Andrej Gorišek J. Stefan Institute, Ljubljana ATLAS BCM/BLM Status Commissioning and First Operational Experience of the ATLAS Beam Conditions and Loss Monitors Based on pCVD Diamond Sensors Andrej Gorišek J. Stefan Institute, Ljubljana 11th Pisa Meeting on Advanced Detectors La Biodola, Isola d'Elba (Italy), May 24 - 30, 2009

Outline Introduction ATLAS Beam Condition Monitor principles of operation commissioning ATLAS Beam Loss Monitor design and installation First measurements with as installed system BCM with cosmic data first beam Luminosity monitoring ATLAS BCM/BLM Status A. Gorišek 2

The ATLAS BCM collaboration CERN B. Demirkoz, D. Dobos, J .Hartert, H. Pernegger, P. Weilhammer JSI, Ljubljana V. Cindro, I. Dolenc, A. Gorišek, G.Kramberger, B. Maček, I. Mandić, E. Margan, M. Zavrtanik, M. Mikuž OSU, Columbus H. Kagan, S. Smith Univ. of Applied Science, Wiener Neustadt E. Griesmayer, H. Frais-Kölbl, M. Niegl Univ. Toronto M. Cadabeschi, E. Jankowski, D. Tardif, W. Trischuk All you ever wanted to know about BCM: https://twiki.cern.ch/twiki/bin/view/Atlas/BcmWiki ATLAS BCM/BLM Status A. Gorišek 3

(misfiring of kicker magnet) Motivation Experiences (recent at Tevatron) show that beam accidents happen LHC will store much more energy than ever before (~3000 bunches with 1011 protons of 7 TeV)  about 200-times more energy stored in beams compared to maximum value in previous accelerators like HERA or Tevatron Potentially dangerous to ATLAS Inner Detector Time constants of magnets in LHC typically much larger than time of one orbit  can act to prevent beam accidents 20-30 Tevatron turns (misfiring of kicker magnet) ATLAS BCM/BLM Status A. Gorišek 4

Beam Accident – Protection ATLAS is furthest from injection – safest (?) Passive protection: ATLAS and CMS have Target Absorber Secondaries (TAS) collimators @ z=±18m: protecting inner triplet of quadrupoles from secondaries produced in p-p collisions and Inner Detector from beam failures Active protection: Beam Interlock System (BIS): two redundant optical loops transporting BeamPermit signals – a logical AND of UserPermit signals provided by user systems (machine beam loss or beam position monitors, experiment Beam Condition Monitors (BCMs), etc.) If UserPermit is set to False optical loop is interrupted  BeamPermit removed, beam dump procedure initiated (beam is dumped within 3 turns ~270 μs) + no injection from SPS ATLAS BCM/BLM Status A. Gorišek 5

ATLAS Spectrometer ATLAS BCM/BLM systems will protect Inner Detector against beam accidents (+luminosity, +trigger,…) 25m 44m ATLAS BCM/BLM Status A. Gorišek 6

ATLAS Inner Detector BCM 4 BCM detectors installed inside PIXEL volume on each side z=±1.84 m, r=55 mm, @ 45o PIXEL SCT B. TRT B. TRT End Cap SCT End Cap BCM ATLAS BCM/BLM Status A. Gorišek 7

BCM – Beam Accidents Protection Continuous measurement with single MIP sensitivity Distinguish between interactions and background (scraping of collimators, beam gas,...)  requirement: better than 12.5 ns width+baseline restoration 2 detector stations, symmetric in z TAS (collimator) event: Δt=2z/c=12.5ns (ideally)‏ Interaction: Δt = 0, 25, … ns -6ns 6ns Time difference ATLAS BCM/BLM Status A. Gorišek 8

pCVD Diamond Material bunch by bunch measurement  fast signal rise time (1ns), narrow width (2ns), short baseline restoration (10ns) very close to BP and IP  radiation hardness (50MRad in 10years of ATLAS operation) pCVD diamond fulfils these requirements (developed in collaboration RD42 – Diamond Detectors Ltd./E6 Ltd.): high resistivity low dielectric constant almost negligible leakage current (room temperature, low noise) – even after irradiation (<100pA) high charge mobility and ccd of >200m proven radiation hardness  talk by H. Kagan on “Diamond Pixel Modules” (Friday afternoon) REQUIREMENTS ATLAS BCM/BLM Status A. Gorišek 9

ATLAS Beam Condition Monitor pCVD sensors of 1x1cm2 and 500m thickness with 8x8mm2 Al finish rad-hard contacts (OSU) 8 detector modules (aluminum oxide base board + 2 pCVD diamond sensors back to back in FE module box) Fast & short signal (FWHM~2ns, rise time<1ns)‏ Agilent MGA-62653 500Mhz (gain: 22 dB, NF: 0.9dB)‏ pCVD diamond Mini Circuits GALI-52 1 GHz (20 dB)‏ ATLAS BCM/BLM Status A. Gorišek 10

BCM Signal Optimization double sensor layout – double decker – noise increase of 30% only 45o mounting angle w.r.t. beam axis – increase of signal by 2 most probable MIP energy loss: 20000eo  signal to noise ratios of 10 achievable ATLAS BCM/BLM Status A. Gorišek 11

BCM Detector modules installed SLA brackets on PIXEL support structure BCM Detector module Beam pipe Pixel ATLAS BCM/BLM Status A. Gorišek 12

BCM Readout Chain analogue signals from BCM detector modules routed behind calorimeter (lower radiation levels – 10Gy in 10 years) where they are digitized by custom board based on ALICE ToT NINO chip individual BCM detector modules are connected to separate NINO boards for electrical ground separation – minimize interference (grounds connected together close to detector modules) ATLAS BCM/BLM Status A. Gorišek 13

BCM Readout Chain rad-tolerant laser diodes transmit signal trough 70m of optical fibers to USA15 counting room optical signals received and transformed into PECL on two 8 channel optical receiver boards PECL signal from individual receiver board connected to Read Out Driver (ROD) based on Xilinx Virtex-4 based FPGA board ATLAS BCM/BLM Status A. Gorišek 14

BCM Data Acquisition personality modules developed for interfacing input and output signals to RODs input signal sampled with 2.56 GHz  64 samples of 390ps for each BC (25ns) connected to ATLAS Central Trigger Processor (CTP), data acquisition (TDAQ), Detector Control System (DCS), Detector Safety System (DSS) and the Controls Interlocks Beam User (CIBU) systems. ATLAS BCM/BLM Status A. Gorišek 15

Signal analysis - NINO signals measured in Time-over-Threshold fashion: 25 ps jitter, 1 ns rise time analogue signals from modules split into two channels of NINO chip in ratio of 1:11 to increase dynamic range of the chip PH corrections for nonlinearity required (look-up table) ATLAS BCM/BLM Status A. Gorišek 16

Signal analysis - ROD cable length differences compensated internally in FPGA raw data stored in DDR2 memory module for more than the last 1000 LHC turns (circular buffer) rising edges and pulse widths are reconstructed in signals (at most the first 2 for each BC) and stored in DDR memory module  LHC post mortem  on L1A signal data is formatted and sent over optical link to Read Out Subsystem (ROS)  in time and out of time coincidences: 9 trigger signals to CTP  + high multiplicity  LHC beam abort system and ATLAS DSS ATLAS BCM/BLM Status A. Gorišek 17

ATLAS Beam Loss Monitor Recently proposed and built a redundant system to BCM Simpler – aims only to be a “safety system” Electronics based on LHC BLM system pCVD diamond sensors used instead of ionization chambers (similar to CDF at Fermilab) ATLAS BCM/BLM Status A. Gorišek 18

LHC Beam Loss Monitor measure and localize beam loses (number of lost particles) measure particle rates with different integration times (running sums in interval of 40µs to 84s) and act on the basis of them exceeding configurable thresholds up to 8 ionization chambers read out by “tunnel card”: BLMCFC converts current into frequency and sends encoded data over optical link to the “surface card”: BLMTC (based on DAB64x card) connection to the combiner card and trough it … to BIC … and beam energy tracker VME bus: logging rates reading out the post-mortem buffer ATLAS BCM/BLM Status A. Gorišek 19

ATLAS BLM system 8x8mm2 0.5mm thick diamond sensors used (instead of ionization chambers as in LHC) 6 sensors on each side (A and C) installed on IDEP Modified BLMTC firmware to receive beam dump signals on front panel LEMO outputs  connection to BIC BLMTC inserted into BCM (standard ATLAS) VME crate VME bus used for monitoring rates and recording the postmortem buffer ATLAS BCM/BLM Status A. Gorišek 20

ATLAS BLM detector module mechanical support: rad-hard PEEK plastic support standard double sided PCB – mechanical rigidity and electrical insulation layers screwed together with M3 screws sensor: 8x8 mm2 0.5 mm pCVD diamond (by DDL) metalized at OSU (7.5x7.5 mm2) assembly: conductive glue, bonding, soldering ATLAS BCM/BLM Status A. Gorišek 21

ATLAS BLM Installation detector mounted to the “Inner Detector End Plate” close to the Beam Pipe 6 detector modules installed on each side z~3450mm, r~65mm IDEP SIDE A view towards IP 1 A 2 A 4 A 3 A 6 A 5 A SIDE C view towards IP 1 C 2 C 4 C 3 C 6 C 5 C ATLAS BCM/BLM Status A. Gorišek 22

BCM Cosmic data November 2008 – 1 week of combined Inner Detector cosmic data-taking Two different triggers: by Resistive Plate Chamber (RPC) Muon Subsystem and Transition Radiation Tracker (TRT) Fast OR mechanism  with combined trigger rate of ~150 Hz 51 M events triggered 131 events with hits reconstructed in BCM ATLAS BCM/BLM Status A. Gorišek 23

Timing plot preliminary preliminary each trigger from CTP triggers readout of 31 consecutive BCs histogram BC of reconstructed hits in BCM width of distributions – convolution of timing distributions of trigger systems and BCM both plots show peak around BC=19 as expected random uniform background preliminary preliminary ATLAS BCM/BLM Status A. Gorišek 24

Channel occupancy preliminary preliminary channels 0-7 are low gain channels (expect to show signal for ~5 or more MIPs traversing the sensor simultaneously) NINO thresholds not calibrated  different noise occupancies of readout channels no hits on C side with TRT Fast OR  also due to known unequal efficiencies of TRT endcaps in the data taking of November 2008 C A preliminary preliminary ATLAS BCM/BLM Status A. Gorišek 25

Track reconstructed Couple of events show hints that cosmic muon track could have passed trough BCM module BCM hit reconstructed along with several hits in SCT and TRT tracking systems TRT SCT BCM ATLAS BCM/BLM Status A. Gorišek 26

First LHC Experience Timing of our RODs was not fully calibrated Monitor hit rates (integration time of 1 s) transmitted to DCS computer over Ethernet showed increase during the events when beam was splashed into closed collimators Diamond (erratic) dark currents decrease when sensors are operated in magnetic field  nominal voltage of 1000V is decreased to 800V during magnet off periods I(A) time ATLAS BCM/BLM Status A. Gorišek 27

Luminosity monitoring Goals of BCM system within the ATLAS Luminosity Working Group: Monitor instantaneous luminosity vertex position monitoring determine dead time beam separation scans Counting number of tracks trough BCM modules – monitoring instantaneous luminosity: BC rate number of pp in single BC (function of luminosity) number of tracks per pp probability of track going to side A ATLAS BCM/BLM Status A. Gorišek 28

Luminosity monitoring - Simulation sum of number of tracks per pp collision in BCM (z,r)-origin distribution of tracks that cross BCM sensor volume ½ of particles from secondaries ATLAS BCM/BLM Status A. Gorišek 29

Summary Two pCVD diamond based safety systems Beam Condition Monitor (BCM) and Beam Loss Monitor (BLM) built and being commissioned for ATLAS experiment First operation experience with BCM obtained throughout last year BCM has further more ambitious goals (data taking, triggering, luminosity monitoring, beam separation scans,…) while BLM is safety system only Looking forward to test the fully commissioned systems in the real LHC environment later this year ATLAS BCM/BLM Status A. Gorišek 30