This was originally the HMC LoI Magnet (a box field,
typically 1 T over 1 m used to measure the momentum
of the large angle particles from the polarised target.
Now it has been modeled from the OAFM (Open Axial
Field Magnet) the ISR magnet recently used by Obelix
experiment at LEAR. With no midification (with the
field along the z direction) it should provide 1.25 Tm
and a intergap of 150 cm.
This is activated by the following card:
C Xcen Ycen Zcen rot bfield bscale kflag
MAGNET4 350. 0. 0. 0 1. 1. 2 SM1m
C
Note that:
- The position at 350 cm from the polarised target is
presently the "official" position
- bfield is used only in connection of klag=0 to provide
a box field (along the z direction) on the AREA connected
to magnet 4
- bscale is a factor to scale up/down the field
- kflag
- 0 box field
- 1 OAFM description via polinomial (not yet implemented)
- 2 OAFM measured map (the measurement takes into account
the axial symmetry --ok to 5% level-- on a 5X5cm2 grid). Off
axis the measured points go up to 160 cm from the axis.
From 150 cm to 200 cm a 1/r^3 law is chosen. At larger
distances the field is 0 (probably not yet realistic)
- 3 free to later use
The relevant routines are:
- fields/magnet/omagini4.F
called by omgbatch/ompro/omgini.F???. It initialize the relevant
array. In the case kflag=2 it transform the map in cartesian
coordinates and interpolate it on a 1X1X1 cm3 grid.
- fields/magnet/omagfld4.F
called by omgbatch/ompro/gufld.F. It provides the field to the
tracking.
There is the plan to add new measurements or calculation of the
field in presence of the new support (to be built) and with the
extra poles to close the gap (for the p-beam programme).
The mechanics is described in the following way
(still provisional in particular the yoke)
using the usual COMGEANT mechanisms. 201 is air with magnetic
field for the container OAFM;
295 is iron with magnetic field for poles and yoke.
C
C--- OAFM
C
PARVOL101 'OAFM' 201 'HALL' 350. 0. 0. 0 'BOX ' 3 190. 400. 400.
C Upper pole?
PARVOL102 'OAU1' 295 'OAFM' 0. 0. 85.5 0 'CONE' 5 10.5 20. 50. 20. 80.
PARVOL103 'OAU2' 295 'OAFM' 0. 0. 106. 0 'TUBE' 3 20. 80. 10.
PARVOL104 'OAU3' 295 'OAFM' 0. 0. 128. 0 'TUBE' 3 20. 90. 12.
PARVOL105 'OAU4' 295 'OAFM' 0. 0. 152. 0 'TUBE' 3 20. 110. 12.
PARVOL106 'OAU5' 295 'OAFM' 0. 0. 176. 0 'TUBE' 3 20. 120. 12.
PARVOL107 'OAU6' 295 'OAFM' 0. 0. 218. 0 'TUBE' 3 20. 140. 30.
C Lower pole?
PARVOL108 'OAD1' 295 'OAFM' 0. 0. -85.5 0 'CONE' 5 10.5 20. 80. 20. 50.
PARVOL109 'OAD2' 295 'OAFM' 0. 0. -106. 0 'TUBE' 3 20. 80. 10.
PARVOL110 'OAD3' 295 'OAFM' 0. 0. -128. 0 'TUBE' 3 20. 90. 12.
PARVOL111 'OAD4' 295 'OAFM' 0. 0. -152. 0 'TUBE' 3 20. 110. 12.
PARVOL112 'OAD5' 295 'OAFM' 0. 0. -176. 0 'TUBE' 3 20. 120. 12.
PARVOL113 'OAD6' 295 'OAFM' 0. 0. -218. 0 'TUBE' 3 20. 140. 30.
C Upper Yoke
PARVOL114 'OYU1' 295 'OAFM' 0. 0. 252. 0 'TUBE' 3 20. 130. 4.
PARVOL115 'OYU2' 295 'OAFM' 0. 0. 286. 0 'CONE' 5 30. 20. 160. 20. 20.
C Lower Yoke
PARVOL116 'OYD1' 295 'OAFM' 0. 0. -252. 0 'TUBE' 3 20. 130. 4.
PARVOL117 'OYD2' 295 'OAFM' 0. 0. -286. 0 'CONE' 5 30. 20. 20. 20. 160.
C Return Yoke
PARVOL118 'OYR1' 295 'OAFM' 0. 250. 0. 0 'BOX ' 3 100. 50. 280.
PARVOL119 'OUR2' 295 'OAFM' 0. 150. 330. 0 'BOX ' 3 50. 120. 50.
PARVOL120 'OUR3' 295 'OAFM' 0. 150. -330. 0 'BOX ' 3 50. 120. 50.
C