Robert Grabit

Optical readout and control systems for the CMS tracker

The Compact Muon Solenoid (CMS) Experiment will be installed at the CERN Large Hadron Collider (LHC) in 2007. The readout system for the CMS Tracker consists of /spl sim/10 million individual detector channels that are time-multiplexed onto /spl sim/40000 uni-directional analogue (40MS/s) optical links for transmission between the detector and the /spl sim/65m distant counting room. The corresponding control system consists of /spl sim/2500 bi-directional digital (40Mb/s) optical links based upon the same components as far as possible. The on-detector elements (lasers and photodiodes) of both readout and control links will be distributed throughout the detector volume in close proximity to the silicon detector elements. For this reason, strict requirements are placed on minimal package size, mass, power dissipation, immunity to magnetic field and radiation hardness. It has been possible to meet the requirements with the extensive use of commercially available components with a minimum of customization. The project has now entered its volume production phase after successful completion of technical feasibility. Components have been identified that meet both the stringent analogue performance targets and are sufficiently radiation-hard for use in the CMS Tracker, where lifetime radiation exposure is expected to reach /spl sim/3.4/spl times/10/sup 14//cm/sup 2/ fluence and /spl sim/150kGy dose. Analogue and digital system performance, as well as the component radiation hardness and quality assurance procedures, are reviewed this paper.

Gamma and neutron radiation damage studies of optical fibres

An optical data link is under development at CERN for readout of the tracking detectors in the future compact muon solenoid experiment (CMS) at the CERN large hadron collider (LHC). Radiation doses inside the experiment will be ∼ 20 Mrad and ∼ 1014 n/cm2 over a 10 year period of operation. The effects of neutron and gamma irradiation on the attenuation at 1550 nm wavelength have been studied in both germanium-doped and pure-silica core single-mode optical fibres. The induced attenuation was greater in the Ge-doped fibre than in the pure-silica core fibres for both neutron and gamma damage. Pure-silica core fibres will be therefore be used in the CMS tracker. The gamma induced attenuation in the pure-silica core fibres was dependent on total dose, allowing a prediction to be made for the transmission losses during LHC operation.

SICAL — a high precision silicon-tungsten luminosity calorimeter for ALEPH

Abstract The design, construction and performance of a silicon-tungsten electromagnetic calorimeter built to achieve an experimental luminosity measurement precision at LEP≤0.1% is described. The detector uses homogeneous construction to give full azimuthal acceptance for Bhabha scattering over polar angles from 24 to 58 mrad. Detailed information concerning shower development is obtained from zero-suppressed readout of the 12288 pads of the detector. Trigger decisions are generated from a rapid flash-ADC system using programmable gate arrays.

Radiation hardness assurance and reliability testing of InGaAs photodiodes for optical control links for the CMS experiment

A radiation hard 80 Mbit/s digital optical link system with 7200 fiber channels is being produced for the CMS Experiment at CERN. A series of tests including radiation damage and thermally accelerated aging have been made to qualify and assure the radiation hardness and reliability of InGaAs photodiodes intended for use in this system.

Radiation hardness qualification of InGaAsP/InP 1310 nm lasers for the CMS Tracker optical links

The series of validation tests for radiation hardness qualification of lasers for use in 46000 optical links of the CMS Tracker detector at CERN, Geneva, Switzerland, are presented. These tests included accelerated radiation damage, annealing, and aging studies, simulating the effect of doses and fluences, up to 2/spl times/10/sup 14/ particles/cm/sup 2/ and 100 kGy, accumulated over a ten-year operating lifetime. The worst-case damage effect, in lasers operating closest to the beam-collision point, is expected to be a threshold current increase of under 6 mA. The lasers tested therefore qualify as being sufficiently radiation hard. The qualification tests also form the basis of future radiation hardness assurance of lasers during final production. An advance validation test of lasers from candidate wafers is defined that will confirm the radiation hardness of lasers before a large number of transmitters are assembled from these wafers.

ANALOGUE OPTICAL LINKS FOR THE CMS TRACKER READOUT SYSTEM

The optical fibre links for the analogue readout of the CMS tracker are based on the direct modulation of edge-emitting lasers located inside the detector volume. The front-end signals are transmitted by single-mode optical fibres and detected in the counting room using PIN photodiodes. One channel link demonstrators consisting of commercially available optoelectronic devices have been fully characterized. The lasers, fibres, and PIN diodes are representative of the devices intended to be used in the final system. The link overall performance is discussed in terms of its static and dynamic responses and is shown to meet the technical specifications of the full readout chain .

80Mbit/s digital optical links for control, timing and trigger of the CMS tracker

The development of a radiation hard 80Mbit/s digital optical link system for transmission of control, timing and trigger signals to and from the CMS Tracker is almost complete. This paper reviews the status of the project and summarises the performance of the most recent prototype components and links.

Energy and spatial resolution of a Shashlik calorimeter and a silicon preshower detector

New projective prototypes of a scintillator/lead sandwich type sampling calorimeter Shashlik with a silicon preshower detector have been constructed and tested with an electron beam at CERN-SPS. The energy resolution is measured to be 8.7%E(GeV) in stochastic term, 0.330/E(GeV) in noise term and 0.5% in constant term. The angular resolution is better than 70 mradE(GeV).

Field mapping and corrections of the magnet of a radio-frequency mass spectrometer

Abstract The design of the magnet for a radio-frequency mass spectrometer with resolving power in the range 105 to 106 is presented. The required homogeneity and initial physical characteristics of the magnet are summarized. Then, the experimental methods which have been used for field mapping and field corrections are explained. Final performances of the magnet homogeneity are given, which already provide a resolving power of 3×105, in agreement with the original goal.

Advance validation of radiation hardness and reliability of lasers for CMS optical links

The production of laser transmitters for 60000 optical links is ongoing for the CMS Experiment at CERN. A series of advance validation tests (AVTs) that assure the radiation hardness and reliability has been performed on 390 edge-emitting 1310 nm lasers taken from 13 different starting wafers, before the laser die have been assembled into final transmitters. The AVT also offered a first opportunity to characterize, with good statistics, the effects of radiation damage, annealing and accelerated aging, using a large number of laser samples.