1. Radiation Monitoring Technologies for the LHC
Active Radiation Monitors
RadFETs;
OSLs;
p-i-n diodes;
Passive Radiation Monitors
Federico Ravotti
(TS-LEA-CMS)
Maurice Glaser
(PH-TA1-SD)

2. Active Radiation Monitors
RadFETs
Build-up of charge in MOSFETs SiO2 layer (Ionizing Dose)
 (integrating measurement).
p-i-n diodes
Bulk damage in high r Si-base
(particle fluence)
 (integrating measurement).
Optically Stimulated
Luminescence (OSL)
Charge buildup in sensitive material detrapped by IR stimulation (Ionizing Dose)
 (instantaneous measurement).
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

3. RadFETs General Sthreshold ~ 1 cGy; S decreasing over ò.
e-/h+ pair generation;
e-/h+ pair recombination;
e- (~psec) / h+ (~sec) transport;
hole trapping;
Interface state delayed buildup.
g responses for different tox
Build-up of charge in SiO2
increase of the p-MOS Threshold Voltage  integrated Dose Measurement
Sthreshold ~ 1 cGy; S decreasing over ò.
Sub-linear
Responses
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

4. RadFETs Details DVth= ¦ (particle type, energy, incidence angle, ..);
MOS exposed in “zero bias” mode;
(2-wires only readout, bigger dynamic range)
Long-distance readout of Vth after IDS bias (seconds time-scale);
Operation at MTC: if T ~ constant, correction it is not needed;
Good reproducibility of the results  producer selection.
DVth= ¦ (particle type, energy, incidence angle, ..);
DVth= ¦ (packaging) in neutron field.
 Care has to be taken in the choice of the proper calibration & packaging for a neutron/HEP enriched radiation environment!
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

5. LHC Exp. RadMon Working Group 06/04/2004
RadFETs at CERN
g-ray calibrations (“zero bias” mode) from producers & measured at CERN
Bare die chips ~ 1-2 mm2 dimension !
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

6. RadFETs Instabilities
“Read-time” instability (“Drift-up”)  during readout, small error (< 5 %) avoided by fixing the readout protocol.
Trapped charge annealing  prompt time-scale (i.e. hours), can induce big errors especially at LDR (> 20 % in a few hrs).
Interface states generation  delayed time-scale (i.e. years), can strongly affect the devices long-time behaviour.
Devices have to be selected on the basis of their annealing behaviors  Isochronal Annealing
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

7. LHC Exp. RadMon Working Group 06/04/2004
RadFETs Isochrones
Regular behaviours
Scaling annealing t Û annealing T;
Annealing periods at increasing T;
Charge annealing is oxide (i.e. manufacture) dependent;
Simple and quick way to identify not suitable behaviours;
Informations about charge spectrum in SiO2.
Data from CERN & CEM2 - Montpellier
Not suitable behaviours
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

8. OSLs General Sthreshold = 100 mGy;
(collaboration between CERN and CEM2 – Montpellier University)
e-/h+ pair generation and trapping;
Infrared stimulation ( nm);
Visible emission ( nm) µ Dose;
24 GeV/c protons (IRRAD1)
After L.Dusseau
Material used at CERN: SrS doped
The readout completely reset the sensitive material !
Linear response
(< 100 Gy)
Sthreshold = 100 mGy;
S dependent on readout electronics.
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

9. LHC Exp. RadMon Working Group 06/04/2004
OSLs Details
Radiation independent response (X, g, p, p, e, ..);
OSL materials characterized with off-line measurements (test bench);
Readout process takes seconds;
Very low fading at room temperature (to be verified);
Pure OSL does not suffer radiation damage;
OSL Test bench
n-OSL tested for the first time: first campaign with 5 mm2 samples performed in 2 different neutron environments.
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

10. Neutron-Sensitive OSLs 1
OSLs with enhanced neutron-sensitivity:
10B(n,a)7Li  Thermal neutrons
1H(n,p)1H  Fast neutrons
OSL pure
OSL+PE
OSL+B
OSL+PE+B
The pure OSL material is sensitive to the Ionizing radiation only;
The n-OSLs show a 20-times increased sensitivity.
Boron doping affects fading behaviour ?
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

11. Neutron-Sensitive OSLs 2
89 %
CERN-PS
IRRAD2
Facility
(FLUKA)
99 %
1 %
11 %
Ljubljana Reactor
- Activation measurements -
Thermal
Fast
CERN OSL
3 %
97 %
Ljubljana OSL
87 %
13 %
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

12. OSL on-line approaches
OSLs deposed on GaAsP photodiodes
OSL+B
OSL
OSL pure
Designed for Space
Intl. Space Station,
CUBESAT / PROBA2
(50 mGy – 100 Gy)
3 cm x 1.5 cm
OSL material + Radhard electronics
= RADHARD INTEGRATED SENSOR
OSL+Paraffin
Support for off-line readout
Optical-Fiber system
The sensor works in HEP environment
(CERN PS-IRRAD1)
OSLs at the edge of a long optical fiber  LED/PD not damaged by radiations.
2003
2004
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

13. p-i-n diodes General Forward bias operation:
Displacement damage in high r Si-base;
Macroscopic Effects:
Resistivity increase µ F (forward bias);
Leakage current increase µ F (reverse bias);
Forward bias operation:
Fast current pulse (~ms), VF on-line readout over long-distances (2-wires);
Sensitivity = ¦ (w ):
w =1.2 mm  S ~ 1 mV / 108 cm-2 ; Frange = 108 ÷ 1012 cm-2 (Feq)
w = 0.3 mm  S ~ 1.5 mV / 1010 cm-2; Frange = 1012 ÷ 1014 cm-2 (Feq)
Commercial diodes BPW34F characterized in 2003.
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

14. BPW34F Osram diodes Response Curve High-fluence measurements:
(CERN-PS IRRAD1 & IRRAD2 facilities)
High-fluence measurements:
- Linear behaviour (Feq):
1.0x1012 ÷ 4.0x1014 cm-2
- Sensitivity (Feq):
1.5 mV / 1010 cm-2
Strong T dependence:
Tc = -5 %·ºC-1;
Thermal annealing:
< 10 % in the first 14 days.
(preliminary)
Max DT over irradiations: ± 0.83 ºC
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

15. “Pad” structures Reverse bias operation:
Off-line measurements after
annealing (4 min 80 ºC)
Reverse bias operation:
(see next presentations)
ST, Italy “Pad structure” of 0.25 cm2 for bulk damage studies;
Off-line characterization;
Very wide fluence range;
Complex Annealing behaviour;
Possible “on-line” implementation for high-sensitivity fluence measurements
After M.Moll
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

16. Passive Radiation Monitors
Polymer-Alanine (PAD) & Radio-Photo Luminescent (RPL) Dosimeters:
Calibration campaign 2003 in the mixed g/n field of CERN-PS IRRAD2 facility
Formation of stable free radicals/color center
after irradiation;
Readout by
CERN SC/RP (“TIS”);
Well known dosimetry systems.
[NIM-B 83 (1993) pp ]
Gafchromicâ Sensitive Films
Formation of a stable dye polymer after
irradiation;
Optical readout (color density);
Different sensitivities/ranges
24 GeV/c protons (HD-810)
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

17. LHC Exp. RadMon Working Group 06/04/2004
Summary
RadFETs:
Responses in HEP/n environments fully characterized. Isochronal annealing studies are ongoing with setup in Lab. 14-R-012.
OSLs:
Responses HEP fully characterized. Neutron-sensitive materials under development.
Annealing studies & test on new on-line configurations are planned.
BPW34F:
Particle responses fully characterized. More on Annealing & readout procedure.
Pad Structures:
Particle responses well known. Looking forward for an “on-line” readout.
Passive Monitors:
Daily used in the operation of the CERN-PS Irradiation Facilities.
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

18. LHC Exp. RadMon Working Group 06/04/2004
and finally …
More on …
p-i-n diodes; RadFETs HEP/n responses, packaging dependence, annealing & instabilities:
CERN Technical Note EST/LEA/ , July 2003 (EDMS No )
RadFETs fast-neutron response: Paper in preparation for NSS Rome, 2004
Special neutron-sensitive OSLs:
Paper submitted to RADECS Madrid, 2004 & CERN Preprints collection
Integration Issues:
CERN-PH-EP , February 2004 (Presented at NSREC Atlanta, 2004)
Passive technologies, PS Irradiation facilities:
Acknowledgments …
- M. Moll, C. Joram, E. Tsesmelis from CERN; L. Dusseau, J R. Vaillé from CEM2 - Montpellier University;
- G. Sarrabayrouse (CNRS, France), A. Holmes-Siedle (REM, England) for their support in RadFETs studies;
- I. Mandic and M. Mikuz from the Josef Stefan Institute, Ljubljana, Slovenia.
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

19. Neutrons Cross-sections
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004

20. Readout parameters F.Ravotti LHC Exp. RadMon Working Group 06/04/2004
Active Dosimeter
External bias
Readout Input
Pre-irradiation output
After irradiation output
Reference Val.
RadFETs
not needed
DC i = 10 mA ÷ 160 mA depending on MTC
1 V to 3 V depending on tox
~ 10 V (1.6 mm) ~ 4 V (0.25 mm)
100 Gy
~ 41 V (0.25 mm)
100k Gy
OSLs (2003 sensor)
± 5V (on-board electronics)
10-15 sec DC stimulation on LED with i = 50 mA
noise ~ 200 mV with Gout=10
~ 2 V with Gout=10
BPW34F (w ~ 300 mm)
Fast pulse (180 ms) with Forward i = 1 mA
0.5 V
~ 50 V (linear operation)
4.x1014 cm-2 (Feq)
Pad structures
Leakage current at full depletion V = 100 V ?
~ nA order
~ mA order
1014÷ 1015 cm-2 (Feq)
PT100 Temp Probe
DC i = 1 mA
0.1 V (0 ºC) #
F.Ravotti
LHC Exp. RadMon Working Group 06/04/2004