Hi all, During my little spare time :) I had a lot of fun in writing a root script simulating the reflection of a track on the RICH mirror. It's now available in brahms_app/do_app/rich The script is called RichMirror.C and you can have a glance at the plot that this script produces here: http://www.nbi.dk/~ouerdane/cal/Rich.html To have a clear view of what's happening, I've drawn the thing in 3 views: top view: (Z,X) plane of the RICH box side view: (Z,Y) plane '' '' '' back view: (X,Y) plane '' '' '' The last view prints out the coordinates of the projected point on the reception plane Once you've got the script, here is what you can do: open bratroot then type: .L RichMirror.C Project(<yOff>, <zOff>, <dTheta>, <debug level>, "<geo file>", <sphere radius>) The most important tunable parameters are yOff and zOff * yOff is the offset between the Y position of the RICH top plane and the Y position of the point where a vertical line (parallel to the Y axis) would be tangent to this sphere (with X = 0) a value of 21.7 cm gives the right angle (9 deg. according to Peter) for the sphere focal line. * zOff is the Z position of the intersection point (in X = 0) between the sphere and the RICH top plane. Tuning this parameter only translates the whole thing in Z. The default parameters are: yOff = 21.7 cm zOff = 0 dTheta = 0 (opening angle in the track direction, phi covers 360 deg) debug = 0 (more prints out some stuff) geofile = "rich.geo" (a geo file contening the RICH dimensions) radius = 300 cm (got this from JJ and Peter, focal is then 150 cm) The track direction originates from the RICH front plane with a completely random position in it (phi between 0 and 360). Theta is chosen randomly between -dTheta and + dTheta. If the projection on the back plane of RICH (before the reflection) is out of the RICH bounds, the process stops. The algorithm for finding the final point is not approximated in any way. I think this should be included in the rich pid module that Claus is writing. I Hope some of you will enjoy it like I did :) Ciao -- Djamel Ouerdane ------------------------------------------o | Niels Bohr Intstitute | Home: | | Blegdamsvej 17, DK-2100 Ø | Jagtvej 141 2D, | | Fax: +45 35 32 50 16 | DK-2200 Copenhagen N | | Tel: +45 35 32 52 69 | +45 35 86 19 74 | | http://www.nbi.dk/~ouerdane | | ouerdane@nbi.dk | o---------------------------------------------------------o
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