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Prompt Detector

Prompt Detector. F. Faccio, A. Marchioro and P. Moreira. Introduction. Objective: Integrated monolithic sensor capable of detecting dose rates ≥ 10 8 rad/s Target functionality: Allow normal ASIC operation for dose rates < 10 8 rad/s

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Prompt Detector

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  1. Prompt Detector F. Faccio, A. Marchioro and P. Moreira

  2. Introduction • Objective: • Integrated monolithic sensor capable of detecting dose rates ≥ 108 rad/s • Target functionality: • Allow normal ASIC operation for dose rates < 108 rad/s • Disable the ASIC operation once a dose rate ≥ 108 rad/s has been detected

  3. Prompt • The answer is a “Prompt dose detector”: • The objective is to detect high radiation fluxes • Should detect: • 5 108 rd/s • Equivalent to 160 fC deliveredin 20 ns (~8 mA photocurrent) • But be insensitive: • To the LHC and SLHC radiation environments • Power supply and substrate noise • PSRR: • -137.5 dB @ 1 kHz • -82.0 dB @ 40 MHz • -26.0 dB @ 1 GHz • The device uses an integrated photodiode to detect the ionizing radiation. 550 mW (368 mA @ 1.5 V)

  4. Using the prompt

  5. n+ diffusion diode substrate contact spacing prevents filling metal opening for light (photo)-diode Several diodes were integrated: • n+ diode on substrate: • 10 x 10 mm x 1 mm • 5 x (10 x 10 mm x 1 mm) • n+ diode on substrate with interdigitated substrate contacts: • 10 x 10 mm x 1 mm • 5 x (10 x 10 mm x 1 mm) • 10 x (10 x 10 mm x 1 mm) • nw on substrate: • 10 x 10 mm x 1 mm • 5 x (10 x 10 mm x 1 mm) • 10 x (10 x 10 mm x 1 mm) • n+ diode on “bfmoat” substrate: • 10 x 10 mm x 1 mm • 5 x (10 x 10 mm x 1 mm)

  6. n+ diode on native substrate: 50 x 10 mm x 1 mm • The highest responsitivity is obtained for the “n+ diode on native substrate” • This diode is not allowed by the CMOS8RF layout rules, however: • It behaves as a diode • It behaves well as a photo-detector • The DRC errors can be waived

  7. Dt = 50 ns P t 2 mm Test setup Tests done at: IXL institute in Bordeaux, France

  8. Test signal: Light pulse: l = 523 nm Duration: 50 ns Equivalent dose rate: Observable: Presence or not of an output pulse Duration of the output pulse Objective: Find the PROMP sensitivity in terms of the “equivalent dose rate” Procedure: Set the threshold current and scan the optical power to find the “dose rate” threshold or, Set the optical power and scan the threshold current to find the “dose rate” threshold Tests done at the IXL institute in Bordeaux, France Results: Two chip tested (time was short) Both functional Identical behaviour Circuit operational between 0.8 V to 1.5 V Efficient detection requires a minimum diode area of 50 x 50 mm2 Detects dose rates of 1 - 2 × 108 rd/s with threshold current of 0.7mA The most sensitive diode is the n+ diode on native substrate Test • During the tests the dose rate wasprobably over estimated by a factorof 4: • The circuit sensitivity is thus very likely 4 times better!

  9. Design guide lines • Objective: • Reliably detect a dose rate of 5 × 108 rd/s • Low threshold must be avoided: • Prevents “accidental” detection of substrate/power supply noise • Use the n+ diode in native substrate: • Highest efficiency • A dose rate of 5 × 108 rd/s with a threshold setting of 2.8 mA was reliably detected • During the measurements the dose rate was (very likely) over estimated by a factor of 4: • Sufficient margin to reliably detect the required dose rate! • The safety margin can be improved by increasing the area of the diode(diode sensitivity proportional to its area)

  10. “Evaluation – ASIC” • Will be made available for users’ tests: • Prompt dose sensitivity • SEU tolerance • Total dose tolerance • Noise tolerance • Package: • To be defined (open lead) • Contains the: • Prompt 2x: • 2 cells • Diode active area: 5000 mm2 • Physical size: 108 × 110 = 11880 mm2 • Threshold current:2.8 mA & 4.2 mA • Prompt 1x: • 2 cells • Diode active area: 2500 mm2 • Physical size: 54 × 110 = 11880 mm2 • Threshold current: 2.8 mA & 1.4 mA • Noisy bugger: • 4 cells • Reversed vias n+ diffusion • Active area (each): 5000 mm2

  11. “Evaluation – ASIC”

  12. Prompt cell layout – diode 2500 mm2 Photo diode Area: 2500 mm2 Transimpedance amplifier 192 mm Schmitt trigger Current reference & Bias 110 mm

  13. Prompt cell layout – diode 5000 mm2 Photo diode Area: 5000 mm2 262 mm Transimpedance amplifier Current reference & Bias Schmitt trigger 110 mm

  14. Summary • A circuit capable of detecting dose rates close to the 108 rad/s: • Designed • Fabricated • Successfully tested • The device contains • An integrated (photo) diode • A transimpedance amplifier/discriminator • The device takes: • Area: 262 × 110 mm2 • Power: ~550mW @ 1.5 V • It can be used to generate (e.g.) a: • Clock disable signal (digital) • Bias power off signal (analogue) • New ASIC submitted for fabrication • Evaluation ASIC • Users tests • Full characterisation: • SEU • Total dose • Substrate noise sensitivity Detailed report on the circuit and theexperimental tests is available: “PROMPT Tests Report” F. Faccio, A. Marchioro and P. Moreira 1. ITAR = International Traffic in Arms Regulations

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