The ALFA laser and analysis tools

The optimal performance of adaptive optics systems can only be maintained i f the wavefront reference is bright and compact. Experience has shown that both of these important criteria are remarkably difficult to achieve with l aser guide stars. This contribution gives an account of the methods by whic h ALFA attempts to reach them. First, the production of a high quality, hig h power laser beam is described. However, this quality is unavoidably compr omised along the path to the launch telescope. In order to rectify this, a new set of diagnostic tools which monitor the quality of the out-going beam has been installed, and these are also described. Lastly, we outline a num ber of possible modifications on which we are working. If successful, these may allow a substantial improvement in the beam quality.