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Active Dosimeters

Active Dosimeters. Federico Ravotti CERN TS-LEA CEM 2 – Montpellier University Maurice Glaser, Michael Moll CERN PH-TA1. Outline. Introduction; T otal I onizing D ose ( TID ) measurement: Rad iation F ield E ffect T ransistors (RadFETs);

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Active Dosimeters

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  1. Active Dosimeters Federico Ravotti CERN TS-LEA CEM2 – Montpellier University Maurice Glaser, Michael Moll CERN PH-TA1

  2. Outline • Introduction; • Total Ionizing Dose (TID) measurement: • Radiation Field Effect Transistors (RadFETs); • Optically Stimulated Luminescent materials (OSLs); • 1-MeV neutron equivalent fluence (Feq) measurement: • p-i-n diodes & PAD structures; • Thermal neutrons detection (Fth); • Status Dec. 2004 & Conclusion. RADWG-RADMON Workshop Day, 01/12/2004

  3. Introduction • RADIATION DAMAGEScan be caused by: • Ionizing Energy Losses (IEL) Total Ionizing Dose (TID); • Non-Ionizing Energy Losses (NIEL) 1-MeV neutron eq. fluence (Feq). • Important to monitor separately TID, Feq and maybe Fth; • The best “dosimeter” for electronics is Silicon itself (or similar Zeff); • Accelerator environments are (t) Active (“on-line”) monitoring; • Monitoring is NOT ONLY for radiation damage survey. RADWG-RADMON Workshop Day, 01/12/2004

  4. Active Radiation Monitors Feq (cm-2) TID (GySi) mainly fast hadrons mainly charged particles and photons Forward biased p-i-n diodes RadFETs Optically Stimulated Luminescence (OSL) Reverse biased PAD structures RADWG-RADMON Workshop Day, 01/12/2004

  5. RadFETs General • e-/h+ pair generation; • e-/h+ pair recombination; • e- (~psec) / h+ (~sec) transport; • hole trapping; • Interface state delayed buildup. VGS iD SiO2 Fixed iD  VGS growths  TID Si RADWG-RADMON Workshop Day, 01/12/2004

  6. RadFETs Details • Dosimetric information kept stored; • 2 wires, long-distance readout; • Sensitivity vs. Dynamic range is (dox); • Dynamic range up to 100 kGySi; • Several ways to reduce T influence; • “Neutron insensitive” devices. • “Saturation problems” can arise at high Feqif oxide is not well chosen! • CERN-PH-EP-2004/045 • Limited lifetime  sensitivity loss (saturation); • Particle-dependent response: • proper calibration! • “Drift-up” when switched on: • proper readout scheme! • Annealing and Interface States generation in oxides: • selection on SiO2 “quality”; RADWG-RADMON Workshop Day, 01/12/2004

  7. RadFETs Selection Procedure Response to some particle fields and at high doses were missing in literature! Response to single radiation and Room Temp. Annealing Accelerated procedure based on the scaling annealing t Û annealing T SiO2 “quality” evaluation (Isochronal Annealing) Response at Low Dose-Rate in Mixed Environment Aim of the 2004 irradiation campaigns Devices packaging options TWO types recommended for CERN purposes ! RADWG-RADMON Workshop Day, 01/12/2004

  8. OSLs General (collaboration with CEM2 – Montpellier University) • e-/h+ pair generation and trapping; • Infrared stimulation (800-1500 nm); • Visible emission (500-700 nm). SrS:Ce,Sm Courtesy of L.Dusseau, CEM2 IR stimulation Peak Amplitude increases linearly with TID OSL The readout completely reset the sensitive material! Photo- sensor sec RADWG-RADMON Workshop Day, 01/12/2004

  9. OSLs Details • Sensitivity from 10 mGy to 102 Gy; • Infinite lifetime (readout = reset); • Zeff (~ 30) close to electronics; • Response NOT particle-dependent; • Different ways to built an OSL-based active dosimeter. • Intrinsically neutron insensitive: • We make them sensitive! • Long-distance readout with 5 wires; • Complicate fading behaviour; • The related sensor equipment for active dosimetry must be radhard: Main problem in the development of this technology at CERN! RADWG-RADMON Workshop Day, 01/12/2004

  10. Neutron-sensitive OSLs FACILITIES NEUTRON SPECTRA OSL+B OSL+PE IRRAD2 Facility TRIGA Reactor First measurements match very well the facility spectra RADWG-RADMON Workshop Day, 01/12/2004

  11. OSL “on-line” approaches • “sandwich” LED / OSL / photo-sensor; • LED current electronically controlled; • Optimized for long-distance readout; • Hardness in n field under investigation: (tested for e,p up to Feq=1011 cm-2). 3 cm x 1.5 cm Integrated Space sensor based on COTS (Version 2) Courtesy of J. R. Vaillé, CEM2 • Gain in sensitivity, reproducibility; • Gain in radiation hardness. • First prototype: 2.3 mV/cGy OSLs deposed on “radhard” photo-sensor & LED • 2 fibers inside 20m x  4mm2 pipewith OSL at one end; • Stimulation = Laser 1060 nm; Light detection = PM. • Less radhard constraints (PM/Laser not exposed!) Fibred system RADWG-RADMON Workshop Day, 01/12/2004

  12. p-i-n & PAD General Displacement damage in high r Si-base Macroscopic effects both linear with Feq FORWARD BIAS Fixed iF voltage increase REVERSE BIAS Chosen VR leakage current increase VF iL iF VR • Readout with fast pulse; • Sensitivity depends on: • Injection level; • Base width (W). • Readout under full depletion V; • Sensitivity depends on sensor volume. RADWG-RADMON Workshop Day, 01/12/2004

  13. p-i-n & PAD Details FORWARD Operation - vs. -REVERSE Operation • High voltage maybe needed. • 2 wires, more complicate read-out; • Very wide Feq range; • Typically ~ 2 nA / 1010 cm-2; • Strong T dependence; • Complex annealing behaviour; • Very reliable devices. • Current pulse; • 2 wires, long-distance readout; • Feq range dependent on diode W; • Typically ~ 1.5 mV / 108÷1010 cm-2; • Strong T dependence; • Relative low room T annealing; • Possible to use COTS! RADWG-RADMON Workshop Day, 01/12/2004

  14. Commercial p-i-n diodes Commercial (thin base) BPW34F Feq = 2x1012 4x1014 cm-2 3 – USE CUSTOM-MADE DEVICES Low Flux irradiation in PS-T7 2004 (Max Feq = 2x1012) 2 – STUDY BPW34F RESPONSE AT DIFFERENT INJECTION LEVELS! 1 – PERFORM PRE-IRRADIATION ON BPW34F Low Flux irradiation in PS-T7 2004 RADWG-RADMON Workshop Day, 01/12/2004

  15. Thermal n detection • OSL doped with 10B: • 10B + n  7Li + a + g (s2200 =3840 b); • Dose deposition in OSL by low range reaction fragments. • More: Ravotti, Glaser, et al., RADECS 2004, CERN-PH-EP-2004/022 • Damage in npn bipolar transistors: • Boron is usual dopant in p-type Si; • Fragment produce bulk damage in transistor base; • Increase of ib for fixed ic  Dib = kth· Fth+ keq·Feq • More: Mandic, Kramberger, et al., ATLAS-IC-ES-0017 (EDMS 498365). • 100-mm layer Fission converter on Silicon: • 235U + n  140X + 95Y + 2n (s2200 = 580 b); • Very high LET fragments  efficient discrimination in mixed field. • More: Rosenfeld, Kaplan, et al., Med. Phys. 26(9), pp. 1989, 1999 RADWG-RADMON Workshop Day, 01/12/2004

  16. Status Dec. 2004 • RadFETs: 9 devices from 4 producers tested: We recommend two types of RadFETs for low (100mGy ÷ 10 Gy) and high (1 cGy ÷ 10 kGy) dose ranges; • OSLs: Need some more development for use as radhard active dosimeter; • p-i-n diodes: • COTS devices:ready to be used, some optimization needed; • Custom-made devices:ready to be used; • PAD structure: • Dedicated batch of devices to be produced; • Thermal neutron detectors: • OSL and diodes with fission converter: working principle shown; • npn bipolar transistorsready to be used (ATLAS). RADWG-RADMON Workshop Day, 01/12/2004

  17. Conclusion • Several techniques for the ACTIVEmonitoring of the TID, FeqandFth have been presented; • All presented devices are reliable and were characterized in various radiation fields; • Most of them are commonly used in Medicine and Space: customization and calibration for CERN applications needed; • ACTIVE monitors are also PASSIVE dosimeters (don’t forget it !!) More on: http://cern.ch/lhc-expt-radmon & http://www.cern.ch/irradiation RADWG-RADMON Workshop Day, 01/12/2004

  18. Acknowledgments Pr. L. Dusseau, J.R. Vaillé and all the team of the “Electronic and Radiation research Laboratory” at the CEM2, Montpellier University, France; I. Mandić, G. Kramberger, M. Mikuž from JSI, Ljubljana, Slovenia; A.G. Holmes-Siedle (REM, UK), G. Sarrabayrouse (CNRS-LAAS, France), A. Rosenfeld (CMRP, Australia); C. Joram, E. Tsesmelis and all the personnel of the PH-Bonding Lab (CERN); All the operators of the CERN-PS accelerator for their assistance during the experiments. RADWG-RADMON Workshop Day, 01/12/2004

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