An experimental setup for exciting semiconductors and dielectrics with picosecond electron-beam and electric-field pulses

An experimental facility for forming high-voltage pulses with amplitudes of 30–250 kV and durations of 100–500 ps and electron beams with a current density of up to 1000 A/cm² is described. The facility was built using the principle of energy compression of a pulse from a nanosecond high-voltage generator accompanied by the subsequent pulse sharpening and cutting. The setup is equipped with two test coaxial chambers for exciting radiation in semiconductor crystals by an electron beam or an electric field in air at atmospheric pressure and T = 300 K. Generation of laser radiation in the visible range under field and electron pumping was attained in ZnSSe, ZnSe, ZnCdS, and CdS (462, 480, 515, and 525 nm, respectively). Under the exposure to an electric field (up to 10⁶ V cm^?1), the lasing region was as large as 300–500μm. The radiation divergence was within 5°. The maximum integral radiation power (6 kW at λ = 480 nm) was obtained under field pumping of a zinc selenide sample with a single dielectric mirror.     

Synchrotron soft X-ray and field-emission electron sources: a comparison

The soft X-ray spectral region and the useful range of electron energy-loss spectroscopy are very similar, both including the energy range 100-1000 eV. Moreover, well-developed monochromators and parallel detection devices with comparable resolution exist for both. Despite the differing interactions of electrons and photons, many complementary experiments in imaging, spectroscopy and diffraction have been performed using both techniques. We therefore compare the brightness, degeneracy, monochromaticity, beam size, source size, spatial and temporal coherence of field-emission electron beams and soft X-ray synchrotron radiation from typical undulators. Recent brightness values for nanotip field emitters and undulators, both measured and calculated, are provided with examples from the Advanced Light Source synchrotron-radiation facility at Berkeley USA. The quantum mechanical upper limit on source brightness, as well as relationships among beam brightness, coherence parameters, and degeneracy, are discussed. Factors which limit these parameters and methods of measurement are reviewed, and the implications for diffraction, imaging and spectroscopic experiments as well as radiation damage are briefly commented on.     

Test bench to commission a third ion source beam line and a newly designed extraction system

The HIT (Heidelberg Ion Beam Therapy Center) is the first hospital-based treatment facility in Europe where patients can be irradiated with protons and carbon ions. Since the commissioning starting in 2006 two 14.5 GHz electron cyclotron resonance ion sources are routinely used to produce a variety of ion beams from protons up to oxygen. In the future a helium beam for regular patient treatment is requested, therefore a third ion source (Supernanogan source from PANTECHNIK S.A.) will be integrated. This third ECR source with a newly designed extraction system and a spectrometer line is installed at a test bench at HIT to commission and validate this section. Measurements with different extraction system setups will be presented to show the improvement of beam quality for helium, proton, and carbon beams. An outlook to the possible integration scheme of the new ion source into the production facility will be discussed.     

A secondary beam separator: A combination of the COMBAS fragment separator with the ion catcher

The development of an experimental facility based on the high-luminosity COMBAS fragment separator and a fast ion catcher is discussed. The main characteristics of the COMBAS fragment separator and the ion catcher determining the advantages of the proposed combination are presented. The developed facility is expected to allow production of secondary radioactive beams with a quality higher than the quality of beams obtained using the in-flight separation technique. It is planned that the facility will be used in a tandem with a post-accelerator for producing single-isotope and monochromatic high-intensity secondary radioactive beams in a wide range of mass numbers A and atomic numbers Z. A list of perspective scientific problems requiring high-intensity and high-quality secondary beams of exotic nuclei is proposed.     

Five-frame, x-ray camera for charged particle, inertial confinement fusion studies

A prototype framing x-ray camera has been developed for photographic studies of inertial confinement fusion (ICF) targets irradiated by charged particle beams. Electron images from five, independently gated, microchannel plates are transported out of the radiation field by means of a toroidal magnetic field and are permanently recorded on film. The calculated, effective exposure time is 相似文献   

Status of the ion sources developments for the Spiral2 project at GANIL

The SPIRAL 2 facility is now under construction and will deliver either stable or radioactive ion beams. First tests of nickel beam production have been performed at GANIL with a new version of the large capacity oven, and a calcium beam has been produced on the heavy ion low energy beam transport line of SPIRAL 2, installed at LPSC Grenoble. For the production of radioactive beams, several target∕ion-source systems (TISSs) are under development at GANIL as the 2.45 GHz electron cyclotron resonance ion source, the surface ionization source, and the oven prototype for heating the uranium carbide target up to 2000?°C. The existing test bench has been upgraded for these developments and a new one, dedicated for the validation of the TISS before mounting in the production module, is under design. Results and current status of these activities are presented.     

An ECRH control and data acquisition system on the gas dynamic trap

A control system for the electron cyclotron resonance heating (ECRH) complex installed on a gas dynamic trap (GDT) facility is described. The ECRH complex is based on two gyrotrons operating at a radiation frequency of 54.5 GHz with a total power of 0.9 MW and is intended for additional heating of the electron plasma component. The general structure of the complex is presented, and the requirements for control signals and parameter-measurement channels are considered. The control-system algorithm and the operator interface are realized using LabView 2010 for Linux. The required set of measurement and control channels is formed using programmable controllers. The developed system is presently used in experiments on microwave heating of plasma in the GDT facility.     

激光等离子体X射线极化光谱研究

为了诊断激光等离子体X射线的极化光谱,研制了一种新型的基于空间分辨的极化谱仪。将平面晶体和球面弯晶色散元件在极化谱仪内正交布置,即在水平通道用PET平面晶体作为色散元件,而在垂直通道用Mica球面弯晶作为色散元件,球面半径为380mm。信号采用成像板进行接收,有效接收面积为30×80mm,从等离子体光源经晶体到成像板的光路约为980mm。物理实验首次在中国工程物理研究院激光聚变研究中心“2×10J激光装置”上进行,成像板获得了铝激光等离子体X射线的光谱空间分辨信号。实验结果表明该谱仪具有较高谱分辨率,适合激光等离子体x射线极化光谱的诊断。     

多种材料软X光平面镜反射率标定

利用北京同步辐射装置(BSRF) 3W1B束线及反射率计靶室,在束流强度40～120mA、贮存环电子能量2GeV专用光运行模式下,做了不同材料掠入射平面镜反射率标定实验。标定过程用高灵敏度无死层的硅光二极管代替X射线二极管(XRD)作探测器,使输出信号提高2～3个量级,可标定能区从150～270eV拓展为50～1500eV能区,对C,Si和Ni材料平面镜给出完整的反射率标定曲线,最终把实验数据与理论计算比对并分析。     

Charge breeding results and future prospects with electron cyclotron resonance ion source and electron beam ion source (invited)

The Californium Rare Ion Breeder Upgrade (CARIBU) of the Argonne National Laboratory ATLAS facility will provide low-energy and reaccelerated neutron-rich radioactive beams for the nuclear physics program. A 70 mCi (252)Cf source produces fission fragments which are thermalized and collected by a helium gas catcher into a low-energy particle beam with a charge of 1+ or 2+. An electron cyclotron resonance (ECR) ion source functions as a charge breeder in order to raise the ion charge sufficiently for acceleration in the ATLAS linac. The final CARIBU configuration will utilize a 1 Ci (252)Cf source to produce radioactive beams with intensities up to 10(6) ions∕s for use in the ATLAS facility. The ECR charge breeder has been tested with stable beam injection and has achieved charge breeding efficiencies of 3.6% for (23)Na(8+), 15.6% for (84)Kr(17+), and 13.7% for (85)Rb(19+) with typical breeding times of 10 ms∕charge state. For the first radioactive beams, a charge breeding efficiency of 11.7% has been achieved for (143)Cs(27+) and 14.7% for (143)Ba(27+). The project has been commissioned with a radioactive beam of (143)Ba(27+) accelerated to 6.1 MeV∕u. In order to take advantage of its lower residual contamination, an EBIS charge breeder will replace the ECR charge breeder in the next two years. The advantages and disadvantages of the two techniques are compared taking into account the requirements of the next generation radioactive beam facilities.     

Investigation of effects of viscoelastic boundary supports on transient sound radiated from a rectangular plate by modal strain energy method

This work considers analysis of transient sound radiation from an impact-excited rectangular plate with viscoelastic boundary supports based on the Modal Strain Energy (MSE) method. Vibration of the plate is approximated by double infinite series in the spatial coordinates. Each term of the series is constructed with vibration modes of beams having the same boundary conditions as the considered plate, multiplied by a time dependent function. Modal loss factor of each mode is obtained by the MSE method. The sound pressure for impact excitations is obtained in the time and frequency domain by numerical integration of the Rayleigh integral. Then effects of width of the viscoclastic boundary supports on the vibration response and the radiated sound pressure are investigated. It is shown that there is an optimum width of the support.     

A cable transducer for measuring angular electron distributions at the output of high-power accelerators

A transducer for measuring angular distributions of pulsed electron beams extracted from high-power accelerators into air is described. The transducer is made of an PK75-9-13 radio-frequency cable and contains a collimator with a small solid angle (～0.01 sr) and receiving electrode (cable conductor). By using a set of the transducers, the spatial-angular distribution of electrons in beams of ИГУР-3 and ЭМИР-М directaction accelerators at the All-Russia Research Institute of Technical Physics has been measured. The background radiation contribution to the measured signal is taken into account by using separate transducers in the same shot.     

Prospects for advanced electron cyclotron resonance and electron beam ion source charge breeding methods for EURISOL

As the most ambitious concept of isotope separation on line (ISOL) facility, EURISOL aims at producing unprecedented intensities of post-accelerated radioactive isotopes. Charge breeding, which transforms the charge state of radioactive beams from 1+ to an n+ charge state prior to post-acceleration, is a key technology which has to overcome the following challenges: high charge states for high energies, efficiency, rapidity and purity. On the roadmap to EURISOL, a dedicated R&D is being undertaken to push forward the frontiers of the present state-of-the-art techniques which use either electron cyclotron resonance or electron beam ion sources. We describe here the guidelines of this R&D.     

The YASHMA-2 Plasma Facility for the Deposition of Coatings on Solid Surfaces

A laboratory facility for the deposition of coatings on solid surfaces using a magnetron-discharge plasma and ion beams is described. Its main performance characteristics and functional capabilities are presented.     

A Radiometer for Plasma Diagnostics in a Magnetic Mirror GDT

A radiometer developed at Budker Institute of Nuclear Physics (Siberian Branch, Russian Academy of Sciences) for diagnostics of the efficiency of the electron cyclotron plasma heating in a mirror magnetic trap (GDT) is discussed. The radiometer is based on the superheterodyne principle. The characteristics of the instrument such as the operating range, sensitivity, frequency and time resolution are adapted to the requirements of the experiments. The receiver is equipped with a system for protection against stray radiation from powerful gyrotrons that are used in the electron cyclotron heating experiments. The radiometric measurements of the plasma self-emission carried out at the GDT facility showed that the new information channel helps to interpret the processes of resonant microwave plasma heating more accurately.     

A neutron diagnostic for high current deuterium beams

A neutron diagnostic for high current deuterium beams is proposed for installation on the spectral shear interferometry for direct electric field reconstruction (SPIDER, Source for Production of Ion of Deuterium Extracted from RF plasma) test beam facility. The proposed detection system is called Close-contact Neutron Emission Surface Mapping (CNESM). The diagnostic aims at providing the map of the neutron emission on the beam dump surface by placing a detector in close contact, right behind the dump. CNESM uses gas electron multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is made of a thin polythene film and an aluminium film; it is designed for detection of neutrons of energy >2.2 MeV with an incidence angle < 45°. CNESM was designed on the basis of simulations of the different steps from the deuteron beam interaction with the beam dump to the neutron detection in the nGEM. Neutron scattering was simulated with the MCNPX code. CNESM on SPIDER is a first step towards the application of this diagnostic technique to the MITICA beam test facility, where it will be used to resolve the horizontal profile of the beam intensity.     

Measurements of the profile of an intense electron beam

Methods for measuring the profiles of high-power electron beams by using a thin tungsten wire moved transversely to the beam have been developed. In one method, the electron current intercepted by the wire is measured and the beam profile is determined from a solution to the Abel equation under the assumption of axial beam symmetry. The second method is based on the detection of the local radiation emitted by the wire being heated by the beam to 1700–2200 K. The wire is additionally heated by an electric current in order to improve the sensitivity and spatial resolution. The measured beam current density is ～5–50 A/cm², and the resolution is ～0.1 cm.     

相对光谱辐射标准光源──合肥800Mev电子储存环

本文简要介绍了合肥800Mev电子储存环同步辐射装置,对其同步辐射的光谱分布进行了测试评价,结果表明,同步辐射的光谱分布实验结果与理论计算值具有较好的一致性。     

Application of a low-energy electron beam as a tool of nondestructive diagnostics of intense charged-particle beams

A new diagnostic instrument intended for measuring the parameters of intense bunches, detecting radiation fields, and performing tomography of intense ion beams is described. The operating principle of the device and the basic scheme of arrangement of its elements are described. The results of simulation of a EBP for several problems are presented. To reconstruct the longitudinal charge-distribution function, the effect detection error of the testing beam on the accuracy of the proposed method is considered. Depending on the problem to be solved, several design versions of the instrument are proposed, which are optimized for diagnosing beams of S-range linear accelerators, detecting radiation fields, studying bunches of superhigh intensity, performing tomography of intense proton beams, and operating in cyclic accelerators.     

Laser pulse-induced transitions on surfaces of bulk material,traced by thermal and secondary electrons

Thermal and electron beam-released electrons were exploited to probe the dynamics of surface modifications, induced by a Q-switched frequency-doubled Nd:YAG laser within areas of 100 μm Φ on bulk silicon and metals. Changes of surface geometry and phase transitions show up as pronounced peaks and steps in the emitted electron currents. They occur within Φ 200 ns after the laser pulse and consume times from less than 5 ns up to 200 ns. Applications of pulsed radiation power for surface machining, recrystallization and vitrification or for production of microstructures on bulk substrates for integrated devices are continually extending (Bäuerle 1984). Laser pulses are most frequently used, in spite of their inhomogeneous absorption, as contrasted to electron and ion beams, because of easy handling of power and no need for vacuum in many cases. The diagnostic methods usually applied to probe the dynamics of pulse-induced transitions are still those introduced at the beginning of the “laser annealing” technique, exploiting light reflection and transmission, and to a minor extent x-ray and electron diffraction, mass spectrometry and electrical conductivity (Khaibullin 1984, Larson 1984). Naturally, each diagnostic tool has a restricted range of useful application, so further methods combining high temporal and spatial resolution and equally applicable to semiconductors and metals are highly desirable. Thermal and secondary electrons are expected to be susceptible to changes of temperature and geometry of a surface, occuring during laser pulse machining. In fact, photon-assisted thermal electron emission was used to probe thermal relaxations in laser-pulsed semiconductors (Leung and van Driel 1984), however, the thermal electrons were not used to trace geometric modifications. Furthermore, secondary electrons have not yet been tested as a probe for very fast single effects. This report describes first results, demonstrating the usability of emitted electrons as a probe for nanosecond transitions on surfaces of bulk material. An electron optical equipment was built, consisting of electron gun, condensor lens and specimen chamber, allowing synchronized laser and electron beam pulsing of the specimen. Its surface was probed by the photo-thermally emitted electrons and ions or by the secondary and backscattered electrons, which were generated by the focussed primary electron beam. The latter was pulsed in order to suppress electron radiation damage. For laser treatment a pulse of a Q-switched frequency-doubled Nd:YAG laser (FWHM 20 ns) was focussed with a lens and a dielectric mirror onto the specimen, which could be viewed with a microscope for aligning the laser and the primary electron beam. Both beams had a diameter of 100 μm (FWHM) on the specimen. The emitted charges were collected by a shielded scintillator/multiplier detector of the Everhart-Thornley type, having a rise time of = 3 ns and being protected against excessive green laser light by an edge filter. Despite the simp1e set-up, rapid changes of the surface by vaporization, melting, solidification could readily be observed within areas down to 30 μm Φ on the nanosecond time scale. Flow and disrupture of liquid layers occur after the laser pulse, delayed by several 10 ns (Figs. 1 and 2). The dispersion of metal liquids by temperature-induced gradients of the surface tension may consume times from below 5 ns (Fig. 2a) up to 200 ns (Fig. la). It is signalized by a large increase of electron emission, probably due to Schottky effect at charged transient tips within the disintegrating liquid. First order phase transitions involving latent heats are readily indicated by thermal electrons. Solidification of a melt, for instance, shows up in the emission current as a prolonged plateau with an abrupt drop within 20 … 40 ns (Fig. 3). Summarizing, secondary and thermal electrons are well suited to trace single transitions on the surface of bulk material on the nanosecond-micrometer scale. In contrast to other diagnostic probes the spatial resolution may be increased well below 1 μm by improved focussing of the primary electron beam.