iSolo ® Gas-less Manual Alpha / Beta Counting System
Features
- Portable, manual, single-sample alpha/beta counter
- Automatically identifies and compensates for radon, thoron and progeny interference
- PIPS® silicon gas-less detector
- Developed primarily for air filter analysis
- N NiMH battery power for 10 hours or more
- Universal, auto-sensing power supply
- Optional scintillation cosmic guard detector
- Compatible with essentially all filter types and multiple sizes
- Compatible with iLink™ iSeries™ Communications Software for remote setup and download of data to a computer
- CE compliant
iMatic, iLink and iSeries are trademarks of Canberra Industries, Inc.
iSolo and PIPS is a registered trademark of Canberra Industries, Inc.
HyperTerminal is a trademark of Hilgraeve, Inc.
Microsoft and Windows are registered trademarks of Microsoft Corporation in the United States and/or other countries.
Millipore is a registered trademark of Millipore Corporation.
Description
The CANBERRA iSolo® is a portable, firmware based, single-sample, manual, gas-less alpha/beta counter designed specifically for the analysis of air filters and smear or swipe samples. The iSolo discriminates both radon and thoron and their progeny from transuranic and fission product materials on the samples. It weighs slightly less than 19 pounds, even with an optional guard detector installed; uses a solid state silicon PIPS detector for alpha and beta detection; can be operated for 10 hours or more with internal batteries and is totally self contained. The iSolo represents a major technological breakthrough in air filter analysis.
The Problem is Radon
Counting air samples from either CAM units or stationary samplers can pose serious problems for the health physicist. Why? Radon, thoron and their respective progeny emit alpha particles with energies from 6.0 MeV to 8.78 MeV. The low energy peak tails from these detected alphas mask the spectral region where alphas from transuranic (uranium, plutonium, americium and curium) alphas would be (See Figure 1). Even the smallest amount of radon/thoron interference on a filter paper can cause 'falsely' elevated DAC values. Radon/thoron is the problem, but the real difficulty is knowing when the values are false - caused only by radon/thoron interference and not a plutonium or uranium release.
What is iSeries?
iSeries is an intelligent series of products designed specifically for the analysis of filter samples. The i stands for intelligent - intelligent because the products provide a new and innovative level of technology. iSeries instruments detect the presence of radon, thoron and their progeny and compensate for the interference they cause. Filter counting will never be the same again. The CANBERRA iCAM (intelligent Continuous Air Monitor) was the first iSeries instrument to use this technology. The iSolo algorithms are logical extensions of the successful iCAM product technology. iSeries instruments are designed specifically for filter analysis - the iCAM for air samples and the iSolo for air and smear samples. The iSeries - iSolo intelligence takes the real time monitoring application ability of the iCAM and extends it to the laboratory and field analysis of smears and air filters.
The Traditional Approach
The traditional approach for determining the activity of long-lived radionuclides present in air is to sample a measured volume of air through a filter, generally in a stationary air sampler. The filter is transported to the laboratory and counted on a gas flow or similar low background alpha/beta counting system. If the reportable alpha DAC value is above maximum permissible limits and radon/thoron is suspected, the filter is quickly counted again. By this time workers have remained in the area for several hours, without respirator protection. When the results from the second count show that the alpha DAC value is still above permissible limits, workers are evacuated from the work area until a determination is made by the lead technician on shift. By the time a ratio calculation is performed and the activity is deemed to be from radon/thoron interference, several more hours have passed. Time is money and downtime is expensive; but employee safety must always come first, and ratios are not always correct. Days may be needed before the alpha activity reported is absolutely identified as radon, thoron and their progeny.
The iSolo Approach
The CANBERRA iSolo solves this problem with a new and innovative approach. Gone are the days of waiting for hours or even days for radon/thoron interferences to decay away before an actual activity is known. With the iSolo, you will know within minutes if the alpha activity is due to transuranic or fission product material or naturally occurring radon and thoron. A pulse height spectrum, similar to the one shown in Figure 2, is acquired in a multichannel analyzer in the iSolo.
A series of peak evaluations are performed on the original acquired spectrum. When all of the corrections are made, a residual spectrum, similar to the one shown in Figure 3 (shown in red) results and from this residual spectrum the iSolo reports radon compensated, true alpha and beta activity on the front panel LCD display.
Figure 4. Original data shown in log scale. 
Figure 5. Compensated data shown in log scale. |
Not only are the numerical results shown on the iSolo's screen, but the 256 channel spectra of both the original and radon compensated data can be seen as well. (See Figures 4 and 5) The spectra can be viewed in linear or log scale, and the scale can be set automatically or manually by the user. The X axis of a compensated spectrum is shown in the middle of the display to accommodate channels with negative data. |
Complete Solution
The CANBERRA iSolo is a complete solution for the analysis of filter and filter type samples. The iSolo, unlike any other alpha/beta counter, is based on the same technology as CANBERRA's iCAM. The iSolo provides reliable measurements of transuranic and fission product activity on filter samples in the presence of radon/thoron interferences. Using a patent pending technique, the iSolo applies auto-adaptive spectrometric compensation for the radon/thoron interferences.
The iSolo radon/thoron compensation algorithm adjusts to all types of filter media from glass fiber filter media for smear analysis to Millipore® membrane type filter media for air sampling. The iSolo adapts to these different filter media types automatically. No additional calibrations or special instrument settings are required. The iSolo lets health physics technicians focus on their job without calculators, manual ratio calculations, downtime, and guesswork. Two built-in, operator-adjustable alpha and beta alarm levels are provided to alert the operator when a critical limit has been exceeded. The operator can then proceed quickly with the necessary actions without the added worry of making a mistake. An optional iSolo anti-coincidence guard detector provides rejection of external gamma and cosmic radiation to minimize the overall system alpha and beta background.
The anti-coincidence guard detector utilizes a customized 'wrap around' plastic scintillator. The guard detector surrounds the sample detector optimizing the rejection of low angle external gamma and cosmic events. The light pulses generated within the scintillator are coupled to a photomultiplier tube where the light is converted into an electrical signal that is used to anti-coincidence gate the data collection of PIPS sample detector events. When throughput and sensitivity are essential, the iSolo with optional guard is unsurpassed among other portable alpha/beta counters.
The iSolo provides the system operator with gross alpha/beta results, but that is only the beginning of what it does. There is absolutely no spillover to compensate for. Pulses from detected charged particles are sorted by energy. A lower level discriminator is set at 125 keV and any particle with energy greater than this threshold but less than 2.2 MeV is identified as a beta. A particle with energy greater than 3 MeV and less than or equal to 9.6 MeV is identified as an alpha. The 3 MeV to 6.4 MeV portion of the alpha region is further divided into three overlapping regions; a uranium region, an americium/plutonium region and a curium region. These regions allow the user to reasonably determine which nuclide is present in a sample if a high compensated alpha result is encountered. The following regions may be selected to be reported on the iSolo hardcopy printout. Energy values are approximate.
- Total Alpha Region: 3.0 MeV to 9.6 MeV
- Uranium Region: 3.0 MeV to 5.0 MeV
- Uranium, Am and Pu Region: 3.0 MeV to 5.6 MeV
- Curium Region: 3.0 MeV to 6.4 MeV
- Total Beta Region: 125 keV to 2.2 MeV
Standalone Instrument - No Computer Required
The iSolo is a firmware based instrument and does not require a computer to set up or operate it. The entire program is stored in flash memory. New programs may be downloaded as a file via HyperTerminal using the RS-232C interface. There are no PROMs to change and no housings to remove to get to them. The entire process to upgrade the iSolo program takes less than five minutes.
iLink iSeries Communications Software
If computer control and/or the ability to download iSolo results into a Microsoft® SQL Server database are desired, iLink iSeries Communications Software is available for this purpose. iLink provides the operator of iSolo systems the ability to program the majority of the iSolo features with a computer, rather than through the use of front panel buttons. iLink also includes an embedded version of the Microsoft SQL Server database for the storage of iSolo data.
All iLink functions are controlled via an intuitive graphical user interface. These functions include the ability to enter sources, enter sample and guard detector voltages and thresholds, setup the system printer and print mode, edit or create iSolo report templates, establish iLink and iSolo securities, create User, Calibration and QC procedures, backup and restore iSolo system personalities, and export data in comma separated (CSV) or Tab-Delimited formats. An example screen of the iLink User Procedures Editor is shown in Figure 6.
iLink is compatible with the Microsoft Windows 2000 and XP Professional operating systems. Multiple iSolos can be interfaced to one computer depending on the number of available RS-232 ports there are on the computer.