CONSTRUCTION AND TEST OF A TRANSVERSE SUPERCONDUCTING HOLDING MAGNET 15th CB Meeting Mainz March...

CONSTRUCTION AND TEST OF A TRANSVERSE SUPERCONDUCTING

HOLDING MAGNET

15th CB Meeting

Mainz

March 8th, 2010

Henry G. Ortega Spina

March, 2010Henry G. Ortega Spina A2-Collaboration

CONTENTS

• Motivation• Frozen Spin Mode• Simulation• Construction• Tests & Results• Conclusions & Outlook


• Spin polarized targets needed to complete nuclear physics experiments, in particular to study internal structure of nucleons in detail.

• Information about polarization observables inferred from differential cross section of photoproduction.

MOTIVATION


Beam

Target

Photoproduction of pseudoscalar meson with polarized beam and target

EGP

PTP

FHP

dd

P

PPP

z

y

x

unpol

circlinlinunpol

- -

- -

- -

- -

4,

4

2,0 Target

Beam

EPGPP

PPTP

FPHPP

Pd

d

d

d

circlinz

liny

circlinx

lin

unpol

2sin

2cos

2sin

2cos1


• “Internal” superconducting holding magnets for longitudinally and transversally polarized targets.

• Design and construct an “internal” superconducting holding coil for transverse polarization.

MOTIVATIONMOTIVATIONMOTIVATIONMOTIVATION


• Frozen Spin Target scheme: cooling down, high magnetic field and optical pumping.

• Spins direction chosen beforehand with holding magnets.

• “External” holding magnets are very large and provide strong fringe field.

• First “internal” holding coil discussed in 1980 (Niinikoski, 1980) and developed in 1992 (Dutz et al., 1995).

FROZEN SPIN MODE


The Mainz Frozen Spin Target

Copper: T=300K 70K

HTS: T=70K 4K

NbTi: T=4K 1.5K


Microwave system

NMR system

Magnet


• “Racetrack” coil: magnetic field highly non-uniform and not appropriated for a cylinder.

• “Saddle” coil: winding must fit to the so-called overlapping

ellipse or “cosine” shape of current distribution.

SIMULATION


0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 900

1

2

3

4

54.1

0

I ( )

L1 ( )

L2 ( )

L3 ( )

L4 ( )

900

Ideal case for dipole magnet:

cos)( J

4-layer dipole:

N1=N2=138

N3=N4=78

SIMULATIONSIMULATIONSIMULATION


TBkAcmJ y 36.055 2

By (G) vs. X (cm) By (G) vs. Y (cm)



SIMULATION


• Copper/scandium wire with 54 Nb-Ti filaments embedded in it.

• Cu:Sc=1.35:1• Alloy composition:

Nb47wt.%Ti• Diameter=0.222mm• It achieves currents up to

50A at 4.2K and 1T.

CONSTRUCTION


CONSTRUCTIONCONSTRUCTION

17cm

10cm


Copper holder

Insert Cryogenic Hall generator


TESTS & RESULTS

• First test in a helium dewar and magnetic field in the centre of the target region.

• Field homogeneity could not be analyzed.

• Different currents applied and Hall voltage measured with the probe.

TESTS & RESULTS


TESTS & RESULTSTESTS & RESULTS

Magnetic field obtained from the Hall voltage (black) with a mean loadedsensitivity of 0.95 mV/kG.


AI 20

GaussElarperpendicufromDeviation

GaussEysensitivitMag

estimationError

B

01.152)º20(:

)76.19,20.14(:.

:

TESTS & RESULTS

GaussB

GaussBsim47.2533

73.2520

exp

TESTS & RESULTS


TESTS & RESULTS

• Transverse holding coil implemented within the Mainz FST and tested under beam conditions in December (2009) and February (2010).

• Stable temperature around 30mK and holding field corresponding to 30A (~0.4T) at 1.5K.

• Butanol target polarization greater than 80% and relaxation time of 1000 hours.



Positive DNP

Negative DNP

Holding field


• After many attempts a transverse holding dipole magnet has successfully been constructed.

• Magnetic field was measured in the centre of the target cell region. The obtained values were very close to those given by the computer simulation.

• The transverse holding coil was implemented in the cryostat of the Mainz FST and satisfactory tested observing no quenches or polarization loss.

• New measurements with transverse polarization throughout this year and data analysis in a near future.

CONCLUSIONS & OUTLOOK

Jen ĉio!Koran dankon por via atento!

Speciala danko al Oleksandr Kostikov


GAUSSMETER

Lake Shore cryogenic Hall generator HGCA-3020

Operating temperature range: 4.2K-375K

Diameter: 6.35mm

Active area: 0.8mm

GAUSSMETER


ELLIPSE GAP WIDTH


• Energy levels of particles with spin are splitted in the presence of an external magnetic field.

• Spin polarization is the asymmetry in the populations of the levels.

FROZEN SPIN MODE

kT

Bg

NN

NNPS

2tanh

2

12/1

FROZEN SPIN MODE

CONSTRUCTION AND TEST OF A TRANSVERSE SUPERCONDUCTING HOLDING MAGNET 15th CB Meeting Mainz March...

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