Patricia Aguar Bartolomé
OVERVIEW
 Magnetic Holding Field
- Solenoid design
- Numerical calculations
- Solenoid test
 Target Cell Preparation
 Measurement of Polarization
- Mechanical rail system
- External holding field
Patricia Aguar Bartolomé
MAGNETIC HOLDING FIELD
Polarized targets require a magnetic holding field, B0,
to provide a quantization axis.
SOLENOID
The strength and uniformity of the
field play an important role in obtaining
long polarization relaxation times.
•
Depolarization effects due to field
gradients should be smaller than
the relaxation due to surface effects.
Main constraints

Produce magnetic holding field of 7G with a relative field gradient of 10-3 cm-1 for
6 bars in the target cell area.
 Appropriate outer radius to fit inside the Crystal Ball detector.
 Target cell dimensions determine the inner radius.
 The outgoing particles have to pass the coil
minimization of the wire thickness.
Patricia Aguar Bartolomé
MAGNETIC FIELD CALCULATION
• Numerical calculation of the field and gradients with a finite
element code (FEMM)
• Geometric parameters for the solenoid
Parameter
Value
Solenoid length
80 cm
N0 windings
1457
Current
0.3 A
Inner coil diameter
0.82 cm
Outer coil diameter
0.83 cm
Copper wire diameter
0.053 cm
• Coil wound on a CFK-tube with cross section of 82 x 1 mm2 and 120 cm
length.
• B magnitude determined using the three axis magnetometer MAG-03 MS
(Bartington Instruments Ltd.)
Patricia Aguar Bartolomé
SOLENOID TEST
Magnetic field for a solenoid
L=80cm
7
B(r=0cm)
B(r=1cm)
B(r=2cm)
6
Homogeneity for a solenoid
L=80cm
5
-3
1.0x10
dB(r=0cm)
dB(r=1cm)
dB(r=2cm)
-4
8.0x10
3
-4
6.0x10
2
-4
4.0x10
-1
z (cm )
B(G)
4
1
0
-20
0
20
40
z(cm)
60
80
100
-4
2.0x10
0.0
-4
-2.0x10
Target
Region
-4
-4.0x10
-4
-6.0x10
-4
-8.0x10
-3
-1.0x10
-20
0
20
40
60
80
100
z(cm)
Patricia Aguar Bartolomé
TARGET CELL DESIGN
• 20 cm length and 6 cm diameter
• Non-magnetic materials in order to avoid depolarization of the gas
- Quartz glass cell coated with Cesium
- Aluminum caps
- 50 mm Mylar windows metalized with Aluminum
• 3He gas target (P = 6 bar)
1.3 1022 nucleons / 20 cm
• First tests with prototype are in process
Patricia Aguar Bartolomé
FIRST T1 MEASUREMENT WITH UNCOATED CELL
Patricia Aguar Bartolomé
MEASUREMENT OF POLARIZATION
Mechanical rail system to transport the target cell from the center
of the solenoid to the center of the external holding field
1)
2)
3)
4)
Patricia Aguar Bartolomé
EXTERNAL HOLDING FIELD
Helmholtz coils needed to measure
the polarization
Parameter
Coils diameter
Value
160 cm
Current
4A
N0 windings
150
Copper wire diameter
0.2 cm
Patricia Aguar Bartolomé
TRANSPORTING SOLENOID
Solenoid to bring the target cell from the center
of the CB to the center of the Helmholtz coils.
Parameter
Value
Solenoid length
40 cm
N0 Windings
800
Current
0.3 A
Inner coil diameter
0.82 cm
Outer coil diameter
0.83 cm
Copper wire diameter 0.053 cm
Patricia Aguar Bartolomé
SUMMARY AND OUTLOOK
 Conclusions
 A solenoid produced to provide the holding field for the 3He target was
designed and tested
 First homogeneity measurements of the solenoid with the polarized gas
give values of
 B


Z   1 10 3 cm 1
 B 
0


 First measurement of T1 with uncoated cell gives 4h
 Future
 Fix the leak on the target cell prototype
 Measurement of T1 with coated cell
 Production of mechanical rail system
Patricia Aguar Bartolomé