26.2.02CMS SLHC workshop, D.J.A. Cockerill (RAL)1 CMS SLHC Workshop The CMS ECAL Detector at SLHC D Cockerill RAL 26.2.2004

26.2.02 CMS SLHC workshop, D.J.A. Cockerill (RAL) 1

CMS SLHC Workshop

The CMS ECAL Detector at SLHC

D CockerillRAL

26.2.2004


CMS ECAL at SLHC

Contents

SLHC

Radiation environment

EE, EB, Preshower

Detector performance

EE, EB

Conclusions


SLHC – terms of reference

SLHC

Integrated dose/fluence Factor 6.6 wrt ECAL TDR

Dose and neutron rates Factor 10 wrt ECAL TDR, for 1035 cm-2 s-1

CERN-TH/2002-078 Physics Potential for LHC (107 s/year)

3 years at 1034 cm-2 s-1, 100 fb-1 /y, 300 fb-1

3 years at 1035 cm-2 s-1, 1000 fb-1 /y, 3000 fb-1

Total 3300 fb-1

ECAL TDR , 1997

Radiation levels for 10 years LHC to 5.105 pb-1 = 500 fb-1

Maximum luminosity 1034 cm-2 s-1


SLHC – upgrades

Phase 2 Major hardware changes for 2020

Equip SPS with superconducting magnets

New dipoles in LHC arcs

E C of M 25 TeV

LHC Luminosity and Energy upgrade

LHC Project Report 626

Phase 0 No hardware upgrades

1 2.3 3.6 1034 cm-2 s-1

Phase 1 Hardware upgrades: insertion, injector

3.3 4.6 67 1034 cm-2 s-1

Phase 1 Superbunch, ib 1A, bunch length 300m

to avoid electron cloud effects

~ 9. 1034 cm-2 s-1


SLHC – radiation load

Radiation loads for tests, balance 1) with 2) ? ECAL TDR radiation levels, scaled to 3300 fb -1,

used as the reference point in this talk

1) SLHC design study calculations

Assumes each fill to nominal luminosity

Assumes turnaround time between fills of 1h

Caveats:

Integrated luminosity drops by ~40% if LHC turnaround 6h Fill to fill variations: <Luminosity> a factor ~0.7-0.8 lessEarly beam aborts, factor 2? on integrated luminosity

2) ECAL TDR radiation calculations

A safety factor of 2-3 advised on simulation results

A further factor of 2-3 advised for cables and capacitors


EE at SLHC

Repair of SC array would require the dismounting of EE readout electronics on rear of backplateHigh activation levels, access time limited

Qualify SC components for SLHC before EE build

Supercrystals and their internal components are inaccessible and cannot be replaced. Components:VPTs, HV pcbs, capacitors, resistorsSignal & HV cable, quartz monitoring fibres

5mSv/h

Unshielded dose rate 0.2mSv/h

=3

=1.48


EE Integrated Dose for 3300 fb-1

400

Inner radial limit of activeelectronics

300

200

100

kG

y

EE radial distance from beam pipe (mm)

Maximum Dose at = 3 350kGy (35MRad)

SCs, VPTs, HV pcbs (capacitors, resistors),HV/LV cables, monitoring fibres

Maximum Dose at = 2.6 150kGy (15MRad)

Active ECAL readout electronics


EE Integrated Neutron Fluence for 3300 fb-1

Active electronics behindpolyethylene moderator

50

40

30

20

10

Neu

tron

s/cm

2 /10

14

Inner radial limit foractive electronics

Maximum fluence at = 3 5.1015/cm2 SCs, VPTs, HV pcbs (capacitors, resistors),HV/LV cables, monitoring fibres

Maximum fluence at = 2.6 5.1014 /cm2 Active ECAL readout electronics

EE radial distance from beam pipe (mm)


Supercrystal items, Co60 Irradiation tests

All tests so far OK – no show stoppers, capacitors (unbiased) 9% changeTo do in 2004:VPTs, faceplates, capacitors and resistors to 500 kGyBrunel University source, 1kGy/h, ~ 21 days

2 2.6 320-50 100 200 300 350 400 500

VPT faceplatesVPTsDC 3145 VPT-xtal glue

HT cable, 2KV, LO-GE No461RG 179PE signal cable (not final choice)

Capacitors (HV, unbiased)5

Capacitors (HV, biased) 5

Resistors (HV,LV) 20 2 to 362kGy

Thermal compoundCarbon fibre alveolar composite strength tests to 5MGy!!

Eta (SLHC equivalent) Dose (kGy)


Supercrystal items, Neutron Irradiation tests

All neutron irradiation tests so far OK – no show stoppers1 capacitor, measured under irradiation, long cables, -17%To do:VPTs, faceplates, capacitors and resistors to 50.1014 cm-2

Tests carried out at Minnesota, 252Cf source, 2.14 MeV neutronsNeutron rate 107 cm-2 s-1 rate at = 3 at 1034 cm-2 s-1

Noise induced in VPT from local activation ~ 3200e- 10000e- at 1035 Compton electrons, from s s, enter VPT faceplateLight, from electrons above Cerenkov threshold, yield VPT photo-electrons

2 2.6 310 20 30 40 50

VPT faceplates 7.10**14 (PNPI, Apr 2003)VPTs 2.5.10**14 (PNPI, Sep 1999)

Capacitors (biased) 5

Resistors (HV, biased) 4

Eta (SLHC equivalent) neutrons/cm2*10**14


EE induced activationECAL TDR

Induced activation at = 3 ~0.25 mSv/h<L> = 0.5.1033 cm-2 s-1, cooling time 1 dayA further drop by ~0.7 after some weeks

Dose regulations/adviceDose limit 1mSv/weekAnnual dose limit 5mSv

SLHC at 1035 cm-2 s-1 factor 20 on ECAL TDR Time to Annual dose

= 3.0 5mSv/h 1 hour = 2.6 2mSv/h 2.5 hours = 2.0 0.4mSv/h 12 hours = 1.48 0.2mSv/h 25 hours

↪ for dismounting EE from HE. Done at outer radius.

Repairs on EE: need shielding, remote handling (if indeed repairs actually permitted!)


EE Readout for 3300 fb-1

Set of 100 readout channelsInner radial limitr = 50cm, = 2.6LV regulators to 5.1014 /cm2

PE moderator to reduce neutron fluence

Active readout electronics

Access constraints severe at inner radiiRequire robust LV regulators on EE from outset

Beam

1 hour

Unshielded access time 25 hours


EB at SLHC for 3300 fb-1

APD certificationAll screened to 5kGy (some have received 10kGy) – most OK(some have significant change in breakdown voltage - rejectedmost change by only ~1V, vs. 40V breakdown margin)

Other tests2001, Karlsruhe, 48 APDs, 20kGy, 2.1013 n/cm2 – all OKMinnesota, >1000 APDs, 1-2. 1013 n/cm2 – all OK

Need a programme of APD neutron tests to ~2.1014 n/cm2

and annealing tests at 18oC

Dose 2kGy Neutrons 7.1013 cm-2

= 1.48 at APDsDose 5kGy Neutrons 1.3.1014 cm-2


Preshower at SLHC for 3300 fb-1

Preshower 1.65 < || < 2.6Silicon sensors at –5oC

Neutrons from EEProtected by 4cm of moderator.Further 4cm, upstream, gives 8cm of protection for Tracker

Silicon at = 2.6Neutrons 1.3.1015 cm-2 Dose 700kGy (70MRad)

Beam

EE

Dismounting from inner coneActivation at = 2.8 ~3mSv/h 1.7 hours for annual dose (EE dominated?) Need simulation for isolated Preshower, to determine repair accessibility.


Preshower at SLHC for 3300 fb-1

Silicon sensors to = 2.6 1.3.1015 n/cm2, 700kGy (70MRad)

Increased leakage currentIncreased voltage required to full depletion, <500V for TDR levelsLeakage current compensation tested to 6xTDR ( ~SLHC)

If depletion voltages of 1000V needed,likely that even best sensors will break downWill be at limit of HV supply components

Complete replacement of inner sensors on a fairly regular basis

ElectronicsExpect big trouble with ST LV regulators0.25m chips (front end, ADC, control system etc) “should” survivebut no guarantees or tests to SLHC levels

PACE 0.25m chip – not tested under irradiation yet(PACE DMILL was tested to 6x1014 n/cm2, 100 kGy, and was ok)


ECAL Crystal Performance

20 30 40 % LY loss

LY lossdistribution for 677 xtals

Crystal LY loss from Co60 dose rate studies

At SLHC, =3, at shower max Dose rate = 10 x 15 = 150Gy/h

Data rate, Cantonal Irradiation 240 Gy/h, 2hRepresentative of SLHC worst case

Densely ionising hadron shower effects not included

LY loss calculated from measured induced absorption

Assume all colour centres activated – gives worst case


ECAL LY during LHC fills - SLHC

=0

=2.5

Crystal light yield

LHC luminosity

fill by fill

Colour centre creation dependent on dose rateDose rate changes during fill and with etaMore changes in EB! EE saturates to constant level


Crystal light yield at LHC

Startup Low High SLHC1033 2.1033 1034 1035

100

40

80

Lig

ht Y

ield

%

60

0 < < 3.0

At SLHC, see significant changes in crystal LY<LY> drops by ~25% EB, 30% EE.


Crystal LY changes at SLHC

RMS LYchangesduring fills

Barrel LY changes ~3% through the period of a fillEndcap LY changes ~1% (crystals saturated)

LY monitoring – main challenge in EB

10%

5%

0%

Eta 3.01.50


EE performance at SLHCInitial performance 50 MeV ET, preamp noise 3500e-

Activation noise, SLHC = 2.5, 10000e- 140 MeV ET per channel

Losses

Xtal LY loss 0.7 0.2 Induced abs data

VPT faceplate 0.8 ? Guess, 10% to 20kGy

VPT Q.E. (burn-in study)

0.4 ? 60% loss, 6 days at Ik = 1A 18y at 1034 at = 2.5

VPT gain 1.0 No change observed

Reduced HV 0.9 Working margin

Resultant factor 0.2 (Hadron damage to xtals, another factor 0.5?)

Resultant noise 250 (700 with activation) MeV ET per channel- excluding pileup contributions & other electronics issues

Charged hadron effects on xtal LY need to be taken into account


EB Performance at SLHC

EB noise likely to be ~190 MeV per channel- excluding pileup contributions & other electronics issues

Charged hadron effects on xtal LY need to be taken into account

Leakage Current/xtal

Noise equiv Comment

APD current (TDR) 20A 60MeV With annealing, single

sampling?

APD current (SLHC) 130 A 150MeV As (leakage current)Annealing not included

Add EB preamp noise 140MeV 50MeV in quadrature

Losses

Crystal factor 0.75 190MeV LY loss in crystals

APD - Xtal glue ? Measured to 5kGy?

APD Q.E., Gain ? Reduce gain, leakage?


ECAL at SLHC - Conclusions

EERepairs very difficult if not impossible, activationQualify all components to SLHC levels before EE buildVPT and component irradiation tests in 2004 to 350kGyInduced activity noise could be important limitationCharged hadron effects on Xtal LY, tests to be completed

Detector Noise/channel ET 250 MeV or greater (excl. pileup)EBAPD studies to ~2.1014 n/cm2 neededDetector Noise/channel 190 MeV or greater (excl. pileup)PreshowerReplacement of inner silicon likely to be needed – very difficult


Backup slides


Simulation of crystal behaviour at LHC

Simulation of crystal LY lossColour centre creation and recovery

LHC luminosity according to beam lifetime during fillFill of 20h, turnaround 4h (old regime)Relative fill to fill variations, 0.2 1.0

Dose rate calculated at 1cm steps along each xtalColour centres and LY loss calculated for each cm along xtalCrystal data from GIF for creation and annealing time

constants

LY loss along full crystal iterated in 1h intervalsLY losses calculated for 0<<3.0


SLHC – running time

~45% less Lint if turnaround is 6h and not 1h

Fill lifetime Turnaround (h) T run (h) Lint fb-1/y

15h, L0=1034 1 5 122

15h, L0=1034 6 12 78

6.5h, L0=4.5.1034 1 3 524

6.5h, L0=4.5.1034 6 6 286

Documents

26.2.02CMS SLHC workshop, D.J.A. Cockerill (RAL)1 CMS SLHC Workshop The CMS ECAL Detector at SLHC D Cockerill RAL 26.2.2004