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 -7 per hour) and a high dynamic range of 10 8 (10 13 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. Beam Loss Monitoring System for the LHC Eva Barbara Holzer, Bernd Dehning, Ewald Effinger, Jonathan Emery, Gianfranco Ferioli, Jose Luis Gonzalez, Edda Gschwendtner, Gianluca Guaglio

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The presence of carbon atoms in silicon carbide and diamond makes the materials ideal candidates for direct fast neutron detectors. Furthermore the low atomic number, strong covalent bonds, high displacement energies, wide band gap and low intrinsic carrier concentrations make these semiconductor detectors potentially suitable for applications where rugged, high temperature, low gamma sensitivity detectors are required, such as Active Interrogation, Electronic Personal Neutron Dosimetry and Harsh Environment Detectors. A thorough direct performance comparison of the detection capabilities of semiinsulating silicon carbide (SiC-SI), single crystal diamond (D-SC), polycrystalline diamond (D-PC) and a self-biased epitaxial silicon carbide (SiC-EP) detector has been conducted and benchmarked against a commercial silicon PIN (Si-PIN) diode, in a wide range of alpha (Am-241), beta (Sr/Y-90), ionising photon (65keV to 1332keV) and neutron radiation fields (including 1.2MeV to 16.5MeV mono-energetic neutrons, as well as neutrons from AmBe and Cf-252 sources). All detectors were shown to be able to directly detect and distinguish both the different radiation types and energies by using a simple energy threshold discrimination method. The SiC devices demonstrated the best neutron energy discrimination ratio (E max [n=5MeV] / E max [n=1MeV] ≈5), whereas a superior neutron/photon cross sensitivity ratio was observed in the D-PC detector (E max [AmBe] / E max [Co-60] ≈16). Further work also demonstrated that the cross sensitivity ratios can be improved through use of a simple proton-recoil conversion layer. Stability issues were also observed in the D-SC, D-PC and SiC-SI detectors while under irradiation, that being a change of energy peak position and/or count rate with time (often referred to as polarisation effect). This phenomenon within the detectors was non-debilitating over the time period tested (>5h) and as such, stable operation was possible. Furthermore, the D-SC, self-biased SiC-EP and a semi-insulating SiC detector were shown to operate over the temperature range-60 • C to +100 • C.

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We describe an experimental flight validation payload for detecting atmospheric and space nuclear events with a planned launch date in 2004. The five detector subsystems in the payload employ 27 sensors including Si, CdZnTe, gas proportional counter tubes, photomultiplier tubes, channel electron multipliers, and photodiodes. Detection of events is based on simultaneous measurements of gamma rays, neutrons, and charged particles with wide dynamic ranges of deposited energy and count rates. The sensors and electronics are housed in one package with approximate mass and power consumption of 27 kg and 50 watts, respectively. The instrument uses sophisticated on-board digital signal processing and multilayer triggering algorithms to detect and assess the validity of small signals in a large background radiation environment. This paper presents system configuration and preliminary test data from the first of the two units in development.