A Passive Magnetoelastic Radiation Sensor

Abstract

A passive gamma detection technology, consisting of a fielded sensor and a separate analysis system, is described. The sensor is a small cylinder, about 2.5 mm in diameter and 15 mm in length. It requires no onboard power sources or physical connections for power or data transfer, and retains its cumulative response to radiation. The sensor consists of an amorphous magnetoelastic wire held in a longitudinally-stressed state by a radiation-sensitive material. When the radiation-sensitive material is subjected to gamma radiation, it mechanically degrades, relaxing the stress on the wire and lowering the wire’s magnetic permeability. The changes in permeability are observed by switching the magnetic domains in the wire and measuring the reduction in the Faraday voltage as the stress is diminished. The analysis package is built around an excitation-detection coil set and can communicate wirelessly with the sensor through a metallic or nonmetallic barrier at distances up to about 25 mm. The sensor response is linear up to a dose of at least 7 kGy.

CHIMES: Chemical Identification By Magneto Elastic Sensing

“…Extremely weak magnetic fields are only detectable with exquisitely sensitive equipment that can block out all external magnetic fields. It requires a superconducting quantum interference device (SQUID) with sensitivity at the Femto-Tesla (fT) in a magnetically shielded room (MSR) to detect these extremely weak fields [2], [6][7][8]. Because this technology requires special equipment such as a magnetic shield room and other larger devices possibly a cooling container, the SQUID system becomes too cumbersome and expensive for personal and laboratory use [2], [6][7][8].…”

“…Hence substituting s = j and is the oscillation frequency, = and And this gives (7) It is now apparent that some relationship exists within the parameters given in equation (4). Both represent capacitors at zero and at the pole respectively, this capacitors, each contribute a 90° phase shift for the required 180° phase shift needed for oscillation to occur at [5].…”

“…The double-headed KNF micro diaphragm gas sampling pump features a head connection for the two pump heads that are integrated into the housing operates with an extremely low level of noise [7]. The pump diaphragm is coated with PTFE for chemical resistance and is used in conjunction with the flow meter to sample the amount of gas pumped through the TRM.…”