A device for screening interfering radiation from a radiation source from reaching a radiation receiver. The apparatus includes a set of prism shaped doorways configured to receive output beams from at least one optical device. Etching is performed at a process chamber pressure within the range of about 4 mTorr to about 60 mTorr. The controller can be configured to compute a first threshold level corresponding to background noise and a second threshold level corresponding to sensor noise, and to compute the report threshold value from the second threshold. A cooling device positioned within the housing reduces heat generated during operation of the network-configured computing device.