One generator will last six years or more. CAB tubing will be adequately clear for most agronomy research while offering a toughness and greater flexibility than acrylic tubing. Extruded Acrylic has reasonable toughness, good stability under variances of heat, cold and moisture, and excellent clarity. Extruded Acrylic is more expensive to ship, because of possible breakage. Clarity is not as good as CAB and glue used must not contain solvents.
Polycarbonate tube is also available for maximum strength.
They may use metric dimensions. The 52mm tube with 3mm or 4mm walls would be a good choice. If you tell us the best size available for you, we will construct the bearings on the camera for the right fit. BTC makes custom plastic end caps, which are internally mounted, and sealed against water and soil entry. The leading exterior edges of the cap are beveled to allow easy installation by keeping the tube centered as it travels down the4 bore, thereby minimizing damage to the surrounding soil bed.