May 15 – 20, 2016
EXCO in Daegu, Republic of Korea
Asia/Seoul timezone

Towards a technological prototype for a high-granularity electromagnetic calorimeter for future lepton colliders

May 20, 2016, 11:20 AM
EXCO in Daegu, Republic of Korea

EXCO in Daegu, Republic of Korea


Taikan Suehara (Kyushu University)


A key ingredient to meet the requirements of the physics program at energy frontier machines such as future lepton colliders or the LHC are calorimeters with an unprecedented high granularity. These kind of calorimeters allow for the application of particle flow algorithms that rely on an excellent particle separation within the calorimeter. The R&D program comprises an electromagnetic calorimeter with tungsten with a radiation length $X_0=3.5$~mm, Moli\`ere radius $R_M=9$ mm and interaction length $\lambda_I=96$~mm as absorber material and silicon as the active material. French and Japanese groups within the CALICE collaboration are conducting an intensive program for the development of highly granular calorimeters. A physics prototype with a pixel size of $1 \times 1~{\rm cm^2}$ dedicated mainly to demonstrate the physics potential of a calorimeter has been successfully operated in the years 2005-2011. It has been proven that the pixelised silicon wafers are particularly suited to assure a high separation power while allowing at the same time a stable detector operation over a long time. These are reasons why this technology has been chosen for the upgrade of the forward calorimeters of the CMS experiment at the LHC.The technology is also studied for the upgrade of the ATLAS detector. The design of the (next) prototype for a silicon tungsten (SiW) electromagnetic calorimeter puts the emphasis on the understanding and overcoming of the engineering challenges imposed by the requirements on the detector compactness. The main units of the calorimeter prototype are: - The so called {\it alveolar structure} made of pre-impregnated carbon-fibre and epoxy which is also equipped with the tungsten absorber material. This alveolar structure has been fabricated during winter 2011/12 and is now subject to external mechanical studies including thermal tests. - Layers with a length of up to 1.5\,m that carries up to 8 Active Signal Units or ASUs which is the entity of four silicon wafer, PCB and readout electronics. An ASU features a lateral dimension of $18 \times 18~{\rm cm^2}$ each and in the most aggressive design a height of about 2\,mm. It comprises 1024 cells read out by 16 ASICs. In an initial phase with ASUs carrying only one wafer and four ASICs have been tested that allowed for example to validate the concept of embedded electronics. We have now turned to the production of several fully equipped ASUs that undergo validation in beam tests and on test benches. In both cases the flexible and in many parts scalable data acquisition system will be used. The presentation will report on first results of this validation but will also sketch the main steps of the involved production process that is part is supported but the European AIDA-2020 and since recently by the French excellence programme P2IO. Both programmes seek explicitly to foster synergies between the necessary R&D programs for CALICE, ATLAS and CMS. An overview on synergies is thus part of the proposed contribution for the CALOR conference. The contribution will finally report on the R&D programme on silicon wafers and on irradiation tests carried out in 2015 at Japanese irradiation facilities.


The CALICE collaboration is preparing large scale prototypes for highly granular calorimeters for detectors to be operated at a future lepton collider. Currently a prototype of a silicon-tungsten electromagnetic calorimeter Si-W ECAL will be assembled which in terms of dimensions and layout meets already most of the requirements given by the lepton collider physics programme and hence the detector design. In particular the front end electronics will be embedded into the layer structure of the calorimeter and have to fit within alveolar layers with less than 1 cm in height. In this contribution the design of the prototype is presented and the steps towards the realisation will be presented. Note finally that the presented technology plays also a key role in the upgrades of the LHC Experiments CMS and ATLAS.

Primary author

Taikan Suehara (Kyushu University)


Roman Poeschl (Laboratoire de l'Accelerateur Lineaire (FR))

Presentation materials