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The COMPASS polarized target for Drell-Yan physics

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The COMPASS polarized target for Drell-Yan physics

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The COMPASS polarized target

for

Drell-Yan physics

Informal International Workshop

on

Drell-Yan physics at COMPASS

5-6 March 2007

Torino

Italy

Norihiro DOSHITA

Yamagata University, Japan

N. Doshita, Yamagata Univ.

Contents

- Experimental condition in terms of target

- Transverse polarization with hadron beam

- Present COMPASS polarized target system

- Selection of target material

- Limitation of target size (diameter, length)

- Higher polarization and longer spin relaxation need lower temerature.

Temperature heat input by high intensity hadron beam

- Present Compass polarized target status

- Test in 2007 run

N. Doshita, Yamagata Univ.

Total probability factor of secondly particle productions

N2nd = RN ·N0 +(1 - RN) = 3

RN: Nuclear interaction rate : 40%

N0: Number ofsecondly particles : 6

Experimental condition in terms of target

Transverse mode with hadron beam

- The present system can be used

- Proton target

High polarization, high dilution factor and long relaxation time

- Transverse polarization by frozen spin mode at 0.62 T

- spin relaxation
- - temperature

Cannot be polarized (only at 2.5T can be)

- High intensity hadron beam

(5 x 107 hadrons/second)

- temperature
- heat input
- target size
- cooling power

Nuclear interaction producing secondly hadrons

- Smaller beam focus size

- beam intensity
- for a bead
- - heat input

Smaller diameter target preferred

N. Doshita, Yamagata Univ.

Present COMPASS polarized target

2.5 T solenoid

0.62T dipole magnet

Dilution

refrigerator

(~60 mK in

minxing chamber)

180 mrad

acceptance

beam

Three target cells

(30 + 60 + 30 cm)

mwave cavity

N. Doshita, Yamagata Univ.

F = r(arest f PT)2

r= Material density

arest = rk/(rk + rHe(1-k))

k : packing factor

Selection of target material

Typical polarized proton target materials used in particle physics experiments

N. Doshita, Yamagata Univ.

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

Cooling power

of DR

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

with

-NH3

N. Doshita, Yamagata Univ.

Heat flow diagram

heat flow

T

Temperature of target material

MIP

2 MeV·cm2/g

= constant

Temperature of

Mixing chamber

N. Doshita, Yamagata Univ.

12

T

3

Cphonon(T) = 4 NA kB( )

5

D

Specific Heat

CL = Cphonon + Ccryocrystal + Cnon-crystal

D : Debye temperature

7LiD ~1030K

14NH3 ~235K

Ccryocrystal(T) = ?? For NH3 ,ND3

Cnon-crystal(T) = ?? For butanol?, CH2, CD2

N. Doshita, Yamagata Univ.

d2

- Beam intensity : Ibead
- in terms of one bead

=

· Ibeam· N2nd

D2

Model for calculation of temp. variation

d mm

Ibeam s-1

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)

Total probability

factor of secondly

particle productions

N. Doshita, Yamagata Univ.

Edeposit - Q

T'(ti)=

+ T(ti-1)

n CL(T(ti-1))

Algorithm for the calculation

Beam interval: ti - ti-1 = sec = 1/Ibead

Edeposit = n CL(T(ti-1)) (T(ti) - T'(ti-1))

T(ti)

0 Q dt = 0 (T(ti-1)4 - T04) dt

A

T0 = 65 mK

RK

RK = 50 cm2K4/W

(CrK crystal - 4He)

N. Doshita, Yamagata Univ.

Temperature variation in muon program setup

NH3

6LiD

N. Doshita, Yamagata Univ.

Hadron beam vs beam focus size for NH3

N. Doshita, Yamagata Univ.

N2nd

: Total probability factor

of secondly particles

r

: Material or helium density

k

: Packing factor

L

: Target cell length

EMIP

: 2 MeV· cm2/g

5 mW at 75mK

Ibeam

: Beam intensity

Total heat input in the target cells

•

Qtotal = N2nd · (rm·k+rHe·(1 - k)) · 2L · EMIP · Ibeam

This heat should be removed by Dilution refrigerator

Cooling power of refrigerator

mK

mmol/sec

N. Doshita, Yamagata Univ.

Total heat input in the cells

N. Doshita, Yamagata Univ.

need

- target holder

- microwave cavity

In the draft of proposal

- NH3 as the target material

- 3cm and 30cm long twin target cells

are proposed with enough margin.

N. Doshita, Yamagata Univ.

Present COMPASS polarized target status

- Only transverse run in 2007

- 4cm diameter 3 target cells

- NH3 as proton target

- need test of magnet

- first run for transverse mode

- superradiance

What can be done in this year for DY program?

- Get information of NH3 with the system

- Polarization, relaxation time and supperradiance

- 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

N. Doshita, Yamagata Univ.