higher activity. Beam intensities up to 10⁹ e⁺/sec are expected.     

Short-channel drain current model for asymmetric heavily / lightly doped DG MOSFETs

Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for repetitive operation. A magnetically coupled tangential blower is used for gas circulation inside the laser chamber for repetitive operation. The exciter consists of C–C energy transfer circuit and thyratron is used as a high-voltage main switch with single-stage magnetic pulse compression (MPC) between thyratron and the laser electrodes. Low inductance of the laser head and uniform and intense pre-ionization are the main features of the electric circuit used in the laser. A 250 ns rise time voltage pulse was compressed to 100 ns duration with a single-stage magnetic pulse compressor using Ni–Zn ferrite cores. The laser can generate about 150 mJ at ～100 Hz rep-rate reliably from a discharge volume of 100 cm ³. 2D spatial laser beam profile generated is presented here. The profile shows that the laser beam is completely filled with flat-top which is suitable for material processing applications. The SEM image of the microhole generated on copper target is presented here.     

Collective Phenomena in Strongly Coupled Dissipative Systems of Charged Dust: from Ground to Microgravity Experiments

In present work the formation of dusty plasma structures in cryogenic glow dc discharge was investigated. The ordered structures from large number (～10⁴) of charged diamagnetic dust particles in a cusp magnetic trap have been also studied in microgravity conditions. The super high charging (up to 5·10⁷e) of dust macroparticles under direct stimulation by an electron beam is experimentally performed and investigated. The results of the investigation of Brownian motion for strongly coupled dust particles in plasma are presented. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Combined focusing of an uncharged particle beam by axially symmetric magnetic and electric fields in a vacuum

A way of simultaneously focusing a circular uniform beam of fine uncharged diamagnetic particles in the longitudinal and transverse directions is explored. Focusing is performed by a short magnetic lens and a diaphragm providing a time-dependent electric field. The size of the particles is within the range of 10⁻⁴–10⁻¹ cm.     

Neutralization of an ion beam from the end-Hall ion source by a plasma electron source based on a discharge in crossed E × H fields

The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm² at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O₂ or N₂. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the replacement life of the deposited cathode insertion).     

Integrated target-ion source unit for on-line production of radioactive short-lived isotopes

A new version of integrated target-ion source unit (ionising target) has been developed for the on-line production of radioactive single-charged ions. The target is able to withstand temperatures up to 2500 ^°C and acts also as an ion source of the surface and laser ionisation. Off-line and on-line experiments with the ionising target, housing tantalum foils as a target material, have been carried out at the IRIS (Investigation of Radioactive Isotopes on Synchrocyclotron) facility. The off-line surface ionisation efficiency measured for stable atoms of Li, Rb and Cs was correspondingly 6% , 40% and 55% at the target temperature of 2000 ^°C and 3-10% for atoms of rare-earth elements Sm, Eu, Tm and Yb at a temperature of 2200 ^°C. The off-line measured values of the ionisation efficiency for stable Gd and Eu atoms by the laser beam ionisation inside the target were 1% and 7%, respectively. The radioactive beam intensities of neutron-deficient rare-earth nuclides from Eu to Lu produced by the integrated target-ion source unit have been measured at a temperature of 2500 ^°C. The results of the integrated target-ion source unit use for on-line laser resonance ionisation spectroscopy study of neutron-deficient Gd isotopes have been also presented.     

Discharge and emission parameters of a plasma electron source based on a discharge in crossed E × H fields with various cathode materials

The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm² at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O₂ or N₂. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the replacement life of the deposited cathode insertion).     

Parameters of the beam plasma formed by a forevacuum plasma source of a ribbon beam in zero-field transportation system

We have studied the generation of the beam plasma formed by a forevacuum plasma source of a ribbon electron beam in the conditions of its transportation without an accompanying magnetic field. The ignition conditions in the beam transportation region of the beam–plasma discharge producing a plasma formation of the plasma sheet type with a plasma concentration of ~10¹⁶ m^–3 and an electron temperature of 1–2.5 eV have been determined. The attained values of parameters and the sizes of the plasma formation make it possible to use it in technologies of the surface modification of planar extended articles.     

A compact free electron laser investigation

An electron beam source based on pseudospark discharge was successful in operation at the beam voltage of 200keV and beam current of 2kA. The detailed design of a compact free electron laser using an electron beam by a pseudospark discharge is described. The compact free electron laser consists of a smaller Marx generator with 6 capacitors and switches, a water capacitance of 6nF and a beam source with a high brightness of 3×10¹¹ A/(m rad)². The computer simulation shows that an output power of 101MW is expected at a frequency of 38GHz with a beam energy of 300keV, a current of 2kA and a beam emittance of 48mm mraa.     

The intense neutron generator of 14 MeV neutrons

An innovative intense neutron generator of 14 MeV neutrons for the irradiation of future reactor materials is presented. Negative pions are produced inside a 5–10 T magnetic field by an intense deuteron beam interacting with a carbon target. The pions and the muons from pion decay in flight are collected in the backward direction and stopped in a deuterium-tritium-hydrogen target of high density. Using an 18 MW deuteron beam at 1.5 GeV (12 mA=7.5 × 10¹⁶d/s), circa 10¹⁶gt^– /s can be generated, decaying to muons of which up to 10¹⁵ µ^–/s stop in the D/T/H mixture. Assuming X_c=100 fusions per muon, the µCF source produces 14 MeV neutrons with a source strength of up to 10¹⁷ n/s, i.e. a neutron power of 200 kW. The environment of the second target, the neutron source itself, can be made to resemble part of the Tokamak ring to be simulated for irradiation test samples.     

Improvement of the efficiency of a glow discharge-based ion emitter with oscillating electrons

Ion emission from the plasma of a low-pressure (≈5×10⁻² Pa) glow discharge with electrons oscillating in a weak (≈1 mT) magnetic field is studied in relation to the cold hollow cathode geometry. A hollow conic cathode used in the electrode system of a cylindrical inverted magnetron not only improves the extraction of plasma ions to ≈20% of the discharge current but also provides the near-uniform spatial distribution of the ion emission current density. The reason is the specific oscillations of electrons accelerated in the cathode sheath. They drift in the azimuth direction along a closed orbit and simultaneously move along the magnetic field toward the emitting surface of the plasma. A plasma emitter with a current density of ≈1 mA/cm² over an area of ≈100 cm² designed for an ion source with an operating voltage of several tens of kilovolts is described.     

Discharge in the Atmosphere in a Gaussian Beam of Subthreshold Millimeter Waves

The propagation velocities of a subthreshold discharge excited in air at atmospheric pressure by a pulsed microwave beam with a Gaussian field distribution, a wavelength of 4 mm, and an intensity up to 30 kW/cm² have been measured by means of optical and microwave diagnostics. It has been shown that the motion of a discharge front along the path of the beam toward the region of an increasing microwave field is accompanied by an increase in the velocity from subsonic (~10^–4 cm/s) to supersonic (~(6–8) × 10⁴ cm/s). At the same time, motion toward the decreasing field region is accompanied by a decrease in the velocity from supersonic to subsonic. It has been found that the maximum temperature of the gas in the discharge at velocities of ~10⁴ cm/s reaches ~5.3 kK.     

Target plasma formation by UHF power

The properties of plasma injected into an open magnetic trap of uniform field from an independent UHF source have been investigated. Plasma is created in the UHF source at the frequency of 2400 MHz (power input 150 W) in the electron cyclotron resonance (ECR) regime at the pressure of neutral argon (10⁻⁵−10⁻²) torr. It is established that a rather quiescent target plasma with controlled density within the range of (2 × 10⁸−2 × 10¹²) cm⁻³ and temperature 2–3eV is accumulated in the trap. It turned out that plasma lifetime in the trap is determined by a classical mechanism of particle escape at the expense of collisions, at fixed value of magnetic field in the trap it practically is not changed with the variation of neutral gas pressure and reaches the value ≈ 4×10⁻³ s at the magnetic field strength in the trap equal 1600 Oe.     

Production of intense positron beams at the VEPP-5 injection complex

A source of positrons allowing 5 × 10⁸ positrons accelerated to the energy of 70 MeV to be produced per pulse has been developed. The process of electron-positron pair production in an electromagnetic shower is used for production of positrons. The electromagnetic shower is generated in a tantalum target by a beam of 2 × 10¹⁰ electrons with energy 270 MeV. A high efficiency of positron collection (positron yield Y ≈ 0.1 GeV^?1) is ensured by a unique design of the matching device.