BEAM LOSS MONITORS The BLM system Status of the monitors B. Dehning, G. Ferioli, J.L. Gonzalez, G. Guaglio, E.B. Holzer, V. Prieto, C. Zamantzas AB-LTC Technical Review November 19, 2003 The BLM system Status of the monitors Status of the electronics Delivery schedule, Integration, Installation Summary

THE BLM SYSTEM Purpose: Machine protection against damage of equipment and magnet quenches. Setup of the collimators Localization of beam losses and help in identification of loss mechanism Machine setup and studies Challenges: Reliable (tolerable failure rate 10-7 per hour) High dynamic range (108) Fast (1 turn trigger generation for dump signal)

Families of BLM’s Recent changes in the functional specification for BLMS* and BLMC (LHC-BLM-ES-0001.00 rev2.0) Description Number of detectors BLMA Quadrupoles along the ring (6 per quadrupole), ionization chambers attached outside of cryostat, time resolution 2.5 ms. ~3000 BLMS Critical aperture limits or positions, ionization chambers, time resolutions 1 turn. ~400 BLMS* Critical positions for injection losses, extended dynamic range: BLMSI (ion. ch.) + BLMSS (SEM), time resolution 1 turn. ~100

Description Number of detectors BLMC Collimation sections, BLMCI (ion. ch.) + BLMCS (SEM), time resolution 1 turn, used to set up the collimators. ~110 BLMB Primary collimators, not part of baseline scenario, for beam studies, bunch- by-bunch resolution. 10

Inside view of an ionization chamber from SPS, Volume: ~ 1 Liter, Gas: N2, 30 Al disks of 0.5 mm, Typical bias voltage: 1500 V. Installation of BLMAs on a SSS quadrupole

The Readout Chain

~3400 ionization chambers of 1 dm3 volume STATUS OF THE MONITORS BLMA and BLMS ~3400 ionization chambers of 1 dm3 volume Status of: Technical Specification: ongoing, mostly done Size (length, diameter) Material (chamber, gas) Production procedure (construction, cleaning, filling) Design: Dec ’03 - Feb ’04 Prototyping: June/July ’04 Manufacturing Contracts: contract in preparation (to be produced in Protvino)

Difficulties and possible consequences: Ageing of chambers (investigate SPS chambers at next shutdown) Schedule does not leave time to test different chambers (gases, cleaning, filling procedures) for ageing. Consequence of ageing is an increased need for calibration. Size of chamber to be coordinated with the requirements for transport space along the magnets.

~ 200 locations with 1 ionization chamber (0.1 - 1 dm3) BLMS* and BLMC ~ 200 locations with 1 ionization chamber (0.1 - 1 dm3) and 1 SEM detector (10 cm2) Functional specifications: dynamic range increased recently (1011-1012) install two chambers with different (yet overlapping) response next to each other. Open questions on feasibility of the envisaged measurements might require reiteration on the functional spec.: Activation of the surrounding material (measurement of low level signals) BLMC: Background and cross-talk signals (from other collimators and the second beam) BLMSI & BLMCI: ionization chambers, same kind as BLMA & BLMS Difficulties and possible consequences: Activation, background and cross-talk Implications on setting up of the collimators > problems with disentangling the losses on each collimator, more beam-time needed

BLMSS & BLMCS: SEM detectors BLMSS & BLMCS: SEM detectors. Deadline for production now advanced by 1 year, because BLMS* probably needed for sector test. Status of SEM: Technical Specification and Design: throughout 2004, will try to find existing chamber design which matches our requirements. Manufacturing Contracts: Q4 ’04 Difficulties and possible consequences : Vacuum needs to hold for the whole lifetime. Test of chambers before installation (beam test). Calibration of installed chambers will not be possible. If no existing design can be reused, problem with schedule: BLMSS: for monitoring, not for machine protection BLMCS: scheduled one year later

BLMB 10 detectors Planned to use standard ACEM detectors (or photo-multipliers), and acquisition systems of LHC BCT. Not part of baseline scenario,for refined beam observation. Status: Detectors on stock Difficulties or trade-offs: Lower end of signal limited by background from activation (installed at primary collimators) Possible redefinition of functional specifications after simulation studies

STATUS OF ELECTRONICS Electronics in the tunnel: current to frequency converter + counter + optical data link ~600 cards Current design of current to frequency converter: Signals of 10 pA to 1 mA converted to frequencies of 0.05 Hz to 5 MHz. Status of: Technical Specification: done (W. Friesenbichler) Design/Prototyping: Current to frequency converter (CFC): choice of technology (dynamic range 108), design, prototyping and testing including digital data transmission done (W. Friesenbichler),

improvements pending (E. Effinger, 2004): Test and calibration procedure implementation Protection against high signal levels Increase mean time between failures (double the analogue electronics) Radiation hardness (change of components) Dynamic range (add ADC to get additional sensitivity below the one count rate - 2 pA) Operating conditions (temperature range) Counter and data link: to be done (2004) Manufacturing Contracts: to be done Pre-series to be delivered Q4 ’04 Series to be delivered Q2 ’05

Difficulties and possible consequences: Low signal limit (noise on up to 250 m long cables from monitor to current to frequency converter in LSS and DS) > more beam-time for machine set-up and tuning (loss minimization). Radiation hardness, ageing > Calibration Temperature dependence after irradiation > Calibration Protection against high signal levels > change electronics in tunnel Reliability: Taking the conservative assumption that the loss is seen by one detector only, the estimated failure rate of the current design is 10-100 times to high (2*10-6/h). That corresponds to 0.7% of dangerous losses passing undetected and resulting in magnet destruction.

At Surface: Threshold Comparator + data receiving ~340 cards (DAB with FPGA and VME64 interface) Status of: Technical Specification: done (C. Zamantzas) Design/Prototyping: Hardware developed together with BPM (J.L. Gonzalez) and collaboration with TRIUMF: First prototypes tested (SPS) done Prototype boards May ’04 Software (C. Zamantzas): Design + software simulation first version (Jan. ’04) FPGA implementation on test board Q1 ’04 on prototype board Q3 ’04 Data link (LASER/diode) selection of components: ongoing (test measurement at PSI)

Manufacturing Contracts: Digital analysis board (DAB): together with BPM Prototype cards: May ’04 Pre-series all cards: August ’04 Contract: Q4 ’04 Delivery of all cards Q4 ’05 LASER/Diode: off shelf Difficulties or trade-offs: Expected to fulfill the specifications

BLMCOM: Combiner and Interface to machine controls 24 cards Status of: Technical Specification: to be done (Q2 ’04) Design/Prototyping: to be done (Q3 ’04) Manufacturing Contracts: produced at CERN (Q1 ’05) Difficulties or trade-offs: Expected to fulfill the specifications

Delivery Schedule (Chambers and electronics) CtC: changes in func. spec., cost increase for 200 - 300 new channels to be analyzed (Q1 ’04) Installation schedule for LHC: to be finished Q4 ’06, no problems expected Cables: partly installed, according to schedule Crates: together with BPM (to be defined soon) Chambers + cables to tunnel crates or patch boxes (LSS): finished Q4 ’06 Electronics: to be finished Q4 ’06 Installation schedule for sector test: to be finished Q4 ’05 Storage: no difficulties Complete test at CERN before installation: foreseen Quality control/acceptance issues: no difficulties expected

Integration Interference with other installations: Machine protection and dump: tests of the combined system foreseen Services/cables already ordered: Cables: yes, except: Cables for the recent upgrade of the functional specifications Collimation region (positions not yet defined) Services for installation: 2 teams of 2 persons each, to be ordered Software services: yes

Planning for Installation in the Tunnel Difficulties of access or co-habitation: no. Needs for transport and handling: few pallets to each LHC point Hardware Baseline System is part of baseline Documentation in EDMS: technical specifications of: Ionization chambers: started, Feb. ’04 SEM: Q4 ’04 Current to freq. converter: Q4 ’04 Threshold comparator: Feb. ’04 MTF for manufacturing follow-up: to be done when production of components has started.

SUMMARY Schedule is tight: Analog electronics is late by about 1 year (lack of manpower). Digital electronics is late by about 3 months (DAB board 7 month late). Ionization chamber still on schedule, but problems with availability of technical designer. SEM: If no existing system can be adapted - problem with the schedule. Demands on system have recently increased - implications on the schedule (SEM detectors for sector test) and on cost (200-300 new channels not yet financed).

The BLM design is based on the functional specifications, which in turn rely on a provisional strategy for machine protection. Further changes in the BLM system will become more and more expensive. Identified possible conceptual and/or technical limitations. The main consequences, in case they cannot be solved will be higher need for beam-time for set-up and tuning of the machine increased number of downtimes. Apart from these limitations - production and installation of the BLM system can be in time for sector test and LHC.