Vol.16,

In this paper, a new mechanism of electromagnetic instability, the induced ion-channel instability, is studied. It is based on the transverse driven betatron oscillation of relativistic electron beam induced by an additional magnetic undulator with a period close to the betatron wavelength in an ion channel. As its amplitude is sensitive to the electron beam energy, the driven betatron oscillation may determine electron beam grouping in the ponderomotive potential by selecting the undulator strength and period, and it provides a new mechanism of electron bunching, resulting in electromagnetic instability. Under proper condition, a new free-electron laser based on this mechanism may be realized.

292

Coherent diffraction radiation (CDR), generated by relativistic femtosecond electron bunches passing through an aperture in a metallic foil, is becoming widely used as a high brightness, coherent, polarized, and broadband terahertz radiation source. It is one of the most promising technique for non-destructive beam diagnostics in accelerators. In this paper, how to produce CDR is studied by utilizing femtosecond electron bunches at wavelengths equal to or longer than the bunch length with the aperture size at the condition of a≤γλ/(2π), which is provided by Shanghai Deep Ultraviolet-Free Electron Laser (SDUV-FEL) facility. General characteristics of CDR at SDUV-FEL are analyzed and numerically calculated. The results show that the radiance of this radiation within the frequency range from 0.2 up to 5 terahertz greatly exceeds that available from conventional black body radiation or synchrotron radiation.

296

The digital RF (Radio Frequency) phase detector based on commercial PXI (PCI eXtensions for Instrumentation) modules for the Linac is fully described in the paper. The DBM (Double Balance Mixer) is used as the phase detector and its control and data acquisition system is based on the PXI bus. The software adopts a curve fitting algorithm. The prototype has been tested in the laboratory and the good resolution, accuracy, reproducibility and reliability are expected. The system does not present the problems of analog solution.

318

The new linac and transport line control system of Hefei Light Source (HLS) is a distributed control system based on EPICS (Experimental Physics and Industrial Control System). Industrial PC (IPC) is widely used as not only Input/Output Controller (IOC) but also device controller. Besides industrial PC, PLC and microcontroller are also used as device controllers. The software for industrial PC based device controller is developed based on VxWorks real-time operating system. The software for PLC and microcontroller are written with ladder software package and assemble language, respectively. PC with Linux and SUN workstation with Solaris are used as operator interfaces (OPI). High level control is made up of some EPICS tools and Tcl/Tk scripts.

307

In a fine adjustment mechanism of the second crystal in a double-crystal monochromator, a compression spring is usually used as a return force element, but it often produces permanent deform after some time. A novel fine adjustment mechanism is put forward, which utilizes permanent-magnet as the return force element instead of a compression spring. Its principle and advantages of adjusting the pitch angle and the roll angle are analyzed, and the structure parameters of the permanent-magnet, which is the key part of the fine adjustment mechanism, are optimized. The magnetically adsorbed fine adjustment mechanism has been testified and applied successfully in the double-crystal monochromator of 4W1B beam line in Beijing Synchrotron Radiation Facility (BSRF).

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To explore the medical use of a radioactive ⁹C-ion beam in tumor treatment, which is a double radiation source coming from the external beam itself and the delayed particles emitted internally, some physical experiments are performed at the Secondary Beam Line (SBL) of Heavy Ion Medical Accelerator, Chiba (HIMAC) in Japan before radiobiological research for exhibiting therapeutic value of the ⁹C beam. Intention of the experiments is for producing a radioactive ⁹C-ion beam with higher production rate and purity by means of optimizing the beam line parameters. Finally, a produced ⁹C beam with the production rate of 9.07×10^-6 and purity of 82.88% at full momentum acceptance has been obtained under the optimal conditions of 40 mm-thick beryllium target and 10 mm-thick aluminum degrader. Both momentum distribution and contaminations for the produced ⁹C beam under the optimal conditions are measured. In order to execute further biological experiments of the ⁹C beam project, a uniform irradiation field is made with the wobbling magnets and its homogeneity is up to 93.8% inside central area of 20mm in diameter.

359

Heavy-ion irradiation is commonly used to study radiation damage of high level radioactive waste (HLW) forms, but S ion was never used before. In this investigation, 100 MeV ³²S ions produced by tandem accelerator was used to study radiation effects on pyrochlore-rich synroc which contained simulated actinides. The amorphization and amorphous doses were determined by X-ray diffractometer (XRD) and transmission electron microscopy /select area electron diffraction (TEM/SAED). The vacancy defects induced by heavy-ion irradiation were characterized by using positron annihilation technique (PAT). The experimental results show that the amorphous dose is 0.5 dpa, the defects produced by heavy-ion irradiation are mainly voids, and irradiation could continue to intensify the vacancy defects even after the amorphous dose was reached.

316

Bystander effects induced by low-dose or low dose-rate radiation have put a great challenge to the traditional model for radiation protection. In order to get a better assessment of the adverse effects of radiation, especially the low-dose radiation risk in environment, a radioactive irradiation facility, by which the dose and dose-rate to the biological targets can be controlled by rotating the sample bracket and changing the space between the radioactive source and the targets, was developed. The energy of ourα-radioactive source (²⁴¹Am) is measured averagely 3.5 MeV at the position of the irradiated sample. The dose rate was measured by using a silicon surface barrier detector and a CR39 particle track detector. A dose rate ranging from 0.045 cGy/s to 1.07 cGy/s can be obtained by changing the space length from the radioactive source to the sample dish.

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Basaltic samples from different locations in Aershan area determined by instrumental neutron activation analysis (INAA) have the same distribution patterns of REE and trace elements. The similar REE contents of the same minerals without inclusions from different xenolith suggest that the mantle source region under different active volcanoes have the same composition. The REE content differences between the same minerals with and without melt inclusions selected from the same mantle xenolith indicate that the melt inclusions are rich in REE. The same patterns of trace elements of inclusions and host minerals from different xenolith analyzed by SRXRF suggest that the mantle fluid has no notable heterogeneity in Aershan area.

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The simulating technetium (Tc) separated from HLW was immobilized in perovskite-rich and rutile-rich synroc which contained 85wt% of perovskite or rutile, and 20, 25, 30 or 35wt% waste loading, respectively. The synroc was prepared by hot pressing under reducing condition. The fabricated samples have good physical properties (density and open porosity). The XRD analyses show that the major phase is perovskite or rutile and the minor phases are zirconolite, hollandite and metal alloy. At higher waste loading the metal alloy phase appeared, particularly in the rutile-rich synroc. The scanning electron microscopy (SEM) and backscattered electron images (BEI) show the samples to be homogeneous and densified. The MCC-1 leaching tests (90℃, 28 d) results show that: mass losses are at the level of 10^-3 g•m^-2•d^-1, and the nominal element leaching rates are 10^-5~10^-3 g•m^-2•d^-1. It indicates that the fabricated samples have good leach resistance. According to their physical properties and leach resistance, the perovskite-rich and rutile-rich synroc can immobilize Tc up to 35 wt%. In comparison, Tc immobilization by using perovskite-rich synroc is more favorable.

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To study quantitative change of cerebral blood flow (CBF) on patients with early syphilis,we have established a method on absolute measurement of rCBF by using SPECT with Ethyl Cysteinate Dimmer (ECD) as imaging agent, and the method was applied to measure rCBF on patients with early syphilis. The rCBF values measured by this method are highly consistent with the values measured by other classical methods such as SPECT (¹²³I-IMP) and PET (¹⁵O-H₂O). The rCBF values for early syphilis patients and the normal control show some statistical differences. A routine quantitative absolute measurement of rCBF featured with simple procedures is therefore on the way of maturation.

322

The fluid models of gas discharge in alternating current plasma display panel (AC PDP) cell are discussed. From the Boltzmann equation, the hydrodynamic equations are derived, but this model consumes much computational time for simulation. The drift-diffusion approximation model and the local field approximation model are obtained to simplify the numerical computation, and the approximation conditions of these two models are discussed in detail. The drift-diffusion approximation model gives more satisfactory result for PDP simulation, and the expression of energy balance equation is given completely in this model.

317

EAST is a full superconducting tokamak with an elongated plasma cross-section. It consists of superconducting poloidal field (PF) magnet system, toroidal field (TF) magnet system, vacuum vessel with inner parts, thermal shields and cryostat vessel. The mission of the project is to widely investigate both physics and technologies of advanced tokamak operations, especially the mechanism of power and particle handling for steady-state operations. The cryogenic component is mainly composed of superconducting TF and superconducting PF coils that ensure the ability of sustaining magnetic field for plasma confinement, control and shaping in steady-state. This report describes the process of the structure design of cryogenic component support for EAST.

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