Future activities of the COMPASS polarized target N. Doshita University of Bochum, Germany

Contents ・ The COMPASS experiment ・ The Polarized Target ・ Upgrade for 2006 ~ ・ Summary

CERN and COMPASS

The COMPASS experiment Muon program - Nucleon spin structure --- gluon contribution - Polarized muon beam and polarized nucleon target Hadron program - Meson spectroscopy -Hadron beam and hydrogen, carbon target Physics data taking started in 2002

Gluon polarization measurement in the COMPASS P B : Beam polarization P T : Target polarization f : Dilution factor N : Number of events  : Direction of beam polarization : Direction of target polarization A phys  Gluon polarization - Open charm production events - High- PT hadron production events What kinds of events can be approached to realize PGF ? Experimentally measurable double spin cross section asymmetry via PGF Extraction Dilution factor : polarizable nucleon rate in material D 0, D 0 * Low statistics (double spin asymmetry)

Requirement of Polarized Target Statistical accuracy  A exp A 2N P B P T f A phys = 1 COMPASS polarized target - Target material 6 LiD (high dilution factor), 350g - Magnetic field 2.5T superconducting magnet -Temperature 60mK and 300mW at 300mK by dilution refrigerator Deuteron polarization more than 50 %  Dynamic Nuclear Polarization with Microwave -High polarization -High dilution factor -Large target

COMPASS polarized target 2002 ~ 2004 Magnet : 2.5 T solenoid 0.5 T dipole Still pumping line Twin target cells 60 cm + 60 cm Mixing chamber : 6 L µ beam 3 He precooling line 69 mrad

3 He Pumping line Beam Dilution refrigerator Magnet

Upgrade for 2006 ~

180 mrad Large acceptance - Solenoid: < 100 ppm homogeneity -  ~60cm 2.5T Solenoid, 0.5T Dipole - 30% gain in statistics - ~25 L/hour Liq. He Upgrade part 1

Fit on new magnet To reduce false asymmetry 3 target cells Large cavity talk of Y. Kisselev Upgrade part 2

Ready in next spring Data taking: June 14th ~ Upgraded PT system for 2006

COMPASS Oxford Danfysik magnet OD magnet assembly was finished at December 2004 and has been tested in Saclay. It is almost finished to test the magnet and construct its instruments. The magnet is being delivered to CERN in the end of this month.

COMPASS OD magnet 1 st attempt to get uniform field (June 24 th ): 100 ppm Request is ≤ 100 ppm Target region 130cm obtained less than 100 ppm homogeneity now

Summary - The COMPASS polarized target has been used since The system is upgraded for 2006 ~. - 3 target cells - New large acceptance magnet - New microwave cavity - Expect high statistics and high quality data in 2006

Open charm lepto-production via photo-gluon fusion C C ー D 0 K - +  + D 0 K + +  -

Field Rotation 33 minutes every 8 hours UpstreamDownstream (a) (b) (c) Muon Target material spin direction (a) (c) In order to cancel the systematic error -Spectrometer acceptance -Time dependence variation (b)

Figure of Merit SMC COMPASS MaterialNH 3 D-butanol 6 LiD PolarizationH: ~0.90D: ~0.50 Dilution factor ~0.50 FoM FoM =  (f ‘P T ) 2  : density  : packing factor f ‘: effective dilution factor P T : polarization The beam time needed to achieve a certain statistical accuracy is inversely proportional to the FoM. For the extraction of the real physics Bjorken-x-dependence of dilution factor should be considered.

Dynamic nuclear polarization Electron fast relaxation Electron fast relaxation Electron fast relaxation Electron fast relaxation Spin status Dipolar-dipolar interaction and 0.3K Electron: 99.9% Deuteron: 0.17% Transfer the high electron polarization to deuteron polarization Paramagnetic centers are needed

COMPASS dilution refrigerator 3He flow mmol/sec 2000 L m 3 /h 3 He of 1400 L NTP 4 He of 9200 L NTP L/h

Mixing chamber  TTH1: speer 220 ohm  TTH2: speer 220 ohm  TTH4: RuO  TTH7: speer 220 ohm  TTH6: RuO Calibrated sensors Non-calibrated sensors Beam  microwave cavity mixing chamber microwave guide microwave stopper target material 70 mm 1600 mm upstreamdownstream 600 mm 30mm

Microwave generator 10W output power 2W due to long waveguide 0.2W needed for both cells Microwave stopperholesMixing Chamber Power supply Power control attenuators Microwave system Microwave cavity

NMR System material 6 LiD NMR coil Liverpool Q-meter UT-85 Cable Cu jacket semi-rigid Splitter frequency control PTS 250 Microwave generator Yale card scope 10 ch ADC 12 bit 16 ch ADC 16 bit 96 ch digital I/O bus extender VME-MXI VME-bus NI MXI-2 cable PC in the control room Windows 2000 data acquisition program (LabVIEW) data storage gain selection signal DC offset subtraction ADC/DAC 12 bit trigger signal 10 coils can be measured at the same time.

Average polarization in the whole physics runs in 2003 Red : Upstream Green : Downstream

Isolation vacuum LHe valve Turbo pump control Diffusion pump Vertical, horizontal screens LN2 trap level control 4He roots pump 3He pumps Cooling water security room temperature Air conditioning Pump room Pressures Flow rates Gate valve control Needle valves control Interlock (still heater, MW) CPU Ethernet module Beam area Control room Touch panel intranet PC Profibus PLC (programmable logic controller) System Power : 48V UPS, 49 channels are used Siemens S7-300, CPU315-2DP with 48 kByte memory

3 He flow rate [mmol/sec] MC Temperature [mK] DNP Frozen mode 50% 0% Cooling power