111121123
Irradiation studies of Gb/s optical links developed for the front-end read-out of the ATLAS liquid argon calorimeter
Abstract In the baseline read-out scheme of the ATLAS liquid argon calorimeter, approximately 1500 unidirectional Gigavit/s (Gb/s) optical links are used to transfer data from teh calorimeter to receivers in data acquisition electronics situated up to 200 metres away. In the architecture of the link currently under development, VCSEL's (Vertical Cavity Surface Emitting Laser diodes) mounted on-detector are coupled to PIN-photodiodes located in receivers through graded-index multimode optical fibres. Over 10 years of ATLAS running, the components of the emitter will be exposed to high levels of neutron (1.7 × 10 13 n (1MeV Si) cm −2 ) and gamma (800 Gy) radiation. Their performance has been explored using neutron and gamma facilities and the results of these studies are presented in this paper. No significant levels of radiation are expected for the receiving part of the link.
18954058
Quality Control of Optical Transmitters for the ATLAS Liquid Argon Calorimeter
A quality control test is performed on nearly 2000 custom optical transmitters for use in the Liquid Argon Calorimeter of the ATLAS detector. More than 90% of these optical transmitters passed the test and have been installed in the calorimeter readout system. The acceptance criteria, measurement procedure, and results of the quality control test are presented in this note.
120914328
The 120Gbps VCSEL Array Based Optical Transmitter (ATx) development for the High-Luminosity LHC (HL-LHC) experiments
The integration of a Verticle Cavity Surface-Emitting Laser (VCSEL) array and a driving Application-Specific Integrated Circuit (ASIC) in a custom optical array transmitter module (ATx) for operation in the detector front-end is constructed, assembled and tested. The ATx provides 12 parallel channels with each channel operating at 10 Gbps. The optical transmitter eye diagram passes the eye mask and the bit-error rate (BER) less than 10(-12) transmission is achieved at 10 Gbps/ch. The overall insertion loss including the radiation induced attenuation is sufficiently low to meet the proposed link budget requirement.
17189846
A Serializer ASIC at 5 Gbps for Detector Front-end Electronics Readout
Optical data links are used in detector front-end electronics readout systems of experiments in the Tevatron and the LHC. Optical links in high energy particle physics experiments usually have special requirements such as radiation tolerance, ultra high reliability and low power dissipation. These requirements are often not met by commercial components which are designed for applications in non-radiation, accessible (for maintenance) environment, and for multi-vendor systems so the parts must comply with certain standards. Future HEP experiments such as the upgrades for the sLHC call for optical links with ultra high data bandwidth, higher radiation tolerance and ultra low power dissipation. To meet these challenges and in particular those in the upgrade for the ATLAS Liquid Argon Calorimeter readout that calls for an optical link system of 100 Gbps for each front-end board, we adopted a full custom front-end electronics system design based on application specific integrated circuits. Reported here are the development and test results of two circuits: a 5 Gbps serializer and a 5 GHz phase locked loop, and a block diagram design for the 100 Gbps optical link.
18930090
Installation and Commissioning of the ATLAS LAr Readout Electronics
The Liquid Argon Calorimeter (LAr) is a subsystem in the ATLAS experiment which is being assembled at the Large Hadron Collider (LHC) at CERN. The readout electronics system for the LAr is discussed here. The front‐end of the readout will work in radiation environment. This special requirement has led to the development of a large number of rad‐hard ASICs. The back‐end of the readout employs DSPs to process data to reduce transmission bandwidth. The installation and commissioning of this readout is also discussed here.
55746504
The versatile link, a common project for super-LHC
A common project to develop a bi-directional, radiation tolerant, high speed (4.8 Gb/s) optical link for future high energy physics experiments is described. Due to be completed in 2012, it targets the upgrade programs of detectors installed at CERN's Large Hadron Collider (LHC). The development of radiation and magnetic field tolerant opto-electronic devices, fibre and connectors is described. Both Single-Mode and Multi-Mode versions of the system operating respectively at 850 nm and 1310 nm wavelength are proposed. First results at component and system level are presented, based mostly on commercially available devices.
31462099
Precision stabilization of femtosecond lasers to high-finesse optical cavities
We report on direct stabilization of a femtosecond laser by a high-finesse passive optical cavity. Detailed comparison of two distinct stabilization schemes leads to new understanding of the optimum conditions for cavity stabilization and limitations on the ability to transfer the frequency stability of the cavity to the microwave domain. The stability of the frequency comb is explored in both the optical and the radio frequency domain. With an independent, stable cw laser, we verify that the linewidth and stability of the optical comb components, respectively, reach below 300 Hz and 53 10 ˛14 at 1 s averaging time, both limited by the
20964607
Human breath analysis via cavity-enhanced optical frequency comb spectroscopy
To date, researchers have identified over 1000 different compounds contained in human breath. These molecules have both endogenous and exogenous origins and provide information about physiological processes occurring in the body as well as environment-related ingestion or absorption of contaminants1,2. While the presence and concentration of many of these molecules are poorly understood, many 'biomarker' molecules have been correlated to specific diseases and metabolic processes. Such correlations can result in non-invasive methods of health screening for a wide variety of medical conditions. In this article we present human breath analysis using an optical-frequency-comb-based trace detection system with excellent performance in all criteria: detection sensitivity, ability to identify and distinguish a large number of biomarkers, and measurement time. We demonstrate a minimum detectable absorption of 8 x 10-10 cm-1, a spectral resolution of 800 MHz, and 200 nm of spectral coverage from 1.5 to 1.7 micron where strong and unique molecular fingerprints exist for many biomarkers. We present a series of breath measurements including stable isotope ratios of CO2, breath concentrations of CO, and the presence of trace concentrations of NH3 in high concentrations of H2O.
7079909
Convergent Evolution of a New Arsenic Binding Site in the ArsR/SmtB Family of Metalloregulators*
Acidithiobacillus ferrooxidans has an arsenic resistance operon that is controlled by an As(III)-responsive transcriptional repressor, AfArsR, a member of the ArsR/SmtB family of metalloregulators. AfArsR lacks the As(III) binding site of the ArsRs from plasmid R773 and Escherichia coli, which have a Cys32-Val-Cys34-Asp-Leu-Cys37 sequence in the DNA binding site. In contrast, it has three cysteine residues, Cys95, Cys96, and Cys102, that are not present in the R773 and E. coli ArsRs. The results of direct As(III) binding measurements and x-ray absorption spectroscopy show that these three cysteine residues form a 3-coordinate As(III) binding site. DNA binding studies indicate that binding of As(III) to these cysteine residues produces derepression. Homology modeling indicates that As(III) binding sites in AfArsR are located at the ends of antiparallel C-terminal helices in each monomer that form a dimerization domain. These results suggest that the As(III)-S3 binding sites in AfArsR and R773 ArsR arose independently at spatially distinct locations in their three-dimensional structures.
118401596
Tenfold reduction of Brownian noise in optical interferometry
Thermally induced fluctuations impose a fundamental limit on precision measurement. In optical interferometry, the current bounds of stability and sensitivity are dictated by the excess mechanical damping of the high-reflectivity coatings that comprise the cavity end mirrors. Over the preceding decade, the mechanical loss of these amorphous multilayer reflectors has at best been reduced by a factor of two. Here we demonstrate a new paradigm in optical coating technology based on direct-bonded monocrystalline multilayers, which exhibit both intrinsically low mechanical loss and high optical quality. Employing these "crystalline coatings" as end mirrors in a Fabry-P\'erot cavity, we obtain a finesse of 150,000. More importantly, at room temperature, we observe a thermally-limited noise floor consistent with a tenfold reduction in mechanical damping when compared with the best dielectric multilayers. These results pave the way for the next generation of ultra-sensitive interferometers, as well as for new levels of laser stability.
119207145
Mid-Infrared Frequency Comb Fourier Transform Spectrometer
Optical frequency-comb-based-high-resolution spectrometers offer enormous potential for spectroscopic applications. Although various implementations have been demonstrated, the lack of suitable mid-infrared comb sources has impeded explorations of molecular fingerprinting. Here we present for the first time a frequency-comb Fourier transform spectrometer operating in the 2100-to-3700-cm-1 spectral region that allows fast and simultaneous acquisitions of broadband absorption spectra with up to 0.0056 cm-1 resolution. We demonstrate part-per-billion detection limits in 30 seconds of integration time for various important molecules including methane, ethane, isoprene, and nitrous oxide. Our system enables precise concentration measurements even in gas mixtures that exhibit continuous absorption bands, and it allows detection of molecules at levels below the noise floor via simultaneous analysis of multiple spectral features. This system represents a near real-time, high-resolution, high-bandwidth mid-infrared spectrometer which is ready to replace traditional Fourier transform spectrometers for many applications in trace gas detection, atmospheric science, and medical diagnostics.