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

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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)

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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

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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

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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

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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

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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

=

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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)

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Temperature variation in muon program setup

NH3

6LiD

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Hadron beam vs beam focus size for NH3

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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

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Total heat input in the cells

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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

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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