Two special calorimeters are foreseen for the instrumentation of the very forward region of the ILC detector, a luminometer designed to measure the rate of low angle Bhabha scattering events with a precision better than 10-3 and a low polar angle calorimeter, adjacent to the beam-pipe. The latter will be hit by a large amount of beamstrahlung remnants. The amount and shape of these depositions will allow a fast luminosity estimate and the determination of beam parameters. The sensors of this calorimeter must be radiation hard. Both devices will improve the hermeticity of the detector in the search for new particles. Finely segmented and very compact calorimeters will match the requirements. Due to the high occupancy fast front-end electronics is needed. The design of the calorimeters developed and optimised with Monte Carlo simulations is presented. Sensors and readout electronics ASICs have been designed and prototypes are available. Results on the performance of these major components are summarised.

Forward Instrumentation for ILC Detectors

Detector Technologies for CLIC

Radiation hardness of GaAs sensors against gamma-rays, neutrons and electrons

The Compact Linear Collider (CLIC) is a high-energy high-luminosity linear electron-positron collider under development. It is foreseen to be built and operated in three stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. It offers a rich physics program including direct searches as well as the probing of new physics through a broad set of precision measurements of Standard Model processes, particularly in the Higgs-boson and top-quark sectors. The precision required for such measurements and the specific conditions imposed by the beam dimensions and time structure put strict requirements on the detector design and technology. This includes low-mass vertexing and tracking systems with small cells, highly granular imaging calorimeters, as well as a precise hit-time resolution and power-pulsed operation for all subsystems. A conceptual design for the CLIC detector system was published in 2012. Since then, ambitious R&D programmes for silicon vertex and tracking detectors, as well as for calorimeters have been pursued within the CLICdp, CALICE and FCAL collaborations, addressing the challenging detector requirements with innovative technologies. This report introduces the experimental environment and detector requirements at CLIC and reviews the current status and future plans for detector technology R&D.

Detector-plane prototypes of the very forward calorimetry of a future detector at an e+e− collider have been built and their performance was measured in an electron beam. The detector plane comprises silicon or GaAs pad sensors, dedicated front-end and ADC ASICs, and an FPGA for data concentration. Measurements of the signal-to-noise ratio and the response as a function of the position of the sensor are presented. A deconvolution method is successfully applied, and a comparison of the measured shower shape as a function of the absorber depth with a Monte-Carlo simulation is given.

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Performance of fully instrumented detector planes of the forward calorimeter of a Linear Collider detector

A compact and finely grained sandwich calorimeter is designed to instrument the very forward region of a detector at a future e+e- collider. The calorimeter will be exposed to low energy e+e - pairs originating from beamstrahlung, resulting in absorbed doses of about one MGy per year. GaAs pad sensors interleaved with tungsten absorber plates are considered as an option for this calorimeter. Several Cr-doped GaAs sensor prototypes were produced and irradiated with 8.5-10 MeV electrons up to a dose of 1.5 MGy. The sensor performance was measured as a function of the absorbed dose.

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Investigation of the radiation hardness of GaAs sensors in an electron beam

The beam calorimeter in the forward region of the ILC detectors will be hit by a large amount of electron-positron pairs originating from beamstrahlung, a new phenomenon at the ILC. The by ionization deposited energy in the BeamCal sensor planes can be as high as 10 MGy per year of operation. The FCAL collaboration investigates different alternatives as possible sensor materials: polycrystalline and single crystal CVD diamond and GaAs. The investigation of these materials includes the measurement of the charge collection distance and the radiation hardness against irradiation with 10 MeV electrons in a test beam to doses of several MGy.

Radiation hard sensors for the beam calorimeter of the ILC

This report was done during the DESY summer student program in 2007. The performance of irradiated GaAs being a probable material for BeamCal at the ILC detector will be measured and discussed. The irradiation took place in Darmstadt at the end of June in 2007 in the framework of the project “TestBeam07”. The report considers I-V characteristics as well as results from CCD (Charge Collection Distance) measurements.

https://www-zeuthen.desy.de/students/2007/doc/bernitt.pdf

Petty Bernitt

Papers

Investigation of the radiation hardness of GaAs sensors in an electron beam

Radiation hard sensors for the beam calorimeter of the ILC

Properties of GaAs as detector material for BeamCal