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 ValueSolenoid length 80 cmN0 windings 1457Current 0.3 AInner 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 ValueCoils diameter 160 cmCurrent 4 AN0 windings 150Copper wire diameter

0.2 cm

Patricia Aguar Bartolomé

Helmholtz coils needed to measure the polarization

EXTERNAL HOLDING FIELD

TRANSPORTING SOLENOID

Patricia Aguar Bartolomé

Parameter ValueSolenoid length 40 cmN0 Windings 800Current 0.3 AInner 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