Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5873794
Yasushi Sato, H. Murayama, K. Oda, F. Nishikido, E. Yoshida, Tomohiko Sato, T. Hasegawa, N. Inadama, T. Yamaya, Takahiro Yamada, Y. Unno, A. Yunoki
We have devised a standardization method for a sealed point source that can be applied to nuclides such as 22Na that emit a positron and at least one gamma ray. This method is based on coincidence counting of annihilation radiation and gamma rays using a scintillation detector array. In the present study, we performed Monte Carlo simulations to examine this method for various measurement conditions. EGS5 Monte Carlo simulation results confirm that this method is effective for measurements of a 22Na sealed point source using BGO scintillation detector arrays
{"title":"Evaluation of a standardization method for 22Na sealed point sources for various measurement conditions","authors":"Yasushi Sato, H. Murayama, K. Oda, F. Nishikido, E. Yoshida, Tomohiko Sato, T. Hasegawa, N. Inadama, T. Yamaya, Takahiro Yamada, Y. Unno, A. Yunoki","doi":"10.1109/NSSMIC.2010.5873794","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5873794","url":null,"abstract":"We have devised a standardization method for a sealed point source that can be applied to nuclides such as 22Na that emit a positron and at least one gamma ray. This method is based on coincidence counting of annihilation radiation and gamma rays using a scintillation detector array. In the present study, we performed Monte Carlo simulations to examine this method for various measurement conditions. EGS5 Monte Carlo simulation results confirm that this method is effective for measurements of a 22Na sealed point source using BGO scintillation detector arrays","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"28 1","pages":"427-430"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81190122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5874558
Yuefeng Zhu, W. Kaye, Zhong He, Feng Zhang
An experiment to measure the performance of 3-D position-sensitive pixellated HgI2 crystals cooled below room temperature was carried out using a new ASIC from GammaMedica-Ideas. This ASIC is capable of reading out the digitized pre-amplifier signal waveforms of 121 pixels and the cathode. A significant improvement in energy resolution from 1.48% FWHM at 662keV for the whole detector to 1.09% FWHM is observed on a 18×18×11mm3 crystal at −4800V cathode bias when the ambient temperature is lowered from 70°F to 50°F (about 10°C). This resolution improvement is partly due to electronic noise reduction in the readout system. However, analysis of the pre-amplifier waveforms showed that changes in crystal properties played a more important role. A correlation between total electron trapping and energy resolution was identified. However, the amount of trapping was found irrelevant to crystal performance. Instead, the non-uniformity of charge collection, namely non-uniformity of the material defects, was believed to be the main contributor to crystal performance.
{"title":"Performance improvement of 3-D position-sensitive pixellated HgI2 detectors when cooled from room temperature to 10 °C","authors":"Yuefeng Zhu, W. Kaye, Zhong He, Feng Zhang","doi":"10.1109/NSSMIC.2010.5874558","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5874558","url":null,"abstract":"An experiment to measure the performance of 3-D position-sensitive pixellated HgI2 crystals cooled below room temperature was carried out using a new ASIC from GammaMedica-Ideas. This ASIC is capable of reading out the digitized pre-amplifier signal waveforms of 121 pixels and the cathode. A significant improvement in energy resolution from 1.48% FWHM at 662keV for the whole detector to 1.09% FWHM is observed on a 18×18×11mm3 crystal at −4800V cathode bias when the ambient temperature is lowered from 70°F to 50°F (about 10°C). This resolution improvement is partly due to electronic noise reduction in the readout system. However, analysis of the pre-amplifier waveforms showed that changes in crystal properties played a more important role. A correlation between total electron trapping and energy resolution was identified. However, the amount of trapping was found irrelevant to crystal performance. Instead, the non-uniformity of charge collection, namely non-uniformity of the material defects, was believed to be the main contributor to crystal performance.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"31 1","pages":"3959-3962"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85515607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5874171
M. Brambilla, V. Rebuffel, Markus Mronz, Holger Bruenner
Dual modality imaging is an emerging and fast developing technique due to its advantage in providing complementary anatomical and functional information. Moreover, in the specific case of Fluorescence Molecular Tomography (FMT), knowledge of the detailed anatomical structure of the subject can be very helpful in improving 3D fluorescence reconstruction. In the framework of the FMT-XCT European Project, aimed at the development of a hybrid tomographic x-rays and optical prototype, we propose in this paper a specific micro-CT system, appropriate for small animal imaging and satisfying the needs of the dual-modality approach. The system is minimizing X-ray interference with optical components, and offers improved contrast between internal tissues to be used as prior information for the FMT inversion procedure. For the contrast enhancement goal, a dual-energy approach has been investigated and evaluated. System configuration, acquisition protocol and processing algorithms are described in the following sections. Software simulation has been used for the optimization of the imaging configuration and the suggested specifications and the resulting imaging performances are experimentally validated.
{"title":"Optimization of a contrast enhanced micro-CT in a hybrid fluorescence / x-ray tomography system for small animal imaging","authors":"M. Brambilla, V. Rebuffel, Markus Mronz, Holger Bruenner","doi":"10.1109/NSSMIC.2010.5874171","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5874171","url":null,"abstract":"Dual modality imaging is an emerging and fast developing technique due to its advantage in providing complementary anatomical and functional information. Moreover, in the specific case of Fluorescence Molecular Tomography (FMT), knowledge of the detailed anatomical structure of the subject can be very helpful in improving 3D fluorescence reconstruction. In the framework of the FMT-XCT European Project, aimed at the development of a hybrid tomographic x-rays and optical prototype, we propose in this paper a specific micro-CT system, appropriate for small animal imaging and satisfying the needs of the dual-modality approach. The system is minimizing X-ray interference with optical components, and offers improved contrast between internal tissues to be used as prior information for the FMT inversion procedure. For the contrast enhancement goal, a dual-energy approach has been investigated and evaluated. System configuration, acquisition protocol and processing algorithms are described in the following sections. Software simulation has been used for the optimization of the imaging configuration and the suggested specifications and the resulting imaging performances are experimentally validated.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"21 1","pages":"2194-2199"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86028814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5873759
T. Gandhi, N. Hartsough, J. Iwanczyk, W. Barber
We are combining recent developments in nanomaterials with the concept of silicon photomultipliers (SiPMs) to develop cost-effective, large-area photodetectors for applications in medical imaging and other low-light sensing applications. Silicon nanowires are grown inside of a template made up of an array of insulating nanotubes on a quartz substrate, generating a close-packed array of vertically-oriented nanowires. A gold layer positioned at the bottom of each nanotube acts as the catalyst for silicon growth. By doping the silicon as it is grown, each nanowire becomes a p-i-n photodiode. A resistive layer provides the necessary quenching resistance for each photodiode, and pixels are defined by ganging the outputs of a region of nanowires together. Preliminary results of the growth process are presented.
{"title":"Novel silicon photomultiplier (SiPM) detector arrays","authors":"T. Gandhi, N. Hartsough, J. Iwanczyk, W. Barber","doi":"10.1109/NSSMIC.2010.5873759","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5873759","url":null,"abstract":"We are combining recent developments in nanomaterials with the concept of silicon photomultipliers (SiPMs) to develop cost-effective, large-area photodetectors for applications in medical imaging and other low-light sensing applications. Silicon nanowires are grown inside of a template made up of an array of insulating nanotubes on a quartz substrate, generating a close-packed array of vertically-oriented nanowires. A gold layer positioned at the bottom of each nanotube acts as the catalyst for silicon growth. By doping the silicon as it is grown, each nanowire becomes a p-i-n photodiode. A resistive layer provides the necessary quenching resistance for each photodiode, and pixels are defined by ganging the outputs of a region of nanowires together. Preliminary results of the growth process are presented.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"92 1","pages":"260-263"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84078849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5873855
A. Hidvégi, Patrick Gesler, K. Rehlich, C. Bohm
The European XFEL project requires a high-speed and high-quality clock and trigger distribution system. The main clock frequency is 1.3 GHz and needs to be distributed over several kilometers of distance. At each destination several clock frequencies needs to be derived and triggers needs to be decoded. All clocks and triggers must be phase stable throughout the entire system. However, every component, such as fiber cables and electronic ICs, are drifting with temperature changes. These changes are monitored and compensated. Jitter must be kept below 5 ps (RMS). Three prototypes have been created so far. An evaluation board to test the key concept of the system and a fully functional Advanced Mezzanine Card (AMC), of which a second revision have been designed and manufactured. This paper will describe key concept of the timing system while focus a little bit more on the latest revision of the boards and firmware development.
{"title":"Development of the XFEL timing system","authors":"A. Hidvégi, Patrick Gesler, K. Rehlich, C. Bohm","doi":"10.1109/NSSMIC.2010.5873855","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5873855","url":null,"abstract":"The European XFEL project requires a high-speed and high-quality clock and trigger distribution system. The main clock frequency is 1.3 GHz and needs to be distributed over several kilometers of distance. At each destination several clock frequencies needs to be derived and triggers needs to be decoded. All clocks and triggers must be phase stable throughout the entire system. However, every component, such as fiber cables and electronic ICs, are drifting with temperature changes. These changes are monitored and compensated. Jitter must be kept below 5 ps (RMS). Three prototypes have been created so far. An evaluation board to test the key concept of the system and a fully functional Advanced Mezzanine Card (AMC), of which a second revision have been designed and manufactured. This paper will describe key concept of the timing system while focus a little bit more on the latest revision of the boards and firmware development.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"33 1","pages":"734-736"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78334945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5874315
F. Daver, C. Schiepers, Jason T. Lee, L. Wei, M. Dahlbom
The Genisys preclinical PET imaging system suffers from relatively poor spatial resolution and reconstruction artifacts in the sagittal and transaxial planes due to limited angular sampling. This prevents reliable quantification and delineation of organs and tumors in close proximity. The use of factor analysis (FA) is proposed as a method to mitigate this effect by separation of structures into "factor" images. Two studies are performed The first study involved the application of FA on a synthetically created dynamic image in order to create factor curves. These factor curves were then compared to the synthetic curves used to create the synthetic image The second study applied FA to a dynamic image of tumor-bearing mouse The resulting factor images were assessed in order to determine how well the tumor was separated from other structures. The results from the first study displayed a very strong agreement between the synthetic curves and the factor curves. The second study displayed a prominent tumor presence within the two most significant factors. The results show promise for FA, but further research into optimal conditions must be performed
{"title":"Organ delineation using factor analysis on the Genisys preclinical PET system","authors":"F. Daver, C. Schiepers, Jason T. Lee, L. Wei, M. Dahlbom","doi":"10.1109/NSSMIC.2010.5874315","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5874315","url":null,"abstract":"The Genisys preclinical PET imaging system suffers from relatively poor spatial resolution and reconstruction artifacts in the sagittal and transaxial planes due to limited angular sampling. This prevents reliable quantification and delineation of organs and tumors in close proximity. The use of factor analysis (FA) is proposed as a method to mitigate this effect by separation of structures into \"factor\" images. Two studies are performed The first study involved the application of FA on a synthetically created dynamic image in order to create factor curves. These factor curves were then compared to the synthetic curves used to create the synthetic image The second study applied FA to a dynamic image of tumor-bearing mouse The resulting factor images were assessed in order to determine how well the tumor was separated from other structures. The results from the first study displayed a very strong agreement between the synthetic curves and the factor curves. The second study displayed a prominent tumor presence within the two most significant factors. The results show promise for FA, but further research into optimal conditions must be performed","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"34 1","pages":"2851-2855"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78343543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5873760
Kan Yang, M. Zhuravleva, P. Szupryczynski, C. Melcher
Single crystal of strontium iodide doped with 1% europium (SrI2: 1% Eu2+) was grown by Vertical Gradient Freeze technique. Temperature response and thermoluminescence glow curves of SrI2: 1% Eu2+ were studied. UV excitation spectrum of SrI2: 1%Eu2+ at 298 K shows a broad excitation peak at 367 nm. At ∼ 24 K, additional excitation peaks appear in the range of 265 nm and 285 nm. UV excited emission spectra were measured as a function of temperature. Results indicates the thermal quenching of Eu emission starts from ∼ 400 K. The thermoluminescence curve indicates the elimination of the charge trap at 50 K may significantly expedite the scintillation process thus decrease the scintillation decay time of SrI2:Eu
{"title":"Temperature response and thermoluminescence of SrI2:Eu2+ single crystals","authors":"Kan Yang, M. Zhuravleva, P. Szupryczynski, C. Melcher","doi":"10.1109/NSSMIC.2010.5873760","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5873760","url":null,"abstract":"Single crystal of strontium iodide doped with 1% europium (SrI<inf>2</inf>: 1% Eu<sup>2+</sup>) was grown by Vertical Gradient Freeze technique. Temperature response and thermoluminescence glow curves of SrI<inf>2</inf>: 1% Eu<sup>2+</sup> were studied. UV excitation spectrum of SrI<inf>2</inf>: 1%Eu<sup>2+</sup> at 298 K shows a broad excitation peak at 367 nm. At ∼ 24 K, additional excitation peaks appear in the range of 265 nm and 285 nm. UV excited emission spectra were measured as a function of temperature. Results indicates the thermal quenching of Eu emission starts from ∼ 400 K. The thermoluminescence curve indicates the elimination of the charge trap at 50 K may significantly expedite the scintillation process thus decrease the scintillation decay time of SrI<inf>2</inf>:Eu","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"35 1","pages":"264-267"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77427414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5873727
M. Flaska, S. Clarke, C. Lawrence, S. Pozzi, J. B. Czirr, L. Rees
Almost all commercially applied neutron-counting systems employ 3He tubes for detection of thermal neutrons. However, due to a large number of 3He systems deployed in the field, there is currently a severe shortage of 3He gas. Therefore, novel neutron detection systems are desirable, especially because a large number of detection systems are needed to meet current security demands. One class of detectors that has been explored is capture-gated scintillation detectors which consist of a standard scintillation detector (plastic or liquid) that has been modified to include a neutron capturing isotope. The capture-gated neutron-spectroscopy principle is based on the fact that a single neutron that interacts in a capture-gated detector can create two pulses that are related in time. In this work, we present simulation and measurement results for a cadmium/plastic-scintillator capture-gated detector. The detector consists of 13, 1-cm thick BC-408 plastic-scintillator layers and 12, 0.1-mm thick natCd layers. This detector possesses unique detection characteristics that could find use in nuclear nonproliferation applications.
{"title":"Characterization of cadmium capture-gated detector for nuclear nonproliferation applications","authors":"M. Flaska, S. Clarke, C. Lawrence, S. Pozzi, J. B. Czirr, L. Rees","doi":"10.1109/NSSMIC.2010.5873727","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5873727","url":null,"abstract":"Almost all commercially applied neutron-counting systems employ 3He tubes for detection of thermal neutrons. However, due to a large number of 3He systems deployed in the field, there is currently a severe shortage of 3He gas. Therefore, novel neutron detection systems are desirable, especially because a large number of detection systems are needed to meet current security demands. One class of detectors that has been explored is capture-gated scintillation detectors which consist of a standard scintillation detector (plastic or liquid) that has been modified to include a neutron capturing isotope. The capture-gated neutron-spectroscopy principle is based on the fact that a single neutron that interacts in a capture-gated detector can create two pulses that are related in time. In this work, we present simulation and measurement results for a cadmium/plastic-scintillator capture-gated detector. The detector consists of 13, 1-cm thick BC-408 plastic-scintillator layers and 12, 0.1-mm thick natCd layers. This detector possesses unique detection characteristics that could find use in nuclear nonproliferation applications.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"151 1","pages":"114-118"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77798520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5874319
S. Ha, Zhiyuan Zhang, K. Mueller, S. Matej
The DIRECT approach for 3-D Time-of-Flight (TOF) PET reconstruction performs all iterative predictor-corrector operations directly in image space. A computational bottleneck here is the convolution with the long TOF (resolution) kernels. Accelerating this convolution operation using GPUs is very important especially for spatially variant resolution kernels, which cannot be efficiently implemented in the Fourier domain. The main challenge here is the memory cache performance at non-axis aligned directions. We devised a scheme that first re-samples the image into an axis-aligned orientation offering good memory coherence for the convolution operations. In order to maintain good accuracy, we carefully design the resampling and new convolution kernels to combine into the original TOF kernel. This paper demonstrates the validity, accuracy, and high speed-performance of our scheme for a comprehensive set of orientation angles. Future work will apply these cascaded kernels within a GPU-accelerated version of DIRECT.
{"title":"Efficiently GPU-accelerating long kernel convolutions in 3-D DIRECT TOF PET reconstruction via a kernel decomposition scheme","authors":"S. Ha, Zhiyuan Zhang, K. Mueller, S. Matej","doi":"10.1109/NSSMIC.2010.5874319","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5874319","url":null,"abstract":"The DIRECT approach for 3-D Time-of-Flight (TOF) PET reconstruction performs all iterative predictor-corrector operations directly in image space. A computational bottleneck here is the convolution with the long TOF (resolution) kernels. Accelerating this convolution operation using GPUs is very important especially for spatially variant resolution kernels, which cannot be efficiently implemented in the Fourier domain. The main challenge here is the memory cache performance at non-axis aligned directions. We devised a scheme that first re-samples the image into an axis-aligned orientation offering good memory coherence for the convolution operations. In order to maintain good accuracy, we carefully design the resampling and new convolution kernels to combine into the original TOF kernel. This paper demonstrates the validity, accuracy, and high speed-performance of our scheme for a comprehensive set of orientation angles. Future work will apply these cascaded kernels within a GPU-accelerated version of DIRECT.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"392 1","pages":"2866-2867"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78009572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-10-01DOI: 10.1109/NSSMIC.2010.5874008
M. Capeans, I. Glushkov, R. Guida, S. Haider, F. Hahn, S. Rouwette
Resistive Plate Chambers (RPCs) cover a surface of about 4000 m2, equivalent to 16 m3 of gas volume both in ATLAS and CMS experiments at the Large Hadron Collider (LHC). The use of a relatively expensive Freon (R134a) — based gas mixture makes unavoidable their operation in closed-loop gas systems. It has been observed that the return gas of RPCs operated in background conditions similar to those foreseen at LHC contains a large amount of impurities, which are potentially dangerous for the long-term operation of these systems. During the past few years several RPCs have been operated in the intense radiation field of the CERN Gamma Irradiation Facility (GIF) in order to study the production of typical impurities, mainly fluoride ions, molecules of the Freon group and hydrocarbons. A systematic characterization of cleaning agents has also been performed. Moreover, the tests suggest an optimized configuration of filters, currently under long-term validation at the GIF set-up. The new filter configuration optimizes the filtering capacity for H2O, O2 and RPC typical impurities. An important feature of the new configuration is the increase of the cycle duration for each purifier, that results in better system stability, reduced system downtime and, if needed, it permits to increase comfortably the gas flow in the detectors during the high luminosity running periods at LHC. The filtering optimization studies are complemented with a finite element simulation of the gas flow distribution in the RPCs, aiming at its eventual optimization. A preliminary study on the standard configuration for the RPC gas distribution shows regions in which the gas velocity is 10–100 times lower than in others. With a gas flow of 1 volume exchange every 4 hours (considered the lower limit for a safe operation without radiation) these regions represent about one third of the whole detector surface. The extension of these areas increases dramatically when decreasing the gas flow. A new RPC prototype with a flexible distribution of gas inlets and outlets has been built in order to experimentally quantify the impact of those critical regions on the detector performance and also to verify if a new, more effective solution can be found. The basic idea is that the regions with very low gas velocity define the overall gas flow needed for the detector operation. An efficient removal of the “used” gas mixture inside the RPC volume would permit the reduction of the overall gas flow rate and thus would cut down the operation cost of the large gas systems, without affecting the RPC detector's performance.
{"title":"Optimal gas system for the operation of Resistive Plate Chambers at the Large Hadron Collider experiments","authors":"M. Capeans, I. Glushkov, R. Guida, S. Haider, F. Hahn, S. Rouwette","doi":"10.1109/NSSMIC.2010.5874008","DOIUrl":"https://doi.org/10.1109/NSSMIC.2010.5874008","url":null,"abstract":"Resistive Plate Chambers (RPCs) cover a surface of about 4000 m2, equivalent to 16 m3 of gas volume both in ATLAS and CMS experiments at the Large Hadron Collider (LHC). The use of a relatively expensive Freon (R134a) — based gas mixture makes unavoidable their operation in closed-loop gas systems. It has been observed that the return gas of RPCs operated in background conditions similar to those foreseen at LHC contains a large amount of impurities, which are potentially dangerous for the long-term operation of these systems. During the past few years several RPCs have been operated in the intense radiation field of the CERN Gamma Irradiation Facility (GIF) in order to study the production of typical impurities, mainly fluoride ions, molecules of the Freon group and hydrocarbons. A systematic characterization of cleaning agents has also been performed. Moreover, the tests suggest an optimized configuration of filters, currently under long-term validation at the GIF set-up. The new filter configuration optimizes the filtering capacity for H2O, O2 and RPC typical impurities. An important feature of the new configuration is the increase of the cycle duration for each purifier, that results in better system stability, reduced system downtime and, if needed, it permits to increase comfortably the gas flow in the detectors during the high luminosity running periods at LHC. The filtering optimization studies are complemented with a finite element simulation of the gas flow distribution in the RPCs, aiming at its eventual optimization. A preliminary study on the standard configuration for the RPC gas distribution shows regions in which the gas velocity is 10–100 times lower than in others. With a gas flow of 1 volume exchange every 4 hours (considered the lower limit for a safe operation without radiation) these regions represent about one third of the whole detector surface. The extension of these areas increases dramatically when decreasing the gas flow. A new RPC prototype with a flexible distribution of gas inlets and outlets has been built in order to experimentally quantify the impact of those critical regions on the detector performance and also to verify if a new, more effective solution can be found. The basic idea is that the regions with very low gas velocity define the overall gas flow needed for the detector operation. An efficient removal of the “used” gas mixture inside the RPC volume would permit the reduction of the overall gas flow rate and thus would cut down the operation cost of the large gas systems, without affecting the RPC detector's performance.","PeriodicalId":13048,"journal":{"name":"IEEE Nuclear Science Symposuim & Medical Imaging Conference","volume":"392 1","pages":"1427-1432"},"PeriodicalIF":0.0,"publicationDate":"2010-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78071499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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