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)
Technical Realisation of a Transverse Magnet
[E.Dzyubak et al., NIM A 526 (2004) 132-137, OPERA3D calculations]
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