scholarly journals Slow oscillations in the low-temperature optical reflectance spectra of ZnO: Surface space-charge effect

2007 ◽  
Vol 90 (6) ◽  
pp. 061109 ◽  
Author(s):  
J. Q. Ning ◽  
S. J. Xu ◽  
S. L. Shi ◽  
M. H. Xie
Keyword(s):  
Low Temperature ◽  
Space Charge ◽  
Space Charge Effect ◽  
Reflectance Spectra ◽  
Charge Effect ◽  
Optical Reflectance ◽  
Slow Oscillations

scholarly journals Manipulation of Laser Distribution to Mitigate the Space-Charge Effect for Improving the Performance of a THz Coherent Undulator Radiation Source

Particles ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 238-252 ◽  
Author(s):  
Siriwan Krainara ◽  
Shuya Chatani ◽  
Heishun Zen ◽  
Toshiteru Kii ◽  
Hideaki Ohgaki
Keyword(s):  
Electron Beam ◽  
Space Charge ◽  
Electron Bunch ◽  
Beam Quality ◽  
Space Charge Effect ◽  
Bunch Length ◽  
Charge Effect ◽  
Simulation Code ◽  
Undulator Radiation ◽  
Radiated Power

A THz coherent undulator radiation (THz-CUR) source has been developed at the Institute of Advanced Energy, Kyoto University. A photocathode Radio-Frequency (RF) gun and a bunch compressor chicane are used for generating short-bunch electron beams. When the electron beam energy is low, the space-charge effect strongly degrades the beam quality, such as the bunch length and the energy spread at the high bunch charge condition at around 160 pC, and results in the reduction of the highest frequency and the maximum radiated power of the THz-CUR. To mitigate the space charge effect, we have investigated the dependence of the electron beam quality on the laser distribution in transverse and longitudinal directions by using a numerical simulation code, General Particle Tracer GPT. The manipulation of the laser distribution has potential for improving the performance of the THz-CUR source. The electron bunch was effectively compressed with the chicane magnet when the laser transverse distribution was the truncated Gaussian profile, illuminating a cathode. Moreover, the compressed electron bunch was shortened by enlarging the laser pulse width. Consequently, an enhancement of the radiated power of the THz-CUR has been indicated.

SPACE-CHARGE EFFECT IN UNINTENTIONALLY N-DOPED SILICON

2012 ◽  
Vol 26 (08) ◽  
pp. 1250048 ◽  
Author(s):  
KANKAN CONG ◽  
YANG JI
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Space Charge ◽  
Space Charge Effect ◽  
Charge Effect ◽  
Temperature Range ◽  
Ohmic Behavior ◽  
Current Voltage ◽  
Doped Silicon ◽  
High Bias

We report experimental results on current–voltage characteristics of Au-Ti/n-Si/Au-Ti devices made on unintentionally n-doped silicon, which depend dramatically on temperature and external magnetic field. While such devices show Ohmic behavior in the temperature range 154–300 K, space-charge effect dominates at high bias voltages in the temperature range 77–154 K. In the later case, external magnetic field may increase its breakdown voltage, thus inducing large positive magnetoresistance similar to those reported by other groups.

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