OSL - CERN Indico
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Transcript OSL - CERN Indico
Active Dosimeters
Federico Ravotti
CERN TS-LEA
CEM2 – Montpellier University
Maurice Glaser, Michael Moll
CERN PH-TA1
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
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Introduction
1) 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).
2) Important to monitor separately TID, Feq and maybe Fth;
3) The best “dosimeter” for electronics is Silicon itself (or similar Zeff);
4) Accelerator environments are (t) Active (“on-line”) monitoring;
5) Monitoring is NOT ONLY for radiation damage survey.
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Active Radiation Monitors
TID (GySi)
mainly charged particles and photons
Feq
mainly fast hadrons
Forward
biased
p-i-n
diodes
RadFETs
Optically
Stimulated
Luminescence
(OSL)
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-2
(cm )
Reverse biased
PAD structures
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RadFETs General
(1) e-/h+ pair generation;
(2) e-/h+ pair recombination;
(3) e- (~psec) / h+ (~sec) transport;
(4) hole trapping;
(5) Interface state delayed buildup.
VGS
SiO2
iD
Fixed iD VGS growths TID
Si
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RadFETs Details
Dosimetric information kept stored;
2 wires, long-distance readout;
Sensitivity vs. Dynamic range is (dox);
“Saturation problems” can arise at
high Feq if oxide is not well chosen!
CERN-PH-EP-2004/045
Limited lifetime sensitivity loss
(saturation);
Dynamic range up to 100 kGySi;
Particle-dependent response:
proper calibration!
Several ways to reduce T influence;
“Drift-up” when switched on:
proper readout scheme!
“Neutron insensitive” devices.
Annealing and Interface States
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generation in oxides:
selection on SiO2 “quality”;
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RadFETs Selection
Procedure
Response to single radiation
Response to
and Room Temp. Annealing
some particle
fields and at high
Accelerated
procedure
based on the
scaling
annealing t
SiO2 “quality” evaluation
(Isochronal Annealing)
Response at Low Dose-
doses were
missing in
literature!
Rate in Mixed Environment
annealing T
Devices packaging options
TWO types recommended
for CERN purposes !
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Aim of the 2004
irradiation campaigns
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OSLs General
(collaboration with CEM2 – Montpellier University)
(1) e-/h+ pair generation and trapping;
(2) Infrared stimulation (800-1500 nm);
(3) Visible emission (500-700 nm).
Courtesy of L.Dusseau, CEM2
IR stimulation
Peak Amplitude increases
OSL
Photosensor
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linearly with TID
The readout completely reset
sec
the sensitive material!
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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.
Complicate fading behaviour;
The related sensor equipment for
active dosimetry must be radhard:
Main problem in the
development of this
Intrinsically neutron insensitive:
We make them sensitive!
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Long-distance readout with 5 wires;
technology at CERN!
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Neutron-sensitive OSLs
FACILITIES
NEUTRON
SPECTRA
IRRAD2 Facility
TRIGA Reactor
OSL+B
OSL+PE
First measurements
match very well the
facility spectra
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OSL “on-line” approaches
Integrated Space
sensor based on
COTS (Version 2)
“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).
Courtesy of J. R. Vaillé, CEM2
OSLs deposed
on “radhard”
photo-sensor & LED
Fibred
system
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Gain in sensitivity, reproducibility;
Gain in radiation hardness.
First prototype: 2.3 mV/cGy
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!)
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p-i-n & PAD General
Displacement damage in high r Si-base
Macroscopic effects both linear with Feq
FORWARD BIAS
Fixed iF voltage increase
VF
REVERSE BIAS
Chosen VR leakage current increase
iL
iF
Readout with fast pulse;
Sensitivity depends on:
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Injection level;
Base width (W).
VR
Readout under full depletion V;
Sensitivity depends on sensor
volume.
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p-i-n & PAD Details
FORWARD Operation
- vs. -
REVERSE Operation
Current pulse;
High voltage maybe needed.
2 wires, long-distance readout;
2 wires, more complicate read-out;
Feq range dependent on diode W;
Very wide Feq range;
Typically ~ 1.5 mV / 108÷1010 cm-2;
Typically ~ 2 nA / 1010 cm-2;
Strong T dependence;
Strong T dependence;
Relative low room T annealing;
Complex annealing behaviour;
Possible to use COTS!
Very reliable devices.
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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
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Thermal n detection
1) OSL doped with
10B:
+ n 7Li + a + g (s2200 = 3840 b);
10B
Dose deposition in OSL by low range reaction fragments.
More: Ravotti, Glaser, et al., RADECS 2004, CERN-PH-EP-2004/022
2) 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).
3) 100-mm layer Fission converter on Silicon:
235U
Very high LET fragments efficient discrimination in mixed field.
More: Rosenfeld, Kaplan, et al., Med. Phys. 26(9), pp. 1989, 1999
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+ n 140X + 95Y + 2n (s2200 = 580 b);
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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).
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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
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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
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