future activities of the compass polarized target n. doshita university of bochum, germany
TRANSCRIPT
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
[email protected] 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