Single crystals for radiation detectors

The authors review the techniques used to measure the energy of elementary particles. The methods discussed span more than 20 orders of magnitude in energy, ranging from a small fraction of an electronvolt, where relic remainders of the Big Bang are being looked for, to the 1020 eV domain, where the highest-energy cosmic rays can be found. The emphasis is, however, on techniques employed in particle physics for studying collision processes at accelerators in the GeV-TeV range.

/pdf/energy-measurement-of-elementary-particles-1pz0ir41ph.pdf

Energy measurement of elementary particles

Experimental particle physicists study the fundamental structure of matter with a variety of approaches, which may be subdivided in two classes: accelerator and non-accelerator experiments. Accelerator experiments have the advantage of well-controlled experimental circumstances, non-accelerator experiments offer the possibility of studying processes that are not accessible to the available accelerator technology.

/pdf/calorimetry-in-high-energy-physics-1trl7at44h.pdf

Calorimetry in High Energy Physics

The introduction of a new photodetector, the XP4702, supplements and updates the conventional RTC ∗ photomultiplier range. A new technological concept of plane and parallel dynodes has made it possible to produce a compact large area electron multiplier with good gain and uniformity. This technique paves the way for multichannel PMs capable of imaging with a spatial resolution from 0.5 to several millimetres, midway between those of microchannel image intensifiers and arrays of small (XP1911 (RTC) or R1635 (HTV) type PMs. Mosaic techniques then make it possible to produce photodetectors capable of imaging individual photons in the visible and UV part of the spectrum over areas approaching 1 m 2 , with high time, spatial and dynamic performance. After a brief description of the tube and an account of its mode of operation, we describe some of its chief characteristics. Finally, we suggest some desirable lines of development.

Test of a new 64-channel PMT for imaging

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

A prototye NaI(Tl) detector (the Cluster of 54) of spherical geometry subtending a solid angle of 7.5% of 4? at its center, has recently been assembled and tested. This detector consisted of 54 close-packed but optically isolated NaI(Tl) modules and the associated electronic circuitry. The Cluster of 54 is the predecessor of an almost complete spherical detector, the Crystal Ball, which will cover 94% of 4?. The latter detector is now under construction and is especially designed for the study of ?-rays produced in electron-positron collisions at colliding beam facilities. This article will outline the mechanical, optical, and electronic assembly of the prototype system. Cluster of 54 test data will be presented.

Y. Chan

Papers

Design and Performance of a Modularized NaI(Tl) Detector (The Crystal Ball Prototype)