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The LHCb Pixel Hybrid Photon Detectors. Robert W. Lambert, University of Edinburgh On behalf of the LHCb RICH collaboration. Outline. Introduction: LHCb and Particle ID Hybrid Photon Detectors (HPDs) HPD Manufacture Testing and Results RICH Installation Progress Summary. LHCb. - PowerPoint PPT Presentation
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R Lambert, LHCb RICH PD07, 28th June 2007 1
The LHCb Pixel Hybrid Photon Detectors
Robert W. Lambert, University of Edinburgh
On behalf of the LHCb RICH collaboration
R Lambert, LHCb RICH PD07, 28th June 2007 2
Outline
Introduction: LHCb and Particle ID
Hybrid Photon Detectors (HPDs)
HPD Manufacture
Testing and Results
RICH Installation Progress
Summary
R Lambert, LHCb RICH PD07, 28th June 2007 3
LHCb
LHCb will examine CP-violation in B-mesons [1] Why is there a matter-antimatter asymmetry in the universe? What are the reasons for the parameters in the Standard Model? Is there physics beyond the Standard Model?
R Lambert, LHCb RICH PD07, 28th June 2007 4
LHCb @-100m
RICH 1MagnetRICH 2
R Lambert, LHCb RICH PD07, 28th June 2007 5
RICH 1 and RICH 2
Ring Imaging CHerenkov (RICH) detectors [2] Relativistic charged particles in a medium radiate light Characteristic cone angle, cos = 1/n
RICH 1(Vertical)
RICH 2(Horizontal)
MA
GN
ET
TT
T1-T
3
R Lambert, LHCb RICH PD07, 28th June 2007 6
Cherenkov Imaging
Rings reconstructed Velocity Cone angle ≡ Ring radius Combine with momentum to get Particle ID
RICH 1 for 1 < p < 60 GeV/c RICH 2 for p < 100 GeV/c
~20 hits/ring~4 hits/ring
~25 hits/ring
R Lambert, LHCb RICH PD07, 28th June 2007 7
Ideal Cherenkov Spectra
0.1
1
10
100
1000
100 300 500 700Wavelength [nm]
Ab
sorp
tion
[cm
-1] .
0.0
0.2
0.4
0.6
0.8
1.0
# o
f ph
oto
ns
[arb
. un
its] .
Absorption Water
Absorption OxygenRICH 1 C4F10
RICH 1 Aerogel
Requirements
Stringent requirements for RICH photodetectors– 2.6 m2 detector plane
– Single-photon sensitive
– 65% active area overall
– 80% for cylindrical devices
– Cherenkov Spectrum
– 2.5 mm x 2.5 mm granularity
– 25 ns Clock <25ns response
– 40 MHz Clock 40 MHz read out
– Trigger decision 4s data buffer
– Photon yield High Signal:Noise
– 5-10 year lifetime
– Radiation tolerant 30 krad
– Fringe magnetic field
C4F10
200-600nm
R Lambert, LHCb RICH PD07, 28th June 2007 8
Hybrid Photon Detectors
484 Hybrid Photon Detectors HPDs required [3]+ Photocathode (S20)+ Silicon sensor+ Binary read-out chip
120
mm
87 mm
8192Vacuum
Electrode
Photoelectrons
Solderbump bonds
Ceramic Carrier
Binaryelectronicschip
Photon
Photocathode (S20)at -20kV
Si Sensor8192 pixels
QuartzWindow
R Lambert, LHCb RICH PD07, 28th June 2007 9
HPD Manufacture (1)
Production at IBM, Canberra, Kyocera, VTT, HCM, DEP-Photonis
Full testing and gold plating by LHCb at CERN
Packaging
Ceramic carrier
Brazing and gold-plating
Readout chip
Silicon sensor Bump-
bonding
R Lambert, LHCb RICH PD07, 28th June 2007 10
HPD Manufacture (2)
Encapsulated by DEP-Photonis
Testing by LHCb
Tube body
assembly
Photo-cathode
deposition and vacuum
sealing
Packaging
R Lambert, LHCb RICH PD07, 28th June 2007 11
HPD ProductionHPD production status as of 18th June 2007
0
100
200
300
400
500
600
1-Jan-05 2-May-05 31-Aug-05 30-Dec-05 1-May-06 30-Aug-06 29-Dec-06 29-Apr-07
Qu
anti
ties
HPDs required
Spare HPDs required
HPDs delivered
Total tested
Production
Testing
536 / 550 HPDs Produced
18th June 2007
519 / 536 HPDs Tested
R Lambert, LHCb RICH PD07, 28th June 2007 12
PDTF
Photo-Detector Test Facilities 2 centres (2 stations each) Test 1 HPD/site/day 506 of 519 HPDs pass Failures Replaced.
R Lambert, LHCb RICH PD07, 28th June 2007 13
PDTF Tests
Check out every function of the HPD, from the ground up
Readout ChipConnectionsCommunicationsDAQReadoutDead ChannelsNoisy ChannelsMaskingResponsesThresholdNoise
PhotocathodeDark CountResponse to lightQuantum Efficiency
HPD BodyDimensionsHV StabilityVacuum Quality
Electron OpticsImage SizeImage CentreHV StabilityField Distortions
Silicon SensorIV CurveEfficiency (Backpulse)
R Lambert, LHCb RICH PD07, 28th June 2007 14
Silicon Sensor
PDTF perform a bias scan of each sensor Measures sensor quality
Leakage Current at 80V
0
50
100
150
200
250
300
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
Leakage Current [A]
Fre
qu
en
cy
, HP
Ds Contract
Typical 1A
H527009, 0.46 A leakage at 80V
Operating Point, 80V
Ramp-up
Ramp-down
R Lambert, LHCb RICH PD07, 28th June 2007 15
Readout Chip
Low number of faulty channels Average 0.15% dead channels << 5% specification Average 0.02% noisy channels << 5% specification
Noisy pixels
0
50
100
150
200
250
300
350
400
0 15 30 45 60 75 90 105 120 135 150
Number of noisy pixels (out of 8192)
Fre
qu
en
cy
, HP
Ds
Dead pixels
0
20
40
60
80
100
120
140
160
180
0 15 30 45 60 75 90 105 120 135 150
Number of dead pixels (out of 8192)
Fre
qu
en
cy
, HP
Ds
Specification< 400
Specification< 400
R Lambert, LHCb RICH PD07, 28th June 2007 16
Sensor + Readout
Thresholds and noise Threshold scan performed on all 8192 pixels ~85% sensor efficiency, Typical signal is 5000 e-
Thresholds
0
20
40
60
80
100
120
140
160
600 800 1000 1200 1400 1600 1800 2000
Average pixel threshold [e-]
Fre
qu
en
cy
, HP
Ds
Electronic Noise
0
20
40
60
80
100
120
140
160
50 70 90 110 130 150 170 190 210 230
Average electronic noise [e-]
Fre
qu
en
cy
, HP
Ds
<N> = 145 e-<T> = 1063 e-
R Lambert, LHCb RICH PD07, 28th June 2007 17
HV Stability
PDTF perform a HV scan of each HPD Measures HV stability Pulsed LED used at each voltage step
H527009, a typical HPD H527009, 200k events, LED run
Operating Point, 20kV
Backscatter
Reflections
R Lambert, LHCb RICH PD07, 28th June 2007 18
Vacuum Quality
Ion-feedback (IFB), afterpulse Ionisation of residual gas atoms, particularly He, produces afterpulse At 20 kV, IFB measures the vacuum quality
Residual Gas Ionised
Ion liberates many
secondary electrons
Secondaries measured after characteristic delay
1
2
3
Delayed Ion Feedback
0
50
100
150
200
250
300
350
400
450
500
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Ion-feedback [% of peak # of photoelectrons]
Fre
qu
en
cy
, HP
Ds Specification
< 1%
<IFB> = 0.03%
R Lambert, LHCb RICH PD07, 28th June 2007 19
Dark Count
Thermionic emission, noise, and IR-sensitivity produce Dark Count Specification 5 kHz cm-2
Average 2.6 kHz cm-2 ≡ 0.003 hit / event / HPD in LHCb
Dark Count from 5 Million triggers
0
50
100
150
200
250
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Dark Count [kHz cm-2]
Fre
qu
en
cy
, HP
Ds
Specification < 5kHz cm-2
H520009, 5M events, 2.0 kHz cm-2
R Lambert, LHCb RICH PD07, 28th June 2007 20
Quantum Efficiency
QE is a function of wavelength, large improvement seen Independent measurements: photocurrent from known light level DEP improved the QE with each batch (i.e. with time)
Quantum Efficiency with wavelength and batch
0
5
10
15
20
25
30
35
40
0 100 200 300 400 500 600 700 800 900 1000
Wavelength, l / nm
QE
(DE
P),
hq(l
) / %
1 23 44b 56 78 910 1112 1314 1516 1718 1920 2122 ExpectedMin Spec Typ Spec
H527009 Quantum Efficiency
0.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0 100 200 300 400 500 600 700 800 900 1000
Wavelength l / nm
QE
, hq, (
no
un
its
)
DEP Results
PDTF Results 18.05.06
PDTF Results 03.06.07
Increasedover time
Decreasedover time
Expectation from preseries
Agreement across
measurements
R Lambert, LHCb RICH PD07, 28th June 2007 21
S QE dE
0
10
20
30
40
50
60
70
80
90
100
0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4
S QE dE [eV]
Fre
qu
en
cy
, HP
Ds
SQE dE
S QE dE, integrate improvement in QE across energy Cherenkov light has flat energy spectrum 24% relative increase in S QE dE over expectations from preseries
QE(DEP), hq(E), Summary
0
5
10
15
20
25
30
35
40
45
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Energy, E / eV
QE
(DE
P),
hq(E
) / %
DEP Average
DEP Min
DEP Max
Min Spec
Typ Spec
Expected
Vertical bars are standard deviation, no error is included.Green and Red curves are extrema, no single HPD has this curve
Expectation from preseries
R Lambert, LHCb RICH PD07, 28th June 2007 22
HPDs in use
HPDs fulfil or exceed all requirements for the LHCb RICH
Excellent performance demonstrated in testbeam scenarios
Ring from Pions, over 3 HPDs
124k events, with C4F10
Fre
qu
en
cy
, th
ou
sa
nd
s o
f e
ve
nts
Hit spectrum, 124k events
Hit Count in expected region of ring for 1 HPD
signal
pedestaland noise
PRELIMINARYIn agreement withexpected yields
R Lambert, LHCb RICH PD07, 28th June 2007 23
HPD Integration
HPDs -> Columns+ Magnetic Sheilds+ Level-0 Data Processing+ LV power distribution+ HV power distribution
HPD
L0
LV
HV
R Lambert, LHCb RICH PD07, 28th June 2007 24
RICH 2 Installation
R Lambert, LHCb RICH PD07, 28th June 2007 25
Summary
484 HPDs are required for the LHCb RICH
536 HPDs have now been produced 519 tested at PDTF with 506 passes Excellent results overall 24% relative improvement in QE will directly improve photon yields
RICH is now under installation and commissioning RICH 2 fully populated with HPDs
LHCb is getting ready for data….
R Lambert, LHCb RICH PD07, 28th June 2007 26
References
1. LHCb collaboration, LHCb Technical Proposal, CERN-LHCC-98-004 LHCb, 20th February 1998
2. LHCb collaboration, LHCb RICH, Technical Design Report 3, CERN-LHCC-2000-037 LHCb, 7th September 2000
3. T. Gys, LHCb RICH, “Production of 500 pixel hybrid photon detectors for the RICH counters of the LHCb,” NIM A 567 (2006), pp. 176-179
R Lambert, LHCb RICH PD07, 28th June 2007 27
Backup
Additional slides hereafter
R Lambert, LHCb RICH PD07, 28th June 2007 28
Physics and Photons
RICH crucial to separate Kaons and Pions [1] Similar hadrons, different in mass Contribute to different physics Important to separate
Signal Bd +-
R Lambert, LHCb RICH PD07, 28th June 2007 29
HPDs Realised
Hybrid Photon Detectors
Quartz window
thin metal Photocathode (S20)
20kV acceleratingpotential
Photoelectric effectproduces electrons
Pixelated anode8192 pixels
500 m x 62.5 m
Amplifier, Thresholder, Buffer, Read out
87 mm
120
mm
R Lambert, LHCb RICH PD07, 28th June 2007 30
HPD Production
HPD production status as of 18th June 2007
0
100
200
300
400
500
600
700
1-Jan-05 1-Apr-05 1-Jul-05 30-Sep-05 30-Dec-05 31-Mar-06 30-Jun-06 29-Sep-06 29-Dec-06 30-Mar-07 29-Jun-07
Qua
ntiti
es
HPDs required
HPDs delivered
Anodes required
Anodes delivered
Spare HPDs required
Spare anodes required
Anodes
HPDs
536 / 550 HPDs Produced
18th June 2007
R Lambert, LHCb RICH PD07, 28th June 2007 31
HPD tests at PDTFs - 15th May 2007
0
100
200
300
400
500
600
01/10/05 30/01/06 31/05/06 29/09/06 28/01/07 29/05/07
Date
# o
f H
PD
s
Delivered Scotland
+30 days
+60 days (~contract limit)
Scheduled
Total tested
PDTF Progress
15th May 2007
519 / 550 HPDs tested
R Lambert, LHCb RICH PD07, 28th June 2007 32
QE at PDTF
Uses existing Darkbox PC at -100V, focussing cathodes at -100V, Anode at ground
Quartz-tungsten halogen lamp
(6V, 50 W)LOT Oriel
Fused silica lensf = 50 mm,
diam. = 25.4 mm
IR-blocking filter(Schott KG-5)
bandpass filter (+- 10 nm FWHM)
lamp housing
Calibrated photodiode(Newport 818-UV unbiased)
HPD
hq(HPD) = hq
(pd) * I(HPD) / I
(pd)
I pd (pA) I HPD (pA)
ND filter (where required)
Shutter/iris combination
Shutter/iris combination
100V
RL
R Lambert, LHCb RICH PD07, 28th June 2007 33
HPD categories
150
260
5640
13
0
50
100
150
200
250
300
A+ A B E F
Fre
qu
en
cy
, HP
Ds
Results Summary
HPD Quality Assurance 506 of 519 tubes pass
A+: Exceeds key specifications. A specifically recommended HPD
A: Pass all aspects of tests
B: Falls beneath contracted specifications, but still recommended for use in the RICH
E: HPD qualified for use in the RICH, but is flagged with an issue
F: Clear failure of HPD, such that it is unusable in the RICH. HPD returned to DEP if possible for replacement
HPDswith higherdarkcount
HPDs with high leakage current and with >1% dead pixels
R Lambert, LHCb RICH PD07, 28th June 2007 34
HPD electron optics
Reliable manufacture 73% of centres within 1 pixel of chip centre standard deviation of image size ~ ¼ pixel
Distribution of image centres
-1500
-1000
-500
0
500
1000
1500
-1500 -1000 -500 0 500 1000 1500
X Deviation from centre of Chip [m]
Y D
ev
iati
on
fro
m c
en
tre
of
ch
ip [
m]
Image Radii
0
10
20
30
40
50
60
70
80
90
100
6000 6150 6300 6450 6600 6750 6900 7050 7200
Image Radius [m]
Fre
qu
en
cy
, HP
Ds
1 Pixel
R Lambert, LHCb RICH PD07, 28th June 2007 35
Peak QE
QE peaks at ~270 nm Consistent improvement of QE with batch, All production HPDs are over specifications
<QE> @ 270 nm (per batch)
25
27
29
31
33
35
37
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22batch no.
av
era
ge
QE
at
27
0n
m [
%]
<QE(270nm)> per batch
running <QE(270nm)>
Peak Quantum Efficiency
0
10
20
30
40
50
60
70
80
90
100
20.0 22.0 24.0 26.0 28.0 30.0 32.0 34.0 36.0 38.0
QE at 270 nm [%]
Fre
qu
en
cy
, HP
Ds
ContractMinimum20.0%
<QE> = 30.9%
R Lambert, LHCb RICH PD07, 28th June 2007 36
Backpulse
Efficiency of hit detection, hSi
Pixel chip efficiency important for reconstruction Probability that the chip registers a hit, given a photoelectron has struck Comparing the number of photoelectrons seen by the chip (via normal
chip readout) to the number arriving at the backplane of the Si sensor.
We measure: hsi = (87±2)%.
Fit to charge spectrum at backplane
1 electron
2 electrons3 electrons
4 electrons
5 electrons
R Lambert, LHCb RICH PD07, 28th June 2007 37
Afterpulse
Ion Feedback from Strobe Scan Consistently low, indicating excellent vacuum in all tubes Single HPD, H546002, displayed IFB and dark-count anomalies
Strobe Scan H524004
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 100 200 300 400 500
Delay [ns]
Hit
s P
er
Ev
en
t
Raw hits
Clusters
Poisson estimate
Ion Feedback x 100
Very low IFB <<1%
Delayed Ion Feedback
0
50
100
150
200
250
300
350
400
450
500
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Ion-feedback [% of peak # of photoelectrons]
Fre
qu
en
cy
, HP
Ds Specification
< 1%
<IFB> = 0.03%
R Lambert, LHCb RICH PD07, 28th June 2007 38
Source Sites
HPD sourced from around the world !
Item Source Location Test Location
Readout Wafer IBM France CERN Switzerland
Sensor Canberra Belgium CERN Switzerland
Carrier Kyocera Japan CERN Switzerland
Gold Plating CERN Switzerland CERN Switzerland
Bump-Bonding VTT Finland CERN Switzerland
Packaging HCM France CERN Switzerland
Quartz Window China, Lithuania
Assembly DEP Holland PDTF Scotland
R Lambert, LHCb RICH PD07, 28th June 2007 39
QW Reflections
As predicted by naïve CAD approximations 75% of light reflected off Chromium coating TIR at QW-Air interface ~20% reflection at QW-PC interface
R Lambert, LHCb RICH PD07, 28th June 2007 40
Reflective Effects
Activating QW reflections and Chromium reflections 8.0% more hits (naïve estimate would predict ~11%)
Improved Geometrical Description
1.5 M events, 4,992,419 Hits
Reflections Activated
1.5 M events, 5,393,100 Hits
R Lambert, LHCb RICH PD07, 28th June 2007 41
Backscatter
Only ~85% of all real photoelectrons produce digital hits Thermal effects Thresholding effects Backscatter effects
+ ++
--
-+ -- +
- + - +
Normal Case~5000 e-h pairs
Thermal absorptionv. few e-h pairs, Damage to lattice
Charge Sharing.<5000 e-h pairsper pixel
Backscatter.Smaller amountof energy deposited
Electron “may”Fall back ontoSi sensor
Si Sensor
R Lambert, LHCb RICH PD07, 28th June 2007 42
RICH in UV
Below 200 nm photon yield is limited by absorption of air
Transmittance, Absorption and QE
0.1
1
10
100
1000
100 1000Wavelength [nm]
Ab
sorp
tion
[cm
-1] .
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Tra
nsm
itta
nce
or
QE
[no
un
its] .
Absorption Water (/cm)Absorption Oxygen (/cm)Transmittance window HPDMean QE prototype pixel HPDAerogel Filter
R Lambert, LHCb RICH PD07, 28th June 2007 43
Expected Spectra
Folding in the expected QE
Cherenkov spectrum for RICH radiators
RICH 1, C4F10 RICH 2, CF4 RICH 1, Aerogel
Wavelength [nm]
Ch
ere
nk
ov
Ph
oto
ns