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Application of electrically conductive coatings to ionization counters

IP.com Disclosure Number: IPCOM000226801D
Publication Date: 2013-Apr-22
Document File: 4 page(s) / 62K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is an electrically conductive ultra-low alpha-particle emissive material with an adjustable electrical conductivity. Adjustment is performed by altering the amount of graphite in the material. The invention uses this material in the application of the sidewalls of an ionization counter.

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Application of electrically conductive coatings to ionization counters

In order to provide a large area of uniform electric field, sidewalls are provided in many ionization detectors. The sidewalls provide a constant voltage gradient between the anode (typically at about +1000 V) and the cathode (typically at ground potential). In most applications, the sidewalls are etched or machined from circuit board material utilizing resistors between the adjacent metal rows, or stripes. An example is shown below with eight stripes. (Figure 1) Since the sidewall material is copper, the voltage is constant left-to right, and varies uniformly from top to bottom if the resistors (R1-R7) are identical. The resistance of the resistors is large to limit the current flow, and the resistors are soldered to the stripes.

Figure 1: Sidewalls are etched or machined from circuit board material utilizing resistors between the stripes

Most materials contain trace amounts of uranium and/or thorium, particularly metals. Therefore, many materials used to fabricate alpha-particle detectors in general, and specifically sidewalls, can emit alpha particles. Generally, this is not a problem with a detector that can discriminate and veto events emanating from positions other than the sample (e.g., sidewall, anode, etc.). However, since these materials contain trace amounts of U and/ or Th, they necessarily emit either radon 222Ra and/or 220Ra. The Ra gas can diffuse a fair distance before decaying and emitting subsequent alpha particles. As such, it is possible that alpha particles are emitted in the active volume of the detector, or near the sample. These alpha particles cannot be distinguished from those emitted from the sample, thus raising the "background".

The invention is an electrically conductive ultra-low alpha-particle emissive material with an adjustable electrical conductivity. Adjustment is performed by altering the amount of graphite in the material. The invention uses this material in the application of the

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sidewalls as mentioned above.

The electrically conductive (EC) materials, can be applied onto su...