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References - Bogoliubov Laboratory of Theoretical Physics - JINR

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4 Examples <strong>of</strong> transparent crossing<br />

Examples <strong>of</strong> transparent resonance crossing is given in papers [1–3]. The condition (3)<br />

can be fulfilled only if detuning changed in spin resonance region. The SAI dependence is<br />

shown schematically in Fig. 4 and Fig. 5. SAI changing is plotted symbolic by the dashed<br />

line inside spin resonance region. The detuning shape defines SAI changing in resonance<br />

region.<br />

When condition (3) is violated the width <strong>of</strong> resonance region is defined by crossing<br />

speed and is equal approximately to θres ∼ 1/ � dε/dθ.<br />

1<br />

�1<br />

Ji<br />

a<br />

Resonance<br />

region<br />

J f ��Ji<br />

Figure 4: Transparent resonance crossing in<br />

the case <strong>of</strong> SAI-flip<br />

Θ<br />

1<br />

�1<br />

Ji<br />

a<br />

J f �Ji<br />

Figure 5: Transparent resonance crossing in<br />

the case <strong>of</strong> SAI keeps sign<br />

Another possibility to restore SAI appears, if one uses multiple resonance crossing [4].<br />

At single crossing with constant speed ε ′ = dε/dθ the SAI values before and after resonance<br />

crossing are connected by general FS formulae [7]:<br />

Jf =<br />

�<br />

1 − 2exp<br />

�<br />

− w2<br />

2|ε ′ a |<br />

��<br />

Ji =cos2αJi , sin α =exp<br />

�<br />

− w2<br />

4|ε ′ a |<br />

�<br />

where angle α is defined by speed <strong>of</strong> detuning changing at resonance crossing moment<br />

θ = a. It should be noted that it is impossible to restore SAI after single crossing with<br />

constant speed. The restoration <strong>of</strong> SAI after resonance crossing can be obtained due to<br />

detuning <strong>of</strong> changing in outside resonance region.<br />

The SAI dependence is shown schematically in Fig. 6 and Fig. 7 for the cases <strong>of</strong> two<br />

times transparent crossing.<br />

1<br />

�1<br />

Ji<br />

a b<br />

Jab<br />

J f ��Ji<br />

Figure 6: Two times transparent resonance<br />

crossing in the case <strong>of</strong> SAI-flip<br />

Θ<br />

1<br />

�1<br />

Ji<br />

a b<br />

Jab<br />

J f �Ji<br />

Figure 7: Two times transparent resonance<br />

crossing in the case <strong>of</strong> SAI keeps sign<br />

Two times transparent crossing can be used for spin-flip equipment in the accelerator<br />

ring directly before beam is extracted to external target.<br />

The conditions <strong>of</strong> two times transparent resonance crossing are the following:<br />

a) in the case <strong>of</strong> SAI-flip (Fig. 6): α = β, Ψab =2πm;<br />

b) in the case <strong>of</strong> SAI keeps sign (Fig. 7): α = π/2 − β, Ψab =2πm + π,<br />

409<br />

Θ<br />

Θ

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