17th Crystal Ball Meeting
Institut fr 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 4p- Photon 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 ~ mKelvin (one day) (typical one week measurement period). Frozen Spin Target Relaxationtime
26 mK, 0.44T Relaxation time of butanol at 60 mK depending on the applied magnetic field Target material Dilution factor (fButanol=10/74)
Free electrons Radicals in material by chemical or radiative doping Saturated electrons of target material not polarized (Pauli principle) Dilution factor (fButanol=10/74) determines quality of target material. We have9*1022 pol. Protonsper cm2 in our 2cm long target cell. 2cm Butanol N O CH3 Tempo Filling factor ~ 60% H. Ortega Spina
C4H10O 60% 30mm Filling factor ~ 60% H. Ortega Spina 3He/4He 6% Vacuum 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 Typical NMR Signals Enhanced Signal at 70% Polarisation
after spin rotation Thermal Equilibrium-Signal 0.5% Polarisation 2.5Tesla,1Kelvin Temperature measurement
AVS Picowatt Resistance Bridge ! Systematic error for all asymmetries! Highest Deuteron polarisation due to new
Target material Density and species of the radicals are very important for: maximum degree of polarization polarization build up times relaxation times Trityl-Radikal D-Butanol [Gerhard Reicherz, PT Ruhr-Universitt 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 requiredfield 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 3He/4He 6% Vacuum Long term plans Change from transverse to longitudinal polarisation.
Internal polarising coil for high luminosity and precission experiments. Active polarised target for treshhold experiments.