1. 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

2. MIT-Bates South Hall Ring
Electron energy – 850 MeV
Average current – 175 mA
Polarization – 67 %

3. 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 - Pz78%, 81 pb-1
2004, Deuterium - Pz84%, 130 pb-1
Pzz68%
2005, Deuterium - Pz72%, 180 pb-1
Pzz56%
BEAM
TARGET

4. BLAST detector

5. ABS inside BLAST
ABS location inside BLAST detector results in severe space limitations
ABS is operated inside 2 kG magnetic field.

6. ABS in BLAST magnetic field

7. Measuring residual gas attenuation

8. Sextupole magnets in uniform field
IDEAL SEXTUPOLE
SEXTUPOLE +
- the amplitude of the force doesn’t change
- the direction does

9. Variation of focusing force components with a polar angle

10. Simulations results at the entrance into the cell
BLAST field on
(B0=2 kGs)
T=14%
BLAST field off
T=34%

11. Major ABS modifications
Pumping speed and conductances increased
NEG pumps replaced with shielded cryopumps
Sextupoles incased in magnetic shields

13. MFT field profile
Blast field leaks into RF transitions units and affects both magnitude and gradient of magnetic field.
14
34

14. Dipole BRP Storage cell Aperture Dipole magnet 2.5 kG/cm
ABS
Storage cell
Aperture
Dipole magnet 2.5 kG/cm
Compression tubes

15. 1 1 1 3 3 3 6 6 6

16. Collimator
Beam
Storage cell:
L=60 cm
D=1.5 cm
Collimator
Collimator protects the cell against both SR and injection flashes
It is designed to minimize the detector background

17. 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

18. 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 %