LHC Beam Instrumentation Detectors and Acquisition Systems LECC 2002 Colmar - 9th-13th September 2002 Rhodri Jones (CERN)

Outline Introduction LHC Beam Instrumentation Selection What do we mean by “Beam Instrumentation” What instruments are involved LHC Beam Instrumentation Selection Beam Position Measurement Beam Loss Measurement Beam Intensity Measurement Luminosity Measurement LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Introduction What do we mean by beam instrumentation? The “eyes” of the machine operators i.e the instruments that observe beam behaviour What beam parameters do we measure? Beam Position Horizontal and vertical all around the ring Corrected using orbit corrector magnets (dipoles) Beam Loss all around the ring Especially important for superconducting machines Beam Intensity (& lifetime measurement for a collider) Circulating current and bunch-by-bunch charge Beam size Transverse and longitudinal distribution Collision rate / Luminosity (for colliders) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

More “Exotic” Measurements Machine Tune QF QD SF SD Characteristic Frequency of the Magnet Lattice Controlled by Quadrupole magnets Machine Chromaticity Optics Analogy: Spread in the Machine Tune due to Particle Energy Spread Controlled by Sextupole magnets Achromatic incident light Lens Focal length is energy dependent LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Typical Instruments Beam Position electrostatic or electromagnetic pick-ups Beam Loss ionisation chambers or pin diodes Beam Intensity beam current transformers Beam Size (transverse) synchrotron light wire scanners secondary emission or optical transition radiation screens Beam Size (longitudinal) RF pick-ups or synchrotron light Luminosity ionisation chambers or semiconductors Machine Tune and Chromacitity resonant beam position monitors combined with a PLL system ordinary beam position monitors with data processing LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

LHC BPM System - General Layout ~ 24 Special BPMs for Transverse Damper, Tune & Chromaticity Measurements 24 Directional Couplers & 44 Enlarged Button BPMs for the Interaction Regions 44 Warm BPMs - 24mm Button Electrodes 100 Warm, Button Electrode BPMs Buttons Recuperated from LEP 922 Button Electrode BPMs (24mm) for the Main Arcs & Dispersion Suppressors Total of 1158 BPMs for the LHC and its Transfer Lines LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Arc BPM - SSS Layout LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

LHC Arc Type BPM (String 2) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Arc BPM - Button Feedthrough Beam Screen 49mm aperture Liquid Helium Cooling Capillary 24mm button LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Interaction Region BPMs Liquid Helium Capillaries Stripline Electrode Q2 Coupler Directional stripline couplers Outputs signals only from the upstream port Can distinguish between counter-rotating beams LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Front-End Electronics LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Wide Band Time Normaliser Beam A + (B + 1.5ns) A B B + 1.5ns 1.5ns LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Wide Band Time Normaliser A + (B + 1.5ns) A B Dt depends on position A + 1.5ns A 1.5ns B + (A + 1.5ns) B LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Wide Band Time Normaliser A+(B+1.5ns) B+(A+1.5ns)+10ns Interval = 10  1.5ns System output LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Wide Band Time Normaliser LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

LHC Beam Position System Layout Acquisition Chassis  4 Acquisition Chassis  4 TTC Timing Ethernet Real-Time Network Acquisition Chassis  4 Acquisition Chassis  4 Surface Point (1 of 8) 1/16th of LHC Tunnel SSS containing 2 BPMs F.E. Electronics SSS containing 2 BPMs F.E. Electronics SSS containing 2 BPMs F.E. Electronics Up to 28 Quadrupoles 31 Drop-offs max. 31.25kbit WorldFIP fieldbus for slow control Fibre-optic Link using “blown” fibres 7 Drop-offs max. LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

WBTN - Linearity v Intensity For LHC Arc BPMs 1% ~ 130mm LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

WBTN - Linearity v Position For LHC Arc BPMs 1% ~ 130mm LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

WBTN - Radiation Issues The Front-end Electronics for the Arc BPMs will be located under the main quadrupoles can expect to see a dose of some 12Gy/year Tests in the SPS-TCC2 area during 2000 showed that use of DIGITAL components in the tunnel should be avoided Most memories and FPGA’s too easily corrupted Qualification of components long & difficult LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

WBTN - Radiation Issues In 2001 : Fibre-Optic Link added to LHC BPM system only the minimum of analogue electronics kept in tunnel all sensitive digital electronics located on the surface allows easy access to most of the acquisition system Cost of large scale fibre-optic installation compensated by elimination of 13km of expensive low loss coaxial cable reduction in number of acquisition crates no bunch synchronous timing required in the tunnel LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

WBTN - Radiation Test Results 2001 Test results of the very front-end WBTN card with Fibre-Optic Link Initial performance After 650Gy no significant deterioration in the performance is visible 6.5ps rms jitter 6ps rms jitter LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The LHC BPM Acquisition System Very Front-End WBTN Card 70MHz Low Pass Filters Supplied by TRIUMF (Canada) Single-Mode Fibre-Optic Link 1310nm Diode Laser Transmitter Tunnel Surface VME based Digital Acquisition Board TRIUMF (Canada) (2 x 12bit 40MHz Acq) WBTN Mezzanine Card (10bit digitisation at 40MHz) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Operational Prototype Results in 2001 System extensively used in SPS for electron cloud & instability studies. LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Typical Instruments Beam Position electrostatic or electromagnetic pick-ups Beam Loss ionisation chambers or pin diodes Beam Intensity beam current transformers Beam Size (transverse) synchrotron light wire scanners secondary emission or optical transition radiation screens Beam Size (longitudinal) RF pick-ups or synchrotron light Luminosity ionisation chambers or semiconductors Machine Tune and Chromacitity resonant beam position monitors combined with a PLL system ordinary beam position monitors with data processing LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The LHC Beam Loss System Role of the BLM system: Protect the LHC from damage Dump the beam to avoid magnet quenches Diagnostic tool to improve the performance of the LHC Acquisition requirements: Calculation of quench level equivalent chamber signal Electric currents from 600 pA to 300 A A dump should be requested at 50% of the quench level i.e. from 300 pA to 150 A Extend dynamic range for sufficient sensitivity at low losses Measuring current from 60 pA to 300 A Arc BLM acquisition rate not faster than one turn (89 s) Fastest total loss is ~ 6 turns & will be detected by special BLMs. LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Structure of the BLM Readout Chain transforms particle losses into an electric current 6 per quadrupole (3 for each LHC ring)  ~3000 monitors Analogue Front-End measures current and transmits data from Tunnel  Surface Dump Controller processes data and interfaces to the beam interlock system Ionisation Chamber LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Quench Level Equivalent Chamber Current 600 pA One turn 60 pA LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Charge-Balanced Converter iin(t) + Iref iin(t) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Current-Frequency Characteristics LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Front-End Frequency Evaluation 8-bit asynchronous counting of the reset pulses each pulse represents a constant charge every ~40 s the count from each of the 6 channels are multiplexed serial data stream is Manchester encoded FAW Ch 1 Ch 2 ... Ch 6 Tunnel to surface transmission Two choices Cable transmission (tested for 2Mbit up to 1.8km) Differential signal transmission provides noise immunity High speed driver / receiver pair Fibre-optic transmission Final decision will depend on cable distance and transmission rate LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Typical Instruments Beam Position electrostatic or electromagnetic pick-ups Beam Loss ionisation chambers or pin diodes Beam Intensity beam current transformers Beam Size (transverse) synchrotron light wire scanners secondary emission or optical transition radiation screens Beam Size (longitudinal) RF pick-ups or synchrotron light Luminosity ionisation chambers or semiconductors Machine Tune and Chromacitity resonant beam position monitors combined with a PLL system ordinary beam position monitors with data processing LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Fast Beam Current Transformer Installed in the SPS and LHC transfer lines LHC fast BCT will be a scaled version Capable of 40MHz bunch by bunch measurement Dynamic range to cover 5109 to 1.7  1011 cpb LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Fast Beam Current Transformer Image Current 1:40 Passive Transformer Ceramic Gap 80nm Ti Coating 20W to damp any cavity resonances BEAM Calibration winding 500MHz Bandwidth Low droop (< 0.2%/ms) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Acquisition Electronics Designed by the Laboratoire de Physique Corpusculaire, Clermont-Ferrand for use in the LHCb Preshower Detector. [see Session B53] Uses interleaved, 20MHz integrators and sample & hold circuitry to give 40MHz data. Digital Acquisition PMC size Mezzanine card developed by CERN & contains Fast integrator chip 12bit, 40MHz ADC Timing provided by the TTCbi module, part of the Timing, Trigger & Control system developed for the LHC experiments [see Session P54 – Bruce Taylor] Mezzanine sits on the same VME 40MHz Data Acquisition Board developed for the LHC Beam Position System (TRIUMF, Canada) Analogue Acquisition based on a fast integrator chip LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Acquisition Electronics To VME Digital Acquisition Board Fast Integrator Chip Track & Hold MUX Differential Input from Fast BCT 12-bit ADC 40MHz TTC Input from TTCbi 20MHz Clock Creation LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Acquisition Electronics Integrator Output 25ns FBCT Signal after 200m of Cable Data taken on LHC type beams at the CERN-SPS (2002) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Results from the CERN-SPS (2002) Bad RF Capture of a single SPS LHC Batch (72 bunches) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

The Typical Instruments Beam Position electrostatic or electromagnetic pick-ups Beam Loss ionisation chambers or pin diodes Beam Intensity beam current transformers Beam Size (transverse) synchrotron light wire scanners secondary emission or optical transition radiation screens Beam Size (longitudinal) RF pick-ups or synchrotron light Luminosity ionisation chambers or semiconductors Machine Tune and Chromacitity resonant beam position monitors combined with a PLL system ordinary beam position monitors with data processing LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

LHC Luminosity Measurement Requirements: Capable of 40MHz acquisition Has to withstand high radiation dose: ~108 Gy/year estimated 1018 Neutrons/cm2 over its lifetime (20yrs LHC operation) estimated 1016 Protons/cm2 over its lifetime (20yrs LHC operation) No maintenance Candidates: Ionisation Chambers developed by LBL Good radiation hardness Difficult to get working at 40MHz CdTe detectors developed by CERN in collaboration with LETI (Grenoble) Fulfills 40MHz requirement Not yet proven for the highest levels of radiation LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Polycrystalline CdTe Detectors Experience at CERN with CdTe X-RAY detector running in LEP for beam emittance measurement was used up to the end with total dose 1014 Gray Advantages large number of e- created per MIP (~5  Diamond) very fast response time simple construction LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

CdTe Detectors – Test Set-up Sr90 Source Amplifier Output Averaged Output Histogram ~10ns LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Polycrystalline CdTe Detectors LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Irradiation Test Results CERN-SPS (2001) Irradiation test up to 1015 neutrons/cm2 LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Irradiation Test Results Triga type reactor (Ljubljana,Slovenia - 2002) Irradiation steps 1013 neutrons/cm2 1015 neutrons/cm2 1016 neutrons/cm2 activation of all set-up next step 1018 neutrons/cm2 (2003) LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation

Summary LHC is a superconducting machine tight tolerances on all beam parameters instruments have to measure to better than tolerances Increasing demands for all instruments 40MHz bunch-by-bunch resolution large dynamic range Provides a challenging field of development all the main instruments have been defined Installation of some systems begin next year (transfer lines) Final choices for most instruments foreseen by 2004 LECC2002 - Rhodri Jones (CERN - SL/BI) LHC Beam Instrumentation