9th Crystal Ball MeetingBasel

October 4.-6. 2006Andreas Thomas

Transversely Polarized Target

1.- Possible Physics Experiments

2.- Frozen Spin Target

3.- Technical Realization of a transverse magnet

• 4 complex amplitudes – 16 observables in mesonphotoproduction• Each double polarisation observablegives different combination of amplitudes• To fix the 4 amplitudesunambiguously → 8 real quantities• Cannot choose from the same set

Complete Experiment

Beam Target

Photoproduction with polarized beam and polarized target

EPGPP

PPTP

FPHPP

Pd

d

d

d

circlinz

liny

circlinx

lin

unpol

2sin

2cos

2sin

2cos1

EGP

PTP

FHP

dd

P

PPP

z

y

x

unpol

circlinlinunpol

- -

- -

- -

- -

4,

4

2,0 Target

Beam

Real compton scattering with polarized beam and polarized target

Dispersion relation theoryPTlattice QCD..?

Polarized target „Frozen Spin Mode“

Polarization : DNP at high B-Field (2.5 T)

Measurement : very low T )50( mK

´freeze´ up the spin (0.4 Tesla)

relaxation time h 200 (T,B,Mat.,Rad.,.....)

410#

# protons

radicals

Free electrons Radicals in material by chemical or radiative doping

Butanol Ammonia LiD

30mm

HHHH

HOCCCCH

HHHH

N

H

H

HN

O

CH3

CH3CH3

CH3

Tempo

Radical densityinfluencesMax. Pol.

Pol. BuildupRelaxation time

Beam heating

1. CW-Beam: ELSA, MAMI, JLAB, .....2. Pulsed beam: SLAC, .......

c

QT

ct

trT V),(

Fourier equation

0lim

t

T

t

Assumption: target beads have spherical symmetry

22)( Tr

QrT V

Beam heating

Target material is stored in a PTFE-container and cooled by liquid 3/4helium mixture at 0.05Kelvin

T

r

Thermal conductivity

Kapitza resistance

T2

T1

Tbath

22)( Tr

QrT V

)( 441 bath

K

K TTA

Q

Input : minimum ionizing particle e-

22

cmg

MeV

60% deposition measured with flowmeter

][6.23

nAIcmnA

mWQV

3

43103 T

Kcm

W

acoustic mismatch

R=1mm

Beam heating

Time dependence Pulsed beam

c

QT

ct

trT V),(

sec300

2cm

cD

sec10 52

D

R

mmR 1

[T.J.Liu et al., NIM A405(1998)1-12] SLAC E143

sec103.2 6pulsetnAI 80 34102cm

WQV

Beam size 1.4mm diameter Beam rastering necessary

%75StartP %67AverageP

Short pulse 2.3sec KelvinT 12max

Long break 2 sec Repolarizing the bead

60

mm

beam

target

internal superconducting 'hold ing coil’liqu id helium from the still

100 m mButanol (C4H9OH)

Bonn GDH Coil

Mainz Coil under prepar.30A ~ 0.6 T (200m NbTi)Cooled by Evaporator

horizontal cryostat with integrated solenoid (holding field): Bonn981.2 Kelvin 0.42 Teslaequiv. 780m Cu (100m NbTi)

·  Current leads (30A): Copper T=300K 70 K

Tc SC T= 70K 4 KNiTi T= 4K 1.5K

Technical Realisation of a Transverse Magnet

[E.Dzyubak et al., NIM A 526 (2004) 132-137, OPERA3D calculations]

Epoxy Impregnated, Elasticity Vibration Quench?

[talk Ch. Keith EU-Workshop Rech 2005]

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

Circularly polarized beam Linearly polarized beam

Target polarized longitudinally

Target polarized transverse

Dispersion relation, PT, lattice QCD..?