Apparatus include an atmospheric pressure glow discharge (APGD) analyte electrode defining an analyte discharge axis into an APGD volume, and a plurality of APGD counter electrodes having respective electrical discharge ends directed to the APGD volume, wherein the APGD analyte electrode and the APGD counter electrodes are configured to produce an APGD plasma in the APGD volume with a voltage difference between the APGD analyte electrode and one or more of the AGPD counter electrodes. An electrode can be integrated into an ion inlet. Apparatus can be configured to perform auto-ignition and/or provide multi-modal operation through selectively powering electrodes. Electrode holder devices are disclosed. Related methods are disclosed.

Apparatus include an atmospheric pressure glow discharge (APGD) analyte electrode defining an analyte discharge axis into an APGD volume, and a plurality of APGD counter electrodes having respective electrical discharge ends directed to the APGD volume, wherein the APGD analyte electrode and the APGD counter electrodes are configured to produce an APGD plasma in the APGD volume with a voltage difference between the APGD analyte electrode and one or more of the AGPD counter electrodes. An electrode can be integrated into an ion inlet. Apparatus can be configured to perform auto-ignition and/or provide multi-modal operation through selectively powering electrodes. Electrode holder devices are disclosed. Related methods are disclosed.

According to one embodiment, a neutron position detector includes a gas including a .sup.3He gas and an additive gas. The gas has a gas composition being set so that a total of ranges of a proton and a tritium in the gas is 2.0 to 2.7 mm. The partial pressures are in an extent surrounded by a first gas composition point of the .sup.3He gas of 5 atm and the additive gas of 1.6 atm, a second gas composition point of the .sup.3He gas of 5 atm and the additive gas of 2.3 atm, a third gas composition point of the .sup.3He gas of 20 atm and the additive gas of 0.6 atm, and a fourth gas composition point of the .sup.3He gas of 20 atm and the additive gas of 1.3 atm.

According to one embodiment, a neutron position detector includes a gas including a .sup.3He gas and an additive gas. The gas has a gas composition being set so that a total of ranges of a proton and a tritium in the gas is 2.0 to 2.7 mm. The partial pressures are in an extent surrounded by a first gas composition point of the .sup.3He gas of 5 atm and the additive gas of 1.6 atm, a second gas composition point of the .sup.3He gas of 5 atm and the additive gas of 2.3 atm, a third gas composition point of the .sup.3He gas of 20 atm and the additive gas of 0.6 atm, and a fourth gas composition point of the .sup.3He gas of 20 atm and the additive gas of 1.3 atm.