Hi Djam, Let me iterate, and I just checked the Magnet value in Brag are the correct ones, so the DB has been put in wrongly and I will talkt to Kris on this. In regard to the other offsets, the value given by you are APPROXIMATELY correct but only to about .5 mm compared to final accepted values in AN40. This of course means that if you read the values off the DB matching, dang dx ect will not be as for the data setup. Since the acceptance do not care about deviations at this level - I will repeat myself and say that the proper way to do accpetances is to use the BRAG GEOMETRY (see more later) and NOT the DB geometry otherwise you will end up with small imperfections.E.G. Brag does not care or know about beta-angles as PS did for tuning the DC but it does not matter for acc. and effeciencies calculations. I strongly suggest you read reco-geometries for simulation from .geo file and raw data of course from the DB I agree the Brag default geometry for should be changed to values (something like the ones you give), and should also included a dy. Note that you should not change D4. ------------------------------------------------------ Flemming Videbaek Physics Department Brookhaven National Laboratory tlf: 631-344-4106 fax 631-344-1334 e-mail: videbaek@bnl.gov ----- Original Message ----- From: "Djamel Ouerdane" <ouerdane@nbi.dk> To: <brahms-dev-l@bnl.gov> Sent: Tuesday, June 11, 2002 2:00 PM Subject: BFS geometry tuning > Hi all, > > I've finally found out how to tune the BFS geometry by looking at the > brag source code in src/fms2. > > I inverted some equations that returned the global positions of the > detectors in order to get the "clearence" and "refdist" parameters. > > I could then easily find these params, given the global positions returned > by the DB (all BFS det and magnets). > > Below, you can find the results to be inserted in a kumac with > the BFS on (note that D3 is ok + some dets don't have any tunable Y > position parameter). These numbers were obtained by comparing the 12 deg. > run 5609 to brag. If it turns out that some DB values are wrong, let me > know asap. > > More generally, if it is the wrong way to do it in brag, please provide a > good solution. > > Ciao > Djam > > * T3 default (refdist: -185, clear: 2) > set_param t3 refangle 0.1637 > set_param t3 deltay 0.85 > set_param t3 clear 2.47775 > set_param t3 refdist -188.465 > > * T4 default (refdist: -180, clear: 2) > set_param t4 refangle -1.737 > set_param t4 deltay 0.28 > set_param t4 clear 1.74012 > set_param t4 refdist -183.273 > > * T5 default (refdist: 175, clear: 2) > set_param t5 refangle -3.789 > set_param t5 deltay 0.24 > set_param t5 clear 2.09483 > set_param t5 refdist 171.808 > > * TOF2 default (refdist: 234, clear: 2) > set_param tof2 clear 5.43122 > set_param tof2 refdist 230.615 > > * RICH default (refdist: 346, clear: 6) > set_param rich clear 9.10071 > set_param rich refdist 360.44 > > * D4 default (refdist: 0, clear: 1) > set_param D4 clear -7.17012 > > > > > -- > Djamel Ouerdane ------------------------------------------o > | Niels Bohr Institute | 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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