Transcript Frozen Spin Target

Institut
für Kernphysik
Frozen Spin Target
1.- Polarised Target Operation
2.- Short Term Plans
3.- Modifications
4.- Long term plans
17th Crystal Ball Meeting
Mainz, February 28th, 2011
Andreas Thomas
Operation
Cryostat
Movable
Crystal Ball
4pPhoton
Detector
Movable
5Tesla
Polarising
Magnet
First Beam with Transverse Polarisation started 15th December 2009.
In 2010 we had more than 2000 hours beam on this target.
Cryostat Performance
T=24mK
T=27mK
T=29mK
Dt=40h
Temperature stability:
DT ~ +- 0.2mKelvin (one day)
(typical one week measurement period).
P  P0 e
Frozen Spin Target  Relaxationtime
   (Material, Radical, B  Field, Temperature....)
1600
26 mK, 0.44T
1400
relaxation time [h]
1200
1000
800
600
400
200
0
0,2
0,3
0,4
0,5
0,6
0,7
0,8
holding field [T]
Relaxation time of butanol at 60 mK depending on the applied magnetic field
t

Target material
Saturated electrons of target material not polarized (Pauli principle)
Free electrons
Radicals in material by
chemical or
radiative doping
# radicals
 104
# protons
Dilution factor (fButanol=10/74)
determines quality of target material.
We have 9*1022 pol. Protons per cm2 in our
2cm long target cell.
Butanol
H H H H
H C C C C O  H
H H H H
CH3
CH3
CH3
N
O
CH3
Tempo
2cm
Filling factor ~ 60%
 H. Ortega Spina
C4H10O – 60%
Vacuum
3He/4He – 6%
30mm
Degree of Polarisation
Soldering of the NMR coil (target material has to be kept
under liq. Nitrogen) and installation into the cryostat.
X-ray picture with
Beamspot and
NMR coil from
last week.
NMR System for Polarisation
measurement
B=0T B=2.5T
 p  106MHz
Typical NMR Signals
Enhanced Signal at 70% Polarisation
after spin rotation
Thermal Equilibrium-Signal
0.5% Polarisation
2.5Tesla,1Kelvin
Pdyn  PTE 
AUdyn
AUTE
Temperature measurement
AVS Picowatt Resistance Bridge
P  tanh
B
kT
! Systematic error for all
asymmetries!
Target material
D-Butanol
Density and species of the radicals
are very important for:
•maximum degree of polarization
•polarization build up times
•relaxation times
Trityl-Radikal
[Gerhard Reicherz,
PT Ruhr-Universität Bochum,
Next talk]
Highest Deuteron polarisation due to new
doping material with narrow ESR from Bochum.
Deuteron NMR Signals
Short term plans
Proposal:
•Beam for 3 weeks in April (proton target optimized for ph and h)
•Beam for 2 weeks in May (deuteron target broad band at 1557MeV)
•Dismounting Cryostat after final test (TE-calibration, filling factor…)
•Mounting of EPTagger.
•Mounting of liquid hydrogen target (cell length 3cm or 5cm or 10cm?).
•Test beamtime end of summer/fall.
Modifications: Magnet Technology
DNP at 200mK and 2.5T with 70GHz microwaves.
Frozen spin target (25mKelvin, 0.6T).
Secondary particles punch through holding coil.
All directions of polarization.
Transverse (Saddle coil)
and
Longitudinal (Solenoid)
Internal
Holding Field (1.2K, 0.6T)
High Field 1T
Threshold Production
Transverse Field
Modifications: Internal Polarising Coil
Problem is the required field homogeniety
of 10-E4. Notched solenoid.
3d finite element calculation, optimisation
and precise production needed.
DNP at 200mK and 2.5T
with 70GHz microwaves.
10Layer coil at 50A.
Secondary particles punch
through holding coil.
Higher momentum threshold.
New Coil with 10 layer (2.5Tesla) in
Mainz mechanical workshop.
Modifications: Active Polarised Target
 Talk S.Schrauf
Vacuum
3He/4He – 6%
Long term plans
•Change from transverse to longitudinal polarisation.
•Internal polarising coil for high luminosity and precission experiments.
•Active polarised target for treshhold experiments.