Prototype of a new calorimeter for the studies of nuclear reactions with relativistic radioactive beams

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



MotivationMotivationFAIR, R3B, CALIFA, ProtoZero (CALIFA's prototype)

Characterization of CsI(Tl) crystals and photosensorsCharacterization of CsI(Tl) crystals and photosensorsPhotosensors

Benchtests on small and prototype crystals

Inbeam tests of the prototype Inbeam tests of the prototype and prototype simulationsand prototype simulationsResults of the proton beam test

Results of the gamma beam tests

ConclusionsConclusions



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 nucleiAntiproton PhysicsRelativistic heavy ions collisionsAtomic and Plasma Physics

MotivationFAIR R3B CALIFA ProtoZeroFAIR

Scientific Program

FAIR



R3B: 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

MotivationFAIR R3B CALIFA ProtoZeroR3B

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



CALIFA requirements (R3B LoI, 2005) :

CALIFA: CALorimeter for InFlight emitted gAmmas

MotivationFAIR R3B 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.



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 R3B CALIFA ProtoZeroCALIFA



What scintillating material ?

Motivation

CsI(Tl) emission spectrumCsI(Tl)

Advantageswell known propertiesrelatively high density high light yield cheap to make, easy to handleslightly hygroscopicgood energy resolution with APDs

InconvenientLong 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 4.5163000 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%

380350 310 fast

550 420 480 420 420 315430 415

25 25/213 620 fast 1000 630 300 41 6 35/6Hygroscopic yes yes yes slightly yes no no no slightlyCost (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)


APD quantum efficiency



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




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

MotivationFAIR R3B CALIFA ProtoZeroProtoZero



MotivationFAIR, R3B, CALIFA, ProtoZero (CALIFA's prototype)

Characterization of CsI(Tl) crystals and photosensorsCharacterization of CsI(Tl) crystals and photosensorsPhotosensors


Inbeam tests of the prototype and prototype simulationsResults of the proton beam test


Characterization



Test with small samples: APDs vs. PMTs

CsI(Tl) + APD CsI(Tl) + PMT

Crystal Length cm1 cm5 cm10XP1901

PMT XP1918

XP3102

7.0±0.1 8.4±0.1 12.8±0.16.1±0.1 7.4±0.1 10.7±0.19.1±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±0.124.42±0.12 4.87±0.09 4.72±0.08

4 s8 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



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





APD # A.A. Cap. LPR 1 10x10 std 406 5.2% 202 10x10 std 404 5.4% 223 10x10 std 410 5.3% 84 10x10 std 411 5.5% 75 7x14 std 332 7.2% 236 7x14 std 322 8.1% 237 7x14 std 332 8.7% 328 7x14 std 333 9.2% 399 7x14 low 491 7.5% 2410 7x14 low 484 8.0% 3011 7x14 low 493 8.2% 3112 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



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 cm5 cm10 cm

2.84 ± 0.012.83 ± 0.012.83 ± 0.01



APDs: Temperature drifts

(dM/dT)M1 = 2.8 %/ºCcompares 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 137Cs 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



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



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

5.971x ESR + 1x TF 6.011x ESR + 2x TF 6.031x ESR + 3x TF 6.021x ESR + 6x TF 6.11

2x 65 m ESR

65 m ESR

Different wrapping materials: aluminized Mylar, ESR, LEF.



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



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 workP: 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 9.3P1-S2 4.5 6.4P2-S1 2.2 5.9P3-S2 2.3 6.6P4-S1 1.8 6.5P4-S2 4.3 7.3P5-S2 10.4 7.4

Setup used for N.U. measurements



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



MotivationFAIR, R3B, CALIFA, ProtoZero (CALIFA's prototype)

Characterization of CsI(Tl) crystals and photosensorsPhotosensors


Inbeam tests of the prototype and prototype simulationsInbeam tests of the prototype and prototype simulationsResults of the proton beam test


Inbeam tests



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 TUDInbeam tests

180 MeV proton beam at TSL



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 tests180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD180 MeV proton beam at TSL



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 tests180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD180 MeV proton beam at TSL



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

180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD180 MeV proton beam at TSL

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



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 tests180 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 resonance1 5.618 single escape

5.1070.511

Ep (MeV) E (MeV)

19Fdoble escape

19F(p,)16O



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 reconstruction180 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



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 tests180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD410 MeV gamma beam at TUD



Calibration

Spectra obtained for a prototype configuration with 15 crystals using 137Cs and 60Co radioactive sources.

ProtoZero

Energy reconstruction

AddbackAddback energy spectrum for 60Co and 137Cs radioactive sources.




CalibrationWrapping

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




CalibrationWrapping

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 %




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

EX

PER

IME

NTA

LSI

MU

LA

TE

DInbeam tests

180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD

Mean Multiplicity Experimental: 2.32 Simulation: 2.45

410 MeV gamma beam at TUD



Wrapping

Comparison with simulations

Experimental and simulated observables as a function of the tagged gamma energies.Comparison between simulation and experiment, addingback the energy deposited in the15 crystals, for three different tagged gamma energies.

Inbeam tests180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD

energy resolution full energy peak efficiency crystal multiplicity

410 MeV gamma beam at TUD



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



Thank you for your attention



Extra slides



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



CalibrationWrapping

Spectra obtained for a prototype configuration with 15 crystals using Co56 radioactive source.

ProtoZero

Addback spectrum for Co56 radioactive source.

Inbeam tests

Energy reconstruction180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD410 MeV gamma beam at TUD



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

180 MeV proton beam at TSL 6.1 MeV gamma beam at CMAM 410 MeV gamma beam at TUD180 MeV proton beam at TSL



Prototype crystals characterization

Inbeam test with 6.1 MeV gamma beam at CMAMCsI(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 DarmstadtThis 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.



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 4.5163000 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%

380350 310 fast

550 420 480 420 420 315430 415

25 25/213 620 fast 1000 630 300 41 6 35/6yes 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 (%)



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


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 15.441x ESR 5.97 15.80

1x ESR + 1x TF 6.01 16.281x ESR + 2x TF 6.03 15.721x ESR + 3x TF 6.02 15.581x ESR + 6x TF 6.11 16.60

Crystal wrapping E.R. (%)

Teflon + Aluminum foil 10.00 ± 0.098.68 ± 0.09

Teflon + Copper tape 8.41 ± 0.087.48 ± 0.08

Teflon tape (300 m) 25.95 ± 0.34

Teflon + Metalic adhesive tape

Teflon + Aluminized Mylar



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


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



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





APD # A.A. Cap. LPR 1 10x10 std 406 5.2% 202 10x10 std 404 5.4% 223 10x10 std 410 5.3% 84 10x10 std 411 5.5% 75 7x14 std 332 7.2% 236 7x14 std 322 8.1% 237 7x14 std 332 8.7% 328 7x14 std 333 9.2% 399 7x14 low 491 7.5% 2410 7x14 low 484 8.0% 3011 7x14 low 493 8.2% 3112 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.


Science

Prototype of a new calorimeter for the studies of nuclear reactions with relativistic radioactive beams