Solenoid map access in athena Paul S Miyagawa, Steve Snow University of Manchester

Outline Transition from solenoid map to ATLM Transition region boundaries Implementation in athena Field values in transition region –Barrel –Ends Future work Paul S MiyagawaMagnetic field meeting, 4 February 20082/8

Transition from solenoid map to ATLM Solenoid map results valid in region |z|<2.85m, r<1.10m –ATLM model used outside this region Aim to have field components Bx, By, Bz returned by magnetic field service be continuous across transition from solenoid map to ATLM Need to allow small translation and rotation of solenoid field independent to the rest of the field –Main error in solenoid map is systematic uncertainty of ±0.2 mrad in orientation –Orientation can be determined from real data using resonance masses Paul S MiyagawaMagnetic field meeting, 4 February 20083/8

Transition region boundaries Paul S MiyagawaMagnetic field meeting, 4 February 2008 |z| < m, r < m –100% solenoid map |z| > m, r > m –100% ATLM model else –Use weighted mixture –Weights proportional to shortest distance to boundaries B interp = ( B map *s2 + B ATLM * s1 ) / (s1+s2) 4/8

Implementation in athena Code has been implemented and tested in athena –C++ classes provide user interface –Actual field calculations done in Fortran During job initialisation: –Solenoid field values at defined grid points are read into memory during job initialisation –For displacements and rotations to the solenoid field, the field values are recalculated at the same grid points during job initialisation –Displaced/rotated values are calculated by finding the equivalent point in the original map and interpolating –New values saved as an additional copy of the map (~1 MB per map, ~2 sec for recalculation) During job running: –User requests field values at particular points from magnetic field service –Field service determines in which region the point lies and calls the appropriate subroutine –For solenoid + transition regions, solenoid field values at specified point calculated from the displaced/rotated map by simple linear interpolation between grid points Paul S MiyagawaMagnetic field meeting, 4 February 20085/8

Transition region in barrel Small (0.03 T) mismatch between solenoid measurement and ATLM –Will become smaller with next ATLM version Transition is linear interpolation over 1 cm between maps Paul S MiyagawaMagnetic field meeting, 4 February 2008 solenoid map ATLM model Bz versus R at Z=0 6/8

Transition region in ends Paul S MiyagawaMagnetic field meeting, 4 February 2008 Bz and Br versus Z at R=0.5 m solenoid map ATLM model 7/8

Future work More comprehensive testing of field values from transition region –Especially corners Tilted version implemented, but not yet tested Test in nightlies for release 14 Paul S MiyagawaMagnetic field meeting, 4 February 20088/8