Future activitiesFuture activitiesof of

the COMPASS polarized targetthe COMPASS polarized target

N. Doshita University of Bochum, Germany

Contents

・ The COMPASS experiment

・ The Polarized Target 2002-2004

・ Upgrade for 2006 ~

・ Summary

JuraLac LemanSPSCOMPASSPSLHC

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 measurementin the COMPASS

Aexp =NNNN= PB PT f Aphys

PB: Beam polarizationPT: Target polarizationf : Dilution factor N : Number of events

: Direction of beam polarization: Direction of target polarization

Aphys 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

D0, D0* Low statistics

(double spin asymmetry)

Requirement of Polarized Target

Statistical accuracy

Aexp

Aexp 2N PB PT f A

phys=1

COMPASS polarized target

- Target material 6LiD (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 target2002 ~ 2004

Magnet : 2.5 T solenoid 0.5 T dipole

Still pumping line

Twin target cells60 cm + 60 cm Mixing chamber : 6 L

µ beam

3He precooling line

69 mrad

3He 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

1st attempt to get uniform field (June 24th):

100 ppm

Request is ≤ 100 ppm

Homogénéisation

-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

120

140

160

180

200

-100 -80 -60 -40 -20 0 20 40 60 80 100

Position cm

dB/Bo ppm

+90% (1) 24_06

+90% (2) 24_06

Target region 130cm

obtained less than 100 ppm homogeneity now

Summary

- The COMPASS polarized target has been used since 2002.

- 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

p

μ

c

cq

γ*

μ

k

G

D0 　　 K- + +

D0 　　 K+ + -

Field Rotation

33 minutesevery 8 hours

Upstream Downstream

(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 SMC COMPASS

Material NH3 D-butanol 6LiD

Polarization H: ~0.90 D: ~0.50 D: ~0.50

Dilution

factor

0.176 0.238 ~0.50

FoM 10.3 6.7 16.0

FoM = (f ‘PT)2

: density

: packing factor

f ‘: effective dilution factorPT : polarization

The beam time needed to achieve a certain statistical accuracy is inversely proportional to the FoM.

For the extraction of the real physicsBjorken-x-dependence of dilution factor should be considered.

Dynamic nuclear polarization

External magnetic fielddirection

DeuteronElectron

Ele

ctro

n fa

st r

elax

atio

n

Ele

ctro

n fa

st r

elax

atio

n

Ele

ctro

n fa

st r

elax

atio

n

Ele

ctro

n fa

st r

elax

atio

n

Spin statusDipolar-dipolar interaction

Polarization@2.5T and 0.3KElectron: 99.9%Deuteron: 0.17%

Transfer the high electronpolarization to deuteron polarization

Paramagnetic centers are needed

COMPASS dilution refrigerator

3He flow 30-100 mmol/sec

2000 L

13500 m3/h

3He of 1400 L NTP4He of 9200 L NTP

15-20 L/h

Mixing chamber

TTH1: speer 220 ohmTTH2: speer 220 ohm

TTH4: RuO TTH7: speer 220 ohmTTH6: RuO

Calibrated sensors Non-calibrated sensors

Beam

microwavecavity

mixing chamber

microwave guide

microwave stoppertarget material

70 mm

1600 mm

upstreamupstream downstreamdownstream

600 mm

30mm

Microwave generator10W output power

2W due to long waveguide

0.2W needed for both cells

Microwave stopper holes MixingChamber

Power supply

Power controlattenuators

Microwave system

Microwave cavity

NMR System

material 6LiD

NMR coil

Liverpool Q-meter

UT-85 CableCu jacketsemi-rigid

Splitter

frequency control

PTS 250Microwave generator

Yale cardscope

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 2000data acquisition program (LabVIEW)data storage

gain selectionsignal

DC offset subtraction

ADC/DAC12 bit

trigger signal

10 coils can be measured at the same time.

Average polarization in the whole physics runs in 2003

Red : UpstreamGreen : 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

Eth

ern

et

mod

ule

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

304050607080901001000 mW10 310 2600 mW320 mW125 mW45 mW13 mW5 mW1 mW0 mW

3He flow rate [mmol/sec]

MC

Tem

pera

ture

[mK]

DNP

Frozen mode

50%

0%

Cooling power