The Alpha Magnetic Spectrometer is designed for a long duration measurement of the cosmic-ray spectra at an altitude of 400
km. The particle rigidity and specific energy loss are measured by a ...silicon tracker located in a 0.8
T field. Ground results for the position resolution, detection efficiency and charge determination for singly and doubly charged relativistic particles are presented and discussed in the context of the spaceborne detector.
An X-ray scanner for wire chambers Akesson, T.; Arik, E.; Assamagan, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2003, Letnik:
507, Številka:
3
Journal Article
Recenzirano
The techniques to measure the position of sense wires and field wires, the gas gain and the gas flow rate inside wire chambers using a collimated and filtered X-ray beam are reported. Specific ...examples are given using barrel modules of the Transition Radiation Tracker of the ATLAS experiment.
At present most experiments at the CERN Large Hadron Collider (LHC) are planning upgrades in the next 5-10 years for their innermost tracking layers as well as luminosity monitors to be able to take ...data as the luminosity increases and CERN moves toward the High Luminosity-LHC (HL-LHC). These upgrades will most likely require more radiation tolerant technologies than exist today. As a result this is one area of intense research, and Chemical Vapour Deposition (CVD) diamond is one such technology. CVD diamond has been used extensively in beam condition monitors as the innermost detectors in the highest radiation areas of all LHC experiments. This talk describes the preliminary radiation tolerance measurements of the highest quality polycrystalline CVD material for a range of proton energies and neutrons obtained with this material with the goal of elucidating the issues that should be addressed for future diamond based detectors. The talk presents the evolution of various semiconductor parameters as a function of dose.
The LHC Beam Loss Monitoring system (BLM) makes use of approximately 4000 detectors located around the 27 km ring. Its main purpose is to protect all critical elements of the LHC by requesting a beam ...abort when the measured losses exceed any of the predefined threshold levels. The BLM system integrates the acquired signals in 12 different continuously updated time intervals, spanning from 40 us to 83.8 s, enabling for a different set of abort thresholds depending on the duration of the beam loss. Furthermore, the system takes into account 32 energy steps, from 450 GeV to 7 TeV, as the energy density of a particle shower increases with the energy of the primary particle, i.e. the beam energy and the magnet coil quench level decreases with its increasing current. Due to the differences on the elements under protection and the position of the detector in the tunnel, the system is required to allow a unique set of thresholds per detector. Such thresholds are originally based on thermodynamical arguments and Monte Carlo simulations and tuned with data recorded during the LHC run. The evolution of the BLM thresholds is described in this document. Moreover, the necessity of one set of thresholds per detector requires approximately 1.5E6 to be handled and sent to the appropriate processing modules for the system to function. This thresholds are extremely critical for the safety of the machine. Thus,well established procedures to compute, store and check new or changed threshold values have been defined. In order to avoid human errors, discover non-conformities and voids in the protection during manipulations, sanity checks and constrains have been embedded in the tools. The procedures, as well as the tools developed to automate this process are described in detail in this document.
Cancer therapy using protons and heavier ions such as carbon has demonstrated advantages over other radiotherapy treatments. To bring about the next generation of clinical facilities, the ...requirements are likely to reduce the footprint, obtain beam intensities above 1E10 particles per spill, and achieve faster extraction for more rapid, flexible treatment. This review follows the technical development of ion therapy, discussing how machine parameters have evolved, as well as trends emerging in technologies for novel treatments such as FLASH. To conclude, the future prospects of ion therapy accelerators are evaluated.
Most of the monitors of the LHC beam loss monitoring (BLM) system are installed on the outside of the magnet cryostats, around the quadrupole magnets. Their aim is to prevent quenches and to protect ...the superconducting magnets from damage. The lost beam particles initiate hadronic showers through the magnets and deposit energy in the coils. The gas filled BLM ionization chambers probe the very far transverse tail of the showers. The BLM system relies on GEANT simulations and control measurements to determine the relation between the chamber signal, the number of lost beam particles and the energy deposited in the magnet coil. The specification of the BLM system includes a factor of two in absolute precision on the final prediction of the quench levels. As the shower tails are not necessarily well represented by particle simulation codes, it is crucial to experimentally determine the accuracy of these simulations. An LHC type BLM system was installed at the internal beam dump of HERA at DESY since 2005. The hadronic showers created by the impacting 39 GeV and 920 GeV protons have been simulated with GEANT4. The far transverse tails of the showers on the outside of the dump have been measured by ionization chambers. This paper will present the comparison of simulation to measurement and the conclusions drawn for the LHC BLM system.
We discuss the possibility of creating novel research tools by producing and storing highly relativistic beams of highly ionised atoms in the CERN accelerator complex, and by exciting their atomic ...degrees of freedom with lasers to produce high-energy photon beams. Intensity of such photon beams would be by several orders of magnitude higher than offered by the presently operating light sources, in the particularly interesting gamma-ray energy domain of 0.1-400 MeV. In this energy range, the high-intensity photon beams can be used to produce secondary beams of polarised electrons, polarised positrons, polarised muons, neutrinos, neutrons and radioactive ions. New research opportunities in a wide domain of fundamental and applied physics can be opened by the Gamma Factory scientific programme based on the above primary and secondary beams.
In the years 2009-2013 the Large Hadron Collider (LHC) has been operated with the top beam energies of 3.5 TeV and 4 TeV per proton (from 2012) instead of the nominal 7 TeV. The currents in the ...superconducting magnets were reduced accordingly. To date only seventeen beam-induced quenches have occurred; eight of them during specially designed quench tests, the others during injection. There has not been a single beam- induced quench during normal collider operation with stored beam. The conditions, however, are expected to become much more challenging after the long LHC shutdown. The magnets will be operating at near nominal currents, and in the presence of high energy and high intensity beams with a stored energy of up to 362 MJ per beam. In this paper we summarize our efforts to understand the quench levels of LHC superconducting magnets. We describe beam-loss events and dedicated experiments with beam, as well as the simulation methods used to reproduce the observable signals. The simulated energy deposition in the coils is compared to the quench levels predicted by electro-thermal models, thus allowing to validate and improve the models which are used to set beam-dump thresholds on beam-loss monitors for Run 2.
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