An ion filter is used for a gas detector including a gas electron multiplier. The ion filter includes: an insulating substrate; a first patterned conductive layer on one main surface of the insulating substrate; and a second patterned conductive layer on another main surface of the insulating substrate. The ion filter has a plurality of through-holes formed along a thickness direction of the insulating substrate on which the first patterned conductive layer and the second patterned conductive layer are formed. The one main surface of the insulating substrate is disposed on an upstream side in a movement direction of electrons in the gas detector. The other main surface of the insulating substrate is disposed on a downstream side in the movement direction of the electrons in the gas detector. The first patterned conductive layer has a line width thicker than a line width of the second patterned conductive layer.

A drift tube construction includes a thin wall aluminum tube with a thin wire at its center attached to a terminal. The tube is plugged at both ends. The terminal is embedded at the center of the plug with material insulating it from Drift tube main body. The Drift tube assembly is sealed and filled with a gas mixture. A voltage is applied to the thin wire via the terminal. Current drift tubes employ plastic material to insulate the terminal from Drift tube main body and O-rings to provide a near hermetic seal.

A borehole muon detector for muon radiography or geotomography is provided, the borehole muon detector including a substantially cylindrical housing, which defines a bore, a pair of end caps, each end cap sealing an end of the cylindrical housing and a plurality of sealed drift tubes which are longitudinally disposed in the bore of the housing to form a bundle of drift tubes, wherein each sealed drift tube comprises: a centrally located anode wire disposed on a longitudinal axis; an inner surface which is coated with a cathode coating, the cathode coating divided into a first cathode pad and a second cathode pad by a Vernier pattern; and a timer in electrical communication with the anode wire for measuring a drift time. A system and a method are also provided.

A borehole muon detector for muon radiography or geotomography is provided, the borehole muon detector including a substantially cylindrical housing, which defines a bore, a pair of end caps, each end cap sealing an end of the cylindrical housing and a plurality of sealed drift tubes which are longitudinally disposed in the bore of the housing to form a bundle of drift tubes, wherein each sealed drift tube comprises: a centrally located anode wire disposed on a longitudinal axis; an inner surface which is coated with a cathode coating, the cathode coating divided into a first cathode pad and a second cathode pad by a Vernier pattern; and a timer in electrical communication with the anode wire for measuring a drift time. A system and a method are also provided.