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

RADWG-RADMON Workshop Day, 01/12/2004 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. F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

RADWG-RADMON Workshop Day, 01/12/2004 Introduction RADIATION DAMAGES can 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. F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

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

RadFETs General VGS iD Fixed iD  VGS growths  TID 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 F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

RADWG-RADMON Workshop Day, 01/12/2004 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 Feq if 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”; F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

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 Devices packaging options Aim of the 2004 irradiation campaigns TWO types recommended for CERN purposes ! F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

Peak Amplitude increases linearly with TID 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 F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

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! F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

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

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 pipe with OSL at one end; Stimulation = Laser 1060 nm; Light detection = PM. Less radhard constraints (PM/Laser not exposed!) Fibred system F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

p-i-n & PAD General VF iL iF VR 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. F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

p-i-n & PAD Details FORWARD Operation - vs. - REVERSE Operation 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! 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. F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

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 F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

RADWG-RADMON Workshop Day, 01/12/2004 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 F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

RADWG-RADMON Workshop Day, 01/12/2004 Status Dec. 2004 RadFETs: 9 devices from 4 producers tested: We recommend two types of RadFETs for low (100m Gy ÷ 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 transistors ready to be used (ATLAS). F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

Conclusion Several techniques for the ACTIVE monitoring of the TID, Feq and Fth 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 F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004

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. F.Ravotti RADWG-RADMON Workshop Day, 01/12/2004