1 An X-ray fluorescence spectrometer using CMOS-sensors AD AD vanced MO MO nolithic S S ensors for Supported by BMBF (06FY9099I and 06FY7113I), HIC for FAIR, GSI and EU-FP7 1)Real-time water analysis using XRF 2)CMOS-Sensors 3)Reconstruction of the energy information 4)Improving the quantum efficiency Dennis Doering, Michael Deveaux Institut für Kernphysik Frankfurt for the CBM-MVD-collaboration Sensor development: IPHC Strasbourg

/17/25 Application: X-ray spectrometer M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March Monitoring water quality and trigger on traces of pollution Identifing elements via their characteristic X-ray-fluorescence lines (XRF) Required sensor features: - Good energy resolution - High-rate capability  Adapted CMOS-sensors - Low noise - Low production costs Sample

/17/25 Operation principle of CMOS-sensors M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March SiO 2 N+P+ P- P+ Diode Epitaxial Layer P-Well Substrate N+ Particle Depleted zone e-

/17/25 Charge smearing between pixels M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March P- P+ Diode Epitaxial Layer P-Well Photon Depleted zone One pixel: e- Cd-109-source (support is built up of brass) Ag K α,K β Chip (PCB contains Ba) Drawback: Charge smearing +20°C

/17/25 Cluster of 25 pixels M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March P- P+ Diode Epitaxial Layer P-Well Photon Depleted zone Cluster of 25 pixels e- Disadvantage: Noise contribution of 25 pixels Cd-109-source (support is built up of brass) Ag K α,K β Chip (PCB contains Ba) +20°C

/17/25 Trigger on conversions in the depleted zone M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March P- P+ Diode Epitaxial Layer P-Well Photon Depleted zone e- Cd-109-source (support is built up of brass) Ag K α,K β Chip (PCB contains Ba) Triggercondition: Neighboring pixel carry no charge +20°C

/17/25 Trigger on conversions in the depleted zone M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March P- P+ Diode Epitaxial Layer P-Well Photon Depleted zone e- Cd-109-source (support is built up of brass) Ag K α,K β Chip (PCB contains Ba) Drawback: Reduced quantum efficiency +20°C

/17/25 Linearity of amplification chain M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March Energy[keV]=(0.0364±0.0004) · Q coll [ADC]+(-0.004±0.05) Linear energy scale at least between a few keV up to 25keV +20°C

/17/25 Strategies to increase the quantum efficiency M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March Larger depleted volumes: ⇒ Accelerated charge collection, less diffusion ⇒ Less charge smearing between pixels Aim: Full depletion of the epitaxial layer SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate depleted volume Low-resistivity ~ 30 Ωcm High-resistivity ~1k Ωcm High-resistivity: Decrease of doping concentration in epitaxial layer. Depletion voltage: Increase the depleted volume Sensing diode

/17/25 TOWER-Jazz-Process M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March Larger depleted volumes: ⇒ Accelerated charge collection, less diffusion ⇒ Less charge smearing between pixels Aim: Full depletion of the epitaxial layer SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate depleted volume Low-resistivity ~ 30 Ωcm High-resistivity ~1k Ωcm High-resistivity: Decrease of doping concentration in epitaxial layer. Depletion voltage: Increase the depleted volume Sensing diode TOWER-Jazz-0.18µm process - High-Resistivity 1-8kΩcm - Depletion voltage up to 20V Modified preamplifier - Recharge diode - AC-coupled

/17/25 TOWER-Jazz 0.18µm CMOS process for imager M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March The Sensor: PEGASUS (2015) 18µm thick, 25µm pixel pitch, >1kΩcm epitaxial layer, 12 V bias voltage Cd-109-source Cu-foil Ag K α,K β Less charge smearing  Larger depletion zone

/17/25 TOWER-Jazz 0.18µm CMOS process for imager M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March The Sensor: PEGASUS (2015) 18µm thick, 25µm pixel pitch, >1kΩcm epitaxial layer, 12 V bias voltage Cd-109-source Cu-foil Ag K α,K β Less charge smearing  Larger depletion zone Trigger on neighboring pixels still helps

/17/25 Influence of the leakage current M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March Due to the non-linear response of the recharge diode at +20°C : - Limited energy resolution - Non-linear amplification  Optimizing of the pixel layout required (Pegasus-3)  Cooling to -20°C so far helps

/17/25 Cu-inlay M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March Cd-109-source Cu-foil Ag K α,K β Ag K α,K β +Cu K α Expected excess in Cu-Kα-line observed Energy resolution is σ=122eV

/17/25 Conclusion 15 Application: Real-time water analysis via X-ray fluorescence analysis  CMOS-Sensors proposed Studied two CMOS-sensors: MIMOSA-19 and Pegasus Possible above 2 keV with an energy resolution of 120…190eV At room temperature or slightly cooled conditions  Sensors seem suited for the task Outlook: Obtain higher quantum efficiency due to full depleted epitaxial layer Detailed study of high-voltage CMOS-sensors required DFG proposal submitted M. Deveaux, D. Doering: An XRF spectrometer using CMOS-sensors DPG Darmstadt March 2016