1. Update on quadruple well (INMAPS) MAPS rad-hard characterization and strip front-end simulation
L. Ratti
V SuperB Collaboration Meeting
Università degli Studi di Pavia and INFN Pavia
September Pisa, Italy
OUTLINE
University of Bergamo and INFN Pavia
Massimo Manghisoni, Valerio Re, Gianluca Traversi
INFN Pavia
Luigi Gaioni
University of Pavia and INFN Pavia
Alessia Manazza, Lodovico Ratti, Stefano Zucca
4-well MAPS rad-hard characterization
charge sensitivity and noise
charge collection with IR laser
Strip front-end simulations
operation at small peaking time in the outer layers
operation at lower temperature

2. 4-well MAPS rad-hard characterization
Quadruple well MAPS irradiated with neutrons up to 1e14 1MeV eq n/cm2 (JSI, Lubljana)
Substrate features: 12 um thick epi-layer, std (~10 W cm) and hi (~1 kW cm) res
Charge sensitivity, noise, charge collection (IR laser) measurement

3. Quadruple well MAPS front-end
Charge preamplifier
Shaper
Discriminator
Pixel logic
By suitably changing this voltage (in such a way that time to return to baseline is 2 us), the front-end can be made to work in good agreement with simulations (from the standpoint of gain, noise, peaking time)

4. Waveforms at the shaper output – std res
VRIF_MIR set in such a way that the time to return to baseline is ~2us
No particular trend detected with the fluence

5. Noise and charge sensitivity – std res
MAPS operated at VRIF_MIR such that time to return to baseline is about 2 us

6. Waveforms at the shaper output – hi res
VRIF_MIR set in such a way that the time to return to baseline is ~2us
A trend seem to emerge – peak value decreasing, corrected VRIF_MIR increasing with the fluence  significant (more than in the std res case) increase of the leakage current?

7. Noise and charge sensitivity – hi res
MAPS operated at VRIF_MIR such that time to return to baseline is about 2 us – confirmed decreasing trend in the charge sensitivity with fluence

8. After a neutron fluence of 1e14 cm-2
Laser tests
Infrared laser, l=1064 nm, step=5 um, sigma of the laser spot=3 um
Before irradiation
After a neutron fluence of 1e14 cm-2
Sample from the std res set

9. Laser tests – normalized peak value
Higher degree of radiation hardness for the hi res case (maybe not as high as expected)

10. Strip front-end simulations
Operation at smaller peaking times in the outer layers (to overcome noise issues due to leakage increase in irradiated devices)
Operation at DT=-6 °C (assuming RT=20 °C)
Detailed presentation by Massimo Manghisoni (including data on the individual contributions from the different noise sources) uploaded with this same presentation

11. Detector model and parameter
from the latest fluence estimate

12. Equivalent noise charge for inner layers (0-3)

13. S/N @1 MIP for inner layers (0-3)

14. ENC and S/N @1 MIP for outer layers (4-5)
Same chip for the outer layers as the one developed for the inner layers

15. Optimum S/N @1 MIP for outer layers (4-5)

16. Conclusion
Rad-hard characterization of quadruple well MAPS in progress – first results confirm higher tolerance for hi res substrate
Operation of the strip front-end at small peaking times might help keep S/N above 10 also after several years in the experiment
At such small peaking times, the advantage of operating the system at 6°C (probably also 8 °C) below RT seems negligible