Fast response to short-pulse optical excitation in
intrinsic and Ce-doped garnet scintillators
G. Tamulaitis, A. Augulis, V. Gulbinas,
S. Nargelas, E. Songaila, A. Vaitkevicius,
Vilnius University, Lithuania
E. Auffray,
M.T. Lucchini
CERN
M. Korjik, A. Borisevich,
A. Fedorov, V. Mechinsky,
Research Institute for
Nuclear Problems, Minsk,
Belarus
Task 14.2
Test infrastructure for innovative calorimeters with optical readout
Outline
•
•
•
•
•
•
Motivation
Experimental
Photoluminescence in PWO
Photoluminescence in GAGG:Ce
Conclusions
Outlook
TARGET:
To develop a test station for the characterization of timing properties of scintillators
TARGET:
To develop a test station for the characterization of timing properties of scintillators
OBJECTIVES:
Fast optical response in
scintillators
Novel principles of
optical readout
TARGET:
To develop a test station for the characterization of timing properties of scintillators
OBJECTIVES:
Fast optical response in
scintillators
Novel principles of
optical readout
RESULTS:
Two-photon absorption. Significant
and sensitive to irradiation in PWO,
weak in garnets.
Main
publications:
E.Auffray et al., NIMA, 804, 194 (2015)
TARGET:
To develop a test station for the characterization of timing properties of scintillators
OBJECTIVES:
RESULTS:
Main
publications:
Fast optical response in
scintillators
Photoluminescence rise time.
In subpicosecond domain in
PWO and YAGG:Ce,
nanoseconds in GAGG:Ce
Free carrier absorption. Fast in
PWO and YAGG:Ce, strong
influence of Gd sublattice on
hole dynamics in GAGG:Ce.
E.Auffray et al., available online
in J. Lumin.
E.Auffray et al., submitted to
Optical Materials
Novel principles of
optical readout
Two-photon absorption. Significant
and sensitive to irradiation in PWO,
weak in garnets.
E.Auffray et al., NIMA, 804, 194 (2015)
Setup for study of
nonlinear absorption
(pump and probe, two-photon
absorption, free carrier
absorption, light-induced transient
grating techniques)
Time-resolved photoluminescence spectroscopy
EXCITATION:
DETECTION:
Hamamatsu streak camera.
FWHM of the instrumental
response function : 2.95 ps
Yb:KGW oscillator (Light Conversion Ltd.)
emitting at 1030 nm
80 fs pulses at 76 MHz repetition rate.
Harmonics generator
(HIRO, Light Conversion Ltd.);
the third 343 nm (3.64 eV)
and fourth 254 nm (4.9 eV) harmonics
New results on
photoluminescence
in PWO
New features have been discovered 20 years after the material
approval for collider experiments!
PWO
PWO
-10
-5
0
5
10
15
20
Time (ps)
Initial stage of spectrally integrated photoluminescence kinetics (dots),
the instrumental response function (green line), and
the best fit obtained using a bi-exponential decay function (red solid line)
The rise time is below
the time resolution
at the instrumental
response function with
FWHM of 2.95 ps
Luminescence intensity (arb. units)
Luminescence intensity (arb. units)
Luminescence kinetics
@254 nm
PWO
103
102
@343 nm
1
10
350
400
450
500
550
Wavelength (nm)
600
650
Both regular WO42- and defectrelated WO3 luminescence centers
show subpicosecond leading edge
of the luminescence transient
Luminescence intensity (arb. units)
PWO
PWO
@254 nm
Decay times:
1 = 3.8 ps and 2 = 683 ps @ 343 nm exc.
1 = 5.9 ps and 2 = 824 ps @ 254 nm exc.
0
200
400
600
Time (ps)
Initial part of photoluminescence kinetics at 343 nm
excitation (blue line) and 254 nm excitation with pulse
energy of 15 mJ/cm2 (red solid line) and 1.5 mJ/cm2
(green dotted line).
Both at 343 nm and 254 nm excitation,
the kinetics of luminescence
within 400-500 nm and 500-600 nm
are identical
Intensity
@343 nm
10
3
10
2
10
1
10
0
0-10ps
50-150ps
400
500
600
700
 (nm)
The fast components observed open new
opportunities for fast timing with PWO!
Photoluminescence
in GAGG:Ce
GAGG:Ce
Luminescence spectra
at two excitation wavelengths
EXCITATION
100
GAGG: Ce
Absorbance (d)
3.0
2.5
80
60
2.0
1.5
1.0
40
20
0.5
200 250 300 350 400 450 500 550 600
Wavelength (nm)
0
Transmittance (%)
3.5
Luminescence intensity (arb. units)
4
10
GAGG: Ce
3
10
@343 nm
2
10
1
10
@254 nm
0
10
400
500
600
700
800
Wavelength (nm)
At the same excitation pulse energy and absorption coefficient ,
PL intensity is considerably lower after predominant excitation of Gd3+ ions 
nonradiative recombination during the excitation transfer to radiative
recombination centers is important
GAGG:Ce
Luminescence intensity (arb. units)
Photoluminescence kinetics
GAGG: Ce
@343 nm
@254 nm
The instrumental function
with FWHM of 100 ps
0
10
20
30
40
Time (ns)
Luminescence intensity (arb. units)
Two rise components:
• Shorter than the instrumental
response function;
• Slow component with with the rise
time of
8 ns @ 254 nm exc.
2.5 ns @ 343 nm exc.
50
60
This is in consistence with the 2 ns rise time
observed in GAGG:Ce under gamma
irradiation [M.T. Lucchini et al., NIMA, 816,
176 (2016)].
GAGG: Ce
100
@254 nm
@343 nm
• PL decay is monoexponential
• Decay times: 60 ns at 254 nm and 70 ns at 343 nm
10-1
10-2
50
100
150
Time (ns)
200
250
Conclusions
• An experimental setup enabling the study of fast processes in
scintillators in sub-picosecond domain is developed.
• A sub-picosecond rise time of luminescence in intrinsic PWO
scintillation crystal is demonstrated.
• Three luminescence components are revealed in PWO. In addition to
the decay component with the decay time of ~10 ns, fast and
intermediate components with decay times of 4-6 ps and 600-800 ps
have been observed.
• The rise of the luminescence response to short pulse excitation in
GAGG:Ce takes several nanoseconds even at the direct resonant
excitation of Ce3+ ions.
• This feature is explained by the position of the excited Ce3+ levels in
the conduction band.
• The luminescence response time is influenced by the capture of
nonequilibrium carriers by matrix-building Gd3+ ions.
Outlook
• Combining our optical test bench with pulsed X-ray tube will be very
important for future study of fast phenomena in scintillators;
• We are seeking for collaborators for this combination and additional funds
to get a ns pulse X-ray tube, which is commercially available.
• Combining the optical test bench and X-ray tube will enable us to study:
- fast processes under the conditions of ionization;
- fast processes in inorganic and organic scintillators;
- fast processes in semiconductors including wide-band-gap diamond.