Systems and methods are disclosed for detecting temporary high level impairments, such as noise or interference, for example, in a communications channel, and subsequently, mitigating the deleterious effects of the dynamic impairments. In addition, it is also possible to extract a part of an image or the whole of an image of a stored taken image to be registered as a mask pattern. The first end of the fastener defines a head and the fastener includes a threaded portion which extends between the second end of the fastener and the head. Through this manner, distortions of the photosensitive film pattern upon development are compensated and a target photosensitive film pattern can be more accurately acquired. The present invention allows a cathode temperature to have a high temperature and hence, it is possible to enhance the electron irradiation characteristics even when a degree of in-tube vacuum is lowered.