Zero displacement ionization chamber

A displacement-free ionization chamber comprising:

• a thimble chamber including:
• a first electrode of a generally cylindrical shape;
• a second electrode having a substantially cylindrical shape, different in size from said first electrode, said second electrode spaced from said first electrode by a predefined air gap;
• said first and second electrodes comprising a material density balanced with the air in said air gap for producing an overall thimble chamber density proportional to the weighted density of the material and air by normal radiation path lengths to said chamber, wherein the density of said chamber is substantially the density of water, such that said ionization chamber has an effective zero displacement when submerged in water;
• and
• means for electrically connecting said first and second electrodes to a voltage power supply.

In a displacement-free ionization chamber comprising:

• a thimble chamber including:
• a first electrode having a predetermined thickness and length;
• a second electrode having a predetermined thickness and length separated from said first electrode by a predefined air gap;
• wherein said first and second electrodes and said air gap are shape and density balanced by weighting the normal path lengths of radiation rays through said thimble chamber, thereby effecting a thimble chamber having an overall density substantially the same as water yielding a zero displacement when placed in water.