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Jun, Sun

Publications and source records attributed to Jun, Sun.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Study on Reactor Physical Module Method Used in THR Simulator

In order to apply heat in winter 5 MW low temperature nuclear test heating reactor (THR) was designed by Institute of nuclear and new energy technology, Tsinghua University, China. This test reactor is a model for the large-scale nuclear heating reactor (NHR). The primary loop in NHR is integrated nature circulation. Integrated nature circulation improved the safety of the reactor. Under the serious environment problem, the nuclear heat is one of the means of solving the pollution problem in China. So, the study on NHR comes to be important and necessary. The simulator is a good tool to study the transient status and understand the feature in a reactor. There were many studies on the NHR simulator but the point physical model was always selected before. The aim of the work in this paper is to build three dimension reactor physical module which can be used in THR simulator. It is the base for the study on NHR simulator.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2012

A high-efficiency overmoded klystron-like relativistic backward wave oscillator with low guiding magnetic field

A klystron-like relativistic backward wave oscillator with a ratio of transverse dimension to free-space wavelength being about four is presented. In the beam-wave interaction region, the electron beam interacts with surface wave and volume wave simultaneously. The cathode holder plays an important role in the reflection of backward waves. A guard electrode, an electron collector ring, and a reflection ring are used to optimize the beam-wave interaction. The particle in cell simulation results reveal that microwaves with a power of 2 GW and a frequency of 12.3 GHz are generated with an efficiency of 42% when the diode voltage is 400 kV, the beam current 12 kA, and the magnetic field 0.48 T.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Design and numerical simulations of a high power 0.15 THz oscillator

An overmoded rectangularly corrugated relativistic surface wave oscillator is designed and theoretically analyzed to produce the high power terahertz radiation with a TM{sub 01} mode. The design is fully verified and optimized by 2.5D particle-in-cell simulations. A high power terahertz wave is obtained with the output power of 285 MW at the frequency of 0.148 THz with conversion efficiency 20% when beam voltage is about 400 kV, current 3.8 kA, and the magnetic field 6 T.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

High efficiency coaxial klystron-like relativistic backward wave oscillator with a premodulation cavity

The klystron-like relativistic backward wave oscillator (RBWO) combines the transition radiation with Cerenkov radiation and has demonstrated microwave output of high power and high efficiency. The coaxial slow wave structure device can produce microwave with a lower frequency in a smaller cross section. For the purpose of high efficiency, low frequency, and miniaturization, a coaxial klystron-like RBWO with a premodulation cavity is presented. Particle-in-cell simulations show that a microwave with power of 1.15 GW and frequency of 2.1 GHz is generated with conversion efficiency of 48%, whereas for the device with a reflector, the efficiency is 38%.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Plasma expansion and impedance collapse in a foil-less diode for a klystronlike relativistic backward wave oscillator

Klystronlike relativistic backward wave oscillator (RBWO) can produce microwave power exceeding 5 GW with a high efficiency larger than 40%. In the experiment of klystronlike RBWO, for about 1 MV peak diode voltages, increasing magnetic field from 1.43 to 1.89 T slowed the impedance collapse until it was suppressed completely. The introduction of a stainless steel obstructing ring aggravated the impedance collapse, whereas replacing the stainless steel obstructing ring with a flat stainless steel provided a more stable impedance variation during the pulse duration. These impedance collapses did not affect microwave generation seriously and may be attributed to the radial expansion of cathode plasma initialing from the cathode shank so that part of reverse currents were collected at the anode wall, contributing to the measured diode current. On the other hand, it was found that microwave generation shot-to-shot reproducibility was closely related to the diode impedance variation. When there was no or very low microwave measured, diode impedance collapse appeared at the latter of the pulse. The microwave generation shot-to-shot reproducibility was improved greatly after the electron collector was enlarged on radius with 1 mm. A possible explanation is that the anode plasma produced from electron collector expands axially and enters the diode region at a very high velocity of several mm/ns. The movement of the anode plasma in the beam-wave interaction region affects the microwave generation, which reduces the microwave power during the whole pulse duration significantly.

43 PARTICLE ACCELERATORS↗