Vol.21,

The longitudinal modulation to the electron beam by a coherent seed laser pulse is widely used for generating fully coherent, short wavelength radiation in various harmonic generation free electron laser (FEL) schemes. After introducing the density modulation, microstructures down to attosecond scale are produced over the distance of one seed laser wavelength. In order to take into account the microstructures in the theoretical and numerical analysis, in the frame of undulator period averaged approach, a modified model for harmonic generation FEL is developed in this paper. With the modified model, three harmonic generation FEL examples are investigated by employing Shanghai soft X-ray FEL (SXFEL) parameters. In FEL schemes with ultra-high harmonic generation and ultra-short pulse, the modified model presents some interesting aspects which are helpful for understanding of radiation pulse evolution, bunching efficiency and noise propagation issues.

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The response of a 14 MeV neutron-based prompt gamma neutron activation analysis (PGNAA) system, i.e. the prompt gamma-rays count rate and the average thermal neutron flux, is studied with a large concrete sample and with a homogeneous large sample, which is made of polyethylene and metal with various concentrations of hydrogen and cadmium using the MCNP-5 (Monte Carlo N-Particle) code. The average thermal neutron flux is determined by the analysis of the prompt gamma-rays using the thermal neutron activation of hydrogen in the sample, and the thermal and fast neutron activation of carbon graphite irradiation chamber of the PGNAA-system. Our results demonstrated that the graphite irradiation chamber of the PGNAA-system fairly operates, and is useful to estimate the average thermal neutron flux of large samples with various compositions irradiated by 14 MeV neutrons.

510

In this paper, the beam quality and percent depth dose curves for different field sizes of CyberKnife® system were investigated by Monte Carlo simulations using the PENELOPE code, which has been used to simulate 6 MV photon beam. In water phantom, the absolute doses were calculated for Φ10–60 mm collimators, and percent depth dose curves were evaluated for Φ30–60 mm collimators. The agreement of dose distributions of the calculation with measurement was within 3.0%. The mean energy of photon spectrum was 1.46 MeV, and the beam quality index was 0.632, which was slightly smaller than that of measurement.

359

In this paper, the proton image quality of three designed phantoms is studied by the Monte Carlo simulation tool FLUKA, and is compared with that of the photon, and electron imaging. The passages of parallel beams were simulated by the phantoms for protons, electrons and X-rays, and the fluence and energy spectra of exiting particles are recorded. The proton energy loss imaging has a high quality under low transmission proton fluence, and its quality is superior to that of electron and photon fluence. The results demonstrate that proton energy loss imaging is especially suitable for the samples of hundreds of nano-thicknesses.

450

In this paper, the ^99mTc-octreotide scintimammography as a useful complementary technique of mammography was evaluated in diagnosing breast cancers. The 45 breast lesions were consecutively detected by mammography, and ^99mTc-octreotide scintimammography, and both combination technique on the basis of self-examination, physical examination. Clinical diagnosis was confirmed by histopathologic analysis. Radioactivity uptake ratios for tumor vs normal breast tissues (T/NT) were calculated using regions of interest. In the breast cancer groups and the benign lesion groups, the average uptake ratios of the ^99mTc-octreotide were 1.63±0.19 and 1.09±0.13, respectively, and t was 9.638 (P<0.001). Based on sensitivity, specificity, accuracy, positive predicting value, and negative predicting value, ^99mTc-octreotide scintimammography was 87%, 79%, 84%, 90%, and 73%, the mammography was 65%, 64%, 64%, 80%, and 45%, and both combination was 95%, 100%, 97%, 100% and 92%, respectively. This showed that the ^99mTc-octreotide scintimammography was more useful than mammography in the evaluating suspected breast cancers, and the combination technique can accurately discriminate lesions.

333

The stresses in the coupling superconducting solenoid coil assembly, which is applied in the Muon Ionization Cooling Experiment (MICE), are critical for the structure design and mechanical stability because of a large diameter and relative high magnetic field. This paper presents an analytical stress solution for the MICE coupling coil assembly. The stress due to winding tension is calculated by assuming the coil package as a set of combined cylinders. The thermal and electromechanical stresses are obtained by solving the partial differential equations of displacement based on the power series expansion method. The analytical stress solution is proved to be feasible by calculating stresses in a tested superconducting solenoid with 2.58 m bore at room temperature. The analytical result of the MICE coupling coil is in good agreement with that of the finite element which shows that the transverse shear stress induced by Lorentz force is principally dominant to magnet instability.

323

The performance test of a CsI(Tl) crystal (70×27×23 mm³) was performed by applying the pulse shape discrimination technique for identification of light charged particles . The crystal is coupled to a photomultiplier tube during an experiment with ⁶He beam. The pulse waveform is fully recorded by employing a high precision digital oscilloscope. The fast and slow gates are used for the pulse shape discrimination and the best values for the gate widths were determined to be 0.5 μs and 1.67 μs, respectively. The ⁶He, ⁴He and ³He are successfully discriminated with this technique.

371

The thermal conductivity of uranium dioxide in the temperature range of 300–2400 K was estimated by non-equilibrium molecular dynamics calculation using Fourier law. The Kawamura function was adopted as the interatomic potential function. The calculated thermal conductivities are found to be strongly dependent on the temperature of the simulation cube. The thermal conductivity simulation results are compared with the experiment results and agreed well with the experimental results when the temperature is above 600 K. The thermal conductivities scale effects are found to be existed in uranium dioxide nanometer thin film. The approximate mean free paths of phonons in different temperatures can be examined.

407

A low-noise readout integrated circuit for high-energy particle detector is presented. The noise of charge sensitive amplifier was suppressed by using single-side amplifier and resistors as source degeneration. Continuous-time semi-Gaussian filter is chosen to avoid switch noise. The peaking time of pulse shaper and the gain can be programmed to satisfy multi-application. The readout integrated circuit has been designed and fabricated using a 0.35 μm double-poly triple-metal CMOS technology. Test results show the functions of the readout integrated circuit are correct. The equivalent noise charge with no detector connected is 500–700 e in the typical mode, the gain is tunable within 13–130 mV/fC and the peaking time varies from 0.7 to 1.6 μs, in which the average gain is about 20.5 mV/fC, and the linearity reaches 99.2%.

446

The impact of the integral non-linearity (INL) to the time resolution of HPTDC (High Performance Time to Digital Converter) is presented in this paper. An INL correction method based on look-up table (LUT), is proposed to minimize such INL and improve the time resolution. This scheme is implemented in a single Field Programmable Gate Array (FPGA) device for real-time compensation. The INL characteristic estimation is based on a statistical approach, in which a sufficiently large number of random input signals are measured. The prototype tests show that the deviation for time resolution due to INL can be reduced greatly, from more than 80 ps to less than 20 ps, which can meet the requirement of BES (Beijing Spectrometer) III Time-Of-Flight detector.

357

The instability occurring in OTSG (Once-Through Steam Generator) of movable nuclear power plants is presented by a multivariable frequency domain theory. As concerning coupling interactions of OTSG tubing, it is more efficient for analyzing the instability of OTSG compared the common single variable method. A mathematical model for the system is derived from the fundamental equations by using the perturbation, Laplace-transform and the nodalization techniques. The stable boundary and parameters which influence the stability of the system are evaluated through computer simulation. Numerical examples are given in the paper and the predictions of the model agree with the experimental results well.

356

A three dimensional Fricke-(PVA-glutaraldehyde)-xylenol orange (FPGX) hydrogel dosimeter was prepared by chemical crosslinking method. Dose determination was performed by measuring the absorbance change of the dosimeter before and after irradiation using UV-Vis spectrophotometer at 585 nm. The dose response of the FPGX hydrogel dosimeter related to absorbance change was linear, when it was irradiated by X-ray in the range of 0~2 Gy. The stability of the dosimeter before and after irradiation was evaluated by studying the change of absorbance with time.

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