Bandwidth optimization FFT analysis of average BCM MIP signal

Confirmed in CERN SPS test beam, 200 MHz BWL on LeCroy LC564A: signal decrase by 1.5, noise by 2 → S/N increase by 4/3

Front-end electronics Two stage Fotec HFK500 amplifier

1st stage: 500 MHz Agilent MGA-62563 GaAs MMIC low noise amplifier (A = 22 dB, NF = 0.9 dB)

2nd stage: Mini Circuits Gali-52 InGaP HBT broad-band micro-wave amplifier (A = 20 dB)

Amplifiers tested for radiation hardness Up to 1015/cm2 reactor neutrons and protons from CERN PS Agilent: ~ 20 % amplification loss observed with Si

diodes, no noise increase Gali-52: 0.5 dB amplification loss FE amplifier OK for BCM application

X

2 detector stations, symmetric in z

TAS events: t = 12.5, 37.5 .. ns

Interactions: t=0, 25, 50 .. nsΔ

Sensors Polycrystalline CVD diamond sensors chosen

Radiation hard – shown to work at > 1015 particles/cm2

Fast signals – high velocity and cut-off due to trapping Small leakage current – no cooling required

Procurement in collaboration with CERN RD-42 Sensors produced and conditioned by Element Six Ltd. Metallized with proprietary radiation hard process at OSU

Sensor properties Size 10 mm x10 mm, active 8 mm x 8 mm (metallization) Thickness ~500 μm Charge collection distance ~220 μm Holds ~ 2 V/ μm, operating voltage 1000 V, current ~ nA

Sensor assembly – two sensors back-to-back at 45° to increase signal

Signal ⊗ 1.4, noise unchanged for 0 → 45° Signal ⊗ 2, noise ⊗ ~1.3 for single → double-decker

Mounted on Al2O3 ceramics, through-holes and bonds supply HV to top/bottom, signal sourced from middle

Diamond Pad Detector Telescope for Beam Diamond Pad Detector Telescope for Beam Conditions and Luminosity Monitoring in ATLAS Conditions and Luminosity Monitoring in ATLAS

Diamond Pad Detector Telescope for Beam Diamond Pad Detector Telescope for Beam Conditions and Luminosity Monitoring in ATLAS Conditions and Luminosity Monitoring in ATLAS

AbstractBeam conditions and the potential detector damage resulting from an anomalous event such as a full LHC bunch blasting into the collimators have provoked LHC experiments to plan their own monitoring devices in addition to those provided by the machine. ATLAS decided to build a telescope with two stations of four diamond pad detectors each. Equipped with fast electronics with shaping time of 1 ns it allows time-of-flight separation of events of beam anomalies from normally occurring p-p interactions. Placed symmetrically about the interaction point at z=±183.8 cm and r~55 mm (η~4.2) it will provide also a coarse measurement of the ATLAS LHC luminosity.The stringent timing requirement to resolve signals half a bunch crossing apart, coupled with the radiation field of ~1015 π/cm2, prompted the usage of 500 μm thick pCVD diamond pad detectors of 1x1 cm2, operated at an unconventionally high electric field of 2 V/μm. Two diamonds are glued back to back and tilted at 45° to the tracks to enhance the signal. Two stage high-bandwidth low-noise pre-amplifier composed of discrete components provides signal amplification of ~ 40 dB, with signal rise time of 1 ns, pulse width of 3 ns and base-line restoration in 10 ns. Low-loss coaxial cables are used to lead the signals ~14 m outwards, where they are processed in the NINO time-over-threshold timing amplifier-discriminator ASIC, thus preserving timing and amplitude information. Further processing of the optically transmitted signals, including timing coincidence and amplitude analysis, and event history tracing that could eventually lead to a beam abort request, is foreseen by an FPGA-based system in the ATLAS service cavern.Ten detector modules have been assembled and subjected to tests, from characterization of bare diamonds to source and beam tests. The latter were performed last December at KEK and this summer in the CERN PS and SPS beams. A silicon telescope for efficiency evaluation across the detectors has been used for the CERN beam tests. Final electronics and services were used. Based on performance, eight of the modules will be selected for installation on the pixel support structure by the end of this year.

M. Mikuž1, V. Cindro1, I. Dolenc1, H. Kagan5, G. Kramberger1, H. Frais-Kölbl4, A. Gorišek2, E. Griesmayer4, I. Mandić1, M. Niegl4, H. Pernegger2, W. Trischuk3, P. Weilhammer2, M. Zavrtanik1

1Univ. Ljubljana/Jožef Stefan Institute, Ljubljana, Slovenia, 2CERN, Geneva, Switzerland, 3University of Toronto, Toronto, Canada, 4FHWN, Wiener Neustadt, Austria, 5Ohio State University, Columbus, USA

Goals Provide distinctive signature of beam anomalies in ATLAS such as

Beam scraping at TAS collimators: single 7 TeV proton yields ~ 1 MIP/cm2 around beam-pipe, serious detector damage from complete beam loss

Beam gas interactions Stand alone device providing information about genuine

interactions Monitoring of interactions at LHC start-up Luminosity assessment: on-line and off-line

Requirements Fast signals

Rise-time ~ 1 ns Width ~ 3ns Base line restoration in ~ 10 ns to prevent pile-up

Single MIP sensitivity S/N ~ 8 for perpendicular MIP before irradiation

Installation close to the beam pipe at η ~ 4.2 Radiation hardness up to 30 MRad ( 1015 π/cm2 ) No possibility for maintenance – robust detector

Working principle Distinguish interactions from background via time of flight With two symmetric stations at ±Δz/2

Interactions: in time Background: out of time on one side by Δt = Δz/c

At high luminosity expect ~ one hit per side for each bunch crossing Interactions at Δt = 0, 25, 50 … ns Optimal separation of background at Δt = 12.5 ns ⇒ Δz =

3.8 m

183cm

38 cm

ATLAS

44 m

Pixel

BCM

BCMmodules

Realization Two stations with four detector modules each

Mounted on pixel support structure at z = ±183.8 cm Sensor at r ~ 55 mm, about 20 mm from the beam pipe

Sensor with Autest metallization

Sensor on ceramics in module box

Amplifier schematic

1st 2nd stage

Amplifier in module box

Si diode signal Si diode noise Gali-52 amplification

Non-irradiated/irradiated Agilent FE comparison

BCM module tests Bench tests

30 MBq 90Sr source; ~ MIP signal QA for BCM modules Module stability tests Noise independent of HV Good reproducibility of signals Signal stable to 4 % during 24 h

NINO back-end chip tests Differential timing amplifier-discriminator (1 ns peak, 25 ps jitter) LVDS output with width proportional to time-over-threshold Radiation tolerant design by CERN-MIC Signal split 1:12 into two inputs to increase dynamic range Tests confirm suitability as BCM back-end chip

Beam test at KEK in December 2005Few GeV/c pion beam BCM signal amplified in 300 Mhz OrtecRecorded by CAEN 2 GHZ sampling ADCTracking by MWPC (T3, T4)Parasitic to Belle PID upgrade testBCM signal required in trigger

Mail to: Marko.Mikuz@ijs.si

Erratic leakage currents in pCVD diamonds Leakage current increases by factor >100 on day’s time-

scale Erratic behaviour on time-scale of minutes Phenomenon observed at BaBar at lower fields 1 V/μm

Excess current vanishes in magnetic field > 1 T BCM noise insensitive of current in nA ↔ μA range

2.8 days @ B =2 TBCM @ 45°

90Sr waveform Signal: max 34-36 nsNoise: all data 0-20 ns

NiN

O T

OT re

sp

on

se

to 1

-4 M

IP s

ign

als

KEK beam-test results S/N ~13; caveat: noise estimate

BCM in triggerAsymmetric amplifier

Coarse MWPC tracking Extrapolation to BCMScattering in material

Qualitative performance estimates only

Beam test in CERN PS and SPS in summer 2006 CERN PS: T11 & T9 line (3.5, 12 GeV) CERN SPS: H6 & H8 line ( >100 GeV) 4 BCM modules read out Analogue readout: ORTEC + CAEN ADC TOT readout: NINO + CAEN ADC Final HV/LV supplies (ISEG, SCT) Final HV/LV cables & connectors Final signal coaxes (GORE 1.4 m & Heliax 12 m) Bonn Si telescope for precision tracking (4H, 4V planes)

Special thanks to Bonn telescope crew (Jaap, Lars, Markus)

BCM inside telescope: good tracking, cuts on scatteringBCM signalcable (black)

BCM HV/LVcable (red)

BCM modulesin holder

Bonn Sitelescope

BCM adapterbox (~PP2)

H8 pion beam

Set-

up

in

SP

S H

8 t

est

beam

Preliminary analysis of CERN PS analogue data 3 runs from 12 GeV T9 beam 22 k events with good Si tracks (hits in ≥ [3V,3H] planes) Central diamond region chosen Signal: max in 2 ns window Noise: single sample well before signal, fit positive values S/N ~ 14 ± 2, consistent with KEK and source tests

Analysis of CERN PS TOT data Quasi on-line analysis Si tracks with hits in all planes Central diamond region Efficiency vs. NINO threshold Noise occupancy vs. threshold Efficiency saturates at > 95 %

22 k events with good Si

telescope tracks

BCM signal

X-Y @ 1st Si

Cut @ 180 1.7 k events with Si tracks inside red box

Noise20±2.6

SignalMPV~280

X-Y for signal > 180

Typical BCMpulse

ν [MHz] ν [MHz] ν [MHz]