出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：For several years, CALICE has been testing highly granular calorimeter prototypes using analogue readout. These devices are envisaged for particle flow [1] application in a future linear collider detector. A novel alternative, especially interesting for the hadron calorimeter, is to use a simplified digital (= 1 – bit) readout coupled with very small cell sizes. In the past year the first large scale (1m³) digital HCAL has been operated by CALICE in test beams at Fermilab. This detector uses glass RPCs as active elements within an iron absorber structure. The RPCs are read out through 1x1 cm² pads with a single threshold, providing a digital image of the hadronic or electromagnetic shower with high spatial resolution. We report on the technical performance of this calorimeter, and show first physics results on shower reconstruction. A related approach is to use RPCs with two-bit readout, providing three threshold values, referred to as a "semi-digital" HCAL. In 2010 a full 1m² plane was tested in a beam, and a full 1m³ is being tested at CERN in 2011. The electronics of the prototype was "power pulsed", a technique which is envisaged to reduce power dissipation in an ILC detector [3]. The performance of these RPCs was also tested in a 3T magnetic field. Alternative technologies for a digital HCAL are also being studied, both Micromegas, for which 1m² planes have already been tested in beams, and GEMs for which 30x30 cm² units are currently being tested. Second generation analogue devices are also under construction, and we report progress here. The focus of this work is to develop technical solutions which could be scaled up to a full-size detector. We report the development of a highly segmented electromagnetic calorimeter based on silicon sensors with 5x5 mm² segmentation, covering details of the sensor design, readout electronics and the mechanical and thermal issues of detector integration. An alternative technology based on scintillator-strip sensors is also being developed. The second generation analogue HCAL is based on scintillating tiles that are individually read out by silicon photomultipliers. The prototype will contain about 2500 detector channels, corresponding to one calorimeter layer.
