TY - JOUR
T1 - Electrical Breakdown Triggered by a Free Conducting Spherical Particle in Saturated Liquid He I and He II under Uniform dc Field
AU - Hara, Masanori
AU - Nakagawa, Hiroshi
AU - Suehiro, Junya
AU - Shinohara, Teruaki
N1 - Funding Information:
The authors wish to thank Dr. T. Satow of the NIFS for useful discussions, Mr. K. Imasaka for arranging the experimental equipment, Mr. I. Sakai for manufacturing the electrode system, and Mr. T. Yoshiki and Mr. Y. Maeda for assistance in the measurements of the breakdown voltage. This work was supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan, and the cooperative research funds from the NIFS and the 21st Century COE Program, Japan.
PY - 2003/12
Y1 - 2003/12
N2 - This paper is concerned with the pre-breakdown phenomena and the breakdown voltage characteristics, in the presence of a free moving conducting spherical particle, of saturated normal liquid helium (He I) and saturated superfluid liquid helium (He II) under uniform dc field. Experiments show that the particle lifts off around the theoretical value of the lift-off electric field, and the particle oscillates between the electrodes at higher applied voltages. In that case, the microdischarge appears just before the charged particle collides with the oppositely charged electrode, and the bubble is generated at the moment of every collision of the particle with the electrode. It is confirmed theoretically as well as experimentally that the maximum bubble radius in He II is nearly proportional to the Ein1/3, which is the released energy from the particle for the bubble generation. The insulation environment before the electrical breakdown suddenly changes at the λ-point since the bubble behavior in He I and He II greatly differs. In the characteristics of the breakdown voltage vs. liquid pressure, a clear discontinuity appears at the λ-point. Furthermore, the breakdown voltage in the parallel plane gap contaminated by a particle is lower than that in the rod-plane gap without a particle. It is found that the breakdown voltage characteristics are closely related to the trigger effect of the microdischarge and the bubble generation.
AB - This paper is concerned with the pre-breakdown phenomena and the breakdown voltage characteristics, in the presence of a free moving conducting spherical particle, of saturated normal liquid helium (He I) and saturated superfluid liquid helium (He II) under uniform dc field. Experiments show that the particle lifts off around the theoretical value of the lift-off electric field, and the particle oscillates between the electrodes at higher applied voltages. In that case, the microdischarge appears just before the charged particle collides with the oppositely charged electrode, and the bubble is generated at the moment of every collision of the particle with the electrode. It is confirmed theoretically as well as experimentally that the maximum bubble radius in He II is nearly proportional to the Ein1/3, which is the released energy from the particle for the bubble generation. The insulation environment before the electrical breakdown suddenly changes at the λ-point since the bubble behavior in He I and He II greatly differs. In the characteristics of the breakdown voltage vs. liquid pressure, a clear discontinuity appears at the λ-point. Furthermore, the breakdown voltage in the parallel plane gap contaminated by a particle is lower than that in the rod-plane gap without a particle. It is found that the breakdown voltage characteristics are closely related to the trigger effect of the microdischarge and the bubble generation.
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U2 - 10.1109/TDEI.2003.1255780
DO - 10.1109/TDEI.2003.1255780
M3 - Article
AN - SCOPUS:1642567392
VL - 10
SP - 1022
EP - 1031
JO - IEEE Transactions on Dielectrics and Electrical Insulation
JF - IEEE Transactions on Dielectrics and Electrical Insulation
SN - 1070-9878
IS - 6
ER -