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| MOPC024 | Calculation of Coherent Synchrotron Radiation in General Particle Tracer | space-charge, electron, emittance, synchrotron | 118 | ||
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General Particle Tracer (GPT) is a particle tracking code, which includes 3D space charge effect based on nonequidistant multigrid Poisson solver or point-to-point method. It is used to investigate beam dynamics in ERL and FEL injectors. We have developed a new routine to simulate coherent synchrotron radiation (CSR) in GPT based on the formalism of Sagan*. The routine can calculate 1D-wake functions for arbitrary beam trajectories as well as CSR shielding effect. In particular, the CSR routine does not assume ultrarelativistic electron beam and is therefore applicable at low beam energies in the injector. Energy loss and energy spread caused by CSR effect were checked for a simple circular orbit, and compared with analytic formulas. In addition, we enhanced the 3D space charge routine in GPT to obtain more accurate results in bending magnets.
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*D. Sagan, EPAC06, pp. 2829-2831. |
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| MOPC086 | IFMIF-EVEDA Accelerator: Beam Dump Design | linac, vacuum, quadrupole, rfq | 259 | ||
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The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA cw deuteron accelerator prototype for verifying the validity of the accelerator design for IFMIF. A beam stop will be used for the RFQ and DTL commissioning as well as for the EVEDA accelerator tests. Therefore, this component must be designed to stop 5 MeV and 9 MeV deuteron beams with a maximum power of 1.12 MW. The first step of the design is the beam-facing material selection. The criteria used for this selection are low neutron production, low activation and good thermomechanical behavior. A thermomechanical analysis with ANSYS has been performed for a few materials which show good behavior from the radiological point of view. The input data are the expected beam shape and divergence at the beam dump entrance produced by the high energy beam line quadrupoles, a conical beam stop shape and the preliminary design of the cooling system. As a conclusion of the previous studies a conceptual design of the beam stop will be presented.
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| MOPC096 | Design of a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade | collimation, simulation, impedance, insertion | 289 | ||
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The Phase II upgrade to the LHC collimation systems calls for complementing the 30 high robust Phase I graphite collimators with 30 high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. Design issues include: |
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| MOPD017 | G4Beamline Program for Radiation Simulations | simulation, radiation, target, controls | 481 | ||
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G4beamline, a program that is an interface to the Geant4 toolkit that we have developed to simulate accelerator beamlines, is being extended with a graphical user interface to quickly and efficiently model experimental equipment and its shielding in experimental halls. The program is flexible, user friendly, and requires no programming by users, so that even complex systems can be simulated quickly. This improved user interface is of much wider application than just the shielding simulations that are the focus of this project. As an initial application, G4beamline is being extended to provide the simulations that are needed to determine the radiation sources for the proposed experiments at Jefferson Laboratory so that shielding issues can be evaluated. Since the program already has the capabilities needed to simulate the transport of all known particles, including scattering, attenuation, interactions, and decays, the extension involves implementing a user-friendly graphical user interface for specifying the simulation, and creating general detector and shielding component models and interfacing them to existing Geant4 models of the experimental halls.
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| MOPD032 | Neutronics Calculations to Support the SNS Accelerator Facility | proton, radiation, target, linac | 520 | ||
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The Spallation Neutron Source (SNS) is an accelerator driven neutron scattering facility for materials research that recently started operations. After commissioning, the facility started at low power and is presently in the process of a power ramp to reach the Megawatt power level within two years of operations, maintenance, and tuning cycles. Extensive neutronics work for shielding development and dose rate predictions was completed during design and construction for various operational and shut down scenarios. Now that the facility is successfully operating, there is still demand for neutronics analyses for radiation-protection support. This need arises from redesigning some parts of the facility, facility upgrades, designing additional structures, designing test stands for accelerator structures, and verification and code validation analyses on the basis of the measured data.
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| MOPD038 | First Radiation Monitoring Results During Elettra Booster Commissioning | radiation, booster, injection, monitoring | 535 | ||
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The new injection system for the Elettra storage ring is based on a 100 MeV linac and a booster synchrotron, where the electron energy can be raised up to 2.5 GeV. The new machine is designed to perform full energy injection, also in top-up mode. Outside the shielding, radiation monitoring is performed through a real-time network of gamma and neutron dosimeters as well as through TLD passive dosimeters. The radiation monitors placed next to the beamlines are interlocked with the machine operation and prevent injection into the storage ring if the alarm threshold is exceeded. This paper reports the first results of the radiation monitoring performed during the new injector commissioning.
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| MOPP031 | Challenges and Concepts for Design of an Interaction Region with Push-pull Arrangement of Detectors - an Interface Document | alignment, interaction-region, radiation, collider | 616 | ||
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Two experimental detectors working in a push-pull mode has been considered for the Interaction Region of the International Linear Collider [1]. The push-pull mode of operation sets specific requirements and challenges for many systems of detector and machine, in particular for the IR magnets, for the cryogenics system, for alignment system, for beamline shielding, for detector design and overall integration, and so on. These challenges and the identified conceptual solutions discussed in the paper intend to form a draft of the Interface Document which will be developed further in the nearest future. The authors of the present paper include the organizers and conveners of working groups of the workshop on engineering design of interaction region IRENG07 [2], the leaders of the IR Integration within Global Design Effort Beam Delivery System, and the representatives from each detector concept submitting the Letters Of Intent.
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| MOPP123 | Design and Fabrication of the Cornell ERL Injector Cryomodule | vacuum, linac, insertion, alignment | 844 | ||
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The Energy Recovery Linac (ERL) development effort at Cornell will first produce an ERL beam source. The source will consist of a DC photo-gun, a buncher cavity, beam optics, and then an SRF Injector cryomodule to accelerate the 33-100 mA cw beam from 0.3-0.5 MeV to 5-15 MeV. The Injector cryomodule is based on TTF III technology with modifications to allow cw operation and the flexibility to accommodate the wide range of beam currents, bunch lengths, and beam energy. To deliver the 0.5 MWCW average power to the beam, the Injector cryomodule will contain five SRF 2-cell cavities, each cavity having two 50 kWCW coax couplers to deliver power from 100 kWCW klystrons, of which there are five for the Injector. Both the couplers and klystrons have been tested with 30% overhead in performance. Cold beamline HOM loads are placed between each cavity and outboard of the first and last cavities. Details of the Injector cryomodule design will be presented along with insight gained from the fabrication process, which will benefit the future ERL Linac cryomodule design and proto-typing.
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| MOPP125 | A Superconducting RF Vertical Test Facility at Daresbury Laboratory | radiation, cryogenics, superconducting-RF, controls | 850 | ||
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A superconducting RF vertical test facility (VTF) has been constructed at Daresbury Laboratory for the testing of superconducting RF cavities at 2K. When fully operational, the facility will be capable of testing a 9-cell 1.3 GHz Tesla type cavity. The facility is initially to be configured to perform phase synchronisation experiments between a pair of single cell 3.9GHz ILC crab cavities. These experiments require the cavities to operate at the same frequency; therefore a tuning mechanism has been integrated into the system. The system is described, and data from the initial operation of the facility is presented.
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| MOPP141 | Commissioning of the ERLP SRF Systems at Daresbury Laboratory | booster, linac, radiation, gun | 889 | ||
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The Energy Recovery Linac Prototype (ERLP) has been installed at Daresbury Laboratory and its baseline commissioning completed. The SRF systems for ERLP comprise two 9-cell, 1.3 GHz accelerating cavities in the injector (or Booster) cryomodule, which provide a nominal energy gain of 8 MeV for the injected 350 keV beam from the photo-injector. The beam is then accelerated in an identical two cavity cryomodule in the energy recovery main Linac, giving a final ERLP energy of 35 MeV. Each SRF accelerating cavity is powered by commercially available Inductive Output Tubes (IOTs) and the analog LLRF control system is identical to that employed on the ELBE facility at FZD Rossendorf. This paper details the commissioning experience gained for these systems and highlights the ultimate performance achieved.
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| MOPP148 | Design of a Magnetic Shield Internal to the Helium Vessel of SRF Cavities | linac, superconductivity, background, controls | 898 | ||
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The TRASCO elliptical cavities for intermediate velocity protons (β=0.47) employ a coaxial cold tuner of the blade type. To meet the perfomance goals of the 700 MHz cavities in the foreseen horizontal cryostat tests, the cavities are being equipped with a magnetic shield which lies internally to the cavity helium vessel and has a simple mechanical design and assembly procedure.
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| TUPC018 | New Experimental Results with Optical Diffraction Radiation Diagnostics | radiation, electron, background, target | 1083 | ||
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The characterization of the transverse phase space for high charge density and high energy electron beams is demanding for the successful development of the next generation light sources and linear colliders. The interest in a non-invasive and non-intercepting beam diagnostics is increasingly high due to the stringent features of such beams. Optical Diffraction Radiation (ODR) is considered as one of the most promising candidates to measure the transverse beam size and angular divergence, i.e. the transverse emittance. An experiment, based on the detection of the ODR angular distribution, has been set up at DESY FLASH Facility to measure the electron beam transverse parameters. In this paper we report the recent results on the incoherent diffraction radiation produced by a 1 GeV energy electron beam going through a rectangular slit.
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| TUPC021 | High Bandwidth Wall Current Monitor for CTF3 | resonance, coupling, impedance, electromagnetic-fields | 1092 | ||
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Wall Current Monitors (WCM) are commonly used to observe the time profile and spectra of a particle beam by detecting its image current. For the 3rd CLIC Test Facility (CTF3), a WCM having a very large bandwidth (100kHz-20GHz) is in principle required. This very stringent request was critically reviewed because the low cut-off frequency of 100 kHz is quite outstanding. It was initially chosen because of the bunch train length but, in reality, because of the high frequency cut-off of 20GHz, the low frequency cut-off should rather be related to the maximum expected Missing Bunch Ratio (MBR). The solution that we propose has a low frequency cut-off of 2GHz corresponding to an MBR of 1/6 for 83ps bunch spacing. If needed, it could be lowered to 400MHz (MBR equal to 1/30). That solution has been fully characterized both from an electromagnetic and from a mechanical point of view. The first tests of a prototype are foreseen in February 2008.
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| TUPC064 | Design and Commissioning of a Quadrant BPM for the LNLS Beamlines | vacuum, photon, synchrotron, instrumentation | 1200 | ||
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We have recently designed and installed the first quadrant beam position monitor in the MX2 beamline. The whole monitor, including its electronics, was installed in vacuum to reduce errors from current leakage and noise coupled outside the vacuum chamber. Aspects of the mechanical and electronic design of this fluorescence-based beam position monitor, as well as the commissioning results are presented.
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| TUPD035 | Modeling of the RF-shield Sliding Contact Fingers for the LHC Cryogenic Beam Vacuum Interconnects Using Implicit and Explicit Finite Element Formulations | vacuum, simulation, superconducting-magnet, alignment | 1503 | ||
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The short interconnect length between the LHC superconducting magnets required the development of an optimised RF shielded bellows module, with a low impedance combined with compensation for large thermal displacements and alignment lateral offsets. Each bellows is shielded by slender copper-beryllium fingers working as pre-loaded beams in order to provide a constant force at the sliding contact. Unless the sliding friction and some geometrical parameters of the fingers are kept within a limited range, a large irreversible lateral deflection towards the vacuum chamber axis may occur and eventually block the beam aperture. The finite element analysis presented here simulates this failure mechanism providing a complete understanding of the finger behavior as well as the influence of the various design parameters. An implicit non-linear two-dimensional model integrating friction on the sliding contacts, geometrical non-linearity and plasticity was implemented in a first stage. The design was then verified through the whole working range using an explicit formulation, which overcame the instabilities resulting from the sudden release of internal energy stored in the finger.
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| TUPP041 | CSR Shielding in the Beam Dynamics Code BMAD | radiation, synchrotron, synchrotron-radiation, simulation | 1634 | ||
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Short bunches radiate coherently at wavelengths that are longer than their bunch length. This radiation can catch up with the bunch in bends and the electromagnetic fields can become large enough to significantly damage longitudinal and transverse bunch properties. This is relevant for many accelerators that relies on bunch compression. It is also important for Energy Recovery Linacs, where spent beams are decelerated by a potentially large factor. Because this deceleration increases the relative energy spread, all sources of wake fields, especially Coherent Synchrotron Radiation (CSR), become much more important. In this paper we show how the beam dynamics code BMAD computes the effect of CSR and how the shielding effect of vacuum chambers is included by the method of image charges. We compare the results to established codes: to Elegant for cases without shielding and to a numerical solution of simplified Maxwell equations as well as to analytical csr-wake formulas. Good agreement is generally found, and in cases where numerical solutions of the simplified Maxwell equations do not agree with the csr-wake formulas, we show that BMAD agrees with these analytic formulas.
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| TUPP066 | CERN SPS Impedance in 2007 | impedance, kicker, quadrupole, synchrotron | 1691 | ||
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Each year several measurements of the beam coupling impedance are performed in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of its evolution. In parallel, after the extensive and successful campaign of identification, classification and cure of the possible sources of (mainly longitudinal) impedance between 1998 and 2001, a new campaign (essentially for the transverse impedance this time) has started few years ago, in view of the operation of the SPS with higher intensity for the LHC luminosity upgrade. The present paper summarizes the results obtained from the measurements performed over the last few years and compares them to our predictions. In particular, it reveals that the longitudinal impedance is reasonably well understood and the main contributors have already been identified. However, the situation is quite different in the transverse plane: albeit the relative evolution of the transverse impedance over the last few years can be well explained by the introduction of the nine MKE kickers necessary for beam extraction towards the LHC, significant contributors to the SPS transverse impedance have not been identified yet.
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| TUPP074 | A New RF Shielded Bellows for the DAΦNE Upgrade | impedance, coupling, simulation, storage-ring | 1706 | ||
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A new RF shielded bellows, using the technology of omega shaped strip of beryllium copper material, has been developed and tested on the DAΦNE Upgrade*. The RF omega shield is composed by many Be-Cu strips held by an external floating ring**. Thermal power loss on strips can be easily extracted and dissipated allowing high beam current operation. Leakage of beam induced e.m. fields through the RF shield is almost suppressed. Twenty omega bellows were manufactured and installed in the DAΦNE storage rings and showed good properties up to a stored beam current of 700 mA.
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*DAΦNE upgrade: A New magnetic and mechanical layout. PAC07. pp. 1466-1468, Albuquerque. |
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| WEPD025 | A Feasibility Study of Superconducting Dipole for the Early Separation Scheme of SLHC | luminosity, dipole, separation-scheme, simulation | 2461 | ||
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In the framework of the LHC luminosity upgrade an early separation scheme is being studied for the final phase (L~1035 cm-2 s-1 with substantial changes in the IR). In this paper we compare a Nb3Sn and a Nb-Ti cos(θ) design: the aim is to explore the benefits and the limits of a compact solution with respect to the detector's constraints and the energy deposition issues. We propose to put the dipole system (cryostat and magnet) at a location starting at 6.8 m from the IP. The preliminary cross section, the achievable integrated field, the energy deposition on the magnet are presented and discussed.
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| WEPD036 | Radiation and Thermal Analysis of Superconducting Quadrupoles in the Interaction Region of Linear Collider | quadrupole, radiation, extraction, linear-collider | 2488 | ||
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The upcoming and disrupted electron and positron beams in the baseline design of ILC interaction region are focused by compact FD doublets each consisting of two small-aperture superconducting quadrupoles and multipole correctors. These magnets will work in a severe radiation environment generated primarily by incoherent pairs and radiative Bhabhas. This paper analyzes the radial, azimuthal and longitudinal distributions of radiation heat deposition in incoming and disrupted beam doublets. Operation margins of baseline quadrupoles based on NbTi superconductor and direct wind technology as well as alternative designs based on NbTi or Nb3Sn Rutherford cables are calculated and compared. The possibilities of reducing the heat deposition in magnet coils using internal absorbers are discussed.
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| WEPP030 | LHC Luminosity Upgrade: Protecting Insertion Region Magnets from Collision Debris | insertion, luminosity, cryogenics, dipole | 2584 | ||
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The Large Hadron Collider built at CERN now enters a starting-up phase where with the present design luminosities up to 1034 cm-2 s-1 will be reached after the running in phase. A possible upgrading of the machine to luminosities up to 1035 cm-2 s-1 requires a completely new insertion region design, and will be implemented in essentially two phases. The energy from collision debris is deposited in the insertion regions and in particular in the superconducting magnet coils with a possible risk of quench. We describe here how to protect the interaction region magnets against this irradiation to keep the energy deposition below critical values estimated for safe operation. The constraint is to keep the absorber size as small as possible to leave most of the magnet aperture available for the beam. This can be done by choosing a suitable material and design minimizing the load on the cryogenic system. We will describe a proposal of a design for the phase I upgrade lay-out (i.e., luminosities up to 2.5 1034 cm-2 s-1).
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| THPP088 | Design Considerations for the PS2 Beam Dumps | injection, extraction, simulation, kicker | 3569 | ||
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Studies have been made to evaluate and differentiate necessary beam disposal functions for the proposed PS2 accelerator. The paper describes briefly the different beam dump functionalities required for the PS2 machine and its transfer lines, and makes some first estimates about the expected beam loads. This data has been taken as input for comparing the different technical options for the dump systems, in particular to simulate the radiological impact of different internal or external beam dump concepts. The numbers derived have been used to help in evaluating the feasibility of the technical alternatives.
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| THPP093 | Conceptual Design of the PEFP Beam Line | target, proton, vacuum, linac | 3581 | ||
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In the Proton Engineering Frontier Project (PEFP), 20MeV and 100MeV proton beams from a 100MeV proton liner accelerator will be supplied to users for proton beam applications. Switch magnets will share the beam to three directions, two fixed beam lines and one AC magnet. The two fixed beam lines will be used for isotope production and power semiconductor production. An AC magnet will distribute the beams to three targets simultaneously. To provide flexibilities of irradiation conditions for users from many application fields, we designed beam lines to the targets with wide or focused, external or in-vacuum, and horizontal or vertical beams. As far as possible we designed the simple beam lines to reduce the construction cost. The details of the beam line conceptual design will be reported.
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| THPP128 | Failure Mechanisms of Power Systems in Particle Accelerator Environments and Strategies for Prevention | radiation, power-supply, simulation, proton | 3661 | ||
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This paper discusses the mechanisms that cause degradation and failure in DC-DC converters destined for high radiation and magnetic field environments, particularly those encountered in accelerators. Failure mechanisms discussed include transformer saturation, loss of PWM control, and power supply turn-off. Degradation mechanisms that produce circuit performance outages include circuit parameter drift in Mosfets due to temperature and Vgsth reduction. Environmentally induced drift of current limit, voltage references, and switching performance are also presented. The author’s background in worst case analysis of Space based power supplies gives them particular insight into the radiation impact, assessment, and mitigation of such phenomenon. A variety of techniques for identifying and reducing the probability of these failures are presented. Methods include analysis based strategies, modified switching timing and control, improved gate drive circuitry, proper component selection, and appropriate shielding. Results are provided for a 3kW supply developed for the LHC at CERN using COTS in an 45kRAD TID, 7.7·1012 neutron fluence, and 300 Gauss magnetic field environment.
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| THPP129 | New Generation of AD-measurement Cards for High Accuracy Measurements | power-supply, controls | 3664 | ||
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Current transducers, together with the AD conversion of the measured current, are the key elements of high precision power supplies. The accuracy of commercially available current transducers is within the range of a few ppm. Any degradation of this precision by the succeeding stages must be kept as small as possible. Therefore, the accuracy of the AD conversion has to be at least in the same order of magnitude. The presented AD-measurement card improves the accuracy of the available, already calibrated precise ADCs by correcting the remaining errors. The necessary accuracy can only be achieved by measuring and correcting the miscellaneous errors of ADC and involved components, like voltage reference, antialiasing filter and input amplifier. From the measured deviation a correction look-up table is derived and later processed. Other implemented means for the improvement of the precision are the stabilization of the temperature, minimization of the electromagnetic influence by galvanic isolation, reduction of electrical noise and a fully differential signal path.
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