S. Chapuy

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.

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

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.

Recent progress in low-temperature silicon 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.

Cryogenic technology for tracking detectors

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.

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

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

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

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

Irradiated silicon detectors operated at cryogenic temperatures: The Lazarus effect

ciency has been measured at 77 K, showing that the low-temperature operation considerably decreases the bias current. This is also the case when forward voltage bias is applied, which then becomes a suitable option. In this condition, the sample shows a charge collection e

Charge collection efficiency of irradiated silicon detector operated at cryogenic temperatures

ciency in excess of 65% at 250 V corresponding to a most probable signal for a minimum ionizing particle of 21 000e~. ( 2000 Elsevier Science B.V. All rights reserved.

Review on the development of cryogenic silicon detectors

The charge collection efficiency (CCE) of high resistivity silicon detectors, previously neutron irradiated up to 2/spl times/10/sup 15/ n/cm/sup 2/, was measured at different cryogenic temperatures and different bias voltages. In order to study reverse annealing (RA) effects, a few samples were heated to 80/spl deg/C and kept at room temperature for several months after irradiation. For comparison other samples (NRA) where kept at -10 C after irradiation. The RA and NRA samples, measured at 250 V forward and reverse bias voltage, present a common temperature threshold at 150 K. Below 120 K the CCE is constant and ranges between 55% and 65% for the RA and NRA sample respectively. Similar CCE was measured for a device processed with low resistivity contacts (OHMIC), opening the prospect for a consistent reduction of the cost of large area particle tracking.

Charge collection efficiency of an irradiated cryogenic double-p silicon detector

An increasing interest in the behaviour of silicon detectors at cryogenic temperatures has been awakened by the discovery of the so-called Lazarus effect, namely the recovery of charge collection efficiency (CCE) by means of cryogenic cooling. We measured the CCEs of three single diodes previously irradiated with different neutron fluences. The current-voltage characteristic were measured at 300 and 77 K, showing that the low-temperature operation considerably decreases the steady-state current. This is also the case when a forward voltage bias is applied, which then becomes a suitable option. At 77 K, in the case of samples irradiated with 5 x 10 14 neutrons cm -2 , the CCE is completely recovered. A third sample irradiated with 2 x 10 15 neutrons cm -2 shows a 60% CCE at 250V forward bias.