The Beam Loss Monitoring system plays a crucial role in the CERN's Super Proton Synchrotron beam monitoring and machine protection. With the upcoming renovation of the system, the acquisition electronics can be based on an innovative ASIC designed by CERN. This paper presents the development of the control and digital processing electronics for this BLMASIC, reviews the architecture and design choices, discusses implementation details, including the controls and redundancy schemes, and highlights some preliminary results. The conclusion outlines the future development steps, and emphasises the interest of this simple and robust architecture using LpGBT and VTRx for critical systems.

G. Sterbini, D. Amorim, G. Arduini, H. Bartosik, R. Bruce, X. Buffat, L. Carver, G. Cattenoz, E. Effinger, S. Fartoukh, M. Fitterer, N. Fuster-Martinez, M. Gasior, M. Gonzalez-Berges, A. Gorzawski, G.-H. Hemelsoet, M. Hostettler, G. Iadarola, R. Jones, D. Kaltchev, N. Karastathis, S. Kostoglou, I. Lamas-Garcia, T. Levens, A. Levichev, L. E. Medina-Medrano, D. Mirarchi, J. Olexa, P. S. Papadopoulou, Y. Papaphilippou, D. Pellegrini, M. Pojer, L. Ponce, A. Poyet, S. Redaelli, A. Rossi, B. M. Salvachua Ferrando, H. Schmickler, F. Schmidt, K. Skoufaris, M. Solfaroli Camillocci, R. Tomás-Garcia, G. Trad, A. Valishev, D. Valuch, C. Xu, C. Zamantzas, P. Zisopoulos. CERN, CH-1211 Geneva, Switzerland

Due to the secondary showers generated when a particle hits the vacuum chamber, beam losses at an accelerator may be detected via radiation detectors located near the beam line. Several sources of background can limit the sensitivity and reduce the dynamic range of a Beam Loss Monitor (BLM). This document concentrates on potential sources of background generated near high gradient RF cavities due to dark current and voltage breakdowns. An optical fibre has been installed at an experiment of the Compact Linear Collider (CLIC) Test Facility (CTF3), where a dedicated study of the performance of a loaded and unloaded CLIC accelerating structure is undergoing. An analysis of the collected data and a benchmarking simulation are presented to estimate BLM sensitivity limitations. Moreover, the feasibility for the use of BLMs optimised for the diagnostics of RF cavities is discussed.

A new fast diagnostic tool was installed in the CNGS facility in 2011 following the neutrino time-of-flight results published by OPERA in September 2011. Among others, four polycrystalline CVD (pCVD) diamond detectors were placed in the secondary beam line about 1200 m downstream of the CNGS target in order to measure the beam structure of the muons which are produced together with the muon neutrinos. Upstream of the CNGS target, a fast beam current transformer measures the proton beam structure. The sub-nanosecond single-pulse time resolution of pCVD diamond for a minimum ionising particle in combination with a GPS system allows the measurement of the GPS timing of individual secondary particle bunches crossing these detectors with a precision of < 1 ns. The complicated structure of the CNGS muon beam in 2011 necessitates the combination of adjacent bunches in order to compare the proton beam structure with the muon beam structure. An analysis of the detector signals was carried out, which provides an independent timing measurement at CERN with a precision of 1.2 ns. Uncertainties from other sources as cable lengths add up to 3.4 ns, resulting in an overall precision of 3.6 ns. The distance between the beam current transformer and the diamond detectors has been measured to (1859.95±0.02) cm. The nominal time-of-flight of (6205.3±1.7) ns for a 17 GeV/c muon, as present in the CNGS muons beam, falls within the uncertainties of the measured time-of-flight of (6205.2±3.6) ns. Hence, the GPS timing measurements performed at CERN are consistent.

Unexpected beam loss might lead to a transition of the accelerator superconducting magnet to a normal conducting state. The LHC beam loss monitoring (BLM) system is designed to abort the beam before the energy deposited in the magnet coils reach a quench-provoking level. In order to verify the threshold settings generated by simulation, a series of beam-induced quench tests at various beam energies has been performed. The beam losses are generated by means of an orbital bump peaked in one of main quadrupole magnets (MQ). The analysis includes not only BLM data but also the quench protection system (QPS) and cryogenics data. The measurements are compared to Geant4 simulations of energy deposition inside the coils and corresponding BLM signal outside the cryostat. BEAM-INDUCED QUENCH TEST OF LHC MAIN QUADRUPOLE Agnieszka Priebe*, Knud Dahlerup-Petersen, Bernd Dehning, Ewald Effinger, Jonathan Emery, Eva Barbara Holzer, Christoph Kurfuerst, Eduardo Nebot Del Busto, Annika Nordt, Mariusz Sapinski, Jens Steckert, Arjan Verweij, Christos Zamantzas, CERN, Geneva, Switzerland Abstract Unexpected beam loss might lead to a transition of the accelerator superconducting magnet to a normal conducting state. The LHC beam loss monitoring (BLM) system is designed to abort the beam before the energy deposited in the magnet coils reach a quench-provoking level. In order to verify the threshold settings generated by simulation, a series of beam-induced quench tests at various beam energies has been performed. The beam losses are generated by means of an orbital bump peaked in one of main quadrupole magnets (MQ). The analysis includes not only BLM data but also the quench protection system (QPS) and cryogenics data. The measurements are compared to Geant4 simulations of energy deposition inside the coils and corresponding BLM signal outside the cryostat.Unexpected beam loss might lead to a transition of the accelerator superconducting magnet to a normal conducting state. The LHC beam loss monitoring (BLM) system is designed to abort the beam before the energy deposited in the magnet coils reach a quench-provoking level. In order to verify the threshold settings generated by simulation, a series of beam-induced quench tests at various beam energies has been performed. The beam losses are generated by means of an orbital bump peaked in one of main quadrupole magnets (MQ). The analysis includes not only BLM data but also the quench protection system (QPS) and cryogenics data. The measurements are compared to Geant4 simulations of energy deposition inside the coils and corresponding BLM signal outside the cryostat.

Most of the beam instrumentation developed for LHC has been designed to allow bunch-by-bunch measurements: Beam Position Monitors, Beam Current Transformers, Wall Current Monitor, Wire Scanners, Synchrotron Light Monitors, Schottky Monitors, Longitudinal Density Monitors and Luminosity Monitors. The current status of all these devices i s presented highlighting their already achieved performances in 2010 and their known limitations (hardware or software). The plans for upgrades in 2 011 will finally be discussed.

The LHC beam loss monitoring system provides measurements with an update rate of 1 Hz and high time resolution data by event triggering. These informations are used for the initiation of beam aborts, fixed displays and the off line analysis. The analysis of fast and localized loss events resulted in the determination of its rate, duration, peak amplitudes, its scaling with intensity, number of bunches and beam energy. The calibration of the secondary shower beam loss signal in respect to the needed beam energy deposition to quench the magnet coil is addressed at 450GeV and 3.5T eV . The adjustment of collimators is checked my measuring the loss pattern and its variation in the collimation regions of the LHC. Loss pattern changes during a fill allow the observation of non typical fill parameters. Overview of LHC Beam Loss Measurements B. Dehning, M. Dabrowski, E. Effinger, J. Emery, E. Fadakis, E . B. Holzer, S. Jackson, G. Kruk, C. Kurfuerst, A.Marsili, M. Misiowiec, E. Nebot Del Busto, A. Nordt, A.Priebe, C. Roderick, M. Sapinski, C. Zamantzas, (CERN, Ge neva), V. Grishin (CERN, Geneva; IHEP Protvino, Protvino, Moscow R egion), E. Griesmayer (CIVIDEC Instrumentation, Wien) Abstract The LHC beam loss monitoring system provides measurements with an update rate of 1 Hz and high time resolution data by event triggering. These informations are used for the initiation of beam aborts, fixed displays and the off line analysis. The analysis of fast and localized loss events resulted in the determination of its rate, duration, peak amplitudes, its scaling with intensity, number o f bunches and beam energy. The calibration of the secondary shower beam loss signal in respect to the needed beam energy deposition to quench the magnet coil is addressed at 450GeV and3.5TeV . The adjustment of collimators is checked my measuring the loss pattern and its variation in the collimation regions of the LHC. Loss pattern changes during a fill allow the observation of non typical fill parameters. INTRODUCTION The main function of the LHC beam loss system is the protection of superconducting magnets against quench or damage by the measurements of the lost proton initiated secondary particle showers. 3600 ionisation chambers detect the losses at almost every element around the ring distinguishing between the counter rotating beams. The beam loss measurement data streams are recorded with 1Hz and high time resolution data ( 40μs, 2ns,) triggered by events. The1Hz data stream includes for every channel 12 different integration windows with a minimum duration of 40μs up to83s. For integration windows with a duration of less than1s the maximum value is selected of the values calculated for a particular integration time during the previous second. This procedure allows to determine losses with a minimum duration of 40μs even if data are only logged with a frequency of1Hz.The LHC beam loss monitoring system provides measurements with an update rate of 1 Hz and high time resolution data by event triggering. These informations are used for the initiation of beam aborts, fixed displays and the off line analysis. The analysis of fast and localized loss events resulted in the determination of its rate, duration, peak amplitudes, its scaling with intensity, number o f bunches and beam energy. The calibration of the secondary shower beam loss signal in respect to the needed beam energy deposition to quench the magnet coil is addressed at 450GeV and3.5TeV . The adjustment of collimators is checked my measuring the loss pattern and its variation in the collimation regions of the LHC. Loss pattern changes during a fill allow the observation of non typical fill parameters. INTRODUCTION The main function of the LHC beam loss system is the protection of superconducting magnets against quench or damage by the measurements of the lost proton initiated secondary particle showers. 3600 ionisation chambers detect the losses at almost every element around the ring distinguishing between the counter rotating beams. The beam loss measurement data streams are recorded with 1Hz and high time resolution data ( 40μs, 2ns,) triggered by events. The1Hz data stream includes for every channel 12 different integration windows with a minimum duration of 40μs up to83s. For integration windows with a duration of less than1s the maximum value is selected of the values calculated for a particular integration time during the previous second. This procedure allows to determine losses with a minimum duration of 40μs even if data are only logged with a frequency of1Hz. ANALYSIS OF FAST LOSSES In summer 2010 first events with a footprint of being very localised (see Fig. 1) and short occurred (see Fig. 2). The beam loss is generated by a beam coming from the left side between the second and third cluster of monitors. The monitors are located at the quadrupole magnets and the in between located bending magnets are not observed. Signals are seen in monitors for beams due to particle crosstalk. A typical fast loss has a FWHM dose rate of about1ms. For more detailed analysis the losses are DCUM [m] 2190

The reliability concerns have driven the design of the Large Hardron Collider (LHC) Beam Loss Monitoring (BLM) system from the early stage of the studies up to the present commissioning and the latest development of diagnostic tools. To protect the system against non-conformities, new ways of automatic checking have been developed and implemented. These checks are regularly and systematically executed by the LHC operation team to ensure that the system status is after each test "as good as new". The sanity checks are part of this strategy. They are testing the electrical part of the detectors (ionisation chamber or secondary emission detector), their cable connections to the front-end electronics, further connections to the back-end electronics and their ability to request a beam abort. During the installation and in the early commissioning phase, these checks have shown their ability to find also non-conformities caused by unexpected failure event scenarios. In every day operation, a non-conformity discovered by this check inhibits any further injections into the LHC until the check confirms the absence of non-conformities.

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.

The beam loss monitoring system 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 detectors are used at 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 card, which acquires, digitizes and transmits the data via an optical link to the surface electronic. The usage of the system, for protection and tuning of the LHC and the scale of the LHC, imposed exceptional specifications of the dynamic range and radiation tolerance. The input dynamic allows measurements between 10pA and 1mA and its protected to high pulse of 1.5kV and its corresponding current. To cover this range, a current to frequency converter in combination with an ADC is used. The integrator output voltage is measured with an ADC to improve the resolution. The radiation tolerance required the adaptation of conceptional design and a stringent selection of the components. .

In the frame of the design and development of the Beam Loss Monitoring (BLM) system for the Large Hadron Collider (LHC) a flexible test system has been developed to qualify and verify during design and production the BLM LHC data acquisition card. It permits to test completely the functionalities of the board as well as realizing analog input signal generation to the acquisition card. The system utilize two optical receivers, a Field Programmable Gate Array (FPGA), eights flexible current sources and a Universal Serial Bus (USB) to link it to a PC where a software written in LabWindows/CVI© (National Instruments) runs. It includes an important part of the measurement processing developed for the BLM in the future LHC accelerator. It is called Beam Loss Electronic Current to Frequency Tester (BLECFT).

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.

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 -9 and a constant loss of 3 . 10 -12 times the nominal beam intensity can quench a dipole magnet. A fast loss of 3 . 10 -6 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.

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.

Measurements have shown that the gain of the imaging system of the Ionisation Profile Monitor (IPM) changes over time, in a non-homogenous way. This ageing effect is caused by changes in the Micro Channel Plate (MCP) channel wall secondary emission coefficient, due to electron scrubbing. The MCP is only capable of emitting a limited number of electrons during its lifetime, and after a large number of electrons have been emitted, the gain is gradually reduced. To measure this ageing effect, and to be able to compensate for it, a remote controlled, built-in calibration system was developed. An Electron Generator Plate (EGP) produced by Burle, Inc. was used as the electron emitter for the calibration system. In this paper, computer simulations of the system are presented. Promising results were obtained from these simulations. Results from experiments conducted at low magnetic fields, coincide with the results of the simulations. Both simulations and experiments indicate that the proposed calibration system should not deteriorate the performance of the IPM during beam profile measurements. Presented at DIPAC’05 – 6/8 June 2005 – Lyon FR SIMULATION OF AN ELECTRON SOURCE BASED CALIBRATING SYSTEM FOR AN IONISATION PROFILE MONITOR H. H. Refsum∗, B. Dehning† , J. Koopman, CERN, Geneva, Switzerland

In total, over 5700 changes to the BLM thresholds were made during 2015. The new thresholds are based on the operational experience from Run 1, on new simulation models and on results from quench tests performed so far. Following the first experiences with operation at 6.5 TeV, a series of adjustments were made throughout the first operational year of Run 2. An overview of the main changes since the start of the LHC operation and their impact on the machine protection will be presented, focusing on the impact on availability during operation in 2015. The paper will conclude by discussing the remaining main updates, and by proposing a threshold strategy for the start-up in 2016. BEAM LOSS MONITORING SYSTEM At the beginning of Run 2, the beam loss monitoring (BLM) system had 3929 detectors out of which 3518 were connected to the Beam Interlock System (BIS). Although there are three types of detectors employed by the LHC BLM system, only Ionization Chambers (IC) are connected to BIS. The two other types, LIC (108 in LHC) and SEM (191 in LHC) are currently installed for additional measurement purposes [1]. Among the changes to the BLM system between Run 1 and Run 2, there were the relocation of 816 detectors from the side of MQ magnets to on top of the interconnects of the MB magnets in ARCs and DSs, and the replacement of SEMs with LICs in the injection regions (IR2 and 8).