Proton detection with the r3b calorimeter two layer solution iem csic sept 2006 report
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CONSEJO SUPERIOR DE INVESTIGACIONES CIENTÍFICAS. MINISTERIO DE EDUCACIÓN Y CIENCIA. Proton detection with the R3B calorimeter, two layer solution IEM-CSIC sept. 2006 report. O. Tengblad, M. Turrión Nieves, C. Pascual Izarra, A. Maira Vidal. outline. Why a two layer solution

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Proton detection with the R3B calorimeter, two layer solution IEM-CSIC sept. 2006 report

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Proton detection with the R3B calorimeter,

two layer solution

IEM-CSIC sept. 2006 report

O. Tengblad, M. Turrión Nieves, C. Pascual Izarra, A. Maira Vidal


  • Why a two layer solution

  • Limitations - requirements

  • “Conclusion”

Energy loss of charged particles: Bethe-Bloch equation

energy loss detected

incident energy (MeV)

Proposed scenario

  • Two layers detector:

  • Simplification

Ë=f(D E1 )+ g(D E2)


D E1

D E2

the estimated final energy is proportional to the energy deposited in each layer

SRIM Simulations: Deposited energy of protons

Fit: Gaussian with a constant background

SRIM Simulations: protons

DE1+s(DE1) DE2+s(DE2)

  • Material: LaBr3(:Ce)

  • Thickness: 1mm+20mm

  • Monte Carlo: SRIM 2003


D E2

D E1

Energy resolution

E DE1+D(sE1) DE2+s(DE2)


protons of 200MeV

deposit an energy of:

1mm LaBr3= 1.49±0.23 MeV

20mm LaBr3= 31.32±1.13 MeV





First Conclusions

  • If not fully stopped, two DE-detectors are required

  • A too thin detector gives bad estimation of the energy leading to bad resolution first detector should be thick in order to totally absorb protons up to rather high energy

  • Second detector placed to solve the ambiguity on the signal

  • The gammas will deposit most of the energy aroundthe first hit, which we want to be the first detector, why this crystal should have a good Eg resolution.

  • Two detectors of different materials with a unique PM or APD? Optically compatible



Detector spectral response matching

  • Emission and absorption spectra do not overlap » emitted light is not re-absorbed

  • Emission spectra shifted to lower energies

  • LYSO:

  • lexcitation [nm] =262, 293, 357

  • Max. lemission [nm] =398, 435

Hautefeuille et al. J. of Crystal Growth (in press)

Emission spectra




Max. lemission [nm] Decay time[ns]


BGO 478300

CsI pure31516

LYSO (Ce)42045-60



LaBr3 (Ce)38016

LaCl3 (Ce)35028



SRIM simulations: protons

  • Materials: LYSO(:Ce) + LaBr3(:Ce)

  • Thickness: 30mm + 20mm

  • Monte Carlo: SRIM 2003

D E1

D E2


Energy resolution

DE1+D(sE1) + DE2+s(DE2) E + sE?

protons of 200MeV

deposit an energy of:

30mm LYSO= 67.44±1.77 MeV

20mm LaBr3= 43.50±3.11MeV





Gamma absorption

  • Minimum absorption for g ~5MeV

  • 55% of g absorbed in 30mm LYSO (Prelude)

Second Conclusion

  • Protons

    • Two detectors are required to detect 300 MeV protons

    • The energy of the incident protons can be estimated with an error of ~3-4% with the LYSO + LaBr3(Ce) solution

  • Gammas

    • Most of the energy of the gammas is deposited around the first hit, why this should happen in the first layer!

    • 55% of g are absorbed in 30mm LYSO when the energy of the incident gammas is 5MeV

    • >55% of g are absorbed for E≠5MeV in 30mm LYSO

    • The rest will be absorbed in the second layer

    • If first gamma detected in second layer; event discarded

    • However, the gamma resolution in LYSO is about 6%

    • If this g-resolution is good enough one would choose LSO + LYSO as the resolution of LaBr is too good to be place as second layer.

Final Conclusion

  • To obtain the optimum situation both for protons and gammas;

    • First crystal layer relatively thick and of a material with excellent gamma resolution,

       LaBr3(Ce) of 30 mm l= 380nm decaytime= 16ns

    • Second crystal layer of a material emitting at shorter wavelength and with a decay constant different in order to separate the signals and that the second detector is transparent to the first.

       LaCl3(Ce) of 150 mml= 350nm decaytime= 25ns

This will detect protons up to 280 MeV with an

proton energy resolution of the order of 2%.

One could, however, live with a much shorter LaCl3(Ce) or one could combine the LaBr3(Ce) with pure CsI as a cheaper solution.

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