Alpha Sciences Inc.
Gas Flow Counter Operations

 Alpha Sciences Ultra Low Background Alpha Particle Counting Systems

For over 25 years, the equipment at Alpha Sciences Inc. has been providing low background alpha counting services used as an industry standard to determine trace contamination of alpha particle emitting radionuclides found in IC process materials. Our original model, the 1850, has been upgraded with PC based acquisition features, making the tool more effective in analyzing data, while maintaining those features that make it easy to use and very reliable. Additionally, several different sizes and configurations are available.

The Ultra Low Background Counting System is comprised of three main component sections:

1. An ultra low background gas flow proportional counter/chamber, refered to as the detector;
2. A P.C. based data acquisition system;
3. A dual stage gas regulator with gas flow controller.
 

ABOUT THE DETECTOR

The detector consists of two chambers separated by an extremely thin Mylar film (window). The first chamber, or detector chamber, contains the anode structure and uses a special P-10 nuclear counting gas which flows through the detector at a very low flow rate. The sample chamber contains the sample tray, which positions the sample close to the Mylar window. As alpha particles are emitted from the sample, they pass through the Mylar window and ionize the P-10 gas in the detector chamber. These alpha particle ionization tracks in the detector are sensed, amplified, discriminated, and then counted for a predetermined period of time.

 

HOST P.C. and ELECTRONICS

The electronics portion consists of two sections. The analog section includes a charge sensitive preamplifier, the detector bias power supply, an amplifier, and a discriminator (set for 1 MeV). This analog electronics module is attached to the back plate of the detector housing , and derives its power from the system host P.C.  The alpha particle generated signals from the detector are amplified and discriminated, and then routed to the CIU (Counter Interface Unit), which allows up to four ASI Alpha Particle Counters to be controlled from a single host PC.

A serial port cable and signal board make up the second electronic section and are housed within the P.C. casing. The user programs the P.C. for a selected data acquisition period (dwell time) and this data is displayed on the monitor as a time histogram. The histogram is in graphical representation, wherein the horizontal axis represents time intervals, and the vertical represents the alpha count value for that specific time interval.
 

WORKING WITH RESULTS

During the test or at the conclusion of the test, the user may define the "Region Of Interest” or ROI by using simple point and click commands. If we wish to display the ROI during a test, the screen is paused to allow manipulation of the ROI bar. However, the counter is still functioning in the background, and the live screen can be brought back after the ROI is observed. The alpha counting program, known as ProXL software, automatically calculates the integral for the total count period, removes the established background from the value, and then divides then result by the defined sample area. Finally, a correction factor is applied to adjust data based on detector counting efficiency. The display then provides the corrected data for net alphas per centimeter squared per hour. The data is stored in electronic format, and can be printed should the user wish a permanent hard copy or record.

SYSTEMS AND SERVICE

For both heavy end use and occasional sample counting, Ultra Low Background Alpha Counting Systems and Services are available from Alpha Sciences Inc. Complete systems are available which include NIST traceable calibrated detectors and discounts on future software upgrades. Sample counting services in our labs using our equipment are available for a wide range of sample materials, from pastes and powders, to sheet and mold forms. Please contact us for our current system and service pricing.

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