Prototype Calorimeter for Relativistic Radioactive Beam Studies

Martín Gascón                                                           Santiago de Compostela, December 10 th
, 2010   1/34
                           Motivation        Characterization                  Inbeam tests
Prototype of a new calorimeter for the studies of nuclear
reactions with relativistic radioactive beams
Santiago de Compostela                                                    10th. December, 2010
Martín Gascón

, 2010   2/34
MotivationMotivation
FAIR, R3
B, CALIFA, ProtoZero (CALIFA's prototype)
Characterization of CsI(Tl) crystals and photosensorsCharacterization of CsI(Tl) crystals and photosensors
Photosensors
Benchtests on small and prototype crystals
Inbeam tests of the prototype Inbeam tests of the prototype and prototype simulationsand prototype simulations
Results of the proton beam test
Results of the gamma beam tests
ConclusionsConclusions

, 2010   3/34
FAIR: Facility for Antiproton Ion Research
New accelerator facility in Darmstadt (Germany)
Antiprotons, stable and radioactiveion beams
Primary intensity: (1012
ions/s)@ 230 GeV/u
Nuclear structure and Astrophysics with exotic nuclei
Antiproton Physics
Relativistic heavy ions collisions
Atomic and Plasma Physics
Motivation
FAIR                 R3
B               CALIFA             ProtoZeroFAIR
Scientific Program
FAIR

, 2010   4/34
R3
B: Reactions with Relativistic Radioactive Beams
  Calorimeter / gamma spectrometer
  Silicon arrays around target for recoils
  Large acceptance superconducting dipole
  High resolution neutron detectors
  ToF wall for chargedparticle id.
  High resolution magnetic spectrometer
Motivation
FAIR                 R3
B               CALIFA             ProtoZeroR3
B
R3B experimental subjects
Detectors
Challenging research program including QFS,
knockout,  fragmentation,  fission, ...
  Nuclear structure far from stability
  Reactions of astrophysical interest
  Study of the EOS of asymmetric matter

, 2010   5/34
CALIFA requirements (R3B LoI, 2005) :

CALIFA: CALorimeter for InFlight emitted gAmmas
Motivation
FAIR                 R3
B               CALIFA            ProtoZeroCALIFA
Gamma sum energy
Gamma multiplicity
Gamma energy resolution
Calorimeter for high energy light charged particles Up to MeV in Lab system300
Good lightcharged particles energy resolution
(Esum
)/<Esum
> < 10%
(N)/<N> < 10 %
< 5 % E/E (gammas at 1 MeV)
Total absortion efficiency 80 % (up to ESRF
= 5 MeV)
< 1%  p/Ep (protons at 300 MeV)
H. Álvarez-Pol et al. Nucl. Inst. and Meth. B 266 (2008) 4616-4620
  To fulfill all these requirements is a challenge that
gives CALIFA its unique characteristics.
  This challenge is even greater if we take into account
the constraints imposed by experiments with relativistic
ions in inverse kinematics.

, 2010   6/34
CALIFA: Geometry
Motivation
  Gammas emitted by moving sources at relativistic energies suffer the relativistic
Doppler Effect.
  Calculation of their energy in the Source Reference Frame (SRF) requires an
accurate measurement of both the Lab energy (LRF) and the emission polar angle.
A limited polar angle resolution
would contribute to the uncertainty
of the gamma energy in SRF
Doppler Effect Constraint
Doppler factor as a
function of the polar
angle.
Angular distribution of gammas in the LRF
Detector design
The optimal polar angle granularity to guarantee the required
energy resolution should be determined
  Totalabsorption efficiency requirement is determined by the
length of the scintillating material and dead volume (empty space
and material as wrapping and support structures)
FAIR                 R3

, 2010   7/34
What scintillating material ?
Motivation
               CsI(Tl) emission spectrum
CsI(Tl)
Advantages
well known properties
relatively high density
high light yield
cheap to make, easy to handle
slightly hygroscopic
good energy resolution with
APDs
Inconvenient
Long scintillating decay time
NaI(Tl) CsI(Tl) CsI(Na) BGO LYSO PWO CsI (pure)
5.29 3.86 3.67 4.51 4.51 7.13 7.1 8.29 4.51
63000 49000 39000 60000 45000 9000 32000 100 16800
< 3% 3.5% 7% 6% 7.5% 10% 7.1% >10% 7.5%
N/A N/A 3.8% 4.9% N/A 8.3% N/A N/A 4.3%
380
350 310 fast
550 420 480 420 420 315
430 415
25 25/213 620 fast 1000 630 300 41 6 35/6
Hygroscopic yes yes yes slightly yes no no no slightly
Cost (per cm3) $30 $30 $2 $5 $5 $9 N/A $2 $5
LaBr3
LaCl3
Density (g/cm3
)
Light Yield (ph/MeV)
E/E 662 keV (PMT)
E/E 662 keV (APD)
Peak(nm)
Fast Decay (ns)
FAIR                 R3
              APD quantum efficiency

, 2010   8/34
CsI: what length?
Three different crystal sets
were evaluated in
simulations for the
CALIFA calorimeter
Barrel specifications
short:       9 12 cm
medium: 1115 cm
large:      1418 cm
Motivation
Conclusions
  The geometrical efficiency was higher than 80% for large and medium specifications
  The fullenergy peak efficiency decreased from 70% (0.5 MeV) to 50 % (10 MeV)
  Crystal Multiplicity goes from 2 crystals (0.5 MeV) to 7 (10 MeV) for the whole calorimeter. It can
reach 9 crystals in the Endcap, and it is limited to 4 crystals in the Barrel due to the Lorentz Boost
  Energy resolution contribution due to polar angle uncertainty is below 3%
Geometrical efficiency Several observables were studied to define the crystal geometry
FAIR                 R3

, 2010   9/34
ProtoZero: Design and construction
Crystal sample corresponding to ~ 90º polar angle
APDs tested in this prototype
15/16 bi frustumshaped CsI(Tl) crystals
15/16 LAAPDs (7x14 mm    2
, 10x10 mm 2
an
d 10x10 2ch)
16 preamplifiers (Cremat, Mesytec)
ProtoZero
Motivation
FAIR                 R3
B               CALIFA            ProtoZeroProtoZero

, 2010   10/34
Motivation
FAIR, R3
Characterization of CsI(Tl) crystals and photosensorsCharacterization of CsI(Tl) crystals and photosensors
Photosensors
Inbeam tests of the prototype and prototype simulations
Characterization

, 2010   11/34
Test with small samples: APDs vs. PMTs
CsI(Tl) + APD CsI(Tl) + PMT
    Crystal Length cm1 cm5 cm10
XP1901
PMT XP1918
XP3102
7.0±0.1 8.4±0.1 12.8±0.1
6.1±0.1 7.4±0.1 10.7±0.1
9.1±0.1 9.9±0.1 16.5±0.2
ER at 662 keV for a 1 cm3
CsI(Tl)  coupled to  a S86641010 APD and to a Photonis XP1918 PMT for 8 s shaping time.
Characterization
Shaping                Crystal Length
time 1 cm 5 cm 10 cm
4.68±0.12 5.11±0.12 4.74±0.12
4.42±0.12 4.87±0.09 4.72±0.08
4 s
8 s
Energy resolutions in % (FWHM) (at 662 keV)
obtained for different PMTs and different crystal
lengths at 4 s shaping time
Best energy resolution values in % (FWHM)
(at 662 keV), obtained for different crystal
sizes using a Hamamatsu S86641010 APD.
M. Gascón et al., IEEE Trans. Nuc. Sci 55 (2008) 1259-1262

, 2010   12/34
APD characterization
Procedure to compare different APD series and to disentangle the APD contribution to the energy resolution
Characterization
The APD contribution to the energy resolution was found to be 0.12% for the 10x10 APD.
These LAAPDs were proven to work properly in a wide dynamic range
M. Gascón et al, IEEE Trans. Nuc. Sci 57 No. 3 (2010) 1465-1469

, 2010   13/34
APD # A.A. Cap. LPR
1 10x10 std 406 5.2% 20
2 10x10 std 404 5.4% 22
3 10x10 std 410 5.3% 8
4 10x10 std 411 5.5% 7
5 7x14 std 332 7.2% 23
6 7x14 std 322 8.1% 23
7 7x14 std 332 8.7% 32
8 7x14 std 333 9.2% 39
9 7x14 low 491 7.5% 24
10 7x14 low 484 8.0% 30
11 7x14 low 493 8.2% 31
12 7x14 low 492 9.8% 32
Cap=Capacitance
O.Vb ID
(nA)
A.A.=active area (mm2
)
O.Vb = Optimal bias voltage (Volts)
LPR = Light pulse resolution @ 5.105
eh
Characterization
   The best performance was found for the 10x10 Hamamatsu APDs

, 2010   14/34
APDs: Bias voltage and gain curves
Left: Energy resolution (Cs137) vs. bias voltage for a 5 cm long crystals  coupled to Hamamatsu S86641010 APDs.
Right: Typical gain curves of the S86641010 APD using  5 cm length CsI(Tl) crystals.
Conclusions
Gain variation smaller than 1%
can only be achieved with bias
voltage variations below 350 mV
Relative gain variation due
to bias voltage variation at
optimal bias voltage for
CsI(Tl) crystals coupled to
S86641010 APDs
Characterization
Crystal length Gain variation (%/V)
1 cm
5 cm
10 cm
2.84 ± 0.01
2.83 ± 0.01
2.83 ± 0.01

, 2010   15/34
APDs: Temperature drifts
(dM/dT)M1
= 2.8 %/ºC
compares well with the 2.5 %/ºC
provided by Hamamatsu
Characterization
APD Gain Drift  at RT
Mean Peak position and Temperature vs. time.
Total and gain drift corrected
spectra for a 137
Cs radioactive
source.
A PT1000 probe was placed near the
APD to get the temperature information
  The detectors  were cooled down using
LN2 vapor and warmed up by a heater
Experimental setup

, 2010   16/34
Test with prototype samples: crystal quality and optical coupling
Photograph of raw crystal samples from five providers.   P1P5:  Amcrys, Hilger Lanzhou, Saint Gobain, Scionix
Characterization
Crystal quality
Optical coupling
  For temporary bonds:  optical grease, and optical pads.
  For permanent bonds:  Scionix RTV 681 optical cement
  The result was found to be strongly dependent on details of the
contact, such as the amount of optical grease used, homogeneity or
the presence of air bubbles
Optical cement and optical greases
  The crystal quality depends on a set of factors such as
transparency, surface treatment, polishing, and cutting edges.
  The samples with the best quality in the visual inspection did
not necessarily provide the best values for energy resolution and
lightoutput

, 2010   17/34
Test with prototype samples: crystal wrapping
Averaged Lightpulse resolutions
(FWHM) obtained using a LED
with different 10x10 mm2
exit face
crystals and different wrapping
configurations, coupled to an
XP5A08 PMT without optical
grease. 1x,2x,3x,6x are the number
of layers of 75 m Teflon tape
  The ideal wrapping has not only to reflect
the incident light but also to break up internal
reflections and preferentially direct reflected
light towards the photosensor.
  Best results for prototype crystals are
generally achieved with 2 layers of ESR (2x
65 m thickness)
Characterization
Conclusions
Setup for determining the optimal wrapping configuration for prototype crystals.
Wrapping configuration for prototype crystals
Wrapping L.P.R (%)
5.90
5.97
1x ESR + 1x TF 6.01
1x ESR + 2x TF 6.03
1x ESR + 3x TF 6.02
1x ESR + 6x TF 6.11
2x 65 m ESR
65 m ESR
Different wrapping
materials: aluminized
Mylar, ESR, LEF.

, 2010   18/34
Test with prototype samples: Light Output
The largest Light Output was found for crystals
with the largest exit face.
Conclusions
Characterization
Energy resolution (FWHM) vs. photopeak channel for different samples,
without optical grease between the crystal and the photomultiplier.
Setup used to compare
the crystal light output
Tested crystals with 10x10 and
7x14 mm2
exit faces

, 2010   19/34
Test with prototype samples: Nonuniformity in light collection (N.U.)
Conclusions
  Important differences in lightcollection non
uniformity for each crystal, even for two samples
coming from the same provider
  The E.R. can be bad for a good N.U. and vices
versa because the E.R. is measured only at the
crystal entrance face
N.U. and energy
resolution E/E (662
keV) for some samples
tested in this work
P: Provider
S: Sample (S1 or S2)
Characterization
Light collection nonuniformity determination
for P1S1 (best) and P5S2 (worst) samples.
M. Gascón et al., IEEE Trans. Nuc. Sci 56 (2009) 962-967.
sample N.U. (%) E.R. (%)
P1-S1 1.1 9.3
P1-S2 4.5 6.4
P2-S1 2.2 5.9
P3-S2 2.3 6.6
P4-S1 1.8 6.5
P4-S2 4.3 7.3
P5-S2 10.4 7.4
Setup used for
N.U. measurements

, 2010   20/34
Study of the energy resolution
Comments
  Remarkably different performances were
found among the measured samples, even for
two samples coming from the same provider.
  The best energy resolution values obtained
were around 6% at 662 keV  (5% at 1 MeV)
which are close to the CALIFA requirements
Top:  Experimental energy resolution as a function
of the incident gamma energy.
Bottom:Experimental spectra of the two detection
systems P1S1 (red curve), and P2S1 (blue curve),
in response to 662 keV rays. The energy
resolution values obtained for the P2S1 sample are
significantly better than P1S1
Characterization

, 2010   21/34
Motivation
FAIR, R3
Characterization of CsI(Tl) crystals and photosensors
Photosensors
Inbeam tests of the prototype and prototype simulationsInbeam tests of the prototype and prototype simulations
Inbeam tests

, 2010   22/34
The Svedberg Laboratory (Uppsala, Sweden)
10x20 mm2
exit face bifrustum shaped CsI(Tl) crystals,
  coupled to Hamamatsu 686710x20 APDs (2 channels)
  preamplifiers: 4 ch. Cremat CR110 mounted in a
common card in our laboratory
  crystal wrapping ESR (Enhanced Specular Reflector)
130 m thick per crystal
  Proton beam energy 180 MeV
   A 2 mm thick Double Sided Silicon Strip
Detectors (DSSSDs)  consisting of 32x32
perpendicular strips
  25 mm thick copper and iron degraders for
calibration  (protons at 92.7 and 120 MeV)
ProtoZero Experiment
180 MeV proton beam at TSL                         6.1 MeV gamma beam at CMAM               410 MeV gamma beam at TUD
Inbeam tests
180 MeV proton beam at TSL

, 2010   23/34
Energy spectra
Comments
Energy resolutions are
around 1%, which fulfills
one of the main
calorimeter requirements
  This values seem easily
achievable for protons at
this energy.
  Beam was impinging  in
the boundary between
crystals #1 and #3
To the left of the peaks,
those events losing  a
certain energy can be
observed
Spectra of incident 180 MeV protons obtained for each crystal of this prototype configuration
Inbeam tests
180 MeV proton beam at TSL                         6.1 MeV gamma beam at CMAM               410 MeV gamma beam at TUD180 MeV proton beam at TSL

, 2010   24/34
Proton identification
Comments
  Certain peak
degradation
  energy
resolution ~3%
Events sharing the
proton energy between
crystals  #1 and #3
produce a peak which is
more than 1 MeV below
the main peak
      Conclusion
Correlation between Crystals #1 and #3.          Addback between Crystals #1 and #3.
Left: Beam profile obtained with the DSSSDs, relative positions of all the detectors (#1 to #4),
and selection of protons hitting A) the boundary between crystals B) region inside Crystal #3.
Right: Spectra obtained for protons hitting in regions A, B and Total.
Inbeam tests

, 2010   25/34
R3BSim (GEANT4 and ROOT)
Wrapping
130 m  per
crystal
(2 ESR layers)
Peak degradation can be reduced using
thinner crystal wrappingsProtons at 90, 120, 180 and 220 MeV, hitting  close to the
boundary between 2 crystals (case B) wrapped with ESR 130
m thick (2 layers)
Inbeam tests
Conclusion

The ProtoZero reconstructed energy spectrum
for 180 MeV protons. The wrapping thicknesses
ranges from 0 to 260 m.

, 2010   26/34
Centro de Microanálisis de Materiales (CMAM)
Protons
Wrapping
5 MV CockroftWalton
accelerator.
Protons at 1 MeV
The Teflon target (LiF)
was 30 mm in diameter,
5 mm thick
Inbeam tests
180 MeV proton beam at TSL                         6.1 MeV gamma beam at CMAM               410 MeV gamma beam at TUD6.1 MeV gamma beam at CMAM
O. Tengblad. GSI Meeting. April 2009
CMAM
CsI(Tl) crystals + APDs (7x14,
10x10, 10x20)
4 ch. Cremat CR110
  Mesytec MSCF16 amplifiers
  DAQ Midas (IEMCSIC)
ProtoZero
6.129 resonance
1 5.618 single escape
5.107
0.511
Ep
(MeV) E (MeV)
19
F
doble escape
19
F(p,)16
O

, 2010   27/34
Protons
Wrapping
6.1 MeV gammarays produced at
the target
E.R = 2.8 % (FWHM) not so far
from 2.2 % (simulation)
Energy resolution
Inbeam tests
Energy reconstruction
180 MeV proton beam at TSL                         6.1 MeV gamma beam at CMAM               410 MeV gamma beam at TUD6.1 MeV gamma beam at CMAM
Energy spectra
of 6 crystals
from this
prototype
configuration
Addback spectrum of 6 neighbor crystals

, 2010   28/34
Protons
Wrapping
Energy range from 3 – 20 MeV
25 keV @ 10 MeV  energy resolution
  photon flux is about 1000 ph/keV/s/cm2
.
  Radiator target: 10 microns Au foil
  64 scintillation fibres: 1x1mm2
Photon Tagger
2x  8 channels Mesytec preamplifiers (MSI8)
Mesytec MSCF16 amplifiers
32 channel sensing ADC (CAEN V785)
DAQ based on the MultiBranch System (MBS)
A PT1000 temperature probe for monitoring
ProtoZero
NEPTUN Facility@SDALINAC   TUD, Darmstadt, Germany
Inbeam tests
180 MeV proton beam at TSL                         6.1 MeV gamma beam at CMAM               410 MeV gamma beam at TUD410 MeV gamma beam at TUD

, 2010   29/34
Calibration
Spectra obtained for
a prototype
configuration with 15
crystals using 137
Cs
and 60
Co radioactive
sources.
ProtoZero
Addback
Addback energy spectrum for 60
Co and 137
Cs
radioactive sources.
Inbeam tests

, 2010   30/34
Calibration
Wrapping
ProtoZero
Time Coincidences
   The photon tagger has 64 pairs of fibers.  Fibers give a signal after each electron hit.
  These signals are in time coincidence with the master trigger (MA) given by any prototype crystal
Inbeam tests

, 2010   31/34
Calibration
Wrapping
ProtoZero
410 MeV energy spectra
   The higher the tagged energy, the lower the statistic due to a lower gamma yield at the radiator
Energy spectra of
the reconstructed
gammas after
selection of several
fibers at different
tagged energies
Peak (MeV)    E.R. (FWHM)
      2.9........................ 4.9 %
      4.0........................ 4.0 %
      7.6........................ 3.4 %
      8.6........................ 2.7 %
      9.6........................ 2.6 %
      10.3 ..................... 2.5 %
Inbeam tests

, 2010   32/34
Calibration
Wrapping
ProtoZero
Comparison with simulations
Comparison for 4 MeV
tagged gammas
Left: frontal view in the R3BSim
program of the beam profile,
together with the entrance
position in the prototype for
1000 emitted gammas (depicted
in red dots).
Right: Beam Profile as tested in
the R3BSim program.
     Energy deposition  (%)                         Multiplicity distribution
EXPERIMENTALSIMULATED
Inbeam tests
Mean Multiplicity
  Experimental: 2.32
  Simulation:     2.45
410 MeV gamma beam at TUD

, 2010   33/34
Wrapping
Comparison with simulations
   Experimental and simulated observables as a function of the tagged gamma energies.
Comparison between
simulation and
experiment, adding
back  the energy
deposited in the15
crystals, for three
different tagged
gamma energies.
Inbeam tests
                    energy resolution                               full energy peak efficiency                                    crystal multiplicity
410 MeV gamma beam at TUD

, 2010   34/34
The main parameters affecting the energy resolution have been systematically studied.
The 4.4% at 662 keV obtained with small samples coupled to 1 cm2
APD was better than those
previously reported in literature.
The energy resolution for 13 cm crystals get worse since their light output is lower, however the
values obtained for some of the APD-crystal assemblies were close to 5% @ 1 MeV, indicating that
they are a suitable solution for the CALIFA Barrel.
Remarkably different performances were found among the measured samples, even for two
samples coming from the same provider.
Prototype CsI(Tl) crystals + APDs were found to have a linear response for protons with
energies between 90 and 180 MeV and for gammas between few keV and 10 MeV.
The obtained energy resolutions for protons fulfills the Calorimeter requirements.
The tests performed at TU Darmstadt showed the effectiveness of the addback procedure.
The simulation of these prototypes reproduced the experimental results with regard of the
observables obtained in the CALIFA simulation and particularly in terms of energy deposition and
crystal multiplicity distribution.
Conclusions

, 2010   35/34
Thank you for your attention

, 2010   36/34
Extra slides

, 2010   37/34
Test with prototype samples: LAAPD readout
Config. 1: single power suply and preamp.
Modest improvement in the energy
resolution (from 6.7% to 6.5%)
E.R. depends on
Crystal quality
Optical coupling
Crystal wrapping
Light output
Temperature drifts
LAAPD readout
Amplifier gain
Shaping time
Bias voltage
NonUniformity
Config. 2: two power supply and 2 preamps.
Energy resolution as a function of the bias voltage. Config. 1 used a single power supply and a preamplifier;
config. 2 used two independent voltage supplies and the currents were added in.
Conclusions
Characterization

, 2010   38/34
Calibration
Wrapping
Spectra obtained for
a prototype
configuration with 15
crystals using Co56
radioactive source.
ProtoZero
Addback
spectrum for
Co56
radioactive
source.
Inbeam tests

, 2010   39/34
Energy calibration
Correlation between neighbors
  A gain relation between #1 and
#2 and between #3 and #4 allows
calibration
   The energy calibration was performed
with protons at 92, 120 and 180 MeV
( 84, 117 and 173 MeV after DSSSD, Box)
Energy calibration
Inbeam tests
Correlation spectra
obtained for neighbor
crystals

, 2010   40/34
Prototype crystals characterization
  Inbeam test with 6.1 MeV gamma beam at CMAM
CsI(Tl) crystals + APDs  have a linear response between 511 keV and 6.1 MeV,
The reconstructed peak for 6.1 MeV gammas showed an E.R.=  2.8%, not so far from the 2.2% estimated by
the simulation.
  Inbeam test with 410 MeV gamma beam at TUD Darmstadt
This test showed the effectiveness of the addback procedure in the range (0.510 MeV)
The simulation reproduces the experimental results in terms of energy deposition and crystal multiplicity
distribution
   Inbeam tests with 180 MeV proton beam at TSL
   CsI(Tl) crystals + APDs have a linear response  between 90 and 180 MeV
   E.R.  = 1% (180 MeV) which fulfills Calorimeter requirements.
   Peak degradation can be solved using thinner wrapping.
Prototype test beams
Conclusions
  Crystals with the largest exit face gave the largest light output.
  Important differences between lightcollection nonuniformity and energy resolution for each crystal, even
for two samples from the same provider.
  The individual readout system for each of the two channels improved energy resolution, at the expense of
greater complexity in both the electronics and the data analysis.
   The results obtained with some of the APDcrystal assemblies were close to 5% (FWHM) energy
resolution for 1 MeV photons, indicating that they are a suitable solution for the CALIFA Barrel.

, 2010   41/34
Why CsI(Tl) + APD
Characterization
Estimated CsI(Tl) emission spectrum
CsI(Tl)
used in several
experiments (Babar,
Belle)
  cheap to make, easy
to handle,
  slightly hygroscopic
  High light yield
(~60000 ph/MeV)
  Good energy
resolution
  Spectral response extends into
long wavelengths. Ideal for CsI(Tl)
crystals
  Higher quantum efficiency than
PMTs
Higher gain than PIN Diodes
  Insensitive to magnetic fields
APDs
NaI(Tl) CsI(Tl) CsI(Na) BGO LYSO PWO CsI (pure)
5.29 3.86 3.67 4.51 4.51 7.13 7.1 8.29 4.51
63000 49000 39000 60000 45000 9000 32000 100 16800
< 3% 3.5% 7% 6% 7.5% 10% 7.1% >10% 7.5%
N/A N/A 3.8% 4.9% N/A 8.3% N/A N/A 4.3%
380
350 310 fast
550 420 480 420 420 315
430 415
25 25/213 620 fast 1000 630 300 41 6 35/6
yes yes yes slightly yes no no no slightly
Cost (per cm3) $30 $30 $2 $5 $5 $9 N/A $2 $5
LaBr3
LaBr3
Density (g/cm3
)
Light Output (ph/MeV)
E/E 662 keV (PMT)
E/E 662 keV (APD)
Peak(nm)
Fast Decay (ns)
Higroscopic
APD Quantum efficiency (%)

, 2010   42/34
Test with prototype samples: crystal wrapping
Averaged Lightpulse resolutions and
energy resolution (FWHM) obtained
using a LED with different 10x10 mm2

exit face crystals and different
wrapping configurations, coupled to
an XP5A08 PMT without optical
grease. 1x,2x,3x,6x is the number of
layers, and TF is Teflon tape
For small samples:  four 75 mthick layers of Teflon tape covered by a 5 mthick layer of aluminized Mylar
Best results for prototype crystals are generally achieved with 2 layers of ESR
E.R. depends on
Crystal quality
Optical coupling
Crystal wrapping
Light output
Temperature drifts
Amplifier gain
Shaping time
Bias voltage
NonUniformity
Characterization
Best wrappings for small and prototype crystals
Setup for determining the optimal
wrapping configuration for
prototype crystals.
Wrapping configuration for prototype crystalsWrapping configuration for small crystals
Wrapping L.P.R (%) E.R. (%)
2x ESR 5.90 15.44
1x ESR 5.97 15.80
1x ESR + 1x TF 6.01 16.28
1x ESR + 2x TF 6.03 15.72
1x ESR + 3x TF 6.02 15.58
1x ESR + 6x TF 6.11 16.60
Crystal wrapping E.R. (%)
Teflon + Aluminumfoil 10.00 ± 0.09
8.68 ± 0.09
Teflon + Copper tape 8.41 ± 0.08
7.48 ± 0.08
Teflon tape (300 m) 25.95 ± 0.34
Teflon + Metalic adhesive tape
Teflon + Aluminized Mylar

, 2010   43/34
Test with prototype samples: Amplifier gain and shaping time
  The best results were generally achieved when the amplifier gain
was set to cover the full dynamic range of the MCA
  Shaping times between 4 and 8 s seemed to be a good
compromise: they provided good energy resolution without
incurring pileup effects.
E.R. depends on
Crystal quality
Optical coupling
Crystal wrapping
Light output
Temperature drifts
Amplifier gain
Shaping time
Bias voltage
NonUniformity
Left: Energy resolution vs. amplifier gain for 4 s shaping time.  Right: Energy resolution vs. shaping time for 1, 5
and 10 cm long crystals coupled to a S86641010 APD (4 s shaping time and 380 V bias voltage).
Conclusions
Conclusions
Characterization

, 2010   44/34
APDs: Bias voltage and gain curves
Left: Energy resolution vs. bias voltage,
keeping the photopeak at a constant
channel, for a 5 cm (top) and 13 cm long
crystals (bottom) coupled to LAAPDs.
Right: Typical gain curves of the
S86641010 APD (top) and S86641010  2
channel APD (bottom) using CsI(Tl)
crystals.
Conclusions
  bias voltage variation below
0.35V can guarantee a gain
variation smaller than 1%
Relative gain
variation due to bias
voltage variation for
all crystals.
Characterization

, 2010   45/34
APD # A.A. Cap. LPR
1 10x10 std 406 5.2% 20
2 10x10 std 404 5.4% 22
3 10x10 std 410 5.3% 8
4 10x10 std 411 5.5% 7
5 7x14 std 332 7.2% 23
6 7x14 std 322 8.1% 23
7 7x14 std 332 8.7% 32
8 7x14 std 333 9.2% 39
9 7x14 low 491 7.5% 24
10 7x14 low 484 8.0% 30
11 7x14 low 493 8.2% 31
12 7x14 low 492 9.8% 32
Cap=Capacitance
O.Vb ID
(nA)
A.A.=active area (mm2
)
O.Vb = Optimal bias voltage (Volts)
LPR = Light pulse resolution @ 5.105
eh
Characterization
Experimental setup
for comparing
different APD series
  The APD contribution to the
energy resolution was found to be
0.12% for the 10x10 APD.
  The APD dark current can be
obtained using a NHQ 225 ISEG
power supply
   The 10x10 Hamamatsu APD
showed the best performances.

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