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B. Dehning,
E. Effinger,
J. Emery, G. Ferioli,
G. Guaglio,
E.B. Holzer,
D. Kramer,
L. Ponce,
V. Prieto,
M. Stockner,
C. Zamantzas
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ABSTRACT: An unprecedented amount of energy will be stored in the circulating beams of LHC. The loss of even a very small fraction of a beam may induce a quench in the su- perconducting magnets or cause physical damage to machine components. A fast (one turn) loss of 3 . 10 <sup>-9</sup> and a constant loss of 3 . 10 <sup>-12</sup> times the nominal beam intensity can quench a dipole magnet. A fast loss of 3 . 10 <sup>-6</sup> times nominal beam intensity can damage a magnet. The stored energy in the LHC beam is a factor of 200 (or more) higher than in existing hadron machines with superconducting magnets (HERA, TEVATRON, RHIC), while the quench levels of the LHC magnets are a factor of about 5 to 20 lower than the quench levels of these machines. To comply with these requirements the detectors, ionisation chambers and secondary emission monitors are designed very reliable with a large operational range. Several stages of the acquisition chain are doubled and frequent functionality tests are automatically executed. The failure probabilities of single components were identified and optimised. First measurements show the large dynamic range of the system.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: The beam loss monitoring (BLM) system is integrated in the active equipment protection system of the LHC. It determines the number of particles lost from the primary hadron beam by measuring the radiation field of the shower particles outside of the vacuum chamber. The LHC BLM system will use ionization chambers as its standard detectors but in the areas where very high dose rates are expected, the secondary emission monitor (SEM) chambers will be additionally employed because of their high linearity, low sensitivity and fast response. The sensitivity of the SEM was modeled in Geant4 via the Photo-Absorption Ionization module together with custom parameterization of the very low energy secondary electron production. The prototypes were calibrated by proton beams. For the calibration of the BLM system the signal response of the ionization chamber is simulated in Geant4 for all relevant particle types and energies (keV to TeV range). The results are validated by comparing the simulations to measurements using protons, neutrons, photons and mixed radiation fields at various energies and intensities.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: The strategy for machine protection and quench prevention of the Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is mainly based on the beam loss monitoring (BLM) system. At each turn, there will be several thousands of data to record and process in order to decide if the beams should be permitted to continue circulating or their safe extraction is necessary to be triggered. The processing involves a proper analysis of the loss pattern in time and for the decision the energy of the beam needs to be accounted. This complexity needs to be minimized by all means to maximize the reliability of the BLM system and allow a feasible implementation. In this paper, a field programmable gate array (FPGA) based implementation is explored for the real-time processing of the LHC BLM data. It gives emphasis on the highly efficient successive running sums (SRS) technique used that allows many and long integration periods to be maintained for each detector's data with relatively small length shift registers that can be built around the embedded memory blocks.
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
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ABSTRACT: The LHC beam loss monitoring (BLM) system must prevent the superconducting magnets from quenching and protect the machine components from damage. The main monitor type is an ionization chamber. About 4000 of them will be installed around the ring. The lost beam particles initiate hadronic showers through the magnets, which are measured by the monitors installed outside of the cryostat around each quadrupole magnet. They probe the far transverse tail of the hadronic shower. The specification for the BLM system includes a factor of two absolute precision on the prediction of the quench levels. To reach this accuracy a number of simulations are being combined to calibrate the monitor signals. To validate the monitor calibration the simulations are compared with test measurements. This paper will focus on the simulated prediction of the development of the hadronic shower tails and the signal response of ionization chambers to various particle types and energies. Test measurements have been performed at CERN and DESY and compared to Geant4 simulations.
Nuclear Science Symposium Conference Record, 2006. IEEE; 12/2006
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E.B. Holzer,
B. Dehning,
E. Effinger,
J. Emery, G. Ferioli,
J.L. Gonzalez,
E. Gschwendtner,
G. Guaglio,
M. Hodgson,
D. Kramer,
R. Leitner,
L. Ponce,
V. Prieto,
M. Stockner,
C. Zamantzas
[show abstract]
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ABSTRACT: One of the most critical elements for the protection of CERN's Large Hadron Collider (LHC) is its beam loss monitoring (BLM) system. It must prevent the superconducting magnets from quenching and protect the machine components from damages, as a result of critical beam losses. By measuring the loss pattern, the BLM system helps to identify the loss mechanism. Special monitors will be used for the setup and control of the collimators. The specification for the BLM system includes a very high reliability (tolerable failure rate of 10<sup>-7</sup> per hour) and a high dynamic range of 10<sup>8</sup> (10<sup>13</sup> at certain locations) of the particle fluencies to be measured. In addition, a wide range of integration times (40 μs to 84 s) and a fast (one turn) trigger generation for the dump signal are required. This paper describes the complete design of the BLM system, including the monitor types (ionization chambers and secondary emission monitors), the design of the analogue and digital readout electronics as well as the data links and the trigger decision logic.
Nuclear Science Symposium Conference Record, 2005 IEEE; 11/2005
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J.M. Jimenez,
Q. Arduini,
V. Baglin,
P. Collier, G. Ferioli,
B. Henrist,
N. Hilleret,
L. Jensen,
B. Jenninger,
J.M. Laurent,
A. Rossi,
K. Weiss,
F. Zimmermann
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ABSTRACT: A summary of the main results obtained so far from the electron cloud studies using strip detectors, pick-ups, COLDEX and a 100 MHz coaxial resonator will be presented. The spatial and energy distributions of the electrons in the cloud measured by the strip detectors will be detailed and compared to the results obtained with a conventional retarding field detector. The evidence of the scrubbing effect and of the NEG coatings as remedies to reduce the electron cloud activity will also be shown. In a second part, the improved hardware of the experiments will be presented together with the program of measurements foreseen for the 2003 SPS run.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: Introduction The effect of total beam loss in the SPS electrostatic septum (ZS), as could occur during fast extraction for LHC, has been studied by simulation [2]. The energy deposition by impact of an LHC--type beam was calculated to be sufficient to destroy the septum anode wires. To verify this result experimentally, single W26Re septum wires were brought in the beam path. Since no fast extraction from the SPS machine presently exists, a fast wire scanner solution was adopted: the transverse profile of a low intensity LHC--type proton beam was measured using a W26Re wire. Every machine revolution the beam impinged on the wire and caused a local temperature rise. Due to the short revolution period of 23.0683 s at 26 GeV and 23.0543 s at 450 GeV, diffusive effects in the wire were neglected. For low intensity beams the full beam profile was measured. As the intensity was increased the wire temperature rose until the wire broke. The integrated intensity received was calculated, from w
08/2001;
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ABSTRACT: The extraction of protons from the halo of a circulating beam has been repeatedly demonstrated at the SPS. In a recent experiment a coasting lead ion beam was available at a momentum of 270 GeV/c per charge corresponding to a total momentum of 22 TeV/c per ion and the possibility to extract ultrarelativistic lead ions with a bent crystal could be demonstrated for the first time. We present the experimental challenges, the measurements performed during this experiment and the first results
Particle Accelerator Conference, 1997. Proceedings of the 1997; 06/1997
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G. Arduini,
R Bailey,
T Bohl,
H Burkhardt,
C. Carter,
K. Cornelis,
M. Dach,
G de Rijk,
A Faugier, G Ferioli,
H Jakob,
M Jonker,
D. Manglunki,
G Martini,
M Martini,
J P Riunaud,
C. Scheidenberger,
L Vos,
M. Zanolli
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ABSTRACT: In the Lead Ion Facility at CERN [1] Pb 53+ ion beams are accelerated up to a kinetic energy of 4.2 GeV/u in the CERN PS, extracted and stripped to Pb 82+ in the transfer line from PS to SPS where they are injected and accelerated up to 157 GeV/u. The stripping efficiency, emittance growth and energy loss in Al strippers of different thicknesses have been measured and they are in good agreement with the theoretical values. The results of these measurements and considerations on the PS-SPS transmission efficiency are presented. 1 INTRODUCTION The stripper used in the 1995 lead ion run was a 1 mm thick Al foil. Charge-distribution studies with heavy ions at moderate relativistic energies [2][3] have shown that materials with medium atomic numbers deliver the highest fractions of bare ions since the ratios of the ionisation and electron-capture cross-sections are largest in these materials. Al and Cu strippers induce about the same emittance blow-up for the same stri...
10/1996;
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ABSTRACT: Secondary emission monitors using caesium iodide coated thin
aluminium foils have been installed in the SPS transfer channels to
monitor the intensity of the extracted heavy ion beams. Tests have shown
an increase by a factor twenty of their sensitivity with respect to bare
aluminium foils. Luminescent screens viewed with TV cameras are used to
monitor the position and the profiles of the extracted beams. Various
luminescent screen materials have been tested. Results on chromium doped
alumina, thallium doped caesium iodide and quartz are reported. A
dynamic range of 10<sup>3</sup> in beam intensities can be achieved by
using these three materials in turn in the usual three screen tanks.
Intensifiers used together with CCD cameras and video frame grabbers
with incorporated projection calculations are used in conjunction with
these screens. Results with heavy ions in the transfer channels and with
protons extracted from circulating beams in the SPS are given. Detection
sensitivities down to a few tens of protons per video frame have been
observed
Particle Accelerator Conference, 1993., Proceedings of the 1993; 06/1993
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B. Bouchet,
C. Bovet,
A. Burns,
J. Camas, G. Ferioli,
C. Fischer,
R. Jung,
Q. King,
K.H. Kissler,
J. Koopman,
J. Mann,
H. Michel,
R. Schmidt,
L. Vos
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ABSTRACT: Two sets of wire scanners, each for measuring the horizontal and vertical profile, are installed in LEP in a straight section where the dispersion in both planes is zero. The authors present the design and discuss some limitations of the instrument. A carbon fiber with a diameter of 36 mu m moves through the beam with a speed of about 0.5 m/s. The bremsstrahlung photons generated by the passage of the wire through the beam are detected in scintillators located 80-m downstream. During the first months of LEP operation, the fibers were destroyed occasionally. The various causes, tests and remedies are discussed. At injection energy a significant blowup of the beam results from the wire scan and has to be taken into account for the estimation of the genuine emittance. A model of this blowup is proposed, where the effect is renormalized on the actual measured data. This provides an effective data treatment to obtain the unperturbed beam size.< >
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE; 06/1991
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ABSTRACT: Since electrons and positrons are accelerated in the SPS (Super
Proton Synchrotron) for LEP (Large Electron Positron collider)
injection, the detection system of the wire scanner was modified and the
instrument was used to measure lepton bunch profiles. For the
measurement of beam profiles of the high-intensity proton beam in fixed
target physics, a limit was found for the beam intensity which the fiber
can support without heat damage. This allows use of the wire scanners to
measure the profiles at maximum beam energy and intensity without
destroying the fiber. The development of high-precision wire scanners
for the SPS is accompanied by the need for a better data acquisition
system. The new scanners generate more data (up to 32 K per scan) than
the old wire scanners and are driven from electronics residing in a VME
system. A prototype data acquisition system housed in a VME crate and
connected to the operator consoles via a token ring network is described
Particle Accelerator Conference, 1989. Accelerator Science and Technology., Proceedings of the 1989 IEEE; 04/1989
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ABSTRACT: For fixed target operation the proton beam is extracted at 14 GeV over 5 successive turns of each 2.1¿s from the CPS and injected into the SPS. The current from a secondary emission monitor is sampled every 0.1¿s by a charge coupled device. The stored signal is afterwards scanned at a lower frequency and provides an accurate profile evolution during injection. For slow proton beam extraction at 450 GeV a new type of detector has been developed. It uses the properties of the transition radiation created by the beam when traversing a thin aluminium foil. Accurate transverse profiles are obtained by such a detector. The disturbances to the beam are an order of magnitude less than with a classical secondary emission monitor.
IEEE Transactions on Nuclear Science 11/1985; · 1.45 Impact Factor
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IEEE Transactions on Nuclear Science 09/1983; 30(4):2164-2166. · 1.45 Impact Factor
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ABSTRACT: In the SPS collider, counter-rotating beams of protons and antiprotons will be stored at 270 GeV/c for many hours. Each beam will consist of up to 6 bunches of 10<sup>11</sup> particles. A simple device has been developed which allows the transverse profile of each individual bunch to be measured in an almost nondestructive way. <sup>1,2,3</sup>). A fine beryllium wire is passed quickly (/spl I.itilde/4m/s) through the beam. The profile is measured by detecting the high-energy secondary particles produced in the wire. Due to the strong directionality of secondary particle production the profile of each proton and antiproton bunch can be measured simultaneously using two scintillators placed either side of the wire and close to the beam pipe. In addition, profiles of single beams can be obtained by measuring the secondary electron current emitted by the wire. The device has been successfully tested during storage studies with protons.
IEEE Transactions on Nuclear Science 07/1981; · 1.45 Impact Factor
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ABSTRACT: The strategy for machine protection and quench prevention of the Large Hadron Collider (LHC) at the European Organisation for Nuclear Research (CERN) is mainly based on the Beam Loss Monitoring (BLM) system. At each turn, there will be several thousands of data to record and process in order to decide if the beams should be permitted to continue circulating or their safe extraction is necessary. The BLM system can be sub-divided geographically to the tunnel and the surface building installations. In this paper the surface installation is explored, focusing not only to the parts used for the processing of the BLM data and the generation of the beam abort triggers, but also to the interconnections made with various other systems in order to provide the needed functionality.
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ABSTRACT: The beam loss monitoring (BLM) system [1] of the LHC is one of the most critical elements for the protection of the LHC. It must prevent the super conducting magnets from quenches and the machine components from damages, caused by beam losses. Ionization chambers and secondary emission based beam loss detectors are used on several locations around the ring. The sensors are producing a signal current, which is related to the losses. This current will be measured by a tunnel electronic, which acquires, digitizes and transmits the data via an optical link to the surface electronic. The so called threshold comparator (TC) [2] collects, analyzes and compares the data with threshold table. It also gives a dump signal through the combiner card to the beam inter lock system (BIC). The usage of the system, for protection and tuning of the LHC and the scale of the LHC, imposed exceptional specification of the dynamic range and radiation tolerance. The input current dynamic range should allow measurements between 10pA and 1mA and it should also be protected to very high pulse of 1.5kV and its corresponding current. To cover this range, a current to frequency converter (CFC) is used in the tunnel card, which produces an output frequency of 0.05Hz at 10pA, and 5MHz at 1mA. In addition to the output frequency, the integrator output voltage is measured with a 12bit ADC to improve the resolution. The location of the CFC card next to the detector imposes the placement of the card in the LHC tunnel, exposing the card to radiation. The radiation tolerance was defined by assuming a 20 year operation period corresponding to 400Gy. A mixture of radiation tolerant Asics from the microelectronic group at CERN, and standard component was chosen to cope with these requirements.
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