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Transversely Polarized Target 1.- Possible Physics Experiments 2.- Frozen Spin Target 3.- Technical Realization of a transverse magnet 9th Crystal Ball Meeting Basel October 4.-6. 2006 Andreas Thomas
Complete Experiment • 4 complex amplitudes – 16 observables in meson photoproduction • Each double polarisation observable gives different combination of amplitudes • To fix the 4 amplitudes unambiguously → 8 real quantities • Cannot choose from the same set
Photoproduction with polarized beam and polarized target lin lin circ g Beam P P P g g g unpol æ p ö æ p p ö + - ç ÷ ç ÷ Target 0 , , è 2 ø è 4 4 ø Beam Target æ ö s d S ç ÷ P - - unpol W è d ø P - - H F x P T P - - y P - - G E z
Real compton scattering with polarized beam and polarized target a,b,g1,g2,g3,g4 Dispersion relation theory cPT lattice QCD..?
Measurement : very low T t = F(T,B,Mat.,Rad.,.....) ´freeze´ up the spin (0.4 Tesla) relaxation time t 200 h » Polarized target „Frozen Spin Mode“ • Polarization : DNP at high B-Field (2.5 T)
CH3 CH3 CH3 CH3 N O Free electrons Radicals in material by chemical or radiative doping 30mm Ammonia Butanol LiD N Radical density influences Max. Pol. Pol. Buildup Relaxation time Tempo H H H
Beam heating 1. CW-Beam: ELSA, MAMI, JLAB, ..... 2. Pulsed beam: SLAC, ....... Fourier equation Assumption: target beads have spherical symmetry
Beam heating Target material is stored in a PTFE-container and cooled by liquid 3/4helium mixture at 0.05Kelvin T T2 Thermal conductivity l T1 Kapitza resistance a Tbath acoustic mismatch R=1mm r Input : minimum ionizing particle e- 60% deposition measured with flowmeter
Beam heating Time dependence Pulsed beam [T.J.Liu et al., NIM A405(1998)1-12] SLAC E143 Beam size 1.4mm diameter Beam rastering necessary Short pulse 2.3msec Long break 2 sec Repolarizing the bead
Butanol (C4H9OH) horizontal cryostat with integrated solenoid (holding field): Bonn98 1.2 Kelvin 0.42 Tesla equiv. 780mm Cu (100mm NbTi) Bonn GDH Coil Mainz Coil under prepar. 30A ~ 0.6 T (200mm NbTi) Cooled by Evaporator
· Current leads (30A): Copper T=300K 70 K Tc SC T= 70K 4 K NiTi T= 4K 1.5K
Technical Realisation of a Transverse Magnet [E.Dzyubak et al., NIM A 526 (2004) 132-137, OPERA3D calculations]
[talk Ch. Keith EU-Workshop Rech 2005] Epoxy Impregnated, Elasticity Vibration Quench?
Conclusions and outlook 1.- Longitudinal holding Magnet - first test fall of this year with new cryo - Magnet. Field and current lead design ??? - 2nd coil in Mainz workshop (+4 weeks) 2.- Transverse magnet - some money in 2007 from SFB available - manpower (diploma thesis…) needed for calculations and tests - investigation of possibility of commercial production
Real compton scattering with polarized beam and polarized target a,b,g1,g2,g3,g4 Dispersion relation, cPT, lattice QCD..? Circularly polarized beam Linearly polarized beam Target polarized longitudinally Target polarized transverse