Plasma dynamics in the self-magnetic-pinch diode
The self-magnetic-pinch (SMP) diode1,2 is being developed as a source for flash x-ray radiography. The high electric field stresses applied to this diode and material heating from the intense electron beam generate electrode plasmas. While these plasmas are instrumental in beam formation and focusing, rapid plasma expansion from the electrodes can degrade radiographic performance.
LSP simulations of the Self-Magnetic-Pinch-diode
The Self-Magnetic-Pinch (SMP) diode has been modeled in LSP. Presented within this body of work are 2D simulations of the 8 MV Merlin SMP with an optimized anode-cathode (AK) gap and an AK gap that is 50 % larger. Anode plasma is simulated using LSP's hybrid fluid-kinetic algorithms. Both simulations demonstrate falling diode impedance during the pulse, possibly due to gap closure as the anode plasma expands. Output from LSP is used to generate predicted radiographs of test objects using MCNPX and BIE forward modeling. No significant difference is found in the resolution of the predicted radiographs for the two geometries. 3D simulations of the 3.5 MV Eros SMP are also presented. Deliberate asymmetries in the diode setup are simulated to test the SMP's susceptibility to 3D failure modes. It is found that asymmetric emission thresholds for the anode and cathode do not produce lasting significant asymmetry during the pulse. However, an angularly misaligned anode produces lasting asymmetry and spot movement.
Introduction and experience with the primary mail services based on their names for students
Kyushu University provided mail service based on student IDs such as "1AB10123X" to the university students for many years. Using this model, we had problems communicating with the students who graduated from the University and enrolled in the graduate school. The students received new mail addresses based on their new student IDs such as "2AB12789Y". Faculty members were forced to change the student mail addresses in the mailing lists and in their mail client address book. Furthermore, students were forced to notify the e-mail address change to all of their existing contacts. We introduced a new mail system to provide addresses based on the student name, as well as student ID in April 2011. The new naming convention uses the following format: lastname.firstname.999 where 999 is a random number of 3 digits. Students can select some combination patterns of their first and last names for Japanese. We also consider the middle names for foreign students. In the system implementation, we did not have the formal information of alphabetical names for students. We generated alphabetical names from Japanese Katakana names. It is not easy for us to get the appropriate name in this manner. We implemented a confirmation stage of the alphabetical name at first use, and then students can select their mail addresses for their convenience. We paid much attention to the user interface in the system. Since April 2011, the number of users who use the mail address based on their own name has been increasing gradually. This paper will detail the usage status of the new system.