Caching techniques for storing instructions, constant values, and other types of data for multiple software programs are described. The position sensor determines the position of an object, and the image sensor captures an image of the object. The slurry is agitated within the jet pump to effect a partial to full phase separation of the oil fraction from the solids fraction of the slurry. The types may be, for example, a pointed tip, a socket tip, or a grabber tip. In one embodiment, the finite penetration of the field beyond the plane of the chopper leads to non-ideal chopper response, which is characterized in terms of an \u201cenergy corruption\u201d effect and a lead or lag in the time at which the beam responds to the chopper potential. In one embodiment, when an unusually high load is measured at the pin, the temporary roof support controls at the front of the machine are disabled.