Sampling Electromagnetic Calorimeter Research Articles

Measurements of cosmic-ray proton and helium spectra with the PAMELA calorimeter

We present a new measurement of the cosmic ray proton and helium spectra by the PAMELA experiment performed using the “thin” (in terms of nuclei interactions) sampling electromagnetic calorimeter. The described method, optimized by using Monte Carlo simulation, beam test and experimental data, allows the spectra to be measured up to 10TeV, thus extending the PAMELA observational range based on the magnetic spectrometer measurement.

MAPS Technology for Vertexing, Tracking, and Calorimetry

Abstract Detectors at future linear colliders will require unprecedented energy and position resolutions. Two CMOS Monolithic Active Pixel Sensor (MAPS) concepts, TPAC and FORTIS, have been designed to study the issues involved in achieving these requirements. One application proposes MAPS as the active layer of a sampling electromagnetic calorimeter, allowing high granularity calorimeter systems which can utilise particle flow techniques. The TPAC sensors were developed to study this application. These sensors were made with a new fabrication technology and have demonstrated a significantly improved MIP effciency compared to sensors made using the standard fabrication technology. The sensors have been tested at CERN and DESY for their response to positrons, pions and electromagnetic showers. TPAC sensors have also been irradiated using x-rays to investigate their radiation hardness for use in vertex and tracking detectors. A noise increase ≤7% has been observed at 1 Mrad.

Development of readout interconnections for the Si-W calorimeter of SiD

The SiD collaboration is developing a Si-W sampling electromagnetic calorimeter, with anticipated application for the International Linear Collider. Assembling the modules for such a detector will involve special bonding technologies for the interconnections, especially for attaching a silicon detector wafer to a flex cable readout bus. We review the interconnect technologies involved, including oxidation removal processes, pad surface preparation, solder ball selection and placement, and bond quality assurance. Our results show that solder ball bonding is a promising technique for the Si-W ECAL, and unresolved issues are being addressed.

THE ATLAS ELECTROMAGNETIC CALORIMETERS: FEATURES AND PERFORMANCE

In this paper it is shown how a sampling electromagnetic calorimeter based on the liquid argon technique satisfies the very demanding requirements of an experiment at the LHC. Section 2 discusses, using a simplified model, the performance that can be achieved in terms of response time, energy resolution and transverse granularity. Section 3 describes how the calorimeters are realized in ATLAS, their segmentation and how from the readout pulses the energy deposited in the calorimeter is computed. The motivations of a presampler detector in front of the calorimeter are also discussed. Section 4 describes how the energy, position and direction of an electron and a photon are computed. Finally, Sec. 5 briefly illustrates the rejection power of the calorimeter against the hadrons and mentions how a Higgs boson signal in the γγ channel can already be detected with a luminosity of 10 fb-1.

Performance of prototypes for the ALICE electromagnetic calorimeter

The performance of prototypes for the ALICE electromagnetic sampling calorimeter has been studied in test beam measurements at FNAL and CERN. A 4 × 4 array of final design modules showed an energy resolution of about 11 % / E ( GeV ) ⊕ 1.7 % with a uniformity of the response to electrons of 1% and a good linearity in the energy range from 10 to 100 GeV. The electromagnetic shower position resolution was found to be described by 1.5 mm ⊕ 5.3 mm / E ( GeV ) . For an electron identification efficiency of 90% a hadron rejection factor of > 600 was obtained.

A Moon-borne electromagnetic calorimeter

We discuss an electromagnetic sampling calorimeter for the detection of very high energy gamma-rays on the Moon, which is based on the use of scintillating cylinders and plates imbedded in the lunar soil. The use of lunar soil as a calorimeter radiator reduces the weight of the material to be transported to the Moon and minimises environmental impact. Plastic scintillator bars inserted into the regolith about 1.5 m are the active elements of this instrument: at the surface, each bar is terminated by a plastic scintillator plate to veto high energy charge particles. The readout system for the scintillator bars and plates are based on recently developed single photon solid state detectors (Silicon Photomultiplier, SiPM), extremely compact, sturdy and sensitive devices suited for detecting small light pulses in a space experiment. The performance of a regolith-scintillator calorimeter is evaluated and the relevant parameters are optimised using a GEANT4 simulation.

Electromagnetic shower reconstruction with emulsion films in the OPERA experiment

OPERA is a neutrino oscillation experiment designed to perform a ντ appearance search in the CNGS beam from CERN to Gran Sasso underground laboratory, 730 km from CERN. The identification of the τ lepton produced by a ντCC interaction is based on the use the Emulsion Cloud Chamber (ECC) which consists of a modular structure made of a sandwich of passive material plates interleaved with emulsion films. In addition of its very good tracking information capability, used to the detection of short-lived particles, the ECC can be used as a fine sampling electromagnetic calorimeter allowing the study of the τ→ e decay and the νμ → νe oscillation channel. We will report the method developped to reconstruct the electromagnetic showers with ECC and the energy measurement in the 1-10 GeV range.

Beam test results of a high-granularity tile/fiber electromagnetic calorimeter

A prototype sampling electromagnetic calorimeter (17.1 radiation lengths) for future linear collider experiments was built, using 4 cm × 4 cm × 1 mm plastic scintillator tiles and 4 mm-thick lead absorber. Wavelength-shifting fibers were used to guide the scintillation light into multi-anode photo-multiplier tubes. The calorimeter was tested at the beam test facility of the High Energy Accelerator Research Organization (KEK) in 2004. In this article we present our beam test results for the tile/fiber calorimeter focusing on the linearity in energy response, the energy resolution, position resolution and uniformity across the tile front face.

A MAPS-based readout of an electromagnetic calorimeter for the ILC

The physics goals of the International Linear Collider (ILC) require a significant improvement in the calorimetric performance relative to previous generations of detectors. Sampling electromagnetic calorimeters (ECAL) using silicon diodes as the active media are widely considered as a suitably performant—but very expensive–solution. A new digital approach to electromagnetic calorimeter design based on 50 μm pitch Monolithic Active Pixel Sensors is presented as an alternative solution which could offer (at least) the same performance at significantly reduced cost.

The CLAS forward electromagnetic calorimeter

The CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab utilizes six iron-free superconducting coils to provide an approximately toroidal magnetic field. The six sectors are instrumented individually to form six independent spectrometers. The forward region (8°< θ<45°) of each sector is equipped with a lead–scintillator electromagnetic sampling calorimeter (EC), 16 radiation lengths thick, using a novel triangular geometry with stereo readout. With its good energy and position resolution, the EC is used to provide the primary electron trigger for CLAS. It is also used to reject pions, reconstruct π° and η decays and detect neutrons. This paper treats the design, construction and performance of the calorimeter.

APD performance in a luminosity monitor at LEP

Avalanche Photo-Diodes (APDs) are being used as optical readout elements in a sampling electromagnetic calorimeter made of alternate layers of tungsten and plastic scintillators. The calorimeter serves as a small-angle luminosity monitor in the stray magnetic field of the ALEPH detector at LEP (CERN). Its scintillators are coupled both to APDs and conventional PMTs simultaneously via wavelength shifter fibres. In this paper we present results on the overall performance of the APDs, including gain and stability versus time and energy, based on the direct comparison of the two photosensitive devices.

A sampling electromagnetic calorimeter for alpha magnetic spectrometer

We present designs of different three-dimensional (3D) sampling electromagnetic calorimeters for the AMS experiment. The proton rejection power of 3D sampling calorimeters is discussed. A shower shape analysis procedure provides a typical proton suppression factor of ≈10 4 for most of the designs.

Measurement of the proton structure function F2 and σ at low and very low x at HERA

A small electromagnetic sampling calorimeter, installed in the ZEUS experiment in 1995, significantly enhanced the acceptance for very low x and low Q2 inelastic neutral current scattering, e+p → e+X, at HERA. A measurement of the proton structure function F2 and the total virtual photon-proton (γ∗p) cross-section is presented for 0.11 ≤ Q2 ≤ 0.65 GeV2 and 2 × 10−6 ≤ x ≤ 6 × 10−5, corresponding to a range in the γ∗p c.m. energy of 100 ≤ W ≤ 230 GeV. Comparisons with various models are also presented.

The CPLEAR electromagnetic calorimeter

A large-acceptance lead/gas sampling electromagnetic calorimeter (ECAL) was constructed for the CPLEAR experiment to detect photons from decays of π 0s with momentum p π 0 ≤ 800 MeV/ c. The main purpose of the ECAL is to determine the decay vertex of neutral-kaon decays K 0 → π 0π 0 → 4γ and K 0 → π 0π 0π 0 → 6γ. This requires a position-sensitive photon detector with high spatial granularity in r−, ϕ−, and z−coordinates. The ECAL - a barrel without end-caps located inside a magnetic field of 0.44 T - consists of 18 identical concentric layers. Each layer of 1 3 radiation length ( X 0) contains a converter plate followed by small cross-section high-gain tubes of 2640 mm active length which are sandwiched by passive pick-up strip plates. The ECAL, with a total of 6 X 0 has an energy resolution of α(E) E ≈ 13% (E( GeV) and a position resolution of 4.5 mm for the shower foot. The shower topology allows separation of electrons from pions. The design, construction, read-out electronics, and performance of the detector are described.

The CPLEAR detector at CERN

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using K 0 and K 0 produced by the annihilation of p 's in a hydrogen gas target. The K 0 and K 0 are identified by their companion products of the annihilation K ± π ∓ which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the subdetectors are described.

Multiplicity and energy trigger for a sampling electromagnetic calorimeter

We describe the trigger system for the electromagnetic calorimeter of the OBELIX experiment operating at the LEAR ring at CERN. The system has been studied mainly for multiplicity trigger on gamma rays, but energy and angular selections can also be performed. The designing criteria, the electronics performances, as well as the measured trigger capability to select some exclusive reactions are reported.

Systematic investigation of the electromagnetic energy resolution on sampling frequency using silicon calorimeters

The energy resolution, of electromagnetic sampling calorimeters using silicon mosaics as active medium, has been measured for Pb and Fe absorbers at incoming electron energies of 2, 4, and 6 GeV. The energy resolution, found for the Si/Pb and Si/Fe calorimeters, is well represented by σ(E) E = K τ E( GeV) , where τ is the sampling frequency and E the incoming electron energy. The energy resolution can be rewritten as a function of the dead area energy losses (D): σ(E)/E = (K 0(1 + a 1D))% τ E( GeV) with K 0 = (17.6 ± 0.3)%, (22.8 ± 0.8)%, for Si/Pb, Si/Fe, respectively; a 1 = 0.07 ± 0.02 for both absorbers.

MC-simulations with EGS4/PRESTA for an electromagnetic sampling calorimeter

The electron transport algorithm PRESTA, developed to improve calculations of electron transport in the low-energy region, is applied to simulations of an electromagnetic sampling calorimeter using a thin silicon detector. Calculated results by default EGS4, EGS4 ESTEPE, and EGS4/PRESTA are compared with experimental values. EGS4/PRESTA can provide almost the same results as those obtained by selected ESTEPE values without considering the materials used at a speed several times faster than that of EGS4/ESTEPE. EGS4/PRESTA is applied to compensation studies by the SICAPO collaboration in order to understand the reason for reductions of the visible energy of electrons using different methods.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characteristics of scintillating fiber electromagnetic calorimeters with wavelength-shifter readout

We studied characteristics of sampling electromagnetic calorimeters comprising of lead absorber and 1 mm diameter scintillating fibers with wavelength-shifter readout using 1–5 GeV electrons. The volume ratio of lead to scintillator was kept at approximately 4:1 for compensation. Fibers were arranged to be perpendicular to incident electrons. Scintillation lights were detected by a pair of photomultiplier tubes through wavelength-shifter plates placed perpendicularly to the two ends of fibers. Two fiber assembly techniques were employed. Photoelectron statistics and energy resolution were compared with those of conventional tile scintillator calorimeter modules.

Optimization of electromagnetic sampling calorimeters

Abstract Allowing variable sampling steps, we show that an electromagnetic calorimeter can be optimized to give small overall energy fluctuations from sampling and leakage. Compared to the case of constant sampling frequency the benefits are: significantly better energy resolution for a given number of samplers, a significant reduction of the number of samplers needed to obtain a given energy resolution, and a significant compactification of the calorimeter.