First test results of a high-speed beam conditions monitor for the atlas experiment

The paper presents the design and first test results of the high-speed Beam Conditions Monitor (BCM) for the ATLAS Experiment at the Large-Hadron Collider (LHC). The goal of the BCM is to monitor instantaneous rates of collision and background and detect signs of beam instabilities. The detector is based on polycrystalline Chemical-Vapor-Deposition (pCVD) diamond as active sensor material. We have chosen this detector material for its proven radiation hardness and fast signal properties. For the readout of the diamonds we developed front-end readout electronics based on high-bandwidth RF amplifiers. The signal response of the amplifier has been optimized for the ionization current signal of pCVD diamond in order to achieve a signal rise time of /spl les/1 ns and pulsewidth of less than 3 ns. We present test results which were obtained on prototype assemblies in source tests and testbeam. The obtained results demonstrate the feasibility of such a detector system for the ATLAS BCM. The tests yield BCM signals with a mean rise time of 900 ps and a FWHM pulsewidth of 2.1 ns after 16 m of required transmission cable. The recorded signal amplitude distribution yields an most probable signal-to-noise ratio of 8.6:1 for single minimum-ionizing particles (MIP).

I. Introduction

This PAPER presents the design and first test results of the high-speed Beam Conditions Monitor (BCM) for the ATLAS Experiment at the Large-Hadron Collider (LHC). The BCM is part of the radiation and background monitoring system inside the ATLAS Inner Detector. The goal of the BCM is to: Fig. 1. Schematic illustration of four BCM stations around the beam pipe at m. An identical setup is mounted on the +z-side of the pixel detector. •

monitor instantaneous rates of collision and background (e.g., due to beam losses on collimators);

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provide feedback to the accelerator about the beam conditions very close to the interaction point;

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detect signs of beam instabilities and issue warning and alarm signals which can be used to protect other sensitive detector systems or trigger a beam abort.