Mahmoud Bakr

Low-Temperature Operation of a Bulk HTSC Staggered Array Undulator

A use of bulk high-temperature superconductors (HTSs) for an undulator is attractive since a high magnetic field can be generated at low-temperatures. While potential for generation of the high magnetic field is high, in-situ magnetization of the bulk HTSs for periodic field generation is challenging issue. Recently, we proposed a new type of undulator using bulk high-Tc superconductors (HTS) and a solenoid magnet. The undulator, named Bulk HTSC staggered array undulator (Bulk HTSC SAU), consists of a stacked array of bulk HTSs and copper insulators and a solenoid magnet. A proof of principle experiment at 77 K using liquid nitrogen has been carried out. The estimated performance at about 30 K was estimated using results of property measurements for the HTS used for the Bulk HTSC SAU. The expected undulator peak field reaches to 1.08 T for undulator period length of 9.9 mm for the undulator gap of 4.0 mm. This performance is about 2 times higher than that of existing technologies.

Proposal of a Bulk HTSC Staggered Array Undulator

We proposed a new type of undulator based on bulk high‐Tc superconductors (HTSC) which consists of a single solenoid and a stacked array of bulk HTSC. The main advantage of this configuration is that a mechanical structure is not required to produce and control the undulator field. In order to perform a proof of principle experiment, we have developed a prototype of bulk HTSC staggered array undulator using 11 pairs of DyBaCuO bulk superconductors and a normal conducting solenoid. Experimental results obtained by using the prototype undulator and numerical results obtained by a loop current model based on the Bean mode for a type‐II superconductor were compared.

CeB 6 : Emission Performance and Uniformity Compared With LaB 6 for Thermionic RF Guns

Thermionic emission performance from single crystals of CeB₆ and LaB₆ was investigated at different operational loads using a test machine, in order to consider CeB₆ as a cathode for thermionic RF guns in the future applications. To evaluate cathode quality and uniformity for long lifetime applications, Miram curves in conjunction with their associated practical work function distribution (PWFD) were applied to the thermionic emission results. The analysis of the PWFD plot revealed that the variation of the peak in the work function and full-width at half-maximum for CeB₆ is very close to that of LaB₆. This suggests that emission performance, uniformity, and expected operational lifetime of a CeB₆ cathode are comparable with LaB₆ cathodes. In addition, previous simulation results of the back bombardment (BB) effect on CeB₆ and LaB₆ emphasized that CeB₆ presents less sensitivity to BB electrons compared with LaB₆ at a 5.5-μs pulse duration and 8-MW RF power. This gives CeB₆ the potential to replace LaB₆ as a thermionic cathode for an RF gun. A complete analysis of the cathode emission performance and PWFD at different operational loads for CeB₆ prior to a prospective real test is presented.

Emission properties and back-bombardment for CeB6 compared to LaB6

The emission properties of CeB6 compared to LaB6 thermionic cathodes have been measured using an electrostatic DC gun. Obtaining knowledge of the emission properties is the first step in understanding the back-bombardment effect that limits wide usage of thermionic radio-frequency electron guns. The effect of back-bombardment electrons on CeB6 compared to LaB6 was studied using a numerical simulation model. The results show that for 6 μs pulse duration with input radio-frequency power of 8 MW, CeB6 should experience 14% lower temperature increase and 21% lower current density rise compared to LaB6. We conclude that CeB6 has the potential to become the future replacement for LaB6 thermionic cathodes in radio-frequency electron guns.

Current Status of the Non-destructive Assay for 235U and 239Pu Toward More Secure Nuclear Power

Nuclear energy still represents one important option for energy sources that do not emit CO2 even after the Fukushima accident. Right now, it constitutes about 16–17% of the world’s total power supply, and is expected to increase and spread significantly by the coming three decades. Special nuclear materials (SNM), mainly 235U and 239Pu, used as fuels for nuclear power plants are required to be fully controlled and accounted by the IAEA. Non-destructive assay (NDA) for screening SNM is an important for countering terrorism as well as accountability purposes, because it is difficult to detect hidden SNM. NDA methods are mainly classified into two categories in terms of radiation detection; neutron-spectrometry methods and gamma-spectroscopy methods. This paper is devoted to discuss the current status of the NDA different techniques and assess usage of nuclear resonance fluorescence (NRF) technique in combination with quasi-monochromatic gamma-rays generated by laser Compton backscattering as a promising one.

Assessment of LaBr 3 (Ce) scintillators system for measuring nuclear resonance fluorescence excitations near 2 MeV

Nuclear resonance florescence (NRF) is a powerful tool for non-destructive assaying of nuclear materials. Detection system is a key issue for investigating nuclear materials using this technique. For a long time, Ge detectors were used because they have an excellent energy resolution but also have drawbacks of high cost and slow response time. On the other hand, LaBr3(Ce) detectors have high response speed and high detection efficiency as well as easy for assembly. However, a drawback of LaBr3(Ce) crystals comes from the unavoidable internal background levels near 2 MeV. This regime has great importance because it is very rich with 235U and 239Pu levels. We tested two different volume scintillators with 2.13 MeV quasi-monochromatic gamma-ray beam from the laser Compton backscattering (LCS) in National Institute of Advanced Industrial Science and Technology (AIST). We could clearly detect the NRF excitation level from 11B at 2.13 MeV. For this level, the energy resolution for the small LaBr3 (Ce) detector was 1.8% (FWHM), and 2.4% (FWHM) for the large LaBr3(Ce) detector. Potential of this scintillator for non-destructive assay of nuclear material identification is discussed in the light of our results.

FEL Beamline for Wide Tunable Range and Beam Sharing System at Kyoto University

A mid‐infrared free electron laser (MIR‐FEL) facility (KU‐FEL: Kyoto University Free Electron Laser) has been constructed for developing energy materials in Institute of Advanced Energy (IAE), Kyoto University. The tunable range of KU‐FEL was estimated as 5–13.2 μm by numerical calculation to design the MIR‐FEL transport line for application purposes. Aiming to increase the number of FEL users with different desires we decided to develop an FEL beam sharing system that is useful for multi‐utilization at different end‐stations. The transport line and the beam sharing system has been designed and constructed to the user stations. Applications of the MIR‐FEL in the renewable energy research at Kyoto University will start as well.

Simulation of Electron Trajectory in Bulk HTSC Staggered Array Undulator

To realize short-period high-magnetic-field undulator, we have proposed an undulator using bulk high temperature superconductor in a staggered array structure. To investigate the effect of the longitudinal solenoid field on the electron beam trajectory, the magnetic field near the center of this undulator was modeled and the trajectory of the single electron and the undulator radiation was calculated. As a result, we found that the stronger solenoid field had a good effect on the electron beam confinement. However, we found that the radiation wavelength became longer and the peaks of the spectrum became smaller at stronger solenoid field.

Beam Stabilization by Using BPM in KU-FEL

A Mid-Infrared Free Electron Laser (MIR-FEL) facility has been constructed for developing energy materials in Institute of Advanced Energy (IAE), Kyoto University. Since high brightness electron beams are crucial for the FELs, stabilization of the electron beam (beam energy, beam current, bunch spacing and beam trajectory) is very important for a stable FEL operation. For these reasons, the electron beam position which includes the electron beam energy information should be monitored precisely to realize the highly stable electron beam. We have been developing a feedforward and a feedback system using 4-pickup electrode type Beam Position Monitor (BPM) in Kyoto University FEL (KU-FEL) to generate a stable FEL light. A basic design of the BPM readout system has been completed and we have installed BPMs with accuracy of 10 μm for non-destructive measurement in the KU-FEL linear accelerator. BPM signals were observed successfully and a phase stabilized electron beam has been generated by a feedforward system. A feedback system using BPM to stabilize the beam position is under development.

Community acceptance of nuclear power generation in Japan and relevant influencing factors

Acceptance for NPP in Japan was approximately supported by half of the population. This was composed by 11% in favour of expansion and 42% in favour for at least maintaining the current plants in operation. In comparison to previous reports, there is virtually no change in the percentage of those supporting NPP expansion but the remaining have shifted to a more sceptical or opposed view towards NPP.