The gain of silicon photomultipliers (SiPMs) increases with bias voltage and decreases with temperature. To operate SiPMs at stable gain, the bias voltage can be readjusted to compensate for ...temperature changes. We have tested this concept with 30 SiPMs from three manufacturers (Hamamatsu, KETEK and CPTA) operating in a climate chamber at CERN by varying temperatures between 1ˆC and 48ˆC. We built an adaptive power supply that uses a linear dependence of the bias voltage on temperature. We stabilized four SiPMs simultaneously with only one compensation parameter for the readjustment of the bias voltage of four SiPMs. For all tested Hamamatsu and CPTA SiPMs we achieved our goal of limiting gain changes to less than ±0.5% in the 20–30ˆC temperature range.
We report on latest version of the calibration and monitoring system developed for the scintillator tile hadron calorimeter (AHCAL) for the ILC. System is based on original fast (3 ns pulsewidth) and ...precise LED driver called QMB. One UV-LED can illuminates 72 scintillating tiles with SiPM. Distribution of the light pulses uses notched fibres, developed at our laboratory. All parts of the system are continually upgraded to get better results. The system is flexible to all necessary task monitoring and calibration of SiPM detector. It has high dynamic range of precise a few nanosecond pulses. Low intensity LED pulses are needed to obtain nice SiPM single photoelectron spectra. A routine monitoring of all SiPMs during test beam operations is achieved with mid-range a fixed-intensity light pulse. The full SiPM response function is cross-checked by varying the light intensity from zero to the saturation level. In calibration systems we developed, we concentrate especially on the aspect a high dynamic range of precise a few nanosecond pulses. Calibration system has been tested with 2.2m long slab of engineering AHCAL prototype uses 864 SiPM embedded in 3 by 3cm scintillator tiles and represents a part of the biggest planned detector using SiPMs.
We present a study of the response of the highly granular Digital Hadronic Calorimeter with steel absorbers, the Fe-DHCAL, to positrons, muons, and pions with momenta ranging from 2 to 60GeV/c. ...Developed in the context of the CALICE collaboration, this hadron calorimeter utilises Resistive Plate Chambers as active media, interspersed with steel absorber plates. With a transverse granularity of 1×1cm2 and a longitudinal segmentation of 38 layers, the calorimeter counted 350,208 readout channels, each read out with single-bit resolution (digital readout). The data were recorded in the Fermilab test beam in 2010–11. The analysis includes measurements of the calorimeter response and the energy resolution to positrons and muons, as well as detailed studies of various shower shape quantities. The results are compared to simulations based on Geant4, which utilise different electromagnetic and hadronic physics lists.
Gain Stabilization of Silicon Photomultipliers Cvach, J.; Eigen, G.; Kvasnicka, J. ...
2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC),
2017-Oct.
Conference Proceeding
The gain of silicon photomultipliers (SiPMs) increaseswith bias voltage V_{\mathbf{bias}} and decreases with temperature T. For stable operation, the gain G needs to be kept constant, especially in ...large detector systems such as an analog hadron calorimeter operating with 10^{\mathbf{6}} SiPMs 1. Variations of the ambient temperature and heat produced by electronics typically induces gain changes in SiPMs. The method of keeping the gain constant consists of adjusting V_{\mathbf{bias}}when T changes. This requires knowledge of dV/dT, which we obtain from measurements of dG/dV dG/dT. Assuming a linear dependence of G versus V_{\mathbf{bias\, }}and T yields constant values for dG/dV versus T and dG/dT versus V_{\mathbf{bias}} and in turn a constant value for dV/dT. We built a bias voltage regulator that adjusts V_{\mathbf{bias}}. We tested gain stability of 30 SiPMs from three manufacturers (Hamamatsu, KETEK, CPTA) in the temperature range of 1 ^{circ}\mathrm{C}- 50 ^{circ}\mathrm{C} using a climate chamber at CERN. While six of the Hamamatsu SiPMs have trenches to suppress cross talk, all other SiPMs have no trenches. We consider gain stabilization successful if the gain change in 20 ^{circ}\mathrm{C}- 30 ^{circ}\mathrm{C} is smaller than ± 0.5%. In our tests, we stabilized four SiPMs simultaneously with one dV/dT setting. This work was accomplished in the framework of AIDA2020. Do not cite references in the abstract. Do not delete the blank line immediately above the abstract; it sets the footnote at the bottom of this column.
An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer ...sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration/monitoring system based on LED light was developed to monitor the SiPM gain and to measure the full SiPM response curve in order to correct for non-linearity. Ultimately, the physics goals are the study of hadron shower shapes and testing the concept of particle flow. The technical goal consists of measuring the performance and reliability of 7608 SiPMs. The AHCAL was commissioned in test beams at DESY and CERN. The entire prototype was completed in 2007 and recorded hadron showers, electron showers and muons at different energies and incident angles in test beams at CERN and Fermilab.
The energy resolution of a highly granular 1 m super(3) analogue scintillator-steel hadronic calorimeter is studied using charged pions with energies from 10GeV to 80GeV at the CERN SPS. The energy ...resolution for single hadrons is determined to be approximately 58%/ square root E/GeV. This resolution is improved to approximately 45%/ square root E/GeV with software compensation techniques. These techniques take advantage of the event-by-event information about the substructure of hadronic showers which is provided by the imaging capabilities of the calorimeter. The energy reconstruction is improved either with corrections based on the local energy density or by applying a single correction factor to the event energy sum derived from a global measure of the shower energy density. The application of the compensation algorithms to GEANT4 simulations yield resolution improvements comparable to those observed for real data.
Markers of Recurrence and Long-Term Morbidity in Craniopharyngioma: A Systematic Analysis of 171 Patients on behalf of the Craniopharyngioma Study Group: Prs. and Drs. Anne Bachelot, Anne-Laure Boch, Raja Brauner, Jean-Claude Carel, Anne Colobert, Hélène Crosnier, Vonny Derennes, Pierre Doyard, Françoise Getin, Isabelle Guilhem, Muriel Hoang, Claire Josseaume, Julianne Leger, Sylvie Nivot, Christian Pauwels, Graziella Pinto, Michel Polak, Raphaël Rappaport, Dinane Samara, Sylvie Sauvion, Caroline Thalassinos, and Elisabeth Thibaud; Gautier, Alain; Godbout, Ariane ...
The journal of clinical endocrinology and metabolism,
04/2012, Letnik:
97, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Context:
Craniopharyngiomas are often associated with an unfavorable prognosis, but data on their long-term consequences are sparse.
Objective:
The aim of the study was to identify markers of ...recurrence and factors associated with compromised social rehabilitation and altered quality of life in a large cohort of patients with either childhood-onset (CO) or adult-onset craniopharyngioma.
Methods:
Retrospective analysis was performed for 171 patients treated for craniopharyngioma in two academic centers in France between 1972 and 2009. For each subject, data were collected concerning clinical presentation, imaging features, visual sequelae, endocrine and metabolic impact, treatment modalities (surgery, radiotherapy), recurrence-free survival rate, and social insertion, as well as answers to the WHO-QOL BREF questionnaire.
Results:
A total of 65 CO and 106 adult-onset patients were reviewed. If CO was diagnosed before the age of 10 yr, this was associated with a higher incidence of obesity, blindness, and panhypopituitarism, and only 40.7% of subjects had adequate work or school attendance compared to 72.4% of patients with later disease onset. Initial symptoms of intracranial hypertension (SIHT), pterional surgery, and multiple surgery were associated with obesity and poorer social insertion. No determinant of quality of life was identified. In the subgroup of patients treated in the 1990s and later, the progression rate was 59.4% in patients with residual tumor on magnetic resonance imaging compared with a 19.8% recurrence rate in the group with apparently complete resection. Recurrence/progression correlates significantly with male gender, early onset (before 10 yr), and SIHT, but only SIHT at presentation remained a significant predictor with multivariate analysis.
Conclusions:
Craniopharyngioma continues to be associated with severe outcomes. Higher morbidity rates are found in patients with early-onset disease (before 10 yr), initial SIHT, or in whom pterional surgery was required. Markers of recurrence are difficult to identify, with SIHT being the most powerful predictor.
The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the electromagnetic calorimeter, ...the current baseline choice is a high granularity sampling calorimeter with tungsten as absorber and silicon detectors as sensitive material. A ``physics prototype'' has been constructed, consisting of thirty sensitive layers. Each layer has an active area of 18x18 cm2 and a pad size of 1x1 cm2. The absorber thickness totals 24 radiation lengths. It has been exposed in 2006 and 2007 to electron and hadron beams at the DESY and CERN beam test facilities, using a wide range of beam energies and incidence angles. In this paper, the prototype and the data acquisition chain are described and a summary of the data taken in the 2006 beam tests is presented. The methods used to subtract the pedestals and calibrate the detector are detailed. The signal-over-noise ratio has been measured at 7.63 +/- 0.01. Some electronics features have been observed; these lead to coherent noise and crosstalk between pads, and also crosstalk between sensitive and passive areas. The performance achieved in terms of uniformity and stability is presented.
We report upon the performance of an analog hadron calorimeter prototype, where plastic scintillator tiles are read out with wavelength-shifting fibers coupled to avalanche photodiodes. This ...prototype configuration has been tested using a positron beam at DESY with energies between 1 and 6
GeV. We present different detector calibration methods, show measurements for noise, linearity, and energy resolution and discuss gain monitoring with an LED system. The results are in good agreement with our simulation studies and previous measurements using silicon photomultiplier readout.
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