Date: Friday, September 28, 2001 4:33 PM -0400 From: Douglas Hasell To: Timothy Smith , Jim Kelsey Subject: Re: coil axis Hi, Tell you what I'm going to do .... For each coil I will define a coordinate system with origin in the median plane of the coil, midway between the straight sections at the back of the coil, and opposite the target centre (this is probably fairly close to the water pipe and I think it a bit more significant than the water pipe). The Z axis of this system will be parallel to the long axis of the coil and nominally parallel to the BLAST Z axis. The X axis will be in the median plane of the coil and pointing away from the target and the Y axis will be perpendicular to the coil to form a right handed coordinate system. For a nominally positioned coil the coil origin would be at a radius R = 500 mm + 21.0 inches + 10.04 inches = 1288.416 mm and have BLAST coordinates (R cos(phi), R sin(phi), 0.0) for a coil at azimuthal angle phi. (The BLAST X axis is at phi=0.) Coil offsets will be specified as offsets to the centre of the coil in cylindrical coordinates (dr,dphi,dz) so that the coil centre in the BLAST system is ((R+dr) cos(phi+dphi), (R+dr) sin(phi+dphi), dz). Angular offsets will be specified as first a rotation (roll) about the coil long axis, counter-clockwise by alpha, then a rotation (pitch) about the transformed X axis, counter-clockwise by beta, and finally followed by a rotation (yaw) about the transformed Y axis, counter-clockwise by gamma. Note: these are not the Euler angles and in general the order of rotation is important but I will let someone else worry about that. Let me know if there is anything wrong with this. Cheers, Douglas 26-415 M.I.T. tel: +1 617 258 7199 77 Massachusetts Avenue fax: +1 617 258 5440 Cambridge, MA 02139, USA E-mail: hasell@mit.edu