Instrumental background

LSC instrument (Tri-Carb 3170 TR/SL)

A completely computer controlled benchtop liquid scintillation analyzer, provided by Canberra-Packard Instruments, specially configured for extremely low level radioactivity analysis, featuring:

The time-resolved liquid scintillation counting circuitry employs a multiparameter multichannel analyzer (effective resolution of 1/10 keV), and three-dimensional analysis of both the prompt and afterpulses to discriminate between true beta events and background pulses.

The instrument employs a bismuth germanium oxide (BGO) detector guard to lower backgrounds for 3H to 1.0-0.75 CPM, and 14C backgrounds to below 0.3 CPM. High sensitivity is achieved using less cocktail (reducing waste) - the E2/B ratio is about 800 for 3H and 6000 for 14C; limits of detectability are greatly reduced (less than 1 Bq/l of tritium can be measured in water samples in 500 minutes without enrichment).

The instrument includes a built-in computer, which controls all system functions including sample changer, CRT display and data output. Dynamic color quench correction automatically corrects results for the optical quenching effects of highly colored samples, while the luminescence detection and correction feature automatically detects, quantitates and corrects for unwanted or unexpected luminescence in liquid scintillation samples.

The LSC analyzer is equipped with a cassette-loaded bidirectional sample conveyor with sample capacity for either 408 standard 20 ml vials or 720 small 4 or 7 ml vials with Varisette sample changer for intermixing large and small vial cassettes without requiring special adapters.