1. MAENTOUCH Simulation Giles Quéméner – IN2P3/LPC Caen
Written in C++ in the ROOT-Cern framework
Allow fast simulations with small details like mu-metal wires.
Expertise from Pascal Vernin – Retired from CEA Saclay
Many thanks to Pascal and Gilles for their help

2. Simple geometry 2 boîtes imbriquées 2 plans de PM Z = 1.70 Z = 3.10
Ecran 5.5 x 3.5 m2
Centre: (1.5,0,2,1.75) x y z
Bobines Helmotz
(0,-0.9,1.3)

3. Cut View Y=cste Plans PM Z=1.7 m 2.8 m Boîte externe Z=3.1 m
10 mm acier
Centre = (3.8,0,1.7)
2.8 m
0.15 m
Plaques de toit
2 x 10 mm acier
0.20 m
3.4 m
Murs internes
10 mm acier
2.2 m
Plaque de fond
10 mm acier
Plaque de répartition
Coussins d’air

4. Cut View X=cste Plans PM Z=1.7 m Boîte externe 4.2 m Z=3.1 m
10 mm acier
4.2 m
Plaques de toit
2 x 10 mm acier
Murs internes
10 mm acier
3.4 m
Centre =
(3.8,0,1.7)
Plaque de fond
10 mm acier
0.20 m
Only the external blue box and the IN20 wall have been simulated so far

5. Principle
First validation of computed stray field: comparison with the field map provided by IN20 + independent calculations by P. Vernin:
First trial with standard steel showed that this material is not efficient enough.
 all simulations used soft iron.
No real m_r curve implemented. Instead a rather safe m_r = 2000 is used and saturation (B>1.5 T) is checked in all cells.

6. Combination of soft iron box and IN20 wall
(mm)
Wall
Saturation
In wall
Force on coils (N)
Max field
(G) 6
yes - 4 8 no
1.6 G
165
1.3 G 10
173
1.2 G

7. Combination of soft iron box and IN20 wall
Example of 4 mm box, 8 mm wall

8. Mu-metal Shielding Mu-metal cylinder around the PMTs: 1.1 mm thick
F = 219 mm
h extended from 201 to 280 mm (but almost no effect at the level of the cathode and first dynode) x x x
B vs Z computed along 3 different lines
5 cm mesh

9. Mu-metal Shielding Bx By Bz External field: Bx=0, By=0, Bz=1G
Cylinder + grid + endcap
NB: B<0.14 G in whole volume for Bx=1G, By=0, Bz=0 Bx By Bz

10. Mu-metal Shielding Bx By Bz External field: Bx=0, By=0, Bz=1G
Cylinder, no grid, no endcap
NB: B<0.14 G in whole volume for Bx=1G, By=0, Bz=0 Bx By Bz

11. Iron + Mu-metal boxes External box, outside the shielding structure
Mu-metal box, tight to the inner face of the polyethylene

12. 10mm external box + Mu-metal box

13. Iron + Mu-metal boxes External box, outside the shielding structure
Mu-metal box, fixed to the inner face of the polyethylene

14. Margins Tried different thicknesses of iron and mu-metal.
Meet the specification of 0.1 G between 6 and 8 mm of iron combine with 1 to 1.5 mm of mu-metal.
Current design with 10 mm iron mm mu-metal.
~0.5 G inside the detector could be acceptable
 The design provide some margin but we are sensitive to gaps between plates at the 2 mm level