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

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

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

BLAST detector

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

ABS in BLAST magnetic field

Measuring residual gas attenuation

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

Variation of focusing force components with a polar angle

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

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

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

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

1 1 1 3 3 3 6 6 6

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

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

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 %