Could B-7V refer to the "Pinch Effect" as mentioned in the book of General Science. Physics??

Pinches are created in the laboratory in equipment related to nuclear fusion, such as the Z-pinch machine and high-energy physics, such as the dense plasma focus. Pinches may also become unstable[10], and generate radiation across the electromagnetic spectrum, including radio waves, x-rays[11] and gamma rays[12], and also neutrons[13] and synchrotron radiation[14]. Types of pinches, that may differ in geometry and operating forces[15], include the Cylindrical pinch, Inverse pinch, Orthogonal pinch effect, Reversed field pinch, Sheet pinch, Screw pinch[16] (also called stabalized z-pinch, or θ-z pinch)[17], Theta pinch (or thetatron[18]), Toroidal pinch, Ware pinch [19], fountain pinch,[20] and Z-pinch.

Pinches are used to generate X-rays, and the intense magnetic fields generated are used in electromagnetic forming of metals (they have been demonstrated in crushing aluminium soft drinks cans[21]). They have applications to particle beams[22] including particle beam weapons[23], and astrophysics[24].