On the Energy resolution optimization of CsI(Tl) crystals for the R3B Calorimeter Mart´ ın GASC ´ ON Particle Physics Departament Universidad de Santiago de Compostela June 1, 2007 Mart´ ın GASC ´ ON Energy-resolution of CsI(Tl) crytals
On the Energy resolution optimization of CsI(Tl) crystals forthe R3B Calorimeter
Martın GASCON
Particle Physics DepartamentUniversidad de Santiago de Compostela
June 1, 2007
Martın GASCON Energy-resolution of CsI(Tl) crytals
FAIR: Facility for Antiproton and Ion Research
Characteristics:
New accelerator facility in Darmstadt(Germany)
protons, stable- and radioactive-ion beams
Primary intensity: (1012 ions/s)@ 2−30GeV/u.
Good beam quality (beam-coolingtechniques)
FAIR.MPG
Martın GASCON Energy-resolution of CsI(Tl) crytals
R3B experimentReactions with Relativistic Radioactive Beams
R3B
R3B is a versatile experimental setup for full kinematics studies of exotics beams reactions atrelativistic energies (around 700 MeV/nucleon in the laboratory system)
Martın GASCON Energy-resolution of CsI(Tl) crytals
R3B CalorimeterCALIFA: A Calorimeter for in-flight emitted gammas and light charged-particles for R3B Experiment
R3B
The crystal array will surround the R3B target, measuring both gammas (0.5-10 MeV in CoM)and protons (up to 300 MeV).
It must fulfils two requirements: to provide the γ-ray multiplicities and their sum energy, and forother experiments, it must measure the individual γ-ray energies for spectroscopic purposes.
The detector has to stop and measure the total energy of high-energy light charged particleswith high energy-resolution
The required polar angle segmentation and the lenght of the scintillating crystals has beencalculated (GEANT4) for different angular regions.
CALIFA
Martın GASCON Energy-resolution of CsI(Tl) crytals
Experimental setup
Martın GASCON Energy-resolution of CsI(Tl) crytals
Experimental setupCrystals and APDs
Figure: 20 cm CsI(Tl) tapered crystal
Figure: 10x10 mm2 S8664-1010 APD fromHamamatsu
Figure: SD630-73-70-500 APD from API coupledto a 1 cubic cm CsI(Tl) crystal
Martın GASCON Energy-resolution of CsI(Tl) crytals
CsI(Tl) crystals testsMeasurements: APD Gain
APD Gain vs Bias Voltage
Figure: 5 cm length crystal Figure: small crystals Figure: 20 cm tapered crystal
The best energy-resolution can be found by adapting the amplifier gain to keep the photopeakin a constant channel
around 380 V→∆Gain
∆V= 2.84% (1)
The energy resolution depends on both Bias Voltage and Amplifier Gain
Martın GASCON Energy-resolution of CsI(Tl) crytals
CsI(Tl) crystals testsMeasurements: Shapping time
Dependence on Shapping time
For small crystals, 4 µs is a good compromise between energy-resolution loss and pile-upnegative effects.
Martın GASCON Energy-resolution of CsI(Tl) crytals
CsI(Tl) crystals testsMeasurements: Acquisition time
Dependence on Acquisition time
Best values are obtained between 30 and 60 seconds depending on the counting rate
The showed curve has two components: statistics and bias voltage drift, that could beeliminated by controling both temperature and bias voltage
Martın GASCON Energy-resolution of CsI(Tl) crytals
CsI(Tl) crystals testsMeasurements: Amplifier gain
Dependence on Amplifier gain
Energy-resolution improves by increasing the amplifier gain
Martın GASCON Energy-resolution of CsI(Tl) crytals
CsI(Tl) crystals testsMeasurements: Energy resolution
Dependence on Energy resolution
The APDs from API show the best energy-resolution for the CsI(Tl) crystal
The APDs from Hamamatsu show an acceptable energy-resolution and it is almostindependent on the crystal size
Martın GASCON Energy-resolution of CsI(Tl) crytals
Outline
Conclusions
Several tests (wrapping, optical coupling, amplifier gain, shapping time, ...) have beenperformed to optimize the crystal peformance using APDs from API and Hamamatsu
APDs from API shown the best energy-resolution for the CsI(Tl) crystal, nevertheless thosefrom Hamamatsu shown a similar energy-resolution, almost independently on the crystal size
The main drawback of using APDs instead of PMTs is the strongly dependence of the gainwith temperature and voltage.
The limited energy-resolution in the tapered crystal is mainly due to a deficient opticalcoupling with the light guides.
These results fulfil the calorimeter requirements at least for the Barrel section
Martın GASCON Energy-resolution of CsI(Tl) crytals
Outline
Conclusions
Several tests (wrapping, optical coupling, amplifier gain, shapping time, ...) have beenperformed to optimize the crystal peformance using APDs from API and Hamamatsu
APDs from API shown the best energy-resolution for the CsI(Tl) crystal, nevertheless thosefrom Hamamatsu shown a similar energy-resolution, almost independently on the crystal size
The main drawback of using APDs instead of PMTs is the strongly dependence of the gainwith temperature and voltage.
The limited energy-resolution in the tapered crystal is mainly due to a deficient opticalcoupling with the light guides.
These results fulfil the calorimeter requirements at least for the Barrel section
Martın GASCON Energy-resolution of CsI(Tl) crytals
Outline
Conclusions
Several tests (wrapping, optical coupling, amplifier gain, shapping time, ...) have beenperformed to optimize the crystal peformance using APDs from API and Hamamatsu
APDs from API shown the best energy-resolution for the CsI(Tl) crystal, nevertheless thosefrom Hamamatsu shown a similar energy-resolution, almost independently on the crystal size
The main drawback of using APDs instead of PMTs is the strongly dependence of the gainwith temperature and voltage.
The limited energy-resolution in the tapered crystal is mainly due to a deficient opticalcoupling with the light guides.
These results fulfil the calorimeter requirements at least for the Barrel section
Martın GASCON Energy-resolution of CsI(Tl) crytals
The end
Wernher von Braun
Basic research is what I am doing when I don’tknow what I am doing
Martın GASCON Energy-resolution of CsI(Tl) crytals