[1] Univ Edinburgh, Scottish Microelect Ctr, Edinburgh, Midlothian, Scotland
[2] Royal Observ, UK Astron Technol Ctr, Edinburgh EH9 3HJ, Midlothian, Scotland
[3] Univ Wales Coll Cardiff, Dept Phys, Cardiff, S Glam, Wales
[4] Raytheon Infrared Operat, Goleta, CA 93117 USA
[5] Univ Waterloo, Dept Phys, Canadian Project Off SCUBA 2, Waterloo, ON N2L 3G1, Canada
[6] Natl Inst Stand & Technol, Boulder, CO 80303 USA