Experiment planning
From GOSIA
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The GOSIA suite of codes are ideally suited to the design and planning of | The GOSIA suite of codes are ideally suited to the design and planning of | ||
| - | heavy-ion induced Coulomb excitation experiments as well as the subsequent | + | low-energy heavy-ion induced Coulomb excitation experiments as well as the subsequent |
analysis. Coulomb excitation experiments can seem deceptively simple, | analysis. Coulomb excitation experiments can seem deceptively simple, | ||
especially for few-state problems, leading some experimenters to fall into | especially for few-state problems, leading some experimenters to fall into | ||
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on heavy-ion induced Coulomb excitation.<ref>K. Alder and A. Winther, ''Electromagnetic Excitation: Theory of Coulomb Excitation with Heavy Ions,'' North Holland, Amsterdam (1975).</ref><ref>D. Cline, Ann. Rev. Nucl. Part. Sci. 36:683 (1986).</ref> | on heavy-ion induced Coulomb excitation.<ref>K. Alder and A. Winther, ''Electromagnetic Excitation: Theory of Coulomb Excitation with Heavy Ions,'' North Holland, Amsterdam (1975).</ref><ref>D. Cline, Ann. Rev. Nucl. Part. Sci. 36:683 (1986).</ref> | ||
| - | ==Safe bombarding energy== | + | ==Experimental parameter considerations== |
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| + | ===Safe bombarding energy=== | ||
The basic assumption of Coulomb excitation is that the interaction between the | The basic assumption of Coulomb excitation is that the interaction between the | ||
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scattering cross sections at large scattering angles in a manner that mimics | scattering cross sections at large scattering angles in a manner that mimics | ||
the reorientation effect corresponding to a negative static quadrupole moment. | the reorientation effect corresponding to a negative static quadrupole moment. | ||
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| + | Chapter 2 of the Gosia manual discusses the issue of safe bombarding energy in detail. | ||
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| + | ===The semiclassical approximation=== | ||
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| + | The long range of the Coulomb interaction, coupled with the small integrationstep size necessitated by the short wavelength, and the large number of | ||
| + | partial waves that make significant contributions, conspire to make it | ||
| + | impractical to use fully quantal codes with current computers that are capable | ||
| + | of handling the large number of coupled channels important to heavy-ion | ||
| + | induced Coulomb excitation. Fortunately a considerable simplification | ||
| + | can be achieved by assuming a semiclassical treatment of two-body | ||
| + | kinematics as pioneered by Alder and Winther.<ref>K. Alder, A. Winther, K. Dan. Vidensk et al., Mat. Fys. Medd. 32, Number 8 (1960).</ref> | ||
| + | The semiclassical picture exploits the fact that the monopole-monopole Coulombinteraction <math>Z_1 Z_2 e^2/r</math> | ||
| + | dominates and determines the relative motion of the two colliding nuclei. | ||
| + | The semiclassical picture assumes that the size of the | ||
| + | incoming projectile wavepacket is small compared to the | ||
| + | dimensions of the classical hyperbolic trajectory which is | ||
| + | expressed in terms of the [[Sommerfeld_parameter | Sommerfeld parameter]]. | ||
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| + | ==Simulation== | ||
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| + | Gosia can be used to estimate the sensitivity to a particular matrix element or set of matrix elements that will be obtained in a planned experiment and to optimize the experiment for a desired measurement. Refer to the [[Simulation_(experiment_planning) | Simulation]] page for more detail. | ||
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| + | ==Planning tools== | ||
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| + | While Gosia is the obvious tool for planning low-energy Coulomb excitation experiments, the [[Rachel,_a_GUI_for_Gosia | GUI]] for Gosia can offer much greater speed and automation in the planning process, including predicting the measurable count rate and estimating the expected errors in the planned experiment. | ||
==Notes== | ==Notes== | ||
<references/> | <references/> | ||
