Study of a BGO calorimeter using electron and hadron beams from 1 to 50 GeV

A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained ( ) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement.     

An experimental study of the contribution of nuclear fission to the signal of uranium hadron calorimeters

We determined the number of fissions that occur in the development of a hadron shower in a ²³⁸U calorimeter, using a method based on the analysis of induced radioactivity. Measurements were done at 300 GeV (π⁻, and at 591 MeV (protons). The number of fissions turns out to be much smaller (∼ 10 fissions per GeV) than usually assumed, and is very sensitive to the calorimeter configuration. For example, in massive ²³⁸U the number of neutron-induced fissions is 25% larger than in a fine-sampling uranium/scintillator device. The results for calorimeters with a high-Z readout are similar to the massive U case. A significant fraction (10–15%) of the fissions are caused by fast charged particles rather than by slow neutrons. We also determined the total neutron production in the proton beam. It turns out that less than 25% of the neutrons produced in the shower development cause fission. The insertion of low-Z readout layers decisively determines how fast and by which mechanisms the neutrons lose their kinetic energy. The neutron flux in lead is about 40% of that in uranium, but the neutrons are on an average faster. We measured that 4.1 ± 0.4 fisions per GeV are on an average induced in the shower development of an incoming 300 GeV π. An attempt is made to explain these data.The consequences for calorimetric measurements of the hadron energy are discussed.     

A 4-inch silicon/tungsten calorimeter for p-p collider experiments

A 4-inch diameter silicon/tungsten sandwich calorimeter with 64 cm² in active area and 18 radiation lengths in depth has been constructed. The performance has been investigated for incoming electrons of 500 MeV to 4.5 GeV. The calorimeter shows a good linearity over the electron energy region and the energy resolution is well expressed by σ(rms)/E = 17√t/E%, where t represents the unit sampling thickness in radiation lengths and E the incident electron energy in GeV. The agreement between these results and a Monte Carlo simulation is quite satisfactory. The center of shower has been determined with the accuracy of better than 2 mm at energies exceeding 1 GeV.     

Test results of a BaF2 calorimeter tower with a wire chamber readout

The results from a calorimeter tower consisting of BaF₂ crystals coupled to photosensitive, low-pressure wire chambers are presented. The longitudinal and lateral shower development is shown. The results for 108 MeV and 200 MeV electrons yield an energy resolution of

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Possibility of increasing proton rejection by detecting primary cosmic radiation electrons using an ionization-neutron calorimeter

Measurements were made of the neutron yields from a lead absorber 60 cm thick in electromagnetic cascades initiated by 200–600 MeV electrons. A comparison between the neutron yields obtained for electrons and the results of similar measurements for protons and pions suggests that the rejection factor of the proton background is increased ∼10² times when an ionization-neutron calorimeter is used to measure primary cosmic radiation electrons at energies above 100 GeV. Pis’ma Zh. Tekh. Fiz. 24, 66–73 (September 26, 1998)     

Performance of the VENUS lead-glass calorimeter at TRISTAN

The initial performance of the VENUS barrel electromagnetic calorimeter at TRISTAN is described. The calorimeter is composed of 5160 lead-glass counters in a semi-tower arrangement. An energy resolution of 3.8% was obtained for 26 GeV Bhabha events. The neutral pions in the hadronic events were reconstructed with a mass resolution of σ = 16 MeV. The gain of the lead-glass counters was stable within 2% during a four months operation at TRISTAN.     

A π0 and η spectrometer of lead glass and BGO for momenta up to 1 GeV/c

A spectrometer consisting of two sets of bismuth germanium oxide (BGO) crystals and a lead-glass array has been used to measure the π⁰ and η momentum spectra produced from proton-antiproton annihilations at rest. We describe the test of the BGO sets in electron beams of energies from 50 to 450 MeV. We discuss the method of construction and calibration of the lead-glass array, as well as procedures to extract the energy and position resolutions for detected photons. A momentum resolution (σ) for π⁰'s and η's of 4% and 3%, respectively has been achieved at momenta below 1 GeV/c.     

The performance of an L3 hadron calorimeter prototype module with BGO

A prototype of a gas sampling uranium module of the L3 hadron calorimeter was built and subsequently tested with pion beams of energies between 4 and 20 GeV. The construction of the proportional chambers, the assembling of the module, the readout electronics, and the beam test are briefly described. The energy resolution of the calorimeter module alone was measured to be 30.5 ± 3% at 6 GeV, 21 ± 2% at 10 GeV and 18 ± 2% at 20 GeV. For the module together with a BGO crystal matrix in resolution was 29 ± 3% at 4 GeV, 21 ± 2% at 10 GeV, and 17 ± 2% at 20 GeV.     

Light particle detection by BGO scintillators with photodiode readout

The applicability of a BGO crystal coupled to a photodiode for detection of light charged particles in the energy range of 5–170 MeV has been investigated. Energy resolution, light output and scintillation efficiency have been deduced from the data.     

A limited-streamer tube electron detector with high rejection power against pions

The problem of detecting electrons in the 0.5–4.0 GeV energy range, in the presence of a high pion background, has been studied using a new type of electromagnetic shower detector. Its structural properties and the main parameters are given, together with the basic results in terms of energy resolution and of rejection power against pion background. The optimization of this new instrument gives a pion rejection power of ～ 6 × 10^?4 for energy ? 1.2 GeV.     

Electron-pion discrimination in an iron/streamer tube calorimeter up to 100 GeV

An electron/hadron calorimeter consisting of 2 cm/4 cm iron sampling planes and streamer tube readout modules was exposed to particle beams of electrons and pions in the energy range from 1 to 100 GeV. At the highest energies the observed pion misidentification amounted to 0.95% ± 0.21% at an electron detection efficiency of 95%.     

Test results from a uranium hadron calorimeter using wire chamber readout

A uranium gas sampling calorimeter has been tested with electrons and pions between 1 and 50 GeV. A comparative evaluation of the response and the resolution for proportional and streamer mode operation of the gas wire chamber detectors is given for two different gas mixtures.     

The response of a streamer tube sampling calorimeter to electrons

We have constructed a simple modular electromagnetic calorimeter with 0.8X₀ copper absorbers using gas sampling with streamer tubes. To suppress saturation effects we use small cell streamer tubes (6 mm × 6 mm) filled with pure isobutane. The calorimeter has been tested with electrons in the energy range from 1 to 6 GeV. In this range the instrument shows a linear response. The energy resolution from pad and wire signals amounts to $\text{σ ≈}\text{20\%}\text{√E}$. The longitudinal shower profiles are in reasonable agreement with expectations from standard shower calculations.     

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

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.     

Construction and test of a shower calorimeter prototype consisting of scintillating fibers immersed in a heavy metal alloy

A group at Saclay has conceived a new approach to the design of an electromagnetic shower calorimeter using scintillating fibers immersed in a low melting point high density alloy. The fibers point along the general direction of the showering particles. A (second) prototype was built using this principle and tested in a high energy electron beam (1 GeV to 25 GeV) at CERN.The test block measures 80 mm × 120 mm × 265 mm with a radiation length of X₀ = 14.5 mm. The amount of light collected corresponds to 5000 photo electrons/GeV and is linear with energy between 1 and 25 GeV. The energy resolution was found to be $\text{σ/√E = (11 ± 2)\%}\text{GeV}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. The position resolution is of the order of 2 mm. An appreciable reduction from the block surface to the detecting p.m. surface is possible with very little loss of light.In a separate test we found that the clad fibers are considerably more resistant to radiation damage than the naked scintillator.     

Test beam studies of a prototype for the BES barrel shower counter

A prototype of the barrel shower counter for the Beijing Spectrometer (BES) has been tested with electrons and pions in a momentum range from 0.2 to 2.0 GeV/c at the test beam line T1 of KEK 12 GeV proton synchrotron. The preliminary results are now reported. Four kinds of gas mixture were used in the prototype: 40% Ar/60% isobutane, 44.5% Ar/44.5% CH₄/11% methylal, 47% Ar/47% CH₄/6% methylal, and 49.3% Ar/49.3% CH₄/1.4% ethyl alcohol. The results show that using SQS tube as a sampling means in the BES shower counter is feasible for Beijing Electron Positron Collider (BEPC) energy region of 2 × 2.2/2.8 GeV.     

A Si(Li)-Pb shower calorimeter for p-p collider experiments

A silicon/lead sandwich calorimeter with 38 cm² in active area and 10 radiation lengths in depth has been constructed. The performance has been investigated for incoming electrons of 250 to 750 MeV. The calorimeter shows a good linearity over the electron energy region and the energy resolution was well expressed by σ(rms)/E = (16.5 ± 0.5)/√E(GeV) %. Also, it is shown that the deposited energy and energy resolution do not change greatly even when the incident beam position is very close to the detector edge. The agreement between these results and a Monte Carlo simulation is quite satisfactory.     

Accuracy of electromagnetic shower position determination by a wide-gap drift chamber

The electromagnetic shower position was measured by a wide-gap drift chamber placed behind an active converter. Different methods for the shower-position determination based on MHTDC and flash ADC were used. A spatial resolution of 1.9 mm (rms) at an energy of 3 GeV and a converter thickness of 3X₀ was achieved. The transverse charge distribution at different depths of the e.m. shower in the lead-glass was measured.     

Performance of a scintillating glass calorimeter for electromagnetic showers

A scintillating glass electromagnetic calorimeter consisting of 3 × 3 moduls of 8 × 8 × 66 cm³ each has been studied with electrons in the energy interval 14.7 MeV < E < 6000 MeV. An energy resolution of σ_E/E[%] = √1.6²/E[GeV] + 1.0² was achie spatial resolution turns out to be of the order σ = 4 to 8 m depending on the impact point and the angle of incidence; it improves with increasing energy. The observations are in excellent agreement with the result of an EGS Monte Carlo simulation of the detector including optical effects and photoelectron statistics.