The ratio of optical pulse numbers to corona current (ROPC) is proposed to study the correlation between UV radiation
intensity and current strength during AC corona discharge. It’s found that the ROPC curves rose rapidly before a critical
voltage and then the curves flatten with the supplied voltage rising, even if the voltage is increased approximately 1 fold
higher than the critical voltage. Finally, according to ROPC curves, a new method of determining the voltage for corona
inception is introduced, and a novel quantitative analysis method is put forward to judge the level of corona discharge by the
means of optical measurement.
Corona discharge of high voltage lines and equipment has always been an operational and maintenance problem for
electric power utilities. In addition to causing noise and radio interference problems, these luminous discharges, which
result from the ionization of air around an electrode, may also indicate the presence of faulty, damaged or contaminated
high voltage components. Corona can lead to the some components' premature aging and failure. Therefore, it's
necessary to develop a system to identify corona discharge sources and pinpoint the offending component so that it may
be replaced. The corona emission in the solar-blind ultraviolet (SBUV) region (240 - 280 nm) is much weaker but the
solar background is nil. Accordingly, a beam-split scheme, including a catadioptric UV telescope, a solar-blind UV
filter, an intensified-CCD (ICCD), and a visible camera, is applied in this system. The catadioptric UV telescope is
especially designed in this paper. Twain reflecting spherical surfaces, composed the majority of the UV telescope, are
combined with a pair of positive and negative lenses in the front, and a correction lens in the back-end. To be
emphasized, all the elements' surfaces of the catadioptric telescope are spherical, so that it can be manufactured
conveniently. In addition, it has a large aperture of 68 mm, with a focus length of 180mm, so as to improve the optical
resolution, enhance the power of entrance pupil and elevate the sensitivity of the imaging system. A folding mirror is
positioned in front of the telescope's central obscuration so that the UV and visible cameras have a common axis. In
addition, the bispectral image fusion is based on digital signal processor TMS320DM642 of TI company, where the
DM642 device has three configurable video port peripherals (VP0, VP1, and VP2), and each video port consists of two
channels - A and B with a 5120-byte capture/display buffer that is splittable between the two channels. Therefore,
DM642 has enough video ports to satisfy two video-in channels from the UV ICCD and the visible CCD, and one videoout
channel for bispectral fusion. At last, an image fusion algorithm based on pixel is used in experiments, and a
bispectral fused image is given clearly in this paper.
The conflict of longevity of satellite's service and limited life of Sterling cooler decides that coolers should work on the
intermittent mode in space. As a result, The HgCdTe (MCT) infrared (IR) detectors in satellite are commonly subjected
to thousands of repeated thermal cycles from below -173°C to room temperature (20°C), which brings some new
reliability problems. Especially the mismatch of coefficient of thermal expansion (CTE) of different materials may lead
to some unfamiliar failure modes with such low temperature and nearly 200°C span of thermal cycles. In order to study
the characteristics of MCT detectors under the stress of thermal cycles, this paper introduced a special automatic system.
The system is mainly composed of a sub-container of liquid nitrogen, a heater controlled by the PID hardware, and an
object stage on which the MCT detectors to be tested are mounted. Furthermore, the sub-container, the heater and the
stage are positioned in a large vacuum tank. In the course of thermal cycles, the object stage moved up and down with
MCT detectors is driven by a step motor. When it rises to the bottom of liquid nitrogen sub-container, the stage is to be
cooled with detectors, and when declines to the heater, the stage to be heated with detectors, too. At last, two long
wavelength MCT detector samples are tested with this equipment, and the resistance, the signal and the noise are
measured. It shows that all the pixels' resistance didn't change beyond 5% after 5000 cycles. However, the tested signal
of the last pixel of both detectors increased sharply after 1000 cycles, and fell to normal level after 5000 cycles, with its
noise altering a little from beginning to end. A deduction is given in this paper for this phenomenon. In accordance, the
thermal cycle equipment and the experimental data, would supply some references to the design and fabrication of MCT
For the limit of its lifetime, the Stirling cooler is operated on the intermittent mode in satellite in some cases. Thus such cryogenic semiconductor components as HgCdTe mid or long wavelength infrared (IR) detectors are subjected to thousands of repeated thermal cycles from below -173°C to room temperature. Therefore, a series of experiments focused on quality, performance and reliability are essential in order to satisfy the reasonable requirements. Accordingly, a feasible thermal cycle screening system is put forward. And a vast experimental data show that thermal cycle tests play the most effective role in the environment stress screen (ESS).
In this paper, we introduce the system to help to study the main failure mechanisms and improve the performance of the semiconductor components. Such main failure mechanisms as solder-ball invalidation encountered commonly in the detector modules, which is due to the large thermal expansion coefficient mismatch among different materials.
The thermal cycle system is based on the principle of heat exchange. We expect HgCdTe IR detectors be cooled to lower than -173°C and heated to room temperature in a few minutes. Above all, we simulate the heating and cooling system through finite element method (FEM). As a result, the computations reveal that the IR detectors can be heated and cooled at a higher rate than expected. A consequent design of the entire system is founded on the simulation. At last, we adjust the mechanical structure of heat exchange system to the adaptive state to accomplish the ESS.
The thermal cycle screening system includes an autocontrol part and a test part. The autocontrol part is adopted to realize the heat exchange between IR detectors and the environment, and the test one to inspect the temperature and electrical parameters of these detectors. And at least four IR detector samples can be screened at one time.