Calorimetry plays a crucial role in modern experimental physics. Calorimeters are essential tools to extract physics in accelerator and non-accelerator experiments. The physics phenomena at the base of cascading processes in matter and the basic principles of calorimeters operation are reviewed at the light of data obtained from running experiments or from sets of dedicated measurements and the constraints from physics requirements. From this understanding comes the possibility of building powerful calorimetric systems with the optimal performances required by future experiments at high-energy and ultrahigh-energy regimes.

https://iopscience.iop.org/article/10.1088/0034-4885/63/4/202/pdf

Physics of cascading shower generation and propagation in matter: principles of high-energy, ultrahigh-energy and compensating calorimetry

The ZEUS group plans to install planes of large-area silicon diodes in depleted-uranium-scintillator calorimeters to separate electrons from hadrons in jets. This method was tested at 3, 5 and 9 GeV at CERN. Arrays of diodes were studied at depths between about 1 and 9 radiation lengths in a lead-scintillator calorimeter and in a simulated calorimeter consisting of depleted uranium and lucite. The e-h separation efficiency was measured for one and two planes of diodes as a function of depth in the calorimeter. A hadron misidentification of 2% at an electron efficiency of 90% was obtained with one plane of diodes. Addition of a second plane of diodes reduced the hadron misidentification to 0.3% with an electron efficiency of 90%. These results demonstrate that silicon diodes are excellent devices for e–h separation in a calorimeter.

Experimental study of electron-hadron separation in calorimeters using silicon diodes

The electromagnetic section of a hadronic calorimeter, consisting of uranium absorbers and of silicon sampling units with an active area of 0.25 m2, was investigated. The overall performance of the silicon detectors and especially developed associated electronics, seems to be stable and reliable. During a four-week run at the t9, CERN-PS (Proton Synchrotron) electron beam (energies of 2 to 6 GeV), no variation of energy calibration of the calorimeter was observed. The energy resolution for electromagnetic showers was found to be about 19.8% ( τ E ) , where E is the energy of the incoming electron and τ is the number of radiation lengths of passive material interspaced between two active samplers, for a calorimeter depth of 15.6 X0 (radiation lengths), with Si samplers depleted to 200 μm. The fiberglass supports of the silicon mosaics cause a reduction of energy response to electromagnetic showers. It can be exploited to equalize the response of a Si/U hadronic calorimeter to incoming electrons and hadrons.

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Experimental results from a sandwich calorimeter using U absorbers and 0.25 m2 of Si active area

Performance tests of a first calorimeter module using the room temperature liquid tetramethylsilane (TMS) as active element are described. Normal carbon steel has been used as absorber. The charge yield is 70% of that in a very pure sample of the liquid. A long term stability of the signal with a lifetime of half a year has been realized.

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Performance test of a TMS calorimeter

The endcap calorimeter of the CMD-2 detector for the VEPP-2M collider is described. The calorimeter consists of 680 BGO crystals, arranged in two endcaps. The light readout is performed by vacuum phototriodes. For the energy of incident photons from 100 to 700 MeV the energy resolution is 4–8% and angular resolution is 0.02–0.03 rad in agreement with MC simulation.

The BGO endcap calorimeter with phototriode readout for the CMD-2 detector

After a short introduction the situation of electromagnetic and hadronic calorimeters is reviewed. As an outlook important features of future calorimeters are discussed.

Joachim Engler

Papers

Perspectives in calorimetry