NMR system for the frozen spin target to measure the polarisation

13.09.09 Nadja Frömmgen 1

NMR system for the frozen spin targetto measure the polarisation

Nadja FrömmgenInstitut für Kernphysik

Universität Mainz

CB collaboration meetingUniversity of Edinburgh 2009

13.09.09 Nadja Frömmgen 2

Outline

• Principle of NMR

• Detection of the NMR signal

• NMR signal

• Performance test in July 2009

• Conclusion and Outlook

13.09.09 Nadja Frömmgen 3

Principle of NMR

• Irradiation with a HF field• NMR signal results from the difference between absorbed and emitted energy; voltage is induced in a receiver coil• Signal is proportional to the population difference Polarisation

)31.1062( MHzP

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coil

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How is the NMR signal detected?

Series LC resonant circuit

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Series LC resonant circuit

Resonance frequencyLC

2

1

tuning to the Larmor frequency of nucleus via changing C (varicap)

„Resonance parabola“

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Q-curve of the resonant circuit

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NMR signal

TE

TEDNPDNP AreaUnit

PAreaUnitP

TE: thermal equilibrium

kTB

NNNN

PTE

tanh

Measurement of the TE signal as exactly as possible to minimise the error of the polarisation measurement.

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July 2009

• polarising magnet: 2.507 T• cooled to ~26mK• irradiated with microwaves (15mW) for 3.5 hours

up to ~50% polarisation

Performance test: cryostat, microwave apparatus & NMR system

Successfull measurement: TE signal Polarised NMR signal Polarisation curve Relaxation curve

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TE-Signal

In the meantime the noise on the signal could be reduced.

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Polarised NMR Signal

~ 50% polarisation

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Polarisation curve

2 ¼ hours

Pola

risa

tion

[%

]

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Relaxation curve

30 minutes

Pola

risa

tion

[%

]

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Conclusion and Outlook

NMR-System is working well we expect a polarisation of P>90% and an error in the polarisation measurement of ~1.5%

• system linearity measurement• several stability tests• optimisation of the software by M. Korolija from Zagreb• final test of the frozen spin target in October together with J. Usov, A. Neganov, N. Borisov and A. Lazarev from Dubna

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Thank you for your attention!