ID: 10
Corresponding Author: Thomas TOIFL
Experiment: General Interest
Sub-system: Trigger
Topic: R/M field tolerant electronics

Measurements of Radiation Effects on the Timing, Trigger and Control Receiver (TTCrx) ASIC

Thomas Toifl, Paulo Moreira, Alessandro Marchioro
CERN

Abstract:

The Timing, Trigger and Control Receiver Asic (TTCrx) receives and distributes the clock, the trigger decision, and other synchronisation signals. In this paper the radiation-hard version of the TTCrx, manufactured in DMILL technology, is discussed. First, the architecture of the circuit is described, where we concentrate on the changes to the existing prototype and on the measures taken to increase robustness with respect to single event upsets (SEU). In the second part we will present measurements of the circuit characteristics before and after irradiation with gammas and neutrons. In the last part we will then show measurements of the SEU behavior.

Summary:

A tree network of optical fibres will be used for the distribution of the clock, trigger and control signals to the LHC particle detector systems as defined by the RD12 collaboration. At the receiver side, a photodiode converts the optical signal into electrical impulses, which are then received by the Timing, Trigger and Control Receiver ASIC. The circuit recovers the clock and the encoded data from the incoming Biphase Mark encoded bitstream. It contains fine-deskew units to adjust the delay of the clock with a nominal delay resolution of 104 ps. The level 1 trigger and other synchronisation signals, e.g. the bunch counter reset signal, can be delayed by a programmable number of cycles. In addition, the chip decodes slow control data and makes them available to connected electronics on a parallel bus.

In the first section of the paper we will discuss the architecture and functionality of the circuit, where we concentrate on the changes to a previous prototype. We will also describe the design measures taken for increased robustness with respect to SEU effects.

In the second section of the paper we will present measurement results, divided into three parts: The first part contains general performance measures before irradiation. The second part is concerned with the measurement of total dose effects due to gamma and neutron irradiation. In the third part we will then show measurement results for the SEU sensitivity, for which the chip and the photodiode were irradiated in a proton, neutron and heavy ion beam.

Id: 32
Corresponding Author: Juan AGAPITO
Experiment: General Interest
Sub-system: General Interest
Topic: R/m Field Tolerant Electronics

Instrumentation amplifiers and voltage controlled current sources for LHC cryogenic instrumentation

J. A. Agapito(3), F. M. Cardeira(2), J. Casas(1), A. P. Fernandes(2), F. J. Franco(3), P. Gomes(1), I. C. Goncalves(2), A. Hernandez Cachero(3), J. Lozano(3), M. A. Martin(3), J. G. Marques(2), A. Paz(3), A. J. G. Ramalho(2), M. A. Rodriguez Ruiz(1) and J. P. Santos(3).
1 CERN, LHC Division, Geneva, Switzerland.
2 Instituto Tecnol¢gico e Nuclear (ITN), Sacav‚m, Portugal.
3 Universidad Complutense (UCM), Electronics Dept., Madrid, Spain.

Abstract:

Two different topologies for the basic instrumentation amplifier have been studied. Both amplifier and current source circuits have been designed, constructed and tested under radiation. All radiation campaigns have been carried out in ITN (Portugal) research nuclear reactor. A new facility for neutron beam extraction has been constructed. On line measurements of the offset voltages, offset currents, closed loop gain, and bias currents have been performed on the two structures for two different operational amplifiers, OPA124 & TLE2071. A study of the influence of each individual parameters to the whole has been carried out. Three voltage controlled current sources have been made with every instrumentation amplifier. Three values of current for each set of amplifiers have been fixed, adjusted to the different ranges of measurement of the cold mass temperature sensor. On line measurements of the currents are presented as a function of neutron radiation. And finally on line measurements of commercial voltage references are presented as a function of radiation.

Summary:

The influence of neutron and gamma radiation on operational amplifiers parameters was studied and experiments in a nuclear reactor were performed and reported in LEB99. Those tests provided the necessary information to select the amplifier that exhibited a better radiation tolerance to the expected doses in LHC cryogenic system. None of the amplifiers were instrumentation operational amplifiers, to be used in the signal conditioners for the cold mass temperature measurement and control. We decided to analyze instrumentation amplifiers and current source circuits designed with single operational amplifiers using the characteristics obtained in last campaigns. Two different topologies for the basic instrumentation amplifier have been studied. Both amplifier and current source circuits have been designed, constructed and tested under radiation. All radiation campaigns have been carried out in ITN (Portugal) research nuclear reactor. A new facility for neutron beam extraction has been constructed so that the gamma radiation has been reduced and the neutron fluence maintained to a rate as to obtain the whole desired dose in 5 days, 12 hours work. On line measurements of the offset voltages, offset currents, closed loop gain, and bias currents have been performed on the two structures of instrumentation amplifiers for two different operational amplifiers, OPA124 & TLE2071. The radiation is monitored by mean of three photodiodes placed in the center and the two ends of the set of circuit boards.

A study of the influence of each individual parameters to the whole has been carried out. The open loop gain is severely affected by neutron radiation. The circuits under study exhibit a stable closed loop gain as long as the open loop gain is maintained over 100V/mV. When this is lower, the structure with 2 opamp's is less affected than the 3 opamp's circuit. There is also an increase of the common mode gain, which affects in the reduction of the CMRR. These is also more important in the 3 opamp's circuit because of its low CMRR even without radiation. On the other hand the circuit with 2 opamp's needs a restricted voltage sweep values for common mode input. The gain of the reference voltage input is 1 and no significant differences between both structures have been detected.

Both circuits are very sensitive to offset voltage deviations of their components. Input opamp's contribute most largely to the offset voltage of the whole amplifier than any other component. Thus the output offset voltage of the instrumentation amplifier is a function of the characteristics of the input amplifiers. The values of all the individual parameter are compared after radiation with those obtained before and presented in a plot.

Three voltage controlled current sources have been made with every instrumentation amplifier. Three values of current for each set of amplifiers have been fixed, adjusted to the different ranges of measurement of the cold mass temperature sensor. The influence of the deviation of the individual parameters does not affect in the same manner to these circuits as it does to the instrumentation amplifier. When the open loop gain decrease dramatically to a value of 10V/mV the current across the sensor deviates less than 0.2% of its nominal value.

On line measurements of the currents are presented as a function of neutron radiation. Finally on line measurements of commercial voltage references are presented as a function of radiation.

Id: 35
Corresponding Author: Martin DENTAN
Experiment: ATLAS
Sub-system: General Interest
Topic: R/m Field Tolerant Electronics

Overview of the ATLAS Policy on Radiation Tolerant Electronics

Martin Dentan, CERN & CEA-DAPNIA
Philippe Farthouat, CERN

Abstract:

ATLAS Sub-systems will integer a very large quantity and variety of electronics boards which will be submitted to radiations ranging from few krads and few 1E10 n/cm2 to few 10 Mrads and few 1E14 n/cm2, and to energetic particles capable of producing SEE (Single Event Effects). ATLAS Technical Coordination has developed in collaboration with the Sub-systems a new policy on radiation tolerant electronics. It provides guidelines for the pre-selection and for the qualification of all the commercial electronics components that will be used in ATLAS, in order to make sure they will resist to the foreseen radiation constraints. This paper summarises the main guidelines given in the ATLAS Policy on Radiation Tolerant Electronics, and the benefits resulting from this policy.

Summary:

The first goal of ATLAS Policy on Radiation Tolerant Electronics is the general safety of the ATLAS materials and of the persons working on the experiment. Therefore, all the components or systems on which radiation effects can cause fire or induce high and long term radioactivity levels are not allowed.

The second goal of this policy is to help ATLAS Sub-systems to build electronics complying with the level of radiation tolerance which is necessary for their system. This level must be determined by the Sub-systems. It represents the minimum doses and fluences which must be tolerated by the electronics, and the maximum rate of soft, hard or destructive Single Event Effects (SEE) acceptable for the electronics. This level of reliability must be maintained during the 10 years of operation of the experiment. This can be obtained by qualifying ASICs developed with a radiation-hard technology that complies with the radiation tolerance required for 10 years of operation, or by selecting and qualifying standard electronics components (COTS) that comply with the radiation tolerance required for 10 years of operation, or by selecting less radiation tolerant COTS and making sure that it will be possible to replace them if necessary after their expected lifetime.

The third goal of this policy is to help Sub-systems to build electronics within the foreseen schedule. Therefore, it includes a strategy for pre-selection, qualification and purchase of components which is built with the aim of reducing procurement risks.

Id: 39
Corresponding Author: Gunnar LINDSTROEM
Experiment: General Interest
Sub-system: Tracker
Topic: R/m Field Tolerant Electronics

Developments for Rdaiation Hard Silicon Detectors by Defect Engineering - Results of the CERN RD48 (ROSE) Collaboration

Gunnar Lindstroem (cospokesman of RD48) on behalf of the RD48 collaboration

Abstract:

The success of the Oxygen enrichment of FZ silicon as a highly powerful defect engineering technique and its optimization with various commercial manufacturers are reported. Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too. Diode characteristics of test pad- and LHC-strip detectors are compared. The RD48 model for the dependence of radiation effects on fluence, temperature and operational time is verified; projections to operational scenarios for main LHC experiments demonstrate vital benefits. Present microscopic understanding of damage effects including differences caused by charged and neutral hadrons are discussed too.

Summary:

The RD48(ROSE) collaboration has succeeded to develop radiation hard silicon detectors, capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach this objective, a defect engineering approach was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ). Systematic measure- ments have been carried out with various standard and oxygenated material in fluence ranges between 5e10 and 5e14 cm-2 (1MeV-n- equivalent). The defect generation on a microscopic scale was also studied, gaining invaluable insight in the underlying physics. Only macroscopic effects of the O-enrichment with direct relevance for LHC detector application are summarized in the following:

* Leakage current: the damage parameter alpha is material independent (no dependence on conduction type, crystal orientation, resistivity and impurities) and is scaling almost ideally with NIEL (non ionizing energy loss) independent of particle type and energy.

* Effective doping concentration (depletion voltage): the damage induced change in Neff is considerably improved after charged hadron irradiation. Short term annealing (10 days at RT) leads to about 3 times less increase in the depletion voltage as compared to standard silicon and the reverse annealing even shows an unexpected saturation at higher fluences. This amounts to a decrease in the Neff-change by as much as a factor of 4 and is also connected with a 5 times larger annealing time, thus offering an additional safety margin for detectors kept at room temperature during maintenance. To present knowledge these improvements hold only for proton irradiation (in accordance with existing checks for pions), for neutrons a beneficial effect was observed by using low resistivity material (e.g. 1 kOhmcm instead of the standard 5 kOhmcm silicon decreases the change in Neff after 2e14 n/cm² by a factor of about 2).

* Charge collection efficiency: while the measurements for Neff have mostly been performed on test pad diodes using C/V methods, these results have been checked both with test and silicon strip detectors measuring the charge collection efficiency as function of bias voltage. The results show a good agreement between both techniques also revealing that the systematic analysis done with test diodes can reliably be used for strip detectors.

* Model description for macroscopic damage effects and projection to LHC: For the above described effects the "Hamburg-model" had been applied for the O-enriched silicon detectors and relevant parameters were extracted. The application of the model to LHC operational scenarios indicates that by using oxygenated instead of standard silicon the lifetime of e.g. the sensors in the B-layer of the ATLAS pixel detector would be extended to almost 10 years. In fact, the ATLAS pixel group had meanwhile decided to use the RD48 developed technique.

* Optimization of the DOFZ technique: So far feasibility studies with various companies have shown that the oxygenation of the silicon bulk by prolonged tempering after normal oxidation (diffusion of O from the SiO2-Si interface) does not result in any problem. Optimization experiments are presently carried out with O-diffusion in the range between 6 days at 1200C and 8 hours at 1150C.

Id: 42
Corresponding Author: Peter SKOROBOGATOV
Experiment: General Interest
Sub-system: General Interest
Topic: R/m Field Tolerant Electronics

The nonlinear behaviour of p-i-n diode in high intense radiation fields

P.K.Skorobogatov, A.S.Artamonov, B.A.Ahabaev Specialized electronic systems

Abstract:

The dependence of p-i-n diode ionizing current amplitude vs dose rate is defined using twodimensional software simulation. It is shown that analyzed dependence becomes nonlinear beginning with relatively low dose rates near 107 rad(Si)/s. This effect is connected with the modulation of p-i-n diode intrinsic region by irradiation. As a result the distribution of electric field becomes non-uniform that leads to decrease of excess carriers collection. The ionizing current pulse form becomes more prolonged because of delayed component contribution. It is necessary to take into account when p-i-n diode is used as dose rate dosimeter.

The p-i-n diodes are widely used for the measurements of ionizing radiation dose rates. The high electric field in its intrinsic region provides the full and fast excess carriers collection. As a results the ionizing current pulse waveform repeats the ionization pulse with the accuracy of several nanoseconds. To investigate the p-i-n diode possibilities at high dose rates the original software simulator "DIO-DE-2D" [1] was used. The "DIODE-2D" is the fundamental system of equations two-dimensional solver. It takes into account carrier generation, recombination and transport, optical effects, carrier's lifetime and mobility dependencies on excess carriers and doping impurity concentrations. The typical p-i-n diode with 380 micrometers intrinsic region width under 300 V reverse bias was investigated. The simulation of p-i-n diode structure have shown that linear dependence between dose rate and ionizing current is valid only at relatively low dose rates up to 107 rad(Si)/s. In the field of high dose rates this dependence becomes non-linear and ionizing current increases more slowly than dose rate. The reason of non-linearity is connected with the modulation of p-i-n diode intrinsic region by excess carriers. Because of low level of initial carriers concentration the modulation takes place at relatively low dose rates. As a result of modulation the distribution of electric field in the intrinsic region becomes non-uniform that leads to decrease of excess carriers collection. The behavior of p-i-n diode becomes similar to that of ordinary p-n junction with prompt and delayed components of ionizing current. The prompt component repeats the dose rate waveform. The delayed component is connected with the excess carriers collection from regions with low electric fields. As a result the ionizing current pulse form becomes more prolonged and dose not repeat the dose rate waveform. The numerical results were confirmed by experimental measurement of p-i-n diode ionizing reaction in wide range of ionizing radiation dose rates. The non-linear character of behavior and prolonged reaction must be taken into account when p-i-n diode is used as dose rate dosimeter.

References [1]. The "DIODE-2D" Software Simulator Manual Guide, SPELS, 1995.

Id: 43
Corresponding Author: Peter SKOROBOGATOV
Experiment: General Interest
Sub-system: General Interest
Topic: R/m Field Tolerant Electronics

Use of external resistor to prevent radiation induced latch-up in commercial CMOS IC's

P.K.Skorobogatov, A.Y.Nikiforov, A.A.Demidov Specialized electronic systems

Abstract:

It is shown that in the case of external resistor usage to prevent radiation induced latch-up in commercial CMOS IC's we have the increase of IC recovery time up to tens of microsecond due to deep saturation of parasitic bipolar transistors. Under numerical calculations it was found that there is an optimal value of external resistor that provides the minimal recovery time of IC.

The usage of commercial CMOS IC's in radiation environment is restricted by the possibility of its latch-up behaviour under irradiation. The external resistor in power supply circuit is a well-known way to prevent latch-up. This method is found on the restriction of IC power supply current to the level lower than latch-up holding current. The experiments were shown however that in this case we unfortunately have the increase of IC recovery time up to tens of microsecond. Under numerical calculations it was found that this effect is connected with deep saturation of parasitic bipolar transistors on the external resistance. It was found that there is an optimal value of external resistor that provides the minimal recovery time of IC. In the case of low resistance the large recovery time is connected with deep level of parasitic transistors saturation. In the case of high resistance value the recovery time is defined by well-substrate p-n junction ionizing current delayed component voltage drop on the external resistance that increases with resistance growth. For CMOS IC's under investigation the optimal value was near 80 Ohm. This effect must be taken into account when commercial CMOS IC's are used in radiation environment.

Id: 48
Corresponding Author: Eduard ATKIN
Experiment: ALICE
Sub-system: General Interest
Topic: R/m Field Tolerant Electronics

HIGH-SPEED COMPARATOR IC WITH LOW TIME DISPERSION

E.V.Atkin

Abstract:

The high-speed comparator for fast time reference is represented. It can be used as a leading edge discriminator or as a core for building constant fraction discriminator and can be useful for the development of time-of-flight systems.

It is manufactured with a bipolar process. Its main feature is a small time dispersion of output signal (200 ps) at the presence of a wide dynamic range of input signals (overdrives from 10 mV to 1V).

This paper describes the approach to the design of the new version of a low time dispersion comparator. The structure of such a comparator, features of schematics of its separate stages and its parameters are described.

Summary:

The paper reflects the results of the activities, being the continuation of the MEPhI group's efforts on developing precise timing discriminators [1].

The cost effective high-speed comparator IC for fast time reference is represented. It can be used as a leading edge discriminator or as a core for building constant fraction discriminator. It can be useful for the development of time-of-flight systems (such as ALICE TOF), providing a time reference accuracy at the order of tens of picoseconds.

It is manufactured on the basis of an application specific semicustom array with a bipolar process [2].

This paper describes the approach to the design of the new version of a low time dispersion comparator. The structure of such a comparator and its schematics were designed to make it a functional analog of the well-known IC AD96685 from Analog Devices.

The comparator contains three symmetrical differential stages and is added by the circuits of built-in hysteresis (from 0 to 4 mV) control and output signal logic variation. Its main peculiarity consists in the fact, that the small time dispersion of output signal (~200 ps) is specified for a wide dynamic range of input signals (overdrives from 10 mV to 1V) and for a temperature range from 0 to 70 °C. The propagation delays were defined with a 100 mV pulse.

The mentioned parameters were achieved at the expense of using: · non-standard differential stages built as current amps; · dynamic nonlinear loads, providing the compression of input signals.

Especial attention was paid to minimize the static errors and intrinsic noise of the comparator. The following table presents certain comparator parameters.

Parameter Value Units

Input bias current 20 max uA

Input offset current 2.0 max uA

Input offset voltage 2.0 max mV

Input voltage range ±2.5 V

Intrinsic input noise 1.0 rms mV

Outputs provide complementary digital signals fully compatible with ECL 10K logic families. The output signal logic variation is provided by applying a control potential to a separate IC pin.

Power consumption of the comparator does not exceed 150 mW at standard supply voltages of ±5V.

References

1P.Khlopkov et al. A discriminator PCB for precise timing signal generation. Third Workshop on Electronics for LHC experiments, London, Sept. 22-26, 1997, CERN/LHCC/97-60, p. 497-499.

2A.Goldsher et al. A semicustom array chip for creating high-speed front-end LSICs. Same as previous, p. 257-259.

Id: 69
Corresponding Author: Helio TAKAI
Experiment: ATLAS
Sub-system: Calorimetry
Topic: Radiation and magnetic field tolerant electronics systems

Switching Power Supply Technology for ATLAS LAr Calorimeter

H. Takai and J. Kierstead
(for the ATLAS Liquid Argon collaboration)
Brookhaven National Laboratory

Abstract:

The ATLAS liquid argon calorimeter is designing a switching power supply to be meet the harsh environmental requirements imposed by the location where they will be installed. In addition the design addresses the inaccessibility issue. We will present the design and available tests regarding radiation and magnetic field susceptibility.

The ATLAS liquid argon calorimeter is planning to install power supplies for the front end electronics in the gap region between the tile barrel and tile extended calorimeters. The required power for the overall electronics is approximately 150 kW. This requirement rules out the use of copper cables to bring the power to the crates. In this location the environmental and access issues are such that the design will have to follow very tight specifications. The environmental issues are twofold: magnetic field and nuclear radiation. The radiation in the location of the power supply is a mixture of particles from the tails of Hadronic showers. They include photons, hadrons, and electrons. The expected integrated dose over a period of ten years is of the order of 10 kRad, and the overall flux of 1 MeV equivalent neutrons 1x10^12.cm-2. The flux of neutrons above 1 MeV is estimated to be 5 kHz.cm-2. The magnetic field in the region of the power supplies is estimated to be 50 Gauss. The current maintenance schedule allows access to the volume including the power supplies only once a year, therefore reliability and remote monitoring and control is essential. The final requirement that we have to meet is a very limited space.

With these requirements in mind, we have established a strategy for the development of appropriate power supplies. Currently, we expect to have prototypes ready by the end of year 2000. The plan calls for a radiation tolerant and single event upset resistant power supply with remote operational capabilities. At the heart of the power supply blocks of DC-DC converters will be used. A number of these blocks will be connected in parallel to form an N+1 redundant system. Each block will be monitored during the operation for temperature, fatal failure, over-current, and over-voltage. At the present time two potential manufacturers have been identified, Vicor and Modular Devices Inc. Vicor modules meet the requirements for electronic noise, magnetic field, and limited radiation tolerance but have not been tested for single event effects. The DC-DC converter manufactured by Modular Devices is known to be radiation tolerant but has not been tested for magnetic field or SEE effects. The control circuits are designed to be radiation and SEE tolerant.

In spring 2000 we plan to initiate tests for SEE susceptibility using heavy ion beams, followed by tests using 100 MeV or greater protons. We are particularly concerned with SEB or SEGR in the power mosfets as well as possible latchups in the control logic. We will report on the progress on the development of the power supply. In particular preliminary tests as far as radiation is concerned will be discussed.