X-ray Flourescence

It's a rock, man
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So the stuff the guy brings in is junk, but what is that gun-like thing the shopkeeper is using? Whatever it is, he seems confident in the readings he is getting.

Nito XL2 XRF Handheld Precious Metal Analyzer

It's not a Tricorder, but we're getting there. There are several companies making these things, and they've been doing it for a while. New ones cost between $20K and $40K. Used ones can be picked up for a tenth of that.

Functional schematic of a portable XRF instrument

The X-Ray Source is a vacuum tube. ThermoFisher Scientific explains:

Going to the Source: X-ray Tubes by Esa Nummi

 The major X-ray tube components are the cathode, anode, the tube envelope, the tube housing, and the window.

Cathode

The cathode serves to expel the electrons from the circuit and focus them in a beam on the focal spot of the anode. It is a controlled source of electrons for the generation of X-ray beams. The electrons are produced by heating the filament, i.e., a coil of wire made from tungsten, placed within a highly polished nickel focusing cup providing electrostatic focusing of the beam on the anode. Heat is used to expel the electrons from the cathode.

Anode

The anode represents the component in which the x-rays are produced. It is a piece of metal, shaped in the form of a beveled disk, connected to the positive side of electrical circuit. The anode converts the energy of the electrons into X-rays and dissipates the heat, considered the byproduct.

Envelope

An airtight enclosure that houses the cathode and anode. It is often made from metal and ceramic because these materials are able to withstand the tremendous amount of heat generated during X-ray production, but they can also be made of glass.

Housing

Provides protection and absorbs excess radiation.

Window

The X-ray tube window typically is made from beryllium because it allows X-rays to pass through but has sufficient strength to hold the vacuum required for the X-ray tube to operate. When an electrical current is passed through the cathode, the electrons generated by the cathode are accelerated by high voltage towards a metal target, or anode. X-rays known as Bremsstrahlung (“braking radiation”) are produced when the electrons are suddenly decelerated upon collision with the anode. When an atom in the sample is struck with an X-ray of sufficient energy (greater than the atom’s K or L shell binding energy), an electron from one of the atom’s inner orbital shells is dislodged. The atom regains stability, filling the vacancy left in the inner orbital shell with an electron from one of the atom’s higher energy orbital shells. The electron drops to the lower energy state by releasing a fluorescent X-ray. The energy of this X-ray is equal to the specific difference in energy between two quantum states of the electron. These X-rays all have sufficient energy to pass through the X-ray tube window and reach the sample. The measurement of this energy is the basis of XRF analysis.

Process of X-ray fluorescence generation

AZO Mining gives a brief history:

The United Nuclear XRF Probe

The earliest handheld energy-dispersive XRF probe was built by United Nuclear in the early 1980s, which was originally used to investigate highly radioactive holding takes, as well as the presence of uranium in the soil. Weighing over 70 pounds, this tool comprised of a measurement head connected to a cart, where the electronics displayed the received data.

Modified between 1982-1983, United Nuclear commercialized the MAP-1 device, which had the capability to detect uranium, as well as other elements in the soil through the creation of a “front pack,” while also reducing the weight of the instrument to 50 pounds. The evolution of these instruments continued through the 1980s as United Nuclear developed MAP-2 and MAP-3 analyzers for enhanced lead detection purposes.

XRF For Commercial Use

In 1994 electric contracting company Amptek developed the XR-100 X-ray detector for commercial use. This thermoelectrically cooled and simple to use detector replaced the need for liquid nitrogen to cool detectors in many applications. The XR-100 device was selected for the Pathfinder Mission to Mars, where it successfully analyzed rocks and soil in a cost-effective and precise manner.

The first fully-handheld XRF detector was created in 1994 by Niton Inc., a Massachusetts-based company, in which this Niton XL-309 instrument offered intensified analytical performance at a lower price than the previous instruments on the market.

As interest in these analytical systems began to grow, the National Aeronautics and Space Administration (NASA) in conjunction with KeyMaster Technologies designed the first TRACER II unit, which included an argon transmission target. This aspect of the instrument allowed NASA and KeyMaster to create a portable vacuum XRF analyzer that had the ability to perform on-the-spot chemical analysis, which was a task previously only possible in a chemical laboratory.

The first applications of the TRACER II unit allowed NASA to quickly and accurately determine elemental composition on large objects, such as a rocket motor, which was a major breakthrough for this organization. Modifications to the TRACER II unit allowed increased sensitivity to specific metals, including a new ability to measure magnesium and aluminum content in aluminum alloys.

As demands for increased accurate and efficacious handheld XRF tools began to rise, competition between industries to produce grew as well. In 2008, Brucker Elemental produced Bruker XFLASHTM silicon drift detector (SDD) technology that was integrated into the first-ever SDD-based handheld XRF unit, also known as the S1 TRACER. Still a unit with one of the best resolutions, Bruker’s S1 TRACER allows the analysis of light elements, including magnesium, aluminum, and silicon in air, while also providing an increased concentration range for these elements of interest.

This summer plumbers came to the house to install a new water line. They also had some very sophisticated detectors.