Single crystals for radiation detectors

https://www1.cb.uni-bonn.de/fileadmin/user_upload/internal/Publication/Publication_PhysRept_413_2005_KlemptEtAl.pdf

The antinucleon-nucleon interaction at low energy: annihilation dynamics

Methods are evaluated for determining the energy calibration and the response of a 20 cm by 25 cm NaI detector, and for unfolding the detector response from measured spectra of 10 to 30 MV bremsstrahlung. A set of measured γ-ray and electron spectra with energies ranging from 1 to 30 MeV were fit to response functions calculated using Monte Carlo techniques (EGS4) to determine the energy calibration of the spectrometer and the degree of broadening required for the calculated response functions. For electrons, the broadened response was in excellent agreement with the measurements. For γ-rays, there was evidence of collimator-degraded photons in the measured spectra. A matrix of broadened response-functions was generated for use in unfolding bremsstrahlung spectra in the energy range of 0.2 to 35 MeV. The unfolding routine FERDO was shown to provide reliable estimates of the spectrum of photons in the bremsstrahlung beam when this response matrix was used for unfolding. Collimator effects were ignored without significantly affecting the shape of the unfolded spectrum.

Precision response estimation, energy calibration, and unfolding of spectra measured with a large NaI detector

We have designed and tested a new high resolution NaI(Tl) total absorption scintillation counter. The detector is a cylinder composed of a 26.7 cm diameter by 55.9 cm long NaI core with a concentric 10.8 cm thick NaI annulus that is divided into quadrants. The NaI detector is surrounded by a 12.7 cm thick plastic scintillator to veto both cosmic rays and events with significant shower leakage from the NaI. High uniformity of light production and collection throughout the detector is required for superior resolution. The detector has a measured resolution of 1.3% and 1.7% FWHM for 130 MeV photons and 330 MeV electrons, respectively. Computer simulations to account for loss of resolution due to pileup and energy spread of the beam indicate that the ultimate experimental resolutions at these energies are 1.2±0.1% and 1.3±0.1%. The resolutions at these two energies are at least a factor of 2 better than that of any other total absorption scintillation counter available today. Based on shower simulations, the detector is expected to have a resolution of approximately 1.3% for collimated 130–2000 MeV photons.

Development of a NaI(Tl) detector with superior photon energy resolution for use above 100 MeV

An array of 49 NaI(Tl) modules each 20 inch in depth and 2.5 inch × 2.5 inch in cross section has been constructed and its properties, especially energy resolution, explored for positrons in the range 20 MeV – 18 GeV. A subsequent much larger detector, the Crystal Box, has also been constructed from 396 modules of the same cross section, but mostly 12 inch in depth, and operated as a γ-ray and positron detector in a search for rare muon decays. The calibration procedure used for the Crystal Box and its characteristic resolutions in energy, impact point and time are described.

Design and performance of modularized NaI(Tl) detectors with rectangular crystal elements: An array of 49 and the crystal box

We have constructed a modularized array of NaI(Tl) detectors in a half barrel configuration that is about 75 cm long with an inner radius of 25 cm. 96 NaI modules are surrounded by a layer of 48 modules of scintillating glass which have similar dimensions to the NaI modules. Each NaI crystal was shaped as a trapezoidal pyramid and encapsulated in a 1 mm thick aluminium container with dimensions of (43 × 94) × (110 × 94) × 377 mm3. The construction and performance are described along with the gain calibration and monitoring, the beam position sensitivity, the scattering between modules, etc. The fwhm energy resolution of a 5 × 5 array of NaI modules varied from 6.5% for incident electrons at 100 MeV to 3.6% at 1000 MeV

Hajime Yoshida

Papers

Modularized NaI(Tl) detectors in a half barrel configuration