WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Polarized Internal Gas Target in a Strong Toroidal Magnetic

Field

E.Ihloff, H.Kolster, N.Meitanis, R.Milner, A.Shinozaki, E.Tsentalovich,

V.Ziskin, Y.Xiao, C.Zhang

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

MIT-Bates South Hall Ring

• Electron energy – 850 MeV• Average current – 175 mA• Polarization – 67 %

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

BLAST • Toroidal field 3.8 kG

• 2 instrumented sectors in the horizontal plane

- Drift chambers

- Cerenkov detectors

- Time of Flight scintillators

- Neutron detectors

BLAST DATA:

2004, Hydrogen - Pz78%, 81 pb-1

2004, Deuterium - Pz84%, 130 pb-1

Pzz68%

2005, Deuterium - Pz72%, 180 pb-1

Pzz56%

BEAM

BEAM TARGET

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

BLAST detector

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

ABS inside BLAST

• ABS location inside BLAST detector results in severe space limitations

• ABS is operated inside 2 kG magnetic field.

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

ABS in BLAST magnetic field

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Measuring residual gas attenuation

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Sextupole magnets in uniform field

Bohr;BB

B)B/BB(F

;x

B

B

B

x

B

B

BF yyxx

x

;y

B

B

B

y

B

B

BF yyxx

y

;x

B

x

BF y

yx

xx

y

B

y

BF y

yx

xy

IDEAL SEXTUPOLE

);yx(GB 22x ;rGBBB 22

y2x6

rG2F

1r

r

F

F

;xy2GBy )B(F

SEXTUPOLE + 0B

;B)yx(GB 022

x ;xy2GBy ;BBb

6

0

;)2cos(b2b1

)cos()b1(rG2F

2x

;)2cos(b2b1

)sin()b1(rG2F

2y

;rG2FF

;)2cos(b2b1

)2cos(b1

r

r

F

F2

- the amplitude of the force doesn’t change

- the direction does

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Fx (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fx

/|F|

b=B0/B6=0

Fy (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fy

/|F|

b=B0/B6=0

Fx (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fx

/|F|

b=B0/B6=0.2

Fy (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fy

/|F|

b=B0/B6=0.2

Fx (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fx

/|F|

b=B0/B6=0.5

Fy (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fy

/|F|

b=B0/B6=0.5

Fx (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fx

/|F|

b=B0/B6=1.0

Fy (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fy

/|F|

b=B0/B6=1.0

Fx (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fx

/|F|

b=B0/B6=3.0

Fy (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fy

/|F|

b=B0/B6=3.0

Fx (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fx

/|F|

b=B0/B6=10.

Fy (B0=Bx)

-1.5

-1

-0.5

0

0.5

1

1.5

0 50 100 150 200 250 300 350 400

Theta

Fy

/|F|

b=B0/B6=10.

Variation of focusing force components with a polar angle

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Simulations results at the entrance into the cell

-15

-10

-5

0

5

10

15

-15 -10 -5 0 5 10 15

-15

-10

-5

0

5

10

15

-15 -10 -5 0 5 10 15

BLAST field on

(B0=2 kGs)

T=14%

BLAST field off

T=34%

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Major ABS modifications

• Pumping speed and conductances increased• NEG pumps replaced with shielded cryopumps• Sextupoles incased in magnetic shields

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

ABS intensity

0

1

2

3

4

5

6

0 20 40 60 80 100 120

Flux, sccm

Inte

ns

ity

, 1

0**

16

at/

se

cBefore update, BLAST off After update, BLAST on Before update, BLAST on

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

MFT field profile

14

34

Blast field leaks into RF transitions units and affects both magnitude and gradient of magnetic field.

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Dipole BRP

Compression tubes

Dipole magnet 2.5 kG/cm

Storage cell

ABS

Aperture

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Signal from the left and right compression tubes during the scan of MFT transition unit for deuterium

(SFT 2 -> 6 transition is on)

5

5.5

6

6.5

7

7.5

8

8.5

9

0 10 20 30 40 50 60 70

H, Gauss

P, 1

0-8

torr

3 → 4 2 → 4 1 → 4

1

3

6

1

6

1

3

3

6

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Collimator

Collimator

Storage cell:

L=60 cm

D=1.5 cm

• Collimator protects the cell against both SR and injection flashes

• It is designed to minimize the detector background

Beam

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

• The cell protected by the collimator showed no signs of degradation in several months of running

• D-target was flipped between 3 polarization states: V+ (Pzz=1; Pz=+1)

V- (Pzz=1; Pz=-1)

T- (Pzz=-2; Pz=0)

• Intensity and tensor polarization were monitored using elastic eD reaction

• Vector polarization was monitored using inelastic ep channel

• H-target was flipped between 2 polarization states: V+ ( Pz=+1)

V- ( Pz=-1)

• Intensity and vector polarization were monitored using elastic ep reaction

WAO 2003SPIN-2005 November 16, 2004 E.Tsentalovich

Conclusion

• Operation of ABS inside magnetic spectrometer presents a formidable challenge, but it is possible !

• Atomic flux of at/sec into the cell was achieved for both Hydrogen (1 state) and Deuterium (2 states)

• The target thickness within ±20 cm from the center of the cell achieves

• Drifilm-coated storage cell, protected by tungsten collimator, provides excellent preservation of polarization of Deuterium atoms with a 500 G holding field: Pz=84 %; Pzz=68%

• Hydrogen target polarization Pz=78 %

16105.2

213 cm/at107