As far as I know the Quantum devices QBEAM light sources are still
available, they are made especially for the 1/4 litre chambers of the
LI COR 6200 photosynthesis system, with an adaptor that allow it to
be used with the 1 litre chambers as well. I have found it an
excellent cool light source, especially useful for the closed 6200
system and in hot climate where overheating of the leaf and chamber
is a problem. These LED light sources
can produce high intensities because the LED chips are mounted
directly on a ceramic board (good heat sink), rather than inside the usual
plastic housing. If you push a normal high intensity LED too far it is
liable to pop?
However, if you only need 100 micro mol m-2 s-1at a distance of 2 - 3
cm (e.g. through the lid of a licor chamber), you should be able to
make your own array from relatively cheap high intensity LEDs.
Mike
===============================================
Mike Clearwater
Institute of Ecology and Resource Management
University of Edinburgh
Edinburgh EH9 3JU
UK
Ph +44-131-650-5423
Fax +44-131-662-0478
e-mail: m.clearwater at ed.ac.uk
