Institut für Kernphysik

17th Crystal Ball MeetingMainz, February 28th, 2011

Andreas Thomas

Frozen Spin Target

1.- Polarised Target Operation

2.- Short Term Plans

3.- Modifications

4.- Long term plans

Operation

MovableCrystal Ball

4-Photon

Detector

Cryostat

Movable5Tesla

PolarisingMagnet

First Beam with Transverse Polarisation started 15th December 2009.In 2010 we had more than 2000 hours beam on this target.

Cryostat Performance

Temperature stability: T ~ +- 0.2mKelvin (one day) (typical one week measurement period).

T=24mK

T=27mK

T=29mK

t=40h

Frozen Spin Target Relaxationtime

....),,,( eTemperaturFieldBRadicalMaterial

0,2 0,3 0,4 0,5 0,6 0,7 0,8

0

200

400

600

800

1000

1200

1400

1600

rela

xatio

n tim

e [h

]

holding field [T]

Relaxation time of butanol at 60 mK depending on the applied magnetic field

t

ePP

0

26 mK, 0.44T

410#

# protons

radicals

Free electrons Radicals in material by chemical or radiative doping

Saturated electrons of target material not polarized (Pauli principle)

Butanol

HHHH

HOCCCCH

HHHH

N

O

CH3

CH3CH3

CH3

Tempo

Target material

Dilution factor (fButanol=10/74)determines quality of target material.

We have 9*1022 pol. Protons per cm2 in our2cm long target cell.

2cm

Filling factor ~ 60% H. Ortega Spina

Vacuum

C4H10O – 60%30mm

3He/4He – 6%

X-ray picture withBeamspot andNMR coil fromlast week.

Soldering of the NMR coil (target material has to be keptunder liq. Nitrogen) and installation into the cryostat.

Degree of Polarisation

B=0T B=2.5T

NMR System for Polarisation measurement

MHzp 106

Typical NMR Signals

Thermal Equilibrium-Signal0.5% Polarisation2.5Tesla,1Kelvin

Enhanced Signal at 70% Polarisationafter spin rotation

TE

dynTEdyn AU

AUPP

Temperature measurement

AVS Picowatt Resistance Bridge

kT

BP

tanh

! Systematic error for all asymmetries!

[Gerhard Reicherz, PT Ruhr-Universität Bochum,Next talk]

D-Butanol

Target materialDensity and species of the radicals

are very important for:•maximum degree of polarization

•polarization build up times•relaxation timesTrityl-Radikal

Highest Deuteron polarisation due to new doping material with narrow ESR from Bochum.

Deuteron NMR Signals

Proposal:

•Beam for 3 weeks in April (proton target optimized for and )

•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.

Short term plans

Transverse (Saddle coil)

and

Longitudinal (Solenoid)

Internal

Holding Field (1.2K, 0.6T)

Modifications: Magnet TechnologyDNP at 200mK and 2.5T with 70GHz microwaves.Frozen spin target (25mKelvin, 0.6T).Secondary particles punch through holding coil.All directions of polarization.

High Field 1T

Threshold Production

Transverse Field

Modifications: Internal Polarising Coil

DNP at 200mK and 2.5T with 70GHz microwaves.10Layer coil at 50A.Secondary particles punch through holding coil.Higher momentum threshold.

Problem is the required field homogenietyof 10-E4. Notched solenoid.3d finite element calculation, optimisationand precise production needed.

New Coil with 10 layer (2.5Tesla) inMainz mechanical workshop.

Talk S.Schrauf

Vacuum 3He/4He – 6%

Modifications: Active Polarised Target

•Change from transverse to longitudinal polarisation.

•Internal polarising coil for high luminosity and precission experiments.

•Active polarised target for treshhold experiments.

Long term plans