L. Casagrande

Optimization of electric field distribution by free carrier injection in silicon detectors operated at low temperatures

We present a study of the modeling of the electric field distribution, which is controlled by injection and trapping of nonequilibrium carriers, in Si detectors irradiated by high neutron fluences. An analytical calculation of the electric field distribution in detectors irradiated by neutrons up to fluences of 1 /spl middot/ 10/sup 14/ to 5 /spl middot/ 10/sup 15/ cm/sup -2/ shows the possibility of reducing the full depletion voltage at low temperatures via hole injection. For this calculation, we use the detector operating parameters and equivalent neutron fluences expected for Large Hadron Collider experiments. The results of the calculation are in good qualitative agreement with published experimental data, lending strong support for the model and for an earlier proposal of electric field manipulation by free carrier injection.

A new ultra radiation hard cryogenic silicon tracker for heavy ion beams

AbstractWe have designed and built a new hodoscope for heavy ion beams consisting of two tracking stations equippedwith silicon microstrip detectors operated at 130K. Preliminary results from tests performed in the high intensityCERN-SPSPbionbeamshowthatwewereabletodetectandidentifyeachincomingionuptoabeamintensityofB10 7 ions/s.Thebeamprofilecouldbemonitoredon-linewith50mmresolution.Thedetectorperformedsatisfactoryevenafteradoseof90740Grad.r 2002ElsevierScienceB.V.Allrightsreserved. PACS:07.77. n;85.30.ZKeywords:Cryogenicsilicondetectors;Heavyions 1. IntroductionIn the framework of the CERN NA60 [1] andRD39Collaborations [2], we have developed anew cryogenic beam hodoscope, hereafter namedBeamscope, based on silicon microstrip detectorsoperated at 130K. This detector represents thefirst application in a high energy physics experi-mentofthecryogenicsilicontechnology,triggeredbythediscoveryofthe‘‘Lazaruseffect’’[3]in1998anddevelopedbyRD39.Operationofsiliconatcryogenictemperaturesisanattractivetechnologyindeedforapplicationinharsh environments. It has been shown [4,5] thatheavily irradiated silicon detectors operatedaround 130K have charge collection efficiency

Cryogenic operation of silicon detectors

This paper reports on measurements at cryogenic temperatures of a silicon microstrip detector irradiated with 24 GeV protons to a #uence of 3.5]1014 p/cm2 and of a p}n junction diode detector irradiated to a similar #uence. At temperatures below 130 K a recovery of charge collection e

Temperature dependence of the charge collection efficiency in heavily irradiated silicon detectors

ciency and resolution is observed. Under reverse bias conditions this recovery degrades in time towards some saturated value. The recovery is interpreted qualitatively as

Silicon detectors irradiated ''in situ'' at cryogenic temperatures

Abstract Two silicon diode detectors, Al/n + /n/p + /Al, were exposed to fluences of 1.19×10 14 and 2.23×10 15 equivalent 1 MeV neutrons/cm 2 , respectively. After this exposure the detectors were stored at room temperatures for 2 yr (1.19×10 14 ) and six months (2.23×10 15 ). During this time they were thermally cycled around 4.2 K and room temperature a number of times in order to make measurements. The charge collection efficiency is measured to be (at 77 K) 100% for the less severely irradiated detector and 50% for the detector exposed to high levels of radiation. The same results apply to operation at 4.2 K, while no recovery is observed at 195 K. By examining the signal response of the irradiated detectors to α particles, it is shown that some of the radiation damage after reverse annealing is in the form of electron and hole traps, which are either weakly, or not at all, temperature dependent.

Recent progress in low-temperature silicon detectors

Though several studies have proved the radiation tolerance of silicon detectors at cryogenic temperatures, following room temperature irradiation, no previous investigation has studied the behaviour of detectors irradiated ‘‘in situ’’ at low temperatures. In this work, effects of irradiation of 450 GeV protons at 83 K will be presented, showing that after a dose of 1.2 � 10 15 pc m � 2 a charge collection efficiency (CCE) of 55% is reached at 200 V before the annealing. The same results were found at the end of the irradiation, after the sample has spent more then one year at room temperature. This shows that the CCE recovery by low temperature operation is not affected by the temperature of irradiation and by the reverse annealing. r 2002 Elsevier Science B.V. All rights reserved.

Cryogenic technology for tracking detectors

The CERN RD39 Collaboration studies the possibility to extend the detector lifetime in a hostile radiation environment by operating them at low temperatures. The outstanding illustration is the Lazarus effect, which showed a broad operational temperature range around 130 K for neutron irradiated silicon detectors.

Radiation hard position-sensitive cryogenic silicon detectors: the Lazarus effect

A low-mass cryogenic cooling technique for silicon sensor modules has been developed in the framework of the RD39 Collaboration at CERN. A prototype low-mass beam tracker cryostat has been designed, constructed and tested for applications in fixed target experiments. We shall report here briefly the main features and results of the system.

Charge collection efficiency recovery in heavily irradiated silicon detectors operated at cryogenic temperatures

The discovery of the so-called Lazarus e!ect, namely the recovery of the charge collection e

Cryogenic semiconductor high-intensity radiation monitors

ciency (CCE) of irradiated silicon detectors by means of cryogenic cooling has entailed an increasing interest in the behavior of silicon detectors at cryogenic temperatures. We have measured the CCE of a silicon p}i}n diode detector previously irradiated with an equivalent #uence of 1]1015 n/cm2 neutrons of 1 MeV energy. The charge collection e