patricia aguar bartolomé. magnetic holding field - solenoid design - numerical calculations -...
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Patricia Aguar Bartolomé
Status of the Polarized 3He Target
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
• Main constraints
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.
Produce magnetic holding field of 7G with a relative field gradient of 10-3 cm-1 for 6 bars in the target cell area.
Polarized targets require a magnetic holding field, B0,
to provide a quantization axis.
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.
SOLENOID
Patricia Aguar Bartolomé
MAGNETIC FIELD CALCULATION• Numerical calculation of the field and gradients with a finite element code (FEMM)
• Geometric parameters for the solenoid
• 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
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
SOLENOID TEST
-20 0 20 40 60 80 100
0
1
2
3
4
5
6
7
Magnetic field for a solenoid L=80cm
B(r=0cm) B(r=1cm) B(r=2cm)
B(G
)
z(cm)
-20 0 20 40 60 80 100-1.0x10-3
-8.0x10-4
-6.0x10-4
-4.0x10-4
-2.0x10-4
0.0
2.0x10-4
4.0x10-4
6.0x10-4
8.0x10-4
1.0x10-3
Target Region
Homogeneity for a solenoid L=80cm
dB(r=0cm) dB(r=1cm) dB(r=2cm)
z
(cm
-1)
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)
• First tests with prototype are in process
cmnucleons 20/103.1 22
Patricia Aguar Bartolomé
FIRST T1 MEASUREMENT WITH UNCOATED CELL
Patricia Aguar Bartolomé
MEASUREMENT OF POLARIZATIONMechanical 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
Parameter Value
Coils diameter 160 cm
Current 4 A
N0 windings 150
Copper wire diameter
0.2 cm
Patricia Aguar Bartolomé
Helmholtz coils needed to measure the polarization
EXTERNAL HOLDING FIELD
TRANSPORTING SOLENOID
Patricia Aguar Bartolomé
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
Solenoid to bring the target cell from the center of the CB to the center of the Helmholtz coils.
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
First measurement of T1 with uncoated cell gives 4h
13
0
101
cm
BZ
B
Future Fix the leak on the target cell prototype Measurement of T1 with coated cell
Production of mechanical rail system
Patricia Aguar Bartolomé
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