N. Doshita, Yamagata Univ.1 The COMPASS polarized target for Drell-Yan physics Drell-Yan physics...
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Transcript of N. Doshita, Yamagata Univ.1 The COMPASS polarized target for Drell-Yan physics Drell-Yan physics...
N. Doshita, Yamagata Univ. 1
The COMPASS polarized target The COMPASS polarized target forfor
Drell-Yan physicsDrell-Yan physics
Informal International Workshopon
Drell-Yan physics at COMPASS5-6 March 2007
TorinoItaly
Norihiro DOSHITANorihiro DOSHITAYamagata University, Japan
N. Doshita, Yamagata Univ. 2
Contents
- Selection of target material
- Limitation of target size (diameter, length)
Temperature heat input by high intensity hadron beam
- Experimental condition in terms of target
- Present Compass polarized target status
- Transverse polarization with hadron beam
- Test in 2007 run
- Present COMPASS polarized target system
- Higher polarization and longer spin relaxation need lower temerature.
N. Doshita, Yamagata Univ. 3
Experimental condition in terms of target
- Transverse polarization by frozen spin mode at 0.62 T
- Proton target
- High intensity hadron beam (5 x 107 hadrons/second)
- Smaller beam focus size
High polarization, high dilution factor and long relaxation time
Nuclear interaction producing secondly hadrons - temperature- heat input- target size- cooling power
Cannot be polarized (only at 2.5T can be)- spin relaxation - temperature
Smaller diameter target preferred
- beam intensity for a bead- heat input
Transverse mode with hadron beam
N2ndRN ·N0 + (1 - RN) = 3 RN: Nuclear interaction rate : 40% N0: Number of secondly particles : 6
Total probability factor of secondly particle productions
- The present system can be used
N. Doshita, Yamagata Univ. 4
Present COMPASS polarized target
beam180 mradacceptance
Dilution refrigerator(~60 mK in minxing chamber)
2.5 T solenoid0.62T dipole magnet
wave cavityThree target cells(30 + 60 + 30 cm)
N. Doshita, Yamagata Univ. 5
NH3 Butanol
Proton Polarization PT 0.90 0.90
Dilution factor f 0.176 0.135
Figure of merit F 17.2 12.1
Spin relaxationtime at ~60 mK
~500h at 0.5T
(SMC)
~200h at 0.42T
(GDH-Mainz,Bonn)
Selection of target material
F = (rest f PT)2
= Material density
rest = He packing factor
Typical polarized proton target materials used in particle physics experiments
N. Doshita, Yamagata Univ. 6
Limitation of target cell size
Sould be considered heat input by high intensity of hadron beam
- Diameter beam intensity Temperature in terms of a bead of material bead
- Length total heat Temperature input into cells of Mixing chamber
with -NH3
Investigate the possibility of -smaller beam focus size and target cell -higher beam intensity via -temperature variation of the material -total heat input into Mixing chamber
Cooling powerof DR
N. Doshita, Yamagata Univ. 7
Lattice
SpinCs
CL
Liq. Helium
Beam
Edeposit
Ts
TL
T0
RK
RSL
Heat flow diagram
MIP
heat flow
= constant
T
2 MeV·cm2/g
Temperature of target material
Temperature ofMixing chamber
N. Doshita, Yamagata Univ. 8
Specific Heat
Cphonon(T) = 4 NA kB ( )D
T 3
512 D : Debye temperature
7LiD ~1030K 14NH3 ~235K
Ccryocrystal(T) = ?? For NH3 ,ND3
Cnon-crystal(T) = ?? For butanol?, CH2, CD2
CL = Cphonon + Ccryocrystal + Cnon-crystal
N. Doshita, Yamagata Univ. 9
Model for calculation of temp. variation
D mm d mm
- Target material : spherical shape, LiD: d=4 mm, NH3: d=3 mm
- Beam focus = target size: circular cross section (D=30mm for muon program)
beam s-1
Total probability factor of secondlyparticle productions
- Beam intensity : bead
in terms of one bead· beam · N2nd D2
d2
=
N. Doshita, Yamagata Univ. 10
Algorithm for the calculation
0 Q dt = 0 (T(ti-1)4 - T04) dtRK
A
n CL(T(ti-1))Edeposit - Q + T(ti-1)T'(ti) =
Edeposit = n CL(T(ti-1)) (T(ti) - T'(ti-1)) T(ti)
Beam interval: ti - ti-1 = sec = 1/bead
T0 = 65 mKRK = 50 cm2K4/W(CrK crystal - 4He)
N. Doshita, Yamagata Univ. 11
Temperature variation in muon program setup
NH3
6LiD
N. Doshita, Yamagata Univ. 12
Hadron beam vs beam focus size for NH3
N. Doshita, Yamagata Univ. 13
Total heat input in the target cells
30 40 50 60 70 80 90 100
1000 mW103
102
600 mW
320 mW
125 mW
45 mW
13 mW5 mW
1 mW0 mW
mmol/sec
mK Cooling power of refrigerator
Qtotal = N2nd · (m· + He·(1 - )) · 2L · EMIP · beam
This heat should be removed by Dilution refrigerator
•
N2nd
L
EMIPbeam
: Total probability factor of secondly particles
: Material or helium density
: Packing factor
: Target cell length
: 2 MeV· cm2/g: Beam intensity
5 mW at 75mK
N. Doshita, Yamagata Univ. 14
Total heat input in the cells
N. Doshita, Yamagata Univ. 15
In the draft of proposal
- NH3 as the target material
- 3cm and 30cm long twin target cells
are proposed with enough margin.
- target holder - microwave cavity
need
N. Doshita, Yamagata Univ. 16
Present COMPASS polarized target status
- Only transverse run in 2007
- 4cm diameter 3 target cells- NH3 as proton target- need test of magnet
What can be done in this year for DY program?
- Get information of NH3 with the system
- Hadron beam test just before change to hadron program ??- Measure total heat input and nuclear interaction rate- Measure spin relaxation time with 107 hadrons/s
- first run for transverse mode- superradiance
- Polarization, relaxation time and supperradiance