2015.09.22.progress.report

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2015.09.22.progress.report

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2015.09.22.progress.report

progress report tomcat group

On Github enucatl-presentations / 2015.09.22.progress.report

Grating interferometry and Compton scattering

New bunker 4

  • approved up to 160 kV (custom controller chip)
  • thicker beam stop needed for higher voltage
  • mandatory dosimeter inside bunker 5

Tube operation

turn key to the position press blue button on the door

Tube operation

warm up (don't know = 99 days) choose max voltage you want to operate
press on

Tube maintenance

once per year, check both ends of the high-voltage cable: exactly two rings should be visible

Troubleshooting

  • check main switch behind the bunker
  • check warning lamps: no beam if the lamp is broken!
  • contact: Manuel Gautschi mg@controltech-ndt.ch

The Compton energy range

  • bio $> 50$ keV
  • heavy metals $>100$ keV

How does grating interferometry change?

Absorption

no Z information

Differential phase

Dark field

Extension of Lynch et al. 2011

\[ R = \mu_d / \log A \]

Polychromatic model

  • $R(\mathcal{E})$ for each energy from Lynch
  • sum over spectral weights
  • add fixed Compton contribution (energy and material independent)
  • two fit parameters $R_0$, $C$

\[ R(\mathcal{E}) = R_0 + C \dfrac{|n|^2}{\beta} u(\mathcal{E}) \] \[ R = \sum_\mathcal{E} w(\mathcal{E}) R(\mathcal{E}) \]

Silica microspheres

0.16-7.75 µm

Beam hardening

12 mm

45 mm

Conclusions

  • microstructural information from dark field, even on polychromatic sources
  • phase and delta noisy because of the fast visibility reduction
  • no Z from R

Applications

  • lung microstructure size
  • mammography microcalcs and fibers
  • lower energy advised: 100 kVp, 40-60 keV design
  • bones and strongly absorbing samples still a big issue for DPC
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Grating interferometry and Compton scattering